how to build a portable wireless magazine · 2020. 12. 27. · bernard e) jones wireless magazine...

How TO BUILD A PORTABLE AND A TRICKLE CHARGER

WirelessMagazine

JUNE 1929

147

Make the Melody

LOUDERand

CLEARER

Cossor Valves bring in dis-

tant stations with amazing

volume-they increase the

rangeof any Receiver. They

give enormous volume and

purity as well. Cossor

Valves made possible the

wonderful Cossor MelodyMaker. They improve anyReceiver - use them in

yours-your Dealer will

tell you the types you need.

with

CossorBRITAIN'S FINEST VALVES

A. C. Cossor, Ltd., Highbury Grove, London,

11

M8314

Technical Editor:

I J. H. REYNER,Vol. IXB.Sc.(Hons.),A.M.I.E.E.

*Editor

BERNARD E) JONES Wireless MagazineThe Best Shillingsworth in Radio

JUNE, 1929 :: No. 53

Our Show WindowIAM re -introducing you to an old friend this month

-the Chummy, one of the very few portables oflast year that made history. So successful was

this 'Your" that we thought it would be an interestingexperiment for W. James-who was not a member ofour staff when the Chummy was originally designed-to become responsible for a 1929 edition.

The two outstanding features of the new Chummyare (1) it is now suitable for both of the broadcastingwavebands and (2) it has a much lower H.T consump-tion-either of them a considerable advantage.

The Chummy is our second outstanding portable ofthe year-the first being J. H. Reyner's Wayfarer,described in detail last month. This, as you know, isa five -valve super -het, and in the present issue Mr.Reyner takes us "On the Road with the Wayfarerthrough the Southern Counties, and we enjoy ourselvesin Devonshire and Cornwall-in imagination.

We have not finished with portables, and in the nextissue we shall be describing a highly efficient but cheaperset for use principally with the local station.

Our portables are not our only sets of importance thismonth. I should like you to look at the Music Player,which undoubtedly sets a standard of performance.

The economical listener will like the Continental Twowith its choke -fed intervalve transformer. While onlya "two" it gives a performance of which many "threes"might be proud. t

The reader who delights in listening to far -distantstations will find his interest centred in the Short-waveLink, a three -valuer working on wavelengths of between16 and 5o metres.

The article by J. Godchaux Abrahams in this issuereminds us that the holiday season will soon be upon us.He advises us to take our portables when we visit theContinent (what about our vaccination certificates ?)and says that, generally speaking, the foreign customsdepartments raise little difficulty to the visitor bringingin with him a wireless set

Our general articles this month are, as usual, of aninteresting and entertaining nature, and among themis one by S. F. Edge, the motoring pioneer, which pre-sents a somewhat unusual review of the wireless industry.

C Whitaker -Wilson continues this month hisexplanatory articles addressed to the music listener, andon this occasion talks about the "fugue."

Another of our general articles to which readers aresure to turn is "A Trek to the Talkies" in which a cor-respondent speaks of the lure which the "talkies" havefor technically trained men in the world of wireless.

A little piece of apparatus described by W. James inthis issue will prove of value to those readers who havethe benefit of a mains electrical supply. It is an L.T.charger which can be used for accumulator work (it hasa I -ampere output) or for running a moving -coil loud-speaker direct from the mains.

Altogether a very useful number.

Do Not Overlookthe Half-price Blue-print Coupon onPage iii of the Cover

Research Consultant :

W. JAMES

Assistant Editor :

D. SISSON RELPH

CONTENTSPAGE

Valves to Use in Your Set 402Wavelengths of the European

Stations .. . .. 406In Tune with the Trade ! .. 408The 1929 Chummy. Last

Season's Famous Portable Four-valver Re -designed by W.James . . . . . . . 411

Awkward Moments in the Studio !By An Ex -announcer .. 417

Changes in the Country .. 418Found Out ! Verse .. 418Pity the B.B.C. .. 418Do You Know the " Z " Code ? .. 419The Adventures of Alec Trode .. 419The Original Loud -speaker . 420Station Powers That Puzzle .. 420

GRAMO-RADIO SECTIONIs It Worth While ? . .Portabilised Gramo-Radio . .

In the Track of the Needle . .

Speech Reproduction. ByH. T. Barnett, M.I.E.E. .

" If I Were Bass Deaf " . .

A Record Record . .

Building Your Own Gramo-phone. . . . .

Storing Your Records . .

A Good Portable Gramophone

421421421

422423424

424424424

The Trek to the Talkies. B.B.C.Staff Changes .. .. 425

The Music Player. A Four-valver for Radio or GramophoneReproduction .. .. 427

Minor Oscillations. Cartoon .. 433Under My Aerial. Halyard's Chat

on the Month's Topics.. .. 434Radio Lamp Lighting .. .. 436On the Road with the Wayfarer.

By J. H. Reyner, B.Sc.,

The Music Listener. By C.Whitaker -Wilson .. 439

The Short-wave Link. AThree-valver for Reception onWavelengths from 15 to 50Metres .. 441

better Health by Radio ! 446Controversial and Alternative

Broadcasts. By A. A. Gilliland 448

437

PACE

The Letters of Priscilla Playne-Smythe . 450

List of Eastern Broadcast Stations 450Impressions of Broadcasters . . 451Mr. Plarz Gets Magnetised !

Mother Half-hour with Pro-fessor Megohm 452

Building Your Own L.T.Charger. By W James .. 455

Take Your Portable to the ForeignStations ! By J. GodchauxAbrahams .. .. 458

Australian Radio .. .. 459What You Can Get with " W.M."

Sets .. 460Motorised Radio ! By S. F. Edge 462Schoolboy's Wireless Howler .. 463An Optimistic Reader .. .. 463Overheard at the Charging Station 464The Continental Two. A Set

with Choke -fed IntervalveTransformer .. 465

Television in the U.S.A... .. 470Emergency News by Radio .. 470

Reshuffling the World's Call-siens

Get Your Grid Leak and Con-denser Right ! By W. James .. 471

Broadcast Music of the Month. .. 474Fight Between Big U.S.A. Radio

Companies .. .. 478Keeping Batteries Good In-

definitely ..Linking 200 Local Stations by A

New System ..Method in Their Madness !Radio Not to Blame ..A Difference of A Few Years ..Musical Background and the

Broadcast Play ..Leaves from A Listener's Log.

By Jay Coote .. 484Radio Helps the Indian Air

Service ! .. 486Summer Time .. .. 487A New Set Tested. By J. H.

Reyner, B.Sc., A.M.I.E.E. .. 488Short-wave Channels .. 490Nippy's Loud -speakers .. .. 490Wireless Echoes .. 490Dynamic Reproducers .. 490Multi -diaphragm Loud -speakers.. 490Reference Sheets. By J. H. Reyner,

B.Sc., A.M.I.E.E. .. 492Buyers' Guide .. .. 496

478

480480480480

481

Published by BERNARD JONES PUBLICATIONS LTD., publishers of 1

" Wireless Magazine" and " Amateur Wireless." Editorial and Adver- 1

tisement Offices : 58161 Fetter Lane. London, E C.4. Telephone . City 3733,3734. Telegrams : " Beejapee, Fleet, London." Published about the z5th day ofthe month and bears the date of the month following. Subscription : Great Britainand Abroad. 15s. 6d. a year, post free (Canada only, 13s. 6d.) Contributions are

invited and will be promptly considered***An All -wave Lodestone Five with Push-pull Amplifier Next Month

Rpg,isterod at lb. General Post Office for Transmission by Canadian Magazine Pus

401

Wireless Magazine. June, 1929

a se inTWO -VOLT VALVES: Three -electrode Types FOUR -VOLT VALVES -Continued

Make. Type. Impedance.Amp.Factor.

Fil.Volt.

Fl!.Cur.

Make. Type. Impedance.Amp.Factor

Fil.Volt

Fil.Cur.

EdiswanMazda ..Cosmos ...Six -SixtyEdiswanCossor ...Milliard-Marconi...Osram ...Mazda ...Six -SixtyEdiswanMarconi...Osram ...Mullard ...

R.C2RC21 oSPI6B210RCRCzio21oRCPMIA

DEH210DEI-1210H F2I0210HFHF2 10H L2I0HL2 toI'M i HF

i 50,00086,00070,00068,00067,0006o,00051,000

)50,000 I

5 .1

28,00027,00o25,000

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c23,000 i

22,500

io4035354o403635

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PM4D XLF4o7PV4io

DEP410DEP4 1 oLF4ioa

PM44 i oP42.5SPPM254P415P425P425

415XPPV42 5

7,5005,7005,500

. )r 5,000 (

4,5004,4504,0003,6003,5002,9002,25o -I

1 2,000 I. .

158

5.57.57.59883.23.155.54.54.543

444444

4

444

44444

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Cossor ...Six -SixtyCosmos ...

210H F.210LFSP16G

20,00018,00017,000

158.5

16

2

2

1.8

.1

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.09SIX -VOLT VALVES: Three -electrode Types

Mazda ...EdiswanCossor

GP2 10LF210210LF

14,00013,000

1313

2

2. I

.I Make. Type. Impedance. Amp.Factor

t'll.Volt.

..*

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...Marconi..Mullard ...Osram ...Mullard...Cosmos ..Six -SixtyMazda ...EdiswanCossor ..Marconi...DEP215Osram ..Cosmos ..Mullard ..Cossor ...Six -SixtyMazda ...EdiswanMullard...Marconi...Osram ...Cossor ...

DEL2 1 oPM1 LFDEL210PM2D XSP i 6R2151'

LF215PV215220P

DEP215SPi8RR

PM2220P23oSPP227

PV225PM252DEP24oDEPz4o23oXP

1

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13.596.478

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RC6o76o75RC6IoRC

DEH6 1 oDEH610

PM5 B12C610HL610HL6I oLS5BLS5BHF6ioDE50

61oH17HF6o76o75HFPM5XGP6o7LF6I 0PM6D6IoLF

DEL6io

90,00074,00o

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FOUR -VOLT VALVES: Three -electrode TypesMarconi...Osram ...Marconi...Osram

DEL610LS5LS5

7,50o 1

6 000 f' 1

1515

55

665.255.25

.1

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Fil.Volt.

Fil.Cur.

...Six -SixtyMazda ...Mullard

610PLF6o7PM6

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RC4074o75RCRC4104 ioRC

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(Continued

4,2003,600

3.500 -I

3,000

2,750

2,600

2,40o

2000,

1,750

1,600 .1

on page

53.2883.158

3

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i 553.543.73.7

404)

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402

Wireless Magazine, June. 1929

TWO NEWFEATURES

A. --Ball - Bearing Swivel Joint,reducing friction to a minimum, thus allowingneedle to " track" more easily. By preventingpull on the side of the record groove this featureadds to the life of the record.

B.-Offset Pick-up. By offietting thepick-up, in respect of the fulcrum of the arm,error in needle tracking is reduced to no morethan 3°. The motion of the pick-up armatureis always at right angles to the track, also resultingin minimum record wear.

With the addition of the two newfeatures mentioned alcove the B.T.H.Pick-up and Tone -arm reaches a highstage of mechanical and electricalefficiency. With the new B.T.H. Pick-up and Tone -arm you get better repro-duction with a minimum of wear on therecc rd. In a word, your record is beingtreated fairly and you hear it at its best.

Price £2. 5. 0.The above price is applicable in Great

lit in ana Northern Ireland only.

PICKUPCTONFAINWITH BALL -BEARINGS AND IMPROVED TRACKING DEVICE

3208

The British Th.mson-Houston. Co., Ltd., Crown House, dielaych, H .C.z.

403

i Wireless Magazine. June. 1929

VALVES TO USE IN YOUR SET -(Continued from page 402)

FOUR -ELECTRODE VALVES: Screened -grid MAINS VALVES: Three- and Four -electrode

Make. Type. Impedance. Amp.Factor.

Fil.Volt.

Fil.Cur. Make. Type. Impedanco.

Amp.Factor.

Fil.Volt.

Fil.Cur.

Mullard...Six -SixtyCossor ...M arconi...Osram ...Ediswan

P11Ir 22 I 5SG220SGS2I5S215

SG215

230,000220,000

,020000140,000

200190200170170140

2

2

2222

.15

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Marconi...Osram ...Marconi...Osram ...Marconi...Osram ...Marconi...Osram ...

S Point 8S Point 8H Point 8H Point 8HLPoint 8IILPoint 8P Point 8P Point 8

200,000 i

I. 0 l,55 00 1

17,000 i

I. 6,000 {

16o160

40401717

66

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444

4

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KH1XIIIKL iKit

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7.57.5

3.53.5

3.53.5

2.02.o

2.02.0

Marconi...Osram ...Ediswan

S6255625

SG610

i

1175,000

100,000

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FIVE -ELECTRODE VALVES: Pentodes Cossor ...EdiswanCossor ...Cosmos ...EdiswanCossor ...Cossor ...Cosmos ...Cossor ...

MRCMI4IRC

MHFAC/G1\1141

MLFMP

AC/R1\1X P

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EdiswanSix -SixtyM ullard ...Marconi...Osram ...Cossor ...

5E22523oPPPM22PT235PT235230QT

65,00064,00062,500

20,000

8o8o8290

40

22

2

2

2

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.25

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.3Mullard ...Six SixtyCOS-if:Q. ...

PM24415PP415 QT

28,60027,00020,000

626o40

444

.1515 15

A glance through the constructional articles in this issue willgive the novice some hints regarding the best valves for the

various types of circuitsMullard... P1\126 25,000 50 6 .r7

Again Specifiedfor " 1929 CHUMMY FOUR "

FORM° LOG CONDENSERThe SMALLEST, LIGHTEST

.

CONCEALED

PIGTAIL

SINGLESCREW

PRICTIOSBRAKE

"DE LUXE"

and most EFFICIENTCONDENSERS

obtainable.PRICE

6/ -each)tl The "CHUMMYFOUR"

WEIGHT Specifies :4% OUNCES ONONP .ggp,g,

VALVE-HOLDER-Anti-microphonic, as specifiedBAKELITE throughout, includingBASEPLATE. Practically DUST -PROOF.As will be seen fromillustration, Terminalsare provided as well assoldering tags.

THE FORMO CO.CROWN WORKS, CRICKLEWOOD LANE, LONDON, N.W.2

Price

1/3

FLUXITEconquers solder

anyway, it /makes it nut.'

FLUXITE is sold in tins,price 8d., 1/4 and 2'8.Another use for Flux-ite ; Hardening Toolsand Case Hardening.

Ask for leaflet onimproved methods

FLUX1TE LTD.,(Dept. 332)

Rotherhithe, S.E.16

SOLDERINGSET Complete

7/6or LAMPonly2/6

SIMPLIFIES ALL SOLDERINGSpeedy replies result from mentioning " Wireless Magazine"

404

Wireless Magazine, June, 1929

"ALL POSITION"ACCUMULATORS

NON - SPILLABLEFOR ALL PORTABLE RECEIVERS.

JELLY ACIDkeeps the platescompletely immersed in electro-lyte with thebattery in anyposition, and fullcapacity is ob-tained in allpositions evenwhen completelyinverted.

A C.A.V. JellyAcid Cell is specified

for the 1929 Chummy

Four described its

this issue.

6-k

K.C. CONDENSER

The C.A.V. Jelly Acid Battery is making a strong appeal to usersof Portable Receivers. They are not merely adaptations of a

standard cell, but specially constructed with exclusivedevices which in conjunction with the specially pre-

pared C.A.V. jelly acid enable them to claimpreference over other non -spillable types.

With knob, dial Without knob,and slow motion dial or slow -device, '0003 or motion device,0005 12/. 0005

:0003 or 8/

CONDENSERA small variable con-denser for panel

.00,

mount-ing. '0000501 5/6or .0002 .

Catalogue No.0 will be forwarded upon application.

49)ACTON. LONDON. VV 3

K.C. DRUM CONTROLCONDENSERS

With Drum Contrul and slow-motion device, '0003 15/6or . Triple K.C., each con- 38/6denser '0003 or '0005Triple K.C. Combina- 40/.tion of '0003 and '0005

If unobtainable front yourdealer, Write direct to usgiving his name and address

1 itREGISTERED TRADE MARK

r)UBILIERdloW CONDENSERS

Dubilier Condense, Co. (1925), Ltd.,Ducott Works, Victoria Road, N.

Acton, London, W.3 p241/v

Jelly Acta Cellshave been mainstortured by us formany importantpurposes forseveral years past.and are still themost satisfactorynon spillable typeavailable today.

Obtainable fromC.A.V. Depots,Battery ServiceAgents and allWireless Dealers

wEgAtAr(4rCatiP0AINTS

FOR "ARCADIAN PORTABLE"CoilsScreenH.F. Choke ...Battery Switch ...Valve Holders, SprungGrid Leak ClipsCoil Formers ...

Each... Pair

FOR " SHORT-WAVE LINK "Valve Holders, SprungH.F. Choke . .

10/69/66/61/-2/6-/67/6

... Each 2/6

FOR "1929 'CHUMMY 4"Rotary Switch, 3 -way... ...Anode Coil

DUAL RANGE TUNERWavelengths : Low 190- 500 ...

Long 950-1900 ...As used in Ferranti Circuits.

DECOUPLING RESISTANCES500 ohm ... . . Each600 ohm ...

WRIGHT f3 WEAIRE LTD.740 High Road, Tottenham. N.17

Telephones : Tottenham 3847/8

6/6

10/6

1/6

When you send your order don't forget to say you " saw it in the W.M.'"

405

Wireless Magazine. June. 1929

WAEURC)

IN ORDER OFWAVELENGTH

A view in the Grande Place, Brussels

UNDER THE PLANDE BRUXELLES

Wave-length

Station andCall Sign Country

Kilo-cycles

Wave-length

Station andCall Sign Country

Kilo -cycles

25.53 Chelmsford (5SW) .. Great Britain .. 1,751 378 Manchester (2ZY) Great Britain .. 793211.3 Beziers .. .. France.. .. 1,420 382.2 Toulouse (Radio) .. France .. 785219 Flensburg .. .. Germany .. 1,370 391.6 Hamburg .. .. Germany .. 766222 Cork (5CK).. .. Irish Free State 1,350 395 Bucharest .. .. Roumania .. 1. 757238 Borcls..... x .. .. France .. 1,26o 396 Plymouth (5PY) .. Great Britain .. /

24o Nurnberg .. .. Germany .. 1,250 400 Mont de Marsan .. France .. 749243.9 Newcastle (5NO) .. Great Britain .. 1,230 401 Glasgow (5SC) .. Great Britain .. 748.3245 Lille (PTT) .. France 1,224 405 San Sebastian

Linz .. .. Austria .. (EAJ8) Spain .. .. 74425o Kiel .. .. Germany .. I 1,200 406 Berne .. .. Switzerland .. 739

Cassel .. .. Germany .. 411 Dublin (2RN) .. Irish Free State 730253 Montpellier .. France .. 1,185 414 Radio Maroc (Rabat) France .. 724255 Toulouse (PTT) .. France 1,175 416 Kattowitz .. .. Poland .. 721

258.4263.2

Leeds (2LS) ..Cologne .. ..

Great BritainGermany ..

1,1611,140 427

j Frankfurt .. ..Madrid (EA J7) ..

Germany ..Spain .. .. 1 703

265 Kosice .. Czecho-Slovakia 1,130 428 Grenoble (PTT) .. France .. 701267.8 Muenster .. Germany .. 1,120 428.7 Radio Flandre (Lille) France .. 697268 Strasbourg .. .. Alsace Lorraine 1,118 432.3 Brunn .. .. Czecho-Slovakia 694272.7 Kaiserslautern .. Germany .. 1,100 438 Stockholm .. Sweden .. 685276 Turin .. .. Italy .. .. 1,080 443 Rome .. .. Italy .. .. 67728o Liege .. .. Belgium .. 1,070 45o Paris (Ecole Sup.280.4 Konigsberg .. Germany .. 1,070 PTT) France .. 668

Magdeburg .. Germany .. ) Bolzano .. .. Italy .. .. 666283 .{ Berlin .. .. Germany .. 1,061 452 Belgrade .. . , Jugo-Slavia .. 664

Stettin .. .. Germany ..455.9) Danzig . . . . Germany . . 654Dundee (2DE) .. Great Britain .. Wilno .. .. Poland ..Hull (6KH) .. Great Britain .. Klagenfurt .. Austria

285.5 i Bradford (2LS) ..Bournemouth (6BM)Edinburgh (2EH) ..

Great Britain..Great Britain ..Great Britain ..

1,040 456 Innsbruck .. ..Salamanca (EA J22)Aachen .. ..

Austria

France

..Spain .. ..

,.581

Sheffield (6LF) Great Britain .. 462.2 Langenberg .. Germany .. 647..Stoke-on-Trent (5ST) Great Britain .. 468.8 Lyons (PTT; .. France .. 640

291.3 Radio Lyons .. France .. 1.030 476 Berlin .. .. Germany .. 630Liverpool (2LV) .. Great Britain .. ) 482 Daventry Ex. (5GB) Great Britain .. 622

294 Swansea (5SX) .. Great Britain .. i , i Zurich .. .. Switzerland ..1 60 4

299.3 Bratislava .. .. Czecho-Slovakia t,000 490 Oslo .. .. Norway301 Bordeaux (PTT) .. France .. 997 504 Milan .. .. Italy .. .. 595302.6 Belfast (2BE) .. Ireland .. 991.1 512 Brussels .. .. Belgium .. 586

305 Agen .. .. France 982 52o Vienna .. .. Austria .. 577305.6 Marseilles (PTT) .. France .. 981 537 Munich .. .. Germany .. 559311 Aberdeen (2BD) .. Great Britain .. 964 548 Budapest .. .. Hungary .. 548317.5 Dresden .. .. Germany .. 945 550 Sundsvall .. .. Sweden .. 546321.2 Breslau .. .. Germany .. 937 566 Hanover .. .. Germany .. 530322 Vitus (Paris) .. .. France .. 93o 68o Lausanne .. .. Switzerland .. 441323 Cardiff (5WA) .. Great Britain .. 928 760 Geneva .. .. Switzerland .. 395326.4 Gleiwitz .. .. Germany .. 919 825 Moscow .. .. Russia .. 36333o Bremen .. .. Germany .. 909 1,004 Leningrad .. .. Russia .. 299

Naples .. .. Italy .. .. 1,073 Hilversum .. Holland .. 279333

{

Reykjavik .. Iceland ).- goo1,155 Kalundborg .. Denmark .. 259

336 Petit Parisien .. France .. 892 1,200 Stamboul .. .. Turkey .. 25o339 Copenhagen .. Denmark .. 883 1,350 Motala .. .. Sweden .. 222342 Prague .. .. Czecho-Slovakia 873 1,395 Warsaw .. .. Poland .. 215

346.8 Barcelona .. .. Spain .. .. 857 1,450 Moscow .. .. Russia .. 207

350 Goteborg .. Sweden .. 858 1,470 Eiffel Tower .. France .. 203

354.2 Graz .. .. Austria .. 847 1,504 Lahti .. .. Finland .. 199358.9 London (2 LO) .. Great Britain 838 1,562.5 Daventry (5XX) .. Great Britain .. 192361.9 Leipzig . . .. Germany . . 829 1,65o Zeesen .. .. Germany .. 182

368 Radio LL (Paris) .. France .. ) a 1,748 Radio Paris . .. France .. 171

371 Seville (EAJ5) .. Spain .. .. t "3 1,840 Angora .. .. Turkey .. 163I

374 1Stuttgart .. ..Helsingfors ..

Germany1,852Finland .. i. 802

i 2,000Humeri .. ..Kovno .. ..

Holland ..Lithuania ..

16215o

Special Articles on Television and "Talkies" Next Mont406


Is gour wirelessreception

clear and fullof tone?

Satisfied users of

BR/TA/NS BEST BATTER/ES

will assure you that their reception is perfect

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essential forMODEL

best resultsThere is no more satisfac-tory source of power foryour set than a Mains Unit.There is no Mains Unit onthe market more satisfactorythan a REGENTONE.

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A. C.MAINS

6d£4 19s.A.C. Models incor-porate WestinghouseMetal Rectifier.

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illustrated lists.

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MULLARD'S CHOSE A

DOUBLE BEARING.0003 "CYLDON"BEBE REACTION

CONDENSERfor the

S.G.P. MASTER THREE

Follow their advice; there's a reason for it

When it is possible tomake a perfect singlebearing condenser"Cyldon" will make it.

LATEST LISTS FREE ON APPLICATION.

Advertisement of:SYDNEY S. BIRD & SONS, LTD.,

" Cyldon " Works,Sarnesfield Road .: Enfield Town.

'Phone: Grams :2071-2072 Enfield i_ .liacity Enfield

Better service results from mentioning " Wireless Magazine " when writing to advertisers

407


FIN TUN E WITH THETRADE!FETTER LANE'S Review

Six -Sixty Facts

JUST what duo -triangular fila-ment suspension " means I am

still at a loss to know, but that is theonly thing which puzzled me in anew booklet which has just beenreleased, dealing with Six -Sixty glow -less valves. Very intriguing is thatterm " glowless " : it makes one thinkthat the advent of the perfectly" cold " valve has advented-if I mayuse that coined word.

But to come to facts, this Six -Sixty booklet is full of facts, and isparticularly helpful, because it givesthe details of the whole range ofSix -Sixties both in tabular andgraphic form. Altogether, a veryhandy booklet for the amateur whowants to know just how much juice togive his valves in order to get thebest out of them.

And if you are unable to follow theaccurate characteristic graphs givenin this booklet, then you should readyour WIRELESS MAGAZINE morethoroughly, because all this has beenexplained fully from time to time.Get acquainted with " characteris-tics " via the Six -Sixty booklet,pubis ed by the Electron Co., Ltd.,122 Charing Cross Road, W.C.2.

27

Competa Catalogued

WE should be grateful to Mr.Bulgin for placing before con-

structors the best of the world's radioproducts, for he imports the mostfascinating and useful bits andpieces-of the kind guaranteed tomake home -constructors glow withpride-direct from all parts of theworld.

List No. 125 has just been sent me,and I think it should be in thepossession of all who make up theirown sets and want the best and mostuseful of gadgets. Moreover, Com-peta gadgets are used in very manyWIRELESS MAGAZINE receivers, andif you have the Competa list at handit will save time and trouble whenordering if the correct cataloguenumbers can be given.

Speaking for myself, I spent a longtime gloating over the neat little

of Cataloguesswitches, connectors, sockets, andclips; not to mention the range ofCompeta meters and measuring in-struments for all purposes.

If you, too, want to gloat, then-write to A. F. Bulgin & Co., at 9, 10,and II Cursitor Street, E.C.4, or elsemake use of my catalogue service.

28

Lissen's " Three "RECENTLY I said that the

Friars Lane folk had intriguedme by sending in to your " Fetter " twofolders dealing with portable sets andgramophones. Now follows a similarsheet telling about the Lissenolathree-valver, which is a complete,ready-made receiver selling at a verymoderate figure.

A point that will appeal is that it issold complete with all batteries,valves, and, indeed, everythingexcept the loud -speaker. If you haveany thoughts of buying such a setget this folder, because it shows justhow easy is the Lissen receiver tocontrol. Only three knobs, no coil -changing, provision for adding apick-up and so on and so forth.

But Lissen, Ltd., of Friars Lane,Richmond, Surrey, have publishedthis folder, and it is their business totell you about the set ! 29

A SPECIAL SERVICE FORREADERS

As a keen wireless enthusiast younaturally want to keep abreast of all thelatest developments and this specialfeature will enable you to do so with theminimum of trouble.

Here we review the newest bookletsand folders issued by eight well-knownfirms. If you want copies of any or allof them just cut out this coupon andsend it to us. We will see that you getall the literature you desire.

Just indicate the numbers (seen atthe end of each paragraph) of the cata-logues you want below :-

My name and address are

Send this coupon in an unseated en-velope, bearing Id. stamp, to "CatalogueService," WIRELESS MAGAZINE,58/61 Fetter Lane, E.C.4, Valid till June 30

408

and PamphletsReady-made H.T.

THE name Ferranti is I as t

becoming famous for H.T.-from-the-mains units, just as it wasfamous for mains -measuring instru-ments long before wireless wasthought much of.

What made me think of this is thefact that I have just had sent me,by Ferranti, Ltd., of Hollinwood,Lancashire, a kind of a book (itreally is bigger than what I usuallyterm a " booklet "), dealing with anA.C. H.T. unit.

This exists under the type numberBEM r, and is suitable for use on200 -250 -volt A.C. mains, betweenperiodicities of 40 and roo cycles. Themaximum output is roo milliamps,which is quite a useful figure ! It isparticularly worth remembering thatFerranti H.T. units are among the fewwhich comply entirely with theregulations of the I.E.E.

The book gives far more technicaldata about the units than the averageamateur will want to worry about,and it is all precised in the last fewpages, where are given the operatingconditions for well-known makes ofvalves in different sets. 30

Squire Loud -speakers

`HE craze for making upIloud-speakers from partly -assembledcone -kits and reed movements is afairly recent one, but has much torecommend it. Frederick Squire, of24 Leswin Road, N.I6, is specialisingin kits of all kinds for loud -speakers:of all kinds.

One is quite a giant in its way,having a triplex -woven cone 15 in. indiameter and with a girder -sectionaluminium frame. Another, for whichI think portable -set constructorsshould clamour, is a light -weightassembly for inclusion in portable andtransportable sets.

There are many other types ofkit and cone cradles, and they are alldescribed in leaflets which can beobtained from Messrs. Squire. Itshould be noted that the giant cone isdescribed in a folder of its own. 31

(Continued on next page)

Radio /or the Million

T HAVE had sent me Vol. III,1 No. r, of the Mullard publicationRadio for the Million. This gives fulldetails of the Mullard S.G.P. MasterThree, which incorporates a screened -grid and pentode valve-hence thedesignation " S.G.P."

The constructional details are mostexplicit, and if you feel that a receiverof this type is just what you want,then make a point of putting in anearly application for Radio for theMillion.

The address of the publishers isthe Mullard Wireless Service Co.,Ltd., Mullard House, Denmark Street,W.C.2. 32Charge at Home

IAM a motorist, so when I receiveda leaflet describing the Philips

A.C. rectifier for L.T. accumulators, Ijumped over the radio technicalmatter and became thrilled by theannouncement that this charger issuitable for juicing up car batteries.

The leaflet gives full details ofthe type 45o charger, and this willbe found suitable for all generalneeds of amateurs.

Included also is a description ofthe Philips trickle charger, whichincorporates a neat switch for cuttingin and out the charging operation.Philips Lamps, Ltd., Philips House,Charing Cross Road, W.C.2, tellyou all about both chargers in thisleaflet. 33Just Think . . .

" THINK how your set will look1 housed in one of these hand-

some cabinets," is the way you areintroduced to Pickett's cabinets in anew catalogue just issued by PickettBros., Albion Road, Bexleyheath,Kent.

As you doubtless know, Pickett'scabinets are used with many setspublished in the WIRELESS MAGAZINEand, as a matter of fact, with thiscatalogue is being given a reprint ofa page from the WIRELESS MAGAZINEdealing with W. James' BinowaveFour-which was housed in aPickett's product.

The catalogue deals specificallywith Radiola cabinets, and with theRadiola Wireless Bureau in par-ticular. If you take my tip, you'llread carefully through the cataloguewithout taking any notice of the price.

Then look at the price, and apleasant surprise will await you 1 34


RAYMOND'SFOR WIRELESS

27 & 28a LISLE STREET, LONDON, W.C.2Come to Leicester Square Tube d minute)This address is at the back of Daly'sTheatre. Phones: GERRARD 4637 le 2821

C.O.D.Orders despatched earliest possible.Send ORDER with instructions and

pay Postman.C.O.D. APPLIES TO UNITED KINGDOM ONLY.

CHUMMY

FOURW.M., June, 1929.

ALL PARTS STOCKED.

IF YOUR ORDERFOR CHUMMY 4 ISOVER £3 YOU CANBUY EXTRAFORHigh Quality Panel 168, Black or Mahogany,Pair Panel Brackets,G B Clips, Cone Paperand Cloth.

SPECIAL DUALCOIL with reactionand support.Strictly to WM 10/6Specification.

BLUE SPOT 66 K PowerAdjustable Model

Armature.4 pole Bal.

25/FORMO CONDEN-SERS, LOG gTWO .0005 1,1/-ON E .00035. each.

COSSOR L.F. qiTransformer L

HANDSOMEOAK POLISHEDSPEAKER CAB-INETS. 13x13x612/ 1 1 1;73'

Blue Spot /66K (101)

Genuine. Adjustable.4 pole Bal. Armature

ORCABINET

12in. ConeBluespot 35/

With Trietron Unit 27/6The Lot Corn.

Paid U.K.

ALUMINIUM

CRADLEWith fitted 10 in.Floating Cone and12 in. Square Baf-fle Board. Takesall Bal. Armature

Units.

7111Post 9d. U.K.

If you mention Wireless Magazine we will send youas an advt. BLUE SPOT CRADLE & CABINET

As shown 40/ NET Carr. Pd.above.U.K.WE AKE OVENALL DAY SATURDAYALL DAY THURSDAYALL DAY EVERY DAYHours 9 a.m. to 8 p.m.Sat. 9 a.m. to 9 p.m.Sunday morning 11-1.

QUOTA'S IuNSfor SETS

OF PARTSSPECIAL PRICES ONLISTS of 25/- and over.CALLERS OR POST.

DON'T FORGET OURWHOLESALE DEPT. ALL LINES

STOCKED.HOURS OF BUSINESS AS ABOVE.

Illustrated 140 pp. Catalogue 1)-. Refunded 1st 10/.order or free with 10/- and over order.

See Our Advt. "A.W." Weekly.WNIAMAWNIMONSOM

W.M. SPECIAL COUPON (74)1(REPRINT)

FOR EVERY 30j- YOU SPEND RETAIL!iyou CAN BUY ONE OF THE FOLLOWING FOR

3d. each extra (on this coupon)H.B. Choke; Silk Loud -speaker Cord; 9 -volt Grid Bias; PairPanel Brackets; .0001 Reaction; 2 mfd. Msasbridge; 100 ft.Insulated Aerial; 4- or 5 -way Battery Leads; 30 it. ColouredConnecting Wire ; S.M. Dial ; 12 yds. Lead-in ; Fuse andHolder ; 12 Nickel Terminals; 60X Coil; Permanent Detector;Battery Switch; .0003 and 2-meg. Leak; 6 -pin Coil base ;12 yds. Twin Flex; 100 ft. Indoor Aerial; .0005 Variable;Set of 12 Plugs and Sockets (red or black) ; Set of 3 Coil IPlugs with Terminals ; Wave Change Switch ; .01. Fixed.

/Condenser ; 2 mid.

409

ELECTION

RESULTSIf you or any ofyour friends de-sire to build asimple, inexpen-sive and quick-to -make receiver,in time for thebroadcast electionresults, read thefull constructionaldetails for making

BRITAIN'SFAVOURITE

TWOwhich are given inthe current issue of"AMATEUR WIRE-LESS" now on sale.This is a remarkablyefficient set, and willgive most satisfactoryresults. The full-sizeblueprint, which sim-plifies construction,is available now.Included in the articleare instructions formaking an "Election"

Hook-up

AMATEUR

WIRELESSis on Sale atall Newsagents

3d.GET YOUR COPY

TO -DAY


in a butte',There is life in the tones of singer, speaker and instrumentalist alike if you use the LISSEN Battery.For it yields its pure D.C. current so smoothly, so silently, with never a sign of ripple in it, never a

trace of hum, that the purity of rendition before the microphone is truly preserved.And the oxygen content of the large cells (due to the process exclusivelyused by Lissen) is so great that you get months and months of use fromevery Lissen Battery, and reproduction is delightful, perfectly true andperfectly natural all the time.

The Lissen Battery is obtainable at every radio dealer's-ask firmly forLissen New Process. If you insist you will be rewarded by atruth of tone in your loud -speaker which was never there before.

DIRECT FROM FACTORYTO DEALERS' SHOPS-every LISSEN Batteryis fresh when you get it !6o volt (reads 66) .. .. 7/11

too volt (reads rob) . .. 12/1136 volt . .. .. 4/66o volt, Super Power .. .. . 13/69 volt Grid Bias

4 volt Pocket Battery (4/6 a doz.) 5d. eachSingle Cell Torch Battery .. 41-d. each

LISSEN LIMITED, 500-520 Friars Lane, Richmond, SurreyManaging Director THOS. N. COLE.

410

1-

17c 1929CHUM

rrHE design of a four- of five -valveI compact self-contained or port-

able receiver that will provideaverage results as regards tonalquality, volume, and sensitivity incomparison with other sets ' of thesame class is not a difficult matter.

This is borne out by the largenumbers of self-contained receiversmarketed at the present time. Themajority of them employ the samecircuit and give results which arecomparable.

Untuned CouplingsFive valves are generally used.

The first two are coupled by so-calledaperiodic choking coils, or trans-formers, that do not have to be tunedby adjustable condensers, and thedetector is arranged to providereaction to the frame aerial.

This type of set, which is extraord-inarily popular, therefore, has onemain tuning control and a reactioncontrol, and there is, of course, aswitch for altering the wavelengthrange of the frame aerial and con-necting or disconnecting the filamentbattery.


Listeners seem to be quite satisfiedwith a quality of reproduction froma portable set that would be thoughtonly tolerably good were the receivera three-valver connected to an out-door aerial. At the same time, theresults are acceptable to very largenumbers of listeners.

I think this is partly due to the factthat many of those who now listenwith a portable receiver have neverused any other type of set andare, therefore, not in a position tocompare the results. Neither does itgreatly matter whether the resultsare good, bad, or indifferent, ascompared with the finest results tobe obtained from equipment designedto approach perfection.

It appears that what does matteris, first, the fact that portablereceivers are complete in themselvesand, secondly, that they all put up acertain standard of performance.

I am, of course, speaking generallyof the five -valve type of receiver.When one considers the four -valvetype having a single stage of high -frequency amplification employinga shielded valve, with two -knob

411

tuning and reaction, one finds thatquite different results are obtained.

Receivers ofthis type are usuallymore sensitive and are, therefore, ableto bring in more distant stations thanthose of the five -valve single -knobtuning type, and because the high -frequency amplification may be morereadily controlled, there is everyreason to believe that the quality ofthe reproduction must necessarily bebetter

No Need for " Forcing "The user does not have to rely to

the same extent upon reaction forsensitivity and, in fact, so far as thelocal and Daventry stations are con-cerned, the four -valve sets having asingle shielded -grid high -frequencystage do not have to be forced, withthe result that the reproduction isgenerally of the same order as thatprovided by a similar type of setarranged for open aerial working.

I think it is much more difficult todesign a portable receiver having atuned high -frequency stage. Onemust provide the maximum ofmagnification with stability and ease


The 1929 Chummy Four (Continued)

of handling. As there will be twocontrols (excepting when they are" ganged ") they must not be criticalin any way or tuning will be toodifficult, from which it follows thattoo great selectivity is undesirable.

Factors to be BalancedThe various factors which govern

magnification and selectivity have,therefore, to be nicely balanced inorder that the set shall not suffer asregards its ease of handling in com-parison with the true single -controlreceiver of which the five -valve setsmentioned above are typical.

In the previous issue of theWIRELESS MAGAZINE I described twoor three circuits for portables andexplained their advantages. Thereceiver illustrated here employs acircuit which is based upon them.

Circuit ArrangementWe have, first of all, the two

frame aerials wound for the mediumand longer bands of wavelengths.They are centre -tapped for stabilityand selectivity, and are tuned by a.0005-microfarad variable condenser.A switch could be used for connectingthem to the tuning condenser, but inthe set I have employed plugs andsockets for simplicity.

The two frames are wound in thelid of the receiver with the long -wavewinding on the outside of the short-wave winding. Means are provided

This view shows the neat layout ofthe 1929 Chummy-a fine portable

DETAILSOF THE

CABINET

IDimensions of wooden sub -panel

/

72

for short-circuiting the long -waveframe aerial when receiving withthe medium -wavelength one, butstrangely enough, the best results areobtained on the longer wavelengthswith the medium -wave frame notshort-circuited.

With the plugs and sockets pro-vided, it is but the work of a momentto effect the change from one wave-length band to the other.

Biasing the H.F. ValveA single cell is used for biasing the

grid of the high -frequency valvenegatively. This cell gives the grid abias of 1.5 volts and has the effect ofimproving the operation of the stageand minimising the anode current. Itis not by-passed with a condenser, asit was found that the results were notimproved when a condenser wasadded.

Both sides of the frame -aerial tun-ing condenser are alive, as neither setof plates is earthed. But hand -capacity effects have not been noticedpartly because a slow-motion dialhaving the minimum of metal in itsconstruction is employed.

Use the Specified PartsThis point should be remembered

as, should an unsuitable dial be fitted,hand effects may be noticeable.

In the interests of stability, theshield grid of the shielded valve hasconnected to it a fixed resistance

LID FOR FRAME AERIAL

3"

These are the dimensions ofL000 -SPEAKER the main cabinet. Cabinets ofUNIT SUPPORT last year's sets can be adapted

to accommodate the new set

412


A Famous Set Re -designed by W. Jamesof f o,000 ohms and a condenser of

microfarad capacity. This com-bination of resistance and condenserwill prevent trouble in this part of thecircuit, even though the high-tensionbattery develops a relatively highinternal resistance.

Stopping H.F. CurrentsAt the same time, the filter acts as

a most effective stopper in preventinghigh -frequency currents from enter-ing the high-tension battery from thescreen to the valve.

A resistance of ro,000 ohms is notessential. It may have a value of asmuch as 50,000 ohms, but one shouldremember to compensate for thevoltage drop in this resistance bysuitably connecting the circuit to apoint of more than 6o volts on thehigh-tension battery.

There should be no need to employthe full 120 volts, but as there is adrop across the resistance, severalvalues of voltage should be tried.

Amplification without OscillationCare has been taken to ensure that

the high -frequency stage shall amplifywithout oscillating, and for thisreason a high -frequency choking coilis connected in the anode circuit of theshielded valve, whilst a tuned circuitis connected between the negative

aide of the filament and the anode -stopping condenser. This condenserhas a value of .002 microfarad, but Iwould point out that this is not byany means critical.

A two -range tuning coil of smalldimensions has been used and is tunedwith a .0005 microfarad condenser.The long -wave section is wound ina slotted former, which is fitted insidethe tube carrying the medium -wavelength winding. I have foundthis arrangenient to work very well,but only when the windings arcswitched as indicated.

Uniform Reaction ControlThe coils can be so arranged that

witen receiving over the medium -wavelength band the two coils arejoined in parallel by means of asimple push-pull switch, but my testshave shown the method of switchingseparately either the long- or themedium -wave coil to the tuningcondenser to be preferable. Theamplification and selectivity appear

Here you see the 1929Chummy with the valves inposition ready for fixing in the cabinet

to be better, and the single reactionwinding arranged in one of the slotsseems to allow a more uniformcontrol of a reaction to be obtainedwith the variable condenser.

In asking W. James (Research \-Consultant of the "WirelessMagazine") to re -design thefamous Chummy Four weemphasised the desirability ofretaining as many as possibleof the components employedin the original model.

The result is that owners oflast year's Chummy Four willbe able to adapt it to the 1929design with the minimum ofwaste, even to the extent ofadapting the old cabinet.

