349th Consecutive Issue-Seventh Year THE SCREEN GRID … · 2019. 7. 17. · Write for Free...

THE HAMMARLUND-ROff TS HI -Q 29 MASTERDEC. 1st, 1928

REG. U.S. PAT. OFF

The First and Only National349th Consecutive Issue-Seventh Year

15 CENTS

Radio Weekly

HOOVER WOULD END BOARD

SAY HIS FRIENDS

SHORT WAVE TELEVISION

CHANNELS ARGUED

REALLOCATION FACES

CLEANING -UP PROCESS

THE SCREEN GRID UNIVERSAL

New and Wonderful is the Screen Grid Universal, Reaching a Height ofSelectivity and Volume Seldom Attained on Only Four Tubes.

1NEW AC USE FOR DC TYPE TUBES

RA..u.10 WORLD December 1, 1928

New Hook-ups. This hookshows how to wake Short -Wave rReceivers, and Short - WaveAdapters.

How to use the new screen -grid tube in D.C. and A.C.circuits.

How to build Power Amrli-fiers, and ABC Eliminators. Un-to -the -minute information noall new radio developments.

Sot Builders, Trans, Dealers,send for it today!

I(ARAS ELECTRIC COMPANY4039-LI N. Rockwell St., Chicago,

Please send me your Free Book!Na me

Address

City

4015-L1Illinois

State

VICTOREENSuper Coils

Write for Free Blueprints ofNew VIctorsen Omits

Geo. W. Walker Co.2825 Chester Avenue

Dept. B Cleveland, 0.

LONGER LIFEBETTER TONE

MORE VOLUMEA guarantee slip iston. Fill this outinsurance. BuiltTUBES open newton.

contained in each car -and earn FREE tube

to excel, KELLYvistas of radio recep-

401A $1.004X Special Detector 2.00412A 2.00471A 2.00

UX499 1.25426AC 2.00427AC 3.50440 (high mu) 1.50422 (screen grid) 3.50480 3.50

422 SCREENGRIDOur 122 stands up.

440 HIGHgreat for resistance or

Impedance audio

NEW

RECEIVERSCustom -Built to Any Pocketbook!

0 say that these four newTHi -Q Receivers are the great-est instruments ever produced inHi -Q History is equivalent tosaying that they are the mostefficient, most selective, mostsensitive and most beautifullytoned radios in the world.

For example, there is no re-ceiver, to our knowledge, whichemploys the Band Pass Filter-an entirely new system used ex-clusively in the Master Hi -Q 29models. This new developmenteffects absolute flat -top squarecut-off tuning for the first timein radio history. It assures posi-tive 10 K. C. selectivity. "Crosstalk" cannot occur. Oscillation,buzzint, humming and back-ground noises are totally elimi-nated. Stations don't simply"swish" in-they snap in, clearand positive.

There are FOUR Hi -Q Re-ceivers for 1929-the Junior Hi -

AssociateManufacturers

Sangamo Electric Co.Exo. 310g. Co.

-

Hommarlund Mfg. Co.Yaxley Mfg. Co.Beniamin Else. Mfg. Co.Arcturus Radio Co.

Q 29 at $54.35; the Junior A.C.Hi -Q 29 at $101.50; the MasterHi -Q 29 at $99.50 and the MasterA.C. Hi -Q 29 at $151.50 - fourwonderful receivers which meetpractically every range of pocket-book. All these instruments arethe joint creation of America'sten leading parts manufacturers.All are stage -shielded, built onsteel chassis from the finestparts available in the industry.

If You Want RealRadio Value Write for

Our New 80 -Page BookThe new 80 -page Construction Manual

is the biggest and most complete bookof its kind ever published. Tells how tobuild all 4 new Hi -Q Receivers. Photosand diagrams illustrate every detail.Covers power amplifiers, tube and bat-tery combinations, antennae, installatiqn,short-wave adapters, house wiring and awealth of other data on custom-builtradio. Price 25c.

a, Rob artlsun dQ-2L.C'u4 tomeZuitt

RadioHAMMARLUND-ROBERTS - - - - 1182-V Broadway,

AssociateManufacturers

Acme Wire Co. (Parvolt)International Resistance

Co. (Durham Resistors)Radian Co. (Amperite)Eteetrad, Inc. (Truvott)Westinghouse Micarta

New York

BLUEPRINT OF SCREEN GRID 4 -TUBE UNIVERSAL - $1.00Connections Doubly Clear Because Wiring Done on Top of the Subpanel is Shown Separately, andwiring done underneath the subpanel is shown separately. All leads shown in the same direction inwhich they are physically connected. You don't have to reverse the blueprint mentally to visualizethe practical connections. Crystal-clear blueprint safeguards against error. Order your print today.Prompt delivery. Price of complete kit, $35.00 (less tubes, cabinet and speaker).

PHILIP COHEN, 236 Varet Street, Brooklyn, N. Y.

SAVE THOSE TUBES!Many persons havesets with Navytype sockets-thekind with the collaron and the bayonethinge for the pinon the base cf thetube. If you puta UX base tube ina Nary type soc-ket a short mayblow out all thetubes. Play safeand have line con-tact besides. Cooan adapter that fitsUR tubes intoNavy sockets (Cat.No. UX). Price20 cents each.

GUARANTY RADIO GOOD CO.145 West 45th St., N. Y. SCity

BUILD YOUR OWNDYNAMIC SPEAKERComplete set of blueprints and instructions forbuilding your own Dynamic cone speaker. Easyand inexpensive to build at home with few tools.Guaranteed to work; thousands now enjoyingDynamic reproduction. Mail $1.00 today and youwill receive complete set, postpaid.FANSPEAKER RADIO COMPANY

74 Dey Street - - - New York, N. Y.

RADIO WORLD, published every Wednesday,dated Saturday of same week, from publicationoffice, Hennessy Radio Publications Corporation,145 West 45th Street, New York, N. Y., Just eastof Broadway. Roland Burke Hennessy, President;M. B. Hennssy, Vice -President; Herman Ber-nard, Secretary. Roland Burke Hennessy, Editor;Herman Bernard, Managing Editor; J. E. Ander-son. Technical Editor; Anthony Sodaro, Art Editor

KELLY TUBE COMPANY8718 Ridge Boulevard, Brooklyu, N, Y.

RADIO WORLD, a weekly paper, published by Hennessy Radio Publications Corporation, fromPublication Office, 145 West 45th Street, New York, N. Y. Phone: BRYant 0558 and 0559. 15c perC $6 per year. This issue is dated December 1, 1928, and is Vol. XIV, No. 11, Whole No. 349.Entered as second-class matter, March, 1922, at the1879.post office at New York, N. Y., under Act of

Mar ch

December 1, 1928 RADIO WORLD

's02. -e0S.'

'0"

AV- S.$C'

11°S-N31A)

ovV.

V2A-ONN

SNI-4

Nsc0

.NV°13.V

0.1.e so.

ea. 4,re tree,

ece,. 1,,v vet.000-

c9

c3,3 ve,3ecP (kc,Ne'

k:NoV

etg' ekkg' ,/e&

6,

os

%N°ret

het 6g0\36 le IP

-170

c;V

0%. v r!P 4N-0%

vs, ,ccp

ees.

\\,1. N c,viVe

k\s`&ec,e

e 0.431.;10.11S.

6:1/41,-' tc, 44° a,%&

o'c

/5' ti'.0`)' e"0 rm

tk' Ak:N k\eN ,sV\ °

ceNN

V` k,on N).S&

%&

! 5i0Ae,0. 0 k14'

NC-\`)"

' V't.g3k.O0'(

,.,\%era!ce10). i° e

Ns%log,

01..

e e%Nce

OC. z c °

0; \ e.

616dtd MAO !

P Ct)L41CtrCP151

FERRANTIAudio Frequency

TRANSFORMERSand

RADIO PRODUCTSreceit7e preference

by engineers who KNOW

Real audio transformers withfiat curves. Special outputtransformers for all speakersand tubes. High grade ironcore chokes for "B" Eliminators.Three range portable meters.1000 ohms per volt. 10/50/250scale. Three t ange portablemeters. 2,10 ohms per volt.150/7! r, volt and 15 Mill. scalewith switch. By -Pass eon.densers-2M F-400 volt and arovolt.

Circulars sent on request

Send 15e in coin for copy ofl929 ''erranti Year Book

FERRANTI, Inc.130 West 42nd St., New York N. Y.

FERRANTI, LTD.HollInwood

England

FERRANTI ELECTRICLlm.ted

Toronto, Canada

SHORT WAVE $10'17ADAPTER

Completely built-up, ready to receive; includesthree plug-in coils, also built-in plug and cableand tunes 18 to 78 Requires no extratube. Chart tells just where each wavelengthcomes in DC model (for all sets except ACtube sets). List price, $18.50; our price, $10.17

AC model for AC sets. List price, $19.50; ourprice, $10.72.

Order One Now C.O.D.Ten -Day Money -Back Guarantee!

RADIO SUPPLY COMPANY217 Havemeyer Street, Brooklyn, N. Y.

SET BuildersElections have brought back CustomSet building. Business is booming.Thousands of old-timers are clean-ing up. Let Barawik show 3 ou theway to bigger profits, more sales.Send today for Barawik's Big Bar-gain Book - the radio man's bible.

BAIRAWIK CO. 1312 C Canal "a"HICAGO, ii. S. A.

Be a RADIO EXPERTRadio, a new big industry wants trainedmen. The work is fascinating, interesting,pays big. We send you six outfits of Radioparts to give you practical experience build-ing and repairing sets. Write for 64 -pagebook "Rich Rewards in Radio." It tellsyou how you can learn at home in sparetime to become a Radio Expert No obligation.National Radio Institute, Dept Rw Washington. D.C.

.11

000

BLUEPRINTFOR

Bernard's Economy 3Price $1.00

PHILIP COHEN236 VARET STREETBROOKLYN, N. Y.

1,111,41P MPARMAP Wt./NW/ARP/4M INMPAI MPAMPAMPAVAII WMIpoq IP IP IP 1.

