THE RADIO SET of 1950 See Page 458

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HUGO GERNSIIAOc Rittr

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THE RADIO SET OF 1950 See Page 458

Novelty Radio Sets - Radio in Model Homes - Versatile Test Unit How Broadcast Artists Record Their Programs - Contracted Speech

www.americanradiohistory.com i ISERVICE MEN'S ESSENTIALS FOR ALL MEMBERS OF THE ORSMA

WHAT ARE THE SERVICE MEN'S ESSENTIALS? THE OFFICIAL RADIO SERVICE MEN'S ASSOCIATION has arranged to supply a number of "Service Men's essentials" for its members and associate members only. These essentials are priced at cost, plus a small additional fee which is the only source of income that the Association has. No one obtains any profit or benefit, except the Association itself. Whatever profit accrues, is reinvested for the furtherance and enlargement of the Association. By using the letterheads, billheads, etc., you present the business -like appearance to your customers. In addition, the Association has made arrangements with most of the prominent manufacturers to allow special discounts to members, providing ORSMA letterheads are used when ordering.

No. I ORSMA LETTERHEADS These letterheads. shown on the right, are furnished with your name, address and telephone number, printed on excellent paper. They are sold In lots of 100 or multiples thereof. with a distinct saving for single orders of 1,000 or more. Per 100, 60c; per 1000. $3.00. No. 2 ORSMA ENVELOPES These are furnished to match the letterheads, printed with your name and address and seal of the Association. They go hand in hand with the letterheads and are usually ordered in the same Quantity. Per 100, 60c; per 1000, $3.00. No. 3 ORSMA SERVICE RECORD CARDS These serve a double purpose; whenever you complete a Job you fill out the report -bill and hand it to the customer; this is the "psychological moment" to collect. By the use of carbon paper a permanent record is kept. Furnished with name. No. 1-60c per 100 address and telephone number. Per pad of 50, 600; per 10 $3.00 per 1000 pads, each of 50, 83.00. No. 4 ORSMA INSPECTION LABELS The label Is to be filled In with the proper dates, and pasted Inside the set or cabinet where the customer will see It. It 1s a continuous reminder to him that when service Is needed, ho can call you again. The advantage is apparent. Per 100, 60c; per 1000. 83.00. No. 5 ORSMA LAPEL BUTTON At the suggestion of many members a handsome lapel button a44w4nnaim bearing the name and emblem of the Association has been No. 14 -50c each designed. It signifies that you belong to the ORSMA; and 10c in addition it gives your customers a better appreciation of (Plus for Postage) the professional nature of your work. 50e each. No. 6 ORSMA BUSINESS CARDS

These are furnished on a fine grado of paper in two colors with a blotter bads. Thus a "--- they present an incentive to customers to keep them in a place. They a prominent stw Printed with your telephone and bear the official seal of the Associa- tion. ourc per 1000, s4 and Nos. 9 & 10 ORSMA EMBLEM CUTS 4i+ These cuts for printing, advertising. etc.. are furnished In two styles and sizes. They may be used for newspaper or telephone -book advertisements or for printing of any kind. Large size, 11/4 z 11/4 in., $1.35 each; small size. yi x 3 in.. $1.20 each. No. 11 ORSMA MEMBERSHIP SIGN A set of three signs. printed on heavy cards, and having holes punched In order to ss hang in office or store. These are sold to members and associate members. Large enough r to be Quite prominent and the two tone effect makes them attractive. Set of three. 50e. No. 12 ORSMA ADVERTISING DISPLAY SIGN A two color sign printed in largo letters with your name, address and telephone, n.. w. with the seal of the Association. This sign 1s sold in quantities of 25 or more and is ideal for hanging in stores, ofilces, etc., for advertising purposes. Set of 25 cards, $3.00. 4i No. 13 RADIO SERVICE MEN'S ASSORTMENT PACKAGE k .-.,...... This includes one gold filled lapel button. 100 letterheads. 100 envelopes. 50 service record cards, and 100 labels printed with your name and address as described above. The whole assortment costs only -$3.00 -a worth -while saving. Complete, $3.00. No. 3-60e per pad of 50 No. No. 14 ORSMA MEMBER CERTIFICATE 5-S0c each A handsome diploma -like certificate engraved on stiff vellum -bond. The certificate is $3.00 per ten pads, each of 50 personally signed by the President and Executive Secretary and the corporation stamp of the Association is impressed on a red seal attached to It. Your name, certificate number and date of registration are lettered by hand and the Certificate is mailed in a card - hoard tube to insure safe delivery. Each 50c. plus l0c for postage.

iiiiii; a..,,.® TEPHEN MARKO

123 anaht4.D.l,a Tel. 3 -0672 AKRON,O. t. 1 No. per 100 6-75c No. 4-60c 100 $4.00 per 1000 per No. 2 -60c per 100 $3.00 per 1000 $3.00 per 1000 rApplication for OFFICIAL RADIO SERVICE MEN'S ASSOCIATION BC-11-35 Membership in ORSMA 99 Hudson Street, New York, N. Y. Please send me the following RADIO SERVICE MEN'S ESSENTIALS which I have Executive Secretary. ORSMA selected from this advertisement. My remittance for $ is enclosed. Send 99 Hudson Street, New York, N. Y. remittance in form of check or money order. Register letter if it contain., cash. currency or unused U. S. Postage Stamps. Kindly send an application blank for Full Membership Associate Membership

Name

Street or Box Name ORSMA No. City State Address City and State RC-2-35

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 449 OPPORTUNITIES' are many for the Radio Trained Man Don't be an untrained man. Let me show you how to get your start in Radio -the fastest growing, livest money -making game on earth. Jobs Leading to Salaries of $35 a Week and Up Prepare for jobs as Designer, Inspector and Tester -as Radio Salesman and in Service and Installation Work -or for work in a Broadcasting Station -as Wireless Operator on a Ship or Airplane, or in Talking Picture or Sound Work -HUN- DREDS OF OPPORTUNITIES for a real future in Radio! Ten Weeks of Shop Training Pay Your Tuition After Graduation We don't teach by book study. We train you on a great outlay of Radio, Television and Sound equipment -on scores of modern Radio Receivers, huge Broadcasting equipment, Television apparatus, Talking Picture and Sound Reproduction equipment, Code Practice equipment, etc. You don't need advanced education or previous experience. We give you -RIGHT HERE IN THE COYNE SHOPS -the actual practice and experience you'll need for your start in this great field. And because we cut out all useless theory and only give that which is necessary you get a practical training in 10 weeks. TELEVISION and TALKING PICTURES And Television is already here! Soon there'll be a demand for THOUSANDS of TELEVISION EXPERTS! The man who learns Television now can have a great future in this great new field. Get in on the ground -floor of this amazing new Radio development! Come to COYNE and learn Television as it should be learned on Television equipment. Talking Picture and Public Address Systems offer opportunities to the Trained Radio Man. Here is a great new Radio field just beginning to grow! Prepare NOW for these wonderful opportunities! Learn Radio Sound Work at COYNE on actual Talking Picture and Sound Reproduction equipment. ment. You work on real Talking Picture machines and Sound PAY FOR YOUR TRAINING equipment. You learn Wireless Operating on Actual Code Practice apparatus. We don't waste time on useless theory. We give you After You Graduate the practical training you'll need -in 10 short, pleasant weeks. I am making an offer that no other school has dared to do. I'll take you here in my shops and give you this MANY EARN WHILE LEARNING training and you pay your tuition after you have You get Free Employment Service for Life. And don't let lack of graduated. 60 days' after your 12 weeks' training money stop you -my plan makes it possible to get Coyne training period, paying me back with very little money. Many of our students make all or a good start -then you have over a part of their living expenses while going to school and if you should year to complete your payments. There are no strings need this help just write to me. Coyne is 35 years old. Coyne to this offer. I know a lot of honest fellows haven't Training is tested - proved beyond all doubt. You can find out got a lot of money these days, but still want to pre- everything absolutely free. Just mail coupon for my big free book! pare themselves for a real job so they won't have to H. C. Lewis, Pres. RADIO DIVISION Founded 1899 worry about hard times or lay offs. I've got enough confidence in these fellows and in my methods to give them the training they need and let them pay me back Coyne Electrical School after they have completed their training. 500 S. Paulina St., Dept. 25-8H, Chicago, Ill. ELECTRIC REFRIGERATION Mail Coupon Today for All the Facts AIR CONDITIONING H. C. LEWIS, President To assure your thorough preparation for a prosperous future, lin. dude-at no extra cost -a course in Electric Refrigeration and Air Radio Division, Coyne Electrical School Conditioning, taught you by personal instruction and actual work 500 S. Paulina St., Dept. 25-8H, Chicago, III. on latest -type equipment. Dear Mr. Lewis: -Send me your Big Free Radio Book, and all details of your Special Offer, including Electric Refrigeration, Air ALL PRACTICAL WORK Conditioning courses and your "Pay After Graduation" offer. At COYNE in Chicago ALL ACTUAL, PRACTICAL WORK You build radio sets, in- Name stall and service them. You actually operate great Broadcasting equipment. You construct Television Receiving Sets and actually Address transmit your own Television programs over our Television equip. City State Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com (Rdioaft\FOR Tar SERVICE MAN DEALER RADIOTRICIAN

HUGO GERNSBACK, Editor -in -Chief C. W. PALMER R. D. WASHBURNE Associate Editor Technical Editor

WE DO OUR PART

CONTENTS OF THE FEATURING FEBRUARY, 1935, ISSUE RADIO BEGINNERS VOLUME VI Number 8 IN OUR NEXT ISSUE:

Editorial: The Broadcast Industry Hugo Gernsback 453 SUPERHETERODYNE receivers have become so universally The Radio Month in Review 454 popular for use on all wave bands that an understanding Radio Broadcast Pictorial 456 of the principles of radio reception necessitates, also, a The Radio Set of 1950 Hugo Gernsback 458 knowledge of the operation of this type of set. Ún- in obtaining A Modern Picture of Broadcasting _ Lester F. Miles 459 fortunately, most beginners find difficulty Radio in the Modern and "Model" Home 460 this knowledge, and as a means of informing those new Novel Radio Receivers 461 to the art of radio set construction and operation, we "Contracted Speech" on the New York-London are printing the description of a I -tube superhet in the Radiophone N. C. Norman 462 Beginner's issue. This set is constructed on a "bread Broadcast Artists Record Their Programs board" so that the construction and operation will both W. H. Harrison 463 be as simple as possible. Curiosa in Radio 464 transmission has been receiving much publicity What Radio Set Shall I Buy? Bertram M. Freed 466 FACSIMILE the meth- The "Luxembourg Effect" in Radio Reception in newspapers and magazines lately. Most of C. W. Palmer 467 ods used in these devices, though, are too complicated International Radio Review 468 and involved to be of interest to the experimenter or experimen- Short -Cuts in Radio 470 beginner. A new simple system suitable for WLW's "Electric Eye" Lightning Protector 471 tation will be found in the next issue. WHAM's Programs Light Lamps 471 FIDELITY will also receive its share of attention in The Latest Radio Equipment 472 HIGH the beginner's issue -and it will be written so that the The Listening Post for All -Wave DX-ers what it is all about. C. A. Morrison 474 beginner can really understand New Developments in Interference Elimination R. L. Haskins and C. W. Metcalf 475 is published monthly, on the fifth of the month preced- 476 RADIO -CRAFT Build This Versatile Test Instrument Jesse Tillett ing that of date; its subscription price is $2.50 per year. (In Canada A New Portable P.A. Amplifier J. P. Relim 477 and foreign countries, $3.00 a year to cover additional postage.) Helpful Hints about Current Multipliers Entered at the post office at Mt. Morris, III., as second -class matter 3, 1879. D. L. Van Leuven 477 under the act of March are copyright and must not be Low Cost P.A. Amplifier Walter A. Carter 478 Tex+ and illustrations of this magazine A without permission of the copyright owners. We are also 478 reproduced A 5 -Tube A.C. Short -Wave Band -Spread Kit Set agents for WONDER STORIES and EVERYDAY SCIENCE AND Applications of the Generator Type Auto "B" Power MECHANICS. Subscription to these magazines may be taken in Unit G. W. Blessing 479 combination with RADIO -CRAFT at reduced Club rates. Write for New 16 MM. Sound Camera for Home Movies information. Copyright 1935. Continental Publications, Inc. R. D. Washburne 479 ORSMA Members' Forum 480 Elements of 4th Dimension P.A. or Sound Systems HUGO GERNSBACK, President I. S. MANHEIMER, Secretary )Part 2) H. S. Manney and C. R. Shaw 481 Operating Notes 482 Published by Continental Publications, Inc. Publication office: 404 RADIO SERVICE DATA SHEETS: N. Wesley Ave., Mount Morris, Illinois. Editorial and Advertising Advertising No. 131- Stewart- Warner Model R -I23 4 -Tube Office: 99 Hudson Street, New York City. Chicago Superhet. Chassis; Commonwealth Models 260 Office: L. F. McClure, 919 North Michigan Avenue, Chicago, III. and 660 6 -Tube Multi -Wave Superhets. 484 Western Advertising Office: Loyd B. Chappell, 511 So. Alexandria St., No. 132- General Electric Model M -65 6 -Tube Los Angeles, Calif. "Selective Short -Wave" Super.; Stewart -Warner London Agent: E.C. 4 Models R -I 13 and R -I 14 Short -Wave Converters 486 Hachette & Cie., 3 La Belle Sauvage, Ludgate Hill, RADIO -CRAFT'S Information Bureau 483 Paris Agent: Hachette & Cie., Australian Agent: McGills Agency St., Melbourne Be Satisfied to Be a Service Man Charles Golenpaul 485 III Rue Reamur 179 Elizabeth 450

www.americanradiohistory.com RADIO-CRAFT

I WILL TRAIN YOU AT HOME

IN SPARE TIME FOR A

GOOD RADIO JO i

J. E. SMITH, Pres. National Radio Institute TELLS HOW FREE BOOK MAIL COUPON

HERE'S Act today Sor better pay. Act today to break away from a low pay, no- future job. Act to get away from having to skimp, scrape to pay PROOF your bills. Mail coupon for my free 64 -page book. It tells you how I will train you at home in your spare time to be a Radio Expert' Good Position Station about my training that has doubled and WSMK tripled the pay of many. "I hue a good Job, make a nice salary, Many Radio Experts Make and all my success Is $40, $60, $75 a Week due to N.R.I. I am operator of Station Consider these facts -think of the good jobs they stand RSMIK. I highly for. Over 17,000,000 Radio seta in use, over 600 broad- recommend the N.R.I. casting stations, over 40 large manufacturera of Radio Course. It enabled me sets, over 3,000 manufacturers of parts, over 100 Police SAVE MONEY -LEARN AT HOME to pasa the Govern- equipped, airplanes ment examination for Departments Radio and airports Special Equipment Gives You an operator's license." Radio equipped. Thousands of ships touching every sea- lOHR HAJDCK, Jr., 21 Gerard port of the world are Radio equipped. Over 35,000 Practical Experience Avenue, Southern Hills, Dayton, stores selling sets and parts, about 2,000,000 autos Hold your job. need Ohio. No to leave home and spend a Radio equipped and about 20,000,000 unequipped. Loud lot of money to be a Radio Expert. I'll train you US a Week In Spare Time speaker systems wherever people gather, indoors and quickly and inexpensively right at home in your "Although I am do- outdoors. Commercial Radio stations dotting l our coast spare time. You don't need a high school or college ing only spare time lines. Radio a big industry -is growing bigger fast. A education. Many of my successful graduates didn't Radio work, I have hundred $75 a week jobs have grown averaged $18 a week. few $40, $60, to finish grade school. My practical 50 -50 method of I recommend N.R.I. thousands. training -half with lessons, half with Radio equip- training. It is cer- Get ready now for Jobs like these ment -gives you broad practical experience-makes tainly a complete learning at home easy, fascinating, practical and Course. In a short A spare time or full time service shop: installing, main- rapid. There is opportunity you time, it will take a taining, operating -broadcast, aviation, commercial, for in Radio. Old man, give him and police stations. A jobs are becoming more complicated -many need sound fundamental ship, television Radio retail busi- better trained men. New developments are making training in Radio theory. ness of your own. Installing, maintaining, servicing, prac- A service or new jobs. Short waves, loud speaker systems, police tice and design." STEPHEN J. loud speaker systems. sales job with a Radio, auto Radio, aviation Radio, television DRAPCHATY, 407 Wunderlich store or jobber. I'll train you for good jobs in every - Ave., Barberton, Ohio. of Radio. Radio's newest uses are covered by my training. branch Here's a field that's growing. It is where you find Nets about $50 a Week growth besides Sales Many make $5, $10, $15 a week extra that you find opportunity. 0"I have been getting in Spare Time While Learning along line. I aver- Every neighborhood can use a part time service- age ten calls a week. good which neta me about men. I'll start giving you special instruction material, 850. not counting plans, ideas, the day you enroll, for making money in profits on sales. I spare time. Get my book -read how many of my stu- have serviced almost dents make $200 to $1,000 in their spare time while I every make of set and have doubled " I ". have earned more learning than I ever expected. Stanley Tulk, 2706 Hector Street, Montreal, Canada, I owe my success to writes have been doing so much service work I Diticii D?eroaadJ the N.R.I. and its wonderful -"I Course." BERNARD COSTA, haven't had time to study. In two months, I made about and tripled 150 Franklin St., Itroklyn, New $200 in apare time." Lloyd V. Sternberg, 217 Fourth York. Avenue, Willmar, Minn., tells me- "I earned enough in apare time to pay for my Course. In one month I earned $125 in spare time." Yes, my training pays! the salaries FREE Your money back if not satisfied Radio Servicing Tips I'll make this agreement with you. If you are not en- of many Let me PROVE that my Course is tirely satisfied with my lesson and instruction service clear, easy to understand and fas- when you finish, I'll refund your tuition. cinating to study. Send the coupon for a free lesson, "Trouble Shoot- Find out what Radio Offers ing in D.C., A.C.. and Battery Mall the coupon. My book of information on MAI Seta." This interesting lesson ways common Radio's spare time and full time opportunities is gives 132 to correct to any ambitious fellow over 16. Read Radio troubles. I ant willing to free J. E. SMITH. President send this book to prove that you too what Radio offers you. Read about the training ran master Radio -Just as Thou- I offer you. Read letters from graduates -what National Radio Institute, Department 5BX sands of other fellows have done. they are doing and making. There's no obliga- Washington, D. C. Many of them, without even coupon in an envelope or paste it school education, and no tion. Mail Dear Mr. Smith: I want to take advantage of your Special Radio or technical experience. have on a postal card -NOW. Offer. Send me your two books, "Trouble Shooting in D.C., become Radio experts and now earn A.C., and Battery Sets" and "Rich Rewards in Radio." I two or three times their former J. E. President pay. Mall the coupon now. SMITH, understand this does not obligate me. (Please print plainly.) National Radio Institute, Dept. SBX Washington, D. C. NAME AGE

ADDRESS

CITY

STATE .... Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 452 RADIO -CRAFT for FEBRUARY, 1935 ELIFAUO EXPERT THE ONE MAN IN 1000 W4-E0 CAN SERVICE MODERN RADIO REC- EIV .GRS

RADIO SERVICE, WORK. NOW OFFERS GREATEST OPPORTUNITIES SINCE- RADIO BEGAN Radical changes have taken place in radio receiver design during the past year. Circuits and construction are very different from the receivers with which the radio service industry has had its greatest experience. Even more sensational developments with further complications are coming next season. Who will service these receivers? Cer- tainly not the `old timer" who knows nothing about modern receivers! He THIS CIRCUIT ANALYZER can't do it. That is why, right now, AND POINT -TO -POINT there is an urgent demand for reliable RESISTANCE TESTER service men with up -to -the- minute knowl- INCLUDED FIFE edge of modern radio receivers. Such OF EXTRA CHARGE men can step right out and earn up to FOUR LARGE KITS $3 an hour doing nothing but pleasant Of HOME PRACTICE service work in the better homes around EQUIPMENT town. No Past Experience Needed Past experience actually counts for little NOW THE SET f at this time, because the swift changes in SOUNDS GREAT IMAOE$18 TWO OTHER MEN ! receiver construction have made knowl- HAVE. TRIEOTO' TO -DAY f FIE IT Bur THERE'S NOBODY I edge of old equipment practically useless. COULD NT DO IT -s Even though you may not know one tube ELSE IN TOWN á fat WUO CAN FIX ' .4,4,x, ...I from another today . . . still, you can THESE NEW - take R.T.A. training and make more SETS money servicing modern radios than most of the "old timers" are making. R.T.A. graduates are doing it every day. Many of them are making more money as R.T.A. Certified Radio Technicians R.T.A. Membership Keeps You Ahead of Competition than they ever made in their lives before! With your course of training, and without extra cost, you get a valuable lifetime membership in R.T.A. This gives you a big advantage over ordinary service men Be An R. T. A. Man and You'll Be . because we constantly furnish advanced information to our members ... informa- the One Man in 1000 tion that puts money in your pocket while the other fellow is stumbling around in R.T.A. training will equip you to give fast, the dark. complete service to any radio receiver built. To Start You Making Money Right Away The jobs that puzzle and sometimes baffle the Quickly following your enrollment for training with R.T.A. you get, without extra usual service man will be simple as "A.B.C." cost, the R.T.A. Set Analyzer and Resistance Tester ... the handiest piece of portable to you . when you become an R.T.A. Cer- service equipment ever de- tified Radio Technician. It is very possible that vised. Instantly helps you SEND COUPON you will be the only service man in your local- locate the trouble in any ity able to quickly diagnose and quickly repair type of receiver, old or A. G. Mohaupt. Engineer Radio Training Ass'n. of America the new types of radio receivers. Be the one new, and shows you pre- Dept. RC -52, 1513 Ravenswood Ave.. Chicago. III. man in 1000! You can. cisely, what to do about it. Dear. Mr. 5lohaupt: Please send nie your free book of tarts about radio opportunities and how I ran make big money quickly. Also tell me how I can obtain your Set Ai:aly.er and four big marl- RADIO TRAINING mental outfits -FREE OF EXTRA CHARGE. Name ASSOCIATION of AMERICA Address city State 4513 Ravenswood Avenue CHICAGO, ILLINOIS J Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com adio Fos TM[ aff SERVICE MAN . DEALER . RADIOTRICIAN "Takes the Resistance out of Radio"

Editorial Offices: 99 Hudson St., New York, N.Y. HUGO GERNSBACK, Editor Vol. VI., No. 8, February, 1935 THE BROADCAST INDUSTRY An Editorial by HUGO GERNSBACK IT IS a mistaken idea of many radio people that radio his services alone. A crack orchestra commands $1,000 an began about 1920 -21 with radio broadcasting. As a mat- hour, and famous singers as much. The advertiser, ter of fact, of the radio industry goes back to 1903, when course, has to foot the bill for the talent in addition to the it was still called wireless. Even before the area of time consumed on the air. broadcasting, the radio industry had become well established Considering that a page advertisement and millions in the country's of dollars of radio apparatus were turned out largest weekly magazine, which distributes less than three annually in America alone. million copies per issue, costs $8,000 for one But when time, the broad- radio broadcasting came along, the industry cast time of $14,000 for one hour does not seem unreason- took a tremendous upswing, and it is difficult today to give able, and indeed, probably is not for most an exact figure of advertisers, the financial turnover of the entire many of whom have continued their advertising on the air radio industry per year. One thing is certain and that is for years. that is well it over 500 million dollars a year! Of this What are the broadcasters amount, the broadcasting industry gets the lion's doing to help the radio -set share. industry put over their wares and to make it possible for When the term "broadcasting industry" is mentioned, it the listeners should be understood to get sets? Strange to say, actually they do that this includes everything that very little, with the exception goes with broadcasting, from the broadcast of a half -dozen radio manu- transmitter facturers who are also broadcasters. Over 95% of the down to the radio receiving set, and from copyrights to broadcast station advertising fees. In between, do nothing but broadcast. They take it we have many other sub- for granted that somebody will supply divisions of the industry, each of which forms the sets, and in this a distinct they are correct, since the market is supplied, independent uniti. - of the broadcast stations themselves. But for the present discussion, we will confine ourselves One would strictly to the broacasting industry as such. In the United think that the great majority of the broad- States today, we have, to begin with, some six casters would be selfishly interested in seeing to it that hundred there are more broadcast stations which cover the entire country. This listeners to their stations, since their rates figure has not changed materially are based upon numbers of listeners, but strangely enough, during the past eight this or ten years, since those stations which were discontinued assumption is erroneous and the broadcasters, at least were nearly always replaced by the overwhelming majority, trust to luck that someone will others. The stations them- provide selves are made up into so- called networks, whereby cer- the sets to the public. tain key stations are affiliated with a number of broadcast The feeling is very general that there are too many broad- stations throughout the country. There are three major cast stations in this country. Take a city the size of Chi- nation -wide networks, the "Red" and "Blue" of the Na- cago, for instance. In that city, we have alone 16 broad- tional Broadcasting Company and the one controlled by the cast stations. Several of these, not more than four, are Columbia Broadcasting System. In addition to these, we used by the various networks and give excellent programs have numerous minor networks, usually linking several -the best that may be had. What about the rest of the stations to cover limited areas. local stations? With few exceptions, they have little reason In this country, the broadcast stations are reimbursed for existing! As a rule, they supply mediocre .programs, for their financial outlays by advertising or sponsored pro- and if the program is good, it is usually of the phonograph grams, and the amount thus spent by advertisers has variety. Unknown singers, amateur speakers, poor bands reached truly gigantic figures. As an example, the Colum- and poorer orchestras fill -in the commercial gaps that these bia Broadcasting System, in a single month, (October, stations have. As for the time sold on the air by these 1934), had billings of over $1,700,000 for time on the air. stations, such commercial programs are usually the world's Bear in mind that this figure is only what the advertisers worst. Patent medicines of doubtful value, and many other paid for station time in a single month. ventures equally doubtful are broadcast day in and day out. Why do advertisers spend such gigantic sums for broad- Some of the stations blanket a certain neighborhood and casting purposes in offering their various wares on the air? are, therefore, heard better in that neighborhood than other The answer is found in two words, radio listeners. A re- stations. A number of legitimate stores and merchants cent estimate shows that we are approaching the 20 mil- broadcast their products over these local stations, but few lion mark of radio sets in this country alone! Twenty advertisers have made a profit by doing so. And million -because radio sets, with an average of three listeners each, the results to the advertiser are usually mediocre or nil, make an average of 60 million listeners. In other words, the little station must perforce get new advertisers all the approximately one -half the entire population of the country time, and the rates which the merchants pay are whatever can be reached by a coast -to -coast network, and from past they can pay. results obtained by advertisers, their investment to the This is a deplorable state of affairs from tune of approximately $14,000 the standpoint for an hour's program ap- of the neighborhood station, but it has to pears to be a good one; keep up the racket so good in fact, that at the present or go out of business, because it has no other time the three major chains have little evening income -un- time to sell, less the station is sponsored by a rich concern using it all of them being practically sold out. Of course, for these fig- its own propaganda; or by newspapers; or by churches, or ures, high as they are, do not include talent. For instance, other institutions if (when it is not necessary to take on ques- Ed Wynn goes on the air he is reputed to get $5,000 for tionable advertising on the air).

453

www.americanradiohistory.com THE RADIO MONTH

would help people to wear out their This action on the part of some of shoe leather much faster. As for the the largest cities in the country will, automobiles, it might not be a bad idea without doubt, have a mhrked effect on for Mr. Caesar to look in some cars the safes of P.A. equipment, especially and discover that a very large per- the portable types used in stores and centage already have radio sets. the mobile types used during elections Also, the good song writer overlooks and other public affairs; (the loud- one very important point in our esti- speaker above door, lower -center view, mation and that is that the folks who is taboo). stay home certainly must be wearing out the seats of their pants here and there, which they couldn't do if they AIRCRAFT RADIO were walking in the streets, so that should be credited to the recovery item. SAVES VETERAN and how about the folks who insist on sending for all the things that are FLYER advertised on the radio and subse- NCE again, last quently buying them? Has he for- month, radio gotten that? But perhaps we are ask- played the rôle of The dear public should carry 200 lb. portable sets ing Mr. Caesar to work his mentality so that they can wear out their shoes -and thus hero. This time, bring back "goodtimes." at too high a rate. it was through the medium of the De- partment of Commerce station WWO RADIO AMPLIFIERS ON at Cleveland, Ohio. A few minutes after pilot Ray W. PREVENTS STREETS ARE Brown had taken off from the Akron airport, he tuned his "ship's" radio SHOE WEAR CURBED receiver to station WWO to obtain the regular 1 o'clock weather broadcast. BELIEVE it or not, the TOWARDS the middle Instead of the weather report, he wonders of radio of last month, New was startled to hear the radio warning: never c e a s e. The York's fiery little may- "Calling Ray Brown in Lockheed greatest surprises are or, F. H. LaGuardia, NC 539M. Your landing gear is gone! still in store for us. sent a message to the police commis- Calling Ray Brown in Lockheed NC Last month Irving Caesar, New York sioner recommending the strict regu- 539M. You have lost your right song writer, bobbed up in the Washing- lation, particularly at night, of ampli- wheel !" ton offices of the Federal Communica- fiers in the streets of that city. Leaning out of his compartment, he tions Commission, with the amazing A short time before, Philadelphia glanced down at his landing gear to statement that daily radio retards banned the use of amplifiers in stores discover that one of the shock struts not only recovery, but prevents wear- or on streets altogether. These P.A. and the right wheel were dangling in ing out shoes and cars. The song man units had been causing much rumpus the air. In a flash, he knew that meant has it all doped out in this fashion: in the business sections, as numerous landing on one wheel -and his fast You see, the power of the radio is so portable units had been sold to stores, plane had to be landed at a high rate great that all America is hypnotized where music and advertising were of speed. The condition of his landing every night and sits in front of their broadcast to all who passed. gear meant an almost certain crackup. radio sets instead of walking the At this time, he was above the Port- streets or running their cars, and in age Lakes and his first thought was to this fashion, sings Mr. Caesar, people head for one of the lakes and land in don't wear out shoes, don't wear out the water although without pontoons. cars, and thus recovery is retarded!! "Then I decided that the boys would He further states that for two and a be standing by at Akron and would half hours each day 40,000,000 people have the fire extinguishers and emer- are busy at their dials, and while thus gency equipment ready if I cracked engaged they cannot walk down the shoes Amplifiers such as the one shown at the left are shop -lined streets, wear out their strictly prohibited in Philly. They were so numer- or their wearing apparel, nor can they ous that drastic steps had to be taken. ride the highways in their automobiles, 1 rl,ato by L. Sklar.) with the attendant consumption of gas- Radio was the "good Samaritan" which permitted He Fay Brown to land his Lockheed (below) minus one oline, tires and wear on engine. wheel. also recommended than an occasional 24 -hour shutdown on all radio stations would help a great deal. Well, we have a remedy for Mr. Caesar, and that is- manufacturers will now get busy immediately and make up portable sets to be worn by the dear public. For best results these portable sets should weigh not less than about 100 to 200 lbs., because this 1935 454 RADIO -CRAFT for FEBRUARY,

www.americanradiohistory.com Radio is now such a vast and diversified art it becomes necessary to make a general survey IN REVIEW of important monthly developments. RADIO - CRAFT analyzes these developments and presents a review of those items which interest all.

-.up," Brown said afterward. So he heáded back for the home airport. ENGLISH TOWN As coolly as though he were landing a perfect plane, Brown first set down STARTS his tail- wheel. An instant later the good wheel was on the ground and PROGRAM almost miraculously as he eased down the crippled side, the damaged strut DISTRIBUTION settled into place-the plane was successfully landed. WITHIN the past month R A D I o- CRAFT received MODERN news of a relay system which has sprung up at West- CATE CRASHERS wood, England. The idea is to receive HE custom of sending programs on special receivers and send passes to the studios these over land lines to subscribers in of NBC and CBS net- the locality at a nominal sum per week. works has developed a This idea in itself is not startling, 1932 1933 1934 new type of studio nuisance -the gate but when one considers the hold that The ever increasing number of calls for New York's crasher, who operates much on the the B.B.C. has held over broadcasting radio cars is adequately shown in this chart from same style as the "one -eyed Connollys" in that country, until now, some of the police records. of sports events. inside facts become apparent. For ex- Last month, one of these crashers ample, programs can be picked up from Nobody could make out what he was was discovered; causing quite a stir at anywhere, not only from the regular going to do with it, so they finally gave CBS headquarters. For weeks, a young B.B.C. outlets, and if desired, local him one and awaited results. Than was noticed at Lud Luskin's "Big phonograph programs can be distribut- The astonishing part of the incident Show" -each week he was present, ed over these lines. Thus in this local- was that he really needed it! A new dressed in the customary broadcast mu- ity, at least, the strong hold of the orchestra was scheduled to broadcast, sician's regalia of dark suit, white shirt British Post Office and the British in which a Cuban drum -like instrument and bow tie. He always carried a Broadcasting Corporation is broken. was to be used. And the darned thing violin case and Luskin was under the It is expected that the government won't play in ordinary room tempera- impression that he was a "stand -by" will intervene. tures, but has to be heated before musician or possibly from some other using. program. A check -up one evening, The "props" gang are hoping that however, revealed that the "musician" they will go through the winter with- was simply a radio listener who was HOT WORK out some fool introducing an Eskimo using his violin to crash the studio banjo or some such nonentity which gates. IN THE STUDIOS needs sub -zero temperatures before it Another "gag" was tried with Don- HE Columbia Broad - will produce a note. ald Novis-an indignant fan wrote that casting System h a s "Each Monday night the announcer long prided itself on says 'Welcome to the House Party.' I the air conditioning POLICE RADIO have been at the studio five Mondays system used in its studios, so there was and been refused admittance. Why some hullabaloo last month when a pro- CARS IN FATAL do you say 'welcome' if you don't mean gram director insisted on having a it." Novis sent two passes and later stove. Queries and protests were ACCIDENTS discovered that the fan was a prolific shoved aside -"gotta have a stove." indignant letter writer who used this POLICE cars in large way to obtain passes. cities have been successful in allaying the At CBS headquarters, the staff is crossing its fingers fears of numerous cit- hoping to avoid such a condition as the one at the right. izens and saving many thousands of dollars, during the two or three years Is the strength of the B.B.C. broken by this new they have been operating. system of radio distribution (below) which avoids the radio set tax? But along with this good work, is an Globe Photo. ever growing list of casualties caused by the speeding radio cars, themselves. Within the past month another pedes- trian was killed and within a short few months, three victims have been tallied up, in New York City alone. A little investigation and inquiry conducted by RADIo -CRAFT during the past month shows a very good reason for these increasing accidents. Be- tween the time when the first cars were put into service, in February 1932 (in (Continued on page 508)

RADIO -CRAFT for FEBRUARY. 1935 455

www.americanradiohistory.com RADIO BROADCAST PICTORIAL

This young lady is holding a new device-a stop -go signal for public speakers. The light turns yellow, then red at the end of the allotted After listening to the pontificial masses at the Eucharistic broadcasting time. Congress in Buenos Aires, South America, the Pope broadcast his message of welcome and good will to the congress from his library in the Vatican. The value of radio communication in such instances cannot be overlooked. Until Vatican City adapted radio broadcasting seriously, several years ago, it took weeks for such a message to be transmitted to the people of the world. Now it takes only a split second, and the voice itself is transmitted, instead of simply the message.

T A new type of radio telephone which enables captains of fishing boats, harbor craft and yachts to have telephone service at sea is shown above and at the right. A 50 -watt transmitter and super - het receiver are used. It is only necessary to pick up the telephone, press a button on the instrument and say "Marine Operator." Promptly a voice replies "number please" and the call goes through just as any telephone call.

