the first television journal in the world · to expect from every mullard valve. ... dover...

TELEVISIONAugust, 1932 RADIO EXHIBITION NUMBER

AUGUST 1932

New B.L.C. Broadcasts :Official Date

The Future ofRadio Drama

If Lindberghhad been Televised

All About " Radio City "

Vol. 5 No. 54

THE FIRST TELEVISION JOURNAL IN THE WORLD

LOOK INAT THE

LEWCOSREGD.

WE ARE EXHIBITING AT

1503dIolympki

CCIitlO t4AUGUST 19-27ADMISSION I'S

STAND N9153 OLYMPIA

The following are someof the reasons for the

popularity of theLEWCOS

POTENTIOMETER

I

2

3

4

5

It is dead silent inoperation.

Perfect contact is madeby an eccentric rockingplate.

The rocking plate isconstructed to preventfriction on the wires.

It is wire wound anddust -proof, being en-closed by a non -inflam-mable transparent cover

Obtainable in the fol-lowing values: 1,000,5,000, 10,000, 25,000and 53,000 ohms.

LAND SEEthe latest Lewcos lines in Radio Components-especially those suitable for Television Sets.At Stand No. 153 will be on view all the latestdevelopments which help so much to bring youbetter reception, including the new

LEWCOSPOTENTIOMETER

which costs only 3/-, yet will make all the difference toyour set by enabling you accurately to control youroutput to suit varying conditions. It definitely clarifiesreception by giving a far higher degree of efficiencywhich will improve your set enormously.A large model of the Lewcos Potentiometer, illustratingits various advantages, will be on view at Stand No.153,in addition to other famous Lewcos Products.Other Lewcos Products which have been specially re-commended for Television Sets by experts of this Journalare GLAZITE Wire, LEWCOS Spaghetti Resistancesand Twin Flex.

Manufacturersare reminded that Lewcos are particularlywell-equipped for manufacturing RadioComponents to definite specifications.

LEWCOS RADIO PRODUCTS FOR BETTER RECEPTIONTHE LONDON ELECTRIC WIRE COMPANY AND SMITHS LIMITED. CHURCH ROAD. LEYTON. LONDON.E.tO

TELEVISION for August, 1932

GENEROUS HIGH-TENSIONNEVER FAILING, NEVER FLUCTUATING

Whatever type of A.C. Receiver orBattery eliminator you use, thereis a suitable Mullard full -waveRectifier for it-a Rectifier givingits full -rated output of high-tensioncurrent, week in, week out. Con-stant voltage, generous ever -avail-able output-and that consistentperformance which you have learntto expect from every Mullard valve.The D.W.4 is specified for theeliminator for the " Tele-Radio "receiver described in this issue.

from

MULLARDFULL -WAVERECTIFIERS

Type D.W.2. Output 60 mA. at 250 volts]Reduced price 12/6

Type D.W.3. Output 120 mA. at 350 voltsReduced price 15/-

Type D.W.4. Output 120 mA. at 500 voltsReduced price 20/-

/1/.1DE IN ENGLAND

MullardTHE MASTER VALVE

Advt. The Mallard Wireless Service Co., Ltd., Mallard House, Charing Cross Road, London, W.C.2.


ARKS

193

P.P.M. gives'PRICELESS'

REPRODUCTION

cELESTION%he 'Very Sou/ of EXusic

LOUD -SPEAKERS

Realism-quality of tone-know what real radio repro-duction is by hearing aCelestion P.P.M. PermanentMagnet, Moving Coil Speaker-once you have heard it youwill have no other-insist uponyour local dealer giving you ademonstration.

4716INCLUDING

TRANSFORMERThe P.P.M. incorporates animpregnated diaphragm, anda scientifically designed twinsuspension. The new patentedcobalt content steel magnetproduces a very high fluxdensity. Housed in a strongmetal chassis.Please state whether pentode orstandard transformer required.Supplied fitted to baffle as illus-trated. Easy payment terms: 101 -down and 6monthly payments of,Si-.

Celestion Ltd., London Road, Kingston -on -Thames. London Showrooms106 Victoria Street, 5 W.1

A FAMOUS VALVEHOLDER

W.B. 4- or 5 -pin VALVE -HOLDERS FOR A.G.Valves. (Patent No. 320460.)Diam. 2 ins. Used in the testrooms and laboratories at leadingvalve manufacturers. Expand-ing nickel -silver sockets makeit equally suitable for Bananaor solid valve 10d.pins. . . .

FOURARESPECIFIEDIN THIS ISSUEof "Televisionfor the

"VISIONETTE

SS

Made by the Makers of the famous " W.B."

Moving -Coil SpeakersWrite for the new listsof new season's models

Whiteley Electrical Radio Co., Ltd.,Nottingham Road, Mansfield, Notts.

Irish Fret State Distributors:Kelly ,6 Shia!, Ltd., 47 Flat Street, Dublin

194

PROGRESSRadio and Televisiontechnique are constantlyadvancingthere is no finality . .

COLVERN Whatever advances aremade, Colvern Coils will beavailable

COILSCOLVERN COILS are speci-fied for the " VISIONETTE."

1 Type RM1S. 8s. 6d. each.1 Type RM3S. 8s. 6d. each.

2 Screens and Bases, typeC.C.S. 3s. 6d. each.1 10,000 ohm variableColverstat, type S.T.10.

5s. 6d. each. Send for a copy of the Colvern Booklet

No. 10.

Stand No. 245, Radio Exhibition, Olympia.

Go! 4V ERNI MITEDMAWNEYS ROAD, ROMFORD, ESSEX

Insulated

non-remov-D PRICE able head

BELLING -LEEFOR EVERY RADIO CONNECTION

4dvertisement of Belling & Lee, Ltd., Cambridge Arterial Road, Enfield, Middlesex.


_Lrtweilril4,i,,,1.4.-... , , i,_i, ..... alli : I p - - ,-,.y- - ;..-- IFf -iii ii. Joi 1- 43A.1 ,.... .--.._...--. MI MINIIIrl

1,1-, ,i..,:.

and be sure to visit

STAND 281reserved by the publishers of

"TELEVISION"For the benefit of subscribers and the general public tae s?ecial apparatusdesigned by the Technical Editor, Mr. H. J. Barton Chapple, Wh.Sch.,B.Sc., A.C.G.I., D.I.C., A.M.I.E.E., and by Mr. William J. Richardsonwill be on view, enabling every visitor to Olympia to see the actual sets

described in recent issues of TELEVISION. These issues will be on saleat the stand, so that the constructor can immediately obtain full detailsand working diagrams showing how to make similar sets for home use.

Throughout the week technical advice will be given gratis to

interested enquirers, who will thus have the opportunityof obtaining first -band hints on the construction of visionapparatus and on the problems of television generally.

EXHIBITS WILL INCLUDE THE " VISIONETTE " AND ALSO THESPECIAL POWER UNITS FOR THE " TELE - RADIO RECEIVER "DESIGNED AND DESCRIBED EXCLUSIVELY IN " TELEVISION."

Make a note of the number now-

STAND 281AUGUST 19th -27th (except Sunday), JO a.m.-io p.m.

TELEVISION for August, 1932 195

THE FOLLOWING DEALERSARE WILLING TO DEMONSTRATE

TELEVISION" TELEVISORS " KIT SETS COMPONENTS

AMERSFOORT (Holland) .BAGSHOT . . .BEDFORD . . . .BEDWORTHBEXLEY HEATHBICESTER . .BIRMINGHAMBIRMINGHAMBISHOPS STORTFORDBOURNEMOUTH .BRACKNELL . .BRAINTREE . .BRIDGENDBURTON -ON -TRENTCAERPHILLY . .CHALVEY . . .CHESTERFIELDCHIPPERFIELD .COLCHESTERCOULSDON.COVENTRYCOVENTRY.DARLINGTONDEALDEWSBURYDOVEREASTBOURNEEASTBOURNEERDINGTONFELIXSTOWEFOLKESTONEGERRARDS CROSSGODALMINGGRAYS (ESSEX). .KIRKCALDYLEIGHTON BUZZARD

.

LONDON :BATTERSEABAYSWATERBRIXTONBROMLEYCLAPHAM COMMON . .CRICKLEWOOD BROADWAY.EALINGEALING (WEST) .EARLSFIELD . .EAST BARNET

WILLEN VAN LOON . . .LINDFIELDS GARAGE . .JEAKINGS & SON . . .T H. RUSSELLJ. SPENCER (LONDON) LTD.LAMBOURNE BROS.C WEBB LTD.SHANNON & CAPENER

. . H. R. MOORE LTD.. J. E. BEALE LTD.. DRAKE & MOUNT LTD. .. COX'S GARAGE

WRIGHT & ASHWORTH . . ... RADIO & CY-KAR MART . . ..

L. PRITCHARD. ... J. D. HALLIDAY . . . . . .

G. KENNINGTON (CHESTERFIELD) LTD. . .. A. C. GEORGE . . . . . .

. . SHROSBURY & BAKEWELL CO., LTD.. 1 .THE " VIC " WIRELESS STORESMAX. A. BUCH

. . PARKER'S RADIO SERVICES ...C SHARPG CLOUTBICKERS LTD. .DOVER RADIO STORESA. BODKIN & CO., LTD.OWEN H. RELLYSTANLEY'S RADIO .L. E. PULFORD .BOBBY & CO. LTD. .R. F. CHIPPSH J. CHALLEN. . . . . .GRAYS WIRELESS CO. (H. W. FRANKLIN)GIBES & WATSON . ....GRIFFIN BROS. . ....

EDGWARE . .. . . .

FULHAM PALACE ROAD .

HAMMERSMITH . .

HOLLOWAY . .

HOUNSLOW . . .KINGSTON . . .

KNIGHTSBRIDGE . .

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MUSWELL HILLNEW BOND STREET .

OXFORD STREET. .

PECKHAM . . .

PIMLICOWEST NORWOOD . .

WIGMORE STREET, W..WOOD GREEN. .

LUTON . .NEWCASTLE . . .

NEW MALDEN (SURREY) .NORWICH . .

PERRY BAR .PLYMOUTH .

RAMSGATE .RAMSGATEROCHDALEROCHESTERSLOUGHSTAINES . .TONBRIDGE .

WALLINGTON .WALLINGTONWEST BYFLEETWEST DRAYTONWITLEY (SURREY)WORTHING .

E F. KELLYHOPE, NORMAN & CO.QUIN & AXTENSUNIVERSAL ENGINEERSDEMPSEY & COHARDEN & CO.KEEN WIRELESS COL. LEAMANH. HOLLIER & SONSEAST BARNET WIRELESSA. ALDERTONJ. F. WISSON"ECONOMIC "W. H. OATES . . ......JONES BROS. (HOLLOWAY) LTD.SANDERS ELECTRIC & RADIO SUPPLIES .BENTALLS LTDBROMPTON RADIO CO.HARRODS LTDVICTOR RADIO SERVICESKEITH PROWSE LTD.SELFRIDGE & CO., LTD.HAVIL RADIOF DOVE & SONSE. SHELDRICKWIGMORE RADIO SERVICEDISTRICT SUPPLIES LTD..R. J. STEARN & CO.PAYNE & HORNSBY LTDACORN SERVICE STATION LTD. . ..E. A. PRIEST & CO.WELLINGTON RADIO & ELECTRICAL DEPOTW. H. AXWORTHY & COJ. CARMAN . . .E. COVENEY & SONSBANNISTER & FITTONA. F. SMITH & SONS, LTDG CASE & SONS

STORES

. . V. & D. REALEA. T. LANGTONW. BELDINGBULLOUGH BROS.A LONG x Byfieet CornerSPRATLEY BROS. Station RoadG. WOOTON NorthfieldsE. LAMB . . Franklin Road, Durriugton

GIVE YOUR LOCAL DEALER A CALL TO -DAY ,

Stationsstraat 32BSurreyMill StreetTrain Terminus, Coventry Rd.127 The Broadway47 Market Square4! Cam Lane13 Aston Road NorthNorthgate EndHantsBerksRayne RoadKings Bldgs., Adair StreetCross Street73 Princes AvenueNr. SloughVictor LaneThe Common73 Crouch Street24 Chipstead Valley Road143 Lower Ford Street3 Holyhead Road321 North StreetElectrical Engrs.The Galleries4 Townwall StreetII Cornfield Road" Gavinwood," Willingdon191 High Street24.x Hamilton Road48 Sandgate Road6 Oak End WayI2 Church StreetClarence Road270 High Streetxx High Street29 Mostyn Ave., Craig -y -Don

5 Park Road85 Westbourne GroveBrixton Roadx Chatterton Road69 South Sidegg Cricklewood Broadwayx Dare Road97 Northfield Avenue422 Garratt Lane3 Park Parade8 Bank Parade, High Street2 Cheapside, Deans lane24 Fulham Palace Road295 Hammersmith RoadHolloway Roadx x9 Staines RoadSurrey20 Brampton ArcadeS W.8 Firs Parade/59 New Bond StreetW . x.3o High Street77 Pimlico Road493 Norwood Road36/38 Wigmore Street43 High Road7 Manchester Street7 St. Andrew's BuildingsKingston By-pass Road28 St. George's Road303 Birchfield Road106 Tavistock Road65 King Street20 Belle Vue Road27 Milnrow Road215 High Street2 Grove Parade, High StreetKingston RoadHigh Streetg The Parade, 320 Stafford Rd.34e Woodcote Road

196 TELEVISION for August, 1932

11 BUILT TO SPECIFICATION"

LEICESTERAYLESTONE 487

Sooner or later you-if you take your televisionseriously-will find that you want a transformeror a choke which is not made in stock models.Make a note now. that when the occasion arisesyou can get apparatus made to your own speci-fication by " PARMEKO "-and at very littlemore, if any, than the usual stock prices.Probably there is not a reader Df " Television "who is unaware of :he superiority of " PARMEKO "components, and for this reason there is no need to saymcre than that our " to specification " models are madewith precisely the same care and precision as our stockmcdels, and fully uphold the tradition of " the best-regardless." Estimates and specifications prepared freeand without obligation. Write to us if in any difficulty.

Price list A (Transformers, Chokesand Eliminators) on request.

PARTRIDGE & MEE LTD L74ONDON,

W .reCNew Oxford Stet

.1MUSEUM 5070

TELEVISION for Aligiist, 5932

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FERRANTIFERRANTI Ltd., HOLLINWOOD, LANCS. London: Bush House, Aldwych, W.C.2

197

TO OBTAIN THE

BESTout or yourTELEVISORbuild with

DUBILIERCONDENSERS

AND GRID LEAKS

There is no excuse forusing anything else butDubilier-for at their newseason's prices, DubilierCondensers and GridLeaks are in many casesactually cheaper thancomponents of doubtfulorigin and still moredoubtful performance.

For whatever purpose youneed Condensers or GridLeaks-use Dubilier. Thenyou are certain of good per-formance at least as far as thesecomponents are concerned, fortheir efficiency has been provedin tens of thousands of in-stances by experts, amateursand home constructors.

Top left is the Dubiliertype B.B. Paper Con-denser, a high efficiencyCondenser in bakelitecase. Capacities from .09mf. to 4.0 mf. Prices from1/9.Above is the Dubiliertype 670 Condenser, de-signed to fill the demandfor a high -quality, low-priced Condenser. Inall popular capacities, atprices from 6d. to 1/6.On the left is the DubilierGrid Leak, the last wordin strength, permanenceand efficiency. Its priceis 1/-.

DUBILIER CONDENSER CO. ( 19 2 5 ) LTD.Ducon Works. Victoria Road. North Acton. W.3

198

* SPECIALEXHIBITION OFFER

DURING THE RUN OF THE RADIOEXHIBITION ONLY, the price of our

specially constructed

SCANNINGDISCS

IS BEING REDUCED TO

1016STANDARD . . 201 inchALUMINIUM . 30 square holes

BRASS -BUSHED

S. LEE BAPTY60, CRAVEN PARK ROAD, N.W.10

When ordering, please remit sufficient to coverpostage (9d.); also please state size of motor spindle.

TRADE INQUIRIES WELCOMEDWillesden 7084.

`MERVYNTELEVISION

COMPONENTSARE COMING

They include Scanning Discs,Mirror Drums, Lenses, PhonicMotors, All -Mains A.C. Receiversfor sound and vision.

Write for further details of

MERVYN SOUND & VISIONBOX 22, clo "TELEVISION"Bouverie House, Fleet Street, London, E.C.4


Telegrams :Benbrolish Fleet

London

SUBSCRIPTION RATES13/6 PER ANNUM, POST FREE.6/9 SIX MONTHS, POST FREE.