AIR COLUMN HORNS ARE SPLENDID!Especially Those Made of Molded Wood

EVERYBODY who uses a horn loud speaker of the latestair column design, with long tone travel, agrees that the

Model 595 has a travel distance of 8 feet from theunit to the large end of the "bell." Ifmust economize on space, useModel 570, with a 6 -foot tonetravel, with not, quite asstrong reproduc-tion of low notes.But No. 595 is bet-ter and, if you'vet h e room (211A"high, 18" wide, 15"deep), choose thatone. Every pur-chaser is a de-lighted customer.Order one ofthese speciallymoulded woodhorns. Try it for90 days. If notdelighted, returnt and get back

your money, in-cluding any ship-ping charges youpaid! (Note: Nota single one ofthese horns has everbeen returned to us,though we've sold manyhundreds!)ACOUSTICAL ENGINEERING

ASSOCIATES, ***o143 West 45th St., New York City.(Just East of Broadway)

Please ship me at once the following (check off):CI One No. 595 at 810.59, plus a little extra to

defray shipping costs; send it already mountedin FREE baffle board.

o One No. 570 at 87.64, plus little =tea todefray shipping costs; send it already mountedin FREE baffle board.

CI One No. 112 horn motor (universal nozzle) at83.53, plus a few cents extra for shipping.

NAME

you

Model 570. size15" high by 12"

wide by 12" deep, 6 -toot tone travel. FREDbaffle board. List price$13.00. Our price (46%and 2% off list price)...

97.64

Model 112 horn motorADDRESS I ;tends 250 volts withoutIltering (illustrated atCITY STATE Our price (40% and 2%

Uhl). List price $6.00.iff list price $3.5390 -DAY MONEY -BACK GUARANTEE!

type, consisting of anis splendid. Ourtone

Model 595(illustrated above)

Baffle board (notshown) FREE with

each order. List prime818.00. Our p r 1 e (40% and 2% off listorice)-

$10-ss

RADIO WORLD December 1, 1928

De Luxe Carrying Case FREE IWith Each Jiffy Tester Combination!

This Meter Outfit Makes Thirteen Vital Testsin Only 41/2 Minutes!

The Jiffy Testerin its Case is aTesting Labora-tory All by Itself.Leave the metersin the case.Simply lift out theplug, attachingt h e four - prongadapter, if testinga four -prong tube.Put plug in socketof receiver to betested; put tube inTester socket.The B voltmeterautomatically con-nects to the pro-per points whenits tipped leadsare inserting inthe two bindingposts at rear.

..,01i11111111111111/1

This housed JiffyTester, with highresistance vol t -meter for measur-ing B voltages,including those ofeliminators, is aservice kit of thehighest value. Thecase is furnishedin a de luxe finish,with handle. Apatented snaplockmakes it impos-sible for the lid toopen accidentally.The Tester andhigh resistancemeter fit so snug-ly in place thatthey will not jarin transportation.A 5 -day money -back guaranty at-taches t o ea chsale.

Jiffy Tester Comination, shown one-third size, includes 0-10 voltmeter reading AC or DC (same meter reads both) ; 0-20, 0-100nailliammeter, with change -over switch; cord and plug with 4 -prong adapter; 0-300 high resistance voltmeter. Price $13.50.

Complete instruction booklet and de luxe carrying case FREE with each order.

Jiffy Tester a Scientific Trouble ShooterEvery service man, custom set builder, home experimenter, student or teacherone of these Jiffy Tester Combinations Amply accurate for this class ofYou will be well satisfied with assured 5% plusor minus accuracy. Jiffy Tube and Set Tester, consistingof 0-20, 0-100 combination rnilliammeter, 0-10 AC andDC voltmeter and 0-300 high resistance voltmeter. Deluxe carrying ease and instruction booklet FREE witheach order. Jiffy Tester Combination A.

(1)(2)

(3)(4)(5)(6)

(7)

needswork.

$13-50

The 0-300 high resistance voltmeter in "Jiffy Tester Combination A" is accurateto 5% plus or minus, so that at maximum reading it is not more than 15volts off. Those desiring a more accurate 0-300 highresistance meter, never more than 3 volts off, at maximumreading, should order "Jiffy Tester Combination B,"which has a 0-300 meter accurate to 1%, at a cost of$1 extra. Order "Jiffy Tester Combination. B." De luxecarrying case and instruction booklet FREE.

Here Are the Thirteen Vital Tests!to measure the filament voltage, up to 10 volts, of AC and DCtubes;to measure the plate current of any one tube, including any power tube,from less than 1 milliampere up to 100 milliamperes;to measure the total plate current of a receiver or amplifier, up to 100milliamperes. (Hardly any set draws more);to measure the B voltage applied to the plate of tube; the voltage acrossB batteries or B eliminators, up to 300 volts;to determine the condition of a tube, by use of the grid biasswitch;to measure any tube's electronic emission;

to regulate AC line, with the aid of a power rheostat, using a 27 tubeas guide;

Note All That You Get!For $13.50 you receive:(1) fine Two -in -One 0 to 10 voltmeter for AC and DC. Same meter reads both.

Scale especially legible at !Vs to 71/2 volts. This meter reads the AC and DCfilament voltages.

(2) One DOUBLE reading DC milliammeter, 0 to 20 and 0 to 100 milliamperes,with changeover switch. This reads plate current, which is always DC inall sets.

(3) One 0-300 volts high resistance voltmeter, No. 346, with tipped 30" cordto measure B voltages.

(4) One 5 -prong plug with 30" cord for AC detector tubes, etc., and one4 -prong adapter for other tubes.

(5) One grid switch to change bias.(6) One 5 -prong socket. (9) One handsome moire metal case.(7) One 4 -prong socket. (10) One instruction sheet.(8) Two binding, posts. (II) One de luxe carrying case.If 0-500 volt 5% accuracy high resistance meter is preferred to 0 -300 volts, add$1.00, and order Combination C at $14.50.If 0 -500 volt I% accuracy high resistance meter Is preferred to 5% accuracy0-500 voltmeter, add $2.00, and order Combination D at $15.50.[Note-A pair of adapters for UV199 tubes, Cat. No. 999, at $1.00 ertra.These are not sold except with Jiffy Tester Combination.]

to test continuity of resistors, windings of chokes, transformers and circuitsgenerally;to find shorts in bypass and other condensers, as well as in inductances,rosistors and circuits generally;to read grid bias voltages, including those obtained through drops inresistors;to determine the presence of distortion and overloading;

to test for correct bias;

to determine starting and stopping of oscillation.

[Note-Instruction booklet fully informs you how to make each andevery one of these tests in. a jiffy.]

GUARANTY RADIO GOODS CO.,145 West 45th Street, New York City.(Just East of Broadway.)

.. MN MMNI MO MBPlease ship at once your Jiffy Tester Combination for which I will pay post-man advertised prices, but no shipping charges. (Check off below.)El One Jiffy Tester Combination A (0-10 v., 0-20, 0-100 in. a., 0-300 v.,

carrying case, instruction booklet PREP) Price $13.50One Jiffy Tester Combination B (same as above, but with 0-300 voltmeteraccurate to 1%). Price

$4.One Jiffy Tester Combination C (Caine as A, except 0-500 voltmeterplaces 0-300). Price $14.50

El One Jiffy Tester Combination D (same as C, except 0-500 voltmeter isaccurate to 1%). Price $15.50

O Slot of 199 adapters. Price $1.00

NAME

ADDRESS

CITY STATE5 -DAY MONEY -BACK GUARANTY

Vol. XIV. No. 11 Whole No. 349DECEMBER 1st, 1928

15c per Copy, $6.00 per Year[Entered as second-class matter, March,1922, at the Post Office at New' York,N. Y., under Act of March, 1879]

Latest News and CircuitsTechnical Accuracy Second to None

A Weekly Paper published by HennessyRadio Publications Corporation, fromPublication Office, 145 West 45th Street,

New York, N. Y.(Just East of Broadway)

Phone: BRYant 0558 and 0559

Stations1,500 COMPETE

IN FREE DEBUTWith a list of applicants totaling 1,500,

auditions for the free concert -radio de-buts offered by the National BroadcastingCompany for new young artists selectedby the National Music League has begun.An audition committee of ten, chosen bythe League, will pass on the candidates.

George Engles, director of the NationalBroadcasting and Concert Bureau, whichis arranging for the debuts, said that finaldecision as to the winners will rest ona double audition heard by two groups ofjudges. One group, seated in the audito-rium with the artist; will decide on hisabilities as a concert performer; the othergroup will hear the performance overan amplifier and pass upon the artist'sbroadcasting qualifications. Such a finaltest is essential, Engles explained, be-cause the debuts will be of a combinedconcert and radio nature.

Practically every state in the countryis represented on the list.

Arthur Moss Risesto Electrad Presidency

Arthur Moss, treasurer of Electrad, Inc.,in charge of sales and advertising sincethe company was formed, has been elect-ed president of the company.

Electrad, Inc., about five years ago be-gan manufacturing a wide range of high-class radio parts at 428 Broadway, NewYork City, which address was retaineduntil the beginning of last year. Fromthe very inception of the company itsline met a ready acceptance on the partof both the general public and of radioset manufacturers.

Under Mr. Moss' management, thecompany's sales have rapidly increased,until it is now recognized as one of theleaders in the industry. Since January,1927, the company has been located at175 Varick Street, in much more com-modious space and with greatly expand-ed factory facilities.

Mr. Moss' accession to the presidencyof Electrad, Inc., was hailed as indicat-ing a distinctly progressive policy withinthe organization that points to still fur-ther growth.

FREED-EISEMANN Radio Corpora-tion announces the appointment of PhilipVan Doren Stern as advertising manager.He was the company's first advertisingmanager when broadcasting began.

Cry for JusticeBlind Man's Log

Is in Raised LettersCincinnati

When the simple erasure of penciledfigures and the writing in of a few morewill remake a radio log, reallocations ofradio stations mean little to the dial -twister.

Changing a radio log becomes an un-dertaking, however, when a blind listenermust tabulate stations in raised lettersknown as New York Point.

Writing to station WLW, a Danville,Ind., man describes his raised -letter radiolog and his elaborate method of listing hisfavorite stations.

"One chart lists the daily features bystation call letters and hours of broadcastfrom the most dependable stations," hewrites. "The other chart lists the weeklyfeature in a similar manner."