Special features of the 1929Chummy are its adaptabilityfor reception of both wave-bands, materially lower high-tension current consumption,and the inclusion of filter cir-cuits for the sake of increasedstability and efficiency.

Many hundreds of listenersbuilt and praised the originalChummy Four, which exactlya year ago was the first port-able to be offered to the home -constructor which made useof a screened -grid valve. Nowthat it has been re -designed byW. James it will undoubtedlybe more popular than ever.

For the maximum of sensitivity itis clear that the aerial and anodecircuits should be practically oscil-lating, and it therefore seems desir-able so to arrange these two circuits

413

that one does not oscillate very muchbefore the other as the reactioncondenser is slowly turned.

Unfortunately, we have a variablefactor in the valve-no two valves,even of the same type, are exactlyalike and it therefore follows theremay be slight differences as betweenone set and another.

Full Sensitivity for DistanceBut this point of properly at rang-

ing the aerial and anode circuits mustnot be overlooked, for even though itis possible to receive local stationswhen the circuits are not near theoscillating point, it must be recog-nised that the full sensitivity of thereceiver has to be employed for thereception of more distant stations.

Here in London it is not necessaryto employ more than a trace ofreaction when receiving 5GB, whichis a great advantage, as the qualityof the reception is not spoiled.

Additional Filter CircuitThe detector valve is arranged with

a grid condenser and leak in the usualmanner, and is transformer -coupledto the first low -frequency valve. Afilter circuit was found desirable inthe high-tension supply to this valveand therefore ,a zo,000-ohm fixedresistance and a 2-microfarad con-denser are included as indicated.

Very few portable receivers havethis refinement, but it is well worthwhile when reasonable quality ofreproduction is expected. When thisfilter circuit is not used there is a



DETAILS OF LOUD-SPEAKER DIAPHRAGM

.4. FOR JOINING

e%RAD.

IA

(.1t6- RA0.

3/16 FORTURNING

16"

SECTION OFLONE, WAVE,WINDING

FORMER

114

90°

2/4

LONG WAVE.WINDING40 TURNSN° 28 D.5.c.

SNORT WAVE.wINDInG 20 TURE4rig

CORNER BLOCKSOF WOOD

LONE WAVEINEFOFIMER

20 5AWCUTS,,e; APART --

4 EBONITE STRIPSI/2"5O. X 3%. LONG

TERMINAL JOINEDTO CENTRE TAPOF BOTN WINDINGS

S

osTrAsR.T 0

END OF

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START OFL.W.

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SOCKETS

FRAME. AERIAL DETAILS

CORNERBLOCK

EBONITE. STRIPYa"sq. X 3"

Loric

tendency for howling to start asthe battery ages and after a time,of course, " motor -boating "appears.

No Sacrifice of Low NotesThe howling and motor -boat-

ing could have been preventedby using a: transformer having asmall primary winding or lowvalue of inductance, but as theuse of such a component wouldinvolve sacrificing the lowernotes, it was preferred to employa good transformer and a high-tension filter circuit, even thoughthis slightly raises the cost.

The third valve is resistance -capacity coupled to the last bymeans of a popular unit havingsuitable values, and does notneed further description.

The circuit of the receiver willbe seen from this explanation to

Details of copper screen for the

be what might be termed a standardone, as no attempt has been made tosacrifice stability or quality of repro-duction by the employment of asimplified circuit. As might beexpected, the quality is dependent tono small extent upon the constructionof the loud -speaker.

Chief Constructional PointsTurning now to more practical

matters, let us go over the chief

1929 Chummy

points in the construction. On thefront panel, which is of ebonite, arethe two tuning condensers, thereaction control and the combinedwave -change and filament on -offswitch (which, therefore, has threepositions), whilst to the left-handside are three flexible wires thatconnect the frame aerial to thereceiver.

The two aerials are wound in thefront cover of the receiver. A

414

wooden framework is used foithe long -wave winding; it isprovided with three slots havingthirteen, fourteen, and thirteenturns respectively, or a total offorty turns, of No. 28 -gauged.s.c. wire.

Frame Aerial ConnectionsThe centre turn is tapped and

a wire is taken from it to a smallterminal on the ebonite stripfitted in the top right-handcorner of the cover. This striphas four sockets and two of themare connected respectively to thebeginning and end of the long -wave winding.

Four pieces of ebonite suitablyslotted are employed as supportsfor the medium -wavelengthwinding and these are fastened tothe front cover, with the resultthat this winding is smaller in

section than the long -wave winding.

Medium -wave WindingThere are twenty turns of the lip.

z8 -gauge d.s.c. in the full medium.wave winding and the centre turn isconnected to the terminal on theebonite strip. Reference must bemade to the diagrams for details ofthese two windings as it is importantthey are correctly connected.

The receiver itself comprises the


For Reception on Both Wavelength Bandsebonite front panel and baseboard,complete with the copper shield andthe parts mentioned in the list ofcomponents.

At the Back of the SetLooking at the back of the receiver,

one sees on the right-hand side theframe -aerial connections, tuning con-denser, shielded valve and holder,and single -cell grid battery, togetherwith the io,000-ohm fixed resistanceand 1-microfarad condenser whichare joined to the shield of the valve.

In the copper box itself are thehigh -frequency choking coil, anodecoil, switch, tuning condenser, detec-tor valve, and grid condenser andleak. There is no back to the box, asthis was found to be quite un-necessary.

On the left-hand side of thereceiver are the reactionary condenser,transformer, resistance -capacitycoupling unit, detector circuit filter,and the two low -frequency valves.

Use of Wooden Sub -panelThese parts may appear from the

illustrations to be rather crowded,but there is, in fact, ample room,although in order to take the fullestadvantage of the space available thetransformer and resistance unit hadto be mounted on a wooden sub -panel.

The batteries are suitably arranged

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This layout and wiring diagram of the 1929 Chummy can be obtained as a full-sizeblueprint for half-price (that is, 9d., post free), if the coupon on page iii of the cover is

used by June 30. Ask for No. W.M.145. Wire up in numerical order

to give the maximum of room for theloud -speaker. First is the gridbattery, which is held to the under-side of the baseboard by means ofclips. The second battery is the hightension, which is divided into twoportions, one being fitted on each

Back view of the 1929 Chummy, showing how the batteries arepositioned. If desired the high-tension batteries can be turnedround so that the sockets for the wander plugs face directly out-wards. When one accumulator is being used, the other can becharged up ; in this way the set will always be in commisssion

and ready for instant use when required

415

side of the loud -speaker. Similarly,two small filament accumulators areemployed, connected in parallel asindicated in the diagram.

For the loud -speaker a bracket ofwood fastened to the bottom of thecontainer is employed. The positionof this bracket is important as thecone of the loud -speaker must be freeto move.

Wiring Up the SwitchProbably the most difficult part of

the wiring will be to the switch, butone or two of these wires may be con-nected to the contacts of the switchbefore fastening it to the front panel,and it is not difficult to connect all thewires provided the i-microfaradcondenser is temporarily removedfrom the screening box.

This box is not very rigid and if it isthought there may be a chance of itmaking contact with any component,a piece of thick paper may be gluedover the surface where the dangerliesto prevent trouble.

Insulating the Copper BoxThere are many suitable loud-

speaker units on the market whichcould be used in this receiver, but it is



COMPONENTS REQUIRED FOR-Ebonite panel, i6 in. by 8 in. (Resistor, Parfait, or

Becol).2-.0005-mfd. condensers (Formo de Luxe or Utility).2-Slow-motion dials (Harlie).I-.00035-mfd. condenser (Formo de Luxe or Utility).2-4-mierofarad fixed condensers (Dubilier or T.C.C.).I-2-rnfd. condenser (T.C.C., Dubilier, or Ferranti).4-Antimicrophonic valve holders (Formo).I-II/2-volt dry cell (Ever -Ready type UWI).I-High-frequency choke (Igranic, Ready Radio, or

Wearite).i-Two-pole two-way barrel switch (Wearite).1-2-megohm grid leak (Graham-Farish, Edison Bell, or

1--.0002-microfarad fixed condenser (Graham-Farish,Edison Bell or Mullard).

r-.002-microfarad fixed condenser (Graham-Farish,Edison Bell or Mullard).

1-Anode coil with support (Ready Radio, Raymond,Parex or Wearite).

s-io,000-ohm resistance (Graham-Farish).I -20,000 -ohm resistance (Graham-Farish).I-Low-frequency transformer (Cossor).r-Resistance-capacity unit (Marconiphone type A).

THE 1929 CHUMMY FOUR

i-Pair panel brackets (Camco, Raymond, or Bulgin).I-Adjustable loud -speaker unit (Blue Spot type 66K).2 -66 -volt high-tension batteries (Ever Ready typeWi 6s)I -9 -volt grid -bias battery (Ever Ready type GB4).I-Pair battery clips (Bulgin).2 -2 -volt accumulators (C.A.V. type 2NS9).r-Piece of cone paper, 12 in. square.

16-Spring wander plugs, 8 black and 8 red (Igranic,Belling -Lee or Lectro-Linx).

4-Spade tags, 2 black and 2 red (Lectro Linx).r-Screening box (Ready Radio, Parex, or Raymond).

io-Indicating tabs: L.T. , L.T.-, H.T. +2, H.T.H.T.-, L.S. L.S.- G.B. -2, G.B. - 1, G.B.+.

r-Cabinet with baseboard, frame -aerial and loud-speaker fittings (Ready Radio).

I-Small knob for reaction condenser.4 -oz. No. 28 -gauge d.s.c. wire for frame aerial (Lewcos).

io-2 ft. lengths connecting wire (Glazite).Length of rubber -covered flex (Lewcos).

r-a-volt screened -grid valve (Cossor SG22o).r-a-volt R.C. valve (Cossor RC2ro).I -2 -volt H.F. valve (Cossor HF2m).I -2 -volt power valve (Cossor Stentor Two).

Total Cost (approximately) al 4 10s.

necessary to cut a diaphragm to fit.The one employed in the receiverillustrated is cut from two -sheetBristol board 'to the dimensionsgiven. A piece of this material shouldbe carefully marked according to thedimensions ; the outer edge is then cutand also a section equivalent to62 degrees, but do not forget to leavey4 in. for fixing the edges.

Use of Different UnitIt should be understood that the

size of the cone is dependent upon theunit and the space available, with theresult that it may be necessary toconstruct a cone having otherdimensions if a different unit isemployed.

The valves used in this receiver donot have to be carefully chosen orselected ones, but they must be ofsuitable types. In the high -frequencyposition is a shielded valve which issupplied with an anode voltage of1 20, and a shield voltage of 60 ormore according to the type.

Other Three ValuesA high -impedance valve, such as

one of the R.C. type, is used fordetection, and this is followed by avalve of medium impedance, such asan H.F. type. Naturally, a smallpower valve is used in the outputposition.

Grid bias is applied according tothe types of valves used, but usuallythree volts will suit the first low -frequency amplifying valve and nine

volts the 'power valve. The anodecurrent does not exceed xo milli-amperes for all valves, but there maybe slight variations, depending uponthe actual valves used.

Tuning is effected in the usual

FURTHER PHOTOGRAPHSAND DETAILS OF THEANODE COIL APPEAR ON

PAGE 482

manner, the reaction condenser beingturned to put the circuits in a sensi-tive state, whilst searching. Volumemay be varied by altering theposition of the frame aerial or byadjustment of the reaction condenser,

whichever be the more convenientNeither method alters the tuning toany marked extent, and considera-tions of selectivity and the positionof the receiver will' determine thebetter way.

I have not provided for connectinga mains high-tension unit in place ofthe dry cells; this change -over will,however, easily be effected by anyonehaving the equipment.

Guided by Last Year's ModelIn conclusion, I would add, that I

have endeavoured, so far as possible,to be guided by last season's ChummyFour, but have converted it into adual -range receiver.

This is thecircuit of the1929 Chummyas re -designedby W. James.

(GB.lyznNote the use of a dual -wave frame aerialand anode coil, andthe inclusion of filtercircuits for extra sta-bility and efficiency

tiT+

R.C.COUPLIMQUNIT

N1+2

L5

416

Wireless Magazine. une. 1929 4Awkward Moments

in the Studio !BY AN EX -ANNOUNCER

When Tallulah Bankhead Fainted" I Don't Think ! " Norah

the Programme

:: The Sermon That Ended WithBlaney in Difficulties :: Balancing

A Fly in the " Mike"THE red light is on, and the double

doors shut tight. You are in aworld of silence. To cough will deafenmillions-to whisper'may mean spoil-ing an entire programme. The still-ness is unearthly-it rings in the ears.

The only person who seems thor-oughly at ease is the announcer. He,apparently, is used to it. Nonchal-antly, he switches on to inform theworld that Miss So -and -So will singthree songs. The long names andunpronounceable composers he tackleswithout turning a hair.

Dangers on Every SideYet the announcer is beset by

dangers on every side. A hundredand one things may go wrong-through a hundred and one differentcauses. I speak from experience.

Pronunciation is a common diffi-culty, and generally comes when asinger unexpectedly changes hersongs. The news bulletins are usuallyread beforehand to make sure of themore difficult words.

Greater problems arise throughnervous speakers and artists.

What does the announcer do whenan artist faints ?

Microphone FrightThis actually happened once, and

the fainting one was none other thanthe charming Tallulah Bankhead. Itwas her first appearance before themicrophone, and she became avictim to microphone fright, a nastycomplaint that seizes the best of usat times. Even announcers are notimmune.

Miss Bankhead had it badly. Theoccasion was a Sunday night, andTallulah was to broadcast a charityappeal. Before we switched on, shecomplained of nerves, but since that isthe cry of nine broadcasters out often, we tried to calm her and switched

on. Then things started to move.Tallulah gabbled her speech so

quickly that even in the studio wecould not distinguish all her words.On and on she went till the end wasreached. Then, with a little sigh,she fainted, and slithered to thefloor. The public knew nothing of theoccurrence. The official who checksthe programmes had switched off.

The " mike " does not always goto sleep so correctly. Sometimes itis turned off too late-sometimes tooearly. Listeners have often heardscraps of conversation in the studio,obviously not intended for them.Usually, they enliven the monotonyof the programmes. Sometimes theymake them positively uproarious.

Once a well-known cleric had beengiving a particularly uplifting ser-mon, and concluded with the aston-ishing words : " I don't think ! "Listeners did not hear the conclusionof the sentence-" that was too long,was it ? "

Incidentally, when speakers go overtheir time, or a band performs a piecethat takes longer than expected, theannouncer's worst moment comes. Itis necessary that, in order to balancethe programmes some future itemmust be cut out, and choosing onthe spur of the moment which itemto leave out is a job for twentyannouncers!

Cutting the wrong thing may bringin shoals of angry protests fromlisteners, and even taking out theonly possible item is sure to arousewrath in someone somewhere.

Equally tiresome, if not more so, isthe nasty gap that occurs in theprogrammes when items have endedbefore their time. Nowadays, anincreased knowledge of just how longcertain items take have practicallyobviated this difficulty, but theremust be many people who remember

417

Tallulah Bankheadthe holes in the programmes of earlierdays.

Such gaps were always dreadfulfrom my point of view because I hadto make up some impromptu patteron the spur of the moment ; gramo-phones and mechanical pianos werenot always available. When we weregiving an early operatic broadcastfrom Covent Garden, and an intervallasted twenty minutes longer than wehad expected, one of my unluckycolleagues had to keep up a streamof words for twenty minutes !Fun at Manchester

Those early days were well worthwhile, if only for the fun of the thing.When I was on duty at Manchester,shortly after that station opened, asinger failed to keep his engagement.L. du Garde Peach, the well-knownhumorist, had supplied the previousitem, and so he and the StationDirector were called into service. Be- .tween them they gave a splendidduet of " John Peel," although neitherof them could sing !

It is a rare occurrence for a singerto forget her words, but this onceruined a broadcast made by Norah(Continued in third col. of next page)


Changes the Countryr -I-1 HE country has been rescued from1 its solitariness and obscurity.

That is one of the miracles of radio.In these days the best concerts, themost eloquent speakers, the best plays,and the most world-renowned artistscan be listened to in remote ruralplaces, far away from the maddingcrowd.

The B.B.C., in conjunction withrural committees, intends bringingthe villages still nearer the towns.More, there is a movement by whichthe village will be organised in itslife and thought according to a pro-gramme agreed upon. There is onlyone argument against this newarrangement, and that is that thevillages will lose their peculiaritiesin thought and custom. That, how-ever, loses its value when the gainsare taken into account.

Recently a new scheme for ruralrevival was set afoot by the Hertford-shire Rural Community Council andthe B.B.C. A listening set is to beloaned to a series of villages in turn.Some of the villages will loan a setat the same time. They will installthe set in the village hall in winterand on the village green in summer,according to the assembled gatheringand the weather.

The villagers will then listen to abroadcast talk on some agriculturalquestion, which talk will become thestarting point for a debate and dis-cussion. It is believed that thismethod will help the villagers to dis-cover new ways and means of dealingwith their common problems.

A much larger question is openedup, however. There are already morethan 15o societies which receive theiradult education by forming groupswhich listen -in to a lecture or talkwhich becomes a starting point for adiscussion. The villages could easilyfollow suit.

Educational ImprovementFrom an educational standpoint

it would be a vast improvementon the present system of evening andcontinuation classes, w hi c h ar esparsely attended and poorly con-ducted.

A course of talks received could bean inspiration to the villagers, forthey would know they were receivingthe very best the leading thinkers ofthe country could give them. More-over, the gulf in thought and psy-chological outlook that now existsbetween town and country could heeasily bridged. E. B. R.

FOUND OUT !(A Peep into the Future)

I hate to go on,But you're late again, John !

Don't tell me it's due to your missing the train ;Now was it your watch,Or a" soda and Scotch,"

Or were you detained at the office again?

No ! Pause ere you tryTo dissemble a lie,

I've something of import to show you, my pet ;Just look over there,You may very well stare-

It's no less than a neat little " seeing -in" set !

To -night I switched on,And I saw you there, John,

Disporting yourself at a dance at " The Bat,"What makes it more shady,I don't know the lady-

Now tell me, pray, what is the meaning of that!C. P. P.

418

AWKWARD MOMENTS INTHE STUDIO ! /Continued from)

page 41.7

Blaney. She started a song, got half-way through the chorus and thenstopped.

" I'm sorry," she apologised, " I'llbegin again."

She did so, but broke down a secondtime. Eventually, I had to come tothe rescue and suggest she should singsomething else.

I shall never forget the sense ofhumiliation I felt when I had toapologise for a break -down. It some-how seemed to reflect badly on me.To -day, owing to the duplication ofparts, break -downs are rare. At onetime, they were always liable tooccur. Small animals, and eveninsects, were the bane of the engineer'slife. A dead beetle falling on one ofthe wires would cause trouble.

Once, a moth settled on a conden-ser. The next day thousands oflisteners complained of the tremen-dous "oscillation."

On another occasion, listeners-tosay nothing of the whole of the studiostaff-were startled by a loud drum-ming in loud -speakers and headphones.It proved to be a fly in the micro-phone. The tattoo had been causedas it moved about the sensitiveinstrument.

You will probably remember thestoppage caused by a mouse that gotinto the " works " and was electro-cuted. I myself once almost causeda tragedy by wearing new shoes thatsqueaked as I walked towards the" mike."

The announcer's life is a harassingone. Can you wonder I eventuallyturned to other spheres, calmer ifnot quieter ?

Pity the B.B.C.THE B.B.C. is finding a snag in

connection with what it shalland what it shall not " put over."

The trouble first arose duringholiday time, when an enthusiasticholiday-maker, holidaying for thefirst time on the Continent, gave hisviews on Switzerland from theLondon station.

Well, during the following days thepost -bag at Savoy Hill was added toby a number of letters condemning allbroadcasts of this type. One corre-spondent was frank enough to saythat no "advertisement" for foreignparts should ever be heard throughBritish microphones!- B. M.

ANY listener who is familiar withthe Morse code can scarcely fail

to appreciate the necessity for theuse of abbreviations in wireless tele-graphy. There are various stereotypequestions, replies and remarks whichhave to be exchanged frequentlybetween wireless operators while onduty, and it is obvious that a greatdeal of time would be wasted inhandling messages if these queries,etc., were tapped out in full..

Avoiding Loss of TimeIt is equally evident that such a

loss of time could be avoided, and thedesired meaning conveyed just as

- effectively, by using a series ofrecognised abbreviations.

To meet this need, various stan-dardised abbreviations and signalcodes have been devised, among thembeing the familiar " Q " code, whichis, of course, quite well known tomost amateurs who have a knowledgeof Morse and the " Z " code.

The latter, as its name implies,consists of a series of three -letterabbreviations beginning with Z, andhas very probably been a cause ofmystification to a good many short-wave enthusiasts and others whohappen to have tuned in the tele-graphy transmissions from the variouscommercial high -power stations thathandle long-distance traffic.

The " Z " code is a kind of un-official language used by the opera-tors at 'these stations to convey theremarks and queries incidental totheir work.Easy Abbreviations

The abbreviations in this codecover a wide range of meanings, butare fairly easy to remember (owingto their logical composition) andperfectly simple-when they havebeen explained to you ! But to theuninitiated they must appear enig-matic in the extreme. The twoabbreviations that one seems to hearmost frequently, perhaps, from thevarious commercial stations are ZAP,meaning " Acknowledge, please, thereceipt of message," and ZHC,meaning " How are you receiving ? "

There are numerous abbreviationscovering strength of signals andconditions of reception. These


66

fitY0 idtRrtfll

include : ZFB, " Your signals arefading badly " ; ZFS, " - fadingslightly " ; ZGS, " - getting stronger "ZGW, " - getting weaker " ; ZSU,

- unreadable " ; ZWR, "- weak,but readable " ; ZPR, " - readable " ;ZMR, " - moderately strong and

sending " ; ZKQ, "Let us know whenyou are ready to recommence"; ZHS,"Send high-speed automatic . . . .

w. p. m. (words per minute) " ; ZPE,"Send everything in plain language " ;ZSF, " Send faster " ; ZSS, " Sendslower," and so forth.

The Adventures of Alec TrodeTH,TS FUNNY, 1 CANT 6E7

ANYTHING EXCEPT A CONSTANT

"2 LOCALL iNO!

-=

I SHALL HAVE TO LOOK INTO THts

readable " ; ZSR, " - strong andreadable " ; ZVS, " - varying instrength "; and ZSB, " - blurred,not clear and sharp."

The inquiry " ZRO? " means " Areyou receiving all right ? " while ZOKreplies "We are receiving O.K." orZAN, " We can hear nothing."

Atmospheric disturbances are in-dicated by ZLS, " We are disturbedby a storm "; ZSH, " Strong atmo-spherics here"; and ZWC, "Cracklingatmospherics here." Necessary in-structions regarding transmission arecovered by abbreviations such as ZCO,"Send by code each group once " ;ZCT, " - each group twice " ; ZMO,"Wait a moment"; ZCS, "Cease

419

There are, of course, other abbre-viations in the " Z " code, but theforegoing will serve to indicate thelines on which they are constructed.As you will probably have noticed,the second and third letters in eachgroup are generally suggested by theinitial letters of the principal wordsin the interpretation, so that in mostcases it is quite easy to guess themeanings of the abbreviations fromthese letters.

As the " Z " code is an unofficialone adopted by commercial -stationoperators for their own convenience,it is subject to alterations or additionsfrom time to time it the need for themarises. W. O.


707:91dhsireGERMANY recently celebrated

the fortieth anniversary of theoriginal loud -speaker, first demon-strated at Berlin on February 28,1889. An engineer named KarlFrischen, for many years technicalmanager of the Siemens and Halskeelectrical works, seized the oppor-tunity given to him by the fetes inconnection with the fiftieth anniver-sary of the Berlin Polytechnic Societyto give an amazed public a demon-stration of his new invention.

A Clever TechnicianFrischen, a clever technician, proved

himself an able lecturer and anexcellent showman, inasmuch as inorder to enhance the mystery heequipped the stage with a table, apiado, a trumpet, a washing machine,and a bady's cradle, the first ofthese only being used in thedemonstration !

Following a few preliminary words,he bade the trumpet entertain theaudience, an order carried out to theamazement of the spectators by thelatter automatically playing a streetsong popular in those days. Thiswas followed by other well-knownmelodies, no explanations beingvolunteered by the lecturer.

For his demonstration, Frischenhad equipped the table with a loudtelephone apparatus connected byhidden wires to a neighbouring roomat the back of the stage, In whichhe had placed a musician of thephilharmonic orchestra.

When Frischen died in 189o, he didnot realise that the mechanical trickhe had shown to his audience wouldlater develop into an everydayaccessory, almost indispensable to theradio equipment of the man in thestreet, some forty years later.

H. CLIFTON.

Station Powers That PuzzleDifference in Ratings

READERS are frequently puzzledby the fact that whereas in one

publication the power of a broad-casting station may be given as tokilowatts, in another it is stated topossess an aerial energy of 4 kilowattsonly.

No Standard AdoptedFor some considerable time no

standard had been adopted forexpressing the relative powerdeveloped by the transmitter, and forthis reason, according to where themeasurements were taken, thereexisted considerable discrepancy inthe figures given for the individualstations.

With most Continental countriesto -day, an agreement has beenreached to express the power instandard terms, the measurement tobe taken according to a formulaestablished at a recent convention.

Generally speaking, it is wellillustrated by the German studios,which in each instance take the poweras that of the unmodulated directelectric current to the last valve.

Based on this calculation, the actualaerial energy of the German trans-mitters works out as follows :-

High -power stations : Zeesen, 26kilowatts; Langenberg, 13 kilowatts.

Main Stations : Berlin, Breslau,Frankfurt, Hamburg, Koenigsberg,Cologne, Leipzig, Munich, Stuttgart,1.5 kilowatts.

Relays : Aachen, Augsburg, Bre-men, Dresden, Freiburg, Hanover,Cassel, Kiel, 0.25 kilowatt; Danzigand Stettin, 0.5 kilowatt; Magdeburgand Flensburg, 0.5 kilowatt; Muen-ster, 0.4 kilowatt; Kaiserslautern,1.5 kilowatts; Nurnberg, 2 kilowatts;Gleiwitz, 5 kilowatts:

Multiplied ThreefoldThe actual power measured at the

anode of the last valve,-namely,unmodulated direct current, -isroughly three times these figures.

The above explanation will makeclear to readers the reason for which,for example, the Gleiwitz relaytransmissions are picked up at greaterstrength than the mother station,Breslau. J. A. G.

420

Another Triumph forerthe 30 -metre Wave

WHEN the American North Poleexplorer and aviator, Com-

mander Richard Byrd left the UnitedStates on an expedition to the SouthPole some four months ago he tookwith him a crew of eighty men, twoice -breakers, two whalers, and fourair- and sea -planes. The Antarcticbase has been installed at WalfischBay, at the foot of the Ross Barrier,

Several Stations InstalledFor the purpose of communication

between base, airplanes, and storeships, as well as to maintain touchwith the outside world, several wire-less stations have been installed, andby means of the equipment possessedby the ice -breakers, the sailing shipCity of New York, the steamerEleanor Bolling, and the two whalersRoss and Larsen, Commander Byrdhas been able to secure two-waycommunication with South Americaand New Zealand.

Experiments made in radio trans-missions from one of the airplanesresulted in messages being pickedup by station WHD, operated by theNew York Times, and on January24 and 25 Byrd, whilst at a height ofthree thousand feet above the Polarseas, was able to send messages throughNew York to the American Press.

34 Metres Most FavourableTests were made on various wave-

lengths, but 34 metres appeared tobe the most favourable one, and com-munication on this wavelength wasestablished with Mussel Rock, in theneighbourhood of San Francivo.

During the stay of the Byrd txpedi-tion at the South Pole, a number ofAmerican wireless amateurs willattempt to get in communicationwith the explorer. For the informa-tion of readers, the calls and wave-lengths adopted are as follows : -

Sailer City of New York, WFBTand WFA; three portable trans-mitters KFK and WF (50 watts),and WFE (7 watts). The City ofNew York will operate on variouswavelengths-namely : 22.75, 26.55,26.78, 34.05, 45. 59, 53.1, 53.57, 68.1,and 91.2 metres. In each case at thebeginning and end of transmissionsthe wavelengths utilised will bedefinitely announced.

Antarctic Time is five hours in ad-vance of New York Standard Time.

GRIDDA.


, Wireless 6Magazine rdiflogithofection

.A SPECIAL SUPPLEMENT FOR THOSE INTERESTED INTHE ELECTRICAL REPRODUCTION OF GRAMOPHONERECORDS-THE FIRST OF ITS KIND TO BE PUBLISHED

Is It Worth While?ALAS and alack, I am some-

times tempted to think thatall the clever things which arewritten by the Technical Gramoradio Brains of the WIRELESSMAGAZINE are just so much waste ofenergy. Forgive me, please, andlet me continue.

The other day I went to a publichall wherein quite a super amateur -made electric gramophone wasworking. Some acquaintance of theproprietor had made it and, prac-tically speaking, it was quite agood job.Delighting the Heart

It was working from A.C. mains,had an electrically -driven turn-table, a mass of volume controls,knobs and dohickeys, and in totowas just the thing to delight theheart of one well versed in, thetechnicalities of gramo-radio.

But what a disappointment !rhe motor commutator must havebeen dirty or the driving mechanismclogged, for the turntable was run-ning in jerks. Judging by thet;cratch, the scratch filter musthave been out of adjustment orthe pick-up needle had long over-::een its normal period of life.Added to which a bias battery musthave been run down, for the qualitywas positively awful.

Question of VolumeAnother thing which annoyed

me nearly as much, taking intoaccount my own personal taste,was the fact that the volume wasturned right down and the outfitwas playing only a demi jeu. I,myself, like ample volume, and thisis, of course, one of the advantagesyou can get from gramo-radio,because, given proper operatingconditions, there is unlimitedvolume on tap.

To refrain from diverting fromthe original theme, I felt quite

grieved at heart to see an admirablegramo-radio outfit so maltreatedat the hands of a callous, unappre-ciative, non -technical ignoramus.A cheap portable gramophonewould have served him just as well.

KENNETH ULLYETT

PortabilisedGramo-Radio

WHAT fun there will be when,probably next summer season,

portable gramo-radio outfits arejust as popular as are portable gramophone and portable radiooutfits at present.

You know, just between our-selves, I had some harrowingexperiences in the early days ofportable wireless sets. I have, shall

IF YOU WANT A REALLYGOOD GRAMO-RADIOSET TURN TO THEDETAILS OF THE MUSICPLAYER ON PAGE 427

we say, organised a car picnic atthe riverside and anticipated ascene just as those which theartists portray on magazine coversduring holiday -time.

Rarely has my dream come true.Either the bad suspension of the carhas done its " devilist " to the valvefilaments; or the acid has come outof the accumulator and mixed withthe mayonnaise, or the thermosflask has leaked its contents overthe high-tension battery, so thatits potential is not high enough justwhen I want to work the wirelessset.

I have had some fun with portablegramophones, too. Either thehamper has rested its ingloriousweight on a batch of records ; orbaby broke the gramophone springwhile nobody was looking; or theneedles were lost, and subsequentlyfound in awkward places !

As I said, what fun there will bewhen the joys of these two portablemusic -makers are combined ! Butlet me not cast a damper on things.There is, above all these petti-fogging disadvantages, which seeminseparable from picnics (my picnics,at least), the great advantage thatwith gramo-radio one can havemusic, " canned " or otherwise, inunlimited quantity. Which is justwhat I shall want to make thosemagazine cover pictures come tolife. QUEUE.

In the Track of theNeedle

THEexemplified by the linesof track I mean is notHE kind

of the carol, "In my footsteps, good,my page, thread thou in them . '

What I do mean is the needletracking, which should be accuratein order to prevent record wear.

Perhaps not everyone knowsthat in order to minimise wearingof the grooves the pick-up shouldfollow a straight line direct fromthe circumference to the centre ofthe record. This is rarely given byan ordinary gramophone tone -armwhich rotates about one point, andthus, as a pick-up can be made togive more accurate tracking, lessrecord wear from this cause is oneof the advantages of electricalreproduction.

Accurate TrackingMany commercial pick-up arms

are now available which give practically accurate tracking. One ofthem ensures absolute accuracy byarranging for the pick-up to slidealong horizontal supports whichthemselves are fixed. One manu-facturer of a pick-up arm of out-wardly normal design advertisesthe fact that t works within 3 pecent. of accurate tracking.

B. EVERETT

421

Wireless Magazine. June. 1929GRAMO-RADIO SECTION

H. T. BARNETT, M.I.E.E., Discusses This Month

SPEECH REPRODUCTIONTHROUGH YOUR GRAMO-RADIO OUTFIT

THERE are just a few of us whoare more interested in repro-

ducing records of speech than ofmusic. The teaching of languages isprobably the most important use towhich such records can be put, andthen, of course, there is the teachingof elocution, and lastly for the fewbut first for the many comes thereproduction of the large number ofcomedy -talks obtainable from thevarious record lists.

Learning LanguagesFor teaching languages the Lin-

guaphone people have an immenseseries, all extremely useful. Theelementary records have a certaincharm of their own, but the ad-vanced courses are really beautiful.Mr. Roston sent me the advancedFrench course and every record in itis a lesson in elocution as well as inFrench. The H.M.V. list containssome useful sets.

For English elocution one maychoose records by notable speakersfrom nearly every list; many areexcellent, but the majority of themteach what should not be done when

can do-people's tastes in music areso varied.

Now the technical requirementsfor the reproduction of speech withthe utmost possible clearness ofevery syllable are somewhat differ-ent from those necessary for perfectreproduction of music. In the lattercase there must be great amplifica-tion of tone, particularly in themiddle and at the bottom of thescale, but for the former greatamplification of the musical tone inthe vowels tends to cloak the soundof the non-musical consonants thatform the very soul of word noises.

The explosive, the guttural, thenasal, the hissing noises that consti-tute speech consonants lie most ofthem at the top or over the top ofthe musical scale and in any cavern-ous lengthy or extended surfacesuch as is essential for reproducingthe bass of the scale they become inpart absorbed.

Power Without AmplificationFor reproducing language records

for a big class, of course, we musthave power, but this projection must

This is the Loewe pick-up, mentioned by the author

speaking, either to an audience or tothe microphone.

On the popular side there arethousands of amusing talks toselect from and I find them mostuseful; they hold a mixed audience(particularly when many ladies arepresent) in a way music never

not be obtained by the use of greatamplification. A large cabinetgramophone or an R K. loud -speakermounted on a large, thin baffleshould both be avoided.

The best gramophone unit I canspecify for the work would comprise the following parts : a sound -

box having great power and with astylus bar so rigid that no highvibrations shall be lost in it. TheLimit (los. 6d.), 17 Albion Street,N.r, fills this requirement.

The tone arm must be exception-ally clean internally, with its weightdisposed in such manner and itspoints so made as to discourageblast and rattle; and it must bepossible to set it for exceptionallygood touch alignment so that thereshall be no grinding noises.

Best Tone ArmThe Crescent (2is.), 76 City

Road, E.C., is the best arm I haveyet tried either for a sound -box or apick-up.

The horn may be anything youplease so long as it is not too large-& not exceed the size necessary fora large table machine and take carethat all its bends are either gentleor are correct reflex angles and thatits surface is smooth internally.

Of course, its neck diameter mustbe the same size as or but littlelarger than that of the bottom ofthe tone arm tube. Most of the bigfactors carry a stock of such horns;hundreds a day are turned out bythe Limit Engineering Co., but Idoubt if they sell single ones.

If you want a ready-made machinethe best I know for the purpose, oftable size, and reasonable in price, isthe large Edison -Bell table machine(I forget the exact price), GlengallRoad, S. E .i5

Good Portable GramophoneA good portable is ample for the

purpose when it is to be used in anordinary room, and there is justthe right thing on the Micro-Perophone list (76 City Road, E.C.)at 13 17s. 6d. (See page 424.)

For electrical reproduction wemust choose a pick-up that will notblast or rattle. The only one of theten I have tried that does not givethe least trouble on any decentrecord (not necessarily a perfectrecord) and when using every kind

422

GRAMO-RADIO SECTION Wireless Magazine. une, 19291

of needle is the Loewe, and it is thecheapest.

I am now using this pick-up formusic in spite of the fact that afriend tells me "it has a cut offjust below ioo cycles."

As a matter of fact, there is notmuch that gets on to even an organrecord that is below ioo cycles; thedeep fundamentals are suggested tous by the groups of harmonics orupper -partials they cause and whichcair be, and generally are, mostadequately recorded.

Suitable Loud -speakerThe loud -speaker to be used, if of

the horn type,must follow therules for a gramo-phone horn. In ageneral way theworse it is for thebass of the scaleand the drumsthe better it willbe on the con-sonants in speech.

The cheap ship'sventilator typespeakers are ex-cellent and inmany cases showthe consonantseven more clearlythan they wouldbe heard if theperformers werein the room.

If a loud-speaker is 'wantedfor a large class-room, I shouldadvise using thebig Lion en-tirely free fromanything in thenature of a caseor baffle; it is quite the cleanestworking big speaker I know. Ofcourse you must not use a scratchfilter on the set, and an outputtransformer should be avoided.

Importance of NeedlesThe needle to be used is even of

greater importance than for thereproduction of music. It must be afine needle, in the first place, for theavoidance of surface noise and,secondly, because only a very finepoint can follow perfectly the tinysinuosities that represent on therecord the hiss of the letter S.

It must be a rigid needle, other-

wise the tiniest vibrations will neverget up to the stylus bar.

Fortunately the best needles for' showing instrumental characteristicsare also the best needles for speech;these are the fine gauge steel gripneedles, Sympathetic (2s. 6d. theset), Edison -Bell Ltd., GlengallRoad, London, S.E.I5, and Eu-phonic (2s. the set), MurdochTrading Co., 59 Clerkenwell Road,London, E.C. Do not use a needlemore than twice.

Here are some good records.Gloucester's Soliloquy from Henry VIand Hamlet's .Soliloquy by JohnBarrymore (8s. 6d.), H.M.V. Getting

The Lion loud-speaker made byGraham Amplion, Ltd.

a Motor and Getting a Wife, byConstance Collier and Ronald Squire(4s. 6d.), H.M.V. Kate in the CallBox, by Angela Baddely (4s. 6d.),H.M.V. A Bedtime Story, WishWynne (3s.), H.M.V. Impersonation,Anne Penn (3s.), H.M.V.

Four fine discs by Mabel Constan-duros, Nos. 0246, 0205, 0210, 0271.Electron, 3s. each. The Man in theDitch. An Edgar Wallace thriller(3s.), Columbia. Two Black Crows,parts I, 2, and 3 (3s. each),Columbia.Mrs. Buggins Makes a Xmas Pud-ding, Mabel Constanduros (is. 3d.),Broadcast. Broadcasting the Night-ingale (2s.), Winner.

423

" If I Were BassDeaf 11

A reader's comments on the articlethat appeared wider the above title

in the April issue

C INCE you invite readers' opinionson the above, I suggest that we have

here all the makings of a first-classradio controversy, fully up to the highstandard set by our old favourite,Transformer v. R.C. coupling.

"Are note fundamentals necessary? "Mr. Barnett, . approaching the subjectfrom the gramophone standpoint andalso as a power engineer, concludesthat fundamentals are relatively un-important, that most of the bass thatwe hear is " synthetic, " made up fromharmonics and harmonic groups andthat if it were otherwise no powerstation would be habitable for tenminutes.

Since our ears were not provided asdetectors of electrical vibrations assuch, I think he has possibly over-stressed the last factor, but the maintrend of his arguments-that for" natural " reproduction a great dealcan be done by imagination workingwith harmonics-is certainly sound.

Have we not had with us for yearsthe type of parishioner who " hears "the pedal notes of organ transmissionson a set and loud -speaker (horn), whichNoah-very sensibly-left behind whenhe came out of the Ark ?

I think very few people realise howvery few sets and loud -speakers --out-side laboratory specimens-are capableof reproducing really low fundamentalsat all under average working conditions.

For one thing, the power required toproduce a note varies inversely withthe square of the frequency or, morecrudely, a 25 -cycle note requires iootimes the power necessary for a 250 -cycle note-work it out.

What hope has John Citizen gotwith an ordinary power valve, a r5 -voltgrid -bias battery and ioo volts on hisanode? While if his valves will standthe grid -swing necessary, will his ear-drums stand the overall volume pro-duced in average small living rooms ?

No, sir, his hand will go to the volumecontrol and the low fundamentals willgo with it.

The really marvellous thing is thatwe can achieve even reasonablynatural reproduction at all, consideringall the possible sources of attenuation,distortion, resonance, phase inter-ference, sound reflection, etc., presentin any given set and its associatedaccessories and environment.

But at the same time I think thereis a limit to the application of Mr.Barnett's theories. He appears to bean organ enthusiast. Now, to me, oneof the delightful features of this instru-ment lies in those low -throbbing noteswhich are felt rather than heard. I donot suggest that this effect is impossibleon the loud -speaker, but I have yet toexperience it.

Does Mr. Barnett suggest it can be" synthethised " ?

-G. W. PART (Woking)

Wireless Magazine. ...lune, 1929 GRAMO-RADIO SECTION

A Record RecordBy H. T. BARNETT, M.I.E.E.

MOST highly to be commendedand deserving of all possible

encouragement is the Vocalion Co.for recording a major work for issueat a minor price. In the AprilBroadcast list and in the f o in.to 12 in. section, at 2S. a disc, will befound Greig's Piano Concerto in Aminor, played by Maurice Cole anda symphony orchestra (recorded onthree discs) at a total cost, for thewhole work, of 6s.

As Long As a 12 -inch RecordOf course, in common with all the

Broadcast twelves, each side ofeach disc plays as long as a long12 in. record of any other make.

So far as the performance goes, Ilike it as well as any I have heard.The orchestra is a good one andincludes sufficiently prominent tym-

pani. The placing of the micro-phone ensures an excellent balancebetween the piano and the orchestraltone volume.

The work is divided so that thebreaks come at excellent points inthe music. The recording is trueto scale balance, and the engineerhas given the piano a little extrabrilliance of tone without in anyway producing that suggestion ofbreaking glass bottles which bothersme a good deal in the case ofanother recording of this concertwhich I have and which cost me 18s.

Of course, at the present price ofshellac one cannot expect a greatdeal of it in 2S. records, but surfacenoise in this record and other cheaprecords need be no bogy if you willuse (as I do exclusively) fine gaugesteel grip needles.

Building YourOwn Gramophone

LAST month in the Gramo-RadioSection of the WIRELESS MAGA-

ZINE we gave details of the con-struction of a gramophone from akit of parts-a scheme whichundoubtedly appeals to many ofour readers who have as yet notinterested themselves in the radioset's companion instrument, as thegramophone has proved itself to be.

In the original article it wasstated that a Garrard double -springmotor is supplied with the Ales-trian kit; this is wrong. The motoris a double -spring model made by" Collaro and His Famous Band ofEngineers."

A few back copies of the WIRE-LESS MAGAZINE, describing thisinstrument, are available for is. 3d.each, post free.

A Good PortableGramophone

This is theMicro-

Perophoneportablemachine

(See the article by H. T. Barnett on thepreceding pages)

Storing YourRecords

WHAT a wealth of paper andcardboard is wasted in the sale

of a gramophone record ! Mostdealers, when you hand them 3s., or4s. 6d., as the case may be, wasteat least twopence in (a) the normalpaper container for the record, (b)an external paper bag with dinkylittle string handles and, (c) straycatalogues and pamphlets that sel-dom serve their desired purpose.

