january, 1933 modern wireless contents · 2019. 12. 29. · january, 1933(modern modern wireless...

January, 1933 MODERN WIRELESS

CONTENTSVol. XIX. No. 73.EditorialIn the Announcer's RoomEnd of Record Quality ..

FOR THE CONSTRUCTOR:-The " M.W." " Vari-Four "

....

For D.C. Mains-A Simple Amplifier.. .. 16Getting the Whole World on the " Whole -

World " Five . 19A 6 -watt A.C. Amplifier , 21Operating the " Diodion " Super -Seven .. 26

Questions Answered .. 27From "Mike " to Aerial .. . 26Illustrated Technical Terms _ 30The Regentone " Straight -Three " A.C.Receiver ..

At Your ServiceOn the Short Waves .. 53

MODERN WIRELESS. JANUARY, 1933.Page

346

Round the Turntable .. .

The H.M.V. Superhet Ten Auto -RadiogramHow to Obtain Better Radio ..Recent Record Releases .. .

My Broadcasting Diary ,.On the Test Bench ..Spotlights on the ProgrammesNew S.G. Circuits ..Trouble Tracking .

Facts About Field Strength ,.Behind the Scenes of the Big OrchestraWhat Wattage?Using PentodesDo S.G. Valves Amplify?In Passing ..Radio Heat Rays _ .

Radio Notes and News of the MonthSPECIAL SECTION, "THE WORLD'S PROGRAMMES," PAGES 31-49

(See page 31 for Contents.).4s some, of the arrangements and specialties described in Ibis Journal may be the subject of Letter,Patent the amateur and trader would be well advised to obtain permission of the patentees to use the

patents before doing go.1 Edited by NORMAN EDWARDS.Technical Editor: G. V. DOWDING, Associate I.E.E.

Radio Consultant -in -Chief: Capt. P. P. ECKERSLEY, M.I.E.E.Scientific Adviser J. H. T. ROBERTS, D.Sc., F.Inst.P.

Page5657596263656769727376788284889098

S.T.400 COILSSpecified for the S.T.400"and guaranteed to be identi-cal to those employed byMr. Scott -Taggart in his

original receiver.Per pair - - 9/10

THERE IS A COLVERN COILFOR EVERY MODERN RADIO RECEIVER

Every discriminating constructor uses ColvernCoils in his receiver. They are his guarantee thathis set will give maximum performance. Heknows that in fitting Colvern Coils he his fittingthe best.

STRIP RESISTANCESWire -wound. For MainsUnits and Decoupling.Rating 5 watts. Fittedwith terminals and sol-

dering tags.Price-values up to

25,000 ohms -Price-values from25,000 to 50,000

ohms - - - -

1 /9

2/3

SPECIFIED IN THIS ISSUE.A 6 -watt Amplifier.

50,000 -ohms Strip Resistance. 2/340,000- 2,330,000-

5.000-2 3,000-1 700-

1 500-" Vari-Four "

1.000 -ohms Strip Resistance. 1f9

2/31/91/1/9

92/31/9

COLVERN LIMITEDMAWNEYS ROAD ROMFORD, ESSEX.

MODERN WIRELESS January, 1933

BY APPOINTMENTTO H.M. THE KING

RANGE andSELECTIVITY

Superhef Ten Auforadiogram Ten Valve Superheterodyne Radio.

Gramophone. Marconi Valves.

Reproduces Wireless or Records.

Super Moving Coil Speaker for TonalQuality.

Single Wave Change Switch for" Gramophone," " Medium Wave,'"" Long Wave " and " Off."

New Tone or Brilliance Control

Improved Record -Changer, playingeight records in succession withoutattention or repeating.

New device to dispense with record -change at will, making the instrumentan ordinary gramophone.

Price 80 gns. With De Luxe Cabinet95 gns.

Superhet circuit on both instru-ments great range-practically

w every important station obtain-able at full volume withoutoverlap.

Superhet Portable Six Six Valve Superheterodyne Portable

Radio. Marconi Valves.

Balanced Armature Speaker.

Built-in Aerial. Low H.T. current consumption II ma Compact and Handsome Cabinet in

Beautifully Figured Walnut.

Price 17 gns.

On Superhet Portable Six or Superhet Ten Autoradiogram,let " His Master's Voice" show you how to get the utmostin foreign reception to -day !Throughout the wide series of "His Master's Voice" radio sets and radiograms on saleto -day, range and selectivity- the two foremost essentials for long-distance wirelessreception -are present in the same high degree. At the lower end of the price scale isthe "Superhet Portable Six." People are getting America on this remarkable little set.Douglas Walters (radio critic of the " Daily Herald ") describes its selectivity as

excellent " . . ." a station at every few degrees of the scale." And Captain Robinson(radio critic of the " Observer ") says it is "the finest portable radio on the market."At the top of the series is the "Superhet Ten Autoradiogram." All that you could askfor in wireless or gramophone is provided-the same keen selectivity and even greaterrange, plus an automatic record -changing gramophone with all the very latest im-provements, giving radio or records with a tone absolutely unapproached by anyother instrument in existence. Superhet Portable Six, price 17 gns. Superhet TenAutoradiogram, 80 gns. (De Luxe Model, 95 gns.) or by hire purchase.

"His -Master sVoice"True - to - Life

RADIO AND RADIO -GRAMOPHONESThe Gramophone Co., Ltd., London, W. i (Prices do not apply in I.F.S.)


(ModernIllattrelloe!ss

Vol. XIX. No. 73. BRITAIN'S LEADING RADIO MAGAZINE JANUARY, 1933.

This Month's Designs-Station Separating-Result of Madrid Conference.IN this month's issue of MODERN WIRELESS we have

endeavoured to cover the needs of a great many ofour readers who wish for something more than what

may be termed " ordinary " loudspeaker reproduction.The Research Department have for some time past beenworking on the production of two mains amplifiers whichwill provide pure and faithful reproduction plus fullvolume, and readers will note in this issue full descrip-tions of these two interesting units.

The first of these amplifiers is designed for use withD.C. mains to deliver some 2.5 watts of undistorted out-put. The second amplifier has been designed specificallyfor A.C. and gives up to 6.5 watts, thus allowing amplemargin for household purposes and sufficient power forloudspeaker reproduction in small dance halls, etc.

There is yet another product of the Research Depart-ment's work which we feel will interest many readers-a battery four -valve receiver. This set has several out-standing features, not the least of which is the automaticwavechanging and variable -mu volume control. Readerswill find this set quite easy to operate and capable ofbringing in a very satisfactory number of programmes.In short it is an ideal household multi -station receiver.

An Invention Worth WatchingTHE Radio Research station at Datchet under the

Department of Scientific and Industrial Researchhas recently perfected a device which may,

without exaggeration, be described as having very far-reaching possibilities. In brief, the device successfullyeliminates all wireless signals-even on identical wave-lengths-which come from different stations in differentdirections from the actual transmitting station which itis desired to receive.

On test it has been found that any number of localstations may work on a standard wavelength and, pro-vided not more than three of them are geographicallysituated in a straight line, by the use of the device per-fected by the Radio Research Station at Datchet there isno difficulty in working them all at once. With the ever-increasing seriousness of the problem of jamming, thesorting out of different signals becomes more and moreessential ; and we understand that this new inventionmakes use of a stream of electrons which instantaneouslychanges its form in accordance with incoming waves for

NW" .00.411111(111RNM..--

reception. The signals from any required station, forexample, are " caught " and the current which theyproduce is amplified, so as to light a small lamp, flashesfrom which can easily be read by the operators in charge.

An official explained that, in order to demonstrate thepractical advantages, a model has been designed in whicha green light shows the signals to be received, while a redlight registers the confusion which would otherwise resultwhen several stations were operating on the same wave-length at the same time.

We shall await further information regarding thisdevice with considerable interest, for any instrumentwhich is capable of eliminating all wireless signals onidentical wavelengths which are not desired, while pickingout signals from the particular station required, is cer-tainly worthy of the very closest investigation.

More Waves for BroadcastingASHORT time ago the Radio Telegraph Conference at

Madrid ceased its labours. For fourteen weeksthe Conference has been in session, and perhaps

the most important result obtained is that of securingRussia's decision to accept the Conference's findings-even with reservations.

The most important wireless change which will resultfrom the Conference is the increase in long waves forbroadcasting services. The new wavelengths will startfrom 1,131 metres instead of 1,340 as under the presentagreement, and will go up as far as 1,875 metres.

Incidentally, it is worth while remembering that at themoment there are already a number of long -wave stationsoperating above and below the limits prescribed byprevious Conventions. The new wavelengths availablewill be allocated to various countries at a EuropeanConference which will be held in May next, when it islikely that it will be agreed that medium -wave stationswill not exceed 100 kw. in power, and long -wave stations150 kw.

This new Conference, which will be held in Lucerne,will have further problems to tackle in connection withthe dearth of available wavelengths, for European countriesare increasing their broadcasting services very rapidly,and are constantly crying out in competition with olderestablished radio services for more available wave-lengths.


/ ',yr /%/ a aiii/ii/i/ / ,, , , , :

2/ // /, y 0

/ / 7

/rY/iAA4,4e'' ,L

What does an announcer do while a programme is on ? What are the mysteries ofthe announcing and listening rooms, which, for his benefit, are built at the side of

each main studio in London?OUR SPECIAL CORRESPONDENT spends an evening with a well-known announcer

and tells you the answers to these intriguing questions.

ANNOUNCERS are still anonymous. A great pity !An old lady friend of mine, who listens for nearlytwelve hours a day, thinks they are " such

dears "-and I think she's right. As they are anony-mous they can blush unseen under my rowan of praise.

A man who has been on the announcing staff since theearly days of broadcasting was one of my firmest ac-quaintances at Savoy Hill, and one evening last weekhe helped me to elucidate the mystery of where an-nouncers go 'twixt programmes.

Old Order ChangedIf you have ever been lucky enough to see a

programme through in the old Savoy Hill days youwill know why the matter is now a mystery of almostA. J. Alan status!

There were sometimes only two announcers on dutyat a time in the old London studios. The lift was slow.The studios were on many floors. It was a commonthing for an announcer to be thoroughly out of breath,having covered three storeys in thirty paces.

Announcers in those days had to be masters of signlanguage. Everything had to be done in the studio ;no opportunity to get through on the house 'phone andmake studio arrangements for the next broadcast ; noway of knowing that after the next breathless dash upor down stairs to another studio everything would be

4

just ready and waiting for the broadcast. It might evenbe the wrong studio !

Now the express lifts and the special padded listeningand announcing rooms of Broadcasting House havechanged the old order. There is a popular idea thatall the announcers have to do now is to twiddle thumbsin between intervals of breathing their golden voices softlyAgainst the condenser mikes !

It really isn't quite so simple as all that. My an-nouncer friend invited me to see the inner workings ofthe listening and announcing rooms of each main studio.The new gadgets certainly give announcers plenty todo!

" Now here is a typical studio," said the announcer,whisking me out of the lift on to I know not what floor ofBroadcasting House. " There are two microphones,you see, and a plug for an additional gramophone turn-table.

Baffle -Box Speaker" Here are the two signalling buzzers, one wired through

to the control room and the other to the band room. Wehave a code here so that by flashing the control -roombuzzer we can signal to the man at the desk when toswitch on.

" In the corner, you see, there is one of the new re-producers-a mains -driven two -valve amplifier and a

January, 1933

moving -coil speaker in a baffle box. By pushing in thisplug and flashing through to the control room, I canhave the speaker equipment wired up to the dramaticcontrol room. Anybody up there conducting a re-hearsal can speak back to the artistes in the studios."

" It doesn't look difficult," I ventured." Pushing a buzzer button-no, it's not very difficult,"

he said, in -the manner sarcastic ! " Come into thelistening and announcing rooms next door. Then youwill see something."

MODERN WIRELESS

The announcer's desk is at the right of this picture-note his easily adjustable lamp and the gramophoneturntables. The adjoining room is the News Editor'soffice, while the lower picture to the left shows the" BB " Studio where the dance bands usually play.

In the listening room I saw a six -way " mixer." Thisis simply a bank of six potentiometers. They can bewired up in several different ways, so that the inputscan be faded from one to the other. There is a house'phone and a special 'phone wired through to the controlroom. In the corner is another mains -operated am-plifier and moving -coil speaker.

" When I have made the opening announcement,"said my friend, " either from the main studio or from theannouncing room next door, I can at the touch of theswitch connect up the amplifier and speaker with thestudio line and hear what is going on. I can also see,of course, through the double glass window."

Uncannily Pure ReproductionHe switched on the speaker. Some people were talk-

ing in the main studio before a rehearsal and it so hap-pened that they were standing close to the hike. Theannouncer slowly turned one of the six -way " mixer "controls, fading in the microphone close to the group ofpeople.

The effect was uncanny. Although we were entirelysound -insulated from the studio, and could only see the .artistes through the small glass windows, the loudspeakerreproduction in the listening room was so good that itseemed as though we were actually in the main studioand listening to the people talking !

" You see, I don't have to go into the studio to getan accurate idea of what the programme sounds like,"commented the announcer, as I stood bewildered at thepurity of reproduction.

(Continued on page 97)

MODERN WIRELESS

UFRECUWJAUTY

Have you ever wondered why there is a falling off in tonal quality towards the endof a record? The reason is lucidly explained by

F. N. GANDON.

THAT the quality of reproductionfalls off towards the end of arecord has been noticed by

every radiogram enthusiast, but thereason for this trouble is not so obviousas it appears at first sight.

The generally accepted explanationis that the point of the needle wearsand does not follow the variations inthe sound -track as it should ; butwhile this assumption is correct, up toa point, it is only a half-truth. Theneedle fails to follow the track not somuch because it is worn, but becauseof an inherent difficulty in the record-ing process.

Frequency FixingIf a record is examined with a lens

or low -power microscope the wavinessof the grooves is easily seen, and itis clear that if the point of the needleis passed through a groove at a fairspeed it will be thrown from side toside or vibrate.

The speed of vibration or the fre-quency of the note will be governed bythe number of wave -crests passedover per second, and this in turn willdepend on the surface speed of theneedle and the distance between thewave -crests.

At a given needle speed, the fartherthe wave -crests are apart the slowerthe vibration and the lower the note-or vice versa. It will be seen fromwhat follows that the wave -creststend to become closer and closer to-gether towards the inside grooves,and it is this fact which is the mainreason for the falling -off in quality.

The circumference of the outsidegrooves of the average 10 -in. recordis approAmately 29 in. and theturntable steed 80 revs. per minute(approx. 1.3 revs. per second). This

means that the needle passes throughthese grooves at a speed of 29 in.+9.6 in.=38.6 in. per second.

For the sake of example we willassume that b. 50 -cycle note is beingreproduced, which means that theneedle must vibrate 50 times asecond. As we know that in asecond it also travels 38.6 in., it followsthat the distance between the wave -crests must be 38.6 in.±50=.772 in.

Needle TravelWhen we come to the end of the

record, however, it is a different storyfor here the circumference may beonly 11 in. This means that at 80revs. per minute the needle onlytravels 14.66 in. per second, so that thedistance between the wave -crests isonly about 14.66 in.=50=293 in.,as against 772 in. on the outside-inother words, they tend to becomecramped together.

COMPRESSED RECORDING

In the first groove of a record the crests oa 50 -cycle note are widely spaced, butnot so on the last groove. If a high notecould be shown, it would be seen that thecramping on the last groove would pre-vent the needle following the " waves."

January, 1933

This cramping does not do muchharm on such a low note as 50 cycles,for the needle -point can easily followthese comparatively large waves, butit is a very different matter with thehigh notes.

Calculating in the same manner, itwill be found that in the outsidegrooves the wave -crest distance for anote of 3,000 cycles is approximately.0128 in. or 1/80 in. Small as this is,the needle -point will follow it fairlywell, and it is not until the insidegrooves are reached that trouble setsin.

Feeble VibrationsHere, owing to the small circum-

ference, the wave -crest distance of- a3,000 -cycle note may be only .0048in., or, roughly, 1/200 in., which isscarcely as large as the needle -pointitself. The consequence is that itsimply passes through these grooveswithout vibrating at all, or, if it does,only in a very feeble and distortedmanner.

It is clear, then, that the chiefreason for the falling -off in qualityat the end of the record is due toreduced volume or total loss ofsome of the higher notes, owing tothe fact that the needle cannot followthe cramped wave -form. It is onlyexaggerated but not caused bythe fact that the needle -point isworn by the time it reaches the lastgrooves.

Incidentally, the above figuresshow very conclusively the impor-tance of having the turntable speedcorrect. We know that at 80 revs.per minute the needle will vibrate 50times per second for a 50 -cycle note.Suppose the turntable speed isincreased 10 per cent to 88 revs. perminute (a fault often found owingto wear of the speed regulator), thenit is clear that the whole rangeof frequencies will also increase 10per cent. The normal 50 -cycle notewill become 55 cycles, and 3,000cycles will be 3,300 cycles.

Upsets the ToneThe aural effect of this increase in

turntable speed is that orchestralreproduction will appear thin andhigh-pitched, and, what is even worse,a male voice will almost seem to bethat of a female.

It is due to this difference betweenthe inside and outside groove of therecord, that when for some reasonthe amount of recording on a specialdisc is somewhat less than usual, it isstarted at the usual distance from theoutside of the disc ; leaving the blankpart inside.

6

anuary, 1933 MODERN WIRELESS

gorgeCONSTRUCTOP

PURE POWERAMPLIFIERS

FIRST CLASS INSTRUMENTSFOR A.C.and D.C. MAINS -

FULL CONSTRUCTIONAL DETAILS


THE main features of the" Vari-Four " are the auto-matic tuning controls and

the variable -mu screened -grid valve,and this is the first time that thesetwo great advantages have beencoupled together. Added to otherworth -mentioning points, they makea very strong group which place thereceiver well in the forefront ofmodern set designs.

We shall have more to sayspeCifically about the various circuitarrangements later, but we here wantto stress the most important pointin the design of every set, andespecially those wherein some out-standing features are included. Thisis the necessity of choosing thecomponent parts with the utmostcare and accuracy.

In many receivers it does notmatter what parts are chosen, as

The use of the correct componentsis very important if the best is tobe obtained from any set design,and in some cases no alternativescan be given. So be warned, anddo not light-heartedly use non -

specified parts.

long as they are of the correct value.For instance, variable condensersare variable condensers, no matterwhat the make, and often it does notmatter whether they come from thefactory of A, B or C. Similarly, L.F.transformers and coils can be chosenwith a certain amount of latitude.

Alternative ComponentsIn this set, however, it is im-

portant to keep to the specified list,if the full value of the method ofcomponent combination is to beobtained. There is no substitutefor the automatic wavechanging

condensers-Extensers, as they arecalled-and the Telsen Telexors mustbe used, for their screening playsa large part in the success of the set.

Similarly, the coils must not onlybe screened, but if other types andmakes are used, either the tuning willsuffer or the wiring diagram and thelayout of the set will have to bemodified in order to accommodatethem. That is the reason why wesay " see text " against the alterna-tive in the list of components, forthe Goltone coils can be used ifthe following alterations in theconnections are carried out. In theG G R coil the following terminalnumber substitutions for those inthe wiring diagram should be made,the coils being turned round so thatthe wiring is most convenientlyarranged. 1 and 2 remain, 3 be-comes 5 on Goltone coil,4 becomes 6, 5 becomes 4, and6 becomes 3.

The parallel -fed transformer coup-ling unit, too, stands alone inour list, not because it is the onlyone that would be satisfactory inthe set, but because, as there areno standard terminal markings andpositions on these components, suchsubstitution would tend to causeconfusion unless diagrams for everypossible combination of alternativeparts were available.

Other components are interchange-able to some degree, but it will heseen from these remarks how im-portant it is to keep to the list given,and where no alternative type ormake is listed, to desist from usingan alternative.

ALL ABOUTPANEL

18 x 7 in. (Goltone, Peto-Scott, Pere -mobWearite, Becol, Direct Radio, Lissen).

BASEBOARD18 x 10 in.

CABINETFor 18 x 7 in. panel and 18 x 10 in.

baseboard (Peto-Scott, Cameo, Marco,Osborne, Lock, Gilbert, Direct Radio.Pickett).

VARIABLE CONDENSERS2 Telexors (Telsen W180).1 -0003-mfd. differential reaction (Lotus,

Telsen, Polar, Ormond, Ready Radio,Keystone, Bulgin, Utility, J.B., GrahamParish).

1 Preset -0001-mfd.-00015-mfd. max.(Goltone, Telsen, Polar, Forma, Igranie,Graham Farish, Colvern).

FIXED CONDENSERS1 2-mfd. (Dubilier type B.11., T.C.C.,

Linen, Igranie, Ferranti, Telsen, Sove-reign, Peto-Scott, Formo, Goltone).

1 2-mfd. (Lissen type LN134, or see above).1 2-rnfd. (Igranic " Nondu," or see above).2 1-mfd. (T.C.C. type 50, or see above).1 -25-mfd.(Dubilier type 9200,or see above.)1 -01-mfd. mica (T.C.C. upright, Dubilicr,

Graham Farish).1 -01-mfd. (T.C.C. type O.F. with wire ends).1 -0001-mfd. (Dubilier type 670, Goltone,

Graham Farish, Ready Radio, Telsen,T.C.C., Linen, Ferranti, Igranic, Wat-mel, Sovereign, Peto-Scott).

ALL THE PARTS AND ALTERNATIVESVARIABLE RESISTANCE

1 50,000 -ohm potentiometer (Watmelwire contact type, Sovereign, Wearite,Colvern, Igranic, Tunewell, Varley,Linen, Lewcos).

FIXED RESISTANCES1 1,000 -ohm (Colvern strip, Graham Farish

Ohmite, Dubilier, Watmel, Sovereign,Bulgin, Ready Radio).

1 1-meg. grid leak with wire ends orterminals (Dubilier 1 -watt, Goltone,Igranic, Ready Radio, Graham FarishOhmitc, Igranic).

1 -25-meg. grid leak (Graham FarishOhmite, or see above).

1 -5-meg. grid leak (Graham ParishOhmite, or see above).

1 25,000 -ohm (Graham Farish Ohmite,Watmel, Sovereign, Detainer).

1 50,000 -ohm (Graham Farish Ohmite,or see above).

COILS2 Dual -range screened coils (Lissen LN

5101 Goltone G G R-see text).H.F. calm

1 Lewcos type 3I.C., or small Keystone,Telsen, R.I., Ready Radip, Varley,Linen, Lotus, Wearite, Watmel,Sovereign, Graham Parish, Tunewell,Slektun, Goltone.

SWITCHES1 3 -point toggle shorting (Bulgin type

8.87).1 Radio jack -switch (Lotus No. 9).

VALVE HOLDERS1 5 -pin horizontal (Linen type LN739,

W.B., Bulgin, Telsen, Wearite).3 4 -pin (Lotus, Lissen, W.B., Igranic,

Bulgin, Telsen, CIL; Tunewell, Ben-jamin, Junit, Wearite, Formo, ReadyRadio).

L.F. CHOKE1 Ferranti type B8, R.I., Igranic, Lissen,

Varley, Wearite, Bulgin, Telsen, Tune -well, Lotus).

L.F. TRANSFORMER1 Benjamin Transfeeda.

MISCELLANEOUS1 Fuse holder (Bulgin type

Telsen).1 Terminal strip, 6 x 2 in.2 Indicating terminals (Belling & Lee type

It, Bulgin, Clix, Igranic, Goltone, Eelex).2 Terminal blocks each with two ter-

minals (Lissen type LN308 and LN347,Belling & Lee, Sovereign, Goltone).

9 Plugs (Clix, Bulgin, Igranic, Belling &Lee, Eelex, Goltone).

2 Accumulator connectors (Belling & Lee,Goltone, Eelex, Clix).

1 60 111.a. fuse (Belling & Lee " Scrufuse,"Goltone, Bulgin).

5 yds. of systoilex and 6 yds. of 18 gaugetinned copper wire (Goltone).

2 sets of bias battery clips, Bulgin No. 1.Flex, screws, etc.

F5, Goltone,

a

8


BUILDING THEW "VARI-FOUlt

FTER the components have beenchosen, the set must be built.In this case, though the base-

board is fairly well packed, there is noreal difficulty in construction, pro-vided it is done methodically and notin a haphazard fashion.

Baseboard LayoutWhen the panel has been drilled

and the parts mounted on it, it is bestto put this aside and lay out the com-ponents on the baseboard beforeattempting to wire up any of thepanel parts, holding the panel againstthe baseboard every now and then tomake sure that none of the com-ponents on the latter will foul thoseon the former.

Then, with the panel still detached,wire up such things as the valvefilaments and all leads that run alongbetween baseboard components closeto the panel. Such leads as those be-tween terminals of the coils andother baseboard components, thatloisg lead from the output choke tothe 1-mfd. condenser between thecoils, and so on.

Panel ComponentsThen take the panel components

and connect any wires that go be-tween them. In this case there areonly two. One from the slider of thepotentiometer to the earth terminalon the first Extenser, and the otherbetween the on -off switch and theright-hand terminal of the potentio-meter.

ti

A set that " minds its ownbusiness"! What is its business?Why, bringing in stations loudlyand clearly- and only the stationsyou wish-as and when you wantthem. The set will not interferewith other people's stations, andunwanted stations will not interfere

with it.

ti

But there are several leads be-tween the Telexors and the baseboardcomponents, and if longish leads aretaken to the Telexors now, it will beeasier to connect them to their respec-tive points later on.

WAVE -CHANGING IS

A similar method is best employedlater on when the connections to theradiogram jack -switch are made, forthis is not an easy switch to onnectup when in position, for it projectsfairly closely towards the othercomponents, though the diagramshows it flat down so as to give aclear indication of the actual connec-tions.

Start Low DownAlways do those wire,, that come

from the feet of vertical components

QUITE AUTOMATIC

You can turn from a station on the medium waves to one on the long as easily as you canturn from one local medium -wave station to another on the medium waves. Every

station has its own dial reading, one dial serving for both bands.

9-


VARIABLE -MU VOLUME

CONTROLProvides asmooth and widerange control ofvolume beforethe detectorvalve, and sinceit works on theS.G. valve, boththis and the de-tector are pre-vented from thequality - spoilingeffects of over-

loading.

AUTOMATICWAVE -

CHANGEThese Telsenscreened Exten-sers providean automaticchange frommedium to longwaves as theirknobs are ro-tated. Not onlydoes this sim-plify operation,but each stationhas its own in-dividual dial

reading.

SERIESGRID -BIASBATTERIES

The grid bias forthe variable -mumust have afairly high volt-age, and be-cause they areso easy to obtain,use is made oftwo nine -voltbatteries joinedin series. Thesebatteries supplythe L.F. valves

as well.

- _

... /8'7//

_

mote

}

7, /,

0:,?/'

e'

i

.

.orallit,

7, /

401111%,

"F

H Til'AP/N 1 :,;/;/ 9

1

/ "PRNEL i .7 Your t.s'1

HORIZONTALMOUNTING

FOR SHORTWIRING

By mountingthe S.G. valvehorizontally, itis possible tokeep the lead toits anode veryshort, and shortwiring is alwaysa great aid toefficiency. Notehow the valvesare .all arranged

in a row.

DUAL -RANGEAND

SCREENEDCOILS

are importantitems in theachievement ofefficiency. Theirscreening (whichis removed toshow the coils inthis photograph)in conjunctionwith the Exten-ser screeningmakes possiblethe simple lay-out of the re-

ceiver.

L.F.COUPLINGAND DE -

COUPLINGThis componentin conjunctionwith the 2-mfd.condenser to itsleft provides de -coupling for the1st L.F. valve aswell as parallel -fed coupling be-tween the lasttwo valves ofthe set, thusensuring goodquality amplifi-

cation.

10


Variable-Mu-Invariably Successfulor low down on others before tacklingthose at the tops. This helps a greatdeal in keeping the set tidy, and notehow the wires connecting terminalsof the coils remote from the sidenearest the components from whichthey come are taken round the coilsinside the cans. This adds to thescreening of the set, and is a smallbut important point. A goodexample of this is the lead from G ofthe second Telexor to terminal 1 onthe second coil. Note how it curvesround past 3 and 4 inside the screen.

Unusual Terminal PlacingYou may wonder why the terminals

for the aerial and earth are -differ-ently placed from usual. This wasdone for two reasons. The first isbecause it is easier to run the aeriallead between the S.G. valve holderand the .25-mfd. condenser than torun it round ; and, secondly, it cor-responds with the terminal markingof the Lissen terminal block as viewedfrom the back of the set-the wayyou would look at it when wiring, andprobably when connecting up for test.

A similar state of affairs is seen inthe case of the loudspeaker terminals.Although there is no real positiveand negative loudspeaker connectionwhen an output filter is employed,for the D.C. is prevented from enter-ing the speaker leads, yet there is anearthed side, and we have kept thingslogical by making the terminalstamped L.S.- on the terminalblock the one that is connected tothe earth circuit of the set.

Connecting Dial LightsThe batteries are connected by

means of cords, thus doing away withthe necessity of terminals,- and wefind that a great many of our readersprefer this to the alternative methodof using terminals.

The rest of the construction is per-fectly straightforward, and you willfind no difficulty in it. It should benoted that the dial lights on theTelexors have been left uncon-nected.

This is done advisedly becausemany constructors will prefer not toadd this extra drain on the accumu-lator, for naturally the lights makeno material difference to the workingof the set. If it is desired to usethe lamps, the connections are asfollows :

The two terminals of eaoh lightare joined to the corresponding ter-minals on the other ; thus placingthem in parallel. Then take a lead

"AT YOUR SERVICE "-

Here it is-completely wired and ready tofulfil your every wish where foreign

stations are concerned.

from the left-hand terminal of thelight on the second Extenser andconnect it to the filament terminal ofV4 nearest the back of the set.

The other terminal of the secondExtenser dial lamp is joined to themoving vanes of the reaction con-denser, or, if more convenient, to the

STUDY THE

S

1"1

095

At first glance you might think-" Just another Four "-but don't ! Just look into itand you will spot such features as automatic wave change, variable -mu volume -control,

parallel -fed L.F. stage, and other modern refinements of receiver technique.

r

right-hand terminal (looking fromthe back of the set) of the 2-mfd.condenser, which in its turn is alreadyconnected to the reaction movingvanes and to the L.T. circuit on itsnegative side.

You will note that the bias bat-teries-there are two placed side byside-run across the leads from theon -off switch. This is easily carriedout if it is remembered to run theconnections from the left-hand andthe centre terminals of the switchlow down along the surface of thebaseboard. Then, as the batteriesare held in position by the batteryclips, they will be raised sufficientlyabove the baseboard to clear thoseleads.

Switching Grid BiasA three-point switch is essential,

by the way, to break the circuit ofthe grid bias through the potentio-meter as well as the L.T. negative.Without such a switch there would bea constant though admittedly smalldrain of current from the bias batterythrough the 50,000 -ohm potentio-meter even while the set was not inuse.

It may be that some constructorswill prefer not to use a pick-up,though we expect that most of themwill decide to include the jack -switchwhich allows the set to be used as aradiogramophone. This jack -switchcuts off the L.T. supply to thescreened -grid and detector valves

CIRCUIT-IT'S WELL WORTH ITAo VWAr000 Owes ..1:ooOaws

V A- aew.

Xcn. Swerce.

T 0

o40

L5

e

11


while the pick-up is being used, but itcan be quite easily omitted if it isdecided to use the set for radioonly.

Omitting the Pick -UpIn this latter event it would be un-

necessary to have the small ebonitestrip, the battery cord would bestapled down to the baseboard, andthe ebonite strip, the jack -switchand the two pick-up terminals wouldbe done away with.

The alterations in connectionswould be these. The filament con-nection of V3 (side farthest frompanel) would be continued along toV2 and V1. In other words, theconnections between filament of V4and the jack and between V2 and thejack would be omitted, and V2 andV3 filaments would be joined instead.

Then the connection between the.01-mfd. condenser and the switchwould be removed, and the .01-mfd.condenser would he taken direct to

the bottom of the 230,000 Ohmiteresistance close to the grid of V3.

There would then be no connectionbetween the i-megohm grid leak andthe pick-up terminals (the latter beingremoved), though the other connec-tions to the leak would remain.

Moving -Vane ConnectionsIt may seem strange to some that

there are apparently no moving -vaneconnections to the two Telexors.Actually, the moving vanes are

Record Reproduction Simplified YuningThfiltered Output

A

01,7- PC?

0

HOLE INTERAibv4L57R/P.

\\\;,

N.

rNT ,,1

0 00005 MFG,

ENRny

Nor Uszz

.5wIrcH

\\\

0/RL LAMPso,cooPor '4.14-11,1

0005 WO

E-Rars,

Th57r. lk

.

dune

r t

IaI ii r

Among its other advantages the set has no external screening, ensuring easyaccessibility.

PIO

construction and

12


111

common to the frame, and the" earth" terminal acts as the moving -vane connection.

Note how the connections to theL.F. coupling unit are made. TheH.T.1 and H.T.2 terminals are usedin conjunction with the adjacent2-mfd. condenser to provide a de -coupled H.T. supply to V3, and it isimportant that these connections berightly made.

Circuit DetailsThe connection between the two

centre terminals of the coils and tothe .25-mfd. condenser is made lastof all, when the cans have beenplaced over the coils, and is for thepurpose of earthing the cans.

So much for the construction ofthe " Vari-Four." You will haveseen from the theoretical circuitdiagram what manner of set it is,but in case there are one or two pointsthat are not clear, wewill briefly runthrough the circuit.

The aerial iscoupled through apreset condenser (to

THE VALVESTO USE

1-mfd. condenser is placed between.the coil and earth, and anotherbetween the switch contact of theTelexor and the No. 3 terminal of thecoil. By this means there is no dangerof shorting the H.T. to earth whenthe medium waveband (switch closed)is used. Obviously, these condensersmust not be omitted.

The coils used have completely freereaction windings, and, therefore,we can so arrange our differentialreaction condenser that the moving

as the radio volume-control-byvariable -mu valve-cannot be usedfor the pick-up as well.

This external volume -control iseasily fitted -to the motor board onwhich the pick-up is mounted.

It is important that the connectionsto the volume -control be correct, orwhen the control knob is rotated in aclockwise direction the volume willbe decreased.

It can usually be seen to which ofthe two outside terminals of the

RECOMMENDED FOR PURE POWER SUPPLYLoudspeaker.-B.T.-H., Blue Spot, Baker's Selhurst, G.E.C., Ferranti,

Marconiphone, W.B., Lanchester, Ormond, Igranic, Clarke's Atlas.Batteries.-H.T.: This should be of ample size to deal with the require-

ments of the valves chosen. Pertrix, Magnet, Ediswan, Lissen, Ever Ready,Drydex, Marconiphone.

L.T. Accumulator.-Ediswan, Exide, Lissen, etc.G.B.: Two 9 -volt units linked. See above list.Mains Unit-This should have two plus tappings with output to suit valves

chosen. Atlas, Ferranti, Regentone, Ekco, Tunewell, Heayberd, R.I.Aerial and Earth

Equipment.-Elec-tron "Superial."Graham Farish"wilt" EarthingDevice.

H.F. Stage Detector ist L.F. Output OutputMains Unit

Mazda .. .. S.215V.M. H.L.2 L.2 P.220 P.220A.Mullard .. P.M.12V. P.M.1H.L. P.M.2D.X. P.M.2A. P.M.202Cossor .. .. 220V.S.G. 210H.L. 210L.F. 220P.A. 230X.P.Marconi .. V.S.2 H.L.2 L.210 L.P.2 P.2Osram .. .. V.S.2 H.L.2 L.210 L.P.2 P.2Tungsram .. - H.210 L.G.210 P.220 S.P.230Lissen .. .. S.G.2V. H.L.2 L.210 P.220 P.X.240Eta . .. - B.Y.1814 B.Y.1210 B.W.604 B.W.802Six Sixty .. SS.215V.S.G. 210H.L. 210D 220P.A. 220S.P.Clarion .. - H.2 H.L.2 P.2 -

allow variation in selectivity) to thetap on the first coil. This coil istuned by a Telexor (Extenser), whichalso acts as an automatic wavechangeswitch by virtue of the contactsshown on the theoretical diagram,and connected to the three terminalsmarked " switch " in the wiringdiagram.

Avoiding ShortsOf these switch points only one is

used in each case, the " other side "of the switch being integral with themoving vanes of the Telexor andtherefore at earth potential.

That is why in the tuned -anodecircuit (second coil and Telexor) a

vanes are at earth potential. Thisdoes away with any possibility ofhand capacity even when the mostcritical reaction adjustment is beingmade.

The detector valve is resistance -capacity coupled to the 1st L.F., ajack -switch being interposed betweenthe two valves to enable a pick-upto be used on the grid of the 1st L.F.valve. This jack -switch throws thedetector and the screened -grid valveout of action while " gramophone "is beinab used, and by disconnectingtheir filament supply saves any wasteof L.T. or H.T.

Volume -control for the gramophoneside should be arranged externally,

13

three on the volume-control potentio-meter is the one towhich the slider armis likely to go whenthe knob is turned

clockwise, but if there is any doubt,a trial will soon show whether youhave things right or not.

Here are the connections. Twoends of pick-up to two outsideterminals of the volume -control(which should have a value of about50,000 ohms). The centre terminalof the volume -control is connected tothe top pick-up terminal of thereceiver.

Nothing FreakishIt now remains to connect the

bottom pick-up terminal of the set toone or other of the outside terminalsof the volume control. It shouldgo to the one which is approached bythe slider on the knob 'being rotatedanti -clockwise( but if there is anydoubt, try one and then the other !

After the 1st L.F. valve we come tothe parallel -fed L.F. transformer unitand thence to the output valve and itsoutput choke system.

There is, therefore, nothing freakishabout the circuit-everything is care-fully thought out and is the result ofa great deal of experience.


ITH the set completely builtand the accessories to hand,it is a matter of only a few

minutes before the first tests can becarried out. The valves are the firstthings to be placed in position, thevariable -mu valve going in Vi, thedetector in V2, the L.F. valve in V3,and the power valve in V4.

Bias ConnectionsThe two 9 -volt bias batteries are

placed in the two pairs of clips underthe reaction condenser, and they arejoined together with a length of flexbearing two plugs, the plus end of onebattery being connected to the nega-tive end of the other. This leaves aplus and a minus free. If only onebattery is used (see previous page)there is no need for this piece of flexand the two plugs.

Place the bias positive plug into thepositive free end of the battery, andthen place the three negative plugsin as follows : G.B.1 goes into thefree negative end. G.B.2 goes into1.5 volts from the positive end, andthe third- G.B. goes into whateverbias is required by the particularoutput valve you have chosen.

H.T. VoltagesThe H.T. battery is now connected

up with the H.T. - in the minus end,H.T.1 in EO volts, and H.T.2 in thefull maximum of 120 or 150 volts.The L.T. battery connections areobvious. It should be noted that inthe case of the mains unit being usedthe taps are the same as for the H.T.battery, except that probably youwill have the two taps marked"screen" and max. In this case H.T.1goes to " screen " and H.T.2 to max.

There's nothing whatever bother-some about the operation of theset, and with these details toassist you, you will have no diffi-culty in getting the remarkablyfine results of which the Pari-

Four " is capable.

Connect aerial and earth and loud-speaker in. the usual way and switchon. The jack -switch at the back (ifyou have included it) should be pulledout.

Then, with the pre-set condenserscrewed right down, turn the tuningdials to the same reading between 0and 100. Keep them in step untilyou hear your local station (weassume you are testing the set oneevening, or when the local is on), andthen. adjust the tuning on the dialsuntil you are full in tune. We shouldadd that the variable -mu controlshould be turned full to the right for

this, and the reaction knob to theleft.

Probably you will overload thevalves, and so the variable -muvolume -control should be turnedto the left until the volume is atthe right strength for comfortablelistening._ You are on the mediumwaves and should now try to getother stations on that band (be-tween 0' and 100 on the tuning),getting -the .hang of the controlsbefore any attempt is made toadjust for better selectivity if thisis required.

Adjusting SelectivityReaction is applied in the usual

way, by turning the reaction con-denser knob to the right, and youshould try your hand at gettingsome foreigners.Next alter the setting of the pre-set

condenser by unscrewing the knob,testing on your local or some otherstation for the change in selectivitythat will occur. As you unscrew thecondenser knob so will the tuning ofthe set get sharper. and though thiswill also have the effect of weakeningthe distant stations, this loss can bemade up either on the variable -mucontrol or by the use of reaction.

Long WavesEventually you will find a setting

that will give you the best selectivityfor your particular conditions, andthen it is time to try the set on thelong waves.

To do this you do not have tooperate any switches, just turn thetuning dials till they read between100 and 200. This is a definite in-dication that you are now on thelong waveband.

VARIABLE -MU FOR VARIED ENTERTAINMENT

Four con-trols - two for tuning, one for

reaction and one for volume-but what a wide choiceof programmes they offer you And if the radio fare does not take your fancy

you can change to turntable and pick-up for your entertainment.

14


SEEING THE "SIGHTS" OF THE "VARI-FOUR9 9

Showing some of the details of design and construction which mean so much wherethe final results are concerned.

Metal clips placed side by side hold the grid -bias batteries for H.F. andL.F. stage. G.B.-f- is the lead attached to the differential condenser.

Seen as a whole it is the main features whichstrike one; but he small refinements, thatare there for the looking, are really quiteimportant and all do their share in makingthe receiver into a harmonious whole. Apoint which will immediately appeal to dis-cerning constructors is the entire absence ofcomplicating partition screening. The use ofcomponents comprehensively screened in them-selves serves to endow this sensitive receiverwith a degree of stability rarely found in sets

built from unscreened components.

Above you see adjustment of the aerial seriescondenser being made. It has to be carried outonly once, and adapts the set to varying sizes of

aerial and selectivity requirements.

To the left is the fuse being put into place. It isscrewed into its small holder and plays an im-portant part as watchman for any mistakes made

with H.T. connections.

I

lb


f OR

D.CMA1NSA SimpleAmplifieti

all like plenty of volume, so long as it does notinvolve distortion, although battery usershave to be content with much less than those

who have mains if their running expenses are to bekept within reasonable limits. But that is one of theways in which the user of the mains scores.

It is nice to have an amplifier capable of handling alarge output, even if only to be sure that there is nopossibility of peaks causing overloading when workingat moderate volume. But it is not possible to get morepower, in the form of volume from the loudspeaker,than the power that is put into the last valve as H.T.Mains users, whether they have A.C. or D.C., havewhat is practically an unlimited supply of H.T. currentat a very low cost.

Where voltage is concerned the D.C. supply is notflexible like A.C., for the voltage cannot be stepped upjust as desired. That is why the amplifier described hereis designed for mains around 200 volts.

Ideal for the ClubroomWe are not concerned with A.C. mains at all, a

powerful amplifier for them being described in otherpages of this section. What we are concerned with hereis describing a powerful amplifier for D.C. mains.

It has an output of around 2i watts of undistortedpower-quite enough for dancing in the largest ofrooms, and ideal, for instance, for use in that clubroom.It is suitable for radio or pick-up input.

Its simplicity is perhaps the most outstanding feature.

BANISHES OVERLOADING WORRIESand is

TROUBLE -FREE IN OPERATION

Just a few components mounted on a simple woodenbaseboard and then wired up. There are no controls onit, so that it can be installed in the bottom of a gramo-phone cabinet or out of the way elsewhere.

Two indirectly -heated valves of the .5 variety areemployed, the output being a pentode valve, which hasa tapped transformer for the purpose of matching upwith any loudspeaker.

The construction is sufficiently straightforward to bemade quite clear in the diagrams. In the circuitdiagram, pick-up and mains switch connections areshown, and these will not be found in the wiring diagram.Their significance, however, is explained later.

The baseboard is 14 in. by 10 in., and the exactpositions of the various parts can be worked out instantlywith the aid of the scale. The two primary terminals ofthe pentode transformer are permanently wired up, butwhich two secondary terminals are employed dependsupon the speaker used. They provide a wide choice ofratios, the various terminal combinations being explainedin a leaflet given with the component.

Keep to the Values MentionedNote the Ilex lead with a spade tag at its end, which

is joined to the terminal on the side of the pentode valve.Keep to the 350 -ohm and 600 -ohm resistances, as theseare for providing grid bias and are calculated to givethe right voltages for the valves employed.

COMPOSED OF THESE COMPONENTSSWITCH

1 on 00 double -pole toggle switch (Bulgin typo S.104).CONDENSERS

3 2-mfd. (Dubilier type L.E.C., Ferranti, Telsen, Lissen,T.C.C., Igranic, Formo).

1 4-infd. (Duhilier type L.E.C., or see above).2 2-mfd. (Igranic type 700 D.C. test, or see above).1 01-mfd. (Dubilier non -inductive, or see above).

BASEBOARD14 in. 10 in.

RESISTANCES1 10,000 -ohm (Graham Farish, Dubilier, Colvern).1 mains resistance (Bulgin type M.R.1).

15,000 -ohm (Graham Farish, Dubilier).1 350 -ohm (Graham Farish, Dubilier).1 600 -ohm (Graham Farish, Dubilier).

L.F. CHOKES2 smoothing chokes (R.I., Dux, Ferranti, Varley, Bulgin,

Formo, Heayberd, Telsen).

OUTPUT TRANSFORMER1 output transformer (Varley D.P.32, Telsen, Ferranti).

VALVE HOLDERS2 5 -pin valve holders (Bulgin, Lissen, Telsen, W.B.,

Lotus, Benjamin, Graham Farish, Magnum).

L.F. COUPLER1 transcoupler (Bulgin).

MISCELLANEOUS1 terminal block (Sovereign, Belling & Lee).2 terminals (Eelex, Clix, Bulgin, Belling & Lee, Igranic).1 combined mains plug and fuses (Bulgin type F.15).2 yds. of systoflex and 3 yds. of 18 -gauge tinned copper

wire.2 spade soldering tags.