To facilitate the control of signal strength from a broadcasting station in any given direction, the "graphic meter panel" shown at the left was recently developed. It is in use at KYW which opened early last rnonth in Philadel- phia with a directional radiating system to keep down possible interference with other stations. A cathode-ray tube is mounted behind the center of the panel and the signals from each of the four antenna towers form wave patterns on the fluorescent screen of this tube. These patterns can be interpreted to indicate the percentage of output in any direction. This is the first device of this type ever to be installed in a broadcasting station. west nghouse photo.

Another transmitter development appears at the right. It is a portable transmission measuring set, containing an oscillator with an equalized output which is flat from 50 to 9,500 cycles. Measurements can be made between losses of 80 db. and gains of 75 db. to an accuracy of 0.1 db. Western Electric photo. F The odd device at the left, called a Galton whistle is used to test the high frequencies transmitted by radio station W2XR in New York City. This high fidelity station has an absolutely flat characteristic from 25 to over 15,000 cycles, according to claims of the design engineers. The Galton whistle is an extremely high pitched whistle which extends well above the upper limit of audibility. iiiH,ran Pntu..

456 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com An amazing new device, invented by Capt. TENOR ROOM ( SECOND FL OR/ R. H. Ranger, noted for his numerous in- T _ ventions in television and radio communica- t^... tion bids fair to open up an entirely new o,. field to composers and singers, and for ,. 'yf educational purposes. By means of his new invention, Capt. Ranger is able to separate the soprano, alto, tenor and bass parts of a song and transmit each part individually to different loudspeakers and thus train choral singers more scientifically. The basis of the new invention is a small film on which have been recorded five different sound tracks, side by side-one sound track for the soprano, another for alto tenor, bass and the fifth one for the complete harmony. This film is made to pass around a drum before five different photoelectric cells. In front of each cell is an automobile head- ` light bulb and a small lens for bringing the rays of light into focus. Each photo-

; p - "" "° cell light and lens handles one of the five sound tracks on the film and the sound is then made to travel to five loudspeakers located in different rooms -the alto to the alto room, etc. In each of these rooms are a group of boys receiving instruction. Thus the boys with soprano voices 11. listen only to the soprano part of the composition and are able fo follow it with ease. Captain Ranger, in the control room, can listen to the various groups and instruct them accordingly. Halbran photo. y

SOPRANO ROÖM QO OUND FLOOR NORTH)

The photo a b ove shows Capt. Ranger °II in the control room following the score and giving instruction to one of the groups ' of boys he is training with his new system. The photo at the right shows the five - film projector which separates the four parts of the harmony or combines them on the fifth sound track. Two of the rooms in which the boys sing are also shown. 5 SOUND TRACKS

A Broadcasting t h e voices of the zoo presents s e v e r e l problems which are not at once evident to the radio man. First, the animals must be persuaded to make their characteristic sounds. This requires all the skill of the animal trainer - as some animals must be fed or induced with food, while others have to be angered or startled to bring forth their voices. Thus, the lion will bellow at the least

provocation, but it takes much skill to make the captive hippo I. or elephant speak. The enguin and most of the smaller animals, on the other hand, can be easily persuaded with the odors of their favorite foods. And once the sounds have been produced there is the technical problem of making their sounds appear "natural" when picked up on the microphone. It is a well - known fact that sounds, sound effects, etc., often are far from normal when they appear et the loudspeaker of the receiving set. The trumpeting of the elephant, for example, is much too loud to be picked up directly. It must be caught at a distance -and this in itself is a difficult task, as outside sounds make the background annoyingly loud under such conditions. The photos here represent a collection of views of wild animals caught when they were induced to broadcast their natural sounds over various stations in the U.S. during the past few months. They represent much effort on the part of those who tried to bring their voices before the radio audience. UlrrawlT photos. RADIO -CRAFT for FEBRUARY, 1935 457

www.americanradiohistory.com THE RADIO SET OF 1950 Within the next fifteen years, great changes are in store for the radio receiver. Just what these changes will be is predicted here by one who has been successful in foresee- ing many outstanding inventions.

Have you ever wondered how the radio receiver HUGO GERNSBACK would change in the next few years? Is television 1 just around the corner -or will it be some time be- IHAVE in the past twenty -five years predicted a great fore we shall see as well as hear over the air waves? many radio improvements, many of which have come Hugo Gernsback, for the past twenty -five years, true and which had been adopted universally. Thus, has made a hobby of predicting developments in for instance, in the December 1921 issue of my former publication RADIO NEWS, the radio and scientific fields and he has attained long before we had any complete radio sets, and when radio apparatus still a reputation from the numerous times in which he was screwed to an open breadboard, I predicted the radio console was able to see a -I called little further and a little clearer it "Radiotrola" -which is now in than other people. constant use. It is interesting to note that the radio console was not produced com- Once again, he has turned his hand to making a mercially till about 1926. I do not take any special pride in prediction -the radio set of 1950. In this article, these predictions because, after all, technical developments he points out some startling possibilities for this can be prophesied with certainty. It is usually only a mat- radio set -and even more startling is the fact that ter of time before the predicted development catches up these predictions are all based on scientific facts. with the prophecy. In Scientifically, the radio set of 1950 is predicting coming developments, I always had in mind possible to- certain evolutionary day, with a few features which seemed most reasonable exceptions. It is, however, not as to me; and, if they have yet economically practical. as yet not been adopted, it is simply because the art has not developed sufficiently. Therefore, if I make some predictions as to the radio set of 1950, I believe I BROADCAST SMALL CATHODE ROTATABLE TELEVISION do have RECEIVER RAY TUBE not to exaggerate much; and, SCREEN as a matter of fact, the developments which I describe here probably, FRICTION TELEPHOTO PILOT LIGHT will, CONTACTS TO come about much earlier than 1950. TRANSMITTER TELEVISION ' SHADOW BAND It may seem like TUNING a platitude to reit- (PART OF BROAD- APPARATUS erate that the radio set of 1950 will be CAST RECEIVER TRANSCEIVER AND equipped APPLAUSE CONTROLS with television. I, in com- TELEVISION mon with many radio engineers, have TELE-PNOTO predicted television for so many AMPLIFIER ON -OFF years INCLUDING SWITCH that it has almost become a hackneyed SCANNING idea. As I also OSCILLATORS, ETC MOVING have pointed out be- LIGHT AND fore in my various articles, there is POINTER still a "missing link" in connection with PHOTO - FINISH MICROPHONE television; because so far the real solu- TYPE OF PAPER tion of the television problem ON ROLL (that is, (MOTOR. an unmechanical scanner) is still to be DRIVEN) invented. While the cathode ray tube DROP today presents LEAF the best possibility, I PHOTO still believe that it is not the final word, AUTOGRAPH RECEIVER PHOTO AND and that some other means of instan- NEWSPAPER taneous, non- scanning method is in RETAINER the offing. What we require is something that works like the animal eye, which is still the best television instrument NEWSPAPER TWIN CHUTE, ever devised; ON ROLL OPEN ING FOR and which does not scan (MOTOR PHOTO ONLY but transmits the image instantaneous - DRIVEN) - ly AS A WHOLE, rather than by frag- mentary impulses which afterwards have to be all assembled. NEWSPAPER. -PEN` PHOTO AND Anyway, I am pretty certain that a (MOTOR AUTOGRAPH satisfactory solution of television will DRIVEN) PEN' (MOTOR have come about by 1950. Let us start DRIVEN) then, from these premises, with our radio set of 1950. One of the elements VOICE POWER that most designers have disregarded, AMPLIFIER when it comes to television in the home, SOUND CHAMBER is that they insist on fixing the television screen rigidly into the set, which is plain foolishness. When you sit in a room and listen to a radio program, PRE-SET NEWSPAPER. every one in the room can hear it, be- FOURTH DIMENSIONAL RECEIVER, LOUD SPEAKER. cause the waves travel in all directions. With the radio set in which television is incorporated, we have an entirely different technical problem, which is as follows: (Continued on page 493) 458 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com A MODERN PICTURE OF BROADCASTING Here is the "low- down" on just how the business of sending programs to the eight- een million radio listening families is prog- ressing in the U.S. today. Read these interesting and little known facts and figures. LESTER F. MILES

AGREAT DEAL has been written the revenue thus obtained by the TOTAL POWER OF THE NETWORK STATIONS IN WATTS 2.126.000 about American Broadcasting broadcasters is directly responsible for since its humble beginning in the development, improvement, and POWER OF STATION NBC quality of entertainment being pro- IN WATTS 1,610,000 1920. However, some of the statistics i now available show amazing facts and duced today. This progress can best POWER OF growth in the industry, not the least be shown by figures from the annual STATION reports of the Federal Communications CBS of which is concerned with the rapidly IN WATTS increasing listening audience. Commission, 1934, and the Depart- 515, 900 The audience to which the broad- ment of Commerce, Radio Division casters cater is definitely increasing Bulletin, Commercial and Government from year to year. We do not seem Stations, 1923, as follows: .- to have nearly reached the saturation Total number of Radio Stations in estimate, by the United the U.S.A. - 1934 - point. An States Department of Commerce (as 1922 382 The total power of radio stations in 1934. of July 1, 1934) shows 18,500,000 1934, as of July 1 593 radio listening families in the United number of radio sta- This means an audience of 55; Of this total States. tions in the U.S., only 180 are associ- TOTAL NUMBER OF RAMC) 500,000 persons, using the usual figure STATIONS IN THE U.S A 593 Broad- per family. The ated with either the National of three listeners casting Company or Columbia Broad- April 1, 1930, United States Census, of casting System networks. The fol- o w n i n g showed 12,048,762 r a di -o lowing table will show clearly the ex- homes. An increase of over 8,000,000 NUMBER OF the network system of families in four years. pansion of STATIONS radio -owning broadcasting over the period 1928 to CBS 1934. Number of Stations Total Number NUMBER OF of Stations STATIONS Growth of the Networks Year NBC CBS 19?9 58 38 92 NBC 1929 70 54 124 This growth in the radio audience 1930 73 74 147 1931 85 81 inn is a real factor in the past and present 19:1_ 87 87 174 1933 87 R3 170 development of the broadcasting in- 1934 88 92 180 dustry. This growth has encouraged (as of Nov. 1) advertisers in general to present an The power of these stations, of ever -increasing number of fine pro- course, varies greatly. The aggregate grams for your enjoyment. In turn, (Continued on page 501) L- 1934 - The number of broadcasters in the U.S. -1934. Two typical views of network equipment in a national chain; the studio monitoring and output control boards.

RADIO -CRAFT for FEBRUARY. 1935 459

www.americanradiohistory.com RADIO SETS IN THE MODERN AND "MODEL" HOME

Above, a remote- control Clarion Set. "at home." Below, a Crosley "A.C. -D.C." portable, in the home.

Above, an RCA Victor set in home surroundings. Upper right. a "radio music room" designed by L. Alavoine 8 Co.; a Philco set, in authentic 18th century setting.

Above, Philco "high- fidelity" set in an ultra- modern exhibition room by Contem- pore, Inc., at Radio City. The setting is harmonious in color and proportion. Above, a Center, front of "loudspeaker," $3,000, 3 -floor, remote control radio William and automatic phono, installation, Barton Lascase home. Right, Mrs. Lewis by Winner Yager, for Wm. Lascase, 211 accompanies, on the piano, the repro- E. 48th St. duction N.Y.C. Below, a listening post de luxe; ex of a Hammarlund all -wave set ecutive monitoring in her modernistic room, NBC headquarters apartment. Radio City, New York.

Left, a Philco midget set inside the man- agement desk in the f ' clotherÿ ' of "Amer- }:. nw ica's Little House," s the model home, at Park Ave. and 39th eO St., N.Y.C., of the N.Y. Committee of Better Homes in America. Note the I telephone and type- 1 ift y writer

460 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com NOVEL RADIO RECEIVERS

G im bel's (New York) flA010 SET version of the radio - b a r, shown here in two views. A radio for foreign a n d domestic reception and everything desired f o r "interior dec- oration." We're not sure that the fireplace fires. At any rate it's a swell apart. ment -type "fireplace" for a p a r t - m e n t dwel- lers.

Left, from Germany. A compact, extremely simple electric record pickup to be used in connection with any radio set. Special plug is attached for connection to radio chassis. Cabinet can be es - - closed during operation. Used with a midget -type receiv- Below, this novel (to say the least) a neat, er, it makes bit of designing, made for Fanny set -up. } portable Brice is built into a standard baby - grans "cabinet." Radio and phonograph combination, with excellent use of piano sounding board. As Joe would say, "Wanne buy a- piano- rad io 7"

Right, this photo shows "Lazy-tone" in a much less intrigu- ing, yet equally serviceable position -ready to do duty as a full -volumed, fine -toned up.to-the- m i nut e superhet. compact. For tubes employed, see teat under "boudoir" v i e w, lower- right. Light may be used for reading w h e n placed on end table, as shorn. ..,. '

And this, ladies and gentlemen, is called the radio -gram (gram being short for gramophone). The barrel -shaped affair does things acoustically to the music emanat- ing from records or radio and you must admit that it is different. We're not sure we like it but Londonites dol

L e f t, "Radiubar " - eloquently descriptive) A party can get side entertainment fro m this outfit, -and howl Three chassis designs (one exclusively short- wave, the others in- short and cluding Left, a 5 -tube superhet. using a s t a n d a broadcast rd 2A7, 58, 2A6, 2A5 and an 80,- bands). Bar equipment over complete "set containing hooks for slipping includes the bed -head, and a mellow light of eight" of liquor, for reading, should answer mi- highball and cock- pray- tail glasses with lady's (or myman's either!) er for sleepy -time entertainment. decanter set and "Lazy- tone" appears space the malt- A close -up of for in the view shown- at left- center. In's. ( Radiobar Co. il of America.) (\Vretorn Itetll° Me. Co.) RADIO -CRAFT for FEBRUARY, 1935 461

www.americanradiohistory.com "CONTRACTED SPEECH" ON THE NEW YORK -LONDON RADIOPHONE

The Compandor which is being tried in the long -wave transatlantic telephone transmissions is not unlike a pair of gain controls so connected that one is at maximum while the other is at minimum -the purpose is to avoid distortion and "masking" due to background noises.

N. C. NORMAN*

TELEPHONE history records a 70 db. This range may be considered steady extension of the distance to consist of two components. One, Fig. A over which it is possible to con- the volume range, of 40 db., is due to The device under trial in the long -wave trans - vey the spoken word with enough the differences in the speech powers atlantic telephone channel is shown here. of its original character to make the of different talkers, in the ways they speaker as well as the message readily talk into the transmitter, and in such quency range but which will also con- recognizable by the listener. Such ex- variable circuit characteristics as the vey in unimpaired ratio both strong tension is beset with certain difficulties lengths of terminal circuits and the and weak speech sounds. The intensity which are due as much to the varied properties of transmitters. If neces- range of a circuit may be expressed characteristics of speech as to the lim- sary these volume differences can be as the difference in decibels between itations of the means of transmission reduced to a considerable extent by that lower extreme at which speech available. manually operated gain controls. sounds would be masked to an objec- In long telephone circuits of all sorts, Even when these differences have tionable degree by noise or cross -talk the input signal energy received from been eliminated, however, there remain and that upper extreme at which the the subscribers varies over a wide the other variations, of about 30 db., circuit begins to introduce noticeable range. The power ratio of the strong- due to the natural differences in en- distortion due to overloading. Obvi- est to the weakest significant sounds ergy intrinsic to different speech ously, when the intensity range of a often amounts to ten million to one or sounds, modified by variation in em- circuit is in the neighborhood of 30 Transmisslon Research, Bell Telephone Laboratories. phasis, and varia- db. -the same range as that intrinsic tion in the efficien- to speech sounds -very careful regu- Fig. I cy of the transmit- lation is needed to insure transmission The action of the compandor system is shown in the chart at B, while the ter with frequency without loss in speech intelligibility. method is illustrated at A. and load. These va- When the intensity range of a circuit riations are great becomes less than this figure, as it oft- +15 enough so that, on en does on radio -telephone circuits, k such circuits as the transmission degradation of some sort OVERLOAD POINT transatlantic ra- seems unavoidable. sr/ > Up to the present time, improve- ' _W Z IN \ d i o - telephone m ment in this situation has been along aZ a g? Ì g channels, there is ú-15 \\\\\ \\\\\ danger that the in- two lines. The intensity range of the NOISE circuit has been increased either by re- LEVEL 25 \\\\\\\\\ J tensity o f t h e ducing noise or cross -talk, or by us- 30 %///////'; :>: :: ::.;: ii % strong vowel sounds will over- ing amplifiers and other equipment A B C load the amplifiers which will carry more power without when speech is distortion. But there are circuits where REGION UNSUITABLE = PJJJI UNDISTORTED EN DISTORTED transmitted further extension of the intensity FOR TRANSMISSION d SPEECH air SPEECH at high -B- enough volumes so range by either of these two methods that weak conso- would be very costly. TRANSMITTER AMPLIFIER) nant sounds are above the noise Compressing the Intensity Range level. For such cases, a third method of A I I T h e telephone improving transmission has been de- lCIRCUITI engineer is thus vised and is now in commercial opera-

II I faced with the tion over the long -wave radio -telephone problem of provid- channel between New York and Lon- 04- ing transmission don. This method consists of automat- GAIN GAIN facilities which ically compressing the intensity range CONTROL -A- CONTROL will carry not only of the speech before transmitting it, a wide enough fre- and expanding (Continued on page 506) 462 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com BROADCAST ARTISTS RECORD THEIR PROGRAMS A new system for making records of radio programs or local artists, which rivals commercial methods, is described here.

Fig. A-The complete "recorder " -"dubbing" from B to A. W. H. HARRISON*

RECORDING radio programs with delity amplifier, and the turntable is high quality equipment is open- revolved at the desired constant speed ing up a new field for the radio WOULD you like to set up a (either 331í.s or 78 rpm.) A pair of technician, whereby he can real- 'phones or speaker may be cut into the ize substantial profits and build up a profit- making recording studio? circuit to monitor the work. As the new and entirely self- sustaining source One in which you can make lim- end of the record approaches, the re- of income. There are many calls for cording may be switched over to the permanent records of radio programs ited numbers of records for one - other turntable so that recordings of -from artists who desire to hear how tenth the price charged by com- any length may be made. they actually sound over the air, in or- Now, if duplicate records are re- der to improve their diction, musical mercial companies using wax quired, the original is played back, with quality or general delivery -from master records? If you are in- a phono pickup, on one turntable and sponsors who desire to maintain a a new record is cut on the other with permanent record of their programs terested, you cannot afford to the cutting head, feeding the currents and ads schools which desire the -from miss this interesting article. from the pickup through the amplifier use of material which has been broad- to the cutting head. cast, for teaching purposes -from lis- If local recordings are desired, such teners who for various reasons desire as artists who desire to hear how they to keep a permanent record of some will sound, to time programs, etc., a favorite program -and from other pressed recordings (shellac base com- microphone is connected to the input sources, too numerous and too wide- position) is an economy. If more than of the amplifier and the record cut spread to itemize here. this number is needed, the pressed rec- in the manner. Here, phones The technician who has tried to same ords, made from a master record, be- should be used to monitor the record- make recordings up to now has been comes less expensive as each record sadly disillusioned by the inadequacy ing, to prevent acoustic feed -back from by the direct -cut method costs as much affecting the results. Of course, a suit- of available equipment, which is rea- as the original. sonably priced yet of sufficiently high able recording studio must be set up The results obtained with the alloy for local record making. quality to insure good clean records or acetate- covered records compare which can be "sold." With the equipment pictured Figs. favorably with the pressed records, the A, B and C, recordings may be made lifelike accuracy depending, of course, on the alloy or the new acetate -cov- A New Method of the entire in- on every component on page 509) Where the quantity of records re- stallation. (Continued quired is not more than five, a record- It is necessary to mention that the r ing system such as the one shown here, alloy records are used with bamboo, Fig. C which a new type of acetate - The radio tuner (top) and the recording amplifier utilizes cactus thorn or casein needles, while (bottom) from the rear. covered record or a metal alloy record, the acetate -covered discs require a instead of the usual commercial special steel needle. r ',Harrison Radio Co. The Apparatus Required Fig. B The speed- reducing drive to permit operation at The complete recording studio 78.2 r.p.m. 33 -1/3 or should be equipped with microphone, radio tuner, two dual -speed turntables with high quality pickups, high fidelity amplifier, two dual -speed recording turntables with self -grooving cutters and loudspeaker. With this layout recordings may be made of programs broadcast by radio stations (or by direct wire if contract or order warrants the expense of leasing the wire) of performers in the studio and of other recordings. The radio tuner is fed into one of the cutting heads through the high fi- RADIO -CRAFT for FEBRUARY, 1935 463

www.americanradiohistory.com CURIOSA IN RADIO The well -known saying that "truth is stranger than fiction" is amply demonstrated by some of the strange facts which have been collected here from all parts of the world.

PERSONALITY VERSUS BRAWN! general. The teaching staff of this institution will be PRAGUE: Not so formed from the best French orators, announcers, radio long ago Czecho- writers, and playwrights. The school was scheduled to slovakian instruct- begin its activities in October. ors of physical training took a WHO SAYS "SILENT ORBS OF NIGHT "? microphone test in Prague's PRAGUE: The Czechoslovakian state observatory in Stara broad- Dala recently conducted a series of very casting . interesting experi- studio ments. Through a system of photoelectric Only 5 among them cells and amplifiers the light from the moon and from Vega was were found to pos- recorded on phono- sess a radio per- graph records. The sonality. All of moonlight appeared which would seem as a long- drawn- to justify those out clear tone of a who earnestly be- slowly falling and lieve that certain rising intensity. varieties of mascu- This tone was line radio perform- broadcast by some ers can't possibly measure up to a he -man standard. Need- radio stations. less The to say, we are strictly and unconditionally neutral! ancient Greeks' belief in the "Music OVER 20 YEARS OF BROADCASTING of the Spheres" was for BRUSSELS: The broadcasting station of Brussels was able the first to celebrate time practically an interesting jubilee which is probably not proved well known, the twentieth anniversary of the first broad- in this man- cast ner. It is interest- on earth. In 1914 the radio station at the castle of ing Laeken, near Brussels, was inaugurated by the late Bel- to note that gian King, the light rays from Albert I, -a station which was destroyed a few Vega months later by the invading German armies. The program which were transformed into sound were traveling 26% years before transmitted at that time was literally repeated this year reaching and the United States is minus one previously claimed the earth! glory. The supposition that the United States introduced the first broadcast in the world is denied. SOARING AMONG SHORT WAVES DARMSTADT, Germany: During a recent glider-flying contest which took place, R -R -RADIO C-C-C -CURES ST -T -T- TUT -T -T -TERER short -wave telephony was used. The carrying distance was about 45 kilometers (about 27 COPENHAGEN: At a sporting event the winner of a miles) and the 20 2,000 meter race was supposed to be interviewed in front W. power was sup- of a microphone. The reporter of Radio -Copenhagen was plied by a foot - not aware that he had to deal with a stutterer and pulled operated dynamo. the exhausted winner up to the microphone. He started This little trans- to question the runner about his impression during the mitting post acted race. A little pause ... the runner hesitated for a while as a liaison be- . and then answered fluently all questions. Since then tween the commit- he has not stut- tee on the field and tered! t h e contestants The microphone during their flights. fever (fright) Special very light achieved what no receivers of about doctor could do in 7% lbs. were built years. While a for this purpose. good hearty slap The headphones on the back has were concealed in seemed a good way the flier's helmet. to relieve tempo- T h e experiment rary spells of s -s- gave very satisfac- stut - t-t- ter -r- tory results. r -ring, this case wins the prize for a bonafide, prema- HOW EFFECTIVE ARE SOS CALLS? nent cure, unless LONDON : Our cousins from the foggy regions have what there's something we consider a fine batting average for successful response fishy in Denmark! to calls for aid. During a recent period the total SOS calls and police calls resulted in the following figures: 49.18% of calls failed to accomplish their purpose, because STUDYING MAKES 'EM THAT WAY! help arrived too late (due to fog ?) ; 44.75% resulted in PARIS: The syndicate of the French radio journalists successful completion; while only 6.07% of the calls received has decided to organize a "microphone school" for the in- no response. That is pretty good shooting, when the perils struction in radio journalism and the microphone art in and difficulties connected with such work are considered. 464 RADIO -CRAFT for FEBRUARY. 1935

www.americanradiohistory.com ROBINSON CRUSOE A LA MODE national government now in power), powerful transmit- SYDNEYS: Perhaps the loneliest spot on earth is the ters have been installed which are used by the government small coral island, Willis Island, which is situated on the mostly for propaganda purposes. Although receivers in Pacific Ocean some 300 miles from the North Australian private houses are extremely rare on account of the very seashore. Recently two radio operators of the Amalgamated low average income of the largest part of the population, Radio Company re- the total number of radio receivers in China is somewhat turned from this larger than 5,000. The majority of these are local receiv- island where they ers or belong to storekeepers who use them for the entertainment of their customers. The government, which fi- % had remained 14 months -the only nances the entire Chinese radio system, does not collect (- inhabitants. Very any license fees for receivers. little would have The intervention of the government in favor of providing been known about program facilities comes as quite a surprise, from such a Willis Island if it staid and old- fashioned power as China. We cannot help were not for the but wonder if they are at last beginning to accept mod- existence of a radio ern advancements! station there which is of great impor- WHEN GREEK tance to the inhabi- ITAt.!AI d of the sur- MEETS ROMAN? t tants RADIO STATION rounding archipel- ROME: The Ital- ago - supplying ian radio station in ;' weather informa- Boni began August tion and navigation 20 a series of reg- news. Also the in- ular broadcasts in- U.) habitants of the Australian mainland, particularly those tended for Greece, of Queensland, depend on information coming from Willis which together Island concerning cyclonic movements. Willis Island, in- with Albania are 11111,--?*dllÍllia deed, is the center of a dangerous and much feared cyclonic the only countries region. The normal service period on the island for the in Europe without two operators is one year, due to its utter loneliness and their own broad - the storm peril. c asti n g stations. However, they get double pay and can play poker with These broadcasts III sea shells and old tubes -and they can always chat with the a r e interesting ops. on the mainland or on passing ships. from a political point of view be- flk cause through them 't,Y NYNGAp¡ li FRANCE ENGLAND SPLENDID is increased the Italian influence in Greece. Programs in GOOD -WILL Greek are broadcast every Monday, Wednesday and Friday ft-E GESTURE and consist mostly of press information, radio talks and II musical performances. _ COPENHAGEN: During a recent trip of his through THRILLING RADIO RESCUE various European PARIS: The ill -fated German liner "Dresden," out from countries, the man- Bremerhaven with 1,000 passengers aboard, received an ager of the Danish SOS late one evening from a French airplane which gave Broadcasting Com- its location as 30 miles north of Dunquerque. Changing pany, Mr. Holm, her course, the "Dresden" steamed until she picked up the took the initiative light signal from the distressed plane. In spite of heavy to stimulate the in- seas and a strong ternational cooper- gale, the "Dres- ation in the domain den's" boat suc- +III I of radio program ceeded in rescuing 11111 exchange. In ac- the 5 French naval cordance with the aviators immedi- agreement he made with the broadcasting companies of ately before their Belgium, Holland, Jugoslavia, Poland, Switzerland, Sweden, craft went under. Czechoslovakia, Germany, Hungary, Austria, Italy, France and England, their stations will broadcast from special phonograph records, Danish folk songs and the works of younger Danish composers. These records which will be WIRED arranged and recorded by the Danish Broadcasting Com- pany will give an insight into the musical life of Den- TELEVISION mark. FOR GERMANY This idea deserves imitation and can lead to the develop- BERLIN: ment of a lively exchange between nations in the field of In the art and literature. Of great advantage is the fact that future every Ber- such programs are economical, due to the absence of royal- 1 i n e s e telephone ties to pay. Also, they can be arranged within a very subscriber will be to able to install an additional device which will allow him short period and are portable a very high degree. We not may hope that some other broadcasting companies will fol- only to hear but also to see the other party at the end low the leadership of Denmark. of the wire. At the beginning, arrangements aré being made so that these "television" calls can be made only from certain points, so that the "caller" and receiver do not speak from their respective apartments, but from cer- CLEVER PEOPLE-THESE CHINESE! tain main post offices. It is intended to extend the trans- SHANGHAI: All the large cities in China, and also the mission of television also over the power network for uni- smaller provincial towns, have been equipped with long versal use. distance radio receivers which enable millions of Chinese Germany is taking television seriously as a medium of to enjoy radio programs. In Nanking, Canton, Peiping propaganda, also, as we pointed out last month. RAmO- and other residences of the "Kuomintang" (the Chinese CRAFT, Jan. 1934, page 392.

RADIO -CRAFT for FEBRUARY. 1935 465

www.americanradiohistory.com WHAT SET SHOULD 1 BUY? Selecting the radio set, in most families is mily-the cabinet, set selectivity, tone and an auspicious occasion. Yet, despite most volume, and special features of the chassis protracted family discussions on the sub- are discussed, and important purchasing ject it is seldom that the choice is made "do's" and "don'ts" are given. Mr. Freed wisely. In this interesting article, the author speaks from years of experience servicing comes to the aid of Mr. Jones and his fa- "radios" in and around little old New York. BERTRAM M. FREED

WHEN YOU GO SET -SHOPPING- HAT IS the best radio set to buy ?" asks Mr. Jones. (1) DON'T -buy any radio set because your rela- Mr. Jones is only typical of the many persons tive or neighbor has one like it. make inquiry daily to me in my capac- (2) DON'T -buy the choice of the dealer or sales- who this man. Test and select it yourself. ity of radio technician. The question is one that cannot be (3) DON'T -be misled by claims, statements, or answered intelligently before the requirements and economic fancy, high- sounding terms of the manu- circumstances of the buyer are considered. Most people facturer, dealer or salesman. Try the set your- are not interested in the technicalities of radio and are more self. or less contented when programs are received satisfactorily. (4) DON'T -choose a radio set because the cabi- Yet, full appreciation of the individual wants of the pros- net is a pretty one. pective purchaser and of the more important phases and (5) DON'T -take verbal guarantees or promises details of a radio receiver is essential when selecting one to of service or repair. Get them written. benefits and enjoyment. (6) DON'T -permit the salesman to rush the sale derive the greatest possible Take your time and deliberate twice before choos- mind Only That for Which You Have Paid" ing. It is troublesome to change your later. "You Get (7) DON'T- accept any kind of installation. Get With the intense competition, claims, and statements of the one recommended by the manufacturer of receiver manufacturers, the selection of a radio receiver is the receiver. both confusing and difficult for the average layman or even (8) DON'T -permit a few dollars to stand in your radio fan. Obtaining the most value for their money, dollar way to buy the receiver you most like. for dollar, appears to be the principal thought -in -mind of (9) DON'T -buy a radio receiver because the price many buyers. As in the case of purchasing any merchan- has been marked down and may be a bargain. only for You get exactly what you pay for. dise, that is, honest merchandise, you get that (10) DON'T-swallow all the salesman tells you. which you have paid. It must be remembered that the list Make him prove his statements before you buy. price of a radio receiver released by a reputable, established manufacturer is usually controlled by the quality of the cabinet, and there can be no doubt about chassis and the may the fact that a set costing over a hundred dollars is nor- other words, although two radio receivers bear the same than one that sells for less than fifty. Of list price, one may present greater value for the money than mally "better" who is in with his in- course, this statement must be qualified in the case of those the other. The radio technician touch who are not so firmly entrenched or well dustry is particularly qualified on this score to make a manufacturers the needs of the purchaser are known. known and who establish a high list price on their product recommendation after high discount. This high and offer the retailer an unusually Is There a Price Limitation? discount is of the nature of an inducement to the dealer to "push" this particular line of receivers be- How much money are you prepared to spend? This ques- recommend or by the individual considering the cause of greater profit. The salesman, too, ordinarily re- tion can only be answered ceives greater commissions when selling these receivers. In (Continued on page 495) FEBRUARY, 1935 466 RADIO -CRAFT for

www.americanradiohistory.com THE "LUXEMBOURG EFFECT" IN RADIO How little we really know about the propagation of radio waves is well illustrated by this curious phenomenon which is baffling some of the foremost men who devote their time and study to radio and physics.

The "technical room" at fhe 150 kw. Luxembourg station. C. W. PALMER

WITHIN the past few months, channels, for then increased selectivity that on which it was emitted. such eminent authorities would permit their separation. But the "To the theoretical physicist such a as Prof. E. V. Appleton of effect is obtained with stations widely phenomenon is startling indeed. We London University, and Dr. spaced in wavelength. Moreover, when know from Maxwell's original theory B. van der Pol, Dr. B. D. H. Tellegan the receiver is distuned from the medi- of wave transmission in the ether, that and Mr. J. van der Mark of the Philips um -wave station the intruding program waves of different length can travel Labs. in Eindhoven, Holland, have disappears. It must, therefore, be con- through the same free space without been focusing their attention on a pe- cluded that the long -wave (or short- any interaction whatever, and, until culiar phenomenon in connection with wave) program has been weakly re- now, it had been assumed that the transmission of radio signals. This odd ceived by the medium waves-and thus same could be said of a medium consist- effect, which cannot be explained by any on a wavelength entirely different from ing of electrified particles such as the existing theories of wave ionosphere. But this interac- An illustration from Dr. H. T. Stetson's book, "Earth, Radio and the Stars" propagation has been called howing the relative positions of the various ionised reflecting lay ers in which tion of waves in the process the Luxembourg, Efect for he mysterious "Luxembourg Effect" probably takes place, a ccording to of simultaneous reflection lack of a better name. It Prof. Appleton. from the ionosphere shows was noticed, about a year that what we can say about and a half ago, that when a free space does not hold for receiver (located in Southern an ionized medium. A theo- England) was tuned to Ra- retical physicist would sum- dio- Paris, a faint background marize the situation by say- of the program sent out by ing that the principle of the powerful Luxembourg superposition does not hold station was picked up. This in the ionosphere. in itself is not startling, ex- "When we attempt to except for the fact that the plain the matter in somewhat wavelengths of the two sta- greater detail our difficulties tions were separated by a begin and at present there is wide band which eliminated no generally accepted theory the possibility of "cross mod- of this ionospheric cross - ulation" being the cause. modulation, as we may, per- Prof. Appleton, who has haps, term it. It is true, that .. devoted a considerable E LAYER OR KENNELLY- NEAViSIOe LAYER ^@, due to the pressure of radia- amount of time to this mys- which reflects radio waves. Zone ofrnaximum Ionization tion we would expect the terious phenomenon, made electrons in the ionosphere to the following comment re- vibrate a certain amount in cently in World -Radio (Lon- the direction of transmission don) magazine. of the waves with an ampli- "The chief features of the tude which is proportional to phenomenon are easily ex- the square of the wave am- plained. It is found that plitude, and this would give when listening to a certain us the 'square law' we re- station (in the broadcast quire to get a cross modula- band) the modulation of an- Riot balloon l9mi tion effect. But calculation other station entirely differ- 'Settle ivn t shows that such an effect ent in wavelength (in the H,Dhfsfpe]k should be small and insuffi- A.pb neFma.4mi.tt af long -wave or short -wave y cient to account for the ...:íi vuka6u 5.5. \ . . range) is heard as a faint a phenomena observed." background to the desired Later developments of the program. There would be situation than those outlined nothing odd in this result if by Dr. Appleton, reveal that the two stations were in the Luxembourg Effect takes neighboring wavelength t%w',*SIMA basaltic zone! (Continued on page 499)

RADIO -CRAFT for FEBRUARY. 1935 467

www.americanradiohistory.com INTERNATIONAL RADIO REVIEW

EACH month there are received r- loudspeaker as there is no difficulty at the offices of RADIO -CRAFT with motor interference or noise. A hundreds of daily, weekly and 20 ft. wire stretched out on the wings monthly magazines originating serves as the aerial. from all over the world. Two transmitters have been developed. The one shown in Fig. C, is a SINCE the cost of subscribing to 20 -watt unit having a hand generator, by a each of these would be prohib- driven "bicycle" drive. The second is battery operated and has an itive for most radio men, we have output of 1 watt. arranged with technical trans- The instructor can thus give instruc- lators to prepare for our readers tions to his pupil during the flight, as he simply reviews of all the really impor- sits comfortably with a microphone before him and a pair of tant, new developments illus- field glasses before his eyes. trated and described each month in these publications. A DRIVING AID NOTE that the only available in- SEVERAL months ago, in the De- formation is that which is pub- cember 1934 issue of RADio- CRAFr, page lished; the experimenter must 328, a photograph of an accident U' preventer installed in a large bus in adapt the ideas to whatever Germany appeared. This consisted of Fig. A equipment he has on hand. a microphone mounted at the rear of The combined phonograph and double radio set. the large vehicle, an amplifier and a loudspeaker in the operator's booth, so that road noises and signals from RECORDING CABINETS cars behind the bus could be heard by TWO examples of combined radio re- these devices were announced recently the driver. ceivers and phonograph recording in WIRELESS WORLD magazine. The Philips company has just intro- and reproducing devices, made in Eng- duced a similar though somewhat more land are shown in Figs. A and B. The simple device in England, according one shown at A is a receiver and to WIRELESS WORLD. As shown in the TEACHING GLIDING BY RADIO phono combination having an auto- illustration, Fig. 1, this consists of matic record changer and two radio UNTIL recently, the initiation into a weather -proof mike, mounted on the tuners which can supply up to 10 re- the art of flying gliders has been trailer or the rear of a large truck, mote speakers with any one of three limited to "ground" schooling, as even directly coupled to a loudspeaker unit; different programs. the modern gliders will not carry two the only source of current supply This device is made for installation people. This meant that the instructor needed can be obtained from the car in homes, small hotels, offices or other had to give his pupil all instructions battery. The current consumption is locations where more than one speaker before the flight began, followed by equal to that of a small lamp. is required. It closes into a neat con- criticisms if the tyro was successful in sole cabinet, closely resembling an or- making a safe landing. dinary radio receiver. A recent issue of AMATEUR WIRELESS, IRON CORE COILS however, an The second device, at Fig. B, is a contained interesting new type of iron article on how the Telefunken Com- core recording table, having two turn -tables ANOTHERtuning coil has just appeared on for continuous recording, and a radio pany, in Germany, has developed sev- the European market, according to tuner for recording or projecting eral short -wave transmitters and re- advertisements which have been ap- radio programs. This instrument is ceivers for the express purpose of in in pearing all the leading publications. designed more for the recording studio training beginners the intricacies of They possess a high degree of accuracy than the home -it is made in the form handling motorless planes. The in matching and a high efficiency, due of a desk, for convenience. Both of receiver is mounted in the cock- to the method of constructing the pit of the glider, as shown in Fig. D. This receiver contains four tubes and Fig. B weighs 7 lbs. It is equipped with a Fig. D A recording desk with two turntables. The battery- operated receiver in the glider.