Shopping After DarkIt is the a and b in which most of

us are interested, because althoughb can be used for shopping afterdark, when the neighbours won'tsee, it is a nuisance to keep therecords tidily in their paper bags.

I have. overcome this difficultymyself by storing the records ver-tically on the shelves of the recordcabinet, a fairly stout sheet of card-board being placed between eachrecord and the next.

I confess I have not yet takenthe trouble to index the cardsand to keep a file, which, ofcourse, is the obvious thing todo, but "jazz," "serious," and soon are kept apart. It is only thematter of a few seconds to findany one record. The cards, ofcourse, prevent the grooves of onerecord from scratching its neigh-bour.

Cutting Thumb HolesTwo things I shall do in leisure

moments and which can be recom-mended to WIRELESS MAGAZINEreaders are, first, to cut thumb holesin the cards so that any one recordcan easily be pulled out of a bundle,and, second, to attach midget pro-jecting name tags.

J. JACKSON.

Whatever you want to know about gramo-radio,consult the " Wireless Magazine " Technical Staff.For many months they have kept abreast of this latestdevelopment and can reply to any query that may beraised in connection with it.

If your pick-up does not give the results you think itshould-if your amplifier is not quite distortionless-in fact, if you are in trouble of any sort, the TechnicalStaff can put you on the right track.

So that the staff is not absolutely overwhelmed with

queries (and to avoid the trouble of answering any of afrivolous nature, which results from a free service)a nominal fee of Is. is charged for every two questionsasked.

Write your query or queries (not more than two can beanswered for each reader) on one side of a sheet of paperand send it, together with a stamped addressed envelope,a postal order for Is. and the coupon from page iii of thecover, to Gramo-Radio Queries, " Wireless Magazine,"58161 Fetter Lane, E.C.4.

424

[VirelessMagazine. June, 1929

EKPro THE

1CA11L,S

Part of the reproducing apparatusused in the British Phototone

" talkie" system

THE recent resignations amongthe B.B.C. staff have attracted

much attention for the special reason,we suppose, that for some long timethe defection of any B.B.C. officialwas almost an unknown thing. What,then, accounts for the sudden rushafter outside jobs?

Savoy Hill UndisturbedSavoy Hill (writes a WIRELESS

MAGAZINE Commissioner) remainedundisturbed by the early secessionsamong its staff, the feeling of theauthorities being that unless anofficial was loyal enough to stick tothe ship without more or less inflatedemoluments being necessary for thepurchase of his fealty, the B.B.C.would be better off without him.

Further, if a job had to be filledowing to someone's resignation, quitea lot of people would be willing tofill it from outside; but on the otherhand a number of resignations woulddo no harm, as it was not unlikelythat after six years some redundantstaff had been created.

Hence the withdrawal of certainjunior members of the engineeringstaff did not result in any officialexpressions of regret.

The move towards an independentattitude was regarded a little moreseriously when the senior officer in

WHAT THE B.B.C.STAFF RESIGNA-

TIONS MEAN

BY A SPECIAL " WIRE-LESS MAGAZINE"

COMMISSIONERthe lines section, Mr. Attkins, an oldPost Office man, who had a goodknowledge of the, telephone service ofthe country, went over to the films,for he was one who would have to bereplaced.

In other cases such a necessity hadnot arisen.

The departure of the formerdramatic producer, Mr. R. E. Jeffrey,caused a minimum of consternation.Fcr a long time this official had feltthat he was not being given anunfettered hand in the directing ofradio drama and that he was beingsubjected to criticism by officials out-side his department.

The situation created by theappointment of Mr Val Gielgud asdramatic producer and the transferof Mr. Jeffrey to a specially createdpost, that of Director of DramaticResearch, could not pass muster aspromotion for R. E. J., and when hedecided to throw in his lot with the" movie -talkies," it was a wise step.

A "Manufactured" JobThere was nothing further to hope

for from Savoy Hill, where nosteps were taken to appoint a succes-sor for a job which had been " manu-factured" for him with a flourish oftrumpets a few months previously.

Thus the ideas -cum -research aspect

425

The reproduction is from records.As one finishes the other starts,

with complete continuity

of programme presentation revertedto Mr. L. de G. Sieveking, whostraightway devised a "BritishNational Programme," which pur-ported to be given from the broad-casting station of a mythical Ere-whonia ; thereby making many thou-sands of listeners to weep, eventhough it may possibly have causedthe gods to laugh.

Noise.* "Off "Co -incident with the departure of

Mr Jeffrey, one of his lieutenants,Mr. K. V. Wright, also made his exit.He had done his job of directingsound effects most conscientiously;but the development of talking pic-tures furnished an outlet for hisenergies on more advantageous termsthan Savoy Hill could offer him tostay. For the same reason Mr. Mayer,the second in command of noises,relinquished his job and followedMr. Wright's lead.

Some minor resignations ensued,and then a few weeks ago came, per-haps, the most important of the with-drawals that have yet taken place,namely, Captain A. G. D. West's.

Mr. West had provided a goodshare of the brains of the engineeringdepartment. In the early days ofbroadcasting he evinced a predilec-tion for technical research by putting

Wireless Magazine. une. 1929

The Trek to the Talkies (Continued)

up a transmitter on the roof of apublic -house next door to the Old Vicin Waterloo Road, London, for thepurpose of testing receivers installedat 2L0 and the provincial stations.

Transatlantic RelaysHe often sat up all night in the hope

of receiving Transatlantic broadcastsof sufficient quality and strength torelay to British listeners. He con-trived that ingenious broadcast ofthree years ago from a moving trainbetween Potter's Bar and Hitchin,using the telegraph wires whichbordered the permanent way as anaerial-the longest broadcast trans-mitting aerial in the world. Hedevised a wireless "pram," to enableZoo noises to be conveyed to listenersin their own homes by means of aperambulating microphone.

Studio acoustics were also hisespecial province, his latest experi-ment in this connection being theprovision of a small portable organ,consisting of a row of pipes of differentfrequencies, designed to give thepurest sound output possible. Theobject was to measure acousticcharacteristics in the studios and thento move the organ to outside hallsfrom which broadcasts take place, toenable comparative measurements tobe made.

Like most of his work, to which hebelieved in applying the motto"festina lente," Captain West tookhis time over the development of thisdevice, and it was more than twoyears before it reached that state ofperfection which warranted its prac-tical use.

Outstanding IntellectsOne of the outstanding intellects

among the engineering staff, CaptainWest had, it was thought, resolvedto devote his life's work to broad-casting, and it came as a surprise tomany listeners to learn that he haddecided to go over to the GramophoneCompany.

How can these resignations beexplained and have we seen the endof them ? To the latter part of thequestion the answer is No; there willbe several more voluntary departuresyet.

As to the explanation, it may besafely hazarded that until the adventof talking -motion pictures, Savoy

Hill held something of a monopoly inits staff. Apart from a handful ofmen specially trained in certain call-ings, the one body which counted foranything at all outside the B.B.C.were the engineers; and it wasrumoured that so far as these wereconcerned, other likely avenues ofactivity, such as the radio manufac-turing firms, were effectually closedagainst them. The " talkies " havethus proved to be an open sesame.

In defence of the Corporation,however, it should be pointed outthat it is a mistake to compare theposition of the B.B.C. with that of acommercial company in its relationto its staff. The business house, veryoften faced with keen competition, isforced into a species of bargaining forthe services of men and women; notalways because their services are

LOOK OUT NEXT MONTHFOR A SPECIAL ARTICLEON " TALKIES " BY AN EX -MEMBER OF THE B.B.C.

STAFF.

altogether requisite to the greaterefficiency of the concern, but becauseit is sometimes expedient to preventan opposition house from securing anindividual's services.

Further, high -salaried jobs in manybusiness houses serve as valuablepublicity to the firm, according to thestanding, social or otherwise, of theindividual to be engaged. It is notalways a matter of value -for -valuebartering, that is, the payment ofcash for the assessed value of brains.

In the entertainment world, whichis, perhaps, more closely aligned withbroadcasting than any other interest,definite financial standards are ap-plied. In the mercantile world alsosalaries are measured to some extentby the terms of service. Everywheredifficulty exists in introducing basiccomparisons for application to broad-casting officials.

Not only was the B.B.C. calledupon to dig the foundations of a newedifice back in 1922, but it had tofix entirely new standards in connec-tion with employment. In very manycases, apart from all-round ability, itcould not define the sort of previousexperience which might prove anasset in the new sphere. The .policy

426

inclined rather to the engagement ofthe novitiate who could be trained-moulded would be, perhaps, a betterword-to the work for which he wasintended.

It is no exaggeration to say thatmore than 75 per cent. of the B.B.C.staff were paid for work which theyhad never previously performed, andwhatever experience many mighthave gained with the B.B.C., wouldhave had a cash value only to anotherbroadcasting organisation. Thosewho were able to sell their servicesoutside to a highdr bidder mighttherefore be influenced by the eco-nomic necessities of the time to do thebest they could for themselves. Sucha step was not unforeseen.

Where the B.B.C. Scored

To this extent, then, there was nodifference between the B.B.C. and theordinary business concern. Where theB.B.C. probably scored was in theretention of a number of enthusiastsfor broadcasting who would noteasily be tempted away from SavoyHill and who, with the passage oftime, will become specialists in theirjobs.

Outside concerns, it is said, arewatching these developments andwill probably extend their efforts tosecure suitable talent from theB.B.C. Is the Corporation likely tocombat these moves, or to adhere toan attitude of quiescence? It willalmost certainly keep in mind thefact that it is not a profit -makingconcern, and as the guardian of thepublic's money, must beware oflavish expenditure on staff.

Future ReductionsIt will also keep in view the reduc-

tion of effort which will automaticallybe called for when the regional trans-mitters replace the present wide-spread distribution of staff; for thetime is coming when fewer people willbe wanted to operate the machine.

From present indications, it ap-pears that, unlike the ordinarybusiness organisation, whose successgenerally spells expansion, the successof the B.B.C. must lead to compres-sion and jobs will ultimately only beavailable for the pick of the brainsnow identified with the making ofprogrammes.


JESIC ATANIT The FROM 11161DOSAIN6 ORR110114M0

EVEN the most critical listenercannot fail to by pleased with the

excellent performance of the four-valver illustrated in these pages.Very great care has been taken in itsdesign by the WIRELESS MAGAZINETechnical Staff to get the maximumefficiency at every stage.

Music at Any TimeThe Music Player is intended for

those who want music at any time.Not only is it exceptionally efficientfor the reception of broadcaststations, but the low -frequencyamplifying stages also constitute adistortionless gramo-radio equipmentfor the electrical reproduction ofrecords.

As a standard receiver for thereception of all the importantEuropean broadcasting stations andfor gramo-radio work, the MusicPlayer would be hard to beat; itincorporates every modern refinementand a superlative performance isassured.

New Dual -range CoilsUse is made of a new type of dual -

range coils which give excellentresults. An ordinary three -electrodevalve is used for high -frequencyamplification and this is neutralisedon the split -primary principle. Formaximum efficiency, grid bias isapplied to the high -frequencyamplifier. A rheostat is provided forthe control of volume and for ease ofneutralisation.

So that the best reproduction isassured, the detector valve isarranged on the anode -bend principle,a small dry battery being mountedinside the receiver for supplying thebias to this valve and also, thehigh -frequency amplifier.

Between the detector and thefirst low -frequency amplifier, resis-tance -capacity coupling is employed,the anode resistance in this case beingonly ioo,000 ohms so that maximumpurity can be obtained.

The detector is also provided withthe usual " motor -boat " stopper or

Of special interest to thediscriminating amateur arethe following features of theMusic Player :-

Straightforward four -valvecircuit, with neutralised(three -electrode) high -frequency stage, anode -benddetector, resistance -coupledamplifier, and transformer -coupled power stage withchoke output.

Dual -range coils controlledfrom the panel.

Milliammeter to indicatedistortion.

Entire set switched on bymovement of loud -speakerplug.

Insertion of pick-up jackswitches off high -frequencyvalve and alters bias on" detector " valve for ampli-fying.

Two " motor -boat " stoppersare incorporated so that theset can be used without diffi-culty with mains -supply units.

427

stabilising device, which consists of ahigh -resistance (in this case 20,000,30,000 or 4o,000 ohms) in series withthe anode resistance and a 2 -micro -farad condenser connected to thenegative side of the filament.

For Mains OperationThese stoppers are essential in

most cases if the set is to be run froma mains -supply unit, but they are alsoa great advantage when dry batteriesare employed. Run-down batteriesdevelop a high resistance which oftencauses motor -boating and generalinstability; the inclusion of stoppersin a set means that the batteries canbe kept in use longer than wouldotherwise be the case.

In the case of the Music Player astopper is also provided in the anodecircuit of the first low -frequencyamplifying valve as well as for thedetector. Here it is in series with theprimary of the low -frequency trans-former.

Choke Output ProvidedA power valve taking a fairly

heavy anode current will probably beused in the last stage, and for thisreason choke output is provided.This device prevents the directanode current from passing throughthe loud -speaker windings and caus-ing them damage.

Special note should be made of theingenious system of switching theMusic Player. Two jacks are pro-vided, one on the left of the panel


The Music Player (Continued)

Two grid -bias batteries aremounted on the base -board

Note the compact arrangement of the Music Player, an extraordinarily efficientfour-valver that covers both wavelength ranges without coil changing

and one on the right. When theloud -speaker plug is pushed into theleft-hand jack the whole set isswitched on.

When the pick-up plug is insertedin the right-hand jack the high -frequency valve is automaticallyswitched off and the pick-up con-nected in the grid circuit of thedetector valve.

Altering the Grid -BiasIn this connection, it should also

he noted that the plugging -in of thepick-up alters the grid -bias on the" detector " valve so that it actuallyamplifies instead of detects. Mostvalves need a bias of 'IA volts whenused as a detector, but this is in-creased to 3 volts when the valve isneeded as an amplifier.

It has already been mentionedthat the high -frequency valve rheo-stat is used as a volume control; thisis only available, of course, forbroadcast reception, and if a volumecontrol is desired for gramophonereproduction it must be providedexternally. Many makers supplysuch controls with their pick-ups.

Utility of MilliammeterThere are some people who think

that the inclusion of a milliammeterpermanently in the anode circuit ofthe last valve is an unnecessary

extravagance; that is a matter ofopinion. But of the utility of such anarrangement there can be no doubt.

Only by careful watching of themilliammeter can absolutely (11,,-

tortionless reproduction be achieved,and those who really appreciate goodmusic will be glad of the visibleindication that the milliammetergives when things are not quite right.Perhaps the milliammeter is evfn

READ THE GRAMO-

RADIO SECTION IN

THIS ISSUE - ITWILL HELP YOU TO

GET THE BEST RE-SULTS WHEN USING

THE MUSIC PLAYER

FOR GRAMOPHONE

REPRODUCTION

more important for record repro-duction than it is for radio work-thestrength of different records varies soconsiderably.

When the reproduction is distor-tionless and the last valve is not beingoverloaded, the needle of the milliam-meter will remain steady. This isbecause the valve is working on thestraight part of its curve and the

428

average value of anode currentremains constant.

Should the valve be overloaded,however, the valve will not beworking entirely on the straight partof its curve and consequently theaverage value of anode current willfluctuate and the needle of theinstrument will flicker backwardsand forwards to a considerabledegree. When this occurs either thebias on the last valve must be re-adjusted or the input must bereduced.

Using a Volume ControlIn the case of radio reception the

high -frequency valve rheostat will beused, while in the case of gramophonereproduction the external volumecontrol already recommended will becalled into play.

However, if any reader definitelydoes not want to include the milli -ammeter and is willing to rely onlyon his aural susceptibilities to correctdistortion, the instrument can beomitted without detracting from theappearance of the set.

Low -geared Slow-motion DialsWith a sensitive and selective

receiver such as the Music Player is,the use of low -geared slow-motiondials is essential if the best per-formance is to be obtained. Weattach much importance to thechoice of reliable dials and con-densers, and believe that the com-bination employed in this receiver ishard to beat.

As regards controls in general, theirarrangement will be clear from thephotograph that forms part of theheading to this article. The aerial(left) and high -frequency (right)tuning dials are in the centre of thepanel.

Levers for Dual -range CoilsIn a line across the bottom are the

two levers to operate the internalswitches of the dual -range coils andthe knob of the reaction condenser,on the extreme right. The makerssupply with their coils an indicatingplate to be fastened on the panel toshow the positions of the levers forlong- and short-wave reception.

These we have omitted as, in orderto accommodate the milliammeter onthe panel, the coils have been


A Dual -range Four-valver of Fine Qualityarranged so that the levers arepivoted from the top, and not fromthe bottom, as the manufacturersevidently intended. This alteration,of course, in no way affects theefficiency of the coils.

No Need for ScreeningWhile on the subject of coils, we

may take this opportunity of dis-cussing screening. Our experience ofthe particular coils used is that,spaced as far apart as they are in theMusic Player, no screening is neces-sary. The original set is quite stableand no difficulty has been experiencedin neutralising it.

Any constructors who desire to,however, can insert a simple verticalscreen between the two coils. This isa precaution, though, which does notseem to he necessary.

Positions of Jack SwitchesAlong the bottom edge of the panel

are arranged the two switching jacks.That on the left accommodates theloud -speaker plug and switches thewhole set; that on the right accom-modates the pick-up and auto-matically switches off the high -frequency valve when the set is usedfor record reproduction.

From the foregoing remarks it willbe evident to the reader that theMusic Player is indeed what its nameimplies-a first-class source ofmusical entertainment at any hour

Special stabilisers are incorporatedin the low -frequency stages

The dual -range coils used in the Music Player are of a new type, particularly efficientin performance

of the day or night, either forbroadcast reception or gramophonereproduction.

During quite a short test more thantwenty stations were tuned -in at adistance of 16 miles north of Londonon only a 25 -ft. aerial-and a corre-sponding length of wire laid acrossthe lawn to act as an earth con-nection !

Although the set looks complicatedto construct, because of its compactlayout, little difficulty will be

experienced if use is made of a full-size blueprint.

This shows the positions and sizesof all the holes to be drilled, thearrangement of the components, andthe actual numerical order of wiring -up for the best results.

Blueprint for Half-priceThe blueprint can be obtained for

half-price (that is, 9d., post free), upto June 3o, if the coupon on page iiiof the cover accompanies the applica-

RC Anti -Nob° //mi`,,b,

0005

L.7:-

68+ G.B. /.R.-2Here is the circuit of the Music Player. Note that bias is applied to the grids of both the high -frequency and detector valves.

Jack switching is employed for the loud -speaker and pick-up

429



This layout and wiring diagram can beobtained as a full-size blueprint for halfprice (that is, 9d., post free), if the couponon page iii of the cover is used by June 30.Ask for No. WM144. Wire up in the orde'

indicated

tion. After that date the full price ofis. 6d. will be charged, although anextension of time is allowed in thecase of overseas readers.

Address your inquiry to BlueprintDept., WIRELESS MAGAZINE, 58/61Fetter Lane, E.C.4; and ask forNo. WMr44

Laying Out the ComponentsLittle need be said about the actual

laying out of the components. Thereshould be no difficulty at all in thisrespect if full use is made of the photo-graphs and blueprint (or the reduced

reproduction of the latter shownalongside).

When everything has been screwedproperly into position, wiring up canbe undertaken. This, again, is com-paratively simple if the blueprint isfollowed. Each wire is numberedseparately and the connections shouldbe made in the order indicated.

For instance, first connect up wireNo. r and then mark that numberthrough on the wiring diagram. Pro-ceed in numerical order until thewhole of the wiring has been com-pleted.

Choice of Suitable ValvesBefore. the Music Player can be

used, suitable valves must be ob-tained. The choice is a matter of someimportance, for the use of the wrongtypes of valves will completely spoilthe performance of even the best set.

The high -frequency valve shouldhave an impedance between 20,000and 30,000 ohms, whatever the fila-ment voltage may be. A complete

UT. Mt- LT+ LT- E

REACTION ANODE ANODE MILLI- AERIAL DUAL -RANGECONDENSER CONDENSER COIL AMMETER WENSER AERIAL COILCONDENSE

H.F.CHOKE

DETECTORVALVE

R CUNIT tr-STOPPER

Isi L F ANODE ,

VALVE RESISTANCE

111717V-"--"afill4

L FTRANSFORMER RHEOSTAT

NEUTRAL-ISING

CONDENSER

VALVE

, OUTPUTas` \,92-,10KE

POWERVALVE

This plan view of the Music Player shows clearly how all the parts are arranged

TEN REASONS WHY YOU SHOULD BUILD THE MUSIC PLAYER(1. The efficient neutralised high -frequency stage ensures

reception of every important European station.CI. With the use of the correct valves and the guidance of

the milliammeter, distortionless reproduction is obtainedfrom radio or gramophone records.

IQ There are only two tuning controls and the selectivityis of a very high order.

(1 Choke output is provided so that the loud -speakerwindings are completely protected.

There are no connections to alter when switching overfrom broadcasting to gramophone reproduction.

430

fq. A rheostat associated with the high -frequency valve actsas a volume control and simplifies neutralisation.

CI, The set is equally suitable for use with dry batteries or amains unit for high tension.Excellent results can be obtained with an aerial as shortas 25 ft., as many as twenty stations being tuned -induring the course of a short test.

4[1. The construction is quite straightforward ; there is noelaborate metal screening.

CI All the components utilised are of the very best qualityand excellent performance can be relied upon at all times.

Stability is a special feature ofthis fine four-valver

In the Music Player the three -electrode high -frequency is neutralised on the split -primary principle

high tension to be used with the set.If a large mains -supply unit (such

as the Gecophone A.C. model, withwhich the Music Player has beentested) is available, then it does notmatter how great is the consumptionof the last valve, but in the case ofdry batteries due considerationshould be given to their maximumdischarge rate.

However, for use with most moderncone loud -speakers (excellent resultshad been obtained with the Mullard

Wireless Magazine. Jane. 1929]

Sets a Standard for Radio or Gramophone Worklist of valves in order of impedancewill be found on pages 402 and 404 ofthis issue. The actual impedance isnot critical and almost any valve ofthe " H.F." type will do.

Impedance of DetectorThe detector valve should have an

impedance between about 3o,00o and50,000 ohms, more latitude being per-missible here than in the case of thehigh -frequency valve. The lower theimpedance of the detector valve thebetter will be the quality, but volumewill fall off to some extent as valveswith low impedances have low ampli-fication factors.

The first low -frequency valve canbe of the " L.F." or "first power"type, that is with an impedance be-tween 6,000 and 25,000 ohms. Here,again, the lower the impedance thebetter the quality, but at the expenseof volume.

Ample Volume ObtainedDo not suppose that the use of low

impedance valves means that onlyweak signals will be received; thestrength will be adequate for all nor-mal purposes. With high -magnifica-tion valves, signals will be of enor-mous volume.

It is essential to use a really goodpower valve in the last stage, althoughthe choice of a suitable type shouldnot be undertaken without carefulconsideration of the source of the

Two-, four-, or six -volt valvescan be used, as desired

Another view of the Music Player, in which two " motor -boat " stoppers are incorporated

431

type H) a valve with an impedancebetween 2,000 and 4,000 ohms willbe about right.

Using six -volt valves, we have ob-tained good results with the followingEdiswan valves : HF61o, RC6io,LF6io, and PV625X. This is a com-bination that can be recommended,although some people may prefer touse a valve of lower impedance thanthe RC6io for the detector stage.

Operating the Music PlayerThe actual operation of the set is

not difficult. Insert the valves intheir respective holders and adjustthe grid -bias tappings. To the gridsof both the high -frequency and detec-tor valves a bias of i % volts negativeshould normally be applied, while thetap for changing the bias on the" detector " for gramophone workshould be placed in the 3 -volt socket.

The first low -frequency valve willneed between r % and 41/2 voltsnegative as a rule, while the tap forthe power valve will be between ro %and r61/2 volts, with 120 volts hightension.

Use of External Bias BatterySome power valves will need more

than 161/2 volts negative bias, inwhich case an external bias batteryshould be employed or an extra 161/2volt battery mounted on clips insidethe cabinet.

Wireless Magazine. June, 1929!


COMPONENTS REQUIRED FOR THE MUSIC PLAYER (FOUR-VALVER)

[-Ebonite panel, 21 in. by 7 in. (Resiston, Parfaitor Raymond) ... ... ... ... ...

2-.0005-microfarad variable condensers (Cyldon,

s d.

31 --Output choke (Parmeko type No. 2, Ferranti

or Marconiphone) ... ... ... ...4-Antimicrophonic valve holders (Lotus, Igranic

.s.

25

d.

0

Burndept or Ormond) ... ... ... .. 20 0 or W.B.) ... ... ... ... 3 02-Slow-motion dials (Burndept, Ormond or 3- 2-microfarad fixed condensers (T.C.C., Mullard

Igranic) ... ... ... ... ...2-Dual-range coils (Lewcos types DUA and

12 0 or Dubilier) ... ... ... ... ...r-Pair panel brackets, one with battery clip

i i 6

DUP) ... ... ... ... ... ... 70 0 (Ready Radio) ... ... ... ... ... 2 6s-.0001-microfarad variable condenser (Cyldon r-Terminal strip, 7 in. by 2 in. ... ... ... 6

Bebe, Peto-Scott or Bulgin) ... ... ... 5 0 6-Terminals, marked : Aerial, Earth, H.T.-,1-0-5o panel -mounting milliammeter (Sifam) ... 25 0 H.T.-, L.T.-E, L.T.- (Belling -Lee or Eelex) 3 0[-Neutralising condenser (Gambrell, Jackson Of 2-Jacks with plugs (Ormond types No. 4 and

Peto-Scott) ... ... ... ... ... 5 6 TO 01 -55 -ohm baseboard rheostat (Burton, Lissen or

Igranic) ... ... ... ... ... ... 2 9

6-Wander plugs, 2 red and 4 black (Lectro Linx,Belling -Lee or Igranic) ... ... ... r o

r-Grid-bias battery clip (Bulgin) ... ... ...r-Low-frequency transformer (Ferranti AF3,

Brown or Gecophone) ... ... ... ...

o

25

6

0

1-4 Mt -volt tapped dry battery (Siemens type GIor Ever Ready)... ... ... ... ...

I-46 Y2 -volt tapped dry battery (Siemens typeG3 or Ever Ready) ... ... ...

[

3

3

6r -5o,000 -ohm resistance with holder (R I. and Stiff wire for wiring (Glazite) ... ... 2 6Varley, Mullard or Dubilier) ... ... ...r-Resistance-capacity coupling unit with motor-

boat stopper (R.I. & Varley) ... ... ...

5

25

6

0

Length of rubber -covered flex ... ...r-Cabinet with so in. baseboard (Pickett) 35

40

t -High -frequency choke (Lewcos, Wearite or Total Cost of Set (approximately) £15 14 1

Ready Radio) ... ... ... ... 9 6

The no volts high tension shouldbe the voltage on load. This is impor-tant in the case of a mains -supplyunit, where a tapping labelled " 120volts" may give only roo or less witha 15 -milliampere load. A Ferrantivalve tester is a good investment forthe keen amateur, as with its use heis then no longer working in the dark.

Switching the Set OnWhen the various voltages have

been approximately adjusted and therheostat controlling the high -fre-quency valve switched on, the loud-speaker plug should be inserted inthe left-hand jack. This switches thewhole set on.

Now adjust the wave -range leverson the panel for the range desired.For wavelengths between 25o and 55ometres they should be put to theright; turning them to the left, theset will be adjusted for reception onthe band between r,000 and 2,000metres.

Get the Local Station FirstTo begin with it is best to tune to

the local station, so adjust the rangeswitch accordingly. Next turn the

reaction control until the set juststarts to oscillate; this occurs whena rustling or hissing sound is heardfrom the loud -speaker.

Now turn the two main tuning dialsin unison until the station is pickedup. The dial readings are approxi-mately the same over the entirewavelength bands. The differencescan be seen from the followingreadings :-

Aerial H.F. CondenserDaventry, 5GB 83 8oLondon ... 56 5 57Toulouse . 65.5 63Gleiw itz 47 45Radio Lyons .. 38 36Kaiserlau ten . . 31.5 28

75 73.570.5 67.5

Daventy 5 X X 62 57

When the station is picked up tuneit in as loudly as possible. Thenturn off the high -frequency valve bymeans of thebaseboard rheostat andadjust the neutralising condenseruntil the signal becomes inaudible.The set will then be balanced.

For gramophone reproduction, sim-. ply plug the pick-up into the right -

Hui zenRadio Paris

hand jack, leaving the loud -speakerplug in position until it is desired toswitch off completely.Use with H.T. Mains

Those who use the set with a mainsunit for high-tension supply will beinterested in a few remarks on"motor -boating." Mains and unitsused on them vary so much that it isnever possible to tell quite whatwill happen.

For instance, in the WIRELESSMAGAZINE offices, where direct -cur-rent mains are in use, no trouble atall was experienced even when lowvalues of decoupling resistance wereemployed.On A.C. Mains

On the other hand, on alternating -current mains in a town north ofLondon it was found necessary touse the R3 tap on the resistance -coupling unit in the detector circuitand a 50,00o -ohm resistance in theanode circuit of the first low -fre-quency amplifier.

If motor -boating is experiencedwith their values, increase the capa-city of the stopper condensers to4 microfarads

MEMORISETHESESYMBOLS Crystal

Detector

_L

A rial Earth

443%

"1" 21"Headphones Condenser

Variable FixedCondenser Coil

Codwith Slider

e

CoupledCoil, Variometer Wires Cross Wires

joined not joined

432

Wireless Magazine, June, 1929]

*NOR OSCILIATIONSWE_WANT

MORE.TALKS

ONSCIENCE

WEWANTMORE

COOKERy

HINTS

WEWANT

MOREPOETICAL

READINGS

WEWANT

MORE

JAZZ

BY THE UNOFFICIALWIRELESS CHORUS!

433


Sketches byGLOSSO P

Mrs,Irving

Mr. srving,designer ofthe Golden

Arrow

THE SPEED KING'S BROADCAST

On the left you see MajorSegrave, who broke theworld's motoring record,facing the microphoneon his return fromAmerica. He has sincebeen honoured with a

knighthood.

Mrs.Segrave

Summer RecordsHAVE you ever thought of keep-

ing a record of the effects ofsummer on your wireless reception?Such a record would perhaps not beof any great value if taken for one

The Effects of Summer

year only, but records taken for afew consecutive summers would beof the greatest interest and compara-tive value.

I have often wondered why one ofour wireless societies, or some scienti-fic society interested in wireless, hasnot enlisted the services of a numberof wireless listeners, well distributedover these islands, to take carefulobservations of summer effects onwireless reception. Such an investiga-tion would lead to valuable conclu-sions undoubtedly.

For example, it might be possibleto find out in this way the change inthe screening effect of a tree on anaerial as the tree breaks out into itsfull summer foliage. It might alsobe possible to estimate the effect onan aerial of bushes and plants growingdirectly under that aerial.

Another problem which would lenditself well to observation by listenersis the problem of atmospherics and

the effect of atmospherics on differentwavelengths. Perhaps the mostinteresting problem of all would bethe effect of advancing summer ondistant reception.

You will see from this little list ofsummer wireless problems that thereis any amount of work to be done insummer, and, if you kept a summerrecord of wireless reception, thechances are that that record would bedistinctly useful sometime sooner orlater.

.Trying Times

" Bad news to -night," said Georgeas he sat down in the vacant deck -chair in my garden shelter. " Oneof my wireless neighbours threatensto give up wireless altogether."

" I am sorry to hear that, George.I never like to hear of anybody givingup wireless. What is the reason inthis case ? "

"Obstruction and lackof encourage-ment in the home. The poor fellowhas only one possible place where hecan do his soldering and that is in thekitchen between the fire and thegeneral-purpose cupboard. Just as hehas got his soldering bit nice and hotand is about to solder a tricky joint,

Trying Times

44

somebody wants a cup out of thecupboard and he has to move out ofthe way.

"Next time he gets his bit hotsomebody else wants the sugarbasin, next time the pickles, and soit goes on. The poor fellow takes asmuch as three months to wire up aset."

" How very trying for him. Still,I don't see why he should give upwireless on that account."

" Perhaps not, but he happens tobe a very progressive home construc-tor and it takes him so long to makea set that the whole thing is out offashion before he finishes it, and sohe can never catch up, so to speak."

"Why doesn't he move the cup-board ? "

" I suggested that, but he says itisn't his cupboard and it is somethingthat he is allowed to solder in thekitchen at all."

Television the Alternative?Perhaps the most interesting specu-

lation with regard to television atthe moment is the ultimate effectof television on the twin -wave stationsof the new regional scheme. As far asour present limited knowledge goes,it seems clear that a demonstrationof television would not be veryattractive unless it were accompaniedby the simultaneous broadcasting ofspeech on a different wavelength.

Thus television, in its present stageof development, demands two wave-lengths and two transmitters for a

successful transmission. Moreover,it seems likely that television, as itdevelops, will continue to demandthe two wavelengths and the twotransmitters.

The Ultimate Effect

You will remember that the P.M.G.,in his now famous letter to the BairdTelevision Company, gave that com-pany what amounted almost to aninvitation to employ the B.B.C.'stwin -wave station at Brookman'sPark for television experiments out-side the usual hours of broadcastingservices.

Can the Baird system of televisionbe carried out at Brookman's Parkwithout a considerable amount ofaddition to and alteration to theordinary transmitting plant of thatstation? It will be rather a loss if oneof the two transmitters be definitelymarked off for television experimentsand we lose the alternative programmefor which we have waited so long andso patiently.

The Wireless PlayWhat do you think of the B.B.C.'s

present policy of suppressing thenames of the players who take partin broadcast plays ? Do you findyourself better able to concentrate

You Know Absolutely Nothing

on the character presented becauseyou know absolutely nothing of thespeaker, not even his name ?

There may be something in thetheory behind this new wireless playpolicy of the B.B.C., but I, for one,have begun to wonder if the schemewill work out in practice as it isexpected to work out.

If you are anything of a theatre-goer, you will know that it is possiblefor either the player or the play-wright to win your favour. If youare a picture -goer, you will knowthat the film actor alone has theopportunity of gaining your approval,the scenario writer being almost

Wireless Magazine. une, 1929

unknown. Under the new B.B.C.policy, things will again be different.

The players will remain unknown,and it will be the playwright alonewho will have the opportunity ofmaking a name with you.

Under conditions then which are sovery different from the conditionswhich obtain in the other and oldermethods of presenting plays, it isdifficult to foretell what will happen.Certainly, the writer of wireless playsnow has a unique chance of winningfame and fortune. Let us hope hewill make the best of his opportunity.

Simultaneous ReceptionHas someone been indulging in a

little gentle leg -pulling, or is thestory of our south -coast listeners'latest efforts in home -constructioncorrect ? Perhaps some of our south-ern readers can enlighten me.

The story is that, driven to despera-tion by their inability to cope withinterference from Continental broad-casting stations and spark stations,our listeners on the south coast haveabandoned their search for selectivityand are now making sets of maximumunselectivity..

Their determination is that, as theycannot boast of sets which will receiveone station and only one station atone and the same time, they willboast of sets which will receive thelargest possible number of stationsat one and the same time. In otherwords, they are building simultaneousreceivers on the south coast.

The idea of an unselective receivertakes one back to the early days ofwireless. I think I could find in myjunk room an old receiver the tuningof which would be broad enough tobreak records on the south coast.

The most unselective set that Iever heard of, however, was made by awireless friend of mine some littletime ago. The set had three hugecylindrical coils, each with twentytappings. On the panel there werethree selector switches, one for eachcoil, each switch rotating over twentycontact studs connected to the coiltappings. Was the set selective?Well, scarcely. 5XX followed youround the whole of the tappings.

11111 "ti'MSimultaneous Reception

435

Good TravellersFrom your experience of portable

sets, which valves can you recom-mend to me as good travellers ? Thereason I ask the question is this :During the last month I have had acurious experience of valves in transitand I am not sure of its significance.

At the beginning of the month Ihad a new type of portable set broughtto my house for test. The wirelessengineer who brought the set travelledover fifty miles by train. He kept theset with him the whole journey andhe took every possible care of it.When we tried the set we could getnothing from it, and we ultimatelyfound that one of the valves hadgone.

Good Travellers

There were three types of valve inthe set, H.F., L.F. or detector, power,The valve which had been damagedin transit was one of the first type,H.F.

Towards the end of the month, Ihad a new portable set sent to me byrail. The set made a journey of some-thing over fifty miles by passengertrain. When I tested this set, Ifound that one of the valves hadgone, and again it was a valve of theH.F. type.

Rather a coincidence, wasn't it,that the broken valve in each casewas of the same type? Now I am notgoing to conclude from these twoinstances that the H.F. type of valveis a bad traveller. Far from it, but Ishould be very glad to know whichvalves, in your experience, haveproved to be good travellers.

A CampaignIt still remains the fashion in

certain quarters to do nothing butabuse the B.B.C. programmes. Don'tyou think that those who indulge inthis particular form of abuse sotirelessly and tiresomely ought to bemade to realise that one good sugges-tion would be worth a whole bookfulof adverse criticism?

Shouting out for better programmesis such an easy thing to do, but whenit comes to the question of how tomake those programmes better, the


Under My Aerial (Continued)

shouters become as silent as the restof us.

What we ought to do to counter-act the damping effect of this adversecriticism is to start a campaign forthe praise of the B.B.C. programmes.There must be well over ten millionsatisfied listeners in these islands.

It Still Remain..

Suppose each one of us were to senda postcard to Savoy Hill at the endof the month stating which particularitem of the month's programmes hadpleased us the most, what valuableinformation it would be ! The B.B.C.programme staff would scarcely knowhow to contain themselves withdelight at such a collective expressionof our views.

No. I would not suggest that weshould also tell the B.B.C. what wedisliked the most. I have always hadthe idea that the B.B.C. need to betold what we like and not what wedo not like.

.Battery Weight

How much of the weight of aportable set is due to the batteries ?Have a guess at the answer. A tenth,a fifth, a quarter, or what fraction?

I have been carrying a portable setabout with me a good deal lately andmy curiosity has been aroused on thequestion of its weight. I actuallyweighed the high-tension battery andthe accumulator in order to answerthe above query.

Battery Weight

In my portable set, the high-tensionbattery weighs seven pounds, theaccumulator three and a half pounds.The total battery weight is therefore,ten and a half pounds. As the wholeset weighs thirty pounds, the fraction

of battery weight to total weight isas near as makes no difference toone-third.

Would you have thought it, one-third of the weight of a portable setdue to the weight of the batteries ?When you think of the lead platesof the accumulator and the carbon,manganese dioxide and pitch of thehigh-tension battery, you are perhapsnot so surprised.

Anyhow, I have been thinkingwhat a huge fortune there would befor the man who could invent a lightaccumulator and a light high-tensionbattery. Surely light batteries wouldbe one of the biggest boons to us.

Your Own WavelengthI suppose if I were to ask you your

size in hats, gloves, collars or boots,you would be able to tell me immedi-ately. I wonder, though, if you couldtell me your size in wavelengthsjust as quickly.

You know, of course, that thehuman body can be used as an aerial.Probably you have tried receptionon your own receiving set with afinger on the aerial terminal, yourselfbeing the aerial. You may also havetried a " human chain " aerial formedby a number of people holding hands" in series," the person at the " lead-in" end of the chain making contactwith the aerial terminal of the set.

Do you know, though, how tocalculate the natural wavelength ofyour own or somebody else's body?According to an American writer,the calculation is a simple one. Allyou have to do is to multiply theheight of the person under discussionby three, and divide the result by

-

Making Contactfive. The answer gives you thenatural wavelength of the person inmetres.

Thus, if you are a big fellow of 6 ft.your wavelength would be six timesthree, eighteen, divide by five, threeand three -fifth metres. Should yoube an exact 5 ft. in height, yournatural wavelength would be anexact three metres.

George says this natural wave-length formula requires a correctionaccording to the degree of stoutness.He says that wavelength depends oninductance and capacity and that,although a fat man and a thin manof the same height may have thesame inductance, the stout man wouldundoubtedly have the greater capa-city. HALYARD.

Radio Lamp LightingA Novel Method of Switching by Changing Frequency

ORDINARILY street electriclamps are turned on and off in

groups, by men throwing switches inscattered control stations in vat iousparts of the community. Thosecontrol stations are expensive tomaintain.

To replace the men and stationsthe Westinghouse Co. in Americadeveloped a radio device, whichBoston Edison Co. recently began touse on a circuit of seventy streetlights. The device utilises the factthat an electric wire can carry severalcurrents of different frequencies.

There are the carrier current andthe riding currents. In the base ofeach of the seventy Boston lamp -

436

posts now is a small radio receivingset. When a special generation at thecentral station sends waves of 720cycles a second along the light wires,the receiver moves a switch whichconnects the individual lamp withthe lighting circuit; when the fre-quency is 48o cycles, the receiverpulls a switch that disconnects thelamp. All lamps in a particularcircuit go on and off at the sameinstant.

For another group of lamps anotherpair of frequencies would operatethe circuit; and so on. The greatadvantage is that a few men in acentral station could handle all of acity's lighting. F. P.


ON THEROAVWAYFARER!By J. H. REYNER

B.Sc., A.M.I.E.E.

Tea -time music at Tintagel on the Wayfarer, a five -valve portable super -het

y HAVE come to the conclusionI that I am a crank because I takea wireless set with me on holiday.I seem to be regarded as an objectof curiosity by people who pass uspicnicking by the roadside, while ifone ventures to produce the set atan hotel in the evening in order tolisten to the news or to the pro-gramme, one feels rather like thefunny little man in Ridgewell'sdrawings in Punch, who inevitablyfinds himself blushing io the rootsof his hair and in a state of terribleconfusion.

The fact remains that, havingbuilt a portable set, I, at any rate,feel very interested in finding outwhat it will do in remote parts ofthe country; therefore, having de-cided to take a journey to Cornwallfor Easter, I took the Wayfarer withme and brought it forth at variousplaces en route in order to ascertainwhat the performance was like whenone really got away from the localconditions which prevail aroundLondon.

A Wireless Widow?My good lady raised her hands in

resignation on learning of my deci-sion; I suppose she felt that wirelessmorning, noon, and night was suffi-cient and that one might, at any rate,have a little relief on holiday.

I am glad to be able to state thatbefore we had gone very far we wereplaying the other side of the record;in fact, I believe before the end ofthe tour she positively enjoyed hav-ing it with us, and I feel sure thatone of the contributory factors wasthat the receiver always deliveredthe goods, no matter where we were,and it was always a matter of a few

Full constructional detailsof the Wayfarer-a five -valve portable super -hetwhich can be built for£15-were given in theprevious issue of " Wire-less Magazine." Backcopies can be obtained forls. 3d. each, post free.Full-size blueprints areavailable for ls. 6d. each,post free. (Ask for No.

WM139.)

moments only to receive the Daven-try programme.

After nightfall quite a number ofother programmes were received, andaltogether the set was on its bestbehaviour.

We took our time over the journeydown, halting the first night at High -bridge, in Somerset: Here we ob-tained quite a surprising number of

437

stations-Radio Paris, 5XX, andHilversum came in strongly on thelong Cardiff,Radio Toulouse, Langenberg, 5GB,and several other unidentified sta-tions were picked up on the shortwaves.

A Distinct AdvanceI have on other occasions taker.

other portable sets down to this dis.trict, and the present one representeda distinct advance On anything pre-viously used.

