Relvisionadio I

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AC IO ! C RAFT co=pot atiri9 11

RELVISIONADIO I

OVER 125 ILLUSTRATIONS 194 2 iqt your sQtv«Q .. i PRICES? No matter what happens to prices -here at Harrison our large scale purchasing and our tremendous stock enable us to continue to give you the lowest possible prices at all times. ¡t pays to buy from Harrison! DELIVERY? With production facilities already greatly overtaxed, deliveries are falling behind more every day. But, we anticipated this "Back-order Era" and placed protective orders many months ahead. hallicrafters Super Skyrider Right now we have more receivers, Model SX -28. "Tope" in performance. 15 than at any tubes, 2, r.f. stages, calibrated bandspread. parts, tubes, etc., on hand etc. Covers .55 to 42 mc. time in our busy sixteen year history! You get faster delivery* from Harrison! TRIAL? When you buy anything from Harrison it has to be entirely satisfactory or you don't keep it. Try out your next receiver for ten days without charge or obligation by ordering it from us. You get 100% cooperation* from Harrison! TRADE -IN? hallicrafters Sky Buddy By fair dealing we have built up the Model S -19 -R. A six tuber that largest Reconditioned Receiver business offers good results for a a ready market moderate price. .545 to 44 in the world! We have me with continuous electrical hallicrafters Sky Champion for your old set, and that means we can bandspread. Model S -20 -R. Excellent value. Nine give you the very best trade -in allow- tubes, noise limiter. preselector stage, ance. (We also buy receivers, transmit- .545 to 44 mc, bandspread. etc. Socket ters, etc., for cash.) for battery or vibro-pack operation. You get the *best deal at Harrison.' TERMS? Certainly! Charge Account or Easy Pay- ment Plan. Buy your Receiver. trans- hallicrafters mitter, parts, etc., on our easier terms Super Defiant at lowest cost. Model SX -25. Has Your credit is good at Harrison! all the features of sets selling * for nearly twice as GUARANTEE? much ! hallicrafters Ever thing is "guaranteed," but your Sky Traveler best guarantee is the integrity of the person with whom you deal. Here at Model S -29. You Harrison we go far beyond the standard can take it with warranty in order to please you! you! Works on You get a square deal from Harrison! s e l f contained batteries or any * AC or DC line. order! Built -in telescoping I'll be looking for your antenna. 9 tubes, .542 73, to 30.6 mc. bandspread, internal speaker, bat- BILL HARRISON, W2AVA tery recharger. (Send for my latest list of New and Reeon- ditioned Receivers) trmlontillallnleastassoeso gt's HARRISON bot hallicrafters and SERVICE!

11 West Broadway, New York City HARRISON RADIO COMPANY Worth 2 -6276 Get Into RADIO Quick! RADIO TECHNICIANS in Demand More Needed Now Than Ever Before

Learn At Home To Make $30 $40 $50 a Week offers you to make MAIL THE COUPON I Find out about the many opportunities Radio more money Quickly and to prepare yourself for a good -pay job after the War. Whether you're eligible for military service or exempt. you should get my 64 -page Book, "Rich Rewards in Radio." It's FREE. It tells about Radio's present and future opportunities and how I train beginners at home in spare time to be Radio Technicians and Operators; how I tench operating principles of Army, Navy, Civilian Defense Radio equipment. 5 Reasons Why You Should Learn Radio Now (1) The Radio Repair Business Is Booming. Because of the shortage of new sets, and increased interest in Radio programs, fixing Radios offers many extra new opportunities for Radio Technicians. (2) U. S. Government is calling for thousands of CIVILIAN Radio Technicians, Operators and is RADIO TECHNICIANS, OPERATORS hold paying well for their services. (3) Government Orders for Radio Equip- good jobs in the 882 Broadcasting Stations in ment, amounting to millions of dollars are creating opportunities for men the U. S. with average pay among the country's with Radio training to earn good pay, overtime. (4) Radio Is Ready to best paid industries. Aviation, Police, Commer- Expand After the War. Television, Frequency Modulation, Electronic cial, Marine, Government Radio, forging ahead Instruments and Controls will offer new opportunities in the future. even during the War, employ Radio Technicians (5) Extra Pay in Army, Navy, Too! Radio Training offers men and Operators. Soldiers, Sailors, Marines with likely to enter military service, soldiers, sailors, marines, many Radio training win extra rank, pay, are ready for opportunities to win extra rank, extra prestige, more interesting good jobs after their military service is over. I duty and earn up to 6 times a private's base pay. train you to be ready when Television opens jobs Why Many Radio Technicians in the future. Mail Coupon for complete details. Make $30, $40, $50 a Week is a rital Indust ry durü.g wartime, Radio Is one of the country's fastest -eross", peace tiene industries. It Radio Technicians trained Copvernmentl Radio REPAIRING, SERV- branch Ms Radio today; Aviation Commercial. Pollee. Marine. sets in spare time or full time: in Radio businesses of their ICING, home and auto Station: in Radio Factories; Mine Radio Radio fields of Radio are expanding fast during the war. Many more new branches of own. Many hark. will create new peace-time opportunities after Radio sets (there are (Television. Frei tuncy Maculation. etc.). held r r rrleice of Itadlo to ',Ito advantage of these tovseut and future now 50,197,000 in use) the war. N 1 -.n, n the otirvd gives good jobs to opportundl L Soon Learn to Make $5, $10 thousands, offers more Beginners a Week Extra in Spare Time opportunities now r, r before. In feet. many men I train time Radio Terbnid:Inv t Part or T... r.. it::,lin sets In their spare time I give you than ever. Loudspeak- regular pa -,t : prefer to hold their It.o As you pros resa wüh nr Cmnxe. I and show you . rc to ü ,.uly. er Systems are an- special training do jolis. Many men I train pay for their Courses, sham you how to do more and store money- mak.. i,., spend besides. by luit.. c,diu repair work while learning. other source of profit 1 have extra money to for Radio Technicians. Experience While Learning How I Give You Practical student you spend enroll I start ending you toy 6 Big Kits of Radio Parts. As my Many Radio Techni- Very s after you Radio Circuits. Complete Radio Sets. am all about half your time building Radio 'Dating Equipment. Experiments, cians operate their own spare time or full time Prequency Modulated Circuits. You conduct more than 100 Radio make Radio Transmlttere, broad Radio business, servicing, repairing, selling Radio more than 600 wadi measurements your Interest- working with re ltRadioh part half udyingtd nay lesson ntextsyholds sets. Get the facts. Mail the Coupon. makes learning Radio at home faseln acts R. Drarllral, Find Out How I Train You for Good Pay in Radio ItELOWI I'll send my big 61 -page book FREE. It tails about my Course: the MAIL THE COUPON of Radio today: Radian opportunities for the future: shores types of lobs In the different branches doing. earning. 100 men I trained so you can see what civilian and servlre men are letters from more than NOW MAIL TIIE COUPON its an envelope or pasted of a These Men and Hundreds More You owe it to yourself to get these farts penny postcard. J. E. SMITH, President Got Their Start This Way Dept. 2CX. National Radio Institute Washington, D. C. $200 a Month in Own Business For several years I have been in business for myself making around $200 a month. Business has steadily increased. I have N.R.I. to thank for WY start in this field. -ARIDE J. FROEHNKR, sou W. Texas Ave.. Goose Crock. Texas. J. E. SMITH. President. Dept. 2CX National Radio Institute, Washington. D. C. 1 $5 to $10 Extra a Week in Spare Time A Mail me FREE, without obligation, your 64 -page book "Rich Rewards in Radio" which tells about Radio's I am engaged in spare time Radio work. I average now and for the future. (No salesman from $5 to $10 a week. I often wished that I had opportunities enrolled sooner because all this extra money sure will call. Write plainly./ does come in handy.- TIJEODORE K. DuBREE. Horsham, Penna. Name Age Operating Naval Radio Station i am now operating the Radio Range Station, one Address the new simultaneous types, here at the Naval Air Station. Glad to give N.R.I. its share of credit in the success I have had thus tar.- GRIFFIT// City State SECHLER, Radioman First Class, U. S. Navy (Address omitted for military reasons.) RADIO -CRAFT for MARCH, 1942 385 IN THEISSUE k'nr'or porn ting "FM" for Odd Uses for De- HUGO GERNSBACK Plane Jn¡ts e rear Editor-in-Chief Recorder , .. Hor^e Tub Simple me H. W. SECOR CARLOS FROWEIN "M o 9'` .1 Editor Voltmeter Ait9n /anagin Art Director FM F Simple ment "P.P.." Proper Choosing Contents MARCH, 1942 Issue Unit

VOLUME XIII -- NUMBER 7

Mailbag 388 DEPARTMENTS, ETC. Editorial: Radio War Guards Hugo Gernsback 391 Mailbag 388 F. M. Operating Notes 430 RADIO SERVICE SHEETS What Radio Leaders Think About "FM" 392 DATA (See Servicing) 426 Latest Radio Frequency Modulation and Its Future Uses Apparatus 438 Major Edwin H. Armstrong 394 Book Review 431 W2XQR Broadcasts Concert Music on FM.. Russell D. Valentine 397

W45D- Detroit Gives F.M. Antenna Facts 398 RADIO & TELEVISION In This Receiver 2 Tubes Equal 4 WOR's New FM Station 400 Joseph P. Hiatt 440 Foot Pedal Break -In Rod Newkirk, W9BRD 442 FM in 1942 -As I See It J. R. Poppele 401 Calibrated Oscillator for the Ultra -High Frequencies NBC's FM Station fo go to 10,000 Watts O. B. Hanson 402 A. Binneweg, Jr. 444 One of New York's FM Broadcasters -CBS Station W67NY 404 Question Box 446 FM Future at a Glance 406 Radio Kinks 447 "FM" Map Grows Rapidly 407

Chicago Turns to FM Cyril Wagner 408

Mount Washington Highest FM Station A F. Sise 410 Published by Radcraft Publications, Inc. Publication office: 29 Worthington How FM Cuts Out Static 413 Street, Springfield, Mess. Editorial and Advertising Offices: 25 West Broadway, New York City. Chicago Advertising Office: RADIO -CRAFT, 520 North FM Sets for All 414 Michigan Avenue, Chicago, Ill.

FM Station List 416 RADIO -CRAFT is published monthly, on the first of the month preceding that of date; subscription price is $2.50 per year in U. 5. (In foreign countries, K45LA -Only "Commercial" on West Coast... Frank Kennedy 418 75c additional per year to cover postage; Canada, 50c additional.) Entered W55M Milwaukee Calling! -The FM Voice of the Milwaukee at the post office at Springfield as second -class matter under the act of March Journal 420 3, 1879. All communications about subscriptions should be addressed to: 29 Worthington Street, Springfield, Mass., or Director of Circulation, 25 West Broadway, New York, N. Y. RADIO DEFENSE * Ears For The Fleet- Radio, The Naval Reserve -and YOU 421 Foreign Agents: SERVICING London -Gorringe's American News Agency, 9A Green St., Leicester Square, W. C. 2, England. Grid -Bias Resistor Values Alfred A. Ghirardi, B.S., E.E. 423 Paris- Messageries Dawson, 4 Rue Faubourg, Poissonniere, France. Trouble for you in '42 Harold Davis 424 Melbourne-McGill's Agency, 179 Elizabeth St., Australia. Dunedin -fames Johnston, Ltd., New Zealand. RADIO SERVICE DATA SHEET: No. 320: Hallicrafter S27 FM /AM Receiver 426

FM and the Serviceman Bob Stang 428 Text and illustrations of this magazine are copyright and must not be SOUND reproduced without permission of the copyright owners.

A "Tobacco Tin" Hearing Aid Samuel B. Simer 432

386 er Instance of ow IRC Helps Servicemen Build Business

a reminder to call you when THIS little tag, factory - packed with all IRC only serves as also sug- Volume Controls sold through the jobbing trade, future service is required -but it is is designed to be hung on the control knob gested on the tag that customers recommend whenever you use an IRC Control for replace- your services to their friends. This means that the ment. Read it carefully. You'll quickly see that tag actually does double duty in working for you. and there is no better way of building public confi- Use IRC Controls to insure utmost quiet job. dence. No customer will fail to see it. None will long, dependable performance on every con- fail to be impressed with the fact that you have Use the IRC Volume Control Tag to build new used a replacement of highest quality. fidence, insure future business and to build The reverse side of the tag has space for your business from people who may never have heard name, address and 'phone number. This not of you before! Save Time ... Money...Work ... on Control Replacements By actual count, 10,859 of the radio models listed in the IRC Control Replacement Manual call for one or more replacements that can be supplied from the 18 Type D Controls and accessories included in the IRC Master Volume Control Cabinet. The Cabinet equips you for prompt service on the big majority of jobs. It saves you money, because Type D Controls with Tap-in Shafts can often be used in place of costly "specials." It saves time because Tap -in Shafts are easier and quicker to install. Ask your IRC jobber for details- today! RESISTORS and CONTROLS INTERNATIONAL RESISTANCE COMPANY, 401 North Broad Street, Philadelphia, Pa. RADIO -CRAFT for MARCH, 1942 387 MAILBAG SPRAYBERRY PRACTICAL INFORMATION NEEDED QUICK, EASY WAY Editor: RADIO TRAINING TO TRAIN FOR includes Away back in the early "twenties," when I first became enthused with the idea of FULL EQUIPMENT learning what there was to be known at Experience Easily Acquired that time about Radio, and "what makes RADIO it at Home tick," there were no schools available near by from which I, and many others in WEEKS You Do Practice -Giving 8 like me, could get thorough instruction in Experiments. Many Special I'LL FINANCE YOUR TRAINING Features . , . ALL Designed Radio. Progress Mail the Coupon TODAY and I'll to Help You Make Fast The only source of information on cir- not only tell you about my quick, SPRAYBERRY Training tarts easy way to right at the beginning of Ra- cuits, and how to connect apparatus so train for a good pay subject that job in Radio, Television and Sound. in a simplified, logical. understandable we could listen to the programs available BUT. Ill also tell you how you can easily learn Television. Frequency Modu- get It and pay for it. In Easy lation.ssignal Tracing, Mobile Radio (Auto- at that time were periodicals such as monthly payments etartinq ou Tank). Aviation eadlRparctnneestltiaReiand RADIO- deys after 8 week training pertpq. i Rin Set Inalaon CRAFT. work. So, it happens that what success I have LEARN BY DOING' Training Prepares You for a Business of On Real Equipment in Coyne Shops Your Own . Or Good Radio lobs enjoyed for the last fifteen years, as a Simple. easy method of Practical Excellent Training. The great fascinating land Pprogressive service engineer and instructor in Radio You don't need previ- Geld f Radio offers puny opportunities ous experience or a lot of book to the man who wants to get ahead. Communications, U.S. Vocational School, learning. You work on real equip - My Training is designed to give you located in nt In the Coyne Shops at quick acres. to these opportunities. this city, is, almost entirely, cred- Chicago. This 8 wecke training pre - prraERIal. thorough FULL RADIO Your oT raining ill A SEI itable to the knowledge gained by "hooking paree you for a job in service and interfere with your present ork. Not repair work -we also offer radio previous experience Is needed. up" receivers from diagrams and instruc- operating training. Full details of You Get Professional Test Equipment tions found in such periodicals as RADIO - this training will also be sent you Plus Complete i6etrything when you send coupon. With the given CRAFT. EARN WHILE needed to build a Complete Receiver/ LEARNING, interestingOwnnhands. I have found by my experiences, both in Job Help After Graduation tive' experiments withwith We help you part tim to help living uation. led' a modern learning Radio, and teaching it, that the e sad N give 9 u employment service after graduation. TESTER-A.NALYZER,PP, v. requirements Earn While You Learn of the greater percentage of H. C. LEWIS, President, My BUSINESS BUILDERS show you r students is more along practical lines than Electrical use so.3 Pauline SCoyneD 2 H, hicago, III. In handlingromoequipmentmaking Radioe technical. So, my classes are conducted Dear Mr. Lewis: lee shortly after you Please send me lea ur Big FREE Book and details along these lines. That is-my students are of your taught learn PAY -AFTER- GRADUATION -PLAN. COURSE IS SOLD UNDER to by doing, with just enough NAME MONEY -BACKAGREEMENT technical material or radio physics, to let them understand why the radio parts func- ADDRESS tion, as well as how they function. CITY STATE SPRAYBERRY ACADEMY OF RADIO F. L. Sprayberry, President This system of instruction enables me to 520 -C University Place. N. W. prepare the student for an amateur license Washington, D. C. Please in about six months, with six hours'instruc- MONEY FREE copy of 'HOW TO MARE DATAPRINTS I] ash my tion per week. Or prepare him to become Name quite efficient as a serviceman within twelve TESLA -OUDIN COILS Address months. 20e Ea. in order for 10 I notice that, within (Data and Drawings only.) (Mail in envelope or paste the last few years, on penny postcard, RADIO -CRAFT and other radio periodicals 86" Sp'k Tala -Ondin Coil 40e wmwwwmwwm =m = =mmm =w =win = =w =m (1 K.W. Exc. Trf. Data incl.) have forgotten the beginner in radio, except 8" Sti k Tesla -Oudin Coil 40e PREPARE YOURSELF for the occasional insertion of a diagram (14 K.W. Exc. Trf. Data incl.) of a one- or two -tube "blooper" set that Be Sp'k Oudin: 110 Vt. for a commercial radio position "Kick Coil" type 10e through a more often will not work. Instead you have 8" Tesla Works on Ford home study course written for the man who has perfected a wonderful magazine for ad- Coil IOc forgotten higher mathematics and who l' Sp'k Vibrator Hi -Freq. Coil 40c has had a non -technical vanced servicemen, who seldom have time education. to read it. NEW! S ft. Sp'k. Ondin Coil & Exciter This course qualifies Tae you to pass the Federal Also I would suggest that a Question Data Radio Telegraph and Telephone examina- and tions. Answer department be carried for the bene- Induction PIPE as An easily read, and easily understood course. fit of beginners. Moderate tuition fee. Write for particulars. B. F. MILLS, ORE LOCATOR Great Falls, Mont. Induction Type, Data 40a AMERICAN RADIO INSTITUTE Radio Typo 40e ' 1123 Broadway New York City "MUD SLINGING" LEARN RADIO Editor: More DATAPRINTS 40c each! I have not the "honor and glory forever" 5 Meter Superhet. Electric Refrigerator TELEVISION of being a Serviceman, or a % Meter Tr. & Rec. Wheatstone Bridge "Ham," or 20 A.C. Probe. & Ans. Weld. Tranaf. 2 K.W. 600 LICENSED graduates placed in even an (un)Sound man, but I do opine 20 Telephone Hook -Ups past 7 years in shipping, broadcasting, that space in Radio-Craft is too valuable 100 Mech. Movements Rewinding Armatures to be used 20 Motor Hook -ups String Galvanometer aviation, police, etc.; we also by a few of these gentlemen in 20 Simple Bell Circuits teach radio the childish Television Hook-up servicing and repairing; new beginners' sport of throwing mud. 20 Elec. Party Tricks Steel Wire Recorder! class forming Sept. 8th; If anyone contributes something that is Solenoids and Magnets Water Wheels 60 -page catalog new, or helpful, or constructive -get list. Water Turbines free; oldest, largest -or even Pry Eggs on Ice! and Relay and best equipped. educational, I am sure your Photo Cell readers will Experimental Photo - Ring 4 bells: 2 Wires MASS. RADIO show the same approval regardless of phone 20 Teals Tricks SCHOOL whether Radio Control for 13 BOYLSTON ST., BOSTON, MASS., Est.1599 the author is a well known college Models Polarised Relay professor -or some humble modest genius Diathermy Apparatus Induction Balance PATENTS- TRADE In a Little Spanish Town" like Lost Angels Inductor Organ Electric Pipe Thaws: MARKS (Lows Angle -ease) if you please. After Booklet concerning Inventions & Patents all- Bright Jewels do not originate "On Special Prices: 4 prints $1.00; 10 for 1100: Form "Evidence of Conception" with the Single. IOc each. Get New Catalog 100 A. instructions for use and 'Schedule of Sidewalks of New York" -too many Government and Attorneys Fees"-Free Gold Bricks there. LANCASTER. ALLWINE & ROMMEL This is by no means a criticism of Mr. The DATAPRINT Co. Registered Patent Attorneys Moody et al., who are like England- capable 436 Bowen Bldg. Washington, D. C. and willing to help the little fellows, but Lock Box 322D, Ramsey, N. J. instead have to FIGHT them, because they are too jealous to be appreciative and co- RADIO operative. That is why all of the "little COURSES fellows" in Europe fell before a Plague of Inventions Wanted RADIO OPERAT1NO- BROAnCASTINa RADIO SERVICING -a practical course Germs, and their plight should be a precept Patented or Unpdtented for us and U.S. -co- operate and pull to- SPECIAAMATEURRIO TECHNICIAN COURSE We have been successfully gelling Inventions, ELECFRONICS -1 yr. day course 2 yes. eve. gether -find time to help -but be too darn patented and unpatented, since 1924. Write us. Day and Evening Classes. Booklet Upon Request. busy to throw mud! R you hare a practical. useful idea for sale. New York Y.M.C.A. Schools CHARTERED INSTITUTE W. satn Street New York City ACIDOLFUS GERM HITMUSS of AMERICAN INVENTORS Sum ware in Cognito. Dept. 109 Barrister Building. Washington. D.C. 388 RADIO CRAFT for MARCH, 1942 MAILBAG

LIKED MR. GERNSBACK'S ARTICLE TODAY is the time to turn Editor: your RADIO JOB into a DETROLA Three cheers for Mr. Gernsback's article in the September issue on "Radio Service - SECURE POSITION! AUTOMATIC men Arc Gyps." Let us hope that all servicemen throughout the country will read this Do You Went a BETTER JOB? -A Secure time to prepare not agree Mr. Samuel Future? NOW is the RECORD article. I do with Yourself for Lasting, Profitable Steur that all radio repairmen should be Caren in Radio Engineering licensed by the Government, because that CHANGER in Don't fool yourself ! The good jobs -the per- would mean taking an examination, which manent positions in radio don't come easy. RADIO -PHONOGRAPHS many servicemen who are excellent me- The sure way to success is to build your future chanics but poor theorists might fail. If a on a sound foundation of knowledge and . and the ability that you develop a radio so that it will give ability . . man can convert now is your assurance of a steady. sure income satisfactory performance, he is a good that will outlast temporary emergencies such serviceman. as the present. Dividends for increased ability have never before been so certain. CREI tech- Yours very truly, nical training is designed to do just one thing ASTRUCK, -to increase your ability, enabling you to hold FELIX which lead to York, N. Y. the more responsible positions Now higher salaries. Hundreds of CREI students have accomplished this through the help of CREI training -just as many more hundreds TO DO "QUACKS" will do in the future! THE WORLD'S WHAT WITH Editor. WRITE FOR FACTS TODAY! Our free booklet and personal I am a subscriber to your `.R -C." maga- recommendations may hold the zine and also a part -time radio technician. answer to your success. In your to-Operate I say technician because I do not "fiddle' inquiry, please state briefly your background, education, around in servicing receivers. I tell my cus- RECORD CHANGER present position -and whether AUTOMATIC tomers that sometimes it takes longer to interested in home study or They're simple, trouble -free ... A fix some sets than it does others. residence training. child can operate them.You will mar- am a licensed Radio Serviceman and by RADIO this wondrous performance! I CAPITOL vel at that I mean I belong to the Radio Service- Engineering Institute Every men of America (RSMA). Dept. RC -3, 3224 16th Street, N. W., Washington, D.C. Model Has I do not intend to be offensive, by saying a Technician, AH Five I am not a Serviceman but but there are some who are "quacks" and EXCLUSIVE COMMERCIAL INSTITUTE want to ruin our profession just as a DETROLA RADIO "quack" doctor tries to ruin the professional A radio training center for over twenty years. FEATURES physician. Well equipped. Excellent faculty. Practical resi- MODEL 411 dent courses in Radio Telegraphy. Broadcast. a high school graduate and have 1 only Automatic record charger' I am Servicing. Industrial, Television. Aeronautical. The studied theory and fundamentals of radio Drafting, Mathematics and Studio Technique. Automatic with improved speaker forming. Catalog and am taking a "shop course" in servicing Placement bureau. Classes now upon request. and operating; I will soon take a course in Cheger Dept. D, 38 West Biddle Street. Baltimore. Md. radio shop operating and a communications /1 advanced course. pISYS Tee course; this will be an recordings I hope then not only to be able to do RADIOTELEYI5I011 expert radio technician service work, but want. tarent Radio- Tebrbloo school lo Kest trains you Ceadea..noiae- for good Dal Job. Complete instruction Including Radio 2 e less operation. also to hold down a good operating job. Construction and Service. Broadcast Operating. Sound. man never learn too much in this Talking Pictured, Television. Publie Address. etc. Flexi- A can ble plan to meet specific needs d thon with or without roam and board m rec. modern progressive world as it is today. lobs. Transportation Earn 3.:; hile learning. Request Free Catalog.og. ord .eÌectorn MODEL 17 I won't have to worry about the "bread -, 5 -tube automatic radio no trade New type cen- phonograph combination line' like some people who have NATIONAL SCHOOLS P:a:Z« A. whatsoever. amazing o features £ WA. ataJgaMg- LEti Correspondence Courses In tor yr en I like all of your publications of "R -C." in adding or RANO £L£CTRI(AL £NGINORINC moving record... but like best the September, 1941, issue and the two articles : "Isolating the Defective ELECTRICAL ENGINEERINGr did: SFree foatiea .I field. Prepare yourself, at Low Con. fee NeUre Stage," by Wm. Franklin Cook, and "64% uture Modern, llfled. you can unawmend nutria,. recordcord harmharm. . of the Radio Servicemen Are Gyps," by RADIO ENGINEERING Trains You tO b om...mice reel vacua tube Hugo Gernsback, Editor. technician. Eìper. kite furnlebeli Diploma completion. And That's Tu It inn, as 5. INr cour Deferral payment plan. much of licensing hoof la u Beet Yes sir ! I approve very nuoitpr, oies eúua. órli Nowt Not All . . the qualified radio Servicemen under Fed- FREE service- LINCOLN ENSINILIINO NNOOL Ow eNtl'. LINCOLN. NISI. Each play. ten 12 MODEL 419 eral supervision, so that all "quack- or twelve 10' rec. 6.tube automatic radio - men" will be eliminated and that such state- t sie -ha feather- phonograph combination s.right tone -arm. ments as "64% of the Radio Servicemen ..luting needle. be made again. RADIO will never need to Radio or phone.- Are Gyps" MODtt I vote that we get together, we Service- ENGI NEERING, LRFECTTONE! 427 i men, and write a so-called "group" letter broadcasting. aviation and pollee radio. servicing. marine radio telegraphy and telephony. Morse telegraphy and Also Complete from all of us and send it to Washington, railway accounting taught thoroughly. 4R weeks' Engl- F.C.C.) who would probably have neering course equivalent to 3 years of college radio work. Line of (to the An expenses low. Catalog free. School established 1814. jurisdiction over it, and ask them to legis- DETROLA evIennetit The Dodge Institute. T St.. Valparaiso. Ind. late a move to take up the matter and bring 3 -way Personals i it to a solution, so that anyone servicing And Portables graph would have to pass an examination to get RADIO TECHNOLOGY TABLE MODEL like the radio RCA institutes offer an Intemtro course of his license to service, just high standard Miami RADIOS Even then there will be "boot- and Television. PracticalP training with modern operator. New and Chicago schools. FARM SETS de- equipment at York MODEL leggers," but if then the public would Also specialized rouan In Aviation Communi- AND 471 "credentials" of the Service- cations. Radio Servicing and Commercial Oper- conal.- mand proper ating. For Free Catalog write Dept. RC -42. RECORDIOLAS er..1 man, when he arrives to service a set, the slip into oblivion. RCA INSTITUTES, Inc. untie. "quack" would A Radio Corporation M Amorist' Ber iee p e These are merely suggestions, perhaps 75 Varlek St.. New Yort. 1154 Manhandle. Mart. Chicago Your Detrola Dealer else knows a better one. I am COMPLETE NONE- See someone STUDY COUaSEf d my opinion on the matter, ce duetlonl hooka. merely stating ED 0n lightly ed. Sold. do urge that we "spur" the matter rented. exhanged. All but I jects. Money - back license business. guarantee. Cash Mid for about the u sed courses. Fall de- DETROLA Cx eSpCoes 5 72. NORMAN A. ZUERL, talls d Illustrated DETROLA BLDG. DETROIT, MICH. Page bargain Catalog Faga. Write todasl San Antonio, Texas. NELSON COMPANY. S00 Sherman, Dept. C -210. Chicago RADIO -CRAFT for MARCH, 1942 389 A WAR MESSAGE to ALL EMPLOYERS * From the United States Treasury Department *

WINNING THIS WAR is going to take the mightiest effort consideration. You will receive-1, a booklet describing America has ever made -in men, in materials, and in how the Plan works; 2, samples of free literature fur- money! Every dollar, every dime that is not urgently nished to companies installing the Plan; 3, a sample needed for the civilian necessities of food, clothing, and employee Pay-Roll Savings authorization card; and 4, shelter, must, if we are to secure final Victory, be put into the name of your State Defense Bond administrator who the war effort. can supply experienced aid in setting up the Plan. An important part of the billions required to produce To get full facts, send the coupon below the planes, tanks, ships, and guns our Army and Navy -today! Or write, Treasury Department, Sec- need must come from the sale of Defense Bonds. Only tion B, 709 Twelfth St., NW., Washington, D. C. by regular, week by week, pay -day by pay -day investment of the American people can this be done. HOW THE PAY -ROLL SAVINGS This is the American way to win. This is the way to PLAN HELPS YOUR COUNTRY preserve our democratic way of life. It provides immediate cash now to produce the finest, Facing these facts, your Government needs, urgently, 1 deadliest fighting equipment an Army and Navy ever your cooperation with your employees in immediately needed to win. enrolling them in a It gives every American wage earner the opportunity for i2 financial participation in National Defense. PAY 13y storing up wages, it will reduce the current demand -ROLL SAVINGS PLAN 3 for consumer goods while they are scarce, thus retarding inflation. The Pay -Roll Savings Plan is simple and efficient. It provides, simply, for regular purchases by your em- It reduces the percentage of Defense financing that must 4 be placed with banks, thus putting our emergency financ- ployees of United States Defense Bonds through system - ing on a sounder basis. atic-yet voluntary- pay-roll allotments. All you do is It buildsa reserve buying power for the post -war purchase 5 of civilian goods to keep our factories running after the hold the total funds collected from these pay -roll allot- wet ments in a separate account and deliver a Defense Bond It helps your employees provide for their future. to the employee each time his allotments accumulate to 6 an amount sufficient to purchase a Bond. The Pay -Roll Savings Plan has the approval of the American Federation of Labor, the Congress for Indus- PoNNOV trial Organization, and the Railroad Brotherhoods. It is TgIS MAIL B now in effect in several thousand companies varying in Section Department. number of employees from 3 to over 10,000. Treasury St.. In sending 709-12íu D. C. y trae the coupon below, you are under no obliga- ,asbiOßton. rart. ardlne í our a, tion, other than your own interest in the future of your e want informationnformationyl full . country, rush Savings to install the Plan after you have given it your the ray

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This space is a contribution to NATIONAL DEFENSE by Radio -Craft. 0.0 I0-26943-1 Form No. D88-BP-2 390 RADIO -CRAFT for MARCH, 1942 Incorporating RADIO & TELEVISION

"RADIO'S GREATEST MAGAZINE"

. Radio MUST be used to greater advantage in RADIO WAR our war effort .. . GUARDS By the Editor-HUGO GERNSBACK

THE lamentable burning of the Normandie in New York portable transceivers, many models of which arc now available. Harbor at its pier, early in February, teaches us a great Some of these models, which do not weigh more than five pounds, being used for most obvious can contact Police Headquarters or the Fire Department instantly, lesson -how radio is NOT valuable ship purposes, during this war. while the guard walks about the ship. Consider a such as the Normandie. It does not seem unreasonable that a Whether the Normandie fire was of incendiary or natural origin dozen such Radio Guards could have been stationed at strategic need not concern us at the moment ; but a preliminary investigation points throughout the ship. This would mean two things -one, brought out the fact that most valuable time was lost before an that the guards could communicate with each other ; two, that alarm was turned in to the local Fire Department. It seems to be the one stationed on the top deck could have radioed the alarm well established at this writing that it took approximately eleven instantly to the Police or Fire Department. Such Radio Guards minutes before such an alarm was turned in -a sufficiently long should be stationed on all ships during war time. make such headway that the disaster time for the flames to one or two land followed as a necessary consequence. As an additional protection there should be guards, radio -equipped, watching the ship from shore and several Here is an instance where radio could have been used to great more on the dock or pier, because pier and dock fires have been advantage and certainly should be so used in the future, particu- all too numerous and frequently disastrous. Only a month before larly while we are at war. The burning and damaging of the the burning of the Normandie there was a disastrous pier fire, Normandie will not be the last ship that will go up in flames and only a few blocks away from where the Normandie now lies. we may be certain that the enemy is trying to do all he can to Quick radio action could conceivably have saved the pier. war cargo ships from sailing. Sabotage is prevent troop and it is most difficult for nothing new in America. Those who are old enough will remember It should be always remembered that we the Police to patrol the long pier lines efficiently in most of our what happened in the first World War, but unfortunately precau- still do not seem to have learned the lesson. maritime cities. During war time, therefore, additional tions must be taken and for the little expense that is involved Even with the strictest of supervision -which certainly was in posting these Radio Guards, there will be truly enormous lacking in the Normandie case -it will still be possible for savings in ships NOT destroyed. fire ships during this war, and even .the strictest saboteurs to of buildings, and vigilance will probably not prevent the enemy from accomplishing And what holds true of ships also holds true his nefarious work. particularly those buildings which are used for war effort purposes. Every plant, no matter what its description, if successfully fired Ships are common not only in New York but also in San or bombed by saboteurs can prove an important "bottle -neck" and Francisco, Boston, Galveston and elsewhere, and that instant tie up many other plants. For this reason Radio Guards stationed cmmm1nication which should be maintained by them with the on roofs and the surrounding property can be in instantaneous land, is not always made use of. touch with Police Headquarters and Fire Departments, preventing the burning or damaging of the plant. While it is true that some ships have telephone cables going right aboard, most of the larger freighters and even many of the There are several other reasons why ammunition and other sizable passenger ships are not equipped so that (wire) telephone war effort plants should be protected, even those without direct calls can be made directly from ship to shore. Also of importance fire threats. make calls, telephone cables are required is the fact that to such plants to temporarily connect the ship's switchboard with the dock. As has become all too apparent lately, important war These cables are vulnerable and can be cut and sabotaged just draw loiterers and prowlers who are always there for a purpose. have radio They do not happen to be there ust by chance. They are put when they are needed most. Of course all ships do of there stations on board, but these stations are usually not tuned for there by the enemy. Normally, in the very nature things is operator are never sufficient armed guards, but if we substitute Radio instant transmission of police calls, nor the average ship a conversant with putting through calls of this type to either the Guards for the present -day guards and the Radio Guard sees prowler and puts in a call with Police Headquarters, the suspects Police or Fire Departments. Nor has the steamer's radio cabin been instantaneous means of communication with all parts of the ship. can be apprehended even before they know they have observed. Radio works instantaneously and an alert Police Force In most of our larger cities, particularly those along our sea- can pick up prowlers and loiterers in a matter of seconds, as has boards, the police are radio -equipped now. Some of our cities been demonstrated often in the past. now also have Fire Department radio -communication of some sort. It is to be hoped that more use will be made of Radio Guards The idea I propose seems absurdly simple, but when it comes during this war. It will save thousands of lives and untold to protecting ships during war time -when seconds count -there millions of dollars in property, and more important, it will help must be instantaneous means of getting in touch with either the to bring the war to a speedier close. for someone run Police or the Fire Department. Waiting to country's effort across a deck and onto the dock means loss of valuable seconds. A disaster such as the Normandie sets back the How much simpler then is the idea of equipping guards with for months at a time. It should not happen again! RADIO -CRAFT for MARCH. 1942 391 F. M.

John V. L. Hogan Fred Weber J. R. Poppele Lewis Allen Weiss WHAT RADIO LEADERS NOTES ON FM It is gratifying to us as we watch the lines. As one of the latest of JOHN V. achievements L HOGAN rapid progress being made by this new modern broadcasting science, Frequency Consulting Engineer and Inventor, Licensee of branch of broadcasting to reflect on the Modulation is one of war's most important W2XQR and President of WQXR part played by Mutual stations in its de- recruits from the ranks of radio. FM is velopment. Out of 24 commercial FM sta- FROM the FM facts developed by the best proving itself on many battlefronts. tions now operating, 6 are operated by Mu- On the home front, FM is continuing its engineering analysis that I can contribute, tual affiliates or stockholders. These are progress, making I have concluded that wide -band FM gives particularly great strides W71NY, New York City (WOR), W59C, during the past year. At this time, I do not us (as broadcasters or as listeners) the Chicago (WGN), K45LA (Don Lee most effective way that has yet been sug- Net- want to play prophet and predict the course work), W43B Boston -W39B Mt. Wash- of FM's development in civilian life while gested for the practical use of what are still ington, New Hampshire (Yankee Network) called Ultra High Frequency waves (in the nation is at war. However, I am opti- and W45V, Evansville, Indiana (WGBF). mistic for FM's future. There are already spite of the fact that they certainly are no Five Mutual stations longer have commercial FM enough receivers in the hands of listeners Ultra h.f.). The 40 -60 megacycle stations under construction and four others and enough FM stations band is about 1000 times more free of nat- on the air to guar- have applications pending before the FCC. antee a healthy status quo for FM during ural statics or true "atmospherics" than is As an aid in programming, the Mutual has the war and to insure continued develop - standard broadcast band of 550 -1600 made its service available to the six ment of kilocycles. But the high frequency band is FM FM programming and engineering. stations operated by its affiliates and also Certainly there will be no let-up in WOR's more subject to interference from man- to one independent FM broadcaster extensive made "static," such as the electrical noises - activities in Frequency Modula- W47A, Schenectady. These seven stations tion through its FM outlet, W71NY. produced by diathermy, automobile ignition, have been listed on Mutual program W71NY's oil burners and what have you. Along with sheets new 10,000 watt transmitter is Major since the summer of 1941 as an indication of already serving a sizable audience -50,000 Armstrong, I believe that the use of the networks interest in their growth and receivers have wide -band FM on these high frequencies already been sold in New potential development into an active sales York. To the owners of these 50,000 sets gives us not only the inherent benefit of the medium. FM high frequencies One station, W71NY, is origi- \V71NY has proved that FM is definitely themselves in overcoming nating a series of programs to the full net- a superior system atmospherics, but also the ability of wide - of broadcast transmission. work. In war or peace. we intend to continue our band FM (with a suitable limiter in the re- Conscious of its public responsibility ceiver) of overcoming man -made electrical to pioneering in Frequency Modulation, to be alert for and receptive to new methods improve our programming service to our noise. Of course, I may be wrong, but I that indicate think not. progress, Mutual is watching FM listeners, to maintain our research and the developments of relay transmission with- experimentation in all aspects of FM. For In any event, W2XQR may be taken as out the use of wire lines between FM sta- FM is here to stay! an evidence of my faith in wide -band FM, tions. W7INY, New York City, has already both as to the present and the future. been active in this field and it is anticipated DON LEE NETWORK FAVORS FM \V2XQR was, I believe, the first FM broad- that a permanent exchange may soon be LEWIS ALLEN WEISS cast station to go on the air in New York. arranged between New York and W49PH, Of course Major Armstrong's W2XMN at the FM station of Mutual's Philadelphia Vice -Pres. and Gen. Manager, Mutual - Alpine was the pioneer experimental sta- outlet, WIP. Don Lee Network tion, and C. R. Runyon's Yonkers station In accord with the views IT appears that Frequency \V2AG, expressed by Modulation collaborating with the Major on F.C.C. Chairman Fly, I do not believe that will see no about 102 megacycles, serious setback in the com- was far ahead of us frequency modulation will ever totally sup- ing year, despite wartime exigencies. War in point of time, but, as far as I can find, plant our present form of broadcasting. is making \V2XQR beat out its demands on metals and parts. all the rest in trying to Rather, the two methods complement each However, manufacturers will probably use bring you a regular, scheduled, daily broad- other and the opportunity for new fre- their limited of cast FM service. quotas materials for manu- Soon, we hope, \V2XQR quencies and unmonopolized channels for facturing quality FM -AM combination re- will become W59NY and cover the 8500 the dissemination of information, education ceivers. square miles designated as the New York and entertainment are of great interest City service to us. Those who are acquainted with the quali- area. Why don't you take an Mr. Telford ties of FM have wholeheartedly observation on W2XQR (45.9 mc.) as it Taylor, general counsel of accepted the F.C.C., in an address last July empha- the new static -free broadcast system. A now is, and send me a note, giving your consistent growth opinion as to our progress? sized the great opportunity open to FM of FM listeners has been stations to serve as outlets for program noted for Southern California since Don material that might Lee's commercial station K45LA was in- MBC ENTHUSIASTIC ON FM not otherwise be available. Mutual stations have been quick to augurated August 11, 1941. All the promo- FRED WEBER realize the importance of this service. tion in the world will not put a project over General Manager, Mutual Broadcast+ng System like mouth- to-mouth advertising. Written FM TODAY AND TOMORROW testimonials of satisfied THE Mutual Network listeners show that was founded on a the broadcast neophyte steadily is winning basis of additional service to the radio J. R. POPPELE Chief Engineer WOR, New York its place in the public favor. audience. It is natural therefore that any In a few short months sales in this area advance in radio which tends to this ideal RADIO has gone to war. And since this have boomed to 15,000 units. a 400% in- should be of keen interest to Mutual, its is a war of machines -a war powered crease over the original number already in member and affiliated stations. and armed by science -radio is in the front use at the August opening of K45LA. This 392 RADIO -CRAFT for MARCH, 1942 F.M.