SPLITDORF REIN

GOES TO EDISONThomas A. Edison & Co. acquired "a

substantial interest" in the Splitdorf Ra-dio Corporation. Splitdorf products willbe taken off the market by the end of theyear. The company will devote itselfalmost entirely to making radio equip-ment for the controlling company.

The new officers of the Splitdorf RadioCorporation will be Charles Edison, chair-man of the board; Walter Rautenstrauch,president; Donald Ross, vice-presidentand secretary; Arthur L. Walsh, vice-president in charge of sales ; Ralph H. Al-len, vice-president in charge of financeand operation; H. F. Miller, treasurer,and Henry Lanahan, general counsel.The newly created finance committee,consisting of Charles Edison, Mr. Allenand Mr. Ross, will control the finances ofthe Splitdorf Radio Corporation and theSplitdorf Bethlehem Electrical Company,parent company of all Splitdorf interests.

A RADIO INFORMATION clearinghouse is announced by John F. Rider,president of the Radio Treatise Co., 270Madison Ave., N. Y. City, to supply radiodata of all nature, in addition to a reg-ular consulting service. Wiring diagramsof old and present-day manufactured re-ceivers, and also of the popular kit re-ceivers, have been compiled.

Reallocation Severe on SomeBig Broac casters with ManyHundreds of Thousands ofDollars Invested-Board Lis-tens to Appeals from Re-assignment Effect.

That there are kinks in the realloca-tion, principally as to wavelength andtime on the air, and to a lesser degreeas to power allotment, and that thesedeficiencies must be ironed out, orgreat dissatisfaction will result, wasobvious from recent hearings held bythe Federal Radio Commission.

The Commission expected some in-justices would become apparent as thereallocation was tried out. Some of theproblems presented are so knotty that,under the Davis law, it may be fairlysaid there is no solution, but it is acase of equal distribution of necessaryinjustice. Big stations are as hard hitas small ones.

Washington.Representatives of three Illinois broad-

casting stations, two of them in Chicagoand the third in Zion, appeared before theFederal Radio Commission on applicationsfor increased broadcasting time, all on the870 kilocycle channel. One of the stations,WENR, owned by seven public utilitycorporations in Chicago, also requestedpermission to operate with 50,000 watts,instead of the present assignment of 5,000watts.

Spent $750,000

WLS, owned by The Prairie FarmerPublishing Co., and WCBD, Zion, alsowere heard on their applications for modi-fication of their licenses.

John E. Wing, counsel for WENR, toldthe Commission that approximately $750,-000 had been expended for new transmit-ting and other equipment and that underthe new allocation the station was allowedonly two -sevenths of the broadcastingtime.

Wilbur Glenn Voliva. overseer of ZionCity, on behalf of WCBD, 'requested re-turn of the 870 kilocycle channel withfive hours of night broadcasting duringthe week. Under the new allocation whichwent into effect November 11th, WCBD

6 RADIO WORLD December 1, 1928

was placed on 1,170 kilocycleslight operation only.

WLS and WENR inSENATORS CALL

WENR SELFISH

for day -

Favors No Particular Station

William R. Dawes, President of theAssociation of Commerce of Chicago, andbrother of Vice -President Dawes, testifiedthat his organization was interested inhaving for the city and the Central Westthe largest amoi.nt of broadcasting facili-ties possible to obtain. Explaining thatthe organization favored no particularstation, he said that WENR, with itsnew facilities, is capable of serving theentire Central West.

Referring to the utilities companiesowning WNER, Mr. Dawes said:

"They would not use the station in anymanner that would be harmful to thepeople. The Insull companies are desir-ous of developing facilities to the utmostin order to perform the greatest publicservice."

Personal Friendship

Replying to a question asked by counselfor WCBD, the Zion City station, he said:

"Personal friendship with Mr. Insullis not the cause of my presence here. Wewant to get the best broadcasting facili-ties possible for the Radio Commission togive."

John V. L. Hogan, consulting engineerof New York, appeared for WENR andtestified as to the technical details of re-ception on the 870 kilocycle channel. Hesaid that interference that would be pro-duced by a 50 kilowatt station would beless on the 870 kc channel than on othercleared channels and that the value to thepublic would be enhanced in that mil-lions more people would be within reachof the station. A 50 kilowatt stationwould have a service range of 1,000 mileswhereas a .5,000 watt station would have arange of only 300 miles.

Senators Norris of Nebraska, Brook -hart of Iowa and Walsh of Mon-tana, were present in the interest of WLS,which also asked full time on the 870 kcchannel.

The Commission heard the appeal ofWNYC, New York municipal station, thatit be allowed to operate full time on the570 kilocycle channel, which it is nowsharing under the reallocation withWMCA.

The delegation for WNYC was headedby Grover A. Whalen, who was. Commis-sioner of Plant and Structures at the timethe station was installed. Mayor JamesJ. Walker was detained in New York,but George P. Nicholson, CorporationCounsel, tad the Commission \ that themayor was "heart and soul in favor ofthe station." He also said that the stationdoes not enter into any commercial con-tracts.

Educational Advantages

Mr. Whalen argued that the station wasa vital educational factor in the life of thepeople.

Albert Goldman, present Commissionerof Plant and Structures, explained the"City Air College," conducted overWNYC, benefits those people who hadno educational opportunities in theiryounger days. He 'also said that the sta-tion was needed for experiments in con-ducting fireboats and to keep in touchwith the police stations throughout thecity.

Dr. Frederick B. Robinson, presidentof the College of the City of New York,William A. Boylan, .Assistant Superin-tendent of Schools, and Dr. Henry T.Fleck, of Hunter College, testified to theeducational benefits of WNYC. Otherswho testified for the station were Dr.

WashingtonThree United States Senators, before

the Federal Radio Commission, opposedgranting full time to WENR, Chicago, onthe .ground it was owned by the publicutility interests that wanted to broadcastpropaganda. The Senators were Norris,of Nebraska, Walsh, of Montana, andBrookhart, of Iowa.

The Great Lakes Broadcasting Corpor-ation operates the station. This corpora-tion is composed of seven public utilitycompanies. At present WENR sharestime with WLS, formerly owned by Sears -Roebuck, but now owned by "The PrairieFarmer."

"The power trusts have controlled agood part of the earth," said SenatorNorris. "They ought to let us have theair."

Senator Norris referred to the disclo-sures before the Federal Trade Commis-sion of dubious practices by utility com-panies in spreading propaganda. SenatorWalsh went into this subject in detail.

John A. Wing, attorney for WENR,said the three Senators knew very little, ifanything, about the station's programs.Mr. ;Wing submitted telegrams fromGovernor Small and Governor -elect Em-erson, as well as from other Illinois offi-cials, commending WENR as a station ofpublic service, convenience and necessity.

Shirley Wynne, Health Commissioner ofNew York City; Gilbert T. Hodges, presi-dent of the Advertising Club of NewYork; General Robert Lee Bullard andJohn D. Flynn, representing the NationalSecurity League; Hugh Lynch of theMerchants Association of New York;William J. Russell, secretary of theChamber of Commerce of the Boroughof Queens, Christie R. Bohnsack, man-aging director of the station, and Repre-sentative Emanuel Celler of New York.

"Useless Tax Burden"

Eight witnesses appeared for stationWMCA. Frank D. Scott, counsel, calledThomas J. Noonan of the Rescue Society,New York, Oswald G. Villard, editor of"The Nation," Milton Remer, Charles T.Root, and John A. Meeker, representa-tives of the Christian Scientists of NewYork, George Edelhertz, editor of "TheAmerican Hebrew" Edgar Felix, a radioengineer; W. K. Wing, editor of "RadioBroadcast" and Harry Mack, studio di-rector of WMCA.

The witnesses for WMCA attackedWNYC on the grounds that it was auseless burden on the taxpayers of thecity, that it was lacking in technical per-fection, that it was -defective in transmis-sion and that it lacked continuity ofgood programs.

Satisfaction Not General

New York and Chicago are not the onlylarge cities in which there is much dis-satisfaction over the reallocation. Wordcomes from Cincinnati, Ohio that althoughreports of the Radio Commission, labelthe new arrangement of wavelengths as ingeneral "satisfactory," listeners in Cin-cinnati and in all of the Ohio Valley areworking themselves into a frenzy of

Hot Fightdesperate disfavor because of the loss ofthe night programs of WSAI.

Newspapers in Cincinnati and in sur-rounding cities began sending a renewedbarrage of vitriolic telegrams to the RadicCommission as WSAI fans reported thatSunday night's first thrill of getting thesignals of a few distant stations would inno way compensate for the loss of con-sistently good radio reception.

Numerous reports from listeners allover the United States indicate that tomany set owners, station WLW with itsnew 50 kilowatt transmitter is the onebright spot in an otherwise dreary broad-cast outlook.

Enough word has been received at theCrosley station to indicate conclusivelythat practically the whole United Statesis depending on the high powered trans-mitter for 75 per cent of its programs.

Immensely ' Popular

Contributing to the immense popularityof the station at the moment of the re-allocations probably is the fact that WLWwas permitted to continue broadcastingon the 700 kilocycle wave band it has oc-cupied since the radio allocations of 1926.Dealers experienced no difficulty in locat-ing the station in its accustomed placewhile other radio stations were forced tochange their frequency.

Little opportunity to measure the effi-ciency of WSAL on its new 800 kilocyclelocation has been given the Crosley cor-poration since simultaneously with itschange from 830 kilocycles, it was limitedto daylight operation and its programswere greatly curtailed.

Lynch Ends WorkAs CeCo's Agent

In a letter, addressed to all the CeCojobbers in the New York MetropolitanDistrict, Arthur H. Lynch announces thathis relations with CeCo have terminated.

Lynch says that he approves of thismove on the part of the CeCo Manufac-turing Co. He makes no bones about thefact that the change is not of his ownchoice. He expresses his thanks for co-operation and the support jobbers gavehim.

Edward Fiske, formerly assistant salesmanager for CeCo, is taking over themetropolitan territory.

15% of AC HomesHave AC Receivers

Cincinnati.Although there are approximately

9,500,000 American homes equipped withalternating current, only about 15% ofthem, at most, are provided with ACradio receivers, said H. Curtiss Abbott,general sales manager of the CrosleyRadio Corporation.