The next day we Wandered, via thenorth coast of Devon, over Porlockand Lynton, on to Bideford. One ofthe photographs accompanying thisarticle shows us having a picnic onthe top of Porlock, what time theset provided us with aural enter-tainment.

Incidentally, the first photographwas taken in the Savernake Forest,just before Marlborough, where westopped for a few moments andwhere, indeed, I was surprised tofind that London could just bereceived in daylight, although thedistance is some eighty odd miles.

At Bideford, 5GB and 5XX couldbe received without difficulty, whileafter dark I also received a stationat good strength which, so far as Icould gather, was Plymouth. Asthis was fifty miles. away, and as the


On the Road with the Wayfarer ! (Continued)

power of Plymouth is only 200 watts,this struck me as quite good recep-tion.

The next day we continued our

On the top of Porlock-lunch improved by the Wayfarer

progress down the north coast,touching at Boscastle and Tintagel,at which latter place we had lunch.This was again of the picnic variety,and the third photograph shows theset again in commission.

From Another WorldIt will be noticed that in this

particular instance it was found pre-ferable to keep the frame aerial inits closed position, although in theother two photographs the aerial isshown partly open and in its correctorientation. Daventry was quitecomfortably audible in the open airand the lunch-time programme froma London hotel seemed to us almostto be coming from another world.

The journey was continued toPerranporth, just beyond Newquay,where an extraordinary selection ofstations was obtainable. 5XX, curi-ously enough, was rather poor, as hewas liable to fade after dark, althoughthe reception in daylight was not toobad. Radio Paris and Hilversumwere both good, while on the shortwaves 5GB, Langenberg, and RadioToulouse were all excellent.

Land's End and the LizardThe next few days were spent in

wandering down to Land's End andthe Lizard, and generally testing theset, preferably during daylight at allsorts of points. Generally speaking,it was found possible to receiveDaventry under all circumstancesand Radio Paris could also be

received during daylight hours.5GB was just heard during day-

light at the Lizard, but one wouldhardly consider it good reception,

and I found a notice-able tailing off in theperformance as' wegot right down tothe end of Cornwall.In this district, andin similar remote orbadly screened lo-calities, it is prob-able that a pentodewould be of assist-ance ih the last stage.

This can, of course,quite easily be done,as only one L.F.stage is utilised andthe power valve atpresent employed

can be replaced with a pentode with-out any difficulty. The high-tensionconsumption will probably increasesomewhat if this is done; but, in anycase, the consumption of the rest ofthe set is relatively low, so that thisis not a serious disadvantage.

On the whole, therefore, I foundthat the set operated distinctly well.Judging from comments which I wasable to obtain locally, it appears thatthe set is rather ahead of the generalstandard, for it isthing for the averageportable set to givenothing at all insome parts of Corn-wall.

During the teststhe high-tension onthe detector was ad-justed to bring theset to a condition ofsatisfactory liveli-ness. Readers whobuild this set willfind that if the de-tector voltage is in-creased too muchthere is a tendencyto self - oscillation,but a value can befound at which theset is comfortablylively without anydistortion of quality or straining dueto reaction effects.

Those readers, however, who pre-fer to have some form of control overthe sensitivity can do this in a very

438

no uncommon

simple manner by adding a pre-setcondenser in addition to the .00ca-microfarad condenser across fromthe anode of the second detector toL.T. negative.

Increasing the StabilityThe larger this by-pass condenser

is made the more stable the receiverbecomes, and in the original set avalue of .000r microfarad was chosen,as this gave good results underaverage conditions. The connectionof a pre-set condenser (.00003 to.00025 microfarad) between the samepoints, either with the original .000i -microfarad condenser in position orwith it removed, according to whichworks best, will enable a very simplereaction control to be obtained.

Satisfactory Reaction ControlThe H.T. voltage on the detector

should be adjusted so that with thepre-set condenser screwed down thereceiver oscillates. It will then befound that as the capacity of thecondenser is increased the receiverceases to oscillate, and this can beused as a reaction control. Such con-trol has actually been fitted on theoriginal receiver as an experimentand has been found to operate quitesatisfactorily.

A suitable position is in between

The Wayfarer again in use-this time in Savernake Forest

the two tuning controls towards thetop of the panel, where there is aspace already, and where an extracontrol can be introduced withoutdestroying the symmetry.


C. WHITAKER-WILSON Explains in His Second Article the Term FUGUE for

MUSIC LISTENERmf 11 -

-Of

LAST month I endeavour-ed to explain the mean-

ing of the terms Sonata,Symphony, Concerto, andString Quartet. There wasnot room to include an ex-planation of the term Fugue.

We are always hearing a" Prelude and Fugue " an-nounced from London orDaventry : what then, is aprelude and what is a fugue?A prelude is soon explainedby saying that it is a prelude : inother words, it is an introductionto the fugue which follows.

A Matter of KeyAll the same, it would be better

to confess at once that the onlymusical way in which it is really con --n ected with the fugue itself is in thematter of the key. If a composer, inthe old days, wrote a fugue in, say,F major, he generally preceded it by aprelude in the same key.

In course of time the prelude,though still retaining its positionbefore a fugue in the above sense,became somewhat isolated. In fact,it might almost be said that if anyonewrote a small work for the piano orthe organ and had no reason to giveit a special title he contented himselfwith calling it a prelude.

Chopin's " Preludes "Chopin wrote twenty-four delight-

ful works which he called preludes(but which he might have calledanything else) : a very well-knownexample of a lovely prelude in moremodern times is, of course, the onein C sharp minor by Rachmaninoff.

A convenient term, covering, seem-ingly, any musical sins that need it,and yet the title for many beautifulworks. So that a prelude is either suchin the proper sense, or else a corn -

J

fadP a

Two Swiss maidens listen to a Brown loud -speaker

position with no particular form ordesign about it.

The fugue is another matter al-together. The word comes from theLatin and Italian fuga, meaningflight. And a very good name forsuch a composition : it certainly hasthe feeling of being a fugitive !

Perhaps no form of compositionhas been bound by more rules and'regulations; probably no other formin music has had its rules more fre-quently and consistently broken.Laws in music are the sanest thingsimaginable : each and all of themcan be said to have been the outcomeof much thinking and to have beenlaid down with the greatest reser-vation ; no one minds in the least ifand when they are broken-unlessby ignorance. No musician has evertolerated ignorance of his sacred art.

The following sketch of the fugueas a form of musical expression mayin no sense be regarded as a guide towriting one : the whole of this issueof the WIRELESS MAGAZINE would berequired for such a purpose. But itis easily possible to point out to thereader what he should listen for whena fugue is played.

To begin with, a fugue can bewritten for any instrument-such asthe piano or organ-capable of pro-ducing harmonies; or it may bewritten for any reasonable combina-

439

tion of instruments, fromthe full orchestra down-wards.

Fugues are common instring quartet -writing; infact for any combination ofinstruments calculated toshow off the "works" so tospeak.

The most important thingabout a fugue must natur-ally be its chief theme.called the subject. This is

given out first of all, by itself. Afugue -subject may be of any length,but a very few bars generally suffice :there is no sense in making thesubject unduly long. As soon as itends-we will suppose, for themoment, at the conclusion of thethird bar-it appears again in anotherpart, either higher or lower. This iscalled the answer.

Not Always IdenticalThe two, for a technical reason

which I need not explain, are notalways absolutely identical, but nearenough for all practical purposes.What has become of the subject nowthat the answer has taken its place ?The part plainly continues becausetwo voices are heard instead of onlyone. The answer has to be accom-panied by something, of course ; thusthe subject becomes the counter -sub-ject for the time being.

As soon as the subject re -appearsthe answer takes on the duties of thecounter -subject and the original sub-ject -part is free to wander about byitself, the harmonies by now beingin three parts.

Three HarmoniesPerhaps it is scarcely fair to call

them harmonies : they are reallyindependent counterpoints becausethey run counter to each other. At


The Music Listener (Continued)

any rate, by the time the last entry(we are supposing the fugue to be infour parts) has been made every onewill have moved up one, so to speak :the last subject -part will have becomethe counter -subject, the two previousparts will have become free.

Exposition and EpisodesAll this is called the Exposition, and

by the time it is over you will havehad enough of subject and answer forthe time being and will have becomeinterested in what are called theepisodes. Pleasant little turns ofmelody and harmony-all strangelyin keeping with the general style ofthe work-are now indulged in.

Just when you are really absorbedin what is going on you willbe suddenlyaware that the subject has appearedagain-and without the slightestwarning. There will be no elaboratepreparation for its entry, no pauseor other obvious device : it is there,before you can realise it, or else thereis some bad fugal writing !

From now onwards you will findthe interest to be cumulative : everypossible device is resorted to in orderthat you shall be entertained rightup to the last bar.

The subject will begin in one partand then be over -lapped in another;a deep note may be continuouslysounded and the excitement piled up;the answer may appear twice as slow-ly, or twice as quickly-known asaugmentation and diminution : thereis no end to the " dodges "-intellec-tual " dodges " at that !-which willbe employed rather than let theinterest flag.

It is a time-honoured device, thiswriting of fugues; and it is perfectlyamazing how, in the hands of masterslike John Sebastian Bach, real musi-cal emotion has been worked intowhat might appear to be a some-what mathematical form .of music.

Story of Bach's WorksThe most famous preludes and

fugues are those written by Bach forthe piano-or, strictly speaking, theclavichord : there was no piano inhis day, of course. The story of howthose amazing works came to bewritten is by no means out of placehere.

For one thing, there will be someamount of interest for readers of the

WIRELESS MAGAZINE in that theythemselves will naturally be mechan-ically -minded : the story touchesupon the mechanical side of music.

Before Bach's time the keyedinstruments were tunes by what hassince been named the Unequal Tem-perament, or Mean -tone System.This was really a case of an attemptto make tuning too perfect. Thesystem was, roughly, this : a notewas taken as a standard-usually mid-dle C-and all the C's were tunedfrom it. It was a simple matter totune the G's from the C's : violinexperience made that possible. Sothe G's were the next tuned. Afterthe G's, the D's, and so on, by fifths,until the whole gamut had been tuned.

Unfortunately, however, acousticshave ever been deceitful, and it wasfound that, while the simple keyslying around C sounded well enough;

WHEN YOUR PETLISTENS -IN

As announced last month, weare offering three prizes of twoguineas, one guinea and half -a -guinea respectively for thebest photographs of pets actu-ally listening -in which arereceived by June 3o. Get

your camera out now!

those which were more remote (likeB or F sharp major with their res-pective five and six sharps) soundedharsh and out -of -tune. If C, G, D, Aand E were tuned in succession it wasfound that the. E was a different Efrom one produced by tuning a lowerE as a true third from C, and thentuning the octaves of it.

So that, unless you were contentedwith three sharps or three flats, inthose days, you found yourself some-what restrained and restricted . Itwas not long before men saw theadvantage of going into any keywhich they thought' fit for the sakeof the effect which they produced;and it must have been more thanannoying because they could dowhatever they liked when writingfor a string quartet where the instru-ments were free.

But in writing for the clavichordthey found that certain chords weresimply not usable.

Then Bach came on the scenes.

440

As soon as his genius began to develophe saw the necessity, not only ofgoing into extraneous keys fromsimple ones, but of starting in any key." If there is a key of C, without eithersharps or flats," he said, "there mustalso be a key of C sharp which willhave seven sharps : I intend to useboth keys."

Bach's ExperimentAs things were, two instruments

would have been necessary, one tunedfrom C and the other from C sharp.But Bach experimented with thirds,fourths, and fifths, until he succeededin dividing the octave into twelveequal semitones. The system (whichwe have adopted ever since), was arevelation and a revolution at thesame time.

Earlier experiments had been triedwith it-it had to come, of course,because Art could not progress with-out it-but Bach was the first to givea practical demonstration of it. Nosooner had he satisfied himself thatall was well with his clavier than hegave his opinion of it to the world ina very practical manner.

He took each of the twelve semi-tones in the octave, made them, inturn, the name -notes of twelve majorand twelve minor keys, and wrotetwenty-four preludes and fugues, onein each of the twenty-four keys.Subsequently he wrote a second bookof them.

Forty-eight Preludes andFuguesThus were born the famous forty-

eight preludes and fugues, two in eachmajor and minor key, called inGerman Das Wohltemperirte Kiavier-" the well -tempered clavichord."Monuments of the superbest technicalbeauty, apart from their significancein the mechanical and acoustic sense,they remain the harmonic wonders ofthe world. It is perfectly amazingwhat can be extracted out of them :they are as eternal as the pyramidsof Egypt.

Such, then, is the story of the pre-lude and fugue. To those who care tolisten intently while a fugue is beingplayed-or sung, for there are vocalfugues-nothing but the keenestintellectual enjoyment is in store. Afugue is the most satisfying thing inmusic.

enn EfficientThree-valverforReceptionon'Wavelenglhs

fiona5to5Ottietres

GRID TUNINGCONDENSER MASTER

RHEOSTATREACTIONCONDENSER


SpeciallyPetsignedBuilt and Tested

by theat,: -A

ireless MagazineTechnical Staff

EVEN the hardened listener canget a thrill out of short-wave

reception. There is something un-cannily fascinating about receptionon the waveband between 15 and toometres (which this set covers).

We take many scientific achieve-ments for granted nowadays ; butstill a blasé member of the WIRELESSMAGAZINE Technical Staff can bearoused to enthusiasm in describingthe construction of a receiver whilstlistening to a programme from WGY,Schenactady, New York, on the loud-speaker !

No DifficultyA great thing about short-wave

reception is that, provided certainsimple precautions are taken, it pre-sents no difficulties. It is possibleto pick up far distant stations (in theUnited States), for instance, on onevalve if headphones are used-andprovided that conditions arefavourable.

Further than this, if conditions

happen to be unfavourable even amulti -valve set will give no betterresult in proportion. For loud-speaker reception under normal con-ditions a three-valver is ample. Such

store4:1(2"

OPE7W/Ye TO TAKEPomcZ /4',17"Details of cabinet for the Short-wave

Link

SLOT

51'2'

a set is the Short-wave Link Three.From the foregoing it will be

appreciated that the detector valveis of great importance and everypossible step must be taken to ensure

These are the special coils used in the Short-wave Link

441

that the maximum efficiency is ob-tained from it. The question ofsmooth reaction control is, therefore,of paramount importance.

The Short-wave Link is a three -valve set comprising a detector, oneresistance -capacity coupled low -fre-quency stage, and a transformer -coupled stage. Such a combinationgives the maximum efficiency con-sistent with good quality and lowupkeep costs.

Greater H.T. ConsumptionIf two transformers were used, for

instance, the signal strength wouldbe increased, but, on the other hand,quality would be sacrificed, and thehigh-tension consumption would alsobe greater.

In the Short-wave Link great carehas been taken to get the best possiblereaction control-the secret of suc-cess. The leaky -grid principle isused for the detector for the sake ofsensitivity; note that the values forthe grid condenser and leak in thiscase are .000i-microfarad and 5

megohms.

British Short-wave CoilsUse had been made of special

short-wave coils manufactured by aBritish firm of outstanding reputation.There are actually four coils, the firstcovering a waveband of from 15 to 29metres and the second the rangebetween 29 and 52 metres. Withthese coils it is possible to get most ofthe American broadcasts that matter.


The Short-wave Link (Continued)

B14ASEBOAXIOS//

vARIABLEALSYSTAACE.0-500.000 05155MOUNTED ON METALBRAM,

CILAMEATRAEOSTAT

NLUEPRIMTwM 14E

O

FIXEDPLATED

0

ERMINAL2l4 :""

4" -0

TONINGCOADTA5Lft

5E1 MEGRIMS

OPELIALCup

EARTIt AERIAL

This layout and wiring diagram of the Short-wave Linkcan be obtained as a full-size blueprint for half-price, thatis 6d., post free, if the coupon on page iii of the cover isused by June 30. Ask for No. W.M.142. Wire in numerical

order and keep all leads as short as possible

0-50400,0 OM'S 118R/AlifERES/STrecd---*

Circuit of the Short-wave Link, which comprises a detectorand two low -frequency amplifying stages

442

Overseas readers will find the set ideal for thereception of signals from the B.B.C.'s experimentalshort-wave station at Chelmsford, which works ona wavelength of 24 metres.

In detail, the circuit is arranged on the follow-ing lines : In the aerial circuit is an aperiodic coilof five turns ; this is mounted on a pivoted socketso that its coupling in relation to the tuned gridcoil can be varied as occasion arises.

Coils Wound with Bare Wire on Low -lossFormerThe grid coil (two are normally used, as ex-

plained) is provided with special knife-edgecontacts, well separated, so that losses are reducedas much as possible. The grid coil is wound withbare wire, while at one end is provided a reactionwinding of insulated wire.

Special short-wave condensers are used in orderto obtain the maximum efficiency. Both grid -tuning condenser and reaction condenser havea capacity of .00025 microfarad. It should benoted that the end plates of each are at earthpotential, and therefore there are no hand -capacityeffects to upset the tuning adjustments.

Stability is a great feature of the Short-waveLink.

Special Short-wave H.F. Choke EssentialIn the anode circuit of the detector valve there

is a high -frequency choke, as is usual in circuitsemploying capacity -controlled reaction. It isessential that this choke should be specially woundfor the short waves, otherwise difficulty will beexperienced in getting reaction at all.

Smoothness of reaction is controlled by twomeans-there is a potentiometer in the gridcircuit so that the grid potential (through the gridleak) can be finely controlled, and there is also avariable resistance in the anode circuit thatcontrols the potential applied to the plate. Inthis way it is possible to get without trouble themost efficient operating point for the valve-thepoint, that is, where reaction starts smoothlyand can be obtained without overlap.

Those who have had no previous experience ofshort-wave working, and who intend to buildthe Short-wave Link should note that oscillationmost easily occurs when the slider of thepotentiometer is placed at the positive end.

What "Overlap " Really Means" Overlap, " beginners should also note, is the

state of affairs when oscillation persists whenthe reaction condenser is brought back to a lowerreading on the dial than that at which it started.

For example, it might be found that oscilla-tion first started when the dial reading was 3odegrees, but on turning the dial back the reactioneffect might persist until a reading of 20 degreeswas reached; the starting and stopping pointsobviously overlap, and the control is thereforeerratic and irregular.


Build It and Pick Up America Direct !When the circuit is adjusted pro-

perly reaction should start and stopat exactly the same reading on thedial. Moreover, the set should glideinto oscillation smoothly and not bein a condition of either not oscillatingat all or oscillating fiercely. Theimportance of this will be realisedwhen it is remembered that a set isin its most sensitive condition justbefore it breaks into oscillation

Extra StabilityIn the Short-wave Link the varia-

ble resistance in the anode circuitalso serves another purpose besidesallowing of fine control of the anodepotential; in conjunction with a2-microfarad fixed condenser it actsas a motor -boat stopper, and thusgives the set extra stability in opera-tion. The practical advantage ofthis is that the high-tension batterycan be kept in service much longerthan would otherwise be the case.

So much for special features of thecircuit, which is otherwise quitestraightforward and follows standardpractice.

Choice of ComponentsThe choice of components for such

a set is also of great importance, andthe WIRELESS MAGAZINE TechnicalStaff only used in the Short-waveLink those it knows from long experi-ence to be especially suitable. Thequestion of coils, special high -fre-quency choke, and variable conden-sers has already been discussed.

Another most important point isthe selection of good slow-motiondials. For short-wave work suchdials are essential, because tuning is sosharp that it is practically impossibleto get anything at all if ordinaryplain dials are utilised.

Dials Free from BacklashThe slow-motion dials used must

be of good quality and entirely .freefrom backlash; if they are not theset will be in the same state as iithere were bad reaction overlap dueto incorrect circuit values.

Readers cannot be too stronglyurged to use as far as possible thesame parts as employed in the originalWIRELESS MAGAZINE receiver; onlythen can they be certain of gettingthe same excellent results.

Overseas readers who have diffi-

Here is the Short-wave Link, all wired up ready for use.control is a great feature

culty in obtaining parts locally should complete kits- of all the specifiednote particularly that a number of components of any of the sets des-adveitisers in the WIRELESS MAGA- cribed in these pages.ZINE make a speciality of supplying Construction will present no diffi-

Smooth reaction

Only the best quality parts are used in the Short-wave Link, a most efficientthree-valver which can be adapted for ordinary broadcast reception

443


1

The Short-wave Link (Continued)

COMPONENTS REQUIRED FOR THE SHORT-WAVE LINK (THREE-VALVER)

i-Ebonite panel, 14 in. by 7 in. (Resiston,s. d.

1 --Cabinet with baseboard, to in. deeps. d.

Raymond or Northern Radio) ... .. 6 3 (Caxton) 27 62-.00025-microfarad short-wave variable con- Stiff wire for connecting ..r o

densers (Cyldon) ... ... ... 25 0 4-yds. thin flex ... 62-Slow-motion dials (Igranic, Formo or 5-Wander plugs, 2 red and 3 black (Lectro

Ormond) ... ... ... ... . . 15 0 Linx) ... . ro1 -30 -ohm panel rheostat (Lissen, Peerless or 2-Spade tags, red and black (Lectro Linx) 4

Peto-Scott) ... ... ... ... ... 2 .6 4-Terminals marked : Aerial, Earth, L.S.+,3-Anti-microphonic valve holders (Wearite, L.S.- (Belling -Lee or Eelex) 6

Lotus or W.B.) ... ... ... ...i-.000r-microfarad fixed condenser with

insulated series clip (Dubilier) ... ...

7 6

2 6

Sundries . . 0

Approximate cost of receiver ... i9 16 5I-5-megohm grid leak (Dubilier, Mullard or

Ediswan) ... ... ... ... ... 2 6r-Baseboard potentiometer (Lissen) ... ... i 6 RECOMMENDED ACCESSORIES s. d.I-Set short-wave coils with base, for 16 to

5o metres (Marconiphone) ... ... ..4-Ebonite supporting pillars (Bulgin) ...I-Short-wave high -frequency choke (Wearite,

32 02 0

1-Pair phones (Ericsson) ...I-Loud-speaker (B.T.H. type C2) ... . .

1 -2 -volt accumulator (Exide, type CZ2) ...2 -66 -volt high-tension batteries (Siemens

12 645 0

9 6

Igranic or Rothermel) 1-Resistance-capacity coupling unit (Mullard)1-2-microfarad fixed condenser (Dubilier,

Lissen, or T.C.C.) ... ... ... ...I-Variable resistance, o to 500,000 ohms

(Claude Lyons) ... ... ... ...I-Low-frequency transformer (Igranic type

G. Philips or Mullard) ... ... ...1-Pair panel brackets (Magnum, Ready Radio

4 617 6

3 6

8 6

30 0

Standard type) ...1 -16i -volt grid -bias battery (Siemens) ...1-Detector valve (Marconi DEH2ro, Cossor

2 I oH or Mullard PMIHF)1-Low-frequency valve (Marconi DEL2ro,

Cossor 21oL or Mullard PMILF) . .

i-Power valve (Marconi DEP2 5, Cossor 220Por Mullard PM252) ...

22 03 6

ro 6

ro 6

12 6

or Raymond) ... ... ... ...2-Ebonite strips, 21 in. by 2 in.

2 66

Approximate cost of accessories £6 6 0

culty if use is made of a full-sizeblueprint. Every reader can obtaina copy of this for half-price by usingthe special coupon on page iii of the:over by June 30; an extension of

REACTIONCONDENSER

1 sr. L.F.AMPLIFIER,

LOW -FREQUENCYTRANSFORMER

RESISTANCE -COUPLING

UNIT

POWERVALVE

VARIABLE

time will be allowed in the case ofoverseas readers.

Under the half-price scheme thecost of a blueprint of the Short-waveLink is only 6d., post free. Ask for

MASTERRHEOSTAT

GRID -TUNINGCON DENSER oN,

DETECTORVALVE

GRID LEAKAND

CONDENSER

GRIDCOI L

A PERIODICCOI L

POTENTIOMETERSHORT-WAVEHIGH RESISTANCE H. F. CHOKE REACTION COIL

This plan view of the Short-wave Link clearly shows how all the components arearranged. Note how the wiring is kept short and direct

444

No. W.M.142, and address your in-quiry to Blueprint Department,WIRELESS MAGAZINE, 58/61, FetterLane, E.C.4.

Special Points in AssemblyThere will be no difficulty in

arranging the parts if full use is madeof a blueprint and the photographsreproduced in these pages. Thereare only two special points to -note inthe actual assembly of the parts; oneend of the grid condenser is suppliedwith an insulating clip, and thevariable high resistance is mounted onthe metal bracket supplied with it.

Wiring up needs rather more con-sideration. The blueprint (and thereduced reproduction of it in thesepages) indicates the best order ofwiring, and this should be adheredto ; for instance, start with connectionNo. 1 and make it as short as possible.Carry on in order, marking througheach number on the blueprint with apencil as the connection is made;in this way there is no possibilityof error.

Short Connections Come FirstShortness of wiring is of great im-

portance ; and for this reason the leadswhich need to be specially short are


A Three-valver for Reception on 15 to 100 Metresnumbered so that the most directconnections can be made. Thephotographs will be of help in thisrespect.

Constructors can please themselveshow long the battery leads are made.It is only necessary to suggest thatit is better to have them on the longside than to have them too short.

Suitable Valves for the SetBefore the set can be used suitable

valves will have to be obtained. Thedetector should have an impedancebetween 30,000 and 8o,000 ohms, thefirst amplifier an impedance between6,000 and 20,000 ohms, and the lastvalve should be of the power type,with an impedance between 6,000and 2,500 ohms.

Two-, four- or six -volt valves can beused. For the reception of WGY onthe loud -speaker mentioned in thesecond paragraph a good combinationof two-volters was found to be theMarconi or Osram DEH 210, MullardPM2 and Mullard PM 252. A valveof considerably higher impedancethan the PM2 could, however, beused for the second stage.

How to Operate the SetIt is now time to discuss the opera-

tion of the Short-wave Link. Butfirst let the reader clearly understandthat great aerial length is not at alldesirable. In fact an overall aeriallength of 3o to 40 feet will be ample.

Actually the set has been testedat a distance of fifteen miles fromLondon on an aerial about 25 feetin length, with a corresponding lengthof rubber -covered flex laid on theground as an earth connection.

If the aerial to be used is very longa small capacity fixed condenser(say of .00005 or .000i microfarad)can be placed in series with it toadvantage.

Dry -battery H.T. Supply"The high-tension supply is best

obtained from dry batteries and thevoltage should be about 15o for thebest results.

When the set is first used theoperator is advised to start with the29-5o metre coil in circuit. If the aerialis reasonably small the aperiodic coilcan be coupled closely to the gridcoil, but if it is on the large side theaperiodic coil coupling should be

Note that special short-wave variable condensers and a short-wave high -frequencychoke are used in the Short-wave Link

loosened by swinging the coil on itspivot.

To start with, place both variablecondensers at zero and adjust the

to

high resistance at the back of thebaseboard for the minimum resis-tance, that is, turn the knob as far

(Continued on page 447)

By means of a grid potentiometer and variable anode resistance for the detector,very fine control can be obtained with the Short-wave Link

445

I*Wireless Magazine. June. 19291

Provoking Mental Energyand Providing a Useful

Hobby

IS radio any more closelyconnected with health

than is the gramophone, thecinema, or any other kind ofentertainment? Three or fouryears ago there was no reasonto suppose that a wirelessenthusiast should be particu-larly healthy either in bodyor mind.

A Marked EffectNowadays, though, I believe that

broadcasting is starting to make avery marked, if minute, effect uponthe health of our national life.This is happening without manyradio enthusiasts being aware of it,and so you may find interestingthe reasons for which many medicalmen feel confident that radio isbeginning to play its part in health -giving.

A wireless set is an arranger of ahealthful life in an indirect way andin a direct way. The direct result isdue to the fact that regular music,restful entertainment, and even lighteducation "on tap" provokes mentalenergy. The indirect result is owingto the radio enthusiast taking part ina useful hobby of absorbing interest.

A Victorian FailingOur Victorian age has had many

stones cast at it, and I must throwanother. We must reproach theVictorians for failing to understandthat a healthy body cannot live ifthe mind which controls it is un-healthy. And a mind must be madehealthy if a sick body is to be madewell. Before the dawn of this centurytoo much attention was paid either to

training the physical side alone or themental side alone.

How strange it seems to us to -day,that nobody realised that a personcan never be really great, or clever,or even simply happy, if his mind isweighed down with an unhealthybody. Radio is helping to putthings right.

The craze nowadays is for sunlightand fresh air, and, of course, we can-not have too much of both. So someenthusiasts may say, " Yes, I'm verykeen on both the technical and theprogramme side of radio. I listen -in agreat deal and am constantly tryingout new circuits. But when I wantto feel really fit I earth the aerial andthen take a round of the links, orfix up a singles at tennis."

That is a very sensible point ofview, because one must have exercisein order to live. But it is no argu-ment against radio as a health pro-moter. Tennis and golf are exercisesand entertainments for the body,whereas radio as a hobby is an equallyimportant exercise and entertain-ment for the mind. As I have said,the demand for exercise and freshair is a modern craze, particularlyamong the younger people. So, in

446

aaiRestful EntertainmentWithout Worry or

Troublemany cases, I have no hesita-tion in advising a physically -inefficient man to take up anindoor hobby, because I knowthat, if for no other reasonthan to be in the fashion, hewill also take up tennis orsome similar outdoor occupa-tion. I do not think thateverybody takes enough out-door exercise; some take toomuch in comparison with the

indoor work they do, and some takepractically none at all.

The Need for RestSecond only to the need for outdoor

exercise is rest. Exercise, physical ormental, means an outgoing of bodilyenergy, for the body has to workin order to exercise. Occasional restis very necessary, so that the bodymay recuperate its strength.

Radio gives rest; for there is surelynothing like settling down in a cosyarmchair, there to enjoy broadcastentertainment at ease. All broadcastitems are not restful, of course, orthe more weary among us would befast asleep soon after the eveningprogramme starts.

No Effort NecessaryIt is the fact that the entertain-

ment provided needs no effort toobtain which makes radio valuable.It is more restful to the brain thaneven the gramophone, for havingonce tuned in we let the programmepeople do the choosing of items.We do not even have to make up ourminds which record we would like toput on ! And, quite seriously, insettling the minor likes and dislikes

jj

of life we waste a deal of mentalenergy.

Now I have nothing against theventilation arrangements and soforth of theatres, cinemas and con-cert halls. But I cannot help feelingthat it is more hygienic for a man tosit in his own home and hear a con-cert via the radio than to mix withtwo or three thousand people in atheatre crowd, and so risk infectionof 'flu and so on.

Before -breakfast Broadcasts!

When, if ever, we have before -breakfast broadcasts in this country(as, so I understand, are being runwith some success at certain Americanstations) it will be time to considerthe advantages of early - morningbroadcast physical jerks !

I am just as dubious about anybenefits as are the programmeofficials, who will not sanctionsuch broadcasts at the present.

And .even if a typically -militaryS.M. shouted instructions at us, beforebreakfast, to " slo' parms," bend atthe knees and so forth, it is the mercyof radio that we can shut him offby touching out the L.T. switch. Mostpeople, including myself, wouldsooner be in the land of nod

Medical advice is largely a matter ofsympathetic understanding, particu-larly in "nerve" cases. It is an oldstory that a doctor gets a fabulousfee simply for telling a patient thathe isn't so ill as he thinks he is, andthat he ought to take up golf !

Physical and Mental EnergyThere is a reason, of course, and

it is that golf is a game combininglarge amounts of physical and mentalenergy; the secret of good golf is toplay a little and think a lot. Themental activity needed is just asvital from the health -giving point ofview as is the physical satisfactionof making a perfect swing anddriving straight and true down thefairway.

Golf is not a game to everybody'staste. Some people prefer walkingor gardening, and these are hobbieswhich, comparatively, demand nogreat amount of thought. If yourtastes run in this direction, don'tforget that the brain needs exercisejust as much as the body does. Radioas a hobby is a well-nigh perfectentertainment and mental engage-ment; these two factors are essentialfor health of mind. A. K. M.


The Short-wave Link (Continued from page 445)

as poassible to the left. Also put thepotentiometer slider over to thepositive side of the winding.

In tuning the set remember thatthe left-hand condenser tunes thegrid coil, while the i ight-hand con-denser is the reaction control. Therheostat in the centre of the panelswitches the whole set on or off.

For searching, it is a great con-venience to use a pair of headphones;indeed, many stations will be missedif an attempt is made to tune themin on the loud -speaker at first.

The procedure is as follows : turnthe reaction condenser until a loudrustling noise is heard in the phones;this indicates that the set is on theverge of oscillation and in its mostsensitive condition for reception.

The secret of bringing in stationsis to keep the set as far as possiblejust off the oscillation point; thisoccurs when the rustling noiseis loudest. A few minutes ex-perimenting will soon enable theoperator to distinguish between the

[SPECIAL NOTEAlthough the Short-waveLink is especially intended forreception on the 16 to 50 metrewaveband, extra coils can beobtained to cover the rangesfrom 12 to 16 and from 50 to100 metres. Moreover, bymeans of a special coil adaptorand extra coils, the set can beused for ordinary broadcastreception on normal wave-lengths. All the necessaryequipment can be obtainedfrom the firm supplying the

original short-wave coils

"no oscillation," "verge of oscilla-tion," and "oscillation" points.

When this verge of oscillationpoint has been found the grid con-denser should be tuned. After a fewdegrees it will be found that the setno longer shows signs of oscillating.When this occurs the reaction con-denser should be advanced a trifle.Carry on in this way, keeping thereaction in step with the grid tuningas it were, until a signal is picked up,when both controls should be read-justed for the best results.

If it is found that reaction overlapoccurs reduce the voltage applied tothe detector anode by turning theknob of the high resistance to theright and try alternating the poten-

447

tiometer setting. A few minutesadjustment will enable the operatorto get a perfectly smooth reactioneffect.

Beginners should note that tuningis exceptionally sharp in spite of thefact that slow-motion controls arefitted. The dials should be turnedvery, very slowly when a search isbeing made for a station.

Varying Aperiodic CouplingIt is advisable to try varying the

coupling of the aperiodic coil, as thisto some extent controls the reactioneffect. For instance, with a largeaerial it will probably be found diffi-cult to obtain oscillation unless theaperiodic coil is coupled very looselyto the grid coil. The same remarkapplies also to a comparatively smallaerial where the smaller grid coil isin use.

As far as results go, much dependsupon atmospheric conditions overwhich the operator has no control.In the course of an hour one eveningrecently WGY (Schenectady, NewYork, through 2 XAF on 31.9 metres)was picked up and held on the loud-speaker for some time at goodstrength, while Radio Paris andRadio Vitus (37 metres) were heardat good phone strength. A loudSpanish station, not identified, wasalso heard at good strength.

Those who can read morse willfind a station at almost every degreeof the tuning dial.

The following morning at aboutmidday an amateur was picked up.His call has not yet been traced andwe shall be glad to hear from himshould he read this article. Histransmission was on the followinglines :

Stations Only at Half Strength" This is G6TocW testing. This

is G6TocW testing. I find thatconditions are very bad this morning.I find that conditions are very badthis morning. Stations are onlycoming in at about half their usualstrength. Stations are only comingin at about half their usual strength

There is a great deal of interest inpicking up signals of this kind. Theywould be more interesting still if thetransmitters would announce where-abouts they are situated


GERMAN Viewpoints Regarding GERMAN

(igroreffidalitakilikeimicat[A Special Interview with Ministerialrat Hantschel of the

Reichsinnenministerium, Berlin, Recorded by A. A. GULLILANDTRY to approach the German

Ministers of State-yes,certainly-but try to obtain theiropinions on questions relating tobroadcasting in Germany-no,

The Literaphone, a new invention for sending sound by post,developed in the laboratories of Radio Stuttgart

certainly not 1 That was the meaningof the polite answer to my request tointerview one of these gentlemen.

But the chief of the departmentresponsible for the cultural andpolitical " surveillance " of broad-casting in Germany, MinisterialratHantschel, very kindly gave me ahost of valuable information regard-ing the German point of view.

State ControlIn Germany, broadcasting is

submitted to a certain amount ofState " surveillance " regarding thecontents of the programmes sentout by the ten broadcasting com-panies. The men actually re-sponsible for this "surveillance"are nominated locally in the so-called "Ueberwachungsauschuss."

This committee consists of onerepresentative nominated by theReich and of two nominated by therespective Federated States, such asBavaria, Prussia, Saxony, Ham-burg, etc. The committees have apurely negative and preventiveinfluence, and, I am told, veryseldom require to veto a given item.

Apart from this negative committeeeach broadcasting company has acommittee of prominent experts onall the more important phases ofartistic and scientific life, which

makes positive sug-gestions as to the,formation of theprogrammes. Thesecommittees are styledthe "Kulturbeirat."The remainder of theprogramme organisa-tion is completely inthe hands of the in-dividual companies.

MinisterialratHantschel replied tomy question as to thepoint of view takenby the authorities inGermany regardingthe broadcasting ofcontroversial matterin the following

manner ;The different broadcasting com-

panies and the local Ueberwachungs-auschiisse have been advised to be astolerant as possible when passing theusual talks; these, of course, do not,as a rule, touch important con -

Microphone in the large studio at Stuttgart. Onthe left, " door " for stage effects

448

troversial themes of a religious orpolitical nature.

As a result of this tolerance severalbroadcasting companies, among themCologne and Breslau, have instituteda daily or weekly feature in whichsome topical event is treated in amanner which is far from non-controversial.

Two Controversial Talks(Note.-I remember hearing a talk

from Breslau demanding a specialtransmitter for broadcasting parlia-ment speeches, and a talk from Colognetaking a rather one-sided view of anaffair relating to Pamela Wedekind,the daughter of the well-knownGerman dramatist and author.-A. G.)

But to exclude political matter frombroadcasting, Ministerialrat Hants-schel continued, would mean be-littling our intelligence as far asbroadcasting is concerned.

On the other hand, politics are byno means party politics, even if oneor the other political party bears oneor the other important questioninscribed on its banner. Thus politicalquestions should be allowed time inthe broadcast programmes. But also

fundamental cultural questionsshould be discussed.

The Reich has, from 1929onwards, permitted the institutionof discussions of political andcultural themes by prominentexperts known to be of oppositeopinion. Thus the listener will hearthe very best information on onetheme from two extremely reliablesources, but will hear this informa-tion from two totally differentviewpoints.

Konigswusterhausen DebatesThe Reich has not, up till now,

thought it wise to permit thesedebates from every station andhas restricted them to the" Deutsche Welle," the all -Prussianeducational broadcasting companyusing the Konigswusterhausentransmitter. The other stations,

are, of course, at liberty to simul-taneously broadcast these trans-missions. (The stations, as a rule,make full use of this facility as veryprominent men take part in thediscussions.)

As examples of themes shortly tobe discussed I mention : " For andagainst prohibition of alcoholicdrinks," and " Pro and contra capitalpunishment." Themes that are

same good reasons.Another thing was the

question of the interest inthese transmissions of thegeneral public, and theequal allocation of timebetween the twenty ormore parties. Everyparty would wish to speakat the best broadcastinghour.

For the moment thequestion had beenanswered in the decisivenegative, both by thebody most concerned,the Reichstag itself, andby the Ministries. Thereasons given here aregeneral considerationswhich occur on the spurof the moment and notofficial reasons.

Part of testing rack in the Loewe factory,where all valves are subjected to actual

operating conditions before dispatch

generally being discussed in Germanyat the moment and themes which alsoplay a certain part in party politics.

But via radio, these themes will bediscussed in a manner having nothingto do with one or the other of Germ-any's twenty -odd political parties.The discussions will undergo a certainamount of censoring, but this willonly be to eliminate anything whichcould be offensive morally.

Reichstag BroadcastsI asked Ministerialrat Hantschel

about the broadcasting of the GermanReichstag. He answered that theReichstag itself had objected tobeing relayed. Also that there weremany considerations against therelays.

One must always remember theGerman parliament is not a hundredyears old yet and that, therefore,there is not the same parliamentarytradition as in Britain. Membersoften use terms in their more heatedspeeches which never appear in printand which, therefore, should neverbe broadcast and for the very

Third Question


Crystal wavelength regulator for experimental short-wave transmitter at the Loewe works

My third leading question toMinisterialrat Hantschel concernedalternative programmes.

It is most interesting to notethat Germany already has fivealternative programmes forlisteners with valve apparatus ofeven inferior quality. This numberis mentioned because at least fivedifferent German programmes canbe picked up in most every districtof Germany.The reasons are, of course, the

diversity of the programmes sent outby the nine different German mainstations. Good sets can even receivenine alternative German programmes,

resting valves at the Loewe works, Berlin, to see if anyresidual gas has escaped the evacuating process

449

but this would be going rather far.Therefore the urgent need of

alternative programmes, much as theycould be desired from the point ofview of the gently dying crystal -setowner, is not urgent in the case of thevalve -set owner or even of the ownerof the typical German ultra -cheaploud -speaker local valve set, who canreach out for other German pro-grammes. Much as decentralisationis to be deplored on the administra-tive side, it is a very boon seen fromthe programme point of view.

Prohibitive CostOn the other hand, the cost of an

alternative programmeservice for each of thenine main transmitterswould be prohibitive inGermany, in spite of themuch larger fees paid(24s. against los. inBritain), as each ofthe nine companies hasto supply independentlya full programme.

Thus an alternativeprogramme service inour sense of the wordseems far off for theGerman listener, but heis much better off thanwe are, for he can,provided he has a pass-able set, reach out andobtain nine different Ger-man (that is national)programmes at any timeof day or night.

Wireless Magazine, une. 1929

THE LETTERSOF

Stewcombe Manor,Little Bodley, Nr. Hurdham.

5/4/1929.DEAR MR. EDITOR,

I must hasten to tell you of anexperience which I have just had andwhich, I am sure you will agree withme, exemplifies the extraordinarypowers of the Press. That an old-fashioned, simple, secluded soul likemyself should have soared into theeffulgence of a public character fitto be interviewed by a scientist isentirely due to the prestige of yourmagazine, and the event has left mejust a little breathless and twittery.

A/fief/70eunited a touch of the sell -conscious-ness of youth with the assurance whichmarks the truly distinguished.

He introduced himself smilinglyto me as Mr. Shortt and added thathe was the inventor of the famouscircuit which bears his name. Some-how, do you know, I seem to remem-ber reading something about it.

Having seen my letters in yourinestimable magazine, he felt thathe could not possibly come toHurdham (which he was visiting ona char-a-banc for the day, in order toview the neighbouring ruins of White-ford Abbey). without calling upon one

Oal-,

LIST OF EASTERN BROADCAST STATIONS

Countries Call Sign Wavelength(Metres)

Power(Watts)

Shanghai ... .. KSMS 277 50Tientsin ... CRC 280 50Shanghai ... NKS 310 50Peking ... COPK 320 100Shanghai ... KRC 338 250Japan ... JOAK 345 10,000Japan ... JOFK 353 I0,000India... ... 7BY 357 5,000Japan ... JOIK 361 10,000Corea... ... JODK 366 I0,000Japan ... JOCK 370 10,000India... ... 7CA 370 5,000Shanghai ... SSC 370 50Japan ... J OGK 38o 10,000Japan ... JOHK 390 10,000Dairen ... JQAK 395 5,000Japan ... JOBK 400 10,000Mukden COM K . 410 2,000Manila ... KZRM 413 1,000Harbin ... COHB 445 1,000Vladivostok RL2o 48o 1,500Tientsin ... COTN 480 500Nanking ... XOW 495 500

IMIN11.11

Little did I dream, when sendingyou the artless letters which you havepublished from time to time, that Iwas becoming, may I say, famous?