John Shepard, 3rd. Dr. Ray H. Manson E. E McDonald, Jr. G. V. Rockey THINK ABOUT "FM" is evidence of the fast stepping -ahead of tion of an FM broadcasting station and the 1. There will be an FM band for the high FM for the immediate future. design and production of three complete quality and completely reliable local service band may be designated While material parts may be restricted, lines of FM -AM receivers, is that Major and this sta- Armstrong gave the radio industry success- "Local." manufacturers as well as broadcast broad- tions are nevertheless doing their share of ful answers to most of the technical ills of 2. There will be an AM (standard broadcasting. His system gives workable cast) band for the high power AM sta- educating the public to the wonders of the large new art. Special broadcasts answers to the majority of the operating tions required for covering fairly broadcasting be "National." devoted to FM, and showing of explanatory difficulties which have beset the broadcast- areas and this can labeled and ing industry from the beginning. Further- 3. There will be the customary short -wave film in school meetings, club gatherings band for from civic groups are introducing the newest more, if FM is given a chance to make handling programs coining phase of broadcasting to the general public. progress during the war period, it is destined great distances and, in particular, from Complete effect of this "get- acquainted- to be the leading factor in radio expansion other countries. This band can be desig- effort" will probably not be known until during the reconstruction period and, in the nated as "International." after the war has ended and volume pro- meantime, it may become an important Summing up. FM gives to radio broad- duction of receivers is reinstated. But mean- war aid. casters a new lease on life, which provides while the job of educating the public goes Nearly everyone acquainted with radio a new and efficient tool for maintaining and on. Don Lee station K45LA continues daily of F11í, advancing its leadership as the most impor- recognizes the main advantages means broadcasts and when the restricting fetters such as its astounding reduction of static tant for instant distribution of news, are broken the populace will not only its ability, educational programs and mass entertain- and station interference and feature "know" but undoubtedly will ask for "FM.' when using a fully adequate FM receiver, ment give a reproduction which is breath- to FM AS ZENITH SEES IT FM AND THE YANKEE NETWORK taking in naturalness and clarity. However, one of the most important advantages of E. F. MC DONALD. JR. JOHN SHEPARD 3RD FM, from the standpoint of channel alloca- President Zenith Radio Corporation President, the Yankee Network tions, is the assigning of sufficient power THE tremendous swing to FM during and height of antenna to give reliable re- 1941 has been the record for 1941 is one' highly gratifying to all GLANCE at ception to an assigned "service area," which connected with the growth of this newest L which will amaze many people. may be a local community or a whole rural phase of radio art. At the turn of the year, the antenna. It has been estimated that only about area surrounding transmitter approximately 23 commercial and 14 experi- 15,000 FM receivers were in the hands of This guarantees exclusive use of the area mental FM broadcasting stations were on the public on January 1, 1941; by December for the particular FM channel, without the air. The sale of Frequency Modulation 31, the estimate is that there were in the station interference from other transmitters sets built under genuine Armstrong FM neighborhood of 250,000 sets in the hands assigned to the same channel, which may be patent has been strong the country over, of the public. The great majority of these located at a sufficient geographical distance country. even by points not yet served by a FM sta- sets were sold during the last three or four to serve other areas of the tion. The public has been quick to grasp of months of the year, and the rate dis- Here, for the first time in radio, is a sys- the added enjoyment FM has to offer tribution has continued up to the present tem which gives each broadcaster a definite through noise -free reception and true high- time. field of operation (audience). and this op- fidelity tonal range. Unless it becomes essential that all re- eration is not dependent on time of day or Apart from the purely entertainment an- ceiver production be limited to military night, season of the year or condition of gle FM is proving its mettle in a number of needs, there will no doubt be an ever -in- the weather. Thus. in any given locality functional applications. Police departments creasing proportion of FM receivers to AM served by a number of FM stations, the are rapidly resorting to FM for inter -com- receivers being sold. audience appeal will be based solely on the munications between patrol cars and head- New FM transmitters are continually be- quality of the program material furnished. quarters. Just the other day I read of a ing added to the list of those that have been rather than on any advantages of channel most dramatic way in which FM is helping operating for some time, and the FM lis- assignment as in AM. This is a vital FM speed defense. tener is receiving better and better pro- advantage as it takes the guess out of the Transformed over night from a peaceful grams all the time. potential audience which can be served by prairie farmland into a mighty unit in a broadcast transmitter. America's first line of defense production, Under such conditions, one can hardly a large munitions plant, whose location I have anything but an optimistic outlook for The logical ultimate development of FM future of Frequency Modulation. shall not mention is a scene of in-essant the broadcasting will be to replace all local AM activity by day and night. Sprawled over shared channel stations with the interfer- 15,000 acres and housing hundreds of small FREQUENCY MODULATION ence- free FM stations, leaving the high buildings, two essentials of uninterrupted DR. RAY H. MANSON power cleared channel stations to cover production are transportation and commun- large areas and thereby serve sparsely ication -and sometimes a combination of Vice -Pres. and Gen. Manager, Stromberg- settled as well as rural communities. Carlson Telephone Mfg. Co. the two. To provide continuous and instan- The radio receiver of the future must taneous communication between central MY personal opinion of FM, based on thus provide for three kinds of service, if control room and the nine Diesel locomo- over three years of first -hand experi- the owner is to get full coverage with his tives hauling explosives within the plant, a ence, including the installation and opera- instrument : (Continued on page 412) RADIO -CRAFT for MARCH, 1942 393

wrsr1A.i. F. M.

FREQUENCY MODULATION AND ITS FUTURE USES

MAJOR EDWIN H. ARMSTRONG Prof. of Electrical Engineering, Columbia University

SOLVES MANY PROBLEMS effectively on wave lengths hitherto not put The new method solves not only to use and because it has a curious immunity the noise problem but many others to interference from other frequency modu- a) by Bachrach which are inherent in the existing lation stations, even though they may be on system. Due to a number of reasons, the same Mejor Edwin H. Armstrong wave length channel. It becomes present -day broadcasting can trans- possible, therefore, to place stations much mit and reproduce only a part of the closer together geographically, and conse- musical range; that is, instead of transmit- quently to permit the use over and over NCE in a while an invention is made ting the range of 30 to 15,000 cycles which is again of the same channel within the con- that overcomes so many of the prob- required for natural reproduction, the range fines of the United States. So effectively 0 lems with which an industry has been of 30 to 5,000 cycles is about the limit in can this be done that the number of avail- contending that its methods are present practice. In addition, this restricted able channels may easily exceed the de- quickly recognized as the right ones to part of the range which is actually utilized mand, with the factor which determines follow by those who understand its techni- is reproduced none too faithfully by the whether or not a community may have a cal phases. Sometimes the new invention existing system, on account of various dis- local service resting solely upon the com- fits nicely into the established financial tortions which occur in different parts of munity's ability to support it. This alone structure of an industry ; sometimes it does the transmitting and receiving equipment. would insure the adoption of the new sys- not. In the one case, the inventor is met Because of these limitations a radio "sounds tem. with open arms ; in the other, he probably like a radio." The new method is capable of is assured that he really has a very fine transmitting the full frequency range (30 invention and TRANSMITTING THE SPOKEN WORD that if the art were starting to 15,000 cycles), with a minimum of dis- is beyond out afresh no doubt it It the scope of this article to would be adopted, tortion and with practically the full dy- describe the technical processes by which but to replace the existing plant-even namic range (i.e., maintenance of the proper these results though obviously it are accomplished. They were is now obsolete -would relative amplitudes of the loudest and originally described in a paper presented be too staggering a thing to be considered. softest notes) that is required, so that it is History teaches before the Institute of Radio Engineers in that the best method in- possible to obtain a naturalness of reproduc- November of 1935, and date no question evitably forces its way into use to and ul- tion never before achieved ; in short, a re- has arisen as to the technical accuracy of timately becomes standard. Sixty years ago production which does not sound "like a the this description or our understanding of electric light and power industry started radio." what the new method can accomplish. But off on the wrong road in its method of dis- The solution of these problems alone tribution. without entering into a detailed explanation It undertook to distribute electric would warrant the application of the new of the phenomena involved, it would prob- power, using the best ; in fact, it used the technical methods, even though nothing only ably be helpful to explain some of the terms practical method at the time, namely, more was accomplished than the parallel- which the lay reader encounters in press the low- voltage direct current system. ing of the existing service by the new sys- Some years and magazine articles concerning frequency later the soundness of this tem and the gradual transfer of the listen- modulation and to venture a sort of "curb- procedure was challenged by the high -volt- ing audiences per se from the old to the age stone" explanation of how the reduction alternating current system which, sur- new type of broadcasting. But there is an- in is achieved. mounting all noise obstacles placed in its path, other contribution which this system can Radio transmission is accomplished by went forward against powerful opposition make that has very great social and politi- and connecting an electrical pump (the trans- eventually superseded the direct cur- cal significance. mitter) to a conductor known as an an- rent system in over 90 per cent of its ap- For years there has been a shortage of tenna, usually elevated above the earth, plications. Looking back, one can see the "wave lengths" or channel space, and the absolute which pumps electricity into the conductor inevitableness of this result, yet attempt to allocate equitably the inadequate and sucks it out again hundreds of thousands the literature during the time of transition facilities available has been the bane of reflects or millions of times a second. Because of a period of most violent controversy. the existence of those charged with this certain laws of nature, with which we need A large part of the radio industry, par- duty. With present methods, no permanent not concern ourselves for an understanding ticularly the broadcasting division, is now solution is possible; in fact, the interfer- of the subject of this article, this process facing a similar transition period, for a ence situation has become worse in recent causes an exactly similar flow of electricity new principle has been discovered which years due to increases in the number of stain conductors known as receiving antennas furnishes a solution to the problem of tions operating in the United States and to suitably placed within the range of the "static." This term includes all those dis- the construction and operation at high transmission, and this electric current flows turbances which have their origin in natural power of numerous stations located beyond up and down the receiving antenna the same causes, such as lightning storms, and all our southern borders. number of times per second that the trans- those man -made noises which have their The new system offers a solution not only mitting current flows in its antenna. The origin in the various kinds of electrical to the national and international interfer- received current is weaker, of course, than machinery found in towns and cities, such ence problem, but to the problem of giving the current in the transmitting antenna, as electric razors, refrigerators, oil- furnace every community one or more channels on being in fact a most minute replica of the motors, elevators, etc. This new principle the air so that stations particularly adapted current produced at the transmitting point. makes use of a process known as "frequency to local needs can be set up and operated This weak current, however, is applied to modulation," although much more than a without interference. This result has come a receiver. which amplifies it up to a method of modulation is involved. about because the system operates most strength where it may be detected and ob- 394 RADIO -CRAFT for MARCH. 1942 F. M.

Modulator for Transmitter at Major Armstrong's famous "FM" station at Alpine, N. J. The Major personally supervised the erection of the antenna and climbed up into the lofty mast himself to check the details.

served. This constitutes radio transmission, but not communication of in- telligence. In order to transmit in- telligence it is necessary to perform some operation upon the transmitted wave so that this operation may be observed at the receiver. In the case of transmission of the spoken word, the process of im- pressing the voice, or molding it upon the transmitted wave, is called modulation. It has been standard practice to accomplish this by vary- could be done to reduce their effect except alleged inability to work beyond the hori- ing the strength of the current in the trans- to raise the power of the transmitting sta- zon, the necessity of constructing new transmitting antenna in accordance with the fluc- tion ; or, in the case of man -made disturb- mitting stations, and the high cost of new tuations of the voice. This may be called ances, to place the receiving antenna as far receivers. The proposition was also ad- strength, or, technically, "amplitude" modu- away as possible from the source of the vanced that if amplitude modulation was lation. The function of the receiving equip- noise. Subsequently it was proposed to us used in the ultrahigh frequency range, sub- ment is to translate these modulations into frequency modulation, on the theory that stantially the same freedom from noise voice currents so that they may be heard in a these disturbances were essentially ampli- could be secured, as well as the same quality telephone receiver or loudspeaker. In this tude modulation and hence would be re- of reproduction. Subsequently, when the type of signaling the speed of the pump at jected by a frequency modulation system; better quality of frequency modulation was the transmitter is not changed during modu- but it was found that the disturbances con- demonstrated, the proposition was advanced lation ; the electric current flows up and down tained frequency changes as well as am- that the public would not appreciate it and the antenna the same number of times per plitude, and very little improvement result- did not want it. second, regardless of the changes in the ed. However, it was observed by the writer Still later, when a phenomenon was en- strength of the current. during the course of a series of experiments countered in television transmission in large There is another form which is almost as that these frequency changes appeared to cities, which resulted in multiple images old as amplitude modulation. In this form be limited in extent to about the same (ghosts), it was stated that frequency of modulation the strength of the antenna changes in frequency as were being used modulation transmission could not avoid a current is not varied in any way ; it remains in the frequency modulation system. The similar type of distortion. constant. But the number of times that the idea presented itself, therefore, that if the The proposition was also advanced that electric current is pumped up and down in frequency changes in the signaling wave the system was wasteful of channel space the antenna by the transmitter is varied could be artificially increased in extent be- in the radio spectrum and that if ultrahigh (speeded up and slowed down) in accord- yond those changes which existed in the frequencies were ever used in broadcasting ance with the fluctuations of the voice. This disturbing currents, and a receiving system the amplitude method of modulation would type of modulation is known ,as "frequency created which was immune to the ampli- be mom economical thereof. modulation." At the receiving system, where tude modulated part of the static- feebly The writer, disagreeing with all these similar changes in the number of times the responsive to its small frequency changes conclusions, undertook the burden of in- current flows up and down the antenna but fully responsive only to the wide invention to the public and occur in consonance the specially modu- troducing the with those which occur changes in frequency of started the construction of a high -powered at the transmitter, a somewhat different lated wave -a means could be found for or failure would take form of receiving system from the ampli- differentiating between the signaling cur- station whose success This proposal the matter out of the realm of academic tude modulation system converts these rents and the disturbances. discussion. As it was essential that the per - changes in frequency into the voice currents turned out to be a sound one and improve- any "talk in noise reduc- formance be so outstanding that that ¡may be heard in the loudspeaker. For ments of one thousand to one would be silenced, the sta- -five this method of modula- can now be readily produced in prac- down" campaign twenty years tion tion was designed to have a power ten tion was considered to hold no promise of tice. Not only could this advantage be ob- operated times greater than ever before produced at development, and it appeared to have no tained, but, because the system A site was selected practical use whatsoever. in the frequency ultrahigh frequency. most effectively ultrahigh at Alpine, New Jersey, some seventeen miles band, a further advantage over standard construction THE PROBLEM OF STATIC broadcast methods was secured as much north of New York City, and Ever since its earliest days, but par- present in the ultrahigh f re- was started. Meanwhile an amateur station, less static was in Yonkers, New York, ticularly after the invention of sensitive quency range.' \WAG, located amplifying receivers around 1912, radio owned and operated by C. R. Runyon, was with the frequency modulation has suffered from disturbances produced by OPPOSITION TO THE SYSTEM equipped lightning storms and commonly referred to After many years of laboratory work to system. The performance of this station dis- of the bugaboos so cheer- as "static." More recently, with the advent put it in practical form, the system was posed of many of radio broadcasting where receivers are brought to the attention of the Radio Cor- fully predicted for frequency modulation. located in metropolitan areas in the vicinity After witnessing the demonstrations, the poration of America and was demonstrated operators of of all sorts of electrical machinery, it has to its executives and its engineering staff. Yankee Network management, also suffered from so- called man -made at the end of a chain of stations throughout New Eng- These demonstrations began of WDRC in static. For a good many years it was be- 1933 and continued for almost two years, land, and the owners Station lieved that some form of circuit could be Hartford, Connecticut, became interested at the end of which time the Radio Cor- Pax- devised which would separate the signaling poration declined to undertake the task of and started the erection of stations in current from the currents created by these putting the system into public use. Various ton, Massachusetts, and Meriden, Connecti- disturbances, but eventually it came to be im- cut. This entry into the field by two success- reasons were advanced to prove the demon- understood that both the signaling currents practicability of the system, such as its ful broadcasting interests, and the strations which were carried out by the and the disturbing currents were essentially 1 The ultrahigh frequency range may be con. the same in their nature and that very little sidered as below 10 meters (30,000 kilocycles). Yonkers station, stimulated a dozen or more RADIO -CRAFT for MARCH, 1942 395 F. M.

enterprising broadcasters to secure con- ence of certain harmonic distortions which ible to use this, and where it cannot com- struction permits and to start the erection are particularly offensive of transmitters. in the upper fre- pete with the radio relay. This is par- The importance of the part quency ranges. These tones, together with ticularly played in this development true in the mountainous sections by Mr. Run - the increased noise which always attends of the country. The establishment yon's station can hardly be overestimated. the of re- extending of the frequency range, were gional networks entirely radio connected, During the three -year period prior to the the things which were really Alpine being rejected. extending throughout large sections of station's completion, scores of When the harmonic distortions and the country demonstrations were made of this type, is entirely practicable, to representa- noise were removed from the signal by and several such projects tives from all branches of the radio indus- are now under means of the frequency modulation system, way. Very rapid development in the radio try, who were given every opportunity to the full frequency range was instantly examine the ap- relaying field may be expected. system's performance. No one preciated. The reproduction then became Looking was refused the opportunity to at it from the standpoint of the observe the natural. It is difficult now for one to credit broadcaster, it is operation under all conceivable conditions. easy to see that the lower that the contention was actually made that cost of the transmitting equipment, It was possible an its econ- with very little vision to unnatural type of reproduction was to omies of operation, and the possibility of extrapolate this comparison between a 500- be preferred to a natural one. the reduction watt of wire -line costs by the use frequency modulation station and the of radio relays, are all in 50,000-watt WIRE -LINE FACILITIES his favor. For the standard amplitude modulation manufacturer of transmitters, and more broadcasting station, and to forecast what At the present time only one obstacle stands in particularly for the manufacturer of re- the service of the Alpine station would be the way of a full realization of ceivers, there lies like. There the advantages of frequency a vast new market in an were a few enthusiastic disciples modulation industry which has unquestionably reached as a result of some hundreds of demonstra- throughout the country, and that is the a saturation point. tions. limitation upon network Superficially, ohe might operation imposed be led to believe that the industry by the deficiencies of wire -line cónnections. would The performance of the Alpine, Paxton, welcome a development such as this, but and Meriden transmitters These connections as at present set up are the fact convinced the limited the remains that, with a few exceptions, broadcasting industry that change to transmission of a frequency it has not been a was range up to welcomed by the large units inevitable, and approximately 150 applica- 5,000 or 6,000 cycles, with a of the industry. The residual noise level considerably greater burden of the develop- tions were filed with the Federal Communi- ment has been carried almost entirely by the cations Commission. Since the frequency than that required for the full dynamic smaller units. The range of studio orchestral productions. This reasons for this opposi- allocation assignment made no adequate tion are quite obscure, but nonetheless provision for this number of stations, in the they are very real ones. It is important in fall of 1939 the Commission suspended the the interest of the future progress of granting Edwin H. Armstrong is pro- the of experimental licenses in order fessor of radio art that at some time they should be to review the situation and to consider the electrical engineer- brought out into the light of day. point which had been raised by the Radio ing, Columbia University, Corporation PRACTICAL APPLICATIONS of America that the standards New York In which were being used were not City. He was this article, the application of the fre- the best. quency modulation system After a hearing held in March of 1940 the associated with Professor to the broadcast service has been treated. This is, Commission approved the standards which Michael I. Pupin in research of course, were then in use, removed its major application. There are, however, the experimental applications limitation, arranged to issue commercial at the Marcellus Hartley Re- to numerous other services, and the field is licenses as of January 1941, and reallocated search Laboratory of Colum- widening almost daily. At the a part of the frequency moment, the greatest activity is in its ap- spectrum to in- bia University, 1914 -1955; plication crease several-fold the channel assignments to the emergency services, par- for frequency modulation. The served as Captain and Major ticularly to the police service. lower f re- The largest project quency part of the assignment to television, in the Signal Corps of the at the present time which had not fulfilled the is that undertaken by the Connecticut State early predictions United States Army, 1917- Police, have of its readiness to furnish a public service, who in operation nine fixed was rearranged. Nineteen 1919; and is the inventor of stations and approximately two hundred channels had mobile been assigned to television. Each television the regenerative circuit, the stations equipped for two -way channel was sufficiently wide operation with the fixed stations and with to accommo- each other. The date 30 frequency modulation stations. The superheterodyne, the super- installation has been completely successful and the State is effectively lower or Number 1 television channel was regenerative circuit, and a assigned to frequency covered. modulation and the method of eliminating static The two lower television channels moved pro- next largest project is in the City of in radio by Chicago, where some two hundred mobile gressively upward, the new Number 1 means of fre- oc- units are in cupying the old Number 2 position and the quency modulation. process of installation. Numer- old Number 2 moving up into ous other projects for police service and a space pre- for emergency viously allocated to government use. This use by the power companies action by the limitation does not, of course, affect the ' are being put forth, and it is doubtful Commission was taken in static May 1940, and the art prepared to move -eliminating qualities of the system, whether many new installations employing forward. but would reduce the quality of the trans- amplitude modulation will be made in the mission The to that imposed by the characteris- future. It is, of course, needless to say enthusiasm over the quietness of the tics of the wire lines. Some improvement that there are many important reception was as expected, but military the most may be expected in these characteristics, uses ; and its application in the field of air- gratifying result has been the response to the improved but they will probably not be set up to craft appears to be a promising one. quality of transmission. The carry the full frequency The one important field in point had been made, range for a long which prog- and in some quarters time to come. There is, however, a rela- ress has been inexplicably slow has been was strongly urged, that the public would tively not simple solution which is now in use television, where its advantages, particular- appreciate so- called "high fidelity" re- in New England. By means ly on the sound channel, ception; in fact, it of radio relays, could be effective- that did not want it. Boston, Paxton, and Mount Washington ly utilized at once. A limited use has been This contention was supported by refer- have been successfully made of frequency modulation ence to the public reaction linked together, and for the re- which attended within the coming year it should be possible laying of the television sight channel. the introduction of standard broadcast sys- In tem receivers to extend this circuit to include New recent years it is only in the broadcast which had a wider range than York, ** so that no service where interstation the usual 5,000 cycles. wire -line facilities what- interference has One or two attempts ever will be required. No major technical caused serious difficulty, and now this situa- had been made to create a market for re- difficulties tion is likewise ceivers whose frequency are likely to be encountered. about to be cleared up. If range extended up While it may be possible ultimately in the future the demand for broadcast to 7,000 or 8,000 cycles. It was found that to these obtain the same technical performance by channels exceeds the facilities of the channel receivers did not sell well, and when the use of space now they were sold the coaxial -cable method of trans- practically available, the en- the listener made rather mission, will gineering world is drastic use of there be large sections of the prepared to open up new the tone control, which pre- country where it is bands in vented the higher frequencies not economically feas- that space technically known as from being Plan the ultrahigh and micro -wave region reproduced. Hence it was concluded **This for the FM Relay Network, which where that the includes New York City was carried out success- the ratio of the unused channel space com- public, from some impairment fully during the of its sense past year. The advantages of pares to that now in use as of frequency modulation transmission for relaying the unsettled aural perception, did not want the higher to frequency range. Quite purposes was manifested when the programs were the settled parts of the earth. The trend the reverse, how- received without any noise or distortion, after of radio ever, was the case. inevitably will be upward into the What the average listen- having been relayed several times. Such noise- higher frequencies. -Reprinted by er objected free, distortion -less transmission of voice and Permis- to was not the increased range sion from The Annals of the frequencies reproduced, music cannot be duplicated by existing wire tele- of The American but the pres- phone lines. Academy of Political & Social Science. 396 RADIO- CRAFT for MARCH, 1942 F. M. W2XQR Broadcasts Concert Music on FM

RUSSELL D. VALENTINE Specially Written for Radio -Craft

Above--Ruttali D. Valentina chief engineer for WQXR, Now York and its affiliateFM W2XQR, keeps an eye on FM operations. Right -JJohn V. L. Hogan (Ian) and Russell D. Valentine, the engineers responsible for W2XQR, line up the FM transmitter atop New York's Chanin Building.

it has been operating for the Interstate Broadcasting Company and Carlson, and on that series, was presenting ALTHOUGH messages to the public about FM. less than three months from its new an internationally famous radio engineer the first feet above and inventor, applied for an experimental These were, incidentally, the first adver- home, about seven hundred on FM used anywhere. sea level from atop New York's FM license of his own. On October 3, 1939, tising messages Chanin Building, W2XQR, New York, the construction permit for that station was Later, Stromberg- Carlson and WQXR has already shown results which justify the granted by the FCC. A transmitter was cooperated to broadcast the first commercial belief of its founder, Radio Engineer John installed at once at Mr. Hogan's laboratory program over a group of FM stations. This V. L. Hogan, that a major FM station, in Long Island City. Broadcasting from was organized on November 28th of last specializing in concert music, would find W2XQR began on December 11. 1939, year, and has been operating several nights rapid acceptance among New York listeners. making W2XQR the first local FM station a week ever since when the "Treasury of W2XQR was the first FM station directly to begin regular programming on the new Music" program is on the air, from 7:30 affiliated with a standard broadcaster in the band. to 8 p.m. WQXR originates the program station, through and feeds it to W2XQR and W2XMN. New York area, and its parent Because fine music, played to WQXR, was the first in this area actively transcriptions and by artists in person, had W2XMN in turn beams the program associated with the new FM technique. proven such successful program material W65H (FM station) in Hartford, Conn. But, because it was located rather un- for WQXR, the plans for the operation of W2XQR, now, as it awaits its com- favorably in Long Island City, where it W2XQR, from the beginning, were drawn mercial license and increase in power, con- had been established for purely experi- around the idea of providing, through this tinues to broadcast WQXR's programs over mental purposes, it was not until December improved transmission technique, more and 45.9 megacycles from 5 to 10 p.m. daily. 15, 1941, that W2XQR really began func- more programs of fine symphonic music. Most of these programs are musical or tioning in a way which services its com- and faithful repro- news commentary. W2XQR was probably FM, making noiseless a full munity adequately. On that date, it began duction of tones and overtones possible over the first FM station to broadcast broadcasting from the 54th floor of the larger areas for a given amount of power, symphonic program when it, along with Chanin Building at Lexington Avenue and is most ideally suited, we find, as a medium WQXR, on November 27, 1939, transmitted 42nd Street. of good music, because the NBC Symphony Orchestra playing for the transmission Garden. The new location gives W2XQR a radia- in good music exceptional fidelity is from the stage of Madison Square tion increased about sixteen times over that required. The rapid public acceptance of frequency the fact that the of its former site, despite From these early days of experimental modulation, and the increasing interest be- station still operates at 1,000 watts. Shortly, attracted an ining shown through sale of receivers, mail increase W2XQR's FM operation, W2XQR other we hope, we shall creasingly large audience to its broadcasts received at W2XQR and through power to 10,000 watts and begin use of our sources, makes W2XQR's future a bright with full of WQXR's musical programs each eve- permanent call letters, W59NY, need for increasing its one. Mr. Hogan, one of the earliest entrants ning, although the occa- commercial operation. coverage began to make itself felt. into the FM field, has said on many WQXR and W2XQR have made FM sions that "FM has demonstrated its ability ways. WQXR "fed" its At the same time, WQXR "crusaded" service. Its history in several modula- to render an excellent broadcast programs of good music to the first FM for public recognition of frequency almost entirely upon its of 1939, at the future now depends station, Major Armstrong's W2XMN in tion. Back in September acceptance by the listening public." Alpine, N. J., and thus became the first time when no one but radio engineers real- new invention, There is no longer any doubt about that station to have its programs and artists ized the possibilities of the supple- WQXR was broadcasting the "Treasury of acceptance, even though FM is still beard on the new band. mentary to regular broadcasting service. In the meantime, Mr. Hogan, president of Music" programs, sponsored by Stromberg- 397 RADIO -CRAFT for MARCH, 1942 F.M. W45D- DETROIT Front Cover Feature Gives F. M. Antenna Facts radio scheduled to play a vital part in dis- seminating news and maintaining public morale, there will probably be no great slackening in FM's constantly growing popularity. Not only does FM supply the listener with virtually static -less reception, but it provides him with a new source of programs including, especially, fine music that has been all too frequently crowded off the air by "soap operas' and comedians. Surveys have shown that the W45D audience particularly favors concert and classical music by the better -type orchestras - even though they may be transcribed -and the music of the Novachord and organ. In its 18 hours of programs a day, W45D includes a generous portion of classical music shows. Audience response to those has been gratifying. FM is now reaching into thousands of homes giving static -less radio reception to all who have changed over to radios designed to receive the wide -range Frequency - Modulated signal. Set owners are generally encouraged to install outside antennas of a prescribed type, since the proper antenna greatly improves reception. In order to understand the importance of a good receiving antenna, it must be realized that the noise elimination or noise reduction on FM is due more to the presence of an FM signal in the receiver, than to the FM receiver circuit itself. The stronger the FM signal that is being fed into the receiver, the more noises of various sorts will be reduced, and finally suppressed entirely when the signal input reaches the value necessary for that particular receiver to give complete noise suppression. The receiving antenna is the signal "collector" and its efficiency determines how much signal is fed into the receiver. In other words: it is possible for noise to be heard on an FM receiver, if the signal received from an FM broadcast station is TOO WEAK to suppress all noise, or if the receiving antenna used is NOT suited for FM reception. Fortunately it .is rather simple to construct and install a receiving antenna that is much more effective for FD1, than even the best low frequency antenna used by most listeners for AM. An antenna's effectiveness depends, among other things (according to Carl Wesser, chief engineer of station W45D), upon its length in relation to the operating frequency. The higher the frequency, the shorter the wavelength and the more nearly we approach a half -wave in length of the receiving antenna, the more effective it will be.

SIMPLE "FM" RECEIVING AERIAL Photo-The Detroit News A simple way to construct an FM an- Top left- Station W45D occupies the entire 45th floor of the Penobscot building in downtown tenna is by cutting a piece of antenna wire Detroit. Top right -Bay -2 turnstile antenna atop neon ball and tower. Bottom- R.E.L. 3 KW. to the approximate half -wave length of the driver for 50 KW. amplifier. middle of the FM broadcast band. This wire would be about 10' -6 "-0" long. In FM may be a youngster, yes -but a their subtle inflections, overtones, and har- order to make this antenna as effective as mighty healthy one that is growing monics. FM's first -time listener finds re- possible, we should plan on hanging it well up fast. ception as much improved over ordinary in the clear of surrounding objects, or at FM offers two qualities far superior AM broadcasting as AM broadcasting is least by 15 feet, and as high above ground to Amplitude Modulated Broadcasting: (1) over the sound he gets from his shrill, raspy and buildings as we can. This would re- It permits the transmission of a sound telephone. move the antenna well from the receiver, range identical with that of the human car. No wonder Mr. Listener has responded which necessitates a "link" or transmission (2) It is static -less! These two remarkable with contagious enthusiasm! line between the antenna and the set. This advances, developed by Major Edwin H. The number of FM receivers in Detroit transmission line can be Armstrong a piece of twisted (inventor of the super- hetero- alone increased from 1,500 in May, 1941 lampcord, such as is sold in most 5 and 10 dyne circuit) have made it possible for (when W45D began broadcasting) to cent stores. To connect this transmission anyone in his home to hear sounds exactly 12,000 by January, 1942 -and the ratio of line to the antenna, it becomes necessary to as they are created in the studio, with all increase is by no means diminishing. With cut the 11 -foot length of wire in the middle, 398 RADIO -CRAFT for MARCH, 1942 F.M. and insert a small glass antenna insulator at this point. The same type of insulator should be used at each of the "free" ends of the antenna. To the inner ends of the two halves of the antenna we now connect the two wires of the twisted transmission line, while the opposite ends of this line should connect to the two antenna posts of the set. To hang the antenna, rope should be used from the free -end insulators to whatever it is to be tied, since wire of any kind at these points will affect the operation of the antenna noticeably. The antenna, or di -pole, as just described, should be stretched in a horizontal position. This is necessary because it should be in the same position as the transmitting antenna, and. by now most FM broadcast stations are using horizontal "polarization." In hanging a di -pole it should be remembered that this type of antenna is directional and will pick up no signals from the directions of the free ends, and will have maximum pick -up on signals that arrive from a broad- Engineered side direction. Be sure that your antenna is oriented broadside to the general directions from which FM stations are to be received. for If your location is such that desired FM stations are located in various directions Highest around you, it may become desirable to construct a rotatable di -pole. This can be done by substituting two pieces of metal fish Quality pole, or buggy whip car antenna, cut to the required length and mounted on two pairs Reception of small stand -off insulators on a piece of 1" x 2" wood, about three feet long, with Meiuner anal d a pivot in its center, and ropes or some and specially designed other simple means for rotating the di -pole for highest quality re- into the position that gives the best signal ception front local or on the desired station. This arrangement semi - distant powerful can often be used to eliminate signals from broadcast simians ... stations other than the desired one, but provides the solution to many of the prob. operating on the same frequency. All FM lems encountered by broadcast stations serving the same area the modern Sound En- operate on different frequencies. gineer where quality radio reproduction la required. U Ily noise-free T.R.F. circuit with band -pan transformen provide I o'-60 true high fidelity reproduction. Tunes from SSS to 1600 be. to cover the regular broadcast band. Self- powered, operate. on 110 volts, 50.60 cycles. Output connections provide Impedanee. of 2,500 and 10,000 ohms; easily adapted for coupling into 200 or 500 ohm line. Model No. 10.1152 High Fidelity P -A Tuner Kis containing all necessary parse for construction (lees tuba) including detailed instructions and pictorial diagrams. $18.00 List. Meinner Kits are easy to build. Write for New 1942 Catalog - Dept. RN

MT. CARMEL, ILLINOIS "PRECISION-BUILT PRODUCTS"

Music Lovers Opportunity IF YOU HAVE ANY 100,000 Phono -Records OLD PHONOGRAPH RECORDS Trorasmihki are going to be sold by us at the biggest money-saving opportunity ever offered on WE BUY THEM For mojo, s,gno/ place records. Dig thorn up and .ship to us. Classical or ocria/ brvodsrcroé /o We ship anywhere In the world where mail and popular, Victor records. Liberal purchase transmJter freight are still rendering us service. payment sent the day records are received. HERE'S A FEW OF THE BARGAINS! GENEROUS TRADE-IN ALLOWANCE! Set of 25 Popular Dance Records We willill also add an cotre toe allowance on sent u against any purc ose Amade by you. such as Glenn Miller. B. Goodman. $400 We nave u suai records in stock but need . Receiypq T. Dorsey. I. Dorsey, etc. Special more for 'o customers. heeinWe i bosom. Slop/e Coyne record family: 0/pole Set of 25 Hillbilly, Cowboy, or Blues iandnn member of tie preferred - Twià/ed It pays and SAVES! ppM Special $4.00 MAIL and PHONE ORDERS Promptly Filled. Set of 20 assorted Red Seal Wood Drum 12 eaeh Classical double faced records. Rope Special $7.00 (We pay shipping charges on above, east of the Ratios) MUSIC SHOP To Se/ Terms: Send 20% with order. Bal. C.O.D. Music Lovers and dealen can now obtain outstand- but records) ing values from one of the few outlets dealing er C OYNE (nothing lively In PhonoRecords. We can supply all record needs. Write us for Special Bargain Kits M Records consisting of classical or popular. eta. st Cortlandt St.. New York City Simple Rotatable FM Receiving Aerial. RADIO -CRAFT for MARCH. 1942 399 F.M. WOR's New FM Station Power 10KW Freq. 47.1 MC Call W7INY

GREATEST strides in frequency - Left: The vertical coaxial antenna used by modulation broadcasting development W7INY, Frequency Modulation station owned to date are incorporated in the trim, and operated by WOR, New York, is the only compact, 10,000-watt one of Its kind in existence. It was designed transmitter of by WOR engineers and is used for FM broad- W7INY-the FM affiliate of WOR- casting with favorable results. which went on the air the night of Novem- ber 30 with a formal dedication program. Known as Model 506 A -1, the new transmitter was designed and built by Bell Tele- phone Laboratories and Western Electric Company technicians and represents sensa- tional gains over earlier 'Below: The 10,000-watt transmitter of W7INY, FM broadcasting Frequency Modulation station of WOR, New units ; its advantages over the very efficient York. The transmitting plant is located at 444 1,000 -watt unit previously utilized by Madison Avenue, New York City. W7INY are manifold. The transmitter unit as well as the entire technical layout of W7INY located on the forty- second floor of 444 Madison Avenue, New York, is accorded the description of "model facilities ", by prominent engineers who have inspected it. It is the first 10- kilowatt transmitter of its kind, but, despite its pioneering nature, is a laboratory -perfected job that takes to the air as the result of costly research and collaboration by a group of the nation's leading engineers. It serves a radius of approximately 52 miles, on 47.1 mc. (megacycles). A radical new type of amplifier circuit gives the transmitter the distinction of being the first of its kind to use a single tube in the last amplifier. This simplification was made possible by grounding the plate in the final phase. No tuning condensers are incorporated, all tuning control being done by changes in inductance, effected by motor - driven controls. The single tube used in the final amplifier is the brand new type known as 389 AA; it weighs 55 pounds and is one of the heaviest valves developed for FM work. The quality of transmission is so high that provisions have been incorporated by W71NY engineers to have certain possible extreme "highs" compressed ; actually the quality of the set's frequency range can be better than the human ear can hear it; however, this exceptional range taking to the air on FM could ordinarily raise havoc with neighboring FM channels. This protective development is a W7INY contribution to the art of FM and its engineers have the hope that future commercial FM stations will adopt similar methods so that W71NY, in turn, will be safe from external frequency infringement. Distortion at the transmitter is less than one per cent -and this is SOUNDTRANSMITTED VIA LIGHT - regarded as a BEAM: The beacon transmitter and definite technical achievement. There is no receiver, located atop the WOR trace of noise at carrier ; the high -fidelity studios, was aimed c' a photo- electric cell placed alongside he performance is further enhanced by the fact W7I NY transmitter, about I;3 mile that audio characteristics are flat ± I db., away, to relay a portion of the 30 to 15,000 cycles. program dedicating the 10,000 watt transmitter of the FM station. The The original 1,000 -watt Western Electric relay via a tiny invisible beam of transmitter continues in light was observed by military and use as an auxiliary naval communications officers, in standby. Its filaments remain lit at all view of potential defense use of operating hours so it this method that can substitute of transmission. for the 10 -kw. unit in any emergency without the loss of a minute's air time. Both transmitters are controlled from a duplicate speech input and monitoring board. Hammering a nail in wood makes an effective sound effect -via FM. Two Special high -fidelity telephone lines The thud of wood and the ring of link the speech -input board the nail vibrating when struck, are with the WOR extremely high frequency sounds, studios where the bulk of W71NY's inde- but were easily reproduced by FM pendent schedule originates. These wires transmission over W7INY, WOR's cover FM station. s frequencies between 20 to 20,000 cycles and are ideal for FM. In the event 400 RADIO -CRAFT for MARCH, 1942 . .,ear?,c^-+ ..t., r . . --w-uwrMe/nF +.MIMr'r.+#!