Fig. C The 20 -waft transmitter and hand generator which is used for training glider pilots from the ground.

468 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com STopRER SCREEN Br Fig. F Fig. I The automatic transcribing This mike and speaker needs no amplifier. machine. Fig. 2 The ST600 circuit described below. cores. A picture of one of the six avail- machines as a tabulating machine able types appears in Fig. E, below. using this principle will be able to do the same work on printed cards that cell, the doll stopped moving. This the present tabulating interesting display A READING machines do on attracted much at- MACHINE perforated cards. tention and speculation among those AN interesting photoelectric device, The opaque screen can be very easily who attended the show. invented by two Viennese engi- removed and replaced by another so neers, was recently described in RADIO that the change from one type of let- WELT magazine. ters to another does not cause loss of It consists of a movable, opaque time. THE ST600 RECEIVER screen having perforations, each corre- WHEN that well -known English sponding to the characters on the THE PHOTO -CELL DOLL engineer, John Scott -Taggart in- printing matter to be transcribed. troduces AT the Berlin Radio Show this year, a new circuit, radio experi- The printed matter rests on a highly menters and set builders throughout illuminated stand. It is automatically an interesting novelty in light - operated devices was displayed, ac- the United Kingdom "prick up their moved step by step, in such a manner ears" and get that the light reflected cording to RADIO WELT magazine. It out their screwdrivers from each suc- consisted and soldering irons, preparatory cessive small area containing a char- of a doll imbedded in a box, to as shown in Fig. G. making a new set. acter, passes through one of the per - Another box lo- forations in the screen cated in the front of the display booth, Practically an entire issue of POP- and reaches the contained photoelectric cell. During the in- a photoelectric cell, focused ULAR WIRELESS magazine was recently terval in which on a source of light. devoted to the exploitation of his each character is fo- When cused, all the perforated letters of a visitor approached the latest set. This receiver uses the the screen pass between the reflecting booth, the light beam was broken, thus double regeneration scheme employed surface and the photo-cell. When the actuating the photo-cell unit which in in all of his recent sets, and turn, started the it is letter on the screen corresponds to mechanism in the box claimed that extreme selectivity is pos- that on the printed matter, under the doll to function. The latter sible by the correct the light contained an manipulation of to the photo -cell is cut off and a relay electric motor and me- the two feed -back controls. chanical devices which The funda- is operated. Thus a signal correspond- caused the arms mental circuit of the set, disregarding ing to that character and legs of the doll to move in a life- can then be sent like manner. some of the refinements, such as a over a radio transmitter or land line As soon as the light band beam reached to the photoelectric tuner in the aerial circuit, is and picked up at a distance. shown in Fig. 2. Those who wish to It can be seen that such a machine try the arrangement can use this cir- may have many practical applications, particularly for automatic tabulating (Continued on page 492) purposes. Ordinary typewriters can be used then, instead of perforating Fig. 3 Three interesting ways fo make tuning indicators Fig. E from ordinary pilot lamps. Another form of iron -core coil for tuning. This is one of six different types of coils which were just introduced in England.

Fig. G, above The photo -cell operated doll at the Berlin show.

Fig. H, below The photo -cell and amplifier unit.

RADIO -CRAFT for FEBRUARY, I 9 3 5 469

www.americanradiohistory.com FIRST PRIZE $10.00 SHORT -CUTS SECOND PRIZE 5.00 THIRD PRIZE 2.50 Honorable Mention IN RADIO EXPERIMENTERS: Three cash prizes will be awarded for the best "short -cuts" - time- and money-saving ideas -submitted by readers of RADIO -CRAFT; Honorable mention will be given for all other published items concerning radio and its allied fields. Send us your "kinks" right away. ti HONORABLE MENTION (below) AGOOD ground for a portable radio set can be made from a .22 calibre rifle cleaning rod. Since the rod un- screws into four pieces, each about 8 ins. long it can be put into a small cabinet. The handle on the last piece provides a good grip for inserting the SPRING 1` >`0 WINDING REELf FROM rod into the ground. The tip should CAR CIGARETTE LIGHTER be filed to a point and the ground wire soldered just below the handle. The illustration shows how the first The Service Man will appreciate the convenience of this short -cut. section is filed to a point to facilitate insertion in the ground. FIRST PRIZE (above) THIRD PRIZE CHESTER KULWIEC ACONVENIENT way of keeping the service bench test (left) leads out of the way is to use a spring cord reel such as HEAP and r-- ANTENNA used with the automobile cigarette lighter. It will be neces- flexible push- -.....Al! Ifl. AIN sary to use a cord with sufficient insulation for the highest buttons for test- voltage to be tested and see that the connections inside the ing equipment reel are clean and tight. The diagram shows the method of can be made by connecting it. G. E. FooTE any experimenter HANDLE or Service Man REMOVE THE CONTACT BLADES by following the FROM AN OLO JACK plan shown the SOLDER at LEAD left. The switches TO ROD GROUND are old j a c k WIRE blades; the re- 4 PIECES 22 CALIBER turn springs and RIFLE CLEANING ROO PUSH plungers are auto BUTTONS tire valve insides. Two pieces of panel are cut and spaced apart by bakelite tube s PIECES ARE about 9/16 -in. 8 INCHES long. The plung- LONG EACH ers are mounted JOINTS ARE THREADED BAKELITE TIRE VALVE directly over the AND CAN BE UNSCREWED SPRINGS PANELS jacks and throw the circuits from A rifle cleaning rod as a ground. Above -Make your own push -button switches. normal. SECOND PRIZE (left) Below -Emergency tube sockets from old bases. FRANK J. BAUER NEXT time you are in need of a tube socket and it is not convenient to TUBE PIN get one try this handy short -cut. Take TUBE CONTACT an old tube base from a burned out - STRIP tube, and drill out the contact pins, leaving the slightly enlarged holes in the bottom. Then drill holes of about the same size in the side of the base, TUBE METHOD íi opposite the pin holes. Bend copper BASE OF FASTEN- SOCKET or brass strips as shown in the illus- ING CONTACT tration, through the two holes and TO TUBE ¡" F down outside of the base. BASE the RIVET a rI Then turn the base bottom side up CONTACT drill a hole in the center to ac- w and STRIP TO " "' OLD TUBE BASE commodate a mounting screw. A fiber FIBER DISC MOUNTING -SCREW'- HOLE disc riveted to the ends of the metal CONTACT STRIPS FASTENED TO strips completes the job and provides USE OVER- TUBE BASE TO BE USED AS SOCKET suitable tips for soldering to the con- LAP AS SOLDERING LUG tacts. R. M. GRAW

470 RADIO-CRAFT for FEBRUARY. 1935

www.americanradiohistory.com WHAM'S PROGRAMS LIGHT LAMPS An operator of station WHAM in Roches- ter, New York, established a summer camp about 1/4 -mile from the station, last summer, and discovered some interesting facts about the transmission of power by radio. The lamp and the camp site. His only regret was the station sometimes signed off cutting off the "free" power.

OPERATOR George Driscoll of 000 -watt transmitter). To this long the past summer reading by the light the WHAM transmitter staff wire, he connected an electric light which burned without the sanction of has been modestly withholding switch, a variometer and an electric the local power company. Driscoll's one of those scientific wonders which light bulb, with a ground connection to only lament was that the light went the professors describe when they talk the other side of the bulb. out when the station signed off. about "The World a Hundred Years The net result was that the electric This interesting demonstration is, of from Now." light bulb glowed at full brilliancy - course, a form of power transmission Last summer, the young technician in fact the variometer had to be de- by radio. The joker lies in the fact set up a camp in the woods near WHAM tuned to prevent burning it out. that WHAM'S transmitter draws about transmitter and erected a 290 -foot While bewhiskered savants talk 225,000 watts from a 460 -volt circuit aerial plus an 80 -foot lead -in to his about the day when power will be in order to light a 25 -watt 110 -V. bulb tent (incidently blistering his hands transmitted through the air to light at 2,000 feet distance. from the radio frequency energy col- homes and run automobiles, Driscoll At the same station, it is reported that lected by the long wire from the 50,- spent many pleasant evenings during (Continued on page 509)

Here is a most unique application of the photoelectric cell -that of preventing WLW's the huge power output of the largest "ELECTRIC EYE" station in the U.S. from leaking off to ground through the lightning arrestor in- LIGHTNING stalled on the half -wave antenna. This photoelectric cell solved a very difficult PROTECTOR problem for the engineers at WLW.

T THE base of the giant 831 -foot admirably as a giant lightning rod. vertical antenna tower of 500,- It became the problem of design en- 000 watt WLW -the world's gineers to ground the electrical energy most powerful radio broadcasting sta- thus collected from the atmosphere tion-a tiny "electric eye" stands guard while at the same time preventing the day and night protecting the radio au- grounding of the 500,000 watt power dience against interruption in the en- generated by the transmitter. tertainment. The use of the photoelectric cell was This photoelectric cell is the "brain" resorted to after the ordinary method, of a unique device recently developed that of providing a direct lightning by engineers to protect valuable equip- path to the ground by means of a ment against lightning and to prevent safety gap across the base of the loss of broadcasting power through tower, was found to be unsuccessful. troublesome "power follow -up arcs" In adjusting the gap it was discovered across the safety gap that carries that one wider than two inches failed lightning discharges from the tower to provide complete protection while into the earth. with one less than 2 inches the normal While WLW's new vertical radiator peak voltages due to modulation on the antenna increased the station's effic- 500,000 watt carrier would, on occa- iency from 50 to 100 per cent, it was sion, cause discharge across the gap. soon discovered that unfortunately the An even more serious problem pre - huge 450 ton steel tower also served (Continued on page 492)

RADIO -CRAFT for FEBRUARY, 1935 471

www.americanradiohistory.com THE LATEST RADIO EQUIPMENT

A HANDFUL OF BEAUTY! 30 -WATT AUDITORIUM (627) SPEAKER (630) (International Radio Corp.) DESIGNED to handle 30 W. of undistorted output and hav- IT IS hard to realize how an effi- ing a rather unusual efficiency of cient 3 -tube circuit and good 2 db. between 26 and 12,000 cy- toned speaker can weigh no little, cles, this speaker fits in very well and be so small. Complete with indeed for P.A., auditorium, and tubes the set weighs only 33e lbs., outdoor work. Two models are and takes up no more room than listed, one as standard, to take a good sized box of candy -port- care of requirements for a single ability in capital letters! Cases speaker, and a special model in- are of bakelite and plaskon with tended for use with an auxiliary .vide choice of colors. Uses 2 high -frequency model. High -fidel- 6C6s and 1 2A7. ity tone is accredited to improved design of voice coil and output Tiny "Jewel" a real radio sett (627) transformer. Phono -radio super'. porreole. (634)

110 V. A.C. GAS -ENGINE GENERATORS (628) USE HEADPHONES ON FOUR new one -unit lighting ALL -WAVE SETS (63I) plants are listed as 300, 600, 1.000 and 2,000 W. capacity, ideal (Insuline Corp. of America) and large for farm lighting, port- THIS adapter makes it easy to able P.A. jobs. They provide switch in headphones for clear flickerless current at a constant reception of those "marginal" sig- potential of 110 V. A. C. Engines nals. Phones can be used with or are 4- cycle, air -cooled, with 6 V. without speaker operating. The ignition, float feed carburetors, headphones connect to the input Sow mechanical governors, starting circuits of the tubes. A switch motors and batteries with remote connects to the tubes' output cir- starting control. Uses standard cuits, and permits the output New voltage amplifier. (635) automotive available every- parts transformers primary to be short - 110 V. A.C. Lighting where. New Sets. (628) Latest features include circuited, for "headphones only pressure feed lubrication, alumi- -no speaker" operation. Adapters num pistons and connecting rods, for push -pull (illustrated), or dynamic engine balance. Rubber single -tube operation, and use mounting and special muffler re- with 4, 5, or 6 -prong tubes, are l: sult in extreme quietness of oper- available. 0.00 ,_ 1 ation. y BRASS Exact -replacement electrolytics. (636) .00( ION' ;: Ì SLUG \ I8 -WATT CLASS A -BRASS INDUC- Simple inductance Resonator. (629) POLYIRON AMPLIFIER (632) (629) TANCE RESONATOR HERE we have a high -quality HERE'S a tool which should be mobile public address ampli- of real value to inspectors and fier using class A circuits, oper- Service Men. A flexible rubber ated entirely from a 6 V. storage rod contains a polyiron plug and battery. Current drain has been . brass insert in opposite ends. kept low by providing separate To test a circuit incorporating an switches, one for filaments and the air -core R.F. inductance, it ie only other to control speaker current necessary to insert either end of and the high -voltage "B" supply, the resonator into the coil. If Has 3 stages, employing 2 76s and both operations decrease signal 2 2116s. Overall gain is 75 db. with strength the circuit is correctly undistorted output of 18 W. aligned. This simple scheme saves much fussing with trimmers and Above, 10 -wire analyzer kit. (637) padders, and in most cases, makes it possible to quickly adjust for proper values by spacing or cut- "TATTELITES" NEW "VOLT- Below, multi -range meter. (638) resonator ting a few turns. The FUSES can be used at frequencies as high AGE" (633) as 26 megacycles, since losses in / /TATTELITES" protect equip- polyiron cores, even at these high I ment against excess voltage frequencies, are extremely low. breakdown by shunting excess Above, a new 30 W. speaker. (630 The flexibility feature enhances currents, thereby differing radi- the value of this tool over previous cally from the usual current -actu- types of "wands" described in ated devices. They operate by Below, new headphone adapter. (631) RADIO- CRAFT. neon discharge, glowing brilliantly

FOR PUSH -FULL POWER TUBES Voltage fuses and testers. (633) Class "A" P. A. amplifier. (632)

NEON-

' FILLER FOR HEAD- ! TUBE PHONES L

give (number) in description under picture. Name of manufacturer of any device will be sent on receipt of a self -addressed, stamped envelope. Kindly FEBRUARY, 1935 472 RADIO -CRAFT for

www.americanradiohistory.com at the following breakdown po- for use down to 17 meters. Wind- tentials: 100, 250, 500, 1,000 and ings are air -spaced by means of 2,000 V. A unique feature of the ribs. They are also flange grips, higher voltage types is their ad- and neat meter -index inserts for justable ignition point by means wavelength indications. A threaded of secondary electrodes. shelf molded inside permits mount- Uses are many. They protect ing of a trimming, padding or band - instruments, transformers, con- spreading condenser. Available in densers, gaseous rectifiers, radio 4 (A), 5 or 6 (B) prongs. sets against lightning surges, and excessive line voltages. The lower voltage rated types are excellent for locating blow fuses, defective Corking new 5. -W. DX.er. (646) resistors, condensers, etc. By intensity of the glow, approximate voltages are indicated. COMMERCIAL -STYLE AMATEUR SHORT -WAVE RECEIVER (646) (Radio Trading Company) THE DOERLE A. C. 6 bids fair "PORTABLEST" PHONO - to be one of the sensations of RADIO SUPER. (634) the early 1935. Priced down where New "99" and its elements. (639) fans like it, its exceptional effi- only 10x11x13 ciency shows up on loudspeaker sensi- MEASURINGins., and containing a DX performance in a perfectly tive 6 -tube superhet. radio re- bone -tickling manner. ceiver, dual -speed phonograph for A stage of 6D6 R.F. feeds a both 10 and 12 in. records, play- 6F7 in a combined detector and able on both A.C. and D.C. circuits, first A.F. circuit. Regeneration with tone control -this seems to be is smooth. The A.F. output of the portable -seekers' answer. Uses the 6F7 feeds a 37 which in turn 1 43, 1 6A7, 1 6D6, 1 75, and 1 drives a 41 pentode at full output. 12Z3. Matching a husky dynamic speaker to the pentode completes a very satisfying, compact, simple outfit. Single dial tuning on full - GOOD "DYNAMIC" P.A. vision airplane type dial. Set and 12 -in. 5. -W. station locator. (647) speaker are mounted in handsome Pyranol -insulated condensers (640) MICROPHONE (643) black crackle -finish metal cabinet THE designers of this new mike with patterned speaker grill. apparently had experience with sound effects resulting from husky, deep- throated bass voices, for they have made it with adjustable frequency response. Con- struction is exceptionally durable, well able to stand abuse incident to public address work. GLOBE SHOWS S.-W. frequency response is practically BROADCASTERS (647) flat from 40 to 10,000 cycles with a gain of minus 60 db. at 400 cy- AN ACCURATE, readable 12 in. Home- garage battery charger. (641) cles. globe, carrying more than 5,000 names. principal steamship routes, railroads. ocean currents, ( mountain peak heights, etc., is now available to the owners of Handy prod, gripper, retriever. (648) HANDSETS GIVE THAT broadcast, all -wave, and short- "CLASSY" TOUCH (644) wave sets. This globe establishes a prece- (Shure Brothers Co.) dent by printing in red the 'names FFOR the last word in transceiver and call -letters of all important equipment, we feel sure you will short -wave stations. this ter- take enthusiastically to this restrial sphere is a handsome or- "French hand set." The high nament in any den or liberty. output mike is equally sensitive to all voice frequencies. The re- Order -type P.A. system. (642) ceiver is a 2,000 -ohm unit. Four separate leads from mike and receiver are provided so that re- II JINIIlDIgIIla lntIrmIIrnIIn ceiver may be plugged directly into plate circuit of output tube, "SNAPPER" PRODS RE- entirely free from microphone cir- TRIEVE AND GRIP (648) Electro- dynamic microphone. (643) cuit. AREAL handy tool for hams and Service Men. or we miss a sure guess. Push with your thumb and the jaws spring apart. Above, K -12 high -fidelity speaker. MIKE "XP -53 " -A LOW -LOSS Release and that inaccessible lug (649) COIL -FORM DIELEC- is secured mechanically -and elec- TRIC (645) trically. a binding post being pro- High -fidelity radio phonograph. (650) vided at one end for use as a (Hammarlund Mfg. Company, prod. etc. It's a cinch to pick up Inc.) gobs of solder or spare nuts from out -of -the -way corners of the AN IMPROVED dielectric known chassis. PRE as "XP -53" is used in the - newest low -loss plug -in coil forms (Continued on page 511) AMPLI- FIER Mike- receiver hand -set. (644) New "XP -53" coil forms. (645)

RADIO -CRAFT for FEBRUARY, I935 473

www.americanradiohistory.com THE LISTENING POST FOR ALL -WAVE DX -ERS This page is devoted to the radio enthusiast who is solely interested in world -wide reception and facts that will aid him in obtaining the ne plus ultra in radio results.

C. A. MORRISON The radio transmitter at Reykjavik, Iceland.

AST month we took up the subject miliar items may be identified ?" This of verifications, explaining what really is not as difficult as it may seem, they are, and how to secure as nearly all foreign stations announce them. Verifications of reception calls and locations at more or less ir- may be displayed to your friends with regular intervals. By listening closely some feeling of pride, as they furnish you can generally pick out the call, and undeniable proof of your personal re- often the location. Even though you ception of some unusual station or do not understand it, you can put program. Many DX -ers eventually down the exact time it was given and acquire large and valuable collections whether by a man or woman, and any of verifications. These may be dis- other observations that might serve played or filed by various systems. A later in identifying the station. DX -er often shows his originality by the manner in which he displays these How to Identify Stations verifications. I would suggest that all DX -ers fa- One well -known DX -er in Chicago miliarize themselves with the phonetic has the walls of his radio den literally sounds of the letters, in the alphabets covered with hundreds of verifications. This photo shows an interesting experiment in of at least three commonly used for- These are neatly mounted on art - broadcasting conducted recently by a Japanese eign languages. Spanish, German and radio network, in which I board, and grouped into countries. The blind musicians French are the most important, in the exact station and location is neatly broadcast simultaneously from different locations. Telephone lines were used to cue the programs. order given. It is not important to written in india ink below the verifica- learn how to read or write these char- tion. These verifications in a dozen acters but merely to learn how they different languages, and in all colors and shapes provide sound, so that a call can be understood. Your local library, a very attractive and interesting display indeed. or radio club will help you make up these alphabets. (If Some people would rather mount their verifications in sufficient demand is manifested, we shall be glad to give an album, or loose -leaf note book where they may be ar- these foreign phonetic alphabets in this department. -Ed.) ranged in alphabetical order, or by dates of reception and Thus station LSX, in Buenos Aires would be easily rec- be convenient for carrying around. Still others file their ognized when the Announcer said in Spanish " Ellay Essay, verifications away in a letter file. A little time spent in Eckay, or L -S -X. In the call LR4 the announcer would attractively mounting, or displaying your collection is time say "Ellay, Airay, Cuatro, or L -R -4. It would also be well spent. (In this connection it would be interesting for well to familiarize yourself with the Spanish numbers us to know how you display your verifications. Perhaps one to ten. you have some new, or novel system that would be of Various stations use identification signals of various value to your brother DX- ers. -Ed.) sorts which are easily recognizable. Thus XEBT in Mexico has three cuckoo calls. VK2ME Intrinsic Value of Verifications in Sydney, Australia, is famous for the "laugh of the kookaburra "; Zeesen, Ger- Verifications often have an intrinsic value as well as a many uses a musical bar from the German song "Be True hobby interest. Many DX -ers have won various prizes with and Honest," as a interval signal, etc. The signal, or individual verifications, or collections of verifications. Sta- identification of a station should be described in your re- tions putting on "DX programs" quite often give prizes port, along with the exact time given. for the report from the greatest distance, or the best report A brief description of the type of music, together with received. The various DX clubs and radio periodicals often the kind of musical instruments being played at a certain conduct DX -ing contests of one kind or another, in which time is often important in your report. The time of a they offer valuable awards in cash, radio merchandise, or station's signing off should always be given, if heard, and handsome trophies. So often your hobby may be pro- the title of the signature piece if recognizable. ductive of some If you are listening to an unknown foreign station, a The receiving post of Mr. F. K. Moyd at Guana- good radio log, juato in the interior of Mexico. worth -while together with the time heard, and the acknowledgment language employed will generally give you a very good of y o u r ability idea of what station you are listening to, so that you may along this line. be sure of where to send your report. In the case of a Many DX -ers new station on the air, and not yet listed, you are stuck have asked me, unless you can through intelligent and careful listening "how it is pos- decipher the station's identity on the basis of the above sible to send in a methods. Most short -wave stations now give their calls, report for a ver- at least irregularly, in several different languages. ification to a sta- Next month we will take up a brief survey of the vari- tion in which ous well -known radio clubs, giving you a brief history of b o t h music and each of the larger ones, and explaining just what their tongue are for- purpose is, and how they fit into the DX-ing picture. eign, and no fa- (Continued on page 500) 474 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com NEW DEVELOPMENTS IN INTERFERENCE ELIMINATION The problem of eliminating man -made static is getting worse, instead of better according to this interesting story which tells why.

R. L. HASKINS AND C. W. METCALF* One of the field service trucks used in locating noises.

PART I munities from Maine to Florida and a the many interference surveys con- HY is radio interference the greatest as far west as the Rocky Mountains serious problem today ducted by engineers that that, by far, more radio listening public is have proved conclusively than before? Surely it is need of the the largest part of the radio interf er- lack of not for interference experts who can on . not because of any to eliminate ence in any community originates knowledge for tell what must be done the radio listener but technical or engineering but for experts in human re- the premises of if all of the technical information that noise that the interference seldom originates were lationships who can overcome the has been published on this subject make on the same premises with the receiver it would mental inertia which tends to see why combined in a single volume, the other fellow being affected. It is easy to nearly as large as an un- most of us wait for exists for as a rule the make a book take the first steps in clearing this condition abridged dictionary. This volume would to radio set receives the undivided atten- include all types of information from interference. tion of its owner, who does not operate aerial installation Experienced noise investigators cause radio in- simple discussions of location of noise sources apparatus which might complex studies of the effect agree that the while his own receiver is to highly by means of instruments now available terference on noise production and distribution, and that being used. Consequently, the radio and electrical is a relatively simple matter his opera- of the various physical of noise when its listener seldom realizes that of power circuits and the elimination electrical appliances causes a characteristics source has once been determined sel- tion of apparatus which may be connected technical duplication in his neighbor's receiver include descrip- dom presents any unusual in his there -to. It would also problem is that of of the unidentified noises heard conducted to locate inter- problem. The real fact, many listeners are tions of tests persuading the owner of the interf er- own set. In ference sources, starting with so simple surprised to learn that they are in any shutting ing apparatus that he should take the a check as disconnecting or his equip- way responsible for the unsatisfactory appliance and conclud- steps necessary to render existing in their off a suspected ment non -interfering. receiving conditions ing with involved studies of signal -to- community. field strength patterns and not mean, however, that noise ratios, Reason This does allowable interference intensities. Such The as soon as the radio set owner realizes a volume would also contain descrip- Interference surveys that have been how many noise sources are contained tions of the methods that have been conducted in both large and small com- in his own home he hastens to correct found successful in suppressing every them so that the general noise level in of man -made static. may be reduced. known type The inferior of a noise survey truck showing some the neighborhood fact that short -wave and of the instruments used for measuring interference Quite the contrary condition is re- Even the intensity. all -wave receivers are now being more vealed by the reports of interference widely used than ever before does not surveys conducted by field engineers. materially affect the radio interference For example, in a Maine city (which is problem. The fundamental knowledge best left un- named) a woman stopped that has long been available on the the driver of the survey car and asked elimination of noise at broadcast ire- him to check up on the noise heard .. quencies applies equally to elimination in her receiver -noise which she at- of interference at the higher fre- tributed to the operation of hair clip- quencies so long as the characteristics pers in a near -by barber shop. She of high frequency transmission and re- stated that this particular interference ception are taken into consideration. had been spoiling her radio reception and she had writ- Despite the wealth of technical infor a long time that available at the pres- ten to the State Public Utilities Com- formation that is Federal Communica- ent time, the many organizations in- mission and to the radio reception tions Commission in an effort to have terested in improving cleared. through the elimination of man -made the interference to concentrate their The survey engineer quickly deter- static continue the set owner's analysis of efforts on the engineering phases of mined that ignore what the trouble was correct and agreed to the problem and wholly about "filtering" has been found to be the most im- talk with the barber namely, the human his clippers. Then he asked if there portant of all; in the home that of the radio interference prob- were any appliances aspect -5 AELDED noise. On receiving It has been definitely proved in might cause radio lem. ANTENNA permission to test the various electrical LEAD Its (Continued on page 494) Eng. Dept. Toue Deutschman Corp. RADIO -CRAFT for FEBRUARY, 1935 475

www.americanradiohistory.com BUILD THIS VERSATILE TEST INSTRUMENT

The critical radio technician, who wants a really fine portable laboratory for experimental work as well as ordinary set testing, will find many interesting points in this compact, yet versatile, test instrument.

JESSE TILLETT Fig. A -The complete instrument.

THE PURPOSE of this article is to and sectionalized wiring describe a test instrument for the diagrams, radio calibration data and parts lists will be Service Man, or experi- used to convey menter, which has the the essential facts, leav- virtue of ing the exact size of panel and arrange- being somewhat more complete than the average instrument ment of apparatus more or less subject of its type and also to the choice of incorporates several unusual features the builder. which add to its utility. The above plan, in the writer's opinion, is a logical procedure, inasmuch The instrument is essentially of a as fundamental it permits the exercise of individual nature, inasmuch as it preference. consists primarily of a Volt, Ohm, Mil- liampere, A detailed and orderly presentation Capacity, Inductance and Im- of the various pedance measuring instrument, features of this instru- with ment is now in order and we will several additional features, and so con- begin by calling attention to Fig. 1. This cir- structed as to be relatively independ- cuit represents ent of changes in radio the complete schematic receiver design. diagram with every switch, An effort will be made to describe the resistor or other part assigned a number or other features of this instrument in such a identifying way as to permit mark and with all tip jacks a duplicate to be con- designated by function structed, or to assist in and polarity as Fig. D the design of well as number. The rear view of the test instrument, showing the similar apparatus. Rather than show positions of many of the parts. The compactness exact panel layouts and detailed assem- The Switches of the unit can be appreciated from this view. bly data, however, a liberal use of The two main selector photographs, switches at the together with detailed (Continued on page 487)

Fig. I The schematic circuit of the tester which measures volts, ohms, capacity, inductance and impedance values.

J11 F5 I AMP 1 J21 ^ SW4-> :. 100Y PRI. R3l -0-250 ONMS 35 OTEST (`Y) 5CEPTACLEr 25 w. SwM4ÓS-) PT 6V. 25V Spy IOOV 250V 25W 63v 310 w 81 1 J 34 t4-A""^" e IV+ 9 -s J e .--k SW 7 uR EC CAPACITY

SW.6 - 3I e EC LEAKAGE -C2

Nel MA.

NR.2 V. N92 t RI- ARD Ne 3 w RI R13/ 51 2 3 RI I. F4 4F2 4 94 R9- Re Rr b e R25 R6! R4 t ? R 9 0-600 7 oHNS 2 MA MA CK I CK I 4 5 6 6 a IAFF 1.000 I oz R-LOWISMREI SPARE I 7 0-500 0-L A.C. D.C. A IR[1000r1M5009.. 1 IOFF 250v. M100V. 50 v. M25 V. 10V. MV. I 6W. L - POSITION SWITCH RRIo PA 100 IRA 10 , Est ¡ 7I z2 I zS3,24 SW. 2 - RANGE SWITCH

476 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com A NEW PORTABLE P.A. AMPLIFIER A new A.C. -D.C. amplifier for medium -size auditoriums which weighs only 5 lbs., yet rivals many more expensive amplifiers in quality and flexibility of application. The speaker is built -in. Excellent for "hawking" wares. J. P. RELIM*

ANEW portable public address amplifier and speaker A.C. or D.C., and its clarity compares very favorably with constructed in a case weighing altogether only 5 that of more expensive "high fidelity" amplifiers. lbs. and with sufficient volume to fill a medium - A phono. pickup or a single- or double- button micro- size auditorium, is the latest development in this type of phone may be connected directly to the amplifier's input, equipment. for the microphone transformer is already built in. This surprisingly compact apparatus operates on 110 V. The amplifier consists of 2 audio stages, a 77 feeding a 43 and a 25Z5 as a rectifier. (The hookup of the 77 and Fig. I -The circuit of the complete amplifier. 43 is such that it operates in a most efficient manner. The 0.2 NEG 025.MEG RECr 25Z5 supplies the necessary plate current and also satur- O.5-MEO. A.F. A3 A F2 2529 77 ates a built -in 3,000 -ohm speaker field. The reproduction so in public 12 of the bass notes that is important any address 5w amplifier is so evident that any one listening would never guess that the maximum plate voltage on the tubes is only 100 V. The fine results on the low audio frequency are due to the heavy bypassing of all the cathode resistances (REN S and the large coupling condenser between the 77 and 43. LINE CORO) Note: the .5 -mf. condenser in the plate supply of the 77 banishes all trace of hum. The cathode of the 77 uses a 4,000 -ohm biasing resistance

e Mr f ELO rO'l ILO v -/ (Continued on page 511) M MÉG (EA CR) I.000Ow5I AC-DC Leotone Radio Co.

HELPFUL HINTS ABOUT CURRENT MULTIPLIERS Some little known facts about meter shunts are presented here. They should be of interest to every radio technician.

D. L. VAN LEUVEN*

MEG-i THE WORD "shunt" in electrical D.0 ----I CURRENT .00. VOLTS terminology covers a large field; o C OHMS 45v therefore the data that is to follow CONNECTip1S B" will be confined to those small current IN BROKEN . BATT I r- LINES models mostly used by Service Men, experimentors and others. These little instruments of high accuracy and dependability are not, as some have found out, just a piece of Fig. A -A typical meter with added shunts. resistance wire. The resistance element should be non -corrosive, its temperature coefficient practically nil and sion, the thermal effect at one end of it should be free from any tendency to the shunt, being positive, will cancel become brittle from heating due to out an equal amount of negative pres- repeated overloading. sure created at the opposing end; at Questions concerning the error least to a degree which leaves the caused by the possible thermo -couple error negligible. between some high resistance alloys Shunt Circuits and copper have been raised. In In order not to disturb the efficiency shunts constructed like those shown in of a circuit, the shunt's own resistance Fig. A with a thin copper lug exten- should be as low as possible, thus in- D. L. Van. Leuven Labs. (Continued on page 504)

RADIO -CRAFT for FEBRUARY, 1935 477

www.americanradiohistory.com LOW COST 30-WATT P. A. AMPLIFIER By an ingenious application of circuit constants, this amplifier uses the high quality of class A amplification for low volume, while it has the high output only possible with class B, when using an economical layout of parts and low voltage tubes.

WALTER A. CARTER* The appearance of the ampifier with its 8 tubes.