It all happened this way. On Mon-day last, which you may rememberwas a Bank Holiday, I was attendingto my garden, as is my usual practicewhen it is quite impossible for reallynice people to be seen abroad. I wasdirecting the house -boy in the mulch-ing of the herbaceous border, when Iwas informed that a gentleman wishedto see me.

The moment I saw this young man,I knew there was something apartabout him. He was delightfullyunconventional in his attire and

whom he regarded as a fellow scientistand a pioneer blazing a trail throughthe jungle of radio.

He added that he had hardlyhoped to make my personal acquaint-ance, because he had felt it to bealmost impossible that some realperson should have written thoseletters.

In fact, a friend and he had hada small friendly bet about this, myinterviewer having wagered that Icould not exist at all but had, in fact,been " made up " by your staff.

He was so kind as to add that hehad not believed it possible that anyone living person could have writtenthem, but that having had the honour

450

t() meet me i n person, he must ac-knowledge that he had lost his bet,being amply repaid, however, by thepleasure of speaking with me. Inshort, a most delectable young man !

He appeared to be about to takehis departure then, but, of course, Irang for tea and he decided to remain,saying that it was not given to himto meet sympathetic fellow -workersevery day and that "us scientistsmust hang together." How refresh-ingly quaint is the patois of the newgeneration !

During tea, he was so interesting.He told me all about his scientificwork and assured me that the Shorttcircuit which is now in general usewas really only the first, almostcasual, beginning of his achievements.A difficulty in protecting it had robbedhim of almost all benefit from it.

About television he told me somemost interesting things. It appearsthat television is a word compoundedof two elements, one of which means"distance" and the other "sight,"so that there is really nothing revolu-tionary or new in it all. It is merely amodern extension of the old scienceof seeing people further.

After having completed the wholeof his experiments and research, hehad now discovered that the " vision"portion of the subject matter hadalready been patented, leaving himonly the " tele " element which, heassured me, would prove very diffi-cult to protect for the reason thatmere distance was at the disposal ofanyone.

I did not quite follow this but, ofcourse, it will be quite plain to you,Mr. Editor, and in any case, does itnot seem horribly unfair ?

To my unbounded delight, hehappened to have with him a com-plete instrument embodying hisachievements in this field and thishe offered to demonstrate by meansof my reception set, so we imme-diately connected up the two. Although I saw -and heard nothinghappen, Mr. Shortt assured me thatVienna was diffusing pictures atthat time and that his little blackbox was registering whatever wascoming through. And then, do youknow, Mr. Editor, a truly marvellousthing happened

After a few minutes, he opened thelid of the box and inside it, restingupon a miscellany of small devices,was a perfect reproduction of Strube's"Little Man," so clear and so beauti-fully rendered in black -and -whitethat one would almost have sworn itto be a print.

A second experiment unfortunatelyproduced no result and Mr. Shorttconcluded that the Vienna trans-mission must be over. Had I notseen this thing happen with my veryown eyes, I should not have believedit possible !

Mr. Shortt assured me that thiswas really " nothing to write homeabout" and that he had done farmore remarkable things ; in fact, hewas in a position to revolutionise thewhole of the broadcasting world,were he not, unfortunately, socrippled for lack of capital.

On my sympathising with him andenquiring what sum would be neededto bring his discoveries to their fullfruition, he said after slight hesitationthat five pounds would greatly helphim, but that he would not dream ofsuggesting that I should become hispartner for, after all, he said, wehardly knew each other at all.

If, however, I should care to amusemyself with his televisor during myspare moments and thought itsufficient security for a small loan of,say, ten pounds, then he wouldgratefully accept it, and would provehis confidence in me by leaving in myhands this absolutely unique modelof a new device. Of course, I was onlytoo pleased to let him have the moneyand he left soon afterwards, thankingme for what he described as aninteresting and profitable afternoon.

It seems to me to be a terriblepity that this !Angularly gifted andpromising young man should have todepend upon these fortt;itous aids tosuccess, and I hope you agree thatsome Associations (say of reallyauthoritative and competent menlike yourself) should illumine thepath of progress, as it were, byrelieving such pioneers of all sordidpre -occupations. I should be so gladto hear that you accept my viewand that you will act upon it.

Unfortunately I omitted to takeMr. Shortt's address, but he must bewell known to you and easily found.

In a few days I hope to let youhave a full account of the results Ihave obtained by means of hisinstrument.

Yours very truly,PRISCILLA PLAYNE- SMYTHE.

1


Impressions of BroadcastersFrancesDoble,

the stageand screen

star

HughWakefield,the actor of"Mr. Park

Lane "

" Smiling "Billy Mason

As Seenby

ROBERTS

Chick Farr,the

light comedian

Abe Lyman, leader of the Californians

451

StanleyHolloway


Half-hours with the Professor

MR.PLARZ GETS MAGNETISED!NIPPY, you know," said young

Amp in a loud whisper to histriend Plarz, the wireman.

"Whassat ? "Loopy. Bells in the Batfry."Wot, 'im ? "

Amp nodded sagely. There certainly did seem to be someexcuse for the explanation,for the Professor wasstanding over a large coilinto which he was lower-ing and raising his watchon the end of a piece ofstring with an abstractedair.

The two boys watchedhim in silence as the Pro-fessor finally hoisted hisqueer fish out of the ccil, peeredat it through his glasses and then, witha grunt of satisfaction, returned it tohis pocket. Amp, no longer ableto control himself, dived in hispocket and produced a penny.

Baiting the Professor`Here, Professor," he said, "see

if it does the same with this ? "" What on earth are you talking

about? " exclaimed Megohm pettish-ly, noticing the boys for the firsttime. "What is this for? "

"I don't know," said Amp, "butI thought you might see if it workedthe same as your watch did."

" Have you ever seen a watchdemagnetised before ? "

"Oh, yes," said Amp cheerfully." I did it myself once and I hadenough parts left over to make anotherwatch-oh no, that's wrong, that wasdisembowelled-I know mother saidI wasn't to use the word because itwas a horrid one."

Demagnetising His WatchMegohm snorted. ' Really," he

said with some attempt at his lectureroom dignity, " you are incorrigible.Unfortunately, the hair spring of mywatch had become magnetised througha too close proximity to a moving -coil loud -speaker and I was demag-netising it by putting it under theinfluence of a .powerful alternatingmagnetic field."

"Wonderful flow of language he's

This photograph shows how easily anordinary cylin-drical 'or sole-noid coil canbe wound bythe amateur

got, hasn't he ? " grinned Amp, turn-ing to his friend. " He can do betterthan that, too, when he tries. Itsoften quite impossible to understanda word he says."

" Good heavens," said Megohm indisgust, " do you mean to tell me thatyou cannot understand what I amtalking about? Why, I'm sure yourfriend Plarz could tell you withoutany hesitation."

Plarz scratched his head. " Well,"he said, rather ruefully, "as a matter

This month our old friendsProfessor Megohm, Amp and Mr.Plarz discuss magnetism and in-ductance-phenomena on whichthe working of many wirelesscomponents are based. Everybeginner will find the talk ofgreat benefit. All the photo-graphs illustrating this featureare of apparatus that makes use ofmagnetic or inductive principles.

of fact, sir, I didn't catch very muchof what you said. You got ratherbeyond me in the first sentence."

" Do you mean to tell me that youdon't understand the principles ofmagnetism and inductance ? "

"Born and bred on them," inter-rupted Amp, cheerfully. "Come offyour perch, Professor, and tell ussomething about it."

Plarz's temperament was by nomeans as mercurial as Amp's and heinvariably seemed bewildered at these

452

passages between Amp andthe Professor. He lookedat Megohm hopefully,however, as a result of thislast sally, for he wasrather anxious to under-stand more about manyfundamental principleswith which he had to dealin his daily work.

"Oh, all right," saidMegohm, moving to hischair. " I think we hadbetter repeat last time'sperformance and makeAmp tell us all about it."

"Anything you say,"murmured Amp, modestly,trying to appear uncon-

cerned.

Magnetic Fields"Well, for a start, suppose you tell

us what a magnetic field is."Oh Cr-" Amp hesitated. " I

should say," he stammered at length,"oodles of magnetism floating aboutloose, as it were."

"A particularly bright and luciddescription," said Megohm. Amplooked pleased until he happened tocatch the Professor's eye, in whichthere was lurking a nasty gleam.His smile disappeared and he pre-pared for the worst.

" Disregarding for the moment,"said Megohm, " the lax form of Eng-lish which you choose to adopt inexplaining the curious workings o:your mind, we will concentrate on thelast few words namely, 'floatingabout loose."'

Amp in DifficultyAmp adjusted his tie which ap-

peared to be giving him much trouble." If," Megohm continued relentless-

ly, "if our magnetism is floating aboutin this unattached condition, I takeit that we can collect portions of itand put it into bottles if we wish andto carry it from place to place."

"Er, no," stammered Amp, notby any means so cocksure as he hadbeen originally, " it only exists in theneighbourhood of the force producingit."

"Oh," said Megohm. "Then we

require some force, do we, to producemagnetism ?"

" Yes," said Amp. " I mean a coilof wire or something like that."

Megohm picked up a honeycombcoil which was lying on the table andheld it up enquiringly to the boy.

"Oh, but you've pit to pass acurrent round it," said Amp.Dragging It Out

Megohm raised his eyebrows. " Weare beginning to drag it out of you,"he said. " I don't know what Plarzthinks about it, but I should ratherimagine that he is in a more muddledstate than ever."

Plarz grinned sheepishly. " Well,"he said diffidently, " I'm beginningto get a better idea now."

" Hm," grunted the Professor." Well, we seem to have establishedthat if we pass a current round a coilof wire, we produce some mysteriousquantity called magnetism. Youknew that, I take it? " he broke off.Making a Magnet

Plarz agreed. " Yes," he said," I've often made a magnet by wind-ing a coil round a bit of iron. Thenif you connect it to a pocket -lampbattery, the iron becomes a magnetand it will pick up bits of iron andsteel."

Megohm nodded encouragingly."What do you put the iron in themiddle for ? "

Plarz cogitated. " I don't know,"he said at last. " It doesn't seemto work without."

" The effect will not be so marked,: 'said Megohm, "but nevertheless weshall have a magnetic field even al-though there is no iron inside. Letus juqt try that."

Another form of inductance coil-theDubilier Toroid, which has practi-cally no external field. There areother forms of fieldless coils andthe technical name for all of them

is "astatic"

Wireless Magazine, une, 1929

He got up, taking the coil withhim, and connected it up on the benchto a two -volt accumulator. "Now,"he said, "according to Amp, we haveoodles of magnetism-I think that isthe correct expression-floating aboutloose."

Amp grinned." The statement was subsequently

modified," continued Megohm, "toindicate that the magnetic field wasactually linked with the coil in someway so that if we took the coil awaythe magnetic field would move withit. That, I take it, is the idea youwished to convey ? "

" Don't be so blinking sarcastic,Professor," exclaimed Amp. "Evenif a fellow does make a mistake nowand again, you needn't rag him all thetime. Anyhow, what I said after-wards was right, wasn't it ? "

"More or less," agreed Megohm." Now our friend Plarz does not appre-ciate that we have a magnetic field

Tuning coils are inductances. This isa special type of Cosmos coil

here. He is not really convincedthat the magnetic field does not van-ish as soon as you take the iron away.No, no," he continued laughingly,as Plarz attempted to protest, " itis only my fun, my dear fellow. Still,I want to convince you."

So saying he drew from his pocketa small compass and, having firstdisconnected the accumulator, heplaced the compass near the end ofthe coil. "Now," he said, " this com-pass contains a small magnetisedneedle. As you know, this needlealways points towards the northbecause the earth is really one largemagnet and we have all about us avery small magnetic field. It doesnot have any serious effect on largebodies but if we have a small delicate-ly pivoted needle such as this it setsitself in harmony with the magneticfield, and points to the north.

" You know that, of course," hesaid, and without waiting for a

453

A low -frequency transformer workson a magnetic principle. The model

shown is an Igranic Type F

reply he continued : " What I amgoing to do is arrange a local magneticfield of greater value than the earth'smagnetic field and this will cause theneedle to pull out of its normalposition and to take up some otherposition. If the field is strong enoughit will probably move somewhatviolently."

A Different PositionSo saying, he connected the leads

to the accumulator; the needle of themagnet immediately swung roundseveral times, ultimately settling downafter much rocking to a position quitedifferent from that which it formerlyoccupied.

" As you see," he said, " the mag-netic field was very strong and causedsuch a pull on the needle that it wentround and round several times. If Inow release the magnetism, the mag-net will swing back to its originalposition."

This was immediately verified bydisconnecting the accumulator, cut-ting off the current from the coil andtherefore breaking the magnetic field.

Field While Current Flows"Then," said Plarz, much interested,

"you only get the field while thecurrent's flowing ? "

"That is so," agreed Megohm.Plarz thought about it for a few

moments. Then he said : " As far asI remember, it didn't make anydifference which way we connectedup the coil. Is that the same hefe "

" We will try and see," said Me-gohm. So saying he reversed theconnections to the accumulator and


Mr. Plarz Gets Magnetised ! (Continued)

on connecting up again the needleswung round in the opposite direc-tion.

"Goes the other way," said Plarz." He's good, isn't he ? " said Amp,

unable to keep silent any longer.Plarz gave him a vigorous dig in theribs, but said nothing. Megohmignored the interruption and con-tinued his explanation.

Reversing the Magnetism" Yes," he said, " you see, by re-

versing the current, we reverse thedirection of the magnetism. Youwould not notice with the piece ofiron because a magnetised piece ofiron picks up other bits of iron andsteel irrespective of the direction ofthe magnetism or, as we say, thepolarity."

" The how much ? " interruptedAmp.

"The polarity," said the Professor." You know that a bar magnet has anorth pole and a south pole, the northpole being the one which,if the magnetis suspended, will ultimately pointtowards the north. Thus we speakof the way round the magnet as itspolarity."

Plarz had obviously been turningmatters over in his mind. Herehe broke in to ask a question. "Whateffect does the iron have, then ? "

"That is a point which we mustleave for a future occasion," rejoinedMegohm. " It serves to increase themagnetic effect produced by a givencurrent."

Magnetic Induction" You know," went on Megohm.

" you make use of magnetic effectsa great deal in your work, Plarz, justthe same as we do in wireless. Oneof the most valuable properties wehave in electrical work is that ofmagnetic induction. Do you knowwhat that is?"

Plarz shook his head. Megohmlooked enquiringly towards Amp.who rose to the occasion.

" Voltages induced from one cir-cuit to another," he said.

"Your comments are altogethertoo elliptical," exclaimed Megohmin despair. " You obviously havethe right idea, but I do not supposethat Plarz, for example, has learnedanything at all from your statement.What you wanted to explain is that,

Loud -speakers also work on a magneticprinciple. This is the Brown Q model

under certain conditions, the magneticfield produced by one coil can affectanother and cause voltages to beproduced in it. You deal with trans-formers in your ordinary work, don'tyou, Mr. Plarz ? " Megohm lookedenquiringly at the boy.

" Sometimes."" Well, here we are going to set up

a very simple form of transformer."So saying Megohm took hold ofanother coil similar to the first, acrosswhich he connected a pair of tele-phones. He then placed the secondcoil near to the first one. "Now,"he continued, handing the telephonesto Mr. Plarz, "see if you can hearanything."

The boy listened intently, butultimately with a puzzled expressionshook his head. " No," he remarked," I can't hear anything at all beyonda faint rushing sort of noise."

headphones come in the same class a,loud -speakers. These are Brown's

Featherweight type

54

"No, you would not," was thereply. " The magnetic field beingproduced by the first coil is quitesteady. I am going to vary the field,however, by switching the currentoff."

He suited his actions to his wordsand removed the connections to theaccumulator. Immediately therewas a click in the telephones whichcould be heard even by Amp and theProfessor. A similar click appearedwhen the Professor re -connected thewire to the accumulator.

Variation of Magnetic Field" You see," he went on, " when we

make or break the circuit, we causea sudden variation in the magneticfield and this causes a voltage to beinduced in the second coil whichgives rise to the click which you hearin the telephones. That is what isknown as magnetic induction."

"Then y9u only get that if thecurrent is varying. Is that it ? "asked Mr. Plarz.

" Quite right." Plarz thought fora short time, " But," he objected,"all the transformers I know abouthave large iron cores."

" That is only to assist the magneticeffect and to make sure that nearlyall of the field produced by the onecoil passes through the next coil."

Both boys were silent for a fewmoments. Presently Amp said :"When are we coming to the point,Professor ? "

" What do you mean ? "

Megohm's Funny Stunts" You have not told us yet why you

were doing the funny stunts withyour watch when we came in."

" Oh," laughed Megohm, " that is avery simple one. My watch had be-come magnetised through too close aproximity to the magnetic field froma moving -coil loud -speaker and I wastherefore immersing it in a fairlypowerful alternating magnetic field.

"This coil," he went on, pointingto the actual coil which he had beenusing, " was connected to an alter-nator supplying a rapidly fluctuatingcurrent so that I had a state ofmagnetic turmoil, as it were, insidethe coil. Immersing the watch inthis destroyed the permanent magnet-ism in the air space and restored it toits normal position."

111

-...1,^.1"..,tt- ''1Z, 1;11111101Aulutpl t rattaintski.111Or , 1,......1=1.....

HOW TO MAKEA ONEUNIT FORAC.MAINS

THOSE having a supply of alter-nating current electricity may

readily obtain direct current at asuitable voltage for accumulatorcharging, high-tension circuits, thefield winding of a moving -coil loud-speaker, or for grid -bias and otherpurposes without difficulty.

Essential ComponentsThe essential components required

for changing the alternating into adirect current are a transformer and arectifier. These two parts must be ofsuitable design for the purpose forwhich they are required.

Thus, the rectifier must be soconstructed that it will provide,without deterioration, a certainamount of current at a given voltage,whilst a transformer must be soarranged that the desired output isobtained from the rectifier. Further,it is important that the transformerbe reasonably efficient, have windingsof ample current -carrying capacityand be well insulated, in order thatthe rectifying circuit may not be indirect connection with the mainssupply.

Accumulator or Loud -speakerUseThere must be many readers de-

sirous of constructing a low-tensionunit suitable for charging an accumu-lator, or supplying the current forexciting a moving -coil loud -speakerand I therefore propose showinghow a unit giving the maximum


output of one ampere may be built.A Westinghouse metal rectifier of

the one -ampere type will be employed,and a home -constructed transformer.The rectifier has two pairs ofterminals.One pair is marked A.C. and the otherpair D.C.- and D.C.-.

The accumulator to be charged, orthe field winding t , be excited, is,therefore, connected to the pair ofD.C. terminals and the secondarywinding of the transformer to the pairof terminals marked A.C.

In this article our ResearchConsultant describes the con-struction of a simple unit thatwill g:ve from alternating -current mains a direct -currentoutput not exceeding one am-pere at six volts. Such a unitcan be used for accumulatorcharging or the excitation of amoving -coil loud -speaker at

very low cost

This transformer will have aprimary winding to suit the voltageand frequency of the alternatingcurrent mains supply and its second-ary will, of course, be suitablyproportioned with respect to theprimary to deliver a suitable outputto the rectifier.

Now, the amount of the direct

455

e

SPECIALLYDESIGNED

FOR THE "W.M"BY W. JAMES

current output required is likely tovary over a fairly wide range. Thus,one may wish to charge a two-, four-,or six -volt accumulator at one ampereor less.

It is, therefore, important to pro-vide a means with which the out-put may be regulated, for it will beclear that if the unit were designedfor charging a six -volt accumulator,for instance, an excessive currentwould flow were a two -volt accumula-tor connected.

Considerations of EconomyAn adjustable resistance having a

current -carrying capacity of oneampere could, of course, be employedin the output circuit to regulate thecurrent according to the load attachedto the rectifier. But the powerabsorbed by this resistance would bewasted in heat and it is thereforedesirable in the interests of economyto provide a less wasteful form ofregulator.

Tapped Transformer SecondaryThe simplest and probably the

best method is to arrange a number oftappings on the secondary windingof the transformer, because then theactual alternating voltage deliveredto the rectifier may be adjusted. Inthis manner it will be possible, forinstance, to charge a two -voltaccumulator at a half or one ampere,or a six- volt accumulator or to supplyany other circuit that does not takemore than one ampere at six volts,


Building Your Own L.T. Charger (Continued)

4.0.000.0011111mmlusenisaitolow

Plan view of the one -ampere charging unit.The dry rectifier is a Westinghouse typeR4-2.2. Transformers already built up canbe obtained from the Regent Radio SupplyCo., or, if desired, the reader can obtainStalloy stampings and a bobbin for windinghis own transformer from the same firm

which is the maximum output to beobtained from the particular rectifierwe are employing.

The circuit of a simple chargingunit is given in Fig. I and comprisesthe transformer with its primarywinding and tapped secondary wind-ing, together with a one -amperemetal rectifier. There is one pointwhich must not be overlooked whendealing with accumulators and that isthe actual voltage of an accumulatorwhen under charge may approximateto 2.8 volts per cell.

When 6 volts Becomes 8.5 voltsA six -volt battery may therefore

have a voltage of about 8.5 and thecharger must be able to supply oneampere at this voltage.

It is not a very difficult matter tobuild a suitable transformer. Acertain amount of transformer ironor steel will be required for the coreand a bobbin or former upon which towind the primary and secondarywindings. The easiest method is topurchase a quantity of suitable

transformer laminations and thento provide windings composed ofthe necessary number of turns ofwire of adequate size.

The number of turns requiredfor the primary is dependentupon the size of the iron core andits quality, and also upon thevoltage and frequency of themains.

Proportional IncreaseFor a given size of core the

number of turns will have to beincreased in direct proportion tothe voltage of the supply. Thus,if it were found that i,000 turnswas a suitable primary for atoo -volt supply we should have touse 2,000 turns for a Zoo -voltsupply of the same frequency.

When the magnetic propertiesof the iron which will be used asthe core are fairly well known, itis an easy matter to determine asuitable number of primary turnsfrom the simple formula :

E=4.44 fFTvolts,

108

where 1= --the frequency (usually5o cycles per second)

F= the maximum value ofthe flux.

T=the number of turns inthe primary winding.

In applying this formula we haveto make various assumptions accord-ing to practical experience and thento check the results in order todetermine that the transformer willnot overheat andthat the materialsare being wiselyused.

A start may bemade by assum-ing a suitable sizeof core and fluxdensity, for thenwe can write downa figure for all the

figure for the cross section we willassume a sufficient number of stamp-ings will be used to give a centrallimb of square cross section.

The area of the central limb will,therefore, not be far short of onesquare inch. If now we allow themaximum flux density of 64,000 lines

TO A.0MAIM;

METAL RECTIFIER)

Fig. 1.-Circuit of simple charging unit

per square inch and then work outthe formula we shall find a windingof about 1,75o turns will be suitablefor a mains voltage of 250.

For the lower mains voltages fewerturns will suffice. Our 1,75o turns for250 -volt mains amounts to 7 turns pervolt, from which it follows that thevalues given in the table will hecorrect:-

Mains Voltages. Primary Turns.

250 1,750240 1,680230 1,610220 1,540210 1.470200 1,400I I0 770

These figures are correct for afrequency of 5o

LAYER

4/

iL.t_ AYE Fl

Fig. 2.-Showing how Stalloy stampingsare built up

terms excepting the number of turnsfor the primary winding.

For the voltage E in the formulawe write down that of the mains andf 'r the frequency f their periodicity.Experience indicates that a suitablesize of core stamping for this typeof transformer is the No. 4 Stalloy,which has a central limb 15/16 in._wide, and in order to obtain the

456

cycles and theparticular coredescribed. For afrequency of 25cycles, exactlytwice the numberof turns will haveto be used or,alternatively, thecore will have tobe doubled incross section.

When either of these alternativesdoes not afford a satisfactory solutiona proportionate increase may bemade in the number of turns and thesize of the core.

No-load Voltage of SecondaryA comparatively small number of

turns is required for the secondaryand the actual number is dependent

"Wireless Magazine. June. 1929

A Special " -Wireless Magazine " Article by W. Jamesupon the losses in the transformerand the nature of the load. Experi-ments show that a no-load voltage ofabout II is needed in order to chargea six -volt accumulator at one amperethrough a metal rectifier and 8o turnsare provided in the transformer.

Six Tappings ProvidedIt may be desirable to charge at a

lower rate than one ampere, however,and also to charge two- and four -voltaccumulators. This winding is, there-fore, tapped at 70, 65, 6o, 55, 5o and45 turns in order that the output mayeasily be regulated.

Having decided upon the numbersof turns for the primary and second-ary windings we have to choosesuitable gauges of wire, bearing inmind that the winding space islimited and also that the transformermust not overheat.

It was decided to employ No. 3o -gauge enamelled wire for the primary(No. 3o for low voltage mains su/has 'To), and No. 22 enamelled wire forthe secondary and to layer wind.

Enamelled covered wire is perfectlysatisfactory, but it is advisable tocover every few layers with a piece ofthin paper. Random winding is notsuitable.

Insulating the WindingsCare must be taken thoroughly to

insulate the primary from the second-ary with tape or paper, and bothwindings from the core, and it is

therefore necessary to employ eithera suitable former of insulatingmaterial or to wind the coils pancakefashion in a separate former and tocover them with tape.

The first step in the constructionshould be to purchase a sufficientquantity of the No. 4 Stalloy stamp-ings which will build up to give acore about I in. thick. These stamp-ings will cost about 4s. A former maythen be constructed and will comprisea tube and two end pieces of thinPaxolin or other suitable material.

The primary winding may be puon first and the ends be brought outthrough small holes. A winder maybe rigged up in order to simplify thework of putting on the correct numberof turns although, with patience,hand winding is not difficult.

Alternatively, a former may beconstructed with a square core and

PRI. SEC. PR I.

PRI.

0 ern

SEC.

Fig. 4 -Alternative method of arrangingwindings

the primary winding be wound in twosections. These sections must beproperly connected in series after theyhave been assembled and care must.of course, he taken that sufficient

Another view of the unit, which can be used for charging two-,four-, or six -volt accumulators, or exciting the field coil of a

moving -coil loud -speaker such as the Lodestone

457

covering inthe form oftape be pro-vided inorder thatthe insula7tion of thewire shallnot bedamaged.

In thetransformerillustrated,a formercomprisinga circulartube with apair of cir-cular endpieces wasused.

A certainamount of

space is therefore wasted, but owingto the ease with which the wire maybe wrapped on a former of this

END OFPRIMARY

WART OFPRIMARY

'4 OW/6 9:a VA, //AVM WE P.,

ta(cat.dmfINAMMAPECW....C.:000:Korgo:COOLVANICCIVAIVW:06:001.1451Yk

SEFOM DAR(

LAYERSOF PAPER

Fig. 3.-How the winding is put onthe core

description, readers may prefer toemploy one of a similar construction.

It should be remembered that thenumber of secondary turns is fixed;the number of primary turns shouldbe changed to suit the voltage of themains and this automatically givesthe correct secondary voltage.

The illustrations (Figs. 2, 3, and 4)show how the core is assembled.Notice that a pair of core stampingscomprises a T and a u piece and theseare fitted in pairs, first in one directionand then the other.

It is necessary to clamp the core toprevent the laminations buzzing andeventually from damaging the wind-ings. A pair of brackets shouldtherefore be fitted on each side ofthe transformer as illustrated.

Certain of EfficiencyFrom this brief description the

reader who is interested will be ableto build his own transformer and hemay be certain that it will bereasonably efficient. The windingsdo not get hot even when deliveringfull load for a day.

When tested on my own householdsupply of 24o volts 5o cycles thefollowing charging currents wereobtained for two-, four-, and six -volt,accumulators :-

Tap. 6 volt. 4 volt. z volt.

I I.1 1.5 2.02 .8o 1.05 1.72 charging3 .65 .9 1.53 current4 .5 .78 1.31 in5 .35 .65 r.r amperes.6 .2 .55 .9

7 - .35 7



BurndeptScreenedFour

IF YOU ARE GOINGON THE CONTINENTTHIS SUMMER-

-6.&70telkit

HOLLAND ITALY

TO -DAY, with the number ofefficient portable receivers avail-

able to the radio enthusiast, thereexist few valid reasons why one shouldnot form part of the holiday equip-ment, even when a trip to the Con-tinent is the objective.

Few Difficulties RaTsedGenerally speaking, barring one or

two exceptions, but few difficultiesare raised by foreign customs depart-ments to the temporary importationof a wireless set, providing it isclearly demonstrated that it is forthe owner's use only during his stayand that no attempt shall be -nadeto leave it in the country visited

In order to prevent such an eventuality, some foreign authorities demanda deposit returnable on giving proofthat the owner with his importedreceiver is crossing the frontier !

Travellers to Belgium on arrivalat the port of entry must make atrue declaration and will be charged12 francs per kilogramme, roughly is.per pound avoirdupois, for which areceipt is given. Show this documentto the customs on leaving the countryand the deposit will be refunded. Nolistening licence is collected

Should you go to Holland, youwill find the authorities quite amen-able; all they require is a statementto the effect that the importation is atemporary one. They will exact a

J. GODCHAUX ABRAHAMS EXPLAINSHOW TO DO IT WITHOUT DIFFICULTY

deposit amounting to about eightper cent, of its value, and you maycollect this money on your way back.

In the same manner, Germanyallows you to enter her doors withboth photographic and radio appara-tus "in so far as it is required for thetraveller's personal or professionaluse during his journey through theland." As a guarantee of good faithyou will be asked to deposit a sumbased on the tariff, namely, 120marks (say shillings) per ioo kilo-grammes (or 220 lb.). This worksout at about 61/2d. per lb. of wirelessset ! Again, the sum is recoverablewhen the receiver is re-exported.

Both Spain and Portugal affordfacilities to tourists provided withtheir radio equipment, and do not, asformerly, look askance at you orsuspect you as a political spy, if youwalk up to the customs office witha four-valver camouflaged in anattaché case.

Filling in a Couple of FormsIn the former country you may

perhaps be asked to fill up a coupleof forms-a habit acquired in mostcountries since 1914 !-and a depositof two gold pesetas per kilogrammeis exacted; in Portugal no licence isenforced, but a small customs dutyis charged.

Italy allows you to stay withinits frontiers for a period of three

458

SPAIN L SWITZERLAND

months, providing on entry you handover an amount proportionate to 240gold lire per ioo kilogrammes, calcu-lated on the weight of the set. Ifyou take it out again within theperiod fixed by the authorities, youwill get your money back.

France, as usual, is not so lenient,and by a recent law has decreedthat you shall pay twenty-two percent. of the value of your receiver.Moreover, your word as to its valuemay not be taken, but its worth maybe estimated by the Douane, at itsown sweet will.

Swiss OfficialdomSwitzerland, I am afraid, for an

unaccountable reason, creates manydifficulties, and the exact positionwould have to be clearer before Icared to present myself at its Customswith any kind of radio hook-up. Tobe quite in order, before setting outfor a visit to that country, you shouldapply in writing to the DirectionGenerale des Telegraphes et Tele-phones at Berne, the headquarters ofthe Swiss P.M.G.

He will want to know your fullname, home address, nationality,date of arrival, route you intend totake, that is, the frontier town atwhich the authorities may expectyou, where you intend to stay, andfor how long you will honour thecountry with your presence. Appar-

ently when and where you were lastvaccinated does not interest them !

When you have received a permit,you show it to the customs on arrivaland produce the set. Failing thepreliminary application, you will berequired to deposit 20 Swiss francs,or if you are to wing and have nofixed address, 5o francs; over andabove this charge, you will be calledupon to pay on the weight of thereceiver, based on 6o Swiss francsper too kilogrammes. Following thesedisbursements, you fill up a fewforms and on your leaving thecountry the two sums are handedback to you.

Special Licence for ListeningBut bear in mind that the fact

that you have made these depositsdoes not enable you to listen, forbefore doing so you must presentyourself at the post office and afterfurther questions have been fired atyou, pay a registration fee of 3 francs,and obtain a special licence for mini-mum three months, roughly, anotherfair francs Swiss.

Personally, I doubt whether thetrouble is worth it unless you intendto stay in the country for at least thatperiod of time. Now% it strikes methat in view of the increasing numberof broadcast listeners in Europeancountries and the general desire ofthe authorities that their transmis-sions should be heard by foreigners,some means should be found to permittourists to take portable receiverswith them as easily as the averagesnapshot camera, which the majorityof travellers have.

Why Not a Radio Triptyque ?Why not a scheme similar to that

adopted by the various automobileassociations, which, in exchange for adeposit in your native country, issuea triptyque or a customs carnetauthorising you to take your carthrough several foreign countries.

A radio association could take thismatter up on exactly the same lineswith the continental customsauthority. In such an eventuality,we might be called upon on this sideto deposit with such an authorisedbody a sum equal to the highesttax enforced by any foreign countrywe intend to visit. We should be giventhe necessary papers and on ourreturn home with the receiver, wecould secure a refund of the money.It's all so simple, yet why is it notdone?


ustralian RadioAUSTRALIA has made a definite

move toward actively controllingthe quality and calibre of the kind ofentertainment put on the air.

The Commonwealth Post OfficeDepartment has officially informedthe present controllers that it is notsatisfied with the programmes nowbeing distributed and has stressed thepoint that the merit and variety ofthese programmes are not commen-surate with the payment that is beingmade to them from listeners' licenses.

The Postmaster General has theright to withold certain percentagesof license revenue in each State frbmthese broadcasting stations if thePost Office Department certifies thatthe programmes do not merit fullpayment being made to the respectivestations. While this deduction hasnot been made up to the present, thePostmaster General now threatens toexercise his right if the programmesare not improved.

The present revenue for the pro-vision of broadcast entertainmentapart, from patent and copyrightroyalties, is about £240,000 annually,derived nearly exclusively from thelicensing fee paid by the owners ofreceiving sets. On the basis of a fiveshilling fee, a Royal Commissionerin a recent report recommended thepayment of a fixed sum of approxi-mately £5,000 per year to each class" A " station.

It is anticipated that, even withthe reduction of license fees, therewill be in the future a steady incomeof £250,000 a year for broadcastentertainment in Australia. Thisincome, it is stated in official quarters,will be sufficient to give regularentertainments of the best talentavailable in the country and also tobring to Australia some of the bestBritish broadcast entertainers. Byworking in co-operation with theBritish Broadcasting Corporationthere would be, it is argued, a regularinterchange of leading artists betweenAustralia and England, thus furthercementing the friendly relations.

A demand has also been made bythe Government that the first -gradestations establish relay stations inNew South Wales and Victoria.The " A" broadcasting companies areasking that before they are compelled

459

to erect these relay stations or tomake costly additions to the existingstations, they should be grantedanother five years' monopoly of theright to provide broadcasting enter-tainment in the five States they areare at present operating in, namely :New South Wales, Victoria, SouthAustralia, Western Australia, andTasmania.

Nine Months' FranchiseThey maintain that it would be

unfair to ask them to go to the costof establishing relay or subsidiarystations when their present franchisehas only nine months' currency.

At the same time, a strenuouseffort is being made by the smallerbroadcasting stations in Australia toobtain a larger share of the licensingand patent revenue. Appeals havebeen made over the air by the class"B" stations, which are supportedchiefly by advertising, for co-opera-tion of listeners to aid them alongthis line, accompanied by a demandthat there should be a stoppage ofadvertising or paid publicity fromthe " A " stations.

These appeals are said to have theapproval of the leaders of the FederalLabour Party which proposes to makethis appeal a strong point at thecoming elections coupled with thenationalisation of broadcasting inAustralia on lines similar to that ofthe B.B.C. and the governmentstations of the Irish Free State.

Possible Reduction in FeesThe future of broadcasting is one

of special concern to nearly 5o0,00olisteners in Australia, who willwatch with great interest the decisionof the Government. It is believedthat the general effect of this con-troversy will probably be either toimprove the quality of the broad-casts, or to create a lower level ofentertainment with a uniformity inthe classification of stations, and apossible 'reduction in the fees to bepaid by listeners.

Whatever the outcome of theCabinet deliberations may be, theGovernment is apparently deter-mined to strengthen, rather thanrelease its hold on Australian broad-casting. F. P.


J. H. Reyner's FurzehillFour was described in the

December issue; it has one -dial tuning

READERS' OPINIONS THAT WILL GUIDE YOU IN THE CHOICE OF A SET

LODESTONE THREE

EENthough it has no reaction con-

trot, W. James's Lodestone Three(WIRELESS MAGAZINE, March, 1928)gives excellent loud -speaker results, as thisletter about it from an East Londonreader proves :

Being an ardent experimenter, I wishto congratulate Mr. W. James, yourResearch Consultant, on his excellentdesign, the Lodestone Three. I haverecently completed a model of it and findresults exceptionally good.

I tested the set on my workshopaerial, which is badly screened by build-ings and a network of telephone cables.

The reception of 5GB in this districtis poor; even with an ordinary H.F.stage the detector (anode -bend rectifier)is barely loaded. However, on connect-ing up the Lodestone, 5GB " came in "so powerfully that "drastic measures"had to be taken with the H.F. volumecontrol 1 To worry you with a stationlist is unnecessary.

I find the quality with a moving -coilloud -speaker excellent. May I adviseyour readers that an L.F. transformerfor this set must have a very highprimary inductance and impedance. A' cheap " transformer will not do.

FURZEHILL FOURDOUBTLESS because of its one -dial

tuning, J. H. Reyner's FurzehillFour (WIRELESS MAGAZINE, December1928) has been remarkably popular. Hereis a Leeds reader's opinion of it :

Having completed Mr. Reyner'sFurzehill Four, I thought you mightperhaps like to have my opinion.

Let me say at the outset that I amdelighted with it.

The only items in the list of partsrecommended that I substituted werethe L.F. transformers; and .mine areFerranti AF5's, which in my opinionare never an extravagance.

I could not obtain all the parts imme-diately owing to the demand for certainarticles, and so I constructed the setat leisure-carefully and thoroughly-the dual -range coils being the last com-ponents to come to hand, and then mytroubles (?) began !

Personally, I have never seen thiswarning in print, and so, for the benefitof future amateur constructors, I feelyou would be doing a service if youmentioned this point.

When I screwed down my - coilsto the baseboard through the copperfoil I used a bradawl before insertingthe screws to make holes large enoughto take the fairly large screws necessaryfor satisfaptory holding down, and thenapplied the screwdriver to the screwsand tightened them down.

The wood of the baseboard was some-what hard mahogany. Testing out timecame, and I inserted some old butmuch respected valves in three of thesockets, and all appeared O.K. Thescreened -grid valve then went in, andI expected my programme.

Nothing doing until I switched off theL T., and then-lo and behold 1-a"dull" flash. The anode coil I foundwas slightly warm !

I immediately suspected the possi-bility of a coil connection touching thecopper foil (all the wiring had previouslybeen most carefully tested), and so Itook out the coils and noticed thatwhen I commenced to withdraw theanode coil holding down screws thefoil moved ! That was it The screwhad drawn the foil up and shorted thecoil connections.

A repetition has been prevented bycutting away a little of the foil aroundthe screw holes, and that is the tip Iwish you to convey to your readers.

My experience cost me 225 6d. plusthree old friends; and I was very an-noyed about it, too ! Mullard's wouldn'treplace that valve, although the fila-ment was intact (emission gone !), andso I did the right thing by them andbought four as specified.

However, after a week -end's test, Ifound that the PMzD was very micro -phonic. This they have replaced for me,and now I'm satisfied.

All goes well now except the coilchange and, although I have triedrepeated adjustments, I have to "fish"for the place where the coils are bothchanged over-both on the low andhigh -wave positions. Candidly, I don'tlike the system.

460

Mine even now appear to have de-veloped wear, and 1 am afraid I shallhave to substitute them for a pair witha different change.

Perhaps the real trouble is the tandemarrangement, but I cannot see it happen-ing with certain other makers.

Well, now for the performance. I'velogged thirty-nine on the low and tenon the high wavelengths, and identifiedall but four or five.

My local station (I am close) streamsin from zero to zo on an Igranic dial,and I get at least five on the low waveswithout reaction in daylight.

Selectivity is very fair, consideringthe single -dial tuning, and it appears toget better higher up the scale. Ioriginally balanced the set on Pragueat 5o, and it appears to be correct.I have not tried it, but do you think itwould be better to balance lower? Bythe way, the balancing job was veryinteresting-my anode pre-set con-denser being nearly "out."

On the long waves, with the reactioncondenser half in, I can, as you said,rotate the tuning dial and one by onethey streak in. All except Daventry-which nearly deposits itself in mydrawing -room 1

Well, I've said really more than I hadintended, and I will close by thankingyou for a wonderful set. Range, volume,purity, ease Of operation are all there,and, last but not least, one of the mostinteresting sets to make that I havetackled; and I am rather an old handat the game.

ETROM the same reader a few dayslater we also received the following

letter :Since writing you a few days ago

I have had the opportunity of thoroughlytrying -out my Furzehill Four, and I ammore delighted than ever with it.

I noticed a paragraph somewhere inW.M." regarding selectivity with S.G.

valves, and I find that by turning downthe H.F. (volume) control and bringingup strength with the reaction condenserthat I can cut out Leeds (my localstation, % miles as the crow flies) twoor three degrees each side, and I nowhave not the slightest difficulty in

separating all the low waveband sta-tions which are within a few metres ofeach other.

On the long waves Daventry does notinterfere either with Eiffel Tower orZeesen, should I particularly desire tohear either of the latter.

Volume is amazing, and the way theset reaches out is a source of incessantwonder to us. Purity is beyond ques-tion, and I again repeat my appreciationof the two Ferranti AF5 transformers.Mullard 2 -volt valves throughout, witha PM252 (2,600 ohms) for output tomy old Amplion AC3 cone, which in myopinion (and others) is every bit as goodas cabinet cones we've tested up to9 guineas.

For H.T. I use two 6o -volt C.A.V.accumulators of the old type, which Ihave always found very reliable.

The only " snag " in the whole set isthe coil change -over switch, but eventhat rather pleases me, because it givesme something to " finnick " with !

I will conclude with renewed thanksfor a splendid set and wishes to " W.M."for their (as it is) success.

THE CRUSADERDECEPTION of no less than sixty-fivef -A stations on the Crusader Two (WIRE-LESS MAGAZINE, May, 1928) is reportedby a Taunton reader, and we shall be gladto hear from any other listener who canbeat this record ;

Having had the Crusader Two, whichappeared in the May, 1928, issue ofWIRELESS MAGAZINE, in operation forabout four months, I thought youmight like to hear of its performance.You probably know that this district isconsidered good for reception, as thebeam stations at Bridgwater and Somer-ton are near here. My aerial is 4o ft. long,with a biscuit tin as earth.

I have made a few additions to theset-a switch for one valve and apotentiometer in the grid circuit. Myvariable condensers are Ormond, chokea Peto-Scott, transformer a Powquip,and a Dubilier grid condenser and leak,and I have made the aperiodic aerialcoil holder to swing.

The valves are Mullard PMILF and aPR L.F. valve (2 volts), with about6o volts H.T. on both valves. I do notuse centre -tapped coils, as I can obtainsufficient selectivity without them.