F. M.

that both feed -lines fail at the same time (a ing W71NY FM engineers because of its market unavailability-is located here. This very remote possibility) W71NY will still vacr ...... function without an air break; this is as- apparatus includes built -in measuring de- sured by having a supersensitive receiver vices as well as costly -intricate portable in on the control panel constantly tuned in to ,,,,a71.,,.I l..die,.K.I equipment for measuring signal strength WOR. In the event of a landline break, the the field. mere throw of a switch assures a con- Representatives of both the Army and T.T tinuous program feed to the W71NY speech " ,OOV4TO. Navy attended the dedication of W71NY's AT ä; new 10,000 transmitter. Special inter- input. ..o sow+ -watt XW. AT sa, While programs do not originate at the STY. ' AVEN,( est was expressed on the part of military transmitter location, mikes and turntables, and naval observers in W71NY's experi- in addition to special acoustical wall con- ment in transmitting sound over a beans of SLOG O 144(1 use of the trans- vOKCap W,iCVóMn w pETwC light from lite iVOR studios at struction, make possible the *OA 5,00 AT 14 AO eowv AT 444 mitter hall as a studio. Technically T.E ...TTC.H.O..V'ENUE.xVE Broadway to W71NY's transmitter al itself ...M Wf T and practically, the apparatus room can ac- Madison Avenue where the dedication was commodate any "live" program from a Diagram of Lighf -Beam Transmission held. single speaker to a symphony concert. The use of light beams to transmit sound The new 10 -kw. transmitter is equipped 100 -watt unit normally used for short -wave was developed in the laboratories of West- with a brand new 25 -foot vertical coaxial contacting of WOR mobile broadcasting ern Union. Previously tested in the labora- antenna. It was designed by the \VOR units; this transmitter, however, is also at tory, W71NY's experiment demonstrated Laboratories Facilities Division and is the hand for facsimile broadcasting purposes. for the first time out of the laboratory the first and only one of its kind in the world. Laboratory and workshop equipment is latest equipment developed by Western Two vertical 20 -foot aerials are also located incorporated in the transmitter floor layout. Union. Military and naval authorities will on the roof, one to serve the auxiliary 1 -kw. Costly measuring equipment-a considerable study its possible uses in connection with transmitter, the second to accommodate a amount of it designed and built by pioneer- practical warfare.

FM in 1942 As I See It J. R. POPPELE Chief Engineer, Stations WOR and W71NY

IT would take a prophet of the ancient duction, the fact remains that we are con- curtailed is, of course, problematical. But world to tell what the status of fre- tinuing to operate normally. I do not believe that any of us, today quency modulation broadcasting will be Our present plan is to continue to operate engaged in this form of broadcasting ex- twelve months from now. But for those for the same number of hours for the first pect prompt financial returns on our efforts. who may have grave doubts, occasioned by half of the year to come. At that time we We are prepared to carry on for a number the possible limitations of set output due will undoubtedly reevaluate our operation of years before receiving any substantial to war efforts, let's see what we have to in ternis of set sales, audience, and com- return on our investments. date. mercial possibilities. Unless world events The above does not mean to say that there First, there are 50,000 sets on which to and our production set -up take an acute will be no returns. An audience of some receive FM programs in Greater New York, turn for the worse, the chances are we will 150,000 listeners in our area is not an audi- with the National total reaching a quarter continue our activities for the second six ence to be disregarded. Once we know more of a million. Secondly, as of January 15, months on about the same basis. We feel about this audience we will be able to cater 1942 there were 24 commercial FM stations that FM has been developed too far to be more directly to its preferences and we on the air with 39 more in the process of sidetracked, and we regard an audience of will have a story to tell our advertisers. being built. There are 53 applications for 50,000 sets with their multiple listeners Research will do much to foster the com- commercial licenses pending in Washing- for each, an audience worth cultivating. mercial advancement of FM and research ton and 12 experimental stations offering I've been writing about the future. Let's is included in our plans. program service, in most cases prior to consider one or two of the highlights of It wasn't so very long ago that the commercial transmission. the past year. One of the most notable of average man on the street was completely From the above it would seem that FM, these was the linking together of six sta- ignorant of the meaning of the letters "FM' . which started out as a radio step -baby, is tions for point- to-point broadcasting. This It is gratifying to find out that this is no no longer an immature child. FM is here special one -time network, which carried longer the case. Here again. the set manu- to stay and is growing daily. If the manu- commercials, was assembled as part of a facturers and dealers were wise enough to facture of sets should be seriously cur- salute program for \V71NY's new trans- promote FM generally in their advertising tailed during the months to come, there mitter. The technical results were amaz- along with the merits of their individual are already in existence enough sets and ingly successful. The stations involved - sets. They realized that a job had to be stations broadcasting programs to W2 %MN.Alpine, N. J.; \\'65H, Hartford, done and they went out whole -heartedly enough are doing guarantee a healthy status quo pending Conn.; \\'438, Boston ; \V53PH, Phila- to do it. The FM broadcasters resumption of set manufacture. delphia : W39B, Mt. Washington. N. H.. the same thing. If I take W71NY, WOR's station, as a and W47A, Schenectady. N. Y., "blanketed" One indication of the effectiveness of this typical example, it is with the pardonable New England. Although the test was made general education process and the growing one of its "fathers ". Ever since under clear winter conditions, it is easy interest in the subject, is the fact that two pride of York morning newspapers April 1, 1941, the station has been New to realize how such a test under summer large New -the York's first full -time commercial FM out- conditions with attendant static, would have Herold -Tribute and the New York Tuner 30, 1941, W71NY's new been even more dramatic, especially to lis- both now list W71NY's program schedule let. On November at the 10,000 watt transmitter was dedicated on teners in the more remote receiving loca- daily in its entirety. Furthermore, top of 444 Madison Avenue in New York tions such as the mountainous regions of time of the \V7INY dedication in Novem- 1941 \V71NY New England. ber. 1941, the Herald -Tribute published City. During both 1940 and devoted to schedule from 8 a.m. to Not much publicity has been given to a 16 page special FM section, broadcast a daily as a whole, and 11:30 p.m. composed of a small percentage FM as a communication medium for Army this form of broadcasting some Mutual network and Navy use. The reasons for this tracing the rapid advances that have been of WOR programs, which in programs not otherwise heard in our terri- reticence arc obvious, but it is easy to con- made. The interest in newspapers, programs of W71NY's ceive and foresee the potentialities of such turn are guided by their reader interest. is tory, but primarily shape of things to own origination. use. Unpublicized as military use of FM is, a healthy sign of the radio broadcasters are mindful of their con- come. There have been other effective spe- This complete program schedule plus the sections in various areas of original investment capital, reaffirmed tribution to this phase of our national mili- cial newspaper of the country during the past year as well. by the purchase of the 10,000 watt trans- tary efforts, by continuing the fostering mitter is an indication of WOR's faith of frequency modulation transmissions with One point that must not he neglected in FM as a broadcasting medium. Granted its attendant experimentation. during the coming year is program seravee. that the 10,000 watt installation was Up until now the advertisers have been It is not enough to point to the technical planned before the United States entry into extremely helpful in furthering the sales virtues of frequency modulation. People the war, with all of its subsequent poten- of FM sets. How much longer their co- must have something to which they can tialities of limitation of non -essential pro - operation can be expected if production is listen with enjoyment and interest. RADIO -CRAFT for MARCH, 1942 401 ,,

4k °ue*nflFäilit `-"ïwMi3li3-r d ' 7it - ..rn...Gl:.: .w.:.st,:...s,wtsdw.f F.M.

NBC New York

F M Station

to go to 10,000 Watts

O. B. HANSON Vice -President and Chief Engineer, Broadcasting Here is the snappy I KW transmitter for NBC's FM station W2XWG. National Company. The antenna is atop the 1,250 -foot Empire State Building, which gives it superior coverage.

THOSE of us who have made radio mission, i.e., a wider range of audio fre- UHF antenna arrays. Antenna height be- broadcasting our life's work may be quencies than is practicable on present comes an important factor in UHF trans- pardoned, I am sure, for nursing a channels in the standard broadcast band, mission, since ground attenuation of the specialized grudge against those who (3) greater dynamic range in the program signal enters as a factor only when the so brutally shattered the peace of the material being transmitted, and (4) less optical horizon, as measured from the world. For, first the threat of war, and potential interference between stations hav- transmitting antenna, is reached. Beyond then its full impact, have imposed severe ing the same, or adjacent, carrier frequen- that horizon the UHF waves are governed limitations on the growth of radio's promis- cies. by formulas for wave propagation on the ing children. The last -named quality may be traced surface of the ground. Here the UHF sig- One of these is frequency modulation, or to the limiter action in the receiver, and nal attenuates far more rapidly than it does FM broadcasting. The system is complete, the fact that in all UHF reception a direc- within horizon limits. It is desirable, there- its product of a quality beyond question. It tive antenna, of small physical dimensions, fore, to push the horizons as far distant should have its fair chance for a place in may be used to give one signal a distinct as possible. Hence the search for the high- radio's expanding ranges of services to the advantage over another, at locations where est possible antenna locations. American public. The national effort, how- So much for the advantages of FM in ever, demands intense concentration by the ultra -high frequency broadcasting. Where radio industry on every activity that will does the broadcaster stand? The answer carry forward the battle for American The National Broadcasting Company con- will be found in the list of actual and pro- freedom. Like other new radio develop- ducted some of the earliest experiments spective commercial FM broadcasters. ments, FM will undoubtedly fit usefully in FM transmission. They were also one Anticipating the future of UHF in radio into that effort. Meantime we must divert of the first in the industry fo establish broadcasting, the National Broadcasting energy and materials which might other- regular FM program service: W2XWG Company selected the highest building in wise have gone into expanding FM's role went on the air in April 1939 for the New York City for the installation of ex- in the field of broadcasting. purpose of making extensive field tests. perimental transmitters with which to con- Regular FM programs have been broad- All the more laudable, therefore, that duct propagation studies and developments cast since January 1940. NBC will erect in this field. Some of the first experiments some broadcasters and some manufacturers an FM transmitter in Chicago. have carried the cause of FM to the Amer- in FM transmission were carried on at our ican listener as successfully as they have station in the Empire State Building. these last two years. The National Broadcasting Company also A tabulation before me as I write, lists stations on the same frequency would was one of the first in the industry to estab- more than twenty commercial FM stations otherwise be received with approximately lish an FM station. Its Station W2XWG already on the air, with nearly forty in equal signal strength. went on the air in April, 1939, for the pur- process pose of conducting extensive field tests of of completion. Another fifty appli- FM Give 15,000 cations await action by the Federal Com- Channels Cycle Fidelity. the comparative qualities of AM and FM. munications Commission. Figures released The higher fidelity characteristics of FM These findings have been the basis for are attributable in part to the wider audio numerous technical papers and talks. by FM Broadcasters, Inc., indicate that range about 240,000 receivers capable of receiving which can be transmitted in the wider A regular program service five days a FM programs have been bought by the channels allocated for FM by the F.C.C. week, eight hours or more a day, has been public. Forty channels have been set aside in the offered over the NBC station since Jan- Such figures in band extending from 42.1 megacycles to uary, 1940. Since it has been on the air, are impressive them- 49.9 selves, but even more so as an indication of megacycles. Each is 200 kilocycles wide. NBC has received numerous complimentary the future of FM in radio broadcasting. The channel in the standard broadcast band messages from discriminating listeners, is but 10 kilocycles wide, ordinarily limiting who comment on the exceptionally high Advantages of FM. We have evidence, the audio frequency range to 5,000 cycles. quality of the station's performance. Spe- therefore, that FM has appeal for radio In the FM channels we find it possible to cial programs and carefully selected ma- listeners. It has almost complete freedom transmit a range of audio frequencies up to terial from NBC's daily schedules are from static. To critical ears it offers higher 15,000 cycles. This range permits the inclu- heard over the station. In selecting pro- fidelity. Technically stated, the advantages sion of all of the higher audible harmonics, gram material from the network schedules, of FM over AM transmissions (the latter or overtones, of music, which contribute we have favored programs originating in in the standard broadcast band) may be to realism in the reproduced program. the Radio City studios, since these afford stated as follows: (1) reduction of noise These commendable characteristics of us the opportunity of transmitting the wide in reception, permitting a greater signal- FM have sent many broadcasters searching range of audio frequencies that makes FM to -noise radio, (2) higher fidelity trans- for high buildings on which to perch their attractive to our listening audience. 402 RADIO -CRAFT for MARCH, 1942 F. M.

Our present transmitter, of RCA design, was installed under the direct supervision THE CASE OF of NBC's radio facilities engineer, Ray- STRANGE mond C. Guy. Operating on a frequency of 45.1 megacycles, it has an output of 1,000 watts. The principal innovation in SERVICEMAN WALDO MUDD its design is an FM modulator of the type developed by Murray G. Crosby, of the of America. This modu- Radio Corporation Miss Barefarse thing happened lator consists of several tubes, including an Dear Then the same beat- I know that your column is en- again, the very next day. oscillator, a reactance tube, a crystal However, Miss Barefacts, I oscillator, a discriminator and a filter. titled "Advice to the Loveless" ing I am not loveless. As a will not bore you by telling you FM to Be Increased. and Power of Station fact, I have love any more of this sort of thing. per- matter of more NBC holds a commercial construction than I know what to do with. Suffice to say, it was six months mit under which the power of the FM sta- That's why I am writing to you. ago that Arabella first called me. tion is shortly to be raised to. the limits per- You see, Miss Barefacts, I am Since then, she has called me mitted by the F.C.C. in covering a service a radio service man. I make good almost every day. I have fixed all area of 8500 square miles with a minimum money and I'm very happy. I of her radios at least a half signal strength of 50 microvolts. The feat mean I was happy until I met dozen times each and she still will not be difficult, inasmuch as the antenna Arabella Blotts. She is one of hasn't paid me for a single job. location is the top of the Empire State my customers. In fact, she is my What's more, I am afraid to send Building tower, the highest and most ad- very best customer. That's the her a bill. Arabella is funny that vantageous site in the city (1250 ft.). The trouble. way. She might get mad and not antenna array used, incidentally, is the Arabella has a very nice apart- call me any more. After all, she video (picture) component of the familiar ment with about eight radios in it. The first time is the best customer I have. NBC television antenna, the transmission she called me, I went over and fixed two of the What shall I do? characteristics of which are substantially radios in about half an hour. Then Arabella asked Very truly yours, flat over 30 megacycles. me to sit down and have a drink with her. WALDO MUDD. Transmitter equipment with a rating of The correspondence course I took in radio Radio Service Man. 10,000 watts was ordered more than a year servicing didn't say anything about what to do in a * * ago. The manufacturers have found them- case like this. Besides. I don't drink anything but selves so deeply engaged in defense pro- ginger ale. However, Arabella insisted. so I asked Dear Mr. Muddt duction, however, that delivery has been for ginger ale. It was very funny tasting ginger ale Don't worry. Your problem should be an easy necessarily delayed. We hope to be on the and I even felt funny after I drank it. one to solve. My first suggestion is that you marry air with increased power very shortly. NBC Then Arabella sat down beside me. She is a very Arabella Blotti. Evidently that would please her. also holds a construction permit for a sta- big girl. Also, she is very determined. Every time I Then you can repair her radios in your spare time tion at Chicago where an FM transmitter moved away from her, she shoved over closer to and spend the rest of your time at work for which will be completed as soon as possible. me. Finally, I was at the end of the davenport and you will be paid. My second suggestion is that, in Future of FM Broadcasting. The fate of couldn't move any farther. Also. I was at the end the future, you use Sprague Condensers and FM broadcasting will not rest with the of my wits. Koolohm Resistors for every replacement. Once broadcaster. The ultimate arbiter will be When I got back to my shop. I remembered she you install them you can forget them -and so can the American listener. For it is he who will hadn't paid me for fixing the radio. Also, I was your customer. Then, the next time you meet a girl judge for himself whether its superior serv- dizzy and didn't feel like working any more like Arabella, she will have to be more original in ice offsets the cost of a new FM receiver. that day. finding an excuse to invite you back again. The better his service from powerful AM The next day. Arabella called and said both of Sincerely yours stations in the standard broadcast band, the radios I had fixed were broken again and would the less likely he is to be impelled to rush I please come right over. WeB, there wasn't any- GERTRUDE BAREFACTS, to his nearest radio dealer to buy an FM thing to do but go over and fix them. So I did. Editor. "Advice to the Loveless Column." set. Those who do not get comparatively noise -free reception from AM stations are likely soon to become FM enthusiasts. Frequency modulation receivers designed ATOMS are made in five Make up bard -to-get re- to realize the full value of FM's high fidel- different types thus making placements by strapping in- them practically smiversal dividual Atoms together ity potentialities command a higher price for any replacement job with ST Mounting Straps- than the best AM sets. If the listener is whether it calls for a single - supplied free! You'll find the full benefits of FM transmis- section or multi-capacity combined Atoms actually to enjoy the unit, lug mounting, or a con- smaller, often cheaper, and sions in his home he must have a receiver denser with separate posi- fully as reliable. You save incorporating a high -fidelity audio ampli- tive and negative leads. lime - money -space. fier and loudspeaker system. Such a receiver cannot be manufactured to sell at a price comparable to those prevailing for PRODUCTS CO. the most popular AM models. There are. however, FM adapters on the market. SPRAGUE North Adams, Mass. These may be used in conjunction with the listener's AM receiver to yield the full value of FM's noise -free reception. Fidelity, however, is here limited to the characteristics of the AM receiver's audio amplifier and loudspeaker. It is worthy of note that Institute is the most important technical ra- Telegraph Company during college vacation many of this year's more expensive console dio society in the world with 7000 members periods. After receiving his Ph.B. at Yale, models include an FM band. This will add in 74 countries. he joined the laboratory of Professor Regi- to the new service's expanding audience. Van Dyck has been a well -known per- nald Fessenden, at Brant Rock, Mass., A conservative estimate of FM's future sonality in radio from its earliest days. He where he participated in many of the ex- would be that it will progress, not sensa- has made many technical contributions to periments of that pioneer which have since tionally, but steadily. It also seems quite the art, the most recent being the RCA Alert become technical classics. Afterwards he probable that when armies have ceased to Receiver, a device by which civilian defense went to the Westinghouse Company at Pitts- march, when the dive -bomber's scream has workers are notified in times of emergency burgh, to serve as laboratorian, and later been stilled, that FM will march briskly and called to a special radio to receive in- was instructor in Electrical Engineering in into an expanding future alongside that structions for action. This development led the Carnegie Institute of Technology. other infant prodigy of radio -television! to his appointment as Member of the Com- During World War I Van Dyck was Ex- munications Liaison Committee of the Office pert Radio Aide in the U. S. Navy, which of Civilian Defense. His interest in radio experience led to his appointment as Chief dates from his school days. He has some Factory Engineer of the Marconi Wire- New I.R.E. President thirty patents to his credit, and a variety less Telegraph Company of America when Arthur F. Van Dyck, Manager of the In- of interests that are as broad as an industry peace -time radio was resumed. There fol- dustry Service Section of the RCA Labora- which comprises many diverse branches. lowed a period of service with the General tories, has been elected President of the In- Arthur Van Dyck began his career in ra- Electric Company, when he was in charge stitute of Radio Engineers it was announced dio as a radio amateur. Later, he served as of development and design of radio re- today by that technical organization. The a ship operator for the United Wireless ceivers. RADIO -CRAFT for MARCH, 1942 403 F. M.

One of New York's FM Broadcasters CBS Station

Right: CBS radio engineers complete tuning the temporary FM antenna atop the Salmon Tower (left) at 500 Fifth Avenue, New York City, preliminary to inauguration by the Columbia Broadcasting System of a schedule of FM news and music programs. The programs the New York area, which includes W67NY about 8500 square miles.

W67NY, New York City FM station strutted atop the water tank on the roof of top of the tower. The "loop" is an improved of the Columbia Broadcasting Sys- the building. A special bracing has been antenna design developed by Andrew Al- tem, has been broadcasting news and added to the water tank to support the ford, an engineer of the Federal Telegraph music programs six hours daily, pole. The pole is comprised of twelve units Company. One "loop" gives twice as much Mondays through Fridays, since Monday, and weighs 12 tons. Special fixtures were power as the earlier "turnstile" antennas. As December 1, at 3:00 P.M., EST. Broad- made by machine tools to accommodate the the number of loops is increased, power is casts are scheduled from 3 :00 to 6 :00 P.M. swedged fittings of the twelve units. concentrated on the horizon with greater and from 7:00 to 10:00 P.M. The programs The pole was designed to meet the radio efficiency. are carried by high fidelity wires from a specifications of the CBS radio engineering The signal radiated by a four -stack loop studio in the CBS Building at 485 Madison department, and to meet the physical speci- antenna in all directions is equal to that of Avehue to the new temporary FM trans- fications of their construction department. a standard antenna in its best direction mitter atop the Salmon Tower at 500 Fifth The construction job was supervised by using four times as much power. The rules Avenue (New York). Columbia's C. R. Jacobs and Kingdon S. governing FM broadcasting preclude com- A new antenna -supporting pole has been Tyler. Radio engineering was supervised by petitive advantages of one station over built atop the same structure at 500 Fifth Clyde Houldson who had been detached another. A specific area has to be covered Avenue for a permanent antenna that may from other CBS engineering duties to be in each instance; this is effected by making be installed in a couple of months. The pole the engineer on the premises. the most desirable compromise between has a 65 foot mast supported on a 25 foot All materials which went into the con- height of antenna, power of transmitter, and steel base, projecting a total of 90 feet above struction was brought into the building via antenna gain. the tank house steel atop the building. The its 30 West 42nd Street service entrance. A series of matching elements is mounted pole consists of 24,000 pounds of steel struc- They were then carted through the base- on the antenna -supporting pole. With four ture, and its top is 782 feet above the ment and placed on the elevator where they loop antennas there are naturally four sig- ground. were hoisted to the 58th floor. From there nals. With the matching elements, however, Installation of the permanent FM antenna they went through hatchings to the eleva- a single signal arrives in step at the receiver. is to be delayed due to national defense de- tor machine room on the 60th floor. Then Each loop consists of a maze of two and mands on necessary materials. Powered they were raised to the roof through sky- a half inch copper- plated steel pipes folded with a 3- kilowatt transmitter, the permanent lights. Light -weight wood poles, the same to form a six -foot square. There are two installation will operate under the call let- size and shape of the steel sections, were gaps in opposite corners of the square. ters W67NY, and will serve the standard first carried through to check this route to These are metal plates thirteen inches in New York area of 8500 square miles with the roof. diameter, and are condensers used to in- a population of 12,000,000. The temporary The permanent antenna installation will crease the radiation efficiency of the antenna. antenna now in operation covers the same have 4 stacks of "loop" antennas at sixteen Inside the pipes are electrical heating area. It is a single -bay turnstile antenna foot intervals starting five feet from the elements which are used as a protection that first went on the air November 17th. against sleet. They prevent ice from form- Operating at a reduced power of 250 watts ing on the antenna. on that day, the temporary antenna broad- A pair of two and five-eighth inch tubu- cast an unmodulated carrier signal. lar transmission lines connect the transmit- The roof of the Salmon Tower is pecul- FM Listeners! ter in the control room on the 60th floor to iarly well -adapted for an antenna con- Write to the program director of your the antenna. The sound, as in AM radio, struction because it has a workable surface local FM Station: Tell him how the station comes from the broadcasting studio over a area with no spires or decorative orna- comes in at your location, how and what special high quality line. ments. CBS engineers examined fifteen of type of programs you enjoy. etc.- Editor The structure is designed to withstand New York's tallest buildings before they simultaneously a 125 mile an hour gale and decided upon the Salmon Tower. a two and one -half inch ice load, over its The antenna -supporting pole is con- entire 90 foot length. 404 RADIO -CRAFT for MARCH, I 9 4 2 Toe ßtt S¢tV[C[Ry- TOt ßi59 Pzot[t1 fOR A WIDER KNOWLEDGE OF TECHNICAL SUBJECTS, READ THE

BOOKS IN THE RADIO -CRAFT LIBRARY SERIES ET into the swing of reading instructive, authoritative books on technical subjects-Radio,, Air Conditioning and Refrigeration. The RADIO -CRAFT LIBRARY treating all important divi- eo SERIES is the most complete set of volumes individually Book No. sions in these fields. Each book has been written for the purpose of giving you the ABC OF opportunity to specialize in one or more of the popular branches of the various IR CON0110N1Nß subjects and we know of no easier, quicker or less expensive way to improve your elmd111ed accurate the knowledge. The material in each book is very helpful -you'll find them valuable in ae review et subjects on technical of Mis your work. The authors are all well known and are authorities on the englo- a library fundamentals of which they have written. This is the first time that you are enabled to build latest breneh senio" Ineluding of technical bookp by such popular writers. eering. en Present.dó mg data Paul units. BY ALL BOOKS ARE UNIFORM Harrigan. 60o The books in the RADIO -CRAFT LIBRARY BOOS wo.e. SERIES are all uniform. The size is 6 x 9 WITH inches. Each volume contains 64 pages and ERVICINß an average of 50 to 150 photographic Book No, 14 SET ANALYZERS illustrations and diagrams. The books are Darr Theory an excellent grade of book paper GUIDE of the printed on RADIOD Lessato. WU"' 0,0101110P flexible covers. PRICE 50c by N. H and have stiff fitted and Proyer ..ty Reference B$eL ere PER BOOK. All books are sent postpaid. IendYMente of Ned "eel. Ae. Refilo per. H. or Amides * atu+. BY )cnstruction Olr- Par AmD101er No, 21 Audio Useiul Rsdlo McEntee. Book cults end Date INT O I Fee Fertaul KI Hsner ShorlCuto. gook No. jO SERVICING RADIO SOC T P RESISTANCE e .oncr ANALYSIS SBPe rmpneddutael dS ud r Men fer B ^rvlee lRt BI d AyD11eaT.;t BNG Theory Modern Ai lMs et te Everyday procedure Pnblems. Rodlo Servlee creed. By Bertram cfe 22 Book No. NEW LADIO QUESTIONS AND ANSWERS Book No. 16 Queellene AnsweroFuenllY pRACT10Al Ftesl Rene o by Bets Sonless sert BY RADIO CIRCUITS Extorts, Ape E1ebbert A Csmanhendve o All Two.. 60d to the Bore. 23 clrtmu fertrurtor and Book No. men, can. BY 0ar11 EaoerlmsntN. gook No. 20 PRACTICAL Bectera. THE PUBLIC ADDRESS CATN00E'RAY Se, Methods el OSCILLOSCOPE e, Modern ana In+ulllnt ThprY end fad As steing $1300 es Equip- power BweeD Public Address Girtuils, of BY B. Baker New titles are constantly being added to the snelated ODeretion ment SERIES. But, on the Cinuits Met hods Bryant. RADIO -CRAFT LIBRARY Typical Unit, Pnc" of titles are running Measurement of other hand, stocks certain of I 50c A Dlleellonssohs. low, and they may not be reprinted for some *teal Osclllo11 that at this C R Situranr time. We would therefore suggest Icy Charles time you order as many different titles as you 50C Book NOT* in. Remember, that if you delay, are interested AU70MOBILE some of the books may later be out of print. RADIO USE THIS PRINCIPLES Its-- M-- -M- - -- AND PRACTICE - -- n ---- ang Treatise RADCRAFT PUBLICATIONS, Inc., 25 West Broadway, NEW YORK. N. Y. HANDY A Complete spbiect Coveri 1 Gentlemen: Enclosed find my remittance of $ for which send oso, POSTPAID, the from lnstnli- Books indicated below. COUPON pli end tho Servicing B. RADIO -CRAFT LIBRARY SERIES @ 50e EACH arec e. By WHEN Va in ten 1 wanted: 13 1T lr, 17 19 19 20 21 22 23 21 Circle book cumbers II Baker BrrenL cRn IName Address ORDERING

City State Inc. I (Send remittance in form of cheek or ney order: register your letter RADCRAFT PUBLICATIONS, ' If you send cash or unused U. S. Postage Stomps.) RC-342 25 WEST BROADWAY NEW YORK, N. Y. RADIO -CRAFT for MARCH, 1942 405 F.M. FM FUTURE at qIaneQ

75% of nation is now FM conscious .. . Estimated 2,000,000 FM sets will be sold FM STATIONS 48 in 1942 -43 ... 40,000,000 people now in FM SETS FM service areas. EVEN with the war conditions and great 1300 curtailment of sets produced for public FUTURE use, it has been estimated that 2,000,000 FM receivers will be built and sold in 1942 -43 compared to 250,000 FM sets in use January 1st, 1942. Now a total of 128 FM stations are on the official record; 24 FM stations spread across the country are now in daily operation with commercial 36 programs. Thirty -nine FM stations are under construction and many of them will go STATES into operation shortly. There are 53 FM station applications 128 pending with the F.C.C. in Washington. There are also 12 experimental FM stations A B still offering program schedules preparatory, in most cases, to instituting service with commercial FM STATIONS transmitters now being installed. A Seventy -five percent, or 36 out of 48 states IN OPERATION 1941 1942-1943 94 OF UNITED STATES in the Union, are now interested in FM, B. UNDER INTERESTEC IN FM through stations now in operation or soon I' to be active in these states. In many cities CONSTRUCTION FM transmitters are in use by the police. Other commercial applications of FM are its use in despatching trains, communication between fire apparatus and headquarters, transmission and reception of facsimile pictures, FM transmission of voice and music for television, and a number of military uses, including FM sets in army tanks. 111111 111111111111 111111 50.000 FM Receivers in New York. Latest figures on (ales of FM receivers, indicate 111111111111111111111111 that there were approximately 50,000 seta equipped for frequency modulation reception A =JAN. I. 1941 B=JAN. I. 1942 1941 1,942 -3 (ESTiagrER) in the vicinity of New York City alone on 6 MFRS. OF 20 MFRS. OF MONEY SPENT FOR FM SETS-' January 1. The national total is close to the F quarter million mark. M SETS F. M. SETS The New England states may now claim between 22,000 and 24,000 sets, while Chi- cago has reached 25,000 -most of which were sold in the past three months. Other hnhav tµT(--{iti:.:!i large cities include Philadelphia with 12,000; Los Angeles, 15,000; Milwaukee, 6,500; De- FM APPLICATIONS troit, 12,000; Pittsburgh, 8,000. t.tl Figuring on the conservative basis of three persons to each receiver, statistics (I1FtA k' . 90I9UTA11AYITtrd 111 thus indicate that New York's 50,000 re- 40.000,b00 PEOPLE (31 %) OF U.S. POPULATION ceivers serve an audience of about 150,000 listeners. Six different FM stations already IN AREAS ASSIGNED F.M. SERVICE serve this growing New York audience which, recently, has expanded by 15,000 to 20,000 persons each month. Four additional stations are being built. In Chicago four FM stations now operate. The Los Angeles total of 16,000 sets, repre- senting a minimum of 45,000 listeners, has .w.....t.. -1j been achieved almost entirely since last -STAT IC-FREE"'PROGRAM August. SERVICE More Manufacturers Facing FM Produc- i tion. The recently issued trade directory of ,ï:; TOP the Radio Manufacturers Association lists several concerns, hitherto not closely associated with FM, as now producing or plan- ning to produce FM. broadcast receivers for the home. Newest FM Station Approved Will Be Sixth in Philadelphia. Philadelphia's sixth FM station received a go -ahead from the Federal Communications Commission. Already operating in Philadelphia are WFIL's W53PH, and W69PH of WCAU. Under construction are W49PH (WIP), W57PH (KYW) and W81PH (WIBG). The newest FM license, first to be granted by Washington in 1942, brings the total of high frequency broadcast stations in the nation so far authorized to 63. Of these, 24 are now on regular operating schedules. Recently it was estimated that 93% of the population in the six New England states lives within range of W43B and W39B. Only 87% are within the normal range of all 52 AM stations. The AM stations would keep an FM receiver constantly tuned to the nearest FM transmitter. Because no vulnerable wire lines are involved in this method of co- ordination, only an explosion or direct 2-WAY POLICE SYSTEMS hit on the FM transmitter could prevent messages from getting through infallibly to all parts of New England. 406 RADIO -CRAFT for MARCH, 1942 F.M.

FM BROADCASTING STATIONS (As of December 3, 1941)

;nglon Mount t \` W51R W47Á\ ,,IXTG WBXAD W57/ órcester W45D ty. Bester 19»y5ch ec W49D -y rj47t 47Du 5yW63Yri gfield'Har¡{t Wb D g15% b trod in9hamlon' 5 H 49BN Alpinene W31i Wb7NY pp pW47gh Iph W11NY mbus WI P a,W W+5N Ì45C a1i Wetonr,ry W49 W51Ñ55 tX W FI it7,7}XMC 96 Wb)NY St.Louis W 75NY KSIL KS9L

n Rouge L E G E N D Bat.45BR W9FIN- Commercial Stations now operating W9FIN - Commercial Stations under construction - Experimental Stations

-.Reproduced by courtesy of TIDY: magazine.

This map shows the amazing spread of "FM" broadcasting across the nation. "FM" MAP Grows Rapidly

AYEAR AGO most of the stations were But there appears to be a growing number might be expected, for many stations al- strung along the East or West Coasts. of sponsors sure enough of FM's future to ready have their equipment. Today they dot the whole eastern half want to experiment before the rates There also may be a pinch at the receiver manufacturing end. As of Dec. 1, the of the country (see map) ; within a increase. will have com- statistical firm of Ernst & Ernst reported, few months as many cities New York, one of the first centers to get the mercial FM stations as now have standard most backward the public had bought 180,000 sets, with service, has been one of the rate increasing regularly month by month. stations on the basic coast -to -coast net- to promote it. But at the moment, WOR : the works. peddling their Total for October 36,000. Though and CBS both have salesmen is currently running at The section most lacking in FM service a few weeks WQXR, industry's output FM time and within 1,500 a day, FM Broadcasters, Inc., esti- is the whole Midwest from the Mississippi Muzak and WHN will open commercial service west to the Rockies. But in such vast rural the mates that the demand in areas with outlets with coverage as broad as exist- above the supply. areas, AM is expected to be the dominant ing stations. (Muzak eventually will have is 20% to 50% for some to come. Even so, On the other hand, the 20 manufacturers system years another, non -commercial outlet.) like rest of no less than 40,000,000 people are estimated now making FM sets are, the Similarly, Chicago and Philadelphia have the industry, using their precious materials to live within earshot of an FM transmitter. two or more competing stations. Both most of The roster of FM operators now includes on their higher -priced models and W59C and W67C, owned by WGN and these tend to be AM -FM combinations. So many names aside from Major Edwin H. have sold time and both in- CBS, respectively, as long as they continue to make any sets, Armstrong and his clique of enthusiasts, will continue to solicit sponsors. The same that cluding some with such huge investments in they presumably will be making ones is true in Philadelphia, where WFIL and can receive both systems. All the com- AM that they did not exactly welcome WCAU have commenced operating W53PH FM's advent. Among those with commercial panies use Major Armstrong's patents ex- and W69PH respectively. Most other big cept Philco and Crosley. FM stations on the air are Columbia Broad- are due to have competing commercial casting (Manhattan and Chicago), Don cities Estimates for 1942 production range stations soon, which should result in a still hopefully upward from 1,000,000. Lee Network (Los Angeles), WGN drive to get sponsors. (Chicago). The list with stations building bigger The FM network carrying the recent pro- will crimp the broadcasters' was formed for that particular pur- is even more inclusive : Metro- Goldwyn- The war gram Mayer (Los Angeles), Hughes Tool Co. style, of course, but perhaps not as much as pose and will not function again as a group (Los Angeles and San Francisco), NBC except perhaps to broadcast sonic special (Manhattan and Chicago), Westinghouse event later. Columbia and its affiliates, how- (Boston, Springfield, Fort Wayne, Phila- FM Is Here To Stay! ever, already have the skeleton of a huge delphia and Pittsburgh). chain which may emerge at some distant concern. The new, coopera- In view of the small audiences available, The Editors will include many more FM date as a going Network is stymied at the some of the stations have made substantial in future issues of this magazine. tive American articles of a Manhattan outlet progress in selling time. The time costs are on new FM Stations, FM activi- moment for want Articles to its nearest nothing but token rates: W71NY, for FM Set- Servicing, construction of FM capable of relaying programs still ties, North, in Hartford. example, charges $100 an evening hour, Sets, etc. station to the - compared to $1,100 for its parent, WOR. Courtesy "Tide" Magazine. RADIO -CRAFT for MARCH, 1942 407 IOW F.M. Chicago Turns to FM CYRIL WAGNER FM Station. W59C (FM Outlet of Famous fi'GN in Chicano)

Left -Art Avery, WGN and W59C engineer makes a final inspection of the air filter In the new FM transmitter. Above -FM Station W59C helped to introduce FM by means of a popular demonstration before a group of local radio dealers. Right- Carl J. Meyers, Chief Engineer of WGNand W59C (left) and his Assistant. ClydeWhite, during installation of FM Transmitter. REQUENCY modulation offers lis dio, the frequency (number of sound cycles The very high quality teners a better system of of FM transmis- broadcast transmitted per second) remaining the sion and programming has found a reflec- "F ing." That, in the words of Carl J same. The reverse is true for FM, and Meyers, that tion in the sponsors airing programs on chief engineer of WG N is where the big difference comes in. In W59C. and its FM outlet, William A. McGuineas, sales man- \V59C, sums up th c FM the power remains constant, whereas ager of \V59C and WGN, has pointed out reasons for the growing popularity of fre- the frequency is varied over a wide quency modulation range, that distributors of high class commodities broadcasting and at th e in accordance with the sound from the and services have found same time gives an implied a very responsive prediction of it s studio. All this leads : future. us to the question market among FM listeners. To illustrate How can these transmission benefits be ap- his point he called attention to such W59C Meyers gave specific reasons for hiss plied to programming for the good of the sponsors as the Marshall Field and com- praise of FM. He pointed out, as an im- listener? Estelle Barnes, program director pany department store, the Ernest Ricketts portant point in his case, that FM offersoffer of W59C, realizing that music will benefit and Hardings restaurants and the Monarch reception without interference, without most under these conditions, has scheduled Finer Foods company, all quality merchan- static and without noise- reception un- a predominantly musical fare for Chica- disers. This tendency, McGuineas predicted, marred by crashing roars when lightning goland listeners in the 10,800 square miles would continue in the future. streaks the sky or when a neighboring elec- serviced by WGN's FM station. A special trical appliance is switched on. FM orchestra has been formed for exclu- FM, it is true, has advantages. This we sive use on W59C. Stars of opera, radio can see from the above facts. But every t But more than all that, Meyers pointspoint listener must remember out, FM offers and the concert stage have special "live" a few points if he reception with a natural- programs, is to reap the rewards of FM transmission. ness and realism in the reproduction of and a library of high fidelity, vertical cut transcriptions has been col- Meyers points out that although an an- music, speech and sounds beyond the ca- tenna on the FM receiver is not absolutely pabilities of AM (amplitude lected for the W59C audience. modulation) Taking essential, listeners living near the extreme broadcasting. This because FM is capable cognizance of all these facts, Henry Weber, musical director of W59C range of seventy miles from any FM trans- of reproducing the full range of sound, mitter may improve their reception by put- from 20 to 15,000 sound cycles per second. and WGN, has predicted that music will always find a welcome among FM listeners. ting up an antenna on their house top. A All these FM advantages in the field of "For the first time," said Mr. Weber, very short wire will do the trick, Meyers wide range tonal reproductions are ac- "we can reproduce the complete dynamic explained, with the length of approxi- complished by the employment of a differ- range of orchestral and vocal sound. And mately twelve feet offering the best re- ent principle in transmission. In standard that means a great deal. For now that lis- sults. radio employing amplitude modulation the teners can at last hear good music in all If these suggestions are followed, lis- power at the transmitting antenna is varied its naturalness, they will want more of teners will be hearing FM at its best. And in accordance with the sound in the stu- the same." that is radio at its best.