AMERICAN RATE$4.50 PER ANNUM. POST FREE.$2.25 SIX MONTHS. POST FREE.

TELEVISIONProprietors : BENN BROTHERS LTD.

Established 188o

Editorial, Advertisement and Publishing Offices

Bouverie House, Fleet Street, London, E.C.4(Closed on Saturdays)

Telephone :City 0244(to lines)

MSS. AND OTHER MATERIALFOR EDITORIAL CONSIDERATIONSHOULD BE ACCOMPANIED BY ASTAMPED ADDRESSED ENVELOPE,AND SHOULD PREFERABLY BE

TYPEWRITTEN.

Contents August 19 3 2PAGE

NOTES OF THE MONTH . 201

" TELEVISION" AT OLYMPIA : AUGUST igth-27th . 202

B.B.C. AND TELEVISION : OFFICIAL ANNOUNCEMENT . 203

HAS TELEVISION ARRIVED ? : A REPLY AND A CHALLENGE 203

" VISION AND SOUND ON ONE WAVE " 204

THE COMPLETE " VISIONETTE " . . 205

NEWS FROM ABROAD : GERMANY AND THE UNITED STATES . 211RADIO CITY . 213

IF LINDBERGH HAD BEEN TELEVISED . 215

RETAINING HIGHER FREQUENCIES 218

FROM MY NOTEBOOK . . 221

THE NEW " TELEVISOR " . 223

LETTERS TO THE EDITOR . 224THE FUTURE OF RADIO DRAMA . . 226

POINTS FROM THE PRESS : " A REAL ADVANCE " . 227

THE ENTHUSIAST SEES IT THROUGH 229

REPORTS ON APPARATUS TESTED . . . 232

Index to AdvertisementsBaird Television Ltd. 200 London Electric Wire Co. & Smiths Ltd. 11

Bapty, S. Lee 198 Mervyn Sound & Vision x98Belling & Lee, Ltd. 194 Microfuses, Ltd..Benn Ltd., Ernest . . . . iii Miscellaneous Announcements iiiBritish Institute of Engineering Technology Mullard Wireless Service Co., Ltd. 193Celestion Ltd. . . . /94 Oates, W. H. . .Classified Television Dealers .Colvern Ltd.Dossett Studio . .

196194

lit

Partridge & Mee, Ltd.Pitman & Sons, Ltd., Sir Isaac

197

Dubilier Condenser Co. (1925) Ltd. 198 Rotax Ltd. . ivFerranti Ltd. 197 Salter, J. . . . iiiLambert, H. ill Westinghouse Brake Sc Saxby Signal Co.Leaman, L. iii Whiteley Electrical Radio Co., Ltd. 194

TELEVISION for August, 1932 '99

Praised by the Press . . IP

The New Baird model home " Televisor " receiver was exhibited last week in the Baird laboratories at LongAcre. The most important advantage of the new instrument is that the image is reproduced on a screen9 in. high by 4 in. broad, so that it can be seen by a room full of people. In the older model, in which the imagewas produced in a lens, not more than four people could see it at any one time.-The Times.

Improvements on the former television apparatusinclude :

An image which can be seen by a roomful of peoplesimultaneously, instead of by only three or fourpersons.

Sufficient brightness of the image to make itvisible in a room electrically lit, so that it is not neces-sary to put the room in darkness.

Compactness ofthe apparatus,which measuresx ft. 6 in. long by8 in. wide and13 in. high. Thescreen is 4 in.wide and 9 in.high.-The DailyTelegraph.

A new home-" Tele-visor " receiver whichwas demonstrated tome at the Baird Com-pany's headquarters inLong Acre yesterdaygave results of aquality and brillianceconsiderably in ad-vance of any form oftelevision I have seen.-News -Chronicle.

Television hasarrived !

This is no wild

mission was carried out on a short line between two rooms,it was obvious that if comparable results could be ob-tained by wireless the new instrument could guaranteegenuine entertainment value.-Wireless World.

We were considerably impressed by the " Televisor "receiver, the images being clear, and of the real enter-tainment value. The usual flicker does not seem to be

quite so noticeable,while the up and down" float " of the imageis slight. A great im-provement lies in thefact that the " line "effect obtained withthe old scanning discmodel is entirelyabsent.-Wireless andGramophone Trader.

Yesterday the BairdCompany demon-strated to " TheCinema" a new typeof home " Televisor "receiver which is anotable advance onanything they haveyet shown. . . . This,

with the factthat from next monthand for at least twoyears the B.B.C. areto broadcast, perweek, four half-hourtelevision broadcasts

in ordinary programme hours, suggests a counter -attrac-tion that may very well divert further money from thecinema. The new Baird model is a remarkably finepiece of work.-To day's Cinema.

The announcement that the B.B.C. are shortly to takeover the broadcast television programmes hithertoprovided by the Baird Company, and are to transmit anew series of half-hour transmissions on four nights aweek at r x p.m., has coincided very opportunely with theperfection of the new home " Televisor " receiver by theBaird Company.

Our impressions of the new "Televisor " receiver, aswe stated last week, were very favourable, and it cer-tainly marks an outstanding advance on the earliermodel.

Programmes can now be seen in comfort by a numberof people at a time, and in black and white.. . . Whenwe apply the acid test as to whether we ourselves would,at least for the time being, be satisfied with the results,the answer is in the affirmative.-The Wireless andGramophone Trader.

I feel convinced that a real step forward has been madewith the new apparatus.-Wireless Magazine

* THE NEW MODEL BAIRD "TELEVISOR" RECEI /ER *

statement, for yester-day I saw a practical and convincing demonstrationof moving images on a screen that can be seen from anyangle by any number of people.-Daily Mirror.

The quality of the black and white image is very muchbetter than the reddish picture produced by previous" Televisor " receivers. These preliminaries were fol-lowed by a cartoonist, who did some quick -action car-toons on large sheets of paper in view of the audience.Here again the results were remarkably clear.-AmateurWireless.

The image can be viewed without putting the room intotal darkness. The new machine measures, whenclosed, 1 ft. 6 in. in length by 8 in. wide and 53 in. high.From the distance at which we viewed it the imageappeared quite clear, the undesirable line effect notbeing noticeable.-Ekctrician.

Probably the most convincing television demonstra-tion yet given in this country was staged by the BairdTelevision Company at their headquarters in Long Acre,London, W.C.2, on Thursday, June 3oth, when TheWireless World was able to witness the new home " Tele-visor " receiver in action. Although the actual trans-

BAIRD TELEVISION, LTD.133, LONG ACRE, LONDON, W.C.2

'Phone :Temple Bar

5401


TELEVISIONThe First Television Journal in the World

Publishers : BENN BROTHERS, LTD. Technical Editor : H. J. BARTON CHAPPLE, WH.SCH., B.Sc.

Offices : BOUVERIE HOUSE, FLEET STREET, LONDON, E.C.4

VOL. V. No. 54] AUGUST 1932 [IS. NET

Notes of the MonthTHIS issue is published at a moment of ex-zeptional interest in the history of television.On Monday next (August 22nd) the B.B.C.

is to begin the new transmissions, which will begiven regularly from Broadcasting House; the sameweek will see the Radio Exhibition in full swing,when the latest developments in television will beknown to the public. It is expected that visionsets will be shown by several manufacturers, but thegreatest secrecy is being maintained before theExhibition opens. TELEVISION has reservedStand No. 281, where readers will be able to seesome of the special apparatus designed by ourtechnical editor and to obtain advice on their con-structional problems.

* * * * *The B.B.C. transmissions will inaugurate a

new era for television, as the public is assured ofbeing able to look -in at regular hours, and hence topursue experiments seriously. There was generaldisappointment that the date originally announcedwas not adhered to, as the new programmes wereexpected to begin in the middle of July. No

Olympia gets ready for the Radio Exhibition.


announcement of the delay was made, and theRadio Times of July 15th and 22nd gave no refer-ence whatever to television. There was evidently alack of staff work, and in consequence many experi-menters who were eagerly awaiting television's" first night " were unaware of the delay. It ap-pears, however, that the apparatus took longer toinstall than had been expected, and of course theB.B.C. had to make sure of giving adequate trans --missions from the outset. The delay was very re-grettable, but now that the programmes are to beginin earnest, the television public can look forward toa period of increasing interest and activity.

In future issues we shall publish regular reviewsof the new B.B.C. broadcasts. In order to makethe criticisms as comprehensive as possible, we shallwelcome the co-operation of readers, who are invitedto submit their comments on the programmes.A number of, these letters will be published, andeach month the correspondent who sends the bestcriticism will receive a year's subscription to TELE-VISION free of charge. Where a prizewinner isalready a subscriber, his existing subscription willbe extended for a further year. Now that televisionis to be transmitted regularly, we believe that repre-sentative views on the subject -matter and thetechnical quality of the programmes will be of con-siderable interest, especially during the early stages.

* * * * *

What is the television equivalent to the word" listener "? The obvious term is " observer," butthat is hardly distinctive enough, as it is nowgenerally associated with aviation. For want ofa better word, we have used the word " looker -in,"but it is not very pretty. Some American writershave suggested " radio spectator," and even " tele-visioner," but neither term is likely to appeal tothe British public. We are glad to see that theWireless World has drawn attention to this prob-lem, and we join our contemporary in askingwhether any reader can suggest a word that is bothexpressive and pleasant to use.

201

"Television" at OlympiaSurprise Exhibits

THE proprietors of TELEVISION have reservedStand No. 281 at the National Radio Exhibi-tion, which will be held at Olympia from

August 19th to 27th. The accompanying plan showsthe position of the stand, which is in the galleryjust above the main staircase on the north side ofthe Grand Hall.

Free Technical AdviceTo assist those who are new to television and to

enable radio enthusiasts to develop their experi-ments, TELEVISION has arranged for free technicaladvice to be available at the Stand, where visitorswill be able to discuss their television problems withexpert attendants. For the benefit of readers whohave constructed the special sets described in recentissues, a selection of this apparatus will be exhibited,including the latest model Visionette." With theextension of television facilities by the B.B.C., thislatter set has been modified by the designer, Mr.William J. Richardson, in order to give a greaterrange for reception. On another page this monththe complete. model is described, enabling readersto begin its construction at once or to bring theexisting set up to date. Copies of the current issueof TELEVISION and back numbers will be on sale atStand No. 281.

This year the Radio Exhibition is associated with

almost as much " hush-hush " as is usually attachedto the Motor Show. Surprises are promised by ,

some of the biggest firms, and it is expected (thoughnot definitely confirmed) that several vision receiverswill be shown to the public for the first time. Thereare rumours of a new model that will go one betterthan the radio -gramophone by including a visionreceiver as well. It would, in fact, provide the com-plete home entertainment, and whether availablethis month or not, it is certain to be a developmentof the near future. Following the demonstrationto the Press in July, Baird Television, Ltd., havebeen in negotiation with leading radio manufacturers,and probably the latest " Televisor " will be shownby one of the big exhibitors. Here again, however,the plans are not officially disclosed, and the publicmust wait until the opening day to learn whetherthe new model has been completed in time for theShow.

The Exhibition will be twice the size it was lastyear, and will thus reflect the remarkable growthof radio in this country during the past twelvemonths, the turnover in 1931 being no less than£30,090,000. As yet of course, television accountsfor only a small part of the total, but it is adding avaluable margin, which is growing all the time andwill increase greatly within the next few years. Itis estimated that there are already between five andten thousand vision sets in use throughout the

country, and the more enter-

niirTy TELEVIS LON".0; STAND N° 2331

IN GALLERY.STAIRCASETO GALLERY,

q RAND HALL01-YM.P L

AA. 10-27!,

t

MACH c RoAtIADDIsoN

ENTRANCE c STATION

OFFICIALCAR PARK..I HAMMER-SMITH ROAD Bus

STOP yr_

prising wireless manufacturers,already profiting by this newmarket, are taking steps to meetthe requirements of the tele-vision constructor.

Olympia is decorated in silverand blue, a colour scheme in-tended to suggest coolness inthe summer -hot days. But theorganisers are taking nochances with the clerk of theweather, and a special flood-lighting arrangement has there-fore been devised, so thatthe silver may be gildedand the blue turned intoblood -red - a crimson -and -gold effect suggestive ofwarmth!

A report of the exhibits willbe given in the next issue ofTELEVISION ; meanwhile thepublishers extend a warm wel-come to all readers and friendsto visit Stand No. 281.

202TELEVISION for August, 1932

Has Television Arrived?A Reply and a Challenge

IN reply to the article published in our July issue,Popular Wireless of August 6th again explainedits attitude to television. We had expected a

more prompt reply, but our contemporary has solittle to say that the delay is hardly surprising.After paying a compliment to the " earnest investi-gator and experimenter," for there is nothing itwould like better than to see the " dawn of televisionfor the masses," the journal proceeds to give an" impartial and reasoned reply to those ' publicity -mongers ' who insist on maintaining that televisionin the home is an accomplished fact."

We are entirely in agreement with our contem-porary in objecting to " exaggerated and over-optimistic statements " about this science. We objectto exaggeration of every kind and believe it is asdishonest to ignore or withhold facts as to over-state them. That is where we differ from a contro-versialist who constantly draws attention to thedifficulties of television but seldom encourages thosewho are working to overcome them. A typicalquotation from the journal recently illustrates itsattitude towards television. The suggestion wasmade in the Newspaper World that television notesshould be given by the wireless correspondents ofthe daily Press. " What," says Popular Wireless," would be the attraction in that, when not one

B.B.C. and TelevisionThe Editor of TELEVISION has received the fol-

lowing statement from the B.B.C.:-

URING the past few weeks Baird tele-vision apparatus has been installed inBroadcasting House. Television trans-

missions will be carried out on Mondays, Tuesdays,Wednesdays, and Fridays from II to 11.3o p.m.Vision will be transmitted from Brookman's Parkon 261.3 metres, and the accompanying sound willbe transmitted from Daventry on 398.9 metres. Thefirst of these transmissions will be on Monday,August 22nd.

" An earlier announcement by the B.B.C., pub-lished in the June number of TELEVISION, stated thatthe new transmissions were expected to beginbetween July 15th and loth. It was, however,found that the installation of the necessary equip-ment in Broadcasting House required more timethan had been anticipated. The television pro-grammes will be in charge of Mr. E. F. Robb, underthe direction of Mr. Val Gielgud."


newspaper reader in Io,000 will be practicallyinterested in the subject for years to come."

Our contemporary cannot have it both ways. Ifit seriously wants " television for the masses," itcannot at the same time object to the newspapersgiving space to the science, and thus helping to makeit more widely known to the public.

Three points are selected from the July issue ofTELEVISION for " impartial and reasoned reply."

( 1) The first is our statement that " television inthe home is already an actual achievement." Popu-lar Wireless says that this may be " a matter ofopinion," but adds that presumably "radio in thehome was achieved when Marconi first experimentedwith his crude coils in his garden in Italy over thirtyyears ago ! "

To compare television to -day with radio in 1900is, however, quite inaccurate, when there are hun-dreds of vision sets in use, both in this country andabroad, and when the science has already reachedthe stage that merits the serious attention of theB.B.C.

Our contemporary quotes a recent lecturer to theTelevision Society who said that " television hasnot yet arrived " and that the " Baird method hadreached its practical limits." As against this opinion,there are others of equal authority who take anotherview. Mr. Alan Hunter, the well-known radiocritic, says that the images obtained with the latest" Televisor " have " real entertainment value," andthat the stage has been reached when big things mayhappen any day now in television.

As for the Baird method, it is the only one thathas so far been brought into practical use in thiscountry, and hence is engaging the major attentionof television experimenters. Time alone can showwhether it will improve still further, but no less anauthority than the Marchese Marconi believes thattelevision (by whatever method) has " a veryimportant future."

(2) " The B.B.C. programmes are the presentcriterion by which to judge television in the home."In objecting to this statement our contemporaryquotes a recent editorial article from the RadioTimes. which said that " many difficulties strewthe path ahead of television, not the least of whichis that of the present congestion of the ether."

Because there are difficulties to be overcome, thetelevision enthusiast welcomes the interest of theB.B.C., and believes that, just as has been the casewith radio, the technique of television will graduallybe improved and perfected under its auspices. Itseems likely that the congestion of the ether will beeventually solved, so far as television is concerned,

203

by the use of ultra -short waves, and here again, withthe aid of the B.B.C., the future is in the bestpossible hands.

(3) The last point in our article to which objec-tion is taken is as follows : " Only a few yearsago the broadcasting of sound and music was alsorather crude and quite as complex as television. Wequestion whether vision apparatus is any more diffi-cult to construct than the early wireless receivers."