Most of those who have electric setsobtained them during the present year andevery radio manufacturer has been taxedto his production ability tq provide thisoutput.

THE GEORGE W. WALKER CO.,merchandizers of Victoreen products, hasopened .quarters at 25 West Broadway,New York City, for the convenience offans and the trade at large. Here a com-plete stock of the Victoreen products iscarried and complete sets, amplifiers andpower packs are on display.

December 1, 1928 RADIO WORLD

HEARING HELD

ON SHORT WAVE

FOR TELEVISIONWashington.

Argument on an application for a con-struction permit for permanent operationof a television transmitter was presentedbefore the Federal Radio Commission byWNAC, the Shepard Norwell Co., Boston,proprietor. At the same hearing experi-mental television transmitting licenseswere requested by Aero Products Co., ofChicago, and Frank L. Carter, LongIsland City, N. Y.

All three applications were for use ofshort waves for television.John Shepard, for WNAC, explained to

the chairman, Ira E. Robinson, and Com-missioner 0. H. Caldwell that WNAC, ifgranted the television license, proposesto synchronize visual broadcasting withaudible broadcasting. Pictures of an or-chestra leader directing his orchestrawould be transmitted by short waves forreception by the special televisor equip-ment, while the loudspeaker would bringin the music on the regular broadcastwave.

Speeches, vocal solos and other simplecombinations of motion pictures with aud-ible broadcasting can be transmitted atthe present stage of television develop-ment, he declared.

A short wave band of frequencies 100kilocycles wide, in the vicinity of 5,000kilocycles, is desired at this time, saidMr. Shepard. Later, through develop-ment, it may be possible to reduce thewidth of the band to 10 kilocycles, thesame as at present used for addible broad-casting. A power assignment of 1,000watts is desired, Mr. Shepard said; be-cause this amount of power will reachout only as far as 500 watts on regularbroadcasting.

Is It a "Utility"?John Stewart, radio editor of the Bos-

ton Post, declared that a. television sta-tion is desired for Boston, because thevisual broadcasting signals from WLEX,at Lexington, just 10 miles outside ofBoston, "do not get into Boston at all."

Chairman Robinson asked whether pic-ture broadcasting was a "utility" and de-voted to the public interest. Mr. Stewartreplied that he considered the transmis-sion of the picture of an artist as he isbroadcasting to be a utility. The chair-man said \he could see the utility valueof transmitting the picture of an escapedprisoner to facilitate recapture.

Mr. Carter said he desired to converthis amateur short wave station into anexperimental television station.

Still ExperimentalExplaining that he is employed by the

Ludwig Bauman Company, chain storeowners, he said that there have been nu-merous inquiries regarding televisionequipment, and that therefore he wishedto promote television experimentation.

"Television," he said, "is strictly experi-mental at this time."

On behalf of the Aero Products Com-pany, of Chicago, Bert Smith, chief ofthe technical laboratory of that company,said that an experimental license is soughtto ascertain the practicability of tele-vision and further its development. Atpresent, he said, television has not reachedthe practical stage; and the object is toexperiment within the laboratory and, ifthe results seem to warrant, to "put iton the air."

Scientists Invited toTeach via Radio

Addressing the Associated Business Pa-per Editors, at their Fall conference inNew York City, M. H. Aylesworth, presi-dent of the National Broadcasting Com-pany, said he hoped` that "prominent edu-cators and scientists will step out of theirhermitages and speak to every red school-house in the country, over the radio."

He said that radio will decide futureelections, and declared the recent big votein the Presidential contest was due largelyto interest in the campaign fosteredthrough radio addresses. He found thatthe radio served to inform women of theissues better than they were informedpreviously, hence they took a great interest in voting.

U. S. TO CHECK

WAVELENGTHSWashington.

Whether radio stations are maintainingtheir assigned frequencies is a question whichthe Department of Commerce soon will beable to answer vvitfi 'accuracy.

In his annual 'report to the Secretary ofCommerce, W. D. Terrell, Chief of theRadio Division, points out that special radioreceivers and frequency measuring equip-ment have been ordered which will permitplacing in operation a system of accuratefrequency measurements.

One constant frequency station will be in-stalled in a 'centrally located mid -WesternState. Radio receivers as sensitive as anyobtainable will be a part of this apparatus,together with equipment which will per-mit measurements of frequencies to be made,on any radio signal received, with a high de-gree of accuracy. The useful frequencyranges over which it will be possible tomake measurements will be from 10 to 30,-000 kilocycles.

This monitoring station will be able tomeasure the frequencies of a large portionof the United States radio stations as wellas foreign stations whose signals are cap-able of interfering with American stations.On the higher frequencies the latter con-sideration is already of great importance andis becoming a serious matter.

To supplement the work to be done bythe constant -frequency stations located inthe geographic center of the United States,secondary standards of frequency and re-ceivers will be installed in the offices of thesupervisors of radio and sub -offices of thedivision. With this 'equipment it will bepossible to make highly accurate measure-ments of frequency over a range between100 and 30,000 kilocycles.

Three new radio test cars have been addedto the equipment of the division, the reportreveals, making a total of four in activeoperation in the field. Through the use of'hese cars, it is pointed out, considerablemoney has been saved the Government inthe performance of the duties required underthe radio laws.

These cars constitute traveling labora-tories and offices, equipped to perform any'duties pertaining to district headquarters.They carry frequency -measuring apparatus,radio -field intensity measuring equipment,apparatus for the examination of radiooperators and all other equipment necessaryfor the proper performance of any work re-quired under existing radio laws.

The importance of amateurs in the de-velopment of radio is emphasized in thereport. A. new system of amateur callsto indicate nationality is one of the pro-visions of the international radio agreementwhich goes into effect the first of next year.

HOOVER PLANS

TO END BOARD,

INTIMATES SAYWashington.

There has been much discussion amongradio men in Washington as to wlfatHerbert Hoover as President will doabout the broadcasting situation.

Some are of the opinion that he willrecommend that the Federal Radio Com-mission will be abolished and that controlof radio be returned to the Departmentof Commerce, where it was before Con-gress created the Commission. As Sec-retary of Commerce, Mr. Hoover was indirect charge of radio.

Robinson's CommentCommenting on the suggestion that

Hoover would abolish the Radio Com-mission, Chairman Ira E. Robinson ofCommission said:

"Hoover is too big a man to commithimself to such action before he was sureof all the facts."

Judge Robinson further pointed outthat Congress would determine radio con-trol and not the President. He person-ally thought that the Radio Commissionshould be continued whether or not hehimself continued to be a member, andhe would so recommend to Congresswhen the proper time came.

Commissioner Sam Pickard of Kansasis of the opinion that Mr. Hoover had

ing the Commission, as when Mr. Hooverwas Secretary of Commerce he did notwant the administration of the radio lawto remain in that department. For thatreason, Mr. Pickard thought, Mr. Hooverdid not take active measures to preventthe enactment by Congress of the lawcreating the Commission. CommissionerPickard further stated that he did notthink that the new administration wouldwant to be burdened with radio prob-lems in the cabinet.

Visitor Gives His SideOne leading radio man, who had dis-

cussed the subject with Mr. Hoover, said:"Mr. Hoover is opposed to the Radio

Commission. I firmly believe he is justi-fied in that viewpoint, as I have workedin close contact with the Federal RadioCommission and I realize, as does Mr.Hooyer, that some of the members do notunderstand the problems that confrontthem and they are blocking progress.

"There is no doubt that radio controlledby the Department of Commerce will behandled on a business basis. It will bea good thing for broadcasting becausethe Commissioners representing variouszones are continually wrangling for thestations in their own territories and thatstirs up discord and impedes progress.The Department of Commerce will haveno partisan views and will have the in-terest of the entire country at heart,"

THE Philadelphia Storage BatteryCompany; makers of Philco all -electric ra-dios, announced the purchase of an addi-tional 100,000 square feet of ground witha large factory building, which will en-able the company to double its output ofradio sets. Improvements to cost nearly$750,000 already have begun on the prop-erty and buildings, which are located atAllegheny and C Streets, just one blockfrom the present Philco factory, in Phil-adelphia.


KOLSTER SIGNS

BIG CONTRACTS

IN WIRED RADIOThrough the ingenuity of Rudolph

Spreckels, Pacific Coast millionaire, ownerof the majority stock in the Kolster Ra-dio Corporation, the North AmericanCompany, largest publicity utility com-pany in the United States, signed twocontracts with the Kolster Corporation,putting Kolster into the wired radio field.Wired Radio, Inc., a subsidiary of theNorth American Company, actually signedthe contracts.

Gets 600 PatentsKolster is to get 600 patents and at least

one-third of the orders for apparatus, andbids fair to obtaining about $35,000,000 ayear business from the North AmericanCompany.

Some regard wired radio as a comingfield for national distribution of choicefeatures. The newly signed contractsprove that the North American Company,with its vast interests covering the entirecontinent, and the Kolster Company, be-lieve there is an enormous future in serv-ing programs to consumers over the elec-tric light wires. In Cleveland extensivetrials are being made now.

Discussed Five MonthsThe contracts were signed only after

five months of negotiation. Meanwhileother interests the 600 pat-ents held by North American and subsid-iaries, and covering radio in both the en-tertainment and commercial message andfacsimilie fields. General Electric andWestern Electric were said to have beenamong the bidders.

Ellery W. Stone, president of Kolster,said that the 600 patents include manywidely infringed in the radio transmissionand receiver fields today, and that theKolster Company expects to receive largeroyalties, as well as to enjoy a strongerposition in the radio, electric phonograph,and talking movie fields.

The Kolster sets are now installed inColumbia electric radio -phonograph mod-els.

Spreckles' InstituteMr. Spreckles, chairman of the board of

Kolster, and also of the Federal Tele-graph Company, a North American sub-sidiary, said the newly signed contractswere in line with the greater diversifica-tion of the Federal Company's activities,his own idea. The first step was the ac-quisition of C. Brandes, Inc., manufac-turer of headsets and speakers.

"The apparatus contract," according toFrank L. Dame, president of the NorthAmerican Company, "forecasts the arrivalof the industry's latest development, wiredradio, which in the future will supplementbut not displace present broadcasting onthe air.