EDUCATIONAL BROADCASTS ON FM Applications by the Board of Education cast service possible has a distinct advantage adults as well as students. of the city of Chicago, the San Diego in that the close proximity of the non -com- Subsequently, the Board of Education of (Calif.) Unified School District and the mercial educational bands and the new FM the San Francisco Unified School District University of Illinois to engage in non- commercial bands makes it possible to adapt was authorized to use radio for instruc- commercial educational broadcast service is standard FM receivers to receive both types tional, administrative, supervisory and other indicative of the value of FM in developing of broadcast. In other words, the FM re- functions through the medium of 13 studios the five high frequency channels reserved ceivers now being marketed are capable of in schools in that area, all connected with by the Federal Communications Commis- receiving non -profit educational as well as the central broadcast station KALW by sion for non -profit educational use. the regularly sponsored programs. leased wires. An average school station can now be However, the University of Kentucky had More recently the Cleveland Board installed of at the price of one classroom. received a construction permit for a system Education, which serves more than 150 re- This rearrangement of the high fre- to bring educational program service to ceivers in its municipal school system, re- quencies to make commercial FM broad- some 50 mountain schools, available to ceived permission to change to FM. 408 RADIO- CRAFT for MARCH. 1942 Everything in Radio at Lowest Prices

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RADIO -CRAFT for MARCH, 1942 409 F. M. Mount Washington Highest FM Station With tremendous winds sweeping its 100 -foot tower and buildings Station W39B, located on the 6,288 -foot mountain has a radius of 100 miles and reaches fa4 potential "FM" audience of 2,000,000 people. A. F. SISE Member, Engineering Staff, Yankee Network of broadcasting. Everyone was surprised at the good reception obtained and the ease of communication. Signals from these transmitters did not fade out at the optical horizon, as was expected, but went much farther beyond. Encouraged by this fact and foreseeing the great possibilities that lay ahead, Dr. Pickard suggested putting a small radio transmitter, utilizing these very short waves, in an automobile. This was done and many months were spent driving this car about Southern New Hampshire, Maine and Northern Massachusetts, talking most of the time that it was in motion, with Dr. Pickard, Mr. Shaw, The Mt. Washington Observatory and others. During this period Dr. Pickard displayed the most remarkable enthusiasm, which was quite contagious. His was the most inspiring sort of leadership. Night after night he would work with us until nearly sunrise, his enthusiasm, de- termination, always driving us on. His droll wit relieved the most trying moments. Many a night was spent on hill tops, talking with stations in the valley below. It was during one of these trips that Mr. Paul de Mars, then Technical Director of the Yankee Network, spent a considerable period of time talking with the mobile car. Mr. de Mars was troubled with the problem of providing a better broadcasting service to the people of New Eng- land. Coupling a keen imagination with a gift for being able to foresee developments in the broadcasting industry long before many of its leaders, Mr. de Mars saw in these simple experiments the possibility of Left: Ice -covered mast of the Yankee Network's FM Station W39B, Mt. Washington. Tons of these ice an answer to his problem. Accordingly, feathers are continually forming on all exposed surfaces. Right: Another view of the antenna of W39B, Mt. Washington, showing peculiar auto -spring construction of antenna arms. They are constructed to this work was carried on for some time by stand the weights of tons of ice. the Yankee Network under the direction of Mr. de Mars and Dr. Pickard. BACK in the fall of 1932, a little group winds encountered. We all remember our A small radio transmitter using these of people gathered together around first real storm of super -hurricane propor- very short waves was placed in a boat. This the old wood stove in the AMC Hut tions and how the building swayed and boat communicated with Dr. Pickard at his nestled in Pinkham Notch at the base tugged at the chains that held it captive. home, down by the waters' edge at Sea- of Mt. Washington, most lofty peak in brook Beach, N. H. It then put out to sea After two months on Mt. Washington, radio signal was re- New Hampshire's White Mountains. I I left this sending out a that environment to go to Harvard's corded by Dr. Pickard. Over sea water it was one of these five men, who were sit- Blue Hill Observatory under Dr. C. F. ting in this isolated log cabin, listening to Brooks, head of the Meteorological Depart- was easy to tell when the optical horizon Joseph B. Dodge, Chief Hut -Master of the ment at Harvard and Dr. Pickard, to at- was reached. There was no sudden change AMC (sometimes called The Old Man of in the signal received after this point had tempt to communicate with the Mt. Wash- been passed. fact, many the Mountains) tell of his idea of organiz- ington Observatory using the hitherto un- In the boat went ing a weather observatory to record the miles beyond this optical horizon and still explored ultra high frequencies or very maintained excellent communication extremes of weather on the highest point short radio wave -lengths. These waves were with of land in the Northeastern United States. not supposed to travel beyond the horizon the shore station. We were all familiar enough with Mt. and one certainly cannot see Mt. Wash- Encouraged by this experiment and fore- Washington to realize that even on a rela- ington from the Summit of Blue Hill in seeing the great possibilities that might tively good day in the valley below, the Milton, Massachusetts. Imagine our sur- lie ahead, the Yankee Network installed a fiercest of storms might rage on the prise, when with a very rudimentary radio broadcasting transmitter utilizing these Mountain Slopes. transmitter we were able to successfully very short waves. This transmitter was Accordingly, in October 1932, the Mt. communicate with Mt. Washington. Imme- located in the same building with WNAC Washington Observatory was born, under diately improvements were made in the and WAAB, Yankee owned stations at the leadership of Joe Dodge and with the equipment used, and a permanent radio Squantum, Massachusetts. The transmitter active cooperation of Dr. C. F. Brooks of transmitter utilizing these very short waves was in operation for a period of years. Harvard's Blue Hill Observatory, Mr. was set up at Blue Hill. A third station was During this time Yankee Engineers listened Henry Shaw of Exeter, Dr. G. W. Pickard built in Dr. Pickard's residence at Sea- to these programs on receivers installed in of Seabrook Beach, and the N. H. Academy brook Beach, N. H., another at the resi- their homes and in especially made sets in- of Science. The old stage office building dence of Mr. Henry Shaw at Exeter, N. H. stalled in their cars. They finally came to belonging to the Mt. Washington Summit Immediately followed a series of experi- the conclusion that utilization of these very Road Company was made over into suitable ments by this group of men, mostly in their short waves could never in itself solve the quarters for the Observatory. This building spare time, as a hobby that was destined to problems troubling the broadcasters. They was anchored to the ground by means of play its own small part in introducing a solved some of these problems, did some chains to hold it against the tremendous fundamental change in the whole industry wonderful things that they weren't sup - 410 RADIO -CRAFT for MARCH. 1942 F.M. posed to do, but nevertheless, the utilization of these waves under the existing method of broadcasting could never provide a better type of radio service to the public. QW FM ATTRACTS OUR ATTENTION Then, along came "Major ", as he is en- DIRECT -COUPLED AMPLIFIERS dearingly called by his friends. Just at the time when it seemed as though these years FOR DISCRIMINATING MU -.0 i.OVF'.RS of experimenting might be of no avail, or at least no use to us, Major Edwin H. Designed by A. C Shonry Armstrong of Columbia University began to demonstrate to the radio art his new invention called "Frequency Modulation", Those new amplifiers bridge the gop betwes , the lobo- or FM. rotory and the home, and make available for the first In 1935, Major Armstrong first presented time. extraordinary equipment ni lcsi than ordinary a paper before the Institute of Radio En- prices. Built in a new way, without interitage coupling gineers describing his new miracle. The condensers or transformers. Although specifically de- results he claimed from this new and signed fo meet the strictest requirements of profes- type sional sound engineers, these directcouoled amplifiers fundamentally different of radio embody all desirable features sought by the most dis- transmission and reception seemed utterly criminating music lovers. Sund for Litcrotue. impossible, fantastic. Imagine listening to a radio station seventy miles away, during a thunderstorm and enjoying crystal clear AMPLIFIER CO. of AMERICA reception of the program. And doing all this on these very short waves where there 17 W. 20TH STREET, NEW YORK, N. Y. was plenty of room for an almost unlimited number of stations. Well, it just seemed too come in order to good to be true. build a station on SERVICE MEN HAVE BOUGHT OVER 100,000 SUPREME TESTERS Early in 1936 a group of three Yankee this exposed peak, Engineers, Mr. de Mars, Mr. Irving Robin- 6,288 ft. above sea son, Chief Engineer, and myself, took a level, was the weath- Be sure you see the trip to New York City in order to see and er. Mt. \Vashington hear for ourselves this remarkable new in- has the most severe complete SUPREME vention. This was indeed a dramatic occa- climatic conditions of line before you pur- sion. Armstrong was the genius who had any mountain, re- first invented the regenerative circuit dur- gardless of altitude, chase new test equip- ing the early days, of radio. With these that has been visited ment. See your Jobber thoughts in mind it was a most exciting by humans often or write for new catalog. and dramatic occasion when we were enough to provide ushered by the Major into a small room any sort of weather i with a perfectly normal, although large records. Mt. Wash- looking radio receiver in front of us. After ington has more se- a few words of explanation the receiver vere weather than was turned on. Lo and behold utter silence! mountains in WRITE FOR GREENWOOD, Arctic, SUPREME MISSISSIPPI A most impressive absence of any sound. Spitzbergen, other NEW CATALOG ANO PRICES U.S.A. One could hear a pin drop. We thought higher mountains in TESTING INSTRUMENTS the set had broken down, were about to the Alps, or even say something, when startled by a strange Admiral Byrd's Lit- voice in the room with us. It took some sec- tle America in the Antarctic. The world's onds to realize that this was FM in opera- maximum wind velocity was recorded 1'NEW CATALOG tion. The voice was not in the room with us, on Mt. Washington during April 1934, offi- OF SOUND AMPLIFYING SYSTEMS but was one of the Major's associates, Mr. cially clocked by the Observatory at 231 AUDIOGRAPH Sound Systems represent the C. R. Runyon, up in Yonkers, saying hello miles per hour. We have seen ice and rime to us over the air. A few musical selections formations build out from exposed objects latest in Public Address equipment -a com- followed which were of truly unbelievable to a length of eight feet or more, giving all plete line plus pre -tested accessories. clarity, but they were unimportant. We structures on the summit a most weird were still recovering from our surprise at appearance. NEW LOWER PRICES Outstanding quality and performance at that initial silence and that first hello from It was at this bleak and inhospitable the little man who wasn't there. Arctic outpost that the Yankee Network prices that help you meet any competition. It did not take Mr. de Mars long to sell dared to spend $35,000 in 1937, in the belief WRITE FOR YOUR FREE COPY John Shepard 3rd, President of the Yankee that FM held the key to the future of radio Network, the idea that here was the answer broadcasting. An FM station was not built to many of radio's most baffling problems. immediately, but during the summer and AUDIOGRAPH Here was the only manner by which a real fall of 1937 the experimental broadcasting THE FIRST NAME IN SOUND be improved radio service could provided station at Squantum, which operated on the Mlle Men h.dmtrle, --U13 W. NndSIpt snnl, C51cele, for the public. Therefore, in the spring of sanie short waves that FM would use, was 1937, the Yankee Network embarked upon moved to the summit of Mt. Washington. a program designed to provide this new Space was rented in the Mt. \Vashington GOLDENTONE .. 50% OFF FM Service to practically all of the rural brand new building in Observatory's order . the DEAL DIRECT . sections of New England, as well as its operators. FACTORY PRICES. populated urban Our to house this transmitter and 34a more thickly centers. was from Mt. Washington modest experiments of 1932 -1933 suddenly Land leased the took on a big league aspect. Railway Company who own the summit of This brings us right back to where we the Mountain, and the erection of an an- $8.08 t lleeo .,f. V.,:j,.t i. started, Mt. Washington. With height be- tenna tower was commenced. This tower discount, Iv,- .ata! g rag+ ing a dominant factor in this new system of was to be 100 ft. high and had to be espe- odilcoundnts. trial. agent's proposition No obligation. broadcasting, it was only natural that we cially designed and braced to withstand the Mall Postcard to: should consider Mt. Washington. super- tornado winds. OOLDENTONC RADIO CO.. DEPT. RC. DEARDORN. MICH. It was estimated at the outset that some NIGH EFFICIENCY And so, radio Station W1XER went on results in 2,000,000 people could be provided with a Sound National the air during the fall of 1937, with 500 Defense truly perfect interference -free radio service that is why from this location. Most of these people watts power and a temporary antenna. This NATIONAL DE- station was used during the winter of FENSE SOUND could never have been provided with a really SYSTEMSquSTEM Sv tot40,** with. 1937 -'38, and the early part of 1939, to am satisfactory radio service in any other man- Unr erty RiRes weather reports from the Summit HIGH POWER ner as this is mostly a rural population transmit LOUDSPEAKERS spread over a large area. Certainly one of of Mt. Washington to the Yankee Network UNIVERSITY LABS. the most difficult problems we had to over - Studios in Boston, Massachusetts. It also Hi CHRISTIE n. E.Y.C. RADIO -CRAFT for MARCH, 1942 411 F.M.

provided the long sought opportunity to ob- structed a radio station in such a severe first floor there is a public lobby and observe how an FM Station using the same climate before, and no one knew just what servation corridor, where one may view the wave -lengths might be expected to perform kind of a transmitting antenna system to transmitter in operation. from the same location. In addition, it pro- build. vided an opportunity to experiment with During the summer of 1938, the re- W39B is now operating from its tern- different forms of antennas under unusually mainder of the weird antenna tower on Mt. porary home in the Observatory Building, severe conditions. No one had ever con- Washington took form. Instead of wires using a temporary power of one thousand for an aerial, the heaviest -duty truck watts. The broadcasting day begins at 6 :00 springs were used. Eight of these springs AM and continues until 12:00 midnight on N111 weighing 360 pounds apiece were mounted week days. Sundays it goes on the air two on hours later. The program is picked up the gigantic steel pole which rises 50 ft. from above the fabricated four leg steel tower. W43B at Boston, by means of FM Did YOU Buy These springs were chosen as the best and is rebroadcast over W39B Mt. Wash- would ington, for use in Northern New England. available mechanical contrivance that By mid -winter have the necessary electrical properties of W39B should be operating that a from its new home with a substantial in- transmitting aerial and at the same time crease in power. would have a chance of surviving Mt. 1)EFE Washington's climate. The first year of operation of W39B has SE llOND During 1938 -1939 and 1940 the develop- been very gratifying. Continuous rebroad- ment of FM was rapid. However in 1940 casting of programs originating in Boston, Yet? the plan evolved by Yankee in 1937, for with such clarity that they are impossible eventually providing all New England with to tell from the original broadcast, has be- See page 390 an interference -free radio service by means come an accomplished fact. Enthusiastic let- of FM, entered its second phase, the con- ters have been received from listeners EMPOINIMOOMINIMMPOOIMMINININAINNIMINA struction of an FM Broadcasting Station throughout New England, some from sur- on Mt. Washington. prisingly distant points. These letters show In spite of all the obstacles Yankee's FM an appreciation of the better type of radio Station W39B went on the air from the service available through FM. Yankee En- top of storm swept Mt. Washington on gineers have listened in at most of the December 18, 1940, with a regular broadcast cities and towns within the estimated service program. This completed the first step of area. Reception has been as good as, or the second phase of Yankee's FM program better than expected even, in many unfavor- in New England. ably located areas. With the new higher At the time of this writing the new trans- power transmitter installed this winter, Michigan's pioneer F.M. station mitter building is all closed in against the everyone living within an air line distance is now on the air. Independent weather. It contains four double bedrooms, of 100 miles from Mt. Washington -and office, programing bath, flush toilets and two lavatories many people at much greater distances, 18 hours daily. on the second floor, livingroom, dining should be able to enjoy that clear, inter- Owned and operated by The room, and modern kitchen on the first floor. ference -free reception, that only FM can Detroit News, associate station In addition to this, in another wing on the give. wWJ.

Role Cord on Request What Radio Leaders Think About "FM" W45D (Continued from page 393) 4500 Penobscot Bldg. two -way DETROIT. MICHIGAN radio system was required. But Sales statistics for 1941 might be intro- ordinary radio communication could not duced at this point as positive evidence that pierce the shield of static set up by the FM has been accepted with open arms by a roaring Diesel powered generators in the "completely sold" radio public. It would be locomotives. A few years ago the problem simple to observe the past sales record and would not have been possible of solution, to indicate how many hundred percent FM PRACIIIC but today FM came to the rescue. sales PROGRESSIVELY INCREASED No static from month to month during the past year. -whether caused by violent elec- Although the sales record of the industry trical storms, high tension power lines or offers electrical machinery can reception proof in abundance that FM is estab- affect the lished on a foundation of an FM broadcast. And, so, over the roar of of complete solidity, N WORMAVION the exhaust of the powerful Diesel with its future status definitely assured, I Including Frequency Modulation-Television, etc. engines, can vision the reaction of a statistically InsideRadlo Information totali unaffected by the whirling generator located bur- Servicemen- Aircraft Pilots, only few feet dened public to "another flock of figures"! Students. ACDEIS RADIO - a from the receiving set, the apology, sales record MANS GLIDE Contains messages from Without our will not the control room reach the be introduced in this report. 112 Pates, ono Diagrams & Photos engineers in their cabs -simplifying and le complete-gives Authentic The future - Principles & Practices In Con- speeding this vital segment of national de- status of FM, from the stand struction, Operation, Service point of civilian use, will necessarily be & Repairs. Covers clearly and fense production. Concisely Radio fundamentals affected by our war program. For the dura- -Ohm's Law- Physics of Our own FM station, W51C, here in Chi- tion, little can be spent in engineering, sound as related to radio sci- time ence- Measuring Instruments cago, will round out two years of continuous manufacturing and marketing radio receiv- -Power supply-Resistors- Inductors- Condensers broadcasting early in February. Recently ers for civilian use. It is only logical and Transformers and examples--- we increased our power to a full 50,000 reasonable for the entire radio manufactur- Broadcasting Stations -Radio Telephony-Receivers-Diagrams watts and now serve the entire greater ing industry to accept with pride, a well - -Construction- Control systems area. in Loud speakers Antenna systems- Chicago deserved commission the war program; -Auto Radio -Phonograph -pickups-Public Ad- a service commission to build the specialized dress Systems-Aircraft & Afanne Radio-Radio Compass -Beacons -Automatic Radio Alarms equipment required by the Army, Navy, Short Wave-Coil Calculations -Testing- Cathode- Marine and Air Corps. This is not a part ray osclllographs- Statio Elimination- Trouble FM IS A "SURE-THING" BET Pointers -Underwriter's standards -Units and time job! It must necessarily be an "all out" tables-Frequency Modulation- REVIEW QUES- SAYS G. V. ROCKEY, TIONS& SWERS. Ready Reference index, ... duty that will last for the duration. Vice Pres. Meissner Mfg. Co. Happily this war, like all wars, must end. ts kI Information handy Victory in war will introduce a future 4 forte for yourself-FM In End IF 1941 can be employed as a yardstick wherein civilian radio production can and MAL."n COUPON TODAY AUDEh 49 W. 23rd St., N.Y. with which to measure the future popu- will be resumed with a BANG! FM will Mail AU yPublishers %ANNf IINvrlllDDlo ulesdlaoo. fro. >

system the static has been reduced to the FIG. -2. - AUDIBLE TONAL RANGE. vanishing point. Thus, the sound originating in the distant FM studio has travelled through static, and when it comes out of 30 100 500 1000 5000 6 7 8 9 10 11 12 13 14 15 16 your FM receiver loudspeaker it looks like 250 15,000IS the sound that began at the studio. FLUTE You will recall that the second improve- VIOLIN I 192 13500 ment we would make in radio reception would be the elimination of interference be- ORGAN 32 12,000 tween two stations located at the sane or The reason why 8,100 adjacent points on our dial. PIANO 26 an FM receiver picks up only one of two stations located at the same point on the GOOD RADIO dial, is because it has the ability to select the stronger of two FM stations. POOR RADA) AUDIBLE TONAL RANGE 7:712.12111110 The fourth point was the enjoyment of genuine high fidelity. To explain, let's understand what is meant by high fidelity. If FIG.-1 HOW FM. REDUCES STATIC TO THE VANISHING POINT. the numbers across the top (Fig. 2) repre- CARRIER SOUND SOUND ON CARRIER SOUNDISTATICON (ARRIG WHAT RECEIVER DOES ar"ronivüo. ás sent the range of frequency that can be RADIO heard by the human ear, let's see what the CONVENTIONAL range of various musical instruments is. A STATIC STATIC STN AR D + flute has a range of from 250 to 15,000 cycles. A violin from 192 to 13,500 cycles. An organ from 32 to 12,000 cycles and a 61111 11111 l 111 f il hill piano from 26 to 8,100 cycles. HIT ! Now in order to get high fidelity repro- w tiprill Wirql duction of a radio program, the station and the receiver must be able to carry the entire sound frequency range from 30 to 16,000 cycles. Otherwise some of the overtones or high notes from a given instrument will be F. M. RADIO lost and hence a true life -like reproduction STATIC STATIC will not be possible. NO STATIC ! A good conventional radio receiver has rI i++ a sound frequency range of 5,000 cycles

111111 that's all the conventional broad- I I I I I I I I I AEA 1I 11111, ;III ÌitfitIIIIII because cast stations are generally allowed to trans- IIIiitl 11'I''IV W mit. Hence all the higher frequencies are I iiiiiil N IÍliii!1 lost. Then if we cut down the size of the Diagrams reprodue d by courtesy of General Electric Co. loudspeaker and the quality of the sound is The top diagram shows why FM radio is so necessary for high -quality sound reproduction. system in the receiver, which generally The lower diagram shows how FM eliminates static. true in table models, the sound frequency range is even more limited and all the real low and a larger portion of the higher fre- WHY "FM" IS GROWING The carrier wave on the conventional sys- quencies are completely lost. RAPIDLY tem increases or decreases in height in With FM, however, it is possible to accordance with the sound in the studio - transmit the sound frequency range be- If we were to ask you what improvements the distance between each wave remaining tween 30 and 16,000 cycles and all of the in radio reception you would like, you would constant. All changes in the conventional high frequencies are present, so genuine undoubtedly mention: system occur in an up and down direction. high fidelity is possible. wave does Conventional stations are limited to 5,000 1. Eliminate static -man -made, such as On the FM system the carrier cleaners, other not change in height but the distance be- cycles of audible sound because each station electric razors, vacuum is only by an electric arc, tween the individual waves increases or de- has been assigned a channel which noise sources caused wide in which to operate. Since as well as nature- static such as light- creases with the sound in the studio. All 10,000 cycles changes in the FM system occur in a right its operation requires the carrier frequency ning. be centered in each band, the sound fre- 2. Eliminate interference from stations on or left sideways direction. to which Now, the program has left the broadcast quency range is limited to 5,000 cycles. The the same or adjacent channels station is not hampered causes that chattering cross talk, dis- station and is travelling through space to FM broadcasting set. introduce the "bugaboo" in this respect because each station has a tortion and whistles which are so your radio We in to listen radio reception -"Old Man Static." channel width of 200,000 cycles. As the annoying when one is trying of conventional system the FM carrier fre- to a favorite program. Here's what happens to the wave is in each band so the is the condi- (a) quency centered that 3. Eliminate "fading," that static hits it. You will is not but where the station you are tuned when (see diagram) sound frequency range 5,000 tion note that the static, which is really a minia- 100,000 cycles either side of the carrier. to comes in loud one moment, then fastens itself on distorted ture broadcasting station, This band width is ample to take care of disappears the next, causing FM waves pro- 16 reproduction. both the conventional and the full sound frequency range from to ducing a saw -tooth pattern. 16,000 cycles as well as wide volume 4. Make possible the life -like reproduction (b) Now in the conventional system it changes from a soft to a very loud note. of radio programs with crystal clear- has prepared from data ness, in other words, genuine high is necessary to use the entire upper half of This article been fidelity. the wave so the receiver picks up the static supplied by courtesy of Radio and Tele- along with the sound. In the FM system vision Dept., General Electric Co. the upper and lower portions of the wave, HOW FM REDUCES STATIC TO THE off, VANISHING POINT which are affected by static, are cut how allowing the sound wave to come out of To explain, let's see FM reduces interference. If you like this FM number-tell the static to the vanishing point. Note how the the loudspeaker without Editor. Do you want more articles on appearance of the carrier (Fig. 1) is (c) So in the conventional system you FM? What kind? changed when the electrical sound wave is hear the presence of the static as shown placed on it. mixed with the sound, whereas in the FM RADIO -CRAFT for MARCH, 1942 413 F.M. FM SETS

frequencies. Audio response is essentially flat from 30 to 6,500 cycles on the AM bands and from 30 to 15,000 cycles on the FM band. A power output of 6% watts, undistorted, is provided by the push -pull audio output system: full automatic volume control is incorporated. i' Seventeen Tubes -Three Bands : The AM bands cover the Broadcast range, from 540 to 1,660 kc. and the most popular Short -Wave range, from 5.9 to 18.8 mc. The FM band provides full coverage -from 42 to 50 mc. Sensitivity on the AM bands to 5 mv. and on the FM band 10 mv. A 6AC7 is used as an RF amplifier on the FM band with a 6SA7 mixer- oscillator and three 6SK7's as I.F. amplifiers. The limiter is a 6SAC7 and discriminator a 6H6. The RF amplifier on the AM bands is a 6SK7 with a 6K8 as mixer -oscillator, 6SK7 I.F. amplifier and 6H6 second detector. Common to both systems are the 6SQ7 first audio, 6AD7G output and phase inverter, and 6F6G output audio amplifier tubes. A 6AC7 provides interstation silencing on the FM band while a 6E5 is used as a tuning indicator. The rectifier is a 5U5G. This receiver operates on 117 volts A.C., 50 -60 cycles. -Meissner Manufac- turing Co. FM ADAPTER THE G. E. Translator or FM Adapter is shown in Fig. 3. It represents a well- designed FM tuner which can be connected with any good quality radio receiver of the usual AM or broadcast type. Only one simple connection between the FM translator and the AM receiving set is necessary. The translator has pushbutton tuning keys for 6 FM stations, an easily read illuminated dial, and 9 tubes including rectifier. The FM adapter is mounted in a handsome cabinet and it may be placed on a small table alongside the broadcast receiver, or else mounted on top of the present set. The translator cabinet measures 9 in. high, 15% in. wide and 7g in. deep. The adapter is operated from a 110 -volt A.C. circuit and is known as Model JFM- 90.- General Electric Company. BROWNING FM TRANSCEPTOR THE Browning Transceptor or FM Adapter chassis is shown in Fig. 4. This FM Adapter is available in any cabinet and can be connected to any high- quality broadcast receiver of the AM type and thus permit reception of FM programs. Another larger model of this chassis is available as a complete FM receiver. The unit is self -powered and is easily connected to an AM broadcast receiver of the usual type, by merely plugging the output of the transceptor into the phonograph jack. The adapter may also be used with any good audio amplifier system. Browning Laboratories, Inc. PHILCO FM /AM MODELS PHILCO'S FM /AM receiver illustrated in Fig. 5 is unique in that FM programs, standard broadcasts and short-wave programs are all tuned in with a single dial and a single set of controls. Due to a new circuit development every tube in the FM /AM receiver set operates on both FM and AM. The receiver here shown, Model 1013, is a radio-phonograph combination utilizing a 10 -tube superheterodyne with electric push -button tuning. Standard short -wave and frequency modulation tuning bands are made available and there is also an automatic phonograph record changer. A built -in aerial system is provided and an FM di -pole aerial for reception of FM stations. ZENITH FAVORS FM This receiver is also designed to pick up the sound channel of I illustrates a large Zenith model of combination FM and a television program. The audio output is 8 watts, the power FIG.AM receiver containing 22 tubes, the Zenith Concord in a supply 115 Volts 60 Cycles A.C.: and the power consumption Hepplewhite cabinet. This complete musical instrument plays 125 watts. The turn-table is provided with a dual speed motor and automatically changes as many as 16 records at one loading. that can be adjusted to play records at 78 r.p.m. and also slow It also receives the new Frequency Modulation broadcasts, plus speed records at 33 1/3 to 39 r.p.m. The record changer is also the usual standard, short -wave and amateur programs. Three fitted for attaching a home recording unit.- Philco Radio & matched speakers and the Radiorgan-tone color blender -are Television Corp. employed to insure maximum listening pleasure.Zenith Radio Corp. STROMBERG- CARLSON FM /AM SETS CARLSON'S Model 515 -M receiver is illus- MEISSNER FM -AM TABLE MODEL STROMBERG-trated in Fig. 6; it reproduces both FM and AM programs. ACOMPLETE "Dual System" receiver providing Frequency The outstanding features of this receiver are that it has three Modulation reception along with the standard Broadcast tuning ranges -short wave, standard and FM; it has 8 push- and Short -Wave bands is shown at Fig. 2. The cabinet measures buttons -six for favorite stations, one for phonograph or tele- 12%" high by 223/4" wide and I1" deep. The glass -scale dial, vision connection, one for standard or FM radio; and it has edge- lighted, is fully calibrated to indicate frequencies on all bands. tuning, automatic drift compensator and three -gang capacitator Tuning indicator is incorporated in dial scale. for high selectivity. Other important features contained in this A high -fidelity PM dynamic speaker is built in. Wide -band receiver are that it has a tone -true acoustical labyrinth, a 10% I.F. transformers in the AM channel insure full response on all inch leather speaker, high fidelity on the FM band, tone and 4,4 RADIO -CRAFT for MARCH. 1942 F.M. FOR ALL

automatic volume control, separate bass and treble controls, and a phonograph and television connection with built -in -jack controlled from a pushbutton. Other models of FM receivers are avail able.Etroptbcrg- Carlson. CROSLEY FM CONSOLE N Fig. 7 the Crosley FM Console Model 22CA as illustrated. This receiver for both FM and AM reception employs a 12- tube A.C. superheterodyne circuit. A 15 -watt push -pull power output stage is provided. An extra large tuning dial is used on this receiver. This is a great help in tuning in the short -wave stations. The four complete bands covered by this console set arc : Frequency Modulation Band 42 -50 mc., Standard American Broadcast 550 -1600 kc., Police, Airplane, Ship and Amateur 1.6 -5 mc., and International Short -wave and Foreign 5 -18 mc. The Service Switch provides at the twist of the wrist AM, FM Sharp, FM Broad, or Phonograph. A built -in loop antenna is included and a Master Tone Control with 6 buttons provides more than 60 actual tonal variations. The concert loudspeaker is 14 inches in diameter. -The Crosley Corporation. ANSLEY FM /AM RECEIVER THE Ansley FM /AM receiver illustrated in Fig. 8 has a 14 -tube chassis which covers broadcast as well as short -wave reception. It is adapted for the reception of FM by the addition of a 7 -tube unit, providing a total of 21 tubes. This chassis is provided in a variety of cabinet styles. A dual coaxial speaker system is incorporated, with a "tweeter." The power output is 15 watts. The audio frequency range is 30 to 12,000 cycles. A built -in loop aerial with an additional antenna coil for use with an outside aerial where a greater output is desired is also included. Individual bass and treble tone controls are provided. The usual broadcast band is covered and the short -wave band covers 6 to 18 megacycles. An automatic record -changer and phono pickup is also included. - Ansley Radio Corp. PILOT FM /AM RADIO FIG. 9 shows a handsome table model FM /AM receiver designed by the Pilot Radio Corp. engineers. This FM and AM combination is also supplied in console models. The table model here illustrated employs 8 tubes and is furnished with a 6 -inch loudspeaker. The tuning range for AM or standard broadcast band is 535 -1620 kc.; the FM band covers 41.4 to 50.4 mc. A large slide -rule type illuminated dial is furnished. The set is designed for 110 -125 volt A.C. or D.C. supply. The set uses the Armstrong FM superheterodyne circuit. The tone control is continuously variable with a sharp cutback at higher audio frequencies. It operates in an inverse feedback circuit. Pilot Radio Corp. HOWARD FM RECEIVER HOWARD'S Victory Model FM and AM receiver is shown at Fig. 10. This is a 14 -tube, 4 -band combination set. Other cabinet styles are available in the FM /AM models. The Victory Model shown (718X -FM -C) has four bands -the Frequency Modulation (41 -50 mc.), the standard AM broadcast band (540- 1720 kc.) and two short -wave bands (1.7 -5.6 mc. and 5.6 -18 mc.). The audio output stage delivers 10 watts from a push -pull circuit. A tuned RF stage operates on all bands. Other features are electric pushbutton tuning, 12 -inch Jensen FM speaker, bass and treble tone controls, built -in antenna, automatic record -changer and a special compartment for albums. The cabinet dimensions in. high, 35 in. wide and 18% in. deep. Radio are 37% Howard output of 12 watts. A separate bass and treble control is provided. Company. A 12 -inch loudspeaker provides high fidelity reproduction. Special FM SET AND RECORD -CHANGER broad -band frequency coverage is provided for, including a sep- FARNSWORTH button tuning THE house of Farnsworth has introduced among other models arate amplifier and a separate tuning unit. Push- is provided and an illuminated dial the one illustrated at Fig. 11 in a Chippendale cabinet. The for six broadcast stations superheterodyne receiver covers three wave bands -the Frequency governs all change -over switches.Espey Manufacturing Com- Modulation band, broadcast band and foreign band. The set is pany, Inc. equipped with an automatic record- changer playing fourteen 10- inch records or ten 12 -inch records. Other features are the Bilt- FM CONVERTER in -terra with a convenient Rotor directional control at the side Modulation converter for use with astand- for full Frequency of the cabinet, special tone control, high spot dial view ANEWard broadcast receiver has been added to the well -known of all wave bands and a special filter circuit for improved short- is most convenient and practical, elimination Motorola line. This converter wave reception and the of long wave interference. being only 13 inches long, 7% inches high and 6% of particular model measures 42 in. high by the cabinet The cabinet this inches deep. the converter is connected to a standard broad- 13 in. deep. Television & Radio Corp. When 29 in. wide and Farnsworth cast set, it will provide FM reception that is limited only by the quality of the audio amplifier of the radio set itself. It connects ESPEY FM /AM MODEL to phonograph, television or FM terminals of any radio receiver at Fig. 12 is the Espey FM /AM chassis which or phonograph combination so equipped. The dial is calibrated in ILLUSTRATEDprovides three tuning bands -standard broadcast, European FM channels for easy tuning. (Not illustrated.) -Galvin Mfg. short -wave and FM. Fourteen tubes are used with push -pull Corp. RADIO -CRAFT for MARCH, 1942 415

"I F. M. FM STATION LIST

THE month of December saw 24 commercial FM at t one \V63C- National Broadcasting Co., Chicago; 46.3 mc.; 10,800 operating on regular daily schedules. A total of 38 other FM sq. mi. transmitters, approved by the Federal Communications Commis- W79C -Oak Park Realty & Amusement Co., Chicago; 47.9 mc.; sion, are in the process of construction and expected on the air 10,800 sq. mi. shortly. W71RF- Rockford Broadcasters, Inc., Rockford; 47.1 mc.; In addition, 54 applications for commercial FM licenses are 3,900 sq. mi. still pending at Washington. There are also 14 experimental FM INDIANA stations still offering program schedules preparatory, in most W71SB-South Bend Tribune, South Bend; 47.1 cases, to instituting service mc.; 4,300 sq. mi. with commercial transmitters now W49FW-Westinghouse Radio Stations, Inc., Fort Wayne; 44.9 being installed. mc.; 6,100 sq. mi. Data in the lists that follow comprises, in order given, the KENTUCKY megacycle channel which has been assigned (or requested), and W5ISL- American Broadcasting Corp. of Kentucky, Lexington; size of service be area to covered. 45.1 mc. ; 6,298 sq. mi. MARYLAND FM \V59 ? ?- Baltimore Radio Show, Inc., Baltimore; 45.9 mc.; COMMERCIAL STATIONS Now OPERATING: 4,980 sq. mi. CALIFORNIA MASSACIIUSETTS W67B- Westinghouse Radio K45LA-Don Lee Broadcasting System, Los Angeles; 44.5 mc.; Stations, Inc., Boston; 46.7 mc.; 6,944 sq. mi. 6,700 sq. mi. CONNECTICUT \V81SP- Westinghouse Radio Stations, Inc., Springfield; 48.1 mc.; 2,500 sq. mi. W65H -WDRC, Inc.,Inc. Hartford; 46.5 mc.; 6,100 sq. mi. MICHIGAN W53H- Traveler's Service, Hartford; 45.3 mc.; 6,100 sq. mi. W77XL -W JIM, Inc., Lansing; 47.' mc.; 3,000 sq. mi. W53D ILLINOIS -WJR, The Goodwill Station, Detroit; 45.3 mc.; 6,800 W51C- Zenith Radio sq. mi. Corp., Chicago; 45.1 mc.; 10,800 sq. mi. King \V59C -WGN, Inc., Chicago; 45.9 10,800 W73D- -Trendle Broadcasting Co., Detroit; 47.3 mc.; mc.; sq. mi. 6,800 sq. mi. W67C- Columbia Broadcasting System, Chicago; 46.7 mc.; 10,800 sq. mi. MISSOURI K51L-St. Louis University, St. W75C -Moody Bible Institute, Chicago; 47.5 mc.; 10,950 sq. mi. Louis; 45.1 me.; 13,000 sq. mi. INDIANA K59L- Columbia Broadcasting System, St. Louis; 45.9 mc.; 13,000 sq. mi. W45V- Evansville on the Air, Evansville; 44.5 mc.; 8,397 sq. mi. LOUISIANA K49KC- Commercial Radio Equipment Co., Kansas City; 44.9 mc.; 4,400 sq. mi. \V45BR -Baton Rouge Broadcasting Co., Baton Rouge; 44.5 mc.; 8,100 sq. mi. NEW YORK MASSACHUSETTS W3INY -Edwin H. Armstrong, Alpine, N. J. ; 43.1 mc. ; 15,610 sq. mi. W43B -The Yankee Network, Boston; 44.3 mc.; 18,647 sq. mi. MICHIGAN W35NY-Municipal Broadcasting System, N. Y. C.; 43.5 mc.; 3,900 sq. mi. W45D -The Evening News, Detroit ; 44.5 mc.; 6,820 sq. mi. W49D -John Lord Booth, Detroit; 44.9 W51NY- National Broadcasting Co., N. Y. C.; 45.1 mc.; 8,500 mc.; 6,800 sq. mi. sq. mi. NEW HAMPSHIRE W55NY- William G. H. Finch, N. Y. 45.5 W39B -The Yankee Network, Mount Washington; 43.9 mc.; C.; mc.; 8,500 sq. mi. 31,000 sq. mi. \V59NY- Interstate Broadcasting Co., N. Y. C.; 45.9 mc.; 8,500 sq. mi. NEW YORK W47NY -Muzak Corporation, N. Y. \V63NY- Marcus Locw Booking Agency, N. Y. C.; 46.3 mc.; C.; 44.7 mc.; 8,500 sq. mi. 8.500 sq. mi. \V67NY- Columbia Broadcasting System, N. Y. C.; 46.7 mc.; 8 500 sq. mi. \V75NY- Metropolitan Television, Inc., N. Y. C.; 47.5 mc.; 8,500 sq. mi. W71NY- Bamberger Broadcasting Service, N. Y. C.; 47.1 mc.; 8,500 sq. mi. \V57A- General Electric Co., Schenectady ; 45.7 mc. ; 6,600 sq. mi. W49BN -Wylie B. Jones Adv. Agency, Binghamton ; W47A- Capitol Broadcasting Co., Inc., Schenectady; 44.7 mc.; 44.9 mc.; 6,589 sq. mi. 6,500 sq. mi. W63SY- Central N. Y. Broadcasting, Syracuse; 46.3 W51R- Stromberg- Carlson Co., Rochester; 45.1 mc.; 3,200 sq. mi. mc.; OHIO 6,800 sq. mi. NORTH CAROLINA W45CM- \VBNS, Inc., Columbus; 44.5 mc.; 12,400 sq. mi. PENNSYLVANIA W41MM- Gordon Gray, Clingman's Peak ; 44.1 mc.; 69,400 sq. mi. W47P-Walker- Downing Radio Corp., Pittsburgh; 44.7 mc.; PENNSYLVANIA 8,400 sq. mi. W49PH- Pennsylvania Broadcasting Co., Philadelphia; 44.9 mc.; W53PH -WFIL Broadcasting Corp., Philadelphia; 45.3 mc.; 9,300 sq. mi. 9,300 sq. mi. W57PH-Westinghouse Radio Stations, Inc., Philadelphia; 45.7 W69PH -WCAU Broadcasting Co., Philadelphia; 46.9 mc.; mc. ; 9.300 sq. mi. 9,300 sq. mi. W81PH- Seaboard Radio Broadcasting Corp., Philadelphia; 48.1 TENNESSEE mc. ; 9.300 sq. mi. W47NV- National Life & Accident, Nashville; 44.7 mc.; W75P- Westinghouse Radio Stations, Inc., Pittsburgh ; 47.5 mc.; 16,000 sq. mi. 8,400 sq. mi. WISCONSIN UTAH W55M -The Journal Co., Milwaukee; 45.5 mc.; 8,540 sq. mi. K47SL -Radio Service Corp. of Utah, Salt Lake City; 44.7 mc.; 623 sq. mi. FM FM COMMERCIAL STATIONS UNDER CONSTRUCTION: APPLICATIONS PENDING ON DECEMBER 15, 1941: CALIFORNIA CALIFORNIA Don K3ILA- Columbia Broadcasting System, Hollywood; 43.1 mc.; Lee Broadcasting System, San Francisco; 43.5 mc.; 18,050 28,000 sq. mi. sq. mi. K37LA -Earle C. Anthony, Inc., Los Angeles; 43.7 mc.; Tribune Building Co., Oakland ; 46.5 mc.; 1,216 sq. mi. 28,000 sq. mi. Sun Company of San Bernardino, San Bernardino; 44.1 mc.; K49LA- Hughes Tool Co., Los Angeles; 44.9 mc.; 7,315 sq. mi. 17,101 sq. mi. K53LA- Standard Broadcasting Co., Los Angeles; 45.3 mc.; COLORADO 7,000 sq. mi. Eugene P. O'Fallon, Inc., Denver ; 46.5 mc. ; 1,403 sq. mi. K61LA- Metro-Goldwyn- Mayer, Los Angeles; 46.1 mc.; 7,000 DISTRICT OP COLUMBIA sq. mi. M. A. Leese Radio Corp., Washington ; 47.1 mc.; 5,600 sq. mi. K45SF- Hughes Tool Co., San Francisco; 44.5 mc.; 10,800 sq. mi. ILLINOIS ILLINOIS WHFC, Inc., Cicero; 48.3 mc.; 10,800 sq. mi. W47C -WJJD, Inc., Chicago; 44.7 mc.; 10,800 sq. mi. Chicago Federation of Labor, Chicago; 47.9 mc.; 10,800 sq. mi. 416 RADIO -CRAFT for MARCH. 1942 F.M. FM STATION LIST