This sentence our contemporary calls " a puregem " (much as a small boy, for want of a betterreply, might say " funny face "), and it adds thattwo radio receivers, a television instrument, andpower mains are needed for television, whereas at" the very beginning of broadcasting the pro-grammes could be received on a pimple crystal set."

We do not claim that " television for the masses "is here in the sense that the crystal set brought radioto the million ; but we repeat that a vision receivercan he constructed without difficulty by any experi-menter who is familiar with radio technique. Apartfrom the dozens of amateurs who have dealt withtheir work in letters to TELEVISION, we would againrefer to the article in World Radio of June 24th,which described how a vision set was made for afew pounds. Television is still a fairly expensivehobby, but it is not necessary, as Popular Wirelesssuggests, to spend " fifty pounds " on the necessaryequipment to enjoy experimental " looking -in."

Our contemporary concludes by saying that thepublic is even now being told that " anything and

everything can be televised, and is led to believethat good moving pictures by radio can already beaccomplished." We also protest against over -state-ments of this kind, and would repeat (with that"amazing candour" which Popular Wireless finds sosurprising in others) that television is in its infancy,and that the images, are still rather crude. It is,however, a vigorous and growing branch of radiowhich has made remarkable headway and showsevery promise of further improvement in the nearfuture.

Meanwhile, there are several recent achievementswhich our contemporary conveniently ignores ; forexample, the fact that experimenters throughout thecountry succeeded this year in " looking -in " to theDerby, even at such a great distance as Newcastle,and under conditions which were far from perfect.

In its refusal to face the facts and to recognisethe progress already made by television, the attitudeof Popular Wireless is not very different, at theother extreme, from that of the " publicity -mongers "to which it rightly objects. The journal is widelyrespected-it claims to have the " largest radio cir-culation in the world "-and has a real responsibilityto its readers in this matter. It is completely inac-curate to say that " television in the home appearsto be as far away from practical politics as it didone year or even ten years ago," and in the interestsof that impartiality to which Popular Wirelessrightly attaches importance, we again challenge itto prove or withdraw this statement.

"Vision and Sound on One Wave"UNDER this title the Broadcaster publishes an

interesting report from New York, datedJuly 15th, stating that the Columbia Broad-

casting System, one of America's largest broadcastingfirms, is attracting wide attention for its newestengineering feat, the transmission of a televisionpicture and voice simultaneously on one wavelength.The equipment at one transmitter is now beingaltered to give regular television programmes, be-ginning on July 21st. The launching of the newsystem will mark the first anniversary of theColumbia television station. At the receiving endonly one instrument is needed.

Double ModulationMr. William B. Lodge, Columbia development

engineer, told the Broadcaster representative thatdouble modulation was the term which best describesthe new principle.

" When a receiver is receiving a given trans-mitter," he added, " the set is tuned to a particplarcarrier frequency. The signal which reaches the setconsists of this carrier frequency, combined with thefrequencies of speech or music.

" The first step in the new system is to modulatea carrier of 45 kilocycles with the microphone signal.

204

" The television signal such as will be emitted byColumbia's W2XAB transmitter consists of fre-quencies up to 4o kilocycles. In the operation of thesound and picture broadcast, the television signal, upto 4o kilocycles, and the modulated 45 -kilocyclecarrier are combined and transmitted together.

" At the receiving station the set is tuned to thefrequency of the transmitting station, and thendetects and reproduces the above signal. Frequenciesup to 4o kilocycles are applied to the terminals of aneon tube and reproduce the television picture. Aspreviously stated, the 45 -kilocycle modulated carrierwave contains the sound signal, and a receiver tunedto that frequency can be used to obtain the originalsound.

" In the television: receiver, therefore, it is onlynecessary to insert a simple filter at the terminals ofthe neon tube to prevent the 45 -kilocycle voice carrierfrom interfering with the picture, and to add asecond detector with a circuit tuned to 45 kilocyclesto obtain the audio signal.

" It may be interesting to note that a sound pro-gramme may also be detected by a conventionalselective receiver tuned to a frequency of 45 kilo-cycles either higher or lower than that of the trans-mitting station's carrier, or, in the case of W2XAB,either 2,755 or 2,845 kilocycles."


The Complete "VisionetteBy William J. Richardson

As I indicated last month, the original" Visionette " receiver described in the Apriland May issues of TELEVISION has been sub-

jected to numerous tests, in an endeavour to fallin with the wishes of some readers who desiredgreater range and even greater selectivity.

It is felt unnecessary to go into every detail thathas been tried out, but in its somewhat modifiedform the set does undoubtedly meet the demandsjust stated. If any constructors of the original setdesire to make the alterations, they will find thatthese can be effected without much trouble, for inthe main the original layout has been adhered to.

On the other hand, for the benefit of those whowill be building the set for the first time, a com-pletely new theoretical diagram and wiring planshave been prepared. Furthermore, since this issueof TELEVISION will come into the hands of hundredsof readers for the first time as a result of makingits acquaintance at the Radio Exhibition at Olympia,it was felt appropriate to treat the design as anew one and go into its details thoroughly.

The substance of sections of previous articles onthis set will therefore be repeated, and this willsave readers hailing to refer to back issues forinformation. In essence the modified " Visionette "is an attempt to provide an all mains fed

three -valve receiver which will bring in the tele-vision signals within a reasonable range of theBrookman's Park transmitter, which is the B.B.C.'svehicle for broadcasting them. It is quite simple tohandle, and can be used for the reception of sound,if desired, on those occasions when vision signals arenot on the air.

Every effort has been made to give the bestquality of reproduction, as distortion of the signalin television is a factor which must be carefullyguarded against.

The three mains valves chosen are a screen -gridhigh -frequency, an anode -bend detector, and a pen-tode output, a double rectifying valve providing thenecessary rectified H.T.

The Theoretical CircuitThe first consideration is the coils, indicated as

L1, La, La, and L. in Fig. I. These coils are bothof the dual range type, being known as RM IS andRM3S and manufactured by Colvern, Ltd. Thefirst -named is the aerial coil, and the rotor L, is usedas a variable aerial coupling on the broadcast waverange, while a tapping on the tuned winding com-pensates for the increased coupling required on thelong -wave band. No reaction winding is included,

Fig. 1.-Circuit diagram of the " Visionette" as finally modified.


777074.1,7,TW'Rr -41'..4F-T71-77771 11"'17

The apparatus is here shown ready for test, with the valves inposition.

but by means of the rotor coil the aerial load canbe adjusted to give maximum signal voltage acrossthe tuned circuit L2 C4.

With the movement of a double -contact switchfitted in the base, the degree of aerial coupling isincreased by the amount required to maintainmaximum signal strength when tuning on the longwaves. A correct aerial tuning results from theadjustment of angle and height of the coupling coil,which may be of 20, 40, or 6o turns.

SelectivityIn addition to altering the position of this aerial

coil, varying degrees of selectivity are given throughthe medium of the three condensers, C1, C2 and C3.The last two are of fixed capacity, but the first oneacts as both a volume control and selectivity device.The moving plates of this condenser are connectedto the aerial I terminal. One set of fixed platesnow joins the terminal i of the aerial coil, and theother set passes to a short length of flex terminatingin a Belling -Lee spade connector marked " earth."

With the spade connector left free, the condenserfunctions as an ordinary series aerial feed con-denser, and when the spade connector is clipped onto the earth terminal we have the condenser workingas an effective volume control by regulating thesignal feed into the coil L1. This scheme, togetherwith the alternative pair of aerial fixed condensers,C2 and C3, of 0002 mfd. and 005 mfd. capacityrespectively, and the movable aerial coil shouldprovide sufficient varying degrees of selectivity tomeet most situations.

The tuned H.F. signals pass to the grid of V1.a metal -coated Mazda A.C. mains screen -grid valve,type AC/SG, having an amplification factor of1,2oo. The resistance values of the associated cir-cuit have been so calculated that the valve workswith an anode voltage of 200, a screen voltage of8o, and a grid -bias voltage of 2 (approx.).

The anode current under these conditions isapproximately 7 milliamperes, and since the voltageat the extremities of the single H.T. feed is about400, is easy to see how the values of R1 =

206

8o,000 ohms, R2 = 20,000 ohms, R3 = 300 ohms,and R, = 30,000 ohms, were arrived at. The re-sistance R3 and the fixed condenser C7 give the auto-matic bias to the valve, C, and C6 being the usualdecoupling condensers.

It should be noted that, by using this singlehigh-tension feed, the voltage dropping resistancesbecome the decoupling resistances, and functionvery satisfactorily.

Choke FeedingChoke feeding into the tuned grid circuit of the

detector valve has been chosen, a fixed condenserC8 of ooi mfd. capacity passing the signals to thesecond coil L3 L,. This is known as a dual -rangeH.F. intervalve coupling coil, complete with areaction winding and wave -change switch. Thisswitch is ganged to operate in conjunction with thefirst coil L1 and L2, while the coil itself consistsof a solenoid inductance with a section -wound long -wave coil.

In addition, it should be noted that the pair ofcoils are tuned by a ganged condenser (C4 and CO,whose stator plates for C, can be separately adjustedso as to allow for any inaccuracies which mightcreep in owing to the presence of the aerial.

Passing to the second valve V2, this is made tofunction as an anode bend -detector, and is a MazdaAC/HL. Calculations here have been based onan anode voltage of 200 and an anode current ofI milliampere. This makes R5 = 8o,000 ohms andR6 = mo,000 ohms, and although theoretically R7should be 6,000 ohms, I have used a variable resis-tance (actually a potentiometer) of to,o00for this position. My tests have proved to me thevalue of this departure, for it enables the valve tobe adjusted with great delicacy to work at its bestbias setting for efficient rectification to suit varyingsignal inputs. This resistance must, of course, haveno " off " position, otherwise it will break thecomplete anode to filament circuit.

An H.F. choke is, included in the plate circuit,and from here we take the connection to thereaction condenser C of .0003 mfd. capacity.

The constructor should study this view in conjunction withthe photograph opposite.


To obtain satisfactory reception,the arrangement of the compo-nents and wiring should be

followed carefully.

This in turn links with the reaction winding L3.Furthermore, there is a semi -variable condenser of-oot mfd. maximum capacity shunting between valveplate and cathode.

The exact value of this capacity must be ascer-tained on site, stability of operation under workingconditions being one of the prime factors here.

Output StageThe detector stage is resistance -capacity coupled to

the pentode output stage-an Osram MPT4 valve.The chosen value of the capacity of the mica coup-ling condenser C is i mfd., as this gives verygood results for, vision purposes. As in the pre-vious stages, the usual decoupling precautions havebeen taken. The approximate operating data fur-nished by the makers is : anode volts 25o, screen -grid volts 200, and negative grid bias of I 1. Underthese conditions an average anode current of 32milliamperes will pass, with a screen -grid currentof 5 milliamperes.

This valve, in addition to having a rated ampli-fication factor of ioo, gives a maximum undistortedoutput of 2 watts, and there is thus a good reservefor all vision requirements when operating.

Now, it is not always fully appreciated by usersof this type of mains pentode valve that damageto the valve is quite likely to occur if the anodecircuit is broken while the screen voltage is applied.The temptation for the user to switch over fromthe L.S. to vision and vice versa has been counter-acted, therefore, by omitting a simple change -overswitch and fitting terminals. Then the operator willremember to switch off his set before he carries outany changes from aural to vision reproduction andvice versa.


High tension is derived from a double -waverectifying valve V connected up to a mains trans-former in the usual manner. Here the valve is aMallard DW4, which has a maximum output of50o volts, 120 milliamperes. This is too high forour purpose, so the mains transformer speciallymade by Partridge & Mee, Ltd., has a centre -tappedsecondary winding, T, giving 425 volts at 6omilliamperes. This gives a very conservativerating for the whole circuit. For safety a pairof I ampere rating fuses is included in the inputcircuit.

The rectified A.C. passes through a high -qualityL.F. choke, on each side of which is a pair of 4-mfd.smoothing condensers, C and C.

So much, then, for the theoretical side, and atten-tion must now be turned to construction. A completelist of the components required is specified, togetherwith the manufacturers' names and the numberedletter representing them in both the theoretical andwiring diagrams.

Full List of ComponentsTwo dual -range coils Types RMIS and RM3S,

L, L2 and L, L4, complete with screening coversand bases. (Colvern, Ltd.)

One dual -gang variable condenser, 0005 mfd.capacity, C4 and C9. (Formo, Ltd.)

Four 5 -pin A.C. valveholders. (Whiteley Elec-trical Radio Co., Ltd.)

One centre -tapped iron -cored H.F. choke, HFC2.(Wright & Weaire, Ltd.)

Two screen -grid anode connectors. (Belling &Lee, Ltd.)

One 000i mfd differential compact condenser,C1. (Wingrove & Rogers, Ltd.)

207

One '0002 mfd. mica condenser C2. (Ward &Goldstone, Ltd.).

One 005 mfd. mica condenser C8, Type 67o.(Dubilier Condenser Co. (1925) (Ltd.)

One o-i mfd. mica condenser, Type B775, C14.(Dubilier Condenser Co. (1925), Ltd.)

Two i.o mfd. fixed condensers, Type BB, C5 andC10. (Dubilier Condenser Co. (1925), Ltd.)

One o.i mfd. fixed condenser, Type BB, C7.(Dubiliei Condenser Co. (1925), Ltd.)

One Polar pre-set condenser, .00i mfd. max.capacity, C11. (Wingrove & Rogers, Ltd.)

Two 1.o mfd. metal -case mains condensers, C8and C18. (Formo Co.)

Two 4..o mfd. metal -case condensers, C18 and C19.(Formo Co.)

Three 2.o mfd. Type C2 fixed condensers, C15,C18 and C17. (Ferranti, Ltd.)

One low -frequency choke, Type No. 2, LFC.(Partridge & Mee, Ltd.)

One special mains transformer, to specificationT1, T2, T3 and T,. (Partridge & Mee, Ltd.)

One 6,000 -ohm 10 -watt resistance, R11. (Fer-ranti, Ltd.)

One .25 megohm grid leak and vertical holder,R9. (Dubilier Condenser Co. (1925), Ltd.)

Two 8o,000 -ohm wire -wound resistances, R, andR5. (Watmel Wireless Co., Ltd.)

Two 3oo-ohm wire -wound resistances, R. and 129.(Watmel Wireless Co., Ltd.)

One 20,000 -ohm wire -wound resistance, R2.(Watmel Wireless Co., Ltd.)

208

11111111

One 30,000 -ohm wire -wound resistance, R,.(Watmel Wireless Co., Ltd.)

One ioo,000-ohm wire -wound resistance, Ra.(Watmel Wireless Co., Ltd.)

One Iopoo-ohm wire -wound potentiometer, R7.(Colvern, Ltd.)

One .001 mfd. mica condenser, Type 610, C8.(Dubilier Condenser Co. (1925), Ltd.)

One .0003 mfd. reaction condenser, compact type,C12. (Wingrove & Rogers, Ltd.)

One S.G. H.F. choke, HCF1. (L. McMichael,Ltd.)

One 40,000 -ohm wire -wound resistance, R10.(Watmel Wireless Co., Ltd.)

Eight insulated terminals, Type B (aerial 1, aerial2, aerial 3, earth, output +, output -, L.S.and L.S. -). (Belling & Lee, Ltd.)

Four terminal holders. (Belling & Lee, Ltd.)One twin baseboard fuseholder, complete with

I -amp. fuses. (Belling & Lee, Ltd.)One combined wall plug and adapter. (Ward &

Goldstone, Ltd.)One A.C. mains S.G. valve, Type AC/SG,

metallised, Mazda, V1. (Edison Swan ElectricCo., Ltd.)

One A.C. mains detector valve, Type AC/HL,metallised, Mazda, V2. (Edison Swan Electric Co.,Ltd.)

One A.C. mains pentode valve, Type MPT4,Osram, V3. (General Electric Co., Ltd.)

One double -wave rectifying valve, Type DW4,V,. (Mullard Wireless Service Co., Ltd.)

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Fig. 3.-Wiring diagram of the " Visionette," in which the components are indicated by number to assist the constructor.


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Quantity of Lewcos Glazite wire and flex.One oak cabinet and baseboard (see text).

(Peto-Scott & Co., Ltd.)

The cabinet has been made up specially to speci-fication by the Company mentioned, while the base-board consists of a plywood base i8 in. by12 in., secured to three battens, two of which rununderneath the side edges and one at the back.This raises the underside of the baseboard i in.,and enables certain of the components to be mountedvery conveniently underneath, so as not to crampunduly the lay -out above baseboard.