"When plans have been completedwired radio will become available to all ofthe major public utilities of the UnitedStates,"

A central sending station, to cover theUnited States and Canada by land wires,is under contemplation.

NEXT WEEK-issue of Decem-ber 8th-the Holiday Gifts Numberof Radio World. Key to Christmasradio shopping. Bigger in size,with fourteen special treats. Getthis issue for sure!

Police to Use Setsto Trap Burglars

CincinnatiRadio as a police service is to be insti-

tuted in this city, Grove C. Smith, SafetySecretary, announced. There will be aradio set in each police and fire station aspart of a plan developed by Cot Sherrill,City Manager.

"The equipment of fire and police sta-tions as well as fire and police vehicleswith radios is part of the developmentplan of Colonel Sherrill, to bring the FireDepartment within the cooperative scopeof the Police Department." Mr. Smithsaid.

"Colonel Sherrill favors the plan ofgiving firemen. police powers and therebydoubling the police force without addi-tional cost to the city."

Mr. Smith said the radio system wouldbe especially valuable in catching burglarsand highwaymen.

Hammarlund's NewFleet of Capacities

In line with the new shielded sets builtlike battleships, the Hamma.rlund Manu-facturing Co., Inc., 424 West 33rd Street,New York City, has brought out a new1929 multiple "midline" condensers in bat-tleship models, marvels of ruggedness andaccuracy. This new Hammarlund "Bat-tleship" Multiple is the finest condenserjob this concern, famed for its qualityproduction, has ever turned out. Beauti-fully finished, with die-cast frame, platespermanently aligned, free -moving rotor,and recesses in the frame permit directattachment of an equalizing condenser tobalance each unit with absolute precision.The sections of these condensers arewithin IA to V4 of 1% (plus or minus) ofeach other at all points. This is the clos-est matching obtainable. Shaft 3/8 inches,turned down to IA on dial end. These con-densers will answer every need of manu-facturer and fan alike. They come intwo, three and four -gang models. Infor-mative literature on these and other Ham-marlund products will be sent upon ap-plication to the above concern. MentionRadio World.-J. H. C.

A NEW BRANCH OFFICE with ware-house and service station facilities hasbeen opened in Atlanta, Ga., J. L. Ray,general sales manager of the Radio Cor-poration of America, announced. PierreBoucheron, formerly advertising and pub-licity manager of the R. C. A., has beenappointed southern district sales man-ager in charge of the new office. C. R.Westbrook, formerly connected with theNew York sales offices, has been appoint-ed assistant district sales manager.

* * *

SPLITDORF Radio Corporation an-nounced its purchase of the Park City

Electric Company at Bridgeport, Conn.

MINES CHIEF

BACKS RADIO

QUEST OF OILWashington

Use of geophysical methods in prospect-ing for oil is advocated by the Acting Di-rector of the Bureau of Mines, 0. P.Hood in a statement filed with the Fed-eral Radio Commission in support of theapplication of oil companies for shortwave radio channels with which to carryon geophysical explorations.

Mr. Hood quoted Scott Turner, directorof the Bureau of Mines, who had said:

"I wish to call to your attention two im-portant uses for radio for which provisionshould be made before the practicablebands are finally apportioned. These usesare (1) for geophysical prospecting and(2) for experimentation in the possibleuse of radio as an aid to the rescue ofentombed miners.

Easy Ways Known"The easily found mineral deposits, both

of metals and of oil and gas, have ap-parently been located. The remainingdeposits are mostly those which are deeplycovered or of which the structures areobscured.

"It is, therefore, plain that meansfor finding them other than themethods heretofore in use must be devel-oped. The newer methods are known asgeophysical methods because they dealwith the physical characteristics of theearth's crust. The methods are becomingmore and more refined and must contin-ually be improved.

"A number of these methods depend ona signal from a central location which isreceived through the earth at stationssome distance away.

"The retardation Ior acceleration of thesignals through the earth gives a clue tothe structures below, and thus to the lo-cation of a desired deposit. In order toascertain the retardation or accelerationof the signals through the earth, use ismade of radio waves to signal simultane-ously to the various stations.

Measured by Signals"The radio signals are so nearly instan-

taneous in their flight to the stations thatthey make a good yardstick for measuringthe speed of the earth waves. The powerused is small, probably never over 100watts, and the range of the waves is ordi-narily less than 50 miles. Most of theprospecting is done in regions remotefrom radio stations, and therefore offers aminimum of interference.

"The continuing discovery of ore, oil,and gas deposits is a matter which con-cerns the public welfare to an enormousextent, and is comparable in its impor-tance to the continuance of transportationfacilities. The need of the reservation ofpowers up to 100 watts is very great andwill probably increase with time. Repre-sentatives of the National Research Coun-cil, private corporations, and of the Geo-logical Survey have all urged the Bureauto use its good offices in this matter."

DUE TO increased business of theSilver -Marshall Company in the NewYork and Philadelphia territories, Wil-liam G. Davis has been appointed Phila-delphia representative, with headquartersat the M. & H. Sporting Goods Company,512 Market Street, Philadelphia, Pa.

Temporarily Mr. Davis will be underthe supervision of F. Edwin Schmitt, 136Liberty Street, New York, N. Y.

December 1, 1928 RADIO WORLD 9

The Bounty of the AirHow Broadcasting Grew and Prospered

cLARK MAXWELL was the Colum-bus of Radio in the middle fifties

of last century, while Heinrich Hertz wasthe Amerigo Vespucci in 1864. Hertz'name is given to the new phenomena onwhich radio is based. Then came Mar-coni in 1896 as the first colonizer of thenew field of human endeavor; again in1901 as the Lindbergh of trans -Atlanticradio communication; and thereafter asa leader in the development of the com-mercial possibilities as we now knowthem. These are the high spots in earlyradio history.

Eight years ago broadcasting was bornand introduced to the American publicby KDKA of Pittsburgh-owned and op-erated by the Westinghouse Electric &Manufacturing Company. The first reg-ular broadcast service program was in aPresidential election and consisted of re-ports of the count of the votes cast forthe candidates. Today we are impressedby the tremendous use of radio facilitiesby contending political parties.

Startling Growth

Beginning with the one station of No-vember, 1920, there followed nearly 125broadcast stations by the Spring of 1921.The number grew to some 733 stationsby March, 1927. The dollar value of busi-ness in radio receiver apparatus and de-vices grew from $2,000,000 in 1921 and$5,000,000 in 1922, to sixty million in 1923and to $500,000,000 in each of the years1926 and 1927. The number of receivers isvariously estimated as now being from8,000,000 to 12,000,000 and the radio audi-ence at from 40,000,000 to 60,000,000 people.The figures are for American radio ex-clusively.

This growth has been brought aboutunder the compelling pressure of a pub-lic enthusiasm which has abundantly re-warded such producers as have survivedthe pitfalls of quickly shifting demandfor changes in construction and design.

All this has constituted a kind of rev-olution, producing in itself and becauseof its rapid effect upon the social struc-ture, new problems requiring new legis-lation. Congress first acted in 1910, butin 1912 rewrote and enlarged the radiolaw to cover the needs of the day.

While not ignoring the drastic changes

By Louis B. F. Raycroftcaused by broadcasting, Congress passedno new legislation until heavy public pres-sure was brought to bear on it, resultingin the Radio Act of 1927. That act wasamended in the Spring of 1928 by the so-called Davis Amendment. The FederalRadio Commission, created by the Act of1927, thus acquired the problem of ad-justing the facts of radio broadcastingfirst to the amended act and second tothe requirements of public convenience,interest and necessity.

Commissioners' Terms EndAll this, however, according to the pro-

visions of the Davis Amendment, must beaccomplished not later than March, 1929,because the amendment automaticallydischarges the present personnel of theCommission from office.

The Federal Ra,dio Commission haslarge responsibilities entirely to one sideof the broadcasting situation. But thepopular problems in radio today arebroadcasting or how to give seven hun-dred licensed stations and a large addi-tional number of applicants room tobroadcast simultaneously on 89 Americanchannels. The problem has its cheerfulside, but it is getting more and moredifficult to get the Commission to see it.And Congress, collectively, not contentwith badly fumbling the ball, insists onindividually acting as 531 assistant RadioCommissioners, some doing double ortreble duty for those who are less active.

Engineering vs. PoliticsSpeaking with the utmost seriousness,

the problem in radio broadcasting has twoprincipal phases-the engineering phaseand the political phase. Under the lawsof human nature and the practices of poli-ticians both phases must necessarily betaken into consideration.

The Federal Radio Commission adopt-ed the new Allocation Plan after -mostadequate consideration of numerous prob-lems. Prior to the plan a long period ofcompromise and experiment adequatelydemonstrated that to relieve one case ofcongestion in one area inevitably madethe conditions worse in another. Ex:traordinary ingenuity was displayed bythe Commission in an effort to bringabout a gradual betterment of broadcast-

ing conditions without making necessarya radical step equivalent to cleaninghouse and beginning all over again.

We realize that the Federal Radio Com-mission inherited chaos precipitated by apresumptuous Chicago broadcaster whoseized a Canadian channel in the summerof 1926 and successfully upset the author-ity of the Department of Commerce toregulate broadcasting.

Successful Despite Obstacles

Great progress in correcting the subse-quent confusior has been made by theFederal Radio# Commission without can-celling any substantial number of broad-casting licenses. Only after exhaustingevery avenue of escape and studying theevidence of qualified engineers was theconclusion reached that the eighty-nineavailable broadcast channels could notsuccessfully carry the load which broad-casting stations sought to impose upon it.

Many of the stations contributing tocongestion were established during theperiod when the Department of Com-merce was restrained by injunctionagainst refusing licenses.

Successful PlanIn spite of obstacles the Commission

has worked out successfully a definitespectrum of national, regional and localstations giving a fair balance to each typeof service and assuring the higheSt pos-sible quality of broadcasting, not onlyin congested areas within the high-gradeservice range of broadcasting stations,but in rural districts which necessarilydepend upon some degree of distant re-ception for the enjoyment of essentialand important broadcasting services.

Amendment Hampers

Restricted by the requirements of theDavis Amendment to equalize the divisionof powers and channels of each class toeach zone and to States within the zonesaccording to their populations, the Com-mission naturally found its most difficultproblems the first and fourth zones, whichhave far above the average number ofstations.