16


I I

p

And now we can deal with the extra connectionsshown in the circuit diagram. These are not included onthe wiring diagram because they are quite separate fromthe amplifier itself and may be wired some distancefrom it.

First of all, the leads from the mains are taken directto a double -pole mains switch on the motor board.From the other side of this switch two sets of wires aretaken, one direct to the electric motor for the turntable,and the other to the " socket -plug " for fitting to themains adaptor and fuses on the amplifier's baseboard.

5

COMPLETE THE OUTFIT WITH THESEValves. Mazda D.C./II.L., D.C./Pen.Pick-up. Marconiphone, Zonophone, Lissen, Celestion,

Bulgin, Ready Radio, Cossor.Gramophone Motor. Garrard Universal, or H.M.V. Playing

Desk (which includes pick-up).Loudspeaker. Baker's Selhurst, Marconiphone, G.E.C.,

Ferranti, Blue Spot, W.B., R. & A., Epoch, B.T.-H.,Ormond, H.M.V., Igranic, Lanchester, Celestion, Clarke'sAtlas.

This switch thus controls the whole outfit, but a start -and -stop switch is incorporated in both of the recom-mended motors for stopping the turntable by itself.

The volume -control has its outer terminals connecteddirectly across the pick-up itself, and the two wires thatgo to the input terminals of the amplifier come from oneof the outer terminals and from the slider of the poten-tiometer. The value of the volume -control will dependupon the pick-up, but 50,000 ohms will generally provequite satisfactory.

Whenthat it is so inserted that the plus pin is in the socketwhich is also joined up to the positive of the motor.

Keep it the Right Way RoundIf the plug which connects switch to mains is not

inserted in the mains socket the right way round, theset will not work because the anodes will be madenegative instead of positive.

But it is a simple matter to find out whether the plugis the wrong way round, because if it is, the set will bequite dead, whereas the right way round you will hearsomething, even if everything else is not quite as it

ALL READY FOR YOUR MAINS

The pentode output valve is the larger one, to the left, and isconnected up to a special tapped output transformer that enables

correct matching up with the speaker to be obtained.

MOUNTED ON SIMPLE BASEBOARD

The straightforward construction will appeal to all, and makesthe construction as simple as any amplifier could possibly be.

should be. So if on plugging -in you get nothing, justreverse the plug.

It is a good idea once you have found the right way,to mark the plug which goes into the mains so that itcan always be put in the right way first time. The plugcan be a 2 -pin plug or bayonet adaptor plug, accordingto what mains point it has to be attached.

The connecting up of the mains resistance is quiteeasy. As you see from the wiring diagram, one wiregoes to the terminal marked 2- because two -valves areemployed.

The other connection is via the flex lead with spadetag that is joined to the terminal of the fuse andmains connector.

This tag is taken to one of the three terminals, markedin mains voltages. Choose the terminal with the mark-ing nearest to the voltage of your mains. The twoblack terminals are ignored.

Can Follow a Battery ReceiverWhen using the amplifier for radio work it should

follow the detector valve. The method of coupling setto amplifier being by means of an ordinary intervalvetransformer or resistance capacity coupling device, thetransformer secondary or the grid leak being wiredacross the input terminals.

With a grid leak, the end joined to the couplingcondenser should go to the input terminal joined tothe grid of the amplifier valve V1. It is quitepermissible for the amplifier to follow an ordinarybattery -driven set.

Remembering the super -power which the amplifier iscapable of providing, it will be appreciated thatsimplicity of construction, and also of operation, is a

17


I II

most outstanding feature in the design of this amplifier.And for this reason, it is necessary to guard against theimpression that after all it is just an ordinary sort ofamplifier, and not one with super power and first-classquality.

Choose components recommended, keep to the designas shown in the diagrams and photographs, and youwill be assured of really fine reproduction.

44 - MGRkLtj &vim-4

(i) 00

Cr L Ofe ri) G.13Z

(D kct

I,NODE GRID

°

P/tx-up

DvAloraR BOARD0 0

7, 410 rag

WHEN WIRED WILL WORK WITHOUT WORRY

To TERM/NRI_

OF PENTODEON SIDE 6.0

(tE. va)

PENTODE OUTPUTTRANSFORMER

O

0

(f)

tti

O

O_2

OO

qr)

--f-MRINS ADAPTORAND FUSES

MAINSS'RESISTANCE

C. )

)

C )

)

)

)

)

C )

o 4070.5

MR/NS Sw

From the abovecircuit you cansee at a glancethe features ofthe D.C. ampli-fier, while to theleft you can see,also at a glance,how the circuitis made up in asimple practicalform. Incident-ally, the H.M.V.turntable outfitand this D.C.amplifier make

an ideal pair.

)

a

)

)

)

C )

)

C )

)

)

C )

C )

Ii

i0

I0

f you follow this diagram carefully and accurately youramplifier should work O.K. the first time you switch it on.

,,To L0005F'ERKER(SEE mxr)

18


i9

9eIling the Whole Worldon the"unott,sowMitELL, here we are, with two

pages in which to talk aboutoperating the " Whole -

World " Five, which I described inlast month's MODERN WIRELESS.And I think it's ample room, because,in spite of the set's nine controls,it's really very easy to tune. Heregoes !

Dual ControlsIt doesn't matter whether the

cabinet is in position or not, althoughit is, perhaps, a little more con-venient to try the set out beforeputting on its " shell." (It is theneasier to get at the ganging wheels,valve holders and grid -bias plugs.)

To avoid any misunderstanding,and to save frequently writing " in aclockwise direction " or " in an anti-clockwise direction," I intend towrite " turn left " or " turn to theright." " Turning left " is turningin an anti -clockwise direction.

First of all, you want to get firmlyfixed in your mind that there aretwo complete sets of tuning controls,one for short waves and the otherfor what is usually known as " broad-cast " waves-long and short. Animaginary line drawn horizontallythrough the dial -viewing escutcheonof the gang -condenser will separatethe two sets of controls nicely.

Above and BelowThose above are for short waves,

and those below for " broadcast."When one lot is in use, the other iscompletely out of use, except for theon -off switch, the centre one of thethree lower knobs. This alwaysturns the set on and off, no matterwhether it is set for short waves,

Lmedium waves, long waves, or record

Last month the construction of thisset, which strikes a new line in set if

:: design,. was .described in detail.::ri This month you are told how easy

it is to operate.

By A. S. CLARK.

work ; and you push it into switch -off.

The next item to consider is the" transformation " switch thattransforms the set from a broadcastone to a short -waver. This is theupper left-hand one, and you turnit left for broadcast waves and rightfor short waves.

4.10

11.

STATIONSGALORE

If you have never before had a thrill outof radio, you will get one when you firstturn the controls of this receiver I The

number of stations will stagger you.

At the same time as this change ismade, it is necessary to change overthe aerial lead from one aerial

terminal to the other. The aerialterminal for broadcast waves is onthe terminal block at the back ofthe receiver, and the short-wave oneis on the left-hand side of the cabinet(or is terminal 1 on the short-wavecoil when the cabinet is not inposition).

Investigating CarriersWhen you are on short waves:

everything is plain sailing. Youhave just two controls, the slow-motion condenser and the reactioncondenser to the right of it.

The handling of these two controlsis just the same as for any ordinarysimple short -waver. You must re-member to tune very carefully andslowly, and to keep the reaction sothat the set is just-or nearly just-oscillating.

verything that sounds like astation or carrier should be inveuti-gated intently. As soon as you havelogged a few stations you will knowwhere to look for various wave-lengths.

Now, putting the transformationswitch over to the left and the aerialon to the terminal at the back ofthe set, we can go down below forbroadcast waves. Before gettingdown to their operation we willconsider the radiogram switch.

Turning to Pick -UpThis is the bottom right-hand one,

and is turned to the right for pick-up work and to the left for radio.This switch and also the trans-formation switch have central posi-tions which are not used. So becareful to turn them fully in eitherdirection.

19


Turning Round the Knobs and Tuning -in the StationsWhen the radiogram switch is

over to " gramophone," none of thecontrols, with the exception of theon -off switch, is operative. Eventhe volume -control will do nothing,for a separate volume -control shouldbe mounted on the turntable boardfor the pick-up.

Normally, its value should not beless than 50,000 ohms, and it shouldbe of the three -terminal or potentio-meter type. The two terminalsjoined to the ends of the resistance(usually the outside ones) are joinedacross the pick-up, and leads aretaken from the slider and one end-it does not matter which-of theresistance to the two pick-up ter-minals of the set.

Volume ControlAnd that leaves us with the five

controls that perform the duty ofbringing in literally dozens anddozens of foreign stations. Of thesewe have already dealt with the on -off switch, so that there are onlythe tuning, reaction, wavechangeand volume -control knobs to cover.

The wavechange switch we turnto the right for long waves and inthe opposite direction for medium.That finishes with that.

tThen the volume-control-this is

urned to the right to increasevolume and to the left to reduce it.n a similar way the reaction con-

denser is turned to the right toincrease reaction and to the left toreduce it.

An Easy JobThe tuning knob of the gang -

condenser is a double one-that isto say, there are two concentricspindles, the outer one carrying themain knob and the inner one asmaller knob for making fine adjust-ments in the tuning setting. Thetuning reaction and volume controlsare used in just the same way whetherthe set is set for long- or medium -wave reception.

The small tuning knob adjusts thecapacity of an extra condenseracross the front section of the gang -condenser, namely, the section thattunes the detector circuit. It there-fore enables one to adjust for theslight alterations in tuning producedby the use of reaction on this circuit.

We have first of all to balance upthe trimmers on the side of the gangcondenser, and this should be doneon the medium waves. It is anextremely easy job because the

FOR BIG AERIALS FOR

wheels can be turned by the handwithout any fear of their desiredsetting varying as the hand isremoved.

While doing this trimming, set thesmall tuning knob fully to the left,and also the reaction condenser.You should trim on weak stations, ifyou can find any that are weak !Otherwise you should reduce thevolume of the station by means ofthe volume -control until its strengthis low enough for the effect of thetrimmers to be marked.

Full SensitivityAs I warned you last month, after

a certain point (maximum volume)the set may start oscillating when thevolume -control is turned further tothe right. The idea of this is to per-mit the H.F. valves to be brought upto full sensitivity and magnification,no matter what H.T. voltages areused, and whether they are livelyvalves or not.

Work just a little below this oscil-lating point, assuming you do haveto go as far as this to get enoughvolume on a certain station. If youwant still more volume you canalways get it by turning the reactioncondenser to the right a little.

SHORT-WAVE WORK

Underneath the baseboard is a small preset condenser. Normally The components mounted on the shelf are for short-wave work,this is screwed to maximum capacity, but if a very large aerial is and their controls, therefore, do not have to be manipulated at all

used, reduce its capacity a little. when working on " broadcast " waves.


ByK. D. ROGERS.

Full details on getting 6,000 milliwatts of undistortedpower for your loudspeaker.

AMONG the vast ranks of radio set constructors are tobe found all sorts of tastes and requirementswhere designs of receivers are concerned. An

obvious enough statement, but one that bears very closelyon the matter we have in hand.

Some want sets that will give " comfortable roomstrength," whatever that may be, and others would liketheir radio outfit to shake the floor every time HenryHall's drummer gives the skin a whack.

ALL ABOUT THE COMPONENTSFIXED CONDENSERS

2 4-mfd. (T.C.C. type 800 volts working, Dubilier type L.s.c.).1 6-mfd. (T.C.C. type 800 volts working, Dubilier type L.S.C.).1 4-mfd. (Dubilier type BD., T.C.C., Lissen, Igranic, Ferranti,

Formo, Pcto Scott, Goltone).4 2-mfd. (Igranic " Nondu," or see above'.2 4-mfd. (Ferranti type C.6, T.C.C., Dubilier 1,000 -volt type).2 1)1-mfd. mica (Dubilier type B.775, T.C.C., Graham Farish).

RESISTANCES1 50,000 -ohm volume -control (Tunewell type V, Igranic, Wattnel,

Wearite, Colvern, Sovereign, Bulgin, R.I., Varley, Lewcos,Graham Farish).

1 50,'000 -ohm (Graham Farish Power Ohmite, Colvern).1 15,000 -ohm (Graham Farish Power (Bunke, Colvern).1 30,000 -ohm (Graham Farish Power Ohmite, Colvern).1 40,000 -ohm (Graham Farish Power Ohmite, Colvern).1 500 -ohm (Colvern Strip, Graham Farish Power Ohmite, Dubilier).1 700 -ohm C.T. (Colvern Strip).1 5,000 -ohm (Graham Farish Ohmite, Dubilier, Colvern).2 3,000 -ohm (Colvern Strip resistances).3 '25-meg. grid leaks with wire ends or terminals (Lissen, Dubilier,

Ready Radio, Igranie, Graham Farish Ohmite, Goltone).2 '5-meg. grid leaks with wire ends (Lissen, or see above).

SWITCHES1 double -pole toggle (Bulgin type 8,104).1 thermal delay (Bulgin type 5.100, Varley E.P.17).

VALVE HOLDERS4 5 -pin (Lotus, Telsen, W.B., Igranic, Lissen, Clix, Bulgin,

Benjamin, Wearite, Ready Radio).

L.F. CHORES2 (Ifeayberd type 752).

MAINS TRANSFORMER1 (Varley type E.P.24).

MAINS PLUG1 (Goltone type L.S./31 & M.C./9, Bulgin).

FUSES1 double (Belling & Lee, Twin Safety, Bulgin)

TERMINAL BLOCK1 double (Belling & Lee, Sovereign, Goltone, Lissen, Bulgin).

TERMINALS4 (Belling & Lee type B, Igranic, Bulgin, Eelex, Clix).

MISCELLANEOUS1 terminal .trip, 4 x 21 in.1 yd. of flexible metallic twin tinned iron screened tubing (Goltone).1 terminal (Clix, Bulgin, Belling & Lee, Igranic, Eelex, Goltone).1 piece of brass strip, 5 x 1 x in. (for brackets).2 brackets l x 1 x 4 in. (for transformer).1 strip of ebonite, 2 x 9 in.7 yds. of systoflex and 10 yds. of 18 -gauge tinned copper wire

(Goltone, Wearite).1 baseboard, 18 x 12 x 1 in.Flex. screws, etc.

21


40,00000,02

4M0D

50.000OHMS

Cr41V

200 Owes

SM0017ONG Coosa

4

INeAmic oc,ov9,0000V

J.

414155MANSFORAIIET

O

o442

Maws FUSESNom Akt Nesenew. ingo,s IS ENCASED

/5 MEM< SOWS/V.. MA'S

Some there are who are notparticularly worried if a littledistortion, due to overloading orother causes, creeps into theirreproduction (yes, unfortunately,that is true), while others areaghast at the veriest tremor ofthe needle of the output milliam-meter.

What We Aim AtIt is our aim to please every-

one of these diverse set buildersnot the whole of thetime, perhaps-thatwould be an impossi-bility, but atpart of the time. Andin this month'sMODERN WIRELESShas come the turn ofthe large -volume man.The man who wants

J

/4"

74

On the rightis the finalstage. T h edesign hastaken a prac-tical shapeand is shownwith a ghostcover forillustrative

purposes.

a

This diagram showsclearly how the perfor-ated zinc top, which letsout the heat, is attachedto the metal sides of

the cover.V209

/8"

TWOSTAGES

INDESIGN

To the left yousee the amplifierin its theoreticalform, the firststage of evolu-

tion.

a big output not necessarily be-cause he wants a lot of noise, butbecause he wants a really goodmargin of safety from overloading.

It is for this enthusiast that the6 -watt amplifier has been designed,though it will also be useful forthe constructor who wishes tosupply small halls or large roomswith dance music, or other pro-grammes that require a big output.

It may seem that 6 watts is a large

1_1 /14

A table of metal sizes will be found on a following page.

BEND HERE

FULL CONSTRUCTIONALDETAILS OF THE

METAL COVER

output to have just to coverthe overloading contingency,but if a set is to be used forreally good volume and youwant to preclude the possi-bility of a sudden peak in themodulation of the broad-cast programme, or therecord that your pick-up isplaying, overloading one or

DETA/L OFCORNER

71Ad PLATE ANGLE,(<2"X(/E.30,144RED Ar. E.404 CORNER

22


H.T., L.T. and G.B. from A.C. Supplyother of the valves, you must have a surprisingly widemargin of safety.

It is this factor of safety that the amplifier we are todescribe has been designed to provide, whether it is usedas an addition to a radio receiver for broadcast reproduc-tion, or whether it is to be employed only for gramophonemusic.

ALL THE ACCESSORIESValves.

1 Mullard 354V.1 Mullard 164V.1 Mazda P.P.5/400, Mullard D.0.24, Marconi P.X.:25,

Osram P.X.25:1 Marconi U.14, Osram U.14.

Loudspeaker. Marconiphone, Baker's Selhurst,Ferranti, Blue Spot, W.B., R. &.,A., Epoch, B.T.-11.,H.M.V., Ormond, Igraine, Lanchester, Clarke's Atlas,Celestion.

Gramophone Pick-up. Radiophone, B.T.-H. Marconi -phone, Celestion, Igranie, Zonophone, Cos;or, Bulgin.

Gramophone Motor. Garrard Universal, or H.M.V. PlayingDesk incorporating pick-up.

The amplifier is quite " straight " in its design, and ithas been made of such dimensions that it will go in theloudspeaker section of most radiogram cabinets. Nopush-pull or even transformer coupling is employed, allthe stages being resistance capacity coupled.

It is completely self-contained, and is enclosed by ametal cover so that it is quite safe in use, the cover beingunremovable until the power plug is taken out and themains thereby disconnected from the amplifier.

Three Low -Frequency StagesThree stages of low -frequency amplification are used,

the stages being of comparatively low gain, while theoverall amplification is ample for the most insensitivepick-up. With most pick-ups it will therefore be unlikelythat the volume -control can be "fully increased," so thereis plenty of margin.

The output valve is one of the high mutual -conductancetypes, such as the P.P.5/400 or the D.0.24, and the biasand other resistances throughout the instrument havebeen fixed for specific valves, from which it is not advisableto diverge unless you are prepared to work out thenecessary alterations in resistances so that the correctbias and H.T. voltage on the valves shall be obtained.

This is most important, of course, for the voltageadjustment of an amplifier taking 400 volts on the lastvalve's anode must be accurately carried out. The valveschosen for the first two stages are the Mullard 354V. andthe 164V., both indirectly -heated cathode types ; while theoutput valve is the P.P.5/400.

Should the output valve be changed to one of the alter-natives given, only the bias resistance will requirealteration as the anode potential and current requiredare the same in all cases.

Cathodes at Earth PotentialIt will be noted that the bias for the first two valves is

obtained by means of common resistances, a tap beingtaken between them, but so arranged that one half of theresistance carries the anode currents of both valves,while the second half carries only the current of thesecond.

This arrangement of grid bias allows the cathodesof the valves to be at " earth " potential, and thusreduces the possibility of hum. As a matter of fact, thelack of hum, even with the amplifier all out, is verygratifying.

The last valve is as we have said, of the high mutual-conductance type, and, as such, care has to be taken that itcannot give rise to self -oscillation. To prevent any likeli-hood of this, a series resistance is placed in the grid lead,though this resistance must not be of too high a value.The 5,000 ohms chosen is just about right, and this valueshould not be exceeded.

Action of Thermal SwitchThe resistance in the anode circuit of the last valve

(there are actually two resistances in parallel, to reducethe wattage handled by each) is required to cut down thevoltage to the right value, which must not exceed 400.

Naturally, when the amplifier is first switched on thevoltage supplied by the rectifier is greatly in excess of thatfigure, for no load is imposed while the heaters of the valvesare warming the cathodes. To allow the H.T. circuitto be complete to the valves during this time wouldcourt disaster, unless all the condensers that come betweenH.T. and earth (and this includes the grid -couplingcondensers) were of very high -voltage type.

FROM THE MAINS END

So that the H.T. supply is not turned on before the valves have hada chance to warm up-an undesirable state of affairs-a specialthermal type delayed switch is incorporated. It can be seen

immediately in front of the rectifier valve.

2.


Naturally, this would increase the expense of theinstrument, and so a thermal delay switch is included inthe H.T. circuit, which delays the making of the H.T.circuit until such time as the cathodes of the valves havehad time to warm up The filament of the last valvetakes the largest anode current, and therefore acts as themain stabiliser of anode voltage.

The thermal delay switch is a metal gadget which isheated by an amp. of current from the heater circuit of theset. This metal, which is in a strip, gradually becomes hot,and when it reaches a certain temperature it springs up,making contact with a switch point in the component.

METAL MEASUREMENTS1 piece of 24 -gauge tinned sheet iron, 18 in. x 12 in.1 piece of 24 -gauge tinned sheet iron, 7 in. x 12 in.2 pieces of 24 -gauge tinned sheet iron, 18 in. X 7 in.2 pieces of 24 -gauge tinned sheet iron, 12 in. X 7/ in.4 pieces of 24 -gauge tinned sheet iron, 71 in. x 1 in.

1 piece of perforated zinc, 20 -gauge, 18 in. x 12 in.

Through the metal strip and the contact flow the H.T.current, so that until the strip is sufficiently warmed thereis no complete circuit for H.T., and thus the voltage onthe condensers cannot build up. The time taken isroughly 25 seconds, which is sufficient time to allow theheaters to have warmed the cathodes of the valves, sothat as soon as the H.T. circuit is made by the strip a fulldrain of current is applied, and the voltage merely becomesthe normal voltage of the amplifier in action.

Prcir UP--TeRA4

rf

SkhOgR

Consequently, when the amplifier is switched on thereis no sound while the cathodes are warming up, but aftera period of 25 seconds or so there is a click from the delayswitch, a thud in the speaker, and everything is full steamahead.

The actual construction of the unit looks difficult, but itis not nearly so tricky as it appears. It has been designedso as to be perfectly safe in use, it is covered by a metalcover which cannot be removed without the mains connec-tion being taken out, so that there is no danger of shockfrom the somewhat high voltage employed. The amplifiercan be used without the case if desired, but such a movewould be very foolish, and is most strongly deprecated.

About the FusesFuses are incorporated between the input switch and

the rest of the instrument so that the mains are perfectlyprotected should any breakdown occur in the unit, thoughif the components specified are employed there will be nodanger of this occurring.

In an amplifier of this description there can be very fewalternative components listed in our collection of parts,and we strongly advise that alternatives that do notappear should be left well alone unless absolute cer-tainty is felt of their suitability.

The whole outfit is mounted on a sheet iron coveredbaseboard, and a tinned iron screen 12 in. x 71 in. (with

in. turnover for foot) is placed between the rectifierportion and the rest of the instrument. This isdone not so much as a shield against L.F. induction as toprevent the top of the metal cover being pressed down

Concerted Components 9we Concert-Yfall qualityb - BASEBOARD

COVERED MTHMETAL F0/1_ .

tir

0

0 4

A

AIRS

0 4MRS..

O

3.0.0041OHMS

EARTHEDTo Foil

/5000OHMS

50.000OHMS

VOL.CON7!.BRAVEREl Ey_

E4prnea

fOiL

MED

.15A ,dik

war

LOCK/N6 SCREWFOR METAL COVER.

2 MFD

EARTHED TO Foiz

Really high power is obtainable fromthis amplifier-sufficient for quite am-

bitious dance purposes.

Sworn/NaCHOKE

40.000 OHMS

OUTPUTCHOKE

O

RECT. VALVE

V4ESoNtrESTRIP

8R4/DEOI2ex

EARTDTERAHE, re

VERT/EAl..

SCREEN

a

i" f"

31,

4 MFD.. A 0

6 it4FD..

2/0V.00

200 v.." ........O

(ARCHED75

0

MAINSFusEs

M4/NSPzua--

EARTHED TO FOILMA/NS TRANSFORMER.

Make use of this scale for laying -out the components.

MAINSSWITCH

24

January, 1933 MODERN WIRE' ESS

Ample Milliamps. at Five Hundred Voltson to the works should a heavy object be placed on it.The metal screen acts therefore as a strong support,and as a piece of ebonite is used on this screen to takethe wires passing over it, it acts, too, as a useful internalsupport. But that piece of ebonite is essential. Do notrun the wires with their systoflex covering over the metalpart of the screen, for the wires carry high voltages, andsystoflex breaks down comparatively easily at high voltage.Therefore, running it in contact with the metal screen, or

THE OTHER SIDE OF THE " FENCE "

These two photographs have been speciallytaken to aid you in the construction of theamplifier. You will find them particularly

useful when wiring.

with other wires, would very likelyresult in a breakdown.

The transformer is placed on itsside so as to allow easy access to theterminals. It is fixed perfectly rigidlyon two metal brackets, which shouldbe so cut and bent that they allowthe ends of the feet of the transformerto rest on the metal baseboardcovering, while for added rigidity acouple of pieces of ebonite are placedbetween the body of the transformerand the baseboard.

The two parallel resistances in the

anode circuit of the output valve are screwed to theebonite strip on the vertical screen, where they can beconveniently wired up.

An earthing terminal is supplied on the metal cover,and this automatically makes contact with the metalbase and the cover-when screwed down. It is fixed bymeans of a nut soldered to the metal bracket screwed tothe baseboard. The terminal shank then screws into thenut, and when the cover is on clamps this to the bracketquite effectually. This earth terminal is connected directto earth.

The mains transformer is connected according to thevoltage of the mains in the usual way, and then withthe valves in position the cover is screwed on and theearth terminal is connected as mentioned above.

Next, insert the mains plug, connect the pick-up to theinput terminals, connect the speaker to the outputterminals, and everything is ready. Do not forget thatyou will get up to 6 or 6.5 watts of undistorted output, sosee that the speaker used is capable of handling the requiredwattage, if you intend to let the amplifier all out."

Using After Radio ReceiverIf it is desired to use the amplifier with a radio set as

distinct from a pick-up, the coupling between the set(the amplifier should follow the detector stage, of course)should be either transformer, or preferably resistance.

There are alternative output valves which could beused with little alteration except in the bias resistance.The anode currents are roughly the same, and thereforethe voltage would be pretty constant. Such valves asthe Mullard D.0.24, which requires a bias resistance of540 ohms, and the Marconi and Osram P.X.25, whichneed 530 ohms, could be used.

It is essential that the speaker be well matched with theoutput valve if the full value of the amplifier is to beobtained, and though we have employed a choke outputscheme, it must not be forgotten that the transformer onthe speaker should be of suitable impedance and ratio.

WHAT'S WHAT FOR 6 -WATTS

Mows

25


OPERATING THE "DIODION"SUPER -SEVEN

AST month we gave details forthe construction of the" Diodion" superhet receiver,

but had insufficient space for thefew remarks necessary as guide tothe operating of the set.

Condenser ConsiderationsThis is very easy indeed, but first

we would like to clear up some mis-understanding that may occur con-cerning the variable condenser usedfor the oscillator tuning. This caneither be a Polar Aperture condenser,or a Polar No. 4 with separate discdrive and the Aperture type es-cutcheon. In the case of the formerthe drilling diagram of the panel willnot be strictly accurate, for thecontrol knob of the condenser willcome a little above the place shown,which is marked for using the No. 4condenser, with which the panelbalance is perfectly maintained.

It is important that the Aperturetype escutcheon be used, however.as the normal escutcheon suppliedwith the No. 4 condenser does notmatch that used by the Uniknobcondenser employed for the maintuning of the set. Therefore Messrs.Wingrove and Rogers have expressedtheir willingness to supply the Aper-ture escutcheon to those who wantit with the No. 4 condenser and discdrive.

Tuning TrimmingThe H.T. voltage taps were given

last month, and it remains to discusssmall points of operation here. Thefirst thing to do is to gang theUniknob condenser by means of theone trimmer provided on it. Onlythis one is required, of course, becausethe other section of the condenser has

This fine superhetreceiver, whichwas fully describedin last month's -"Modern Wire-less," is very easyto operate, as youwill agree afterreading this article.

a trimmer controllable from thepanel, and this is the section thatis connected to the aerial tuninginductance.

To trim the condenser it is onlynecessary to place this control atminimum, and then to tune in astation and adjust for maximumstrength with the trimmer. A weakstation should be chosen, if possible,and the trimming should be done withcare. Thereafter should the trim-ming go out either up or down thewavelength scale, the separate trim-mer operated from the panel (the

ONLY ONE WHEEL

inside of the two concentric con-denser knobs) will enable perfecttuning to be obtained. The internaltrimming is best carried out on themedium waveband.

As a check-up of the valves thefollowing may be useful. They areplaced as follows in the various valveholders shown in the wiring diagram :V1, variable -mu valve ; V2, H.L.2type ; V3, H. type (oscillator) valve ;V4, variable -mu valve ; V5, H.L.type ; H.L. type ; V7, outputvalve.

Bias BatteriesThe bias applied to the variable -mu

valves should be 16 volts, and thatto the output valve will depend on thetype chosen and the H.T. employed.The first L.F. stage is automaticallybiassed.

As regards tuning, this should I edone very slowly, and it will befound that, while the Uniknob con-denser control is sharp, that of theoscillator condenser will be verymuch sharper.

TO WANGLE ,,

The trimming of the gang condenser is particularly easy as there is but one adjustingwheel on it that has to be set. The only other adjustment behind the panel is for the

series aerial condenser, which, once set, can be forgotten.

28


Shunt -FeedingW. D. (Chesterfield).-" I have

in my set one of the older types of;'L.F. transformer, and, in view ofthe strides made in this directionin the last few years, I am wonderingwhether I could improve my resultsby parallel -feeding.

" Do you think that this wouldbe an advantage ? "

The answer to your questiondepends upon the design of yourtransformer. Suppose, for example,the particular cord used tends tosaturate at low anode current values,then parallel -feeding in this casewould. definitely improve the results.

Generally speaking, parallel -feedshould be used if the primary in-ductance drops to a marked degreewhen the transformer is connecteddirectly in the anode circuit in thenormal manner.

Perhaps, in your case, the primaryturns are few in number, thus givinga low primary inductance. Thisinductance value may be too low toprovide an adequate bass responseeven with no D.C. anode currentpassing through the winding. Hence,parallel -feeding is of little advantage.

However, it can be said fairlysafely that if the physical dimensionsof the transformer are small, improvedresults are obtained when the steadyanode current is deflected from theprimary winding by a resistance -condenser feed.

A Moving -Coil QueryT. L. (Faversham).-- I am about

to purchase a moving -coil loud-speaker of the permanent magnettype, and am rather hazy aboutthe connections to my set.

" am told that it is necessaryto use an output transformer ofsuitable ratio with all moving coils,and I notice that the make I amkeen on already incorporates an

UESTIONS

SWEPEDinput transformer which is mountedon the chassis frame.

Do I have ;to employ anothertransformer in the set ? "

This is an easy one to solve. Ifthe leads from the set to the speakerare to be reasonably short, as theywill be if you intend to use thespeaker in the same room as the set,just join the L.S. terminals on the

TECHNICAL QUERIES

DEPARTMENTAre You in Trouble With Your Set P

The MODERN WIRELESS Technical QueriesE. Department is in a position to give anE unrivalled service. The aim of the depart- =

ment is to furnish really helpful advice "E"

in connection with any radio problem, =E theoretical or practical.= Full details, including the revised scale of F-F.-. charges, can be obtained direct from the= Technical Queries Department, MODERN= WIRELESS, Fleetway House, Farringdon EE Street, London, E.C.4.

A postcard will do. On receipt of this all thenecessary literature will be sent to you, free =and post free, immediately. This applica- =tion will place you under no obligationwhatever. Every reader of MODERN =WIRELESS

should have these details by F.him. An application form is included E.

= which will enable you to ask your questions == so that we can deal with them expeditiously g,E. and with the minimum of delay. Having- this form you will know exactly what in- F-E formation we require -to have before us in E= order to solve your problem.E London Readers, Please Note : InquiriesE should not be made in person at Fleetway == House or Tanis House.EM111111111111111111111111111101111111111111111111i111111111111111111111i

receiver to two of the terminals onthe loudspeaker input transformer.

You will probably find that thistransformer has four terminals towhich connection may be made. Oneof them is common, while connectionto one of the remaining three will pro-vide ratios suitable for power, super-power and pentode valves.

For instance, if your output valveis a super -power, you should wire upyour leads to the two terminalson the input transformer whichgive the required ratio. The maker'sinstructions regarding this pointshould be followed carefully.

27

If you do not intend to use theloudspeaker in the same room as theset, your best plan is to equip the setwith an output filter consisting of a20 -henry choke and 2-mfd. condenser.This will keep the steady anodecurrent out of the loudspeaker leads.

L.F. WhistlesD. R. (Okehampton).-" I have

just fitted an output filter to mydet. and 2 L.F. receiver, and, muchto my surprise, the inclusion of -thefilter has made the set unstable.With the filter in circuit, the receiverwhistles continuously, but directlythe choke and condenser are removedit behaves quite normally.

" Is there anything I can do toremedy the trouble, because I do notwish to scrap the filter scheme ? "

The trouble is probably due toyour layout. Try the filter chokein another position, and also notethe effect of reversing the leads tothe secondary of the L.F. transformer.

But usually it is the cramping ofthe components, or altering the lay-out to- permit the insertion of thefilter choke and condenser, thatcauses troubles of this nature. Whenpossible the cores of transformersand chokes should be joined to earth.

Aerial InsulationR. S. (Wigan).-" My present aerial

has one porcelain insulator at eachend of the horizontal span. If Iwere to add an extra insulator atboth ends, would this improve re-ception ? "

Very unlikely, R. S. One insulatoris sufficient for normal purposes.It is true that extra insulators wouldreduce leakage, but so far as receivingaerials are concerned, one goodinsulator at each end is enough. Intransmission, of course, it is different,and the question of insulation has tobe gone into carefully.


How do the listening -rooms work? What kinds of micro-phones are used ? What are " A," " B," " C" and " D"ampltfiers? How are the programmes controlled? Theseleading questions are answered by a B.B.C. expert, whodeals with the sequence of broadcasting from the microphone,

through the amplifiers, to the aerial !

WHEN I am describing B.B.C. apparatus toenthusiasts I am often asked questions likethis : " Well, what are these A, B, C and D

amplifiers ? " " What microphones are used ? " " Howdo the listening -rooms work ? "

This shows that many interested listeners don't knowthe B.B.C. sequence from " mike " to aerial. I wantto describe this to you, starting with the little listening -rooms at the side of each studio.

There is a listening -room adjacent to each studio,with a double window through which the studio can beseen. Loudspeaker units are provided in each of theserooms, which are acoustically treated to be suitable forhigh -quality loudspeaker reproduction.

Low Volume LevelsThe speaker units are self-contained, and consist of a

two -stage mains -driven amplifier, and a speaker housed ina box baffle.

The use of amplifiers at all speaker points enables theprogrammes to be fed round the building at low volumelevels, and in this way avoids the possibility of cross -talkon to microphone circuits, which might occur if thespeakers were fed from some central point at high volumelevels.

These amplifiers have resistance -capacity interstagecoupling, and an undistorted speech output of 1 watt.

By the use of a speaker in the listening -room adjacentto, but sound -proof from, the studio, it is possible for thoseresponsible to hear the transmission in just the same wayas it is being heard by the public, while the performersthemselves can be seen through the listening -roomwindow.

In recent years the B.B.C. has used the carbon typemicrophone, but a change is now gradually being madeto the condenser type. Provision is made in each studioso that either type of microphone can be used at will.

Current for Microphone AmplifiersThe condenser microphone embodies a single -stage

microphone amplifier, as part of the microphone unit,but no amplification for carbon type microphones isnecessary until the output, readies the control -room.

Microphone plugs, of the multi -pin type, are installedin each studio so that H.T. and L.T. can be provided forthe condenser microphone amplifiers, in addition to thecontacts for the output leads.

The Reisz carbon microphones in our top picture have longbeen stand,..rd B.B.C. equipment, but are now being replaced bythe condenser " mike " below them. We wonder what theannouncer occupant of the studio control box at the left thinks

of the change.28


A number of microphone plug -points are installed in all thelarge studios, and the output ofeach microphone is fed to amicrophone mixing unit in thelistening -room adjacent to thestudio. Thus the output of anumber of microphones can bemixed in the studio listening -room, and the combined outputis passed on a single pair ofwires to the input of the firstor " A " amplifier in the control -room.

This arrangement facilitatesthe balancing of transmissions,and to some extent it obviatesthe need to move artistes aboutduring the performance in which the items are of a vary-ing character.

The control -room equipment consists essentially of allamplifiers and auxiliary equipment required in the chainof transmission between any studio (or outside broadcastpoint) and the S.B. lines feeding the transmitters. It alsocontains the necessary control positions or desks fromwhich any studio can be brought into circuit and the out-going transmission can be checked.

Types of AmplifiersDealing with the chain of transmission followed by a

programme, we find that there are three amplifiers :a microphone or " A " amplifier, a variable gain or " B "amplifier, and a land -line or " C " amplifier. Describing

rEngineers with musical qualifications control the Queen'sHall amplifiers, but we imagine only a " whole -time " radioexpert could handle the transmitter amplifier unit in ourcentre picture. Agriculture and radio may be a queer com-position, but the scene at the top shows them mixing well, at

Brookmans Park.

these amplifiers in order, the microphone (" A " amplifier)is of the three -stage type, resistance -capacity coupled,but with its input and output fed through transformers.

The last stage consists' of two valves with grids con-nected in parallel and separate_ anode circuits, so that theoutput of the " A " amplifier can be split and fed to anecho -room amplifier if artificial echo is required.

These " A " amplifiers have a maximum gain of 50decibels, and a working gain of approximately 40 decibels.The amplifier gain is made variable by a 10 -stud potentio-meter, each stud representing an increase in gain of4 decibels. There are thirty-one "A" amplifiers (of whichthree are normally held as spares). They are mounted in

(Continued on page 94)29


ILLUSTRATED TECHNICAL TERMS

COMPLETELY S'CREENT'll PE S1STANCE

(

"POSITIVE CONTACT

II

OVERLOADING11

ELECTIV IT Y

e APAC Y

" RECTIFICATION30

January, 1933 " The TVorld's Programmes" MODERN WIRELESS

140 RAHNHOW:WH EN AN D WH ERE TOH EAR. THOSE FOREIGNERS-

RY IT DURING YOUR LUNCH HOUR! Asteelworker on a New York skyscraper takes amidday snooze 800 feet above the ground, soothed

by the music from a portable set.

-

CONTENTS OF THISSPECIAL SUPPLEMENT

On the Long Waves.The German Announcer and What He Says.A Visit to Wilno.Other People's Programmes-Italy.Planing Stations with the " M.W." Dial

Diamonds.Station Situation.Simple -Set Searching.Between 200 and 550 Metres.The Sleuth of the Ether.From Here, There and Everywhere.Radiating 50 Kilowatts in the States.An American Super Station." London Calling the Empire."What the Distant Stations are Doing.

T

31

MODERN WIRELESS " The World's Programmes" January, 193'

UM It la

ON THE LONG WAVESAn interesting summary of the latest conditions between1,000 and 2,000 metres, with notes on the stations, including

" mystery " transmissions near the bottom of the dial.

WING to the vagariesof the Russianstations, the " lower

end of the long waves " hasrecently been getting specialattention, and proved to beunusually interesting dur-ing the past few weeks.Leningrad has been testinga new transmitter on about835 metres, and when tun-ing on 1,000 metres in thehope of catching something -interesting, on several occa-sions two transmissionswere heard to the accom-

paniment of one another.Can any reader definitely identify either of these

I newcomers as Moscow ?

A little higher up the long -wave dial, Oslo has beenin great form again. Why this station should some-times get comparatively weak is a mystery, for on hisgood days-and they have been nearly all good days,of late-be is a magnificent programme, and even indaylight can give a good account of himself at thisseason of the year.

* * *

To hear Oslo day after day at good volume, and thento reflect that sometimes he is quite difficult to pick up,is enough to discourage the most ardent investigatorof reception conditions, for there seems no rhyme orreason in the see -saws of which Oslo is sometimes guilty,and as he is liable to change from very good to Very -bad within a couple of days, he is probably the mostperverse station one can try for!

* * *

Kalundborg, on 1,153 metres, appears to be awareof his impending fate, and to be feeling down in the mouthabout it I In a few months' time this wonderful little7.5 -kw. station will give place to the giant transmitterrecently built in England and now being installed atKalundborg.

* * *

The marvel is that, with such low power as is nowbeing used, the little Danish long -waver has been able

! to hold his head so high. East coast and North-Eastcoast listepers agree with me that he is always in therunning with Motala and Oslo for regularity and power(and sometimes in front), and yet those two stationsare enormously more powerful.

* * *

The 1,200 -metre pair-Reykjavik and Istanbul-have yet to find my aerial with any degree ofcertainty ; and, in fact, above Kalundborg the next

b.

worth -while possible is Moscow Trades Union. He isclassed as a " possible " because even when he is knownto be transmitting he often fails to be distinguishableon 1,304 metres.

ifotala, on the contrary, is always in evidence on the I1,348 -metre mark, and, of course, both Warsaw andEiffel Tower, can be- classed as easy.

* * *

For some reason, Konigs Wusterhausen continues tobe something of a wash -out compared with his pastachievements. My experience of this station, during thepast few months, is that he can be obtained, if withsome little trouble, but he is nowhere near the goodprogramme -provider that we could expect him to bewhen considering his performances of a year or more ago.

* * *

Radio Paris, on the other hand; seems to get betterand better. All things considered, the London districtlistener would probably be prepared to swop any other ;six long -wave programmes for Radio Paris, if he had tomake the choice. It is a station that never seems to letone down.

* *

For form's sake we must give Huizen his due, on1,875 metres, for this station puts out a great deal ofgood stuff, and at hours when there are not manyalternatives offered from the rest of Europe.

As only the more interesting stations have beenmentioned in this brief sum-mary, we can safely con-clude that the month onlong waves has been a goodone for most aerials. Es-pecially as there continuesto be a genuine fall -off inMorse interruptions, whichhave hitherto always tendedto mar the long wavebandresults far more than the,medium waves.

* *

The long waveband hasbeen officially increased atits lower end by the MadridConference. It is nowextended from 224 kc. to265 kc. The "new"waves are already occupiedby eight stations rangingfrom Moscow to Kalundborg.This still leaves a numberof stations above 1,000metres not on allottedwavelengths.

32

January, 1933 " The World's Programmes" MODERN WIRELESS

1

11AeGIltraturthc,ERiiiiiiiiiiiiiiii

WilyeasSOME time ago I suggested in these

columns a system wherebylistening to foreign programmes

might be less of a weariness to theflesh by reason of the language diffi-culty than it is. This difficulty, Istated, was a common experience,even with those who possessed aknowledge of a foreign tongue goodenough for ordinary reading purposes.But the difficulty arises through theear's inability (for want of practice)to catch immediately what is beingsaid.

Announcer's Stock -in -TradeMy system is founded on the

simple fact that all announcers usea vast number of expressions whichvary but little from day to day. Itwould present no difficulty to anyEnglishman if he wished to imper-sonate in a sentence an Englishannouncer.

Immediately some stock phrasesuch as this would occur to him :" Before I read the news, here is anS.O.S. Missing from his home, etc.,etc." This is just one of a numberof phrases from the professionalEnglish announcer's stock -in -trade.

The German announcer has hisphrases, too, that he uses with butslight variation day after day. Atpresent they are wasted on us,although if we saw them in printwe could easily translate them.

Listen for ThemMy object in this article is to give

you some of these expressions, whichI commend you first to commit tomemory. Then listen for themthrough your loudspeaker.

You will probably have to listenhard for them. But no matter !Just make up your mind to pick

them out.If you suc-ceed, I amcertain y o uwill not haveto listen hard,

for them in future. They will thrustthemselves on you, in spite of your-self, just as English expressions do.

The first group of stock expressionsI suggest you should master includesthe Call and Closing -down signals ofall the German stations. Thesenever vary. Hamburg is a goodspecimen.

RUDOLFRAUHER

RADIOREPORTER

" Hier ist Hamburg fur die Nord -deutsche Sendergruppe. Hamburg,Kid, Hanover, Bremen und Flens-burg." And its closing announce-ment : " Damit, meine Damen undHerren, ist unser heutiges Tages-programm beendet. Wir wiinschenIhnen alien eine recht gute Nacht !Auf Wiederhoren morgen friih zurgewohnten Stunde ! "

Perfectly simple to translate andequally simple to get once you haveheard and recognised it.

There are also the interval calls to

be mastered. Konigs Wusterhausenoffers a typical one.

" Achtung ! Konigs Wusterhausen.Der Vortrag (or other item) istbeendet. Auf Wiederhoren in zweiMinuten."

Programme DivisionsThe second group is suggested by

the word " Vortrag ' (talk). Broad-cast items in Germany resemblethose at home, dividing themselvesconveniently into the four depart-ments of Musik, Literatur, Vortrcige,Zeitfunk und Sport.

They are Vortrdge (talks), Vorles-ungen (lectures), Mittags konzerte(midday concerts),Abendmusik (even-ing music), Marktberichte (marketreports), Nachrichten (news), Hors-piele (wireless plays), Funkzeitung(radio news), Abendmeldungen (even-ing news), Pressemeldungen orNachrichtendienst (news bulletins),etc., etc. These items are usuallyannounced as briefly as : Wirbringen die Abendmeldungen or SieKoren die Abendmeldungen (Here isthe news bulletin), and concludedjust as briefly with " Hier enden diePressemeldungen." (That is the endof the news bulletin.)

A Common WordThe warning which often accom-

panies such bulletins should also belistened for : " Deren Verbreitungdurch Druck oder Schrift verboten ist."(The spreading of which throughprinting or writing is forbidden, i.e.copyright reserved.)