Furthermore, the cabinet has a solid oak front,with a central cut-out to take the moulded " dial "of the gang condenser. In this way the set canslide in from the back and has a clip on the back.

Component AssemblyAssemble the components exactly as indicated in

the two wiring diagrams. Place the gang condenserexactly in the centre of the baseboard at the front,and since ultimately this condenser will be held rigidby the four screws passing right through the centralcut-out in the cabinet front, it can be held down onthe baseboard by a screw on either side of itsbottom framework, the top of each screw exertingpressure on a small metal strip passing across theframework and resting on -the aluminium base.

Pay very careful attention to the positioning ofthe pair of Colvern coils. The aluminium basesmust be included, and the coils so aligned that thewave -change switch rod is at right angles to thebaseboard edge. If desired, the makers will supplythe coils with the switches ready ganged, but failingthat, use must be made of the link to gang theswitching of the coils and enable both to be switchedfrom one knob movement.

Since the components are held in place both aboveand below the baseboard, it is incumbent upon theconstructor to see that when holes are drilled inthe baseboard to allow wires to pass through, thedrill itself must clear the components and not causedamage.

It will be noticed that the fixed condensers belowthe baseboard are held against the side battens,except in the case of two. For this pair, aluminiumstraps were made to pass round each condenser case,two screws passing into the baseboard to securethem in position.

The aerial series condenser C, is mounted con-veniently on a small right-angled bracket, as alsois the potentiometer R while to accommodate thereaction condenser C12 it is necessary to cut away asmall rectangular section of the baseboard at thefront, and hold the condenser with its one -holefixing nut on a thin brass strap screwed to the base-board edge.

The next task to be undertaken is the wiring, andthe following points must be noted. First of all,wire up the filament connections of the valves. Forthis purpose I employed good -quality Lewcos twinflex, it being borne in mind that each valve requiresa current of i ampere. Tuck the flex round the

210

valveholders as indicated, keeping it on the base-board, since it carries raw A.C. The two fixedcondensers, C. and are soldered direct to theaerial terminal tags. When making connections tothe pair of coils, remember that screening covershave to be put on, and the wires passing from thenumbered terminals must be positioned to keep con-tral with. the slots in the covers.

It is advisable to keep strictly to the wiring runsshown in the two diagrams and portrayed in per-spective in the photographs. In this way there isless likelihood of any mistakes being made, and alsomake your leads with neat right-angled bends.

Two Belling -Lee S.G. anode connectors serve tomake connections to the terminal at the top of theS.G. valves and the terminal at the side of thepentode valve. This is preferable to bare wire,for when removing valves no bare ends of livewires will be inside the set, with the likelihood ofcausing damage.

In addition to using a short length of flex to thetop cap of the vertical grid -leak holder, use flexwire to the two terminals on the left-hand con-denser of the twin gang. This condenser has anadjustment to move its fixed plates through an angleof about 3o degrees, and if the connections aremade with solid wire, movement, and hence thetrimming adjustment, is prevented.

Do not fail to include the earth wires to each ofthe metal coil bases. The short lengths for thispurpose will be seen in Fig. 2, each lead passingfrom terminal 6 to a screw making electrical con-tact with the base.

The First TestWhen the wiring is completed, check it over once

carefully to see that no lead has been omitted, andthen proceed to connect up the set for its trial runbefore housing it in the cabinet.

For the first test join the aerial lead-in to theterminal " aerial 1," and the earth to its properpoint. It is advisable to assimilate the simpleoperating details in conjunction with a loud speaker,so join this to the pair of terminals included forthe purpose.

Place on the pair of coil -screening covers, makingquite sure that none of the wires to the coils touchthe covers, but project through the centre ofthe slots provided. Insert each valve in its holder,not forgetting to add the two connectors to theS.G. and pentode valves; add the fuse -box coverwith its pair of I -amp. fuses, and finally insert themains plug into the house electric -supply socket.

With the wave -change switch knob set to giveeither the medium or 'long waveband, whichevercovers your local station, switch on the mains.After waiting a few seconds for the valves to heatup, proceed to tune in your local station by rotatingthe pair of moving plates of the gang condenserthrough the agency of the right-hand knob on thecentre panel inset, the reaction condenser being setat zero.

If all is in order, the constructor is sure to .be(Continued on page 224)


News from AbroadFrom Our Own Correspondents

GermanyDETAILS are now available of an entirely

new type of modulated light source, de-veloped by the Osram company in conjunction

with the engineers of Fernseh A.G., the companysponsoring Baird television in Germany. When itwas found that the brightness of the ordinary neonglow lamp could not be increased any further, itwas decided to investigate on entirely new lines.

Glowing ElectrodesIt is known that the brightness of a gas discharge

lamp can be increased considerably if one utilisesthe positive column. The drawback of theselamps was, up to now, the very high voltages thathad to be employed with them. However, by usingglowing electrodes, it is possible to construct suchlamps which will work with mains voltages, i.e.about 220 volts. As such values exist in the outputstage of an ordinary mains receiver, lamps usingoxide electrodes can be used directly aftef the out-put valve.

Now, when such a lamp is filled with Natrium,the discharge becomes extremely bright and of ayellowish -white colour. In order that the lamp canbe used with ordinary voltages, it is placed in ametal box which is heated directly from the mains.Thus very bright images are obtained at relativelylow voltages. Photometrically measured, the bright-ness was found to be 126 candles. At maximumoperating conditions the illumination was 10 lux,or 3.55 Hefner candles per sq. cm., compared tothe ordinary neon lamp's 0.04 Hefner candles persq. cm. As Fig. 1 shows, the lamp is U-shaped. Inorder to obtain even illumination over- the whole ofthe surface of the image, a ground -glass screen isplaced over the front of the heating chaMber (Fig. 2).

Fig. 1.-View of the new U-shaped lamp filled with Natrium,which gives an extremely bright discharge.

Fig. 2.-Heating chamber, with ground -glass screen.

A great advantage of this lamp is, moreover, thatit has absolutely no lag, which is of extreme im-portance owing to the very high frequencies thatoccur in modern good -detailed television images.The bright yellow light is very pleasant to look at, asthe images appear somewhat white: The lampshown in the photograph illuminates a surface areaof about 1 in. by 2 in. In order to keep the hightemperature of the heating elements away from thevision apparatus itself, the chamber with the lampis attached to the outside of the back wall of thecabinet.

It was found that in order to avoid the formationof black streaks in the images, the lamp should beslightly " tickled " with high -frequency current, andthe accompanying circuit shows how the lamp isconnected up. The necessary high frequency istaken from a small valve generator, which is notitself indicated. The end of the coupling coil isconnected at the one end to the cathode of thelamp, and at the other end to a metal screen placeda few millimetres away from the lamp, so that thehigh frequency is fed capacitatively.

The optimum operating temperature was found tobe 18o° C. The characteristic of the lamp is thenabsolutely flat from to-ioo milliamperes at 16ovolt's. The optimum brightness is obtained between -30 and 6o milliamperes. The power needed tomodulate the lamp is anything between 1 and 14watts, according to the brightness that is desired.The writer has had the opportunity of seeing some


How the new lamp is wired.

very bright images using an output of only 4 watts.The images obtained in conjunction with this new

Natrium lamp are so bright that 120 -line imagescan be comfortably viewed in an undarkened room.Moreover, projection is possible using an ordinaryscanning disc (not a lens disc) with 6o holes. Theresults were superior to 'those obtained with amirror drum and crater neon under similar operat-ing conditions.

The United StatesBy A. P. Peck

A survey of television " in the home " isgiven by Mr. A. P. Peck, an associate editorof the Scientific American, from which we re-produce the following article by special permission.It is the most complete statement that has so farappeared on the position in the United States at thepresent time :-

" Television is here," saysthe technician ; and the publiclooks around for a television" machine " with which it cansee stage presentations, boxingmatches, horse and automobileraces, and all the other interest-ing events that go to make upour complicated national life.But the public looks in vain.Here is a vision apparatus thatshows a picture the size of apostage stamp; here is one whichgives an image, somewhat dis-torted by a huge magnifyingglass, apparently about 6 in.square. But the images in thesereceivers show only head orhead -and -shoulder views, of oneor at the most two persons, andto see even these limited picturesthe spectator must be very nearlyin a direct line with the apparatus.

Where, then, is the kindof television that will give

us in our own home the equivalent of a motionpicture with sound accompaniment? Quite franklyit is not yet available in the United States. We canto -day go to an up-to-date radio shop and purchasea vision receiver that will actually operate, but itwill have all of the limitations briefly expressedabove. Thus television has or has not arrived, ac-cording to the standards which each person sets forsuch entertainment in the home.

Workers in the television field may be dividedinto two general classes-those who are doing some-thing and telling the world about it, and those whoare doing something and saying nothing. Bothgroups can justify their attitudes. The former isgiving the public a new plaything-crude thoughit is; the latter is working towards a more or lessdefinite end, and prefers to withhold the details ofresults until television on a scale acceptable to themajority can be made available.

A brief survey of the activities of some of theworkers in the first of these two groups will givea general idea of what the present offers.

The engineers of the Jenkins Television Corpora-tion have developed a line of television receiversand reproducers, a console model of which is shown.The image is viewed through a modified shadowbox mounted in the console, being projected on to atranslucent glass screen so that it can be watchedby a small group of people. This company reportsthat it is experimenting with a transmitter operatingin the neighbourhood of 5 metres. In this region con-gestion is at a minimum and the carrier wave can beheld steady enough for satisfactory transmission.

Jenkins' engineers also talk of a new type of" camera " or television pick-up for use in theatresand out of doors, and of a new method of increasingdetbil in a received image. So far this developmentis all in the future, and the receiver with a smallimage, lacking in detail, is all the public can haveat this time.

Mr. William Hoyt Peck with his visionreceiver which gives an image about one

foot high.

In one of the models put outby the Freed Radio and Tele-vision Corporation, a crater -typeneon lamp supplies the lightwhich is modulated by the in-coming signal. This light isprojected through a series oflenses arranged in a spiral on theusual scanning disc. This lenssystem serves to enlarge theimage as it is projected 'on ascreen, and so to make it visibleby several persons at one time.On the front of the cabinet is ahinged arrangement which servesas a shadow box, and which maybe closed to cover the screenwhen the set is not in use.

The latest development at thetime of writing is the lens -mirrordisc of William Hoyt Peck (norelative of the writer). In thissystem, a scanning disc about

ft. in diameter gives an imageprojected on a screen, about


ft. long. Arranged in a circle around the edgeof the disc are 6o lens -mirrors (or the propernumber according to the number of units used atthe transmitter). Light from a crater -type neonlamp is focused through a lens system on to thelens -mirrors, which are individually tilted so thata scanning effect is obtained. The designer, claimsthat far more efficiency is obtained from the neonlamp with his system than is possible with any othersystem in which only part of the light is used atany one instant.

In a demonstration of the Peck system, the writernoted fair definition, but insuf-ficient illumination on the foot -long screen. This was explainedas being due to the lack of asatisfactory light source, which,however, is being developed.The best feature of the apparatuswas the fact that a large groupof persons could view the imagefrom various angles, and did nothave to be directly in front ofthe screen. This factor is onewhich is stressed below as beinghighly desirable in a satisfactoryvision receiver. Peck's inven-tion is not as yet on the market,but licences are being arrangedfor manufacture in the very nearfuture.

Statements from a few of theworkers in the second groupmentioned above-the silent,hard workers-will indicate tosome extent what may be ex-pected in the future. John V. L.Hogan, of Radio Pictures, Inc., who for some yearshas been engaged in intensive development work ontelevision problems, recently told the writer of someof the features that television must possess beforeit can be considered an important factor in ourdaily life. " The image," said Mr. Hogan, " shouldbe at least six inches square with detail sufficient toshow recognisable features of persons in close-upsand recognisable action in scenes which take in morearea. The large magnifying glass for enlarging theimage is definitely out. The image may be vieweddirectly as formed or projected upon a screen. Inany event, the image must be such that it can beseen by a group of people seated as they would bein a home living -room, and not by only one or twodirectly in front of the television receiver. Theapparatus must be simple enough in operation torequire no more attention from the user than isneeded by the present-day broadcast receiver.

" I do not believe that the scanning disc or drum,as such, will be a part of the really successful tele-vision receiver of the future. By this I do notmean that mechanical methods of scanning and re-producing will be discarded in favour of some suchelectrical method as the cathode-ray tube, but thebulky scanning disc must go. Its inherent, undesir-able features cannot be countenanced in a radio visionreceiver that is to be used by the general public."


In the foreground is the Jenkins television"camera," used to pick up visual pro-

grammes.

Mention was made of the use of motion picturefilm for television transmission as opposed to directscanning of actual figures or scenes. Mr. Hoganexpressed himself as follows: " When experiment-ing with television as we are, and as others aredoing to -day, it is essential that all available factorsbe eliminated or stabilised as far as possible. Scan-ning a film does just this with one part of the trans-mitting equipment. All other factors being equal,we know that the transmission to -morrow will bethe same as it is to -day, using the same film, andthus we are able to check differences in operation

that would be more obscure ifdirect scanning were employed.When television becomes anaccepted fact for the generalpublic. I believe that films willfurnish the bulk of the pro-grammes. Their use will makepossible a far wider range oftelevision entertainment thancould be attained by direct scan-ning, although the latter will beof great value for ' spot pick-up 'of news events and the like."

In the United States to -day,then, television seems to boildown to just this: If you willbe content to see pictures thatare not even comparable withthe earliest movies, or if you areexperimentally inclined, you canhave television in your ownhome and can " look -in " on pro-grammes which are available atmore or less regular intervals.If, however, you want 'some-

thing that will compare favourably with your homemovie equipment in quality of image, you cannothave television to -day, and you probably will nothave it for some time to come.

Radio CityRDIO CITY forms part of a new group ofbuildings which are being erected in the heartof New York by Mr. John D. Rockefeller,

Jr. As soon as the project definitely took form,American business interests rallied enthusiasticallyto its support. Mr. Owen D. Young, chairman ofthe General Electric Co., at once took long leases forfour great companies in which he has a guiding hand-the R.C.A., the National Broadcasting Co., Radio-Keith-Orpheum Corporation, and R.C.A. Photo -phone, Inc.

Radio City will include the first television theatrein the United States. American business interestsare backing television. Mr. Samuel L. Rothaf el, theentertainment magnate who has been styled " Mayorof Radio City," said : " Television is not perfect yet.We do not want to start it on a big scale until it is.That was the mistake made over sound films. Butall our stages and studios are being built for tele-vision purposes. The time will soon come when

213

Architect's drawing of the new Rockefeller buildings, withthe giant radio skyscraper in the centre.

London will look -in to Radio City's plays, operas,and films."

The whole group of buildings will be known asthe " Rockefeller Center," and the founder is himselfspending several millions on the project. In thefounder's words, it is a monument " to symbolisethe spirit of co-operation and brotherhood among allnations, upon which enduring peace and prosperitycan be built." The enthusiasm iri New York isreflected in an illustrated brochure which we havejust received from America : '

" New York already has its famous landmarks-the soaring beauty of the Woolworth Building, theneedle -like towers of the financial district downtown,the cool stark majesty of the Empire State Building.But these are isolated and devoted to business alone.Uptown the Cathedral of St. John Divine crownsMorningside Park, the tower of Riverside Churchleaps up to its inspiring heights, and in midtownFifth Avenue stand the twin spires of St. Patrick'sCathedral."

It is claimed that the Rockefeller Center will meetevery requirement of business, and at the same timeit will create an atmosphere of harmony and peace.Huge buildings have sprung up all over NewYork. A great number obscure the individuality ofall except the tallest.

Aiming at buildings of individuality and of lastingimportance, the architects of the Rockefeller Centerhave perfected plans for two relatively low buildingsof studied proportion. These will be known as theBritish Empire Building and the Palais de France.

Last month Lord Southborough laid the founda-tion -stone of the British building, which forms theright-hand side of the gateway to the Center. Herewill be exhibited the finest products of the Empire,with examples of our works of art, antiques, andjewellery. Information will also be available abouttravel facilities. The left-hand side of the gatewayhas been secured by the French Government to housein similar fashion all the finest products of France.Both Italy and Germany are also to be fully repre-sented. The German Government are makingarrangements to secure a building at the corner ofFifty-first Street and Fifth Avenue. When theItalian Government heard of the project, they at onceapproached Mr. Rockefeller with a strong requestto be allowed to participate.

Radio City will include a seventy -story skyscraperand other buildings, which will form the principalentertainment centre of New York-an opera house,a sound theatre, the television theatre, and vaudevilleand drama theatres, together with offices for the bigradio corporations.