The following are the stations re-ceived :

HIGH WAVESHuizen 5 XX KalundborgRadio Paris Eiffel Tower StamboulZeesen Motala Hilversum

MEDIUM WAVESBudapest Dublin CopenhagenBrussels Berne NaplesVienna San Sebastian GleiwitzMilan Hamburg CardiffOslo Genoa BreslauZur'ch Toulouse Swansea5GB Manchester Bournem'thLyons Stuttgart KonigsbergLangenberg Leipzig TurinPTT Paris London CologneRome Graz HorbyMadrid Barcelona NewcastleFrankfurt Goteborg NurnbergKatowice Prague CorkRabat Flensburg


I have had short-wave coils sinceJanuary, and using D.X. coils, I havelogged the following stations, in additionto a number of British amateurs andunidentified Continental short-wavetransmitters :

W8 XK on 62.5 metres.Dutch telephone station on about

4o metres.7MK Copenhagen on 32.5 metres.2 XAF on 31.48 metres.PC J on 31.4 metres.7L0 Nairobi on 31 metres.3L0 Melbourne on 31.55 metres.CJRX Winnipeg on 25.6 metres.5SW on 25 metres.8 XK on 25.4 metres.2 XO 011 22 metres.2 XAD on 19.56 metres.The Dutch station, PC J, is particularly

loud in the daytime. In conclusion, Iwould not part with the Crusader foranything.

JUSTas remarkable are the results

J obtained in Victoria (Australia),where another enthusiastic reader got a12,000 -mile distant station on a loud-speaker. Read what he says :

Reading a report of the Crusader inyour November number, by a reader inSouth Africa, I thought perhaps you maybe interested in my results.

He stated he got loud -speaker resultsfrom a station f ,000 miles away. Well,perhaps the wavelengths differ, but Ihave had loud -speaker results, loud

WHERE"WIRtirSNAGAZINESETS

-IRE INS E

FUREEHIll

FOUR

CRUSADER

TWO

FIDELITYFIVE

LEEDS

CROSS ,o7d6.;:,TAUNTON

ICRUSADER LODESTONE

THREE

Something more than just praise Jorthe WIRELESS MAGAZINE are theletters from readers reproduced inthese pages-they are a definite helpto the amateur who wants to build anew set, for they do give an unbiasedview of what each receiver will accom-plish in different localities.Remember that back copies describingany of these sets can be obtained forIs. 3d. each, post free, and that full-size blueprints are available asindicated on another page of this issue.Readers are invited to send us photo-graphs of WIRELESS MAGAZINEreceivers they have built; for each oneprinted we shall pay a fee of half aguinea.

461

enough to hear distinctly 3o ft. from theloud -speaker, of a station over 12,000miles away. This station was PCLL.

I have logged this station three timesin the last fortnight with this success.They were conducting telephony testswith ANE, which came in almost as well.

I have also had loud -speaker resultsof 2ME, W2 XAF, W2 XAD, W2 XG,PCJ J, and RFN. Other stations I havelogged are 5 SW (about R3 to R4, phonestrength), 3L0 (which is only twentymiles away), 6AG (Perth, 1,700 air miles),a French station I was unable to iden-tify; also another Russian and Dutchstation. Besides these about thirtyAustralian and New Zealand amateurs(this is telephony only).

On the waveband from zoo to 500metres I can tune in 4QG (the farthestA class station from me), which is looair miles, at loud -speaker strength, butas there is only a difference of Io metresbetween 3L0 and 4QG, interference from3L0 was bad.

I have built many sets, but for puritythe Crusader stands alone, and for a two-valver (three -electrode valves) the rangeis splendid.

The only departure from the originalcircuit was to reverse the leads of thereaction coil and the use of a .00015-microfarad reaction condenser in placeof .000l microfarad.

The short-wave coils I wound myselfof No. 16 -gauge d.c.c. wire. The chokeis only a 200 -turn honeycomb un-mounted coil, and there was no troubletaken over the set. The valves I usedwere detector A415 and audio A4o9(Philips).

Wishing that great journal of yoursthe success it deserves.

FIDELITY FIVESO much does a Gerrards Cross reader

think of the Fidelity Five (WIRELESSMAGAZINE, March, 1928), that he fears thepublication of his letter will lead a memberof the staff to demand an increase insalary! His praise, however, is almostsufficient reward :

I have made up your Fidelity Fiveand the mains unit you recommendedfor it.

Of the latter it suffices to say that it isnot possible 'to detect, in the loud-speaker, its existence.

The set is simply magnificent. I com-pared it with another four -stage set onwhich I used LS5A valves in parallel on35o volts II.T. And with half the H.T.,and goodness knows how much less L.T.consumption, I get a roundness of toneand a definition that I have never heardelsewhere-and that on my good Celes-lion, now three years old.

It will tune -in umpteen foreignstations, with careful tuning. But abroadcast receiving set, being a meansto an end and not an end in itself, thatis no way to appraise a set. The pointis that wherever interference, morse,heterodyne whistles, and other delightsof foreign listening allow, it brings themin with wonderful quality.

There is on your staff the world'schampion godfather : he has "namedhis child " to perfection. But I should notshow him this or he will want his salaryraised I


FIRST, let me make the explana-tion which is needed before I

make. any comments on wireless,which is a hobby, an entertainmentand almost a necessity for well overtwo -and -a -half millions of people.

From My Own PinnacleI have been interested in radio

ever since it first became popular inthis country. I am not, as you know,connected with any " tradey " sideof wireless, but as a car manufacturerand as any ordinary person justinterested in anything electrical ormechanical, I have viewed from myown pinnacle the growth of broad-casting.

Perhaps I am not so keen a listeneror radio technician as many otherreaders of the WIRELESS MAGAZINE,but I do think that, when it comes tocomparing radio with motoring,my private opinions may help.

At least, that is how it struck mewhen I was asked to talk about" motorised radio."

Radio Following Car PracticeNow I don't want to make myself

unpopular but " motorised radio " isright. Radio is following car practicein so many things that it is strikinglyobvious to anyone such as myself,who has to be in intimate touch withevery sphere of motoring practice.

You can all see this for yourselves.Do you remember the time whenmotorists were looked upon as" freaks," and Continental cars wereregarded, in lay knowledge, as the

AN UNUSUALREVIEW OF THE

WIRELESS INDUSTRY

best obtainable? I'm talking aboutthe early nineteen -hundreds. I, incommon with many whose names arehousehold words nowadays (Col.Charles Jarrott for example), did mybit towards popularising motoring,and I can tell you we had a very hardjob of it.

We had to fight red -tape officialdomand, what wasjust as bad, oppositionfrom just the class to -day which istaking advantage of the cheapermotoring movement. But we didaway with the red -flag man, we gotroads fit for motoring, and we mademotoring cheaper.

Now where does the wireless comein ? Well, although the boom startedabout twenty years later, some har-dened folk had to go through justthe same pioneering. There was theB.B.C. to found; again there wasofficialdom to fight; and it was ahard job to make the Post Office lookwith a kindly eye on broadcastlisteners; there were some mostdifficult technical problems to solve,and they all had to be solved beforewireless could become the entertainerfor the average man.

Some of my new -motorist friendso -day could never have held an

early nineteen -hundred "giant" witha fifty -horse engine doing the sameas a modern "twelve" or "sixteen,"with high-pressure tyres and withno front -wheel brakes.

Some of my other acquaintances,who are listeners, know nothing what-ever of the working of their sets;they do no* compare with those

462

amateurs who first transmitted andreceived across the Atlantic, or evenwith the few hundreds who used tolisten to Capt. P. P. Eckersley at" Two-em-toc. Wr-r-r-rittle !"

But enough of status comparisons.I see that the radio industry is copy-ing good points from the motoringindustry, and I think it is right to doSO.

Economical Mass ProductionMass production is the most obvious

example. Just after the War, wirelessvalves cost two or three pounds apiece, and they were wasteful ofcurrent. But by means of machineryalmost identical with that which hasmade the mass production of smallmotor parts possible, valves (and verygood ones, too) can be had for only afew shillings each.

Small press work has been devel-oped very largely for car parts, andthe adoption of such methods for radiomanufacture has cheapened costbeyond all realisation. You will seethis for yourself in terminals, thelittle fittings on components, andin the electrodes of valves and so on.Cutting Down the Cost

Bigger things are now being mass-produced for wireless purposes, andordinary listeners, who have no ideaof the actual cost of the parts in theirsets, would be amazed if they couldknow how manufacturers strive tocut down cost by quantity and "flow"production in order to sell sets andparts cheaper, and so to get increasedsales.

All kinds of instances strike me. Ihave just been looking at a friend'snew three-valver, of which he is veryproud; it gets about twenty or thirtystations on the loud -speaker, and Iknow that this is no exceptional per-formance. The complete outfit costabout LIo to £12, which is ridiculousin comparison' with our £1.o to £50sadly inefficient five-valvers of aboutfive years ago.

Cabinet of Pressed Sheet IronThe cabinet, which at first glance

seems to be an excellent example ofthe cabinet -maker's work, is actuallyof pressed thin sheet iron, and theframework is riveted. It is cellulosedto give an imitation wood finishsimilar to that with which some of mycars are turned out; the celluloselacquer was obviously sprayed on,as is done when covering car bodies.

The interior of the set is an exhibi-tion of the very best cheap press-work in soft metal, and the wiring isarranged so that it can be done in" flow " production style by a rowof operatives armed with electricsoldering bits.

Could anything be more " motor-ised"? But, as I say, this is just asit should be, because the car hastaken the brunt of the pioneer woik,and can afford to hand on its experi-ence to industries which, like wire-less, are following it.

Would you care to think that, if themanufacturer of your set had notfollowed car practice, it might havecost anything from 25 to 5o per cent.as much again in initial cost?

I can assure you that radio manu-facturers will, in the next year or so,follow car practice even closer, andsets and parts will be cheaper in con-sequence.

Motorists and ListenersNow there is another aspect which

I know you will want me to speakabout, and that is the relation betweenmotorists and listeners. A questionI am often being asked is : "Will awireless set ever become a standardfitting with a luxury car ? "

This latter development has, ofcourse, already been made in one ortwo cases. Portable sets with frameaerials, with "juice" supplied by thecar battery, have been requested bysome wealthy purchasers when order- ,ing a new car, and of course there aremany thousands of ordinary folkwho take portables with them whenbound on motoring picnics.

"Wireless Magazine. une, 1929

A year or two ago the technicaldifficulties associated with portablesmade their use in cars of necessityvery restricted, but with the adventof screened -grid valves many of the" snags " have been overcome. Ican't put the credit for that on thecar industry ! But I do think that inperhaps a year or so' you will findwireless sets being actually built incars.

This would make radio en routeever so much more popular. Tuningand control panels might be incor-porated with the metal facia boardof the car itself; the wiring mightbe carried out direct from the carbattery, and in the case of fabricsaloons with no metal framework, anordinary aerial might be hidden inthe roof. There is a big scope, apartfrom entertainment, for this kind ofthing.

Many business men and travellerswho are constantly on the road intheir cars would welcome the oppor-tunity to be constantly in touch withthe news bulletins, and I am not oneof those who are always strivingagainst Savoy Hill administrationand saying that nothing valuableever emanates over the ether fromB.B.C. stations.

It is a comforting thought that,at present, the majority of privatecar owners are keen on wireless.This, I suppose, is simply because theaverage motorist (while not such awealthy person as the Treasury likesto think) is generally able to afford,easily, a wireless set of some sort.

Also it is generally the case thatthe average motorist takes an interest

in anything mechanical or electricaland so the desire to " meddle" witha wireless set is intensified.

Now this is bound to affect thewireless industry. Without consider-ing influence, wireless licences areincreasing by leaps and bounds.Since January, 1926, there has beenan increase of about a millionlisteners !

A Boost for MotoringEveryone knows what a boost to

the motoring industry has beengiven by the small -car movement,and newcomers are flocking to carswhich combine a pleasing luxury withlow cost.

I know I am not exaggeratingwhen I say that nine -tenths of thesenewcomers, if not already listeners,will, by reason of their touch withmotoring, be brought into veryintimate temptation by the pleasuresto be had from a wireless set. Thebuying of a car will tend to make thembecome both motoring and wireless" fans."

The Listeners' DebtI have tried to show in what way I

think all listeners are indebted to themotoring industry. Perhaps younever had cause to think about thisbefore. Take a look into your ownset and see if you can find any of theevidence I have quoted.

SCHOOLBOY'SWIRELESS HOWLER

When asked what Columbus wastrying to discover in 1492, the smartreply came that he " was looking for ashort-wave hook-up to get India."

If the WIRELESS MAGAZINE hadbeen published some few years earlier,no doubt his difficulty would have beensolved.

AN- OPTIMISTICREADER

Everybody knows that all WIRELESSMAGAZINE receivers are first-rate.However, we do not advise readersto follow the example of an enthusiastwho boasts that he took a six months'language course in order to be able toidentif) stations picked up on hisWIRELESS MAGAZINE one-valver I

463

Building Your OwnL.T. Charger `wogs 457)

Tap number 1 is the Both turn andtap number 7 the 5oth. Thesefigures show that a sufficiently widerange of current is available, butadditional tappings could, of course,easily be arranged for. They may betaken to a small terminal strip whichmay be fastened to the clamps of thetransformer. The completed unitmay. be employed with suitablechoking coils and condensers forsupplying, the 'filament current fortwo -volt valves. ,

As there is a fall in voltage over thechoking coils and in the transformerand rectifiers it is essential that asmall regulating resistance be em-ployed in order to adjust the filamentvoltage.


Overheard tre Charging StationSOME GOOD ADVICE IN A. PALATABLE FORM

ICALLED in at the local chargingstation yesterday, to collect my

accumulator after its fortnightly"feed." Another customer, however,was just before me-a middle-agedman, carrying a two -volt glass cell.

This he handed to the Expert -with -the -Voltmeter who presides over the

kAUZa .7"

\Vc,I called in at the local charging station

charging station. The E -with -the -Vtook the cell, held it up to the light,ran a critical eye over the plates, andinquired, " When do you want itback ? "

" Oh, there's no hurry," replied themiddle-aged man, " Give it a goodcharge, and I'll call round for it in afew days."

" Right you are," said the E -with -the -V, handing the cell to a waiting

Squeezing the maximum

satellite, who promptly disappearedwith it into subterranean depths fromwhich the faint hum of a chargingplant was audible . . " You're notlike most of my customers ! " addedthe E -with -the -V.

The middle-aged man looked surprised.

"How not-what do yott mean ? "

" 'Why, this," replied the E -with -the -V. "Most of the people roundhere simply won't give their batteriesa chance. I'm only too pleased tocharge them properly, but so manyof my customers simply won't letme ! They bring in the batteries onFriday night, generally in an over -discharged condition, and come roundclamouring for them on Saturday,regular as clockwork ! "

"You mean that they won't leavethe batteries long enough for you togive them an adequate charge ? "

"That's the trouble exactly,"assented the E -with -the -V. "Andthere's no getting them out of it,either. I tell them that hurriedcharging combined with over -dis-charging is thoroughly bad for mosttypes of accumulators,. but it doesn'tseem to convince them.

" All that they seem to care aboutis getting the cells ' cooked' as quicklyas possible, and then squeezing themaximum amount of juice' out ofthem. So they go on paying me torecharge their batteries twice asoften as would be necessary underfair treatment."

" Then I should think it must be aprofitable business from your pointof view !" commented the middle-aged man.

The E -with -the -V shook his head."Not in the long run," he said, "andI'll tell you why; the battery can'tstand up to that sort of treatment forlong, and begins to give ,inferiorresults. Then the owner gets afriend who is an ' expert' to comeround and see what's wrong with theset.

"He pounces on the L.T. batteryat once, says its been faultily charged,and asks, 'Where do you take it ? '' Oh,' says the owner, I get it chargedat So-and-so's.' Well, he evidentlydoes it very carelessly. You take myadvice and try somewhere else !'says the ' expert,' and so, of course,in that way I lose customers. There -

he asked. fore, you see, hurried recharging at

Even the most experienced listener sometimes comes upagainst a tricky problem that he cannot solve unaided. The" Wireless Magazine" Technical Staff has a special depart-ment to deal with such matters.

Just write your queries (not more than two can be asked at

464

frequent intervals doesn't really payme in the long run, and it pays thecustomers still less, only they don'tseem to realise it !"

"But you must surely admit," saidthe middle-aged man, " that it isn'talways the fault of the customer.There are a good many firms adver-

Try somewhere else !

tising that they charge accumulatorswho do the job badly or carelessly,even when the customer is in nohurry to get his battery back.

" In cases like that, it isn't muchuse for the customer to leave hisbattery at the shop for several days.The battery is simply put on one sideuntil there are a sufficient numberin to make it worth while to run theplant, and then they are all slung

" Oh, 1 quite agree "

on together for the shortest possibletime-often at an incorrect chargingrate."

"Oh, I quite agree," said the E -with -the -V, "but the thing to do is tosearch around for a really reliablecharging station, and then, havingfound it, to leave your battery therelong enough for it to be chargedproperly." W.O.

a time) on one side of a sheet of paper and send them, together 1

with the coupon on page iii of the cover, a fee of Is. (postalorder, and not stamps), and stamped addressed envelope to :-

Information Bureau, " Wireless Magazine," 58/65 FetterLane, E.C.4.


AN ALL -WAVE SET WITH CHOKE -FED TRANSFORMER COUPLING

FOR use in a thickly -populateddistrict, where conditions are

none too good, it is usually necessaryto use at least three valves in orderto get loud -speaker reception of anumber of stations. In outlyingareas, on the other hand, particularlyin places on high ground, it is oftenpossible to get remarkable resultswith only two valves.

On the Fringes of Big TownsIn giving our readers details of the

Continental Two, we have in mind themany thousands of listeners who liveon the fringes of big towns and whoare, therefore, in the best position totake advantage of a simple two-valver.

This set has only one tuningcontrol, is not critical as regardsvalves, consumes only about 7 milli-amperes high-tension current andcovers without a break all wave-lengths from 200 to 2,000 metres.There are no coils to change andanybody can operate the set after afew minutes' handling of it wellenough to bring in a number ofstations on the loud -speaker withoutdifficulty.

Above the AverageWe wish, moreover, to state quite

clearly that the performance of theContinental Two is considerablybetter than that of the average two-valver as regards volume and quality.One of the reasons for this is that theintervalve transformer is choke -fed

from the detector anode circuit.Readers of the WIRELESS MAGA-

ZINE must be well aware of the methodof supplying a choke feed (or output)to a loud -speaker in order to preventthe heavy direct current in theanode circuit of the last valve fromdamaging the windings.

Actually, a low -frequency choke is

anode end of the choke itself.The free side of the loud -speaker is

taken to the negative side of the high-tension battery and thus a path forthe signal currents is formed. The2-microfarad condenser, of course,blocks the passage of direct currentthrough the loud -speaker.

In the Continental Two the same

A

.0002.

11-1

2.1=k000

30,000 OHMS

IP, 05

0.25 <"' \c"MFD.

OP 13

0005 311E.C,01-1M3

ion ZMFD

0 HT+

HT-

LT+

LT-

GB+

GB-Here is the Circuit of the Continental Two. Note the choke feed to the

transformer and the "motor -boat" stopper.

placed directly in the anode circuit.This allows the passage of directcurrent from the valve to the high-tension battery but blocks the passageof low -frequency signal impulses. Theloud -speaker, therefore, is joined inseries with a large capacity condenser(usually 2 microfarads), one side ofthe latter being connected to the

465

principle is applied to the inter -valve transformer, the steady detec-tor anode current not being allowedt o pass through the primar ywinding.

Thus full advantage can be takenof a high -ratio transformer and inthis circuit a step-up of 1-6 or 1-8can be utilised without any sacrifice


The Continental Two (Continued)

of quality as would normally occur ifchoke -feed were not employed.

Details of the actual circuit will beclear from the diagram on page 465.It will be seen that a form of Reinartzreaction circuit is employed, butinstead of the capacity being variableand the coil fixed (as is normally thecase with an arrangement of thistype) the position is reversed.

Moving Reaction CoilA small fixed condenser is em-

ployed and the coupling of thereaction coil with respect to the gridcoil is made variable. A high -

There is nothing at all difficult about theconstruction of the Continental Two

frequency choke is included in thedetector anode circuit.

The only other particular featurethat need be specially noted is thechoke -feed arrangement for theprimary of the low -frequencytransformer.

As has already been briefly ex-plained, a low -frequency choke isplaced in the detector anode circuit;this allows direct current from thehigh-tension battery to pass to theanode of the valve, but blocks thepassage of low -frequency signalimpulses.

These low -frequency impulses,

however, find a path through a largecoupling condenser and thence to theprimary of the transformer whichcan have a comparatively high ratio,say 1 to 6 or I to 8, if desired.

High MagnificationBy preventing the passage of

direct current through the trans-former in this way, full advantagecan be taken of its primary induc-tance and a high -magnification valvecan be used as detector.

It is important, however;that thecoupling condenser should be of thevalue specified and that a transformerwith a primary impedance corre-sponding to that used in the originalWIRELESS MAGAZINE receiver shouldbe utilised.

The value of the coupling condenserused in the Continental Two has beencarefully calculated by J. H. Reyner,B.Sc., A.M.I.E.E., our TechnicalEditor, and should be strictly adheredto for the best results.

Although the high-tension currentconsumption of this set will only beabout 7 milliamperes, a" motor -boat"stopper has been provided, so that itcan be used with a mains supply unit -

if desired. A suitable unit for use inthis case is the WiB model made bythe Regent Radio Co.; it gives 120volts at 18 milliamperes from 200 -volt alternating current mains.

Arrangement of " Stopper "The actual " stopper " consists of a

30,000 -ohm resistance in the detectoranode circuit in conjunction with a2-microfarad fixed condenser, oneside of which is connected to thenegative side of the detector filament.

COMPONENTS REQUIRED FOR THE CONTINENTAL TWOs. d.

x-Ebonite panel, 14 in. by 7 in. (Becol, Raymond,or Northern Radio) ... ... ... ... 8

I-All-wave tuner (British General) ... 18 6I-.0005-microfarad variable condenser (Jackson,

Lotus or Lissen) i i 6I-I5-Ohin panel rheostat (Lissen, Igranic or

Peerless) ... ... ... ... ... z 62-Antimicrophonic valve holders (Lotus, Formo

or Peto-Scott) ... ... ... ... ... 3 0z-.000z-microfarad fixed condensers (Trix, T.C.C.

or Lissen) ... 1.. ... ... . 2 6I-3-megohm grid leak (Peto-Scott, Lissen or

Ediswan) ... ... ... ... ... 2 6I-High-frequency choke (Lissen, Wearite or

Ready Radio) ... ... ... ... ... 5 6I-Low-frequency choke (Ferranti type B3 or

Igranic type F) ... ... ... 14 0I-.25-microfarad fixed condenser (Lissen, T.C.C.

or Dubilier) ... ... ... ... ... 2 0

3

s. d.1-2-microfarad fixed condenser (Lissen, Ferranti,

or T.C.C.) 3 6I -30,00o -ohm resistance (Graham-Farish,

Ediswan or Trix) 2 3I-Low-frequency transformer (Marconiphone

Ideal, 8 to I ratio) ... 25 0I-Pair grid battery clips (Bulgin)... 6I-Terminal strip, 9 in. by 2 in. ... 98-Terminals, marked : Aerial, Earth, L.T.+,

I..T.-, H.T. , H.T.-, L.S.+, L.S.-(Eelex or Belling -Lee)

2-Wander plugs, I red and x black (Lectro Linx,Belling -Lee or Igranic)... 4

Stiff wire for connecting (Glazite) 1 oLength of rubber -covered flex ... 2

I-Cabinet with To in. baseboard (Carrington) 23 6

3 0

Total Cost (approximately) ... £7 10 3

466


Special Choke -feed to Transformer PrimaryIf it is intended to use the set only

with dry batteries, this stopper canbe omitted ; it is really only essentialif a mains supply unit is to be utilised.On the other hand, even if dry -batterysupply is employed, the stopper canbe retained with advantage; itsinclusion will usefully lengthen thelife of the battery, which can bekept in use much longer without low -frequency oscillation occurring thanwould otherwise be the case.

Tuner TappingsThere are several special points to

note about the actual componentsused in the Continental Two. In thefirst place the tuner-which has beenpreviously used in a popular two-valver called the Meteor Two (WIRE-LESS MAGAZINE, December, 1928)-coyers, without any gaps, a wave-band of approximately 15o to 2,000metres. This is accomplished by aten -point tapping switch, easily con--

AER1AL-TUN I NG TEN -WAY TAPPINGCONDENSER SWITCH (200-2000 METRES)

LOW -FREQUENCY

TRANS-FORMER

POWERVALVE

G.B.BATTERY,

DECOUPLI NGRESISTANCE

L. F.CHOKE

REACTIONONDENSER

GRID -LEAK&CONDENSER

DETECTORVALVE

The positions of all the parts in the Continental Two are clear from this plan view.

trolled from the front of the set.The reaction coil is pivoted (inside)

at one end of the main coil, itsposition being determined by a knobon the panel. The size of the coil is soproportioned that reaction can beobtained without difficulty over theentire tuning range of the set.

As a rough guide to constructors ofthe Continental Two, we give belowthe wavelength ranges of the differenttappings, and also indicate some ofthe stations that were obtained at adistance 16 miles from Londonduring a short test one evening. Theaerial used was only 25 ft. long :-

The Continen-here all ready

tal Two is shownfor reception.

Tap No. I. -15o(?) to 200 metres.Tap No. 2.-220 to 37o metres.

Stations heard : Nurnberg, Bourne-mouth, London.

Tap No. 3.-300 to 55o metres.London, Daventry Experimental.

Tap No. 4.-35o to Boo metres.London, Daventry Experimental.

Tap No. 5.-460 to 900 metres.Daventry Experimental.

Tap No. 6.-55o to I, I00 metres.Hilversum.

Tap No. 7.-boo to 1,38o metres.Kalundborg, Hilversum.

Tap No. 8.-goo to 1,55o metres.Tap No. 9.-98o to 1,900 metres.

Hui zen, Radio Paris, Motala(phones), Daventry Senior, Hilver-sum.

Tap No. 10.-1,05o to 2,000 metres.Radio Paris, Daventry Senior.

It is important for the best resultsthat the same low -frequency trans-former should be employed as isutilised in the original WIRELESSMAGAZINE set.

Full-size Blueprint AvailableThere is nothing difficult about the

construction of the set, especially if afull-size blueprint is used. A blue-print can be obtained for half-pricethat is 6d. post free, if the coupon on

Wireless Magazine, une. 1929

The Continental Two (Continued)

AnotherTwo

photograph oi the Continentalall ready for reception.

page iii of the cover is used by June30. Ask for No. WM143, and addressyour inquiry to Blueprint Dept.,WIRELESS MAGAZINE, 58/61 FetterLane, E.C.4.

Mounting the ComponentsAfter drilling the front panel,

mount thereon the components asindicated by the photographs andblueprint (or the reduced repro-duction which appears on page 469).

Next, fix the panel to the base-board and place the remainder of theparts in position. When everythinghas been properly laid out, wiring upcan be started. At this stage afull-size blueprint will be invaluable.

A glance will reveal that everywire is numbered. This numbering isnot a haphazard scheme; if theconnections are made in the orderindicated, the wiring will automatic-ally be built up in the most efficientway. As each connection is made, thecorresponding number on the wiringdiagram should be crossed through.In this way there is no possibility oferror.

Suitable Valves to UseBefore the set can be used, suitable

valves must be obtained. In ourtests of the set excellent results were

6o,000 ohms can be used as thedetector, while the power valve canhave an impedance between 2,000 and6,000 ohms. The higher the impe-dance the higher will be the totalmagnification obtained, although iftoo high a value is used for the laststage, quality may suffer to someextent.

A Selection of Two -volt ValvesBelow we give a list of two-

volters that may be tried in theContinental Two :-Detector : Cossor 2 I oRC, Mullard

PMIA, Marconi DEH2Io, OsramDEH2 to, Mazda HEz To, Six -Sixty2 I oliF, Ediswan HFzio.

Power : Mazda LF215, EdiswanPV215, Cossor zzoP, MarconiDEP215, Osram DEP215, MullardPM2, Six -Sixty 215P.For other valves in the four- and

six -volt ranges see the complete listson pages 402 and 404 of this issue.

It is a mistake to obtain good

It is important that the low -frequency trans -specified should be used in the Continental

obtained with two four-volters-aMullard PM3A (the characteristics ofwhich have been recently improved toan impedance of 55,000 ohms and anamplification factor of 38) and aCossor Stentor

Actually, any valve with animpedance between 15,000 and about

468

modern valves and then not to givethem sufficient power to get, themaximum efficiency. In other words,do not be afraid to use a full 12o voltson the anodes. Many listeners stillonly use 60- or 9o -volt batteries andwonder why their reception is not sogood as it should be.


Powerful Enough to Tour Europe !Do not forget that there is always a

voltage drop in loud -speaker, choke,and transformer windings, and thateven when 120 volts is applied to theH.T. terminal of the set, all of thisvoltage is not available for the valveanodes. It pays in results to use ahigh -voltage battery of amplecapacity.

Operating the SetTo operate the Continental Two

(having connected up the necessarybatteries as indicated, and insertedthe valves in their holders), turn theknob of the filament rheostat as faras possible in a clockwise direction;this will switch the set on.

Next, adjust the tapping switch ofthe tuner for the reception of thelocal station. The list of wave-lengths already given will act as arough guide-with most aerials, forinstance, London and DaventryExperimental will be received on tapNo. 4.

Turn the knob controlling thereaction coil until the set just startsto oscillate, this state is indicated bya slight rustling or hissing soundheard in the loud -speaker. Adjustthe knob of the main tuning condenseruntil the desired signal is heard; thenreadjust the reaction for the bestresults.

If Reaction is Too FierceIf reaction is found to be fierce with

the particular detector valve used,then increase the value of the anoderesistance from 3o,000 ohms to5o,000 ohms or even more.

It will. be found that the resultsdepend to a large extent on the finecontrol of reaction and, although thisstate of affairs is by no means ideal, itis inevitable if good results are to beobtained from two valves. The list ofstations already given is some indica-tion of what can be accomplished.

Affect on SelectivityBeginners should also note that

the proper use of the reaction controlalso affects the selectivity of the set.For instance, if it is found that apowerful station comes in over alarge section of the condenser dial,the application of reaction will con-siderably sharpen the tuning andenable an undesired station to betuned out.

CliECKEB BY BlUEMKT IMwm 113 4p

0

LS- LS+ 11T+ IT- LT- LT+

This layout and wiring diagram can be obtained as a full-size blueprint forhalf-price, that is 6d, post free, if the coupon on page iii of the cover is used

by June 30. Ask for No. W.M.143. Wire up in numerical order.

Those who wish to take particularprecautions with their loud -speakerand phones (the Continental Two isideal for really long-distance phonereception) will like to use some kindof output unit external to the set.

For this purpose a I -to -I ratiooutput transformer, such as the

Ferranti OP', or a choke -output unit,such as that made by Igranic, is to berecommended. With either of thesedevices all danger of damage to theloud -speaker or phones is definitelyremoved and the maximum efficiencywill be obtained from them.

469

This concludes our, comments onthe Continental Two. It now onlyremains for you to avail yourself ofthe work of the WIRELESS MAGAZINETechnical Staff and enjoy broad-casting to the full. Just one moreword, though-when you have builtthe set will you write and tell uswhat it will do ?

Such information about sets as iscontained in letteTs such as thosepublished on pages 460 and 461 isinvaluable to your fellow -construc-tors and is appreciated by WIRELESSMAGAZINE readers the world over.


TELEVISION IN THE U.S.A.Regular Programmes Expected Soon

REGULAR television programmessoon will be available to the

American radio public following therecent action of the Federal Com-mission at Washington in grantingexperimental licences to seventeenstations. Some already have beenbuilt, and others are under construc-tion.For Six Months Only

The licences are for six months, andcall for operation in two channels, onebetween 2,000 and 2,200 kilocycles,and the other between 2,75o and

2,95o, corresponding to wavelengthsof 136.3 to 149.9 and io1.6 to 109metres.

Television broadcasts are no longerpermitted on regular broadcastbands except between 1 and 6 a.m.

The following stations receivedauthorisation for picture transmis-sions :-

W2XBW and W2XBV, RadioCorporation of America, owned inNew York and New Jersey.

W3XK, Jenkins Laboratory, Inc.,Washington.

WAAM, Newark, WestinghouseElectric and Manufacturing Co., fourstations in East Pittsburgh, Pa.,and Springfield, Mass.

General Electric Co., two stations,Schenectady and Oakland, Cal.

Pilot Electric Co., Brooklyn.Chicago Federation of Labour.Aero Products, Inc., Chicago.Lexington Air Service, Lexington.

Mass.William Justice Lee, Winter Park,

Fla. B. P.

EMERGENCY NEWS BY RADIOScope of Army -amateur System Increased

THE emergency news servicerendered by members of the

American Radio League in co-opera-tion with the United States ArmySignal Corps has proven so valuablein the past that officials of theseorganisations have decided to in-crease its scope.

Proving Their WorthDuring the past three years this

amateur radio transmitting grouphas proved its worth in broadcasting,emergency reports of tornadoes,floods and other disasters in whichordinary land wires were rendereduseless.

" Three years of operation underthe original plan have demonstratedthe advisability of reviving that planto provide for an expansion of thesystem to cover more thoroughly allparts of the United States," saysMajor General George S. Gibbs,chief army signal officer.

The present plan, which recently

went into effect, calls for the bandingtogether of amateur operators inwhat is known as the Army AmateurRadio Net. This is composed of onestation in each army corps area, ofwhich there are nine in America, andin each department in which amateuractivities are permitted. The controlstation of this system is at FortMonmouth, New Jersey.

Each corps area has its ownamateur radio net, taking in onestation in the capital of each of thestates in the area. This network issubdivided into approximately fivegeographical areas, known as stateamateur radio nets, with the statecapital.having the net control station.

Connected with the state amateurradio nets will be the district amateurradio nets, situated in each state soas to give the best possible service.

The last division of this large net-work is the local amateur radio net,which is composed of all amateursin local areas.

At the head of this league is thechief army signal officer. Otherofficials are corps area signal officers.These officers will appoint an officerto act as corps area liaison agentbetween representatives of the trans-mitting radio amateurs of that corpsarea and the corps area signalofficer.

One amateur, known as the " RadioAide," ,will represent amateurs ofeach corps area. A "Chief RadioAide " will act as army representativeof all transmitting amateurs of theUnited States.

In Charge of All MaterialThe army amateurs net control

station at Fort Monmouth, NewJersey, will have charge of the dis-semination of all material to amateurstations.

Code instruction will be sentamateurs to enable them to encodeand decode government messages atall times. F. P.

" RE -SHUFFLING 'I HE WORLD'S CALL -SIGNS "To the Editor, WIRELESS MAGAZINE.

sIR,-Those of your readers who havefollowed the changes under the Wash-

ington Radiotelegraph Regulations, dealtwith in my article " Re -shuffling theWorld's Call -signs " (WIRELESS MAGA-ZINE for February, 1929), may beinterested in one or two further pointsregarding these changes.

I mentioned that alterations wouldbe necessary in the case of the call -signs commencing with B, used hithertoby British Naval stations. Thesestations, in future, will use call -signscommencing with G, but in a good manyinstances the necessary change has been

effected by merely substitiiting a G forthe B, the original second and thirdletters being retained. For example,BYA, the call -sign used by theAdmiralty station at Whitehall, has nowbecome GYA.

Amateur Call -signsAs regards amateur call -signs, the

definite adoption of the new nationality.prefixes is necessarily a rather slowprocess, and from the latest availableinformation it appears that relativelyfew countries have come to a decision sofar. Of these, some have agreed to theprefixes provisionally recommended bythe Washington Convention (which

470

consisted almost without exception ofthe first letter or first two letters in theseries of call -letter combinations allocatedto each country), and some, again, havedecided on other prefixes drawn from theseries of combinations at their disposal.

I understand, however, that themajority of the countries concernedhave not yet definitely allotted any newprefixes to their amateurs, and soaffairs in this direction are still "in themelting -pot." It should, of course, beborne in mind that the new prefixes,unlike the old unofficial "intermediates,"will really form an integral part of theamateur stations' call -signs.

W. OLIVER.


Get -Your Grid LealZand CondenserRight

HOWANCDE RESIS-TANCE AFFECTSAMPLIFICATION

WE are able to purchase valves ofmany different types and for

convenience they are arranged inclasses according to their electricalcharacteristics. There are valves oflow impedance and others of highimpedance, all of which were designedfor special purposes.

Working ConditionsA particular valve for resistance

amplification might, for example,have an amplification factor of 20 andan anode impedance of 20,000 ohmswhen the high-tension voltage is Iooand the grid -bias is zero. Thisinformation about the valve is, ofcourse, of great importance, but oneshould not make the mistake ofthinking these values of amplifica-tion factor and impedance arenecessarily correct under all workingconditions.

Increased ImpedanceThus, one might employ a negative

grid bias of 1.5 volts and an anodevoltage of zoo. The impedance of thevalve would then be greater than20,000 ohms. Further, if the gridbias were increased to 3 volts nega-tive, the impedance would once againhave risen in value.

Similarly, a reduction in the actualvoltage on the anode would result inthe impedance being increased.

Now let us consider the curve ofFig. I, for I wish to explain theprinciples of resistance amplificationin a very few words. This curve is an

ordinary valve curve taken with ahigh-tension voltage of zoo and,because the resistance included in thebattery circuit is negligible, theanode voltage is also ioo for allvalues of current.

If, therefore, we vary the gridvoltage, Fig. 2A, we only succeed inchanging the anode current. Theanode voltage does not vary and, as aresult, there is no voltage amplifica-tion. In other words, if the gridcircuit of a further valve wereconnected to this first valve thesignal would not affect the secondvalve in any way.

Obviously, what we have to do isto connect in the anode circuit apiece of apparatus in order that avoltage may be set up across it whenthe grid voltage is varied, for then thesecond valve will receive in its gridcircuit a magnified voltage.

We must remember, however, thatthe anode current can also be varied

In this article W. James,our Research Consultant,explains several pointsabout the design ofresistance -capacity am-plifiers that will be newto a large number ofreaders. If your set isnot giving the qualityyou think it should, thisarticle will enable you

to put matters right.

471

PROPORTIONALREPRODUCTIONOF LOW NOTES

by altering the anode voltage. Infact, if the current is varied a certainamount by applying a small alter-nating voltage to the grid circuit, anequal current change will be pro-duced by including in the anodecircuit an alternating voltage of Mtimes the grid voltage. The quantityM is the amplification factor of thevalve.

Equal Anode CurrentsWe may, therefore, represent the

valve of Fig 2A as in Fig. 3, for thealternating anode current will beequal in both circuits, always remem-bering that the voltages must not beso great as to overload the valve.

Let us now connect a resistance inthe anode circuit of the valve as inFig. 4. This resistance is marked RIand there will be a certain fall involtage across it, with the result theanode current and anode voltage willbe reduced.

Effect of Bigger H.T.The impedance of the valve will,

therefore, have increased, but anincrease in the voltage of the high-tension battery will bring the anodecurrent back to its former value andalso the anode impedance of thevalve.

This circuit may be re -drawn as inFig. 4B, where R2 represents the anoderesistance of the valve and RI theresistance connected to the valve.

A small alternating voltage may beapplied to the grid as before, or,


Get Your Grid Leak and Condenser Right! (Continued)

A

-3 -1.5CRID BIAS

Fig. 1.-Ordinary valve curvevolts on anode

with 100

alternatively, an alternating voltageM times greater to the anode, for theresulting alternating current pro-duced will be equal in the twoinstances. But this current will setup an alternating voltage across theanode resistance. Its actual value involts will be numerically equal to theresistance connected in the anodecircuit in ohms multiplied by thealternating current in amperes. Thuswith a resistance of ro,000 ohms anda current of i/io milliampere, thevoltage will be io.

Amplification of Single StageIt we assume that the whole of the

alternating voltage set up across theanode resistance is passed to the gridof the next valve, the amplificationof a single stage is the ratio of thisanode voltage to the grid voltage orEz/Er, Fig. 5. It cannot exceed thevalue M, which is the amplificationfactor of the valve and will onlyapproach this value, because part ofthe alternating voltage is set upacross the valve itself.

This will be clear upon referring toFig. 4B and it is, in fact, easy to seefrom this diagram that the actualamplification is dependent upon theratio of the two resistances. If theyhave equal values, the amplificationwill be exactly one half of theamplification factor of the valve.

A Simple FormulaAs the external resistance is

increased in value and the hightension voltage corrected in order tomaintain the impedance of the valve,the amplification will increase. Thus,when the value of the resistance istwice that of the valve, two thirds ofthe amplification will be obtained.These points may be expressed in thefollowing simple form :-

RiAmplification =M x where

R2 +RI ;

M=Amplification factor of thevalve.

RI =Value of the resistanceconnected in the anode circuit;and

R2=Anode resistance of thevalve.

As an example, one might use inpractice a valve whose amplificationfactor is 20 for an anode impedanceof 2o,000 ohms (with zoo volts on theanode and zero grid -bias). Therefore,the impedance of the valve whenincluded in a circuit with grid -biasand an anode resistance wouldprobably be 30,000 ohms. A resis-tance of ioo,000 ohms would be

ALTERNATING CURRENT11i ANODE. CIRCUIT,

I

ALTERhAntg,

iMPUT

Fig. 2.-Effect of varying grid voltage

suitable for a valve of this type,resulting in an amplification of 15.

If a higher resistance were used, alittle more magnification would beobtained, but it is important toremember that for a given value ofhigh tension the impedance of the

0INPUTAC X M

0Fig. 3.-Another method of representin,

valve conditions

RE3I5TANCE EQUIVALENTTO VALVE IMPEDANCE.

valve will go up as the resistanceconnected to the valve is increased.

A grid condenser and leak c,R3(Fig. 5) are employed to pas's themagnified voltages to the grid of thenext valve and they have to be soproportioned that the signals are notunnecessarily weakened.

Now the impedance of a condenserincreases as the frequency of thecurrent is reduced, with the resultthere is a tendency for the lowernotes to be weakened. The essentialfactors are the resistance of the grid

472

leak, which is in parallel with the grid -filament part of the valve, and thecapacity of the condenser and whatwe have to determine is the relation-ship which exists between them.

We may start by fixing upon agrid leak whose resistance is severaltimes that of the anode resistance andthen determine the capacity of acondenser which will result in noteshaving a frequency of, say, 5o cycles,being passed to the extent of a givenpercentage of the middle frequencies.

Strength of 50 -cycle NoteWe may decide that a 50 -cycle note

shall have about 7o per cent. of themaximum possible strength, or if wedesire very good quality of repro-duction, the percentage may be 9o.

Having fixed these points, it is aneasy matter to estimate the capacityof suitable condensers. Let us assumea grid leak of 500,000 ohms to besuitable when the anode resistance is100,000 ohms. Then a condenser ofpractically .015 microfarad will haveto be used to give us 90 per cent of thefull amplification or one of .006microfarad for 7o per cent.

These grid condenser and leakresistance values may be varied inproportion, always remembering thatif the grid leak is increased in resis-tance, the capacity of the condensershould be proportionately reduced.

Thus, if we have decided to employa grid leak of 2 megohms we shouldhave had to use grid condensers ofone fourth of the above value ofcapacity.