INDIANA New Jersey Broadcasting Corp., Newark; 49.1 mc.; sq. Associated Broadcasters, Inc., Indianapolis; 47.3 mc.; mi. 5,580 mi. 6,665 q. Bremer Broadcasting Corp., Jersey City; 49.5 mc.; 6,135 sq. Indianapolis Broadcasting Co., Inc., Indianapolis; 45.3 mc.; mi. 13,640 sq. mi. NEW YORK Greater New York Broadcasting Corp., N. Y. C.; 48.7 mc.; IOWA 8,500 sq. mi. The Gazette Co., Cedar Rapids; 44.7 mc.; 7,400 sq. mi. Frequency Broadcasting Corp., N. Y. KENTUCKY C.; 45.9 mc.; 8,500 sq. mi. Wodaam Corp., N. Y. C.; 46.7 mc.; 8,500 sq. mi. Ashland Broadcasting Co., Ashland; 46.1 mc.; 4,160 sq. mi. WBNX Broadcasting Co., N. Y. C.; 48.3 mc.; 8,730 sq. mi. Courier -Journal & Louisville Times, Louisville; 45.7 mc.; 13,200 FM Radio Broadcasting sq. mi. Co., Inc., N. Y. C.; 48.3 mc.; 8,600 sq. mi. Knickerbocker Broadcasting Co., N. Y. C.; 48.3 mc.; 8,550 sq. mi. LOUISIANA News Syndicate Co., Inc. N. Y. C.; 47.9 mc.; 8,5W Alexandria Broadcasting Co., Inc., Alexandria; sq. mi. 44.7 mc.; 3,025 The Debs Memorial Radio Fund, Inc., N. Y. C.; 48.7 mc.; sq. mi. 8,600 sq. mi. MAINE WOKO, Inc., Albany; Portland Broadcasting 45.1 mc.; 7,164 sq. mi. System, Falmouth; 47.1 mc.; 3,980 sq. mi. WHEC, Inc., Rochester; 44.7 mc.; 3,200 sq. mi. MARYLAND The American Network, Inc., N. Y. C.; 47.9 mc.; 8,840 The A. S. Abell Co., Baltimore; 46.3 mc.; 6,040 sq. mi. sq. mi. MASSACHUSETTS NORTH CAROLINA Piedmont Publishing Co., Winston E. Anthony & Sons, Inc., New Bedford; 45.7 mc.; 1,787 sq. mi. -Salem; 46.7 mc.; 4,600 sq. mi. OHIO Worcester Telegram Pub. Co., Worcester ; 46.1 mc.; 10,000 sq. mi. United Broadcasting Co., Cleveland ; Columbia Broadcasting ; 48.5 mc.; 8,4220 sq. mi. System, Boston 43.5 mc.; 16,230 sq. mi. William F. Maag, Jr., Youngstown; Boston Edison Company, Boston; 44.7 mc.; 6,930 sq. mi. 43.5 mc.; 12,304 sq. mi. MICHIGAN PENNSYLVANIA James F. Hopkins, Inc., Detroit; 46.5 mc.; 3,050 sq. mi. Pittsburgh Radio Supply House, Pittsburgh; 46.5 mc.; 8,400 sq. mi. Federated Publications, Inc., Grand Rapids; 46.1 mc.; 5,300 sq. mi. Gibraltar Service Corp., Philadelphia; 46.1 mc.; 9,318 sq. mi. Federated Publications, Inc., Lansing; 47.1 mc.; 3,820 sq. ml. William Penn Broadcasting Co., Philadelphia; 47.3 mc.; 9,352 Federated Publications, Inc., Battle Creek; 48.1 mc.; 4,100 sq. mi. sq. mi. King -Trendle Broadcasting Corp., Grand Rapids; 45.5 mc.; Hawley Brpadcasting Co., Reading; 46.5 mc.; 4,275 sq. mi. 4,340 sq. mi. RHODE ISLAND MISSOURI The Outlet Co., Providence; 48.5 mc.; 4,840 sq. mi. Globe -Democrat Publishing Co., St. Louis; 44.7 mc.; 13,083 sq. mi. Cherry & Webb Broadcasting Co., Providence; 47.5 mc.; 6,207 Pulitzer Publishing Co., St. Louis; 45.5 mc.; 11,301 sq. mi. sq. mi. Star -Times Publishing Co., St. Louis ; 44.7 mc.; 12,480 sq. mi. TEXAS NEW HAMPSHIRE Amarillo Broadcasting Corp., Amarillo; 45.1 mc.; Radio Voice 5,629 sq. mi. of New Hampshire, Manchester; 43.5 mc.; 20,290 WISCONSIN sq. mi. Head of the Lakes Broadcasting Co., Superior; 44.5 mc.; 2,754 NEW JERSEY sq. mi. Mercer Broadcasting Co., Ewing Township; 44.7 mc.; 3,700 sq. mi. La Crosse Tribune Co., La Crosse; 46.5 mc.; 7,040 sq. mi.

OPPORTUNITY I i 4 D-L ETS Adrertisements to this section cost 15 cents s Word for each insertion. Name. address and Initials must with $1.00 su1c"rirltion be included at the above rate. Cosh should accom- pany all classified dvertisements unless placed by an accredited advertising agency. No advertisement for less than ten words accepted. Ten percent dis to count six Issues. twenty percent for twelve lieues. Objectionable or misleading advertisements not ae copied. Advertisements for April, 1942 issue, must reach us not later than February 20th, 1942. RADIO Radio -Craft 25 W. B'way New York. N. Y. -CRAFT

EDUCATIONAL. COURSES CORRESPONDENCE COURSES AND EDUCATIONAL books. slightly used. Sold. Rented. Exchanged All subjects. Satisfaction guaranteed. Cali paid for used camas. FULL Complete details and bargain catalog FREE. Write NELSON COMPANY. 500 Sherman, Dept. Chicago. C -242. CONTAINS: LIBRARY SIZE FLUORESCENT LIGHTING 22,000 24' FLUORESCENT BENCH LIGHT $1.49. LESS TUBE. Harold Davis. Jackson. Mississippi. DEFINITIONS MODERN RECEIVERS DICTIONARY OF RADIO WORDS AND TERMS A00 miles) RECORD 1406 -A 77th Ave.. Oakland, Calif. WEBSTER DICTIONARY OF FOR THE AUTO. SALE MOBILE DICTIONARY FOR SALE: 22 CAL. "POWDER- LESS" RIFLE (Crater/ $5.00. Old "Indian Wars" Book (18301 26.00. TABLES. Fleming'. 11908) Principles of Electric Wave Telegraphy TREATISES. ETC. $4.00. Harry Stcor, c/o RADIO -CRAFT, York 25 W. Broadway, FLEXIBLE New City. IMITATION 416 LEATHERETTE TECHNICAL CONSULTANT COVER, SIZE 5'2'x8 TECHNICAL CONSULTANT, MEMBER OF A.A.A.B.. associate member of I.H.E.- A.I.E.E. Receiver and transmitter engineering, trade information, If FILL OUT -MAIL THIS COUPON TODAY! research. Willard technical literary you will take advantage NOW of our special Moody. 1923-16th St., N.W., Wash- subscription offer of ington, D. C. will eight months for $1.00, e send you ABSOLUTELY FREE and POST- RADIO-CRAFT, as WNt roadway, New York. N. Y. this 418 page full library aim MODERN This sa a New Order Extend WEBSTER DICTIONARY -useful and Instructive D my present subscription toPAID everyone. This self- Gentlemen: Enclosed you will pronouncing authoritative end One Dollar dictionary to for -a new work throughout -contains the for TELEVISION (which mat unto -date words now in common Eight Month.. Send ABSOLUTELY FREE and POST. use. 22.000 PAID, my copy or N MODERN WEBSTER REMEMBER definitions in all. It also features a Glossary of DICTIONARY. PEARL HARBOR! Radio Words and Terms. Dictionary of the Auto- mobile, 'Treatises Practical Standard ngl éh tby well known Name Keep 'Em authorities. Metric Tables, Time, State Flower., Flying! National Parka of the U. 8., etc. Addle= This Is time limited offer. so don't delay In returning the Coupon. BUY DEFENSE BONDS City Stale RADIO RC 9.42 n, in, ,,,s,0111111111,anu01wn,au,n,nnn,nn -CRAFT Rtemit by check o 11111, nnnniininninnnn, osar: register . ,,,,.,,, letter tf you send ,-san or win ::ed 25 WEST BROADWAY NEW YORK CITY Postage U.S. RADIO Stampa, -CRAFT for MARCH, 1942 417 F.M. K45LA- ONLY "COMMERCIAL" ON WEST COAST FRANK KENNEDY Chief Engineer, Don Lee FM System.

diated was two kilowatts output for one kilowatt input. This is believed to be the V,., -r+:' first check, by free -space measurement on an FM antenna in the United States. The first commercial FM station on the Pacific Coast, K45LA made its official bow at an auspicious ceremony arranged by Lewis Allen Weiss, Vice President and General Manager of the Mutual Don Lee network, owners and operators of the FM station, on the evening of August 11, 1941. Above-View of FM sta- a large volume of its own origination K45LA, erected atop Using Mt. Lee in Hollywood. tions, the World Recording library and Right - Virginia Simms occasional programs off the Mutual and takes a peep at the in- Don Lee lines, K45LA maintains its indi- ternal structure of the the W. E. Frequency Modu- vidual program structure, although lation Transmitter oper- brilliant musical programs such as the Coca ated by the Don Lee Bands" program, the Broadcasting System in Cola "Spotlight Hollywood. Standard Symphony hour, and the Betty Below -A "bug's -eye" Rhodes show, "Adventures in Melody," view of the 4 -bay turn- Dave Rose, are duplicated from the stile antenna of FM sta. with tion K45LA. Mutual Don Lee network. Lower right photo shows has been found desirable to use a non- the W.E. 1000 watt FM It transmitter; note the directional antenna at the receiver which "blackout" curtains. will receive all stations. A simple type is shown in the illustration which incorporates two horizontal dipole or rod antennas arranged at right -angles. They are vertically spaced about one -fourth wavelength apart or approximately 5% feet. The center of each rod antenna can be supported on a pole. A twisted -pair feeder is connected, one wire to each half of the top section. The connection is made about 12 inches from each side of the center. Another twisted pair is connected to the bottom section in the same manner. Then the two twisted pairs are connected together a little lower down, and continue as one twisted pair to the receiver. This provides an antenna somewhat similar to the "turnstile" antenna used by FM broadcast stations.

NO SERIOUS SETBACK TO FM GROWTH Mutual Don Lee Vice President and General Manager Lewis Allen Weiss recently surveyed radio's position in the present emergency, to foresee an even closer gearing of broadcast operations with the national "all -out" effort to win this war. Said the Pacific Coast executive who is less than 1 %. cycle swing. Distortion manages the 32- station Don Lee chain from The station operates on 1,000 watt power to Mexico, "Twenty -four hour cardioid microphones Canada and Western Electric broadcast schedules are a first step in ra- are used in the studios. listeners, in a total program Don Lee studio's service to Programs originate at the of strengthening morale and keeping the dios at 5515 Melrose Avenue in Hollywood, public informed within bounds of national where all studios, announcer booths and facilities built safety, while making broadcast associated circuits were designed and available to governmental uses 15,000-cycle line leads immediately for FM quality. A the need may require.' over a four -mile path from the whenever directly demands on metals and Lee in Hollywood to the trans- Despite wartime Don studios serious setback in Verlwra/ Pam Ain Ven. Lee. In addition, half a parts, Weiss sees no mitter atop Mt. Modulation, radio's Simple FM Receiving Aerial dozen remote spots have been equipped with 1942 for Frequency newest contribution to an improved, high - of the most special high -fidelity telephone lines leading THE Don Lee setup is one fidelity system of broadcasting. He believes interesting in the United States be- to Hollywood Don Lee studios. tremendous that manufacturers will probably use their cause the Western Electric transmitter, Listener- response has been for manufacture from San Diego to Ventura limited quotas of materials Model No. 503 A -1 is located in a spe- and auditors combination sets, to that some of them live more than of quality FM -AM cial building atop 1,700 -foot Mt. Lee, over- indicate for volume production of cheap 100 miles from the transmitter atop Mt. make up looking Hollywood. AM midget receivers stopped by material The station operates on 44.5 megacycles Lee. Frequency new achievement in free -space meas- shortages. Don Lee introduced and there is no trace of noise at the carrier. A Coast with in- made by the author recently Modulation to the Pacific Audio characteristics are flat, plus or minus urement was of its commercial FM station Frequency when he circled the site in the Goodyear auguration one decibel, 30 to 15,000 cycles. K45LA on August 11, 1941, and has been stability is better than 1,000 cycles at car- Blimp, "Resolute." Proof was obtained that power ra- on a daily broadcast schedule since that rier. The linear modulator has a 75 -kilo- the calculated effective useful RADIO -CRAFT for MARCH. 1942 418 F.M.

New Direct - Coupled FM - AM time, with a consistent growth noted in number of listeners for the area. "Radio will continue to entertain and to educate," concludes Don Lee's managerial AMPLIFIER MANUAL head, "but with one main objective in view a calm, unhysterical welding together of America's mind, heart and muscle in a MB GEO BRUZt By A. C. SHANEY N vr k Chief Engineer, whole effort to defeat the enemy and effect Geooe Amplifier Co. oOAmeriee an early, sure peace." Les Angeles is one of the best cities in the nation for FM. Since Station K45LA went on the air on August 11 an additional have been 15,000 ve sets were put into use, bringing the Union have total number bus- of sets in operation on the Nationalthe service Pacific Coast up 20,000. one of successful bave to At the present the its area. / time there are 2,000 sets being sold per buis! ading full confi- iness in Union with month. Dealers, jobbers, and retailers are National ten years gold re than and well stocked and sales are "going to town" for more fully justified with the have whistle cord tied down, according the results to reports from the Los in the merchandise taken Angeles sector. faith o,, rjttional Union to advantage importance every of equal has but teat N. Unabled deals'. is the fact FM Grows Amazingly my market kept the FM in Philadelphia:- Definite plans for Me to make inauguration of service on W53PH, WFIL's new FM station, were recently an- WHERE YOU FIND nounced. W53PH, Philadelphia's first FM For the Layman, Serviceman transmitter, Recordist and Engineer went on the air Monday, No- vember 10, and operates daily from 2 to 8 ATionA union Regardless of whether you are interested in the finest type of phonograph reproduction, high fidelity recording, p.m. The antenna is located on top of the YOU FIND BETTER sound-on-111m applications, FM or AM programs, you Widener Building in the will find Invaluable Information in this practical handbook. very heart of Phil- Written by the leading exponent of direct -coupled am- adelphia. RADIO SERVICE plifiers who has spent more than 10 years improving and perfecting the famous Loftin -White circuit. Program plans call for no duplication of AM service, with the exception of a few Explains the theory and practical application of: outstanding shows and Variable Speed Non -Overloading PushPull Expansion some special events. Non - Frequency Discriminating Scratch Suppression The schedule will have "news" for five Path -Pull Balanced Direct- Coupled Amplification minutes before each hour and the rest of PushPull High - Frequency Equalization the schedule Push -Pull Low- Frequency Equalization will be classical and semi- PushPull Volume Compression classical music. The station will also in- Automatic Volume Limitation c.ude special events features planned for Automatic Volume Control Calibrated V.U. Indicator FM only, and will release some of the net- Audio Spectrum Control work shows which WFIL is unable to car- Remote Control ry locally. It you are interested in the latest audio development,. you can't afford to be without this complete compilation of authentic article, on Direct- Coupled Amplifiers. 32 Audience Over Quarter Million: -Con- pages 8% x 11'. Over 100 diagrams and Illustrations. tinued gains in sales of FM receivers Priced to Cover Cost of have Printing and Mailing OC boosted the available listening audience for Send Stampa or Coin the country's FM stations far beyond the most optimistic expectations. AMPLIFIER CO. of AMERICA On the basis of reports 17 WEST 20TH STREET. NEW YORK. N. Y. from manufacturers, now turning out about 1,500 receivers a day, FM's national trade association, FM BATTERIES Broadcasters, Inc., has compiled figures showing that over 240,000 frequency modulation sets are today in American fumes. The largest single group is found within the New York City service area where CONDENSERS approximately 50,000 have been sold. in- Chicago's total is well over 25,000. New Transmitting i and civilian tubes, panel England has more than 22,000 sets. Other lamps, cathode ray tubes, areas where ex- need expert FM listener growth has been citer lamps, sound equipment, dustry correspondingly swift include Detroit, photo electric cells, sound ac- NOW I eaq learn pralicientcode 12,000. Los Angeles, 15,000; Milwaukee, cessories, dry batteries, flash h%Shly light bulbs. 1-our opportunity 6,500; Pittsburgh, 8,000. Candler with Several cities where FM stations are still fa with rets. NATIONAL UNION invites .. . your wn under construction already claim sizable right te surprising operatorsorator. quotas of sets. An All redisse and successfulíu1 outstanding example has radio service dealers to enjoy of the d been Philadelphia which, Thousands trained by an until recently, the benefits of the N. U. Shop °beesn tot enjoyed no local FM service and yet had Courses Equipment Plan. The latest in I; =tom. approximately 5,000 receivers available in ,ced OP tube testers and test it homes. equipment raaq. Production schedules, are available to you ... prompt wrae pu Jd together with cur- k rent sales trends, indicate further heavy delivery. More than 60,000 com- increases in the FM listening audience pleted deals prove the success of through this spring's receiver buying. At this plan. Investigate now. the start of 1941 there were approximately 15,000 FM sets in the entire country. Construction permits authorized for additional FM transmitters will further extend frequency modulation service in the cities of Chicago and Detroit. The Federal Communications Commission also approved NATIONAL union Many FM Questions an educational FM station for Memphis, Tennessee. Are answered in articles on the subject, which have This RADIO ¿. appeared in back numbers of this magazine. Send brings the total of commercial FM for list of these "FM" and "Television" Articles broadcast installations thus far sanctioned 57 STATE ST- AMMAN ,fl.J. and the Reference Numbers. by the FCC to 63. RADIO -CRAFT for MARCH, 1942 419 F. M, W55M, MILWAUKEE, CALLING The FM Voice of The Milwaukee Journal

Photo above shows the studio of Station W55M of the Miluxsukce Journal. a beautiful modernistic type building. Left -hand photo shows giant tower supporting FM transmitting antenna and the building housing the transmitter. A great deal of development has been done by the Milwaukee station along the line of a por. table FM transmitter and receiver. An automobile equipped with a special FM mobile set is shown in photo at extreme right. Center photo shows close -up of the FM transmitter control panel in the car.

W55M's Technical Equipment vamped to give us a 15,000 cycle character- the radio desires of the discriminating lis- I). W. GELLERUP istic with noise level of better than minus tener who enjoys good music, and both Chief Engineer WTMJ, W55M, WMJT 60 db. With completion of the studios at sustaining and commercial programs should Radio City next summer, and with the utilize the high fidelity reproductive advan- W55Ì14 Transmitter is a 50 kilowatt THE addition of better acoustic characteristics tage of FM to the utmost. In this respect. nadel built by Radio Engineering Labo- and closer noise tolerances, the overall we believe that there is a place for electrical ratories of Long Island City, New York. It characteristic from studio out through the transcriptions, as well as live talent, on FM employs the new type phase modulator giv- transmitter should be improved appreciably. programs. Experience has shown that the ing the transmitter a modulation character- What is believed to be the first thor- new high- fidelity electrical transcriptions istic of a frequency response that is flat oughly practical pleasure car FM receiver now available to the broadcasting industry from 30 to 15,000 cycles with a variation of has been installed in the car of Walter J. are remarkably well adapted to FM. They plus or minus of % db. Distortion is in Damm, General Manager of Radio for the will provide the means of presenting fa- the neighborhood of 1% over the entire Milwaukee Journal, operating W55M and mous artists and musical groups which frequency range. WTMJ. could not otherwise be heard over an indi- Frequency stability of the transmitter, The outfit consists of the receiver proper, vidual FM station until the American Net- due to a rather unique Frequency Con- speaker, antenna, and control unit. The an- work begins operation. trolled Circuit, is well within the limits re- tenna is a vertical full quarter wave of the D. While music should be the basis of quired by the Federal Communications telescopic type fed to the set proper by a Commission (approximately 200 cycles). FM schedules, we recognize that drama. co-axial cable. The receiver is fixed to the news special events and children's programs Output of the transmitter is fed to the W55M frequency by crystal control. The base of the tower in two three -inch con- have their place. However, every effort will control unit contains a signal strength indi- be made to place such programs where they centric lines. In a coupling house at the cator calibrated in micro -volts per meter base of the tower is phasing equipment. best fit into the daily life of the listener. and a sensitivity control. The main unit of daily luncheon and From this equipment eight 1 inch con- the receiver is installed in the luggage com- E. We believe that centric lines run 220 feet up the tower to a partment of the car with the speaker behind dinner concerts of uninterrupted music two-bay turnstile, this being an antenna the rear seat. The control unit is within should be scheduled, as these two periods gain of one. easy reach of the driver. will make it possible for the listener to In order to cover what is described as enjoy the benefits of FM to the utmost. the Milwaukee trading area, it will be neces- The dinner concert, particularly, should fill sary to radiate approximately forty kilo- FM Programs Important the wishes of many set owners who have watts from the antenna. This means an WAITER J. DAMM hungered for a program of music and not input of between forty -five and fifty kilo- General Manager of Radio one made up of 15- minute units, ranging watts to the transmission line. The antenna THE MILWAUKEE JOURNAL from children's programs to dramatics, sports and news. is so arranged as to allow for the increase ALTHOUGH The Journal Company of the number of bays at a later date thus has been operating a standard broad- F. We believe that by concentrating on allowing an increase of antenna efficiency casting station in Milwaukee since 1925, music during the afternoon, FM will attract if this is found desirable. we look upon FM as a new entity which set owners who do not care for the con- The location of the transmitter is on a will eventually dominate the radio tinuous procession of dramatic shows now hill 1260 feet above sea level. The major scene. on the air. Herein lies an opportunity for portion of the city of Milwaukee is between Our convictions with regard to program- the FM broadcaster to awaken interest in 600 and 650 feet above sea -level so that the ming are. briefly, as follows: daytime radio on the part of those set antenna proper is approximately 600 feet A. If the public is going to buy FM sets, owners who are now a dead loss so far as above the average level of the city. We it needs an incentive -therefore, FM pro- AM broadcasting is concerned. plan to feed this transmitter from studios grams must be distinctly worth -while and G. Lastly, we believe that the FM broad- using either a 15,000 cycle telephone loop fill a genuine need. caster should always model his programs or a studio -to- transmitter radio link. These B. It follows that FM program sched- according to the listening public's demands two circuits will be interchangeable at a ules must be entirely independent from AM and should not permit himself to be swayed moment's notice. schedules. FM's advantages of high fidelity from his set course by the idiosyncrasies of The amplifying equipment at the trans- reproduction and freedom from static are, the advertiser and the advertising agency. mitter is capable of handling frequencies alone, not enough in most cases to make Steadfast adherence to a policy based on from 30 to 17,000 cycles with practically no people switch from AM to FM. genuine public service can open up a listen- distortion. Studio equipment has been re- C. FM should be programmed to meet ing field of unbelievable proportions. 420 RADIO -CRAFT for MARCH, 1942 RADIO DEFENSE!

Top left:- Class in Radio Materiel- U. S. Navy Radio School. Top right:- Naval radio operator's class. Lower left:- Naval class in radio materiel theory. Lower right:- Class in ra dio code reception. -U. S. Navy Photos. EARS FOR THE FLEET RADIO, THE NAVAL RESERVE and YOU

DURING recent weeks, with a total war Radiomen - Servicemen, ex- today are getting it on the ground floor of effort the fundamental concern of this perimenters and amateurs a new field. This training will mean good nation, there has come a sudden and - paying positions for many after the war is nationwide recognition of the vital im- are urgently needed by the over. portance of radio, in air -raid and submarine Navy. Attractive pay and But the Navy offers plenty of advantages defense. The deadly accuracy of initial Axis right away to men who qualify for this underwater and bombing attacks has quick- rating are offered, as ex- training. Accepted applicants become petty ened public interest in radio locators, chief plained in this specially writ- officers in the Naval Reserve immediately. weapon for effective defense against repeti- ten article. They are paid $72. a month base pay, and tions of these enemy successes. To operate are given, in addition, their food and quar- these mechanisms our Navy needs qualified ters, medical and dental care, initial uni- radiomen, and needs them urgently. to build careers for themselves in one of forms worth $118. and, for married men, an Recently, the Navy announced virtually radio's newest fields, the subsequent para- allowance for their dependents of $1.15 a unlimited opportunities for amateur radio graphs have a message and an important day. These advantages come right away operators and radio servicemen in this branch one. upon enlistment. of the service. For men eager to contribute to America's defense, and, at the same time, GROUND FLOOR OF A NEW FIELD TRAINING AT TREASURE ISLAND The Navy's new and secret equipment for Radiomen who qualify for this special An article repared especially for Radio -Craft locating distant planes and other craft is the course of training will be sent to the new by the U. S. Navy Recruiting Bureau. Further in- most important radio development of recent Radio Materiel formation regarding enlistment in the Naval Re- School on Treasure Island serve's radio class may be obtained by writing to years. It's going to be boomed in peace time, in San Francisco, or possibly to the Radio that Bureau, N. Y. also. So men being trained in its operation Materiel School at Bellevue, D. C. An eight

RADIO -CRAFT for MARCH, 1942 421 RADIO DEFENSE

months' course of training follows -in mathematics, radio theory, and the maintenance of radio locators. The course is in- SPECIALS because SUPER be. Training, of tensive; it has to All of the attractive Items listed here are brand new. ALL are in PERFECT WORKING ORDER. In many cases, the parts alone total more than the price we are asking. 100 00 satisfaction guaranteed or your money the war, has been accelerated. But it hasn't refunded. been shortened, or simplified. ORDER FROM THIS PAGE. Use the convenient coupon below. Include sufficient extra remittance for parcel pat charges, else order shipped express. collect. Any excess will be refunded. C.O.D. shipments require 20 °ó deposit. If full remittance accompanies order, deduct 20u discount. Send money order, certified check. new U. S. stamps. No C.O.D. to foreign countries. MUST BE HIGH SCHOOL GRADUATES Work in this new Navy field of radio ORDER TODAY LIMITED QUANTITIES PROMPT SHIPMENTS ASSURED detection is of the most confidential and HANDY WORKSHOP OUTFIT secret nature. Special duties will be assigned WELDING! BRAZING! SOLDERING! to applicants who complete their training 3 -IN -I PORTABLE ELECTRIC TORCH successfully. Consequently, the Navy has to WORKS FROM 110 VOLTS A.C. OR D.C. LINE be sure of its men before it accepts them electric Lorca for training. The following requirements I. Thta t or a toy °but a sturdily for this class of the Naval Reserve have built °maaterials. With been set up. An applicant must: It to bt pe of 1. Be a male citizen between 17 and 50 wldingesotafeini bracing and soldering work, years of age. Here is marvelous article that to the beet of nur whether knowledge has never sold at such a price. This orrdt you've d 2. Be of good character. outfit must be ntbe appreciated. It delivers the previous experience. oods!lt comprises a variable speed universal motor andwill do 3. Be a high school graduate. for 110 A.C. or D.C. Made originally for ita - one obe:gender machinesv. by American Gramophone Co. Motor Amateur pione other welding. auto body 4. Hold or have held an as Is reconditioned and In excellent condition: all repairs, parts are brand Special lever control permits tanks and In- A or B license. Applicants, however, who various speeds up to 3000 .p.m. Measures 71' "x 3I- dustrialatee Otani. overall. Il Alters. fail to meet this last requirement, are not tncluded in the outfit are the following items, as plumbers. sheet met. 1 1 which takes drills ineers. If they are actively Illustrated: excellent chuck al Jobs. etc. necessarily disqualified. other tools-chock 1+ easily screwed t0 motor shaft; maintenance ñ . radio and bicycle repair standartd emery a4" cdbunett Works on beaus. COPP., Iron. steel and engaged to radio repair or service work, wheel. rush e4steelelaota r' other metals!aluminum, standard cloth buffer. 3^' diameter. Total Wt. 0 lbs. 3.10 -1 electric torch is so simply constructed or have had experience in connection with that even a boy petite it after reading the simple ITEM NO. 149 and concise instructions funisped with the nit. Not high frequency design, transmission, or re- Complete outfit. Including motor. ry to know how to strike an I All you do Your Price T$4 95 Ìs plug the torch Into the light socket. adjust the ception, they may still qualify, although carbons per instructions. d presto! -You have an in[1ense blazing name, for, work. The eutht comes they are not actually licensed. In this con- 562 complete with power nit electric cord. hold- WESTON MODEL er. welding rods. bluing ods. solder flux, nection, experience with superheterodyne gle*. and in.erut-Vons. A.C.-D.C. AMMETER own repairing. Han money receivers, u.h.f. equipment, or cathode ray Designed the lave money! Do your dura- Kodaky Co. e Itfilé a hY doing pairing for others. Simple. practical. built msitnetic -vane type ammeter ble and ie to handle -that' why the price Is amazing- tubes, is particularly valuable. which. with suitable shunts. ccan r be ly low. Don't delay -order one today. Shp. Wt.. H lbs. used as a miúlammetor too. Is 2.n iln for ITEM NO. 50 Mounting. atndCldcnlgned é Your Price $6.95 STILL OPENINGS FOR RADIO OPERATORS cover. Shp. WI 2 lbs. Graduates of the course at Treasure ITEM NO. 35 VARIABLE SPEED UNIVERSAL MOTOR Your Price $1.25 Island will be assigned to radio locator POR 110 VOLTS, A.C. OR D.C. not Made cor Dictaphone machine. by_ Gramophone technical and maintenance work, to POWERFUL ALL -PURPOSE INDUCTION MOTOR con- They will be rated as petty -101 USES coodit own.' Spacial ever radio operating. IDEAL FOR EXPERIMENTERS trol permits variable epeOda as Sturdily constructed to precision officers as high Chief Radioman. If shaft Sxt.nnd. rroom,;' both standards. this self - darting ides off motor. Measure. qualified for this rating, they will be paid shaded Dole A.C. induction 7 va" a e diem. overall. motor Is powerful enough for a Oho. Wt. SW ms. $99 a month, plus the allowances specified large variety of Uses. Some of above. these are: Automatic Timing ITEM NO. 11 Devices. Current Interrupters, your Price ... $1.55 Although the majority of the graduates Electric Fens. Eleetrle Chimes. Window Displays. Photocell Con. will be assigned to this special work, open- trot Devises. Electric Vibrators. ings still exist for those who wish to be- Small Grinders. Buffers and AMAZING BLACK LIGHT!! come But the Navy's particular Polishers. Miniature Pumps. Violet Bulb operators. Mechanical Models. Sewing Ma- Powerful 250 -Watt Ultra- need today is radio locator experts. To chines. Phonograph Motors. Cof The best and mat prac- for fee Grinders. Motion Picture tical source of ultrcvlolet obtain and train these men is the purpose Projectors. Motorized Valves. light for general experi- Sirens. and other applications. mental and entertainment of this new course. Con un about 15 walls of we. bakes all fluorescent To reduce the possibility of damaging Dower s and s has s speed of 3.000 substances brilliantly' lumi- r.p.m. When geared down. this nescent. No transformers of enemy successes at distant naval bases, the Fits any sturdy unit will constantly operate an 18 -Inch turntable any kind needed. Navy needs radio men -and it needs them loaded with 200 lbs. dead weight -THAT'S, POWER( standard lamp socket. Made The motor Is of midget dimensions, 3 inches high with special filter glass per- now o n l y by 2 inches wide Dy I Inches deep; hus 4 COBlenient mitting ultra-violet to come through. Brings mounting Hods; shaft Is ?4" long by 3 /IS" diameter. rays and runs the out beautiful opalescent hues in self -aligning oil- retalning bearings; of mate- beet materials. perfect precision assembly and rigid in various types Inspection certify anti assure long rials. Swell for amateur to In high duality, to ob- Designed for 110.20 volts. 50.60 cycles, A.C. only. Duties. plays, etc.. WANTED! life. Rise RADIO OPERATORS ITEM NO, 147 tain unique lighting eiec e. Bulb only. of bulb. YOUR PRICE $1.29 Shp. WI. I lh. WAR Department, Federal Communications ITEM NO. 87 $2.00 Commission, Civil Aeronautics Adminis- YOUR PRICE 100 POWER TELESCOPE LENS KIT tration, Coast and Geodetic Survey, and other Government agencies are needing radio operators. O Make your own high powered 6 WESTINGHOUSE WATTHOUR METER Persons are needed to stand regular watch for O ft. leleseoDel Now you can thrill Completely overhauled and ^-- toe la eup view of the worlds for immediate service.ice. the transmission and reception of radio messages out in apace. See the rings DnyDesignedesigned for regular some oper- ole 2.wi e A.C. and other communications. In eases .!round Saturn. the mountains of 00 it moon! contains 3" diem., circuit. Servicemen ators will be responsible for the maintenance and the Kit in heir sbmta to cheek focal length. ground of ption of se operation of a radio station and its equipment. polished objective lens and 2 suoldering Irons, . Keens others they may have to transmit messages by e Armlomleal eye -pieces, 50x and 100x. a down. If dismantled. in matlon the parts alone would kit vith full instructions. brine the price The teletype as well as in code. ITEM NO. 123 could e To fill the jobs. which pay $1.620 to $1,800 a YOUR PRICE $1.95 as counter chines of is Ó1 kinds. year, an examination was recently announced by NEW -EXTRA LARGE LENS KIT- contains com- Simple to install: 2 wires the Civil Service Commission. Because of the pletely finished 4" diameter ton- heal length ground from the line then sturdily tycoon. vacancies which exist applica- and polished objective lens, three ly" diameter eye- xlncted In heavy metal large number of pieces 0101ng 66g, 1330, and 201)1, an aluminized se. Sleet 81,4" high. 6V," tions will be accepted at the Commission's Wash- w-Ide. da tI. oven! . diagonal for overhead viewing, and a cola filter for 5" notice. Inserl inn In y eyepiece. Shp. wt. 14 Iba. ington office until further ITEM NO. 123Lí ITEM NO. 33 While no paid experience is required, applicants YOUR PRICE "P$3.95 Your Pila $4.50 for these positions must shots that they are able to transmit and receive messages by radio- HUDSON SPECIALTIES CO., 40 West Broadway, N.Y. C. telegraph at a rate of 20 words a minute. trans- ow hand or bug. For some posi- NOW ORDER FROM THIS PAGE. mitting either by IT'S EASY TO ORDER -CLIP COUPON -MAIL who can operate a r tions persons are needed regular typewriter at 40 words per minute, or CO., 40 West Broadway. Dept. RC -9/42, New York, N. Y. HUDSON SPECIALTIES a teletypewriter at 35 words per minute. The age items I'm ordering. My full remittance of 3 ((Delude 1 have circled below the numbers of the are 18 to 55. Persons are to be rated on shipping charges) is enclosed. limits their experience or training and fitness to per- OR my deposit of 8 L enclosed (20% required), ship order C.O.D. for balance. No 0.0.0. order fer Ins than 32.00. (New U. S. stamps. check or money order accepted.) form the work. Circle Item No. wanted: II. 33, 35, 50, 87, 123, 123L 147. 140 Operators who are interested in this work and who would be available for Government employ- Name Addren ment are urged to secure the proper application forms from the Commission's representative at city gnu first- or second -class poet offices, or direct from register letter if you rend cub Or stamps. Beod remittance by check. stamps or money order; the Commission in Washington. RADIO -CRAFT for MARCH, 1942 - SER''ICING- GRID -BIAS Resistor Values ALFRED A. GHIRARDI, B.S., E.E.