The land on which Rockefeller Center will stand,with its frontage on Fifth Avenue, is probably themost valuable site in the whole American continent.

The " Visionette(Concluded from page 210)

impressed with the quality of reproduction (assum-ing a high-class model speaker is in use), and thecomplete absence of any mains hum. Selectivityand one form of volume control is provided throughthe differential condenser C, at the back, while thesecond condenser knob on the left at the centrepanel inset acts as a trimmer, and enables the stationto be tuned in accurately.

Note that the potentiometer R7 should be set atapproximately its mid -position to start with, andshould be adjusted carefully after the station is-tuned in to give the best rectification for the signalstrength then available. Adjustment should also bemade on site to the pre-set condenser, C, althoughthis is done best in conjunction with the reactioncontrol.

Searching for stations is carried out in the usualmanner with the set brought to its most sensitivecondition just off oscillation point, and I am surereaders will find that the receiver fulfils adequatelythe quite modest claims made for its performance.

Unfortunately, up to the time of writing thepromised transmission of television signals by theB.B.C. has not materialised, so that it has not beenpossible to test out this modified version of the

Visionette " in conjunction with vision apparatus.This is a pleasure which must be deferred for afew days, but will be dealt with in full ,in nextmonth's issue.

In conclusion, may, I thank those vigilant readerswho pointed out the little error in the skeletondecoupling arrangement shown as Fig. 2 on page179 of the July issue. Of course, .12. and R7 andR, and R8 should be interchanged.


If Lindbergh had been TelevisedBy Orrin E. Dunlap, Jr., B.Sc.

A fascinating future is foreshadowed in the writer's new book, "The Outlook for Television;" just pub-lished by Harper & Brothers, New York. We have acquired the serial rights of several chapters, the first ofwhich gives a picture of the famous flight across the Atlantic as it might have been watched by television.Mr. Dunlap also deals with the future of exploration and politics as likely to be influenced by this new science.

TO reveal the thrilling possibilities of tele-vision let us go back a bit, into the land ofwhat -might -have -been, where the imagination

links the future with the past. Charles A. Lind-bergh is at Curtiss Field ready to begin his famousflight to Paris, on May loth, 1927. The electriccameras with their all -seeing eyes and sensitivelenses are on duty to snap the scene.

It is two o'clock in the morning. Television screensdepict a murky, dreary scene. Puddles caused bya thunderstorm's deluge around midnight glare liketiny lakes in the flood of the electric lights that arenow illuminating the television scene. The silvernose of the Spirit of St. Louis glistens through thehangar door upon which a television camera isfocused. Word has been broadcast that " Lindy "is preparing to go. Crowds are collecting. Auto-mobiles line the roads around the field, and on thetelevision screen the Nassau county police are seenrushing about to keep the mob off the flying field.

Wisps of fog blow across the field and the tele-visors catch them. It is a dismal scene, but never-theless a dramatic one for the millions who areforsaking slumber to watch an historic event. Theyhear the chatter and comment of the crowds, theshouts of the police, complaints of the wet field.Microphones alongside the radio camera pick upwords that come from the crowd. Someone says itis the height of folly for any plane to take off, evenon a short flight. A spectator at the field looksskywards and holds out the palm of his hand. Hesays it is raining again. But someone runs out ofthe hangar and reports the sky to the north isclearing. Apparently the threatening conditions areonly local.

Outward BoundA policeman's motor -cycle roars across the tele-

vision screen. He is clearing a path through thecrowd for the pilot. It has stopped raining. Thebig doors of the hangar swing open revealing agraceful plane. A truck backs up to the doorway.The Spirit of St. Louis is turned around. The tailis lifted up by careful hands and is made securewith ropes. Every precaution -is taken to avoidstrain before it gets into the air. It is boupd ona long journey on an uncharted pathway alotig theGreat Circle Route that links two continents.

The television screens of all America are illu-minated with activity. Motor -cycle policemen are


seen to surround the truck, and the silver bird ispulled ignominiously along tail first across the field,as a corps of television photographers follow withtheir electric eyes and microphones. Mechanics areseen to stoop occasionally as they walk along to feelthe wheel bearings for fear they might heat upunder the load of 200 gallons of fuel alreadypumped into the tanks.

If is five o'clock. The rain is sprinkling. The.truck moves slowly towards the runway so that theplane will ride tenderly over the rough spots andpuddles that dot the field. The grass is wet andthe ground soggy.

The Sun comes UpThe television scene is becoming a bit clearer.

The clouds in the east are breaking and the firstfaint streaks of light appear. Soon the radio menwill not need the artificial spotlights and flares toilluminate the scene. At last the nose of the Spiritof St. Louis, with a canvas cap over the motor, isat the head of the runway.

The ship is facing the rising sun. A closed carapproaches. A youth in army breeches and a tightwoollen sweater steps out. Men standing on thenose of the plane are pouring in the petrol. Fellowaviators realise this flier will soon be off, and theyare shaking hands and wishing him good luck.The spectators on the field and at the television setsare excited and anxious. Those at the field havewet feet. Those watching by television are com-fortable at home, many of them in night clothes.They wonder if there is any bottom to those hungrypetrol tanks. Finally they see the men climbingclown from the plane. They hear a mechanic tellthe flier that there are 451 gallons in the tanks, 15omore than the plane ever lifted. It is a dramaticmoment.

A mechanic turns over the motor. There is aterrific roar on the television screens as theassociated loud speakers reproduce the noise. Thebirdman is seen donning his fur -lined flying suit.His helmet is shoved back and the goggles rest highon the forehead. He gazes off into space. He isthe most unperturbed man on the field. He climbsinto the pilot's seat and warms up the motor. Thethrottle is open and the great man-made bird roarsand flutters. The television eyes are not missing athing.

Someone runs up excitedly and asks him if he has

2r5-

forgotten his rations. The microphones on dutypick up his answer. The electric cameras point athim.

" P have five sandwiches. That's enough. If Iget to Paris I won't need any more, and if I don'tget to Paris I won't need any more, either."

" How is it ? " asks the pilot." She sounds good to me," replies the mechanic." Well, then I might as well go."It is exactly 7.52 a.m. " So long," he calls

from the tiny window of the plane as he waves tothe crowd.

Moments of ExcitementThe blocks are pulled from beneath the wheels.

The motor roars. Television eyes located all downthe field watch the heavily burdened plane lurchslowly down the runway. The wheels find it diffi-cult to travel over the bumps and soggy field. Shedoes not seem to get up flying speed, at least notenough to rise with the load. The television specta-tors groan. So do those at the field. The planelooks nose heavy and as if it might plunge over onits nose at any moment. It must lift quickly or strikea gully at the end of the runway. Suddenly it hitsa bump which throws it upwards on the televisionpanorama. But the wheels come back to earth.It has not enough flying speed. It looks as if thecraft is too heavy. Suddenly, as if some unseenforce were lifting the wings, they leave the aroundand the plane just skims over a tractor which isdirectly in its path and near the last televisioncamera.

The camera -man turns his lens towards the plane.It is seen to clear the electric wires by barely twentyfeet. But it doesn't seem to rise high. There aretrees ahead. Lindbergh apparently sees themthrough his periscope. He turns a little to the rightand selects the point where the foliage is lowest.The silver wings sweep by and the machine beginsto climb. The sun creeps out from behind theclouds and smiles on the Spirit of St. Louis as it

dips off over the horizon. It is just a mere speckin the television picture now.

A fleeting bird is flying across Long Island Soundon a course that leads to Rhode Island and overMassachusetts Bay to Nova Scotia and on to Paris,3,610 miles away. " Lindy " is otit of sight. It istime for the television audience in the East to go towork. Californians may catch a few hours' moresleep. The next scene will come from Le Bourgetflying field in France. It is almost midnight inParis 33i hours later, when the landing lights flashacross the sky and ioo,000 pairs of eyes are on thewatch for Lindbergh's arrival.

How could it be done? How could the earth'spopulation be spectators at such history -makingevents ? Television will be the answer. It is thewizardry of the age.

Aviation offers other possibilities for television.The bird's-eye view will take on a new meaning.An electric eye linked ,with a radio camera froma lofty perch can photograph a scene and flash it toearth by short waves. On the ground it will beintercepted, recorded on a film and rebroadcastthroughout the country by television. Californiansmay see what the aviator over Manhattan sees as heflies above the skyscrapers. The entire nation maybe taken for a television tour across the GrandCanyon, down the St. Lawrence, or see Broadway's" Great White Way " converted into a nocturnalfairyland of electrical glow. Spectators at homemay see how their city looks when scrutinised fromthe sky.

Airplanes will carry television monocles whichwill enable the pilots to see through fog and dark-ness so that they may land safely. And ships atsea, like the serpents in the story books, will seefar across the waves, far across the horizon andthe curvature of the globe.

Adventure and exploration linked with televisioncameras give the imagination an opportunity tofunction. It will be recalled that the members ofthe Byrd Antarctic Expedition were thrilled by,familiar voices broadcast specially to them from

"How could the earth's population be spectators of such history -making events as the excited scene before Lindbergh'sAtlantic flight ? Television will be the answer. It is the wizardry of the age."


Pittsburgh and Schenectady.Out of the darkness of thelong winter night, throughvarious climes and a mixtureof weather, came voices theidentities of which were faith-fully preserved, and the ringof the voice was true, despitethe long flight across land andsea, across jungles and moun-tains, across the Tropic ofCancer, the Equator, and theTropic of Capricorn, finallyto strike a slender target ofcopper antenna wire stretchedbetween two 'masts reachingup from the ice.

If all that is possible-andit has been done-why shouldradio not carry sight to andfrom the far distant pointsof the earth? Isn't it feasibleto believe that some day anexplorer will soar over theSouth Pole with a televisioncamera, just as the planeFloyd Bennett carried amotion picture eye? Then,instead of waiting for a ship to bring thefilms to civilisation and to theatres throughout thethe land, radio will flash the scene around the globeso that many millions will see exactly what theaviator views and at the instant he is seeing it.The fact that messages have travelled back and forthfrom the isolated regions leads those who have faithin science to believe that as the ear hears so shallthe eye see.

Television in PoliticsTravelling presidential candidates may be rare by

1940. The day is likely to come when they willmake personal appearances before the voters bytelevision. But there may be a danger lurking inthose screen appearances if the radio waves carrythem beyond the Mississippi.

Hughes toured the West in 1916. More thanhalf the states west of the Mississippi voted againsthim. The sages say that he would have beenPresident had he remained in the East. In 1884,Grover Cleveland chose to be a mystery man, so faras the great open spaces were concerned. Hestayed in the East. He won. In 1910, WilliamHoward Taft delivered what was called a poor tariffspeech in Minnesota. That state and others sur-rounding it went strongly Democratic. In 1919,Woodrow Wilson went into the West to championthe League of Nations. He collapsed in Coloradoand returned to the national capital broken in health.President Harding made a Western tour and diedin San Francisco.

Some of the wise men say that Alfred E. Smithshould have remained in the East. But he wentWest in person, as candidates may do by televisionin years to come. Smith lost. The brown derby


"In 1928 the nation tuned-iti to Hoover. Whentelevision enters the political campaign, it will bemore realistic than a mere radio battle of words."

did not charm the West.Hoover made personal ap-pearances and speeches inOmaha, Oklahoma City,Helena, Minneapolis, Mil-waukee, and Rochester. Tenyears ago only the people inthose cities attending thepolitical mass meetings wouldhave heard him. But in 1928the nation tuned -in.

Hoover spoke in New Jerseyand they heard him in Cali-fornia. He fired the openinggun of his campaign at PaloAlto and was heard in Maine.Radio in 1928 made the pre-sidential race a national affairwithin the home circle andtook it away from the frontporch.

Possibly when televisionenters the campaign, " redfire " and bunting will comeback. Gestures will be inorder. The campaign will bemore realistic than a mereradio battle of words. But

the election bulletin boards in front of the news-paper offices are likely to disappear as the returnsare flashed on television screens.

Images of statesmen and their friendly gestureswill mingle among the nations. Television willusher in a new era of friendly intercourse betweenthe nations of the earth. Current conceptions offoreign countries will be changed. Television willperform in this respect in much the way that Lind-bergh saw aviation creating new friendships whenhe said to the Japanese in Tokyo:

" We have come to Japan for an opportunity ofmeeting your people and learning a little more ofthe country which in our schooldays was known tous in America as being on the other side of theworld. When we were children, we thought ofJapan as a land filled with people who were differentfrom us as though they lived on another planet.We marvelled at their ability to walk upside downand that they kept from falling off the earthaltogether."

And so television will enable the inhabitants ofthe earth, who do not have the opportunitiei oftravel, to see how their fellow -men live on the otherside of the globe. They will learn to enjoy theirmusic, drama, and national scenes. Suspicions willbe obliterated. New friendships will result.

When the Japanese Premier, the late Hamaguchi,broadcast the first message of good -will to listenersin the United States his voice was remarkably cleardespite its long flight by short wave across thebroad Pacific to the Californian shore. He openeda new era in international relations between theUnited States and the East. Then the airplane ofLindbergh flew over for a visit. The next link inthe chain may be television-when Japan will seeAmerica and Americans will see the Japanese.

217

Retaining Higher Frequencies1. The Band-pass Filter By E. G. Bowen, M.Sc.

THE television amateur is well acquainted withthe fact that the frequencies in televisionsignals are higher than those met with in

ordinary broadcast reception. Speech and musicconsist mainly of frequencies up to 5,000 cycles asecond, and excellent quality is obtained if a wirelessset is capable of reproducing these frequencies. Buttelevision signals may have a frequency as high asio,000 cycles a second, and a receiver which givesgood results on speech and music will not always besatisfactory for vision reception.

Particular care must be taken of these higherfrequencies in their passage through a wireless setif they are to appear undistorted and at sufficientstrength in the output to give detail to the televisionimages. Much has already been written of the pre-cautions necessary to prevent loss of higher fre-quencies in the audio -frequency amplifier and theoutput stages, but little has been said about thelosses in the early stages of a receiver-in thetuning circuits which pick up the signals in the firstplace. Tuning circuits can cause considerable lossof high frequencies, and in an ordinary receiverno provision is made to balance out or return thisloss.

How the High Frequencies are LostThe resonance curve of a simple tuning circuit

tuned to a frequency of i,000 kc./sec. (a wave-length. of 300 metres) is shown in Fig. 1. Thiscurve shows to what extent the circuit responds toradio frequencies in the neighbourhood of 300metres, and assuming the sideband theory, it will alsoshow to what extent it responds to audio -frequen-cies which are superimposed on a carrier frequencyof i,000 kc./sec. For instance, an audio -frequencyof 5,000 cycles a second (i.e. 5 kc./sec.) superim-posed on the resonance frequency of i,000 kc./sec.gives rise to two sideband frequencies of 995 and1,005 kc./sec., which would be received at only 3oper cent. of their proper strength, i.e. a note of5,000 cycles a second would only be received atabout one-third of the strength of a low note of,say, too cycles a second. Evidently such a circuitis responsible for a considerable high -note loss.

Examination of the figure shows that the fre-quencies of about Io,000 cycles a second found intelevision signals would be cut down to but 15 percent. of their proper strength. Such a loss is fargreater than any which may occur in subsequentstages of a receiver, and it would be well to considerhow it can be eliminated or at least cut down to aminimum.

A tuning circuit made up of a poor coil and con-denser is heavily damped and has a wide resonancecurve, as shown dotted in Fig. T. There is now

218

reasonable response to sideband frequencies up to10,000 cycles, and in this respect a poor, heavilydamped circuit is to be preferred to a carefullymade, lightly damped tuning circuit. But the poorcircuit will respond equally well to the transmissionsof other wireless stations working on a wavelengthnear the one being received. It is not a selectivecircuit, and must therefore be ruled out.

The Ideal Resonance CurveWhat is required is a resonance curve having

the nearly flat top of the heavily damped circuitwith sharp steep sides, so that there is no responseto outside frequencies. The ideal resonance curvethen is a rectangle, as shown in full line in Fig. 2.(In this and subsequent figures, no particular reson-ance frequency is specified. The curves are drawnabout a zero line, on either side of which is a scaleof kilocycles off resonance. This is a more con-venient method of drawing curves than the methodof Fig. t, since it shows immediately the width ofthe band of frequencies covered by any particularresonance curve.)

This rectangular resonance curve shows equalresponse to all frequencies up to io,000 cycles asecond, and no response to frequencies outside. It

PERCENTAGERESPONSE 100

NO.

.

20

990 995 1000 1005 1010FREQUENCY IN KILOCYCLES.