THE AMPLIFIER described in this article is an excellent example of a low -cost, high -quality power amplifier. The author has found, through experience and investigation, that an amplifier capable of delivering 20- to 30 -W. output, with low distortion levels will meet 90% of the requirements in the P.A. field. Previous high price listing on systems of this size has limited their use to a minority of dealers and radio men and it was to circumvent this condition that the present amplifier, one of a series recently designed by the author, was developed. Four stages, utilizing low cost tubes, produce an output of 30W. at a distortion level of less than 7% and an overall gain of 94 db. The audio range, over a frequency spectrum of 25 to Consulting Eng., Mario Radio Prods. Co. (Continued on page 510)

5 -TUBE A. C. SHORT -WAVE BAND -SPREAD KIT SET Here is a simple, reliable short -wave receiver that can be built by anyone, yet it supplies full loudspeaker volume. BERNARD ERDE*

WITH THE increasing interest tubes, including the 80 rectifier. A permits band -spread tuning on any in all -wave receivers, many type 78 tube serves as a tuned R.F. part of the short -wave spectrum. new sets have made their ap- amplifier; a 37 is employed as detec- Regeneration in the detector is con- pearance on the market. However, tor; a 77 is used as the first A.F. trolled by a resistor connected in the man who likes to make his own amplifier and the second A.F. stage series with a .001 -mf. fixed condenser. sets has been somewhat neglected by contains a 42 pentode. This provides a smooth action, which manufacturers and it is with this fact A dual tuning condenser tunes the is free from most of the troubles en- in mind that the kit set shown in the two tuned circuits with a single dial, countered in such circuits. accompanying illustrations was de- and across each of the sections of this The A.F. amplifier in this set is signed. condenser are connected the sections equipped with a phono. connection so As seen in the circuit, it has five of a 5 -plate midget condenser which (Continued on page 608) Chier Engineer, Insuline Corp. of America. OPIO 7.-

The circuit of the receiver is at the laft- all values are shown, as well as coil connections and color codes. The rear of the chassis is at the right.

478 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com APPLICATIONS OF THE GENERATOR TYPE AUTO "B" POWER UNIT There are numerous applications for the small rotary converters used for auto radio sets, besides their intended application. This article clarifies some facts about these units and outlines ways in which they may be employed. G. W. BLESSING*

derives its armature, consequently one set of similar to transformer design. THE GENEMOTOR excitation is provided name from the method of its fields is all that is required for proper The field a motor- gener- excitation. By proper coordination of through a series and a shunt winding, operation, namely, winding being placed on ator or converter, in a modified form. steel and copper in design, together half of each but lit- with highly efficient bearings, the size opposing poles in the field lamination, The theory of operation needs a few hundredths as practically all has been reduced to remarkably small which is spaced only tle explanation, inch from the armature. The Service Men are familiar with this dimensions; 2% x 4 x 5 ins. long. The of an weight is less than 7 pounds. shunt winding consists of a compara- principle. number of turns connected In the past, the chief disadvantage The armature in this unit is tively large ineffi- equipped with two commutators, one directly across the input brushes, while of motor -generator sets was the consists size required for for the input winding and the other the series, or starting winding ciency, weight, and turns of somewhat heav- a given output. These disadvantages for the output. The voltage developed of only a few at the output terminals is determined ier wire. The series winding serves have been eliminated by combining to furnish - the input and output winding on one largely by the ratio of input to output two functions. In addition turns, which is calculated in a manner (Continued on page 499) Engr. Carter MOON Co

NEW 16 MM. SOUND CAMERA FOR HOME MOVIES Here is the first sound camera commercially available for making "talkies" at home. The films may be loaded or unloaded outside of the dark room and the manufacturer processes the films free of charge. The sound camera with its carrying case and lenses.

R. D. WASHBURNE The winding THE HOME movie enthusiast can permits considerable latitude in the the reel, for rewinding. pic- operating conditions. With the separate crank swings out of the way, when not now make his own "sound" can be with a simple fool -proof mike, a portable amplifier and battery in use, while the starter button tures in position, allowing the opera- sound camera for 16 mm. film that has box can be obtained, to supply the de- locked the market by sired volume for recording on the film. tor to step into the picture himself or just been introduced on to the acting and the RCA Victor Company, Inc. -the This sound camera is equipped with pay closer attention to be sold to the public. a three lens turret with fittings for sound effects. first of its kind fitted for The camera, shown in the accom- two telescopic or other special lenses, The base of the camera is panying photograph is arranged for in addition to the standard "F -3.5" a standard tripod mount and a bracket "spot" picture tak- lens furnished with the device. By is available for convenient mounting either "studio" or boxes ing. In the rear of the case is a mike simply turning the turret, the desired of the amplifier and battery which permits the operator lens is thrown into the operating posi- used with external microphone record- mouthpiece is not shown in the to make a running comment of the pic- tion, thus permitting accurate focusing ing. (This set -up tures being taken-such as sports for both close -ups and long range photo here.) events, news, etc. The mike mouth- shots. A telescope view-finder on one side piece is easily removed to permit a A visual footage indicator is of the camera automatically deter- separate microphone to be attached for mounted in a position where the oper- mines the range of the camera and the studio or similar types of movies. This ator can easily watch for the end of (Continued on page 510) RADIO -CRAFT for FEBRUARY, 1935 479

www.americanradiohistory.com SeRVICE MEH's AS 'O MEMBERS' y FORUM

This department is devoted to members and those interested in the Official Radio Service Men's Association. It is the medium for exchanging ideas, kinks, gossip and notes of interest to those who comprise the membership.

RESISTANCE -CAPACITY TESTER (5) 55, 85, 2A6, 75. can more easily be tapped gently to (6) 227, 57, 56, 67, 224, RADIO- CRAFT, ORSMA Dept.: 235, 236, help show the short. The illustration, I am submitting a diagram and de- 38, 39, 44, 64, 65, 68, 551. Fig. 2 shows one socket only, but all tails of a very inexpensive and simple (7) 59. sockets are treated in the same man- tester for Service Men. It employs Other uses of the instrument will ner. MANITOBA HARDWARE readily suggest themselves to those only a single milliameter, 0 -5 scale. Or if who are interested or who desire to the constructor wishes to further HANDY FORMULA simplify this unit's construction a construct this instrument. CARD C. VOGAN Readrite 2 scale 0 -20 and 0 -800 meter RADIO -CRAFT, ORSMA Dept.: can be substituted. The diagram shown The subject of Ohm's Law is ever new and is self -explanatory as to the parts and HEATER -CATHODE SHORT TEST ever old. We have tables connections necessary. Also, the galore on various phases and expres- RADIO -CRAFT, ORSMA Dept.: sions of it. drawings indicate layout and compact- Since the quick heater tubes have ness of this instrument. (Fig. 1) In my 30 years in the radio game, I been out, there has been a decided in- have never seen published a complete Place a 201A tube in tester and use crease in the number of heater cathode the meter as an ohmmeter by short- list such as follows. I feel sure its shorts that occur in this type of tube. publication will be welcomed by many ing the test prongs when switch A is To test for this short on the older types moved to test position. It will measure and numerous electrical and radio of short tube testers, the addition of fans. up to .5- megohm. It is indispensable a S.P. off -on switch is all is that need- E =(I x R), (W - I), (KW x 1,000 for locating shorted condensers and ed to show this defect while the tube n, open resistors. ('R x 1V), (MA x R= 1,000), Calibrate meter into is hot. (1,000 x W - MA). ohmmeter by testing known resistances The heater is invariably connected E'= (W x R). in it. The following tabulation indi- direct to the cathode in the testers and I =(E= R), (W+ E), (KW x1,0001E), (/R x R). cates the necessary. sockets for test- breaking this cathode connection and _ ing types of tubes: P- (W - R), (KW 1,000 x E). running it to the switch and from the R = (E _ I), (El-W), (W _ P), switch back to the heater is the only (1,000 x E = MA), (1,000,000 x W + MA+). Tubes MA= (1,000 x E _ x _ rewiring needed. A good tube will R), (1,000 W E), (1) 226, 171A, 45, 201A, 210, 200A, NO ( - R x 1,000). show reading when the switch is M V = (I .' R = 1,000), (W + I = 1,000), 2A3, 30, 31, 20, 250, 34, 40. open but will show a fluctuating read- (W - MA - 1,000). (2) 280, 281, 82, 5Z3, 83. ing if there is a short up to .1 -meg. w (DC) = (E s I), (lIP x 746), (Es =R), (3) 247, 43, 33, 49, 52, DA. A single -throw switch is used in (E x MA - 1,000), (MA "- x R - 1,000,000), (I' x x (4) 57, 58, 77, 78, 2A5, 89, 41, 42. R), (1/746 HP), (Joules Seconds). preference to a push button as the tube (Continued on page 499)

Fig. I, left. 400 1,500 A. \ Cl OHMS OHMS The tester on the left is a development of one ORSMA member as an improvement over existing types of instruments. It is an ohmmeter, capac- ( ity meter and tube tester. Fig. 2, below, The testing of quick heater tubes is facilitated by this change in the tube tester. It will be found to be of much use in servicing work.

TO rB TO METER.. GRID flit GRIO TMGRID IN SHIFT TEST CLIP..., n ( PLACE Ol A TUBE SHIFT NE PRODS SOCKET FOR OHMMETER) SW. OLD /l CONNECTION 1 b,c-2 0 20 100 TEST PIN ,3 FOR °N 6.3 JACKS /1 t SWITCH Q jÌtYQs 20 MA . SCALE %Ad ` 7.5 NORMAL HEATERS ADDED I l0 V AC. VI, 0- 5 MA. A,e1,B,C, 3 S.P.S.T SWITCH -- SWITCHES

480 RADIO -CRAFT for FEBRUARY, 1935

www.americanradiohistory.com ELEMENTS OF oQQQS?SJn

4TH DIMENSION MICROPHONE AMPLIFIER.

SPEAKER\ /IÌ\ P.A. OR 1,T .._.- -. -._ - SOUND /- 'BAFFLE - EAR NEgD E AD SYSTEMS Fig. I -The knot hole effect.

Some practical considerations of the factors entering the installation of hi- fidelity equipment.

H. S. MANNEY* AND C. R. SHAWL

Fig. 2 -How sounds are localized. PART II

FOURTH dimensional sound is not Recent interest in auditory perspec- s-/...'''' A a new (angled idea in acoustics, in tive and fourth dimensional \ 0 A sound fact it probably is the MICROOHOK`E / ,,\ /// oldest seems to point a finger in the right di- AMPLIFIER phenomenon in the world which rection and, at the same time, focus at- STETHOSCOPE can be associated with those prehistoric tention to the weak spots in our present inhabitants gifted with a sense of hear- systems. Let us briefly analyze the -A- -B- ing! Primitive man rapidly learned to major defects of our apparently interpret "per- and localize sounds, i.e., judge fect" applications, with an ¡HOLES\ distance open mind their and direction, for his towards recognizing and eliminating all very existence depended upon an obstacles which prevent the attainment FENCE acquired ability to accurately gauge the of perfect artifically recreated sound. direction and speed of motion of some If we were to ask a sound system menacing and moving sound source. engineer what major types of distortion f1J Modern man, on the other hand, has are being found in present sound re- -C- -D- been so enthralled with his accomplish- producing installations, he would prob- ment of artificially recreated sounds, ably reply, "(1) frequency distortion Fig. 3- Simulating natural hearing. that many vital and missing links were (which is produced when all of the not known to be lacking and were never various audio frequencies are not re- mused -until somebody found them! produced equally well). (2) amplitude Who would have condemned the "life- distortion (or harmonic distortion like" reproduction of our 1922 radio which occurs when (-7-1I7I/5I a given increase in t horns 2 1 2 3 4 -in 1922? Who would have said the volume of sound at the microphone -B- that the "natural" reproduction of our does not cause a proportionate increase first talkie pictures was far from per- in the sound output of the loudspeak- fect? The thrill of accomplishment ers). (3) phase distortion (which is i I y7I7l l7i7lTlTl usually temporarily blinds us to minor noticed when some audio frequencies t 2 3 4 S 6 1 and major defects 2 3 4 5 6 7 8 of our creations. travel faster than others and con- -C- -- Now that the various applications of sequently reach their destination ahead public address equipment are accepted of their 'brothers')." Fig. 4-Placing mikes for sound localizing. things of the past, what is wrong with The sound technician these would un systems? This question will undoubtedly omit, (4) directional sound $ -A- doubtedly be precisely answered by the distortion (which is produced new developments when a { which . . , will take place recreated sound appears to $ $ . . come / I in the from c- P.A. field within the next year. some direction other than the one you s 'Research would naturally expect to hear it from). -e- Engineer, Columbia Sound Systems Co. ,fr" tDesign Engineer. Columbia Sound Systems Co. (Continued on page 497) 1.- '---1/ $ 4-- (it)

Fig. 7 Fig. 5. above -The best mike positions. The most common cause of directional distortion in amplifying sounds for stage effects. Fig. 6. below -Stage sound effects.

AXIS OF SOUND WAVE AS IT APPROXIMATE SNouLD BE CENTER OF -A- PROJECTED AUDITORS

HAIR ems- WOOL

ANGLE OF DIRECTIONAL MICROPHONE DISTORTION AXIS OF REPRODUCED GORSIGUNINAL OD ORIGINAL SOUND SOUND AXIS OF WAVE ORIGINAL SOUND WAVE AXIS Or PROJECTED SOUND WAVE nl)

AMPLIFIER SPEAKER TILTED TO MICROPHONE SPEAKER CORRECT DIRECTIONAL CHANNEL DISTORTION AMPLIFIER. RADIO -CRAFT for FEBRUARY, 1935 481 www.americanradiohistory.com THE ANALYSIS OF RADIO RECEIVER SYMPTOMS OPERATING NOTES

normal small plate opening in the 45 WHAT THIS DEPARTMENT socket was large enough to pass a fila- DEFECTIVE TUBES- 1 -C, IS FOR ment prong, as in Fig. resulting in a low resistance path to ground of Are not to be considered as It is conducted especially for 300 volts and placing both grid and the subject for an Operating In There- the professional Service Man. plate at about ground potential. Note. It is assumed that all Serv- the most unusual fore, the normal 300 volts was prob- it will be found ice Men test tubes when making troubles encountered in radio ably far reduced to entire set of tubes any possible a service call. Their experiences service work, written in a prac- and it is unlikely that getting through would have pos- of testing tubes, tical manner, by Service Men for signal on the subject sibly passed the 45's. Analyzer plug unless most unusual, are not of you. had been correctly inserted and hence sufficient interest to other Service Have you, as a professional gave a true reading. Cure, turn tube. man, encountered any unusual Repair, not wanted, so with a word of Men. Operating Notes should be or interesting Service Kinks that future caution about tampering, the confined to those faults which are may help your fellow workers? job was done. characteristic of, and repeatedly If so, let us have them. They will occur in connection with a par- be paid for, upon publication, DEWALD AC547 -A ticular model of radio receiver. at regular space rates. SET came in dead. Power transformer was obviously shot as all insulation was badly charred. Why had piece lead, rosin fluxed. Electrolytics MAJESTIC MODEL 90 it burned out? The electrolytics were were left in. See Fig. 2 for schematic. SET was dead when inspected. After at first suspected, but after a new cleaning and testing tubes and look- transformer was installed and new ing to aerial and ground as per usual, electrolytics had been temporarily in- SPARTON 93I no signal was audible. Voltages and stalled (since the old ones drew more SET was received dead. Cause, open currents were all within reason so than normal current) it was found that 1250 ohm parallel 182's bias re- chassis was not as yet pulled. This set by twisting the chassis the filament sistor. Repair, use 5 -watt wire -wound is so structurally built that it is hard voltage was cut in half and the trans- type. Set was now operable, but noisy. to see if the 45's are lit and after the former hummed badly, indicating a Cause of noise, the normally 15,000 - voltage and current tests the 45's were filament winding short. This was found ohm bleeder was 45,000 ohms by meas- replaced, in turn, after taking them where a socket prong was intermit- urement, and was replaced with a 10- out of the analyzer. Finally, it was tently grounding half of the filament watt wire -wound job. Also contribut- noted that one 45 was not receiving supply. The way the set was fastened ing, was the dual (one can) 15 -5 Mf. filament current, so this was checked, in the cabinet after someone had wet electrolytic condenser, each sec- and the 2.5 volts was there O.K. at tampered with it, or due to tampering tion of which was drawing far too each socket. Tube, rechecked, was with filament prongs was the primary much current, not steadily, but inter- O.K. On close scrutiny (refer now to source of trouble. Bending the prongs mittently so as to vary the available Fig. 1, A, B, C) it appeared that the had caused the trouble in the first supposedly steady D.C. to the rest of case, I believe. After possibility of the set. A third cause of noise was a was, so far, 45's () 300V. shorting was removed set dirty condenser gang, plus poor align- O.K., but oscillated badly. This was ment. After all was in order, the set TODD cured, as so often is the case, by clean- was fine. A few weeks later it came in ONMS TOTAL ing rotor contacts and wiper contacts again with a complaint of fading and at all TO 27 -:: and securely soldering wipers and 1 ID (Continued on page 505) ïT { P chassis grounds together with a one-

Fig. 3 IR I, left Fig. Various faults in a Sparton 931 are shown in the The circuit of the amplifier appears at A, while partial circuit diagram. the way in which the tuba was reversed, thus pre- A venting operation, is depicted at C. (NOISY) POOR ELECT .(WET) 182'$ VOICE 15 MP DREW 20 MILLS P -P COIL ZííIIT e00 J (REPLACED) FIELD COIL 4275V OHMS Fig. 2, below SW) 1 28000\144445 47751 GRD g A short in the filament winding caused an overload 45 ijil to the power transformer. A 80 RECTIFIER. (ELECT.) _ = 4MR. 4MF. ' (al 4508. 350v.

A r 8 xl 80 s-.....__NORMAL POOR OHMS MF ELECT - ARRANGEMENT ti TH M a PLACED S,POOR MGR EWA (REPLACED)NOISY -- (200 %t s0 &WOHMSAS ó

1(2 300v 600OMÑS10CrAL FIELD YELLOW (REPLACED)/ IT S.-TO ALL COIL HEATERS ti MEASURED 45.000 OHMS TO DEY. P ANO / IIOY A.C. (NOISY) USE 10W WIRE WOUW) 484S(ß F) ONE HALF OF THIS WINDING 1.250 0111.5 38p TROUBLE f j GROUNDED MECHANICALLY rAU5ING RUN NORMAL PLATE PROW 110V.. HEAVY DRAIN ON TRANS. AND FINALLY SW. WIRE TYPE SOLDER x2 AT 'WAND PASS A1-mw0Or10-CAUSE A.C. RUINING IT BY NEATING.Ql5PLACED) (CAUSE III TROUBLE WIRE .TOST OS SNORTING Du1 a-0 ANErrITÓRUONO. TEUSEIILG OP DUO SET (300V. ALMIOST DIRECT TO GROUND for FEBRUARY, 1935 482 RADIO -CRAFT

www.americanradiohistory.com RADIO- CRAFT'S SPECIAL NOTICE Those questions which are found to rep- INFORMATION BUREAU resent the greatest general interest will be published here, to the extent that space permits. (At least 5 weeks must elapse between the receipt of a question and the appearance of its answer here.) Mark such inquiries, "For Publication." Replies, AN A.C.-D.C. P.A. SYSTEM 1, 5 hy.; Choke 2, 500 hy.; Choke 3, magazines, etc., cannot be sent 30 hy.; C.O.D. Back issues Choke 6, 8 hy. 250 mils. of RADIO -CRAFT (304) Mr. Arthur Dridz, So. Sudbury, Mass. prior to December, 1932, Will a 16 hy. choke are available at (Q.1) On page 33 of the July 1934 issue do in place of the 30 50e per copy; except the following issues: hy. unit specified for 7/29, Of RADIO -CRAFT is a diagram of a small Choke 37 2, 3, 4, 6, 7, 9 and 11/'30; 6, 8 and A.C.- What make are 9/'31; and D.C. P.A. system of 2 watts the output transformera T6 10/'32, which are out of print. output. I am and T7? Succeeding issues about to construct this set but are still available at the would like to (A.) The resistance regular price of 25e per copy. ask a few questions to clear up some values of the chokes, Inquiries points according to the author, to be answered by mail MUST which are confusing to me. are as follows: be accompanied by 25c (stamps) Choke 1 for each In your column you stress -about 200 ohms separate question; answers the importance Choke are subject to of a 110 -V. D.C. speaker. Will the ordinary 2 -about 6000 ohms subsequent publication if considered of Choke 3 -about 300 ohms exceptional interest. speaker of 1000 to 1800 ohms generally used Furnish as a choke in Choke 5 -about 80 ohms sufficient information (in refer- the filter systems do? I have ence to magazine articles, a 1000 -ohm speaker A 15 hy. choke be sure to men- at hand and I would like can be used as Choke 2, if tion issue, page, title, author and figure to know what the differences are in the field all other values are maintained close to their numbers), and draw a careful diagram coils of this speaker and the speaker you men- specified values. (on separate paper) when needed to ex- tioned. The output transformera, plain your meaning; use only one side T6 and T7 are the paper. of (Q.2) In using a both Jensen transformers List each question. Be SURE wire -wound resistor in- and are supplied to sign your name stead of the cord type, with the speakers when the AND address. would a 5 -watt unit speakers are Enclose only a STAMPED and do 7 ordered under self -ad- their respective numbers. These dressed envelope for names and addresses (Q.3) is the quality of this speaker very numbers are 5599 -A and 5600; they are spe- of manufacturers; or, in connection with good? I have heard many small ones with cially made units designed for the amplifier at correspondence concerning corrections to terrible reproduction. the request of the author Mr. articles, as this information is I intend to use the M. R. Jones, Jr. Individual gratis. amplifier for a phono. pickup amplifier. designs can be furnished at an additional service charge. (Q.4) Could the circuit be modified by The fee may omitting be secured by addressing the inquiry to the the choke and placing the speaker PHONOGRAPH RECORD DEMON- SPECIAL SERVICE department, field in its place? and fur- STRATOR nishing COMPLETE specifications of de- (A.1) The 1000 -ohm speaker you mention sired information and available data. will be quite satisfactory for use with the (306) Mr. J. B. Nelson. Baton Rouge, La. amplifier. In fact, you can use any speaker (Q.) I am thinking of installing some sort designed for connection across a 110 -V. D.C. of phonograph device in my store, to aid in line. These speakers have field the merchandising of phonograph coils of vari- records. I once of about 1300 ous resistance values, ranging from receive numerous requests for the records ohms. This field is used 1000 to I as a filter choke in 2000 ohms, depending on the field carry, but most people wish to hear the plate supply. strength the rec- It will be noted that needed. orde before they buy them and an ordinary a switch is incorporated (A.2) you phonograph cannot in the amplifier for changing from the regular If decide to use a wire -wound do justice to the new re- pickup to resistor in place of the power cordings. an external source. This is included cord type, it so that automatic will be necessary to use one I have in mind the construction record changing devices or having a power of an am- other sources of signal rating of 50 watts. The tube filaments plifier designed particularly for this purpose may be "cut into" the re- amplifier input. This feature quire approximately 80 watts and as -one that can be placed on the counter greatly increases consid- and the usefulness of the demonstrator. erable heat is developed (especially if with a suitable pickup will reproduce the the It is quite possible to make this ventilating facilities are rather poor, as in a phonograph music to advantage. Can you unit in one compact cabinet, but it should be closed cabinet) it is advisable to use a supply me with a suitable circuit for such an remembered wide that if the speaker is included, safety margin. amplifier? I prefer one that is completely some precautions are necessary to prevent (A.3) The quality of the speaker power operated and all contained in a acoustical feed- depends portable back from taking place on its design, size of cone, size cabinet. between the speaker of baffle and and the input source. the impedance match between the power tube (A.) The circuit for a popular commercial and speaker. record demonstrator is shown at Fig. Q.306. (A.4) While the speaker field might be used It will be noticed that it contains four tubes, as the filter choke, it is doubtful if the plate including the rectifier. The values of all re- GRID -DIP OSCILLATOR sistors current for the two tubes in the amplifier is and condensers are shown on the dia- (307) Mr. C. L. Weatherwax, Chicago, sufficient to activate gram so that Ill. the field winding suffi- it will be a simple matter to (Q.1) Your article "How to Build a Grid ciently. follow this design in building your demonstra- Dip Oscillator" on page 154 of the September tor. The power transformer may be any unit 1934 issue was found extremely interesting available which supplies the desired output and I intend to build one, but voltages. have several "HIGH- FIDELITY AMPLIFIER" The transformer TI is a coupling questions that I believe will be of general transformer for matching the pickup to the interest. (305) Mr. Clarence Senobe, Rockford, Ill. tube grid. The constants for this transformer Can an oscillator of this type be used to line (Q.) I have read your article about the must be determined according to the imped- up inductances that are not in a circuit high- fidelity amplifier which appeared on page ance of the or pickup. The transformer T2 is a set? That is, to make 3 or 4 R.F. inductances 160 of the September 1934 issue of RADIO - push -pull input audio CRAFT. transformer, while T3 of the same impedance (inductance ? -Ed.). I note the correction which appears in is the corresponding output the December issue regarding unit. The latter (Q.2) To align I.F. transformers before they the speakers, transformer may be included in the speaker, are placed in the set? but I am still in doubt about several points. and should be designed to couple two 47 tubes (Q.3) Also, on What are the resistances of the following page 168, paragraph on to the voice coil of the speaker. The field coil aligning R.F. circuits in sets, you chokes as numbered in your amplifier-Choke of the say set muet dynamic speaker should have a resist- be left off, volume control full on and connect oscillator to grid cap and ground. Do you leave the grid Fig. Q. 306 cap on the tube and clip the The circuit of a phonograph grid side of the oscillator amplifier designed for demonstrating phonograph records. to the lead or should it be disconnected from the tube? PICKUP w3 ,N (6.550)(6$50)/4(3.250) Rt) (A.1) This type of oscillator is ideal 0.2-mm. for RECeRD TAPPED AT 0.I-MEG 40.000 OHMS EACH) making inductances L EXT match, whether they are moorINPUT 7 R6 C7,400MMF located in a circuit or not. The coils in 80,000 I, ques- ONM5 tion should be connected one at a time to the oscillator C6 and the resonant position found on Er- TEPM t , EtV 0.5-MF the dial. In some cases it may be necessary 55)3 (S.y wovT (2.3) 02MF J to connect a condenser across the in RT EO,RECT. C OMF coil order (IL-MEG to bring its resonant SW frequency within the range of the oscillator. In this case, the same l J. .4 condenser should be used for all coils to elimi- C2 MEG. nate the possibility of condenser differences. 4 MF When the resonant points for the 2CM F coils have been found, it is an easy matter to remove or R3 add 0.11- turns, or space out turns in order that the EG) V2 resonant points for each coil may coin- cide. (.360)4(15) 44 (A.2) 60 ossa I.F. transformers may be aligned be- 1.300 oNM fore they are mounted in the set, but this line- FRLO RS CS CDR 'fÑirOAs up is not always final, as differences in wiring n0v, C4 and layout of parts, as well as associated cir- 10MF 25ÓONM3 PUSH-PULL. S.C. cuits sometimes make differences in the align - (Continued on page 505) RADIO -CRAFT for FEBRUARY, 1935 483

www.americanradiohistory.com 131 Radio Service Data Sheet

STEWART -WARNER MODEL R -I23 4 -TUBE SUPERHET. CHASSIS tubes in multiple -purpose connection) (Receiver Models 1231 to 1239; temporary circuit is shown. Incorporates the new

of this set is 3 W. A .02 -mf. may be read with a standard This receiver has the feature of high selec- The output Tube voltages to one side of the power meter; the figures are standard tivity, due to the use of a superheterodyne condenser connected high- resistance line prevents static interference due to lights the of tube being tested, with a rec- circuit, yet it incorporates only three tubes for type being operated, etc. tifier output of 350 V. in the receiver proper. DYNAMIC REPRODUCER OET.2 1/ LP O1.MF. DET I & OSC. 002-MF .02-MF (Lammy) (600¢) RECT PT. 6A7 FT 6F7 (600'() 41 80 MMF.260 I 1 1 MF. , IrT2 (1000'() WC+ J 4Nß

sl- K - áöooNMS FIELD ÑFV .05 (w:i COIL O.IIAF II 1,500 ONU$.,, (100V) 350V (100V.)J OHMS OHMS .51ME)G. ÌH- w 7.500 OHM (' /awl ('/ -a 500 OHMS M) YOLUME CONTROL 1 ELECT.y 6MF. ,y (40oV) SWI 1i 25600 OHMS MEG. 5 MF (350V). , ELECT ELECT n (2oOYl 2w.) ('/ew) 110V., KC A.C. (TEMPORARY CIRCUIT I. F. 456

COMMONWEALTH MODELS 260 AND 660 6 -TUBE MULTI -WAVE A.C. -D.C. SUPERHETS. 15 200 -550 meters.) (Incorporates tone control, phono. pickup jacks, A.V.C.; ranges: 260- 15 -50, 200 -550, 800 -2,250 meters; 660- -50, voltages for this receiver, meas. VOLUME VOLUME STATION vo: J`AL Operating INDICATOR CONTROL SELECTOR ured to chassis ground, are as follows: Tube Cath- S. -G. Plate Type Volts Volts Volts VI 3.5 95 95 V2' 1.2 65 95 V3 3.5 95 95 o V4 1.0 60 SPEAKER. V5 14.0 96 85 () Oscillator plate potential, 95 V.; oscillator control -grid. 1 -V. The voltage across the speaker field is 120 V. The modifications of the model 260 chassis, in a detail illustration. as the 660, are shown TONE WAVE BAND WAVELENGTH A feature of both models is the use of an air- CONTROL SWITCH sw HANTE SW. plane -type dial of "tuning" type, for operation Meter Band D -19 Meter Band MO supers. of the volume control, as shown in photo. A -49 Commonwealth models 260 and B -31 Meter Band E -16 Meter Band C -25 Meter Band

t F 0.5MEG 1:1112.A TIP GIS .02- AF2 .006-MF RF ()ET 1 P O5C MEG. M F 02 .006. 6D6 6A7 606 COÑT'OL'AE A75 43 1 MÌ ) 7:7"

M(. TOO 5MF/ 0HMz 0NEG 05- CONTRR MEG --,

.25 MEG `175 OHMS 2525 MF RF DET. 1 D OSC. 606 657 1 F

DOI LMT GH TS u u

v6 COHMI15 200 OHM 53 OHN-i S - MF12 úEG

10.000 nRD COIL 0I (WDEL 660. 00t5 4000 IS T0 50. AND OHMS (MODEL 260, 15 TO 50. 200 TO 500 I F 456 KC METERS) 2250TéÉ RSj 110 V, T P.t DC

RADIO -CRAFT for FEBRUARY, 1935 484

www.americanradiohistory.com BE SATISFIED TO BE A SERVICE MAN! `YES MA'M YOU Charles Golenpaul* CAN USE THAT grass in the other pasture, which always YOUR nicer. seems greener and causes many a budding radio Service Man to go wrong. For instead of sensing and realizing the opportunities field of servicing, in the many radio men cast envious eyes in other direc- BURGESS tions such as manufacturing. broadcasting, communication, and engineering. research And all the while, the real opportunities for big returns lying virtually at their feet, are ignored. overlooked if not actually BATTERIES Let's see this radio servicing picture in its true values, therefore, instead of turning our backs to the opportunities right while craning our at hand necks and straining our eyes and ears, but mostly 1 OR our imagination, to see the opportunities 8 HOURS endeavor. in other fields of radio Radio servicing is both a business and a profession. it calls As a business for business -like methods, efficiency, economy, profit. profession it calls As a EVERY DAY" for a thorough knowledge, skill, reputation, and proper equipment. Of the tens of thousands of so- called Service Men now attending to the radio sets of the nation, age only a small percent- can truthfully qualify as Service Men and professional in the strict business sense. The vast remainder are simply jacks -of -all- trades handy men - -who might better be and trouble -shooting door bells lawn mowers and bicycles than the intricacies broadcast receiver. of a modern The opportunities for the radio Service Man, then, are not so much on the other side of the fence and in the pastures fields, but rather of other radio in his own back yard. What he needs much a ladder whereby is not so to climb that fence and land in the other fields, as a shovel and even a plow whereby and to dig deep for knowledge experience and business methods. His own field IF THIS young "Service Man" were full a vast and profitable is capable of grown crop, if only he will put in the necessary time today, and effort and initiative into its cultivation. he'd be telling owners of battery operated sets During my many years in the electrical contracting field and the that dry batteries can now be used 7 radio field, I have made the acquaintance or 8 hours a day and radio of thousands of electrical men. The similarity between both fields -at no increase in the cost per hour! me forcibly, although has always struck it seems that the radio man never thinks that way. And I have also come in contact engineers with numerous electrical and radio engineers, and have noticed their activities EVERY SERVICE remunerations and opportunities. and MAN KNOWS many battery If there set be a close parallel between electrical and radio owners who believe they will get more hours of then. let's look at trades, the electrical contracting field. There are through- service if their out the country many thousands of electrical batteries are used only 3 or 4 hours a of contractors taking care the needs of their communities. The capable day. This is equipped, adequately contractor, well belief no longer true. BURGESS Engi- financed, and possessed of a good business sense, enjoys a nice business neers have proved, year in and year out. When times are by tests made in our Laboratories good, he sells some electric appliances electric and installs considerable and in actual use, that you wiring; and when times are dull, he handles can now use BURGESS and repair much servicing work, and some wiring alterations. The Batteries 7 on the electrical wear and tear or 8 hours every day and get the maximum equipment of the community, going on all the while, depression or otherwise, serves to provide him service we've built into them!* at all times. with steady work Does the good electrical contractor envy the electrical engineer? Hardly- The electrical contractor has existed now ades. for several dec- DOUBLE THE kNJOYMENT of your battery He knows his opportunities -and the other fellow's set He knows that the limitations. average run of electrical engineers, working for customers by telling them of the BURGESS 8 Hour large corporations, do not get as much in one earn in month as he can Day. If you'd one week. He also knows that electrical engineering like complete, technical information are few and far between, while electrical jobs by engineers are turned out about the BURGESS Power House the tens of thousands every six months by universities -the 100% DRY, colleges and special and schools. Hence much supply and not enough 400 Hour "A" Battery which retails for $3.20 demand . . . too much -or uncertainty about that career built up year after year on the basis about BURGESS of just a job . too little money- making end of the venture to do with the and too much being considered an expense rather than a business -producing force. "B" and "C" Bat- trical contractor certainly No, the wise elec- does not envy the electrical engineer. teries, Nor the manufacturer. Nor the research write the Firmly worker and laboratory. installed in his own little community, working year B U R G E S S year on the homes and after factories and shops of that community, the electrical contractor digs in deeper and deeper. BATTERY CO., intrenched. He becomes firmly He is part of that community. He builds future. He is on for the Freeport, Illinois. mighty sound ground. And when he is retire, he still has ready to a business to sell out at a good price. Now the radio Service Man, still a youngster since radio servicing is hardly older than a decade. might well take a leaf from trical contractor who the elec- is, indeed, his older brother. The radio Service Man can well look at the radio engineer in electrical the same light as the contractor sees the electrical engineer. From point he now such a view- realizes that of radio engineers there are already many . and every too *For .. six months a fresh crop turned out by economical operation of 7 versities and uni- to 8 hours a day, sets schools . . . large corporations buy radio engineers should be practically any salary at powered by batteries of proper they wish to pay . and, after is still a job, all, a job capacity. Set owners shou subject to the whims and decisions of an ask their ownership in impersonal Service Men to recld- most cases. ommend type and size of bat- Meanwhile the radio Service Man is usually on his teries best suited for their use. working for others, own. Or if he usually is with a small organization wherein he can strongly intrench himself. And all the while himself he in intrenching in the community through his good work and pleasant sonality in many homes. There per- is real security here, which the usual radio engineering job sadly lacks. As for remuneration, there is nothing for which to envy the average radio engineer. Engineering salaries are no greater than aver - Aerovox Corporation. URGESS (Continued on page 492) BATTERIES AND FLASHLIGHTS Please Say That You Saw It in RADIO -CRAFT 485 www.americanradiohistory.com Radio Service Data Sheet 132

GENERAL ELECTRIC MODEL M -65 6 -TUBE "SELECTIVE SHORT -WAVE" SUPER. 5,400 -15,350 kc.) (Incorporates tone control and A.V.C. Dual -range reception: 540 -1,500 kc.; With range switch "in," align R.F. circuits 80 W. Operating vol- () Figures for detector section of tube; Power consumption, at 540 and 1,400 kc.; padder, at 600 kc. In tages for this receiver are given below. (A') rams.: (t) total current. Between the limits of the higher- frequency the "out" position, align at 15 megacycles. Type Plate Plate in the design of this set are (The position, of two maximums, of the oscil- Volta Ma. range selected using the Tube Volts Volts included four of the internationally assigned lator and first -detector trimmers, V1 3.0 100 265 6.0 broadcast bands, located at 19, 25, lower trimmer capacity for the oscillator and 265 2.0 short -wave the correct ones. V2 3.0 100 31 and 49 meters. higher for the detector, are V3 3.0 100 265 6.0 this receiver a double reduction vernier Both adjustments must be made as indicated. In peak the R.F.) V4 1.5 35 100 1.5 drive having two concentric knobs giving a irrespective of output. Merely trimmers are at bottom of coils; V5 16. 255 240 35.0 10-1 and a 55 -1 ratio of speed reduction are The R.F. 600 kc. padder, at chassis rear. V6 725' 75.07 used. Undistorted output, 1.75 W.