THERE are man in- tances when the When making all such calculations be sure serviceman has no ready means Reprinted from new 2nd revised edition of of the RADIO Trouble Shooters Handbook. to determine first: identifying the value of a faulty bias Copyright, 1941, Radio & resistor Technical Publish- (1) the net plate voltage at which the -as in the case of "Orphan," ing Co. Copyright in Canada and Great Brit- tubes are working "Special Brand," or other receivers employ- ain, and all countries subscribing to the ing Berne Convention, by Radio & Technical (2) the net screen voltage (if a tetrode a special and unfamiliar resistor color Publishing All code (or none Co. rights reserved. or pentode) at all), and for which no (3) the correct value grid schematic circuit diagram with resistor of bias voltage values is readily required at these plate and screen available. for both of them, the resistance value of voltages the bias resistor to be employed is usually NET "PLATE VOLTS" (4) the plate and screen currents for one AND "SCREEN VOLTS" half of that specified in the chart for a tube at the given net plate and screen It must be remembered that the net "plate single tube of the same type and operating voltage voltage" (voltage actually existing between at the same plate and bias voltages. This is (5) the number of such tubes passing plate and cathode) is equal to: true unless stated otherwise in the table. their cathode currents through the The wattage rating of the bias resistor bias resistor. Net plate voltage = Total B- Supply vol- employed for the push -pull arrangement Remember that the net plate voltage alone tage - (voltage drop in plate -load re- should be the nearest commercial size that (not the total B- supply voltage) determines sistance + grid bias voltage) is approximately double that of the bias the correct value of grid bias which must Similarly : resistor specified for a single tube. be applied to the tube by the grid -bias re- Net screen voltage = Total B- Supply vol- sistor. tage (voltage drop in HOW TO "CALCULATE" - screen resistor BIAS -I- grid bias -RESISTOR VALUES voltage) HOW TO It is the net voltages Although the correct self -bias resistor CALCULATE BIAS -RESISTOR (which are, there- "WATTAGE" SIZE fore, always less than the B- supply voltage) values for all present tubes are tabulated in that alone determine the correct value of the chart mentioned, it is well for the serv- After the necessary "resistance" value of grid bias to apply to the tube. The reasons, iceman to know exactly how to calculate the the grid -bias resistor has been calculated, therefore, for compiling this grid -bias re- resistance and wattage ratings of the self - attention must be directed to see that the sistor chart* on the basis of net "plate volts" bias resistor required, for any tube or tubes actual resistor selected is of sufficient size and "screen volts" are: under any specified operating conditions, so and heat dissipating ability (wattage rating) to carry the (1) that it is easier for that he will understand how to calculate current without excessive the serviceman bias resistor values temperature rise. The actual wattage dis- to refer to standard tube data when for all new tubes which are brought out in the future. The grid -bias sipated in a resistor can easily be calculated the net "plate volts" and "screen volts" from are specified resistor value for self -bias is given by the the following formula (which is de- following formula: duced indirectly from Ohm's law) (2) that since it is the actual net "plate E, X 1,000 volts" and "screen volts" applied to E' the tube R - Watts that determine the correct (Ib =- grid bias to apply to it, + Ir) n R if one is to where R the grid -bias resistor value in determine the correct grid bias and = where E = the voltage drop across the grid -bias resistor ohms resistor (volts) to use, he should the grid -bias required know the net "plate volts" and "screen E,= in volts (at R = the resistance in ohms volts" the plate and screen voltages at actually being applied to the which When selecting the actual resistor for a tube the tube is operating) given use, the wattage value given by the In some Is = the plate current of the single foregoing formula circuit arrangements, particular- tube, in milliamperes should he multiplied by ly in resistance- coupled amplifier circuits from 2 to 10, depending upon such factors employing high resistances ¡e = the total screen current of the as the amount of air circulation, mounting in the plate cir- single tube, in milliamperes cuits, the voltage -drop in the plate load n position and proximity of other heat -pro- may be appreciable, and = the number of such tubes passing ducing parts, which will exist when the the actual net "plate their cathode volts" may be considerably less than the currents through resistor is mounted in the place provided "B- supply volts." the grid -bias resistor for it. For a given wattage dissipation, the For triodes, the screen current term, I, larger the resistor, disappears, and no the lower will be its DETERMINING CORRECT BIAS screen voltage need be operating temperature WHEN NET considered. per unit of surface PLATE OR SCREEN VOLTAGES DIFFER area. FROM For tetrodes, the "screen current" is that THOSE SPECIFIED of the single screen grid. It is well, also, to remember two useful For pentodes, the "screen current" is the CUT -OFF BIAS VOLTAGE mathematical relations for determining the sum of the screen -grid and suppressor grid Since servicemen must often replace vol- correct grid bias voltage to apply to a tube currents. ume controls which vary the grid bias on when the net plate or screen voltages being For pentagrid converters the plate, total one or more tubes in the receiver, they applied to it are known. These are: screen, and oscillator plate currents must be should be familiar with the matter of "cut- (1) For Triodes: off" bias and the formula for calculating it. First, look up (in a Grid Bias Resistor Chart)* the bias volts specified for a net plate The "cut -off" is the point where plate cur- voltage nearest to that actually being applied to the tube. Then, rent ceases to flow as the grid voltage is Desired Bias actual net plate voltage being applied made increasingly negative. In grid -bias type volume control circuits, the volume Specified bias nearest specified net plate voltage control resistor value should be such that or, Desired Bias = the control range is never extended into the specified bias X actual net plate voltage being applied "cut -off" region, otherwise serious distor- nearest specified net plate voltage tion will result. For triode tubes, the form- (2) For Screen -Grid Tubes: ula for the "cut -off" voltage is: First, look up the bias volts specified for a net screen voltage nearest to that actually Plate voltage being applied to the tube. Then, "Cut -off" voltage = Desired bias = Mu specified bias X actual net screen voltage being applied It must be remembered that this simple nearest specified net screen voltage formula applies to triode tubes only. It cannot be used for calculating the "cut -off" BIAS -RESISTOR VALUE FOR TUBES added to obtain the total cathode current IN PUSH -PULL bias voltage for tetrodes, pentodes and term represented inside the parenthesis in variable -mu tubes. The Tube Characteristic When two tubes are operated in push -pull the formula Chart and the Grid -Bias Resistor Chart and a single common bias resistor is used The required "resistance value" of grid - previously referred to give the "cut- bias resistors be *See pate 54T-Ohirerdl's "Radio Troubleshooter's Hand - can calculated in this way off" voltage values for these more compli- boòk" -2nd revised edltlm. for anv tvne and anv mrmtrar of fn},oe ro }Prl }anse of enñae

RADIO -CRAFT for MARCH, 1942 423 SERVICING TROUBLE FOR YOU IN '42 HAROLI) DAVIS`

COILS WITHIN THE IRON CORE

NEW

PLASTIC OLD CHASSIS (METAL) COILS OLD MÉTAL PAINT 60 CYCLE TRAP (GROUNDED) HI-EFFICIENCY SHIELD A.0 I-F TRANSFORMERS NEW OLD DYNAMIC DYNAMIC OLD NEW LARGE IRON CORE CARDBOAR SHIELD GLASS II l METAL TUBES LARGE INSTEAD MAGNET PAINT COIL VERY SMALL OR OF METAL FIG.2. TIN FOIL TO INCREASE COATING EFFECT OF, LARGE MAGNET. AIR AIR GAP ALUMINUM GAP IS VERY LOUD SPEAKERS- SMALL SHIELDS 5 CONDENSER SIZES ONLY-

a sizes of condensers instead of Among the problems which will confront the Serviceman in the "war months" ahead, he will find only few a minimum, and parts requiring aluminum and copper several hundred for his servicing requirements. Again, tube types will be cut down to will be reduced almost to the vanishing point.

The "nigger in the woodpile" of course possible to obtain. In fact, plain tin wire is IF necessity is the mother of invention, spaghetti slipped over the old girl is certainly being kept busy will be replacement parts. In case you now being used, with se. Not for insulation. these days. What I With the OPM haven't heard, they're gettin' scá snatching away materials as fast as in- only getting scarce, but the ones they plan These five types will have to suffice, and genious scientists can develop them, and the on giving us are about on a par with those to answer in advance the questions of those whole nation hitting a new high in sales we tumble around in our `junk box" every who want to know how they are going to and business upturn. And the changes being day. put them into the "peace-disturbing" made to cope with this situation by radio Typical of what may be expected in the midgets, in the words of a well -known radio parts and set manufacturers will leave their future is the electrolytic condenser. When engineer, "build an annex!" And he didn't signs on the radio serviceman. the RMA committee appointed to see what smile when he said it! For years now, the serviceman has been they could do about this business, started This and many another "How" is going taught not to fool with patch- work -to checking the thousands of types and to have to be answered by the serviceman localize the defect and then throw in all new varieties being manufactured, they were himself. When the manufacturer was court- parts in that particular circuit, if the case amazed. No wonder there was an aluminum ing your business, he tried to give you the showed the slightest tendency of becoming shortage! Hundreds upon hundreds of con- things you wanted. If you wanted a con- stubborn. densers, each different from the other only denser with a red band around it, he made Good servicemen have been those, who, in the length of the leads or the shape and it. Today the manufacturer believes you are when a defective section of a condenser color. old enough, so that your wants will not hurt bank was found bad, threw in a complete you. They are certainly not going to hurt done new bank of the exact duplicate variety, 5 CONDENSERS -TAKE 'EM OR LEAVE 'EM! him. The OPM has already that! did the job up so that it rivaled the original Needless to say a stop has been put to factory installation and prided himself on I has -F TRANSFORMERS not having wasted much time. Well, in a this. A strong standardizing program the gone into effect and the replacement trade But the electrolytic condenser isn't few months we are going to look back and - not going to get. We are Yes, which means you, as a serviceman -have only thing we're say, "Those were the good old days ". not going to get some I -F transformers, too. it appears that in a few more months, time been promised five puny condensers with the nation's And, the ones they are going to give us are is going to be the thing of which we have which to take the hum from their own de- fact radios. These five consist of 20 mf. 150 v., so camouflaged that even the mostest! And this, in spite of the signer wouldn't recognize them. that the telephone will be ringing off the 20 mf. 450 v., 25 mf. 25v. (for cathodes), down on their 8 mf. 350 v. and 8 mf. 450 v. Moreover, It all started when some guy discovered wall, and customers will be manu- knees begging for attention. they will be in a cardboard container with that it took 9 pounds of copper to So what ? So they Radio engineer, Designer and Writer lugs, wire being an item which is almost im- facture 1000 I -F coils. 1942 424 RADIO -CRAFT for MARCH, SER \ /ICING cause of improper functioning is alignment broad in tuning but its secondary is quite trouble. Due to the limited transmitting sharply tuned. For best possible alignment scope of FM, a number of stations located here it is advisable to use a sweep -modu- some distance apart may be on the same or lated signal generator used in conjunction adjacent frequencies. Usually this will not with an oscilloscope. The signal generator cause trouble because, unlike AM, if two should be tuned to the middle of the I.F. signals are received at the same point on band and the secondary aligned at the peak an FM dial, the signal two times or more frequency of the I.F.s. With the method stronger than the other will be heard to described, proper discriminator alignment the exclusion of the other signal. Sometimes is indicated by a crossover pattern on the the receiving location may be midway be- 'Scope. A properly proportioned pattern tween two transmitters so that both signals with lines of equal length represents an are received with equal strength. In this ir equal voltage output from both diodes. The case antenna rotation will usually cut down 'Scope is connected so that its vertical de- the strength of one to its exclusion. The bet- flection plates are connected across the out- ter sets use R.F. stages but there are no put resistor network of the discriminator, special precautions as regards aligning these and the signal generator is fed into the grid stages. Their purpose, as in AM sets, is of one of the preceding I.F. tubes. Synch image elimination, to prevent signals at pulses from the sweep circuit are fed into I.F. frequency from causing interference, the 'Scope to keep the pattern stationary. and for whatever gain can be obtained. To Proper alignment procedure is to adjust further prevent I.F. interference, wave the discriminator transformer primary for traps are used in the I.F. circuits. Where maximum amplitude of the entire crossover they are not used, and I.F. interference is pattern, and the secondary for proper posi- had, it may be necessary to insert such tioning of the crossover point, midway be- traps in the circuit. Frequently re- alignment tween peaks. of the I.F.s will eliminate such interference. Alignment can be done with an AM signal A glance at some standard I.F. circuits will generator in the following manner. Connect show that common practice is to load the a VTVM across one diode load resistor as I.F. transformers with resistors so as to meter feed an output and the unmodulated Performance . . Eye Ap- broaden their response in order that they signal at I.F. frequency into one of the peal Value Sen- will pass the wide band of frequencies re- preceding I.F. stages. Adjust the dis- sationally Priced at S19.65, ve quired. This method, of course, results in criminator transformer primary for maxi- Dealer Net Price low gain, but should one of these resistors mum deflection. Then connect the VTVM Here k an AC -DC VoltOhm- Milllammeter with open or change its value sufficiently, the across the entire resistor network ads the ranges you want Iasily readable on of the the large 7' instrument with extra -long 6" scale. high mu tubes used in the circuit would both discriminator diodes and adjust the in a w up -to- the -minute thr e -tone c a DC cause a considerable change in the I.F. re- Volts 0-10 -50- 250 -500 -1000 at 5100 Ohms per volt secondary for the equivalent of the cross- DC: 1000 ohms per volt AC. AC Vets 0- I0.50- sponse curve. If no oscillation is caused this over pattern, which in this case will be the 250 -1000 at 400 ohms per volt: DC Ma. 0 -1 -I0 -100; Resistance ranges; 0 -1500 Low Ohms; 0- 150.000 will not be too serious, as the limiter will point at which zero deflection of the VTVM Ohms and 0 -7.5 and 0 -IS Megohms. Maroon case usually flatten the curve if it is not too will occur. This is because at the proper with red and silver panel. attached handle. extreme. For a common cause of I.F. oscil- alignment point the voltage output of both Dealer Net Prise, $19.65 lation, look at the loading resistors. diodes is equal but opposite in polarity. The For Catalog Write -Section 31,; College Drive One of the principal advantages of FM VTVM connected across the entire network reception is the relative absence of noise. reads the resultant voltage which at this READRITE METER WORKS, Iuffton, Ohio Almost all noise caused by natural or man- point would be zero. made static is eliminated or cut down to a The alignment procedures discussed are point where it is not heard through a the critical ones. As concerns the oscillator, carrier. Noise caused by defective com- R.F. and Mixer stages, these are aligned GETS DOWN TO BUS /NESS ponents and tubes is not eliminated, how- exactly as are the equivalent stages of an ever, and is a frequent cause of complaint. AM receiver. RCP Test Equipment The signal tracer is the best means for dis- covering sources of such noise. Because of ..priced down, tool the high frequencies used, the field strength WGEO and WGEA Beam News to You are just as determined around wires is considerable and for this Europe: -Co-operating in one of the great- as the est American to out thend to n entlals for reason signal tracing probes must be shield- est short -wave radio projects ever under- e duration fthe cemergency. a stir ri v. then, for ed right douai to their ends. Placement of taken in this country, WGEO and WGEA, eia in the ent equipmentr you buy nay. .. parts is also very critical and when making powerful international stations of the G. E. ore for test instrument than You need? Not if you replacements the serviceman must be very Co., in Schenectady, N. Y., have revised are of the thousands changing over n these critical careful to locate the new part exactly where their schedules to send a continuous stream limn to CC tnt Equipment. In designing this low -cost line. RC engineers got right the old one was or oscillation will frequently of news to Europe, from 10:00 a.m. to 6:00 down to business, saving materials for defense . money for you. Every essential is yin every result. Moving a by -pass lead from a p.m. six days a week (approximately 3 :00 model in the complete RCP line, engineered ahead to increasee your efficiency. enable you to handle more jobs grounded point on the chassis by as little p.m. to 11 :00 p.m. in Western Europe and lees tim Only the `thrills" have been eliminated!llminaeedl That' why `today. more than ever. it pays specify as one -half inch will frequently cause 5:00 p.m. to 1 :00 a.m. in Eastern Europe). RCP test equipment-and get what you for. trouble. The new schedule includes broadcasts by Ak for CATALOG NO. 125 Just oft Press In aligning the limiter stage a departure WGEA in seven languages-Swedish, Fin- from AM alignment procedure is necessary. nish, Italian, German, French, Portuguese, In AM work, a weak signal below the and Spanish, and by WGEO in Spanish, RADIO CIT AVC threshold is desirable. In FM work a French, and English. It is now in effect. PRODUCTS COMPANY, IN signal strong enough cause to the limiter In addition, WGEO will continue its 15 se PARK PLACE NEW YOR grid to draw current is used. This will minutes of news sent out six evenings a cause loading of the I.F.s and a change in week in Czech and its Sunday afternoon resonant peak and for this reason the broadcasts of news in Greek. OUR SUPER SPECIAL limiter transformer is aligned first, feeding WGEA, which will be beamed to Europe _ - the signal into a previous I.F. stage. The on 15,330 kilocycles (19.56 meters), oper- RCP 411 -- output indicator is placed across the limiter ates at 50 kilowatts. WGEO, which will Supertester grid resistor is AVC source. on 9530 kilocycles which the broadcast (31.48 meters), Complete 319.07 After the limiter stage is aligned we with its license for 100 kilowatts is the most Only align powerful short-wave Hero', a tester the other I.F. stages, leaving the station in the western designed for top output meter in the same circuit and ad- hemiçphere. efficiency. Flo' justing for maximum deflection. After the .Jena of 33 In- I.F.s are aligned, we turn to the discrimina- dividual instru- tor stage. This portion of the circuit is 51nts. range AC -oC voltmeter le from O to 5 000 equivalent to the 2nd detector of our AM :. volts. AC -DC amps from 25 . DC !MER AL - set functions in 1na. C is O to 0-200. AC ill, but a different manner. In ' WC r yÓa completer took of ORadio B City iaoducts operation it is similar to an AFC dis- Teat Instrume ts. order today for prompt del very REPLACEME protection against rising priors. criminator stage. Its purpose is to convert you on your Radiio needs!Ask foror fret catalog. variations in frequency to variations in ¡kW "WY amplitude at audio frequencies. The dis- i ADSON RADIO CO. 221 Fulton St.. New York. N. Y. criminator transformer's primary is quite

RADIO -CRAFT for MARCH, I 9 4 2 429 SERVICING

Operating Notes DISPOSAL SALE' . ZENITH 6D410 r Complaint: Dead. Trouble sometimes can AMPLIFIERS & PARTS be traced to a shorted 0.03 mf. by -pass condenser connected from the primary of out- THIS sale comprises parts used in put transformer to cathode of 35L6G type the construction of Juke -Boxes; tube. Replace to make set operative again. made by well known amplifier manufacturers such as: Rauland and CROSLEY 855 Operadio. All equipment is recondi- Complaint: Tunable hum. A loud hum tioned and in perfect mechanical and when a station is tuned in and which can be electrical condition. eliminated when you slightly offtune can be traced to a defective 8 mf. electrolytic Photo shows condenser. This condenser is one of a 30 watt ampi. group of 3 condensers in the same can and is located under the chassis. Replace the whole can of condensers to avoid future trouble and the set will play OK.

CROSLEY 635 Complaint : Whistles. Check the 0.02 mf. OIEX condenser located between the screen grid RID and cathode of the 6A7 tube; replace -to Sound Systems stop whistle. . RCA RC-457 411 anlpl. shipped Complaint: Distortion. Check the 0.01 Ready to operate for Every mf. coupling condenser between plate of 2ní1 12 WATT PUSH -PULL 2A3 AMPLIFIER Tube complement 2- 2A3, 1 - -5 . l-e7 and 1 -5Z3. detector and grid of output tube, replace To be used with one or two 2500 ohm dynamic speak- condenser and check output tube, so as to ers 18 ohm volet colt May be changed mer to use Requirement P.M. speakers. Input for magnetic pickup. Variable be sure to clear up trouble. tone control. Schematic furnished to change unit over JOHN STEPHENS, to use crystal pickup, crystal microphone Come to Radolek - Public Address Head- d P.M. speakers. $8.75 quarters -where you get more for your mon. York, Penna. Shipping Weight 25 lbs. W ey Dependability in Performance, Styling, 15 WATT PUSH -PULL 655 AMPLIFIER and Reserve Power. Radolek Deluxe PA Tube complement 2-6R5, 1 --6A6. 1 -76 and 1-6Z3. Sound Systems, in 15, 30, 50 and 100 watt . . SENTINEL 240 -W FARM RADIO SET To be used with one or two 2500 ohm dynamic sizes, every desirable feature dead. One of speakers 16 ohm voice coil. May be changed over to incorporate - Inoperative. Oscillator Vari- multiple input channels, built -in input and screws, which mounts tuning condenser to use P.M. speakers. Input for magnetic pickup. mixer controls, AVC, "feedback" tone control able tone control. Schematic furnished tu change chassis, touching plates of oscillator section. unit over to use crystal pickup. crystal circuit, output impedance selection, elec- microphone and P.M. speakers. tronic mixing system -all engineered for plus It may be a good idea on sets of this model Shipping Weight is lbs. $9.85 performance. Models for permanent, portable still to be sold or that come in for other 30 PUSH -PULL 6L6 AMPLIFIER or mobile use. Wide choice of microphones, WATT service note the position of this screw Tube complement 2 -6L8, 1-SA8. 1 -C8, 1-6Z3, speakers and related apparatus. to amplifier as is. has Input for magnetlo pickup. volume and to replace with shorter screw or use a control, variable tone control. Supplies field current the Best at Lowest Cost to one or two 2500 ohm dynamic apeaken. output Get washer if it is close to touching condenser impedance Y.e, 3.2. 4, 5.3, 8. and 16 ohms. Full Redolek's modern direct policy and volume plates and this is usually the case. 30 watts output. Schematic furnished to change unit over to use crystal pickup and crystal, dynamic estes on every amplifier design make it pos- SYLVAN SIGMUND, or velocity microphone and change over sible for you to get the finest, most modern Sigmund Television Service, to use P.M speakers. equipment at rock bottom prices. Thousands Shipping Weight 25 tbs. $12.05 of successful Radolek PA installations are Peruque, Mo. proof of quality, dependability and top AU Amplifiers Less Tubes & Speakers. performance. Send the coupon today for complete information) . PHILCO 1940 -41 Complaint of pushbutton drift off stations JENSEN IO INCH EVERYTHING NEW IN RADIO on a Philco 1940 -41 with permeability tuned ELECTRO- DYNAMIC oscillator on pushbutton tuning can be cor- SPEAKER Radolek stocks every replace- rected by replacing dual 370 mmf. fixed ment part to repair any radio - 2500 OHM every type of tube - every- condenser that is placed across the oscilla- FIELD thing for auto radio installa- tor circuit, with a new Philco part or two 16 ORM tions, transfer and repair. silver mica condensers of approximate VOICE-COIL . t value. EACH $2.95 , MARSHALL WAGNER, Shipping Weight 7 lb.. RADOLEK'S Baltimore, Id. RADIO SERVICE GUIDE R.C.A. MAGNETIC . . RCA Contains hundreds of up- Defective crystals on record -players are PICK -UP HEAD to -the- minute service IMPEDANCE 3000 OHMS items, test equipment, usually easily detected by pressing on the sound apparatus, eta- at side of the tone -arm while playing a record. SMp. weight I lb. EACH $1 .89 lowest prices. Indispen- Press toward, then away from the center of sable to every serviceman, dealer and sound engi- record, noting change in volume. Be sure NATIONALLY ADVERTISED TUBES neer. Radolek gives you that the needle is a good steel one when (in sleeves) what you want when you making the above test, as some special need it. Send for your 6L6G 6N7 56 copy of this great new needles give a misleading effect. 6B5 53 57 Radolek catalog today) MARSHALL J. WAGNER, 2A3 6A8 6C6 Baltimore, Md. 76 - Fast Service 5Z3 Large Stocks Each .49 Each .30 Each .25 EMERSON AC -DC 1941 .. Ship. weight ca. 8 oz. Additional tubes 4 oz. ea. a hum In cases where sharp sixty -cycle DAY AS that sounds like an outside interference is ORDERS SHIPPED SAME disappears when RECEIVED. All goods are sent Ex- heard, the trouble usually Parcel is tuned in. Replace 20 -20 press collect if no money for RADOLEK CO., Dept. C -64 a strong signal mf. filter condenser. Post is included in remittance. Cus- 601 W. Randolph St., Chicago, III. MARSHALL WAGNER, tomers in Foreign countries are re- Baltimore, d. quested to remit in U. S. currency or Please send information on Radolek Publio International Money Orders and in- Address Equipment - also the Big Radio money to ship goods Service Guide. . , . GENERAL ELECTRIC HB-403 clude enough prepaid. Order from this ad. Name Complaint : the set would distort ; the resistance of the diode load, the volume 25,-, deposit required on all C.O.D. orders. Address-_ -. control, measured ten megohms. It should PEERLESS RADIO have been 1 meg. Replacement was made, and trouble cured. AND SOUND CORP. Dealer Serviceman Sound Eng. WILLARD MOODY, 25 S. JEFFERSON ST, Dept.342 CHICAGO, ILL. L- J New York, N. Y. 1 430 RADIO -CRAFT for MARCH. 1942 SERVICING

BOOK REVIEW Ib, READY RADIO SERVICING For SSE HOOK, 5th Edi- dL.L r, 'itl,r 'i ,,, GET tion. (Reprinted in 1941.1 Published by Supreme tulles, triodes, gas diodes, thyratrons and igni- Publications, Chicago, III. Size 8% x 9°) ins., trons. stiff paper covers, illustrated. Price $2.50. The motion of charged particles in electric and magnetic fields is discussed and the practical FOR A REAL This book was prepared by the staff of consult. application of this phenomena to such devices as ing engineers and instructors of the Radio Tech- cathode ray tubes, the cyclotron and the mag- nical Institute. The subject material has been se- netron. lected from the latest sources and is up -to -date. Other topics which the engineering student This book is especially adaptable for "home must understand today are the kinetic theory of study" use. The material is presented in twenty - gases, electrical discharges in gases, how recti- two lessons. At the end of each lesson a series fiers work, photo -electricity, triode characteristics, RADIO CAREER! of questions are given, in order to enable the the action occurring in multi -electrode tubes, reader to test himself on the knowledge he has voltage amplifiers and various types of audio acquired in the lesson. frequency power amplifiers. Some of the lesson titles are: Elementary Elec- This 722 page book is a must for the radio tricity; Radio Batteries; Radio Frequency In- student who wishes to know exactly what is ductances; Radio Tubes; Meters -Testing Meth- going on inside a vacuum tube. The subject mat- Make 1942 Your Year! ods; Elements of Radio Transmission; Photo- ter is the result of class -room experience in electric Cells. teaching radio engineering to students at the Throughout the book very helpful charts and College of the City of New York. diagrams are given. The Radio Tubes Characteris- tics charts and the Reactance and Resistance in I. C. S. Radio Courses, Studied at Parallel line graphs are especially interesting. Arso PERPETUAL TROUBLE SHOOTER'S MAN- the "service hints" given on various sets, includ- UAL, Vol- XII, by John F. Rider (1941). Pub- Home, Prepare You Jar Part -time ing Belmont, Crosley, General Electric, Majestic, lished by John F. Rider Publisher, Inc. Hard RCA and many other sets are very helpful to covers of looseleaf binder 9 z II% ins.; pages or Full -time Rado Jobs! the Serviceman in general. measure 8% z II ins.; volume is 4 ins. thick, has 1,648 pgs. Price $10. MOST -OFTEN -NEEDED SERVICE NOTES ON During 1942, many thousands of men will RECORD PLAYERS, AUTOMATIC CHANG- The new Vol. XII, "Rider Manual." in addition achieve success and prosperity in the grow- ERS, WIRELESS UNITS AND HOME RE- to being a compilation of servicing data, intro- ing field of radio. Will you be among CORDERS. compiled by M. N. Reitman (1941). duces something new in manual make -up: Published by Supreme Publications, Chicago, Ill. "Clarified Schematics." them? You may be -if you get the sound, Size 8% z 10% ins., stiff paper covers. 128 pages. In this new section, involved circuit arrange- practical training that is essential to suc- The first eight pages in this book present gen- ments in more than 200 receiver schematics are cess in radio work. eral information and apply to all makes. Through- dissected and individually diagrammed for con- A few hours of your leisure time each out the book many different units are described, venient reference. This eliminates the necessity especially automatic day -in the comfort of your own home - record changers and recorders. of "buzzing out" a circuit during servicing, to may qualify you for big earnings in this While these units are listed under one specific determine the continuity of manufacturer, they are actually used in combina- a circuit not readily field. And studying an visualized in the complete receiver diagram. Time rapidly expanding tions of other makes. This is true, since many I. C. S. Radio Course is a thrilling adven- different manufacturers have used the identical is also saved because individual circuits are record- changers and recorders. available for study. for possible sources of trou- ture in practical science. By becoming familiar with all the data included ble, even though the master diagram shows only Every one of the five I.C.S. Radio Courses in this manual, the reader will be able to find one of the possible circuit arrangements (as for includes Frequency Modulation and Tele- the material needed more quickly and will also example where the master diagram shows is learn all the important facts dealing with auto- vision -and designed to enable you to switches in position for Band 1 reception, but capitalize on the profit -opportunities which matic record changers, home -recorders, phono play- Clarified Schematics show additional positions ers, and wireless oscillators, so that he will be able of these new developments are opening to to repair the units of similar types not listed in the switches [Band 2, Phono, etc.].) trained men. this book. The master diagrams include not only circuit Some of the companies represented: Wilcox- arrangements but also essential servicing data Your Choice of 5 Courses Gay orp., Belmont Radio Corp., Detrola Corp., such as intermediate frequencies, operating volt- RCA Manufacturing Co., Inc., and many others. ages, alignment frequencies, coil resistances, For those who wish to secure broad, corn - The fact that the book is profusely illustrated ratings of components, dial cable adjustments, prehensive training, I. C. S. offers a Gen- makes it easy to follow the instructions given. etc. The cross -index of Vol. XII, a separate eral Radio Course and a Radio Operating 44 -pg. booklet, also covers Vol. XI; the many Course. The I. C. S. Pract - cal Radio Ser- PRACTICAL RADIO MATHEMATICS -A Book- hundreds of radio receiver models shown by com- vicing Course enables you -o begin practice let for Home Study, by M. N. Reitman. Published plete schematics by Supreme Publications, Chicago, Ill. Stiff paper in Vol. XII cover sets made soon after you start studying -many stu- covers, size 5% x 8% ins., 32 pages. since May, 1940. and embrace some export mod- dents pay for the course out of earnings els, communications receivers, electronic music is This book is intended for the general student, instruments and wireless record before it completed! (Note to Selectees: Serviceman and others interested in elementary players. The Radio training is a big advantage in the radio mathematics. A table of radio symbols is intricacies of automatic record changers are illus- included and the opening chapters deal with trated and described in detail. Army.) numbers, fractions, decimals, and simple radio It is noteworthy that a set of "double- spread" The Sound Technician's Course is an formulas. Pages. showing large diagrams in double- width, advanced course for the service technician. The Standard Resistor Color chart is given ; also examples of how to apply Ohm's Law, how are included. The houseorgan Successful Servic- The Sound- Picture Projectionist's to read graphs, etc. Later chapters deal with ing is sent each month to purchasers of Rider Course deals with operation, maintenance series- parallel circuit calculations. inductance of Manuals. and repair of sound equipment. such as is coils, reactance and impedance -and their calcu- used in talking -picture installations. lations, amplifiers and calculation of the ampli- RADIOTELEPHONE PROCEDURE fication factors, etc. The closing section deals -U. B. One of these I. C. S. Radio Courses, or a with AIR CORPS. This booklet can be obtained for service hints, point-to -point testing, the 10 cents (cash, no stamps) from the Superin- combination, may fit you for bigger earn- decibel (with a table giving the values of differ- tendent of Documents, Washington, ent gains in DB and the power ratio values). D. C. ings than you ever dreamed possible -and Radio students will find this book very inter- at a cost of only a few dollars monthly! VOCATIONAL AND PROFESSIONAL MONO- esting as it contains descriptions and diagrams Mail this coupon immediately for full details. GRAPHS-The "Program Side of Radio," by covering such important subjects as weather re- George Jennings. Published by Hellman Publish- ports, radio call signs, radio range stations, pro- ing Company, Inc., Boston, Mass. Paper Covers, cedure for communicating with Civil Aeronautic size 6 z 9 ins. Soft paper covers, 15 pages. Administration range stations, etc. Some of the All I.C.S. Courses Price 50e. valuable data included in the appendix are -symbols of the weather report, chart of wind direc- include FM and This interesting monograph was prepared by tions, sample teletype weather reports, standard the Program Director of the Radio Council, Chi- control tower light signals, phonetic alphabet. The cago Public Schools, Chicago. Ill. It has been chapter on Range Stations is very interesting and TELEVISION carefully prepared to supply the following au- contains special drawings showing the field strength thoritative information: Personal qualifications pattern of the two pairs of towers used in required for engaging in the work ; scholastic radiating the "A" and "N" signals. INTERNATIONAL COR ESPONDENCE SCHOOLS training needed: complete analysis of employment opportunities; remunerations received: chances 1941 RADIO DIAGRAMS ON SERVICING Box 2878 -G, Scranton, Penna. for advancement: frank statement of INFORMATION. rdvantages and disadvantages; possib;lities for Compiled by M. N. Reitman. Explain fully about your course In the both men and women in the vocation or profes- This hook, measuring 84 x 1014 inches, contains subject marked X: sion. 192 diagrams most often needed by the radio C GENERAL RADIO service man. The general radio student will find ELECTRONICS. by Jacob Millman. Ph.D., and this book valuable for reference and study, as it C RADIO OPERATING Samuel Seely, Ph.D. Cloth covers, size 6% x 9% contains diagrams of the standard popular re. PRACTICAL RADIO SERVICING ceivers, C inches, 722 pages. Illustrated. Published by all the way front a pocket size set to a G SOUND TECHNICIAN McGraw -Hill Book Co., New York. N. Y. large console multi -tube job. A few of the manufacturer's sets covered will give some idea of the p SOUND -PICTURE PROJECTIONIST This volume is intended for the serious student wide scope of electronics of the volume. We find such names as and assumes that he has a good Admiral, Air King. Allied Radio, Belmont Radio, Name Arie grounding in mathematics. The general student Croslev. Detrola, can learn Emerson. Zenith, General Elec- much from this ambitious work also. tric. Philco, RCA, Sears Roebuck, Westinghouse, Address as the diagrams and text presented very clearly Noblitt- the action taking Sparks, Packard -Bell, Montgomery Ward, place in electronic devices. The Midwest, Majestic, Hallicrafters, Howard Radio first chapter deals with electronic principles, and Lafayette. City Stat RADIO -CRAFT for MARCH, 1942 431 SOUND

Two photos above show chassis and also exploded view with mike, batteries, of c. IT is difficult to understand why servicemen generally permit such a lucrative field as the hearing -aid business to be monopolized by a few large concerns, A "TOBACCO TIN" unless they are perhaps dazzled by the high - pressure (pseudo ?) medical advertising in which some of these concerns excel. HEARING AID Servicemen's standards of tone quality are generally rather high, and they have S. B. SIMER difficulty adjusting themselves to the limitations of response set by the size and power feedback, or, to a poor quality or poor - Mount the insulated binding strip one of hearing -aids; particularly those to be fitting receiver. Intelligibility is not inch from the side as shown in Fig. 7. worn on the person. However, hearing -aids achieved by cutting the lows, but by care- The exact position of each item may be are a necessity, and a lucrative business. ful workmanship and perfect tube and cir- determined from Fig. 7. Keep grid and Therefore, the serviceman should inform cuit performance. plate leads separated as far as possible- himself of the essential facts of the business, The pocket type hearing -aid, described particularly, those belonging to separate and take his rightful place in this field. here, is recommended to the serviceman tubes. Use spaghetti tubing and thin fibre These facts are as follows : as being particularly suited to his require- insulation in tight spots. (1) An instrument will not restore the ments for easily available, standard parts The output transformer or choke should easy and quick perception associated with and tubes; and, has power and quality be mounted with the iron core parallel to normal hearing and an active mind, so don't equal to any such device sold. the base plate. The transformer shown, is be discouraged if a customer doesn't under- one I bought to match a miniature receiver, stand everything said to him immediately. AMPLIFIER FITS IN TOBACCO TIN taken from an old carbon hearing -aid. The (2) The instruments overload easily, so The container is a common, smoking to- receivers on these old instruments are fair- don't try to demonstrate full power in a bacco tin (or its equivalent), which is ly good, even when the rest of the old in- noisy place or with radios on loud. given a coat of crystallizing lacquer, or strument is plain junk. Ten ohms output (3) The receivers must be of the best flock, when completed. It measures 3á" winding on the transformer will match quality, sensitive, and fit the ear absolutely thick x 3" wide x 4%" long, approximately; practically any of them ; with the exception close. Leakage of sound in the phone's rear a convenient size for personal wear. . of one make, which requires a higher im- chambers, such as through the cord en- pedance of 200 ohms. The bottom is fastened in by a fold of For all crystal phones, including the trance, must be sealed with wax to Prevent the metal over the end. This is filed through feed -back, and loss of quality. If miniature miniature, the output chokes listed should and the bottom ( Fig. 1) is pushed out and be used. phones are used, an individually molded ear- is hereafter called the top. The hinged top piece is essential ; it must fit the car and the If desired, one can make room for a tone of the tin is to be the bottom of the hear- control in this hearing -aid by using a "Half receiver perfectly -allowing no leakage of ing aid, and is convenient for inspecting sound. Otherwise, all quality is lost, and and Half" telescoping tobacco tin, and ex- and replacing the tubes without the neces- panding the two halves enough to make the high -grade microphone and vacuum tube sity of opening the entire instrument. amplifier are of no -reat benefit. room for the other control. In this case, Most any dentist can and will insert a The top will be replaced in the tin -up- the cords are brought in through small greased cotton plug a quarter inch into the side down -to make a smoothly rounded holes drilled in the top wherever possible. ear canal and make a plaster cast of the top of the instrument (Fig. 2). Inside the This control would be % megohm, wired ear, which can then be sent to S. S. White top, solder two 7/16" standard machine in series with the crystal receiver. 3, and & Company for a molded earpiece. washers, as shown in Fig. and punch Considerable variation of tone may be (4) A standard circuit, using standard file the holes. The hole for the switch is had by selecting the proper choke, and by parts -with the usual crystal receiver -will %" x % ". At one end the volume con- the usual tone control methods of series give satisfactory results in practically all trol is placed. The cords for the microphone, resistor and shunting condensers. cases. A few people, perhaps, have peculiar batteries, and receiver are threaded through If the user does not require the maximum hearing losses of a short frequency range, the other end hole, and the D. P. S. T. volume of the instrument, the inverse feed- rather than the usual extensive loss of either, slide switch is soldered in place in the cen- back arrangement is very satisfactory. the high, the low, or perhaps the middle tral hole. This switch is too large, and Figure 8 shows how to adapt a cheap range. These people are likely to be dis- must be trimmed down, as shown, in order two-cell flashlight case to use one cell from satisfied with any hearing aid, whether it to fit into the space allowed. (Fig. 4.) a Burgess 4 FH 1.5 volt battery. These is fitted from an audiometer hearing test Cut a piece of thin sheet metal 2A" x cells, of which there are four in each hat - or not. The usual customer can be satisfied 43ÿ" and solder on the top along the side tery, make an inexpensive and durable "A" easily by selection of microphone, receiver, for a base for the parts and sockets. supply. and circuit tone adjustment. (Fig. 5.) The writer has had the personal experi- (5) In a "pocket type" hearing aid, one Take the wafer sockets and remove the ence of being utterly unable to reconcile thing is of the utmost importance! That is excess material as shown in Fig. 6. his hearing needs with any audiometer intelligibility. A hearing aid with indis- The sockets are mounted by soldering chart. My hearing test chart shows exten- tinct and ragged response is a sure business their filament minus prong tab directly to sive loss of high frequencies ; yet, any at- loser and must be avoided. Poor results the chassis. Two and one half inches from tempt to emphasize the highs, and thus are almost always due to undesired circuit top of tin to bottom of glass base of tube. (Continued on page 434) 432 RADIO -CRAFT for MARCH, 1942 79 W2W 7jrpe O6 SjQTV[C2 M4i![[4ll RADIO CIRCUIT MANUAL -1941 The Only EDITED Manual Ever Published !

DIRECTORY OF RECEIVERS MANUFAC- TURED IN 1940 AND UP TO JUNE, 1941

MORE INFORMATION IN HALF THE NUMBER OF PAGES The valuo of a service manual is measured not b r the number of pages but by the amount of useful information. Thus. n only 736 pages this Radio Circuit Manual covers over 200 receiver models MORE than does any other competitive manual in twice the number of pages.

HOW DID WE DO IT? . . . By increasing the sire of our page; by discarding non- essentlal data and editing the balance: by listino only those receiver. which the Sers ire Engineer will definitely have to repair no communications or export receivers, no shortwave sets or amplifiers. no eI,ctronoIt devices, ete.); by many months of hard work based on a definite plan of procedure and a clear understanding of the actual reguiremen-s of the Service Engi- neer. There is no ''dead weight" information to ad 1 bulk to this Manual. Every word counts. Every minute of reading time is well spent. OUTSTANDING FEATURES Contains data on more than 1800 receiver models: -more than any other radio service manual. Only 736 pages' -less than half the bulk of any other manual and more than 1.3 lighter. All information is EDITED! -all non -essential data deleted and th, balance checked and correlated with 'he schematics and sketches. 40ee larger page permits listing of all information on one page. (A few unavoidable eases excepted.) I.F. peaks for all superhet circuits are boidly displayed in black boxes; none missing, all accurate. No space wasted on communications and export r amplifier el elronic musical Instruments, etc. -a 100°,, Service Engi- neer s Manual.