Fig. 1.-The response curve of a simple tuning circuit at1,000 lee./sec., or 300 metres.


PERCENTAGERESPONSE

- , ---roof \... --

1

1

801

-60

40

20

15 10 5 0 5kc. OFF RESONANCE

10 15

Fig. 2. ---An ideal rectangular resonance curve. The responseof a band-pass filter is shown dotted.

would therefore be ideal for the reception of tele-vision signals. It remains to find a tuning circuitwhich has such a resonance curve.

The Band-pass FilterAs might well be imagined, it is impossible to

design a circuit having this ideal shape, but some-thing very similar can be obtained by using a band-pass filter, which as its name implies passes a bandof frequencies to the exclusion of all others. Thefilter has the double -humped resonance curve showndotted in Fig. 2, which approximates closely to theideal rectangular form required.

A band-pass filter is made up by combining twosimple tuning circuits. This does not mean usingtwo distinct circuits, separated by a valve, perhaps,as in a conventional H.F. amplifier, but using twocircuits coupled together, so that signals in one arefed directly into the other and then on to thevalves. Three types of filter are shown in Fig. 3,in which coupling is by :

(a) mutual inductance between the coils;(b) inductance coupling through a small coil com-

mon to both circuits ;(c) capacity coupling by a fixed condenser com-

mon to both circuits.

a a

Fig. 3.-Band-pass filters inwhich coupling is by (a) mutualinductance (M) between the coils,(b) inductance coupling throughinductance (L.), (c) capacitycoupling by fixed condenser (C,,,)

a a a


The first is the familiar loose -coupled tuner usedsome years ago in wireless receivers. Its uniqueproperties were not universally recognised in thosedays, and it was only used as a circuit whose selec-tivity could be varied by varying the coupling be-tween the coils. The second circuit is very similar,but there is fixed coupling by means of the small coil

To prevent unwanted interaction between thetuning coils, it is usual to place a screen betweenthem, or to use completely screened coils. The capa-city -coupled filter (c) is again similiar to (b), buta coupling condenser C. is used to feed energy fromone circuit to the other.

As the properties of all three are similar, theywill not be dealt with separately. Instead, only thecapacity -coupled filter will be considered, as it isperhaps the most convenient for ordinary use; withreservations, its properties may be taken as char-acteristic of all three.

The Capacity -coupled Filter

Fig. 3 c was drawn to show how the capacity -coupled filter compares with the others, but this isnot the most convenient way of connecting it up inpractice. The more usual method is shown inFig. 4, which gives in addition a set of resonancecurves for wavelengths of zoo, 35o, and Soo metreswhen the coupling capacity is oo8 mfd.

It is evident that as the wavelength increases thepeaks become more pronounced and the distance be-tween them increases. The peak separation increasesfrom 7 kc. at 200 metres to 25 kc. at Soo metres.At 35o metres the peak separation is a little under20 kc., and the response to frequencies up to 10 kc.off tune is greater than the response at resonance,i.e. at 35o metres the higher audio -frequencies upto 10,00o cycles a second are received at greaterstrength than a low note of, say, loo cycles. Suchan accentuation of the higher frequencies would beextremely useful in a television receiver in com-pensating for the inevitable losses which occur inthe low -frequency stages.

We have just seen that the peak separation in-creases with increasing wavelength. It can be shownthat for any one wavelength the peak separationwill increase as the capacity of the coupling con-denser is decreased-a small coupling condensergives widely spaced peaks, while a larger one draws

2 It)

them together. The actual peak separation is givenby the formula: /I ,

Peak separation (in cycles)= (02C,2-"2/rL

where co = 2 7T X frequency in cycles.L = inductance of either coil in henries.r = equivalent series resistance of one tuned

circuit in ohms.C,,, = coupling capacity in farads.

Using this formula, we can calculate the capacityof the coupling -condensers which would be requiredfor the reception of television signals from the Lon-don Regional station on a wavelength of 356 metres.Assuming the tuning coils each have an inductanceof 200 microhenries, and the series resistance ofeach tuned circuit is 10 ohms, the calculation leadsto a coupling capacity of oo8-mfd. It was thiscapacity which was chosen for drawing the curvesof Fig. 4. It can be seen that the curve at 35ometres is one which gives excellent response to side -band frequencies up, to io,000 cycles with sharpcut-off above this frequency.

Using the Band-pass FilterHaving now found the coupling capacity which

gives the necessary response curve, we can go onto consider briefly some practical details.

It is essential that the coils of a band-pass tunershould be accurately matched and that the condensers

PERCENTAGERESPONSE

Q-) N8060

20

15 10 5 0 5kc. OFF TUNE

10 15

Fig. 4.-Resonance curves of a band-pass filter having acoupling condenser of -008 mfd. at 200, 350, and 500 metres.

220

Fig. 5.-Cont.ecting a band-pass filter before (a) a screened -grid valve, (b) a triode detector valve.

should be ganged. There are quite a number ofsuch coils now on the market, matched and com-pletely screened, and there are also many excellenttwo -gang condensers which are suitable.

For the f lter are required a pair of screenedcoils, a twin -gang condenser, the capacity of eachsection being the usual 0005-mfd., and a non -in-ductive coupling condenser of oo8-mfd. The filtermight be connected directly in front of a screened -grid valve as in Fig 5 a, but in this case, subsequenttuning circuits would themselves cause a loss ofhigh frequencies. Perhaps the tuner would be atits best in a receiver employing no H.F. stages. Itwould then be connected in the grid circuit of thedetector as in Fig. 5 b. Reaction could be appliedto increase the signal strength if required.

Those who try out this form of tuning circuit arereminded that while the band-pass filters at presenton the market are perfectly suited for the receptionof broadcasting, they do not respond to a sufficientlybroad band of frequencies to be of the greatest valuein a receiver designed for vision reception. Thetype of filter described above with its coupling con-denser of oD8-mfd., having an unusually broadresponse curve, is ideal for the reception of tele-vision signal -3, but it is unsuitable for ordinarybroadcast reception. For satisfaction its use shouldbe confined to the reception of vision signals fromthe London Regional station when there are nopowerful transmissions working on a neighbouringwavelength.

In the second part of this article I hope to dis-cuss, not methods of preventing loss of higherfrequencies, but methods of compensating for thelosses which io occur in the simple tuning circuitsof an ordinary receiver.


From My NotebookBy the Technical Editor

A D.E. Field DayANY activities undertaken by radio societies

to keep their numbers together during thesummer months call for special commenda-

tion. I was therefore very pleased to hear of thesuccess which attended the direction -finding com-petition organised by the Golders Green & HendonRadio & Scientific Society. As in previous years, Iwas appointed a judge, but important business un-fortunately prevented my attendance. The com-petition was the most successful held so far, andover eighty competitors were in the " field," includ-ing a contingent from the Pye Radio Society ofCambridge.

Several modifications were made to the schemeas compared with previous years, the most im-portant being that it was divided into two parts.For the first part the transmitting station wasmobile, and the object was to locate its direction,but for the second part it was stationary and con-cealed in a field near Ridge Church, and the objectwas to discover it exactly.

A second transmitting station (5RD), the exactposition of which was known to all, was used as areference or check of thegreatest value, as it was quickly discovered thaterrors due to local conditions were by no meansconstant even in a small area. By means of thisstation, not only was it possible to check the ap-paratus in use, but the errors just mentioned couldbe compensated. The use of such a station seems

Television constructors will be interested in a recipe forcold solder, which is given on page 230.

to be of the highest importance in this type of work.The groups were located in an area about twelvemiles away from the mobile and hidden trans-mitting station.

It is interesting to note that the equipment ofthe transmitting station was essentially mobile. AnML rotary transformer, type L.E.H., supplied thenecessary high tension, the power developed beingabout 8 watts, and the various groups reported ex-cellent signal strength.

Mansfield Rotary ClubA week or two ago I made a journey to Mans-

field, Notts, and spent a most enjoyable day. Firstof all I gave an address on television to the Mans-field Rotary Club. After explaining the principlesof transmission and reception, I suggested about adozen applications of television to home and busi-ness life. The ensuing discussion was most illu-minating, and proved that the Midlands are fullyalive to the vast potentialities of the wonderfulscience to which this journal is devoted.

After, this, Mr. A. H. Whiteley, the genial andpopular managing director of Whiteley ElectricalRadio Co., Ltd., took me round his works. I wasamazed to find how this firm had grown as a resultof its policy in giving the public a " sound " deal(need I mention that their speciality is loudspeakers ?). In any case, they are planning to moveto larger premises within the next month. I wasprivileged to hear the new " hush-hush " speaker,which will be ready in time for the Radio Exhibi-tion, and I was delighted with its performance, aconclusion which readers can substantiate for them-selves when they visit the Show.

A New Photo -electric CellThe value of photo -electric cells is not confined

to television, and development in this work is mostimportant and full of possibilities. I was thereforeinterested to see that the Westinghouse Companyhave now put a special type on the market. I sawthe first model early in the year, but refrained fromtalking about it, as supplies were then not available.

The cell consists simply of a disc of copperoxidised on one side by a special treatment tocuprous oxide. When light radiations impinge onthe oxide surface, photo -electrons are liberated fromwithin the body of the oxide and move towards thecopper. Thus, if an electrical circuit is made bycontacts on the copper and oxide faces, on illumina-tion a current flows round the circuit from theoxide to the copper. The direction of the currentwithin the cell is, of course, in the reverse direction


to that of the electron flow. It is claimed by themakers that the current so generated is relativelylarge, and can be measured on a galvanometer ormicro -ammeter even with small illuminations.

AmplificationTo give the maximum power output for a given

illumination, the circuit must be arranged so that theexternal resistance is equal to the internal resistanceof the cell. This latter resistance may be taken as1,800 ohms, but naturally varies slightly with in-dividual cells. The cu,rrent generated by the cellthrough a fixed resistance is directly proportionalto the quantity of light radiation falling upon it,provided that the quality of the light remains thesame.

The output of the cell can be easily amplified bymaking use of the following property. When acurrent is passed through the cell from an externalsource in the same direction as the generated photo-current-that is to say, when the positive terminalof the external battery is connected to the negativeterminal of the cell-then, on illumination, the re-sistance of the cell decreases and more currentpasses. Then the change in current for a givenquantity of light is very much greater than thenormal generated current, and when translated intoa change of voltage drop across a high resistance(say io,000 ohms) in series with the cell and bat-tery, is easily amplified by means of valves.

The makers state that the current passed throughthe cell should not exceed 4 or 5 milliamperes.

A Vexing _QuestionThe London Electric Wire Co., manufacturers

of " Lewcos " radio products, have for some timepast taken a serious view of conditions existing inthe wireless trade to -day. They assert that the cut-ting of legitimate retail prices can ultimately haveonly one effect-that of a general lowering of qualityand a growing paucity of dealer -service to the buy-ing public. This company therefore resolved on abold policy. They have decided to limit strictly thenumber of manufacturers and wholesalers withwhom they will do business, and will refuse quitedefinitely to have any dealings with firms suspectedof, or known to be, price -cutting. These efforts willnaturally receive the strongest support from theRadio Manufacturers' Association and other tradeorganisations which are fully in accord with theirideals.

Behind the ScenesThe successful televising of the Derby and its

projection on a large screen at the MetropoleCinema, Victoria, received so much publicity in thePress, that it rather pushed into the background thedaily, transmissions of television which wereeffected between the Baird studios at Long Acreand the cinema. Actually, these played an im-portant part in the whole week's work, and as itwas part of my duties to be " behind the scenes "

222

I am sure readers would like to hear a little moreof what happened. The television interlude had,of course, to work to a definite time schedule inorder to fit in with the normal picture performance,and a few minutes before the tabs " were due tobe drawn the cinema organist played popular music.As the transmitters had been set running in theBaird studios just previously, the engineers behindthe stage switched on the amplifiers, struck the arc,set the motor running which revolved the mirrordrum, and projected the flying spot of light on tothe screen.

The announcer took his place before the trans-mitter, and in this way acted as a subject for fram-ing and phasing the image ; that is, getting every-thing into perfect synchronism at the receivingend. The microphone circuit was then tested, andthose persons present in the studio were told towatch for the red light to appear, when absolutesilence had to be observed except by the individualwho was being televised.

Two TransmittersTwo transmitters were in use, the familiar spot-

light disc one being used for close-ups and somesemi -extended scenes, and the newer mirror -drumone for the remainder of the semi -extended sub-jects and for all the extended scenes. Change overfrom one to the other was reduced to the mereturning of two knobs on the control panels.

After the announcer had explained from the stagewhat was represented by this demonstration of tele-vision, the curtains parted and the image ofMr. Bridgewater, the announcer in the Bairdstudios, appeared on the screen. He in turn madea short introductory speech, but before concludingwas interrupted by a telephone call from the stage,in order to prove that the performance was agenuine portrayal of television. At the suggestionof the manager, members of the audience maderequests which were passed on to Mr. Bridgewater,who carried them out in a genial fashion. Only onone occasion was he really perturbed, and that waswhen he was asked to black his face. Unfortun-ately for him, an artist in the studio had a tube ofblack paint in her bag, and amid laughter from theaudience he proceeded to smear over his face aliberal quantity of the paint which was squeezedinto his hand.

Set TestingTo a designer and service engineer the question

of testing radio sets looms large on the horizon; infact, to anyone who has the welfare of his home re-ceiver at heart, fault finding and testing is of ex-treme importance. I was therefore glad to see thatthe new edition of Testing Radio Sets (published byChapman & Hall) has been extended and revisedto bring it into line with modern knowledge andpractice. It contains a considerable amount ofpractical data, and will form a very useful additionto the library of any wireless and televisionenthusiast.


411101MINIMIONSOM

The New "Televisor"FURTHER details are now available of the

new Baird " Televisor," which was brieflydescribed in TELEVISION last month.

The scheme of this ingenious apparatus is shownin the accompanying diagram. The beam of lightfrom a metal -filament projection lamp (located atthe back of the instrument and on the base) ispassed through a lens and then concentrated on apair of nicol prisms, between which is placed aBaird grid cell. This is one of the most importantparts of the instrument.

A New Grid CellAs is well known, a beam of light consists of

vibrations in two directions at right angles to oneanother. The action of a nicol prism is to ex-tinguish the vibrations in one direction, or, in otherwords, to plane polarise it. If no cell was inter-posed and the second nicol prism was arranged topolarise the light in the opposite plane, the netresult would be that no light would get throughthe combination.

The new Baird grid cell, consisting principallyof small condenser plates immersed in a liquid callednitro -benzine, has the effect of turning the plane ofpolarisation through an angle, with the result thatthe extinction of the light is not complete and acertain proportion of the light from the lamp passesthrough the second nicol.

This particular cell has no inertia, and the amountof rotation of the plane of polarisation variesexactly with the strength of the signal applied tothe plates of the grid cell. Furthermore, it has theenormous advantage that it will work at voltagessuch as are available in any good wireless set.

By applying the received television signals to this

The new Baird television transmitter, which hasbeen installed in Broadcasting House for the B .B.0

programmes beginning on August 22nd.


cell, therefore, the amount of light passing out ofthe second nicol prism seen in the diagram is pro-portional to the magnitude of the signal strength,and in this way we secure a light variation which isproportional to the reflected light picked up at thetransmitting end when exploring the subject.

SCREEN PULLED OUTFROM FRONT 0, CRS.

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On passing from the nicol-prism grid -cell com-bination, the light reaches an inclined mirror, is thenturned through an, angle, and finally passes throughanother lens to be focused on to a revolving mirrordrum.

The mirror drum merely replaces the lightperforated disc employed in the simple models oftelevision apparatus. The drum is made fromaluminium and purposely lightened by havingsections cut away, and 3o mirrors are positionedround the edge. Each mirror is inclined at aslightly different angle from its immediate neighbour,with the result that as the drum revolves the lightprojected on to each mirror is thrown as a spot onto any screen placed in its path, and this spot ismade to move vertically from the bottom of thescreen to the top. As each mirror takes charge ofthe spot of light, it is made to create a strip oflight, these individual strips joining together toproduce a total light area of approximately 9 in.high by 4 in. wide.

On the case of the new " Televisor " are twoswitches which control respectively the mains feedto the motor and the mains feed to the filamentlamp, while a knob just above is linked to a rheostatfor adjusting the motor speed.

When the motor is switched on, the drum is runup to its normal speed of 75o revolutions perminute, and since the familiar Baird automaticsynchroniser is incorporated, this pulls the druminto step with the transmitter motor. For framingand phasing the image, a large knob is providedat the side of the instrument near the back. Thisrotates the carcase of the motor and will move theimage up or down ; by turning it through therequisite number of degrees, the image can bemoved to right or to left according to the numberof light strips that it may be out of phase. Theresultant images are quite brilliant and are blackand white.