CM; 2.A1 50,000 OMM5 a0-140 1 AV C / 035-HF 2B7 02-Mc 2A5 0054.4 (EACN) )Aw2 \ aolau IIIW o. b )(sow MEG Ó VS ÑiIwS. (SI SW r Il/ É6 x i 1 wC01 sav ï so. Bo SECT ,BN_ FI1. aN Y ELK 0 FMF no.0 COL áU001 aNó 1 (250) 10, VS L/5.3 3.500 C 01.145

IlOV.A.0 0.000 ONM

STEWART -WARNER MODELS R -113 AND R -114 SHORT -WAVE CONVERTERS line powered; R -114 -2 V., set powered.) (Wavelength ranges: 200 to 16, and 65 to 20 meters. Model R -I 13-6 V. filaments, within the specified various "B" tap. Note the following data. veniently be obtained The plate operating voltages, with it may be lowered by inserting a suit- voltages, are as follows: (1) Do not tap off at the plate terminal limits, plate supply will only result in coupling able high resistance in series, with the plate Voltages of any tube. This Tube Available Plate the converter and set through the common supply lead. Type 170 210 250 270 thus causing feed- (4) As a check on any resistors you may plate circuit impedance, voltage of the V1 14 16 19 20 oscillation. add, it is well to test the plate back in the converter. V2 69 70 83 89 (2) The voltage supply should be as near 37 tube at the tube socket be approximately 90 V. when tested receiver obtains its power 250 V. as possible. Below this voltage, cer- It should The model R -113 satis- with a high resistance voltmeter having a from the 110 V. A.C. power line which drops tain makes of tubes may not function The factorily as oscillators on the higher radio resistance of 1,000 ohms per volt. the voltage to 6 V. across filament. There are a few sets on the market designed to derive its filament frequencies. Below 180 V., the oscillator tube (5) model R -114 is in which the negative "B" supply does not power from a "2 V." set; (Resistor X is then of the converter may not oscillate at all on radio frequencies, so that no reconnect to the chassis frame. When the con- required.) Both converters utilize plate power the higher of this type, the unit. ception will be obtained. verter is to be used with sets obtained from the set, or a separate "B" wire of the converter, which is supply to the power tubes, or the If the supply voltage to the converter is in black ground The plate develop also the negative "B" return, must not be D.C. supply to the field of the dynamic re- excess of 280, the oscillator tube may indicated by a connected to ground but to the negative of the producer if it is in the positive aide of the parasitic oscillation, persistent the broad- and annoying steady whistle. "B" supply system at a point inside filter system, usually makes the most satis- set should be grounded location for the (3) If the supply voltage cannot con- cast set. The broadcast factory and easily accessible in the usual way. Volume and tone on short waves are con- ANT. (B UE) 400 OHMS 26.000 OHMS receiver adjustments. (y4 w.) (2w)\ ((Yé trolled by the broadcast v,/ LOW) To tune the short -wave converter, proceed as 05C. r0 -awT- TERMINAL follows: 3708 56 OF B.C. SET (1) Turn the selector switch of the short- -(RED) f wave converter all the way to the left. 45MS (2) Turn on the broadcast receiver and 250V with the volume control all the way on, tune O.0 1 to zÁo) it to some point between 900 and 1.100 kc. .02- (333 to 273 meters) at which no station can i(6 be heard. If a silent spot cannot be located on the dial between these two points, disconnect the aerial. This will sharpen the tuning of the set and enable a silent spot to be found. Tune 315 OHMS t GNO. (IN POWER. the set exactly to the center of this silent spot MACS) COW: FL-113, 110V, THE VOLUME CONTROL FULL ON, ONLY) , A.0 ` WITH J and reconnect the aerial. s the broadcast re- SW (3) Make certain that ceiver is set for maximum sensitivity by pro - t.F. IS 273 TO 333 5W.3 2'/2V PILOT (OUTPUT adjusting all of its auxiliary tuning LIGHT VL MET ERS- 9OOT0 1.100KC) -V2 BLACK -RED perly a controls. Lack of DX reception may be due to a poor O OL-MF OL-MF. .L ` BUCK -RED L 5' I insensitive broadcast set. (FIL. WIRING OF R114) (200Y.)T (200V)S antenna system, or an

RADIO -CRAFT for FEBRUARY. 1935 486 www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 487

resistance values from 1 to 100,000 ohms and VERSATILE TEST positions 8 and 9 are left blank and marked "spare." Attention is directed to the number- INSTRUMENT ing and other designations on the contact arms Shhh!Shhh1 of' each individual deck, for the clearer under- (Continued from page 476) standing and guidance of the reader. As will be seen, the contact arms on Sw. I numbered lower left and lower right of diagram are de- 1, 2 and 3, and also designated +MA., +V. signated in such a way as to minimize errors and -M. -V. connect to the corresponding ter- QUIET in connection and to illustrate fully the correct minals of "M" through Sw. 3, the A.C. -D.C. positions for each of the several functions and switch, and contact arm No. 4 is used to pick ranges, as well as the proper designations to be up Fl. The numbering of the contact arms is placed on panel markers. In order to make started with the switch deck nearest the panel these various functions even clearer, however. and read downward. /ndiaidurerTESTED additional sectionalized and detailed sketches Referring now to the switch at lower right - for NOISE have been prepared will and be discussed later hand side of Fig. 1, it will be seen to consist under the designations Figs. 2 and 8. of a range -changing Referring switch and is designated again to the main selector switches. Sw. 2. The functions of this switch will be it will be seen that the one at the lower left considered in detail under Figs. 2 and 8 and it You of Fig. 1 is designated Sw. 1 and further defined seems necessary at this time to call attention Can't Hear as a "position switch." This switch performs the to only one detail of this switch, and that is the Noise, duty of switching the Weston model 301 univer- marker strip beneath, which shows the correct Because sal meter (designated as "M ") into the various panel designations for the entire switch. The positions shown on the marker strip immediately voltage and current markings are It Isn't There! below placed on the the switch. The positions are also num- top line, the abbreviation M. being used for bered from left to right; these numbers re- milliamperes and V. for volts, the milliampere presenting the contacts on the individual HERE switch designation occurring on alternate positions of decks reading from left to right in a circular switch and preceding the numbers; and the IS manner and looking down on top of the panel. voltage designation appearing on each position The first sets THE position the circuit up for the of switch, except number 9, and following the measurement of 0 -1000 volts, the individual numbers (or voltage and current values, in other SECRET ranges being controlled in turn by Sw. 2. The words). of second position on Sw. I takes care of the D.C. The ohmmeter milliampere ranges from 5 to 500 and a range scale multiplying factors ap- of 0 -1 ma. is provided on position pear beneath the voltage and milliampere mark- 3. ings on Position 4 merely provides for the convenient position numbers 1, 2, 3, 4 and 5 and ELECTRAD'S checking of the A.C. line setting through the the impedance and capacity range numbers (designated ZI, Z2, Z3, connection of the 6 -volt A.C. range of "M" Z4) appear at bottom of New QUIET across a 5 -volt tap on transformer position numbers 6, 7, 8 and 9. The above "PT." Posi- arrangement tion 6 similarly permita checking the D.C. out- was used to conserve engraving VOLUME CONTROL put of rectifier "IV" using, of course, the D.C. or other lettering required on the markers. range of "M." This position places the meter While on the subject of switches I and 2, it TH E resistance element is in series with 25,000 ohms, across a 26 -volt tap may be well to mention that it is quite essential baked on the flat outer rim on the voltage divider network. which is across to choose a switch having very low contact the output of the rectifier. This position also resistance for use as a range switch, as the con- of a rigid Bakelite ring. Over permits checking resistors of relatively low tacts are required to carry considerable current. this, the special -alloy floating con- values and with limited current handling capa- The switches chosen should also be rugged and city, by connection across the meter through the durable. One change was made by the writer tact gently glides in a straight agency of a plug inserted in 313. This is an in the switch designated as Sw. 2 which had path. open -circuit phone jack with springs insulated best be explained in some detail. The switches from the frame and connected directly across the used by the writer were constructed in such a Result: the smoothest, quietest, D.C. movement of "M." A zero adjustment is way that the spacing between the center mem- volume provided through variable resistor R32, in series ber of switch and the individual contacts on each longest -lived control ever with the A.C. line supply. Connection to this switch deck was rather small and to correct this devised. Absolute quiet is further circuit could have been made through tip jacks, condition and increase the safety factor on high guaranteed by individual testing but as it was the only one which was not pro- voltages, the bottom deck of Sw. 2 (designated tected by a fuse, and could not be so protected, as number 4 and +V.) was removed and of each control at the factory. a different type of connection was desired to temporarily disassembled and enough metal was act as a reminder that no fuse was in the filed off the edges of the individual contact points The molded Bakelite case, with remov- circuit. to give a clearance between these points and the able metal end-cover, projects back - In addition to measuring low resistances in center extension members, lying between the panel only I/2 inch, when mounted. parallel with "M" with Sw. 1 in the check D.C. points, of a fraction more than one -sixteenth of New -type power -switch (approved by position, this switch can be returned to the "off" an inch. position and underwriters) attached by a single "M" can be connected across ex- screw. Extra -long, easily -cut aluminum ternal shunta for the measurement of D.C. The Meter amperes; if at any time such magnitudes of Leaving the subject of switches for a while, shaft. Made in all standard sizes. current must be measured. let us take up other circuit details of Fig. 1. Position 6 on Sw. 1 arranges the circuit for First let us consider the indicating instrument, the measurement of high resistance and also or meter designated as "M." This instrument impedance, capacity, and inductance. Position has already been mentioned but as two depar- 7 arranges circuit for the measurement of low tures from standard were necessary, we will have to explain a few details. To begin with the writer did not care for the scale which is standard equipment on the Weston universal . d Ite- Fig e ' meter. Therefore, a scale for a Weston model t Unit 465 volt- ohmmeter was l, owcr- Compare this view with secured and substituted ,ittachcd Fig. A. for the original scale. Doubtless the Weston people can supply this instrument with the above scale already installed if requested. The second departure from the standard arrangement of the above meter was the removal of 110 ohms of resistance from the 5 -volt A.C. multiplier which comes mounted in instrument case and which was temporarily removed to facilitate //WM-- stripping off the above resistance. The resistor referred to is designated RI in Fig. 1 and is RESISTOR shown inside meter case. The arrangement of the other parts within the meter case is also shown for reference. The resistor marked "shunt" comes fastened to the back of the meter case and is a corrective shunt for the D.C. ranges. The reason for removing a portion of ËLËCTÄÄD the wire from RI is to compensate for the in- Electrad, clusion of fuse n, which has an average resist- 175 Variek St., ance of 110 ohms. Were correction for this not New York, N. Y. provided for, there Please send new 1935 Re- would be an error on the sistor Catalog. Cheek here louver voltage ranges. It is a very good idea to for folder on new QUIET Vol- avoid changing a delicate instrument like the Woe Control. universal meter under discussion and though the writer made the abge changes he feels strongly urged to recomfMnd that the instru- Address___.__ .._.._.__..._.._....- -- ...._.._ ment be ordered from the factory with the de- RC -1 Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 488 RADIO -CRAFT for FEBRUARY, 1935

sired scale and with the A.C. multiplier resistor condenser across the voltage divider. In fact wound to 110 ohms Less than the standard value. this was tried experimentally and was entirely If the fuse is eliminated, no change in the satisfactory. but the choke was added for the standard value of Rl would be necessary. The sake of a more nearly pure D.C. for use in error. if fuse is included but no correction made conjunction with the electrolytic condenser in Rl, will be slightly more than two per cent leakage tests. on the 5 -volt A.C. range and half that on the As mention has just been made of electrolytic 10 -volt range. condenser leakage tests, it may be appropriate Several references have been made to F1 and at this point to call attention to Sw. 6 and Sw. we may as well give detailed consideration to 7, since these switches are an important part c§t:00.0.141, this and the other fuses at this point. One of of the electrolytic condenser tests. and are not the several advantages of the instrument we shown in EC leakage test details in Fig. 3D. It have been discussing is the inclusion of fuses in will suffice to say that Sw. 6 when depressed. the various circuits in such a way as to afford places the D.C. milliampere ranges of "M" in complete protection to the meter at all times series with the negative side of the condenser MAYBE and also to afford protection to the various under test and the negative side of D.C. supply multipliers and shunta, except resistors R19, furnishing the leakage test voltages. as seen by YOU'RE R20, R23 and R24. The circuit requirements do careful inspection of circuits. When Sw. 7 is not permit the protection of these four resistors depressed, the condenser under test is removed but protection is afforded the meter at all times. from connection to the D.C. power source and MISSING SOMETHING The fuses will blow at 11A to 8 times overload, is connected across the capacity measuring cir- except the 1 /100 -ampere fuse which blows at cuits of the instrument through the connections Practical Mechanics Here in Sprayberry's about 16 times normal load. However, caution to J? and J8. of Radio Service is the ONLY COURSE de- be exercised in the use of all the func- signed exclusively for men already in the should Circuit Details service business -the ONLY ONE that brings tions of the instrument described as there is no PRACTICAL help on every phase of servic- way by which we can prevent a certain amount IC is believed that the purpose of the tip jacks ing with a bare minimum of theory, mathe- of pointer "slamming" on overloads consider- at upper left and upper right of Fig. 1 are matics, etc. And it is the ONLY COURSE ably in excess of normal current carrying rating sufficiently clear not to require detailed discus- offered without costly bindings, high pres- of the meter but still not of sufficient magnitude sion, particularly as they appear again in Figs. sure selling, etc. a price so low that -at reason fuses 2 and 3. However, J9 and J10 marked K -F every serviceman owes it to himself to in- to blow the fuse. The for using vestigate. Until you do, you may I5e miss- in the voltage and current measuring circuits and CG respectively may be mentioned in passing something of utmost importance. is obvious, but the writer believes the fusing of ing. These two jacks permit connection to the the meter branch of the resistance and imped- 3 -volt battery supply used on low ranges of the NOTICE ! ance measuring circuits. while not so obvious ohmmeter and this permits a grid -shift test to IMPORTANT perhaps, is just as important, inasmuch as the be made while checking a radio set. If a higher Now -without extra cost -you get com- is voltage is needed for this purpose, it is suggested of the meter is thus protected in event connection plete easy instructions on the use two of the smallest type 3 -volt flashlight most accurate and inadvertently made to a voltage source while that OSCILLOGRAPH -the be in series, with the free measuring instrument to be made measuring resistance or impedance. batteries connected universal and the free posi- available to servicemen. Several lessons on In purchasing the fuses. it will be advisable negative post joined to J10 been to J5, the spare tip at top this all -important subject have just to purchase several of each in order to have a tive post joined jack Course not one tip We are added to the Sprayberry -at sufficient number on hand for replacement pur- of the left -hand row of jacks. cent of added cost to you! with Fig. 1 and will proceed to poses. This applies particularly to Fl because finished now discuss Fig. 2 and then Fig. 3. HELP it is a of certain calibrated circuits and THIS COUPON WILL part be noticed that in all the diagrams it can not be shorted out or replaced with other It will YOU SAVE $3.00 2 and Fig. 3 we do not show 7 values (as can the remaining fuses) in emer- shown on Fig. the position switch, nor do we show gency. the builder feels that the slight com- Sw, 1, If A.C. switch. It is assumed that of circuit through the use of fuses is Sw. 3, the -D.C. IF.L.SPRAYBERRY2548 nglon Ú'cldC2N.W plication have been set to the correct not in line with personal preference they can these two switches Please send without obligation on my part, This avoids confusion and lessens the by adding 110 ohms to the resistance position. details of SPRAYBERRY'S PRACTICAL ME- be omitted number of connections and leads to be traced CHANICS OF RADIO SERVICE. Also tell values specified for resistors R2 and R18, leav- of famous in Figs. 2 and 3 and since the functions of how I can get the new series ing the value of Rl the same as originally sup- Sw. 1 and Sw. 3 are not at all complicated and SPRAYBERRY DATA SHEETS (regular price, plied with the meter. Deck number 4 on Sw. 1 have been explained in the discussion of Fig. 1, $3) at no additional charge. could then be left off and connections to con- no further comment seems necessary. Perhaps 4, 5, 6 and 7 could be tied to cor- tacts 1, 3, we should note the fact that wherever direct Name responding contacts on deck 3. Through con- is shown in Figs. 2 and 3. the would then be made in place of the current function nections the D.C. portion of "M" is the Complete address remaining fuses. resistor across corrective shunt supplied with the meter (men- RC 2/35 tion of which was made earlier). Careful com- The Power Supply Unit SPRAYBERRY'S PRACTICAL As the power unit, comprising PT., 1V, and associated apparatus, serves so many functions Fig. 2 MECHANICS SAEIO SERVICE and is so intimately involved in these functions. Details of the measuring circuits. is directed to certain features of this attention 32 unit. As will be seen by inspection, the trans- Fl.VO0,AMO. R2 -A- O MC 4,840 OS former PT.. consists of a 100 -volt primary with D.CV, fylOONMS -pyri SERVICEMEN input through REC, Sw. 4, variable resistor R32 04900 THOUSANDSDf ea `f3y aa and the secondaries consist of a 6.3 -volt winding .ÉQ say the , wG for supplying the heater of 1V, and a high volt- ,O 5Ó0Mál EG %(eGNMS í5 age secondary tapped at 5, 25, 230, 250, 270, ( CONDENSER 290 and 310 volts. The function of R32 is to S. permit dropping the line voltage to 100 volts to Nwl _ / ANALYZER satisfy primary voltage requirements and to N14OECK 1 2 3 4 5 6 7 8 9 permit proper zero adjustments on the high OF SW.2 t00pV. 5001!2521 IOa/ 50V. 25V 10V 5V "Simplifies Radio Service" resistance and impedance ranges. The purpose 32 of the 5. 25 and 250 volt taps on the secondary Fl1/qOAMP, -M'- -B- "I certainly am more than pleased is to supply correct voltages for the various A.C.V. 91.000 ...ma Emma with the TOBE CONDENSER impedance ranges as will be mentioned under OC and don't see how , _ 48 a8 R7 R5 45000 R3 ANALYZER Fig. 3. The 230, 270. 290 and 810 volt taps, in OmMS any real service organization ]I 0.5- .M5 245 RG ¡ C2 EG EG. Ra_ SdS could do without it. It has addition to the 250 volt tap already mentioned, ¡MEG / certainly located troubles provide for an adjustment of the A.C. input / 1 /em ó'iíEMS / MF 1 (/ for me which might have to rectifier 1V, so as to establish an approxi- I I/ r 1'1 taken hours otherwise. mate equality between the A.C. voltages and the 35^ NwE I cannot praise it too rectified and filtered D.C. voltages at the output 94.14 DECK 1 2 3 4 5 6 7 8 9 highly and feel that OF SW. 2 1000V 500V 250V. I50V. 50v. 25V. 10V. 5V. It isi a labora- of the voltage divider. This arrangement is tory instrument provided for convenience in operation and avoids 33 F2 44I4R RIO. 150 OHMS is no large changes in the setting of R32 MCr,< / -C- -there frequent and ww,- guessing about when shifting from resistance to impedance F3 -%A mR the state of 0-500 yly measurements and between the various ranges SITYM .y a condenser sums provides for the 101 with this test - of these functions. Also it RIE 513 812 in characteristics of 1V with 31/ ia5omws 20.45 r.5oMA5 loewss er." Paul C. Conover, University of Ill., gradual change the 1/31dIn Champaign, Ill. aging and for correct readjustment of voltage values when 1V is replaced. NQ3 r""' Y $11.40 net to servicemen The filter is a condenser input arrangement. N8.3 DECK. I 2 3 4 5 8 7 5 9 the required D.C. OF Sw.2 503MS. 2001xA. 254AA. 51.15. maufacturers and service both for the sake of getting Recommended by set output voltages. without the excessive A.C. input schools. voltages which would otherwise be required, and 6,34 Sold by leading service supply hoslses. to secure the maximum filteration possible 511/200-AMP. also 0C.MA. / -- with a single- section filter. As a matter of fact. AÇe Corporation the single filter choke could have been omitted °-t J .low. TobeDeutschmann without effect the resistance measuring . YlY CANTON, MASSACHUSETTS any of functions, using simply, about a 2 or 8 mf. ] Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 489 parison of these detailed sketches with the corn- resistor was used to raise the effective value plete schematic in Fig. 1 should clear up any of the meter branch of circuit to 200 ohms on doubtful factors and establish in the reader's account of the difficulty of getting very low mind a clear picture of all functions and re- values of resistors for the 500 -milliampere lations. range. Raising the effective resistance of "M" Figure 2A shows the D.C. volts position of permitted a correspondingly larger value of "M" and makes clear the manner in which the shunt resistor to be used. Such an arrange- voltage ranges are chosen by number 4 deck of ment also tends to minimize the effects of long Sw. 2, also gives values of all resistors and leads in the wiring and of other extraneous shows that the multiplier network is a corn- resistance which in a low resistance circuit, and bination of parallel and series resistors. Should particularly in a parallel circuit, would introduce T-ROU$lf any one of the multiplier resistors below 250 error. volts become open, only that range would be Extreme care should be used in making all affected. The series arrangement for the two connections of course, but this is especially highest ranges was used for reasons of economy. true in making the connections between the SPOTS Figure 2B shows the A.C. voltage measuring individual resistors RI I, R12, RIS and R14 be- network and the only comment that seems neces- cause an open circuit between any of these sary is to call attention to the blocking con- resistors might cause the burn out of "M." denser connected between J1 and J6. The ab- The measurement of current involves a similar breviation OM simply means output meter and procedure to the voltage measurement, con- the use of this arrangement for blocking a D.C. nection being made to Jl and J3 with Sw. 1. set Component in a receiver's output circuit is al- to the 500 ma. position; Sw. S to D.C. position ready familiar to the experienced radio man. To and range switch Sw. 2 to desired range. measure voltage, connection is made to J1 and Figure 2D shows the 0 -1 ma. range and is so J2 and position switch Sw. 1 (on Fig. 1) is simple as to need little comment, connection set to the volts position. Sw. 3, also shown on being made to Jl and J4 with Sw. 1 set to the Fig. 1, is set to A.C. or D.C. as the case may 1 milliampere position and Sw. 3 set to D.C. be, and range switch Sw. 2 is set to desired Position. range. All D.C. voltages, and A.C. voltages Next we proceed to Fig. 3. Figure SA shows, above 10 volts. are read on lower scale of "M" in detail, the resistance measuring ranges from and the offset scale above the D.C. scale is used 1 ohm to 100.000 ohms. These ranges could all to read 5 and 30 volts A.C. have been obtained, by certain changes. through Figure 2C shows the series shunt arrangement the same means employed in the high resistance used for current measurements. The series measurements but it was desired to make ranges shunt was used in order to permit the various up to 100,000 ohms independent of connection ranges to be selected by a single arm on the to an A.C. source. Measurements are made by range switch. Since current shunts are made of connecting test leads to J7 and J8. setting Sw. 1 relatively heavy wire and since they are pro- to the low resistance position, Sw. 3 to D.C. tected in this circuit by fuses, there is little position and Sw. 2 to desired range. The zero chance of an open circuit developing and there- adjustment is then made either by shorting test fore the series arrangement is justified in this prods or by depressing Sw. 5 (which is shown particular case. In general the so- called parallel between J7 and J8 on Fig. 1) and adjusting arrangement is favored, one advantage being R25, the 600 -ohm variable resistor across "M." that the individual shunts can be made by the for a full scale reading. After this, connection the constructor (by the "cut and try" method) is made to the resistor to be measured and whereas the arrangement here must be calculated. ohms scale on "M" is read, multiplying by the Attention is directed to the inclusion of R10, a scale factor of 1, 10 or 100 depending on setting 150 -ohm resistance in series with "M." This of Sw. 2. UP AND coming service men know inefficient equipment means lost Measuring High Resistance time, inaccurate work and unsatisfac- Fig. 3 tory results. More and Tasting possibilities of the unit. Figure 3B shows the arrangement used for the more, they are measurement of high resistors from 100,000 ohms turning to the Readrite No. 730 Tester to 10 megohms. Operating voltages are taken ¡ R25.0-6000NMS -(1_ because it takes guess Fÿ/oo_ from a 25 volt and a 250 tap on a voltage the work out of - R19 shown will R Z 3160NÚ5 divider. Intermediate taps are but servicing and enables them to quickly qONN' 0 IS not be discussed here as they will be explained when discussing Fig. 3D. It will be noted that and accurately locate trouble spots. RIB R20 the combined values of all resistors used in the 15V. 1.5V The No. 730 Point-To -Point Tester is de- ;E:,53-* voltage divider totals 10,000 ohms, and this, signed especially for speedy and efficient 1.3oóälNS # =Bi r across a 250 -volt source will allow a bleeder cur- servicing. rent of 25 ma. to flow. Since this may seem an It is extremely flexible. Volt- -. s age can easily be checked in any tube cir- excessive bleeder current, we will explain briefly 114.2 1 will be cuit. Also measures resistance, capacity 2 6 7 8 9 the reason therefor. It noted that on , R,4,n i, account of the ratio between the 25 -volt tap and and continuity. Tester socket terminals are N4.1 AND 001.2 DECKS OF 5W.2 the 250 -volt tap, that the current flow through arranged according to RMA standards. It 113 TO RECTIFIER TO RECTIFIER AND nLTE0. the voltage divider remains relatively constant is unnecessary to remove chassis from cabi- c 2S9V0LTS lU AND FILTER= '-N- F1IAOOANa when the meter circuit comprising "M," the net when localizing defects. R-Z R2`' wNr R29 fuse Fl, Resistor R2. and Resistor R16, is con- 4.BAooNN. - eav 110000 ...../../0,-40 25 This tester includes two meters-one for r 0 :. nected across the -volt tap. The total effective 17 resistance of voltage divider as a whole is prac- reading AC, the other for DC. These meters gg p I.RI/ 250 tically unaffected. In practice this means that are rugged, compact and accurate. Separate \ NMS :,,As R27/?0000NÚ5 20.0úNMi in effect we have a constant current flow which meter ranges are made possible by connect- is -- r ins o o o divided between resistors R29 and R30 (the 02A5ÚEG. ing to a single pair of jacks and using the C11.2 -B- voltage dropping resistors for the 25 -volt tap) selector and the meter circuit, and that because of the switch. DC ranges are 15, 150, / r 3 4 S 6 7 8 9 300 and 600 volts. (1,000 ohms per volt). l rIE'1 Ali Ñé ( N4.2 DECK IS INACTIVE changing ratio between these two parallel cir- DECKS OF S.V 2 ON NIGN-RESISTANCE RANGES) cuits (when measuring various resistors between Milliamperes are 15 and 150. The AC 1e i/oro the values of several thousand ohms and one voltmeter ranges are 10, 25, 150 and 750. E. 00'..- TORECIOIER O A megohm) an error of progressively increasing :M.A tSV. R2 110aN5 magnitude will occur as higher and higher values YOUR JOBBER CAN SUPPLY YOU t2sV of resistance are measured. G A somewhat similar At the R12.20,DOOQIMS- R2t dealer's net price of $18.60 17 230v.2 ( condition exists to a lesser degree on the 250- 1213. 5.0000NpS" ti 0545ME6. volt tap but would be a serious matter on the R2A. 265 OHMS--, 25 -volt tap if correction for this error were not READRITE METER WORKS 250 made. Correction for a single range 139 College Ave. NEI -C- could be Bluffton, Ohio st 270V made when the ohms scale of "M" was initially "...N12 calibrated but would not hold exactly for mul- (-290v ., (----". tiples of this range. Further, in our case we MAIL COUPON FOR CATALOG RT NoNEiaK5GF52 IOV are working with an instrument which cM5 ELi ESi As z already i has the ohms calibration on its scale and we áwet, r III -pDI- SV23V30/.RIOL Iw`Ji6w. must make circuit characteristics such as to Readrite Meter Works ENEF.Si 139 College Avenue, Bluffton, Ohio. Ate -R76 secure agreement with this scale. EU Since the error above is roughly in inverse Send too catalog on Iteadrite No. 730 Tester and folder EE9Y " --RIO , proportion to the ratio between the resistance proving Readrite leadership. J * -R27 4) I ISOE of "M" and its series resistors, and the resistance of the voltage divider, a practical remedy Name IM R132 R121 F3 F4 25V -R28 G.13 is to make the resistance of the voltage divider -R29 as low as possible, thus increasing the ratio and MA. } 1 2 3 5 6 7 B 9 -R Address. sOOA.N gOw. 8MA SIM. decreasing the error. This. of course, results in C an increase of bleeder current the volt- 11 1/4"NE.3 DECK OF 5W 2 TO RIMIER AND nLTER-/ through age divider, and in our case, a value was chosen CITY state..._._...... _..... Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 49J RADIO -CRAFT for FEBRUARY, 1935