A "CUSTOM- TAILORED" MANUAL

THE OLD TYPE MANUALS -Bulky, FOR SERVICE ENGINEERS E.-. heavy, hard to handle. snare c.a..- Ing. less USEFUL data despite greater Here, at last, is a Service AI:uu:aI deliberately PLANNED for the Service number of pages. Engineer. Instead of a mere hodge -Dodge collection of service data, as manuals have been in the past, this RADIO CIRCUIT MANUAL is an orderly compilation of essential radio diagrams and service information, carefully edited and uniformly presented for the maximum convenience of the busy Service Engineer. All time -consuming, non -essential data have been weeded out, and the remaining information, vitally important to the rapid and efficient servicing of modern radio receivers, has been laid out in a logical, easy -reading style which cuts time from the day's work. Because of this and other features which are self- evident upon first 'observation. it has been possible to list all information pertaining to a given model on a single page. In 796 pages this Manual presents essential service data on over 1800 receiver models;-more than any other existing service manual on the market! ONLY ONE MANUAL PER YEAR! OUR NEW MANUAL -Lighter. com- The new technique used in compiling this RADII) CIRCUIT pact. easy to handle takes half as MANUAL - 1941 makes it possible to include in a single book all the new receiver much room on the shelf- more USEFUL :models informaton despite fewer number of which the radio industry can produce in a single year. This factor - 7,1 . pages. lobe repres. an important saving to all Service Engineers. MANUALS ORDER YOUR MANUAL NOW READY! A PERMANENT RADCRA FT PUBLICATIONS. INC., IMMEDIATELY -NOW! 25 West Broadway, INSTITUTION New York, N. Y. Get your copy directly from us by filling out Gentlemen: Enclosed $10.00. leand fling the ient coupon shown at ONLY This Radio Circuit Manual -1941 is NOT Ond my remittance of for time proposition. Next which rend me, POSTPAID, my copy of ft, get it directly from your favorite year there will be a the RADIO distributor. Radio Circuit Manual -1943. the following year, CIRCUIT MANUAL. -1941. 1943 and so on indefinitely-each Manual better rag pages; i 135/s 101/4 a in thick; than th! ther as new m thode are o ked out loose leaf, leatheroid. covered Name stiff binder; net for expeditingand implifying the work of the weight atfa lbs 1000 practicing service Engineer. Address City State RC -3 -12 RADCRAFT PUBLICATIONS, (Send remittance In (mm c4 cheek or money INC. order; register your letter If you send ra)il.) Pm 25 WEST BROADWAY NEW YORK, N. Y. RADIO -CRAFT for MARCH, 1942 433 SOUND

3 Megohmsio IO MegoMw (FeeeñorA) (according to audiometer theory for fitting .os MF hearing -aids) replacing the loss, invariably 155 caused me dissatisfaction and no noticeable increase in intelligibility. The high pitched sounds, even though made very loud, do not scent clear, and cause me annoyance by interfering with the lows, which I do understand. Therefore, in my opinion, if a serviceman adjusts the tone of an instrument to make it agreeable and comfortable to the user, he is doing all any one can do the user. Classis for IOMF 25V HOW TO FIND CUSTOMERS' NEEDS The best way to learn the requirements 6000 omu of a prospective customer is to have a s.,lch couple of sets made up, with tone control, Drill for VC. - Sw. 2 Standard machine washers. end of lin to be used by the customer for a day or Bottom See Fg 3 F,k lruh . two. If the customer wants a set with tone control -very well -it adds a profit for you, T but it won't be used much after the first J DPST month. S.wi/chf 1 The writer has noted with great interest Sokke aller recent growing propaganda for licensing conpk/ed Cords á Volume Control the ,r of hearing -aid dealers ; the argument being [ that special knowledge and skill is required with a proper hearing -aid. Clam off legs 1`n to fit a user Round corners. ' Solder This argument is not convincing to of holes. Fig. 3 anyone who takes the trouble to ascertain torte deficiency, if any, ILIIIIII ° e===': the facts. First, the is corrected by the tone control and cir- - Crawl cuit. Second, the air conduction versus bone OP may be settled by sup- conduction argument Remore ends plying both types of receivers, and per- Fig. 4 mitting the return of the one not desired. Third, it is not the province of either the licensed hearing -aid dealer, or the radio serviceman, to pretend that he is able to Solder person should or Top -N decide if a particular should not use a hearing -aid, and particularly one incorporating the miniature type air conduction receiver, with the ac- 2fx4é companying earpiece. In short -find out if the doctor says the ear canal may safely be Fg. 5 plugged by the earpiece. No large line -operated hearing -aid should be supplied with more power output than two type 6C5 tubes in push -pull, unless an automatic volume control is used. Briefly, hearing-aids represent a nice after bending Cu? oft Solder business, and price competition is not de- ¡I 1ÌI111 sired by anyone but the hearing -aid user; shut out t 111 111 licensing would be a neat way to 111111 the radio serviceman. Fig 8 The Astatic Model 218 is a good choice ¡ 111111 when the customer is extremely hard of hearing, or for bone -conduction sets. A P/os - Cen /er cunfoof -A' Minus- Solder /o case 4 Parts List RESISTORS '' 10 megs. chassis One -I.R.C., /a -W., Outside Foil lo drams F Minus -Sob*, lo u(ouy' Diode P/k- Skor/ to One-I.R.C., %M.. 5 mega. (for feedback, if desired) Two -I.R.C., 4s -W., 3 mega. II Megohm D One -I.R.C. 'A -W.. 2 megs. Three-I.R.C., }y! W., I meg. One I.R.C., 55 -w'., 10,000 ohm. One I.R.C., %Av., i.000 ohm. CONDENSERS Three Cornell -Dubilier, .05 mf., 200 V., paper. Two Aerovox, .01 mf., 200 V. "Postage Stamp" size mica condenser. MISCELLANEOUS One -"Pipe Tobacco" tin. One-Astatic Microphone Co., Model L -1 (Crys. N tal) Microphone . (with three -foot cord). or Model 218 for bone conddction instruments. Optional -Shure Bros. No. 76 -B Lapel Mike. One -Brush Development Co., A or B Crystal Headphone. OI One -Stancor Hearing-Aid Chokes (Five Part MF Numbers available for Various Tubes and Tone Response, Nos. C65, C66, C67, C75). One -Central Lab. Vol. Control, "Elf," 2 megs. One -Insuline Corp. of America, D.1'.S.T. Slide Switch. One -2 -Cell Flashlight Case. One-4 FH L5 Volt Dry Battery (contains four cells). One -Eveready Hearing -Aid Battery No. 455 and connectors. 45 Volt. One -Cornish Wire Co.. 20 ft. Replacement An- tenna Lead Wire (for A & B battery leads). Two -RCA Radiotrons, ISS. 4' One -RCA Radiotron, 3Q4. Dry Electrolytic, Fig 7 Mnus eonnec%w, here ' One -Cornell -Dubilier 'Beaver" Mòophae Ca&4 (if Capacity 8 mf., 150 Volts. -Dubilier "Beaver" 10 mf., 25 Volts. Diagram of The amplifier together with microphone, and details of construction are shown. One -Cornell MARCH. 1942 434 RADIO -CRAFT for -. Ttl 1 S 1ITUL DESK ttiv(y -D, \ QN^j W\( WITH ANY REMINGTCIN PORTABLE TYPEWRITER

A beautiful desk of handsome Walnut grain, finished with rich Burgundy top which will fit into the decorations of any home, and made of sturdy fiber board, is now available for only one dollar ($1.00) extra to purchasers of a Remington Portable Typewriter. The desk is so light child can move it, so strong it will hold six hundred (600) pounds! What a combination this desk and a Remington Portable Typewriter make -a miniature office in your home! Learn complete details of this offer. Mail the coupon today!

Remington's Amazing Combination Offer

How easy it is to get this combination of a desk and Remington Deluxe Noiseless Portable Typewriter. Just imagine, a small deposit and the balance MONEY ABACK on Remington's easy 10 pay plan. This will actually make you immediately Portable T,ieremites Ddw Noiseless beck g.n Remington asp tl.. The . viJ .,,b m 1. the possessor of this amazing office -at -home combination. You assume Is sold on bái4ru doo of days paying ilt ,h 'on.a in buvng ono obligations by sending the coupon. e4 nod,1.1nothing gn. You e pay plan. Tvpe.nd¢, on Remington

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SPECIAL CARRYING CASE The Remington Deluxe Noiseless Portable is light in weight, easily carried about. With this offer Remington supplies a sturdy.

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RADIO -CRAFT for MARCH, 1942 435 SOUND The PENETRON

Windows that whisper, walls that talk, floors that carry music, tables in night clubs that greet distinguished guests, pianos reproducing radio programs and regular disc records, automobiles that talk-are but some of the practical applications of this new sound instrument.

Photos above show front and side views of the Penetron sound reproducing instrument; it is held fo the glass of a store window by lock vacuum cups as indicated. Photo below -How easy it is to place the Penetron into a new Location -the rubber vacuum cups it in position.

ANEW and revolutionary sound repro - installation and the inconvenience. No spe- duction instrument has recently been cial tools or ability is necessary to install it. invented by Glen Holland, an indus- Simply press it against the window, run trial designer of Bronxville, New the ribbon (concealing the wires) back to York. the display or background (and thence to Mr. Holland has named it the Penetron. the amplifier), adjust the volume and col- It is made in two styles, dynamic and PM. lect your check. It's as simple as that. It embodies all of the conventional features Mr. Holland has found that the best, of either kind of loudspeaker except that and in the end, the least expensive source it incorporates a patented voice -coil and of sound for this application of the Pene- stylus assembly. When this stylus is pressed tron, is a sound track on regular 16 mm. against any hard surface such as glass, safety film. He also has a machine which wood, steel, concrete, etc., it transmits to is rented either with or without the Pene- such surface all of the vibrations emanating tron, which will pick up the sound to film; from the voice -coil. The latter is actuated it is entirely automatic. The film used in from any of the conventional sources- radio, the machine is spliced together at the ends, amplifier, electric record -player, etc. The making it endless and it can be made to Penetrons range in size from the largest, operate any kind of animated display, flash which is used in window displays and meas- lights, operate continuously, intermittently ures about 12 inches by 7 inches by 5 or at predetermined intervals. inches high, to the one used on your piano Home Use: This developed from Mr. measures about 5 incites in Holland's meeting Rubinoff, the popular at home, which Rubinoff diameter and 3 inches high. it did not disturb the neighbors across the violinist, on Broadway recently. Window Displays: The most spectacular street or next door. The same store expects was listening to the playback of some re- use it again in connection with a holiday cordings he had made of piano accompani- installation of the Penetron to date in win- to volun- dow display, was made in Franklin Simons display and this time sound will consist of ment for his violin. Mr. Holland The display a woman's voice in a whisper, reminding teered to let him hear how they would sound on Fifth Avenue in New York. placing the consisted of pastel -dyed baby chicks and a the passers -by of the event. on an actual piano. By simply microphone was placed in the brooder to The Penetron in this application lends Penetron (small size) on the sounding many uses not possible heretofore board of a piano and playing the recordings pick up the chirping of the chicks. The itself to player Penetron was held against the inside of the with the regular public address systems. (disc) through the regular record of small rubber For instance, in a display of beach clothes and amplifier, it reproduced them almost display window by means them. vacuum cups and carried the sound to the there could be the sound effects of waves as if Rubinoff himself were playing feature of this breaking on the beach and the water re- For music from popular or classical crowd outside. The special Technically it will is that the sound may be kept at a very ceding; a dude ranch display with the sound records it is unequalled. or of horses neighing and whinnying; a camp- entail cutting out the speaker of the exist- low level, so that it is heard only three an ade- four feet away from the window, but along ing scene with the sound of bird calls, ing radio or record player through the entire length of the window. When a crickets, frogs, etc. It gives show window quate amplifier and providing a lead to the on the out- displays a new dimension of sound at- Penetron in the piano, but this is a com- sign is placed over the Penetron nonetheless side of the window, there is no apparent mosphere. The nuisance element of the paratively inexpensive job -but not nec- regular public address system in such ap- a job for radio dealers and repairmen. source of sound emanation. It was no ac- essary to secure a license to use sound since plications is eliminated; also the cost of Tables in Night Clubs: Although 436 RADIO -CRAFT for MARCH. 1942 SOUND

tuai installations of this have as yet been slip off the roof and is ready for the next made by Mr. Holland, a few demonstra- customer. INTRODUCING tions have been made and a contract with Naturally it follows that the Penetron in one night club seems a certainty. The' this application is a natural for use in Penetron in this applicdtion may be either "drive -in" movies. Heretofore one had to HA the dynamic or PM type, the latter is try to catch the sound accompanying the preferable, and the instrument is attached picture from a loudspeaker placed some- OVA to the underside of the table. It is not where in the lot. On a cool evening it be- N necessary that every table in the restaurant came quite uncomfortable before the pro- ,MA or night club have a speaker attached, since gram finished because it was necessary to the sound emanating from one will be leave the windows down in order to hear c sufficient to carry to those immediately sur- the sound. With this device you simply sR rounding. But, used in place of the conven- drive in, pay your admission, the attendant tional public address system, it is most places a speaker unit on the roof of your effective. All the speaker units are con- car (rumble scat, if it is an open car) and nected through the amplifier to the micro- you enjoy the picture with the window, phone on the stage or band- stand. The open or shut! 5!RVII master of ceremonies and the orchestra, Other Applications: Tests have proven soloists or other performers use it. Certain the following applications o£ the Penetron. of the tables are reserved for special guests, but Mr. Holland believes further experi- FRANK FAX and as they come in and are seated, the mentation is desirable before they are, in- M. C. greets them through their own table. cluded in the repertoire of remarkable ef- You can imagine the rush on the part of fects that may be achieved. On numerous John Q. Public to get one of the chosen occasions during a demonstration of the tables! The real advantage, aside from the Penetron, the inventor has whispered into showmanship described, is that the fidelity a microphone and the device has carried it of sound is noticeably better and is obtained with high fidelity through four and six inch YOU probably wonder who I am, through most of the P.A. systems in night hollow tile walls, and, amazing as it might writing you under that handle clubs; the level of sound can be much lower, seem, through eight inches of reinforced above. Well, I'm a Sylvania engineer which makes it much more comfortable and concrete. The applications indicated from assigned to the one task of helping less annoying to the guests. this would be for its use in churches, thea- you all I can with your problems and Talking Automobiles: Mr. Holland is tres, auditoriums, etc., where present sound your selling. negotiating at present with one of the large facilities are not giving the best results. distributors of gasoline for use of the Pene- In auditoriums with poor acoustic quali- I've quite a staff to help me, too - tron in filling stations. In this application ties a number of Penetrons, Mr. Holland backed by the Sylvania engineering and it would carry a sales message on film and believes, installed in the floor and walls promotion departments in full force. the speaker would be placed on the roof would carry the sound to every point with Our purpose is to give you a SERVICE- of the car as it a comes to stop before the equal clarity, volume and fidelity and with- MAN SERVICE, like gas pump. As tank is the of which the the being filled the out echoes. This also indicates the use of radio business has never seen. customer in the car would hear the story the new system for annunciator systems in about the new oil, or tires, etc. The entire large industrial plants and factories, where Yes, apersonal service for you individ- inside of the car would carry the message, they now use a bell or other calling system, ual radio experts -all sec to answer but it would be barely audible outside. As which operates only when the person paged any technical questions you send me, the car drove away the speaker unit would happens to hear his number or name called. and to supply whatever promotion helps your own business needs. Pictures below show the limited range of the average loudspeaker used for show window attrac- What's it to us? Just this: the more tion purposes, and by comparison, how all of the people standing in front of a store window hear we can help you do a better job, the the voice or music as reproduced through the vibration of the glass. more business you'll get and the more. Sylvania tubes you'll need. So come on with those questions that have been puzzling you. Send 'em to INSTALLING me today, and see how this new SYL- ORDINARY LOUD SPEAR ER VANIA SERVICEMAN SERVICE can help you in a big way. Address your queries _pp MATERIALS NISC£L L ANEOUS WIRES to me personally: Frank Fax, Hygrade t \1\\ 1 TOOL ROO e TOOLS EXTENSION LADDER Sylvania Corporation, Emporium, Pa. I \1\\\\\ . NAILS, SCREWS ETC Our advice, course, is i LABOR of absolutely , l\ ) \\\\ MEN ,.i, .A Two - MINIMUM FREE. So are some of the sales helps \ \ OF S NAN NOUNS / I we can you %I supply - with all others available at substantial savings to you. , Just take a look at the typical "helps" lil11111 1 k II II t I)lü -\ listed below: I. Window displays, 15. Service hints booklets dummy tube cartons, 16. Technical manual REGULAR SPEAKER timely window stream- HIGHLY DIRECTIONAL SMALL RANGE ers, etc. 17. Tube base charts OF EFFECTIVE SOUND 2. Counter displays 18. Price cards 3. Electric clock signs 19. Sylvania News 4. Electric window signs 20. Characteristiasheets 5. Outdoor metal signs 21.Interchangeabletube charts 6. Window cards 22. Tube complement 7. Personalized postal books INSTALLING' cords PENETRON 23. Floor model cabinet 8. Imprinted match books 24. La rge and small serv- MATERIAL. *ow' 9. Imprinted tube stickers ice carrying kits 25. LABOR: ow. MAN 10. Business cards Customer card Index MMIMUM OF FIVE flies "MUTES 11. Doorknob hangers 26. Service garments 12. Newspaper mats 27.31m1 business forms 13. Store stationery 28. Job record cords 14. Billheads (with customer receipt)

PENETRON NON-DIRECTIONAL- HEARD CLEARLY AT ANY POINT ALONG WINDOW SYLVANIA RADIO -CRAFT for MARCH, 1942 437 LATEST RADIO APPARATUS*

NEW "SELF- SOLDERING" UNITS QUICK FUSE -CHANGER Jigger, Inc. Littlefuse, Inc. TRANSCASTE R 215 West Illinois St., Chicago, III. 4797 Ravenswood Ave., Chicago, Ill. WIRELESS! of practical avilira. lions. Will broadcast soirs music from !room or floor in h ime n store in building WITHOUT eCONNECT- ING WIRESI Operate from any Transmitihy favorite recordings the any radio without - t eencoradin land Pho- nograph. Your radin VAdi ecomeá a public ad- A NEW product, Jiggers, should have great inter-eon, dress system appeal to all electricians. electrical service and ntith a aster. maintenance men. contractors and manufacturers Home broadcasting without wires. Great fufun for - Irae as detective device to listen of electrical products. Each jigger is a small, self parties. auditions. uses Include LS secret conve dona. A few' other soldering unit that contains just the wireless 5d. nix line tracer, mindd reader. contained trick ventriloquist. ngo announcer. t ie tiny. etc. correct amount of 50 -60 solder and flux her- impossibles enumerate many other unes in this are Wired, a waterproof heat -gen- limited s Transcastere fully metically sealed .within laboratory Ì lguaranteed shell. To obtain a strong, perfectly as to rils atreádwmashipknwl erating outer AN entirely new convenience for changing damage In transit. n soldered electrical connection, it is only necessary touch a fuses in close quarters- replacing a blown DE LUXE MODEL TRANSCASTER-TRANS. to push the wire splice into the unit and on inspec- inwtnl0-7lmit tá shell ignites and pro- fuse in a twinkling -and giving notice HITTER \that high.RdetitHrea lighted match to It The tion that another spare is required, are features without connection wires to mote radio set. No duces the proper temperature to flow the solder sacrifice of lity or power. Operates fe' m dropped compactly embodied in a Spare Fuse Holder and or d.c. Frequency range 1500 to 1750 $4'95 into the splice. The burnt shell is then announced by Littlef use. kc. Price Dena tubes and nuke) .. perfectly soldered splice is Puller combined, just Set of 4 Matched Tubes for Deluxe Model 51.95 off and a smooth, Incorporated. f t SPECIAL 5-TUBE TRANSCASTER feie,"titae: revealed.- Radio -Cra The fuse in circuit goes through one end of vice has been engineered especially for advanced e Holder, perimental and professional use Employs two ex- the soft rubber rectangular Littlefuse tremely high -gain pre- amplifier stages ahead of the between the clips. Above, and at right-angle. is modulated oscillator. When used with 'staff maudioicmnmono it will pick and transmit a whisper. HAMMER FINISH KIT an opening in the holder for the spare fuse. with mike concealed anyplace in room. Suitable for work. for use with orders. etc. When inserted. the caps of the spare fuse project Ppecialurnrice, complete with 5 ready to General Cement Mfg. Co. for plug into any or d.c. outlet (less beyond the holder, affording an easy grip 515.00 919 Taylor Ave., Rockford, III. two fingers. TRANSCASTER ACCESSORIES Dynam eÓ When the fuse In circuit blows, all the operator (Fig. E) 52.95. 525 List Wide Range response db. Crystal has to do is to pull and reverse the holder. DI 53.45 FEarphoneSM keR(Fig.f Al $ .25. One end of the holder and puller is painted red. Until a fuse change is necessary, the red TELEJECTOR end is underneath, out of sight. When a reverse RADIO'S MOST AMAZING ACCESSORY is made. putting the spare fuse in circuit. the Pirko up telephone cony pal ions without tapping red end is brought into full view on top. To an wireswr Merely place device rra telephone instrument and listen to loth asides of any telephone or service man this red signal instantly conversation through the loud speaker f your radio. inspector Works from ally or d.c. otet. Complete with indicates that a fuse has blown and that another ready to s e tubes, 57.90 spare is required. If the end is black and both the H. G. CISIN, Chief Engineer THE ACCOMPANYING illustration shows an fuse in circuit and the spare are still serviceable. ENGINEERING INSTITUTE new Hammer Finish Kit which in- Fuses are easily removed and replaced. ALLIED interesting fuse holder and 91 Warren St.. Dept. 81, New York. N. V. of and a bottle of hammer "Windows" in the spare puller cludes a can cement in view at all finish spray, with a special nozzle for spraying keep the elements of both fuses the liquid onto the treated surface. This finish time'.- Radio -Craft in desired by many radio set -builders and experimenters in general. and no doubt they will be greatly pleased to learn that such a kit Is available OIL- FILLED PLUG -IN on the market.- Radio -Craft CAPACITORS Aerovox Corporation 30 -WATT "JIFFY" SYSTEM New Bedford, Mass. Allied Radio Corporation SOLVES EVERYDAY 833 West Chicago, III. YOU GEM AHEAD IN LIFE How many times have you lest money because of gJackson (Blvd., take figuring? ynti know how to 67 t= fitly?? discounts. interest rates.iytaxes all the other calculations you to eat p with in your dandaily life? Are you having trouble qualifying for Army or Navy pro. Motion because you're not u mathematics? Here Is the honk that gives 'a .oral backen ouml In mathematics that takes all the u Irritation and drudgery out of it. You dont need to be scared of ,md,h,natica. Ieeause here's the subject Captained siili,,,ut trilla. with. out useless computations. Here's the book for men in the armed forces: for business technicians ndec aflennen. a ila ining ,,.1 Inc everyday mathematic problems in ca.y-to.understaml words and illustrations. Yen. It's the key to a simple ,mdcrslandttl of ,tithe. Lice. It's a real home -study course in math ..... ,tics for the man who's alert m importanceportance of mathematics in We world today.

ELEMENTARY MATHEMATICS EASY -SIMPLIFIED- PRACTICAL CONTENTS OF BOOK. I. Arith metic-Addit ion-Subtractiun-multl- puciton- Div ivi,,,,, IN STEP with the growing popularity of the to those rush PA widely DCHAPTERcllmate- Perccagert hat n-fir Proportion.rli>ttmcuone- HERE'S the answer jobs- plug -in capacitor technique, already CHAPTER III. The Metric System. difficult speaker installations. The wax -filled types. CHAPTER IV. flow to Measrire Surfaces ami Capacity to those used in the electrolytic and paper Hkometry). KNIGHT 30 -watt "Jiffy" can be set up in no the Aerovox Corporation of New Bedford, Mass.,. CHAPTER V. Powers and Involution -Roots And Evo- lution. time. Sturdily constructed speaker cases easily announces a new Series -72 oil- impregnated oil - atiCraftsman-e fold -down speaker fits into Manual Rand Technical ONLY mount on the two ingenious filled capacitor with four -pin base that Thermometer conversions-con 'ions -Graphs or stands, which may be placed wherever as distinguished from the Plotting - of tripod a standard UX socket, the Slide Rule. you desire. The stands can be extended from 96 octal base of other plug -ins. CHAPTER VII. Special Mathematics 50c for the Radio Technician. POSTPAID to 78 inches and are provided with adjustable The aluminum-sprayed tin -plate round can CHAPTER VIII. Commercial Calcula. tions- Interest Diacouutx -short Cut swivels. comes in 2, 21/2 and 3 inch diameter sizes. and Arithmetic. with IX. Weights and nleasurls_Useful Tattles. The complete system includes : 1 30 -watt Am- from 21/1 to 4% inch high. It is provided a CHAPTER with lugs, so as to be held securely Cash er Money Order. plifier with Phono Top and Tubes: two 12-inch mounting ring Send Stamps. and in accordance with Underwriters fadiapaaatla took. Dynamic Speakers; 1- "Untplex" low -feedback in place $nd fodav n,r Y r pv of 4fa -ins are avail- it ron te carri.rl .:udii' to'oar porbf.(sìza as a in.) mike; 1- takedown stand; compact portable case requirements. These oil -filled plug up to 16 ofd., and (221" x 19%" x 16" closed) : and 2 -tripod able in single -section units E speaker stands. All necessary cables and instruc- up to 4 -4-4 mfd. in multiple -section units. in T CIIMIrAx maximum results are included. For 110 both the 400 and 600 v. D.C.W. ratings.- Radio- 1917 S. State St., RC -342, Chicago, III. tions for a volts, 60 cycles A.C. -Radio -Craft Craft. 1942 438 RADIO -CRAFT for MARCH, LATEST RADIO APPARATUS

NEW VACUUM -TUBE energy and random noise 73 %. The axial polar pattern is symmetrical at all frequencies. VOLTMETER Improved "Ultra" wide -range frequency re- Hewlett Packard Company sponse from 40 to 10,000 cycles assures full reproduction of music, of speech. 481 Page Mill Rd., Palo Alto, Calif. crisp reproduction The new moving -coil unit is highly immune to mechanical- vibration and wind noises. This new performance is made possible through the "Uniphase" single -unit construction, which eliminates the necessity of using two dissimilar microphone elements in one microphone for ob- taining true unidirectional operation. The new microphone is functional in design and modern in appearance. Compact, sturdy construction makes it easy to handle in the studio or to take along on "remotes." The Super -Cardioid is available for immediate delivery in three models: Model 556A for 35 -50 ohm circuits, Model 55613 for 200 -250 ohm circuits, Model 556C, high impedance.- Radio -Craft RADIAL CONE SPEAKER PROJECTORS University Laboratories 195 Chrystie St., New York, N. Y.

TYPICAL of the extent of the Aerovox line of mica capacitors are the units with meter - mounting brackets. Two types of mounting brackets are available and adjustable to con- HERE is a new vacuum -tube voltmeter which nect directly to meter terminals for r.f. by- should be of particular interest. passing of meter windings. A choice of mount- With the Model 400A Vacuum Tube Voltmeter ings, terminals, sizes, ceramic standoff insulators measurements up to 1 megacycle are now as and other features complete this outstanding simple as measurements with the usual multi - molded -in- bakelite mica capacitor line. Ask local Aerovox jobber about Aerovox micas. Ask range meter at d-c. This new meter may ordi- for catalog -or write us direct. narily be used with no precautions whatsoever; there are no adjustments to make or check before A COMPLETELY new line of Radial Cone taking a reading; the high input impedance will Speaker Projectors designed for uniform sound not affect the circuit being measured; a large projection in all directions has been announced overload will not damage the instrument ; and by University Laboratories. the accuracy is excellent because waveform errors The model RBP radial projectors, not only have and turnover effect are minimized. the pleasing appearance and compact construc- The meter has a frequency range from 10 cps tion of the flat ceiling type speakers, but, in addi- to 1 megacycle. Nine voltage ranges are provided tion, have the high tone quality of a large, well BEDFORD, MASS., U. S. A. with full scale sensitivities from .03 to 900 volts. designed wall speaker enclosure the manufac- The voltage scale is linear and a decibel scale turers claim. It is the "infinite barre' seal,d In Canada: AEROVOX CANADA LT i ., Hamilton, Ont. based on 600 ohms and 1 milliwatt is provided. acoustic chamber in the Model RBP which i EXPORT' 100 Varich St., N. Y., Cable 'ARLAB' The reading of the meter is independent of line responsible for the added bass response. voltage and tube characteristics. The flat -top design is suitable for ceiling or This instrument is excellent for all types of single suspension mounting. Waterproof for out- audio frequency work. It is particularly valuable door use. All steel construction with "Floating at the present time for carrier current, supersonic Rubber" speaker mounting and "Non Resonant" measurements, television, and measurements rubber rims: especially useful for music repro- throughout the broadcast field. -Radio -Craft duction in defense factories. Available for 12 inch and 8 inch cone speakers.-Radio-Craf t J. -T. HIGH -GAIN ANTENNA BANDS FORMS Jefferson- Travis Radio Mfg. Corp. CROLITE COIL ON 6 380 Second Ave., New York, N. Y. Henry L. Crowley & Co., Inc. DIAL SCALES I Central Ave., West Orange, N. J. JEFFERSON -TRAVIS RADIO MFG. CORP. 20 TIMES EASIER FOREIGN OF NEW YORK has augmented its extensive TUNING with SUPER line of aircraft, marine, and mobile radio com- BAND SPREAD RADIO! munication equipment by the addition of a new type of antenna, known as the J -T High -Gain rurÌ.L SPEAKER, Antenna. PUT THIS CHASSIS TUBES, PUSH The basic element of the High-Gain Antenna is IN YOUR PRESENT its tuning coil assembly, which consists of a SUTTON TUNING, weatherproof high Q coil, enclosed in a metal CABINET shield. This is surmounted by a short whip. Ex- MAGNA TENNA treme flexibility of mounting is provided for by LOOP AERIAL. a base stud, by means of which the tuning coil '44502? COMPLETE assembly can be supported on a tubing or pipe TRADE -IN READY TO PLAY of appropriate length. TIIINIC easier The High-Gain Antenna is of advantage in that of It ... 20 times to tune ... 10 times (1) a more sensitive than ordinary radios! Crystal -Cleo it permits shorter or lower antenna to be High Fidelity Tone. Famous 30 -day trial plan fully used without loas of operating efficiency and (2) protects you and enables you to prove Midwest's amazing it makes for greater efficiency when it is the THE production of precise coil forms in new 1942 Super Spread Band pcforr:mnre Crolite, combining mechanical in your own same height or length as would be a conventional and electrical home, without obligation. I4rite today. Your same on a type antenna. characteristics meeting the most rigid specifica- 1 f postal card will do. tions, is one of the many Send for big FREE 1942 The tuning coil assembly provides an accurate National Defense activi- 9BAND ties in the recently of L. Catalog, showing Radios, means of matching the transmitter to the antenna enlarged plant Henry Radio - Phonos, Home CONSOLE at the operating frequency. Crowley & Co., Inc., in West Orange, N. J. These Recorders from Standard models of the High -Gain Antenna for toil forms range from a fraction of an inch $12.95 to 9212.50. to several inches COMPL(n marine and vehicular use are described in a com- in diameter, are helically grooved to take different sized wires and winding pitches, E-Z TERMS prehensive data sheet published by the manu- T .16 TUBES USER .f eNTS !PANTED facturer. Radio -Craft and have a plurality of different holes accurately positioned for winding taps as well as threaded MIDWEST RADIO CORPORATION holes for mounting screws. Various Crolite DEPT. CINCINNATI. OHIO NEW SUPER -CARDIOID MIKE "bodies" or formulae are utilized in meeting tlhe 12-G Shure Bros. radio characteristics required at different operating frequencies, particularly the 225 W. Huron St., Chicago, Ill. in ultra-high- MAKE OLD RADIOS NEW frequency spectrum. You can learn quickly to modernize all sets. Lack of A -Cardioid" new sets will make a tremendous market for this serv- NEW "Super Broadcast Dynamic These precision coil forms start from solid ice in 1942. Cash -in by improving audio circuits. Microphone has been announced by Shure extruded rods or tubing, of Crolite, which are modernizing cabinets, adding feature+ usually found on Brothers of Chicago. This new Series "556" in- subsequently turned and bored to correct late model sets. Practical rob -s neat+ w Ith schematics outside and photographs make the work easy. You are told how troduces a "Super Cardioid" polar pattern that and inside diameters, followed by grooving and to obtain modernization work. what to charge. and is twice as unidirectional as the Cardioid, from drilling and tapping. The pieces are then fired how to complete the Job quickly and efficiently. of Complete, 81/2 x 11 inches, manual only 81.10. post- the standpoint receiving front sounds and at critical temperatures in kilns, assuming the paid. Money back guaranteed. rejecting rear sounds, yet has wide-angle front final rock -hard characteristic of Crolite.-Radio- SUPREME PUBLICATIONS pick -up. Decreases pick -up of reverberation Craft 320 8. Jefferson St. Chicago. III.

RADIO -CRAFT for MARCH, 1942 439 Radio & lalevii cn Radio eonJtzuction

The unusual receiver here described by Mr. Hiatt is shown in the photos above and at the left. The meter shown on the front panel is used for the purpose of indicating the voltage applied to the filaments of the tubes. The large shield can covers the tuning coil. The set operates on batteries and will make a very fine portable.

/{¢c¢iv¢r 2 TUBES EQUAL 4 JOSEPH P. HIATT

ECONOMY of space is the watchword triode 1J6G is the tube here under consid- frequency amplifier, which keeps all dis- today. We give thanks to the tube de- eration; it is a two -colt tube and very turbances caused by the second section - signers, who have crowded two tubes into a economical in "A" battery consumption. which operates as a grid bias detector - space where only one was previously found, In this set the first section of VI is away from the aerial, or interference with and this without loss of efficiency. The twin operated as an aperiodic (untuned) radio other sets in the immediate neighborhood,

The diagram for building two -tube receiver here described is simple and easily followed.

fjFC H/ CI

TI VI C6

41110 411. 4110 4111, CIO Ill 410 OS as ffi as as 0-0 + o 45 45 45 PB + - O 0 g

-I- 03- - C ae SW TOP VIEW OF SOCKETS

440 RADIO -CRAFT for MARCH, 1942 Radio eanitzuction Radio Televbion

Meters wave length Grid coil turns Tickler turns Coil space Between coils

10-20 5 No. 24 DSC 5 No. 26 DSC 1" '4" 18-38 9 No. 24 DSC 7 No. 26 DSC 1 ,4" 14" 35.75 16 No. 24 DSC 11 No. 26 DSC 154" 34" 70-145 30 No. 24 DSC 15 No. 26 DSC Close wound 54" in the nature of howls or whistles. The first Bear in mind that a good long aerial will section of V2 serves as an audio trans- do wonders when opportunity to erect one former-coupled amplifier, the second section, is possible, and a good ground connection also transformer -coupled, acts as an output works still greater wonders. 1M tube, thus producing four tube results in This set, though not designed for a porta- very little space. ble, can easily be adapted to that purpose, 4 STANDARD TYPES -. This circuit is of the "variable- condenser" so the constructor may be able to develop f Amperite Regulators replace over controlled regeneration type and has been something very interesting along that line. es of AC -DC Ballast Tubes now irr-f thoroughly tested in experimental practice I would suggest omitting the speaker and mperites are real REGULAtORS . . and found to be unusual in efficiency, as connect about three good headsets in series tented Automatic Starting Resistor well as sufficiently powerful to operate a and use only 90 volts on the plates, which is initiai surge and saves pilot I permanent magnet dynamic speaker with would surely produce results that would be ... Ask Your Jobber. volume to spare. highly satisfactory in every respect. Care should be taken to use insulating shoulder washers in mounting all variable List of Parts condensers, verniers and phone or speaker jacks from the base or panel, except the re- HAMMARLUND C1 -50 mmf. star type MC variable midget con- generation control condenser, which need denser v not be so protected. C2-140 mmf. star type MC variable midget con- 1 To the beginner who wants the greatest denser C3-20 mmf. star type MC variable midget con- returns for his time and money expenditure denser C4-260 mmf. star type MC variable midget con- (and we all do), this is a mighty good bet, denser as there is nothing ticklish or critical throughout the whole process of construc- SPRAGUE THE tion or operation, but a diligent watch must CS, C7, CII and C12 -.01 mf. bypass fixed con- be exercised all the while, so nothing densers that C6 -.0001 mf. bypass fixed condenser goes astray. C8- -.0005 mf. bypass fixed condenser WAY TO REPLACE These tubes are but C9 -.004 mf. bypass fixed condenser eight -prong tubes C10-.I mf. bypass fixed condenser only six prongs are used, and the prongs are not far between which makes it advis- I.R.C. BALLAGT5 able to figure about the approximate length RI -3 megohm 1 watt resistor of wire each connection will require, and R2 -5000 ohm 1 watt resistor R3- 10,000 ohm 1 watt resistor WRITE FOR REPLACEMENT CHART solder them to the socket terminals before R4- 15,000 ohm 1 watt resistor final mounting of the socket on the base. By AMPER/TE C sal uopwr, raw rosa. M T this method number 24 bare copper wire can Miscellaneous be employed for all the connections, except 1-CS -3 shield can for coil 1 -Form fitting tube shield for 1J6G Row To the battery leads, which must pass through 1-4" NATIONAL vernier dial the metal panel and require insulation pro- 1-4 prong EBY socket Learn 4- HAMMARLUND SWF coil forms CODE tection. 1 -Midget short phone jack Whether you wish to enter radio as a career or merely The radio frequency -detector tube as well 1 -Twin jack for antenna and ground add another valuable and fascinating accomplishment to as the regenerative 2 -IMP cord tips your achievements, the AR Electric Master Teleplex Code tuning coil must be 1 -Phone plug Teaching Machine will show you how. Teleplex reeer a your 1 sending In visible dots and dashes on a specially shielded, and the shielding well connected -25 feet roll of hookup wire prepared pound spool DSC No. 26 magnet wire waxed paper tape and then sends back to you to ground to make it most effective. 1- at any speed you desire. It does not merely allow you I- pound spool DSC No. 24 magnet wire code. It is code. No The regeneration control is of the variable 1- iece 44" outside diameter bakelite tubing, 6" experience needed. lone There are NO PER - condenser type, as it is the most simple to I2-i6 soft rubber plumbers' washers PORATfONS NO INK. Far superior to install and easiest to operate. 12- Insulating 5" shoulder washers anything ever developed 1 -FROST DX special headfnnes The panel and base is a standard a marvel of sim- stock 1-6" KNIGHT P.M. dynamic speaker plicity. while not des- sheet of aluminum 8" x 18" cut in the center, 4-154" bakelite pointer knobs ignated as standard 2 -1" bakelite pointer knobs equipment, Teleplex is making two sheets 8" x 9 ", and while one used at many U.S. 2 -1% volt EVEREADY ignition cells Army Poste, Naval of these pieces is used as a front panel, the 3-45 volt EVEREADY B battery cells Training Stations as other is so bent that it forms a base and 1 -754 volt EVEREADY C battery cell well Sr by the Arnold- 1 -0.3 READRITE voltmeter an Tel. & Tol. Co. support when bolted to the front panel. The 1- Aerial kit Also by prectloally nhool 1 -Spool rosin core solder every private m base is 2%" above the bottom of the panel, teaching 1- Soldering iron and many foreign governments. We furnish you complete while the base dimensions are 5%" x 9 ", thus 1 -Water pipe ground clamp sourer. ¡ecludhig practice messages. the All Electric Mas- leaving space R5 -10 ohm MALLORY- YAXLEY rheostat ter Teleplex. plus a personal sen ice on a MONEY BACK to spare. VI and V2 1J6G RCA tubes GUARANTEE. lav cost. Easy terms. Without obligation In the photograph showing the front Ti and T2 type T47Á25 THORDARSON audio write for booklet panel, the push -button for the voltmeter is transformers SW- YAXLEY double -pole single -throw switch TELEPLEX CO. located above and to the left of the tuning I- Aluminum panel, 8" x 18" x 1/16" thick. (See dial. The knob directly text.) 107 HUDSON ST. JERSEY CITY, N. J. above the tuning (CAUTION) -Be sure to use soft rubber dial is the vernier tuning condenser, which plumbers' washers between panel and sockets. is connected in parallel with the main tun- Whatever YOU WANT ing condenser. The voltmeter is located In A above and to the right of the main tun- "Hams" -Please tell the Editors ing dial. The phone or speaker jack is lo- what type of articles you would HEADSET cated to the right and on a center line with You'll find in a Cannon - the tuning dial. The knob below and to the like to see in the Amateur Section Ball Guaranteed Head- set: Sensitivity. Clarity right is the regeneration condenser control; of this magazine now that War the one immediately under the main tuning of tone. Dependable per- has been declared and a general formance. Quality at dial is the pushbutton double -pole single - fair price. Folder C -3 il- Scient¡Oca Ply throw switch, which opens A, B and C ban placed on Amateur Station suite lustrates complete line. Heavy bar tUSE. battery circuits -all at the same time. The nets greatly in. Write Headset Head- operation. Let us hear from you, e their em- quarters. knob below and to the left of the dial is Ciency. the 10 ohm rheostat; the two acorn nuts Pronto I- Editors C. F. CANNON COMPANY are 6 -32 and clamp the base onto the panel. SPRINGWATER, N.Y.