223

Letters to the EditorTWO-WAY TELEVISION

To the Editor of TELEVISION

SIR,-I was interested to see your reference tothe two-way television system of the AmericanTelephone & Telegraph Co., as I had a first-handexperience of this apparatus in New York recently.

It is the longest wired -television system in theworld, and my brother and I had a television talkacross these wires. We were actually three milesapart, and yet we could see and talk to each otheras easily as we could across a tea table. Later wecompared notes and found that the details of ourexperience were exactly similar. This is what hap-pened to me.

A chic young lady ushered me into a lovely oak -panelled room. It looked, with its gay cretonnes andbowls of fresh flowers, just like a drawing -room inGrosvenor Square. After a five-minute wait theyoung lady returned and escorted me to the tele-vision booth. It is a little larger than a telephonebooth and contains a swivel chair and elaborate ap-paratus on the back wall. I am instructed not totalk longer than three minutes and not before I see ared light on the screen. The door is then shut andlocked.

For a moment there is silence and darkness.Then, with a noise like whirring dynamos the redlight appears. As the colour fades my brother'sfeatures are focused on the screen. The imageflickers badly at first, but gradually clears. Mybrother smiles and greets me. His voice is clearand natural, but his words do not quite synchronisewith the movements of his lips. He has deepshadows around his eyes and mouth. He makesthe same observations at his end, and remarks withbrotherly candour that I fook " fifty years old."

Soon after this a voice interrupts our talk with" the time is now up. Please conclude your con-versation." I watch my brother stand up and reachfor his hat. Then the picture fades and the lightsgo on.

When I stepped out of the booth I found a guidewaiting to take me through the research laboratories.He was very courteous and answered most of myquestions, but was not revealing: We both knewthat all the patents and valuable ideas lay behinddoors marked " Strictly Private." I saw enough,however, to realise what infinite pains are beingtaken to make television as simple and effective asthe telephone.

In a very real and personal sense, television shouldrob distance of some of its terror. The lover andhis sweetheart, and mother and her child, the manand his business, all dislike the anxiety and uncer-tainty of separation. When, however, they are ableto see as well as talk to each other, they should notfret about the miles that lie between them.

224

The international value of television should be-come equally great. Wireless, aviation, and thecinema have shrunk the world to a considerabledegree. Television will reduce it still further, andmay even accomplish what all the conferences inEurope have failed to accomplish, namely, the break-down of national and racial barriers. If this betoo much to hope for, then let us content ourselvesthat it is at least a step in the right direction.

Yours faithfully,MARY NEWELL MARDEN.

43 BELSIZE AVENUE,N.W.3.

" NEWS " BY TELEVISIONTo the Editor of TELEVISION

SIR,-With reference to the article in your Julyissue headed " News by Television," we would liketo point out that a similar device was in regularoperation in connection with our broadcast pro-grammes, and was described in TELEVISION forNovember 1930, under the heading " StudioTopics," a continuous message being broadcast bymeans of a tape pulled past the scanned area at alow speed, thus giving an effect at the receiversimilar to the news bulletin electric signs which existin London and elsewhere.

It might interest your readers to know that anapparatus of this type was built by us with a viewto being used in Siam to transmit Siamese charac-ters by telegraphy, and also as a form of televisiontape machine, ordinary printed tape being trans-mitted.

The apparatus gives a very rapid method oftransmitting visual printed matter, but it is ques-tionable whether it can compete with the ordinarytape machine, which is already developed to a highdegree of efficiency, and gives a permanent record.

We may sty that the apparatus is described inBritish Patent No. 324.029.

Yours faithfully,BAIRD TELEVISION LIMITED,

R. E. LAYZELLE,Acting Secretary.

133 LONG ACRE, W.C.2,July 18th, 1932.

The Editor forwarded the above to the contributorof the article, Mr. H. M. Dowsett, M.I.E.E.,F.Inst.P., who writes :

The Marconi Television " News " transmitterwhich I described in the July number is designedsolely for the purpose of transmitting one particulartype of picture, a long strip of transparent tapewhich fills the whole of the frame, and this is thecentral feature which controls the mechanical design


The latest model of the Marconi News Transmitter.

of the apparatus. The electrical design is basedfundamentally on the frequency band available forthe television transmission, and this determines thelength of the frame for a given picture frequencyand number of scan lines per picture. The objectin view is to transmit the maximum amount of in-telligence possible in a given picture area deter-mined in this way, and this results in the use ofstraight-line scanning, preferably along the lengthof the picture.

Special apparatus of this kind, designed solelyfor the purpose of transmitting news, has manyfeatures which differ from apparatus used for" head -and -shoulders " 'pictures. This last-men-tioned apparatus can, of course, be employed totransmit a scan of any suitable object, such as, asuccession of letters or a still picture, or even acinematograph film, but where the sole requirementis the efficient transmission of news, no one wouldemploy such apparatus, as the same frequency bandwhich would be sufficient to enable a message to betransmitted and read at the receiver at a rate of120 w.p.m. when employed with " head -and -shoulders " apparatus would only allow a few lettersto be scanned at a time on the screen. This, inturn, would necessitate a low message speed forintelligibility, and, further, the curved scan lines ofthe disc transmitter mentioned in TELEVISION" Studio Topics " for November 1930 would in-troduce distortion of the type which it is preferableto avoid.

The above arguments apply equally to the newmodel, of which a photograph is enclosed. Itdiffers from the apparatus described in the JulyTELEVISION by employing a lens drum and simplified


optical system in place of the aperture druid withseparate projector lens. This increases the opticalefficiency and allows the apparatus to be made upin a more compact form.

The Marconi apparatus described is covered byBritish Patent No. 373,288.

GRAMOPHONE RECORDING


SIR, -*--A few months ago one of your readersasked whether anyone had succeeded in - makinggramophone records of television.

At present I am experimenting recording theBerlin (KonigswusteFhausen) cinema transmissionsand have met with fair success. Among the repro-ductions are the following:

(I) The words Pause and Ende (reproduced fromright to left and backwards).

(2) A blonde and brunette who are apparentlylaughing and talking.

(3) A man shaving.I have not yet been able to record the London

transmissions owing to their removing to Broad-casting House, but I expect good results, and wouldbe delighted to loan or give any successful recordsto readers for experimental purposes.

Surely there is a future for this? We have theBlattnerphone-Stille system for programme record-ing; why not for " bottled " television programmes?

Yours faithfully,F. G. R. PALMER.

ST. THOMAS STREET,SUNDERLAND.

ORIGIN OF THE WORD TELEVISION


SIR,-Looking for a reference in back numbersof TELEVISION, I have just noticed a short notepublished on page 93 for May 1931, dealing withthe origin of the word " Television." It is statedthat, failing another claimant, the distinction ofhaving coined the word television belongs to Dr.Alfred Gradenwitz, a well-known German technicalwriter, whose priority is stated by an article pub-lished in 1909.

The statement must be corrected, because, in fact,there is another claimant whose priority dates backas far as 19o0; that is to say nine years before Dr.Gradenwitz's. This claimant is Mr. ConstantinPerskyi, who presented at the Congres Internationald'Electricite held in Paris from August 18th to 25th,190o, a report on the researches and present statusof television at that period. The word television iscommonly employed in this report.

It is not only to correct an historical point thatI am addressing you, but also for the opportunityof giving to those interested in television a biblio-

225

graphical reference that I think is not generallyknown even by television- experts. Mr. Perskyi'sreport was published in the work entitled CongresInternational d'Electricite-Paris, 18-25. Aoilt,1900. Annexes publies par les soins de M. H.Hospitalier (Paris, Gauthier-Villars (Publishers),1903). The author mentions the television appara-tus invented by Nipkow, Kachmetiew, Szczepanik,Schaller, and Poloumordvinow.

Very truly yours,FEDERICO S. BASSOLI.

VIA CASTEL MARALDO 2,MODENA, ITALY.

The Future of RadioDrama

BROADCAS TING has developed a new tech-nique in drama which is likely to be furtheraffected by television. As a general rule,

plays written for the stage are not satisfactory forthe wireless, and in the absence of the visual ele-ment it has become necessary to write special playsfor the broadcast programmes. This new techniqueis now highly developed, and although originatedin order to compensate for the absence of sight, thewireless play has gradually become a distinct formof art which is highly interesting in itself.

The perfection of television will introduce a newfactor in the matter. When it becomes possible tobroadcast large scenes, the stage will once morerival the film in its influence, for thousands of peoplewill be able to look -in to the best plays of the day,just as they now listen -in to the great orchestrasand singers. Whether the present " radio drama "will still have a following will depend on the extentto which its individuality is preserved and developed.From an artistic standpoint, there need be no con-flict between the radio and the television play, assome writers seem to imagine. Even the RadioTimes, which recently discussed the problem in aleading article, to some extent confuses the issuein its anxiety to defend the present form of broad-cast play.

" During the past ten years," this journal stated," radio drama has become accustomed to ' blindness,'and is now on the way to creating a sound -playtechnique that is both original and stimulating. Oncerestore its sight and you are faced with a problemof another calibre, the presentation of a sound -and -sight drama that, for obvious reasons, must lack theauthenticity of the stage and the mobility of thescreen."

This statement is obviously true, but instead ofmaking the simple point that " sightless " drama isa separate art, it implies that it is actually superiorto the televised play. Naturally, this opinion didnot pass unchallenged, and Mr. Dallas Bower, aleading sound -technician and author of radio plays,wrote to the Radio Times about it. He classed radiowith the film as possessing " the great common factor

226

of physical freedom "; while the stage is crampedand confined by its three walls, radio and the cinemacan rove far and wide, taking their audiences withthem. " The fact of the matter is," he concluded," that television, as an exclusive art, will possess thesame basic constituents as the cinema. I think itsuse, when it is technically perfected, will, apartfrom the broadcasting of news and topical events,be mainly seen in the ' transport ' of sound films tocinema halls, and, eventually perhaps, to the home."

In reply the Radio Times pointed out that, whileMr. Bower may have prophesied accurately thefuture of television as a vehicle of drama, he hadcompletely missed the point of the argument. Thereply continued:

When we referred to ' a drama that must lackthe authenticity of the stage and the mobility of thescreen' we were envisaging the employment of tele-vision, not as the medium for transmitting film -plays, but as the medium for transmitting a tele-vision drama produced in its own studios and usingthe facilities of sound -and -sight at first hand. Inthis event, the broadcast play, on the visual side atleast, would be almost as limited as the stage play,for the studio, or studios, would become virtually atheatre in which the physical action involved mustbe confined to the amount of scenery which can beset up at any one time. This limitation on thevisual side would also, to a large extent, immobilisethe aural side of the production. The sound -playof the present day is happily free from suchlimitations.

Magical Quality" Television, when it comes to perfection, will be

a novelty of magical quality. As such it will attractwide interest, particularly among that section of theradio audience which has found imaginative difficultyin listening to plays of sound alone, and which willtherefore insist upon its use in the broadcasting ofdrama. Our point here, like the point of the state-ment to which Mr. Bower took exception, is not somuch that television will inevitably destroy radiodrama as a medium of scope and interest (it mayeven be that ingenious minds will devise meanswhereby the discreet and partial use of vision willenhance the appeal of the broadcast play), but thatthe introduction of 'the visual element will not, asthose who decry ' blind ' drama to suggest, eitherimmediately or necessarily add to the attractions oflistening to a play transmitted by wireless."

It may be some while before television is ableto transmit a full-sized stage, but when that becomespossible the interest in the " legitimate drama " willcertainly be increased. The public must hope thatthe B.B.C., in preserving the present form of broad-cast drama, will not allow it to hinder the evennewer development of the televised play.

Certainly the facilities available at BroadcastingHouse should help the development of radio drama.The television broadcasts will be transmitted underideal conditions, and it is likely that many subjectshitherto regarded as too ambitious for television willbe included in the new programmes.


Points from the Press" A Real Advance "

TELEVISION continues to attract widepublic interest, and further comments haveappeared in the newspapers during the past

few weeks. Some writers take a cautious view ofthe future, others look forward to big developmentsin television.

This division of opinion is referred to by theNewcastle Evening Chronicle in connection withthe B.B.C. television broadcasts. " It will be in-teresting to watch the reaction of the small but in-fluential section of the wireless Press, which haspersistently belittled British television, to the newera which begins next week. Up to the presenttelevision critics have been divided into two schools-those who claim that Mr. Baird and his engineershave made astonishing progress, and those who havepersisted in speaking of television as being very un-satisfactory and still in its infancy. When theDerby was televised recently we gave examples ofthese two schools, both of whom saw the samedemonstration and differed violently not on theoriesbut on eye evidence."

" For the first time the images have real enter-tainment value," states Mr. Alan Hunter in theLiverpool Echo, referring to the new " Televisor "described in the July issue of TELEVISION. When yousee a face on the screen you can instantly recog-nise who is at the other end. When a cartoonistgets busy you can laugh at his sketches because theoutlines are clearly visible on the screen. I saw avery similar sort of Baird machine demonstratedsome weeks ago on the roof of a well-known storein Oxford Street, London. Then the images weresent over a special 6 -metre transmitter erected atLong Acre, a mile or so away.

Any Day Now" The combined effect of these two recent demon-

strations, the first to show the practicability of ultrashort waves for television images and the second toshow off the improved Televisor, is to lead one toconclude that television has now reached a stagewhen big things may happen any day.

" Almost insuperable technical troubles appear tohave been overcome to produce the present en-couraging results, although as a matter of fact theseveral features of the new Baird television systemhave been known for years. The old scanningdiscs have been replaced by mirror drums. Theneon lamp has given way to a modulated bunchedfilament light source-hence the black -and -whiteeffect. In a word, the Baird people are now makinguse of all the best features of the television systemsof the world.

" An experimental 6 -metre transmitter is testingout the possibilities of short-wave television at Long


Acre, the Baird laboratories. And not far away theB.B.C. is testing its 7 -metre transmitter on the topof Broadcasting House. Link up these facts withthe successful demonstrations of the new BairdTelevisor and you have a working hypothesis thattelevision is getting nearer.. . .

" The immediate possibilities, as I see the situa-tion, are considerably more exciting than they haveever been in the past. For, if the new Televisorsare marketed at a reasonable price and listeners canbe assured of an extensive service, there is goingto be a rapid spread of the ' looking -in ' habit."

The Other ViewOn the other hand, a delay of " a year or two at

least," is anticipated by " Tuner " in the YorkshireObserver, who discusses the progress of televisionsince he saw a first demonstration some years ago.His remarks seem to suggest that he has not per-sonally seen the latest apparatus, but in any case" Tuner " looks forward to television screens atleast I ft. square in size.

" We are all eagerly awaiting its coming; we arelonging for the day when, in the comfort of ourown homes, we shall be able to see and hear theartists who perform for us. But don't let en-thusiasm run away with us. Despite the time whichthe B.B.C. is proposing to devote to it, despite theyears of labour which have been spent upon it, tele-vision to -day has not yet definitely reached the stageof being of entertainment value. It is still merelya novelty, and rather an expensive one at that."

Referring to the latest demonstration, " Tuner "continues : " The progress made was demonstratedin London last week, when images were reproducedon a screen measuring 4 in. by 9 in. The earlydemonstration showed the image in black andorange, but the latest revealed that black -and -whiteimages are now possible. The results were fairlystable and could be seen comfortably by a room fullof people.

" That, I believe, is the extent of the progressmade in this country as revealed by official reports.I have reason to believe that experiments made bythe Marconi people have met with even greatersuccess, but the trouble is in making the models atsuch a price as to make them worth while.

" In Germany and America equally rapid strideshave been made following absolutely independentlines of thought. In America images have beenprojected on to a screen 6 ft. square, while inGermany more attention has been paid to detail andthe reproduction of better images.

"Thus, despite all this progress-very commend-able progress-I still maintain that television has notyet reached the entertainment stage, nor is it likely

227

.ts'f T1717 .rrt777777777;S771-.."'7-7,74

to do so for a year or two at least. When thattime arrives we should have a screen measuring atleast 1 ft. square, on to which an image is thrownas good as we are accustomed to seeing at thecinema."

The B.B.C." This time I think there has been a real advance,"

states Amateur Wireless. " For one thing, thepicture is much bigger. More important, the toneis very much better, the images being in black andwhite.