of approximately half the rated maximum cur- This completes our discussion of the circuit Before You BUY Try rent output of rectifier 1V. details, but there are several comments necessary With the above arrangement the maximum regarding certain points which will be taken up possible error of divergence from resistance at this time. Several references have been made calibration of "M" would be roughly 4 per cent, to Sw. 6, Sw. 6, and Sw. 7 and it seems desir- at a point on the meter scale corresponding to able to mention the fact that these switches something in excess of the highest resistance were made up by the writer from the contact BUD calibration. Since readings are not ordinarily springs off several old phone jacks. However. taken at the extreme left end of scale, and since with a slight repositioning of apparatus the even when they are, the crowded condition of equivalent manufactured push switches can be I,+ 5 DAYS the resistance calibration at this point precludes used and these are specified in parts lists. an extremely accurate determination, the net I ABSOLUTELY FREE error, in practice, is of too low a value to read. The Instrument as an Analyzer To measure resistors from 100,000 ohms to So for no mention has been made of the BUD engineers challenge you to duplicate Bud's 10 megohms, connect test leads to J7 and .18, set method employed to gain access to the socket sensational performance and proved depend- Sw. 1 to R -Z, Sw. 3 to D.C.. and Sw. 2 to RX1M connections of a radio set for analysis pur- ability at any price! BUD'S FREE FIVE-DAY TRIAL or RXSOM, as required. Then connect test in- poses. While it is quite possible for the con- enables you to accept that challenge, with no strument to 110 -volt A.C. line through agency structor to make up a socket selector unit, the of cord and obligation to you! Write today for beautifully plug connected to REC., (shown on writer chose to use a standard commercial unit Fig, 1) and throw switch Sw. 4 (also shown on for this purpose, and a Weston model illustrated descriptive folder, prices, and full 666, type Fig. 1) to the "on" position. Allow about one 1 -A socket selector unit was employed. Pro- details of FREE FIVE -DAY TRIAL offer. minute for the rectifier tube to reach operating Vision was made for plugging this unit into pin temperature. Then make zero adjustment in a jacks at top of test instrument as shown in the manner similar to that mentioned in connection photograph of the front panel. PORTABLE SOUND SYSTEMS with the low resistance measurements, using Nothing has been said about the dimensions however, the variable resistor R32 for this ad- of the instrument we have had under discussion. ELECTRO DYNAMIC UNITS justment. By using care in the arrangement of apparatus and employing a "double deck" layout, the writer Impedance Measurements succeeded in -slating all apparatus on a 7 x 10 CARBON MICROPHONES in. panel Figure 3C shows the impedance measuring with an approximate depth of 5 ins. This circuits. Impedance, of course, may comprise was enclosed in a carrying case 10a/a ins. AMPLIFIERS square inductance, or capacity or a combination of x 61/2 ins. deep, outside dimensions. these two. An inductance also has resistance, However, it is suggested that unless the prospective 4, 5 & 6 FT. ALL ALUMINUM but the resistance of most inductances can be builder of such apparatus has had con- TRUMPETS neglected without introducing serious error. siderable experience with the construction of Our circuit therefore, measures inductance or compact equipment, that the parts be spread capacity, or the effective impedance of these out on a larger panel. FIELD EXCITERS The method of elements at 60 cycles. This is accomplished in marking the switch positions and tip jacks also deserves brief comment. The AIR COLUMN HORNS a manner similar to the measurement of resistance, using an A.C. voltage and the A.C. range two main switches Sw. 1 and Sw. 2 are provided of "M" instead of corresponding D.C. func- with a flat metal plate with oblong openings LOW AND HIGH FREQUENCY tions, as was done when measuring resistance. cut at positions corresponding to the various UNITS FOR WIDE RANGE In using the impedance measuring functions of taps on the switch. These plates were given several coats of black auto enamel baked THEATRE USE our instrument, a reading must be taken on on. the voltage scale of "M" and compared with an and were then rubbed to a dull gloss with pumice auxiliary scale or chart. The required charts stone and oil. Paper markers were then made by on and scales have been worked out for the values typing the designations very thin paper, at positions corresponding to in BUD SPEAKER COMPANY used in our circuit and will be discussed later. openings the To measure an impedance, connect to an A.C. switch plate, and then using this as a negative 1145 JACKSON STREET TOLEDO, OHIO, U.S.A. to make a photographic, or line as described for high resistance measure- "contact print" resulting in a black background with white let- ments, set Sw. 1 on R -Z, Sw. 3 on A.C., and ters. The same idea was used in making the Sw. 2 to the range desired. Connect test leads to J7 and J8 and after making zero adjust- long narrow markers for the tip jacks. Of course heavier -BUILD YOUR OWN ments, place test points across the component a grade of paper can be used and - placed under the switch plate, that is without to be measured. Read the 100 -volt scale on using the Short Wave Receiver the meter and compare to auxiliary scale shown photographic print idea at all. The holders for the jack markers on Fig. 4. tip are sections 5 Meter Transceiver cut from old telephone switchboard card hold- Figure 3D gives all details of the electrolytic ICA can supply you with Just what you . ers. All other markers were cut from thin want through toar favorite mail condenser leakage tests, except the functions of sheet brass, engraved, nickel plated, and filled order house a discount of 40% from Sw. 6 and Sw. 7 which were discussed in suffi- with black lacquer. Of course, the entire panel the list noires Shoup. When you buy ICA i cient detail under Fig. 1. The purpose of the Kits or parts, are assured can be engraved if desired. You of quality voltage at and dependable perfonnanca. c. extra taps on the divider, the right Attention is now directed to the several photo- which were mentioned pre- of the diagram, graphs which, it is hoped, will assist in a clearer ICA 5 METER viously, are now apparent and through their understanding of this instrument. Figure A use various voltages can be picked up through TRANSCEIVER shows the instrument in its case, with cover 8 condenser under test. .. A quality transceiver Sw. for application to a removed, and with the Weston socket selectors, Use the nearest voltage to the rated working \ in 3 models; 2 volt, adapters, jumper cables, line cord and plug and 6 volt or A.C. model. voltage of the condenser and after connecting other accessories spread out in front. ,' So easy to build! the condenser to J11 and J12 (observing proper The three push buttons at the bottom of the Made completely of polarity) and waiting a few minutes for leakage com- panel, reading from left to right, control Sw. 7, Ica parts. Comes a value, the 25- milliampere plete with Instructions, to assume normal Sw. 5, and Sw. 6, respectively. The two rotary diagrams, etc. List range of "M" is connected in series with the prices switches immediately above are Sw. 1 and Sw. 2. $19.50, S19.25, $19.75 (respectively) negative the condenser by depressing side of Just above these switches are Sw. 4, Sw. 3, and Sw. 1 must be set 0 -500, Sw. 6. Switch to MA, "special" jack J13. Then on left of meter is 3 2 to the 25- milliampere ICA SHORT WAVE RECEIVERS Sw. to D.C., and Sw. shown R32, the line control, and on the right range for this test. Sufficient protective resistance is always in the circuit to limit current to 1 a safe value. If leakage is less than 5 milli- Fig. 4 amperes, Sw. 2 can be moved to the 6- milli- Reference scales concerning taster. ampere position. The capacity test can now be made by resetting Sw. 1 to R -Z, Sw. 3 to A.C., ZIpAECT 22610 .-MICROFARAD6+ Z3í100 24í1000 E 3 5 6 7 a 10 a 16 20 30 m and Sw. 2 to the range desired (either Z1 or 2 Z2) and depressing Sw. 7, the resultant reading being compared to auxiliary scale. To avoid v a to so 40 sD 60 70 80 so Ioo discharging the condenser through "M" in the VOLTS capacity test, it is advisable to depress Sw. 6 lt DIRECT 23%10 - NENRIES'- 23%100 24%1000 co 10 4 1.5 1.5 .6 .7 .6 .5 .4 .3 .2 just prior to depressing Sw. 7. Hold Sw. 5 5 3 2 0 in a depressed position for an instant after II 145115i5, 555q1 N 1,1115 r111ii I11il l Iti l rl l 1l l rI l l depressing Sw. 7 in order to discharge the con- 0 10 l0 30 40 50 60 lD e0 90 100 A whole line to choose from; I and 2 tube battery The may now be taken by VOLTS sets, and 3, 4 and 5 tube All Electric models. Here denser. reading are the world's easiest kits to build. Each comes releasing Sw. 6. 21 DIRECT 22410 -IMDEOANCe- 238100 2441000 complete -to -point diagrams. Licensed ith point connection co 3100100O coo coo 440 500 400 300 2D0 100 50 under RCA and Hazeltine patents. List prices Perhaps we should mention, in and up. Write for facts before build! leakage test, that the average high ( $9.95 You with the 1 I Iff¡íllrl Jf'rJ¡rrJr1!1!!11!!! tJ,5tr15 J,irl 11y I5'rI has a leakage grade new electrolytic condenser, o w 20 30 40 50 60 70 00 90 100 NEW 1935 CATALOG current at rated voltage, of approximately .1 -ma. VOLTS BIG of capacity. There is Sent on receipt of 10e coin or stamps to cover cost o or less, per microfarad PARALLEL RESISTANCE handling and mailing. Lists hundreds of parts, kit, some discussion as to the maximum permissible 0 2 10 30 3D 40 50 601080 100 200 400 400 u dnd ar ssorles. Supply limited so send now to avoid leakage a condenser may have before being dis- l,appoinl ment. I , I\5rf 5'i,1 1411 +h414.irr carded, but the consensus of opinion seems to INSULINE CORP. of AMERICA 0 10 20 30 40 50 60 m 80 90 WO ma. per microfarad of capacity con- VOLTS 23 -25 Park Place, Dept. C -25, New York, N. Y. be that 1. stitutes the upper limit. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 491 of the meter is shown R25. the low ohms zero of accuracy. In general such a high order of adjuster. On the upper left and upper right accuracy cannot be expected or realized in prac- of the panel will be seen the tip jacks. In the tice for the following reasons. First, the in- upper center of the panel, just above the meter herent error in the indicating instrument. On NATIONAL UNION is a flat bakelite plate, or cover, of the same a D.C. movement of the popular panel mounting length and width as the Weston socket selector.. type for example, the accuracy rating is usually This plate is removable and covers a small 2% of full scale. On a 50- division scale this -tells you how to "well," or box -like enclosure below the main would mean one division. As this error is con- panel. which houses the 5 fuses. The circular stant throughout the entire arc of the scale, the holes on the two ends of this flat plate are total error may become quite large at small immediately over the two tip jacks into which values, say, for instance one -tenth of the total MERCHANDISE the Weston socket selector is plugged when in scale. On an A.C. instrument of the copper - use. oxide rectifier type the accuracy rating is usually Figure B shows a back -of-panel view during 6% of full scale. Add to these possible errors process of assembly and wiring. Identification the errors in calibration and the errors in read- of principal parts should be easy by comparison ing due to paralax and to the characteristic RADIOSERVICE with front view of panel in Fig. A. Principal crowded condition of the scale at the extreme parts are also designated with the same designa- ends and you will have some idea of the net tions used in schematic diagrams. The meter accuracy of the instrument in practice, though does not show in Fig. B because of the resistor all possible errors have not yet been enumerated. mounting panel, which is supported on small However, the picture is not always so bad as studs projecting from aluminum back panel, and our outline would seem to indicate due to the covers the meter with exception of the meter fact that the errors are not necessarily additive. studs, which can be seen projecting through the In our particular instrument there was an ad- resistor mounting panel near center. ditional factor to be allowed for, namely, the Figure C shows a back view of instrument divergence between the reactance ranges when after sub -panel had been bolted in place and using the 5 -volt range of our copper -oxide all wiring had been completed. As can be seen, meter and multiples of these reactance scale this sub -panel is used to support the parts used values when using the 25- and 250 -volt scales in the power supply and also the two 1.5 volt of meter. This divergence is due to the change cells used in the measurements of low resistance in effective circuit resistance on the lower volt- values. There is also a recessed panel secured age ranges of our meter, due to the current to upper end of sub- panel. which provides for density characteristics of the copper -oxide rec- the mounting of Sw. 8, J11 and .112 and REC.. tifier unit. We have divided this error ap- the A.C. line receptacle. The recessing of these proximately between the lower and higher parts flush with the outer surface of their sup- ranges in order to permit a single scale to porting medium permits the insertion of the in- serve for all ranges. The greatest error on any strument into a carrying case in such a manner of the ranges is at the extreme left of scale as to provide clearance from the aide of the and decreases as pointer moves to right. All case, for these parts. Perhaps we had best add readings should be taken on a range that permita that an oblong opening was cut in the end of a reading as near center of scale as possible, the carrying case to permit access to this panel. for best accuracy. and was finished off with a nickel-plated escutcheon plate. Unfortunately this could not List of Parts in be shown the photograph. The small panel One Weston model 301 A.C. -D.C. universal meter at the left center marked CP is merely a con- with D- 71780. mod. 665 scale and special 6 V. nection panel for all connections going to main multiplier resistor (see text), M; panel above. All other designations are in ac- in 1935 SELL One Weston socket selector, model 666, type cordancewith schematic diagrams. 1-A; Figure D is similar to Figure C, but shows more clearly the manner in which sub -panel is Two pairs of Weston jumper cables, No. under the Sign supported below the front panel. D-71785-6; It was intended originally to describe in de- One Weston ground lead, No. D- 71787; tail, the method of calibration for the capacity, One I.R.C. precision resistor, 4,840 ohms, R2; of Efficiency ! inductance, impedance and parallel resistance Two I.R.C. precision resistors, 6,000 ohms. R3, scales. However, this is a subject really requir- R23; Service Dealers! Get in on National Union's ing separate consideration, and therefore, we Three I.R.C. precision resistors, 20,000 ohms, R4, great service merchandising plan for 1935. shall assume the reader is familiar with such R16, 1122; Supplementing the free shop equipment of- methods and content ourselves with the presenta- One I.R.C. precision resistor, 45.000 ohms, 115 ; fers which will be continued, National Union tion of Fig. 4. which shows the auxiliary scales One I.R.C. precision resistor, 95,000 ohms, R6: will help service dealers to increase their required. If the same type of meter is used as Three I.R.C. precision resistors, 245,000 ohms, business through tried and proven sales, ad- employed by the writer, and the same value of 117, 1115, R21: vertising and merchandising plans. Ideas, resistors and voltages are used, the auxiliary One I.R.C. precision resistor, 250,000 ohms, RS; campaigns, and the material to carry them scales of Fig. 4 can be relied upon within ap- One I.R.C. precision resistor, 500,000 ohms, 119; proximately the limits of commercial tolerance. One I.R.C. precision resistor, 150 ohms, R10; out will be made available to National Union Perhaps a word regarding the inherent limita- One I.R.C. precision resistor, 40 ohms. 1111: Service Dealers in 1935. Now, more than tions of the deflection method of measuring One I.R.C. precision resistor, 7.5 ohms, 1112; ever you need National Union f resistance and reactance may be in order at One I.R.C. precision resistor, 2 ohms. R13; this time. The writer has frequently seen refer- One I.R.C. precision resistor, 0.5 -ohm, R14; DIRECT MAIL AND CANVASSING : Printed matter ence made to resistance or reactance calibra- One I.R.C. precision resistor, 1,300 ohms, R17; that will sell for you and explanation of how to use tions in such a manner as to imply a high order One I.R.C. precision resistor, 1.050 ohms. 1118; it to best advantage ... yours on this plan. One I.R.C. precision 316 1119; resistor, ohms, EFFICIENT BUSINESS FORMS : Forms designed to One I.R.C. precision resistor, 25.5 ohms, 1120; make your business 'click'. Chosen from pieces used Fig. C One I.R.C. precision resistor, 265 ohms, 1124; by outstanding Service Dealers in all parts of the country View of rear -outside "deck." One Continental Carbon resistor, 201,250 ohms, ... yours on this plan. 3% tolerance, 1130; DISPLAY MATERIAL : Special displays to acquaint One Continental Carbon resistor, 203,750 ohms, set owners with your shop as the place to go for Sv.!8- 3% tolerance, R29; efficient radio service ... yours on this plan. ID 'Min One Continental Carbon resistor, 2,051,000 ohms, - J11 3% tolerance, 1128; SPECIAL SELLING PLANS: Ideas that have made J12 One Continental Carbon resistor, 2.072,000 ohms, money for others revealed and fully explained so you I RECT. 3% can use them. Prizes, too, for your ideas will be tolerance, 1127; announced, One Continental Carbon resistor, 2,136,000 ohms, 3% tolerance, 1126: You, Mr. Service Dealer, will be set to make the One Continental Carbon resistor, 2,125,000 ohms, most of your business in 1935 if you tie up with CH--- 3% tolerance, R31: National Union. Send coupon or write for National One Continental Carbon rheostat, 250 ohms, 25 Union circular which gives details of the Service W., R32; Merchandising Plan. Cl-. One 600ohm variable rheostat, R25; One jack switch. Sw. 3; CP- One push switch, Sw. 5: National Union Radio Corp. of N. Y. RC-235 R26- Two push switches, Sw. 6, Sw. 7; 400 Madison Avenue, New York City One single circuit insulated frame jack. 313; Send me the circular which telle about your Mer- Twelve tip chandising Plan R27 jacks (color and type as desired) ; One switch, Sw. 8: Two switches, Sw. 1, Sw. 2; Name R28 One General Transformer or Kenyon special power transformer, (see description) PT; RT One 1 /100 -Amp. fuse; Street One 1/32 -Amp. fuse; One 1/8 -Amp. fuse; One 8/4 -Amp. fuse; City State . Please Say That You Sato It in RADIO -CRAFT

www.americanradiohistory.com 492 RADIO -CRAFT for FEBRUARY, 1935

One 1 Amp. fuse; Ten fuse clips; INTERNATIONAL RADIO One toggle switch, Sw. 4; One Cornell -Dubilier paper condenser, 600 V. REVIEW rating, .6 -mf., C2; (Continued from pape 469) One Cornell -Dubilier paper condenser, 900 V. cuit to advantage in adapting it to available rating, 3 mf., CI; parta. One General Transformer choke. 30 hy., 500 ohms or less D.C. res., Ch; One RCA Radiotron rectifier tube, 1V ; TUNING INDICATOR WITH PILOT One midget receptacle and plug, REC; LAMPS Two 1.5 V. No. 2 dry cells, B; One panel of desired dimensions, material for UMEROUS schemes have been devised for N giving visual indication of tuning, for Exact Duplicate sub- panel, supply of sheet brass, aluminum, a wire, solder, lugs, test leads, 4 -prong socket, highly selective sets of the superhet. type. Most A.C. cord, screws, nuts, etc., etc. of these involve the use of special neon tubes REPLACEMENTS or galvanometer movements limited to rather narrow operating conditions, which must be to exactly in order to permit correct When you MUST use identical replacements, adhered simply remember Aerovox Exact Duplicate Re- operation. placements. Designed specifically for most stand- WIRELESS MAGAZINE, in their latest issue, ard sets . finest replacement units obtainable presented a group of circuits, using ordinary . embodying Aerovox high -quality construction BE SATISFIED TO BE A small lamps such as pilot lights, as tuning indi- throughout. cators. SERVICE MAN The circuit in Fig. 3A shows an indicator For instance: Aluminum can electrolytic, two (Continued from page 485) lamp fed from a 2% V. winding of the power cardboard case electrolytics, and an auto -radio transformer and coupled to a transformer L in vibrator condenser pictured above -each exactly age radio servicing salaries, and most instances in matching units the the output circuit of a power detector any in intended sets. Character- considerably less. As for a the very istics positively matched, but Aerovox quality is future, nat- receiver. more than a match for some original equipment. ure of radio engineering virtually compels a In this particular case an increase in signal salaried job with a sizable corporation. or with strength will produce an increase in plate cur- And for general repairs, don't overlook the Ultra the uncertainties of consulting engineering as an rent. Under no- signal conditions, the inductance Compact PM5 and PM6 Hi -Farad Electrolytics alternative. Meanwhile the radio Service Man of the coil L is sufficiently high to choke down all -round units . minimum stock and has always the opportunity to be on his own, to the current passing through the lamp. But as investment ... maximum applications and profit- be independent, to build up something which no the circuits are tuned to resonance the rising making. one can take away from him. plate current through L saturates the core so Catalog just off the press So let's see this radio service field in the right that its impedance is reduced and the indicator FREE DATA 1935 covers entire condenser light. It's a real opportunity -but also a chal- lamp increases in brilliance. and resistor line. Also sample copy of monthly lenge. Merely to be called a Service Man, with- If an ordinary pilot lamp A, Fig. 3B, is in- Research Worker. out having the proper backing for that title. is serted in series with the plate supply to the insufficient. There are tens of thousands of radio A.V.C. tube V, then, the current falls off as Service Men in that category. To get the real signal strength increases, and the lamp will rewards out of radio servicing, one must have indicate the correct tuning point by going out proper training, ample experience. real salesman- The shunt resistor R is inserted in order to ship, a true business sense, and unlimited initia- preserve the plate supply to the tube in case the tive and energy and honesty. lamp burns out. Equipment, too, is necessary. Radio sets and On the other hand, if the lamp is arranged as tubes of today are far too intricate for the shown at C, in Fig. 3, then it will indicate the C O R P O R A T I O N handy-man methods. Test equipment is essen- correct tuning point by rising to maximum bril- 77 Washington St. : : Brooklyn, N. Y. tial, not only out on the job but in the shop. liancy. because as the plate current through Unless a radio Service Man is properly equipped, tube V falls off, the potential drop across the . p, he is quite unable to get his share of radio. resistance R, follows suit, and a higher voltage S4der He is like the surgeon attempting a major oper- is applied to the lamp from the "B" supply. ation with bare hands and no instruments. The view at Fig. 3D shows a visual indicator 4` Surely .not impressive, certainly not prepared for based on a combination of both bulbs. The bulb the work, and absolutely unfit to collect a pro- A, which throws a general illumination over the z M fessional fee. The stage setting, either in the dial is arranged in circuit as in circuit B. It doctor's case or the Service Man's, has lots to do gives a full light as long as the circuits are out with collecting worthwhile fees. of tune, but grows dim at the point of resonance. Still one more point: parts. Good parts are The lamp B which is placed just behind a always the cheapest at any price. Because good tuning slot or arrow, M, is arranged as in cir- parts can be installed and forgotten. They per- cuit B and increases in brilliance with increase form satisfactorily. There are no complaints, no in signal strength. comebacks, no return calls at your own expense. As the signal is tuned in, the general illumi- No ill will created against you. After all, your nation of the dial gradually fades away, while time is more valuable than the few cents one the light thrown on the window suddenly in- way or the other between a good part and a poor creases to a maximum. This produces a striking part. You cannot afford to take chances with effect -and one which can be used to advantage WRIGHT -DECOSTER questionable parts. by the experimenter in practically any modern Lastly, there is the matter of personality. Its set. worth cultivating, for it builds confidence and Speakers patronage and profits. Getting into the homes of the community, gaining the acceptance of Available Everywhere many households, the Service Man is in position to recommend not only radio sets and appliances. WLW'S "ELECTRIC EYE" It is our well known policy to but also other home equipment. Here is a won- (Continued from page 471) derful opportunity to build up towards a radio when it was found that once the appliance trade, - rented itself endeavor to do all of our busi- and electrical and even an oil arc was started across this gap. either by ness through the legitimate whole- burner and air -conditioning business. lightning discharge or by an abnormally high A veritable gold mine lies before the radio voltage. the arc could not be extinguished as sale distributors. Therefore, any Service Man in the average community; but like power from the 600,000 watt transmitter kept recognized distributor of Radio all gold mines, he must first of all ascertain the it "alive," draining practically all of the sta- equipment can quote you prices approximate location of the ore, then go to work tion's power from the antenna into the Around. digging and digging, and finally refine that After various types of gaps, current trans- and show you samples of ore he finds. by skill and patience and hard formers and rectifiers were tried unsuccessfully, WRIGHT -DECOSTER Speakers. work, in order to get the gold as his ultimate engineers resorted to the use of the photoelec- reward. tric cell device. A Weston photronic cell, with Many a radio has been made Many a radio Service Man of today can be its associated relays, was installed in a double the prominent dealer of the community tomor- shielded box on the brick wall surrounding the a better radio with a WRIGHT- row. Compare such a future with that of the antenna base insulator. A long tube contain- DECOSTER Speaker. Write for radio engineer who holds a more or less uncer- ing light baffles was installed so that cnly light tain job with a corporation, which tenure is from a point directly in the safety gap could catalog-a speaker for every pur- subject to the constantly changing whims of strike the photoelectric cell. The relay operated pose. different managements. by the "electric eye" was connected in such a So you see, the grass in the radio servicing manner as to remove the station's plate voltage WRIGHT -DECOSTER, Inc. field is mighty green and plentiful if you will to the final amplifier whenever the photoelectric only do a bit of digging and plowing and seed- cell was excited and to reapply it the instant 2251 University Avenue, St. Paul, Minn. ing. It's mainly beneath the ground. But the the arc was extinguished. Due to the high speed Export Dept. M. Simeon & Son Company. potential crop is there if you but do your share of the control circuits. the interruption to serv- 25 Warren Street. New York Cable Address: Simontriee, New York -and stop envying the other whose opportu- ice is so slight as to be barely perceptible to the nities are very much overrated. ear. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 493 RADIO SET OF 1950 e`P (Continued from page 458) Ge:` If the radio set stands against the center of a wall for instance. then the person who sits in a chair near the same wall cannot possibly see the television image, and he has to move around in order to see image. Sa`c;s the For that reason, the television- equipped radio set of 1950 SatQe will have the television screen in a compact box ecs or case which can be swiveled on top of the set. in such a manner that the screen can be made PQ s4°` apa t to face anyone anywhere in the room. To ob- o 40 tain this result, the television apparatus proper aoa eta''e'i o, must be on top of a cabinet where it can rotate .S i freely through 360 degrees. When the radio set 1 `F+ o N is not in use, means can be provided to disguise P. e the television screen as a decorative picture or s Ns a what not to harmonize with the decorations ovt Fa of the room. T' o4esabc As I pointed out in a previous article (see RADIO -CRAFT for April, 1934) it is already pos- eSpt. aoò ,Itoc+ sca4,eoJ sible today to receive by means of radio, not c ep c' only facsimile 4 . 6,4 s te transmissions, but even a com- Q1` oaeJQ ace°te ee ec° tQlae ac a plete tabloid newspaper, which can be printed ae while you sleep by A a ot fi' o the radio receiver. By the V e 2,0 sro co 0 3.41 time S you wake up in the morning, the tabloid e IN o+ atb 0e. o oa ce newspaper is already printed for you. The full g°YO +e te ot sec ot vo , +(. ae . tee 4 coo instrumentality how this is done, with all the e t e sc ot a 65 apparatus described, in 4t was shown the above e o issue of RADIO -CRAFT. S `bc 4a o `oses,aQb e `j sa¡oc°a `°ßb The radio set of 1960 will have such a facsimile taoaeta sch of ;ace, '+s 0 5 at`P á efo printing arrangement built into it. But right . oo 4 4. aò+OQ+eS `e5s in addition to this, I wish to speak of another Ja» s aúh a oas4t'r, feature which, as far as I know. has not been A p ,.,1

www.americanradiohistory.com 494 RADIO -CRAFT for FEBRUARY, 1935

space provided in her radio set and, within a that no two programs will end at the exact time. few minutes, be in communication with her hus- At the present time, most of the important pro- YOUR band who may be sitting in his automobile 20 grams start and stop on the hour or the half - BUILD OWN miles away from home. hour. This could be changed so that one net- I know that a lot of people will throw up work would run on the hour or half -hour; the their hands and howl at this suggestion. The other fifteen minutes later. These are simple SHALLCROSS cry will go up that the ether lanes are already details that could be worked out in such a man- no crowded and cluttered up with transmitters ner that there would be no occasion for clash- that even if we wanted, communication of this ing as far as applause is concerned. Sooner or UNIVERSAL type would be useless ; because no one would be later, this idea will be used, and the transceiver able to understand anything. This is not true is the solution of the problem. at all. I have had this idea in work for the Yes, the 1960 radio receiver will be complex. TESTER past two years in RADto- CRAFT'S sister publica- If you compare the 1936 receiver with the crystal tion SHORT WAVE CRAFT, where the pros and set of 1920, you will also say that the 1936 radio cons of this idea of mine have figured in a is complex, even as compared with the receiver For $41.50 Complete discussion, hot and heavy. After all the smoke of 1922. Progress always means more com- is clearing, the fact remains that below 6 meters, plexities, and the radio set is no exception to VOLTS fortunately, you cannot transmit further than this rule. The 1960 radio set will be ever so A.C.-D.C. about about 20 miles. In general, that means much more complex than the one of 1985, but 5-25- 100 -25U- that you cannot go much beyond the horizon. it will be vastly more enjoyable than the present - 1000 ohms Thus, for a certain area, there will be far less day set and vastly more efficient. per volt congestion even than there is today ; because on MILLI- a few dozen frequencies, assigned for each dis- AMPERES trict, with an automatic frequency lock on your radio set, there could not be too much con- INTERFERENCE ELIMINA- D.C. gestion. will, become 1 -10. 100 -1000 It therefore, a rather simple thing to converse by means of your own TION CAPACITY set with your friends a few miles distant. This .001 -10 MN. will be especially useful for communication in (Continued from page 475) Paper or appliances he found that the washing machine outlying districts ; as farms, electrolytic such on between was exceptionally of condensers houses. automobiles, motorboats, and producing an large amount yachts, man -made static. This fact was reported to the INDUCT- many other applications, not to forget private airplanes, of which there will be many in 1960. woman, with the recommendation that Ehe ar- ANCE range for "filtering" the motor so that she her- 1- 10,000 Henrys In case of accident, for instance, on the road, automobile, by means of transceivers, can self would not be responsible for the same type of quickly summon aid. The same is true of motor disturbance, inflicted on her neighbors, that .5-5,000,000 ohms D.C. Resistance boats and airplanes. she had found sufficiently annoying to cause But the idea of the transceiver does not stop her to complain to every possible authority. Did she approve of this suggestion? Indeed she did for new Bulletin here by any means. I still have in mind another Send 6c in stamps the idea one which has constantly bothered radio not. In fact she said "When everyone else in No. 611 -P containing the complete wir- engineers, and for which no solution has been this neighborhood has quieted his appliances, I will take care of my washing machine. Until ing diagram and operating instructions offered so far -and that is the item of applause will by the unseen radio audience. I believe the then, I do nothing." That the coat interference is for this modern serviceman's instrument. transceiver is the solution for this problem. It of eliminating is well known that a radio station has, up to not a major factor contributing to the unwilling- now, never had an accurate means whereby it ness of many individuals to silence the noise- makers on their premises is proved by another HALLCROSS could check up how many listeners there were. MfG. COMPANY I visualize the radio applause idea somewhat incident which occurred during the survey just CIecttkal J ea.noia9 laittemmali as follows: mentioned. A particularly vicious interference .antLicceatatt loti /mti On the radio of 1950 there will be a special was traced to an oil burner in the home of one of the wealthiest men in the community. He had 700 MAC 0A0I .011LIVAl0 button or switch. You are listening to a radio been much interested in having survey COILING DALE, PA. program, at the end of which the announcer the noill asks for you. you like conducted, so when the engineer reported where an expression from If interference found, the artist or the program, you merely throw a had been the chairman of switch; this immediately transforms your radio the survey committee said, "I know he will take receiver into a transmitter. A certain note, let care of that trouble." On being asked. how- lose FOR us say a whistle of 600 cycles, is automatically ever, the owner of the oil burner stated that he . planned to purchase a new burner within a few transmitted, by means well known today. Some- gellrNn j/ , months and would insist on a "filtered" burner where in your district there is an elaborate radio net maintained by the radio station or network at that time. He did not feel that it would to which you are listening. This special radio be worth while to spend any money to elimi- set receives your 500 -cycle note, which is nate interference from the old burner. sent such would leave a major inter- E out in lieu of applause. By means of a special Since action t resonance meter, a needle will fluctuate, showing ference making reception impossible for many CATALOG a certain intensity received. Suppose there listeners, the survey committee offered to re- goo that purchase the equipment at its full Chock full of BARGAINS are a thousand individuals sending out at the "filtering" in RADIO SETS, Long and same instant a note on the same frequency. All price when the new burner should be installed, Short Wave Apparatus. will superimpose, one on the other, and the effect if only the noise might be eliminated at once. NEW ISSUE Servicemen's Repair and Re- Even this proposal, which insured the appliance placement Parts. Electrical will be as if a powerful transmitter were radiat- JUST OUT Appliances and hundreds of ing that note. The more powerful the note, owner against any chance of loss, was refused - lulvicellnneous specials nt the higher the meter at the receiving set will in- and the noise is probably still blasting the best TREMENDOUS SAVINGS. programs in that community. Get this big new Bargain Book. It's abso- dicate. In other words, the more people applaud, lutely FREE without obligation -just send the stronger the indication of the special re- us your Name and Address on a post Card ceiving set belonging to the broadcast station. What Can Be Done? WRITE FOR YOUR COPY NOW. If the applause lasts for, perhaps, five seconds, In the two examples cited, there was no tech- the meter will have vibrated up to a certain nical difficulty involved in eliminating the inter- OFF PRESS figure on the dial -let us say 68. By means of ference. A filter costing less than five dollars JUST THE a slide rule, the engineer in charge immediately would have kept the washing machine from af- RADIO CIRCULAR CO., INC. calculates that, in order to get this much gain, in same building, 225 RC VARICN ST., NEW YORK fecting even the radio the there must have been 3,859 transceivers sending while a filter costing less than ten dollars, plus the applause impulse. In other localities, scat- a little shielding of ignition spark wiring, ,would tered all over the country, we have the same have made the oil burner absolutely silent as instrumentality and, within a few seconds, the far as radio is concerned. Technical knowledge key station will have been informed exactly how could not, however, surmount the obstacles in- -Stop Guessing!- many people applauded. This result may vary terposed by individuals who felt that their con- a few per cent; but the difference will not be venience was of greater importance than was Radio servire Is easy when you know lust where very important, and a pretty accurate estimate the successful completion of a noise elimination to look for the troubles. And. the securing of of the total number who applaud can thus be profitable fees for the repairs makes the work campaign. still more attractive. A CHUCRHER eliminates made. Expensive you say? Yes, it is expensive From this brief discussion it should be evident goers -work in "What is Wrong and What to for the radio stations; but when you figure how that the elimination of man -made static, which Charge." This trouble -localiser, with a reauy incomes profitable repair -priser schedule included, enables tremendously great the of the radio must be accomplished if short -wave reception, radio men to localise any trouble In any radio, stations are, you will also understand that they television. and high fidelity transmission are to Quickly, right in the field . . without disman- will gladly go to this expense so that they can tling the radio. It looks official, and permits you be satisfactorily conducted, is no longer depend- easily to convince set -owners that you are not get accurate information as to the listening ent on the development of new engineering guessing at either the trouble or the price of the audience. methods but awaits only a means of making repair lob. Your competitor makes good money by using a CHUCKEERI There may be a few slight objections to the the fruits of present technical progress available Send $1.00 NOW for yours, postpaid. scheme; for instance, there are two programs to the majority of radio listeners. The engi- on the air, on two networks. Which applause neer has done his work -now let us learn how FREED'S RADIO CO. goes to which station, or which applause goes to utilize it. Publishing Division R to which program, on what network? The an- (Additional and more detailed information on 5053 Baltimore Ave. Philadelphia, Pa. swer is the time element. The competing sta- the subject of radio noises will appear in a sub- tions can readily split their time, in such a way sequent issue of RADIO-CRAFT.-Ed.) Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY. 1935 495 In connection with short-wave reception, the WHAT SET SHOULD I BUY foregoing is not intended as a "scare," or as a (Continued from page 466) promise of poor reception when a short-wave And Now! $12 Condenser receiver is operated under these conditions. purchase of a radio set. Almost all the reputable Special short-wave antenna systems have been manufacturers produce a line of radio receivers devised and are available whereby the effect of Analyzer Added to from lesa than fifty dollars to more than two these electrical disturbances is reduced con- hundred, in different price ranges, so that any siderably in most instances, and eliminated in SUPREME 85 t'Neonized" buyer may select a receiver within his price others. Where a receiver is to be installed in an class. Naturally, all things being equal, you apartment or office building which operates get more in a two hundred dollar set than you elevators, or motors for some special purpose. TUBE TESTER can get with one in the $69.50 class. It is only another type of special antenna may be erected. when a last year's model or one of a bankrupt Whether this is necessary or helpful can only manufacturer is offered, that it is possible to be determined by one experienced in these obtain a high -priced receiver at a low figure. matters and cognizant of the particular location Here. of course, you must realize that current and conditions. model receivers usually present more in the way One important point to consider in connection of improvements and refinements. So far as with all -wave and short -wave receivers is the bankrupt stock is concerned, the integrity and ease of tuning. On the shorter waves. it re- value of a responsible manufacturer no longer quires great patience to isolate and bring in stands behind the receiver and it may also be distant broadcasts, unless the band -spread is more difficult to secure parts or service when sufficient to provide appreciable space between such a receiver is in a state of dis- repair, besides scale divisions. This means simply using higher the possibility of higher prices for replacement vernier ratios or providing auxiliary small con- parts. In some other - cases, a radio set may densers in parallel with the main tuning con- be obtained at a lower price than the market densers. To avoid multiplicity of controls the price by those persons who know some one vernier dial method is preferable, particularly "who can get it for them wholesale." This is when it can be changed for various bands. Many splendid (when accomplished) but more often sets today have all bands marked clearly in than not, such sale does not carry with it the kilocycles and megacycles, eliminating all "fish- usual service guarantee tendered by a dealer, ing" for elusive programs. and should trouble develop in the receiver. as is quite possible, the cost of repair involved may amount to more than the saving. First-Chassis; Second- Cabinet Very often, those who are desirous of purchas- Although a cabinet enters into the satisfactory ing receivers go to a retailer with some partic- operation of a radio receiver to a great extent ular brand and model in mind because of the so far as tone quality is concerned. the selection fact that they know or heard of some friend or of the chassis should be considered of prime AT NO EXTRA COST importance. Choose three four different re- relative who owns one of these radio sets and is or Shorts and leakages in capacitors have been obtaining satisfaction therefrom. This is un- ceivers within your price range and arrange responsible for many a kick -back on repair jobs wise, since it not only prejudices the purchaser them side by aide so that you may compare each which apparently checked 100% when they left your in that set's favor despite the superior qualities under the same conditions. Most retail estab- lab. Baffling faults in Automatic Volume Control circuits that finally caused a trip the of another in the same price class, but that lishments have demonstration booths for this of purpose to aid in choosing a radio set. set back to the factory. or the replacement of ev- same receiver may not operate in like manner ery capacitor in the circuit, have had the root of in the purchaser's home because of different A feature often heard in connection with late their trouble in capacitor leakages that not even a conditions. The fact that the cabinet style may model radio receivers is automatic volume con- high -range ohmmeter could detect. Knowing this, not blend with home furnishings is another fac- trol, or "A.V.C." This is most desirable and alert radiomen are now awake to the fact that e idea of obtaining affords ease of operation which was not obtained 100% job of modern servicing must include a com- tor in this case. Although the plete a concensus of opinion from a number of set in older type receivers. If you reflect, you condenser (or capacitor) analysis. owners is valuable as regards some certain radio may remember that on your old set when you And Supreme -the organization of practical radio no were listening to a powerful station it was service men and engineers -now gives it to you. In- set, it is usually best to make reservations cludes it as a still further distinction to the most and to select the set which will best suit your necessary to turn down the volume control. distinguished tube tester in radio service work. needs and taste after making a complete test Tuning the receiver to a less powerful or weak Think of it, a $12.00 condenser analyzing equipment for yourself. station always meant advancing the setting of is now incorporated as standard design in SU- the volume control so that this station could PREME 85 "NEONIZED" TUBE TESTER. Without a Before advising Mr. Jones upon a radio set, penny of extra cost! the suggestion is made to visit his home to be heard. If you suddenly tuned in a powerful the type of receiver which would be station without first reducing the volume, the Now that famous, unerring Neon light provides determine volume analysis of capacitors as well as of tubes. Positive mot efficient in his location. At the same time, radio receiver would operate at too great away until you turned down the detection of leakages, shorts, opens. Every desired a "line" on the size and design or style of the and "blast" test of any capacitor, regardless of size. cabinet could be secured. Since Mr. Jones is volume control. With automatic volume control. And every serviceman can well afford to mod- married, his wife should accompany him to the or A.V.C. as it is called, this procedure is un- ernize with the SUPREME 85. Not only because it might have something to necessary when listening to local stations. the is low in first cost. but particularly because it retailer so that she soon returns first cost and plenty more besides. say about the cabinet style before the purchase receiver equipped with A.V.C. may be adjusted for normal room or desired volume for one and because it puts your service on a 1935 plane, and not after. giving you a 3 in I Tester, namely (I) TUBE TEST- station and all other stations will be received ER; (2) TUBE LEAKAGE TESTER; (3) CONDEN- at or almost at the same volume level without SER ANALYZER ... at the price of one. What Are Your Pre -Purchase manipulating the volume control. Another ad- As part of its service to Supreme owners, and Preferences? vantage of automatic volume control is the realizing that its own reputation is built on the ability of the receiver to minimize the effect reputation of the users of its instruments for a Before you even pay a visit to a radio store. of "fading" which is prevalent when receiving progressive service, SUPREME makes this high class why not try to analyze just what you do want distant stations by automatically raising or condenser analyzer equipment available to Present in a radio receiver? Are you interested in a set lowering the volume as it fades so as to "bring owners of Model 85 at nominal cost. Write for information. that is very sensitive and is capable of receiving in" that station at steady volume, unless the very weak signals from distant stations? But signal fades out beyond the sensitivity limits of Ask your jobber for a demonstration of this most you consider whether such a receiver outstanding tube tester in radio service work and must also the receiver. By this is meant that unless the other Supreme instruments. Send accompanying would operate well in your location. Should receiver is unusually sensitive, the fading signal coupon for complete 1935 Catalog. you live adjacent to an electric train, trolley may become so weak that it would be difficult or electric bus, or near a power house, reception to receive that station even at full setting of would be seriously marred by the electrical dis- the volume control. SUPREME "NEONIZED" In this case, turbances created by these devices. For your purpose, it is necessary only to know TUBE TESTER a very sensitive receiver would be a poor choice, volume control action is obtained 85 -P of that automatic unless of course. you have intentions changing by reducing or increasing the sensitivity of the near future. If you are Dealers Net Cash your location in the receiver, and since in a receiver so equipped $3 9.95 interested in receiving foreign broadcasts such as the automatic volume control holds the volume Wholesale Price is possible with the many good short-wave and fairly constant, it is more or less difficult to Supreme Model No. 35 all -wave receivers on the market today, it must the exact on the dial to set a $29.95 man -made electrical dis- determine point Tube Tester be remembered that station so that the best tone quality may be increase in intensity upon short waves. Supreme Model No. 333- turbances obtained. For this reason, many receiver manu- Standard Radio Analyzer $29.95 Even though your neighborhood be entirely free incorporate some means whereby sta- trolley cars, trains. etc., you may be facturers Supreme Model No. 333- from tions may be tuned in accurately, and in some DeLuxe. Radio Analyzer $39.95 located on or near a busy thoroughfare. Here, cases, without the necessity of even hearing good short -wave reception will be difficult since by means of r motor vehicles the station. This is accomplished SUPREME INSTRUMENTS CORP., the ignition systems of produce a "shadowgraph," "tuning meter," or neon 515 Supreme Bldg., Greenwood, Miss. a deal of interference only upon the high great bulb arrangement which is so connected in the Please send complete detailed Catalog 1935 frequency short-wave bands. You may think, to Supreme Instruments. such receiver that it will indicate the exact point however, that although automobiles produce the dial valuable feature. interference, traffic diminishes considerably to- tune the station on -a Name wards late evening, but at this time, very little Address foreign reception, if any. may be obtained be- Testing the Automatic Volume Control cause of the difference in tome. It should be There are all kinds of automatic volume con- City State remembered that it is midnight in England trols. some very effective and others less efficient. Jobber Preference when it is only 7 p.m. in New York City. Probably the best test to make to determine Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 496 RADIO -CRAFT for FEBRUARY, 1935