Konzert is a common word -youshould not miss, though it is likelyyou may not recognise- it whentacked on to another word and usedas a compound. For instance, thereare all sorts of concerts, such as :Morgenkonzert (morning concert),Mittagskonzert (midday concert),Nachmittagskonzert (afternoon con-cert), Vesperkonzert (evening concert),Orchesterkonzert (orchestral concert),Orgelkonzert (organ recital), Leichtes

33

MODERN WIRELESS " The World's Programmes" January, 1933

(

Klassisches Konzert (light classicalconcert), Schakplattenkonzert (gramo-phone recital), Blaskonzert (brass -band concert), Militdrorchesterkonzert(military band concert), Unterhal-tungskonzert (social concert, etc.,etc., each of which would be an-nounced as follows : " Das Abendprogramm beginnt mit einem, orch-esterkonzert unter der Leitung vonHerrn S." (The evening programmebegins with an orchestral concertunder the direction of Mr. S.) ForAbend programm you might substi-tute " das heutige programme" (to-day's programme), das Winter pro-gramm,, das Sontags programna (Sun-day's programme), das morgige pro-gramm (to -morrow's programme),etc.,etc.

Concluding ExpressionsA number of expressions are used

to conclude a concert, among whichthese are the commonest : Damitschliesst unser heutiges Programm."(That concludes our programme forto -day.)

" Damit ist das Abend programmbeendet." (That concludes our pro-gramme for to -day.)

" Damit beschliessen wir unserheutiges programm." (We are nowclosing down.)

An interval between two con-secutive items often brings theannouncement : "Wir machen einePause von drei Minuten," or " Wirlassen eine Pause von drei Minuteneintreten " (There will be an intervalof three minutes), or "Nach f antMinuten beginnen wir mit einemBeethoven Konzert" (In five minuteswe shall begin with a Beethovenconcert).

Sports News" Sportdienst," " Sportvortrdge,"

" Sportiibertragungen " (sports news)is always of interest, so to begin withbe satisfied with learning a fewexpressions that occur in suchbulletins.

" Das Spiel wurde in Londonausgetragen ' (The match was playedin London).

" Das Spiel wurde wegen Nebelabgebrochen ' (The match was aban-doned through fog).

" Munchen unterlag gegen Berlinmit zwei Toren zu Null" (M. lost toB. by two goals to nil).

Typical Phrases" In Herrendoppel siegte A. gegen

B. mit sleben zu fiinf " (In the men'sdoubles A. beat B. by seven gamesto five).

" In Damendoppel siegte C. gegenB. mit neun zu sieben" (In thewomen's doubles C. beat B. by ninegames to seven).

" Der Tenniskampf wurde ausget-ragen " (The tennis match wasplayed).

Popular PastimesAmong the popular pastimes that

are frequently mentioned in a Sport -funk (sports bulletin) are : das Boxers(boxing), das Sportiest (sports meet-ing), das Bingen (wrestling), dasSpeerwerfen (throwing the javelin),das Diskuswerfen (throwing the dis-

Hawai iibertragen " (On October 8thdie Blame von Hawai will be broad-cast from the Theatre an der Wien).

NachrichtenNews (Nachrichten) paragraphs

have also their quota of stockphrases,' frequently beginning withthe following :

" Eine interessante Mitteilung fiber. . . gibt heraus dass . . . " (An in-teresting communication about . . .

says that . . .). " Ein Wiener(Abendblatt bringt die Nachrichdass . . ." (A Vienna eveningpaper reports the news that . . .).

AND DON'T THEY LOVE IT !"You won't find much drudgery about lessons when they are conducted via the radio.Our picture shows part of a school broadcast from Langenberg. It would seem that theschoolmaster is more popular than tome we know of-perhaps he has spared the rod

and found that it has not spoilt the child

cus), das Pferderennen (horse racing),der Radsport (cycle racing), and dieRegatta (the regatta) ; while duringthe season there are certain to benotices of Der Schneesport (wintersports), das Eisschiessen (curling),der Eisplatz (open-air ice rink), dieKunsteisbahn (artificial ice rink),der Skiverband (ski -club), and dasSchlittschuhlaufen (skating).

Coming EventsProgramme announcements (die

Programmbekanntgabe) usually takethe form of the following : " Am6 Oktober findet eine Studio aufzih-rung der Oper " Alkestis " von EgonWeelisch state" (On October 6ththere will be a studio broadcast ofthe opera " Alkestis," by E. W.),or " A us dem Theater an der Wienwird am 8 Oktober die Blume von

" Nach bulgarischen Nachrichten er-fahren wir . . ." (According toa Bulgarian message we learn that. . .). "Nach russischen Meldungenetfahren wir . . .") (A Russianmessage informs us that . . .).

Giving EncouragementThe selection that I have made

must not be regarded as being inany way complete, for it is nothingmore than a fragment of what Ger-man announcers say. It should,however, help you to make a startor give you an idea of what youshould be on the look out for.And, what is more important still,the mastery of this fragment aloneshould give you all the encourage-ment you need to persevere withwhat seems at the moment an im-possible task.

34


IHAVE spent a most interestingtime at the Wilno station,thanks to the courtesy of the

Polskie Radio concern.The director of the Wilno station

is M. Witold Hulewicz, a lover ofEngland and the English, who triesto get as much programme time aspossible for English announcementsand items of interest to listenersoutside little Poland.

The station is not actually in theinteresting old town of Wilno, butis a short furmanka ride out intothe suburb of Lipowka, three milessouth.

First -Rate QualityThe Chief Engineer at Wilno is

M. Tadeus Dabrowski. He workshand in glove with the Warsawengineers and was connected withthe Wilno radio activities before thepresent station was built. It wasDabrowski who designed the ultra-modern concrete station buildingwhich caught my eye as we cameup the drive.

The transmitter is not of Polishconstruction and the contracts wereput to outside firms. The quality isfirst rate, as I had several oppor-tunities of judging, both on localreceivers and in the station controlroom.

The building looks very much likea coastguard station, and it is sur-mounted by a conning tower erec-tion in concrete which heightensthis impression. The " conningtower " is actually something to dowith the aerial lead-in. Imme-diately above the building there isthe usual T-shaped aerial on twolattice masts about 180 ft. high.

TOWILN

The Polish authorities say that Wilno is intended as arelay station to Warsaw for increasing cryStal range.British listeners would welcome a 16 -kw. relay ! Ifyour receiver will tune to 563 metres (higher thanBudapest), you will welcome the chance our Roving

Reporter gives you to pay a visit to Wilno.

A powerful receiver is worked atWilno and, owing to the frequencycontrol of the Polish transmitter,the greatest care is taken to seethat no stations on adjacent wave-lengths wander off their allottedwavelength channels !

AND A -HUNTING WE WILL GO ! "

The hunting -horn call -sign of Wilno appears to be so popular withthe staff that they can't even keep it out of their radio plays,one of which was being broadcast when this picture was taken.

This aerial system is not massive,but, then, Wilno is not a very high -power station. It is intended mainlyas a relay of Warsaw to increasethe crystal -set range.

During my visit it has struck meforcibly that a large number o.people around Wilno, Katowice,Lw6w-and other places which arefamiliar on British amateur recep-tion logs --are poor farmers who canonly afford small crystal sets. The16 -kilowatt relay provided by Wilnois invaluable to them. There isalso a population of about 200,000in Wilno itself.

Flood -Lit PanelsThe transmitting gear is carried

on aluminium panels which areflood -lit in a very futuristic butuseful fashion. All the gear isenclosed, and only the peak volt-meters and flow meters can be seenon the outside.

The power comes from the localWilno station and is rectified bysix -phase banks of valves at thetransmitter.

M. Dabrowski is in charge of thetesting and receiving gear at thestation.

The programmes are under thecontrol of Roman Pikiel, but, ofcourse, most of the programmematerial comes from Warsaw.

Wilno does not take the earlymorning Warsaw programmes, butstarts up with a news bulletin ofits own at about eleven o'clock inthe morning, and then takes themain programme from Warsawtill the early evening at about sixo'clock.

File of RecordsThen there are local news but-

tetins and a short programmeannouncement of items which areto be given exclusively throughWilno for the following few days.

Unless anything special is comingfrom the Wilno studio, the stationswitches on to the Warsaw land -line circuit. The relay is alwaystaken by line from Warsaw, butthere is an emergency receiverwhich can be pressed into use forradio relaying.

When there are items on thePolskie Radio programme whichare not of interest to local Wilnolisteners, gramophone records areput on. There is a big file of records,

many of them British, in the studioante -room.

Very probably you have heardthe hunting -horn call which isgiven as an interval signal andbefore the general call at the com-mencement of the programme.

One of the announcers gives this,and there is a gramophone recordof it which can be used when thelady announcer, Joan Piekarska, ison duty in the studio ! The assistantannouncer, M. Zapasnik, is thehunting-hor expert!

Miss Piekarska is a good linguist.She is expert in the Lithuanian andWhite Ruthenian dialects, and talksgiven from Wilno in these lan-guages are often delivered byher.

Five LanguagesThe announcer in the War-

saw studio can speak English,French and German, as well asPolish. So when Wilno takesthe Warsaw programme, pre-ceded by its local announcementfrom Miss Piekarska, there isquite a flow of oratory in fivedifferent languages before theprogramme opens.

Wilno has two fine sportsstadia, and the engineers arearranging for outside broadcastsfrom one of them. During thenext month or so you may hearsome of these through Wilno.

One of these stadia is a fineoutdoor place, cut in a hillsideoverlooking the town, and itshould be easy to get an O.B.

TWIN BABIES !Used as we are to seeingthe massive aerial systemsof high -power transmit-ters, we shall probablyconsider the two 18o -ft.lattice masts of Wilno asquite childish affairs! But

they're very efficient.

from here. The only trouble isthat there are no telephone linesin the neighbourhood, and it meansrunning special cables.

Church RettlysBy the way, when you hear

church services from Wilno, notemanating from Warsaw, you maybe interested to know that theycome from the well-known OstraBrama Church, with a famouseikon which is the centre of attrac-tion of thousands of pilgrims fromall parts of Poland.

The Polskie Radio Companyhave, after a long conference withthe Church authorities, obtainedpermission to have two microphonesin the Ostra Brama.

Conversational .\-errsWhen Wilno switches off from

Warsaw and gives its own newsbulletin, an official from the localnews agency takes charge.

Business and sporting events ofthe district are dealt with in aconversational manner, until theautomatic cuckoo call of Wilno,superimposed on the transmission,shows that it is time to switch backto the parent Warsaw programme.

NEW TRANSMITTERFOR TOULOUSE

Radiophonie du Midi, Toulouse,the owners of the well-known stationRadio -Toulouse, announce that thenew 60 kw. in aerial station has justbeen completed. The station wasbuilt by the S.F.R. of Paris, andwas ordered in 1930.

The transmitter has been erectedat the ChAteau d'Agnan, some 20miles from Toulouse, and the ohcastle has been completely transformed. But the exterior has beenkept much as it was.

I understand that the momenthe Post Office grants the require.permission, the station will start off

35


OTHER PEOPLE'S PROGRAMMESNo. 2. Italy

It is very true that one halfhalf lives. And theenjoy hearing foreignas much as the mangoing on. Last monthof the German pro.we are off on a trip to Italy

the world doesn't know how the othercasual listener doesn'tprogrammes nearlywho knows what iswe told you somethinggrammes this time

to see how they do things in the landof gondolas and volcanoes

HERE can be hardly any doubtbut that the mention ofItalian programmes will im-

mediately call to your mind thevoice of the charming lady whodaily announces, to the unconcealeddelight of British listeners, theprogrammes from Radio Roma.

Charming VoiceMaria Luisa Boncompagni is the

name of this lady who has, on thestrength of her voice alone, receivedmore proposals of marriage andmore enthusiastic letters than the

THE LITTLE STUDIOWere it not for the microphone in thecentre of this studio, the smaller of thetwo at Trieste, it might well be mistakenfor a drawing -room in some comfort-

able country home.

most .successful film star. There isprobably no announcer who is betterknown throughout the world.

But although Italian broadcastingis so closely tied up with Maria Luisa,there is a great deal more than thatto the programmes.

As a matter of fact, even in therealm of announcing a Radio Roma'sfamous voice has a rival farthernorth. Signora Iolanda Sivizzi,whose picture you see on the nextpage, is one of the chief reasons whyenthusiastic listeners tune to 247metres and listen to Trieste !

One of the most interesting thingsabout Italy's programmes, therefore,is that lady announcers have beenfound so successful. The " goldenvoices " of Europe are without doubtheaded by Signqras Boncompagniand Sivizzi, and the programmesbecome more intimate and morecharming for that very reason.

Fine Opera RelayThe actual programmes of Italy

differ very little from those of therest of Europe. If you listen toRome or Naples or Trieste or Florenceyou will hear light music and opera,jazz and drama, talks and sportingevents.

But there is no doubt that in thematter of operatic relays Italy leadsthe world. And little wonder whenyou consider that at Milan, one ofthe main broadcasting centres of thecountry, is situated what is probably

(although Americans will be up inarms at once !) the leading operahouse in the world-La Scala.

I have heard these actual perfor-mances in Milan and as a result Inever fail to listen to the Milano -Torino -Genova -Firenze group whenrelays from La. Scala are advertised.

Not RomanticOne is naturally apt to connect

Italy with romance-the canals ofVenice, the bay of Naples and theisland of Capri, the historic buildingsof Rome and so on. But, as a matterof fact, very little of this romanceis reflected in the radio programmes.

EXPOSED TO THE WINDSThis fine commanding position makesTrieste's aerial a friendly landmark for

miles around.

36

January, 1933 " The lVorld's Progranmes" MODERN WIRELESS

ti

Trieste -The Most 1Progressive of Italian StationsItalians enjoy their football re-

sults as much as we do. They liketheir dance music in the evening.They have their talks on hygiene,and drama, and books. Shippingnews is given a prominent place in

HERE IS "RADIO ROMA "The Rome station has come to meanSignora Boncompagni to innumerablelisteners, and so we give you this oppor-tunity of meeting the charming ladywhom you know now only as a voice.

the day's events, and gramophonerecords help to fill up the emptyhalf-hours.

All very like England, isn't it ?But there are several ways in whichItalian broadcasting excels.

Regional SchemeAt the moment a regional scheme of

broadcasting is in force, and althoughit is rumoured that all the broad-casters are soon to be linked togetherwith only one or two national pro-grammes for the lot, the variousdistricts still vie, with one anotherin discovering bright ideas for broad-casting.

For instance, once a year thestations in the north take a relay fromSiena. This town is famous through-out Italy for its annual horse race,which takes place in the publicsquare-a most dangerous racecoursesince it is built entirely of stone andhas the added attraction of beingbuilt on a slope I

Still, nobody seems to mind a fewbroken bones, and the whole townturns out to watch the race which isrun on ponies between representativesof the rival communities.

As each rider is allowed to foul hisopponents as much as he wishes,even to the extent of knocking them

off their ponies, the broadcast be-comes rather a thrilling affair.

Programmes in Italy take up lessof the day than they do in otherEuropean countries. Morning trans-missions from the provincial stations,at any rate, are rather intermittentand, with the exception of Rome," early to bed " seems to be thegeneral rule.

Quality, Not QuantityIt would seem that quality, not

quantity, is the order of the day,for there is probably no countrywhere you will find more time de -

STARTING YOUNGThis chip of the Fascist block has nostage fright when facing the microphone.She looks determined that listeners shallpay attention to what she has to say

voted to music of the more seriousorder. Even variety programmesconsist for the most part of" straight " singers and chambermusic. The robust comedian, whois such a feature of our own varietyhours, is rarely heard in Italy.

Whether such a programme policy,high-minded as it is, suits theaverage Italian listener is a mootpoint, for the number of wirelesslicences issued to Italians is ridicu-lously small for the total population.

Trieste is probably the most go-ahead of all the E.I.A.R. stations,and some interesting broadcasts havetaken place during the past fewmonths.

There was the very successfulrelay of the launching of theOceania, one of the new giant linersbuilt in the famous shipyard ofMonfalcone. And the delightful after-noon when listeners were taken overto the Fascist colony which has beenestablished at Cologne for providing

sun treatment for Italian children.There is a little picture of some ofthem on this page.

Children Take PartDuring this broadcast the children

themselves gathered round the micro-phone and took part in the pro-gramme, an idea which is practisedvery widely with the programmes ofTrieste.

Every Monday and Thursdayspecial broadcasts are arranged forwhat correspond to our Boy Scoutsand the programmes are a real" children's hour." The boys takepart all the time, sing songs and joinin the discussions which are raisedby lectures on patriotic, scientific,and nature subjects.

It is little wonder that these broad-casts are popular and receive the goodwishes of so many Italian listeners.

School For TalkersTo return to Signoras Boucom-

pagni and Sivizzi. These two ladies,in company with the other announcerswho are less heard of but none theless efficient, have set a very highstandard in radio speech. As aconsequence a school has recentlybeen started in Florence for thepurpose of teaching budding radiotalkers the technics of announcing.

Although there is really very little

SIGNORA IOLANDA SIVIZZIOne of the very good reasons why so manylisteners all over Europe tune their re-ceivers to Trieste's wavelength. SignoraIolande is the possessor of a charmingvoice which upholds the prestige of the

Adriatic seaport against all corners.

difference in the main features ofEuropean programmes, each countryis proud of its own individuality,and Italy is in no way behind theother countries of Europe in pro-viding programmes which expressthe very best in art and music ofwhich the country is capable. Anda very good best it is, too.

37

MODERN WIRELESS " The World's Programmes " January, 1933

WE have already received a verylarge number of apprecia-tions of the " M.W." " Dial

Diamonds," introduced to listenerslast month. And in the presentnumber another pair of these won-derful aids to station -placing is em-bodied in the " Station Placers " thatis given to every reader.

Last month the dial readings from0 to 100 were covered, and thismonth the corresponding Dial Dia-monds for 0 to 180 degrees are pro-vided for the benefit of those whosetuning condensers are marked inthat way.

Essentially SimpleThe principle involved is, of course,

exactly the same, and even the noviceat this game can fill in his stationsand use the Diamonds straightaway to identify unknown stations.

We need not do more than re-capitulate the method, as it is soessentially simple ; you simply haveto place the exact dial readings ofany known stations on their respec-tive station lines. Then, when youhave a goodly number strung outdown the Diamond, pencil a line inlightly to connect them all together.

Real AccuracyThat line will connect every station

line with a certain dial reading,showing you the spot on the dial tolook for that particular station.Could anything be simpler or moreeffective ?

Similarly, if you have a programmecoming in, but do not know whatstation it is, the dial reading in ques-tion will be connected with a certain

PLACINGSTATIONS

with the44 M. W." DIAL DIAMONDS

A practical explanation of the methodof using this month's Free Gift.

station line-andthere you are!That is the stationtuned -in.

Now, to get real accuracy and soforth it is obvious that the moreknown stations you can put in thebetter. And the accuracy with whichyou place them is of great import-ance, as it affects neighbouring read-ings ; and if it is far wrong it willthrow them right out, too.

Getting a HumpA practical little point worth

mentioning is to use a sheet of paperto follow the various lines along. Itis much easier to place it along aline than to follow the line with theunaided eye. For there is bound tobe a great number of lines when wehave one for every wavelength used.And arrange the edge of your paperto move along the edge of theDiamond, so that the names thereare not obscured by it.

Here is another interesting pointabout usingthe Dial Dia-monds. If astation shiftsoff his wave-length he givesyou a humpon the curve.Incidentally,h e probablygives otherlisteners thehump, too, forwaveleng thwobbling i ssure to causeinterferencewith theirprogrammes!

So if yourcurved line

seems to want to stray, at anypoint, you can mistrust the stationin question as one who is probablyworking off his correct wavelength.

For Powerful StationsAt the time of writing, Fecamp is

doing this, his wavelength being theone below Cork's, instead of whichhis dial reading is now slightly above.The hump on the curve shows thisirregularity up very clearly.

The only other cause of humps onthe curve is the marking in of thewrong dial readings. But youwouldn't do a thing like that, wouldyou ?

For very powerful stations, thatspread over several degrees of thedial, it is often a good plan to takethe aerial right off, or the earth, oruse a short aerial, just to get anaccurate reading.

This is especially helpful whenthe H.F. condenser is not the onethat is being taken as the basis ofthe Dial Diamond readings.

TEUTONIC THOROUGHNESSThe attention to detail of German technicians is well exemplifiedby this photograph of the control room at Munich (533 metres,

Go kilowatts).

38


STATIONSITUATION

In the following list are recordedall the principal long- andmedium -wave programme pro-viders now regularly availablein this country, in ascending

order of wavelengths.

Wavelengthsand Remarks Occupied

ByFrequencies

FROM 200 to 300 METRES211.3 m. Newcastle1,420 Ice. (Great Britain).

214.3 m. Aberdeen1,400 kc. (Great Britain).

The above two stationsusually relay the National

Programme.

216 m. Shared1,391 kc. Wavelength.

The two low -powered sta-tions on this wavelengthare Halmstad (Sweden) andRadio Chatelineau (Bel-

gium).

217 m. Shared1,382 kc. Wavelength.

Itarlstad (Sweden) andKonigsberg (Germany) arethe two low -powered sta-tions sharing this wave-

length.

218 m.1,373 kc.

2214 m.1.355 ke.

Salzburg(Austria).

Pori (Bjorneborg)(Finland).

223 m. FecamP (Radio Normandie)1,345 kc. (France).

For some time now Fecamphas been working abouttwo metres higher thanthis, the allotted wave-

length.

224.4 m. Cork1,337 ke. (Irish Free State).

226 m. Htidiksvaff1,328 kc. (Sweden).

227.4 m. Flensburg1,319 kc. (Germany).

229 in. Uddevalla1,310 kc. (Sweden).

Ilddevalla is the lowest -powered station in Europe.

231 m. Common1,301 kc. Wavelength.

This wavelength is used bythree low -powered Swedishstations - Halsingborg,

Malmo and limes.

2321 in. Shared1,292 kc. Wavelength.

Wavelength shared byKiel (Germany), and

Norrkoping (Sweden).

235 in . odz1,283 ke. (PLoland).

For experimental trans-missions.

235.5 m.1,274 kc.

Christiansand(Norway).

237.2 m. Common1,265 kc. Wavelength.

Bordeaux Sud Ouest andRadio Nimes (France) andOrebro (Sweden) occupy

this wavelength.

239 m.1,256 kc.

240 m.1,250 kc.

Nurnberg(Germany).

Radio Balers(France).

240.6 m. Stavanger1,247 kc. (Norway).

Although of very lowpower, this station is oftenheard in Britain, especially

in the North.

242 3 in. Belfast1,238 kc. (Northern Ireland).

242.7 m.1,236 kc.

244.1 m.1,229 kc.

Liege Experimental(Belgium).

Basle(Switzerland).

245.9 m. Common1,220 kc. Wavelength.

Swansea (Gt. Britain) occu-pies this wavelength withBerne (Switzerland), Carta-gena (Spain), Cassel (Ger-many), Eskilstuna(Sweden), Kiruna (Sweden),Linz (Austria), &Me(Sweden), and Turku (Abo)

(Finland).

247.7 m. Shared1,211 kc. Wavelength

Trieste (Italy) and Kalmar(Sweden) share this wave-

length.

249.6 in.1,202 kc.

Vaaberg(Sweden).

252 m. Common1,193 ke. Wavelength.

252 m. is occupied byAlmeria and Barcelona(Association Nat.) (Spain),and Trollnittan (Sweden).

253 m. Gleiwita1,184 kc. (Germany).

Relays the Breslau Pro-grammes.

255 m. Toulouse P.T.T .1,175 kc. (France).

257 m.1,166 kc.

259 m.1,157 kc.

New

261.6 in.1,147 kc.

263 8 m.1,137 kc.

365.4 in.1,130 kc.

Herby(Sweden).

Frankfurt -am -Main(Germany).

station this season.

London National(Great Britain).

Morayski-Ostrava(Czechoslovakia).

Lille(France).

267.6 m. Shared1,121 kc. Wavelength.

Oviedo (Spain) and RadioValencia (Spain) share this

wavelength.

270 m. Shared1,112 ke. Wavelength.

Bremen (Germany) andBari (Italy) share this

wavelength.

272 m. Rennes1,103 he. (France).

273.7 in. Turin1,096 kc. (Italy).

276.5 in. Heilsberg1,085 kc. (Germany).

East Prussia's Regionalstation relays the KOnigs-

berg programmes.

279 in.1,076 ke.

Bratislava(Czechoslovakia).

280 in. Radio Liege1,071 ke. (Belgium).

281 in. Copenhagen1,067 ke. (Denmark).

Same programme asKalundborg on 1,153 m.

282-2 in.1,063 kc.

Lisbon(Portugal).

283 m. Common1,058 kc. Wavelength.

Berlin Relay, Magdeburg,and Stettin (Germany)share this wavelengthwith Innsbruck (Austria).

286 m.1,049 ke.

287.6 m.1,043 kc.

Montpellier(France).

Radio Lyons(France).

288.5 m. British Common1,040 kc. Wavelength.

Scottish National sharesthis wavelength withBournemouth and Ply-mouth. (The latter is alsoexperimenting with neigh-

bouring wavelengths.)

291 in. Viipuri (Viborg)1,031 kc. (Finland).

293 in. Shared1,022 kc. Wavelength.

Kosice (Czechoslovakia)and Limoges (France)

share this wavelength.

296.1 in. Hilversum1,013 kc. (Rolland).

Increases power from 7 to20 kw. at 4.40 p.m.

298.8 m. Tallinn1,004 kc. (Estonia).

FROM 300 TO 400 METRES

301.5 m.995 kc.

North National(Great Britain).

304 m. Bordeaux Lafayette986 ke. (France).

307 in.977 kc.

Falun (Sweden) andZagreb (Yugoslavia) oc-

cupy this wavelength.

SharedWavelength.

3099 m. Cardiff968 kc. (Great Britain).

Pietarsaari (dacobstad)(Finland) is also on this

wavelength.

312.8 m. Common959 kc. Wavelength.

Cracow (Poland), Genoa(Italy) and Radio Vitus(Paris) share this wave-

length.

315 ni.950 kc.

Marseilles(France).

38


How the Stations are Waiting For YouWavelengths Occupiedand Remarks byFrequencies

319 m. Common941 kc. Wavelength.

Dresden (Germany), Naples(Italy) and Sofia (Rodno-Radio) (Bulgaria) are all

on this wavelength.

322 m. Goteborg932 he. (Sweden).

325 in.923 kc.

328.2 m.914 ke.

Breslau(Germany).

Poste Parisien(France).

331.5 m. Milan905 kc. (Italy).

The above three are allnew high -power stations,and being " neighbours '=are very difficult to separ-ate, except on selective

sets.

335 m. Shared896 he. Wavelength.

Cadiz (Spain) and Poznan(Poland) share 335 m.

338.2 in. Bnissels No. 2887 kc. (Belgium).

Flemish is the languagealways used in announce-

ments.842 in. Brno878 kc. (Czechoslovakia).

As pronounced, the namesounds like " Birno."

345 in. Strasbourg (Brumath)869 kc. (France).

Both French and Germanare spoken -man and

woman announcers.

849 m. Radio Barcelona860 ke. (Spain).

351 m.855.5 kc.

3521 m.852 kc.

856 in.843 kc.

Leningrad(Russia).

Graz(Austria).

London Regional(Great Britain).

356.3 m. Tiraspol842 ke.(Russia):360.5 m. Stuttgart (Miihlacker)832 kc. (Germany).

383.3 m. Algiers825.3 ke. (N. Africa).

Usually announces inFrench, but English and

Arabic sometimes used.

364 M.824 kc.

8676 in.816 kc.

Bergen(Norway).

Fredrikastad(Norway).

368.1 in. Common815 ke. Wavelength.

Wavelength shared byBolzano (Italy), Helsinki(Finland), Seville Union

Radio (Spain).370.4 m. Radio L L Paris810 he. (France).

The " L L" is pronouncedclearly, and as in English.

372 in.806 he.

Hamburg(Germany).

376.4 in. Scottish Regional797 he. (Great Britain).

Sometimes referred to asthe " Falkirk " station.

378.6 m. Moscow792.5 kc. (Russia)

381 in.788 he.

Lwow(Poland).

385 m. Radio Toulouse779 ke. (France).390 in. Archangel770 ke. (Russia).3896 m. Leipzig7699 ke. (Germany).

This is now Europe's mostpowerful station.

394 in. Bucharest761 kc. (Roumania).398.9 in. Midland Regional752 kc. (Great Britain).

FROM 400 to 153 METRES.

403 m. Radio Suisse Romande743 he. (Sot tens) (Switzerland).

Announces in French.408 m. Katowice734 ke. (Poland).

Polish generally used, butalso answers correspon-

dents in French.413 m. Dublin725 kc. (Irish Free State).

New station at Athlonenow announcing as " Dublin."

416 M. Rabat7214 kc. (Morocco),419.5 m. Berlin (Witzleben)715 he. (Germany).4243 m. Common707 he. Wavelength.

Wavelength shared byMadrid Union Radio,Madrid Radio Espana(Spain) and Moscow -

Stalin (Russia).

430.4 in. Belgrade007 ke. (Yugoslavia).

The name sounds like" Baograd."

431 in. Parede696 ke. (Portugal).

436 in. Stockholm689 kc. (Sweden).

This wavelength also occu-pied by Malmberget (Sweden).

441 in. Rome680 ke. (Italy).

Works In conjunctionwith Naples as " Roma -

Napoli."447.1 in. Common671 he. Wavelength.

Aalesund (Norway), Notod-den (Norway), Paris (EcoleSuperieure) (France), andRjukan (Norway) share

this wavelength.

450.1 m.665.5 kc.

Odessa(Russia).

453.2 in. Common662 kc. Wavelength.

Eight stations are on thiswavelength -Bodo (Nor-way), Danzig (Free City),Klagenfurt (Austria),Porsgrund (Norway), Sala-manca (Spain), San Sebas-tian (Spain), Tromso (Nor-way), Uppsala (Sweden).

459 m. Schweizerischer Landessen-053 he. der (Beromiinster)

(Switzerland).Announces in German.

465.8 in. Shared644 ke. Wavelength.

Lyons La Doua (France)and Tartu (Estonia).

473 m.635 kc.478 m.630'2 kc.480 m.625 ke.488.6 m.614 kc.

The name" Radio Praha."

493.4 m. Trondheim608 ke. (Norway).497 in. Moscow603.6 kc. (Russia).5001 in. Shared599 ke. Wavelength.

Florence (Italy) and Nijni-Novgorod (Russia) share

this wavelength.509 ns. Brussels No. 1590 ke. . (Belgium).

Announces in French.517 in. Vienna581 kc. (Austria).

The name is pronounced" Randio Veen."

525 in. Riga572 kc. (Latvia).

The name is pronouncedRe-ga."

533 M. Munich563 kc.

The name is prono(Gunenn").eeda" Munchen."

542 m. Shared554 he. Wavelength.

Palermo (Italy) and Sunds-vall (Sweden) both work on

this wavelength.550 in. Budapest No. 1545 he. (Hungary).

Pronounced " Booda-Pest,Hongrie."

Langenberg(Germany)Sebastopol(Russia).

North Regional(Great Britain).

Prague(Czechoslovakia).sounds like

FROM 1,000 TO 2,000 METRES.

1,000 m. Moscow300 he. (Russia).

1,034 m. Kiev290 he. (Russia).

1,071 m. Tiflis280 kc. (Russia).

1,083 ni. Oslo277 kc. (Norway).1,116 m. Moscow (Popoff)268.5 he. (Russia),1,153 in. Kalundborg260 ke. (Denmark).

Linked with Copenhagen,and announced " Kalund-

borg Kobenhavn."

1,1715 in.256 kc.

Tashkent(Russia).

1.200 in. Shared250 kc. Wavelength.

Istanbul (Turkey) andReykjavik (Iceland) share

this wavelength.

1,229-5 m.244 he.

1,237 in.242.5 kc.

1,280 m.238.1 ke.

Roden(Sweden).

Vienna Experimental(Austria).

Novosibersk(Russia).

1,304 in. Moscow (Trades Union),230.1 kc. (Russia).

Often talks in differentlanguages -German,French, English, etc., for

propaganda purposes.

1,348 m.2225 kc.

1,350 in.222.2 kc.

Motala(Sweden).

Kasbah(Tunis).

1,411 in. Warsaw No. 12125 ke. (Poland).

The name Warsaw soundslike " Varshova."

1,445.7 in. Eiffel Tower, Paris207.5 he. (France).

Announced as " TourEiffel."

1,481 in. Moscow (Old Komintern)202.6 kc. (Russia).

1,538 m.195 ke.

Ankara(Turkey).

1,554.4 in. Daventry National193 he. (Great Britain).

1,635 m. Ktinigs-Wnsterhausen183.5 kc. (Zeesen) (Germany).

This is the German Gov-ernment's official stationfor important announce-

ments.

1,725 in.174 ke.

1,798 in.167 Ire.

1,875 in.160 he. (Holland).

Exchanges transmissionswith Hilversum every

three months.

Radio Paris(France).

Lahti(Finland).

Hnizen

1,935 m. Kaunas155 kc. (Lithuania).

40


Y " simplesets " Imean

those onwhich search-ing is not quiteso simple asit is on thosewith one ortwo screened -grid H.F.stages. On thelatter, one moreor less justturns the knobsand waits forthe stations tocome in, butwith det. and

SIMPLE'S=SEARCHING

Telling how the man without elabor-ate H.F. stages on his receiver canget the best long-distance results by

the expenditure of a little trouble.

one L.F. ordet. and two L.F. it is that littleextra skill with the knobs thatmakes so much difference.

It is with these simple sets, too,that a little hotting -up produces themost noticeable effects. In fact, theyare just where the enthusiast scoresover the " any - old - how - will - do "man.

Don't misunderstand me and thinkthat it is difficult to get stationswithout H.F. amplification ; just theopposite is the case, for it is in respectof the more distant foreigners andless powerful " wallahs " that thedetails of this article count.

Give it the "once-over " and see ifthere is not some count on which youcan ginger -up your results a bit.

Consider your aerial first. Withthe super sets, any bit of wire is asgood as something more like a realaerial, but for simpler sets it is muchbetter to have a large aerial, and asmall aerial coil or tap, than the otherway round.

It Pulls Its ShareWhy ? Because your aerial circuit

then approaches nearer to the trueaperiodic, and results will be muchmore evenly good over the wholerange of the dial.

Well, that's a start. Here's anotheron the same lines. The earth connec-tion has to pull its share on a det. andL.F. ; you can't make up for itbefore the detector, so leave the gas -pipe to its proper job, and dig a holein the garden or furrage out theascending water main.

Now everything in the garden islovely ; we can give the set a firstgeneral survey. Whew ! Look atthose old valves ! They've stood youin good stead long enough.

New steep -slope valves will putmany a weak station on your log as" received at full speaker strength "instead.

Even if your valves are modern,see that they are getting enough H.T.voltage to enable them to perform asthey should !

The Weakest LinkAnd here's an ear -searching ques-

tion : " Is your loudspeaker a sensi-tive one ? " Maybe you are losingquite a lot if it is not. Unless you areconfident about its capabilities, whynot take it round to the radio shop

FOR YOUR DELIGHT

The best orchestras in Europe are alwaysat your command by the turn of a knob.And so powerful are modern trans-mitters that you need have no elaborate

receiver.

and compare it with some of the laterones ?

Forgive me if I seem to be harpingrather on this " old stuff on newsets " business, but it's the same oldtheme of " the weakest link, etc."and it's no use putting a good horseon to a cart without wheels ! Still,here's a tip for every simple -setsearcher.

Very often a station will not appearon your speaker because it is notpowerful enough to be heard without

those final titi-vatings of thereaction knob,and until youcan hear it youcannot, ofcourse, start thetitivating.

Sounds a bitimpossible toovercome per-haps, but whynot have apair of t e 1 e -phones fordoing the firstsearching andadjusting ?

The set's out-put can go to

the two centre points of a double -polechange -over switch, the outer pairsgoing one to the speaker and theother to the 'phones. You can thenchange over " in no time."

Also, a 50,000 or so variable resis-tance across the 'phones will saveyour eardrums if you have anyqualms about them.

It's surprising what a tot more youwill get with the 'phones to aid you.And if you just want to log stations,then you'll have to add another leafto your log when you add the 'phonesto your set !

Experiment with VoltagesOf course, I must follow the recog-

nised procedure and warn you that asmooth control of reaction is vital fordistant reception. No, " plops,"please !

If you have not already got thebuild-up as smooth as possible, thenmake it your first duty to experimentwith H.T. voltages on the detector'sH.T. tapping. Even go so far as tofit a separate terminal for the de-tector if it is supplied in doubleharness with another valve.

Long -wavers are always goodstand-by stations, and you don't needquite such sharp tuning on thelong -wave band. So why make RadioParis and the other stations withslower -moving frequencies squeezethrough that small series aerialcondenser ?

A simple on -off switch across theaerial series condenser will do thetrick for you nicely.

There's no end of fun to be gotout of making a small set performprodigies of foreign station recep-tion, and the only secret is care ofdetails. Happy searchings !

41


Y/1

BETWEEN 200AND 550 METRESHow Many Stations-Too Powerful forComfort-Notable Absentees-A BorderLine Case-Punch Behind Trieste.

Forget the Eggs and Bacon!

THE direction in which an aerial lies, itsposition relative to neighbouring trees andso forth, must undoubtedly have some

influence upon the stations it receives best ; and that iswhy the writer recently welcomed the opportunity oftrying out a " plate aerial " receiver. It was a D.C.mains set (2 S.G.'s, det. and pentode), and no externalaerial or earth connection at all was used. What the setgot, it had to pick up without even a frame aerial orother aid, its only lead being a six-footer to the nearestlamp -socket.

* * *

How many stations should a good set get in suchdifficult circumstances ?

It was installed on the third floor of a Central Londonhouse, and its performance there was watched veryclosely, as only stations coming over really well couldhope to provide entertainment in such circumstances.

* * *

In brief, these were the outstanding points about themedium waves :

London National was at least twice as strong as theRegional, and was too powerful for comfort even indaylight.

North National and Midland Regional were bothvery good after dusk ; North Regional was fair, ScottishRegional about the same, and the other medium -waveB.R.C. stations not worth bothering about.

* * *

Of foreigners, twenty-six good programme -valuestations were obtained at different times, Fecampat the bottom and Budapest at the top, both beinggood. The best of the intermediates were Nurnberg(239 metres), Trieste (247 metres), Turin (273 metres),Heilsberg (276 metres), Hilversum (296 metres), Bor-deaux -Lafayette (304 metres), Breslau (325 metres),Poste Parisien (328 metres), Milan (331 metres), Stras-bourg (345 metres), Leipzig (390 metres), Sottens(or Radio Suisse Romande) (403 metres), Beromtinster(or Schweizerischer Landessender) (459 metres), andBrussels No. 1 (509 metres).

* * *Notable absentees from this selection of the " best "

stations are Rome, Toulouse and Stockholm ; allcould be received, but were not comparable with theabove -named for strength or reliability.

* * *

Katowice was a border -line case, very good somenights but not always. Florence, also, only just missedspecial mention. -

In brief, therefore, the set always had plenty oflikely stations to pick from, in spite of the factthat its self-contained aerial was never intendedfor anything but " local " listening ; and the alternativeswere really good ones, quality and strength, indeed,being far beyond expectations.

Probably the freedom from disappointing fadingwas due to the fact that the tests happened to synchronisewith a time when general reports on reception showedit was a very good non -fading period. The way thatLeipzig, for instance, would hold on for an hour or soat really magnificent volume without a single trouble-some fade was remarkable.

* * *

As an example of the unexpected results which maybe obtained when working with a small cabinet -containedaerial of this type, the case of Trieste is worthy of note.He-or, rather, she, for it was our old friend, the younglady !-was quite clearly audible at 8.30 one morning,in bright sunshine !

" Quite clearly audible " does not mean big strength,however ; for, as a matter of fact, the room was quiet,and to catch every word one had to stand near the loud-speaker fret. But it shows that there is some real punchbehind Trieste when it canmake one forget the eggs andbacon for a moment !

A close check-up withother listeners, ordin-arily situated, confirmsthe foregoing selectionsas the most reliablestations of the pastfew weeks ; and, bythe same showing,Riga, on 525 metres,may have surprisedsome listeners, for hewas clearly receivedunder the receptionconditions outlinedabove at 7.15 p.m.one evening. Anylistener who wants toadd Latvia to his bagof countriesshould certain-ly try for Riga.

42


%SLEUTH ofthe ETHER

Much has been heard recently of the checking station at Brussels, where M.Braillard and his officials keep a stern and watchful eye on the wavelengths ofEurope's broadcasters. Our special correspondent to -day takes you on a visit tothis station and explains how the tests are made and what happens to those"wicked" stations who stray from their allotted figure. So let's start straight away.

-TN the company of one of M.Braillard's officials I paid avisit last week to M. Edm.

Divoire and the famous Brusselswavelength -checking station of whichhe is assistant director.

" What I want to see," I stressed," is the actual wavemeter which spotsthe defaulters in the European etherand which is used to check the B.B.C.wavelengths."

Meters that Check MetersMy guide did not disappoint me.

Together we went to the U.I.R.checking station in a quiet suburb ofBrussels, and I saw not only thewavemeters which check Europe'sbiggest broadcaster, but the mastermeters which check the wavemetersthemselves.

Most of the apparatus is in anordinary living -room ; in fact, abig rack containing a tuning -forkcontrol and a multi -vibrator gearsynchro- clock is at the side of afireplace. In another rack are sixsuperhet wavemeters (in three pairs)and two receivers covering wave-lengths -of 200-600 and 1,00-2,000metres. These superhets aremounted up in a very professionalway on two wooden tables.

Measuring Field StrengthThere are sets of 'phones in front

so that the operators can check upthe wavemetet readings aurally aswell as on the milliammeters in theplate circuits. All the wiring iscarried through shielded conduitsand underneath the floor to thebattery centre. There are no loosewires at all to be seen anywhere nearthe set. The Brussels station cer-tainly looks like a laboratory ! On aseparate table is a large frame aerialin a stand, and a small set which is

one of the two used for field strengthmeasuring.

" About two hundred frequencymeasurements are made every even-ing, and this schedule has beencarried out for the past five years,"explained M. Divoire's assistant." As the number of stations on theether has increased so our staff hashad to get busier and take morefrequency readings. Every monththe average readings for each stationare plotted on a graph, and these arepublished for the benefit of broad-casting authorities."

The dual -wave sets have manyinteresting features-especially to akeen wireless SEEN-BUTlistener who, as I do,builds his own setsand likes to knowwhat the laboratorypeople consider bestfor world-wide re-ception.

The standard re-ceivers have twoH.F. stages withthree tuned circuitsand two L.F. stages.The 'phones are usedfor rough checking,but there is also acalibration deviceworking in conjunc-tion with the hetero-dyne wavemeters.This little job hasto be done withgreat rapidity andaccuracy, for direct-ly a station is tunedin the wavemeter istuned down to itand the readingtaken-all within afew seconds.

" Practically every evening isspent in checking up the leadingforeign stations in this 'way," con-tinued my guide. " Last month'sgraph of frequencies is taken, andthe alterations noted. Sometimesstations jump considerably in theirwavelengths, especially if some otherstation outside the union has comeon with higher power since theprevious readings were taken, andthen, perhaps, one of the stationsto be measured has had to choosean entirely different spot in the etherto come to roost."

Accurately CalibratedWhile the average amateur can

afford to turn the dials aimlessly,the operators at the two checkreceivers have to spot each stationand plot the wavelength variationall within a few seconds. The Brusselswavemeters, which are now used bythe leading companies connected withthe U.I.R., are the result of theexperiments made by the men atthis laboratory.

The technical committee's stationis out in the suburbs of Brussels,so that it is well away from electricalinterference, and the wavemeterscan be accurately calibrated.

They are solidly -built jobs. Theyhave big slow-motion dials with avernier control, and a magnify -Ma,glass for the reading. It is possible t o

NOT HEARD

A long -wanted improvement for broadcast music has beentried out at the Budapest station. The conductor is enclosedin a glass -fronted, soundproof room, and hears the orchestralmusic just as the listener hears it, via a loudspeaker. He con-trols the orchestra in the usual way and also by means ofcoloured lights. Budapest is the only broadcasting station in

the world to have such a system in use.

43

MODERN WIRELESS "The World's Prograinmes" January, 1933

get an easy reading to one -twentiethof a degree. As a matter of fact, Iunderstand that they get an accuracyof about one part in ten thousandwhen checking wavelengths between1,000 and 2,000 metres.

They showed me how easy it is towork the meters. First the hetero-dyne valve of the wavemeter wasswitched on and allowed to run up toits normal working temperature, sothat the meter would be quite accur-ate. The station was rapidly tunedin on the high-mag. receiver.

" Heilsberg," said the set operatorin a toneless voice. It is his duty tocheck over the same stations timeand time again !

WHERE THEY WATCH

I looked inside an open cabinet ofone of the Brussels testing metersand saw solid -looking variable con-densers with aluminium balancedcylindrical armatures, air -spaced in-ductance coils on Pyrex supports,and extremely rigid -looking wiring.

Harmonics at WillThese meters are regularly tested

against the standard wavemeter atBrussels, which is a tuning fork ofthe type used by the B.B.C. to controlthe relay station wavelengths. Thetuning fork, of a special alloy calledElinvar, vibrates at 1,000 cycles persecond. It is caused to vibrate bythe A.C. current in the grid and

THE WAVELENGTHS

Some of the wavelength -checking apparatus at the Brussels " Ether Police Station,"where all stations are tuned in nightly and their exact frequencies noted.

The calibrated dial of the wave -meter was rapidly turned and thelocally -generated oscillations weremade to beat with the carrier of thestation received.

Aluminium ArmatureAt first the beat note was a low

note of quite considerable intensity,but rapid manipulation of the wave -meter dial brought the beat note to adead silence. A calibration curvewas hurriedly consulted and thereading on the wavemeter dial gavethe frequency of the transmission inkilocycles.

anode coils of the power valve whichdrives it and which is in turn con-trolled by the waggling of the fork.