Extensive time-sharing has been neces-sary in these zones to equalize conditions.

Schools Hard Pressedfor Sets for Lessons

Every possible means of obtaining ra-dios is being resorted to by schoolsthroughout the country to listen to Wal-ter Damrosch's R. C. A. Educational Hourfor school children.

Casual references in the thousands ofletters received at the offices of the Ra-dio Corporation of America and the Na-tional Broadcasting Company reveal thatradio equipment is being borrowed fromprivate homes for school use, bought byindividual teachers out of their own sav-ings, loaned by public-spirited businessmen, and even home -constructed by pu-pils, so that the Friday morning musicalprograms given by the dean of Americanconductors may be heard.

Also the sale of sets and parts has beenaccelerated.

Birds in Voice Testfor California Honors

Oakland, Calif.Twenty-two birds will assemble before

KGO microphones during the next sixmonths, each presenting its own qualifica-tions for the high office of state bird ofCalifornia.

Bert Harwell, who has had a hand instarting the movement for a Californiastate bird, will be the radio spokesmanfor feathered candidates who might be-come temperamental and refuse to whistle.

So that an intelligent vote may be castby the public, Harwell is using radio toacquaint listeners with the various birds,their songs and their habits. He speaksover KGO every Tuesday at 6:30 p. m.

Netherlands, Norway,Canada Ratify Pact

WashingtonJ. H. Van Royen, the Netherlands Min-

ister ; Alexis H. G. 0. Lundh, Charged'Affaires, Norway ; and Vincent Massey,the Canadian Minister, have deposited withthe State Department ratifications of theInternational Radio Telegraph Conventionand the general and supplementary regula-tions relating to it, in behalf of their gov-ernments. The ratification of the Nether-lands included Dutch East Indies, Surinamand Curacoa. The United States ratifiedthe Conventibn on October 8th.

The Convention was drawn here at in-ternational conference taken part in bymost of the countries of the world and itwas designed to regulate international ra-dio communications. It was signed Novem-ber 25th, 1927 and goes into effect January1st, 1929.


AWHEN the filaments or the cathodes

of amplifier and detector tubes areheated by alternating current taken fromthe power lines a hum arises. The fre-quency of most of this hum is twice thatof the supply and part of it has the samefrequency as the supply. For example,if the frequency of the supply current is60 cycles, most of the hum has a fre-quency of 120 cycles per second and parthas a frequency of 60 cycles.

The heater type of tube is relativelyfree from hum, but it does produce some.The so-called filament type tubes produceconsiderable hum, and when the so-calledDC tubes are heated by AC the hum isintolerably great, except when AC is usedon the last tube only.

But the DC tubes are very desirablebecause of their favorable amplifyingcharacteristics. Many devices have beenbrought out with a view of solving theproblem of heating the filaments withpower taken from the AC line. The moresuccessful of these involve rectifiers. Inone case the rectifier takes the form ofan A battery eliminator. A heavy dutycharger is interposed between the AC lineand the radio receiver filament circuit,and the heavy rectified current is filteredas well as may be by low inductance chokecoils and 'electrolytic condensers.

In another case the filaments of the_,tubes are connected in series and thensupplied with rectified and filtered currentof low amperage and high voltage.

Disadvantages of MethodsWhile these two general methods are

used quite extensively with good results,they bring up certain points for discus-sion. The A battery eliminator may besubject to difficulty of filtering heavy cur-rents. But this method is the more suc-cessful.

The series filament method has the dis-advantage that the receiver circuit re-quires radical changes. And these changesusually lead to many complications.

It is very, difficult to construct a circuitwith series filaments without introducingregeneration in both the radio and audiofrequency levels. Consequently there ismuch hum, oscillation and frequency dis-tortion. Besides these troubles, themethod is wasteful of power and rend6rs

ew Lasy Waywith Hum

the circuit inflexible with respect to typeof tubes that can be used.

A New MethodBut there is one possible method which

is relatively more efficient than the seriesconnection method and is less subject toHum than any other method that has beensuggested, at least for the same efficiencyand cost. This method has not been pub-lished heretofore, but it has been usedexperimentally for some time.

The advantages of the method shouldcommend it to engineers who are lookingfor new developments.

The method is simple in conception andin application. And it is as flexible as thedirect method of heating filaments withAC. In fact, it is based on heating thefilaments with AC, not with AC of com-mercial frequencies, but with frequenciesof such magnitude as to render the huminaudible, yet not so high as to constituteradio frequencies.

Super -audible Hum

Since the highest frequency that anyhuman ear can hear is somewhat below20,000 cycles, and since the main humcomponent has a frequency twice that ofthe supply current, it would seen that ifthe filaments were supplied with a cur-rent of 10,000 cycles there would be noaudible hum in the output.

The question now is how such a fre-quency can be produced with sufficientpower to heat the filaments of DC tubesordinarily used in a radio receiver, andto produce it with reasonable efficiency.The solution is available.

We have a tube, the -50 type, which asan oscillator is rated at 25 watts. Cer-tainly an oscillator generating a 10,000cycle frequency could be assembled whichwould make a wattage of 10 watts availa-ble for the filaments. That is much morethan most receivers require.

250 Tube is Used as10,000 Cycle Frequency,Tubes or Any Other-

Never BeforeBy J. E.

Technical

Let us assume a six -tube receiver usingthree screen grid tubes, or tubes havingthe same filament requirements, two ofthe -01A tubes, or other tubes requir-ing a filament power of 1.25 watts, andone power tube, the filament of which canbe heated by 60 -cycle current. Such areceiver would require a total 10,000 cyclewattage of 3.8 watts. That could easilybe extracted from a, -50 type oscillator,with some power to spare for additionaltubes, when the rating of this tube asan oscillator is 25 watts.

In order to get a considerable powerfrom such an oscillator, it is necessaryto supply the plate of the tube with ahigh, steady voltage, say 45Q volts ormore. This can be obtained from a platepower supply such as is used for high -power amplifiers. If two -81 type rec-tifiers are used, sufficient current couldbe obtained for the oscillator as well asfor the tubes in the amplifier, includingone or two -50 type tubes.

The 10,000 Cycle OscillatorThe oscillator circuit may be any one

of a number of well known circuits ; forexample, the one illustrated in Fig. 1. Theoscillating circuit consists of the largestcenter -tapped winding on transformer T2and the condenser C9, both of which are

FIG. IA CIRCUIT ILLUSTRATING A NEW TYPE OF A BATTERY SUBSTITUTE. AN OSCILLATOR, DERIVING ITS PLATEPQWER FROM A B BATTERY ELIMINATOR, IS USED TO SUPPLY A 10,000 CYCLE CURRENT TO THE FILAMENTSOF THE TUBES IN THE RECEIVER. THIS IDEA WAS CONCEIVED 'AND TESTED BY J. E. ANDERSON IN

DECEMBER, 1926.


o Heat Any Filamentless ACOscillator, to GenerateDeliver 10 Watts to DCAn Absorbing InventionPublished

AndersonEditor

connected between the grid and the plateof the oscillator tube. A condenser CSis used to isolate the grid from the platevoltage and R3 is a suitable grid leak.The plate voltage is applied through achoke coil L3 to the center -tap on theoscillating coil. Condenser C13 may beused as an additional filter condenser.

Resistor R2 is used to supply a nega-tive bias to the oscillator tube, andcondenser C11 by-passes this resistor.Neither of these two parts may be nec-essary, for in this type of circuit the gridleak maintains the grid at the requiredbias.

Transformer T2 should be of specialconstruction. air, lami-nated iron or compressed iron dust. Ifthe laminated core is used the laminationsshould be much thinner than those usedin 60 -cycle transformers. Low voltagewindings should be placed on the core aswell as the oscillating winding. The ratioof turns should be adjusted so that therequired filament voltage is maintainedacross the smaller windings. Theremight be one winding for 3.3 volt tubesand another for 5 -volt tubes, or theremay be a winding of suitable voltage foreach tube in the receiver. These low volt-age windings should be center -tapped inorder that the filament circuits may bebalanced for the heating current.

0

- 26

OcrL gyps

C2

If the plate current supplied to the os-cillator tube contains a ripple, this willappear as a modulation on the 10,000 -cycle output of the oscillator. One mightthink that this would defeat the purposeof the arrangement ; that is, that it wouldintroduce a 120 -cycle hum into the am-plifier. But this ripple will only producea periodic rise and fall in the amplitudeof the 10,000 current, and hence in theheating effect of the current. It hasbeen proved that the proportion of humfrom this effect is negligible when thefilaments are heated by 60 -cycle AC. Andin this case the rise and fall of the cur-rent is from zero to maximum. The rip-ple will produce only a very small riseand fall in the amplitude of the 10,000 -cycle AC. Hence the modulation will notproduce any audible hum. It is for thisreason that the extra filter section L3C13may not be at all necessary.

Filament Current ControlIf the AC line voltage varies, the 10,000 -

cycle filament current will vary in thesame proportion. Hence if the line volt-age remains reasonably constant the fila-ments will not be subjected to dangerousvariations. The filament current will beof about the same constancy as if theheating current were taken directly froma 60 -cycle transformer.

But some control of the filament currentundoubtedly will be necessary. Any con-trol of the intensity of the oscillationswill control it. The oscillations may becontrolled by controlling any one of thethree voltages applied to the oscillatortube. For example, it may be controlledby inserting a rheostat in the filamentcircuit of that tube, or by inserting a highvariable resistor in the plate supply lead.Again, it may be varied by varying thevalue of the grid leak R3, or by varyingthe resistor R2, if this is used. Whenthe filament currents in the varying tubessupplies with 10,000 -cycle current has beenadjusted once it should not be necessary

-26

aL5g

aa06

R-27

G P

nn

to readjust as long as the oscillator tubeholds out.

Suggested CircuitFig. 1 indicates all the ricce,,,ary con-

nections. First there is a power trans-former Tl, which has three 7.5 volt wind-'ings. One of these is for the filamentsof the rectifier tubes, one for those ofthe power amplifier tubes and another forthat of the oscillator. There is also ahigh voltage winding to supply the cur-rent to be rectified. All should be center -tapped.

The filter and voltage divider are stand-ard. R4 is a resistor to supply the gridbias for the power tube or tubes. CIO by-passes it. If a separate grid voltage sup-ply is used, both R4 and CIO are unneces-sary.