the efficiency of the A.V.C. is to tune a receiver string and, especially, wood percussion instru- to a weak distant station with the volume con- ments. Try to distinguish between them. (The HOW TO BUILD, TEST trol set for comfortable room volume, and then kettle drums are tatted to different bass notes - AND REPAIR to quickly tune the receiver to a strong local can you "tell" one from another ?) If possible, station. There will be very little change in listen to the same program on each receiver. volume with a good automatic volume control. Undoubtedly, one receiver will appeal to you RADIO Then try tuning in all the different local stations more than the others, but do not make this a SETS and see how much the volume level varies as you conclusive test. do so. Check this on each of the receivers that In this connection, you must remember that you are testing, adjusting the volume control the mental ear sometimes supplies certain notes to the same level in each case. or tones that may be lacking, especially in the In order to overcome one of the disadvantages case of a familiar melody or selection. Listen of automatic volume control, (which lies in the to the receiver for twenty minutes or more be- fact that electrical interference which may be fore making your choice. It is very likely that picked up by the receiver as you tune from you may "tire" of the reproduction as most one station to another and that might originally frequently occurs when realism is lacking. This be weak, is "amplified" by the A.V.C. and "tiring" effect is due to "nerve fatigue" and is Radio Construction brought to the volume level for which you have caused by the effort expended in compensating set the receiver) -manufacturers have infor certain deficiences in reproduction. corporated a "sensitivity," "quiet A.V.C." (or Library "Q.A.V.C. "), "inter- station noise supressor," or Including Television, Short -Wave Receivers and Auto "silent tuning" control in many of their re- Tone Controls Radios. 3 Volumes, 5y a6 -1177 561 illustration pages, ceivers. Therefore, since the tastes of different in- This practical Library includes: PRACTICAL RADIO- dividuals vary, The fundamental principles of radio, presented in an manufacturers add tone controls understandable manner. Illustrated with working dia- Inter -Station Noise Suppression to receivers so that the receiver response may grams. PRACTICAL RADIO CONSTRUCTION AND be varied. Why not try the tone control and REPAIR -Methods of locating trouble and reception This faults and snaking workmanlike repairs. Discusses mod- "Q.A.V.C." control serves only to reduce determine just how it changes tone quality. Are ern Short -Wave Receivers and Installation of autmnobile or eliminate noise that is heard when tuning the bass notes emphasized by cutting off the radios fully. RADIO RECEIVING TUBES- Principles from station to station. and helps to a underlying the operation of all vacuum tubes and their great high notes? Or are the low tones brought out use in reception, remote control and precision measure- extent in securing further satisfaction from without affecting high -frequency response? The ments. your radio set. Of course, this control- will not latter, of course is the most desirable. but is Helps you to understand modern type receiving sets - reduce interference or noise is heard full of construction data and practical kinks for the ex- that with usually found only in the better -grade receivers. perimenter. or on the station setting. In some receivers, In any event, a good tone control is a valuable 30 Days' Free Examination the silent tuning control is in the form of a adjunct to a Easy set to aid in compensating for Terms switch to reduce the sensitivity of the receiver various tones. McGRAW -HILL between stations, and in others, as a variable FREE EXAMINATION COUPON adjustment so that the sensitivity of the receiver Cabinet Considerations r may be adjusted to suit existing local conditions. MCGRAW-HILL BOOK COMPANY, INC. The latter is preferable since any degree of So far as the cabinet is concerned, it is a well - 330 W. 42nd St., New York. inter -station noise suppression may be secured. known fact that the larger the cabinet, within Gentlemen:-Send me the RADIO CONSTRUC- reason, the lower TION LIBRARY, all charges prepaid, for 10 deys' Determine which of the radio seta of your the fundamental tones a Free Examination. It satisfactory I will nd $1.50 choice are equipped with some kind of sensitiv- speaker can reproduce. When low tones are in 10 days. and $2.00 a month until $7.50 ahas been ity control and test each for the heard in a midget receiver or on a radio set in paid. If not wanted I alti return the books postpaid. amount of noise suppression that is possible to be obtained. a small cabinet, they usually comprise "over- Names..._ Adjust the control for silent tuning and rotate tones," perhaps one or two octaves higher than Home Address..._..._...._.. the station selector from station to station, the fundamental note, resulting in unnatural listening for any electrical disturbances, if any, reproduction. The construction of the cabinet between stations. A good noise suppressor will also enters into perfect reproduction. Should render the receiver inoperative between stations. the walls or-frame of the cabinet be flimsily Name of Company held together, or of thin material, certain resonant tones may be set up which will distort the The Factor of "Selectivity" true tone. Determine the method of construc- A very important factor to consider in choos- tion. Are "glue blocks" employed? Or are ing a set is selectivity. Selectivity of a re- screws simply used to "hold the cabinet to- UNIVERSAL ceiver is the ability to tune in any particular gether"? In some receiver cabinets, both glue station without any interference from another blocks and bolts are employed. Perhaps it may ALL -WAVE station which may be broadcasting on an adjoin- be expedient at this point to mention that to ing band, 10 or 20 kilocycles away. Try tuning choose a radio set because the cabinet appeals ANTENNA SYSTEMS the receiver to a fairly strong local broadcaster, to the eye. despite the fact that another receiver for example, at 760 kc. and determine how many is far superior but that the cabinet does not suit ARE kilocycles or degrees that the dial may be turned exactly, is poor policy and one that should and EASY TO on either side of the 760 kc. before the station will be regretted. Possibly the receiver of your is tuned out. Make this test on each of the choice can be installed in a cabinet that pleases I NSTALL!- sets to which you are listening. Proceed in like you more. Should this be the case, first deter- and bring manner with some station on the higher fre- mine whether the tone will suffer as a result let us say, 1,400 kc. of the change. You must remember that in quencies, at Should the most the station be heard 20 -30 kc. on either side of the cabinets are built around the radio receivers of WORLD'S specified frequency, then reception of another creditable manufacturers, and not simply installed FINEST station only IO or 20 kc. away from this station in any that may be available. The design will be difficult because of the "cross- talk." A and style of the cabinet are usually carefully PROGRAMS receiver with good selectivity will "tune out" engineered to bring out the most of which the with a station within not more than 16 kc. on either receiver and reproducer are capable. aide of its allotted A very sharp GREATER band. tuning receiver-one that boasts of 10 kc. separation - VOLUME will often interfere with tone quality. As a further test for selectivity, if possible, (that is. and if you live in the East -Ed.) tune in WOR at LESS NOISE 710 kc. and then see if you can tune in WLW at 700 kc., without interference AMERTIAN TRANSFORMER TOBE -wave from either all antenna kits may be station. Of course, this test must be made at a BULLETIN erected in several ways depending time when both stations are broadcasting. upon the convenience of the location. A complete catalog of Model 35 -shown above -$4.95 list. How to Test for "Good Tone" transformers for all Sold leading amateur P.A., at supply As a result of much experience, it does seem voice transmission houses. that the majority of prospective purchasers and radio deem tone quality the most decisive single re- work are included in this Tobe Deutschmann Corporation quirement in a radio receiver. The question new book of the American here which must be answered is: how can the CANTON, MASSACHUSETTS average layman determine which receiver has Transformer Co. which you the best tone or reproduction? This is only a can obtain by writing to this matter of individual taste, for in many in- which magazine a n d requesting 1935 RADIO stances, a receiver "sounds good" to one person may appear "flat" to another. Your bulletin No. 652. CATALOGI All models: AC -DC midgets; dual ear is the best judge. Regardless of the fre- L and world -wide all -wa e farm. bat- quency range or realism of tone the manufac- If you are interested in f tery and car -at factory mires! Write turer claims the receiver may the buyer ü for 24 -page Bargain possess, transformers of high quality Catalog and 30 -DAY must and should teat for himself. Most likely plan. Prices AGENTS for high fidelity work do not TRIAL WRITE I the best method is to tune in the music of a from $9.95 UP. concert or symphony orchestra in which many miss this interesting book. GOLDENTONE RADIO CO., instruments comprise the aggregation. Listen t 22 Daemon Bldg., Detroit, Mich for the kettle drums and the different wind, Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 497 ELEMENTS OF 4TH DIMEN- Spatial Relationship NO RADIO MAN CAN With the correct technique and the use of SION SOUND present highly perfected equipment, it becomes AFFORD TO BE a relatively simple matter to attain a reality (Continued from page 481) of reproduction so lifelike in tone, volume, and sound sources, waves spatial relationship to the original WITHOUT THIS BOOK As the directional properties of sound unbelievable sensation of reality is expe- in simple sound that an are particularly characterized rienced when a fourth dimensional sound illusion A handy pocket manual ... 104 pages fields, we will limit our discussions to these is created. Such a system will enable the auditor . . , 150 cuts and diagrams com- sound fields. It should, however, be borne in sound as it moves ... differentiate be- to follow a source of moving mind that the ears normally through space in much the same manner as you pact essential information showing tween directly radiated sound and reverberant who is speaking components, direct and would normally hear a person you how to get the best performance sound because the two or singing while moving. reverberant, differ in character: the latter being for every device employing vacuum modified in phases and quality by the surround- The importance and value of such a sound tubes! ings, and augmented by the previous sounds, system is briefly discussed in Vol. 1, No. 3 of which have not yet completely died away. In the Shur Technical Bulletin, to quote, "In order for these complicated sounds to become most public address applications the entertainers YOURS directional (which is a common phenomenon of are in full view of the audience. If the ultimate natural hearing) both hearing centers must re- in entertainment value is to be attained, it is FOR ceive two different versions of the heterogeneous desirable that the system be laid out and oper- sound waves as explained in our introductory ated so that the entire presentation is as real- article. istic as possible. In the ideal system none of the sound projecting equipment would be visible to the audience, and the sound would appear to The "Knot Hole Effect" come directly from the performers themselves. The greatest drawback of practically all sound The ideal condition is easily attained with a systems is the so- called "knot hole effect" fourth dimensional sound system." (Fig. 1A) which arises from the large variation between the size of the original sound source and Fourth Dimensional Sound Application reproduced sound source. The aesthetic value of a symphony orchestra, for instance (which is The question might now be raised "What uses usually spread over a large area) is completely can you make of such a system ?" Let us first lost in the usual forms of reproduction because briefly review what can or has been done with the reproducer concentrates the sound source to fourth dimensional sound systems and then we an imaginary pin head and produces what is will describe a new technique required to attain acoustically termed as "sound dazzle," a condi- these results. tion which "blinds" the listener to the exact One of the most effective applications was location of the various orchestral instruments recently demonstrated in one of the more pro- (Fig. A.) This effect is least conspicuous when gressive legitimate theaters during a presentation speech from a fixed location is being repro- of Norman Bel Geddes' Hamlet, wherein an un- duced inasmuch as the concentration of the usual number of sound effects were introduced. original sound (coming from the orator's mouth) A perfect illusion of natural howling and whis- closely simulates the concentrated sound waves tling of the wind was attained in one scene by produced by the loudspeaker. It follows, there- projecting a recorded wind storm from an fore, that. in order to maintain a natural realism elevated loudspeaker. Another scene, which in reproduction, the reproducing system should represented the crowd climbing a mountain to project sound from an area corresponding to storm the castle, was realistically presented the size of the original sound source. One through correct sound technique whereby the Here's method for accomplishing this is described later. murmurings and shouts were first heard in the a new technical manual This so- called "dazzle effect" is of particular distance and gradually increased in intensity as that's just as necessary as your interest because it explains in a simple manner the procession slowly circled around the moun- voltmeter in service work. 104 the essential causes for differences in the hear- tain. Finally the sounds blended into the stage pages ing sensation when listening to natural sounds actions as the crowd rushed onto the stage. To of essential technical information and their artificially reproduced versions. When produce this effect, the sound was first fed into complete data on over 90 types an orchestra is normally heard. each instrument all speakers at low volume and gradually ac- sets up an acousti -physiological circuit between cented in two of the speakers situated on one of receiving tubes . . base sym- itself, and the two centers of hearing, through side of the stage and then gradually shifted to bols . recommended operating central interpretive center of the speakers at the other side. The volume was both ears to the conditions . amplifier classifica- hearing (Fig. 2.) A five -piece orchestra sets up then slowly raised to equal the intensity of sound .. five different circuits all of which blend into which was being set up by the actors off stage tions . , . receiver circuit diagrams a pleasant sensation of "wide anale" (natural) as they were preparing to make their entrance. . over 150 cuts and diagrams hearing. A simple test to recognize this form One critic speaking of the play. said "Reproduc- of hearing is ability of the auditor to isolate tion throughout the entire show was so realistic in all. It shows you how to get the any one of these circuits and determine the that the audience was probably unaware of how best performance from every kind exact placement of the various instruments. the sound effects were produced. So real was of set -and the price is only 10c! The next time you listen to an orchestra (from the sighing of the winds as the king knelt be- a favorable which enables you to receive fore the cross on the mountain that the audience Fill in position was affected." the coupon below, attach direct waves and few reflected sounds) close your noticeably 10c in stamps, and mail eyes and try to place the various instruments. Although the stage offers the most unusual TODAY! for spectacular sound effects, there Try the same test when listening to a radio opportunities HYGRADE SYLVANIA CORPORATION program and you will experience the "dazzle are many other equally useful applications of a -dimension system in everyday oc- effect." fourth sound Makers of Factories currences. For instance, any small orchestra SYLVANIA TUBES ST. MARY'S, PA. can realistically increase its apparent size to to Eliminate Sound Dazzle HYORAOE LAMPS EMPORIUM, PA. Attempts equal the proportions of a large symphonic ELECTRONIC PRODUCTS SALEM. MASS. offer unlimited and Knot Hole Effects ensemble. Musical presentations CO B. B. Corp.. 1934 CLIFTON. N. J. applications for startling arrangements which While these prevalent shortcomings of pres- are limited only by ingenuity of the sound tech - ent day sound systems are not popularly rec- nician and the musical conductor. "The Flight ognized, sound technicians have attempted to of the Bumble Bee," for example, can be so improve their presentations by employing two presented that the buzz of the bee cavorts above or more microphones, multi -speakers and in- the orchestra. Likewise, "The Sliding Trom- dividually peaked audio amplifiera. Although bone" can be slid from one side of the stage to THE SET- TESTED RADIO TUBE these systems produce new, novel and unnatural the other. hearing sensations; they tend to overburden an Church installations offer a fertile field for a modern fourth dimensional sound system already bewildered interpretive center, instead C 10c- TECHNICAL MANUAL -10c of making it respond to artificially recreated which projects the preacher's sermon from the sounds exactly as it would normally interpret pulpit, the choirs' singing from the singers, and Hygrade Sylvania Corporation, the corresponding natural sounds. the pealing of the bells from the belfry. while Emporium, Pennsylvania. (B -19) the organ music is projected directly from the The use of one microphone, one amplifier and sound Please send me the new Sylvania Technical Manual. console. Most technicians arrange their 1 enclose 10 cents In stamps. two speakers (Fig. 3A) is analogous to apply- P.A. system equipment so that all sounds are ing a stethoscope to the knot hole in Fig. lA projected from the same direction regardless of and expecting to hear natural sounds. The use their point of origin. Needless to say, such a of two microphones, one amplifier and two sound set -up is far from realistic. speakers (Fig. 3C) corresponds to listening Banquets, circuses, and similar gatherings in Address ..._.__....._._..._.--_ ..... - .- ...... - _._..- through two stethoscopes arranged as shown in which sound plays an important part can be Fig. 3D and again expecting to get natural hear- given a heretofore unattainable realism by the ing reactions. Both of these systems produce a proper applications of a high -fidelity sound sys- City State.. high degree of directional distortion. tem. free from directional distortion. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 49B RADIO -CRAFT for FEBRUARY, 1935

direct presentations, that the loudspeaker be comparatively close to the microphone. Feed. back is avoided by using acoustic insulation (hair or wool) behind the microphone and be- hdnIonl of Music a Realih hind the reproducer, Fig. 6A. Under some con- Malces the l ditions of installation, precautions must be taken Out of the Columbia Sound Laboratories comes something new to prevent intense reflected waves from in striking -4th Dimension Sound-the greatest single development the microphones so as to avoid feed -back. scientific sound reproduction. It is not merely a new model. It is a result-one you can hear -one you can sense. Even though your present amplifier seems to sound Selection of the Microphones In right, send for our FREE booklet "Sound - Inasmuch as the microphones of our perfect Four Dimensions" and discover what you have sound been missing. system correspond to our ears during normal hearing processes; it is essential that we Ask also jot our FREE pampblet on Columbia Hsgb- Fidelity Sound Systems. select sound pickup devices with characteristics similar to our normal hearing mechanism. If we base our selection of microphones upon /N.. the following considerations -1. Frequency re- OLUMBIA SOUND CO sponse; 2. Effect of frequency response upon I35,LIBERTY ST. NEW YORK.N.Y. the direction of the sound source; 3. Sensitivity; 4. Ease of installation; 6. Price -we would select the following microphones listed below in order Determining the Type of Installation of their performance: 1. Crystal (10 -cell edgewise arrangement) Before dimensional system is a fourth sound 2. Ribbon (Velocity) installed is necessary to definitely determine it 3. Dynamic (Moving coil) just what is to be the operating scope of the 4. Condenser system. it is be used solely for pickup If to of 5. Carbon (Double button) a stationary sound source, a bi- dimensional arrangement is employed wherein one or more While the first two are to be preferred for microphones are placed at some advantageous high -fidelity work, any one of the others may position for best pickup. If moving sound is to be used for reproduction of speech. be picked up from one plane, horizontal or vertical, a tri- dimensional system is utilized. Micro- Selection of the Amplifiers phones arranged in a semicircle or straight are In one suitable high -fidelity 4- channel pre- line (in the plane of pickup). moving sound If amplifier, a 2 -3 stage selection is employed to is to be up in both horizontal and ver- ALL -WAVE SIGNAL GENERATORS picked boost the gain when used with a low level ribbon tical planes, a quadra- dimensional sound system l % Accuracy. Grid Stabilisation microphone. The power amplifier is built in is employed with microphones so arranged that fundamental bands by two separate unita, each one of which is com- Model Four each unit up a proportionate amount of 333 -RC Switching. Frequencies from picks posed of two clear channels utilizing two 2A3 83 to 5.000 ke. on direct reading dial. No charts or curves sound depending upon the position of the sound to consult. This model works on AC. DC or batteries. 10.5- tubes and delivering 10 watts per channel (40 130 v. line. 39 oscillator feeds 30 amplifier stage with source. watts total). Special precautions are taken neon tube for 1000 cycle modulation on DC. lioth modu- Three important that reader points the should in the design of both the -amplifier and lation and output controls Included. Instrument comes in bear in mind relative to this new technique pre perfectly shielded black crystal finished all -steel cabinet are: power amplifier to completely eliminate (within Suitable for laboratory or better class of service work. (1) A fourth dimensional sound system can high -fidelity limits) all frequency distortion. Complete with all tub es foror be used for bi- or dimensional work. $21.85 tri- phase distortion, and amplitude distortion. Shipping wt. 6 lbs. (2) In all of the various types of P.A. in- Three fundamental bands. 132 stallations to be described, the same pattern or Model 37-7 AC to 3800 W. by awdtrhing. No should Selection of the Speakers charts or graphs because 1% accuracy has been attained on arrangement of the microphones be main- dial directly. Engraved bakelito panel on black crackled tained in the placement of the loudspeakers so For ideal results, the loudspeakers should Steel cabinet. AC model complete with tube that the wave front of the projected sound is have radiating characteristics identical with for only - $9.507 Shipping wt. 4 lbs. identical with the sound wave which is inter- those of the original sound producing devices. Neon tube modulates 37 tube cepted by the microphones. Any deviation in Inasmuch as the angle subtended by the more Model 37 -s oscillator. Scale reads kc di- and microphones rectly from 135 -380. with all the important Intermediates. arrangement between speakers intense portions of the sound field at any given 175. 900, 450. 950. 465 spotted on chromium- etched scale. will result in a form of phase distortion which frequency is somewhat greater for the baffle- Lower scale for Wrest band on 4th harmonic. Engraved may. under certain conditions. cause serious type speaker than for the horn type, follows bakelita panel on black crackled steel cabinet. it Complete with both tubes for only $6.50 sound wave interference. that for concentrated sound sources voice, high - Shipping wt. 3 lbs. (3) Each microphone is connected to its own frequency wind instruments, etc., it is more de- DELTA RADIO CO., 135 F Liberty St., New York, N.Y. pre -amplifier, power amplifier and bevy of sirable to use horn -type speakers. speakers. Another important characteristic which favors If the performance is to be picked up from horn -type speakers is that it radiates effectively some horizontal platform upon which the speak- from only one side. This feature prevents feed- 7P01NThI1 E er or performer will move from side to side, back as well as other acoustical effects which the microphones (and their respective speakers) might adversely influence the auditor while FELL 20 FEET should be placed in a straight line across the listening to a presentation from some particular stage as indicated in Fig. 4. position. AS EVER The exact spacing of the microphones is de- For high -fidelity results, three speakers should -STILL GOOD upon five factors. be used FEEDBACK! pendent at the termination of each output chan- ...AND STILL NO nel, Johnston P. A. Service, 1. Polar response characteristics of the micro- for high, middle and low frequency repro- Oneonta, N.Y.. writes us: phones. duction. "We are certainly well velocity 2. Response (output level versus distance) mike (the7th -Point Mike). characteristics of the microphones. Installation Considerations We believe that no other THIS 3. Number of microphones employed. As previously mentioned, the positions of the mike can take the punish- ment it has and still work. 4. Length of platform from which sound must speakers play a vital importance in maintaining One time it fell 20 feet to be picked up. the effect of realism. Each speaker should be downs of the ground. And 5. Maximum height from which sounds will so located that it projects the sound in the same times it has seen rain. We mobile outfit. originate. general direction as the sound wave is traveling, use it in our when the microphone intercepts rood Lt's just as good no If we presume that the correct microphones it (Fig. 6B). a wonderful help If, for some reason, it is impossible locate ever. Also and amplifier equipment are chosen. then it only to in Minima fang acrouatital the speakers as suggested, then they may be Or- remains to divide the length of the platform feedback." Guaranteed. placed off the sound from your wholesaler, a number of divisions equal to twice the direct axis of the original der into wave, but or write for illustrated Bul- number of microphones to be employed and the direction of the projected wave 72. NOT must be so adjusted that letin TNIS placing one microphone at every other division minimum directional /lwr>sferra del (Fig. 4). distortion takes place (Fig. 7). It should of soc BROADWAY NEW rO course be understood, that any serious directional When sound is to be picked up from one distortion will affect the illusion of reality. For stationary elevated position. three microphones best results, speakers should never be tilted more /QMPERITE are distributed upon the stage while the fourth than 30 degrees and preferably less than 16 is located near the elevated source of sound. degrees. VELOCITY MICROPHONE If the source of sound moves is in only one upward direction, the third microphone is placed in line with the direction of the mov- Adjustment and Operation ing sound. Figure 5A shows the various posi- During normal operation, all channels are SERVICEMEN ATTENTION! tions (A, B, or C) for locating the third micro- attenuated to any desired degree of volume. It phone depending upon the direction taken by the is absolutely essential, however, that all channels -TIME IS MONEY! are accurately balanced to compensate for any parts. moving sound source. 24 -hour service on all replacement is to take commercial deviation in output of the micro- We carry most complete stock of standard When movement of the performers lines. Let us help you with any problem on place in a vertical direction the microphones phones. Tore- amplifier and power amplifier. In P.A. receivers or transmitters. should be placed as diagramed in Fig. 5B. practice this is accomplished by placing a fixed RADIO SHACK Because of the desirability of creating the sound source (1000 cycles) equidistant from the UNCLE DAVE'S illusion that the amplified sound is coming di- four microphones and adjusting the attenuators Albany, New York Phone 4 -5746 356 Broadway rectly from the performer, it is essential for on the preamplifier until the output meter Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 499 readings of the four channels are alike. For normal reproduction, the controls are not GENERATOR TYPE POWER changed, for any moving sound source will automatically produce more or less output from any UNIT one of the microphones, depending upon its (Continued from page 479) proximity. For trick sound effects, the controls on the ing the starting torque, it serves to provide Solve power amplifier are thrown into the input circuit better regulation of the genemotor under vary- which provide for the distribution of sound from ing load conditions and acts as an input filter. Any and Every any one microphone into any one, two, three or The filter circuit in the automobile type gene - four channels and their corresponding speakers. motor is interesting in that it is possible to The spectacular illusions of moving sounds which install all necessary condensers and inductors Servicing Problem can be created by this system, are far too numer- within the housing, thus conserving a great ous to mention. amount of space. One of the features of this with Now that we have a glimpse of what pro- type of "B" supply that makes the small filter cedure to follow in order to provide perfect possible is the very low ripple voltage present, artificially reproduced sound, it remains for the before entering the filter. The measure of the sound technicians to change their technique in initial ripple voltage on a well- designed unit is 1 order to recreate sound as it naturally occurs always considerably less than 1 per cent of the in our own fourth dimensional (sound -Ed.) total voltage, and it is at a frequency which re- world. quires a small amount of inductance to provide complete smoothing. To obtain this low ripple MASTER UNITS voltage, it was necessary to take certain precautions in the original design, the most impor- {{ tant being to keep the speed reasonably slow "LUXEMBOURG" EFFECT as well as to insure perfect commutation. IN RADIO New Application (Continued from page 467) The majority of radio technicians have recognized the small rotary generators operating place only at night and that it occurs only from a storage battery as a dependable "B" (according to Dr. van der Pol) when the great supply for auto -radio receivers, but, have failed circle joining the desired station and the point to consider the many other applications and sales of observation passes the undesired or inter- possibilities of this product. It is the purpose fering station at a distance not greater than of the following few paragraphs to call your 176 miles. In other words, the two stations attention to the possibilities in this new field. and the receiver must be in a straight line (to Recently there has been a growing demand a greater or less extent). for replacement units as a substitute for vibra- It has been found that the Luxembourg Effect tor assemblies. A number of such units have takes place continually, not only on the broad- been developed to fit in the popular makes of cast and long waves. but also on short-wave auto radio receivers. The accompanying photo transmissions. illustrates the conversion of a genemotor in a SERVICE men and technicians who As a means of arriving at some explanation Ford auto radio. The ease of installation and of the effect, the World Radio Research League, dependability should create considerable inter- have seen and used the precision a group of radio enthusiasts banded together est with those engaged in the auto -radio service instruments in the Triplett Master by World -Radio magazine, has solicited the aid field. Unit line pronounce them today's of radio listeners and experimenters all over Service Men located in or near rural sections the world. It is requested that whenever the where A.C. power is not available, have found most advanced developments. background of an interfering station is heard the special "B" eliminators offered for sale to Triplett Interchangeable Master Units make that is not transmitted on an adjacent channel, be a valuable adjunct to the regular service en- possible different combinations of testing a record of the date, time of listening, location terprise. Models are available operating from equipment to suit every servicing require- of the two stations, number of miles separating 32 -volt farm lighting systems or from a 6 -volt the stations and the listening point and any storage battery. Recently several of the storage ment ... no matter how difficult or com- other interesting facts be recorded. RADIO -CRAP, battery manufacturers have developed a long plicated. These units may be used as fur- readers may send in their records to this mag- life 2 -volt cell to operate the 2 V. series tubes nished, or, placed in convenient portable azine where they will be coordinated and for- over long periods of time. A special genemotor cases that hold one, two, three or four warded to the secretary of the above association has been developed to work in conjunction with units. where they can be used to advantage. this new 2 -volt cell which should, under normal Since these peculiar observations cannot be use, provide the user approximately two months Triplett Master Unit, No. 1205, justified by some of the most eminent author- "A" and "B" service from a single recharge of includes: ities according to existing theories of radio the battery. No. 1200 Volt- Ohm- Milliammeter. DC transmission, it seems logical to assume that One of the greatest problems of the customer scale readings: 1/5 to 1,000 volts (2,000 some important facts have been overlooked in or installer of mobile P. A. equipment is that of ohms per volt) -20 microamperes to 250 arriving at these theories, and it is difficult to an economical and reliable "B" supply. Most milliamperes-0 predict what far -reaching effects this will have systems require a relatively high consumption to 3,000,000 ohms. AC on our present methods of radio communication. from the battery in ratio to the power output scale readings: 1 to 1,000 volts. Capacity of the amplifier, or if the fan belt driven type charts furnished. Dealer's net price, unit is used within the motor car, it requires the only $21,67 engine to be continually running to provide the No. 1210 Tube Tester. Tests all tubes. necessary energy. The chief advantage of the rotary type eliminator is that when used with Contains the most efficient short check the properly designed amplifier the ratio of known. Analyzes each plate of multi - ORSMA MEMBER'S power input to power output approaches the plate tubes. Dealer's net price, unit highest efficiency that can be obtained in such only $20.00 FORUM installations. In a forthcoming article we will No. 1220 Unit Tester. Makes all series or describe several efficient amplifier circuits to be parallel (Continued from page 480) used in conjunction with the genemotor, as well meter connections to the set sock- as furnishing data for converting existing A.C. ets. Dealer's net price, unit only $ 8.33 x I x Power W (AC) = (E Factor). amplifiers so that they can be operated from No. 1230 All -Wave Signal Generator. Fre- W -Hra. _ (E z I x Hrs.), (W z Hrs.). either A.C. power or storage batteries. A can- quencies: 100 KC to 18 Megacycles. Per- KW .= (E x I - 1,000), (HP x 0.746), (W - 1,000). vass of the numerous sound truck users will K W -Hrs = (E x I x Hrs - 1,000), W z Hre - 1,000). fect attenuation. Modulated or unmodu- provide the Service Man with a large number lated. Dealers net $15.33 Amp -Hrs = (I x Hre), (E = R x Firs), of prospects in this new field. price only (W = E x Firs), (KW x 1,000 z E x firs), Numerous special applications will become ap- No. 1205. Complete with above four units (. /W + R x Hre). parent to the wide -awake dealer and Service in case, Dealer's net price $71.33 Coulomb (Q) = (I x Seconda). Man, once he has investigated the many possi- Joule (J) = (E x I x Seconds), (W z Seconds), bilities in the use of the genemotor. An inter- YOUR JOBBER CAN SUPPLY YOU - (It xRx Seconds). esting incident describing one of the many ap- TRIPLETT ELECTRICAL INSTRUMENT COMPANY HP= (W - 746), (KW - 0.746), (E x I _ 746), plications was experienced recently upon visiting 109 Main Street Bluffton, Ohio (KW x 1.341), (W x 0.0013), (748 W). the projection room of a small theatre. An ar- Epic= (HP it 746 = E x I), (FiP z 748 = W), ray of resistance elements were mounted on the Mail Today For Details! (Brake HP - Elec HP). wall for the purpose of reducing the 110-volt Input= (Output - Effie), (Output z Losses). D.C. (the only current available) to the a proper TRIPLETT ELECTRICAL INSTRUMENT COMPANY Condensers in Series 1 C' z Ca voltage for the exciter lamps and the projection or =Corn 109 Male Street, IlluItton, Onlo machine. Nearly a kilowatt of energy was con- Gentlemen: Resistors in Parallel 1 1 C'-I.0 sumed to provide the 60 watts necessary for Please Bend your latest literature on Triplett Instru- the filaments of the lamps. The operator was ments. Ct Ct astounded to learn that the D.C. could be re- Condensers in Parallel duced to the required voltage by the use of a Name or =C1 +C2 +C3, etc. or small converter weighing under 15 lbs., which Address Resistors in Series R1 +R2 +R.3, etc. consumed less than 100 watts instead of the orig- City Slate HARRY W. KRUG. inal 1000 watts. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 500 RADIO -CRAFT for FEBRUARY, 1935