The multi -vibrator provides har-monics which can be selected at will forchecking up the ordinary wavemeter,including those used by the B.B.C.

At practically every station wherethere is not a piezo crystal or a drivevalve, a tuning fork is used to controlthe wavelengths, and you wouldthink that the Brussels engineerswould be satisfied with the workingaccuracy of their tuning fork forchecking up the wavemeters. Not so,however.

Almost every day the mastertuning fork and the multi -vibratorare checked against another standard.A synchro-clock (driven by a syn-chronous motor), running at a speedof a thousand cycles a second, isgeared down to give a dot on a paperstrip every thousand periods. One ofthe two pens bearing on the paperstrip makes a dot when driven by thesynchro- clock. The other pen printsdots at the same period from timesignals transmitted by the RoyalObservatory of Brussels.

Checking Field StrengthIf the tuning fork does not drive

the synchro-clock at exactly theright speed, the error will be shownup by the dots on the paper strip notcoinciding. As a matter of fact, thetest has hardly ever shown any error,but it is regularly done to make surethat even the master tuning fork isnever out of truth.

" Wavelength checking is not theonly job we have to do," said theguide. " This station is one of ten(including your B.B.C. Tatsfieldstation) which are Continental ethergendarmes ! We are the watch dogsof the ether, and the field -strengthmeasuring sets here at Brussels andat the other stations enable depth ofmodulation, quality, ' spread' andother vital matters to be checked sothat the broadcasters can know ifeverything is O.K. at a distance. Itis so easy to get false readings fromlocal sets near the transmitter.

Local Oscillator" For this work we have a super -

het. with a frame aerial. The signalafter detection is recorded on a milli -ammeter recorder. This gives anexact reading of the depth of modu-lation, but a standard must beknown, and here again a localoscillator is used periodically tocheck up the readings on our field -strength sets."

Before leaving Brussels I saw theoffice staff of the Gendarme whoseharsh duty it is to deal with theblack -lists of stations which do notstick to their wavelengths, and thechief engineers of which have to begiven polite reprimands !

A job needing tact!

44

January, 1933 The World's Programmes" MODERN WIRELES;

BARI, ITALY. The new Baritransmitter was-like thosefor Trieste and Florence-manufactured at the Chelms-ford, Essex, works of theMarconi Co.

MADRID, SPAIN. The EAQstation that works on 30.4metres with a power of 20kilowatts is to be the officiallink of the Radio ClubIbero-Americana, w hi c haims at achieving a betterunderstanding between thePeninsula and America.

* *

KAUNAS, LITHUANIA. The recent in-crease in power from 2.5 to 7 kilowattswas the result of installing a newmercury vapour rectifier.

* *

LILLE, FRANCE. The site for the newstation to be built under the Ferrie Planhas now been officially ceded.

* *

WINNIPEG, CANADA. The V E 9 J RWinnipeg station is now working on25.6 metr on weekdays from 10.30p.m. to 1 a.m. (22-30-01.00).

*

RADIO PARIS, FRANCE. A special formof modulation, known as the Chireixsystem, or " de -phasing modulation,"is employed by this popular Frenchstation.

* *

ALGIERS, N. AFRICA. English

*

lessons are now broadcast onTuesdays at 21.45 (9.45 p.m.).

* *

SHANGHAI, CHINA. Owingto the chaotic condions ofradio in China, Shanai hasabout 27 different stations,many of them oed bywireless firms.

PRETORIA, S. AFRI. Ithas been suggested hat a 44..

figh

wn

CAt

FROMHERE, THERE ANDEVERYWHERELast-minute flashes from the world's broad-casting stations to keep you up to date with all

changes and interesting happenings.Spanish BUCHAREST, ROUMANIA. There is a

possibility of Bucharest shifting itswavelength from 394 metres, owingto the very bad interference experiencedfrom Leipzig's news transmitter.

* *

MOSCOW, U.S.S.R. The fiat has goneforth that radio must cost less to theState, which is generally taken tomean that some form of licence will beintroduced soon.

* * *

RADIO BARCELONA, SPAIN. Theanimated dialogues sometimes heardfrom Radio Barcelona on 349 metresare not what they seem, for Barcelmiahas the world's only ventriloquistannouncer, who often conducts animatedconversations with himself !

* * *

VIENNA, AUSTRIA. The new transmitterbeing erected at Bisamberg will not be

listenets complain of PosteParisien !

* *

" RADIO THESALONIK,"GREECE. This, the firstGrecian broadcastingstation, is to work on 270metres, probably for twohours a day, commencing at11.45 and 19.15 (11.45 a.m.and 7.15 p.m., respectively).

* *

K AM / KAWA, JAPAN. Thisreceiving station, near

Tokio, was the one successfully con-cerned in the recent two-way telephonybetween Japan and the League ofNations' station at Geneva.

* * *

BUDAPEST, HUNGARY. Owing to anartistes' strike, the regular operas fromBudapest may be abandoned.

* *

TOKIO, JAPAN.. The humorously -call -lettered Tokio station J 0 A K has beenin trouble because its listeners saythat the programmes are too dry !

* * *

TRIESTE, ITALY. This station hasrecently been getting over extremelywell in the early mornings.

* * *

RADIO TOULOUSE, FRANCE. The newstation which has been getting over wellon 385 metres is situated at Château deSt. Agnan.

*

special Afrikaans-speakingstation be erected at PretoriaBloemfontein.

* *

MOOSE JAW, SASKATCHEWAN. Pro-grammes from the Moose Jaw studioare now re -broadcast from V. E 9 J R,on 25.6 metres, from 10 to 10.30 p.mon Sundays (22.00-22.30).

*

THE FEBRUARY NUMBER

MODERN oiVIRELESSwill be on sale February 1st.

Be sure of enjoying another big " World'sProgrammes" Supplement.

ORDER YOUR COPY NOW

or ready by the New Year, as hoped, butis expected to be on the air in theearly Spring.

* * *

POSTE PARISIEN, FRANCE. As mighthave been expected, listeners to thePoste Parisien are complaining ofinterference from Breslau. And Breslau

* *

WEST REGIONAL, GREATBRITAIN. Test trans-missions are expected totake place in April.

* * *

BUDAPEST, HUNGARY. Thenew station to work onsuper power is being pro-ceeded with rapidly, but noofficial date of opening hasyet been fixed.

* * *

AMSTERDAM, HOLLAND.Nearly half the listeners ofHolland have no set of theirown, but listen via radioexchanges.

* * *

BERLIN, GERMANY. Con-tinuing Germany's regionalscheme, Berlin is to have ahigh -power station. It willprobably be working thismonth (Januar**y). *

VIENNA, AUSTRIA. To thenew Vienna station belongsthe distinction of owningthe highest -powered valvein Europe, if not in theworld. It is a 300-kilowatter,of German design.

THE VATICAN, ITALY. The Vaticanstation has now taken to ultra shortwavelengths, a half -metre link havingbeen installed to connect the Pope'ssummer residence at Casteldongolfo.

*

MALTA. Although there areno broadcasting stations onthe island, a licence fee of oneguinea per annum ischarged!

* *

PLYMOUTH A new transmitter is to be installed andwill experiment on a lowerwavelength than the presentone, until the best availablewavelength has been bound.

* * *

NEW YORK, U.S.A. A featureof the Christmas programmeswas a relay from a churchat Bethlehem.

45

MODERN WIRELESS " The World's Programmes " January, 1933

RADIATING 50 -KILO.WATTS

IN THE STATES

W T IC- Hartford, Connecticut --is an Americanbroadcasting station. It has, during its sevenand a half years of service, been heard all overthe world, from Kamchatka to Cape Town, andfrom Aberdeen to Sydney.

Little wonder that the officials of WT IC areproud of their 50 -kilowatt transmitter!

SWINGINGVALVES

The water cooling jac-kets of the roo-kilowattvalves can be tilted ontheir axes to facilitateremoval of the valves.The operator seen aboveis holding one of thevalves after removal andthe tilted jacket is seenempty. On the left yousee the control -room,which is situated ad-jacent to the studios.Arrangements are madefor a land -line to NewYork, and programmesfrom WE A F are relayed

daily.

THE LONG AND THE SHORT OF ITThe lady on the left is comparing one of the big transmitter valves with thelittle quartz crystal which is used to control transmissions. Below is the maintransmitter room with the central control desk. The complete transmitterapparatus can be started up and closed down by means of a single switch

on the control engineer's desk.

46


PAN AMERICANSUPER

STATION

February, 1925, saw the first broadcast from The Travelers' station, Hartford, Con-necticut, U.S.A., and since then the microphone has been used solely for broadcasting.This is such a rare occurrence for a 50-kilowatter in America, that we feel it merits an

article to itself !

HERE are not many super -powered stations in theworld which are used solely

for broadcasting purposes.Station W T I C, however, which

is situated at Hartford, Connecticut,U.S.A., is one of these. It is astation with a 50 -kilowatt punch ;and it broadcasts on a wavelengthof 282.8 metres, equivalent to 1,063kilocycles.

The station is owned and con-trolled by one of the big commercialand insurance concerns of theeastern States, with which is incor-porated The Travelers' BroadcastingService Corporation.

In the Front RowThe Travelers' station made its

formal bow to the American publicon the night of February 10th, 1925.It was an immediate success. Somuch so that within a few years itdeveloped and grew far beyond itsoriginal size.

To -day, indeed, The Travelers'station, W T I C, at Hartford,Connecticut, is in the very frontrow of the American giant broad-casters. It has been heard all overthe world, from Calcutta to James-town, in South Africa, from Aber-deen to Sydney, from Japan toAlaska.

If you look at your map ofAmerica you will see that the townof Hartford is situated near to theeastern coast of America, not farabove New York. Here are locatedthe studios and the administrativebuildings of The Travelers.'

The actual broadcasting plantand aerial are situated ten mileswest of the town on a 200 -acremountain site, which was chosenafter careful tests had been madeupon something like ninety differentsites. It is to this most carefulchoice of site that W T I C'sextraordinary range is, in manyways, due.

Excellent Beacon.The aerial towers of W TIC

comprise the usual 200 -it. steelstructures now common to most ofthe big broadcasters in America.They are lighted up at night,thereby being rendered visible formiles around and forming anexcellent beacon for airmen.

The transmitter proper is housedin a massive but beautiful buildingof New England architecture, beingadequately spaced in a large roomsome 2,000 sq. ft. in area. Belowthis, on the ground floor, is dis-tributed the associated power equip-ment, technical offices and store-rooms, whilst the floor above the

transmitter is reserved for anyfuture developments of the station.

The transmitter of W T I C iscrystal -controlled. So efficient isthe control of frequency thus ob-tained that, although the FederalRadio Commission of America per-mits a variation in frequency of500 cycles in a million, the normalfrequency -variation of W T I C'stransmitter is never more than 20cycles in a million. This degree ofcontrol refinement is attained bymaintaining the thin wafer crystalsOf quartz which serve to control thefrequency at a temperature whichis absolutely constant.

The temperature of the W TICcontrol -crystals is not only heldconstant to within a fraction of adegree by means of a thermostatic-ally -controlled heater, but in otherways the effects of even this slightvariation have been reduced to aminimum.

Continuously CooledThe transmitter itself is for the

greater part of the usual Americantype, its chief feature being thegiant 100 -kilowatt valves which areemployed. Two of these valvesare used in the 50 -kilowatt poweramplifier of the transmitter.

Some idea of the immense amountof energy handled by these valvesmay be gained by a considerationof the fact that if they were notcontinuously cooled by a uniformflow of ice-cold water they wouldwithin a few seconds generateenough heat to melt their copperjackets.

All the voltages required for thetransmitter are derived throughrectifiers, generators and trans-formers working off a primarysource of 2,300 volts A.C. Thevalve filaments take 600 amps.,which current is supplied by a largemotor -generator working off theinitial supply of current ; 10 : 1transformers step-up the initial A.C.current to 20,000 volts D.C., whichforms the main plate supply of thevalves.

Aulontatie Relays.The transmitter is, of course,

semi -automatic in operation. Itcan be started -up by the pullingover of a single switch, and indicat-ing instruments which check everycircuit of the broadcasting plant areprovided with automatic relayswhich give warning wheneveranything goes amiss with " theworks."

The supervisor controlling thetransmitter sits at a central desk inthe transmitting -room, and signal

lights which alter from red to greenlike small traffic lights indicate tohim whether any given portion ofW T I C's giant broadcasting appara-tus is functioning correctly or not.

No WastageThe aerial tuning circuit of the

transmitter is situated away fromthe main plant. The 50 kilowattsof broadcast power which isgenerated by the transmitter is ledover a thick transmission line to an" aerial tuning house," some 500feet distant from the transmitterbuilding, and situated directly belowthe aerial, which, incidentally, com-prises one of the " T -cage " type.Here the radio energy is feddirectly up into the aerial to bedissipated into space with the leastpossible amount of wastage.

pated as useless heat close to theaerial; practically the whole powerof the transmitter being flung offfrom the aerial in a serviceablemanner.

Hartford, Connecticut, is notvery far from New York. and it isnot surprising to learn that stationW TIC is linked in synchronisationwith the famous W E A F, of NewYork City.

A Shared ChannelThis is a radio arrangement which

is the first of its kind in wirelesshistory. W TIC operates half theavailable broadcast time on its ownwavelength, after which it changesover to W E A F's wavelength,thus sharing the latter channelwith the New York station.

An altogether interesting arrange-ment and one which in the futurewill become more and more inevidence no doubt.

SHORT-WAVE" SHORTS "

A new station at Madrid, usingthe call -sign E A J 7, is transmittingirregularly on 29/ metres.

A recent addition to the list ofshort-wave stations is Y V-11 B M 0,Venezuela, working on 48'95 metres.

The Norddeich station, D A N, isworking regularly with severalGerman ships on 36, 24 and 18metres. This station has also beenheard just below 5 metres, butprobably harmonics were respon-sible for this.

Several British amateurs are nowworking on telephony on the 5 -metre band, and may be received atgreat strengths up to distances of atew miles with the simplest ofreceivers. If you should hear anamateur transmitter testing on" 56 megacycles " you will knowthat you are down in the region of51 metres.

The new Empire Station atDaventry commenced its regulartransmissions on December 19th.Five wavelengths will eventuallybe used, one of which will almost

CRYSTAL CONTROLLED

Crystal -control is used for theoperated on the centre panel.operating the rectifier control.

credentials o

The location and design of theaerial system, the wire earthingarrangement of the transmitter, thevery effective insulation of the steelaerial towers, and the location of theaerial itself at a distance from thetransmitter, all go to make up aradiation system for station WTICof the highest efficiency. Hencesurprisingly little of the trans-mitter's output of energy is dissi-

wavelength of W T I C, and isTo the left, the engineer is

Fifty kw. and 282.8 m. are thef this station.

certainly be in the neighbourhoodof that now used by Chelmsford,G 5 S W. The others are expectedto be in the regions of 48 32, 18and 16 metres.

Those who have never neardSouth America should look out forRio de Janeiro (P R B A) on 31'58metres. He is strongly received onmost evenings after 10 P.M.

47


" LONDON CALLINGTHE EMPIRE "

A first-hand description- specially written forreaders of "The World's Programmes "- of theEmpire transmitters at Daventry which startedtheir broadcasts to every corner of the Empire on

the 19th of last month.

ON the top of an unusually coldand windy hill near Daventry,under the giant masts that

help to make 5 X X a real " National"transmitter, are a number of un-assuming little wooden masts and aneat little brick building which aredestined to become far more famousthan 5 X X, 5 G B, or, indeed, anyventure that the B.B.C. has yetmade.

The New "Baby "I was lucky enough, on my visit to

the Empire station, to find twoengineers who were old friends ofmine, who also took such pride in

the B.B.C.'s new baby " that theynever tired of showing people round.When they found someone, like my-self, who was as keen on short wavesas they were, and who didn't per-petually worry them about who wasgoing to pay for the Empire pro-gramme, they simply couldn't bestopped !

The result was that in six hours orso I don't imagine I missed much ofthe organisation that will control" Stations GSA to G S G."

In the modest -looking, squat build-ing that you have already seen in

illustrations, is housed the mostcomprehensive system of short-wavetransmitters in the world. Also, ifthe hopes of the engineers are realised,it will be the most efficient.

The general scheme is alreadyfamiliar, I expect, to most readers.The Empire is divided up into five

zones," and for each of these asystem of beam aerials has beenerected at Daventry. Each zone,with the exception of Australasia,will be served simultaneously withthe same programme on two differentwavelengths.

Not Much "Alternative "This policy has been criticised by

the non -technical Press, who thinkthat an alternative programme shouldbe provided. Actually it wouldn'tbe much of an alternative, for it willgenerally happen that only one ofthe two wavelengths will be reallywell received.

A system of eighteen outsideaerials enables all the necessarychanging to be done, although,naturally, it is all carried out frominside the transmitter building. WhenI saw the two transmitters they werearranged so that each could be

worked on four different ve-lengths, the changes not taking morethan a few mintites. -

To do this, four quartz crystalsand four complete crystal -oscillatorstages form the first unit of each ofthem. These are followed by fre-quency -doublers and amplifiers driv-ing the final stage, with an input of50 kw. The Empire would rejoicecould it but see those 5 amps. at10,000 volts going into the last stagesof the two transmitters !

Beautifully ArrangedFrom the last units two leads go

off to - aerial feeder panels," whichare really glass panes at which thefeeder lines from all the variousaerials end. A kind of super -plug -and -socket connection, about the size of asparking -plug, is used for this im-portant job.

The transmitter -hall is beautifullyarranged, one transmitter runningdown each side, the power -suppliesbeing at the far end and the twocontrol desks in the centre. Thecontrol -room for the programmesarriving from London is a separateunit just inside the main door.

At one side another hall " housesfive huge radiators and fans, coolingthe water which flows round the valveanodes and tuning coils-for even thecoils have to be water-cooled on a joblike this. On the other side of thebuilding are housed the banks ofgenerators supplying all the require-ments of grid bias and filamentcurrent-a matter 40() amps. at 26volts for the main amplifiers alone I

When the programmes commence,(Continued on page 49)

South African listeners are among the most enthusi-astic supporters of the new Empire transmitter especiallyas the preliminary tests have been so successful. Theseare the aerials used for the South African transmissions.

48

January, 1933 " The World's PrograMmes" MODERN WIRELESS

ir ONG distance reception upon themedium waveband appearsto be undergoing a gradual

but revolutionary change. A fewyears ago we never dreamed of re -receiving South American broadcast-ing upon this band. Compare thatstate of affairs with the present day.

Now we are almost certain toreceive one or other Buenos Ayresstation if we sit up late enough.Peculiarly enough, this sudden changeof conditions has not, as might beimagined, been brought about by anincrease of the .power of the SouthAmerican stations.

Is It Unreasonable ?The power and, in most cases, the

wavelengths are the same now asthey were when we were unable toreceive them. Even more interestingis the fact that the highest power asyet employed by any of these stationsis 10 kw., and L R 3 (one of themost powerfully received BuenosAyres stations) employs only 3 kw.,Although it will shortly be increased.

In consideration of these facts is itso unreasonable to expect morechanges in reception conditions,changes that may result in ourreceiving Australian and New Zealandbroadcasting regularly ?

WHAT THEDISTANT STATIONSARE DOINGExtracts from the log of "M.W.'s"own station searcher who listensto the world's programmes sothat you may know the conditions

in the ether every month.At the present time New Zealand

and Australian enthusiasts can re-ceive European broadcasting com-paratively readily. One may remarkthat with all Europe's high-poweredstations they most certainly should.The interesting point, however, isthat besides receiving numerousEuropean high-powered stations, anumber of the low -powered stationsare heard fairly regularly. Thesestations include Leipzig (when em-ploying 2.5 kw.) ; Gleiwitz (5 kw.) ;Hamburg (1.5 kw.) ; and RadioToulouse (8 kw.).

American enthusiasts also hearAustralian and New Zealand, to saynothing of Japanese, stations regu-larly.

Daylight Reception1932 was renowned for its day-

light reception. Even so, the lastmonth has beaten all its prede-cessors in this field.

Genoa ; Trieste, Stavanger ;Nurnberg ; Bordeaux Lafayette ;Bordeaux Sud-Ouest ; Flensburg ;Fecamp ; Heilsberg ; Bari ; Hilver-sum ; Poste Parisien, Paris ; Stras-bourg ; Radio Toulouse ; Dublin ;Ecole Superieure ; Katowice ; Rome ;Langenberg ; Brussels, and Budapest

have provided good loudspeakersignals upon many occasions. Atslightly lesser strength I have re-ceived Viipuri and Helsinki (both inFinland), and Fredriksstad and Pors-grund (Norway).

As night comes on the log swells toamazing proportions, and such sta-tions as Lwow ; Tallin ; Riga ;Trondheim (Norway) ; Sundsvall ;Ljubljana ; Belgrade ; Bucharest ;Lisbon (C T 1 A A) (when trans-mitting) ; Orebro, and Christiansandhave been heard regularly, strengthbeing about equal to the NorthRegional transmitter.

Held Its OwnReaders may remember a remark of

mine in these notes regarding an all -electric orchestra, known as the" Therrain Electro-Ensemble," whichbroadcasts regularly over the Colum-bia Broadcasting System stations.

A similar orchestra was broadcastfrom Berlin recently.

Generally speaking, the instrumentswere very similar to the instrumentsafter which they were named. Theelectric -piano was an exception.

The complete orchestra held itsown against any ordinary orchestra ofsimilar size.

L. W. O.

"'LONDON CALLINGTHE EMPIRE "

-continued from page 48

the following arrangements will beused, although modifications aresure to take place later on as therequirements of each zone becomeclearer : Australasia, 25.5 metres,9.30-11.30 a.m. ; India, 25.3 and16.9 metres, 2.30-4.30 p.m. ; Africa,31.3 and 49.6 metres, 6-8 p.m. ; WestAfrica, 31.5 and 49.6 metres, 8.30-

10.30 p.m. ; and Canada, 31.5 and 49.6metres, 1-3 a.m. All times are G.M.T.

I note from the aerial arrangementsthat provision has also been made forserving Africa with a wave of 13.97metres, India with 31.5 metres, WestAfrica with 25.5 metres, and Canadawith 19.8 metres.

The reason for using 25.3 as well as25.5 metres and 31.3 as well as 31.5metres is that one transmitter shallhandle each pair. Thus when No. 1transmitter has been transmittingto Africa. on 31.3 until 8 p.m., theother will be all ready to go on 31.5

for West Africa at 8.30, while, ifnecessary, the first is being changedover from 49.6 to 25.5 metres.

With the possible exceptions ofW 8 X K and W 2 X A F, the Empiretransmitters will be the highest -powered short-wave broadcastingstations in the world. Being, for thepresent, the most modern, it may betruly said that a big step in short-wave radio technique has taken place.We can say no more for the timebeing, except that " the proof of the

-pudding is in the eating 'W L. S.

49


"Fs

THERE was a time when radio -minded folk would indulge inheated -arguments concerning

the merits of S.G. amplification, andthe question usually resolved itselfinto the straightforward issue ofwhether the composition of a three-

valve circuit was better as a detectorand two L.F., or as an S.G.-det.-L.F.arrangement.

Far From Being Dead _

Nowadays the merits and ad-vantages in certain respects of S.G.amplification are almost universallyadmitted. But that should not betaken as an implication that the oldand ever -popular det. and two L.F.circuit is dead. Far from it.

It just means that from the point ofview of the modern requirements of ahigh degree of selectivity combinedwith reasonable sensitivity, the S.G.-det.-L.F. scheme is, commercially,the better proposition.

You will notice that we say " com-mercially." That is because in manyother respects the det. and two L.F.combination still has a lot to com-mend it. For instance, apart fromwhat in these days is the primarilyimportant consideration of lower cost,the fact that it has only one tunedcircuit is reflected in the ease withwhich it can be operated.

Commendable ActionIt is for these and other reasons

that we commend the action ofMessrs. Regentone in producing anall -electric version of the " old love."

The Regentone "Straight -Three "-a model of which was recently sub-jected to " M.W 's " tests-is a good,reliable set. By comparison, ob-viously. it cannot be expected to give

THE REGENTONE"STRAIGHT -THREE" A.C. RECEIVERSome first-hand information about an interesting three -valve A.C. set. It hasa.detector,followed by two L.F. stones. and will appeal greatly to lovers of this

" straight " eirenit arrangement.

By A STAFF TECHNICIAN.

a measure of selectivity .commen-surate with that given by an S.G.arrangement, but in all other respectswe are justified in referring to it asan ideal " family " receiver.

Sprinkling of AlternativesAfter all, the suitability of any

set for modern conditions necessarilydepends upon the uses to which youwant to put it, and if contentmentin the radio sense is obtained witha set that gives superb reproductionof the local stations with a fairsprinkling of reliable alternatives,then this Regentone instrument isjust the thing for you.

It is built into an attractive solidwalnut cabinet-it incorporates anexcellent moving -coil loudspeaker-it is dead simple to operate, and it isavailable at the extremely modestprice of £12 complete. It might, infact, be regarded as the most con-vincing argument that we have yetfound in favour of the retention of theno-S.G. combination.

Turning, for a moment, to theactual controls, the central upper oneis the knob by which the set is tuned,and immediately below it is the four-way switch control giving medium

USES METAL RECTIFIER

The mains rectifier for high-tension can bespotted to the left of the chassis, while to

the right is the inductance.

waves, long waves, gramophone and" off " positions.

On the left is a control which isprimarily for the purpose of adjustingselectivity, but it also constitutes amost useful pre -detector volume con-trol on powerful local transmissions.

*1111 0.111111

it

TECHNICAL SPECIFICATIONNUMBER OP VALVES.-Three-detector,

L.F. and pentode.GENERAL DESCRIPTION. - AR -electric

three -valve receiver for A.C. mains, 200-E50 volts, 40-100 cycles. A moving -coil loudspeaker is incorporated. Canbe used with mains aerial. Sockets areprovided for pick-up and external L.S.

CONTROLS.-One for tuning, one for vol-ume, one for selectivity, and switchgiving medium long -waves, " off," and" gramophone " positions.

DIMENSIONS.-Height 20 ins., width (atbase) 17 ins., depth 10 ins.

PRICE.- £12 complete.MAKERS.-Regentone Ltd., Regentone

Works, Worton Road, Isleworth,Middlesex.

The one remaining knob-that on theright-controls reaction, and in conse-quence it only comes into use when itis desired to receive distant stations.

No Trace of InterferenceProvision is made at the back of

the instrument for the usual aerialand earth connections, and socketsare also provided for a gramophonepick-up and for an external loud-speaker. In addition, an ingeniousplug and socket scheme enables thereceiver to be used in ' conjunctionwith a mains aerial, under whichconditions it works very well.

In our practical tests, which wereconducted with an outside aerial ofaverage dimensions, the strength ofthe local stations had to be con-siderably reduced in order to providecomfortable listening. There wasnot the slightest trace of interferencebetween them, indeed, by carefuladjustment of the selectivity controlwe found it possible to separate theLondon Regional and Midland Re-gional stations, which speaks volumesfor the efficiency of the set.

As a result of our tests it is withconfidence that we recommend thisset as a good, reliable domesticinstallation.

so


AT YOUR SERVICE mo

OUR TRADECOMMISSIONER

AHAPPY New Year to you all, andmay 1933 be a bumper yearfor radio. It ought to be if

the energy many firms are puttinginto their businesses takes effect.

"Astride of the TimesThe introduction to the Wearite

catalogue contains the words quotedabove, and an examination of thecontents fully endorses them. Therange of components emanating fromthis go-ahead concern are varied andnumerous, and the reading of thebook alone is interesting, whether ornot you are on the look -out for apiece of radio apparatus.

Always in the forefront of superhetcomponent design, we find that Messrs.Wright & Weaire have now extendedtheir range of oscillators, intermediates,and so on, to include a f our -gang coilassembly which consists of an aerialunit, a band-pass H.F. unit andoscillator to be tuned with an ordinaryfour -gang condenser.

The heterodyne filter for cuttingout interference is a new line that isparticularly interesting, and I hearthat the ingenious Q.V.C. volume -control and combined switch is goingvery well. Strip resistances and R.D.resistances cover a wide range ofvalues a n d wattages. Screenedchokes have also attracted theattention of the powers -that -be atTottenham, and several models areavailable.

But it is in the mains transformersand the L.F. chokes that I am par-ticularly interested, for here we findthat very substantial price reductionshave been made possible by re -design-ing a number of components andintroducing other new ones. Theresult is that the Wearite range ofmains apparatus is one of the finestI have struck at anything near theprice. Just you get one of. thesecatalogues and see for yourself.

Marconiphone PromotionWe heartily congratulate Mr. J. H.

Williams, who since April last has

Some trade news and views thatare of interest to readers, whetheror not they are connected with the

radio industry.Members of the trade are invitedto send items of interest, or photo-graphs, to be included under this

heading.

been a director of Marconiphone Co.Ltd., on his appointment as ManagingDirector. Mr. Williams' career withthe company has been almost meteoric-starting as sales representative (weare told) in Manchester, he rapidlyclimbed the ladder till now, somenine or ten years later, he has reachedthe top.

Mr. G. R. Osborne, too, is anotherwho is on the upward trend in thesame firm, and we are delighted tohear of his appointment recently asSales Manager. I knew this youngenthusiast years before broadcastingwas ever thought of, during the darkdays of '14-'18, when he joined thethen Marconi International MarineCommunication Co. Ltd., and sohave been following his progress withparticular interest. He should do wellas Sales Manager, for above every

BEFORE AND AFTER

A scene from a " Pathetone Weekly " film showing an H.M.V. gramo-phone contemporary with Caruso alongside the latest superhetauto -radiogram. The former plays the original Caruso records, and

the latter the new re-recording of the famous tenor's voice.

thing he is a real enthusiast in theworld of radio:

Blue Spot SuccessesI was having a chat recently with

Mr. Brown of the British Blue SpotCompany, Ltd., and I was interestedto hear that the Blue Spot batteryreceivers introduced at the recentshow are in great demand. I'm notsurprised-they are jolly good.

The Annual Banquetand Ball

Mr. J. H. Whitley was the guest ofhonour at the annual banquet andball of the Radio Manufacturers'Association at the Savoy Hotel lastmonth, which was a great success.It is always a lively, cheerful gather-ing, and this time it seemed betterattended than ever. 'Twas a merryshow !

New Ferranti ChartA constructors' chart for a four -

valve battery set has recently beenissued by Messrs. Ferranti Ltd. Thewell-known Ferranti band-pass cir-cuit has been used, and push-pull

output is em-ployed. Thecost, exclud-ing batteries,valves andcabinet, is£11 12s.

ClimaxD.C. SetA D.C. mo-

del of the" Climax Band-pass " Threereceiver hasbeen broughtout, and issimilar to theA.C. one in per-formance. Itis stated thatthe perform-ance on a

51


Many Interesting New Componentsgramophone of the new set is oneof its outstanding features. The priceis 16 guineas.

H.M.V. at SheffieldThe Special Products Branch of

The Gramophone Company has in-stalled a loudspeaker address systemin Sheffield Town Hall so that speechescan be heard from any of the fivehalls without difficulty. Incidentally,the apparatus can be used, not onlyto make a speaker audible in the hallin which he is speaking, but also willbroadcast his voice throughout thebuilding should occasion warrantwholesale " reception " of the speech.

I understand that broadcast pro-grammes and gramophone recordrecitals will also be available throughthe same medium in the near future.

Claude Lyons and B.A. T.I have just received a couple of

lists of B.A.T. products from ClaudeLyons Ltd. They include practicallyeverything. you could wish in the wayt)f switches, resistances, chokes,power transformers, and gramophonemotors and pick-ups. A very widerange of transformers for A.C. sets isprovided and, as with all ClaudeLyons' parts, you can be sure thatthey are good. Ohms WithoutTears " is the way Mr. Lyons intro -

resistances can be obtained in threeranges of percentage accuracy,namely, 10, 5 and 2 per cent, the priceranging in the case of the 1 -watt orsmaller types from 101d. for the 10 percent, to is. for the 5, and ls. 3d. forthe 2 per cent accurate resistance.

It would take a lot of space to go atall thoroughly into the many pages ofthe catalogues, and I would stronglyadvise all my readers to send to 40,Buckingham Gate, S.W.1, for copies,so that they may peruse them attheir leisure, and have them at handwhenever they are in search of radioparts.

There is no accessory requirement of the discerning enthusiast which cannot befound in the extensive Ediswan range. The random array of sample lines shownhere presents a picture of quality apparatus to delight the eye and whet the appetite

of every " must -have -the -best " set owner.

Electric Co. It contains practicallyeverything that you could wish for inthe way of batteries, loudspeakers,pick-ups, and valves, in addition to alot of smaller lines that are well up tothe high standard that Ediswan set.

Some of the chief lines are shownin the photograph on this page,wherein you will recognise the B.T.-13.moving -coilspeaker unitwhich can

GROUPEDEFFICIENCY!

FERRANTI, FORWARD !

Mr. V. Z de Ferranti receiving from Ann Penn the silver cupawarded by the " Evening Chronicle " for the best value -for -money set at the Manchester Exhibition. The set chosen by the

public ballot was the Ferranti Superhet.

duces the B.A.T. resistors, whichfollow the gradually getting popularcolour system of resistance indication.Here again a very wide range of valuesis available, and the prices are low.

A special feature is that the

An InterestingBook

I have before mea most interestinglittle book issuedby the IgranicElectric Co. Ltd.,and describing thevarious electricamplifying and re-producing equip-ment that are pro-duced at their Bed-ford factory. Thebook is in additionto the standardIgranic catalogueof ordinary radiogoods, but it isworth sending forif you are interestedin power amplifica-tion as supplied to

public address systems and dance halls.

A Powerful TeamI suppose that one of the strongest

teams of components and accessoriesis that marketed by The Edison Swan

52

be obtained in several types, rangingin price from round the £3 mark fora cabinet model of the Minor R.K. tosomething like £7 15s. for the A.C.model of the senior R.K.

Pick-ups in two varieties are avail-able, while the huge range of Mazdavalves needs no explanation to ourreaders. These valves have alwaysbeen in the forefront of radio valvedesign and none has enjoyed a betterreputation for efficiency and long life.

Ediswan dry H.T. batteries, too,have recently set a standard ofreliability and efficiency combinedwith low price that has been the talkof the radio trade, while the wetvariety have long been recognised asexcellent value for money.

The Extralife accumulator for L.T.supply is one that deserves specialmention. At 4s. 3d. for the smallestit is wonderful value. And so I couldgo on enumerating the many attractivelines of this old -established firm, forwhenever you turn among the linesemanating from the various factoriescontrolled by Ediswan you find some-thing worth while, something you cando with in your radio outfit.

January, 1933 MODERN WIRELES;

MY gentle hint that a short-waveclub in this country might bea good thing has brought forth

a host of suggestions, some of themhelpful and some otherwise. Per-haps I had better make it clear atonce that I was not thinking of tread-ing on the toes of the InternationalShort -Wave Club, which has a LondonChapter in full swing, and others, Ibelieve, in the course of development.

Now that this Club is actually soplaced as to be able to hold meetings,the cause of my original suggestionhas been largely. removed. At thesame time, however, there is stillplenty of room for local short-waveclubs, and if I can do anything toassist in their formation I shall bemore than pleased to do so.

I should like to say quite definitely,by the way, that (flattered as I amby the suggestions that I should starta club myself) I have not the neces-sary spare time to take on any" extras " for a very long while !

Dark HintsSome of those who read this may

have noticed dark hints in " PopularWireless " about a superhet for short-wave broadcast reception, that is onmy bench at the moment. Thereis no harm in saying at this stagethat it is intended for readers of" M.W.," and that it will be describedin full as soon as possible.

So many readers in the " Outpostsof Empire " have written pleadingletters for a real big loudspeaker set-preferably a superhet-that afterdue consultation with the PowersThat Be I started attacking theproblem.

SHORTWAVE

W.L.S.

No nutter what branch of short-wave reception claims yourspecial interest, you will findthese pages by our popular con-tributor make mem ttttt only good

reading." W. L. S." combines a ripe ex-perience and knowledge of hissubject with a special aptitudefor clear writing on the techni-calities, end cheery comment onthe S topics of the moment.This month, anwng other items,he has some interesting things tosay about a forthcoming short-wave super -heterodyne receiver.

Short-wave superhets to -day area very different proposition from theirbrothers and cousins of a few years

RADIO " FIRE ALARM "

Part of the equipment of this forest " fire-ookout ' is a complete portable trans-

mitter and receiver, which is used forreporting and communication during fires.

ago. Luckily for us all, the changeshave been in the direction of a generalcleaning -up of the design. Compo-nents, too, have improved vastly,with the result that it should now bepossible to get as much out of fivevalves as one used to expect fromseven or eight.

Beautiful StabilitySuperhets are of little or no

interest to the " ham," or even to theman whose idea of Paradise is to sitand listen to the said " hams." WeakC.W. signals are best dealt with by amuch smaller and quieter set. Thesuperhet shows up best on telephonytransmissions that are alreadymoderately strong on a smaller set,and its great advantages are, ofcourse, the enormous signal -strengthobtainable and the beautiful stabilityand ease of handling.

Signal -frequency amplification withS.G. valves is all very well down to40 or perhaps 35 metres ; but afterthat it becomes rather questionablewhether it is worth while. To obtaina small amount of amplification for agreat amount of trouble is a state ofaffairs that proves rather unpopularwith the average radio man, who, asa rule, wants something for nothing !

Getting Every OunceWith a superhet one can, of course,

get every ounce out of the S.G. valveworking at the intermediate frequencyof 100 or 110 kilocycles, and thefeeling that a valve is being fed withexpensive watts and not (Icing any-thing for them is entirely removed.

It is nice to note the return ofmoderately good conditions after.

53


the rather wretched state of affairsthat existed throughout the latesummer and autumn. December is agood month, as a rule, and Januaryand February rarely let us down.What a blessing it is for all of us thatthe bad radio months are usually themonths in which outdoor pursuitstake up most of our time.

Vagaries of the EtherWe short-wave fans are far more

dependent upon the vagaries of theether than are the folk who simplytune in whatever broadcast stationthey want, when they want it. But,when one comes to think of it, doesn'tthat make it far more interesting ?If one could always sit down to theset and tune in Sydney, would it notbegin to pall after a few weeks ? Idon't think. I should find any thrill inshort-wave work were it not for the

glorious uncertainty." associatedwith it.

Hard ThinkingIt is rather amusing sometimes to

ask a fervid broadcast -listener whyhe has never thought of taking up theshort waves. " Too much trouble,"says one. " Never heard of 'em,"says another.

Others will talk glibly about beingmore interested in " quality repro-duction," listening the while to anoverloaded amplifier working into acheap loudspeaker.

The whole fact of the matter is thatshort waves are being treated toomuch as an entirely separate branchof radio. The day will come, un-doubtedly, when all commercial re-ceivers will cover the " ultra shortsas well as the other bands, but some-one will have to do some hard thinkingand evolve a real wavechange schemebefore that happens. I freely admitthat it has got me beat.

Crazy PeopleThe designing of a scheme that will

make it possible to tune over theshort, medium and long wavebandsis, of course, relatively simple.Plenty of sets have been described in" M.W." and " P.W." that areadmirable in this respect. Whatno one has yet done is to devise a

set that will give equally easyoperation on all bands. Somethingthat will tune in Sydney as if he were,say, Langenberg is what we all want.

This can be done with care on aset for short waves only ; but theall -wave set with this desirablequalification is something that I haveyet to see. May the day come soon.Even when it does, there will still becrazy people like you and me who goon building our own sets just for thefun of the thing !

Palatial LaboratoryIncidentally the mental pictures

that one or two correspondents ofmine have formed of my own gearare distinctly amusing. One describeshis idea of my " shack " as a palatiallaboratory with yards of benches,and at least thirty different short-

#ERIRL ERRM

GRIDLER"(

-000//ifFDTun/NC

CONDENSER

TRY THISARRANGEMENT

GRID CONDENSER

t

\\\Ill/®k ilf

" on the hop " with nothing but themodest single-valver rigged up !

I never allow myself to be caughtwithout anything, and this " single "is the Set that Must Not Be Pulledto Pieces. As a " stop -gap " it isquite unrivalled.

" I am rather doubtful if it will befound satisfactory in the matter ofwavelengths. It looks to me as ifcertain zones may find that the trans-missions meant for other parts mayturn out to be better than their own."Read W.L.S.' comments on the newEmpire station on a following page.

I am often asked, by the way, for myidea of " the ideal layout " for adetector stage. Personally, I don'tthink there is such a thing as anideal layout for anything, but the

accompanyingsketch shows anarrangement ofparts for the de-tector that seemsjust about asefficient as one canmake it.

All the leads areshort and direct,and yet the coilsare well away fromthe " iron and steeldepartment "-amore importantpoint than seems to

76 ERRTH be generally apprec-FO/L UNDER iated. I was enter -8/754 -8°'98°A taining myself the

other day by read-ing some of my ownarticles in " M.W."back in 1927 and1926, and I seemedto be far moreworried in thosedays about keepingthe field of the coilsclear than I am now.

I admit that wemay have beenrather over -enthus-iastic then, when

the " low -loss " craze was at itsheight. Nowadays we realise that theterm " low -loss " means absolutelyzero ! But then-what a craze it was.Anything that looked more like askeleton than a variable condenser hadthe horrid adjective pinned on to it,and cost 50 per cent more accordingly.

It is a matter of lasting regret tome that I have not been able to keepintact one of my receivers of sevenyears ago. Doubtless we should enjoya hearty laugh at its performance

x889

What do you think of W.L.S.' answer to those who have askedhim for an "ideal layout " for a detector stage ? Our short-wave expert says "I don't think there is such a thing as anideal layout . . . but this arrangement seems just about as

efficient as one can make it."

wave receivers all rigged up ready tobe switched on at a moment's notice.He apparently thinks that I am the" mad millionaire " of fiction, with avast fortune all tied up in short-wave gear.

I don't know where this strange ideacame from, unless he thinks that allthe sets that I design and describe areleft permanently rigged up where theystarted !

Suffice it to say that the averagecasual caller might easily catch me

54

January, 1933

nowadays, for conditions have fallenoff almost continuously since thememorable winter of 1927-8. I shallsee to it that my single-valver,previously referred to, becomes " im-mortal," if only for the sake ofaffording me some cheap amusementin 1940 !

As we are entering upon anotheryear (and all best wishes, by the way,to my readers !), it is rather interestingto speculate on what developmentswe may expect to see. Personally, Idon't expect- much more than ageneral improvement in the standardof transmission and reception.

No RevolutionsNothing revolutionary appears to beon the way, but everything is alwaysimproving in a quiet way, and, takingthis in conjunction with the fact thatconditions are now due to improvealso, we may be better off when Iwrite my last notes for 1933.

I think we can truly say that 1932has seen an improvement in reliability.Reception of American stations, forinstance, is no longer looked upon asthe achievement of the expert. Whena man says he has heard America onshort waves, the usual reply is : " Andso he jolly well ought to ! " Which isas it should be. We don't treatbroadcasting as a miracle any longer,and even our beloved " DX " is fastbecoming a commonplace.

A Step ForwardOne thing that I am looking forward

to is a higher degree of accuracy inmass-produced components. This ap-plies particularly to short-wave people,whose chief trouble in trying out anew set is still to find exactly wherethey are. When things are so goodthat I shall be able to describe a setin " M.W." and to guarantee that, ifsimilar components are used, Sydneywill be found on 33.5 degrees, thenwe shall have moved another stepforward.

Short-wave stations are all bunchedtogether in groups, so closely that it isa real problem to identify a stationwithout waiting, perhaps, for a longspeech in a foreign tongue before anyannouncement is made.

The accurate calibration of anyparticular short-wave set is an easymatter, but standardisation is, as yet,quite a long way off. Incidentally,very few people seem to possess aheterodyne wavemeter, although Ifind my own one of the most usefulpieces of gear about the place. I havemade references to this before, andthey have nearly always broughtforth requests for the design of suchan instrument. The reply is simple-just make yourself an ordinary oscil-lating detector, and there you have it.

Handy WavemeterUse good components, wire the thing

up rigidly and, above all, put arespectable slow-motion dial on thetuning condenser, and you will then

MODERN WIRELESS

I have purposely refrained fromtalking about " what is on the air'this month, partly because nothingvery startling has happened since thebeginning of November in the way ofnew stations. By the time you readthis, however, the Empire station willbe on the air-another milestone inshort-wave radio.

I am rather doubtful whether it willbe found satisfactory in the matter ofwavelengths. By this I don't meanthat it will be a failure for anyparticular zone, but it looks to me asif certain zones may find that thetransmissions meant for other partsmay turn out to be better than theirown ! Australasia, for instance, mightwell find thatthe 31 -metre programmeis better than the 25. This is only a

ANOTHER USE FOR PARABOLIC REFLECTORS

Although looking rather like some micro -ray apparatus, the instrument in the topphoto is actually a microphone assemblyfor use in large halls, the reflector beingused to concentrate sound in the micro-phone. Below are seen the two sizes ofreflectors which have been used very suc-

cessfully.

have a heterodyne wavemeter thatshould serve you very well. Don'tchange the valve about or even alterthe H.T. voltage, or you will naturallyplay havoc with the calibration.

I find that a 16 -volt grid -biasbattery and a very small 2 -voltunspillable accumulator may beincluded without making the wave -meter too bulky, and if it is made ina small aluminium box with a handleon the side, it becomes very convenientto walk about with.

55

long shot on my part, but I am goingby our own experiences in thereception of foreign parts.

By next month we shall all knowwhat things are like, and I willtherefore " close down " until then.


ROUND theTURNTABLE

Gramophone Record Correction-Lifting Top" or " Bottom' -The Multitone Transformer An Excellent Loudspeaker.

By " TONE -ARM."