Three screen grid tubes and two -01Atype tubes are indicated in Fig. 1. Butonly the filalkent circuits are outlined inorder that the connections to the 10,000 -cycle source may be shown.

It is believed that the oscillator, includ-ing all the parts, will be much cheaperboth to buy and to operate than anyother type of filament current supplywhich has yet been suggested. And itis further believed that the hum in areceiver operated with it will be so lowthat no other battery substitute can ap-proach this one.

It is not necessary to give the constantsindicated in Fig. 1 except those strictlypertaining to the oscillator, since this partalone is new in 'this application. If thefrequency of the current generated in theoscillator is to be 10,000 cycles, the prod-uct of the effective inductance of the os-cillation winding on T2 and the capacityif condenser C9 should be .25, the in-ductance being measured in millihenriesand the capacity in microfarads. Fur ex-ample, if C9 is .01 microfarad, the induct-ance should be 25 millihenries.

The value of R3 may be from 5,000 to25,000 ohms. CS may be a .25 or a .1 infd.condenser. It must stand voltages atleast up to 600 volts. C9 should be amica condenser and it should be able towithstand voltages about as high as C8.Trnasformer T2 must he designed for thejob with which it is to work.

(Further discussion. o% this absorbingtopic will be published next week.]

-20

in. el

R2

5 V.

T3

Hq

C7

tin

-//2

0 5# Pedr.Pei- AMP0 B+ DET.

0 8-

0 POWER SUPPLY

©110 V. RCLINE

THE PRESENT METHOD OF USING AC ON THE FILAMENTS, AS CONTRASTED WITH THE ANDERSON METHOD.


The Hammarlund-PART I

THERE is an old adage, "If you wanta thing done right, do it yourself," but

in these modern days the latter portionmight be amended to read-"have it doneunder your own supervision." This oldsaying and its modernized version applyparticularly to radio receivers-eitherbuild one yourself or see that it is builtaccording to your own requirements.

For the man who wants a receiver thatwill bring in the station to which hewishes to listen and bring it in so that itsounds as nearly like the original per-formance as is possible, the new Ham-marlund-Roberts Hi -Q 29 Master Modelis the end of his search.

Here is a set in which is incorporateda new circuit-using band-pass filters inthe radio -frequency amplifier-and anaudio -frequency amplifier insuring repro-duction of the highest quality. The setcan be installed in any one of a numberof different model cabinets or consoles,so that it can be made to fit in with al-most any type or style of home decora-tions.

Come of Fine AncestryHammarlund-Roberts receivers need lit-

tle introduction to the radio fraternityas a whole, because for nearly five yearsthey have been considered among thefront rank of receivers developed in theUnited States. The receiver herein de-scribed is by far the most efficient setbearing this name, as may be ascertainedby reading the theoretical description.Improvements are included in this newmodel, as well as features that, as faras is known, are not to be found in anyother set, regardless of price.

The Master Hi -Q 29, when built ac-

cording to specifications, is a genuine"coast -to -coast" instrument. In selectiv-ity nothing like it has ever been producedoutside of certain laboratory instruments,which are far too costly for general use.This receiver, for the first time, as faras is known, employs a band-pass filterwhich insures flat -top, square cut-off tun-ing with a selectivity of 10 kc. "Crosstalk" is thereby eliminated. Only a singlestation can be tuned in at one time, evenin large cities where many high-poweredstations are broadcasting at once. Sta-tions do not slide in gradually, with agradual increase in volume. They snap in-clear and undistorted.

Little Effort to Build ItFidelity and tonal quality and absence

of distortion have always been featuresof Hammarlund-Roberts receivers andagain this year the Master Hi -Q 29 willbear the same scrutiny as would its fore-runners. The signals are clear and canbe modulated to whatever degree of vol-ume desired.

The Master Hi -Q 29 has been so de-signed that it can be constructed with aminimum of effort on the part of thebuilder. The accompanying diagrams andillustrations will furnish the builder withcomplete details, which should be ade-quate to the enthusiast of average expe-rience.

It is well known that the prime requi-sites for a first-class modern receiver arequality of reproduction, selectivity andsensitivity, and that they are by no meansindependent of each other. They areclosely bound theoretically with the de-sign of the whole and it is for this reasonthat only the best receivers have all three

Both Plate and Grid CircuTuned, Affording Band -PaSelectivity that Sti-Battery Operated ModTheory Reveals Why

By Lesli

features. The new Hammarlund-Robertreceiver possesses these three requisite:to a remarkably high degree, and a care-ful study of the principles emyloyed in thedesign will reveal the reasons for the ex-ceptional operating qualities.

Circuit Remarkable InnovationThe Master Hi -Q 29 uses a remarkable

circuit which is entirely new in radicreceiver design. The underlying princi-ple is described by Morecroft in his book"Principles of Radio Communication," ir.the section devoted to "coupled circuits.'When such a circuit is used in a receiverit is quite obvious that the result is lessradio -frequency distortion and greater se-lectivity. Until the advent of the shield -grid tube this type of circuit was notpractical, and even with these tubes thelayout is quite elaborate and thereforeonly adaptable to high -quality receivers inthe higher price class.

Briefly, the tuning system used in theHi -Q Master provides selectivity greatereven than the old-fashioned "hair-trigger"regenerative set expertly operated; sensi-tivity (amplifying power) equal to a Su-

9

-

METALBASE

222

CIRCUIT DIAGRAM

CoC> C>o CoC,C) C)

r

222L.

201-A

-/

201-A

HAMMARLUNO - ROBERTS"HI- Q 29" RECEIVER

(MASTER)(FOR BATTERY OPERATION)

dfA -B- A+ B+ B+ B+ C -

45V. 90 V. 135 V. 41/2 V. 2


bents Master Hi-Screen Grid Tubes are

ilter for Extraordinaryreserves all the Modulationescribed - Fascinatingis New Circuit Excels

Biles

`e'er -Heterodyne, and an output from the')udspeaker as distortionless as that ob-tined from a crystal and headphones.To start at the beginning, the layman

iadily will agree that good selectivity ishighly desirable attribute of any radio

t. Good selectivity, howeyer, has hith-to been understood to mean sharpnesstuning, which is not conducive to qual-

3r of reproduction. For example, theodern high -quality audio transformersow available make possible the construc-"tin of a practically perfect audio ampli-ing system. If a power tube is usedthe last stage of such an amplifier and

$` output fed into one of the better typeeakers, the audio amplifying and repro -icing system leaves little to be desired.

The Conflict4--lowever, this system can amplify and

'produce only what is fed into it by thetector tube, which in turn receives the

11

anal from the radio -frequency amplifier.fence it is evident that even a perfect;dio system cannot provide a high qual-,°r output from a loudspeaker if distor-

On is introduced in the RF amplifier,

FIG. 1

THE CIRCUIT DIAGRAMOF THE HAMMARLUND-ROBERTS MASTER HI -Q29 RECEIVER. THE CIR-CUIT EMPLOYS TWOSCREEN GRID TUBESWITH SPECIAL BANDPASS FILTERS BETWEENSTAGES, WHICH MAKETHE SELECTIVITY EX-CEPTIONALLY SHARPWITHOUT CUTTING THEHIGH FREQUENCY SIDE

BANDS.

FIG. 2

THIS SHOWS THE LAYOUT AND STRUCTURAL FEATURES OF THE HAM-MARLUND-ROBERTS MASTER HI -Q 29 RECEIVER.

due, let us say, to excessively sharp tun-ing, technically known as "side band cut-ting."

This illustrates the conflict between thetwo desirable characteristics, quality andselectivity.

Also the attainment of a high degree ofradio frequency amplification (sensitiv-ity) is a distinct asset, if it can be attainedwithout instability (tendency toward self -oscillation of one or more tubes) whichimpairs the quality of reproduction.

Want High Gain

High amplification is desirable becauseit enables the set owner to receive pro-grams from very distant stations when hefeels so inclined, and also because it makespossible quite satisfactory reception fromlocal and moderately distant stations ona small indoor antenna even in unfavora-ble locations.

However, selectivity and sensitivity arealso incompatible.

One of the reasons for this condition isnot generally understood, and is evenmore seldom taken into consideration. Theaverage receiver owner or experimenterbases his judgment almost entirely on the"apparent" selectivity.

This is quite natural, since the actualselectivity of a receiver can only he de-termined by a series of very carefulmeasurements. The apparent selectivityof the ordinary radio set decreases as itssensitivity increases.

Where Broadness Sets In

Therefore, of two receivers having ex-actly similar "actual" selectivity and onehaving say three times the sensitivity ofthe other, the set having the higher sensi-tivity (or amplification) will invariablyseem broader or less selective.

The enormous amplification and ex-tremely low plate -to -grid capacity of thenew screen grid tube at first glance wouldseem to make it almost ideal for use asradio frequency amplifier, The manu-facturers of these tubes state that a volt-age set-up of forty or more per stage isobtainable at broadcast frequencies. Inaddition the plate -to -grid capacity is saidto be of the order of one -fortieth of one

mmfd., or about one four -hundredth asgreat as that between the plate and gridof the 201A type tube.

Since it is this plate -to -grid capacityof the ordinary tube that is so trouble-some in the design and construction ofmulti -stage radio frequency amplifiers,many schemes have been devised to neu-tralize this capacity.

None of these schemes has been entirelysuccessful, however.

[Other phases of this circuit wilt be dis-cussed next week, issue of December 8th.]

LIST OF PARTSFive Hammarlund No. ML -17 .00035 mfd.

Midline Condensers.One Hammarlund No. "Hi -29" Coil Set.Two Hammarlund No. SDW Knob -Con-

trol Drum Dials (walnut).Three Hammarlund No. RFC -85 Radio

Frequency Chokes.Five Benjamin Cle-Ra-Tone Sockets, No.