" Added to the success of this demonstration isthe increased activity on the part of the B.B.C. Itis significant of the new importance that is beingattached to television at Portland Place that tele-vision broadcasts are shortly to be given fourevenings a week. What is not so generally under-stood is that these broadcasts are being conductedentirely by the B.B.C. engineers. Correctlydescribed, these should be called B.B.C. televisionbroadcasts-by the Baird process. This procedureis not a mere quibble, for it means that the B.B.C.is open to try, if not immediately to broadcast, anyother system of television that may happen along.

" Some sort of guarantee to purchasers of theBaird apparatus is obviously only fair, and theB.B.C. has made quite a long-term promise to standby the Baird system of television transmission. Noone can pretend that the present owners of BairdTelevisors enjoy anything like a television service,so that if at some future time a really foolprooftelevision system were developed and madecommercially practicable, it is not likely thatexisting apparatus would get a great deal of con-sideration.

" Meanwhile the main hope of television seems torest in short-wave transmission around the 7 -metreband. The r+ -kW transmitter is now testing on topof Broadcasting House, and there is no knowingwhen the B.B.C. may attempt to broadcast its tele-vision on 7 metres. Real success in this directionwould mean a considerable speeding up of a nation-wide participation in television, because the cost andmaintenance of these ultra -short wave stations isquite small. Moreover, the service area of eachsuch station is limited to about twelve miles, so therewould be no interference."

Towards Perfection" There is certain to be a steady increase in the

perfection and in the practical application of tele-vision. Many avenues of progress will be openedup within the coming twelve months," states theNorth Western Daily Mail.

" Educational, commercial, and entertainment usesof television are already being planned.

" The cost of equipment and apparatus presentsthe principal obstacle in the way of progress, butthis will be overcome in the same way as it hasbeen in the radio business. In the meantime weshould study the theory and practice of television

228

which offers infinite scope for anyone with a scien-tific turn of mind.

" First, I believe, it is essential to develop thecorrect mental attitude towards ' seeing in.' Radiobroadcasting, in its early days, seemed incredible toimaginative people. We are no longer awed bylistening -in, but none can failto be deeply impressedby television even in this sophisticated age. Andthe more profound our first impressions, the greaterwill be our interest and enthusiasm for this newscience. The person who just accepts television asa new mechanical device cannot hope to assist inusing it intelligently and usefully."

Television Boom Soon,With this heading the North Mail, Newcastle,

prints an interview with Mr. Thomas Payne, thefirst director of the Newcastle B.B.C. station anda keen television experimenter. " With regulartransmissions from the B.B.C. headquarters for thenext two years, there will be a great incentive to thewireless enthusiast to experiment with televisionjust as he did in the early days of sound broad-casting. The men who built their own sets andwere constantly improving on them are the men whowill make their own Televisors for a mere 12 or 13,whereas if they buy Televisors, the cost will beabout £30. Given a good receiver of, say, fourvalves, and a 220 -volt electric supply, there isnothing to stop them.

" In the past experimenters have not been en-couraged, because television transmissions wereduring the day and not at fixed times. Big strideshave been made in the Baird process, so that theold country is leading the world. It is possiblenow to receive a black -and -white picture in the lightto a size of 9 in. by 4 in.

Many Inquiries" Within recent months Tyneside wireless dealers

have received hundreds of inquiries from radio en-thusiasts on the possibility of television reception intheir homes. They have had to be advised of thedifficulties consequent on the unfixed times fortransmissions and have been content to wait untilthe B.B.C. could announce a definite programme oftransmissions. Now," said Mr. Payne, " it iscoming, and within a few months you will see awonderful interest manifested in television. Ex-periments are taking place at the North RegionalStation at Moorside Edge with a view to relayingthe television transmissions, and if they succeed,there will be further encouragement to. ' lookers -in ' in the north -East."

This view is supported by the Daily Dispatch.Manchester. " The small but keen band ofNorthern television enthusiasts are awaiting withinterest the new series of sight -and -sound pro-grammes which are expected to begin nextweek. . . . Now that the B.B.C. are to sponsortelevision, it is anticipated that thousands of Englishhomes in the near future will be equipped withtelevisors."


y:.

',V

TheEnthusiast

Sees itThrough

THE real enthusiast is always with us, at leastthat is our conclusion from the corre-spondence that reaches the Editor every

month. We are naturally delighted to hear fromprevious contributors to these columns, and trustthat others who have not written to us for sometime will take this hint. In addition, as manynew readers will be making a start with televisionreception, now that the B.B.C. are to broadcastvision signals in the evenings, may we take thisopportunity of extending to them an invitation towrite and tell us their experiences. Share withyour fellow readers the " ups and downs " you en-counter, and you will encourage others to furthereffort !

An InvitationWe may perhaps repeat what we said a few

months ago on the birthday of TELEVISION. Thismagazine is now in its fifth year and is still ableto report the progress of those readers who areinterested in the constructional side of television.This is indeed a triumph, and it is to be hoped thatfor many years to come we shall still be able to boastof their support.

One of the most useful ways in which readerscan assist other television workers is by their con-tinued interest in this Enthusiast series. It is im-possible for us to hear too often from amateurconstructors. A monthly contribution would beacceptable should the writer have anything new toreport in so short a time. Occasionally we have hadto write to old enthusiasts to discover what they aredoing, and we usually receive valuable material inreply. Don't wait until you are asked ! Write*when the spirit moves you, and make full use ofthe space which is always open to you!

News from CambridgeMr. J. Forster Cooper, of Toll Bar, Barton Road,

Cambridge, is one of our old stalwarts, and hiswork in building vision apparatus to receive boththe English and German transmissions shows thathe is still as keen as ever.

" As can be seen from the photographs," hewrites, " my new apparatus is of the same shapeas that manufactured commercially. It differs,however, from the Baird ' Televisor,' in the pos-session of a sound receiving set, of provision forthe reception of German transmissions, and of aloud speaker.

" The first photograph shows the front view ofthe apparatus and the various controls. Theseare : tuning and reaction for the set ; two switchesfor the neons ; motor switch and speed resistances;racking knob; meter; fuse and the two viewing

Front view of Mr. Forster Cooper's vision receiver.


Back view of the apparatus; the two aeons in their boxes havebeen swung back for inspection.

tunnels. The back of the machine may be seenclearly in the second photograph. The two neonsin their boxes have been swung back for inspection.For vertically scanned transmissions I use a Bairdneon, while for the others a standard beehive lampbehind ground -glass is quite satisfactory. Thethird photograph is a view of the inside.

" In order to make the transmissions seem morerealistic, I am using the viewing tunnel as the loud-speaker baffle. This makes the sound appear tocome from the image, as in the cinema, and theresult, in my opinion, is much better than with aseparate loud speaker.

" I am using a Baird disc and synchronising coils.In order to cut out motor :nterference, whichaffected the sound much more than the vision, Ihave connected two 2-mfd. fixed condensers acrossthe motor brushes, and taken their centre point tothe motor carcase. This has improved matters con-siderably, in spite of the fact that I am still worriedwith a miserable 9o -cycle supply. This is to bechanged soon, and will, I hope, permit me to obtainbetter results and a steadier image.

" It must be noted that if German transmissionsare to be received correctly, the disc must be re-versed, because the Germans scan in a clockwisedirection. This means that if the neon and lensbe mounted at the top, the pictures will be the rightway up, but reversed. This last, however, does notmatter much. The set used for sound is a small2 -valve detector and L.F. power battery -operatedreceiver, which is coupled straight to the viewingtunnel and loud speaker.

" I am looking forward to the new series oftransmissions from Broadcasting House, but I wishthat some other wavelength was available for vision.Even in Cambridge, only fifty-eight miles fromBrookman's Park, the difference between LondonNational and London Regional is very noticeableat times." Mr. Forster Cooper concludes by givinga recipe for cold solder, which he thinks will in-

230

terest other readers of TELEVISION. " All that isrequired is to mix aluminium powder, amyl acetate,and acetone into a thick paste. This may be appliedto any wiring connections simply with the fingers,and sets hard in about five minutes. No heat orsoldering iron is required."

Vatehing the DerbyAnother earlier contributor to this Enthusiast

series, Mr. N. M. Button, of 9 Richmond Avenue,Breaston, nr. Derby, has made many improvementsto his apparatus since he wrote to us last year.With the wireless receiver and home-made visionapparatus now in use, he experienced a real Derby" thrill " by watching the race at home instead ofmingling with the crowds at Epsom. Hearty con-gratulations, Mr. Button, and more power to yourarm in the coming months ! In the course of twoletters he says :

" It was in the November 1931 issue that youpublished photographs of my first televisionreceiver, and since that time I have been makingsteady headway. I am now sending you a photo-graph of my new apparatus.

" After trying several old D.C. motors on the250 -volts A.C. mains without any success, a Bairduniversal motor together with the necessary re-sistances was finally decided upon. As can beseen from the photograph, the complete set is builton similar lines to the Baird model. The outsidecasing is made of oak -faced plywood, with a metalwell cover to protect the scanning disc.

" A plywood cradle holds the motor, a Meccanocogwheel and spindle are used for rotating themotor, and coils are used for the usual framingdevice. At first terrible interference was givenfrom the motor, and earthing the centre point oftwo 2-mfd. condensers added more interference.After earthing the centre point to the motor carcase,the trouble was almost eliminated.

" The neon is a Philips double -spiral type (withresistance removed), which gives a uniformlyilluminated surface over the whole of the lens. Thevoltage from the 250 -volts Heayberd eliminator isdropped by a 3,30o -ohms heavy-duty resistance tothe neon. This lights the neon to its correct bril-liancy, and it is then modulated by the output signalpulses in the orthodox manner. I can now

Interior view of Mr. Cooper's receiver.


guarantee a correctly shaded picture with everydetail showing.

" Although the London National transmitter isnot received here half so well as the LondonRegional, the broadcast on Derby day was receivedwith success! The parade of the horses was clearlyseen, and although it was impossible to distinguishindividually one horse from another, the whole ex-periment provided a thrilling half-hour."

In his second letter Mr. Button explains that hehas made a few alterations to the receiver, and re-placed the neon with one of the Baird flat -platetype, with which he hopes to obtain even betterresults when the regular transmissions begin. " Mylast neon has worked wonderfully well, but to passsufficient current through in order to hold thepicture, there was a tendency to make the neon toobright and lose all detail. As already explained,my receiver has four valves, which are battery fedand take about 26 to 30 milliamperes; the set andneon can therefore be worked off one eliminator.When worked in this manner the neon has to be fed

...N.N.--ImIlVision receiver constructed by Mr. X. 31. Button.

whenever the receiver is in use, in order to keepthe voltage of the eliminator from rising." Detailsof the receiver are shown in the diagram.

VOLUMECo/gram

DiFF:CONOF

4.,

140

.,NIP

...

MEG:2-

ill ill(6drievaEo)000sAIFD

1

(6~7 Sw/TrN

SHORTWAVE

-0005MED ,...

8q000OHMS.4f

OSRRIA

A 0

471/ 6omp

IPECTIF/ER

HeArEtEvo ZI3/.

30000 30,0004- OHMS OHM5-1,-

hWO htlFD

fat -=..71

.000341FD(PRESET) <=)' /00,000 OHMS

NEC.AT.. LE3V.,:COS

5 G 2 /5 Apc 60 TURN /a)TRR HL2/0 OSRAM

7 A - - ' .0003MED..

4/1//c22

0 4.WD 1..4z/WED/00/na.

(412,44

He-4,YEERDCHOKE

35,000OHMS

2A1F0

COLVERN 0002MFD COL VERN COILCOIL

-5MEG:

-0002AfFD

-41!

6.0000NmS

2MFD

-/S

Prz201/ENRYCHOKE

B0

250 V Dat 60 m/a

0*A

Afro

11111111ME

MFD TELEVISION

Rpoico 11

Syni COIL -IX:

L50

3R/RDNEON

0^=7v/600 OHMS FOR BR/RDNEON5.500OHMS FOR PH/L. LIPS NEON

Circuit diagram giving details of Mr. Button's home-made receiver.


irFret. iu7/77,,,V7Tr 7777.

Apparatus TestedThe Technical Editor of TELEVISION will be pleased to receiveapparatus, components, etc., from manufacturers for test and,

if found suitable, for review in these columns.

New Lewcos PotentiometerA potentiometer is an indispensable component

with modern set design, but unfortunately many ofthese products fail to perform their normal functionsatisfactorily, the principal objections being thatthey are both erratic and noisy in operation.

The new Lewcos model, however, has undoubtedlybeen carefully designed, and is obtainable in thefollowing values-i,000, 5,000, 10,000,, 25,000 and50,000 ohms. Its construction is certainly verynovel. First of all the wire -wound resistance is heldin a cylindrical moulding, and this with the contactare completely dustproof, since they are enclosed ina non -inflammable transparent cover.

The usual rubbing -arm contact, unless special pre-cautions are taken, is prone to be " noisy " in use,so Lewcos make their contact with the resistancestrip by means of an eccentric rotating plate. Thespindle terminates in a small brass collar with aneccentric hole. A small " axle " holding the plateengages in this hole at one end, and at the otheris a metal cross strip. Pressure is applied by adouble -leaf spring, and rotation of the knob causesthe plate to make pressure contact at differentsections of the winding. With this method there isno friction on the wires and hence no wear, whilethe component is quite silent in operation, as weproved to our satisfaction in tests with a samplemodel.

The rated resistance value was substantiallycorrect, and we unhesitatingly recommend this veryneat and workmanlike component to our readers.It is well finished, and is sold at the low price of 3s.

D.C. Mains Variable-mu ValveTHE new Osram V.DS valve-a variable-mu

type for use with D.C. mains-is fitted withthe standard type of 0 -25 -amp. i6 -volt fila-

ment heater and indirectly heated cathode.In common with those valves employed with

alternating current, the characteristic has been de-signed to give a linear control of volume by variationof grid bias. In addition, the maximum mutualconductance at minimum bias is of a very high order,leading to sensitive reception where it is necessaryto use only a single stage of H.F. or L.F. Wheretwo or more stages of H.F. amplification are em-ployed, any tendency to instability due to the highmutual conductance can be checked in the " vari-able -mu " type of valve by the simple method of anincrease in the fixed portion of the grid -bias resist-ance. The value of this fixed portion of resistancewill limit the maximum conductance to any desiredvalue.

This valve is designed with a maximum mutual

232

conductance of 2.4 milliamperes per volt, and a gridbias of approximately 4o volts; that is to say by anincrease in grid bias to 40 volts the mutual conduct-ance can be reduced to approximately 0-005 mA/volt,thus giving ample range of volume control. Ac-cording to the makers' figures, the rated character-istics are as follows;

Filament Voltage . 16Filament Current . . o-25 amp.Anode Volts . . . 200 max.Screen Volts . . . . 8o max.Mutual Conductance . mA/volt

(measured at Ea=zoo, Esg. =80.,Mutual Conductance . . . . mA/volt

(measured at Esg=f3o, Eg=5, or Esg=5o, Eg=2Mutual Conductance . . . rpoos mA/volt app.

(measured at Eg=4o)Anode -grid inter -electrode capacity . ooo25 m.mfd.Fixed portion of grid -bias resistance . too ohms approx.*

In a sample we tested the figures given werefound to be substantially correct, and readers whohave a direct -current mains supply in their homeare strongly recommended to use this valve whenconsidering the question of H.F. amplification andsmooth volume control. The price is 19s.

New Kit SetsThe popularity of kit sets remains unabated, and

the reason is very simple. The home constructorfinds a real joy in assembling the parts which go tomake up a receiving set. He finds it instructive sofar as elementary wireless technique is concerned.He learns to know just what is in his set, what re-lationship each component bears to others, and inthe event of a fault at any time in the future hefeels competent to go over his set to make thenecessary adjustments or replacements without thefear of doing some irreparable damage.

It was therefore interesting to have details oftwo new kit sets which are being marketed for thecoming season. Reference is made to the CossorAll -Electric " Melody Maker," Model 337, retailedat fI I 15s., and to the G.E.C. Thirty-three " MusicMagnet," retailed at i9 9s., According to advanceinformation, both sets seem excellent propositions.

Celestion Loud SpeakersAlthough it has not yet been possible to test

samples of the new season's Celestion products, wehave been privileged to hear the complete range ofthese in operation at the company's wo,rks. Un-doubtedly the new models are in the highest classfor lifelike tone, sensitivity and ability to handlepowers more than adequate for normal use. Thespecial Hyflex diaphragm is partly responsible forthis, coupled with new forms of permanent magnets.The midget with the loud voice is the PPM Soundex,sold at 27s. 6d. in chassis form or 50s. completein cabinet. Complete test reports will be given later.

* Depending on screen volts. The value of the fixedportion of bias resistance will restrict maximum mutualconductance to any desired value.


4

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