THE technical side of gramophonerecord production has im-proved tremendously during

the last few years, but manyowners of radiogramophones do notrellise that even now the record is farfr n perfect, and needs " correct-ing " in some form or another.

Record "Fall -Off "Records have characteristics that

fall off at the high note as well as thelow note end of the musical scale,and for this reason many pick-upsare now designed with definite " lifts '

at the top and bottom of the scale.This has a good effect on all averagerecords, but it does not necessarilycater for all, and often you will comeacross a disc that has a particularlyhigh-pitched recording on it.

Such is the case in some of theGracie Fields' records, and in thesethere is " too much high stuff " whenreproduced by one of the brillianttypes of pick-ups. Records are notstandard in their curves, unfortu-nately, and it is advisable to havesome form of adjustible corrector ifyou are considering correction inyour radiogram.

Variable HumpingThe corrector will have to provide

a variable humping for the lower endof the scale, for no record or pick-uphas yet come to my notice having theproper amount of bass. The otherend of the scale will not usually re-quire lifting, it is more likely to needdecreasing, as in the case of theGracie Fields' records.

I am experimenting now with avariable tone control that may proveuseful in this respect. It does awaywith the need for a complicatedsystem of stages of amplification,

at the same time it -allows boththe high and the low notes to belifted, or reduced, as well as either inturn. Most schemes can only tackleone of the two at a time, and themethod is quite simple. I hope itwill prove properly effective, for Iwant to use it on my own radio -gramophone.

Potentiometer ControlOne of the best devices so far in-

troduced to the public is the Multi -tone transformer, whose characteris-tics are altered at will, within certainlimits, by means of a potentiometercontrol. This can be placed in the

FOR CORRECTING THE " PICK-UP "

Here is the Multitone transformer and potentiometer mentionedin the text. It is suitable either for pick-up control or use in

an amplifier.

set or it can be used as an inputtransformer for the pick-up outsidethe receiver. In this latter respectit enables the same results to beobtained, a lift of bass or treble can

56

be achieved, and the makers recom-mend that this input be used withanother Multitone inside the set,either one or other of the transformershaving the potentiometer control,but not necessarily both:

Reducing High NotesA simple way of reducing the high

note response of a pick-up is toconnect a resistance across it, thevalue of the resistance depending onthe pick-up. A further improvementon this is a resistance of the variablevariety in series with a condenser ofabout .01 mfd. across the pick-upwindings.

But the Multitone gives a muchmore desirable result, by allowingthe response curve of the transformertp be swung, from giving a lift at the'bass end, through straight-line nor-mality to the rising high note response.It is ingenious and thoroughly soundin theory and practice, while theresults are most satisfactory.

Good SpeakersFrom pick-ups and tone controls

let me go on to loudspeakers. It isobvious that all the tone controllingin the world will be wasted unless theloudspeaker that is to handle theresult is a good one. And thetrouble is that poor loudspeakers arestill by no means unknown. I havespent some time testing speakersrecently, and though my tests haveincluded all sorts and prices, I have

been surprised atthenumber of goodmodels there areabout.

LeadersAs I have said,

there are poor ones,but the generalstandard is com-mendably high,though there arenaturallysomethatstand out as leadersin their classes.The Ferranti Ml isone of these, as isthe Epoch 99K, andits sister speakerthe 99X.

The Ferranti Mlis a permanentmagnet type of nosmall cost,but the money

spent is well placed, for theresponse of the speaker is excellent.It is not by any means insensitive ; infact, it is one of the most sensitivemodels I have tested.


MMFA

THE H.M.V. SUPERHET TENEG

A luxury instrument embody -114 ing every modern improvement.

Erg 1E11151F3FilrilliiliglilfIlERE 111f31 llama

EN it fell to my lot to test theH.M.V. Superhet Ten Auto -radiogram, I realised that I

was indeed fortunate. For is not thisde -luxe 'receiver the acknowledgedRolls-Royce of radio ?

Some months ago I was privilegedto visit the Gramophone Company'sgreat works at Hayes, and to see theH.M.V. receivers in the process ofmanufacture. The visit was illu-minating ; the great care with whichevery part is machine -finished andtested is amazing. Not only is everycomponent tested individually, buteach completed receiver is given themost exhaustive try -out before it isfinally passed as being fit for thepublic to handle.

Absolutely First -ClassThe whole of the H.M.V. range is

absolutely first-class, and the Auto -radiogram, which is the most luxuriousreceiver in that range, is in everysense of the word representative ofthe very best in modern radio andgramophone practice.

On the radio side you have aninstrument capable of bringing inevery programme in Europe, togetherwith a degree of selectivity givingtrue razor-sharp station separation.

So far as reproduction is concerned,it goes without saying that a firmwith H.M.V.'s wide experience wouldnot be found wanting in this respect ;the quality on both radio and gramo-phone is fully in keeping with the restof the instrument.

On the gramophone side we havethe well-known and ingenious H.M.V.

I.

AUTORADIOGRAMBy an

" ltl.W ." Staff Technician.

EfillaRRIFEIERIVIfflIEffillfillEfiEgITIKETIMITIIEMEEIZIEGFIFfIEFIFEIVIEFIVll63.1/4.F11F1361EMEENEFIEFIVIMIRIFEMEgUalFil1E1

FIL

f/1

liRlitiallEEMMEIYEE1111111EfilifilEFIIIII

The cabinet in which thisde -luxe receiver is housedis beautifully constructed of

specially picked walnut.

automatic record -changer which playsup to eight records.

The circuit provides much that isof interest.

There are ten valves, including therectifier, and the circuit is basicallythat of a superhet. On the medium -wave range, the waveband covered isfrom 210-500 metres, and on the longwaves 900-2,000 metres.

Free from HarmonicsThe aerial coil is coupled by a

band-pass filter to a preliminaryH.F. amplifier, which incorporates avariable -mu V.M.S.4 valve. Theoutput from this stage is applied tothe first detector, into which theoscillations from a separate oscillatorvalve of the M.H.L.4 type are fed.

The oscillator circuit is designed tobe free from harmonics, and the firstdetector is also band-pass coupled tothe first intermediate frequency-

-

amplifying stage, which in turn iscoupled by a third band-pass unit tothe second intermediate frequencystage, variable -mu valves being em-ployed in each case.

Then, we have still another band-pass unit, through which the signalvoltages are applied to the seconddetector, working as an anode bendrectifier, with a specially decoupledanode circuit.

Push -Pull OutputThis completes the radio chassis,

and the output from the seconddetector is taken to another chassisupon which is mounted the L.F.amplifier. There is a filter betweenthe second detector and the L.F.side, which prevents any high -frequency currents flowing throughinto the output end of the receiver.

The L.F. chassis comprises a resist-ance capacity stage, coupled to apush-pull output.

Up to 41 watts of undistortedenergy are available from the twoP.X.4 push-pull output valves, andthere is a tone control in this portionof the receiver, which is extremelyuseful in the event of heterodyneinterference being experienced.

All the tuning controls are" ganged," and operated by a singleknob, special care having been takenwith the trimming of the oscillatorcondenser so as to ensure that atevery point on the wave -ranges thefrequency of the oscillator is 125kilocycles different from the frequencyto which the first H.F. stage istuned.

TECHNICAL SPECIFICATION IN CONDENSED FORMGENERAL DESCRIPTION.-A ten -valve (in-

cluding rectifier) superhet radiogramophonewith automatic record -changer that playseight records continuously, or repeats onerecord indefinitely.

CIRCUIT DETAILS.-V.1-variable-mu H.F.amplifier ; V.2-first detector ; V.3-oscillator ; V.4 and V.5-variable-muintermediate -frequency amplifiers ; V.6-second detector ; V.7-first L.F. stage ;V.8 and V.9-push-pull output valves ;V.10-rectifier.

CONTROL ARRANGEMENTS.-RADIO : Onefor tuning, one for volume, one for tonecontrol, one for local -distant switching,and one four-way switch.

GRAMOPHONE : Main volume control atfront operates on both radio and gramo-phone. In addition, there is a switch tostart the gramophone motor, a three posi-tion switch which enables the instrument tobe used (a) as an ordinary gramophone ;(b) as an automatic record -changer, and(c) for the repetition of one record indefin-itely. A small press -button at the frontenables any record to be rejected.

SPECIAL FEATURES.-(1) High selectivityand astonishing sensitivity on radio side.(2) Effective tone control. (3) Simplicityof operation. (4) Illumination of only theappropriate wave -length scale. (5) Auto-matic record -changer. (6) Superb cabinetwork.

PRICE.-Standard cabinet model, 80 guineas.Special cabinet, 95 guineas.

MAKERS.-The Gramophone Company, Ltd.,363/387, Oxford Street, London, W.1.

57

lv


Every Station Brought In at WillThe radio chassis is ingeniously

mounted on rubber so as- to "givefreedom from microphonic troubles,and is readily accessible for valvereplacements, etc,

The main condenser gang is alsomounted on rubber to ensure that novibration is transmitted to the con-denser fiats. In fact,' the workman-ship everywhere is of an extremelyhigh order and indicative of soundengineering practice.

Practical FeaturesAnother feature which is evident

of considerable forethought is theassembly of the three pilot lamps forilluminating the medium and long -wave scales, and also. the gramophoneindicator. To make replacementseasily possible, these three pilot lampsare assembled on a small panel, whichis instantly removed without dis-connecting any wires.

With regard to the controls, apartfrom the tone control. wavechangeand local distance switches, which ina sense are only subsidiary controls,the radio part of the instrument isoperated by just two knobs, the maintuning control and the volume regu-lator. With these two knobs everystation in Europe worth listening tocan be brought in at will. The scalesfor both medium and long waves arecalibrated in wavelengths, and whenyou want to hear a particular stationyou turn the knob to the appropriatesetting, and if that station is on youhear it.

A COMPLETE HOME ENTERTAINER

The automatic record -changer, seen above, plays eight recordscontinuously or repeats one record indefinitely: The receiveris also equipped with a tone control and " local distant " switch.

Tln local distance switch is a verypractical feature, and cuts down thefull sensitivity to that small fractionsufficient for listening to the localprogrammes in comfort:

Frankly, the sensitivity and selec-tivity 'of this Superlet Ten Auto -Radiogram were absolutely amazing,and the reproduction both on radioand gramophone left nothing to bedesired.

FULLY ACCESSIBLE

The receiver consists of twoseparate chassis, each of whichis mounted on rubber so as to

absorb shocks. There is a filter betweenH.F. and L.F. amplifiers which preventshigh -frequency current from getting into

the L.F. stages.

It is really surprising that suchremarkable results can be achievedwith the retention of one -knob control.

The loudspeaker is, of course, anenergised moving -coil, and sockets areprovided for the connection of anadditional loudspeaker or remote

volume -control.Although the

instrument is com-pletely all -electric,there is no traceof any backgroundhum, or, in fact,any indication thatthe receiver is con-nected to the mainsat all.

The fascinatingrecord - changingmechanism is a joyto use; you just loadup the turntablewith the eightrecords you wish tohear, after whichthere is no need to

go near the instrument until theyhave all been played. Nothing couldbe more delightful !

In so far as externals are concerned,the cabinet work bears evidence

58

everywhere of the finest possiblecraftsmanship. It is made fromspecially picked walnut, built upon asolid pillar framework, and is pro-vided with hand -carved legs. As anarticle of furniture it could not beimproved upon.

In fact, this H.M.Y. receiver is thefinest de -luxe model that it is possibleto obtain, and for sensitivity, selec-tivity and quality it is in a class byitself.

The Gramophone Company are tobe congratulated on the production ofsuch a magnificent design.

s'affig3gmiR000063,0@eNgiEgt,?.00MO & A CABINET FOR THE g

EXPERIMENTER °e6

By J. UTTLEY. 6.6.

O % @OCNDES) @ :,tElatMe,,E;t

NOWADAYS, the experimenter'sboard layout is not permissiblein most houses. On the other

hand, the conventional " cabineted "set does not offer much scope to thosewho like to try out various changesand alterations in their sets.

Faced with this handicap, I madea special form of cabinet which, whilenot offending customary taste, yetgives one every facility for makingrapid alterations.

The size of the cabinet is somewhatlarger than usual and is made solid,i.e. without a lid. It is then cutdiagonally in two, making two partspractically identical, one part formingthe housing of the set and the otherserving merely as a lid.

It will be obvious from the sketch

EASILY BUILT

A slot should be cut at the back of the" lid " to display the terminal strip.

that a set can be built in it with thesame ease as on the conventionalbaseboard and front panel, while theremoval of the back gives immediateaccess for making any later altera-'lions.


mom twol'BETTERRA:

AGAIN we must extend oursincere thanks to innumerablereaders who have proffered

congratulations, and again we mustinsist that grateful though we arefor unoualitled appreciations, weextend an even heartier welcome toconstructive criticisms and sug-gestions.

Our aim is to please all our readersall of the time, and we shall be greatlyassisted in our attempts to achievethat ideal if large numbers of ourreaders will tell us what they want 1

THE COMPILERS.

USING SEVERALLOUDSPEAKERS

THERE are two ways in which anumber of loudspeakers canbe connected. These are

illustrated in the sketch on thisPage. :

When in series the energy from theset goes through each loudspeaker inturn, and when in parallel the energyis offered as many alternative pathsas there are loudspeakers.

The series method is easier forsimple distribution schemes, such asthe connecting up of two or threespeakers in different rooms of a house.

n4'co tttttt ended Mei'hodAnd this is the method we recom-

mend for general home use whereordinary types of loudspeakers areconcerned.

But it cannot always be the bestmethod-radio is never so simple asthat 1

For perfect results every loudspeaker

ought to have its own output valve,but listeners are not likely to adoptsuch measures. And in any case itis not going to be worth while insmall installations.

If two or three of those smallmoving -coil loudspeakers, each with

paralleling of two (or even three)will not drop the value a great dealbelow that required for the bestworking of the power valve.

Normal transformer primaries inparallel might reduce the impedanceseriously and the normal alternative

SERIES AND PARALLEL CONNECTIONS

1

LoupSPEAKERS

/N PARAL LEL

LOUD SPEAKERSN SER/ES

To _SET

To SE rR2964

On the left is a loudspeaker wired up with a loudspeaker unithaving no cabinet or baffle, for the purpose of brightening thehigh notes. The other two sketches illustrate how to join loud-

speakers in series and parallel.

its own input transformer, are to bejoined up together, there is a planof a most attractive nature which canbe adopted, so long as an ordinarypower valve is used.

Each transformer (on the speakers)will have tappings enabling it tobe matched with different valve out-puts.

Join up the transformers in parallel,using the " pentode " tapping ineach instance. The object of doingthis is to prevent the impedance ofthe anode circuit dropping unduly.

The tapping for the pentode willprovide the maximum primary im-pedance, and one hopes that the

of having them in series could easilysend it up unsatisfactorily.

Of course, if the impedances ofloudspeakers or, if they have them,their transformer primaries areknown, it is possible to work outfairly good circuit mnditions for themwith quite ordinary valves.

If a set embodies an outputtransformer for a moving -coil speakerof low resistance, there are two waysof connecting another speaker to it.

It can be joined in either series orparallel with the primary of thetransformer if it has a high resistance(its input transformer primary wind-ing, should it be fitted with such, is

Whether you build your setsor buy them ready-made,you'll always find somequery cropping up regardingmaintenance, installation ormodification. This specialmonthly feature solves allsuch problems for you in anattractive and entertaining

manner.

for our purpose, " high resistance,"as is any loudspeaker not normallyneeding a transformer), or if it is amoving -coil its moving -coil connec-tions can be taken direct to thesecondary of the set's output trans-former in a series relation with theother speaker.

But it should be noted that we donot claim any of these arrangementsto be perfect. On the other hand,there is often little audible effectin departing from the strictest rulesand regulations of output matching I

MAINS UNITSIZES

Tins is a subject upon which wehave already commented inthis section, but it is obvious

that there is still one point whichcauses some confusion of thoughtin the minds of readers.

Many appear to leave it firmlyfixed in their minds that if a mainsunit will not provide sufficient11.T. current for a set, it will in-evitably cause instability, howlingand hum.

Not the Prime CauseShortage of current is not likely

to be the prime cause of suchtroubles.

But the mere fact that it existssuggests, that an attempt is beingmade to use a " small " unit with alarge set. The small unit is notlikely to be smoothed or decoupledenough for a receiver givingcomparatively great amplification.

WHAT EVERY WIRELESS ENTHUSIAST SHOULD KNOW

THE RNYTNAVC BOMP BOMPSiNMOST DANCE ORENE5TRA5'kwE

/WADE Br PLUCKING THE SM/N65OF B/6 F/DLACE5 OR CELLOSNOT Br DRUMS .1

vp-P 17rmospRERicsARE FEWER //YWINTER TIME

',..LARGE

,

trl FIXED cONDENSER5OW Witt 1/040.5.100CKING' k5,...,4,,,,,,,,,,,,,..S 09RG

Ricci r 'iELECTV '1,' ,A-AC/Lir/97E 72-iNiNeppp., EVEN AFTER4111

BZir DO NOT AFFECTTHE SEr.f sELecnv kfRiNs OR

13,977-ER/ES ARE D/SCONNECTE d 2V247

SOME BBC EFFECTS ARE , V WERE S XX5XX RADIO

I PARIS 5XXVIENNA

VIENNA vi ENNAVIENNA VIENNA

iwEcuun4 WE A NNWvif 5 ranoNs FAD.

*MAI AiAvLom6sirmr,44t PIANO

/5 ONE OFelrFTTNE HRROEST

INSTRUMENTS raTRAwy,tivr

59


All About Decoupling and How to Add ItSmoothing and decoupling tend torun directly proportional with sizeand price

Therefore, a mains unit must bechosen for a particular set and notbought haphazardly. And amplemargin should be allowed againstany future greater current demandsthat might be levied on it by achange to a bigger power valve oreven a bigger set !

THE NEED FORDECOUPLING

DECOUPLING is a fairly recentthing, and in view of thismany may well ask whether

it is of really vital value or just apandering to a new knowledge of thetheory of wireless.

Actually, decoupling is often quiteessential, the reason being thatmodern apparatus is so much moreefficient.

Indeed, the amplification achievedby a quite ordinary H.F. stage is

THE VITAL

obviously reside in a component orcomponents common to the two ormore " voltage taps," though inmany modern mains units steps are

EASY TO FIX

Decoupling

ITEMS

Some degree of " decoupling " is to be foundin practically all modern sets.

colossal compared with the resultswhich used to be obtained.

That is why it is supremely desir-ous to prevent any uncontrolled feed-back from the one valve to another.

Beech CouplingOne of the most likely points for

a coupling to exist between thevalves, quite apart from the normalinter -valve transformers (but thesework " forward "-the right direc-tion), is in the H.T. supply.

The anodes of all the valves are

SO SIMPLE!

This simple circuit is fully ex-plained in the accompanying

article.

taken to H.T. and the H.T. Is suppliedby an H.T. battery or mains unit.Batterie, possess internal resistancesand these increase with age in thecase of the types used for H.T.

That resistance can, and oftendoes, act as a coupling resistance.

The coupling in a mains unit will

fitted externally toa set.

taken to provide adequate decoupling.We show a theoretical diagram of

the two decoupling components, aresistance and a fixedcondenser, in circuit.

Their object is toprevent L.F. impulsespawing from theplate of the valve tothe H.T., or vice versa.

The resistance, asits name suggests, isa difficult obstaclefor the impulses topass through, whilethe condenser allowsthem to slip away toearth. This is arather loose descrip-tion, but it is sub-stantially correct.

Decoupling can beadded externally to aset in an H.T. lead(generally the detectorneeds it more than theother valves), and wegive the connectionsin the second dravdng.

For detector andL.F. valves the con-denser should have a

capacity of at least two mfds. andthe resistance be of 25,000 ohms orso. But the resistance need onlybe 600 ohms in the case of H.F.valves.

In serious cases of instabilitycommon H.T. feeds must be avoided.We'll discuss this point in a futureissue, for we have already overrunour allotted space for this particularsubject.

ADDINGSMOOTHING

TT must be admitted that thesmoothing incorporated in somemains units is not particularly

good. We cannot help thinking thatit is the belief of at least a few manu-facturers that the listener will toleratea certain amount of hum.

No doubt some will, but it is ascertain that as many more will not,and it is to these that we now addressourselves.

Isolating R.T.Often the fitting of an output filter

will reduce hum considerably. and inany case it is a rather essential ar-rangement when H.T. is derived fromthe mains, because it isolates the loud-speaker and its leads from the H.T.

We have dealt with the output filterin a recent instalment. But it maybe decidedly advantageous to intro-duce additional smoothing " earlier "in the set.

'Generally, it is the detector valveH.T. feed which demands the addi-tion. The connections are exactly

the same as for adding external de -

coupling, except that an L.F. chokereplaces the resistance : therefore,the second illustration in the lastarticle applies.

This extra smoothing also acts asa decoupler, so it serves two usefulpurposes. We draw our readers'attention to a particular make ofL.F. choke in the photograph.

This make, the R.I. " Audirad."has the attractive feature that itchokes at a high frequency as well asit does at a low frequency.

Stopping II.F.It is well known that a great deal

of interference at times creeps through

WHEN BADSPEAKERS MAY

IMPROVE RESULTS

ALOrDSPEAKER may contributeto a set's selectivity by beinginefficient! Strange though

that may sound, it is perfectly true.Supposing the loudspeaker is very

poor on the high audio frequencies.If the programme to which you oftenlisten suffers from a heterodyne, the

STOPPING THAT HUMMING

Showing how extra smoothing can be inserted between a set anda mains unit.

from the mains in the form of H.F.irregularities, and so the " Audirad "must score over ordinary chokes tosome considerable extent in some con-ditions.

It is advisable to enclose the chokeand condenser in a small wooden boxand, naturally, the connections haveto be carried out with insulated wireand made carefully.

If there is room to accommodatethe components inside the set, thisshould be done.

Ordinary shielding is not usuallyvery effective for stopping mainshum, and certainly it is waste of timeexperimenting with small partitionshields, such as are often quiteeffective for preventing H.F. fieldsfrom inducing currents in com-ponents or wiring.

We have encountered hum whichhas been generated by a mains com-ponent feeding into an H.F. choke.This has been cured by using a resist-ance instead of the H.F. choke in thedetector circuit.

THAT OPENDOOR

TN the winter time doors areI mostly kept closed, but when

rooms get stuffy they may beopen for periods.

A 'door can at times have a con-siderable effect on the operation of aloudspeaker. The reason is plain tosee.

Removing ReflectionThe walls of a room largely affect

its acoustic properties, and the doorof the average -sized living -roomconstitutes quite a large proportionof the surface of one wall.

And there are reflective as well asabsorbent effects to bear in mind.If a loudspeaker is directed at adoor, the plain wooden surface ofthis may cause considerable reflection.Obviously, this ceases when the dooris opened.

Bear these points in mind if yousuddenly notice a change in thequality of your loudspeaker-it maybe that door.

loudspeaker will render it faintly or,perhaps, not at all !

On the other hand, many loud-speakers are deficient in the bass.

BASS DESERTION

A small baffle of this kind isalmost useless in preserving

the bass.

But the application of reaction em-phasises bass notes unduly.

Righting WrongsThe " bass -less " loudspeaker pro-

vides compensation and the " over-all " results are much better thanthey would otherwise have been.

Of course, it is not always thatone fault will tend to cancel outanother like that, but quite frequently" two wrongs do make a right," andat any rate produce something nearerto " rightness " than would other-wise be possible without elaborateand expensive measures being taken.

USE A FUSE

FUSES are as necessary to elec-trical engineering as light isto a lighthouse. Radio re-

ception is a branch of electricalengineering, but it is not usually

60


Another Instalment of Better Radio Next Monthconcerned with very high voltages orlarge currents.

Nevertheless, the current used inany set, mains or battery, will causedamage if it is not confined to itslegitimate paths. For example, ifthe H.T. is applied to the filamentof a battery valve it will burn it out.

SAVING THE CELLSLE/40 STRIP

52965

It is suggested that there shouldalways be an accumulator fuse.

That fact is well known. But wewonder if it is realised that a tinytwo -volt L.T. accumulator is capableof doing much greater damage ?

Extremely heavy current can bedrawn from the smallest of accumu-lators-enough current to melt acopper wire if It is " shorted " acrossthe terminals.

L.T. DangersThat is bad for the accumulator,

but if it had a celluloid case or thered-hot metal fell on to some otherinflammable material- !

Therefore, if the listener is liableto experiment with his set, or if the

THE RIGHT PLACE

The correct place in the circuitto insert an H.T. fuse.

L.T. accumulator is, of necessity,rather exposed in its position, wewould advise him to fit an L.T. fuse.

A half -ampere wire fuse will beneeded for the average battery set.Not a flash -lamp type of fuse ; thatwould be no good as its resistancewould cause a voltage drop.

AND THE G.B. ?

Some G.B. battery voltages arenearly as high as small H.T.'s1

On the other hand, the flash -lamptype of fuse is perfectly satisfactoryin an H.T. circuit and is widely used.

Double -Duty FusesBut it should be noted that one

fuse in the negative H.T. supplylead does not provide complete pro-tection. There may be a consider-able voltage difference between H.T.positive leads.

However, it will give pretty com-plete safeguarding to the valvefilaments, and it is these which arethe most delicate items in most sets.

In large receivers the grid biasmay attain the dimensions of a smallH.T. battery, and the experimentermay well ask himself whether itmight be advisable to insert a fuseto guard against short circuits from it.

Actually, the fuse used to guardagainst the H.T. can be made tooffer protection against grid -biasshort circuits as well.

The fuse must be connected up asshown in the illustration-that is,between the H.T. minus and theL.T. minus.

The grid -bias positive connectionIs then taken to the H.T. minus ter-minal instead of to the L.T. minus orone of the points in direct connectionwith it.

With this circuit arrangement andproviding the fuse is trustworthy(important point, that), the valvefilaments will be protected againstboth H.T. and G.B.

TESTINGACCUMULATORS

you must never- test an accumu-lator on "open circuit," oryou may get misleading read-

ings. It should always be tested on" load "-that is to say, when it isactually connected up to the set andthe set is switched on.

The battery ought to be tested atweekly intervals at least, although itthere is any doubt about its capacity,tests should be made even more fre-quently.

It is a good plan to keep a " log "for an accumulator in which thedates of charging and testing are

ANOTHER KIND OF " S.G." !

The advisability of testing for specific gravityof the acid is often not realised.

noted, together with the appropriatevoltages and specific gravities.

The voltage must never be allowedto drop below 1'8 volts per cell. (Im-mediately after a charge the voltagemay rise to 2'5 volts, but there is arapid drop until about 2 volts isreached, after which the voltageremains fairly constant for a com-paratively long time.)

The Acid TestBut a voltage test is not a complete

test; the specific gravity of the acidought also to be tested, especially ifthe capabilities of the charging stationare at all questionable. (Many ofthese seldom, if ever, test acid,and so often let the batteries in theircare gradually deteriorate.)

When an accumulator cell is dis-charged the " B.G." of its acid willdrop to between 1 and 1.15, and aftercharging it will rise to 1.225 or higher.

The correct figures for a particularbattery will be supplied by the makersand are, indeed, nearly always printedon a label on the battery itself.

They vary with different makes toa little extent, and needless to saythese and any other instructionswhich may be given should be closelyadhered to. The lives of manyaccumulators are greatly shortened

because their users fail to carry outthe simple servicing necessary.

But servicing does not end withvoltage and specific gravity tests.Careful watch should be kept overthe condition of the plates.

At the first sign of sulphation expertattention is desirable. And if aquantity of sediment collects, itshould be cleaned out.

Also, the terminals must be keptclean and completely free fromcorrosion.

CUTTING OUTHETERODYNE

WHISTLESWE have already pointed out

that heterodyne whistles are" sometimes lost in inefficient

loudspeakers. At the same time onehopes one's speaker is not in thatclass, for it is not every programmethat is marred by such interference.

It is possible to obtain heterodynefilters which can be cut in or outof action, as desired.

A quite simple method of eliminat-ing heterodynes Is to connect afixed condenser across the secondaryof an L.F. transformer in the set ifone is used. The condenser mayneed to have a capacity of as muchas *005 or even '01 mfd. in cases I

Tone ControlOf course, this is a drastic measure,

and many high notes fall by thewayside as well as the heterodynewhistle. But it is not easy to cutthis out without doing that.

It can be done with elaboratetuned filters in such a way that

even higher notesare not seriously cutdown, but suchschemes are notwithin the province ofthe average listener.

We rather inclineto the use of conven-tional tone controls,for these provide aneasy means of adjust-ing the conditions ofaccentuated or re-duced high or lownotes, and thus per-mit the heterodynesand " monkey chat-ter " to be nipped offat will, though, ofcourse, legitimatehigh notes have to goas well.

However, they canbe brought back atonce when desired.

Heterodyne whistles can sometimesbe cut off ltty a skilful adjustment ofreaction. The more reaction youapply in a set, the more, generallyspeaking, are the high notes reduced.

Very often the selectivity controlcan be operated to sharpen tuningand reduce volume, the latter thenbeing restored by reaction. Thisgenerally gives a considerable reduc-tion of heterodyne interference, theoverall effect being to vary the highnote response within fairly wide limits.

TONEVALUES

In the previous article we referredto the use of tone controls foreliminating hererodyno whistles.

We are all in favour of applyingtone adjustments of this nature.But we do not consider tone controlshould be allowed to develop into akind of music mangle with whichindividual listeners would be expectedto mess about with their audio -frequency spectrums until they gotsounds which pleased their individualears.

The aim should merely be tomake a set give the closest approxi-mation to " straight-line " resultspossible in all conditions.

We believe it to be against theinterests of good listening to temptlisteners to sharpen or mellow par-ticular items.

MISLEADINGMETERS

ACHEAP, low resistance volt-meter may give very mislead-ing readings at times. You

see, when it is connected in circuitits own resistance may upset thecharacteristics of the circuit it isbeing used in connection with.

Particularly is this so when anattempt is made to measure theoutput voltages of a mains unit. Avery high resistance voltmeter isneeded for that.

A "CLOSED" CIRCUIT

The resistance of a voltmetermay affect its readings.

With a low resistance voltmeterthe readings will be much lower thanthey should.

As au alternative to a high -resist-ance voltmeter, which is an expen-sive instrument, mains unit outputscan be measured with milliammeters-

If it is remembered that theamount of current a valve will passdepends upon the voltage on itsanode and the grid bias used, itwill be seen that it is a simple matterto employ the valve -maker's charac-teristic curves to provide the infor-mation desired with the assistance ofa milliammeter.

A FEW GENERAL TIPSARRpNeE .SNAP 2.TSwiraiesro

PRESS Down,FOR "Qff#

Az wgrs 57-RNoRA, AccemiuzgroR

RuseER,C,,ovp,OR RA/LO /11RGRZ/NE

NT 'GLOWZEROS ro GETK/NKEO OR roBE

STRR/NED

.00/Vi" use ori &Amesavir iv/7w R Ale rgz

PRETES SE T unaess YOuRRE/ Siax's ro De so

61


-RECENTRECORD

RELEASES

BROADCASTANOTHER year has come, but still the same flood

of gramophone records continues. Isn'tit marvellous how the various companies

keep it up ? Some twenty to thirty fresh discshave been brought out by Broadcast, and good-ness knows how many by the other gramophoneconcerns.

As a mere one person I can but relate how thevarious records react on me In the hope that itwill be a useful guide to you when you decideto visit your local dealer. My opinion may notbe yours, for there is no accounting for tastes.However, here goes. This is what I think of thevarious Broadcasts that have been placed beforeme for review and description.

Taking them at random, I start with The ThreeGinx singing The Old Man of the Mountain andWhile We Danced at the Mardi Gras (on 3265).The first is quite a lively item artistically sungby this harmonious trio, but it would be betterfor more careful diction. Still, the effect is pleasingand the rhythm is good, especially where thepiano takes up the melody. The second numberis a waltz, and is quite tuneful without beingoutstanding in any way. The vocal solo partcould be better, and should not be so disjointed.

From this let us go on to the dance orchestrarecording on 8105 of When Mother Played theOrgan and What Would Happen to Me ? byJoe Green's Band. The former is a semi -sicklywaltz of the old Victorian -memory style, the mostrelieving part being the introduction of a Hawaiianguitar towards the end. The other tune is verymuch better, and at times is almost snappy,though the trumpets could be brighter withad vantage.

Keep Your Last Good -night For Me and BigBen Saying Good -night are the two items chosenfor 3270 by The Blue Mountaineers. This is agood band, and I am always ready to listen torecords it has made. In this case the latter tuneis a bit monotonous, but that is not the fault ofthe band but the composer, and it will appeal tomany though the words are not particularlyclever. The former is a sugary foxtrot that iswell played'. If colia be 'improved by betterorchestration.

Strange Harmony and When the Stars WereShining, both from La Tosca, and ,sung byJosef Schmidt on B101, are worth hearingHe is- said to be very popular on the Continent.and has often broadcast from Berlin. He takes -thelatter record too slowly for my liking, and I muchprefer it in Italian rather than German, withmore dramatic rendering, but there is no gain-saying the fact that it is a good record in manyrespects. I am looking forward to the nextSchmidt recording.

The Blue Danube will always be a favourite,and played by- Eugene's Magyar Tzigane Bandwe get something of the true gipsy element inIts rendering, though it may not exactly fit inwith the general pnblic's conceptions of thewaltz Accompanying this on 3271 is The Skaters'Waltz, which will also Meet With approbation, Iimagine.

So 'much for the " twelves " this month. Hereare some of the smaller Broadcasts which are worthmentioning. Charlie Higgins is still going strong,this time in When I Was Twenty-one and With MeBagful of Nuts and Some Sweets in Me Mouth on918. Both are cheerful records that will helpmany of us these tiresome days.

The Rhythm Rascals are as good as ever in acouple of dance discs, 923 and 924, containingWe're a Couple of Soldiers and Marching AlongTogether on one, and We Just Couldn't Say Good-bye and Say It Isn't So on the other. The lattertwo numbers need no introduction they areamong the most popular of present-day dancetunes, while the former of the other two men-tioned bids fair to become one of the best-sellers.They are well played, and at the low price of ls.it is difficult to conceive a better bargain.

I must lust dodge back to a couple more of thelarge Broadcasts, this time to complete the" Internationals," of which the record of JosefSchmidt is one. The two I want to put before youare B102 and BI04, containing respectivelyAlfred Bere's Orchestra playing Famous Waltzesof the World and Ralph Kirberry and His Orchestraplaying Love Me To -night and Isn't it Romanticfrom the latest Chevalier film. I refrain fromcriticism here as I want you to hear them andchoose for yourself with an unbiassed mind.You may or may not like them according to yourtaste in what goes to make a good record.

COLUMBIAThe nominal Christmas season is over, but I

fancy a great many of my readers have not yetthrown off the pantomime spirit, and so referenceto a record that came out too late to be includedlast month, Crazy Pantomime, will not be wasted.

This is the second of the famous Columbia onParade records, the first being issued a year ago,and is No. DX410. It is really excellent, and isanother all-star entertainment, but conceivedon quite different lines from the first. The storyis that of Cinderella, but hotted -up in a fashionthat allows Flanagan and Allen, Peggy Wood,Harry Tate, Norman Long, Biotite and SonnieHale, Stanley Holloway, Naunton Wayne, Billy

A brief selection fromsome of the records re-leased during the month.Only a few are discussed,but they are representativeof the many brought outby the various gramophone

record companies.

Leonard and Debroy Somers and His Bandplenty of scope, of which they take full advantage.The fact that the story, as we know it, is sadlytwisted makes no difference, for it is a crazypanto, and the efforts of Flanagan and Allento announce, stage-manage, change scenery andthe like keeps the pot boiling furiously throughout.You will like this record, and after you haveheard it once or twice you will like it more, forthere is plenty to, take in, and the finer pointsand subtleties are not, always realised at one ortwo hearings.

Another sure laughter -raiser is the Roostersrecord The Village Concert on DX390. It is broadhumour, but the poor village vicar will always bethe butt of stage and film, and here, again, plentyof capital is made over his idiosyncrasies. Thisrecord will go well.

Arthur Prince, the ventriloquist, and his boyJim are probably the best known of all thehundreds who go M for this ever -fascinating typeof entertainment. They are certainly unsurpassedas a clean, happy and, above all, clever recordduo. Insubordination is the title of their disc,and I must say it appeals to me very much indeed.

The opposite must be said about Old Jim'sChristmas Hymn, which, to my mind, savoursmore of sheer sob -stuff rather than pure pathos.You feel that ordinary tears are not to be deemedsufficient, and that they must be supplementedwith plenty of the real Hollywood glycerine beforethe recording staff will be satisfied that their jobhas been well done. The number of this sea ofslop is DB954.

ruly-Fousand Quid and The Stillness of theNight (DB978) are two Norman Long typicals.They are both good, though they are not a bitalike in subject. The former is true in its senti-

ments, while the latter is a light song of thecynical variety. I enjoyed both.

Albert Sandler can be relied upon to make agood record, and the latest is no exception to therule. I like both sides of DB971 and think youwill, too. The titles are well known, You LovingMe and Marcheta.

Christopher Stone referred on the radio toAccordeon Nights as interminable, meaning,I suppose, that the series of records bearing thattitle appears to be everlasting, for DB983 containsParts 9 and 10 of this small library (by Gerald°and His Accordeon Band). Let them go on, say I,for they are both tuneful and excellently recorded.I am not going to tell you what is on this discyou must hear it for yourself, and hearing willmost likely mean purchasing, for it is very good.

Mr. Flotsam and Mr. Jetsam are not so good asusual in Down With Dora and The Spooning of theKnife and Fork. The ideas are -good in eachinstance, but the vocal balance seems to be not sogood as usual; and baying set such a highstandard we are prone to expect it to be keptup. (DB973.)

To be serious once more, or, rather, to turn to arecord with a serious aspect, we must pick upDX419. ' This contains -the famous Te DeumLaudanius, subg by 10,000 voices at the,MethodistUnion Conference at the Royal Albert Hall.It is a pity that it is taken so slowly, but probablythat is unavoidable where -such a large gatheringhaS to'follow the organ. The recording is excellentand the record is full of majesty.

Mr. Jetsam, or Malcolm McEachern, rolls aboutdown in the depths on DX417. He sings TheSong of the Volga Boatmen and The Mighty Deep.I prefer the latter, for Jetsam has too much tolive up to in Chaliapin's " Volga Boatmen " tobe able to get away with it as he sings it in therecord under review. His diction is never goodat the best of times, and slovenly singing ruins asong of that description faster than it doesthe ordinary sort of hail -fellow ballad.

And talking of diction reminds me of the finestdance -band vocal singing from a clarity point ofview I have ever heard. The singer is, I believe,Val Hosing, and the band Henry Hall's B.B.C.Dance Orchestra.

The fact that the record is really intended forkiddies may account somewhat for the exception-ally good pronunciation by the vocalist, butwhatever the cause, the disc is a real tonic toany who deplores the tendency of many moderndance -band singers to be audible but inarticulate.The numbers are The Teddy Bears' Picnic andHush, Hush, Hush, Here Comes the Bogey Man,and the catalogue number is DB955. You shouldnot miss this ; it is tuneful and the recording is,as the singing, well-nigh perfect.

I have no room to go fully into the other recordsI have received from this Company, but adviseyou not to miss hearing Nos. DX418 and 385.The first is a Layton and Johnstone Negro SpiritualMedley, with fine singing by fine artistes, and theother is a lively Convivial Medley by DebroySomers' Band.

H.M.V.There are several specially fine records in the

latest batch of H.M.V.'s, and one of them is beingplayed by my radiogramophone as I write. Irefer to that made by Richard Crooks and issuedshortly before Christmas. It contains The Starof Bethlehem and The Holy City on a red labeltwelve -inch disc. The recording is excellent andRichard Crooks' voice rings out with a fullnesstoo often missing from recordings of tenor vocalists.Whether you like sacred music or not, and despitethe fact that Christmas has passed now, you shouldget this disc. It is a record that will give endlesspleasure. (DB1798.)

Then we come to another red label twelve-incher, made by the B.B.C. Symphony Orchestraassisted by the organ on one side, and alone onthe other. The record contains Elgar's Pomp andCircumstance Marches No. I in D major (containingthe famous " Land of Hope and Glory ") andNo. 2 in A minor.

The recording itself Is perfect in both, and therecord makes a most dramatic example of thepower of the radiogramophone. The drums andthe brass instruments in the latter number of therecord are especially well brought out. Again Iadvise you to get the disc ; it will be a revelationin good " canned " music. The orchestra is underthe direction of the composer, so that we mayrest assured that the interpretation is just right.Sir Edward Eiger has passed his 75th birthday,and may rightly be regarded as the grand old manof British music. (DB1801.) He is now writinga Symphony dedicated to the B.B.C.

Of lighter calibre is the Snacks in Bars, which isthe title chosen by the New Mayfair Orchestrafor disc No. C2486. It is described as a supermedley, which it undoubtedly is, for it ranges allover the place among popular airs of merelytheatrical to classical style. I do not knowwhether H.M.V. are prepared to send lists of thetunes incorporated in the record, but if so ft wouldmake an excellent competition test. I cannotcall to mind the names of all the pieces, thoughtheir airs are well enough known to me.

(Continued on page 100)02


I

ADCASTINGDIARY

Studio OrganisationHAVE been bearing about a development of R.B.C.organisation which is particularly interesting. Aftera period of investigation and experiment, it has been

decided to appoint a studio manager who will function inthe satire way as a night editor in a newspaper office.

The idea arose from a consciousness that a great manylittle errors could be prevented by the presence of aproperly qualified and sufficiently senior co-ordinatingofficial. The scheme has now been applied, and alreadythe programmes have benefitted.

Television DevelopmentThere is renewed activity on the television front.

Mr. Isidore Ostrer, the head of the British Ga.nmontgroup, who is now in control of the Baird Company, ispressing forward both in research and in the productionof receivers. Simultaneously electrical musical industriesare launching a new method of television on ultra shortwaves with what is believed to be the cathode - rayprinciple.

There is no immediate competition for the reason thatthe latter process is still concentrated on the reproductionof films, whereas the former still speeialises on directtransmission of images on middle wavelength channels.

Trouble in ScotlandAgain there is trouble in Scotland, whence come

rumours of discontent and ructions. The difficulty thistime, however, is internal and not external.

Mr. Cleghorn Thomson, the ambitious and versatiledirector of the B.B.C. work in Scotland, has managed toacquire for himself and his staff a large measure ofindependence and initiative. He has gathered roundhim a little group of young and talented men and women,most of whom are in sympathy with Scottish Nationalism,either on the artistic or the political side.

The exercise of this " new freedom " is bound now andthen to lead to differences of opinion with the B.B.C.headquarters in London. The most serious of these sofar appears now to be in progress.

London officials, both singly and in groups, are visitingEdinburgh almost weekly when previously they wentabout once a year. There is danger of a public explosionwhich certainly would play into the hands of thoselisteners, particularly in the Highlands, who are discon-tented with the present service provided by the B.B.C.

Our Own Broadcasting Correspondent keeps acritical eye on the affairs of the B.B.C., and eachmonth, for the benefit of listeners, comments franklyand impartially on the policies and personalities

controlling British broadcasting.

More AnnouncersIt is understood that the B.B.C. has decided to

strengthen its corps of announcers at Broadcasting House.The strain on the comparatively few announcers formerlyemployed is believed to have prejudiced their efficiency.

The report now is that several more permanentannouncers will be added, and the individual task lightenedto that degree.

B.B.C. and Overseas PressHaving solved the main problems of copyright and

performing rights connected with the Empire BroadcastingService, the B.B.C. is now faced with a new difficulty.This arises from the attempt to prevent Overseas news-papers from reproducing programme details a whole weekin advance.

The B.B.0 apparently hoped to retain this copyrightfor one of its own publications. The reply of the Empire

RADIO AS A RELAXATION

Quite a lot depends upon Roosevelt who recently " won out " inthe U.S.A. election, and he in turn depends quite a lot on his

radio-and his cards-when not engaged in strenuous duties.

newspapers, in particular the weeklies, is that if anysuch restriction is imposed, they will boycott all referencesto the Empire Broadcasting Service.

63


Candid Comments on Radio Topics of the DayMy hope is that the B.B.C. will give way, recognising

that it will need all possible publicity to carry the EmpireService to a lasting success.

Wireless Exchanges in Crown ColoniesThe Empire Broadcasting Service has created an

opportunity for the development of wireless exchanges ina great new field. Many of the Crown Colonies have nobroadcasting of their own and therefore cannot relay theEmpire Service. Also, conditions of direct reception onshort-wave sets are extremely difficult in several of themore thickly populated tropical areas.

It is therefore logical to conclude that in these placeslocal distribution by wireless exchanges is easily thebest method. I understand that a big syndicate is beingformed to deal with the situation on a comprehensive scale.

More Money for BroadcastingThere is good reason for believing that Sir John Reith

has done very well for the B.B.C. in his new deal with theP.M.G. and the Treasury over the distribution of licencerevenue. Negotiations lasting nearly a year have cometo an end in a sense highly satisfactory to the broadcastingauthorities., Details are still secret, but there is no doubt that theB.B.C. will get a new arrangement allowing it moremoney and on a more permanent basis than at present.

The News BulletinThe reorganisation of the B.B.C. News and Topicality

Talks, which I forecast some months ago, is now takingshape. Additional staff has been acquired, and the NewsDepartment given more independence and resources.This is a decided advance.

BRESLAU'S BIG BROADCASTER

A close-up inside the great 6o -kw. Breslau station which is nowgetting over extremely well on 253 metres. It uses a new tele-

funken type of "non -fading aerial."

The only anxiety remaining is that news will retain itsindependence and avoid submergence in the main body oftalks. Incidentally, the disappearance of the provincialnews bulletins is greatly regretted by Regional listeners,

A RADIO TELEPHONE CONVERSATION

In simulating someone speaking over the telephone, a special mikeand earpiece are employed, the latter being held close to the

microphone. A most realistic effect is obtained in this way.

amongst whom an agitation has begun for its restorationon an extended scale.