Loud -speaker ResponseWhen an ordinary loud -speaker is

used the grid condenser and leak maybe so proportioned that a 50 -cyclenote has 7o per cent. of the strengthof the higher notes. No benefit wouldresult by providing for stronger lowtones, as in 'all probability the loud -

R

R

B

Fig. 4.-Resistance in anode circuit


A Special " Wireless Magazine " Article by W. Jamesspeaker would not respond and motor -boating would be more likely to occur.

We have assumed grid bias to beemployed with valve V2 (Fig. 5) inorder to prevent grid current. Over-loading must be avoided or distortion

Fig. 5 Application of grid bias

will be produced by the condenserbecoming charged and the effectiveresistance of the grid circuit becomingless than that of the grid leak takenby itself.

Low Anode ResistanceWhen the resistance -coupled stage

is connected to a large power valve, itis advisable to fit a wire -woundgrid leak of fairly low value, such asioo,000 ohms. A coupling condenserof approximately .07 microfaradwoukl then have to be used in orderto obtain 90 per cent. of the fullamplification at 5o cycles and, be-cause the amplifying valve is con-nected to the power valve, it will haveto be one of the type with a fairly lowimpedance. The valve will, in fact, beof the semi -power type and a fairlylow value of anode resistance will besuitable.

The coupling condenser must havea high value of insulation resistance.This is particularly important whenhigh resistances are used, as a leakagecurrent may materially alter the gridbias of the valve to which the gridleak is connected. Similarly, thevalve itself must be perfectly hard,that is, there must be no trace ofreverse grid current.

Stray and Self -CapacitiesIn this short article I have not

mentioned the effects of stray circuitcapacities and the self -capacity of theamplifying and power valves. Theyusually reduce the amplification ofthe higher frequencies, but providedthe values of the anode resistance

and grid leak are not too great, theeffect will not be serious.

The points I particularly wish toemphasise are, first, the amplificationis dependent upon the value of theresistance connected in the anodecircuit, the anode impedance of thevalve and its magnification factor;secondly, for a given proportion oflow notes the grid condenser musthave a certain size dependent uponthe resistance of the grid leak.

The condenser and grid leak inseries with the grid of the followingvalve connected to the junction of thecondenser and leak, is a combinationwhich tends to reduce the relativestrength of the low notes and it istherefore necessary that these twoparts be correctly chosen.

It is the best practice to employ agrid condenser which is much largerin proportion than any of thosementioned above. A condenser of.5 microfarad could, for example, beused with a grid leak of .5 megohm,in order to make certain that none ofthe low notes present at the begin-ning of the amplifier shall be lost. Acombination such as this has otheradvantages, but there is also thedisadvantage that complete anodecircuit filtering is essential.

AVIATIONCALL -SIGNS

Special notes on the article" When Air -liners Talk byRadio !" which was published

in the April issue.

THOSE readers who are interestedinreception of the inter -aerodrome

wireless -telegraphy messages on 1,400metres,dealt with in my articleentitled" When Air -Liners Talk by Radio !"(WIRELESS MAGAZINE, April, 1929),should note that since this articlewas written certain of the aerodromestation call -signs and aircraft mark-ings have had to be changed inaccordance with the new Radiotele-graph Regulations of the WashingtonConvention.

As regards nationality marks foraircraft, the letter M has been allo-cated to Great Britain in additionto G, while France will continue to useF, Italy I, and Japan J ; the UnitedStates have the choice of K, N, or W.

473

Nationality marks used by othercountries will in future comprise thefirst two letters of the call -sign, thenew marks for some of the nearerEuropean countries being as follows :

Belgium, ON, 00, OP, OQ, OR,OS, or OT;

Denmark, OU, OV, OX, OY, or OZ;Irish Free State, EI;Portugal, CS, CT, or CU ;Sweden, SA, SB, SC, SD, SE, SF,

SG, SH, SI, S J, SK, SL, or SM.

Marking on AircraftIn the case of the actual markings

on the aircraft, the hyphen separatingthe nationality marks from theregistration marks will, of course, beplaced after these first two letters.The hyphen is omitted in the wirelesscall -sign, which is otherwise identicalwith the lettering on the aircraft.

In the official table of the new air-craft markings, issued recently, thereis no mention of Holland or Germany,but I find from wireless messagesreceived that the Dutch 'planes arenow using call -signs commencing withPH, while the German ones areapparently retaining, for the presentat any rate, their old call -signs con-sisting of the letter D, followed bynumerals. Presumably the latterwill eventually be brought into linewith the five -letter call signs whichare the rule for aircraft of othercountries.

The alterations in the aerodromecall -signs are not very extensive,except in the case of Germany,where those of all civil aerodromestations have been altered so as tobegin with DD instead of AE.

Rotterdam's ChangeThe call -letters of the Rotterdam

aerodrome station (previously PCR)are now PHW, and evidently thischange was effected in order to avoidconfusion with PCR, Kootwijk, 'theshort-wave commercial transmitterwhich used to be known as PCRR,but has recently altered its call -signto a combination of three letters inconformity with the new regulations(one of which provides that landstations shall use threeLletter call -signs) by dropping the final R.

Probably the last letter in the newRotterdam call -sign was suggestedby the initial of Waalhaven; the placewhere the aerodrome for Rotterdamis actually located. ' W. OLIVER.


GwenLewis atthe piano

REVIEWEDBY

STUDIUS

AS the so-called "merry month ofMay" is supposed to be the fore-

runner to summer, a little lighter faremight well be hoped for in the musicalprogrammes. From an orchestralstandpoint, the only concerts of notehave been those given at the People'sPalace, Mile End, the concluding oneof the series given this week being oneof the best of the whole number, as most representativeof popular and, at the same time, classical music.

BROADCASTMUSICTIEMONTH

Two Items That Create EnthusiasmLiszt's " Hungarian Fantasia " and Du kas tone -

poem "L'Apprenti Sorcier" can always be relied uponto create enthusiasm, and the two conductors, SirLandon Ronald and Percy Pitt, were well representedby their own respective works, " Adonais" and " AnEnglish Rhapsody," the latter a trifle dull, but perhaps,therefore, thoroughly characteristic of its theme.

There is no doubt that these concerts, built on thesame lines as the other Queen's Hall Proms., un-doubtedly fill the same purpose, and it is a pity not togive a similar series even when the real Proms.commence in August.

Better Vaudeville ProgrammesThere has been a great increase in vaudeville broad-

cast activity and also, one is glad to note, an improve-ment in the material used, due largely to the fact thatexperienced and -known artistes are being utilised. One

Is always ready to welcome newcomers to any art,and no doubt the B.B.C. have made many interest-ing "discoveries"; but for general entertainmentpurposes one learns to rely upon trained artistesalready known to the great masses of the public.

Amongst the stars of the month may be con-sidered Albert Whelan, the Australian entertainer,and Percy Honri, one of the first players of theconcertina after "Dutch Daly" had introducedthis instrument to the "halls." Mr. Honri makeshis debut in broadcast, and on May 14 was asso-ciated with Julian Rose, Scott and Whaley, andMabel Marks.

Some Famous Vaudeville ArtistesJoe Hayman and his wife, Mildred Franklin, are

also amongst the famous vaudeville artistes. Mr.Hayman, known all over America, was one of thefirst to give us the comic "Cohen on the Telephone"

sketches over here. Norman Long, anotherearly broadcast star, Jack Morrison, Claphamand Dwyer, and " Stainless Stephen " are allreal wireless stars.

EdwardNichol,

tenor

" The Radio -activities "Mabel Coristanduros has formed,

in addition to her broadcast work, alittle company called "The Radio -

activities," and apparentlyfrom their seaside reports

have done very well. Themembers include Olive

Groves, Harold Kim-berley, Claude Chand-ler, and a fine violinist,Peggy Cochrane, heardearly over the ether,and known throughoutthe country not only

:JulietteMcLean,soprano

for her concert solos, butthe fine Vocalion records,and just recently in theirBroadcast series a gem ofplaying in Mendelssohn'sConcerto.

Some of the radio re-vues also have proved '

successful, one ofthe latest being

(Continued onpage 476)

474

AlexLeitch


The ever popular 66K unit

The Blue Spot Chassiscarries the Unit

Build up your own cone speaker using thefamous Blue Spot 66K unit. To make a conespeaker equal to any you have yet heard be-comes simplicity itself if you follow the instruc-tions given with every Blue Spot unit-and youwill be delighted with the reproduction of anyand every programme.

Here is the Blue Spot Metal Chassis, completewith cone in position ready for affixing theunit-simplicity itself-and takes five minutesto assemble.

Blue Spot 66K 4 -pole balanced arma-ture unit : (adjustable), Price 25/- To bolt the chassis to a baffle board, which

your dealer can supply cut to size, or toBlue Spot Metal Chassis (complete a cabinet of your own choice completes anwith cone), . . Price 12/6 inexpensive speaker giving results little short

of amazing.

F. A. HUGHES & CO., LIMITED, 204-6 Great Portland Street, LONDON, W.iDistributors for Northern England, Scotland and North Wales: H. C. RAWSON (SHEFFIELD & LONDON) LIMITED,

too LONDON ROAD SHEFFIELD; 185 PRINCESS STREET, MANCHESTER.

Speedy replies result from mentioning " Wireless Magazine"

475

1


Broadcast Music of the Month (Continued from page 474)

A Year in An Hour,written by Ernest Long -staff, with a cast thatincluded the names ofJack Morrison, AnonaWinn, and Harry Pepperand Doris Arnold.

Excerpts from musicalcomedies also are alwayswell liked, and still morethe occasions when awhole play is broadcast.Owing to copyrightrestrictions, and theseare not always easy toovercome, The IslandPrincess announced forMay r r, promised ex-cellent fare ; also a special5GB programme which reversed themusical order of things by " Jazzingthe Classics," first turning classicalnumbers into modern syncopation,and then the modern type of danceafter the style of old masters. Idealartists were found in the persons ofToni Farrell, Jean Harley, and GeorgeBarker with the Birmingham StudioOrchestra.

King of InstrumentsAt one time restricted only to

church uses, or occasional wheezingson old American organs and har-moniums in stray families, of late, the

organ has become once more the" king of instruments." Withexamples set by the big cinemaorganists, such as Pattman, andEdward O'Henry (at Tussaud's),

the gramophone records, suchas the Broadcast withBerkely Mason, and now

an increase inwireless relays,

the instru-ment revealsits value.

This monthfrom 5GBhas seen aseries ofweeklyorganrecitalsThe DorisTrio-EnidLewis (piano),Kathleen

Washbourne(violin) andPaulineTaylor

('cello)

relayed from St.Michael, Coventry, nowknown as CoventryCathedral, and given byDr. Harold Rhodes, atone time assistant toSir Walter Parratt atSt. George's Chapel,

Morava, violinist

Windsor. Several organists also ofinternational fame have beenheard, including Joseph Bonnet,known on the Continent and inAmerica and Canada, also GuntherR.amin, organist of St. ThomasChurch, Leipzig. Playing with LiccoAmar, the violinist, a special relaywas made from the BishopsgateInstitute on May 15.

Experience proves that the smaller

476

stringed orchestras and quartetsbroadcast better than when largeorchestras are employed, especially inthe studios. Certainly the month hasheard some very pleasant work ofboth types from the restaurant.orchestras, such as those of AlbertSandler and Moschetto, and the smallclassical bodies, such as the J. H.Squire Celeste Octette, the GershomParkington Quintet, the Olof Sextet,the Spencer Dyke Quartet, and TheDorian Trio and Gladys Noon Trio,and the Intime Trio which consists ofthree famous artists, Suzanne deLivet, Cecil Bonvalot, and CedricSharpe.

Famous Individual SoloistsThe individual soloists, too, have

included world-famous stars, AlbertSammons, Beatrice Harrison andArnold Trowell amongst them, whilefavourite broadcasters, too, are NorrisStanley, Frank Cantell, KathleenMoorhouse, and Edith Lake.

England's so-called "nationalinstrument," the piano, has hadmany good exponents. One of thefinest for all broadcast purposes is Mr.Victor Hely Hutchinson; the art ofbroadcasting is not given to allartistes, though it would be hard toconvince them that their broadcastresults are not always on a par with


The CoburnSisters

GlynEastman .

THE CHANNEL Tuivoitt

40

SiZ4cto.ok DARIO VALVES,

10 You

VALVESA better Valve at a lower Price-Darioare the only valves at half -price which are

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Wireless Magazine. June, /9291

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477


Broadcast Music of the Month (Continued from page 476)

their concert platform interpreta-tions. It is here where Mr. Hutchin-son scores.

Amongst the classical pianistsnoted are Gordon Bryan, Borowsky,whose recital took place recently,Edward Isaacs and Howard Jones,while on the lighter. side we haveBilly Mayerl and Patricia Ross -borough, whose excellent Duophonerecords have also just been issued.

Some Fine Voices HeardVocalists attract by sheer force of

numbers, and although in some fewcases diction leaves room for improve-ment, we still hear "gel" for girland " loove " for the tender passion,still some fine voices have been heard,quite apart from the stars of the opera.such as Miriam Licette, DenisNoble, Noel Eadie or Heddle Nash.

One can always rely upon artistessuch as Megan Foster, Vera Gilman,

Dorothy Kitchen, the Coburn Sisters,and Olive Kavann to give artisticinterpretations and good choice ofwork. Unique interest, too, was lentalso to a recent Belfast concert ofRussian music, when Morava, abrilliant young singer, was heard in

REMEMBER THAT Y 0 UCAN GET A FULL - SIZEBLUEPRINT OF ANY SETCONSTRUCTIONALLYDESCRIBED IN THIS ISSUE.CAN BE OBTAINED FORHALF-PRICE IF THE COU-PON ON PAGE III OF THE

COVER IS USED.

Russian folk songs. He gave Russiangypsy songs and songs of theUkraine.

Much time, almost one might sayover -much time, has been spared fordramatic performances, and onecannot entirely commend the choice

of August Strindberg's gloomy workThere Are Crimes and Crimes forthe ninth of the B.B.C.'s great plays.

A Barrie PlayWe understand that Sir James

Barrie has given permission for hisplay The Old Lady Shows HerMedals, to be included among thespecial play broadcasts to Scottishschools, early in the summer term,The broadcast will be given by theArdrossan and Saltcoat Players, whowon the Scottish Community Festivalwith this work.

Those who remember the playKaleidoscope, given last September,which depicted in novel form thewhole life of an ordinary man, will beinterested possibly in the performanceon May 31 of a feminine Kaleidscope,in which the author will deal with awoman's life, employing similarmethods.

Fight Between BigU.S.A. Radio

CompaniesTNSISTENT has been the rumour1 of a merger between the RadioCorporation of America and theWestern Union Telegraph Company.Presidents of both companies haveadmitted " conversations," but deniedmerger plans.

Recently it became apparent thatat least one current merger denialwas supported by facts. AbruptlyR.C.A. threw down the gauntlet tothe Western Union and announcedthe birth of Radio Corporation ofAmerica Communications, Inc., tocompete directly with United Statestelegraph companies.

Two Giants in the FieldIt is generally known Western

Union and Postal Telegraph (Inter-national Telephone and Telegraphsubsidiary) are the two giants in thefield. Mr. Newcomb Carlton, as

President of the super -giant, WesternUnion, took up R.C.A.'s challenge.

Unimpressed by the wireless threathe snapped : " The Radio Corporationhas nothing we now wish to use, andif we ever need anything they have,we can get it from other sources. For

the time being, at least, we will viewthe disposal of the Radio Corporationas an interesting scientific develop-ment"-

If war there,is to be, the telegraphcompanies now appear to have thewhip hand. R.C.A. radio circuitsterminate at New York on the EastCoast and San Francisco on the WestCoast, devoid of any stations in thewhole interior. Not only, can ittransmit no domestic messages, butall messages from the interior forradio transmission abroad must berelayed to the coast over WesternUnion wires.

Tentative and temporary areR.C.A.'s " agreements " with thesecompanies ; therefore, to escape thisbondage, R.C.A. Communications hasapplied to the Federal Radio Com-mission for 66 wavelengths to beused in domestic service. It will meanextending to 31 inland centres radioservice by R.C.A. Communications.

Two radio rivals to the newborncompany have already appeared.Earliest of all in the field wasUniversal Wireless CommunicationsCo., of Buffalo, which obtained lastyear from the Federal Radio Com-mission a generous helping of wave-lengths.

Postal Telegraph itself is the otherrival; it has also applied to the Com-mission for domestic wavelengths.

F. P.

478

Keeping BatteriesGood

IndefinitelyHOW radio set owners in the

Arctic maintain their batteriesis described by George Wendt, whoarranged special KDKA broadcaststo the Arctic and Antarctic, asfollows :

" In the first place, all radio setsin the Far North are operated fromdry cells, both H.T. and L.T., asthere is no possible means wherebythey can charge storage batteries.In the early days it was found thatthe shelf life of the dry batterieswas too short to last throughout theseason.

Thawing Out!" Experimenting for a season or

.two showed them that by freezingthe dry batteries they would remainindefinitely inoperative, and so thispractice has been universally adoptedthroughout the Far North. Whenthey are ready to use batteries theybring them into winter quarters andgradually have them thawed out.

"This practice is common through-out the Far North and has been usedsuccessfully for several years."

B.T.

Wireless Magazine June, 1929

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479

;,333 SCR


Linking 200 Local Stationsby a New System

ANEW process of broadcasting byshort - wave synchronisation,

after two years of laboratory work,is being exploited by the ContinentalBroadcasting Corporation of NewYork.

Linking 200 Local StationsAccording to Mr. P. M. Titus, vice-

president of the company, the plan isto link 200 local broadcasting stationson a single channel by means of anew process of short-wave synchron-isation-by the employment of twoshort waves of 7,000 kilocycles and7,90o kilocycles, which differ infrequency to create a broadcastingfrequency falling about goo kilocyclesor within the broadcast band.

By local modulation of the wavesat each station on the chain, the high -

frequency waves emanating from thetwo proposed super -power key stationswould be picked up by the scores ofsmall stations on the channel andamplified to sufficient signal strengthto service the particular community.

There would be no programmesbroadcast from the two 50,000 -wattkey stations; these stations wouldmerely " manufacture " the carrierwave, and the local stationq on thechannel would amplify this wave andbroadcast their programmes in syn-chronism.

Commissioner Caldwell of theFederal Radio Commission is infavour of granting licences for twoshort-wave stations at Fredericks-burg, Va., and one each for broad-casting stations at Richmond andAlexandria, Virginia.

Method in Their Madness !The Union of Married Wireless Enthusiasts

MHE average wireless enthusiastI is a most unmethodical fellow.

He keeps his coils in the knife -drawer,his valves are carefully wrapped incotton wool, and placed in the bestmantelpiece vases, terminals lurkbehind the clock, odd wire and oddgear mysteriously appear in the tea-pot, and-but ask his wife !

My New UnionSo I propose the Union of Married

Wireless Enthusiasts. It shall havea central head office, which will bestaffed by experts in forms-ex-income tax collectors, if possible.They shall be responsible for visitingmembers' houses and inspecting thedisposal of apparatus. A prize of,say, a moving -coil loud -speaker, com-plete with illuminated certificate ofmerit, shall be presented each monthto the member who stows his gear tothe approval of a committee of mar-ried women.

Fines for CarelessnessMembers who are found to be care-

less with such precious components asvalves or accumulators shall befined 5, or a month's N.E. (no ex-

perimenting). Habitual offendersshall be debarred, for one year, fromconstructing a new set.

Each member will be required tocomplete a monthly return, in tri-plicate, somewhat on the followinglines :

1. How many spare valves haveyou? (Burnt -outs must be included).

2. Where are they?3. Describe the location of your

set, batteries, loud -speaker and sparecoils.

4. Where are your screws, terminalsand wire ?

5. What apparatus have you dis-covered about the house during themonth? (Your official wireless denis exempted.)

6. What gear have you missedlately ?

And a large space for remarks.Questions 2, 4 and 5 will, of course,

be answered by the members' wives,who, also of course, are responsiblefor enrolling their husbands.

The annual subscription will be-but excuse me a moment, one of myhousehold has just discovered a valveof mine in the coal scuttle.

W. M. G.

480

RADIO NOT1 TO BLAME

ENGLAND is not to be excludedfrom the regions of the earth

that have been visited by an unusualamount of rainfall in the last sixyears. These have been particularlywet, some of the heaviest and mostpersistent rains occurring during thesummer months.

If there are still some who believethat radio is responsible, the RoyalMeteorological Office comes forthwith final facts and figures settlingthis point for ever.Some Statistics

Figures produced in this reportshow that although rainfall has beenhigh from 1921 to 1927, it was stillhigher in the period from 1911 to192o, when radio was much less inuse, and considerably higher from1871 to 188o, when practicallynothing was known of radio waves.

" It is true," the report asserts,"that electrical phenomena are oftenassociated with rain, and that insome experiments artificial cloudshave been formed by electrical means,but the electric discharges in theseexperiments are of an entirely differ-

wireless."The meteorologists point out there

should be more rain around broad-casting stations, where radio wavesare concentrated, than elsewhere-if radio has anything to do with rain-fall. The facts, however, show other-wise.

No Worse Near Transmitters"The heavy rainfall of the past

few years," the report states, "hasnot been in any way more remarkablenear the great wireless stations than inother parts of the country, but thatradio, becoming so prominent at thesame time, has anything to do withthis rainfall is absurd." F. P.

A DIFFERENCE OF A FEWYEARS

MIMES have certainly changed-five years ago a wireless amateur

would say to one of his colleagues :"Your new wireless receiver is very

fine, old man, it sounds almost as goodas a gramophone."

To -day that same wireless enthusiastwould remark to his friend :

"That new gramophone of yours isreally excellent-it reproduces musicand the voice almost as well as yourradio set I "

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Musical Back-ground theBroadcast

t.eBroadcast Play

THE average broadcast playlAbours under many disadvant-

ages, most of which are obvious tolisteners. The players have to dependon their voices entirely for effect,there is no scenery or action, so"incidental music" is introduced inorder to assist " atmosphere " as faras possible.

How dull and drear a moviepicture seems if there is no music,no matter how exciting the plot, howspeedy the action ; every picture storyis better told on the screen if it has asuitable and effective musical back-ground. This background and accom-paniment must needs be efficient andsuitable, however, or its object islost entirely.

In a First-class CinemaJust lately we witnessed a picture

which had for its subject the downfallof Tsardom and Bourgeoisie; this wasshown in a first-class cinema in alarge provincial town.

The customary orchestra was of atleast twelve performers, but when wewere present the music was beingsupplied by a lady pianistwho thump-ed and rattled the 1812 Overture ofTschaikowsky for nearly two hourson end.

Words are not invented whichcould possibly express the tiresome-ness which this constant repetitioncaused to the ear; the thing wasnothing short of ridiculous and utterlyruined what was, after all, not a badpicture.

Unsuitable MusicIt is not for a moment suggested

that the B.B.C. have ever carriedmatters to such an extreme as this,but not once, but on several occasionswe have listened to a broadcast playwherein the "incidental music" wasquite unsuitable for the spoken play.

It is obvious, especially to a trainedmusician, that some of the musicarranged for broadcast plays has beentreated in the manner of an after-math instead of a thing of importance,and a considerable step-up will bemade when more attention is givento the musical background of plays.



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" Wireless Magazine" when corresponding with advertisers

481


The 1929 Chummy (Continued from page 4161

REACTION SCREENING ANODE -TUNING ANODE AERIAL -TUNINGCONDENSER BOX CONDENSER COIL CONDENSER

WOODENSUB -PANEL

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This view of the 1929 Chummy clearly shows the arrangement of all the parts

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END OF SHORTWAVE COILGOING TO SWITCH

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482

MUSIC AND THEBROADCAST PLAY

(Continued from preceding page)

If we consider for a moment thetremendous number of operas whichhave been written, serious and light,the amazing thing is that so very fewhave retained their hold on the public.If we analyse why this should be so,we will find that in practically everycase of the survivals music and librettoare absolutely wedded to one another.

Gilbert and SullivanIt seems, in fact, as if one could

not exist without the other, theGilbert and Sullivan Operas beinggood examples of this.

Music can suggest every possiblehuman emotion; it can also providea fitting prelude to any train ofevents which may occur, and it cansupply a suitable accompaniment towhat is being spoken.

The music accompanying a broad-cast play need not necessarily be" descriptive "; we do not wish togo back to Victorian days with theBattle March of Delhi and Battleof Prague style of descriptive piecesin which the poor piano was supposedto give faithful imitations of horsesgalloping, guns firing, moans of thedying, etc., etc., ad nauseam.

Closer Study of the TextBut there appears to be no reason

why a closer study should not bemade of the text of a play, and thenhave appropriate music selectedwhich should not only accompanybut also "suggest" what follows inthe play.

Even if this does not bring per-fection, it will at least assist andremove what is often unnecessaryand inartistic. Doc PAGE.

A number of readers have recentlyassumed that the information couponwhich always appears on page iii ofthe cover can be sent instead of afee of Is. when questions are beingasked.

This is not so, however, and allquestions sent to the WIRELESSMAGAZINE Technical Staff must beaccompanied by a postal order foris. (a purely nominal fee to checkthe tendency to' frivolous querieswhich results from a free service),a stamped addressed envelope, andthe special information coupon (thelast to ensure that only bona fidereaders shall make use of the service).

Described in this issue.

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When you have read the sixty -odd articlesin this issue give a thought to your pal. Poorfellow ; what he has missed if he has neverseen the Wireless Magazine" !

Of course, you do not want to part withyour own copy-no ccWireless Magazine"reader ever does-but why not let us send leads thehim a free specimen ? YOU know how he way inwill appreciate it: radio !

" The Best Shillia!sworth in Radio"Tells You Every Month All You Wantt© Know About Recent Pro teas inRadio Des? n-Look Out for the Next,.

Issue on June 26 !% FILL IN THIS COUPON NOW l'or

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Put this coupon in an unsealed envelope bearingid. stamp

Mention of the " Wireless Magazine" will ensure prompt attentio7

483

Wireless Magazine, June, 1929]

rr HAT an interval signal is a useful itemA is proved by the fact that although the

Italian authorities were not in favour of it,they are now carrying out experiments at twoof their stations. At present-temporarily, Ibelieve-Naples transmits the morse symbolE (one dot) and Milan a T (one dash) atintervals of seven seconds.

It was at first thought that the initials of thecity or thecall letters of the station could be

Radio utilisedfor Communist

propaganda

LEAVES FROM A

LISTENERS LOGRecorded Vijay Cooter

used, but later it was decided that the simpler form ofsignal would be more effective, and in view of its not toorapid reiteration, less wearisome to local listeners. If theidea meets with general approval, an individual signalwill be given to the other Italian studios.

Copenhagen's Low -note BuzzBy the way, Munich is not the only city which now

uses a hooter preceding the call; I find that Copenhageninvariably gives out a low -note buzz at the opening of itsbroadcast. Moreover, when the entertainment finishesearlier than the hour at which the time signal is relayedfrom the Civic Hall Tower; namely, midnight B.S.T.,you will hear three short hoots, and the carrier wave isswitched off without any further announcement.

Just as virtue has its own reward, so patience shouldbe allotted a con. pensating prize-and I claim it. Forsome weeks I have gone all out for the Finnish high -power station so unfortunately placed in close proximityin the long -wave band to Eiffel Tower.

When I Caught Eiffel Tower BendingRegularly every evening, for more nights than I care to

record, I have endeavoured to disentangle these twotransmissions, and as luck would have it, a day or so ago,by a mere fluke I caught FL bending. The Paris trans-mitter had moved down slightly, and a turn of the frameaerial gave me on three nights excellent reception ofthe Helsingfors concerts.

The difference in frequency was not great, I admit,and I had all my work cut out to avoid the Frenchman,but the directional properties of a small frame aerial

overcame the difficulty and from thisrelatively clear broadcast I gleaned alot of information.

The male announcer gives out thecall, at regular intervals, sometimesat full length, at others in an ab-breviated form : "Huomio I Huomio !Suomen Yleis Radio Lahti Helsinki."The first word repeated twice issynonymous to the German" A chtung !" or the French "A llo "

Calling in SwedishNow, on Tuesdays and Fridays,

the broadcasts are made in Swedish(on Tuesdays through Helsingforsonly), and on these days the call is inthat language, namely : "Giv akt !

Giv akt Finlands Rundradio Lahti Helsingfors." As arule, you will find that the station closes down at anearly hour; it is seldom that it is on the air later than9.3o p.m. B.S.T., although on some ope'a nights thetransmission may be extended.

Daily at 8.45 p.m. a news bulletin is broadcast in boththe Finnish and Swedish languages; they are not muchalike, and your reception of the latter might lead you tobelieve that you had picked up a Scandinavian, but listenfor the call; it will put you right.

The signals from Lahti are powerful, and but for thefact that unless you possess a very selective set, FL willinterfere with you. I do not doubt that they would bereceived in the United Kingdom as easily as the broad-casts from Motala. Bear in mind, however, that theEiffel Tower, for the present, closes down at 9 p.m. andmay thus, on certain nights, give you the long -wished -foropportunity of reaching out to Finland.

More stations to log I Have you picked up the call"Radio Beograd," put out by the new Belgrade (Jugo-Slavia) transmitter? Although not a giant, its power isabout equal to that of 2LO. When it can be disentangledfrom its neighbours, in the region of 45o metres, it can beheard fairly well in the British Isles towards the laterpart of the evening. Try for this station towards i i p.m.B.S.T., when almost daily it comes on the air with a jazzband or a popular orchestral concert.

In view of the fact that but few foreigners can under-stand the Serb or Slav languages, announcements are

(Continued on next page

484

Wireless Magazine, June,. 1929

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LEAVES FROM A LISTENER'SLOG (Continued from preceding page)

made in French, Italian, and Magyar ,at times during the evening, you willalso hear an English and German call.

A New 12-KilowatterOn another wavelength, namely

277.8 metres, in the immediatevicinity of Milan, you are sure to pickup the words Radio Feriby. This, youmay care to know, is the cry of thenew 1f2-kilowatter recently installedin the neighbourhood of Bratislava(Czecho-Slovakia). Here, again, tofacilitate identification, details of theitems broadcast are given out in somefive to six languages.

Neither of these two new stationshas adopted, up to the present, aninterval signal, but the announce-ments and calls are put out sofrequently that they should leave nodoubt in your mind regarding thenature of your capture.

Budapest on the Loud -speakerBy the way, a short stay I made

recently at a popular South Coastresort gave me nightly opportunitiesof receiving the Budapest pro-grammes at full loud -speaker volume.One fact I noticed among others wasthat in every instance French wasused as an alternative language toMagyar ; in fact, several political talkswere presented in that language. Themusical programmes from Budapeston most nights are very good, and,believe me, when the studio takesyou over to the Cafe Spolich or to the


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485


Leaves From a Listener's Log (Continued)

Hotel Britannia for the gypsy bands,the broadcast is so interesting thatyou will find some difficulty indragging yourself from the receiver.These transmissions frequently lastuntil well after midnight.

Not the Title of a Film!The Battle of the Giants ! No, this is

not the title of a film, but a forecastof the near future as it affects thebroadcasting world.

Look at the list of big transmittersalready in existence, under construc-tion, or proposed by many EuropeanStates. What do we find ? Moscow,Motala, 5XX, Zeesen, and EiffelTower working daily. According to aGerman repert, the authoritiesseriously contemplate increasing thepower of Zeesen to 200 kilowatts;Eiffel Tower, still on 15 kilowatts, isto be boosted up to zoo kilowatts.To this we must add the early advent

' of Oslo with 6o kilowatts in the aerialand Bucharest with 24 kilowatts(actual). Sweden, not to be outdoneby Norway, has also placed an orderfor the supply of a super -powerstation.

Italian 50-kilowatterWhen Turin was officially opened,

it was definitely stated that thestation would eventually become oneof the most powerful on the Continent,

yet Rome has laid down plans for theerection of a 50-kilowatter

Turn to Poland, where the PolskieRadio has decided to install in theneighbourhood of Warsaw a " super "

Old readers of the "WirelessMagazine" will remember wellthe enthusiastic reception thatwas given by listeners every-where to the Chummy Four,which was described exactly ayear ago. It was then the firstportable set with a screened -grid high -frequency stage to beoffered to the home construc-tor and its popularity was littleshort of amazing.

This year we have persuadedW. James to re -design thisfamous portable, using as faras possible the same materials,so that those already possessingthe old type of receiver canreadily convert it to the1929 model.

The great points about thenew design are that the set willreceive on both wavelengthbands and the high-tensioncurrent consumption is ma-terially lower.

Tell your friends about the1929 Chummy. which is fullydescribed in this issue.

capable of putting 50 kilowatts inthe aerial, or to Czecho-Slovakia,which has stated its intention toproceed with the construction atPrague of a station normally workingon an equal power.

Again from France comes thenews that the P.T.T. authorities, as acounterblast to Stuttgart and Frei-burg, which at present are the trans-missions best heard in Alsace-Lor-raine, has formulated a scheme for theerection of a big station at Strasbourg,and to this we add Switzerland, whichfavours a proposal to build twosemi -giants at Gros de Vaud andSuhrental with a small net -work ofrelays.

Re -equipment for High PowerAll such probable additions to the

medium- and long -wave band areover and above the re -equipment atincreased power of such cities as Graz,Goeteborg, Hoerby, Bratislava,Brussels, and the shortly to beexpected newcomers such as Mahrisch-Ostrau (Czecho-Slovakia) and otherstations coveted by more recentadherents to broadcasting systems.

Disarmament !Visualise all these giants on the air

at the same time, during the day andevening; such a struggle forsupremacy may lead to possibilitiesunforeseen. We have heard so muchabout the Disarmament of thePowers that I am seriously wonderingwhether in a more or less distantfuture we may not read of con-ferences relating to the Disarmamentof the Super -Powers '

Radio Helps the Indian Air Service !THE wireless organisation for the

air mail service to India, whichwas recently opened, is such that theaircraft engaged will be in touch withaerodrome ground stations throughoutthe 4,700 air miles of the journey.

On the London to Basle section,the present wireless organisation forContinental aviation will be employed.The aircraft are fitted with Marconisets of 15o watts power (type AD6),adapted for communication overdistances of 200 to 30o miles by tele-phony or morse.

Three Flying BoatsFrom Basle the night train to

Genoa makes the connection withthe second section of the air route,from Genoa to Alexandria, operated

by three Calcutta flying boatsfitted with the more powerful Marconitype AD8 sets.

These sets are also adaptable fortelephony or morse, enabling thepilot to keep in touch with Italianand British Air Ministry wirelessstations until arrival at Alexandria.

In addition Imperial Airways, Ltd.,which is conducting the London -Karachi service, has stationed a depotship in the Greek Archipelago. Thishas been fitted with a Marconi valvetransmitter of %-kilowatt power(type U) and suitable receivingequipment (Marconi type RG19Receiver), and will be capable ofcommunicating with Malta, Alexan-dria, and other stations concernedwith the service.

486

At Alexandria a change is made toaeroplane again for the final sectionof the route, through Basrah andover the Persian Gulf to Karachi.Part of this section has been inoperation for some time, employingDe-Havilland aircraft fitted withMarconi AD6 apparatus and com-municating with R.A.F. stations anda 1/2 -kilowatt station at RutbahWells.

Two Marconi StationsDuring the flight from Basrah to

Karachi, the machines will be intouch with two Marconi stations inPersia, at Chabar and Bunda Abbas.The terminal wireless station atKarachi is one of the most powerfulaerodrome stations.

Summer TimeFROM Sunday, April 21, Great

Britain, France, Belgium, andSpain, which habitually use Green-wich Mean Time, advanced theirclocks sixty minutes, thus bringingthe hour forward to correspond withthe time adopted by the. CentralEuropean States.

The Continent is roughly dividedinto three belts, different in time bysixty minutes for each fifteen degreesof longitude, East or West of Green-wich; and this indicates local meantime for the zone extending sevenand a half degrees on each tide of themeridian, but in practice, the beltmay be extended to cover theboundaries of states or provinces.Thus, actual local time of a city ortown may vary by several minutesfrom the standard time adopted bythe country in which it is situated.

Central European TimeCentral or Mid -European Time

covers such countries as Germany,Austria, Hungary, Czecho-Slovakia,Denmark, Italy, Jugo-Slavia, Lithu-ania, Luxembourg (Grand Duchy),Norway, and Sweden. Finland,Greece, Poland, Roumania, Esthonia,Western Russia, Latvia, and Turkeywork on Eastern European Time, orone hour in advance of B.S.T. WinterTime is standard throughout, andno summer change is effected.

Holland, normally twenty minutesin advance of us during the G.M.T.period, becomes forty minutes behindus when our Summer Time reigns;later, usually in May, she alters herclocks, in the same manner by sixtyminutes, and again remains twentyminutes ahead of us.

No Alteration in MoroccoIt will be found that the trans-

missions of both the Algiers andRabat (Morocco) stations do notcoincide in time with ours, for thatportion of North Africa is comprisedin the G.M.T. belt, and no alterationis made.

On the other hand Russia advancedher clocks by one hour on March 31last, so with our alteration there stillremains between the United King-dom and that country (e.g. Moscowand Leningrad), inasmuch as it affectsthe Soviet broadcasting stations, adifference of two hours.

As already stated, no alteration iscan ied out in Central Europe.


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Only £10 10 0 Complete'Phis set comprises screened -grid valve, de-tector and two transformer coupled stages,and is complete with Valves, Batteries, Loud-speaker and handsome solid oak cabinetwith protecting lid. One dial control only.Components for all sets described in this issue in stock.

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'Wireless Magazine. une. 1929

ANEW SETTESTEDBy J. H. REYNER, B.Sc., A.M.I.E.E., at the Furzehill Laboratories

ThePhilipsAll -ElectricTwo-valver

IN the early days of broadcasting,the use of A.C. mains for elimina-

ting the high-tension battery wasregarded as an experiment, since itoften brought in its wake suchtroubles as unpleasant hum anddistortion in the amplifier. Yet, inspite of these disadvantages, theeconomy of the system was such thatit was utilised by many experimenters.

Practical DevelopmentAs the science of wireless progressed

so was the H.T. eliminator perfected,until it has proved itself, without adoubt, to be the most economical andreliable form of H.T. supply. Not,however, until comparativelyrecently has the all -mains receiverdeveloped from the experimental tothe practical stage.

A Wonder BoxAny doubt on the subject of all

mains -operated receivers must surelybe conipletely dispelled by a demon-stration of the new Philips two -valveset. One might imagine that a two -valve receiver including an H.T.,L.T., and grid -bias eliminator wouldbe a rather bulky article, but thislittle Philips set has overall dimen-sions of only jo in. by 7 in. by 614 in.,and is certainly what one might terma wonder box. Yet, in spite of itscompact dimensions, our examinationrevealed that many up-to-date con-trivances and refinements are fitted.

The entire receiver is housedin a metal case, one end ofwhich may be removed forinspection of the valves, ofwhich there are three-adetector, a pentode, and arectifier for the H.T. supply.

The controls are placed on apanel at the other end of theset. In the centre of the panelthere are a number of sockets,into one pair of which a plugis fitted. This varies a seriescapacity in the aerial circuit,which enables the selectivityto be adjusted to suit localconditions.

The top right-hand knobgives a slow-motion control fora drum -drive variable con-

denser, the scale of which can beinspected through a window on thetop of the set. Smoothness ofoperation is ensured by a spring -loaded pulley working in a slot of thedrum control.In thecentre of thepanel we havethe reactioncontrol, whichagain ispleasant tooperate on allwavelengthsand, more-.over, requiresonly slightalterationwhen tuningfrom one endof the scale tothe other-avery usefulfeature.

At the topleft-hand sideof the panelthere is arange switchhaving three positions, one for theshort waves from 200 metres, anotherfor the medium wavelengths, and thethird for the high wavelengths up to2,000 metres. No other adjustment isnecessary when changing from onewavelength range to another.

A plug and socket for loud -speaker,

This view of thePhilips two-valvershows the back ofthe set with thecover removed forinspecting the

valves

488

a second one for inserting a gramo-phone pick-up, and aerial -earthterminals are placed at the other endof the set beneath the valve panel.Thus there is no necessity for theexternal leads to be visible whencontrolling the set.

Its Performance on TestIt was with no little interest that

we placed the set on test. Aftercpnnecting up the aerial, earth, andloud -speaker, the plug was insertedin the 24o -volt 50 -cycle A.C. Mains :a brief time elapsed and then the setburst into life-not as one might haveexpected with the usual 50 -cycle hum,but just the pleasant breathing noisewhich comes from an accur_ulator-operated set.

Adjustment of the range switch andalteration of the aerial tappingbrought in the local station atsurprising volume and clarity.Adequate strength could be obtained

with ease onuch stations

as 2L0 at 12miles, 5GBand 5XX at70 miles.

AboveNormal

The results,both as re -g.,. rds strengthand clarity,are certainlybetter thancan be ob-tained witha normal two -valve set,because in thefirst place themains -oper-ated detectorvalve is moreefficient than

the normal type and, secondly, apentode output valve is employedwith adequate H.T. potential.

On foreign stations, the set behavedin an exemplary manner : due to thesmoothness and constancy of reactionone could tune -in quite a number of


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A NEW SET TESTED(Continued from preceding page)

stations without so much as movingany control other than the tuningcondenser. Naturally, with a set ofthis type, the strength from distantstations is not very powerful but, atthe same time, a number may beobtained comfortably without over-doing the reaction adjustment.

Quite Shock -proof.

We have alxeady remarked uponthe good quality reproduction obtain-able from the set : this is no doubtdue to the care taken to eliminateany tendency for back -coupling tooccur in the high-tension, grid -bias,and loud -speaker leads. Anotherpoint worthy of mention is the markedabsence of hum, even when receivingdistant stations. Finally, one mayobserve that both aerial and loud-speaker are completely isolated fromthe mains and are, therefore, shock-proof.

At a price of L I 2 los., this two -valve receiver represents excellentvalue and can be recommendedwithout hesitation. The makers arePhilips Lamps, Ltd., x45 CharingCross Road, W.C.2.

Readers of the "Wireless Magazine"who would like to see test reports ofany particular commercial receiversare invited to communicate with us.Every effort will be made to meet. . their needs in these pages. . .

Junit Valve HolderTHE popularity of four- and five -

electrode valves has increased to alarge extent during the past year, andit has therefore been necessary to adaptthem for use with the normal valveholder, although this latter componentis not always most convenient for thesetypes of valve.

A valve holder made by the Junit Manu-facturing Co. has been designed speciallyfor use with the new four- and five -electrode valves. It may be mountedeither in a horizontal or vertical position,and will therefore hold a screened -gridvalve in the correct plane for screening.

An additional terminal is fitted to theholder and serves as a junction for aflexible lead to the extra terminal onthe pentode and a rigid connection toH.T. positive.

The four sockets of the holder aremounted on a small square mouldingand the connections are taken out tofour terminals at the corners. Holesare drilled in the moulding for mountingthe holder in two separate planes. Thecomponent, which is well finished, shouldprove useful to set builders.

489


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Short-waveChannels

THE agreement between theUnited States and Canada for the

division of short-wave radio channelson the North American continent,which recently went into effect for aterm of three years, is as follows :

For mobile services, 190 channels ;to amateurs, 124; for experimentalvisual broadcasting, 84 ; for generalexperiments, 3 ; for general com-munication services, 228; making atotal of 639 short waves.