RADIO -CRAFT for MARCH, 1942 441 Nadia 7a¢viios ateut Radio Foot -Pedal Break -In The foot -operated switch described herewith enables the operator to switch from the transmitter to the receiving position and vice versa instantly and with a minimum of effort. As many circuits as desired may be opened or closed by this simple foot -operated switch.

ROD NEWKIRK, W9BRD

THE most up-to -date c.w. amateur stations which can be obtained. And use of the tions are equipped to work 'break -in.' This switch will become something of a sixth is operation wherein both the station sense after a period of use. transmitter and receiver are used simul- As compared with break -in, there is the taneously. The advantages of such a setup disadvantage that the receiver is dead dur- are immediately obvious when compared ing the 'send' periods and the frequency of With the usual "take turns" operating tech- t'he station in contact cannot be continuously nique. Wasted power, time and patience are monitored. This makes such a foot- switch avoided, for when interference or fading affair undesirable for traffic and network sets in while you are transmitting, the sta- use. tion with whom you are in contact merely But against this are the following ad- presses his key to stop your sending. vantages : No circuit changes are necessary This is really the most intelligent way in the station for installation, such as key- to operate since it comes closest to simu- ing, bias supply, etc., -just put the foot - lating actual conversation. One doesn't pedal in parallel with the present switches shut one's ears when speaking in person you have to throw by hand for send -receive. with a friend, or over the telephone. The transmitting antenna can be used for The reason that so comparatively few reception, resulting in improved receiver amateurs use this system is that of the performance. Power is conserved in that constructional disadvantages encountered. power supplies may be switched on and off. The transmitter must be keyed in the One power supply can be used for two oscillator stage so that there will be no purposes. (Here at W9BRD a 200 volt sup- signal from the station rig heard in the ply is switched from the e.c.o. to the re- receiver to interfere while listening. This ceiver preselector and back.) No doubt usually requires that the transmitting many amateurs will put the pedals to many By simply rocking the switch back and forth other uses and arrangements. stages following the oscillator be externally transmitting and receiving with the foot, the The foot -pedal switch shown in draw- biased to prevent damage to tubes and com- circuits are opened and closed. the ponents due to rising current without ex- ing can doubtless be improved upon and is given merely to illustrate general construc- citation. (The power supply is kept running tioning properly when so few other stations tion. The contacts themselves may be of during communication.) use it (except the traffic handlers). ordinary roundhead bolts ; they must be Furthermore, it is usually more difficult Hence we have a vicious circle which carefully filed and adjusted so that all cir- to secure a T9X note from the transmitter to discourage widespread use of tends cuits close simultaneously and with a mini- when the oscillator is keyed. This is espe- break -in. cially true an electron- coupled or self- mum of arcing. If there is too much spark- of the next best thing to actual excited oscillator. Considerable experiment- Obviously, ing and arcing of the contacts of high volt- -in is be able to switch from the ing with supply voltages, voltage regulation, break to age circuits relays should be used. Leads send to the receive position and vice versa etc., may be required before a satisfactory to the unit should be neatly cabled and well- instantly and with a minimum of effort. note is obtained. insulated ; those carrying quite high cur- handswitch or switches for this Then, too, the station receiver must be Using a rent or voltage should be suitably insulated purpose is a handicap to speedy operation sufficiently shielded from the transmitter and of heavy cable. Contacts should be in besides being an inconvenience. Some form field to prevent blocking when the trans- no way exposed. foot -operated switch is in order. In mitter is Break -in is no pleasure if of a No dimensions are given as that is up to keyed. the accompanying drawing is what was there is a great racket in the receiver while the individual. A pedal for switching three at W9BRD. keying. Care must be taken to see that the evolved here circuits naturally will not have to be as wide receiver is not damaged by its antenna It is a glorified teeterboard with receiver as one for switching six. Overall length picking up ri. energy from the transmitting circuit contacts on one side and transmitter should be kept not much longer than twelve antenna; this means that a short, non - circuit contacts on the other. The foot inches for installation convenience and the resonant antenna should be used, preferably rests on the part designated as A and a mike protruding part on which the foot rests run at right angles to the regular transmit- spring or two keeps the pedal in the re- should be close to the floor for maximum ting antenna. ceive position on the side away from the comfort. Thus it is evident that a sturdy, high - foot. Slight pressure by the foot auto- While in communication, switching can grade receiver is needed for efficient break - matically opens the receiving contacts, kill- be accomplished so swiftly that it conveys in work, especially with weak and DX sig- ing the receiver and then closing the trans- the impression you are using actual break - nals. A circuit, used in conjunction with mitting circuits for the send position. in. It is handier for use in 'phone stations the transmitter keying, can be used to pro- This idea is probably being used by many than 'push -to -talk; both hands being free. Vide bias for the receiving tube grids to kill amateur stations and yet is not widespread Another thing, should you ever be suddenly the receiver when the key is pressed. practice. There is practically no limit to called from the operating able you will One thing about break -in which appeals the number of circuits which may be never accidentally leave the high voltage to most anyone is the fact that no send -re- switched with the gadget nor the combina- on. ceive and stand -by switching is necessary ; Knife switches in parallel and in series when one wants to receive he simply listens with the foot -pedal leads will enable you to and when one wants to transmit he just be- Other Uses! operate the transmitter independent of the gins keying. This elimination of all switch- The Radio and Electrical experimenter pedal for antenna adjustments, etc., and ing probably has caused the most converts will find many other applications for this to open all circuits to the transmitter foot- operated switch, such as switching to break-in, as there is otherwise little use whether or not the pedal is accidentally from phones to loudspeaker; switching closed by someone else while you work on to go to all of the trouble usually en- from one set to another, etc. countered in getting a break -in system func- the transmitter, changing coils, etc.

442 RADIO -CRAFT for MARCH. 1942 I can Clive You IMMEDIATE DELIVERY on Hallicrafters Receivers!

If you want a better receiver - here is your opportunity.

Isell more amateur receivers than anyone else, because I really make it to your advantage to buy from me. I have the biggest stock and can give you the best trade -in on your present receiver. I can do this because I finance all terms myself and give you the best of the breaks. You can also have a ten day free trial, I want you to always be satisfied and know exactly what you are buying. Why not trade -in your out-of -date receiver now, it may be worth a liberal trade-in allowance from me. You know there must be a very good reason why we, located way down here in Butler, Missouri, have grown to be the WORLD'S LARGEST DISTRIBUTOR OF AMATEUR RECEIVERS. The best reason for our success is my personal service on every order received. Drop me a line today, tell me what you want, it will pay you to get acquainted ... remember you don't have to wait, I can make immediate shipment!

For the Western States we also have a big complete store

at: JAA'S. W9ARA 2335 Westwood Blvd. SHOP West Los Angeles, Calif. HENRY RADIO BUTLER, MISSOURI 4 VIILD , LAIU ENT DISTRIBUTORS OF SHORT WAVE RADIOS" RADIO -CRAFT for MARCH, 1942 443 Radio %alavieron {Omettez %2adio

IF 45 VOLTS ON O- /MA.OR 1 OEPENO,NG 0N PLATE MAY USE 0-SMA. J PLATE VOLTA06 HEADPHONES % ( /5.000 OHMS, / W. B- CALIBRATED 2 ®

RFCJ OSCILLATOR ) II0V .005 n' AC For the / MIS ALL CHOKES - .FC. TOR FC4 D 6-VOLT 40 TURNS, N9. .36 ENAM W/RE STORAGE BATTERY ON OWEL RODS. RFC4 OR 6.3 VOLTA.0 SPACEB TURNS 6'APP Ultra -High Frequencies SECONDARY OF A F/LAMENT TRANS.. 84 4. 5 PHONES) BA250V/FOR FIG.1- DETAIL DIAGRAM OF WAVEMETER CIRCUIT- A. 13INNEWEG, Ir, EA/Am /20 ( 9/ WIRE, / OM. J/5 000 /5-MF The short -wave experimenter will find this Oscillator MIDGET TYPE no RANGE 55.230MC very useful -it enables one to ascertain the wave- 400 105 00025 -MF. length by measuring the current in 380 /00 4 TURN the A -A SCIES 15.-3/,3/ Oscillating circuit. 360 95 >UB/NG 3 %2'O/A. NS /OE 340 90 RANGE 18-66 MC. circuit wires AB and CD (Fig. 1), your 320 85 \I oscillator will operate close to the fre- 300' 80 3 /MOLE WAVEMETERS quency I FOR ?NE N EWER FREQUENCIES- of the oscillator have constructed 280 F 75 Ú FIG. 2 and calibrated. The lengths of wires AB 260` 70 A wiring diagram of the and CD maintaining each at the same 240 65 Calibrated Oscillator is length, were varied and for each length of shown at the top of the 220 60 oscillating circuit the frequency of opera- ` -up of diagram. Hook was measured. 200 55 for tion The results, given later, B-B SCALES WEWRl.20 simple wavemeter: leo 50 will enable you to tell quite closely where T0 high frequency shown your will I 160 45 at Fig. 2; Fig. 3 shows oscillator operate (C is plate I I a curve for terminal.) 140 40 ` IvANeto how to draw T NALS. a typical oscillator. 120 35 Checking the Results 100 30 lI (B) +O . .2 .3 4 .5 .6 .7 .8 .9 /0 1/ 12 .4 .4 Say you built the oscillator and meas- O 10 20 6.0 70 (R)- WAVELENGTH /N FEET ured the wires as will be clear later, so that F/G.3 ^CONSTRUCTION CURVE FOR 75 CM- /0 METER OSC L LATOR - your oscillator was operating on say 5 meters exactly. We don't care whether it is THE most important point to know when strung tightly which requires troublesome 5.05 or 4.95 meters for the time being, be- operating at ultra -high frequencies is the and perhaps undesirable fixed supports of cause we can check it up and find out more wavelength at which the oscillator is op- some kind. The 955 tube makes it possible exactly later on. We thus can come fairly erating. Many experimenters wish to know to construct an oscillator and measure the near a correct value and not be far off. the wavelength of operation and they have length of the oscillating circuit to find the Using a simple regenerative receiving set no calibrated wavemeter. A calibrated re- frequency of operation. (one tube), near the oscillator, tune in a ceiver is also often useless because it will In Fig. 1, a complete diagram of con- short-wave station around 30 meters the not pick up unmodulated waves such as nections for the wavemeter is shown. A 955 wavelength of which you know or can those produced by simple oscillators. In fact, tube has its cathode supplied from a fila- easily find. Say, it was a 30-meter station, there are very few people indeed that have ment transformer. Two chokes are used in and the wavelength was exactly 30 meters. any kind of receiver, let alone a calibrated the filament transformer leads. If head- Tune in this station exactly. Now listen in one, that will pick up oscillations at a wave- phones are to be used to listen for beat - the headphones of the oscillator of Fig. 1. length of 10 meters and lower. notes with other oscillators or regenerative It should be near the sixth harmonic of the I have perfected a new type of wave- receiver, connect as shown. If headphones regenerative receiver, but it would be only meter that generates an ultra- short -wave are not needed, omit the phones and close luck if you heard it in the phones without and does not have to be calibrated but the the lead. If you use a gridmeter as shown, any adjustments at all. If you don't hear wavelengths can be found by simply meas- and it is 0/1 milliampere D.C. 1 maximum the sixth harmonic, move the regenerative uring the lengths of the leads in the os- scale, shunt it with a resistor so it reads receiver dial, keeping the tube oscillating, 1 is until you do hear it in headphones. Be cillating circuit. This is a new idea ; it is 1/5 milliampere when milliampere the known that coil specifications can be given, passing through it ; then its maximum range sure the coupling between the oscillating but it is also true that it is very easy to will be 5 milliamperes which is the required circuit and the regenerative receiver is very slip up in these specifications and so change maximum scale- reading when 250 volts is close. For example run the parallel wires the frequency materially. The present wave- used on the plate of the 955 tube. of the oscillator near the top of the coil meter is perhaps the most perfect in this The chokes are all made as described in in the receiving set. You could adjust the lengths of the wires AB and CD in Fig. 1 respect of any, because its oscillating circuit Fig. 1. Drill the dowel rods at the ends and until you hear the sixth harmonic of consists only of two straight wires, the tie a heavier wire around the rod, soldering do the lengths of which can be very exactly deter- the choke wire lead to the heavier wires 30-meter frequency, but this would not be mined. It is possible (if a 955 tube is used) which are used as leads. Boil the rods in hot very easy. It is better to tune the receiver to build an oscillator to specifications that paraffin before you wind the wire on. around until you can pick up the harmonic on the short -wave oscillator headphones. will oscillate very near any desired frequen- A 15,000 -ohm 1 -watt grid resistor is the cy. To find the frequency of operation, sim- correct value to use. Then you can gradually adjust the oscillat- ply measure the wires and take the wave- ing circuit wires until you hear the sixth length of operation from a prepared graph Use of Wavemeter harmonic of the 30 -meter wave. You could which is shown later on in this article. The oscillating circuit of the oscillator first calibrate the receiver dial from known stations and then it would not be necessary A common method for measuring fre- consists of a pair of parallel wires and the to adjust the lengths of the oscillating cir- quencies is the use of two parallel wires correct lengths to use will not vary very cuit wires. and a shorting bridge, but these wires have much with different 955 tubes. Hence, if I to be made rather long and they have to be tell you how long to make the oscillating It will be seen at once that you can cali- 444 RADIO -CRAFT for MARCH. 1942 Vmateatt Radio Radio g Telavieiow

brate your oscillator for different lengths of quire a great degree of accuracy and do wires by first calibrating the dial of your not care to operate their oscillators as trans- regenerative receiver. This receiver need mitters. The only danger for error there TECHNICAL have only one tube. A simple '30 tube re- ever was, was the possibility of turning in generative detector can be used if desired. the wrong harmonic (5th instead of 6th, If you do not wish to calibrate your os- etc.), but this danger has been eliminated BULLETINS in Fig. the wave- by furnishing you with calibration data for cillator (as 1), transfer Technical bulletins give reliable information in length measurements from its tuned cir- the oscillator. easy- to-follow form, and save valuable time cuit to a wavemeter circuit having a good Fig. 3 shows the calibration curves. I otherwise spent in laborious reading of numerous dial upon which you can mark the wave- took a lot of readings using one of these books. Every subject is treated briefly and con- length values. You could also plot a cali- oscillators having parallel wires and plot- cisely, yet completely. No complicated math- bration curve (wavelength or frequency ted values all the way from 75 centimeters ematics, chemistry, electricity, or theory. Each values vertically and dial- setting values to 10 meters which took quite a little time. bulletin is written in simple language, horizontally, for example). The results are shown in Fig. 3. PRICE EACH POSTPAID In Fig. 2, you will find the complete di- $1.00 As an example of how to use the graphs ORDER BY NUMBER mensions for the high frequency wave - of Fig. 3, the lines show that 80 mc. is meters. Build up some simple tuned cir- found when a wire length of 2 ft. is used in 0- 103-AUTOMOBILE SPECIALTY CHEMICAL cuits having shield front case and large each wire of the two parallel wires of the PRODUCTS.-Formulas for products used by automobile plain 4 -inch dial and the back open so you owners: Penetrating Oil, Chromium and Nickel Polish, oscillating circuit. The wires in the oscillat- Radiator and Cooling- System Cleaner, Anti -Dimming can couple small coil to oscillating circuit. ing circuit were always each of the same Paste for Windshields. Protective Battery -Terminal Coat- Tuning In length, which is the basis for the curves of ing, Auto -Finish Cleaner, High Gloss Rubbing Wag For precise adjustments, tune in a har- Fig. 3. If you don't like "feet," change it to Polish. Road -Tar Solvent- Polishing Cloth. monic by adjusting the regenerative receiver inches by dividing a foot length line into D -111- BUILDING TRANSFORMERS.- Simple, non - to zero beat with the oscillator. The accu- twelfths. Remember that 328 ft. is one mathematical methods for designing transformers. Also special transformers for ultra -violet lamps, Neon tubes, racy will be more than sufficient for ordinary meter. As another example of the use of the etc. work, and with the measurements of the curves, in this case the other curve which D124- SOLDERING. -How to produce perfectly sol- oscillating circuit known (as will appear uses the other two scales, the lines show 240 dered Joints. Solders and soldering fluxes and how to make them. How to make electric soldering irons for later), you can't be very far off. In fact, mc. at .35 ft. length for each oscillating light and heavy work, how to construct an alcohol blow- some may accept the measurements as they circuit wire from right at the tube seal to pipe. are and feel content, since they will not re- the condenser terminals themselves. 0. 136--SMALL A.C. ARC WELDER CONSTRUC The books listed below have never been sold by us before. The TION. How to build are welder. for fusing iron and steel value of each book Is 50e. They are exactly the same as RADIO sheet up to 3/16 Inch In thickness and rods as large as & TELEVISION'S 50c blue books which have been on the market use on 60 for years. ik inch in diameter for 114-volt, -cycle and SPECIAL For short time only we are selling these at a special reduced or on 220 60 me :es 25 cycles, A.C., -volt A.C. price of only 75e for the 3 books. All of the books contain numerous photographic illustra- D -142- ELECTRIC MUFFLE FURNACES. How to tions and diagrams and have stiff flexible cover. design efficient electric muffle furnaces for heat-treating metals, case -hardening, enamel -baking, firing porcelain, melting metals, etc. Temperature up to 1630 degrees Fahr. and up to 2000 degrees Fahr.

0. 107 -ELECTROPLATING WITH COPPER, NICKEL AND CHROMIUM. -Latest methods, formulas, and trade secrets that will enable anyone to do professional. work. Includes formulae for cleaning, directions for polishing, and buffing, eta

D. I I2- ELECTRO- MAGNETS.- Eleetro- magnet design so clearly explained that anyone can build magnets for Practically every purpose. Complete data covering both A.C. and D.C. magnets.

D- 123 -MIRROR SILVERING.- Slmplifed directions for resilvering old minors and making new ones. Con- li expert. Popular Book Corp.. tains all details required to become an Colored 25 W. Broadway. mirrors, front - surface mirrors, transparent mirrors, and New York. N. Y. photo mirrors. Gentlemen: Enclosed you win find remittance for 75c lush, new D -137- ELECTRICAL METERS. -Information to build S. or money order accepted) which U. stamps for to alternating or please send me at once your 3 books experimental electrical meters metsure ABC OF TELEVISION SHORT WAVE GUIDE direct currents. Including ammejers, soltmeters and watt- SHORT WAVE RADIO QUIZ ROOK meters. O .145 -HEAT TREATMENT OF IRON AND STEEL. Name -Complete and specific directions for modifying the char- Address acteristic, of iron and steel by heat treatment. Rose to various of and how to City State RC 3 -42 identify the kinds steel iron; anneal, harden. and to temper. 19-131- REMOTE -CONTROL SWITCHING.--Cantrol- 10 BEST RADIO BOOKS 10 CENTS EACH ling electrical devices at a distance by means of tele- RADIO FANS EVERYWHERE -these fine amazed at the wealth of information con - dial. ten cent text books give you an excellent tained in these handy books. Excellent for phone foundation for the study of RADIO. They are reference -ideal for every technical library. 0. 138 -GOLD -LEAFING METHODS. - All details clearly written, profusely illustrated and con- YOUR MONEY BACK if you are not satisfied. about handling gold -leaf for gilding. Reliable, practical tain over 16.000 words in each book. You')) be PROMPT SHIPMENTS methods so that anyone can do tho work in an expert No. I -HOW TO BUILD FOUR DOERLE SHORT No. 5- BEGINNERS' RADIO DICTIONARY manner. WAVE SETS No. 6-HOW TO HAVE FUN WITH RADIO No. 2-HOW TO MAKE THE MOST POPULAR No. 7-HOW TO READ RADIO DIAGRAMS ALL -WAVE I- AND 2 -TUBE RECEIVERS BEGINNERS No. 3- ALTERNATING CURRENT FOR BEGIN- No. 8 -RADIO FOR T f.CHNIF11x No. 9- SIMPLE ELECTRICAL EXPERIMENTS NERS CHICAGO. ILL No. 4 -ALL ABOUT AERIALS No. 10- TELEVISION 1917 S. STATE ST. (DEPT. 342) BOOKS ARE ALL UNIFORM P DEPT. 342 Every book In the GERNSBACK EDUCATIONAL LIBRARY has 32 pages -with Illustrations varying from 30 to 66 in number. F.arh tltlo volume contains over 15.000 words. Positively radio's greatest book buys) If you TECHNIFAX 1917 So. State, Chicago, III. do not think then, books worth the price asked. return them in 21 hours and your money will be instantly refunded. Enclosed find S for which please send me following Technical Bulletins: RADIO PUBLICATIONS 25 WEST BROADWAY NEW YORK, N. Y. postpaid the

RADIO PUBLICATIONS. Dept. RC-3-42 Nos. 25 WEST BROADWAY, NEW YORK, N. Y. Gentlemen: Please send immediately, POSTPAID, the book numbers circled below, I am enclosing cents -mach book being 10e. 1 2 3 4 5 6 7 8 9 10 NEW NEW Name Send FREE listing of 48 new 10o publications. Name Address Street and Number City State Remit by check or money order -register letter if you send rash or unused U. S. postage stamps City and State .MAIL COUPON TODAY! j RADIO -CRAFT for MARCH, 1942 Radio g 7a1avieion Ruaition l?ox Edited by HERMAN YELLIN, W2AJL

Loud -Speaker ou Crystal Set gain. This tickler can be wound over the Wave Trap end of the dowel holding the regular I.F. ] Can a loud -speaker be used with a coils, using about 15 to 20 turns of No. 30 Can you give une some information on crystal self -R. J. Kolb, St. Louis, Mo. wire. Try reversing the tickler connections constructing a leave -trap for use with my all -uwve received Bengak, N.Y.C. A. Any speaker, even the smallest, re- to get proper regeneration. -R. quires a very much larger amount of power A. The wave -trap shown in the diagram to operate than an earphone. The power Reducing Amplifier Hum can be connected in series with the antenna output available from a crystal receiver is ] lead to the receiver and tuned to the fre- that obtained by rectifying the R.F. voltage : I have an amplifier using a 617, 6SJ7, quency of the interfering station, which intercepted by the antenna, and this is very 6CS and push -pu!! 2A3 tubes. The 617 is will result in eliminating that and any other small indeed, so that unless the receiver used for the microphone while the phono- station on that frequency, from the receiver is located under the very shadow of a pow- graph is connected to the 6SJ7. Can you tell input. In order to handle a wide frequency erful broadcasting station, there would be me how to reduce the hum which results range, several coils will be needed. They an insufficient amount of power to actuate when the mike gain -control is turned upI can be either of the plug -in type or built the speaker. -John Quoddy, Long Beach, Calif, onto a switch. In either case, the coil and condenser should preferably be shielded. Frequency Wire 3 -TUBE RECEIVER HOOK -UP range Turns size 1.500 -3,500 kc. 60 #24 wound on I y" diam. 3,500 -8.000 kc. 35 #18 154" diam., 1" long F. C 7,000. 15,000 kc. 20 #18 15(s" diam., M" long oMF 000r- lT4 CAC14) I MEG 54 Simple wave -trap to cut out an i/ AI 155 interfering station. Jz(MEW 4- A 3 -tube receiver dia- . . 140 MAW s°,c gram of interest to the OF"/ radio experimenter. A .000I- hook -up MF. regenerative which can be used with Io ti plug -in coils to cover all MEGS. short wave bands. It is shown with low voltage 100.000 battery tubes, but any 250.000 other tubes can be used, OHMS with a suitable current ANT. supply. This set will work a loudspeaker and is suited to battery opera- 50.000 RECE /VER OHM tion. REGEN. CONTROL

O A Bf a5V. Garage Door Opener

Compact Portable Query A. First make sure you are using shield- Recently I attached a motor to the ed cable from the microphone to the am- garage doors so they will open and close What kind of coils are used in the plifier input. Second, your grid leads to the by turning a switch. Is there any way I can Argentine's Compact A.C. Portable shown first two tubes should be as short as possi- operate the motor by remote control from on page 10 of the May 1941 issue f-L. ble, and if longer than one inch, should be the alomobilef-E. M. Price, Confluence, Myers, New York City. shielded. Your diagram is technically cor- Pa. A. The R.F. coil contains two primary rect, so these two items should correct your A. On page 298 of the September 1940 windings, one for standard long antennas difficulty. Frequently, however, a new 6J7 issue of this magazine there appeared a and the other for doublets ; however, any tube will also eliminate the hum as many constructional article on a sensitive receiv- standard single primary R.F. coil can be 6J7 tubes, although perfectly satisfactory er- operated relay, which could be actuated used. The oscillator is also a standard two - for other purposes, will prove to have too by the noise emanating from the auto's ig- winding coil. The single I.F. transformer much hum when used in a high -gain am- nition system. The relay can be connected is however a special coil, providing a plifier. A little experimenting will soon dis- across the switch controlling the door tickler for regeneration, to increase the close what the cause of the hum is. motor.

BATTERY RECEIVER WITH PUSH -PULL OUTPUT STAGE

500 -2 I 33 MMF. / Cr R.FC. INPUT TRAN5F. -"Dv

7.000 OHMS OUTPUT TRA NSF.

Aff i 50,000 OHM"' -/3%2V. Ct'0 I Á,2V REGEN CONI 90V 4/2V. 0 135V.

Nave's a more ambitious hookup for a battery receiver. It can be built for short -wave reception with plug -in coils, or just for "b oadcast" reception if desired. The push -pull output stage gives excellent reproduction. The set may be operated from a power -pac 446 RADIO -CRAFT for MARCH, 1942 Radio iGittfe Radio g 7alat ieion

First Prize HOME -MADE DRILL INTERFERENCE ELIMINATOR I recently ran out FLUORESCENT LAMPS of small drills and then ARMATURE came upon this idea for drilling coil forms. File off the head of a small brad, sharpen- MAGNE7 FLUORESCENT WIRE COUPLED L AMP CLOSE TO ANT. OR ing the point if necessary and use it as a am.10.14 FINAL TANK /F regular bit. Mine actually cut through the '1/ /, LAMP REFUSES TO GLOW w /rH- bakelite form quicker and more easily than OUT CONNEC- the standard bit. If you file the point, be TION sure that the pyramid effect remains, as shown in the accompanying diagram, since this is the cutting surface. The only difficulty may be is ANT. that encountered that after TUNING two or three holes have been drilled the bit is apt to bend, but they are cheap R.F ,nough to replace.-Richard Jeff rey. STAGE TO A.C. "e-TRANSFORMER 1

Interference in radio receivers caused by doorbells can be eliminated in two ways: Burnt out fluorescent lamps may l e used (1) By connecting a condenser across the to advantage by Radio Amateurs. They contacts of the bell, or (2) by making the may be used as indica- resonance or output bell an alternating current type. Since most on the They may be tors transmitter. bells now work on a transformer, this can mounted on the panel of the R. F. stage of be easily done. The wire leading to the the transmitter, or coupled to the closely armature contact of the bell is removed and feeders. If R. is not antenna the F. output connected to the coil, as shown in the dia- great enough light lamp, wire to the a gram. The bell will vibrate as well with connected it should be placed close to to this connection on A.C. as it did previous the only tank coil or the antenna post. Not to the change. The armature may have to does it serve this purpose but it also beauti- HAR PEN oe stiffened slightly to permit vibration. fies the transmitter with its glow. It may - PO /NT V. Petrucelly, Jr. be used as a modulation indicator on phone transmitters, since it will glow brighter when the audio voltage is impressed on the carrier. Alexander Riccio, W2NBI. TO RESTORE LETTERING "B" POWER SUPPLY PACK To reprint numbers I purchased in a In many cases a small power supply may 5 -10 cent store for a dime a dater (see be found useful on the service bench to test SCREWDRIVERS FROM OLD sketch) which stamps the month, day, and small receivers or adjust a speaker. The year. I used the numbers of the days to writer built a unit as shown in the diagram SAWBLADES herewith and found it especially useful for Old sawblades of hacksaws reprint the numbers on the selector switch. are made of this purpose. an excellent steel and are too good to throw Aluminum paint works better than ink or This pack can also be employed to ener- away. Cut them in half lengths, grind enamels to print with. For numbers such as the gize a 2500 ohm dynamic speaker by omit- teeth away and grind end 300, 140, etc., where three digits are needed, the without the ting the choke and second capacitor. The spanning hole just to the shape you need. the final zero was made by changing the output of the supply is about 100 volts with Without any cost you are able to make dater around to utilize the "O" of "Oct." a current of between 12 to 30 mils. yourself a set of screwdrivers from the MA., D.C., A.C. and other signs can also "T" represents a 2% v, transformer; "V" width of 9" to about 1/16" for very small be printed with a little ingenuity by the a '27 type tube, "Cl" and "C2" 4 mfd. screws, sunken and concealed screws. The user. If larger words or numbers are capacitors, "CH" 30 henry choke. W. figure below may give some ideas. If you wanted. (get a small set of rubber type, -/. Stubblebine in "C-D Capacitor." keep the hole of the sawblade, which usually with holder). -Robert Lindberg. fits into the mounting of the saw, on the opposite end of the shaping, you are able to keep your screwdriver set nicely together NUMBER with a safetypin as often used for curtains, DES /RED which permits you to take the screwdriver out easily. R. Glass. "TEN CENT STORE. DATER P WPPNKL E PHONE FINISHEO JAGK PANEL

NUMBER PA /NTED WITH AL UM /NUM PAINT

published on these pages will win their senders S months' subscription to RADIO & TELEVISION. The RADIO KINKS best kink published each month will win e 2 years' subscription. Read these kinks; they will be of real use to you, besides indicating what is wanted. Send a typewritten or ink description with sketch of favorite to the Kink Editor RADIO -CRAFT for MARCH, 1942 447 Radio g %alavieion Radio /Kinke EARPHONE CUSHION NOW -A REALLY HIGH -POWERED- This earphone cushion can be made from a rubber sponge obtainable from any five EVERYTHING and ten cent store.-Mox Goodstein. IN RADIO Radio Engineering Sets. parts. wppliei public address systems. amateur equipment, testers. kits and fluores- t lighting at lowest prices. Huge stocks, bought months ago Library ready for shipment the same day your order i rued The Defense Program is making big demands on our industry but be se of our advance buying we e able to fill your orders promptly and of ficiently,

BURSTEIN-APPLEBEE COMPANY NOTE: 1017-14 MLGrE, KANSAS CRT, MO. The Library comprises a selection of books culled from leading Mc- Graw -Hill publications in the ra- .u»..s....,...... :2'á<. wÜä':t:2L' .á:: dio field. SPONGE ae RUBBER DISC especially selected by radio specialists of Mc- GLUED ON TOP um and Abnef Graw -Hdl publications OF PHONE CAP BIG PRIZE CONTEST to give moat complete, dependable coverage of 64 wonderful prizes -$100 U.S. Defense facts needed by all whose fields are grounded on Bond, 7 -Tube All -Wave Radio, Set of radio fundamentals Aviation Books, Woodworking Lathe. available at a special price and terms Model Goa Engine, Power Scroll Saw, Daisy Air Rifle. and many other prises THESE books cover circuit phenomena, tube the- valued at $400.00 given away FREE. ory, networks, measurements, and other sub- CONTEST OPEN TO ALL jects --give specialized treatments of all fields of Costa nothing to enter. Wirt valuable pries. practical design and application. They are books Gat Seienre end Maehaniea at your news- ALIGNING TOOL dealer today for full details. Or send 16c of recognized position in the literature -books you direct to Science and Mechanics. Dept-A4. will refer to and be referred to often. If you The tool !lay he made front an old pipe 800 North Clark Bt.. Chicago. for copy. are a practical designer, researcher or engineer stem, or piece of round hard- rubber. Drill in any field based on radio, you want these books AND the help they give Problems a hole in the material, then clamp a screw - SCIENCE MECHANICS for in hundreds of On Sale of A11 Newsdealers throughout the whole field of radio engineering. head of the proper size firmly in a vise 5 VOLUMES, 3319 PAGES, 2289 ILLUSTRATIONS and heat very hot with the soldering iron. 1. Eastman's FUNDAMENTALS OF VACUUM TUBES While keeping the head hot, gently but 2. Termlin's RADIO ENGINEERING 901c4.0 4zi!/PILtaPIa 3. Everitt's COMMUNICATION ENGINEERING firmly force the tool with the hole in it 4. Hood's HIGH FREQUENCY MEASUREMENTS 5. Henney's RADIO ENGINEERING HANDBOOK over the head and keep it there until cool. - Adson Radio 429 10 days' examination. Easy terms. Special price under Aerovox Corporation 430 this offer leas than books bought .eparately. Add these Tony Frotid, IV9S'KY. standard works to your library now: pay email monthly Allied Engineering Institute 438 Installments, while you use the books. Allied Radio Corporation 409 10 DAYS' FAKE CXAMINATION -SEND COUPON American Radio Institute 388 RUBBER ROO Amperite Corporation 441 OR P/PE STEM McGraw -HiI Beek Cs., SS W. 42nd Street, N. Y. C. Amplifier Co. of America 411, 419 Send me Radio Engineer n Library, 5 vole.. for 10 Audel & Co Theo 412 days' examination ono approval- In 10 day. I will send Burstein-Appleby Co 448 53.00 plus few cents postage, and $3.00 monthly till System Co 419 $24.00 Is paid, or return books postpaid. (We Pay post - Candler orders accompanied by remittance of first In- Cannon Co., C. F 441 eúÌlment.) Capitol Radio Engineering Institute 389 Name Classified Ads 417 Chartered Institute of American Inventors 888 Address Commercial Radio Institute 889 Coyne Electrical School 388 City and State Coyne Music Shop 399 Data Print Co 388 A,eltron Detrola Corp 389 Dodge's Institute 389 Company RC-3-42 Don Lee Network 412 Goldentone Radio Co. 411 CLAMP /N VISE AND HEAT Harrison Radio Co Inside Front Cover Do you need BEFORE FORCING INTO Henry Radio Shop 448 HOLE WHICH /5 SLIGHTLY Hudson Specialties Co 422 SMALLER THAN HEAD Hygrade Sylvania 437 BINDING POSTS? International Correspondence Schools 431 The XL PUSH POST with Its Spring International Resistance Co 387 Anton Constant Contact and 888 lek Lancaster, Allwine & Rommel connection. 389 Manufactured In All Aluminum Typa M Lincoln Engineering School lit 12e each. Mass. Radio School 388 Aluminum Body. Bakelite Top Type Book Co., 448 each. I MATCHING TRICK McGraw -Hill Inc at 1St 411 Types CO or NP. ALL BRASS- STAIN- Meck Industries, John LESS STEEL SPRING & PIN. PROVEN by When using a tube with a high plate Meissner Mfg. Co. 399 240 or SALT SPRAY TEST as NON. CORROSIVE at 280 each. resistance, it is not satisfactory to use an Midwest Radio Corp 439 Manufacturers and Dealers Liberal National Radio Institute 385 Discount. audio transformer and a resistance coupling National Schools 389 X. L. RADIO LABORATORIES National Union Radio Corp 419 420 West Chicago Ave.. Chicago, III. Nelson Co. 389 New York YMCA Schools 388 Peerless Sound & Radio Corp 430 Radio City Products Company 429 TIME -SAVING OPERATOR LIC. COURSE Radio -Telco Institute 448 430 This New Course sill get you a License to Operate Tele- Radolek Company vision, Facsimile Itadlotelephone and Broadcasting Sta- RCA Institutes 389 tion.- realest, Inexpensive. Short -rut Course by A. RCA Manufacturing Co. Back Cover Binneweg, Jr., B. Sc. Includes 15O-Page Book for self - Readrite Meter Works 429 study. showing digrams necessary. Answers over 700 435 Necessary Questions. We answer any other Questione by Remington Rand, Inc Mall. NO CODE NE(-ERR,UIY. Send $1.00 now for Self - Solar Mfg. Corp. 429 Study Bonk. Pay another $2.00 when leak Is received, Schott Co., Walter L 448 and $1.00 later when you complete II:,. I'oursr. Science & Mechanics 448 Sprague Products Co 403 RADIO -TELIO INSTITUTE Sprayberry Academy of Radio 388 524 Fairbanks Ave., Oakland. California Supreme Instruments Corp. 411 Supreme Publications 439 Technifax 438, 445 Teleplex Co 441 Amazing Ilew "WALSEO" Treasury Department 890 Triplett Elea. Instrument Co 425 University Laboratories 411 STAPLE DRIVER W45D 412 fn..- . ,... ne doig dept.,. Mae, Weston Elec. Instrument Corp. cab, sly Y ch n s half the W_re Inside Back Cover n be , in c beh `é .,oldingt -ple X.L. Radio Laboratories 448 .Jble .ledah a hammer and o,d.ary o.p... Drbes stapineds Mrsoven .ell.. bric', moiler, etc. Magasine .oils automatically and holds strips of staples which coma in several colon. AA your jobber (While every precaution is taken to insure for demonstration and catalogue 41.0 of a0 WALSCO PRODUCTS means higher voltages. I used the primary accuracy, we cannot guarantee against the or write WALTER L. SCHOTT CO. of one audio transformer and the secondary possibility of an occasional change or omis- sion in the preparation of this index.) 5264 W. Pico Boulevard. Los Angeles, California of another in series. -IV. D. Lyons. 448 Printed In the U.S.A. RADIO -CRAFT for MARCH. 1942 LST1iU%1E1TX /a,//wZan9Pu//!

Weston Model 774 Checkmaster

Weston Model 669 Vacuum To the serviceman who owns WESTON Tube Voltmeter r .r .. .. test equipment, that name on each instrument panel has real meaning these days. Normally, it means long, uninterrupted service and substantial savings in instrument replacement costs. It means all this and more today. It means that he has tools that will give him dependable service ... work and earn for him without inter- Weston Pocket -Size ruption ... all during the uncertain Weston Mode! Test Instruments 772 Super- Sen.si. period ahead. Weston Electrical In- tive Analyzer strument Corporation, 599 Freling- huysen Ave., Newark, New Jersey.

Laboratory Standards ... Precision DC and Specialized Test Equipment ... Light AC Portables ... Instrument Transformers Measurement and Control Devices ...

. . . Sensitive Relays . . DC, AC, and Exposure Meters...Aircraft Instruments... Thermo Switchboard and Panel Instruments. WESTON Electric Tacho meters... Dial Thermometers. :FOR OVER .73 YEARS LEADERS IN ELECTRICAL MEASURING INSTRUMENTS'. From the Earth to the Moon - that's the distance that the 80,000,000 metal tubes manufactured since 1935 would reach, placed fifteen feet apart'

Proved by ACCEPTANCE... Proved by PERFORMANCE! LJAW°°means MODERN!

ACCEPTANCE! In a little over six years, two -thirds of the total! more than 80,000,000 -yes, 80 million "DESIGNED FOR - PERFORMANCE -and performance alone RCA Metal Receiving Tubes have been METAL TUBES" -is the cause of such leadership. Metal used by the Industry in over 300 elec- tubes permit the designer to turn out Means Better Equipment! tronic applications. And today, RCA is better equipment ... more efficient, more Look for metalenvelope tubes iu turning out more metal tubes than ever dependable! For six years, the equipment you buy and sell. before -for 1941 production outstripped the majority of important receiving -tube Remember that metal tubes all previous records! VAmrt tatOUn give the highest etóciency...the improvements has appeared highest performance standards ... ACCEPTANCE! Of the six largest -selling first in metal types - and the highest reliability. And duo receiving tube types throughout the en- many advantages still ap- $1 means -- lasting customer- satis. tire Industry ... four are metal types- pear only in metal types! Fn faction... extra good -will for you!

ivilnY,AL VB ie31 RCA Manufacturing Company, Inc., Camden, New Jersey A Service of the Radio Corporation of America In Canada. RCA Victor Company, Ltd., Montreal