Ultra Short -Wave WorkInteresting results are being obtained from the ultra

short-wave experiments which are taking place from thetop of Broadcasting House. These are 'concerned withmuch more than television.

Although it is early days yet to speak with certainty,I have a feeling that these experiments will lead to bigchanges in the whole system of national distribution,solving, in particular, the vexed problem of how to dealadequately with local interests.

Visitors at Broadcasting HouseThere is no slackening in the popularity of Broadcasting

House as one of London's show places. Royalty has beenwell represented, Prince George being the latest memberof the Royal Family to be reported as a visitor to B.H.Distinguished men and women clamour for admission, andit is a matter of no little embarrassment to the staff ofB.H. to gratify their wish.

The difficulty is not made any easier of solution by thediscovery that the regularly organised tours of thebuilding have been interfering with studio work.

Removal of TelevisionProblems of congestion are already beginning to arise

at Broadcasting House which have prompted the B.B.C.to consider seriously how best to accommodate its tele-vision activities.

The suggestion has been made that television shouldbe conducted at some suitable place outside the B.B.C.Headquarters in Portland Place. It is understood thata search is now being made.

64


Goltone H.F. Coupling UnitTHE screening and compactness

afforded in the Goltone H.F.Coupling Unit make it a most

attractive article. It is approximatelythe size and form of a screened coil,and contains a high -efficiency H.F.

FOUR IN ONE !

This Goltone unit contains four componentsin a shielding "can."

choke, a decoup-ling resistancea n d condenser,and a couplingcondenser. Ascreened anodeconnector is takenthrough the topof the " can."

The unit is welldesigned and con-structed both asto its componentparts and as awhole. In addi-tion to the

increased efficiency and freedomfrom coupling troubles which mayreasonably be anticipated from itsuse, it should be noted that its price,9s., is such that the individual com-ponents could hardly be purchased ascheaply separately. A further gainis the simplifica-tion of wiringthat results.

We have alsohad the opportun-ity of testingfurther samples ofthe new GoltoneH.F. choke, whichachieves a high inductance andlow self -capacitythrough theemployment ofspecial methodsof construction.We find them tobe perfectly satis-factory in everyway.

Our comments regarding someinteresting new components.

A Heayberd Mains UnitIt is not a coincidence that one of

the new Heayberd mains units isstyled the M.W.1. It is cataloguedas such as a graceful tribute tothe MODERN WIRELESS Research

SMALL SIZES-LARGE INDUCTANCE

New Bulgin H.F. chokes having outstanding characteristics.

A COMPLIMENT FOR M.W."

A magnificent Heaybea rd mains unit, known as the M.W.1and designed in accordance with a suggestion from the " M.W.'

Research Dept.

Department, to whose suggestions itmainly owes its existence.

Its special feature is that it has analternative output switch whichenables it to operate to full efficiencywith either a battery set or in con-junction with an A.C. receiver.

Obviously this adaptability is ex-tremely valuable. Many, perhaps amajority of A.C. mains users, starttheir mains set experiences by runningmains H.T. for a battery set. Butwhen they come to change over toA.C. valves they discover that a unitwhich may be adequate for batteryvalves is not likely to prove suitablefor running A.C. ones to advantage.

65


Observations on Some Interesting Components

The lieayberd M.W.1. is perfect forboth tasks.

It has three tappings, including awidely variable one, and its maxi-mums are 150 volts, 30 milliamps. (forbattery sets), and 200 volts, 50 milli -amps. (for A.C. sets). Its smoothingis first-class, and hum does not creep

AN EFFICIENT COMPONENT

A Slektun H.F. choke for the short waves.

through from it even with the mostsensitive of sets.

Its construction is robust, and itmeticulously conforms with theI.E.E. and other recommendations.We can unhesitatingly recommendit to the attention of the keenestconstructor or to any set possessorwishing to take power from A.C.mains.

FROM BOTH SIDES

A photo of the Sound Sales transformer taken in front of amirror.

Bulgin H.F. ChokesA. F. Bulgin & Co. have produced a

striking range of screened H.F.chokes. They are all of unusualsmallness, and must rank as amongthe neatest radio apparatus of theseason.

But despite their dimensions, orperhaps we should have said in addi-tion to them because compactness is initself an advantage in almost anyradio component, these Bulgin chokeshave outstanding characteristics. TheH.F.8, which sells at only 2s. as ageneral purpose choke, has an in-ductance of no less than 198,000microhenries and a self -capacity ofabout 3.5 mfd.

The H.F.9 lists at 3s. 6d., and withits 250,000 henries, and even lowerself -capacity, it can undertake practi-cally any duty in a set, includingthat of S.G. inter -valve coupling.

The H.F.10 has twice the induct-ance of the H.F.9 and only about halfits self -capacity. Retailing at 5s. 6d.,it is a super -choke in every sense ofthe word.

On test these chokes gave per-formances fully up to what theirspecifications promise.

Slektun Short -Wave ChokeShort-wave enthusiasts should bear

in mind the Slektun short-wavechoke when selecting componentsfor their sets and adaptors. It is awell -made and highly efficient com-ponent. It is wound sectionally,and its two terminals are widelyspaced, one being at the bottomand the other at the top. Thebottom one is inclined outwards to

facilitate connec-tions to it.

We used one ofthese Slekt-unAloft- wav e chokesin a set coveringthe wide wavebandof from about 12to 100 metres (withcoil changes), andno difficulties dueto " choking " ofany kind were

.experienced.

Sound SalesTransformerThe Sound Sales

H.8 Super -ShieldedMains Transformerembodies an66

ingenious and useful feature. Unlikeany other transformer which has cometo our attention, it has a fuse, andthis is held in any one of three pairsof clips in accordance with the mainsvoltage with which the transformeris to be used.

BELLING -LEE TWINTAPS

The Twintap enables two wander -plugs tobe accommodated in one socket.

The three clips correspond with210, 230 and 250 volts. These areuseful figures, and the 230 is, ofcourse, the voltage at which thegrid scheme is being standardised.

SMOOTH AND CERTAIN

The Lissen potentiometer volume -control

Although the transformer is verycompact in construction, its per-formance is above the average.Indeed, its voltage regulation issuperior to all but a mere one or twoof the many which we have testedduring the past year or so.

We should certainly advise con-structors to acquire full details of theSound Sales productions.


January 1933 MODERN WIRELESS

The Banished Audience-Neu) Play Technique-A Hint on Manners-What's in a Name ?-This Copyright Business.

Applause on TapHE B.B.C. has had a great deal to

say in its 1933 Yearbook aboutthe uninformed and irrespon-

sible criticism of the Press. On thesubject of studio audiences, however,most of the critics and many of theB.B.C.'s own artistes have been incomplete agreement.

Some of these audiences have be-haved, during recent months, in suchan extraordinary way that it has beenseriously suggested that the applausein vaudeville programmes was sup-plied by a gramophone record, oper-.ated at will by the producer.

Be that as it may, I am glad to seethat the B.B.C. has so far deferred topublic opinion as to try the experi-ment of. abolishing applause in allprogrammes by staff producers.

It is a bit early yet to give an" informed and constructive criti-cism" on this very sensible departure-but I should like to know what youthink about it.

Radio and Orange BlossomThe merry month of May seems to

have been transferred to the frosts ofDecember, judging by the number ofradio romances last month.

The most interesting, of course, wasthe engagement of Harold Warrenderand Ann Todd. This has a very specialradio connection, since Louis Goodrich-well known as a wireless playwright-seems to have played the part offairy godfather.

Do you remember his play, Annand Harold," and its sequel, " MoreAbout Ann and Harold " ? Well,Louis Goodrich told me the other daythat, having been responsible for in-troducing Mr. Warrender and Miss

Todd, he wrote those plays especiallyfor these two talented artistes.

It is so rarely that " make-believe "romances come true that we are extrahearty in wishing Ann and Harold "every happiness.

True To His ReputationJohn Tilley, whom I always

consider as my special discovery,is a participant in radio's otherromance.

True to his reputation of drollhumour, John Tilley has solemnlyannounced that he proposed to MissKathleen More in a taxi ! The worst

RADIO RACONTEUR'SROMANCE

Mr. John Tilley, who sprang into fameovernight after a broadcast of one of his" mock " lectures, with his fiancée, MissKathleen More, to whom he proposed in

a taxi

of being a popular radio and stagestar is that it leaves so little time forthe lighter side of life.

So here's all the best to Mr. Tilleyand Miss More-with the pious hopethat he may keep his lectures for stageand microphone !

67

A Pretty Problem Indeed !Here's a pretty problem for one of

you to solve. Why it is that Christo-pher Stone, with the aid of an albumof gramophone records, can producevariety programmes which are sovery much better than studio produc-tions ?

It's no good your saying that hehas a much wider range of artistes tochoose from, because the majority ofhis lighter programmes contain recordsby the same people whom we arealways hearing in the studio.

And another thing-records seemto " get over " so much better thanthe real thing ; much clearer andaltogether better in tone. For this Ican find no excuse.

Can it be that Christopher Stoneknows something of public entertain-ment, and knows, too, how to put itover ? I hardly dare to make thesuggestion when I think of thetalented young University men whohave charge of the programmes-butthere it is !

As an afterthought, I never seemto have heard a complaint thatChristopher Stone's variety pro-grammes suffer through lack of ap-plause. Queer, isn't it ?

Where Are The Playwrights ?At quite regular intervals I bewail

the fact that new names so rarelyappear underneath the titles of radioplays. At the present moment I canthink of only six playwrights whosework is worthy of attention in thefield of radio drama.

Louis Goodrich, du Garde Peach,Dulcima Glasby and Philip Wade arefour of them-the other two you canfill in for yourselves I

MODERN WIRELESS janualy, 1933

Dance Bands That Fail to AmusePhilip Wade's last play, inciden-

tally (" Family Tree " it was called),was not only well up to his usual standard, but also introduced quite anew piece of technique-the readingby a principal character of entries in adiary taking the place of the usualcommentator between the scenes.

The secret of the success of thesefew playwrights is, of course, that theywrite about ordinary people who doordinary things in an ordinary way.

Some time, ago a play called "Water-loo " was broadcast, and opened up anew line in radio play construction ;the re-creation of the past.

The play was not too well handledon that occasion by the producer-but that is no reason why the experi-ment should not be repeated to ourentire satisfaction.

retort that I do know bad mannerswhen I meet 'em.)

Don't you often sigh for the dayswhen announcers were so very apolo-getic if things went wrong, and MissCecil Dixon was always ready to fillup the awkward pauses with pianomusic ? Or do you prefer thedeath -like " tick-tock " which isour present reward for patientlistening ?

Those Dance BandsIt is always a popular move when

some famous dance band comes tothe studio during the early part ofthe evening programme. But I doimplore the B.B.C. to show a littlediscrimination.

In the Programmes4.-PHILIP WADE

Philip Wade, radio dramatist and actor,aged 36. Born at St. Annes-on-Sea,Lancashire ; educated at Arnold HouseSchool, Blackpool, and the United College,Bradford.

Served in Mesopotamia as an officerwith the 6th Batt. Loyal N. Lancs.Regiment.

Began his acting education in 1919under Sir Frank Benson, in whose com-pany he later met his wife, Alice de Grey.

First broadcast a small part in aHoward Rose production in 1925, and

My Little GrumbleI am afraid that my little grumble

against the B.B.C. this month israther a big one-breach of promise,in fact !

I wonder how many of you can-celled appointments, as I did, to hearEvelyn Waugh in the " UnnamedListener " series ? And again thefollowing week to hear his father'sreply.

Actually neither of the Waughscame to the studio ; this was disap-pointing. Their talks were read forthem ; this was a pity. The B.B.C.offered no explanation or apology ;this was an insult to listeners.

Accidents will happen, even in thebest regulated families. But theB.B.C. will never win the respect andthe admiration of licence -holders solong as it pursues a policy of puerileself-righteousness.

(Yes, Mr. Yearbook Editor, youmay call me irresponsible ; you maysay that my criticism is destructiveand of no help to the B.B.C. But I

A certain band-which out of thekindness of my heart I will not name-was almost unbearable recently fortwo reasons.

First its announcer had a voicelike a very mournful parrot; and,secondly, it considered that the non -dancing listener could be entertainedby what are known, I believe, as" comedy numbers." But what thereis of comedy in a number of bands-men indulging in unmusical back-chat, I fail to see.

This Modesty BusinessThere is a very funny rule at the

B.B.C.-I have mentioned it before-which says that members of the staffshall remain anonymous, so far asthe listening public is concerned.

The rule, for some extraordinaryreason, seems to apply to announcers,engineers and paragraphists in the" Radio Times," but not to pro-ducers, orchestra conductors, actorsor staff playwrights.

68

Unfortunately the situation is com-plicated by the extreme modesty ofcertain members of the staff.

When you were enjoying the recent" Communications " pr ogr a mme,weren't you annoyed that the authorand producer was called merely" The Outside Broadcast Director,"instead of being given his real name,

This was no fault of the B.B.C.,since Mr. Cock was given a free handwith the programme, even to theextent of being permitted to publishhis name.. But Mr. Cock was toomodest, with the result that one ofthe best. programmes of the year wasveiled under a cloak of anonymity.

The rule is a silly one, anyhow.There should be no question of " giv-ing permission to publish a name."Credit should be given either to every -

has played characters, big and little, inbroadcast plays regularly ever since.

After playing in C. B. Cochran'sNew York production of " This Year ofGrace," acted in the B.B.C. RepertoryCompany in 193o, during which year hewrote his first radio play, " Boss,"which was produced by the NorthRegional station last August.

This was followed by " Oranges andLemons " and " Family Tree," bothof which were produced by HowardRose with great success.

Is one of the few radio exponents of" simple plays about everyday people."

one or to no one. This half-and-halfbusiness is a farce.

A B.B.C. TriumphWhat a fine example of the B.B.C.'s

technical methods the recent relaysfrom the Savoy Theatre have been.

The Gilbert and Sullivan perform-ances were so perfectly done thatthey might have come from the studio.There was never any suggestion thatthe singers were moving away fromor coming closer to the microphone.Congratulations to all concerned.

What a nuisance this copyrightbusiness is ! Ten years to wait for afull relay of a Gilbert and Sullivanopera ; and then the promised radioversion of " Sunshine Susie " can-celled because the rights could not bearranged.

Our Best ThanksOur congratulations this month are

shared between Philip Wade andGerald Cock. The former for his bril-liant play, " Family Tree," and thelatter for the Savoy relays.


4*

The success of the S.G. valve in detector circuits, although it was designed primarily forbetter H.F. amplification, says J. English, marks yet another triumph for the multi -

electrode valve over the triode.

IHAVE already given an account,in two recent articles, of someof my experiments on the

S.G. valve as detector with parti-cular reference to resistance -capacitycoupling. The success of this newapplication of the valve, which wasdesigned primarily for better H.F.amplification, marks yet anothertriumph for the multi -electrode valveover the triode.

At an early stage in the develop-ment of the R.C.-coupled S.G.detector certain indications led me tobelieve that there might be possi-bilities in the same scheme as an H.F.amplifier. I knew that if the ideaworked at all well it would possesscertain definite advantages, not theleast practical being the very smallH.T. current required.

Tried BeforeAny appreciable economy that can

be effected here is of vital importanceto all users of receivers powered fromH.T. batteries, especially so if thereceiver is a portable.

Resistance -coupled H.F. stages havebeen tried before, right back in the

THE FIRST CIRCUIT0000.0 CUPS

200040 CHOW

ClvaLfr.,

11" 111Frs.1 rtrgs

It was not very sens.tive, but resultswere distinctly promising.

early days of radio, when long -wavereception was the rule. This method,however, was quickly dropped infavour of tuned -anode and trans-former couplings when medium -wavetransmissions became more promi-nent, as on these wavelengths theold R.C. amplifiers were no good atall.

Promising ResultsYou can well imagine, therefore,

that when, some months later, I setup the first resistance -coupled S.G.stage, it was not in a particularlyhopeful mood that I commenced ex-periments.

The first circuit to be investigated,the idea for which, as I have alreadymentioned, came from the S.G.detector, is shown in Fig. I.

You will notice that it is practicallyidentical with this S.G. detectorscheme : the same resistances wereused with a slightly smaller couplingcondenser between S.G. and detector.The H.F. input was obtained from asimple tuning circuit, a dual -rangecoil timed by an Extenser, so that highselectivity was not expected !

However, rather to my surprise,the performance of the receiverdefinitely indicated that the S.G.was giving appreciable H.F. amplifi-cation, especially on strong trans-missions. Although this trial H.F.stage displayed nothing like the highsensitivity of the normal S.G. stage,I was not disappointed.

No Back -CouplingFrom this hopeful beginning I had

now little doubt that a much better60

performance could be developed stepby step.

It is worth noting that a slightnegative bias was found essential forthe proper functioning of the S.G.,while the potential of the screengrid appeared to have a markedinfluence on the effective H.F.amplification.

In a circuit such as this there is nohelpful regenerative back -couplinginto the input circuit, such as you getin the normal S.G. stage and whichaccounts for much of the sensitivityof the latter.

Subsequent TestsThe next step was to find out what

were the best operating conditions asregards resistances and voltages forthe S.G. itself.

I suspected that the optimum re-sistance values of the S.G. detectorscheme, as used here, were not thebest for the S.G. as an H.F. amplifier,and this subsequent tests confirmed.A higher screen potential was founddesirable with a reduction in theanode resistance.

THE NEXT STEP

OVI

The circuit as modified after the firstexperiments.

MODERN WIREI FSS January, 1933

Some Interesting Circuits for You to TryFor the latter, an average value

found suitable for the valve used (aCossor 215S.G.) was 200,000 ohmswhen the total H.T. current was nomore than half a milliamp. at 150volts H.T. ! You should compare thiswith the total consumption of yourS.G. stage, which may be anythingfrom 2 to 3 m.a. or more.

It :was also found that the adjust-ment of screen potential was morecritical than in the normal S.G. stage.Above and below a certain narrowrange of voltages sensitivity was muchreduced.

Outstanding FeatureFor convenience of rapid adjust-

ment the screen potential was derivedat this stage from a potentiometer(100,000 ohms) across H.T.H- andL.T.-, although the original schemeof a tapped anode resistor and seriesscreen resistance is equally effective,but not so convenient for experi-mental requirements.

After making these modificationsin the conditions affecting the valveitself, I noticed an immediate im-provement in the performance of theH.F. stage, but results, althoughquite good, were still below normal,except for the reception of strongsignals.

The next step, an important one,was to insert a tuned circuit beforethe detector with reaction from thelatter into this grid coil. The circuitwith modifications at this stage isshown in Fig. 2.

QUITE INTERESTING

AT-

Aa3

It is simple and easy to operate, butlacks the punch of Fig. 2.

I had anticipated that this additionto the R.C. coupling would improvethe sensitivity of the S.G. stage, butI did not expect quite such an all-round improvement in reception.The receiver now behaved excellently,sensitivity being only slightly belownormal, while adequate selectivitywas obtained with perfect stability.

The latter quality proved to be the

outstanding feature of the circuit,there being no tendency to " spillover " even near the zero tuningcondenser positions. No shieldingwas incorporated in this experimentalreceiver, other than a screened dual -range coil for the tuned -grid circuit.

Even this screening would hardlyseem necessary with a suitable lay-out of the two coils and associatedcomponents.

Perfect StabilityAs a direct comparison, I replaced

the anode resistance by the usualH.F. choke, restoring normal screenvolts, when uncontrollable oscillationresulted over the lower half of thetuning range.

Obviously this arrangement ofresistance -coupled S.G. has, compared

ANODE -CURRENT -GRIDVOLT CURVES

6

ec) opft

54

6 o. Ct

i 0°0

1ita15°S,7e°

I.2I.'

c

.9

8

7

6

.4

3

2

-qv -3v --ZteFia.4 RIP77S

The operating conditions were closely in-vestigated with the aid of these curves.

with the popular H.F. choke -feedsystem, the advantages of simplerlayout, perfect stability and reducedH.T. current consumption. All threeare of some importance and amplycompensate for the slight loss ofsensitivity.

You will perhaps get a better ideaof the general behaviour of the three -valve receiver of Fig. 2, the thirdvalve being the output stage, fromthe following results.

Satisfactory on Long WavesMany foreign stations were re-

ceived at good speaker strength,without interference from the locals,reception being particularly satis-factory on the long waves. Altogetherthe performance of the S.G. itself atthis stage of experiments wasdefinitely pleasing.

70

Some time was now devoted toinvestigating other possible circuitsto find the most suitable arrangementfor this new S.G. amplifier.

THE TEST RECEIVER

Marked improvement in results followedthis modification of the Fig. z circuit.

However, after testing severalpossibles, I finally returned to thetuned -grid cum resistance coupling,as this appeared to give the bestresults. Nevertheless you may beinterested in some of these circuitswhich have certain advantages.

For instance, the circuit of Fig. 3is quite interesting.

Easy to OperateHere we have only one tuned

circuit, the input to the H.F. valve,with reaction from the S.G. itselfthrough quite a small condenser.As there is only one tuned circuit,satisfactory selectivity can only beobtained by using a band-pass tuneror the Moderator tuner shown in thediagram.

The circuit is simple enough andeasy to operate, but it lacks the" punch " of the arrangement ofFig. 2, unless, of course, a speciallysensitive detector is used.

Plotting CurvesAlthough at this stage in my ex-

periments I was getting a betterperformance from the R.C.-coupledS.G. stage than had been anticipated,I was not yet satisfied that itsfullest possibilities had been realised.Further progress could now only bemade by more detailed experiment.

Accordingly, the operating con-ditions of the S.G. valve were closelyinvestigated. Possibly a few briefreferences to this work will interestyou.

To begin with, anode -current -gridvolts curves were plotted for differentanode resistances, other series ofcurves being taken to observe the

(Continue,/ on page 92)


v.44,4414,4 (3/0)14,:tof ,sztys

"Nothing less than thebest will satisfy me"

FIXED CONDENSERS.In a complete range of capacities uprightor fiat mounting. Registereddesign No. 723271. Every con-denser is tested on 750 voltsD.C. The capacities are ac-curate within fine limits. Everycondenser can be thoroughlyrelied upon.

1f-116

LITLOS VARIABLECONDENSERS.Compact and efficient. Accurately gaugedbakelite dielectrics and solid brass pigtailconnections to moving vanes.All capacities up to -0005 MFD.in tuning straight line capacityand differential types. 2'..

OHMITE RESISTANCES.The most popular and efficient type offixed resistance for all generalpurposes. "Better than wire -wound." All values 300 ohmsto 5 megohms.Also in HEAVY DUTY foruse where the load is high. Allvalues 300 ohms to 100 000 2f3ohms.

1'6

Graham Farish set a very high standard for his com-ponents when he began business in the earliest days ofwireless.Since then firms have come and gone. Graham Farishgoes from strength to strength on the quality andefficiency of his products. Year after year the Bromleyfactory sees some new addition-to cope with theconstant increase of demand.Graham Farish components are now specified by everywireless expert and journal. Follow the experts.

A AMC PO E TS

Masons Hill, Bromley, Kent.Export Office : 12-13, Fenchurch Street, London, E.C.

71


TROUBLETRACK INjUDGING from the letters I get,

one of the most commontroubles with the modern

high -magnification, battery -operatedreceiver is instability. I am, of course,referring to home -built sets used withH.T. batteries in varying conditions,and with mains units.

Those sets which give trouble areusually ones with two L.F. stages. Insome cases the first L.F. stage mayhave a decoupling resistance andby-pass condenser, but no attentionseems to be paid to the second stage.

I wonder why, when all that isneeded is a 10,000 -ohm resistanceand a 2-mfd. condenser. My advice toconstructors who are up againstinstability is this.

Cramped ComponentsFirst of all, go over the layout and

make sure that the trouble is not dueto a faulty disposition of componentsor bad wiring. For instance, com-ponents that are cramped together-grid and plate leads practicallytouching-these are factors whichproduce instability.

TRACKING TROUBLE "

Another form of " trouble tracking "-P.C.Thistlewaite, of the Bradford Constabulary,with the portable receiver he has evolved

for anti -bandit use by mobile police.

Suppose the S.G. valve tends tooscillate when the circuits are broughtinto tune. The first question to askoneself is whether the screening -gridhas any decoupling.

An Effective RemedyIf the answer is no, the obvious

procedure is to insert a 1,000 -ohmresistance between the screening -gridand its H.T.+ terminal and toconnect a 1-mfd. non -inductive con-denser between the screening -grid and

Every month the Chief of the" ." Query Departmentdiscusses some of thecommon difficulties whichcan often be so troublesome.This time he deals with theneed for adequate decoupling

the L.T.- filament terminalvalve holder.

An easily applied scheme but veryoften an effective remedy.

On the L.F. side, if there is only onestage, a 15,000 or 20,000 -ohm resist-ance in series with the H.T. lead tothe detector, together with a 2-mfd.condenser connected to earth, shouldbe sufficient. If there are two stages,then a second decoupler is an advan-tage.

The value of this resistance is, ofcourse, lower, because the valvefollowing the detector is normally an" L " type and takes a higher anodecurrent.

If the set is not stable whenthoroughly decoupled in this way,there is something seriously amiss.

Speaking of decoupling reminds meof a query I had from a reader whowanted to supply his set from asingle H.T. tapping. His idea was touse the 150 -volt tap on his mainsunit for the det. and two L.F. valvesin his receiver.

Not DifficultThere is nothing very difficult in

this provided the characteristics ofthe valves are known. For example,we will suppose that the current takenby the detector at, say, 80 volts, is2 milliamps. Then by simple arith-

72

metic the resistance required in orderto break down the voltage shouldhave a value of 35,000 ohms. Themethod of arriving at this figure issimple. By Ohm's Law the volts tobe dropped multiplied by one thou-sand and divided by the current inmilliamps gives the value of theresistance in ohms.

Convenient SchemeIn this case the volts to be dropped

are 150 less £0, which equals 70.70 times 1,000 divided by 2 gives usthe answer.

The scheme is a convenient onebecause the resistance also forms partof the decoupler, which is completedby a 2-mfd. by-pass to the L.T.negative filament.

So far as the first L.F. stage isconcerned, suppose we decide toapply 120 volts to the anode, thecurrent taken at this voltage being,say, three milliamps (at the propergrid bias).

Marked AdvantagesGetting down to arithmetic once

more we find that the volts to bedropped times a thousand divided by3 is 10,000. This is a nice figure fora second stage decoupling resistance,and we can again complete the schemeby adding a 2-mfd. condenser as before.

On the last valve we shall need allthe available volts and no " breakingdown " will be necessary here.

The method can be applied to anyset, but only holds good for a givencombination of valves.

The advantages are specially markedin those instances where accumulatorsare employed for because mul-tiple tappings mean an uneven load onthe cells-that is, one batch of cellswill be giving out more current thanthe others.


AWIRE carrying an electric cur-rent is surrounded by a " field "or area of electro-magnetic

energy so long as the current flows.You see this elementary principle

illustrated at Fig. 1. Here a wirecarrying a fairly heavy current passesthrough a sheet of thick card uponwhich some iron filings are scattered.The filings arrange themselves along

" SEEING ENERGY "

Although it cannot be seen, a field of energysurrounds a wire carrying current. Thesimple experiment shown above (which youcan perform yourself) makes the force

demonstrable.

the lines of electro-magnetic force,thus demonstrating the existence ofa field of energy surrounding thewire.

Now, a broadcasting station maybe likened in some way to a wirecarrying a current, for it is surroundedby a somewhat similar field of energy,and it is, of course, upon the fluctua-tions of the intensity of this field ofelectro-magnetic energy that we de-pend for the signals which we receive.

Equal in StrengthA wire carrying a current has, as

you will notice from a glance atFig. 1, an energy field which is equalin strength at equal distances onevery side of it.

Ideally, the energy -field of a radiotransmitter would be similarly equal

Nact()MoutFl ELD

5411RENGTHBy J. F. CORRIGAN, M. Sc., A. I.C.

There's something more than mere valves and circuitsin the efficiency of a transmitting station. Thesurrounding country has quite a lot to do with the

14 11

service area.

in strength at equal distances on allsides of the transmitter.

However, to get these ideal con-ditions the earth's surface would haveto be flat and of uniform electricalproperties, and the transmitting aerialwould have to be freed from all possiblescreening influences. Under theseconditions the energy field surround-ing the transmitter might be repre-sented by a series of concentriccircles of ever-increasing radius, thesignal energy at any point of the samecircle being the same. Fig. 2, per-haps, will serve to illustrate moreclearly what I mean.

Nothing Like ItIn actual broadcasting practice,

however, you get nothing approachingthis ideal of uniform field -strength.Instead of having concentric circlesdrawn round a broadcasting station torepresent its field -strength, you getirregular " contours," of the sortdrawn at Fig. 3, all points on the samecontour line receiving the transmittingstation at equal strength.

During the last few years a lothas been done to eliminate thesesignal -strength contours which existaround every broadcasting station.Practically every station in the worldhas been re -designed. The majorityof them have sought more suitablesites for their aerial structures, andthe electrical characteristics of theareas which these stations serve havebeen more thoroughly studied.

Nevertheless, there is not a stationin the world which has not4its own

73

particular field -energy contours,although in a large number of in-stances these contours have, by care-ful study and research, been roughlypulled into approximations to irregu-lar concentric circles.

Screening EffectsThe presence of areas of unequal

signal energy in the electro-magneticfield surrounding a broadcasting sta-tion is due to several causes, chiefamong which are the electrical char-acteristics of the earth in local areas,and, also, the screening effects to

IMPOSSIBLE IDEAL

The perfect energy distribution of a trans-mitter shown here would do away with" blind spots, " but the surroundingcountry would have to be flatter than the

Sahara I

which ether waves travelling outwardsfrom the station may be subjected.

Screening effects may be causedby the presence of high building


Every Transmitter Has Its Characteristic Contourcontaining a preponderance of steel-work. These will absorb some of thebroadcast energy of the transmitterand will cast a " shadow " in the pathof the ether waves.

In the days when the old B.B.C.used to sling up its provincial aerialsbetween convenient factory chimneys,there used to be a good deal of thisparticular type of screening in thetransmission. Nowadays, however,when the B.B.C. favours greatlyelevated sites for the aerials of itstransmitters. local screening of thissort is practically eliminated.

Suppose, however, a mountain getsin the way of the outgoing broadcastwaves ? You cannot remove themountain. Therefore, the mountaincasts a " shadow " in the path of thewaves, a " shadow " which results in acertain local area adjacent to thatmountain being made into an area ofpermanent low -field strength.

Highly AbsorptiveThere are areas of this nature among

the metalliferous mountains of Corn-wall, along the valleys of South Wales,and in the hills of Central Wales.

In some of these districts owing tothe presence of metalliferous ores, theland is rendered highly absorptive ofelectrical energy, and a consequent de -

THE SHAPE OF THE " FIELD"

The irregularities in the earth's surfaceand its varying electrical properties causethe distribution of energy from a trans-mitting aerial to follow the erratic

" contours."

crease in signal energy takes place.The presence of large inland

stretches of water sometimes has asimilar effect upon radio wavestravelling outwards from a trans-mitting station. The water, beingconduotable and absorptive, attractsth . waves and passes them to earthmore easily than the land.

The authorities of the New York

station, W E A F, at Bellmore, LongIsland, have made a very seriousstudy of the signal strength variationof their station's waves in and aroundNew York. They measured the vary-ing intensities of their transmissions inmicrovolts per metre, and they foundquite an extraordinary series of field -strength variations within a compara-tively short radius of the station. Suchvariations were attributed to the pre-sence of enormous masses of steel inthe high New York buildings. Otherstation authorities, following suit,have conducted similar tests, andobtained similar results.

Very Little ComplaintAs a matter of fact, however, in

this country, if high city buildings dothrow radio " shadows " in the path ofthe waves, these " shadows " areusually wiped out within a very shortdistance owing to the refraction anddefraction of the waves from thesurrounding areas into the shadowarea. Consequently, in these isles wenow hear very little complaint con-cerning this trouble.

?)SEZ1463,0&0068)@EMR6g011,DP

a SERVICING L.T.Some accumulator tips which will

keep your L.T. m good order. g7?

g By J. UTTLEY gg g6:)'-ik,WPCF9OCM9&940q349,83 4W3

HEN sediment begins to collectat the bottom of an accumula-tor it is usually in a pretty

bad condition, for through carelesshandling or charging the plates havebegun to disintegrate.

If the sediment is not removedthere is a risk that the plates willshort-circuit, when the accumulatorwill be ruined. In many cases it canbe removed by draining off the acidand filling with distilled water, andthen up -ending it in a basin of distilledwater. By gravity a lot of the sedi-ment will drop out and the operationcan be repeated several times.

A Good JobIf the plates are very close together

this cannot be done, but if the casingis made of celluloid, a piece of thebottom can be cut out with a braceand a centre bit. After the sedimenthas been washed out through thishole the piece can be replaced and agood joitmade with a patch of cellu-

loid moistened with amyl acetate.Many accumulators, particularlythose supplied with insulated ter-minals, give a lot of trouble throughcorrosive deposits on the terminals.In some cases it becomes so bad asto interfere with the making of a

IN THE SHADE

_

RALPOWOWS

,72.13445

--- ------

----- - _ _ _

Reed:,OP

514.00W

SOME A/RYES ozhvG Rs-A-4screro Age)/Airo SNAvotv,ZeeR

FIG. 4

The presence of a mountain or high build-ing between receiving and transmittingaerials causes weak reception because anelectrical " shadow " is cast by the

obstruction.proper connection. This seems to bedue to the use of lead and brass inthe connection.

When a liberal application ofvaseline does not cure the trouble, thebest plan is to scrap the terminals andto attach Clix plugs of suitablecolours to the battery leads.

These can be screwed into threadedlugs of the plates and will make afirst-class connection.

When using an extra large accumu-lator, which has to stand on thefloor, it will be found that the usualbattery leads covered with cotton orsilk are not very suitable. In suchcircumstances, .rubber -covered wire,as used by motorists and known aslow-tension wire, is much safer andstronger.

Don't Use a JugThe trouble with this is that the

double lengths of wire cannot betwisted together to form a cable.If, however, a piece of string ofapproximately the same diameter becombined with them, it then becomesa simple matter to plait them togetherand produce quite a presentable cable.

When topping -up accumulators orhigh-tension batteries of the wet type,it is better not to use a jug, but toemploy a pipette or a hydrometerfilled with distilled water.

By this means an exact quantityof liquid can be added and there is norisk of slopping water over the outsideof the casing.

74


FOR YOUR"VARITUNE" 4The outstanding feature of the BenjaminTransfeeda is the distortionless amplifi-cation which it gives throughout themusical range, particularly at lower fre-quencies which usually are only broughtout by de -luxe transformers. Use theBenjamin Transfeeda in your Varitune 4in conjunction with a high-class loud-speaker, and you will have a perfectcombination for natural and sparklingreproduction.The Transfeeda is particularly specifiedfor your Varitune 4 and you can get onefrom your dealer for 1 1 /6d. In case ofdifficulty do not substitute but write tous direct.

The famous BenjaminV ibr older with itssprung contacts is stillthe Constructor's mostpopular valveholder-

price 10d.A good push-pull switchis an asset to every setconstructor. TheBenjamin, one of theearliest and best, costs

9d.

BENALMNThe Benjamin Electric Ltd.,Tariff Road, Tottenham, N.17

The Dubilier Type B.B.Paper Condenser istested to 500 Volts*D.C.and is suitable for 200Volts D.C. working.Capacities from oo to4*0 mF. Prices from 1/9.

EveryDUBILIERCondenserbeforebeingofferedfor sale is3 timestrebletested

P.3.

manufacturersE, constructors

FIND

DUBILIERCONDENSERS

so exceptionallyreliable

75


REHM 1 THE SCENESof the BIG ORCHESTRA

i11111111111/1=11111111111.1=111111111111=1111111111/ =11111111111= =1 111111111=11111111111= 11(11111111=11111111111S

IF you are in London and go to the Queen's Hall, yousee the B.B.C.'s big orchestra in full force and in" party " attire of full evening dress. You see

Dr. Boult, or maybe Sir Henry Wood, or Sir LandonRonald, in the place of honour and handling the baton intrue concert style.

On the other hand, if you are one of the lucky ones,with your name on the B.B.C. waitinglist for a visit to a broadcasting studio,you may see the Symphony Orchestrain quite a different light. You may seethe orchestra, or at least a section of it,giving a Sunday evening concert fromone of the big studios, or playing ininterludes of musical comedy.

New York and Berlin are proud of theirgiant orchestras, but there is surely noneso versatile as the group of one hundredand fifteen players sponsored by theB.B.C. On a Friday they may be tackling the oiches-tral part of a big choral work in the Queen's Hall. OnSunday afternoon it may be Bach, and in the eveningBrahms.

Hall nights. It can carry out symphony concertsquiring a medium -size orchestra of eighty or so, as in thebig studio on Sunday evenings.

One section tackles dramatic programmes, musicalcomedy and so forth, requiring between thirty and fortyplayers, while another does light orchestral and lightsymphony concerts, with anything from forty to seventy

players.

..h Did you know that there are .1:

:: occasions when the B.B.C. °:: Symphony Orchestra includes ::iisaxophones and banjos? A .4if. B.B.C. correspondent here ex- iiii plains the when and how of h.

this strange circumstance. .::,

Several Separate JobsOf course, the full total of one hundred and fifteen is

not 'alwa,ys at work. The big orchestra can be subdivided,and that is where it has a big pull over any other Nationalorchestra for concert work, broadcasting or gramophonerecording.

Dr. Boult, who, of course, directs the B.B.C. musicalpolicy, helped by Mr. Owenllase, the B.B.C. AssistantMusical Director, has arranged for the orchestra to doseveral separate jobs.

It can tackle symphony concerts requiring a full modemorchestra of at least one hundred-that is, on Queen's

For these jobs there are two alterna-tive subdivisions of the orchestra. Theseare 79 and 36, and 68 and 47 playersrespectively.

The B.B.C. Theatre Orchestra, withS. Kneale Kelley as leader, and con-ducted by Stanford Robinson, hastwenty-four players, and it is thisorchestra which you hear so 'often inmodern vaudeville. The T h e a t r eOrchestra is not in any way a sub-

division of the Symphony Orchestra, but consiks ofseparate picked players who make it a whole7time job.

It is a little " lighter " thUn the main B.B.C.Orchestra. Some of the players combine 'cello, banjo andguitar, while one clarinet player and one 'cellist also playsaxophones.

In Full MusterThe full B.B.C. Orchestra of 115 is led by the popular

Arthur Catterall, and last, year the band turned upin full muster to more than twenty Queen's Hallconcerts.

Music of this kind is at least a ten -hour -a -day job,The big fees said to be earned by the principal playersare worth while, and, in any case, it must be rememberedthat the Queen's Hall concerts pay for themselves.

If you go often to B.B.C. concerts, you will know that76


the official method of styling the sections is A, B, C, Dand E. A is the full 115. B and D are the two largersubsections of 79 and 68 players, C and E the smallerdivisions. Each works under the title of the B.B.C.Symphony Orchestra, followed by the appropriate letterdenoting which section is playing.

You may have heard of the B.B.C. Bach Orchestra.This is made up from the strings of the C section of themain orchestra.

A difficulty with all these sections is rehearsing. Whilerehearsals are on for a Queen's Hall concert, the membersof one subdivision may be needed to tackle a lightmusical programme.

The interest in big orchestral items has been increasedby inviting a number of well-known conductors to certainof the concerts given by the big orchestra. In addition toa number of distinguished foreign conductors from manycountries, Sir Henry Wood and Sir Landon Ronaldare also counted as among the " guest" condUctors.Many of these have officiated at the Queen's Hallduring the week and in one of the big studios on Sundayevenings.

Ultra -Modern Chairs-and ShirtsleevesThe B and D sections of the orchestra turn up

for these big studio broadcasts, and -after the polishedappearance of the big orchestra at the Queen's Hallpublic concerts, it is an interesting sidelight to see themembers of the first section seated on their ultra -modernmetal chairs and playing at their ease in shirtsleeves-at least, so far as the males are concerned!

Dr. Boult conducts as many rehearsals as possible, andit is in order to relieve him from some of the executivework connected with a big orchestra that Mr. Mase wasappointed Assistant Musical Director. During rehearsalshe is assisted by Mr. Stanton Jefferies, of the Balance andControl staff. (Mr. Jefferies was the Musical Director ofthe old British Broadcasting Company, and his musicalknowledge is invaluable in getting the right microphone" balance " for the orchestra.)

The Queen's Hall positions for the players are now fixed,but they are altered considerably at each big studio


a II I III/ n 1III

The Wireless Symphony Orchestraat the Queen's Hall and (above)the B.B.C. control room adjacent to I . --

the hall.

IIIIIMMI

DR.ADRIANBOULT

HMI III rill I rrri 11

!III II II III IffM IIIIIIIIlIn II IIII MINEIIIIIII II IM III / II I/M Il I

77


WHATVITTARG

THE A.C. power output obtainedfrom the last stage of areceiver or amplifier is a

measure of the volume of sound ; anoutput valve is used for the sake oftis output and is judged on its output-and yet valve manufacturers donot publish figures giving the outputobtainable from their valve=. Which.seems absurd.

No UnanimityIt is generally understood, however,

that this secretiveness is due to thefact that there is not completeunanimity among the principal valvemakers concerning the correct methodof ascertaining the maximum outputof a valve. Admittedly, anymethod is bound to be some-thing of an approximation; butit would surely be wise to waiveacademic precision and to adoptsome formula known to besufficiently accurate far all prac-tical purposes.

The amusing part of it all isthat though members of the

....

By JEREMY GREY.

it is probably too much to hope thatthe near future will see such a schemeof grading, let alone an official ratingof valves on an output basis.

Fair ComparisonAt the same time, serious amateurs

and experimenters definitely requireto know what output they may expectfrom a given valve when fully loaded,not only to assist them in the designof receivers and in judging theefficiency of their equipments, butalso to permit fair comparison be-tween valves of different types.

Fortunately it is not difficult toarrive at a fairly accurate determina-tion of the maximum output by a

precision, is sufficiently correct forall practical purposes.

The method is based on the well-known anode volts-anode currentcurve and load -line construction, buthas been simplified to avoid the com-plications of trial -and -error attempts.The actual mode of procedure isdescribed below, while a simple ex-planation will be found at the end ofthis article.

All that is necessary iJ a set ofanode volts-anode current curves ofthe valve under review, and theusual working data supplied by thevalve manufacturer-nam-ly, therecommended grid bias and workinganode current at maximum anode

voltage, and the optimum valueof the load.v

00

How much power can you get from your power iivalve? That is, undistorted power. It's a

useful item to know, and can be calculated quite neasily in the manner described by our contributor, ::

.4.who also explains his method. ...B.R.V.M.A. are precluded bytheir rules from publishing outputinformation in printed form, they arepermitted to give this informationeither verbally or in writing to any-one who cares to make a personalinquiry !

Percentage of DistortionOne solution to the difficulty would

be to " grade " valves according totheir maximum output, allowing fora definite percentage of distortion,say 5 per cent second harmonicdistortion in the ca e of triodes andthe same amount of third harmonicdistortion for pentodes.

But the laws of the B.R.V.M.A.are, apparently, as unchanging asthose of the Medes and Persians, and

4**0method which, although open tocertain objections on the part ofsticklers for absolute mathematical

IS IT BIG ENOUGH ?

The size of a valve is no guide to its powerproperties. You must know somethingabout its characteristics if you want tobe sure that it will handle enough without

distortion to suit your purpose

Enlarged DrawingsFortunately it is now the

general practice of valve makers topublish in their catalogues anodevolts-anode current curvesfor all output valves. Althoughthe printed curves are usuallyon a somewhat small scale, it is

possible to use them for this calcula-tion, but for greater accuracy itis advisable to make an enlargeddrawing on squared paper, increas-ing all dimensions about threetimes.

Only two of the complete familyof curves need be drawn, namely;those corresponding to zero grid volts,and to grid volts equal to twice therecommended maximum grid bias.

The diagram on the next page showscurves drawn from the characteris-tics of the Mullard D.0.24 outputvalve, which is a three -electrodevalve designed to operate at ananode voltage of 400. The maximumgrid bias for this valve is 34 volts,and as no curve at twice this voltage

78


FOR YOUR

S. T. 400

Ask

to

see

them

at

your

dealer'sAdvertisement ofJackson Bros. (Lon-don Ltd.), 72, St.Thomas' Street,London, S.E.s. Tele-phone: Hop 1837

J.B. DIFFERENTIAL.0003, 4,'6. 0001, 4/-.Insulated centrespindle. Bakelite di-electric between vanes.

J.B. MIDGET. 00004. Completeas illustrated, 4;'-.

Small dimensions.Low minimum ca-pacity. Ebonite insu-lation. Rigid one-piece

frame.

J.L.4 CONDENSER.design:d for the

S.T.400.

Slow-motion type(35/1).

Capacity, 0005. Com-plete with 3" dial, 7/6.Extra heavy gaugevanes. Rigid nickel -plated frame.H i g h -grade ebonite

insulation.

TRADE A P`Ct\L

DOWNAND BALANCE

IN EASYMONTHLYPAYMENTS

D.C. 15/25 H.T. for3-4 Valve Sets fromD.C. Mains. 39/6 Cash.

A.K. 22. H.T. and L.T.for 2-8 Valve Sets fromA.C. Mains. 77/0 Cash.