Division by CountriesThe appointment by committees is

as follows : The United States, 112exclusive channels and 34 shared withCanada and Newfoundland; Canada,38 exclusive channels and 48 sharedwith other countries, principallyMexico and Cuba; Newfoundland, 11channels shared with the UnitedStates; Cuba, 15 channels shared withCanada, and 5 for exclusive long-distance communication; othernations, including Mexico, 16 channelsshared with Canada, and 8 exclusivefrequencies. F. P.

Nippy'sLoud -speakers

ALTHOUGH it is a sorry fact thatloud -speakers should have to

utter such mundane things as "twosausages and mash," or "steak andkidney pudding," it is neverthelesstrue.

It came as somewhat of a surpriseto me to learn that J. Lyons & Co.,Ltd., have installed loud -speakers inmany of the kitchens of their biggerrestaurants, and- these are used as aroom -to -room communicator in orderto keep the kitchen organisation intouch with consumers.

250,000 People DailyThe same kind of apparatus is

employed as in some of the dailypaper machine rooms and the necess-ity for loud -speakers in, say, a CornerHouse, will be understood when it isrealized that in the famous CoventryStreet Corner House alone a quarterof a million people are daily servedwith food and drink.

Were it not for theloud-speakers bymeans of which waiters and waitresses

can order dishes just when they arewanted, many iced and other colddishes would be ruined were theybrought out of the ice safes into thegreat heat of the kitchens beforeabsolutely necessary.

The mechanism employed in theloud -speaker devices is very similarto that encountered in everydaywireless practice. F. Tup.

WirelessEchoes

AT the Academy of Science atOslo, recently, Professor

Stoermer lectured on the muchdiscussed echo phenomena in con-nection with short-wave signals fromthe wireless station at Eindhoven,Holland, which were observed lastOctober. A close watch was kept fromNorway to Spit zbergen, but nofurther echoes were heard until thelatter part of February, when they

I TELL YOUR FRIENDSABOUT

THE 1929 CHUMMYwere heard in Norway, England, andEindhoven.

The time between the dispatch of asignal and the echo varied from eightto twenty-five seconds, and it is nowtaken for granted that whatever theexplanation may be the phenomenonis genuine and not imaginary.

F. P.

DynamicReproducers

FOR the present, at least, theAmerican home -constructor finds

great difficulties in building loud-speakers of the moving -coil type; ifhe desires to construct them, he cando so only by obtaining a completeset of iron castings specially made toorder, and the demand for suchcastings is not yet sufficiently heavyfor manufacturers to produce themas a stock line.

For this reason, the enthusiasticexperimenter in the United States iseither forced to obtain the completekit for building the moving -coilloud -speaker from Europe, or mustbuy a finished model at a muchhigher cost.

490

While on the subject of moving -coil loud -speakers, according to anAmerican wireless journal, the correctdefinition for that type of instrumentas adopted by the American RadioManufacturers' Association is asfollows :-

"A dynamic loud -speaker is one inwhich a portion of the conductorcarrying the alternating signal cur-rent is a part of the moving system,the force producing the motion beingdue to the location of this conductorin a magnetic field."

It seems to me that it would bevery useful if the British Manu-facturers' Association were to issue ahandbook giving definitions of everywireless component. G111 DDA .

Multi -diaphragmLoud -speakers

NOT content with attempting toget the low notes with the aid of

" super " large diaphragms, the inven-tive genii are turning their attentiontowards loud -speakers which cover awider frequency range than normalby the use of more than one dia-phragm connected to the driving unitof the reed or moving -coil type.

A Dozen DiaphragmsOne multi -diaphragm loud -speaker

recently patented incorporates abouta dozen diaphragms of differing sizes,the whole bonded together in a kindof umbrella -shaped diaphragm unit,with the apexes of each one taken tothe driving rod of the reedmechanism.

The idea, of course, is that thesmaller diaphragms respond morereadily to the high notes, while thebass is "kicked out" by the largerdiscs. A similar effect is the result ofthe joining together of the two sheetsof a linen -diaphragm instrument, butit is a little difficult to see whatadvantage is gained by taking thingsto extremes and having a batch ofdiaphragms all connected to onedriving unit.

Secret of SuccessFor experimenters who want to

carry out tests of multi -diaphragmhome-made jobs it need only behinted that success usually lies in thedirection of having as small a movingmass as possible between the drivingunit and the driven member. S.

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The !lactic No. 6Indicator and Slow- 111.1.Motion Dial makest suing a real -pleasure. Accurate,quick and smooth.No backlash.

319HARLIE BROS. (Dept. X), BALHAM RD., LOWER EDMONTON, N.9

Telephone: Tottenham 3446


" THE

SERVICE

THIS

EVENING "One night it is the preacher. Another nightit may be the Premier. Yet another nightand it is just the programme. But all's oneto the Exide Battery. Whatever the listenersare listening for, the Exide Battery pays it outin full volume and unfluctuating flow. And ifyou instal the Exide Battery in your ownset - you will be following the highestwireless authorities and making sure of

the best results.

EXIDE L. T. BATTERYType CZ4. 4o amp. hrs.Single Cell, 2 volts 13/6In crate 19-There is a size in the famous " C"series of Exide Batteries to suit

every set.

x i eTHE LONG LIFE BATTERY

Note the prices of Exide Trickle Chargers:For H.T.-£3 : 7 : 6. For H.T. & L.T.-£5 : 0 : 0.

Obtainable from Exide Service Agents and all reputable dealers.

EXIDE BATTERIES, CLIFTON JUNCTION, NR. MANCHESTER'London Sales and Service Derot: 215-2.9 Shaftesbury Avenue W.C.2

When replying to advertisements please mention " Wireless Magazine"

491

G90


Two more newLOTUS

ComponentsA new Lotus Transformer-new Lotus Druni Dials-addthese to the next set you make,and note the efficiency their

high Lotus quality gives.

Lotus Transformer: This is aL.F. Inter -valve transformer sowound and with the primary andsecondary coils so placed in relationto each other that self -capacity isreduced to a minimum. 12/6

Lotus Drum Dials: Made withtypical Lotus care and finish, theseDrum Dials are designed, of course,for use with Lotus LogarithmicCondensers, but they may be usedwith any type of variable condenser.

Prices :Lotus Drum Dial, fitted with

two '0005 Condensers ... 29/6Lotus Single Drum Dial, fitted

with one 0005 Condenser 14/9Lotus Dual Drum Dial, with-

out Condensers ... 18/ -Lotus Single Drum Dial,

without Condensers ... 9/- 0005 Condenser 5/9 00035 Condenser 5/7'0003 Condenser 5/6'00025 Condenser 5/3.00055 Condenser ... ... 4/9

iLL)111U1SCOApoNLSIs

Made by Garnett, Whiteley & Co., Ltd.,Lotus Works, Liverpool

'Wireless MagazineREFERENCE SHEETS

Compiled by J. H. REYNER, B.Sc., A.M.I.E.E.

Month by month these sheets can be cut outand filed-either in a loose-leaf folder or oncards-for reference. The sequence of filing is

a matter for personal choice. In a short timethe amateur will be able to compile for himselfa valuable reference book.

WIRELESS MAGAZINE Reference Sheet

Power RectificationTypical valve character-istic with indication of

operating conditions

MAXIMUMSIGNAL VOLTAfE

MOBULATLEIPORTION OF

VOLTAIQE.

FOR effective distortionless rectification amodified form of anode -bend rectification

may be employed. This method, however,makes use of the straight portion of the valvecharacteristic and should not, strictly speaking,be known as anode -bend rectification.

The method is based on the fact that modern

vo 126

telephony transmitters do not utilise a highdegree of modulation, some 3o per cent. to5o per cent. being the limit for all ordinarypurposes. This gives a factor of safety on suddenincreases of signal strength which would other-wise tend to produce blasting. This being thecase, the high -frequency carrier received doesnot vary in intensity below from 0.7 to 0.5 of themaximum value.

The method of rectification employedconsists in utilising a valve having a relativelylarge straight portion to its characteristic, suchas a power valve of a suitable type. This isbiased to such an extent that approximatelyone-half of the characteristic is curved, theremaining half being straight.

If signal voltages are applied to the valvebiased in this comlition, the maximum portionsof the signal will lie between the zero point andthe beginning of the curved portion. Thus, allthe variations produced by the modulation willlie on the straight portion of the curve andsubstantial linear rectification will result.

In order to arrange for this form of rectifica-tion it is necessary to choose the value of gridbias somewhat critically. Too little grid biasdoes not give rectification and too much gridbias does not give sufficient straight portion tothe curve.


Choke Output Circuits, Current InT T is sometimes of value to know the approxi-

mate alternating current likely to pass in thechoke of a choke -coupled output circuit. Theeffective inductance of a choke or transformerdepends essentially upon the alternating currentflowing in addition to the polarising effectproduced by any steady current which is passing.(See Sheet Not .)

Tests were therefore made at the WIRELESSMAGAZINE Laboratories in order to determinethe approximate order of alternating currentlikely to be flowing in a choke -output circuit.For this purpose, an alternating -current meterwas arranged in such a position that it wouldindicate the alternating current flowing in thecircuit without being affected by the directcurrent. This steady current was of the orderof 15 milliamperes, a super -power valve pre-ceding the choke -output stage.

Voltages of varying frequency were appliedto the input of the amplifier and the signalstrength was adjusted to give what was con-sidered a good loud -speaker strength in anaverage -sized room. The voltage on the inputof the amplifier was then kept constant at thisvalue irrespective of the frequency. Thecharacteristic of the amplifier had already beenpre -determined and it was known that therewas little. variation in the amplification over thewhole range of frequencies.

No. 127

The test indicated that the current in thechoke -output circuit varied in accordance withthe frequency of the current, tending to increasein value as the frequency was reduced. Thisis whit one would expect, since the effectiveimpedance of the choke decreases as thefrequency falls so that more current would bepassed through the choke by the alternatingvoltages existing in the circuit. The table belowgives the approximate order of current obtainedas a result of these tests.

It must he remembered that these tests aremore an indication than a definite measurement,since they only apply to one particular set ofconditions. The inductance of the choke inquestion was zo henries and the valve precedingit was a Mazda P227.

Frequency(cycles/ sec)

AlternatingCurrent in Choke

(milliamps)

0.57,6210.52

256 0.46512 0.39,024 0.33

2,098 0.274,096 0.21

492


Amateur WirelessHAND OOKS

each 216 net

Of all Newsagents and Booksellers, or 2/9 post free fromCassell and Company Limited, La Belle Sauvage, E.C.4.

The Shielded Four -electrode ValveTHEORY AND PRACTICE

By Capt. H. J. ROUND, M.C.Capt. Round is one of the greatest authorities in the worldon radio science and practice, and his book is a completeguide to the principles under which this latest and mostremarkable valve should be operated.

Loud -speaker Crystal SetsHow to Make and Manage ThemProvides working instructions for building a number of highlyefficient crystal sets; making an attachment for simple con-nection to existing wireless set; and designs for crystal setsembodying the crystal loud -speaker system.

Wireless -controlled MechanismFor AmateursBy Raymond PhillipsThis book is an illustrated practical guide to the making andusing of short-range wireless control apparatus, and it hasbeen written so simply that it can be understood by anyenthusiast possessing an elementary knowledge of wireless.

The Practical " Super -het " BookExplains what the super -het is, what it does, how it works, andhow to build up a number of super -het sets made of testedBritish -made components.

Perfect Broadcast ReceptionBy Ernest H. Robinson (5YM)Explains how most sets fall short of the ideal and how toobtain perfect reception. Is virtually a popular exposition ofthe main problems of transmission and reception. Veryvaluable alike to listeners and experimenters.

The Short-wave HandbookBy Ernest H. Robinson (5YM)Describes in very simple language the wireless apparatus usedin short-wave work, shows how to make it and how to use it,and explains the technical principles with which the beginnerwill need to become acquainted.

The Practical Wireless Data BookThe intelligent novice, and particularly the home constructorand the keen wireless amateur who is always rigging updifferent circuits and experimenting for progress, will find thisData Book extremely helpful.

The Wireless Man's WorkshopBy R. W. Hallows, M.A.Written by a practical home constructor, this book-con-taining much useful wireless information-enlightens readerson the selection and right methods of using the tools andmaterials used in constructing wireless sets.

The Book of the NeutrodyneBy J. H. Reyner, B.Sc. (Hons.), A.M.I.E.E.

CONTENTS : Why Neutralising is Necessary; Systems of Neutralising; Difficulties Encounteredin Neutralised Circuits; How to obtain Good Selectivity Without Loss of Quality; Design of

High -frequency Transformers ; Lay -out in Neutralised Receivers ; Some Suitable Circuits.

Price 1/6 net, or post free for 1/9.

A Useful Series for Wireless Amateurs

Casselltr=11:53gr321:161:3MaBelleSauvage,

493

Books


Build the 1929 Chummy Fouras described in this issue. £

1 Cabinet, with baseboard, frame aerial, andloud -speaker fittings as specified .. 2 0

.. .1 Ebonite panel, 16 in. by 8 in., ready

127

2 Slow motion dials (Brownie) . 72 Formo variable condensers, .00051 Formo variable condenser, .00035 .. 62 Dubilier fixed condensers, 1 mfd. 51 Dubilier fixed condenser, 2 mfd. 34 Anti -phonic valve holders .. 51 Ever -Ready U.W.1 Cell, 19 volts 01 Wearite H.F. choke .. .. . 61 Wearite 2 -pole 2 -way barrel switch .. 51 Grid leak, 2 megohm .. 11 Fixed condenser, .0002 .. 11 Fixed condenser, .002 .. 11 Anode coil, with support .. .. 101 Resistance, 10,000 ohms (Graham Parish) 21 Resistance, 20,000 ohms (Graham Farish) 21 Cossor L.F. transformer .. .. .. 1 11 Marconiphone R.C.C. unit .. .. 81 Pair panel brackets . .. .. .. 21 Blue Spot Speaker unit, type 66K .. 1 52 Ever -Ready 66 -volt H.T. batteries .. 1 51 Ever -Ready 9 -volt grid -bias battery .. 21 Pair battery clips .. .. ..2 C.A.V. 2 -volt accumulators, type 2.N.8.0 1 41 Piece cone paper, 8 in. square .. ..1 Piece ornamental cloth .. .. 1

18 Spring wander plugs (8 black and 8 red).. 84 Spade tags (2 rod and 2 black) ..1 Copper screening box, as specified ... 6

10 Indicating tabs, as described .. ..Connecting wire and sundries .. .. 2 1

1 Small knob4 cm. 58 D.S.C. frame aerial wire .. .. 2

012 8

s. d.

Set of Valves for above 02 113Any parte supplied separately as required.The 1929 CHUMMY FOUR PORTABLE, ready wiredand tested, including Cabinet, Valves, and Royalty,218 0 O.The following supplied ready wired and tested or partsseparately The Short-wave Link, The Music Player,The Continental Two, and all apparatus describedIn "Wireless Magazine" and other radio journals.Lists free on application, including particulars ofMagnum Portable Receivers and Universal Three(15 metres to 2,000 metres).

OMNORA LTD. Home Cons. ructionSpecialists.

258 NEW CROSS ROAD, LONDON, S.E.14.Phone : New Cross 1273.

tukdi Inc 4.>124-1/

Even as

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a/Ptoztot-"CLAROSTATS" are " specified "in all the modern circuits. WHY?


Litz Wire, Use ofT ITZENDRAHT wire, usually termed Litz,

is a high -frequency cable specially designedto minimise high -frequency resistance. Thewire, instead of being solid, is constructed of anumber of strands, all of which are insulated onefrom the other and each of which in turn comesto the surface of the cable.

If a wire is employed which is solid over thewhole of its area, the currents are forcedtowards the outside of the wire by the magneticfield existing in the wire itself due to thepresence of the high -frequency currents. If thecable is made up of a number of strands allinsulated one from the other, however, this isnot possible so that the whole of the copper inthe wire is effective in carrying current.

Litzendraht wire is made by twisting thinstrands of insulated wire into cables consistingof groups of three. Thus, for example, a nine -strand cable would not be made up of ninewires stranded in the ordinary manner. Threewires would first be stranded to form a triplecable and the nine -strand cable would be madeby taking three three -strand cables and braidingthem up together. Similarly by taking threenine -strand cables, we obtain a twenty-sevenstrand cable, this being the largest size used forordinary winding purposes. .

No. 128

For special requirements, more elaboratecables still have been used consisting of threetwenty -seven -strand cables stranded together,and so on, but a limit is reached where the lossin the actual dielectric formed by the insulationon the wire begins to overcome the slight gaincaused by a further sub -division of the wire intostrands and it is only in exceptional circum-stances that such extremely multiple cables areemployed.

The purpose of building the wire up intogroups of three in this manner is to ensure thateach strand in turn comes to the outside of thecable. With ordinary methods of strandingcertain wires lie in the centre of the cable thewhole time and are thus no better than a solidcore. It is necessary to ensure, therefore, thatany wire used as Litz is really stranded in thismanner and is not just a number of twistedwires. In particular, it is absolutely essentialthat each individual strand of the wire should beseparately insulated in addition to any overallcovering on the cable if any benefit is to result.

The table given in Sheet No. 129 indicatesthe general types of Litz wire in use for wirelesspurposes and the approximate correspondinggauges of solid wire to give equal copper area(equal D.C. resistance), and . equal overalldiameter.


Litz Wire, Sizes

IT is often useful to be able toestimate rapidly the approximate

gauge of Litz wire required to wind aparticular coil within given dimensions.The table given here indicates thevarious classes of Litz wire commonlyemployed for wireless work and thecorresponding gauge of solid wirehaving the same D.C. resistance.

The third column indicates theapproximate equivalent gauge of D.S.C.wire, assuming the Litz to be of thetype in which each strand is enamelledand the whole cable is double -silkcovered.

No. 129

of

Size ofLitz Wire

9/3627/36

9/3827/38

9/4927/409/42

27/429/44

27/44

Equivalentgauge of

wire to givesame D.C.resistance

EquivalentD.S.C. toenamelled

and D.S.C.Litz

23 21

19 17

26 23

21 19

28 25

23 2030 2725 22

34 31

27 24

WIRELESS MAGAZINE Reference Sheet No. 130

Pick-up ControlTT is necessary to fit some form of volume

control with a gramophone pick-up in orderto adjust the strength to one's own require-ments. Different records give varying strengthsof signal and it is necessary to have some formof control over the volume of sound produced.

It is further desirable to control the input tothe amplifier rather than the output, as toostrong an input will cause overloading on thevalves with consequent distortion.

One method is to place a volume controlacross the pick-up itself. In the early days thiswas made a simple variable resistance, but it isnow recognised as preferable to utilise a high -resistance potentiometer. This should have avalue of about soo,000 ohms and should beconnected up as shown at A.

A method which is rapidly gaining favour,however, is to use a valve in the first stage of theamplifier which Gan handle the maximumvoltage delivered by the pick-up without anytendency to distortion and to control the volumebeyond this valve. The advantage of thisscheme is that it is easier to obtain a volumecontrol in this manner which does not alter thefrequency / esponse.

The method shown at A, even under the bestconditions, tends to cut off the high frequent ie3as the volume is reduced. If the pick-up is

applied directly across the grid of the first valve,then any of the well-known methods of volumecontrol may be used with the coupling devicefollowing the first valve.

One very useful method, shown at B, is that ofconnecting a variable resistance across theprimary of the transformer. As this resistanceis reduced in value so the amplification isprogressively reduced and this method has theadvantage that instead of cutting off the highfrequencies, it tends to accentuate them, whichin many instances is a desirable feature since themajority of pick-ups cut off towards the upperend of the scale.

Tees hiethOdS of pick-up control

494

WirelessMagazine, June, 19291 .4 FULL-SIZE BLUEPRINTSFOR EVERY REQUIREMENT

Each blueprint shows the position of each component and every wire and makes construction a simplematter. Copies of " Wireless Magazine" and of " Amateur Wireless " containing descriptions ofall these sets can be obtained at I s. 3d. and 4d. respectively, post free. Index letters "A.W." refer

to "Amateur Wireless" sets and "W.M." to "Wireless Magazine" sets.CRYSTAL SETS The Q3 (D, RC, Trans)

WSEVEN-VALVE SETS

Lodestone Three (HF, D, Trans) :: WMM124I29All these 6d. each, post free. Simple Screen Three (HF. D, Trans) WM 131 ls. 6d., post free.

. . ..Two -programme Set .. .. .. WM2,5 Dynamic Three (SG, D, Trans) .. WM136 Simpladyne (Super -het) WM22Centre -tap Set .. .. .. .. WM5o At Home Three (D, 2RC) .. .. WM141 PORTABLE SETSSuper Set AW 64 *Short Wave Link (D, RC, Trans) .. WM142.

" Best -yet" Set .. .. .. .. AW114 Split -primary (HF, D, Springtime a (D, Trans) , , . , WMIF:111'7-:1929 Crystal Receiver . .. .. AW165 Modern Tuned -anode (HF, D, Trans) AW 38 Countryside 4 (HF, D, 2 Trans) .. WM17 r/6

A Daventry-Local Crystal. Set .. .. AW185 Tetrode 3 (HF, D, Trans) . .. AW 36 Chummy 4 (HF, D, RC, Trans) .. WM8o r/6Special (D, 2LF) Chummy 4 (with modification forONE -VALVE SETS Economy 3 (D, 2RC) .. .. AW 48 LS and HT) .. .. .. WM8oa 1/6Short-wave (D, RC, Trans) .. .. AW 50 Pilgrim Portable (D, Trans) .. WM94 if -

All these Is. each, post free. Ether -searcher (D, RC, Trans) .. AW 52 Wayfarer Portable (Super -het) .. WMI39 116Long-range Hartley .. .. .. WM54 Standard (D, 2 Trans) ... ... AW 56 *1929 Chummy (SG, D, Trans, RC) W111145Reflexed One for the Loud -speaker WM66 Hartley DX (D, RC, Trans) .., ,... AW 63 Holiday 3 (D, 2 Trans) .. .. AW32 11 -Special One . WM116 Broadcast 3 (D, RC, Trans) ... ... AW 76 Table Grand 4 (HF, D, 2RC) .. AW93 i/6Reinartz One .. .. WM i 27 Selectus 3 (HF, D, Trans)

AWAW 8841 Attach6 Portable 2 (HF, D) .. AW96 I/ -All -wave Reinartz .. AW 2 Q -coil 3 (D, RC, Trans)Daventry Portable (D, Trans) .. AWro5 x/-Hartley DX .,..

27British Station Three (HF, D, Trans) .. AWIzz Daventry Loud -speaker Portable

Economy One .. eAW

71 Optional Two -three (D, 2LF) .. .. AW124 (2HF, D, RC, Trans) .. AWro7 1/6Loud -speaker Special .. .... AW 78 "Simpler Wireless" Mains Three (D,2LF) AW126 Town and Country (HF, D, RC,

.Ultra -sensitive Hartley One .. AWr o3 Simplicity Screen -grid Three (HF, Trans) AWIll 1/6Fan's Short-wave One .. . AW119 D, Trans) .. .. .. .. AW132 House and Garden (SG, HF, D,

.. .. ve

Super Reinartz One .. AW12.7 "Proms" Three (D, 2 RC) .. .. AW137 RC, Trans)Beginner's One-valver . , . AW14.0 Adaptable Three (D, 2 Trans) .. AWI39 " Best -yet " Portable

.. AVVI t 6 t/6

New -style Baffle Three .(D, RC,. Push-. (SG, D, 2 Trans) AW136 1/6TWO -VALVE SETS pull-Pricer/6) House Portable (SG, D, RC, Trans) AW168 1/6All -wave Mains Three ((HF, D, Trans, Arcadian Portable (SG, D. z Trans)Al! these Is. each, post free. Rectifier-Price 1/6) .. .. .. with Linen -diaphragm Loud -

Two -programme 2 (D, Trans) .. .. WM56 All-purpose Short-wave )Three (D, RC, speaker (half -scale) .. .. AW177 1/6Q -coil 2 (D, Trans) .. .. .. WM62 £5 5 o Portable (D, Trans) .. AW181 i/-Crusader (D, Trans) .. .. .. WM69 Screen -grid Q -Coil Three (HF, D, Talisman Portable (SG, D, 2 Trans) AWIS4 r/6Aat-dweller's 2 (HF, D) .. .. WM76 AW1 soTwo-Daventry Two (D, Trans) WM97 New -style Mains Three (HF, D, Trans- AMPLIFIERSTetrode Short-wave Two (SG, D) . WM99 Price 1/6) .. .. .. .. AW151Key -to -the -Ether Two (D, de) Vwrs,IV,Ii4413057 All -Round Three (D, RC, Trans) .. AW155 All these ls. each, post freeMeteor Two (D, Trans) 14 James Special Three (HF, D, Trans) .. AW156 Super -power Unit (2 v.) WM1o3Clipper Two (D, Trans) All Britain Three (HF, D, Trans) .. AW158 Signal Booster (HF Unit) .. Wt8Twinflex (Reflex) .. .. .. WM138 Bantam Three (D, RC, Trans) .. .. AW 16o Auditrol Amplifier ..

wmMi;2*Continental Two (D, Trans)AW 37 .

.. WM143 Hartley Dual -range Three (D, RC, Trans) AW166 One -valve DX Unit ..Utility (RC, Trans) ..

Rover 2 (HF, D) AW 53 Listener's Three (HF, D, Trans) Price W68General-purpose z (D, Trans) .. AW 55 4d. free with copy of "A.W." .. AW169 Screened -grid HF Unit ....AWYule (D, 'Trans) AW 59 Binowave Three (D. RC, Trans) .. A W i7z One -valve LF Unit .. AW 7930/- 2 (D, 'Trans) a AW 61 Clarion Three (SG, D, Trans) .. .. AW175 Super -power Push-pull .. AW 8Economical 2 (D, RC) .. .. AW 66 1929 Favourite Three (D.,R.C. Trans) AW179 Hook -on Short -waver .. AWto46Two-wave (D, 'Trans) .. .. AW 83 Purity Amplifier..

AAWW1I778Ultra -selective Hartley (D, Trans) AW 90 FOUR -VALVE Add-on Distance -getter . Oceanic Short-wave (D, Trans) AW 91 Screened -grid HF Amplifier .. .. AW138'Trapped Reinartz (D, Trans) .. AW 92 All these Is. 6d. each, post free. " A.W." Gramophone Amplifier (3RC) AW r62"Q" 2 (D, Trans) AW 99 Revelation (HF, D, RC, Trans) Searcher Unit (H -F.) .. .. .. AW176Simplicity (HF, D, 2 Trans) .. WM49Long Distance Two (HF, D,) ..

AAAWWWi31°24

Gramo-Radio 4 (D, RC, a Trans Push-WM7o

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A.C. Mains Eliminator .. .. WM4 tScreened grid 4 (H.F, D, CRC) .. .. WM77 I/ -Ace of Twos (D, Pentode) .. .. AWI43 Five -pounder Four (HF, D, RC, Trans) WM91 Portable Cone Loud -speaker .. WM73 1/-Home Two (D, 'Trans)rans) .. .. .. AW14.6 Frame -aerial Four (HF, D, 2RC) .. WM85 "Junior" Moving -coil Loud -speaker WM8t 1)-Chapman-Reinartz Two (D, Trans -4d. Universal Short-wave Adapter .. WM8z 1/ -Touchstone (HF, D, RC, Trans) .. WM logwith copy of "A -W.") .. .. AW148 Linen -diaphragm Loud -speaker .. WM90 //-Reyner's Furzehill Four (SG, D, 2Globe DX Two (SG, D,) 'I'rans) .. . .. .. .. WM1 la Valveless A.C. Power Unit for L.T. WM too -6East to West Short-wave Two (6, Trans) AW159 Valveless A.C. Power Unit for H.T. WM lox -/6Economy Screen -grid Four (SG, D, RC, .. WMIxt z/ -Beginner's 'Fwo (D. Trans) ,. .. AW i 71 Simple Cone.. .. AW i 74 Trans)

. .. WWItax -/6Auto Two (D. Trans) Buzzer WavemeterAll -Main Two (D, Trans) .. .. AW18o Binowave Four (SG, D, RC, Trans) .. WMii 9

Standard -coil Four (HF, D, 2RC) .. WMI22 James H.T. Unit for A.C. Mains WMI25 I/-.. WM126 1/-THREE -VALVE SETSLodestone Loud -speakerDominions Four (zSG, D, Trans) . WMI34

The Drum Major (HF, D, RC, Trans). WM137 James H. T. Unit for D.C. Mains W.V1 x 33 If.*Music Player (HF, D, RC, Trans) WM144 *Short -Wave Adaptor for

All these I s. each, post free. All-purpose 4 (HF, D, RC, 'Frans) .. AW 43 Dominions Five W111140 1/-Five -guinea 3 (HF, D, Trans) .. .. WM29 Special 4 (HF, D, zLF) .. . AW 7o Heterodyne Wavemeter .. .. AW 7 4 -Metropolitan (D, 2 LF) WM48 "Q" 4 (HF, D. RC) . .. . AW 98 Rectifying Unit for " Simpler Wire -Everyday (D, 2 Trans) .. .. .. WM52 Explorer Four (HF, D, RC, Trans) .. AW120 less" Sets AW 62 IF

I -IMusic Charmer (D, RC, Trans) .. WM6o Summertime Searcher (2F, D, Trans) AW r 28 Adapter for Short-wave Super 6 AW 67a -/6Britannia (D, RC, Trans) .. .. WM67 Overseas Short -waver (HF, D, 2 Trans) AW 133 H.T. from A.C. Mains .. .. AW 73 1/ -Pole -to -Pole Short -waver (D, RC, Trans) WM89 Ranger Four (SG, D, RC, Trans) .. AW14.5 H.T. Eliminator for A.C. (zoo v.Glee -singer Three (D, 2 RC) .. .. WM9z Facility Four (HF, D, 2 RC-Q-coil) .. AW r54 output) .. .. .. .. A. 2 1/--Aladdin Three (HF D, LF) .. .. WM95 Broadcast Picture Four (HF, D, 211C).. AW163 L.T. and H.T. Mains Unit (DC) AW 123Inceptor Three (SG, D, Pentode) Price The Orchestra Four (D, RC, Push-pull) AW167 Knife-edge Wavetrap .. .. AW 131 -/6

IS. 3d. with copy of "W.M." . . WM los All Europe Four (2HF, D, Trans) .. AWi73 All -metal Eliminator for HT. .. AW t35 1/-All -wave Screened -grid Three (HF, D, Stability Four (HF, D, RC, Trans) .. AW182 Duplex -diaphragm Loud -speaker AW 142 If -

Pentode) .. WMito Power -plus Loud -speaker .. .. AW149 1/-.

Gramophone Three (D, 2RC) .. .. WM1 r5 FIVE -VALVE SETS Linen -diaphragm Loud -speakerwith Baffle .. .. -Standard Coil Three (HF, D, Trans) .. WM117 All these Is. 6d. each, post free.Festival Three (D, 2 LF-Dual Imp) .. WMii8 Exhibition 5 (21 -IF, D, RC, 'Frans) .. WM33 Pedestal Cone Loud -speaker .. AWL 64 1/ -

Wide -world Short -waver (SG, D, Trans) WMizo Listener's Speaker, price 4d. withPhoenix (zI-IF, D, 2LF) WM42New Year Three (SG, D, Pentode) .. WM123 1928 Five (21 -IF, D, 2 Trans) .. .. WM46 copy of "A.W."All -the -world 5 (2HF, D, 2RC) .. WM63 Arcadian Linen -diaphragm Loud -Cataract 5 (HF, D, RC, Push-pull) ..

..WM79 speaker (full-size) . .. AW177 1/-

D.0 Unit (KTA blueprint of any one set described Empire Five (2SG, D, RC, Trans) WM96 AW 178

in the current issue of the "Wireless Fidelity Five (HF, D, 2RC-parallel) .. WMI3o Short-wave Adaptor (IV.).. .. AW183 1/-

Magazine" can be obtained for half- Individual 5 (2HF, D, 2 Trans) .. AW 25School 5 (HF, D, 2RC) .. .. AW 85 Send, preferably, a postal order

price up to the date indicated on the "Q"Gang-control Five (2HF, D, 2 Trans) AWi6i ( stamps over sixpence in valuecoupon (which is always to be found SIX -VALVE SETS unacceptable) toon page iii of the cover) if this is sentwhen application is made. These I s. 6d. each, post free.

Nomad (2HF, D, RC. Push -Pull, 'Trans) W31 ; Wireless Magazineblueprints are marked with an asterisk Connoisseur's Six (2HF, D, RC, Push-pull)(*) in the above list and are printed in WI \ 88

bold type. An extension of time will beEagleSixHF, D, RC, Trans) .. WM106Short-wave(3 Super -6 (Super -het, Iiiv76677A

Blueprint Dept., 58161made in the case of overseas readers Adapter for above (see miscell Fetter Lane - E.C.4t*,+44

4N5


,

"Wireless Magazine" Buyers' Guideand Classified Index to Advertisers

Month PageBATTERIES

Chloride Electrical StorageCo., Ltd. ... June 491

Edwards, Rowland, & Co.,Ltd. ... May

Ever Ready Co. (G.B.),Ltd. JuneLesingham, F. L. ... MayLissen, Ltd. ... ... JuneMorris, J. R. ... ... AprilOldham & Sons, Ltd. ... AprilSiemens Bros. & Co., Ltd. MayTudor Accumulator Co.,

Ltd. ... ... MayVandervell, C. A., & Co.,

Ltd. ... June 405

CABINETS

Carrington ManufacturingCo., Ltd. ... ... May

Caxton Wood Turnery Co. AprilDay, Will, Ltd. ... MayEdwards, F. W.... ... May 381

Hobbies, Ltd. ... MayPickett Bros. ... ... June

397407

369

410

303271

310

377

383

295

391

397

Month PageCONDENSERS (Fixed)

Dubilier Condenser(1925), Ltd. ...

Telegraph Condenser

Co.... May

Co.,... June

COMPONENTS

379

479

Bulgin, A. F., & Co. ... June 487Day, Will, Ltd. ... ... June 485Formo Co. ... June 404

Garnett, Whiteley & Co.,Ltd. ... ... June 492

Wright & Weaire, Ltd.... June 405

DIALS

Cason Mouldings...

EBONITE

... June 491

American Hard RubberCo., Ltd. ... ... May 392

British Ebonite Co., Ltd. May 397

Potter, H. B., & Co., Ltd. June 491

Month PageMAINS -SUPPLY EQUIPMENT

Clarke, H., & Co. (MICR),Ltd. ... ... May

Philips Lamps, Ltd. ... MayRegent Radio Supply Co. JuneWestinghouse Brake and

Saxby Signal Co., Ltd.... June

PORTABLES

Bedford Electrical & Ra-dio Co., Ltd. ... ... May

Dunham, C. S. .. ... MayEdison Bell, Ltd. ... MayHart Collins, Ltd. ... MayLever, Eric J. (Trix), Ltd. MayMcMichael, L., Ltd. ... MayPeto-Scott Co., Ltd. MayRolls Caydon Sales Co.... May

RESISTANCES

Igranic Electric Co., Ltd. MayLyons, Claude, Ltd. ... June

Paroussi, E.

SCREENS

. . June

SOLDERING FLUX

399389407

485

391400385381395306383313

369494

491

489

397

CHOKES

London Electric Wire Co.and Smiths, Ltd. ... April

Partridge & Mee, Ltd. ... June

COILS

209

481

British General Manufac-turing Co. ... ... June 493

Cason Mouldings ... April 303

London Electric Wire Co.and Smiths, Ltd. ... June

Cover ivRothermel Corporation,

Ltd. ... ... MayStone Manufacturing Co. April 285

Simmonds Bros. ... April 299

Turner & Co. ... ... MayWright & Weaire, Ltd. May

GRAMOPHONE EQUIPMENT

Alestrian Gramophone Co. May 375

British Thomson -HoustonCo., Ltd. ... June 403

London Electrical Co. ... May 307

Peto-Scott Co., Ltd. ... MayCover ii

HEADPHONES

Ericsson Telephones, Ltd. April 283

KITS

Fluxite, Ltd. .

SWITCHES

Bulgin, A. F., & Co. ...

TERMINALS

Belling & Lee, Ltd. ...11

Eastick, J. J., & Sons ...Lectro Linx, Ltd.

June 404

May 383

June 485487 & 489June 487June 485

TRANSFORMERS

CONDENSERS (Variable)

394

391

Bird, Sydney S., & Sons... June -',O7

Dubilier Condenser Co.(1925) , Ltd. ... June

Formo Co. . . MayIgranic Electric Co., Ltd. AprilJackson Bros. ... .. JuneLissen, Ltd. . . . . MayOrmond Engineering Co.,

Ltd. ... ... April 293

405

394291

481

316

Bedford Electrical & Ra-dio Co., Ltd. ... ... April 285

Evison & Payne ... June 487

H. & B. Radio Co. ... June 483

Northern Radio Co. .. June 487

Omnora, Ltd. ... . June 494

Peto-Scott Co., Ltd. . . June 485

Raymond, K. . . . June 409

Ready Radio Supply Co.... JuneCover iii

LOUD -SPEAKERS

British Thomson -Hous-ton Co., Ltd. ... ... May 315

Brown, S. G., Ltd. ... May 385

Celestion, Ltd. ... ... June 489

Hughes, F. A., & Co., Ltd. June 475

Whiteley, Boneham & Co.Ltd. ... ... May 392

Brown, S. G., Ltd. ... June 477Igranic Electric Co., Ltd. June 479Lewis, S , & Co , Ltd. ... May 381Marconiphone Co , Ltd. May

Cover ivVALVES

British Thomson -HoustonCo , Ltd. ... ... April

Cossor, A. C., Ltd. ... JuneCover

Edison Swan Co., Ltd. ... MayImpex Electrical, Ltd. ... JuneMarconiphone Co., Ltd. April

CoverMullard Wireless Service

Co., Ltd. ... ... AprilVALVE HOLDERS

207

ii307477

iv

295

,

Whiteley, Boneham & Co.,Ltd. ... June 491

WAVETRAP

Harlie Bros. ... April 299 496

NC/ reless Magazine. June. 1929

THE 1929 CHUMMYEQUAL TO ANY 20 GUINEA MODEL

KITOF PARTSwith Valves and

Accessories(Complete to the last screw)

£14 : 6 : 0

READYRADIO

SPECIFIEDPARTS

AReceiver

ofProven Performance

IMMEDIATE DESPATCHSERVICE

PRICE LIST OF ORIGINAL PARTS.

Polished Oak Cabinet,with Loud -speakerand Aerial Fittings,and silk - coveredgrille : 0 : 0

Dual Range AnodeCoil 10 6

Copper Screening Box6

Special Cone Paper

RELIABILITY COUNTS -Our experience is at your disposal.

(Trade enquiries)

9

TEL. No.HOP 5555

(Private Ex.)

£ s. t.1 Rolston ebonite panel, 16 in.

by 8 in. .. 8 02 Formo de Luxe .0005 mid.

variable condensers .. 12 02 Harlie slow-motion dials .. 7 6I Formo de Luxe .00035 mid.

variable condenser .. 6601 Small Knob with pointer

2 Dubilier 1 mid. axed con-densers .. 5 0

1 T.C.C. 2 mfd. fixed con-denser .. .. 3 10

4 Anti - microphonic valveholders .. 5 0

1 Igranic high - frequencychoke .. .. 5 0

1 Wearite two -pole two-waybarrel switch with exten-sion and knob .. .. 3 9

1 Graham Farish 2-megohmgrid leak .. 1 0

1 Graham Farish .0002 mid.fixed condenser .. 1 0

I Ready Radio anode coil,with support .. .. 10 6

1 Graham Farish 20,000 ohmresistance 2 3

1 Graham Farish 10,000 ohmresistance .. 2 3

1 Graham Farish .002 FixedCondenser 1 0

1 Cossor low-freluency trans-former .. .. 1 1 0

Inclusive Total

£ s. d.1 Idarconiplsone, type A,

R.C.C. unit .. 8 0

2 Panel brackets .. 2 0

1 Blue Spot 66K adjustableloud -speaker unit .. 1 5 0

2 Lissen 66 -volt high-tensionbatteries .. 15 10

1 Lissen 9 -volt grid -bias bat-tery I 6

1 it -volt dry cell, type U.W.1Bulgin battery clips .. 1

2 C.A.V.. type 2 N.S.9., 2 -voltaccumulators 1 4 0

1 Piece of special cone paper,8 in. square .. 9

1 Set of Igranic spring wanderplugs, .. .. 4 0

4 Lectro Ling spade tags, 2black and 2 red

1 Ready Radio copper screen-ing box .. .. 6 6

1 Set of Indicating tabs .. 91 Ready Radio cabinet, with

baseboard, loud -speaker,and frame aerial fittings 2 0 0

Wire for frame aerial (4 on.28 d.s.c.) . 2 5

20 ft. °legit% quantity offlex, screws, etc. .. 2 6

Complete set of valves, S.G.,detector, L.F., and power 2 16 0

£14 :6 :0Free blueprint with all orders over £2.

COMPLETESET

carefully built tospecification

(Pest Report Supplied)

f16 :16 :0(including royalties)

IMPORTANT :

IT IS WISETO USE

CORRECT PARTS

All drilling free4! Frame Aerial,

wound I Loud. speaker,

Assembled andmounted

2Extra

Extra

Any part can be supplied separately

READY RADIO SERVICEHOME AND ABROAD

INLANDAll orders despatched post free in sealedcartons, or by rail, carriage paid. Pack-ing cases 2/6, credited on return.

OVERSEASAll orders carefully packed and insured,all charges forward.

Cash with order or C.O.D.

READY RADIO SUPPLY CO.159, BOROUGH HIGH STREET, LONDON BRIDGE, S.E.1

tThree minutes from London Bridge Stations)

'GRAMS :

READY HOP 5555LONDON.

Halt- BLUEPR IN T Coupon Valid untilprice June 30, 1929kW., ANT DAL sET CONSTRI,AaluNALLY DESCRIBED LN THIS 16SUK,

SendFreed INFORMATION Coupon ValiduntilJune 30, 1929Is.

NOT MORS THAN TWO QUESTIONS ru BE ASKED AT A rudui

1


DUAL COILS

TOENSURE

PERFECTRECEPTION

USE THELEWCOS

H.F. CHOKE

UNSCREENED

Pat. No. 285723 and others Pending

This new Lewcos Coil has a wavelengthrange of 235-55o and i,000 -z,000 metres.

It is Litz -wound and wonderfullyselective, and is designed for

either base -board or panelmounting with one

hole fixing.

DUAL UNSCREENED AERIALCOIL (Ref. DUA) AND H.F.TRANSFORMER (Ref. DUP)ARE SPECIFIED FOR THE

" MUSIC PLAYER "

11E61)

Ask for

G!LECOLOUREDCONNECTINGWIRE ANDBEWARE 0 FIMITATIONS

THE LONDON ELECTRIC WIRE COMPANY AND SMITHS LIMITEDCHURCH ROAD LEYTON, LONDON, E.10

Printed in England: Published by BERNARD JONES PUBLICATIONS, LTD., 58/6/ Fetter Lane, London, E.C.4.Sole Agents for Atrica: CENTRAL NEWS AGENCY LIMITED. Sole Agents for Australasia: GORDON & GOTCH, LIMITED. June, 1929.

how to build a portable wireless magazine · 2020. 12. 27. · bernard e) jones wireless magazine...

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