9040.One Sangamo .00025 mfd. Fixed Mica

Condenser.One Sangamo .001 mfd. Fixed Mica Con-

denser.One Carter No. 11S "Hi -Pot" Potentiom-

eter with switch, 100,000 ohms.Two Thordarson No. R-300 Audio Trans-

formers.Four Parvolt S mfd. Series ZOO By-pass

Condensers.One Durham Metallized Resistor, 1%

megohms.Two Amperites No. 1-A.One Amperate No. 112.One Yaxley No. 660 Cable Connector and

Cable.One pair Yaxley No. 422 Insulated Phone

Tip Jacks.Two Eby Engraved Binding Posts.One "Hi -Q 29" Master Foundation Unit

(containing drilled and engraved West-inghouse Micarta panel, three completealuminum shields, drilled steel chassis,shafts, binding post strips, Fahnestockclips, fixed resistance units, resistormounts, brackets, clips, wire screws,nuts, washers and all special hardwarerequired to complete receiver). Ham-marlund Mfg. Co., Inc.

14 RADIO WORLD December 1, 1928THE Universal Circuit, using a screen

grid tube as the radio frequency am-plifier, is shown herewith for the first timeanywhere, and moreover is presented withthe full confidence that it will rank asone of the outstanding four -tube receivers.

It does about all that can be expectedof a four -tube set; in fact, a little bit

L; g

G N D.

CAP,

eL21c -

R

222 240 OR20/-R

0 PL

he Screen20I -R T2 1/2-R

By Herman

CENTER TAPS ON THE TUNED WINDINGS OF THE COILS, PHASE REVERSAL IN THE SCREEN GRID PLATECIRCUIT AND FEEDBACK THROUGH A JUNIOR CONDENSER OF 50 MICRO-MICROFARADS MAKE THE NEW

SCREEN GRID UNIVERSAL A "BEARCAT."

more, because it is strong indeed on dis-tance reception, while possessing tonethat is bound to please.

Let us discusS one of the difficultiesand show how it turns out to be a de-light.

Local stations come in so loud that atfirst we don't know exactly what to doabout cutting down the volume to com-fortable limits. It is rather annoying.On the other hand, when we bring in adistant station, and far distant ones mayhe confidently expected of this receiver,we want the volume to be "as loud as alocal." How can that be done? Onlyby having the locals come in altogethertoo loud, with easy means of reducingthe volume to an enjoyable limit, andthen, when tuning in a distant station,give the set the full works-maximumvolume. Then the same comfortable vol-ume to which the local was reduced willbe present in the received distant signal.

Too Much Is Just EnoughIn other words, locals must come in too

loud, if distance is to come in loud enough.That is the rule for any receiver. Andthat is the main reason why a volumecontrol is imperative in any receiver thatproduces this plethora of local volume.

The usual 20 -ohm rheostat will not doas volume control, in the present receiver,because the volume is so enormous ;therefore, a 50 -ohm rheostat is used. Itperforms its necessary work excellently.

The woods are full of four -tube sets,some of them with a screen grid tube infront, so it is pertinent to inquire intothe reasons why the present receiverranks with the very best of them, and isfar better than most.

It would be rather presumptuous to as-sert it is the best of all, since only oneScreen Grid Universal is in existence, awlwhile it has been tried out with consci-encious pains, given the practical test ofreception, there still remains the questionwhether it will prove, besides a wonderfulreceiver, something easy to build and towork.

Simplified by BlueprintThere is a blueprint available, and any-

body can follow that. Besides, this arti-cle is intended not only to induce radioenthusiasts to rally to a new and out-standing development, but also to informthem on the making, operating and re-

pairing of the circuit. With a piercedaluminum subpanel, with sockets affixedand with self -bracketing front, as thestarter, and with a drilled front panel,there is nothing to it except to follow thesimple blueprint to the logical conclusionof a superlative receiver, one that hastuned in a 500 -watt transmitter 1,000 milesaway, night after night, without fail.

It is all right for a receiver to bringin distance on eccentric occasions, for allfavors are thankfully received, but thereal test is that of repetition-not mereoccasional repetition, but nightly repeti-

LIST OF PARTSLl, L2-One Screen Grid two -winding RF

transformer, with center -tapped sec-ondary; Model 5RF for .0005 mfd. orModel 3RF for .00035 mfd.

L3, L4-One Screen Grid high impedanceinterstage coupler, with center tappedprimary; Model 5TP for .0005 mfd.or Model 3TP for .00035 mfd.

CI-One .00025 mfd. Aerovox grid con-denser, with clips.

C2, C3-Two Hammarlund Midline .0005mfd. or .00035 mfd. tuning condensers.

C4-One Hammarlu.nd junior condenser.Cat. No. MC11 (50 mmfd.)

R1-One Lynch metallized grid leak, 2 to.10 mg.

R2-One No. 622 Amperite, with mount.R3, R4, R5-Three No. lA Amperites with

three mounts.Rh-One 50 -ohm rheostat.T1, T2-Two Thordarson R-300 audio

transformers.SW-One filament switch.PL-One pilot light bracket with lamp.Two dials.Two knobs.Four binding posts (Ant., Gnd., Speaker

plus, Speaker minus).One 10x20 -inch aluminum self -bracket-

ing subpanel, with sockets affixed, andincluding hardware and insulatingwashers.

One 7x21 -inch drilled bakelite frontpanel.

One nine -lead battery cable.Four Kelly tubes as follows: One 42?

screen grid, two 401A and one 412A(for 135 volts maximum), or one 471A(for 180 volts maximum).

A, B and C supplies; cabinet and speaker.

tion, unfailing repetition ! And in thatdirection the Screen Grid Universal castsits winning beam.

The Screen Grid Universal takes mostof the enormous extra gain afforded bythe screen grid tube for amplification pur-poses, but uses the excess for increasingselectivity. This sounds rather puzzling,perhaps. If you have a device that af-fords unusual amplification, under condi-tions that may also require unusual se-lectivity, you might use all the amplifi-cation as amplification and not havenearly as much selectivity as is needed.It can be said fairly about four -tube setsthat they have been sensitive enough,as a rule, but rather shy on selectivity.

The Happy CompromiseIf one desires greater selectivity, with

the same number and type of stages, hecan obtain it only at the expense of vol-ume. The broader tuning is the louder ;the closer tuning is the softer. Indeed,the volume declines at a faster rate thanthe selectivity increases.

Now, it is all right to use the screengrid tube for maximum volume, in multi -tube circuits, if you can devise some wayof controlling the receiver.

In a four -tube set you can use a screengrid radio amplifier as a maximum am-plifier, but what about selectivity? Surelyyou want that to be better than whatyou've been used to in four -tube sets.Then, too, you want more amplificationthan with an ordinary RF tube. TheScreen Grid Universal does both-givesboth greater selectivity and still increasesthe sensitivity and volume enormously.

One of the attractive points about ahome -constructed or custom-built set isthat it may be suited to the location inwhich it will be used. It has flexibility.If it is moved to a different type of loca-tion. where the requirements are different,a few minutes and the simple changesare perfected, and the receiver works justas well as it did in the other place. Yettake a factory -made receiver that workswell in one location. It lacks versatility,perhaps, to make it work just as well inanother location, because it is a standard-ized, mass -application product, not suitedto individual needs.

Here, in the Screen Grid Universal, wehave a wide range of selectivity-good, tostart with, much greater, if needed. Forinstance:

(a) The grid return of the screen grid


Grid UniversalBernard

tube may be made to the center -tap onthe two -winding coil used as the antennacoupler, as shown in the diagram, whichapproximately doubles the selectivity.

(b) The condenser C4, a junior type, byreverse feedback center -tap connection,may increase the selectivity as much as athousand percent, even on top of the pre-vious selectivity gain.

(c) A series fixed condenser may beconnected in the aerial lead.

(d) The primary winding of the an-tenna coil may be halved by removingturns.

Still Enough Volume

Even after you have used maximum se-lectivity, you still have good signalstrength, due to tuning the primary cir-cuit in the screen grid output, to the step-up ratio to the untuned secondary, toregeneration, and to transformer coupledaudio, which gives the greatest possiblestable volume that a two -stage amplifieraffords.

Looking at the diagram, the simplicityof the circuit is apparent, and one wouldsay there's "nothing to it"-meaning, itis hoped, nothing that approximates a dif-ficulty. And yet there are two strangeconnections: the grid return of the screengrid tube, which goes to the F minus postof a 5 -volt tube, and the twisted connec-tions, in the screen grid plate circuit.

The grid return to F minus of a 5 -volttube is simply an easy means of obtaininga negative grid bias of 1.7 volts on thescreen grid tube, represented by the dif-ference between minus 3.3 volts and minus5 volts. This point has arisen in previ-ous circuits published in RADIO WORLD.

The reverse feedback through the ju-nior condenser C4 is made possible byreversing the leads of the primary windingL3 in the plate circuit of the screen gridtube. If this reversal were not made thecondenser C4 would act solely as a dam-per or neutralizer, whereas with the re-versal established the effect is that of avery superior order of regeneration in thedetector tube. This arises from the feed-back being put in phase with the grid cir-cuit of the detector tube.

Each stage reverses the phase 180 de-grees, when the coil windings are in thesame direction and the respective con-nections are made in the same relativeorder, with plate and grid winding termi-nals and B plus and grid return windingterminals in the same relative positions.

Therefore the grid circuit is out ofphase with the plate circuit, unless thephase is reversed, and that's exactly whatis done by turning the connections aroundin the winding L3. It simply means con-necting the plate where B plus otherwisewould go, and connecting B plus whereyou would otherwise connect the plate.

Coil Connections

Considering the interstage coil used,which is a Screen grid coil, Model 5TP for.0005 mfd. and 3 TP for .00035 mfd., theprimary winding is on the outside. Thesecondary, which is on a separate form onthe inside, is wound in the same direc-tion. When the coil is mounted upright,with binding posts on bottom, the pri-mary or outside winding's binding postsshould be to the right, as you look at thecoil from the rear of the subpanel. Thebinding post nearer the front panel goesto plate of the screen grid tube, the corre-sponding one at right, nearer the rear,goes to B plus 135 volts, while the sec -

sockets affixed, and the drilled Bakelitefront panel, or prepare your own frontand subpanel. The front panel is 7x21inches and the dimensions are given onthe panel vi

349th Consecutive Issue-Seventh Year THE SCREEN GRID … · 2019. 7. 17. · Write for Free...

Documents

Transcript of 349th Consecutive Issue-Seventh Year THE SCREEN GRID … · 2019. 7. 17. · Write for Free...