THE OLYMPIABALLOT WINNERS Why pay at least 50, - ayear for quickly exhausted drybatteries ? Get your H.T. from themains with an " ATLAS " Unitfor less than a shilling a year.There's a model for every receiver,fitted in a few minutes withoutalterations to set or valves.Ask your dealer for a demonstra-tion to -day, and insist on" ATLAS," the Expert's choiceand winners of the " WirelessWorld " Olympia Ballots. Noothers can give such a reserve ofhum -free power.Manufactured and Guaranteed for x2 months byH. CLARKE & CO. (M/CR), LTD.,PATRICROFT, MANCHESTER.LONDON : Bush House. W.C.2. Glasgow :The G.E.S. Co., Ltd., 38 Oswald Street.

MAINS UNITS111.1111111

POSTNOW!

Messrs. H. Clarke & Co. (M/cr), Ltd.,George St., Patricroft, Manchester.

Please send full details of the complete rangeof " ATLAS " Mains Units.

NAME

ADDRESS

34/1

79


HMS.Applicable to Both Pentode and Triode Valves

is shown in the published graph, theappropriate curve at grid volts equals68 has been sketched in between thecurves taken at grid volts 60 andgrid volts 70.

The next step is to take some con-venient voltage occurring somewhereabout the middle of the anode voltsscale of the graph. In this case 400volts has been taken. This is marked" B " in the diagram.

Operating PointDivide this figure by the optimum

load of the valve,which for the D.0.24is given as 4,000 ohms, and multiplythe result by 1,000 :

400000X

1,000 = 100.4

Call this number milliamps., andmark it on the anode current scale asat A in the diagram.

Next plot the " operating point,"i.e. a point on the graph correspond-ing to a voltage equal to the maximumanode volts, and the working anodecurrent at maximum grid bias. Forthe D.0.24 these figures are 400 voltsand 63 milliamps., and the opera-ting point is plotted at 0 on thediagram.

Join the points A and B by astraight line, and then draw a lineparallel to AB and passing throughthe point 0, terminating on the gridvolts 0 curve at X and on the " gridvolts equals twice maximum gridbias " curve at Y.

The output is calculated as follows :Scale the points X and Y in milli -amps. and in volts.

In the diagram, X corresponds to117 milliamps. and 175 volts, whileY corresponds to 16Z milliamps. and587 volts.

Simple ExplanationSubtract the voltage values and

milliamp. values as follows :587 - 175 = 412 volts.117 - 16.5 = 100.5 milliamps.

Multiply these two figures togetherand divide by 8 :412 v. x 100.5 m.a.

8=5,176 milliwatts,

which is the maximum output.The explanation of this method of

calculation is really quite simple.In our calculation we have assumed

a voltage of 400, and we know theresistance of the load to be 4,000 (theoptimum recommended load for theD.0.24), so that under these condi-tions the current flowing in the load

SOS

circuit would be 400 divided by4;000 equals 1 amp. By multiplyingby 1,000 this is converted to milli -amps., namely, 100 milliamps.

The points A and B thereforecorrespond to the load current andvoltage across the load respectively,

WORKING FROM CURVES.0

2 00

I 20

20

'9.°04/7.00,

I. 4207- 2222:122,0 2).2. at. 00.. 290 totli..0,22

1

.5,...

rs62. 112/2.0

.210201 GR. "SO

01,2242172.

.70

-- ---1- -----4 - ------- -100 .200 000

ANODE VOLTS

It is as well to re -draw the valve curves ona bigger scale so that readings may be

made thoroughly accurate.

and it is obvious that correspondingvalues for any other set of conditionswith the same load would be repre-sented by lines parallel to AR

We know that wider working con-ditions the anode current of the D.0.24when operat,A1 at 400 volts H.T. andat the recommended grid bias of34 volts will be 63 milliamps., andtherefore the " load line " for thevalve under working conditions must

000 GOO 700 000

IS IT LOUD

not only be parallel to AB, but mustpass through the point 0.

Again, because we are assuming thevoltage applied to the grid to be themaximum permissible (namely-equal to the grid bias, we know thatthe load line must terminate on theanode volts - anode current curvestaken at zero grid volts and 68 gridvolts.

The difference between the anodecurrents at X and Y gives the ver-tical distance between the crest andthe trough of the anode current

-variation, i.e. twice the amplitudeof the anode current variation.

The Effective ValueSimilarly, the difference between the

voltages represented by X and Ygives twice the amplitude of thevoltage variations across the load.

The effective or R.M.S." valuesof the anode current variation of thealternating voltage across the loadare equal to the amplitude 5- ,r2;

The maximum output in milli -watts, therefore, which equals R.M.S.volts multiplied by R.M.S. milliamps.,must be equal to (Y volts -X volts)divided by 2 %/-2-, multiplied by(X milliamps. -Y milliamps.) divi-ded by 2 and a simple mathe-matical deduction shows that this isequal to (Y volts -X volts) x (Xmilliamps. -Y milliamps.) 5- 8.

ENOUGH ?-A MATTER OF TASTE

The question of what is a desirable level for loudspeaker volume is a matter of individualpreference. What may be considered loud by some would be just right for others, butit is most important that whatever volume you desire a valve capable of handling it

should be used.80


TONEthe

FULLYin our

FullinterestingReadL.F.radiograms.Howreproduction

EASILY

PRICE

Free

topic

booklet

particulars

whyTransformer

it

FITTED

kiln

on

information.the Multitone

increasesat

RADIOGRAM

CONTROLof the

EXPLAINED(M).

applicationof circuits

Toneis essential

basswill.

TO ANY

T

moment

S,:nt

and

and

Control

miur

other

treble

SET

Post

for

OR

...................TONE CONTROL L.F TRANSFORMER

MULTITONE ELECTRICCOMPANY LTD.95.98, WHITE LION STREET, LONDON, N. I. NORTH 5063

M C ,5

means

THIS WEARITEHETERODYNE

WHISTLE FILTER UNIT

MUSH - FREEPROGRAMMES

THE more sensitive your receiver the more prone it is toheterodyne whistle interference-and the greater the needfor this Wearite Whistle Filter. With a host of really

good programmes always available there is now no need tohave distant reception marred by this interference. ThisWearite Unit is made in two types: 'A' to cut off at 3,500cycles for normal use, and B' calling off at 5,000 cycles forthe music critic: With it only the programmes

reach your speaker-the Wearite Filter 0/0HAVE YOU GOTYOUR COPY OFTHE WEARITEBOOK No. 01 ?Whatever Set you maycontemplate building besure to have this bookby you-it contains fulldetails of Chokes, Resist-ances, Volume Controls,Mains, Transformers.Switches. etc.SEND NOW!

is a barrier to heterodyne whistle, Will (BOAfit any Set. Write for special leaflet. types)

WAE N TEcompoivEth-s.WRIGHT & WEAIRE, LTD.740 High Road, Tottenham.

'Phone: Tottenham 3847-S-9

C.I 999

FORMO Matched Coil and Condenser Assem-blies solve the problem of making your setselective. You have a complete and accuratetuning unit giving the finest possible band-pass tuning. Perfectly matched coils andcondenser give .-accurate selectivity andmuch finer quality,A FORMO Matched Unit provides the homeconstructor with something new in perform-ance and in straightforward set construction,Ask your dealer. Write for catalogue incase of difficulty;

DUAL CANCCat. No. 72C

33'TRIPLE CANC BAND PASS ADAPTORCat. No. 69C to bring your set up to date

A simple way to obtainadequate selectivity Is with46/6

FORMO 23, Golden Sq., Piccadifly Circus, London, W.1. designed by a tending wire-less journal. Write for Free

Head Office & Works: Crown Works, Regent's Park, Southampton. illustratedconstrurtiondetails.

show you how to have" Super -Radio " at less costTunewell Coils and Components are recommended forthe best sets, S.T. 300, S.T. <too, etc. They definitelygive better results and save you money, too. Choose yourneeds from Tune- - amm

well " Guide to To TUNEWELL RADIO LTD.,S'uper-Radio" 54, Station Road, London, N.11.which includes I Send New " Guide to Super -Radio " to :

3 FREE NameBLUE PRINTS I

Send coupon now forAddress

a copy FREE. L1.6

81

CONVERT YOURSET with this/

CABINET IThe Cameo Waverley '-a handsome cabinet forconverting your set into a modern Radio -gram.Wonderful acoustical properties. PolishedWooden Panel 5,- extra. Attractively finished inOak or Mahogany. Oak £5-10-0. Mahogany16-15-0See this cabinet at our showroom and send forFREE Cameo Cabinet Catalogue givingparticulars of the complete range.

CarringtonManufacturingCo. Ltd., Showroom: 24.Hatton Gardens. London.

E.C.1.'Phone: Holborn 8202.Works: South Croydon.

Post in let, envelope.

Name

Address


USING

Valuable hints on the working of this type of output valve that will enable you to getbetter results with it.

By R. W. HALLOWS, M.A.

THE pentode is one of the mostinteresting valves that wehave, and if given a fair chance

it can produce astonishing results.But it is no exaggeration to say thata very large proportion of the pen-todes in use are not operated in sucha way that they can show their realpowers.

You have read, of course, of theway in which the pentode works, butlet me briefly refresh your memory.It is really a screened -grid valveadapted for use as a low -frequencyamplifier by the provision of a thirdor auxiliary grid. The screened -gridvalve, plain and simple, cannot beused for work on the low -frequencyside, since its peculiar characteristicsmake it unable to handle anythingbeyond a very small input.

Currents That Rise and FallWhat actually happens in a

screened -grid valve is this. Supposethat we set the screening -grid voltageat 75, and start with the plate at 10volts positive, gradually increasingthe plate potential. To begin with,the plate current rises as the positiveplate potential is increased. Thencomes a fall in the plate current,accompanied by a rise in the currentflowing in the screening -grid circuit.This continues until plate and screen-ing -grid potentials are very nearlyequal, after which the plate currentrises and the screen current falls.

Why does the plate current fall offwhilst the plate voltage is risingbetween certain values ? As the plate

Saturation PointOn leaving the plate these come

within the pull of the screening grid(remember that an electron is at-tracted by a positive charge) and flyto it. Thus the screening -grid currentrises, whilst the plate current, starvedby this secondary emission of elec-trons, falls. When the plate potentialbecomes only a little less than thatof the screening grid the capture ofelectrons by the latter tails off, andthe more positive the plate is madenow the greater is the plate circuit

DROPPING THE SCREENVOLTS

A 269 e f/G. /We can bring down the volts on the priminggrid by inserting a resistance between

A and B.

is made more positive the speed current, until the saturation pointof electrons from the filament is is reached.increased. Some of them strike the In the pentode an auxiliary grid isplate with such velocity that they placed between the screening gridsmash other electrons out of it. and the plate. This third grid is

connected usually to the mid -pointof the filament, and is thus stronglynegative with respect to the plate.

Electrons knocked out of the plateare repelled by the auxiliary grid andsent back to their proper place. Thepentode's characteristics, then, arewithout the kinks that occur in thoseof the screened -grid valve.

Should It Be Less ?One of the most important points

of pentode work concerns the rela-tion of the voltages on the screeninggrid and on the anode. Most valve -makers tell you that it is best, as arule, for the screening -grid potential(for some reason this is usually calledthe priming grid in a pentode) to be alittle less than that of the plate.Therefore, if we are to have one H.T.tap, as in Fig. 1, we must drop thevoltage to the screening grid.

Having decided that this is to bedone, do not try, as some people do,to bring down the priming -grid volt-age to a more proper figure by theexpedient of inserting a plain re-sistance between points A and B inFig. 1.

Decoupling RequiredBut why not ? It looks perfectly

easy. In fact, we can work out thevalue required. Suppose that thepriming -grid current is 2 milliamperes

82


How It Works and How to Work Itand we decide to bring the voltagedown to 100 ; then, to find therequired resistance we divide thevoltage to be dropped (say, 20) bythe current passed-that is, .002ampere-and the answer is 10,000ohms.

Up in the AirBut if you try to use such a re-

sistance you will find that the valvegoes, metaphorically, of course, rightup in the air. You cannot employit without a full decoupling circuit,and by far the simplest way is to usea separate high-tension positive tap-ping for the priming grid of yourpentode.

With some of the modern pentodesthe results obtainable where correctplate and priming -grid voltages areused are simply astonishing. Takethe Mazda Pen.220. The priming -grid voltage with this valve shouldbe about 10 per cent less than thatactually applied to the plate.

If, therefore, the plate voltage isactually 116, that on the priminggrid should be about 102. Withthe average impedance (transformerprimary, choke or loudspeaker wind-ings) in the plate circuit you willobtain something very like thesevalues if you use the 120 -volt tappingfor the plate and the 102 -volt for thepriming grid. Connected in this way,and given a negative grid bias of3 volts, this little valve is capable ofdelivering a third of a watt of undis-torted output, or quite as much asmost people require from the loud-speaker in rooms of average size.

A valve with very similar charac-teristics, and a very jolly one to use,is the Marconi P.T.2. Both of thesevalves when treated in the waydescribed deliver this amazing outputfor a total high-tension current con-sumption in the neighbourhood of 5milliamperes.

Why Not Try It?Whatever kind of pentode you use,

remember that you are wasting high-tension current if you don't keep thepriming grid a little less positive thanthe plate. You are also shorteningthe life of the valve to some extent,for the smaller within reason the platecurrent the longer is it likely to last.

I would recommend you thereforeto do a little experimenting with yourpentodes. Fit a separate high-tensionpositive lead for the primary grid,

and see how much you can reduce thepotential without adversely affectingreproduction.

One meets a number of people whohave fitted pentodes to existing setsand have been grievously disappointedwith the results obtained. Theyexpected a tremendous increase inthe volume ; they found sometimesvery little increase ; sometimes actu-ally a decrease ; and they wondered-they still wonder-why. The reasonis that the pentode is a valve of veryhigh impedance.

Speaker ImpedanceThe figures are not often given

nowadays by makers, but they rangefrom about 30,000 to 60,000 ohms,according to type. The impedance ofthe loudspeaker naturally varies withthe frequency. At 100 cycles it maybe taken as roughly equal to the D.C.resistance, but for matching purposes

TAKING OFF " TOP "

Q2699

7,3

Z. T

FIG. 2A fixed condenser (C) and resistance (R)are usually connected as shown to correct

excessive " toppiness " in a pentode.

it is desirable to know the figure forabout 1,000 cycles.

Too Much TrebleThis can usually be obtained from

the makers. In any case, it isimmensely lower than that of apentode valve, and it follows that tomatch the two a big step-down mustbe provided in the output circuit.Unless the loudspeaker is speciallywound for these valves a pentodeoutput choke is not usually sufficient ;a transformer is required as well. Thedifference in the volume (and, ofcourse, in quality) obtainable issimply astonishing when the pentodeis properly matched to the loud-speaker.

It is also urged against the pentodethat its reproduction is apt to be on

83

the shrill side. It gives far too muchtreble and not sufficient bass. Thisis perfectly true if you do not takesteps to correct the " toppiness " ofthe pentode. And what steps can betaken ?

A High -Note FilterThey are very simple. The com-

ponents required are a fixed con-denser with a capacity of about002 mfd., and either a variableresistance with a maximum of 50,000ohms or a set of fixed resistancesranging in 5,000 -ohm steps from20,000 to 50,000 ohms. The resistanceand the condenser are connected inseries and wired as a rule as shownat R and C in Fig. 2 ; that is, acrossthe primary of an output transformer,between the plate and high-tensionpositive terminals of an output choke,or straight across the loudspeakerterminals if a specially wound loud-speaker is used without filter circuitor transformer.

Alternative MethodYou can, though, if you prefer it,

connect them between the plate andL.T. -, as shown by the dotted linesin the drawing. The effect of thiscombination of resistance and capacityis to weaken the high notes and tomake the response of the valve muchmore level to the whole range ofmusical frequencies. Experiment willshow you just the value of resistancewhich gives the reproduction thatappeals to you.

One last point. It is not a bad thingto make a regular practice of providinga five -pin valve holder for the outputstage of any wireless set that has onlyone L.F. stage, fitting an extra high-tension positive lead for the fifthterminal. You can then use either apower valve or a pentode in the setwithout the slightest alteration in thewiring, though, of course, it will benecessary to employ an output circuitsuitable for the valve in use.

Pentode or PowerThe advantage of being able to

insert a pentode or a power valveinto the last holder at will is that insummer time, when the strength ofthe more distant stations falls off,you can exchange your winter powervalve for the summer pentode andthus compensate to a very greatextent for the seasonal decline involume.


To raise a question such asthe above is rather astonish-ing in view of the general useof screened -grid valves. Butour contributor-Oliver Hall, D.Sc.-gives some extremely enlight-ening facts, figures and ex-periences in this connection.

THE question which forms the titleof this article may, at firstsight, appear a little ridiculous.

During the last five years the screened -grid valve has become more and morepopular, and its efficiency has increasedin truly reniarkable fashion.

In high -frequency amplification thescreened -grid valve has no rival. Whyask, then, if the screened -grid valvereally does amplify ? It must amplify,or we should never use it as freely aswe do in our modern receiving sets.

Worth Looking IntoQuite so, but if we may assume that

all screened -grid valves amplify, wemost certainly should not assume thatall the S.G. valves in use amplify asmuch as they ought to.

Some of our modern screened -gridvalves have amplification factors oftwo and even three hundred. Howmany such valves amplify two or threehundred times ?

This question 9f S.G. amplificationis one which is nell worth looking into,especially if, in so doing, we learn howmuch it is Possible to make such avalve amplify under varying condi-tions.

As .we all know, the S.G. is a valvewith an extra electrode in the form ofan open -mesh screen between thegrid and plate.

It has the usual three electrodes-filament, grid and plate. But it has,

S:6.DalvesmfiliT/7

in addition, this extra electrode, thepurpose of which is to shield theoperating, or control, grid from theplate or anode of the valve.

There is no need for us to worryourselves as to the manner in whichthis additional electrode, or screen -grid, reduces the capacity betweenthe plate and the control grid of thevalve. It is sufficient for us to realisethat we have this extra electrode in thescreened -grid valve, and that we giveit a positive potential from our high-tension battery.

Balanced -Valve RectifierThus we give the plate or anode of

our S.G. one positive potential, andthe screen -grid electrode a differentpositive potential. It is by varyingthese two positive potentials to theplate and screen -grid of a screened -gridvalve that we can learn that thisingenious valve gives us an amplifica-tion factor which varies between verywide limits.

To measure the amount of amplifica-tion it is necessary to have some

30

28

6 26

Vi

c 22

20

0

fzt

II /4JF /2Q

/6

10

Table 1

Aerial seriescondenser(mfd.) -0001 410005 .000025

Strength ofDavent ryNationalin micro-amperes 5

reliable instrument of the valve -voltmeter type.

The writer uses an instrumentwhich is usually described as a" balanced -valve rectifier." In thistype the steady plate current of thevalve is balanced out by a current inthe reverse direction from the filament -heating accumulator. The balancing -out current is adjusted to the correctvalue by means of a variable resist-ance, and the actual measurement ofthe rectified current is made on asensitive galvanometer, reading from0 to 120 microamperes.

A TEST ON THE DAVENTRY NATIONAL77 758

FicI OUTDOOR AERIALANODE VOLTAGE OFS.G. VALVE15 VOLTS THROUGHOUT

18 24 30 36 42 48 54 60 66 72 78 84 90 96 102S.G. VOLTAGE OF 5,0. VALVE

By means of this graph it was quite easy to work out the actual amplification obtainedunder the conditions outlined.

109 /14

84


TRIMMERS. These areconveniently operated fromthe top and cannot go out ofadjustment.VANES. Accurate spacing ofvanes is obtained by precisionmachine assembly, therebyentirely eliminating possi-bility of error.MATCH ING. This is accu-

FEATURES AND PRICES:-rate to within I of i per cent.plus or minus a mid.FRAME. All - steel frameand rigid construction ensuresthis accuracy being maintain-ed under all conditions of use.BEARINGS. Strong springjournal bearings give absolutefreedom from shake or endplay.

POLAR

3 x '0005 - 25/64 x 'coos - 34/ -Super -het Type(comprising twosections oo05and one trackingsection) - - - 27/6All Prices include

covers.

CONDENSERS

HITCH YOUR TUNINGTO A " STAR " .. .. and your tuning system will undergo a vast improve-ment. Tuning will be much easier and there will be amarked increase in selectivity. This is mainly due tothe dead accuracy of the matching and to the extremerigidity of construction which maintains this accuracyunder all conditions and prevents continual adjustment ofthe trimmers.Examine a Polar "Star" at your dealers and note itsunique features.

ONE OF THE BESTThe " 13 ireless Trader "test report said :" . . . remarkable accuracyhas been obtained. This isundoubtedly one of the bestgang condensers on themarket . . . "

POLAR DISC DRIVEFor single or ganged con-densers.Another Polar aid toeasier tuning and greaterselectivity. It has awonderfully smooth yetprecise action and en-sures really accuratetuning. Scale is clearlymarked and easily read.Fitted with lamp- riholder. Price 4

Write for the Complete Polar Catalogue " M."

LTD., Polar Works - - Liverpool.188-9, STRAND, LONDON, W.C.2.

WINCROVE & ROGERS

Correspondence in all languages. Represeatative for France: W. A S,m1/.6, Rue Deguercy, Paris.

EnjoySHORT-WAVE

Reception-The latest Magnum Short-waveAdaptor is suitable for bothA.C. Mains and Battery Sets.Price, including coil 40/80metres. Cord and Plug. 39/6.Extra Coil, if required. 18/40metres 3MODEL FF. For sets usingBritish Valves.MODEL T.A. For sets usingAmerican Valves

MODEL T.S.G. For sets usingBritish 8.0. Detector Valve.MODEL T.A.S.G. For sets usingAmerican 8.0. Detector Valve.Full particulars with a list ofshort-wave stations and freetrial offer, on request. Particu-lars of the latest Burne-Jones"STENODE" are now available.

BURNE-JONES & CO LTD. 29:113174LONDON.7Glii S.E.1."4"6-Telephone: Hop 6257 & 6258.

SbUttish Agent : Mr. ROSS WALLACE, 54, Gordon Street, Glasgow, Cl..

,MODERN WIRELESS.,REVISED ADVERTISEMENT RATES

SINGLE Insertion - . £40 0 0per page and pro rata to eighth page

6 CONSECUTIVE Insertions 37 10 0Per page and pro rata to eighth page

12 CONSECUTIVE Insertions 35 0 0per page and pro rata to eighth page

ONE INCH single col. (2 in. wide) 1 10 0Minimum Space (half inch single col.) - 15 0

All communications respecting advertising mast be made to

JOHN H. LILE, Ltd.,4, Ludgate Circus, London, E.C.4zhy72.6.i.and NOT to Editoria or Publishing Office.,

Twenty seven and sixTwenty seven and sixpencewill purchase an R. & A.Bantam Permanent MagnetMoving Coil Reproducer. Asmall outlay for a Repro-ducer capable of renderingspeech and music withpurity and volume. Thereis no value to equal it, norwill you find a speaker to

equal it at the price.INCLUDING 3RATIO

FERRANTI TRANSFORMER

27'6Ask your dealerto demonstrate

REPRODUCERS & AMPLIFIERS, Ltd.

WOLVERHAMPTON.

)(0

"BANTAM"PERMANENT MAGNET MOVING COIL REPRODUCER

85


Connecting the balanced -valve rec-tifier to outd6or aerial and earth, andtuning to Daventry National, readingswere taken with three settings of theaerial -series condenser. These read-ings are given in Table 1.

It should be noted that the highestamplification factor obtained was424, and that this highest valuepersisted from 60 to 78 volts on thegrid -screen of the S.G. valve.

In the next set of readings taken on

Table 2

Large outdoor aerial. Aerial series condenser, '00005 mfd.Anode volts of S.C. amplifying valve, 120.

S.G. voltage ofS.G. valve .. 0 221 45 48 51 54 57 60 63 66 69 72 75 78

Strength of Day -entry National(microamps.).. 0 45 74 75 75 77 78 85 85 85 85 85 85 85

Amplification ofS.G. valve .. 0 221 37 37 37 38 39' 421

A stage of screened -grid high -frequency amplification was thenplaced in front of the balanced -valverectifier, the coupling between theS.G. valve and the rectifier being thefamiliar choke -condenser, or tuned -grid coupling, which is withoutdoubt the most popular type ofhigh -frequency coupling in use to-day.

Highest AmplificationThe aerial -series condenser was

fixed at 00005 mfd. With theanode potential of the screen -gridamplifying valve fixed at 120 volts,the screen -grid voltage was variedin steps of 3 volts from 45 to 78volts, and the strength of DaventryNational was taken at each voltagestep.

Readings of the strength ofDaventry National were also takenwith screened -grid voltage at 0 and

Daventry National the anode voltageof the screened -grid valve was fixedat 15 volts. The screened -grid voltage

the screened -grid valve are also givenin Table 3, and these amplificationfactors are illustrated in the form ofa diagram in. Fig. 1.

Perhaps the most interesting featureof the diagram in Fig. 1 is the way in

which the amplification factor ofthe S.G. valve rose quite sharplyfrom 10 to 28 as the screen voltagewas increased from 18 to 51, andthen fell almost equally sharply asthe screen voltage was further increased from 66 to 111.

Transformer CouplingThe highest amplification factor,

28, persisted from screen volts 51 to..66. This highest amplification factor,28, should be compared with thehighest factor, 424, in Table 2.

As a next experiment, transformercoupling was tried for the S.G. valve

in place of the choke -condenser tuned -grid coupling.

The transformer was of ratio 1:1,

Table 3

Large outdoor aerial. Aerial series condenser, '00005 mfd.Anode volts of S.C. amplifying valve, 15.

S.G. voltage of S.G. valve.. 18 21 24 27 30 33 36 39 42 45 48 51 54Strength of Daventry

National (microamps.) .. 21 26 31 36 40 43 50 50 52 55 55 56 56Amplification of S.G. valve 10 13 15 18 20 21 25 25 26 27 27 28 28

S.G. volts .. .. .. 57 60 63 66 69 72 75 78 81 84 87 90 93Strength of Day. Nat. .. 56 56 56 56 54 53 52 50 48 48 45 42 38Amplification .. .. .. 28 28 28 28 27 26 26 25 24 24 22 21 19

S.G. volts .. .... .. .. . .. .. .. 96 99 102 105 108 111 114Strength of Day. Nat. .. .. .. .. .. 35 32 30 27 26 25 28Amplification ... .. .. .. .. .. .. .. 17 16 15 13 13 12 14

was varied in steps of 3 volts from 18to 114 volts.

The readings taken of the strength

Table 4Large outdoor aerial. Aerial series condenser, '00001 mfd.

Transformer coupling. Anode volts of S.C. amplifying valve, 15.

S.G. volts of S.G. valve .. 18 21 24 27Strength of Daventry National (microamps.) 25 52 95 120+Amplification of S.G. valve .. 33 69 127 160

22i volts. The whole of the read-ings are given in Table 2.

Since the strength of DaventryNational with aerial -series conden-ser 00005 mfd., and the balanced -valve rectifier alone was 2 micro-amperes (Table 1), it is easy towork out the amplification factorof the S.G. valve for each screened -grid voltage in Table 2.

This has been done, and the ampli-fication factors are given in Table 2.

of Daventry National at each step of3 volts are given in Table 3. Thecorresponding amplification factors of

the primary and secondary windingsbeing of equal length, and being woundon the former simultaneously. The

amplification given by this high -fre-quency transformer was immediatelyseen to be very much greater thanthat given by the choke -condensercoupling.

In order to make measurements ofthe strength of Daventry National,the aerial series condenser had to beturned almost to its minimum capa-city position.

The readings taken of the strengthof Daventry National are given inTable 4, and the amplification factorsgiven in that table were worked out

Table 5Indoor aerial. Aerial series condenser, '0001 mfd.

Anode volts of S.C. amplifying valve, 15.

S.G. volts of S.G. valve .. 18 21 24 27Strength of Daventry National (microamps.).. 2 - 3 5 14

I 30 I 3341 120

80


Superiority of H.F. Transformer Demonstratedon the assumption that the normalstrength of Daventry National onaerial -earth alone was / microamperefor that position of the aerial seriescondenser.

Next, instead of the outdoor aerial,a small indoor aerial, 10 ft. long,was used, the earth connection beingretained. Readings taken of thestrength of Daventry National aregiven in Table 5. The 1 : 1 high -frequency transformer was used, andthe aerial series condenser was set at0001 mfd.

Comparing ResultsTable 4 brings out very clearly the

superiority of high -frequency trans-former coupling for a screen -gridvalve. Comparison with Table 3, inwhich the highest amplification factoris 28, shows that transformer couplinggives many times more amplificationthan choke -condenser coupling.

Tables 4 and 5 also show how much

more sensitive to voltage transformercoupling is than choke -condensercoupling. In Table 2, when the

of the S.G. valve 15, the highest ampli-fication occurs with screened volts any-where between 51 and 66 inclusive.

Table 6

Indoor aerial. S.G. voltage of S.G. amplifying valve, 75 volts.

Anode volts of S.G. valveStrength of Mid. Reg.

(microamps.)

0

0

3

0

6

0

9

0

12

0

15

0

18

0

21

0

24

.

27

1

30

1

33

3

Anode volts .. . . 36 39 42 45 48 51 54 57 60 63 66 69Strength .. .. . . 34 41 60 75 93 105 60 50 50 44 44 47

Anode volts .. .. .. 72 75 78 81 84 87 90 93 96 99 102 105Strength .. .. .. .. 60 65 65 60 63 55 30 10 4 3 3 5

Anode volts .. .. . . .. .. .. 108 111 114 117 120 123 126 129 132Strength .. .. .. .. .. . 8 15 32 52 70 88 105 120 120+

anode voltage of the screened -gridvalve was 120, the highest amplifica-tion occurs for a screen voltage any-where between 60 and 78 inclusive.Similarly in Table 3, with anode volts

Table 7

Indoor aerial. S G. voltage of S.G. amplifying valve, 69.

Anode volts of S.G.valve .. .. .. 18 21 24 27 30 33 36 39 42 45 48 51 54

Strength of Mid. Reg.(microamps.) .. .. 0 0 1 2 5 42 49 65 82 102 52 53 48

Anode volts .. .. 57 60 63 66 69 72 75 78 81 84 87 90 93Strength .. .. .. 42 41 42 38 38 35 33 33 13 5 2 2 3

Anode volts .. .. 96 99 102 105 108 111 114 117 120 123 126 129 132Strength .. .. .. 5 11 20 34 45 55 67 75 85 93 98 104 107

oar

a

QJ

oto

a

O

VI

THE MIDLAND REGIONAL PROVIDES SOME

F/G 2 INDOOR AERIAL I

120 SCREENS.G. VALVE

GRID VOLTAGE75 VO4.76

OFTHROUON0111

100

80

60

40

20

e -

r

IO

CC

When transformer coupling is usedthe voltage adjustments to anode andscreen of the S.G. valve are muchmore critical. This is shown in Table 5.

For the readings given in thistable, the anode voltage of the S.G.valve was kept at 15 volts. Changingthe screen voltage from 18 to 33 voltsincreased the strength of DaventryNational from 2 to 120 microamperes;that is to say, this change in screen -grid voltage from 18 to 33 increasedthe received strength of DaventryNational sixty times.

Medium -Wave ExperimentsIn the next experiments, a change

was made to the Midland RegionaLTransformer coupling was againemployed.


MORE STRIKING FIGURES

120

100

FIG 3SCREEN

69

I I I I I

N000p Aseuru.GRID VOLTAGE OF

2.0.V4CILVEVOLTS THOUGHOUT.

80

60

40

20

-12 24 36 48 60 72 84 96 108 120 0 12 24 36 48 60 72 84 96 108 120 132

ANODE voLTS OF S. o. VALVE ANODE VOLTS OF 5.0. VALVEThe effects of screen voltages are strikingly shown in these two figures, which depict the readings in graph form when an indoor

aerial was used for receiving the Midland Regional.87


I11117111111111111111111111111111 111111111111111111111111111M

HAVE observed from time totime in the public prints articlesby gentlemen with speculative

minds, dealing with the possibleeffects on history which might haveoccurred if our forefathers had knownhow to telegraph by radio.

A General OmissionIn most instances these articles

have been concerned with wars orbattles, and I may point out, inpassing, that they generally omit totake account of the fact that bothbelligerents would possess radio;thus Nelson would have been advisedby wireless that Villeneuve hadskedaddled to a certain port, butVilleneuve would have been warnedby the same means that Nelsonwas after him, thirsting for glory,

BETTER THAN FIDDLING

FINESTIVAIsTABLe

\tir

ri31

'1,4 Iirr,hit, I w'

NAINts

-1

if Nero would have been less of avillain."

" warm work " and a spot of the" Nelson touch."

But wars are only certain threadsof history ; there are other com-ponents of the pattern, notablypeaces and treaties, ladies, marriagesand divorces, murders, discoveries,trade, literature, religion, art, cookery,sports and science.

I leave to a more leisured writerthe interesting task of describing

PASSINGLooking Into the Past and Future

medieval and Renaissance scenesin a radio setting. All I can say isthat if Nelson had had radio theGreat War would have been foughtin early Victorian days and theTreaty of Versailles would havebeen revised before we were born.

This month our contributor takesyou back into the Middle Ages andamusingly surveys radio's pro-bable position in the brave daysof old. What, too, he asks, wouldhappen if we could see into radio's

future ?

Much more fruitful would it beto cogitate upon the doings of ourancestors in times of peace. I imaginethat Nero would have been less of avillain if he had been able to keepin radio communication with Whit-stable and secured the best of theoyster crop.

Again, Henry the Eighth wouldhave found radio very convenientin his traffic with the Pope overdivorces ; indeed, if matters wereso advanced that radio was in commonuse, no doubt the modern craze for" forms " was also coexistent with it,and Henry had a pad of blankdivorce forms in a loose-leaf folder.

But I am afraid that radio wouldhave fitted ill into the brave days ofold, when there was so much timeand it ran so slowly. Undoubtedlythe pioneers of the art would havebeen severely discouraged-burnt atthe stake, as likely as not-in theirefforts to induct indecent speed intothe methods current at the time,when wars lasted thirty years, andmen lay in dungeons half a life-time before being brought to trial.

Free From DangerBroadcasting, perhaps, might have

found a footing in the baronial hallsand manor houses,' and the jesterswould have been able to crack theirmost outrageous jokes free from thedanger of being stunned by a marrow

88

bone or tied up by the thumbs.The Talks Department of . the periodwould have " put over " piquantdiscussions, in Latin between Johnof Wadham and William of Ware.

And the songs=bh, dearie, meHighbrows, with low brows andmatted hair, would twangle on theharp or lute, and yowl somethinglike this :

Sith ye londis withouten feere,Engelischmanne schall trinken beere;

and lots more like it.

Giving the NewsIt is easy to conjure up vision

or shouldshould I say auditions ?-of theNews Bulletins. " Hugh of Highburyhath ge-scoren ys nyne scowre and ten

A PROGRAMME CRITIC

"Broadcasting might have found a footingin baronial halls."

geol thys seesonne, to ye grete baneof Jack of Wollwhyche, wot hathpyled uppe but a meeslye ate scowre."" Hys majestie ye Kynge weds yefourthe tyme." (By the way, thenewspaper placards would at the sametime appear with, " Bluebeard DoesIt Again.")

" Sporte. Roger of Runcorn hathdefeaten ye recorde for ye longe-distance walke, having ge-walkenfrom Caring Crosse to ye. AldegattePumpe in ye space of fyvve houresand two scowre minuts of ye clocke."

Having let my imagination playround the idea of running com-mentaries on bear -baiting and witch -burning, I hasten to obliterate the


Not a Great Step Between Knowing the Future and Seeing Ithorror by suggesting that for thespace of two minutes we should insilence consider the England ofElizabeth with bicycles, top -hatsand a Communist party. That'sbetter.

The persistent hankering of somefolk for communication with Mars,

THE FIRST EDITION

" Hys majestie ye Kyngetyme."

and their assumption that theMartians are much more advancedthan we, makes me wonder whetherwe are to the Middle Ages peoplewhat the Martians may be to our-selves. If, like Mark Twain's Yankee,we found ourselves suddenly plungedback five centuries, eh ?

Desire to EscapeTripping over a lot of garden cut-

tings on the floor of the drawing -room,placed there in lieu of a carpet, andducking under the halberd of theman-at-arms on duty on the otherside of the keyhole, we should passshiveringly up and down dozens ofstone steps, including a corkscrewstairway with a rope banister-finding a mastiff with bloodshot eyesand a long-distance odour, comingdown-and make our way to thestudy through a dark passage smellinglike a family vault and embellishedwith fungi.

We should rush to turn on the radio-and it would not be there ! Nothingbut a fat monk kicking up a din onsome sort of primitive ukulele !

We should desire to escape for afew hours at the Palladium, hasteningaway 'in a nice little saloon car. Butwe should be invited to ride fortymiles through mud to witness a

miracle play," our steed being acarthorse, one of those big chapswith hairy feet and plaited greymoustachios.

We should write with quills dippedin charcoal and water ; we shouldwait three years to get a message

weds ye fourthe

taken to Turkey and the replybrought back. The chickens wouldsneak the water from the water -

clock and the rats wax fat on thebedroom candle.

We should sleep on odd bits ofmangy fur, stark naked, in a draught,and we should die quickly of plague,cholera and typhoid superimposedon appendicitis, and wake up wherewe belong-in a world of radio.

Professors of ForesightIf those Martians were able to

project themselves to earth by beamwireless or rocket post, they wouldbe puzzled till their tentacles curledinto knots. I am ready to bet thatif they were placed in front of, (a) agrid leak, (b) a haggis, (c) an assistantinspector of holes in watering -carts,and (d) a pair of charlady's button -up boots, they would be unable tosuggest to what use any one of thoseobjects could be put, except, perhaps,the inspector, who they wouldprobably mistake for a giant wood-pecker.

Of this I am quite certain ; theywould laugh themselves into spareparts at the sight of the humaneyebrow, and would be deeply con-cerned to have an explanation why ahorse's back leg hinges point to therear and those of an elephant pointforrards ! And they would not omitto inquire why Society does notexecute men who use " moustachecups." (Ugh !)

H. G. Wells' idea about professorsof foresight brings to us a vision ofbrass doorplates inscribed: " Prophecyin all its branches." If the facultyof knowing what will eventually bewritten on the pages of the futurereally exists and can be developed,many remarkable results would ensueif it were brought to a practical stage.

Very GratifyingBetting and sweepstakes would

disappear, and there would be a dealof running off to non -extraditioncountries. Weddings would be rareevents, so my next-door neighbourtells me. ( I can hear " her " throughthe wall !) Some of our jolliest palswould immediately become teetotallersin an effort to save ole man liver, andthereby would perhaps alter theirdestinies to that of drowning.

Personally I should find' it verygratifying to be able to say to theB.B.C., " Look here ! I see that in

1933 you will broadcast a lot oStravinsky, Honegger and Mossolov.Well-don't do it ! "

Not a great step between knowingthe future and seeing it. Wells' ownstory, ",The Time Machine," tells youa lot about this sort of delirium. Thethought of seeing one's self twentyyears hence, bewhiskered and sur-rounded by grandchildren, or in Dart-moor-or perhaps tuning -in to nextyear, only to gaze on a blank screen, istoo far removed from my philosophyof life for me to harbour it. Itwouldn't do me a bit of good to knowwhat a fix I shall be in to -morrow,nor would the information help meout of to -day's soup.

Fruit Before BlossomIt seems to me that generally

speaking Dr. Pangloss was right andthat everything which is, is U.K.,because this is the best of all possibleworlds ; not that it couldn't improveif the human race didn't exist !

SEEING'S BELIEVING

"The thought of seeing one's self twentyyears hence."

The Middle Ages did not enjoyradio because you cannot have thefruit before the blossom. And weourselves have just about as muchas we can bear. Possibly our posteritymay be strong enough to gaze withequanimity upon a scroll of futuremisfortunes and await smilingly thekick to come. But not so yourobedient servant.

Here's to 1933!I want to relish my victuals until

they or myself are suddenly snatchedaway, rather than that every beatof my heart should sound to me likethe ticking of a clock nearing TheHour.

So, here's to 1933 ! Let it do itsdarnedest, but it will not get us down.It's another year and the suns andseas of holiday are waiting for us.


As wireless develops so do we findthat its uses become more andmore varied. In addition to

ordinary communication we can nowlocate deposits of gold, silver, copperand other minerals buried far beneaththe surface of the earth, guide battle-ships, transmit photographs and pic-tures, sound the depth of the sea orascertain the height of an aeroplane,to mention only a few of radio'saccomplishments.

An Intriguing DreamAnd now we find that wireless is

leading us into the realm of heat, forrecent investigations have shown that,under certain conditions, ultra -shortwireless waves can be made to generateheat.

Does this mean thatwe shall be able to broad-cast heat by wireless aswe broadcast concerts ?It is an intriguing dream,and there are manycompetent investigatorswho think that it will come to thatsome day. On the other hand, thereare sceptics who ridicule the idea.

Merged Into LightLet us examine the possibilities

one way or the, other. While transmitting heat by wireless may be inthe far -distant future, there is nodoubt that our investigations intoshort wireless waves will enable us tolearn a great deal more about heatwaves than we know at the moment.

It is, indeed, perfectly natural thatshort wireless waves will produce heat,because as the frequency of thewireless waves increase so do theyapproach nearer to the frequencyof heat waves. In fact, somewhere inthe depth of the spectrum infinitely

short wireless waves (and by in-finitely " is meant waves far shorterthan the ordinary ultra -short waves)must merge into the ordinary heatwaves.

For the first time investigation isbeing carried on in this region of thespectrum, and it is more than likelythat some new rays will be discoveredwhich are partly wireless and partlyheat waves.

The only form of heat ray which weknow is the ordinary ray transmittedby fire ; yet there must be quite anumber of different kinds of heatrays just as there are a number ofdifferent kinds of light rays. At an-other part of the spectrum heat wavesmerge into light waves, and we knowa good deal about light waves.

results of Clerk Maxwell's electro-magnetic theory of light. Hence, lightwaves led to the discovery of wireless,and now wireless waves are leading ustowards new discoveries in the fieldof heat waves.

There is what might be called avast unknown area between ultra -short waves and heat rays which yetremains to be explored fully. It istrue that some of these rays have beenproduced in the laboratory, but theirpossibilities have not yet been fullyexploited, and in this area must liesome very interesting rays which wemight call wireless heat -rays.

Secret of the SunThe possibilities of wireless heat -

rays are very interesting. At presentthe ordinary heat ray is

" Shall we be able to broadcast heat by wireless aswe broadcast concerts?" asks G. H. Daly in thisilluminative review of the possibilities of the future.

Ordinary white light, for instance,can be split up into a number of colourrays-green, blue,, indigo, violet, red,orange, and yellow. Ultra -violetlight makes popular photographypossible and cures rickets, while theinfra -red rays enables us to see in thedark.

The Unknown AreaIn the same way there must be a

more or less corresponding number ofvarious kinds of heat rays if we canbut isolate them. It is interesting tonote here that the light ray was insome respects responsible for thediscovery of wireless.

The first wireless waves weregenerated by the German, Hertz, whenhe was endeavouring to verify the

90

quickly damped out bythe atmosphere, unless,of course, it comes fromsome tremendous sourceof natural energy suchas the sun.

We have not yet discovered whythe sun is capable of transmittingsuch a tremendous amount of energy,and it must not be regarded as a bigbonfire in the sky which sends out itsheat by reason of its size. There issomething much more mysteriousand complicated than that respon-sible for the eternal heat of the sun-something to do with atomic dis-turbances and ether rays.

Thus in probing into the realm ofthe heat ray we may discover somenew and extremely powerful manner ofradiating heat energy.

The most interesting possibility ofall is in the creation or discovery ofa heat wave which we can transmitby wireless just as we transmit asound wave at the moment by


" Two = Ways In Which We May Transmit Heat By Radio "converting it, into electrical impulses.That is to say, the heat wave wouldbe radiated into the ether, but wouldbe undamped and unperceived untilit was picked up by some detectingapparatus like the wireless set.

There ara two ways in which wemay transmit heat by wireless. Wemight superimpose a new type ofheat ray on to the ordinary wireless'waves ; transmit it through an ordi-nary wireless transmitter and thenreconvert it back to heat at thereceiving end. This would followthe present practice of converting,speech and music into wireless waves,radiating them and then reconvertingthem back to the original sound at the -receiving end.

Romantic PossibilitiesAlthough this method is not entirely

out of the question, the ether isalready overcrowded ; and even if asystem were developed for con-verting heat energy into ordinarywireless energy, there would be noroom for it as matters stand at themoment, to say nothing of the atmo-pherics which also might result !

A second method is to discover awireless heat -ray which uses apart of the spectrum entirely differentfrom ordinary wireless waves. It isconceivable that this ray would remainin the ether until detected by somespecial form of detector, and would notcause interference to ordinary com-munication at all. This second typeof wireless heat -ray is the least un-likely, and if the present scientific agecontinues to develop then this is themanner in which we may expect ourheat to be broadcast.

The romantic possibilities of broad-cast heat are almost beyond the powersof imagination to describe. Polarwastes would be made habitable,overcrowded countries, such as Chinaand Japan, could send their surplusmillions to these new countries.

Warming the ArcticOur northern winters could be made

much less rigorous ; it would be quiteeasy to warm up our streets and parkseven in the coldest weather ; wecould walk about in winter in lightsummer clothing, and heat would betransmitted to our homes as cheaplyas concerts are at the moment.

Such possibilities may sound some-what exaggerated, but man is everseeking after more and more comforthere below, and nothing is so likely to

accomplish this as the disepirery ofwireless' heat -rays which can beradiated to the fhrthest cOrnersof theearth. ' -

ESSENTIALLY THE SAME

I./EAT WAVES

. W/REZ.ESS-11E4r WAVES

[UNEXPLORED PORT/ 0A1\OF THE SPECTRUM f

WAVES OF / MILLIMETREr\f\f\f\f\WIRELESS WIVES OF / METRE

/frfE7wEs

/ 0 0 METRES

There is an essential similarity between heatwaves and radio waves-but a vast differ-ence in frequency-and between these twoeffects there is an unknown area of the

spectrum to be explored and exploited.

1M200&C3043c3313'S&n&02 BEHIND THE SCENES 2

OF BROADCASTING 2(3 Some glimpses of past and present

103control -rooms.

cmg,c9ec9e."4.ec3§9,gsq3

THE control -room is the nervecentre of broadcasting. It ishere that the programme

material from outside sources, differ-ent studios, and sets of studios, ismoulded into a suitable form forpassing on to the transmitting station.

Whatever this material may be, aprogramme relayed from some distant

91

country or a talk from an adjacentstudio, it is all regulated and, whennecessary, corrected so that it formselectrical impulses of a consistentstrength and, as far as possible,quality? -

You will have noticed that theB.B.C. aims at maintaining as even avolume level in your loudspeaker asit can. This is the work of thecontrol -room engineers.

Sometimes you can detect whenthey are increasing the amplificationunder their control because there isa step-up in the breathing, rushingbackground noises which are alwayspresent though usually not in suffi-cient power to be obtrusive.

Past and PresentOn another page in this journal you

will find some details of B.B.C.control technique, in an article entitled" From Mike to Aerial." And alsopictures of some of the apparatus inuse at broadcasting headquarters.

It all looks very pleasing, and yet,while complimenting the B.B.C. onits efficiency, I sometimes sigh for thefreedom of the past.

In earlier days, control -rooms wereoften rough-and-ready affairs operatedlightheartedly if not haphazardly.

I have sat in a British broadcastingcontrol -room smoking a cigarette andchatting to the men on duty whilethey were actually engaged in hand-ling big broadcast features.

But such a thing is not likely tohappen in the magnificent control -room at Broadcasting House. Thisis all very official, scientific, andelaborate.

Preventing BreakdownEverything is duplicated and tripli-

cated so as to eliminate the possibilityof a complete breakdown.

There are hundreds of " telephoneterminals "-the ends of telephonelines which radiate from BroadcastingHouse to all parts of London andGreat Britain.

Practically all those hotels, theatres,cinemas, etc., from which broadcastsare given have private lines to radio'sheadquarters.

But no direct connection is madebetween these buildings and Brook -mans Park. There is just a prelimin-ary amplification to build up astandardised volume level, and thenthere is the control engineer's ap-paratus with which incidental volumevariations are carried out. G.V.D.


&@tgg) 6g6pwAgo@ftegEg @

a DO S.G. VALVES,Z3AMPLIFY ? D

-continued from page 87t gloaaaaaaaaaaaaaaaaaaa

*5!.

A short indoor aerial of 20 ft. ofwire was used, the aerial wire runningacross a room to the top of a doorand thence out to a staircase, theheight of the open end of the aerialbeing 12 ft. An ordinary earth con-nection was used, and the tuning coilconsisted of 45 ft. of wire wound inthree sections of 15 ft. in a three -slotted former.

Indoor Aerial ReadingsThe' high -frequency transformer

used to couple the screen -grid valveto the balanced -valve rectifier was ofratio 2 : 1, the secondary windingbeing twice as long as the primarywinding. The two windings, primaryand secondary, were wound simul-taneously on the former until the,primary winding was complete. Thesecondary winding was then continuedalone.

With this indoor aerial two sets ofreadings were made of the strengthof Midland Regional. In the first setof readings, given in Table 6, thescreened voltage of the S.G. valve waskept at 75 volts; and the anode voltagewas varied, in steps of 3 volts, from0 to 132 volts.

These readings are illustrated inthe form of a diagram in Fig. 2.

The second set of readings was madewith a screen voltage on the S.G. valveof 69 throughout. These readings aregiven in Table 7, and they are shownin the form of a diagram in Fig. 3.

Important FeaturesSince it was impossible to get a read-

ing on the strength of MidlandRegional on the indoor aerial withoutthe screened -grid amplifying stage,actual amplification factors cannotbe given in Tables 6 and 7. The dia-grams in Figs. 2 and 3, however, showseveral important features.

First of all, Fig. 2 shows thatwhen the screen voltage of the S.G.valve was left at 75 volts, the ampli-fication of the valve rose very sharplyand uniformly as the' anode voltagewas increased from 33 to 51 volts.After this latter anode voltage theamplification fell, rose again and fellagain, until at anode voltage 99 theamplification was as low as it was at33 volts.

From 102 volts on the anode, theamplification began to increase, and

after 111 volts there was the samesharp and uniform increase as therewas from 33 to 51 volts.

It is most interesting to note thatthe two straight lines in the diagramin Fig. 2, showing these sharp anduniform increases in amplification,are practically parallel. It is equallyinteresting to note that the S.G.valve used in these experiments gavethe same amplification at anodevolts 51 as at anode volts 126.

Lower Anode VoltageRound about anode volts 51 the

voltage adjustment is very critical,otherivise the sugtion might bemade that, in order to save batterycosts, this particular S.G. valvemight be used with screen voltage 75and anode volts 51, instead of anodevolts 120.

The first point to note about Fig. 3is that with 69 volts on the screenof the S.G. valve instead of 75, theamplification given is not so great.Fig. 3, however, shows the samegeneral features as Fig. 2. There isthe same sharp, uniform rise inamplification in the first part of thecurve, though the maximum ampli-fication is reached at a lower anodevoltage, 45 instead of 51.

The S.G. Does MagnifyFrom the maximum amplification

at anode volts 45, the amplificationgiven falls unevenly until anodevoltage 90 is reached. Then it in-creases sharply, but not uniformly,as the bending of the curve shows. Inthe corresponding part of the diagramin Fig. 2 we had a straight line,showing uniform increase of ampli-fication.

A comparison between Figs. 2and .3 shows that a screen voltage of75 volts, as specified by the manu-facturers of this particular valve, ismuch better on the whole than 69volts.

Glancing through the results whichhave now been described, tabulatedand illustrated in this article, we seethat our title -question is answeredmost emphatically. The screened -grid valve does amplify, and in nosmall measure.

High AmplificationWith choke -condenser tuned -grid

coupling, the amplification given byan S.G. valve may easily exceed thefigure 40 (see Table 2). Even withinverse voltages-that is, with theanode voltage of the S.G. valve lessthan the screened -grid voltage-theS.G. valve may give an amplificationfactor of over 25 (see Table 3).

92

aaaa a a413

gi -continued from page 70

&,IFE8)&0Eg50EP&EPO,Oge.

effect of variation in screen potentialand grid volts. From these curvesmuch information of interest wasgleaned.

A few of them are reproduced inFig. 4, each for optimum screenvolts. Notice that these curves are,over the major part of their length,straighter than the correspondingcurve for normal voltage conditions.

This improvement is, of course,brought about by the combinationof high ,anode resistance and thespecial ratio of screen and anodevolts. In the case of the loweranode resistances, the straight portionis of sufficient length to accept a strongsignal without rectification or cross -modulation.

These curves also show that thevalue of anode resistance should bechosen with regard to signal inputstrength, amplification required andany restrictions of H.T. current con-sumption.

Incidentally, all the anode re-sistances used in these experimentswere of the metallised type with avery small self -capacity. Other kindsof resistor either gave poor amplifica-tion or none at all.

NEW S.G. CIRCUITS

A Little Too InvolvedExamination of curves similar to

those of Fig. 4 gave me a clue to thenecessity for a particular screenvoltage, but this is a little too involvedto go into here. It was found,however, that the optimum screenvoltage, which increases with decreas-ing anode resistance, was not reallycritical; 10 volts or so either waymakes little difference, although anymarked divergence from this bestvoltage range results in a noticeablereduction in volume.

After further study of these charac-teristics I chose as the best all-roundvalue for practical test, with an S.G.of normal type, an anode resistor of150,000 ohms, when the optimumscreen potential is between 30 and40 volts, for 150 volts H.T., and thetotal H.T. current no more than .9 m a.This is so small that there is not muchobject in reducing it farther, while inview of its performance the S.G.certainly earns its keep here !

A test receiver was now set upincorporating this anode resistor withprovision for the required voltagesjust mentioned, the circuit being



"GOLTONE" SCREENED COILSNOW SPECIFIED FOR THE

" VA R IF 0 R"You will remember the " GOLTONE " SCREENED COILS were

selected by the designers for the " M.W." Star, Blue PrintSet, the " PROGRAMME PRINCE."

Use the "GOLTONE" Screened Units, Types G.G.O.and G.G.R. in your " VARI-FOUR " and be

certain of the utmost efficiency andconsistency in perform-

ance.

OTHER "COLTONE" COMPONENTSSUITABLE FOR THE "VARI-FOUR "1 .0001 Midget Condenser, each ... 5d.1 1-meg. Grid Leak, each ... 7td.1 -25-meg. Grid Leak, each ...1 -5-meg. Grid Leak, each ...1 Binocular H.F. Choke, each ... 2161 Valveholder (screen -grid type) each 11-3 4 -socket Valveholders, each ... 6d.1 Grand L.F. Transformer, each ... 11,61 FuseHolder(sinallscrewtype)each 2d.1 .06 -amp. Fuse Bulb, each ... 4td.2 Triparte Terminals, with en-

graved discs, each- ... 3d.Insulating Sleeving, 1t mim,

18's -gauge Tinned Copper Wire.1-1b. reel, 6d., Ob. reel ...

3 Fairs Terminal Blocks, per pair(complete with screws).

01.141, it:2r.4,,sPecifiedAPiet66SOR1EIVE0

Pe'4441,1' .P:,61.t yeacii LS-3142et

EtIllese?& te eta7Pleettt

.iPe ItoliPat-81747k3' e4 O. 3ir cl*1, 21blerottaltoatcit77211

PKzegt-?:etiptsit,ugh,2411eard5 Goldston§ t.

PENDLETON ..It, MMlCtIfSTfR

21-

1/-9d.

FREETwo 4 -page folders,with numerous ex-cellent descriptionsof the variousscreened coils, withI a r g e illustratedRadio Catalogue.FREE on request

Three Ideal Books for BoysHOBBY ANNUAL

Price EV. netEVERY BOY'S HOBBY ANNUAL is thefinest book of its kind ever published. It ispacked with brightly written articles onpractically every hobby and subject ap-pealing to the boy of to -day. Every boywho is keen on making things and find-ing out how things work will want thiswonderful book. It is profusely illus-trated with photographs and drawingsthat show how in the simplest way.There are also two large folding photo-gravure plates.

The MODERN BOY'SANNUAL Price 6P. netThe MODERN BOY'S ANNUAL is packedwith up-to-date attractions for all brightboys of all ages. It deals in fascinating andchatty fashion with Aeroplanes, Ships,Railways, Speed -boats and Seaplanes,Motor -cars and Motor -bikes, and otheritems that every up-to-date fellow wantsto know about. There are also hundredsof wonderful photographs and pictures,beautiful coloured plates and three com-plete adventure stories. Get your copyto -day.

The MODERN BOY'S BOOK OF

Motors, Ships & EnginesPrice 716 net

A team of experts have written the intensely interesting articles, full of the romance ofman's Mastery of Speed on Land and Water, which appear in the MODERN BOY'S BOOKOF MOTORS, SHIPS and ENGINES. This magnificent NEW book is crowded withhundreds of fascinating pictures and well -written articles which tell of great achievementsin things mechanical. It also contains four coloured plates.

On Sale at all Newsagents and Booksellers93


IMNIIPOM9q3C3r83C9q3g0G4X3sE009G9 (g

FROM " MIKE " TO wAERIAL w

WCel 0-continued from page 29

DaWE8,%043)EE)E505@5E3

one group with their inputs and out-puts brought out to jack fields, sothat any amplifier can be used forany studio should a particular ampli-fier develop a fault during a trans-mission.

It may be of interest to note thatseparately -heated cathode valves areused in these amplifiers, and that greatcare has been taken to avoid " valve-ponging."

R.C. CouplingThe " B " amplifiers are of the

three -stage type, with resistance -capacity interstaging coupling, theinputs and outputs being fed throughtransformers. The gain of each ofthese amplifiers is 46 decibels, and isvariable over a range of 35 decibelsby means of a volume -control poten-tiometer, but they are set normally fora gain of approximately 38 decibels.

Immediately preceding each " B "amplifier is a main volume control,which gives a variation of 2 decibelsper stud, and this is used for control-ling the strength of the transmissionand for fading -out purposes.

The range covered during control-ling is about 30 decibels, but for fadingout a total loss of nearly 50 decibelsis introduced before the circuit isactually broken. This ensures that theprogramme is reduced almost to in-audibility before the circuit is dis-connected.

The function of the land -line ampli-fiers is two -fold. In the first place,they act as " trap " valves with alltheir inputs connected to the out-going programme (i.e. the output ofthe " B " amplifier), but with theirinputs isolating each trunk -line con-necting to the various transmittersor distribution points. Thus troubleof any sort on one line is. preventedfrom interfering with the service onanother.

Flexible Volume ControlSecondly, if the volume is insuffi-

cient on, say, the London -Leeds S.B.circuit, the gain of that " C " amplifiercan be increased without a corres-ponding increase occurring in thevolume of the programme on, say, theLondon-Daventry land -line.

The need for the flexibility of suchan arrangement needs no stressing,since careful adjustment of the output

levels to lines is essential. There arein all twelve " C " amplifiers, eachhaving two 10 -watt type power valvesin the output stage.

There is also installed in the control -room a fourth type of amplifier whichis used when an incoming transmissionfrom some distant point, such as aprovincial studio centre or an O.B.point, is received in the control -room.The " D " amplifier raises the incom-ing transmission to the same level asthe average level output of the " A "amplifier. Thus it can be fed directlyto the " B " amplifier and controlledin the manner to be described later.There are in all six " D amplifiers,each designed for a maximum gainof 36 decibels.

Trap valve amplifiers are providedin the control -room to avoid the pos-sibility of any fault on a local circuitaffecting the outgoing transmissionThe trap valve amplifiers are arrangedwith their inputs across the chain oftransmission, their 'outputs feedingloudspeakers in listening -rooms, house'phone circuits, etc., in 'the building.Thus, if a short-circuit occurs on thehouse wiring it does not affect theoutgoing transmission.

No InterferenceAll amplifiers are designed to give

a flat response curve over a band offrequencies of 30 to 8,000 cycles persecond. Elaborate decoupling ar-rangements are incorporated to ensurethat there shall be no mutual inter-ference between amplifiers, and thatswitching operations on one bankshall not cause noises in another chainalready in use.

There are six transmission and eightrehearsal control positions or desksin the control -room, and these arenovel.

In addition to the usual studiosignalling keys and lights, each con-trol position is fitted with a completeset of punching keys. These punchingkeys operate a series of relays whichenable any studio circuit to be set upfrom any control position in oneoperation.

By " set up " is meant that themicrophones are polarised, the variouspower supplies switched on to thatstudio's " A " amplifier, and the nec-essary connections made between theoutput of that studio's " A " amplifierand that particular control position.

Certain of the control positions areprovided with more than one channel,and it is thus possible to set up a studioa few minutes before it is actuallyrequired, and merely to fade -overfrom the outgoing to the incomingstudio by the turning of one handle.

94

gg&890q3C3GGf3f3gGS(E30(83.4",:e3

G9 NEW S.G. CIRCUITS q9'6Ja, -continued from page 92 6a

03O@EMPEgEg@Vg4' g6gEtifi*MAI@

shown in Fig. 5. This may not appearvery different from Fig. 2, but certainminor changes in the latter, plus theimproved valve conditions, produceda marked difference in results.

Apart from the experimentalpotentiometer control of screen voltswe have a small coupling condenser of0001 mfd. (actually a semi -variablewas used), while the detector grid istapped down the tuning coil with asmall condenser shunting its anodeto earth in addition to the differentialreaction condenser.

Taiping down the detector gridnoticeably improved selectivity with-out loss of volume, while the beneficialeffect of the anode shunt condenserwas quite marked on the long waves.

The potentiometer control of gridbias for the S.G. is very useful ; alter-natively a 9 -volt cell would be suitable.

Now for some actual results. Selec-tivity was of a very satisfying order,while cross -modulation was notnoticeable, a slight increase in negativebias assisting here. It was also found,that the G.B. potentiometer actedvery woll as a volume control.

Hand -CapacityTuning was slightly more critical

than with the normal S.G. stage, bothcircuits requiring to be exactly intune for full sensitivity. Tuning,however, is by no means difficult.

Then as regards stability the re-ceiver was entirely satisfactory, no" spilling over " occurring at anywavelength, while reaction was quitesmooth and hand -capacity troublesaltogether absent.

On distance reception the receiverbehaved even better than before,numbers of foreigners being receivedat excellent volume (bar fading) andquality.

As far as I could judge, this newH.F. stage was now working just aswell as the standard S.G. amplifier.In fact, by comparison, the latter wasneither as selective nor as stable.

To sum up the advantages of thisnew type of S.G. stage, we have,first, reduced H.T. current con-sumption, which means greater valveefficiency ; and, secondly, securedrocklike stability without complicatedscreening or critical layout. Inaddition, we eliminate the moreexpensive and less certain H.F. chokefor an easy choice of resistances tosuit different valves and conditions.


An Invaluable Book forTHE HOME CONSTRUCTOR

comPe1-

Tracing Trouble

How Your Set Works

Every conceivable aspect of Radio is compre-hensively dealt with in the Complete Handbookof PRACTICAL RADIO.There are articles on the Simplicity of ModernHome Radio, Famous Modern Circuits, Short-Wave Favourites, " The Power They Use "(concerning Radio Stations), etc., etc.There are pages of advice for those who arethinking about getting a set and exhaustiveinstructions on putting in a set.There are hints on modernising old receivers,on tracing trouble, on finding Stations . . .

There are pages of constructional details andcomplete and lucid explanations of the wholeprinciple of radio.So much that will be absolutely invaluable toyou, whether you are a radio fan or just one ofthose who like to " listen -in." Here are just afew of the Contents :

"What Set Do You Want? "Erecting an Aerial

Choosing Your LoudspeakerYour Valves

Hints on Super-Hets.The Radio -Gramophone

How to Build a Simple ReceiverTelevision Developments

How Your Set WorksSearching for Stations

Separating the ProgrammesForeign Broadcasters

Radio DistancesHow to Make an Adaptor for Short Waves

Short -Wave FavouritesTracing Trouble

etc., etc., etc.All this, and much more, for Sixpence-in the

Complete Handbook of

PRACTICALRADIO

NOW ON SALE 611.At all Newsagents and Bookstalls

93


BATTERY or A.C. SETSRead what " Popular Wireless "say about the IIEAYBERD M.W.1Mains Unit.-

" The outstanding feature ... an alternative outputswitch enabling a choice of two outputs to be made.It is a magnificent Unit and its adaptability makes ita most attractive proposition. The smoothing isexcellent and I regard it as the peak of mains unitachievement. Readers having A.C. mains shouldmake a special point of acquiring literature about itand studying its specification ... before making theirchoice of unit. It has a generous output and is de-signed and built on really sound engineering lines.-December 3rd, 1932.

HEAYBERD M.W.1 MAINS UNITAlternative Outputs :

30 ma. at 150v. or 50 ma. at 200v. H.T.L.T. 4v. 5 amps. for A.C. valves.

TAPPINGS: 40/120v. Var. S.G., 175v. and200v. fixed (Max.).

Price.... 1 2'7/6 ....Complete.Incorporating Heayberd Transformer,Double -wound Chokes, 16 mf. (800v. test)Condensers, Westinghouse Rectifier, Safetyfuse and all necessary resistances completein neat steel case. GUARANTEED ThreeYears.

POST COUPON NOWI enclose 3d. stamps for latest Handbook

Mains Power for your Radio." Packedwith aseful Technical Tips, Hints andDiagrams for running my radio from themains.

Mr

Address

EAVBERMONARCH OF THE MAINS.

M.W.1

10,FINSBURY STREET, LONDON, E.C.2.One minute from Moorgate Underground Station.

-TATA= WW1' B.T. BATTERIES.Give long service, improved volume andtone: very economical.Replacements for Taylor or Standard batteries at towprices; details post tree; also Bargain List. RadioKits and parts at lowest prices.M.TAYLOR.57.StudleyRd.,Stockwell,London.

Write forIllustrated Catalogue ofRADIO CPANIOPH 0 N E

CABINETSof exclusive moderndesign, made bycraftsmen, in highlyfigured Oak, Walnutor Mahogany. postfree.Remarkable ValuesCabinets made toorder a speciality.Maker, under licence,

of theHOWE BOX BAFFLE.Recommended by theB.B.C. Pull details

request0 E..Es ETEt1DCabinet Maker,SWINDON. Estimates Free. Eat. 1$66.

IPLEASE be sure to mention " Modern Wireless "when communicating with Advertisers. THANES I

6tevtEngr@rgEN4@c8,6grg@%@%

ON THE TEST BENCH g-continued from page 66 L.`71

%aDO&00060006Egi40@0E3)

Useful DevicesOne of the most ingenious of the

smaller radio devices of the seasonis the Belling -Lee Twintap. Thisretails at only one penny, but itsusefulness is out of all proportionto its price. Briefly, it enablestwo wander -plugs to be connectedto a single socket.

The Twintap is, in effect, a plughaving two socketsti_ It is often asource of irritation to iire constructorthat he cannot insert more than oneplug in a grid -bias or H.T. batterysocket, and frequently there must besome loss of efficiency on thataccount. The Twintap completelyovercomes the obstacle, and allconstructors should be in possessionof at least one or two.

The Lissen PotentiometerThe Lissen volume -control po-

tentiometer is one of the best unitsof what is probably the most compre-hensive range of radio products madeby any one manufacturer in thiscountry.

And what a marvellous exhibitionof twentieth-century craftsmanshipthis range constitutes. There ispolish and finesse on every singleitem bearing the name of Lissen,from the simplest gadget to the largerof the complete radio receivers.

Comparatively simple though avolume control may at first sightappear to be, its complete successdemands very high standards ofmechanical and electrical skill. Asmooth knob rotation must be backedup by a smoothly continuous re-sistance change, and the one withoutthe other is useless.

The Lissen potentiometer volumecontrol does not fail on either count,and in action it gives an even grada-tion and a complete freedom fromnoises.

As would only be expected of sucha firm, Messrs. Lissen are well to thefore in the manufacture of thosecomparatively recently introducedcomponents-completely canned coils.These, by the way, are not to beconfused with their less efficientpredecessors-more or less ordinarycoils with " tin hats " on. Modernscreened coils are specialised pro-ductions, as different from theseas any ostensibly similar thingscould well be.

In addition to single units, Messrs.Lissen are making a useful two -coil

96

assembly, both coils being mountedon the one chassis and operated bythe one wavechange knob.

Such an assembly has, of course,several advantages over two singlecoils. We have used Lissen two -coilassemblies in various types of setswith conspicuous success.

Perm col PanelsWe have been asked to give our

opinion regarding Permcol panels.This we do not find difficult, for wehave employed a large number duringthe past year or so. Permcol panelshave beautifully polished surfaces,and they " work ' easily withoutundue chipping.

, They retain their attractive sur-faces unimpaired even after exposureto sunlight and other trying conditions.Electrically they reach high stan-dards, and surface leakages are notencountered when they are used.

Preh ResistancesThese well-known components are

now being made in this country, andthe range covered is said to includeevery form of resistance, variable andotherwise, for all normal purposes,including double- and triple -gangedresistances and potentiometers, com-bined resistances containing two sep-arate strips operated by concentricknobs, variable resistances with switchcombined, heavy-duty types withabnormally high current -carryingcapacities, potential dividers, etc.

We have had the opportunity ofthoroughly testing two of the variabletypes of Preh resistances. Theyembody excellent actions, smooth andpositive, and both mechanically andelectrically they conform with highstandards.

iP0%000000%0000%0E'VEg PRACTICAL POINTS ib Measuring Bias-Improvised Trimmer '03'

ZtP,30**Z003C9QGc330c1PLIGGOO

Voltmeters are not much use formeasuring automatic bias voltages,but a milliammeter in series with theresistance itself affords an accurateguide, the current passing (in amps.)being multiplied by the ohms of theresistance to decide the voltage acrossthe resistance.

*

Quite a good emergency trimmingcondenser can be made from a shortlength of twisted flex wire, one endbeing left free and the other connectedto the fixed and moving vanes respec-tively of the main condenser. Thecapacity of this trimmer will dependupon the length of the twist, so it iselmily varied, as may prove to benecessary.


;%'39f3433(X3f9G. f,!3S345!9f9(83f3GcS3g

IN THE ANNOUNCER'S a6-3 ROOM9 -continued from page 5 a

ocs,ozoc3cm3q3cDoc3oczeq:

" Now, as there is no programmeon, I can take you into the announc-ing -room," he continued. " While Iam using this studio group for a pro-gramme, the red light glows outsidethe announcing -room."

This announcing -room idea is quitenew. There used to be little cabinetsat the side of the Savoy Hill studioswhere the announcer could talk on thehouse 'phone while a broadcast wasgoing on from the studio. The cabinetswere too tiny and too echoey for himto use a microphone.

Complicated WiringThe new announcing -rooms are

padded just like the studio and thereis a special microphone for the an-nouncer in charge of each studio.

" Here you are," he said, " this ismy abode while the main studio is inuse. For all important broadcaststhere is an operator in the listening -room, and he signals to me that every-thing is going O.K. Here is my micro-phone for inter -spacing announce-ments in the main programme, andhere is the potentiometer, whichchanges over from the microphone tothe studio microphones."

The announcer showed me the -wir-ing of his control desk. It is reallyamazing that just one small unit ofthe new studio should entail so muchcomplication. Apart from all thecontrol switches and faders, there isa complicated decoupling circuit forthe announcer's microphone.

In addition to the microphone" fader " there is a dual control forcutting down the 300 -volt high-tensionsupply to the condenser " mike "amplifier.

" These controls are just as accurateas those in the main control -roomupstairs," explained the announcer," and it is possible for the balance ofthe artistes in the main studio to beadjusted here. It means that anefficient announcer must not only havecultivated a B.B.C. accent (sic !), butmust be a dramatic and musical critic 1"

IFIONDV,ODERN MAUFOR 1111- 1 RR E SS" WM

T heir sterling quality com-mands the attention of alldiscriminating constructorsFor the

TWO VALVE D.C. AMPLIFIEREACH

2, 5 -Pin Valveholders, List No. VH.5, 101d.1, D.P. Mains Switch, List No. 5.104, 2/-1, Mains Plug & Fuse, List No. F.15, 3,61, Transcoupler," List No. LF.10, 11,61, Mains Resistance, List No. MR.4, 11,6

For the 6 watt A.C. AMPLIFIER1, D.P. Mains Switch, List No. 5.104, 2,-1, Thermo Delay Switch, List No. S.100, 7;'6

Hundreds of similar high-classcomponents are illustrated withwiring diagrams in our 80 -PageCatalogue M.' Send 2d. Postage.

9 4 Claw Ga..

A. F. BULGIN & CO. LTD., Abbey Road, Barking, Essex.Telephones :Grangewood 32.0o Si 3267.

HAND CRAFTSMANSHIP!BUILT LIKEA PIANO.

Used by B.B.C., famous;experts, 3,000 clientele.

FOR YOURRADIO -GRAM.

The sort people desire to possess and keep. Taste-ful beauty-Piano finish-advantages also ofPIANO TONE baffle chamber.The BETTER REPRODUCTION-that your Setand Speaker is really capable of-gives you aJoyous sense of achievement.Sent ON APPROVAL-direct from the makers-Prices 651- to £15 (Cash or Deferred) you mayreturn at our expense if you wish to part with it.

Photographs and lists FREE I

PICKETTS Radio Furniture (N.W.),Albion Road. Bealeyheath. Kent.

I1UI10 SUPPLIE-Send your het of Radio needs tar our quotation-Kits,Parts. Sets, eto. Everything in Radio stocked; promptdelivery. 7 days' approval. Catalogue free. Taylex

and standard Wet H.T. replacements stockedIf.TAYLOR,57StudleyRd.,StockwelLLondon

I Make

The DAILY SKETCHYOUR Picture Paper

The Magazine forthe MANLY BoyCHUMS has been famous for many,

many years-and is now morepopular than ever. Every month it iscrammed with splendid yarns of thedaring exploits of well-known ex-plorers, sea mysteries and excitingtales of school and sport. There arealso articles on hobbies and films, andeight pages in PHOTOGRAVURE.

CHUMSAt all Newsagents-Monthly 1/ -

FOR EVERY SET- there's a SEND NOW FOR LATEST LISTS

PILOT AUTHOR KITPEIO-SCOTT CO. LTD. 77, CITY RD. LONDON, E.C.I CASH - C.O.D - or H.P.

97


CLIX KITS RADIO NOTES andTime andTrouble Saversfor Constructors

CONSTRUCTOR'S KITSContains all the componentsnecessary to give perfect A.,E., H.T., G.B., L.T., and L.S.contacts to any two- or three -valve receiver.

9 PANEL TERMINALS,2 SPADE TERMINALS,6 " MASTER " PLUGS.

From all Dealers 3 1

S.T.400 KITContaining all the contactcomponents as specified andrecommended by Mr. Scott -Taggart.

3 Specified G.B. WANDERPLUGS,

9 H.T. " MASTER " PLUGS,11 PANEL TERMINALS.

From all Dealers 4fOn the left is shown the Clix

Master " Plug. Price lid.Clix supplies the finest range of contactcomponents in existence. Folder " M "gives full details. Write for your copy.

I WS I git li I A TA

LECTRO LINX Ltd., 254, Vauxhal Bridge Rd., S.W.1.

SPECIFIEDand recommended by

Mr. Scott -Taggartfor the

4The Varley N ICLET was speci-fied in the original "S.T.300,"and Mr. G. P. Kendall, B.Sc.,Chief Engineer of ReadyRadio, has chosen it in pre-ference to all alternatives forinclusion in the Ready Radio" S.T.400 " Kit. See that youget THE S.T.400 NICLET-specially designed and labelledfor this great set by Varley.

TheREADY NOW

S.T.400NICLET 7/6

axlePromv... Oliver Pelt Ooncro, Ltd.

Add, of Oboe, Yelt Control Ltd., 103, Kfitestuali, W. C.2Tel.: Holborn 5303.

NEWS of the MONTH

Ultra Short -Wave TelevisionTRANSMISSIONS of television by

the Baird process are now be-ing sent out on Wednesday and

Friday from 3 p.m. to 5 p.m. on the7.3 -metre B.B.C. transmitter atBroadcasting House.

These transmissions are entirelyexperimental, the subjects trans-mitted being, for the most part, theartistes rehearsing in the televisionstudio in preparation for the regulartelevision transmissions.

Images with 90 lines up to as manyas 240 lines in place of the present30 -line pictures have been trans-mitted experimentally in the Bairdlaboratories, and when ultra short-wave broadcasting becomes estab-lished the result of this research willbecome available to the public. Inthe meantime amateurs within rangewith ultra short-wave receivers willbe able to take advantage of thetest transmissions from the B.B.C.aerial.

The Baird Company will welcomeany reports.

New Year GiftEvery listener should get a copy of

the B.B.C.'s 1933 Year Book, whichhas just been published by the B.B.C.at 2s. Besides a wealth of informationof a statistical kind regarding broad-casting, there is an enormous amountof general information which shouldprove of fascinating interest to everytype of listener.

An Illuminating ReviewMany eulogistic reviews have been

published concerning this Year Book,most of which we agree with, but inparticular do we_agree with ..CaptainErnest H. Robinson, -who, writing inthe " Observer " recently concerningthe Year Book, said : " We see in ita self-satisfaction which often ap-proaches the smug, and it would bealarming were it not offset by lightfrom another facet which shows ushigh ideals and a sense that there isa long way to go before they Can beattained."

That one sentence is probably themost illuminating which has yet beenwritten° concerning the Year Book,

Lord Ponsonby's TalkA good deal of nonsense was written

in the Press about Lord Ponsonby'srecent talk, but as Lord Peel wasallowed to give a reply it is difficultto see how the B.B.C. can be accusedof allowing a one-sided talk to bebroadcast which, according to the" Patriot," allowed Lord Ponsonby to" deliver a philippic against our wholesocial system."

The " Patriot " expresses the viewthat " for such purposes a noble giftof science has been used, and it maybe questioned whether Hollywoodfilms of Jewish manufacture, reekingof sex and vividly portraying crimeand vice in many aspects to our youthand maidens, have done more harmto the national moral than the B.B.C.What it will do next, unless it isbrought under the control of Britishpatriots, who can tell ? "

The National ViewpointWell, of course, that is gross exag-

geration, and it certainly makes clear -thinking people sincerely hope thatthe sort of British patriot extolled bythe writer of the above quotation inthe " Patriot " will never be allowedto have any control of the micro-phone.

The B.B.C. has always proved itselfamenable to correction, when correc-tion is necessary ; and, although ithas allowed certain people to beindiscreet before the microphone,there is no real justification for sayingthat the B.B.C. is unpatriotic or thatit is in any way biassed in its viewson national and international affairs.

B.B.C. BaitingAnyway, B.B.C. baiting is poor

sport, and is certainly overdone thesedays. It is small wonder that awriter in the Year Book reproachesthe Press for its lack of constructivecriticism.

Under One MetreMarchese Marconi, in a recent talk

before the Royal Institution, directed(Continued on page 99)

January, 1933

e%o%o@tammeavigg,s5Eg000RADIO NOTES ANDNEWS OF THE MONTH

0 -continued from page 98

ogeol3Goozo,;:Geq3c93c63q3q3

attention to the only partially ex-plored range of wireless waves under1 metre in length, and emphasised theincreasing interest in the importanceand use of short waves, indicating tosome extent a return to the earliestdays of wireless when such wave-lengths were employed.

First Practical ResultsBelow One Metre

The Marchese went on to point outthat the application of micro -rays topractical communication beyond thelimits of laboratory experiments wasfirst made by International Telephoneand Telegraph Laboratories, who,some eighteen months ago, gave ademonstration of telephony acrossthe Straits of Dover, using the remark-ably short wavelength of 18 centi-metres.

The quality of the speech trans-mitted on that occasion was betterthan that of a normal telephoneconversation between two subscribers

area, and no fadingwas detected.

Curbed By CurvatureAs a result of these tests, the

Marchese explained, the engineersconcerned were of the opinion thatthe maximum distance betweenstations must, from the straight linepropagation of the waves, be con-ditioned by the curvature of the earthand the altitude of mountains. Incertain cases, between ranges of highmountains, intervals of over 100miles could be bridged direct ; butordinarily relay stations about fiftymiles apart, or less, would be requiredfor long-distance working on theseultra short waves.

Inverted MiragesMarchese Marconi states that he

has effectively demonstrated thatthese very short waves could over-come the supposed obstacle condi-tioned by the curvature of the earthand distance between the twostations considerably in excess of theoptical range ; and the theorists arecertainly at a loss to explain such aresult, for it is true that whateverwavelength is used, there is alwaysa certain amount of bending, andeven with the short-wave lengths oflight we can, to some extent, " seeround a corner "

It is also likely that extraordinaryelectrical effects in the atmosphere-for example, magnetic storms andthunder storms-may produce in-verted mirage effects.

Further experiments on this subjectare to be carried out, and everyoneinterested in ultra short waves willeagerly await the results.

B.B.C. GovernorsAs we go to press, it is announced

officially that the King has beenpleased to approve the following threeappointments to the Board of Gover-nors of the B.B.C.:

To be Governor and Vice -Chairman :Mr. Ronald Collet Norman.

To be Governors : Viscount Bridge -man and Mrs. Mary AgnesHamilton.

For Four YearsThe appointments are for a period

of four years, from January 1st, 1933,to December, 1936, when the B.B.C.'spresent Charter expires. The threeretiring Governors are : Lord Gain -ford, the Vice -Chairman ; ViscountessSnowden, and Dr. M. J. Rendall.

Last Year's ExtensionConsiderable disappointment is ex-

pressed at the non -election of Lady

MODERN WIRELESS

Snowden, but it will be recalled thatabout a year ago the original appoint-ment of Lord Gainford, Lady Snowdenand Dr. Rendall for a period of fiveyears was extended in each case foran extra year owing to the specialwork on which the Governors werethen engaged in connection withEmpire broadcasting.

New Vice -Chairman WellKnown in London

Mr. R. Collet Norman is a brotherof Mr. Montague Norman, the Gover-nor of the Bank of England. He hasbeen a member of the L.C.C. since1907, and an Alderman since 1922 ;was Chairman of the L.C.C. in 1918-19and a member of many departmentaland other committees.

Viscount BridgemanViscount Bridgeman is a former

Conservative Cabinet Minister, andwas Secretary for Mines, 1920 ; HomeSecretary, 1922-21 ; and First Lordof the Admiralty, 1924-29.

An Author, Too !Mrs. Mary Agnes Hamilton is a

politician, novelist and journalist, andthe eldest daughter of the late RobertAdamson, Professor of Logic, Glasgow


SPECIFIED FOR 51.400For eight years Belling -Lee products havebeen the most consistently specified com-ponents offered to the public. WHATbetter recommendation is avail/able ?Another interesting specification. Mr. G. P. Kendall,B.Sc., has again chosen Belling & Lee Terminals, etc.,for all Ready Radio kits this year.

S.G. ANODE CONNEC-TORS. Fully insulatedeven when disconnected.Safeguards S.G and Pen-

tode Valves. 4d. each.

" BOW -SPRING"WANDER PLUGStrong Spring andwide self -adjustment. 11d. each

SPADETERMINALSWith thepatent Belling -Lee grip andpermanentlettering o n

the handle.

(Regd. Design)TWIN -TAP BATTERYPLUGS. To take two con-nections from one Battery

Socket 1d. each.

BELLING -LEEFOR EVERY RADIO CONNECTION

Advt. 0.1 Belling & Lee, Lid., Cambridge Arterial Rood. Enfield, Max.

99

MODERN WIRELM January, 1933

@Egw&oosvg,w&@a63

a RADIO NOTES ANDNEWS OF THE MONTH

WS, -continued fronz page 99cz1

ocgacmteo0,0eoFgo @&30

University. She was Socialist M.P.for Blackburn, 1929-31, and wasformerly Parliainentary PrivateSecretary to the Postmaster -General.

She was a member. of the British"delegations at the Leaglie of Nationsassemblies in 1929 and 1930 ; whilstamong her many books are bio-graphies of Mr. MacDonald andMary MaCarthur. She has also writtenseveral novels, 'including one thriller," Murder in the House of Commons."Listeners will remember her chieflyas a B.B.C. critic of new novels.

No EntertainmentRepresentative

So far, no criticisms of the newGovernors have appeared in the press,but general surprise is felt that thePrime Minister has not thought fit toappoint at least one new Governorwith some definite understanding ofthe psychology of entertainment.EiP00@at8e000000656PEPPEEM)%

RECENT RECORDRELEASES

from e 62

OPEg@OE/PE150-conti @t.%nued @)68)0g@paggig0CCaaAA

The recording is a little thin at times, but on thewhole the disc is a good one, and those who arefond of musical switches with plenty of switch willthoroughly enjoy it.

Some of these records have perforce been men-tioned before-last, month to be precise-whenthe special Christmas discs were mentioned, butI had not then had time to review them properly.So here goes with a favourite that is bound tohave a wide sale-Gracie Fields' Christmas Party.It includes as additional " bait " to the publicGracie's mother, who sings with her famousdaughter a couple of duets.

The whole record is one that will have a goodgeneral appeal, for it is undoubtedly attractiveas an entertainment provider, and Gracie singsseveral of her most successful songs on it, Including" Our Avenue," " Singin' in the Bathtub " and" My Ohio Home " in her own inimitable way.She is a wonderful artiste, isn't she? Whether ornot you like her as a singer, you have to admitthat. (C2487.)

The idea of Paul Jones in the home is a goodone, and several records with the idea of providingthat ever -popular dance feature have been issuedlately. One of the best,however, Is undoubtedlythat by nay Noble and his New Mayfair Orchestraon C2497, being Parts 5 and 6. It includes suchfavourites as " Gipsy Moon," " 0o, that Kiss,"" You're My Everything " and " Mona Lisa "among the sections of the " Paul Jones."

A great deal of fun can be obtained with thistype of record if you have a few friends in thehouse, for quite an interesting dance can be heldin one's own room if a small selection of dancerecords has one or two of these "Paul Jones"' discsincluded. The sections are not too long and somonotony is never threatened, while they arelong enough for one to get. quite decent dancesout of them. '

Jeanette Macdonald is too well known on thetalkie screen to need any introduction, but inspite of her fame I must say I do not like herrecords Isn't it Romantic ? and Love me To -nightfrom her film of the latter name. The tunesthemselves are not attractive, and somehow thenumbers " miss the boat." Jeanette's voice maybe O.K. on the talkies, but I do not care for iton wax, though I think the fault lies more withthe material at her disposal in the way of a songthan in the artiste herself. These two songs arelifeless throughout. (B4288.) It is not a record

jllllllllIIIIIIIIIIIIIIIillillllplllltIlllllllllllllllllllllllllillllll

NEXT MONTH Full details for making

A SUPERHET for SHORT WAVES.E:

" MODERN WIRELESS"On Sale Feb. 1st - 1/-

7J111111111111111111111111111111111.111111H111111111111111111111111llilliF

from the talkie film, I suppose, instead of a brand-new recording ? Anyhow, I suppose it was donein America.

One of the funniest records I have heard for along time is Double Damask, in which the trials of

.Cicely Courtneidge, say a. couple of shopassistants, are depict The sketch is one thathas been broadcast, believe, but It is one thatyou can listen to again and again without becom-ing weary of it. On the other side is that amusingtelephone girl sketch, I'll Give Her a Ring, whichwhile not so good as " Double Damask," is never-theless very good. It is a bit overdone, and CicelyCourtneidge is a bit too fond of rolling those It'sof hers, thereby taking away from the possiblereality of the character she is impersonating.No 'phone girl carries on quite so much as she.(B4314.)

After Cicely I must mention her husband, whowith his brother Claude Hulbert makes an amusinggangster record, entitled The Hulbert Brothers inChicago. It is fully up to the Hulbert style.(B4332.)

Old Moore's Almanac, a " comedy " dance num-ber by Ray Noble and Co., is not too good. Thetune is lively enough but the vocal refrains arepoor. By the way, is that Leonard Henry takingthe vocalist's part ? It certainly sounds like him.(B6269.)

EMODO%0 S60 00000Eg OW&00 BEHIND THE SCENES OF tz4 THE BIG ORCHESTRA 663

-continued from page 77 0ozezeg(59,s3 toms Qi943433

broadcast. Large chalk cross marksare made on the floor to show thepositions of the strings and the brasssoloists.

Very often before the hundred orso players of one of the subdivisionsstart to do any serious rehearsing inthe morning, the engineers have tospend over an hour in deciding wherethe trombones shall be or where thepianist can be put so that the pianodoes not " blast."

Our Orchestra AbroadThese are only a few of the trials

of modern broadcast music with abig orchestra. Special tests have hadto be made for cross -Channel broad-casts of the B.B.C. Orchestra and forInternational relays.

A number of programmes have beengiven recently in the big studio foreither the National or Regional pro-grammes at London and also for dis-tribution on the European landlinecircuit. A number of German stationshave been particularly anxious toinclude relays of the B.B.C. Orchestrain their programmes, and we, inreturn, have borrowed " an occa-sional German orchestral broadcast.

A Big Hook -UpFive European countries were

recently covered by a big studiobroadcast of the B.B.C. Orchestra.All but one took the programme bylandline link on the cable which runsunder the Channel, but Norway tookthe B.B.C. Orchestra broadcast byradio link, and an official Norwegian -receiver tuned -in to 5 X X.

INDEX TO ADVERTISERS

Belling & Lee, Ltd. ..Benjamin Electric Co., Ltd. ..Bulgin, A. F., & Co., Ltd...Burne-Jones & Co., Ltd. ..

Carrington Mantg, Co., Ltd. ..Clarke, H. & Co. (M/cr.), Ltd. ..Colvern, Ltd. 1

Complete Handbook of Practical Radio 95

Dubilier. Condenser Co. (1925), Ltd 75

Formo Co. .. 81

PAGE99759785

978179

General Electric Co., Ltd. ..Gilbert, J. C. (Cabinets)Graham Farish, Ltd. ..Gramophone Co., Ltd...

Heayberd, F. C., & Co.

Jackson Bros. ..

PAGE. . Cover iv

9671

2

96

.. 79

Lectro Linx, Ltd. .. .. 98London Electric Wire Co. & Smiths, Ltd.

Cover ii

Multitone Electric Co., Ltd.Motor Ships & Engines ..

Peto-Scott Co., Ltd. ..Pickett Bros. (Cabinets) ..

8193

9797

PAGEPifoo, Ltd. .. . . Cover iii

Reproducers and Amplifiers, Ltd. .. 85

Taylor, M...........96 and 97Tunewell Radio, Ltd... .. 81

Varley Products ..

Ward & Goldstone, Ltd. ..Wingrove & Rogers, Ltd. ..Wright & Weaire, Ltd. ..

98

938581

All communications concerning advertising inModern Wireless ' must be made to

John H. Lile, Ltd., 4, Ludgate Circus, London,E.C.4. Telephone: City 7261.

FOR ADVT. RATES SEE PAGE 85.

Printed and published by the Amalgamated Press, Ltd., Fleetway House, Farringdon Street, London, E.C.4. on the let of each month. Address forAdvertisements : John H. Lie, Ltd., 4, Ludgate Circus, E.C.4. Telephone : City 7281. Registered for transmission by Canadian Magazine Post. Subscriptionrates : Inland and Abroad, 17/- per annum ; 8/6 for six months. Sole Agents for Australia and New Zealand : Messrs. Gordon & Gotch, Ltd. ; and for SouthAfrica: Central News Agency, Ltd.-January, 1033. S.G.

No

january, 1933 modern wireless contents · 2019. 12. 29. · january, 1933(modern modern wireless...

Documents