with an asterisk are the ones which will be LISTENING POST heard most frequently in the central, or eastern All RADIO REPAIR What to Listen for During January - States. of these stations are being heard February more or less frequently on the Pacific coast. MEN -AMATEURS Broadcast Band Japanese Stations (Continued from page 474) Waue- Call Location lenpth Kr. Power January and February usually are very good JOCK -2 Nagoya 255 1175 10.000 Roebuck and Co., months for DX -ing on the broadcast band, and JOBK -2 Osaka 277 1085 10,000 off, bring a peak reception JOFG Fukui 303 990 300 The World's Largest Mail Order in North America for Company (in the Radio and Parts signals from all directions except Australia -New JOXK Tokushima 306 980 500 Zealand. The Australia -New Zealand signals are JOBG Maebashi 309 970 500 business for almost 20 years) an- at their peak intensity JOOK Kyoto 313 960 300 nounce for restricted distribution a during the month of JOAG Nagasaki 323 930 500 March, and often show considerable strength JOQK Niigata 326 920 500. new Radio Parts and Amateur during the latter part of February. April is JO K -2 Keijo 333 900 10,000 Equipment Catalog. often a good month for this type of reception JOAI -1* Tokyo 345 870 10,000 also. when spring static on these frequencies JOFK* Hiroshima 353 850 10,000 will DX -ing. The JOIE* Sapporo 362 830 10,000 24 -HOUR SERVICE permit latter part of Febru- JOCK -1* Nagoya 370 810 10.000 ary will on the other hand show a very definite JOCK Kumamoto 380 790 10,000 Everything carried In stock -the decrease in the signal strength, and regularity JOHK* Sendai 390 770 10,000 broadest guarantee ever written - with which signala from Europe are received, JOPK Shiauoka 384 780 500 Complete satisfaction or your mon- and by the latter part of March these stations JOBK -1* Osaka 400 750 10,000 JOSK Kokura 408 735 1 111 ey refunded. have nearly vanished entirely with the exception of Newfoundland, JORK* Koehi 417 720 II and Nova Scotia. JFBK Tainan 417 720 1,000 Write today for catalog No. 83R61. We are very fortunate in being able to pre- JOJK Kanazawa 422 710 3,000 We will put your name on our mail- sent one ofa the first authentic. and up -to -date JOKE Okayama 429 700 500 ing list and send you this big, new complete lists of Colombia S.W. stations direct JOVE Hakodate 441 680 500 from Colombia. This list was JOLK Fukuoka 441 680 500 as soon as is press. compiled by Sr. JFAK* catalog it off the Daniel Semper Ortega of Bogota, Colombia, and Taihoku 44S 670 10,E reaches JOCG Asahigawa 458 655 us through the courtesy of Mr. Robert JOUE Akita 465 645 300 Weber, of West McHenry, Illinois. JQAK Darien 465 645 500 SEARS, ROEBUCK There will soon be a new station at Me- JODG Hamamatsu 472 635 500 and CO. dellin. This will be ready about the time this JONK Nagano 472 635 500 CHICAGO, ILL. article comes out and will operate on both long JOTK Matsue 480 625 500 and JODK -1* Keijo 492 610 10,000 short waves. On short waves it will use JOAK -2 Tokyo 508 590 10.000 5,930kc, but the long wavelength is not yet decided. When completed it will use 2 %kw, but NOTES: JOAK -1 will be raised to 150.000 watts. the first tests will be with only 1kw. HJ1ABB JOOK will be raised to 100.000 watts. JOBK -1 to 100.000 SERVICEnIEN! watts. and JOSK to 10,000 watts. The daily programs of at Barranquilla is soon to inaugurate a long - JOAK -1 are generally relayed by all .1- stations except Step Ahead of the rank and file- wave transmitter to work simultaneously with JOBK, JODE -1, JOAK -2, .IFAK. JQAK. etc., of which JOUK, .IODK -2, .IFAK. .IFBK and JQAK relay partly -1 with "CASE RECORDS the present short -wave transmitter. JOAK -1, white .TOAK -2 has its own program. of an edu- of BROADCAST cational nature, no tousle ever ',One transmitted. Its RECEIVER REPAIRS" Tuning in the Japs programs are often relayed by JOCK -2, JOBK -2. etc. The .I- stations tranrmit the programs of JOAK -t from ADD 10,000 Hours to your Our good friend and colleague, Captain Horace 7:00 a to 9:45 p.m. J.C.T. 15:00 p.m. to 7:41 a.m. experience! L. Hall, us during January. February and March: mille they ELIMINATE GUESS sends the following up- to- the-minute begin an hour earlier In the morning at other seasons of WORK IN YOUR SERV- list of Japanese broadcasting stations. This in- the year, JFAK. .IFISK, and .IQQAK transmit one hour ICING! formation is very timely as the Japanese stations later than the other stations due to the difference in time. e DON'T PUZZLE YOUR A dully newscast in English Is transmitted by the J -sta- PROFITS AWAYI will be at their beat during this period. Those tiens at 4:55 a.m. E.S.T. Your work is already done and recorded for you In "CASE RECORDS." This 9112^ loose -led binder contains 1,500 alphabetically and numerically Radio -Craft's Foreign DX For January- February arranged 'VASE RECORDS" Calendar of SUCCESSFULLY COM- PLETED SERVICE JOBS! EASTERN .STANDARD TIME Each CASE RECORD tells all detaila for satisfartorY Jan. 6 Sun. 2:05-3:05 a. m. 830 kc. 25,000W Buenos Aires. Argentina LR5 repair. SUPPLEMENTED QUARTERLY FREE for 1 6 Sun. 3:10.5:10 a. m. 1,270kc. 1,5001V Santo Domingo, D. R. HIX year. 108 receiver makes . .. 3.000 modela. 10 Thurs. 1:00 -2:30 a. m. 1,096kc. 10,000W Madrid, Spain EAIT ... the FASTEST Technique known to the Profession! 12 Set. 5:00 -7:00 p. m. - 6,120kc. 49.02M New York City, N. Y. (SW) W2XE 16 Wed. 12:01 -2:00 a. m. 1,031kc. 5.000W Parede, Portogal CT1GL First Supplement NOW READYI 20 Sun. 1:00-2:00 a. m. 959kc. 100,000W P. P., Paris. Fonce Rend each now and receive 1st Supplement With "CASE 22 Tues. 2:00-3:00 a. m. 1,I90kc. 40.000W Buenos Aires, Argentina LS2 RECORDS" and our DATA SHEET on 'BUILDING Feb. 3 Sun. 2:05 -3:05 a. m. 830kc. 25.000W Buenos Aires, Argentins L115 AN ANALYZER ADAPTER" also. 6 Wed. 2:00-3:30 a. m. 913kc. 60,0001V Toulouse, France on return of Manual within 10 days. 10 Sun. 2:00 -3:30 a. m. 830kc. 25,000W Buenos Aires, Argentina LR5 Refund Weekly Sat. 12:30-1:00 a. m. 980, 6140, CAPITOL RADIO RESEARCH LABORATORIES. INC. 11,S70kc. KDKA DX Club, Pittsburgh. Pa. KDKA m. KFI DX Los Angeles, 1503 21st Street, N.W.. H. K. Bradford. Weekly Sun. 2:30-3:00 a. 640ke. 50,000W Club, Calif. KFI Washington. D.C. President NOTES: On LR.S's Itroadwast of February 10th a silver- mounted and engraved Maté Pot will be given to the lucky DX -er sending in the but report on this broadcast to Radio Excelsior, LR5, Buenos Aires, Argentina.

Colombian Short -Wave Broadcasters WET AND DRY ELECTROLYTIC Call Location Freq. Power Slogan ont/ Omner Hours. Eastern .Std. Time Voz Daily, 5 p. m. PAPER AND MICA CONDENSERS ABB Barranquilla 6,400 300W "l,a de Barranquilla' -10:00 Apt. 715 Elias J. Pellet B. Sun. at 5:00 a. m. RECOGNIZED FOR HJ1ABD Cartagena 6.100 50 SUPERIOR QUALITY HJIABE Cartagena 6,100 15 Jose M. Fuentes Wed., 8 -10:00 p. m. IN Apt. 31 Mon. at 10:00 p. zu. DX Trans. THE,WORLD MOVE R HJ1ABG Barranquilla 6,000 100 La Voz de los Laboratorios OLD of II *D1NO Jimeno G and Cia. FORURE IVERYW HEU CATALOG HJ2ABA Tunja 6,150 500 Ecos de Boyara Fri., 11:00 a. m.-1:00 p. m. OF EXTREMELY Pompilio Sanchez C. Tues., Thur., Sat., 7 -10:00 p. m. SOLAR MFG. CORP. HJ2ABC Cucuta 5,900 50 La Vox de Cuenta Daily, 11:00 a. m.-1:00 p. m. 599 asosowY COMPACT TYPES Pompilio Sanchez C. Daily, 6-9:00 p. m. NEW Oaa HANDY FOR SERVICE HJ3ABD Bogota 1,110 Colombia Broadcasting Daily 7-11:00 p. m. Apt. 509 7.400 Alfords Radio Mon., Wed., Fri., 6 -7:00 p. m. HJ3ABE Bogota 1,200 50 La Voz de Bogota Wed., Sat., 6 -7:00 p. m. HJ3ABF Apt. 317 6,200 50 C. Uribe & Rafael Moreno Daily, 7 -11:00 p. m. HJ3ABH Bogota 1,005 Wed., Sat., 6 -7:00 p. m. Apt. 565 6,060 La Vos de la Victor Sun., 4-8:00 p. m. UNIVERSAL HJN Bogota 681 1,000 Radio Nacional Daily, 6 -11:00 p. m. 6.080 50 Ex. Sun. and Holidays Hi- Fidelity HJ4ABB Manizales 7,140 Radio Manizales Tues., Fri., 7:30-10:00 p. m. Apt. 175 Roberto Baena V. Sun., 2:30-5:00 p. m. Silveroid Records HJ4ABC Pereira 1,000 50 6,090 50 A new. Improved type of cellulose -coated alu- Wed., Fri., 7 -11:00 p. m. minum disc-Unusual tonal quality- Merveloudy HJ4ABE Medellin 5,930 Medellin Radio Mon., natural reproduction-Lowest background level Apt. 239 Arturo Alzate Ciraldo Tues., Sat.. 6:30-10:00 p. na. yet attained-ran be eut with usual sapphire HJ5ABC Cali 5,100 30 La Vos de Colombia Daily, 11:00 a. m.-Noon. pointa end will play bock with any non -metallic Calle 12 R. Angulo Tues., Fri., S-10:00 p. m. needle -For personal recording.. program audi- H.T5ABD Cali 6,500 La Vos del Valle Daily, 7 -10:00 p. m. tions, air checks and transcriptions. H KE Bogota 7,100 138 Observatorio Nacional de Mon., Thurs., 6:00 P. m. Ex. UNIVERSAL MICROPHONE CO., Ltd., San Bartolome. Rev. P. 424 Warren Lane, Inglewood, Calif., U.S.A. Simon Sarsola Course at Univ., Tues., Sat., 8-9:00 p. m. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY, 1935 501 A MODERN PICTURE OF BROADCASTING RADIO CITY (Continued from page 459) power in watts is the astounding figure. Once TESTERS again, for comparative purposes, let us glance and at the table below, the figures representing the aggregate power in watts of the network stations. ANALYZERS Year NBC CBS Total Watts 1931 807,750 273.200 1,080,0.0 1932 891,200 476.950 1.368,110 Do More -Cost Less 1933 1,114,800 498,800 1,613,600 1934 1,610,100 615,900 2,126,000 las of Nov. 1) The total number of stations shown below, QUALITY is important in testing represents the number of outstanding licenses equipment. Accuracy is essential. or construction permits issued by the Federal Adaptability for all present and future Radio Commission as of January 1, 1934. Seven other stations including three in Hawaii, two in needs is valuable. Convenience and Porto Rico, and two in Alaska are also licensed looks are desirable. But high MODEL TUBE good TESTER by the Federal Radio Commission. price isn't necessary. 304 There are 101 stations in the U.S.A. licensed to use greater power before local sunset than The new Radio City "DEPENDABLE" The only rube tester show- $19.95 after. The table given below shows the amount Analyzers provide all of ing leakages above one -mil- Ready to of wattage, in aggregate, of the National Broad- Testers and lion ohms. Neon -light indi- Operate. casting Company's networks, the Columbia those features at the lowest cost. And cator. "Good -Bad" meter. $15.65 Broadcasting System's network, and a good com- their reputation with service men and Tests all today's tubes and provides for 50% increase. KIT parison of the total wattage represented by the dealers is unsurpassed. Complete units, balance of the radio broadcasting stations in the One -button operation. U.S., not affiliated with either of these network ready to operate, or money- saving kits. Etched metal panel. Leath- in erette case. Counter and organizations. The maximum power the table Write Dept. RC -2 for 1935 Catalog. portable models. therefore is that used during the day, the minimum power that used during the evening hours. Per cent RADIO CITY PRODUCTS CO. Watts of Total 28 -30 West Broadway, New Power of NBC Stations- Marlmurn 1,139.250 61.2 York City 511oho= 1,106,800 61.0 Power of CBS Stations- Maximum 491,550 26.4 Minimum 478,800 26.4 Power of other S. Stations- Maximum 232.165 12.4 Minimum 227.815 12.6 Source: Federal Radio Commission Report of January 1, 1934. NBC and CBS figures do not FRANKLIN include their Canadian or Hawaiian affiliate stations in this table. TRANSFORMERS Although the NBC and CBS networks are the two important broadcasting networks in the "Most Sock Per Dollar" U.S.A., other networks are in existence: some of them affiliate with either the NBC or CBS GENERAL REPLACEMENT networks on a part -time basis. The CBS and Years of experience dating back to the early days of separate A & B NBC networks, as to number of stations, have already been outlined. Following is a list of power supplies are incorporated in present Franklin units designed for other networks and the number of stations af- every purpose. filiated with these networks. American Broadcasting System -18 Stations - SOUND No other network affiliations. Inaugurated October 14, 1934. (Atlantic States.) Public address transformers to match hundreds Don Lee Broadcasting System -12 Stations - of impedance combinations. Catalogue con- Affiliated CBS network. (Pacific Coast States.) tains large number of circuit diagrams includ- League of Wisconsin Radio Stations, Inc. -7 Stations -Affiliated CBS network. ing Class A Prime. Mason -Dixon Radio Group -5 Stations -No other network affiliations. (Southern States.) AMATEUR Michigan Radio Network -8 Stations -No other network affiliations. A complete line for filament, grid or plate Mutual Broadcasting System -4 Stations -No other network affiliations. supply, chokes, Class B modulation, etc. Illustration shows one type. New England Network -5 Stations-Affiliated NBC Network. Share your transformer problems with Boyd Phelps W2BP -W9BP in Northern California Broadcasting System -2 charge of this department. Stations -No other network affiliations. Southern California Network -4 Stations -No other network affiliations. WRITE FOR CATALOGUES, GIVING YOUR JOBBERS NAME Southwest Network -11 Stations -CBS network affiliations. No. 51 General Replacement No. 70 Sound No. 52 -C Amateur 'Yankee Network -11 Stations -CBS network affiliations. (New England States.) FRANKLIN TRANSFORMER MFG. CO. Two U. S. broadcasting systems have gone 607 22nd Avenue, N. E. Minneapolis, Minn. out of existence in the past few years, one of them recently. They are: Amalgamated Broadcasting System -6 Stations. Iowa Broadcasting Company -3 Stations. The stations associated with these two networks are in operation either independently or have affiliated themselves with other networks. Network organizations pay huge annual tolls GOOD NEWS to the various telephone companies for wire charges. From the only present available figures one can readily understand just how high this aggregate figure must be when all the ABOUT THE NEW 1935 various networks are taken into consideration. The annual wire tolls for the year 1931 were: MANUAL National Broadcasting Company- $2,799.916.71, OFFICIAL RADIO SERVICE For the Columbia Broadcasting System- $1,964,- 655.68. A combined total of $4,764,572.39. With the expansion of the network system of broad- The 1935 OFFICIAL RADIO SERVICE MANUAL is now casting, the tolls may reach even higher peaks in future years. It is practically impossible to ready for delivery. Turn to the announcement on page 506 forecast the rate at which this expansion will take place. of this issue, and read full particulars about this excellent This progress is further emphasized by the book. total investment of capital required by the broadcasters. This investment reached the Please Say That You Sau' It in RADIO -CRAFT

www.americanradiohistory.com 502 RADIO -CRAFT for FEBRUARY, 1935

amount of $25.000.000 in 193L In 1933 that JUST OFFTHEPRESS/ amount had been increased to $30,000,000*, a jump of $6,000,000 during the peak of the depression. FREE The broadcasting industry has never been Many Auto-Radios Radio and marking time. During 1931 and 1932 -33, the National Broadcasting Company had planned Installed Last Summer Amplifier and constructed the most modern broadcasting CATALOG studio plant in the world, in Radio City, and 1935 the recent increase of power at station WLW Now Need Servicing! from BARGAIN 50,000 watts to 500,000 watts is the result Auto -radios installed during the past 124 of many long months of experimenting at a six months usually RADIO tremendous need some minor CATALOG PAGES expense. adjustment -new tubes, new suppres- OF BIG The radio advertiser has been the one great sors or other parts. Perhaps the job factor in all this expansion, as his use of the will even be more difficult-then you'll MONEY radio has been the source of revenue by which find how needy the Auto -Radio Serv- the broadcaster could continue operations. They ice Manual is to repair the job quickly. SAVING have spent, according to National Advertising VALUES Record, $33,842,485 in the first ten months of 50 1934 on National Networks in the U.S. alone. Sr LIST Filled with latest ncign Portable. Mobile and Rack and Panel. Yet the listener is not overburdened with Pnblk. Addre s Ampl.acre. Sbort -Wave and Ml -Wave Receiver adver- mud Converters. Inter-Office Call Sleterne. Test Equipment. Re- tising material as an average. In fact, the ad- placement Porto. Kato. 'rube.. and Ae,n.orin -All at unbent able Rock Bottom Prices! vertising material has become less in volume than ever, though the commercial programs have 1 WE ARE HEADQUARTERS FOR been on the increase. No better illustration PUBLIC ADDRESS SYSTEMS 1 of this point can be found than in H. S. Hetlinger's Buy Direct from the Manufac- "A Decade of Radio Advertising," where he turer and Pay Only One Profit states: COAST TO COAST RADIO CORP. Year Daytime Night time 1931 2 min. 35 sec. 2 min. 39 sec. 123 -K W. 17th St., New York,N.Y. 1932 2 min. 28 sec. 2 min. 39 sec. *McGraw Hill Co., "Electronics." Manual S e THE These figures represent the actual time of com- MODEL 22 TESTER ;. mercial material on a sponsored program of 30 pirccu;ry - Gomplete minutes in length, and are compiled from an of JI average 75 of programs annually chosen at ran- R9dio RMe,'ers dom from CBS and NBC network files. Automobile For the sake of better illustration of what the advertiser and pays to broadcast a one -hour pro- '. Ftt114nstallation gram over the several networks with headquart- SboOting Guide ers in the East, a tabulation of the gross rate . rouble between the hours of 6 p.m. to 11 p.m. has been prepared. This tabulation is as of October 1, To everyone who now purchases the OFFICIAL 1934. AUTO-RADIO SERVICE MANUAL this big 48-page Supplement is issued FREE. Practically all of the latest sets. together with servicing In- National Broadcasting Company formation will be found in these new pages. The new Supplement does not increase the cost of the Coast to Coast Red Network (84 outlets without book to you, but gives you an Auto -Radio WLW) $14,120.00 Servire Manual that is right up-to - the -minute with serv- Key Station -WEAF -only 508.00 ice notes. The greatest value possible for the (t C Coast to Coast Blue Network (61 outlets without money. Beautiful quartered oak WLW) 13.520.00 Money case, veri- chrome lettered bakelite S23s Key Station -WJZ -only 900.00 Good in Servicing Auto- Radios panel, 314" D'Arsonval type meter These figures do not include charges for talent or pro- If you are overlooking servicing auto radios. you're 2% accuracy. Tests all -day tubes with gram material. missing a great deal of business. The auto -radio present business had its greatest boom last summer when ample provisions for the future types. Neon thousands of sets were sold. By now many of leakage and short test of all tube elements. Di. Columbia Broadcasting System these same sets require servicing and with hundreds of them rect reading. Provisions for resistance and con- Coast to Coast CBS Network (86 Cities) $15,775.00 right In your own community. you can build up a good auto denser test. Key Station- WABC-only 950.00 -radio servicing business. WRITE FOR CIRCULAR ON OUR NEW COMBINA- In a short time you can easily add 25% profit or These figuren do not Include any charges for talent or more to your regular servicing business. TION UNIT. Tube tester and volt -ohm -meter. A complete Program material. electrical -radio service outfit in one unit. $34.90. A.C. D.C. METER 0-I MIL -AMP. $4.90. List of sets covered in the Manual ALL TYPES and kinds of ROTARY SWITCHES. Our American Broadcasting System, Inc. Acme Radio Mfg. Co. P. B. Mallory & Co. new bulletins describe ell the above units. Mailed on Allied Corp. request. (Inaugurated October 14. 19341 Radio Melborn Radio Mfg. Co. Basic Network..._..._._.....__.._...... $2,490.00 Atwater Kent Mfg. Co. Montgomery Ward & Co Audiola L L ELECTRIC COMPANY Optional Service..._._- ..__..._.._ 280.00 17 Stations Radio Co. National Co., Inc. & Total Autocrat Radio Company Noblitt -Sparks 336 MADISON Dept. 15 -R MEMPHIS. TENN. 2.760.00 Ind.. Inc. AVE. - Automatic Radio Mfg. CoPhllco Radio & Tel. Corp. The program builders have not neglected to Carter Genemotor Corp. Pierce-Airo, Inc. keep pace with Century Radio Prods. Co. Premiar Electric Co. other phases of the broadcasting Chevrolet Motor Company Radio Chassis, Inc. industry. Their efforts have been largely guided Consolidated Industries, RCA -Victor Co.. Inc. by the audience response. This audience re- Ltd. Sentinel Radio Corp. Crosley Radio Corn. Sparks- Withington Corp. sponse, mostly in the matter of mail, varies from Delco Appliance Corp- Stewart Radio & Tel. Corp KenRad year to year, but 1934 has produced a noticeable Detroit Radio Corp. Stewart -Warner Corp. increase in volume. In 1932 the networks re- Emerson Electric Mfg. Co. Stromberg-Carlson Tel. Radio Tubes Fada Radio & Elec. Corp. Mfg. Co. ceived 4,771,000 communications, and in 1933 Federated Purchaser, Inc. Transformer Corp. of Am. DEPENDABLE LONG LIFE this had dropped to 3,175,000. However, for Ford -Majestic United Amer. Bosch Corp. the Fanklin Radio Corp. United Motors Service first ten months in 1934, 4,235.106 communica- Calvin Mfg. Corp. U. S. Radio & Tel. Corp. Ken -Rad Radio Tubes are made tions have been received as compared to 2,586,- General Electric Co. Utah Radio Prods. Co. 597 for the January- October period of 1933. General Motors Corp. Wells- Gardner Company to give clear, dependable recep- A. H. Grebe & Co. Wholesale Radio Serv. Co, tion. They satisfy customers and Of all the programs broadcast by the major Grigsby- Grunosv Co. Rudolph Wurlitzer Mfg. networks, an average of 85 to 90 per cent annu- Chas. Hoodwin Company Co. build good will for dealers. Write ally, are from the studios of the broadcasting International Radio Corp. Zenith Radio Corp. for full information. companies, and the remainder represents the Over 200 Pages portion of programs originating at points out- THE KEN -RAD CORP., Inc.,Owenaboro, Ky. side of studios. Over 500 Illustrations Division of The Ken -Rad Tube and Lamp Corp. Personal contact with the listener is now the 9 x 12 Inches Also Mfrs. of Ken -Rod Incandescent Electric Lamps aim of the majority of the broadcasters. Much of this has been accomplished by direct sur- Flexible, Loose -Leaf Cover veys through representatives of the broadcasting companies, either by direct contact or via the telephone. Studio audiences are closely tested MAIL THIS COUPON TODAY! for their reactions to every type of program the finest The ever -increasing figures of radio-owning GERNSBACK PUBLICATIONS, INC. RC2 -35 families surely shows how well the program 99 Hudson Street, New York, N. Y. G et RESISTORS Enclosed pill find my remittance of $2.50 for builders are meeting the listeners demands, as you SUPPRESSORS which please send me One Copy of the OFFICIAL. erratic and varied these demands and require- AUTO -RADIO SERVICE MANUAL with FREE 98- CONDENSERS ments may be. page Supplement. Send remittance in check or money S.. rem* ,e.pe,oeooie, ona .nonutgcturer CUM., ih,ouem There has an increase order. Register letter If it contains cash or currency. been in the dramatic WE PAY POSTAGE. Out Me world, e., upon Con..nentol for quohty and service type of programs as well as the sponsored mu- unswoossed. New caterer show complete fines of resistors. sical programs of a classical nature during the cute rode Suppressers, ono condensers. past year. There is also a present trend toward Name Ask tour /oboe, et Vanne by longer unit programs, best illustrated the Address rCONTINENTAL CARBON inel fact that on the national networks of NBC there are now 16 weekly programa of one hour dura- City State .1).a LORA, APE ( I.LI'Fl AND 01110 tion. Please Salt That You Saw It in RADIO -CRAFT

www.americanradiohistory.com RADIO -CRAFT for FEBRUARY. 1935 503 With the annual variation of audience response comes an equal variation of what that 12 BOOKS TO HELP audience wishes to hear. These desires and re-. YOU LEARN MORE quests change the percentage of time allotted to the different types of programs, and although Grunow, sometimes these changes are very slight from Flash ABOUT one year to another, they do denote the careful RADIO attention to these requests by the program direc- Sparton, Zenith, Motorola, tors. Following is a list of program types and Illustrated at the the percentage of time allotted to each on a right and left national network. Covering a period of three etc., approve the Model OC are two books In years, the reader may easily note the variation. the Radio - Craft Library in the majority of cases entirely due to the au- Series. dience reaction. Program Sept. 1932 Sept. 1933 Sept. 1939 Music 66.3% 72.0% 68.6% Literature 9.8 10.6 11.8 Lectures 6.9 5.7 6.5 Outstanding Events...- 3.1 1.3 3.2 Current News...._ 1.0 .7 1.4 Women s 1.7 .8 .7 THE RADIO -CRAFT LIBRARY SERIES -a most Children's 2.8 2.9 2.1 complete and authentic set of volumes-treats In- Physical Trainiug..._ 2.3 2.2 1.7 dividually. important divisions of radio. Each book ]religion 1.8 1.6 1.5 has been designed to give you the opportunity to learn Reports .6 .1 .1 one or more branches of radio. The authors of the Novelties 3.7 11 2.4 books are well -known to everyone. Each is an expert radio man; an authority on the subject-each Is ther 100.0% 100.0% 100.0% -war oughly familiar with the field which he represents. In order that the broadcasters may be thor- All Books Uniform oughly acquainted with the reactions of the gen- , The volumes In the RADIO -CRAFT LIBRARY .. ,, SERIES are all uniform. 6 x 9 inches. Each hook eral public, extensive campaigns are being in- contains on an average of 50 to 120 illustrations. The augurated so that as much data may be accumu- books are printed on an excellent grade of Paper lated as possible. Early in this year, 1934, as which makes the type easy reading. an illustration of this fact, the National Broad- Here Are the Series: casting Company investigated the existing use R.F. Signal Generator for servic- Book No. I of radio receivers in daytime as compared with RADIO SET ANALYZERS evening hours. As the plans were formulated. ing ALL -WAVE Sets And How to Use Them By L. VAN DER MEL it was evident that such a survey would un- The service engineers of these Book No. 2 cover many other facts about radio -families leading set manufacturers have MODERN VACUUM TUBES which would aid in the fututre formation of unanimously approved the And How They Work By ROBERT HERTZBERG programs more in keeping with the desires of CLOUGH -BRENGLE Model OC Book No. 3 the listeners. In order that you may understand R.F. Signal Generator as being THE SUPERHETERODYNE BOOK how thoroughly a survey of this nature is con- the finest instrument for servic- All About Superheterodynes By CLYDE FITCH ducted, and the time and labor necessary in ob- ing their new ALL -WAVE re- Book No. 4 taining the desired information, there will be ceivers. MODERN RADIO HOOK -UPS 45,216 figures in the final statistical material, Here are some of the outstanding features of The Best Radio Circuits By R. D. WASHBURNE out of necessary 10,000,000 tally marks made the Model OC that have brought it this un- a equalled Book No. 5 by a staff of sixty -three people working a total recognition: 60 k.c. to 30 m.c. con- HOW TO BECOME A RADIO tinuously variable fundamental wave output; of 1,189,000 man -hours. A total of 386 inter- each instrument hand calibrated to accuracy SERVICE MAN viewers obtained 727,031 half hour unit- inter- By LOUIS MARTIN within Sz of 1% over entire range; three tube views in 209 cities throughout the United States. electron coupled circuit; A.C. -D.C. line opera- Book No. 6 Of these, 94,087 were by telephone, and 632,944 tion eliminates batteries. Write BRINGING ELECTRIC SETS were obtained from weekly schedules, kept un- for complete description. Corn- $29,94 UP TO DATE of 3,043 housewives píete with tubes. By CLIFFORD E. DENTON der supervision, for 208 Net, only half -hour periods each. A terriffic amount of Book No. 7 work and tabulation -in order that the indus- RADIO KINKS AND WRINKLES Get These Manufacturers' Reports ! For Service Men and Experimenters try may further develop and bring to you, By C. W. PALMER through your radio, what you like. ------r_ - Employment in the broadcasting industry dur- Book No. 8 I The CLOUGH -BRENGLE- Co. ing *99,000 RADIO QUESTIONS AND ANSWERS 1933 reached a total of employes at 1130 W. Austin Ave. Chicago, U. S. A. By R. D. WASHBURNE the peak of the seasonal employment period. The - Send me actual reproductions of reports on tests of Book No. 9 industry paid these employes a total of *$114,- the Model OC made by leading set manufacturers AUTOMOBILE RADIO AND SERVICING 000,000 during that year. Although there are no Iand descriptive literature; also bulletins on Instru- By LOUIS MARTIN direct figures available, the trend during this ments checked below. Book No. 10 year, 1934, is very definitely upward, and all in- p Model U E Volt- Ohm- MiIllammeter ALL HOME RECORDING AND dications seem to point to higher employment D Model U C Vacuum Tube Voltmeter I ABOUT IT tJ Model U B Audio Oscillator By GEORGE 1. SALIRA during the fiat ten months of this year as compared to the same period of 1933. u Cathode Ray Servicing lasts. I Book No. II in power POINT -TO -POINT RESISTANCE The general trend regard to of broad- MEASUREMENTS casting stations seems to be towards higher I By CLIFFORD E. DENTON power, as indicated by a number of regional sta- Book No. 12 tions increasing their power from 1,000 watts I PUBLIC ADDRESS INSTALLATION to 6,000 watts daytime. The general feeling is AND SERVICE that the same increases will eventually be grant- - Address By 1. T. BERNSLEY ed for night time purposes. Since the inception of the Federal Communications Commission, BIG DISCOUNT OFFERED which has replaced the Federal Radio Commis- When writing to advertisers, please say you sion, in part, a feeling of general optimism has saw it in RADIO -CRAFT. Books or More pervaded the industry. Every cooperation is be- When Five (5) ing given the new commission by the broad- Are Ordered, Deduct 20% from casters, in order that a complete understanding Your Remittance of the problems confronting the broadcasters may guide any legislation contemplated by the FOR GERNSBACK PUBLICATIONS, INC. commission through the regular channels. 99 Hudson Street, New York, N. Y. No one can readily predict what the next few Service Men MAIL THIS COUPON TODAY! years will bring forth in the broadcasting in- Amateurs and dustry, but if the past few years are any indi- GERNSBACK PUBLICATIONS. INC. cation, the developments, improvements, and Experimenters 99 Hudson Street, New York. N. Y. probable program innovations, will truly be I have circled below the numbers of books In the startling enough to those of us who are all too Paper - Mica which you are RADIO -CRAFT LIBRARY SE1ilES as to send nie, and hove deducted 20% for ordering prone to take this industry "something for live (5) books or more. I have included my remit- granted." Oil tance in full, at the price of 50c each, when less than live hooks are ordered. .McGraw Hill Co.: "Electronics." Electrolytic The amount of my remittance is (stamps. checks or money orders accepted). Circle Backed by .cala -pt of scientific r numbers wanted: atarren and duality production. 1 2 3 4 5 6 2 8 9 10 11 12 wee 1910.0 Available leading aupplkr.. uGB the neat time. Name - RACIO -CRAFT INDEX Address ...._...__._ By Subjects, Issues and Authors, the July 1929 to of CORNELL-DUBILIER June 1932 issues RADIO -Craft are CORPORATION State indexed and cross -indexed, in a publication you City may obtain for only 25e cash). AU book. are .ant postage prepaid (stamps or Write 4347 BRONX BOULEVARD RC -235 to us for this. valuable 24 page reference; its use will save you time and money! NEW YORK Please Say That You Span It in RADIO -CRAFT

www.americanradiohistory.com 504 RADIO -C RAFT for FEBRUARY, 1935

Dealers ! Servicemen ! MAKE YOUR OWN CUR- A MAGAZINE WHICH NEEDS Wo repeat our "gel -acquainted" offer of last month due NO INTRODUCTION to the encouraging response from the readers of Radio- RENT MULTIPLIERS Craft wishing to save money on TO SHORT -WAVE FANS (Continued from pape 477) RADIO TUBES SPEED troducing the least effect on the current circuit. Pi in tube developments since 1924 This shunt resistance is limited, of course in SHORT WAVE CRAFT Listed below aro Included many popular types of tubes proper proportion, to that resistance contained for short-wave use. ALL 'MIES ARE GUARANTEED This popular monthly ma gaging. SHORT t\'AVE CRAFT, FOR A PERIOD OF SIX MONTHS. in the meter. For example -if a meter is re- contains everything you want to know about Short Waves. Net Net Net Net constructed so that it requires only one -half the The wonders of world -wide short -wave reception are clearly Type Price Type Price Type Price Type Price former current for full scale deflection, the ef- described and illustrated. latest prurt lrnl infor- OIA $ .27 38 $ .50 77 $ .54 2A5 $ .50 mation for radio fans. experimenters and "hams" will be 210 1.13 19.44 .54 78 .54 2A6 .50 fect will be (concerning the necessary shunt found. Tells you how to build short -wave receivers and 12A .41 91 .50 60 .32 2A7 .60 resistance) that of reducing the internal resist- transmltlers ; construct sets nt one and two tubes or as 22 .68 42 .54 2231 1.13 2117 .68 many as seven. eight or more. Tells best foreign stations 24 .50 93 .57 82 .41 ance of the meter by one half. The shunt to log and when to tune them-Includes newest n l best 6A7 .60 circuits 26 .29 45 .33 93 .50 6117 .63 resistance could then be lowered accordingly. of the thee. SHORT WAVE CRAFT is iedited 27 .32 41 .59 by Hugo Gernsback. 84 .59 6C6 .50 This is a very vital point to be considered as 30 .36 48 1.35 X99 .45 NEW FEATURE RECENTLY ADDED -To the short 31 .36 210 V99 6D6 .50 present -day radio circuits and tubes may use 1.13 .56 6F7 .72 wave fan who has lagged and obtained verification of the 32 .63 55 .50 966 3.26 largest number of short -wave 5Z3 .54 a very low voltage on one or more of the tube stations from all over the 33 .63 56 .33 485 .65 world during one month. will be awarded a magnificent 34 .68 57 .50 192 .74 127,3 .50 elements. 24' silver trophy. 35 .50 58 .50 18216 .74 2. Z5 .72 36 .50 71A .32 183 .74 Type 1 -V .50 Switches 37 .39 75 .50 2A3 .80 -1662 I. Special This Month Only! If your jobber cannot fill sour order promptly, send it Of course, the most accurate shunt hookup is direct to us for Immediate shipment. one having no switches in the circuit, but this For the month of January only. we offer readers of this No order for ess than $3.00 can be accepted. Send 25% magazine the opportunity to read radio's greatest short- deposit. balane C.O.D. All tube prices shown are does not suit our present -day requirements which wave magazine at a special saving. The regular subscrip- net-and orders are F.O.B. factory. IF FIFTY call for the measurement of a few microamperes tion price is $2.50 per year. You can now get SHORT WAVE TUBES OR MORE ARE ORDERED, ORDERS up CRAFT for the nest ARE SHIPPED PREPAID. to twenty or thirty amperes. This must be 22-1440th accomplished by the use of switches. and it be- 8 MONTHS FOR $1.00 SPEED RADIO CORP. ity. N.Y. comes a case of "name your poison." Jobbers, Large Users-write for Special Offert Single or multiple shunt circuit arrangements 4 -Color Cover using bi -polar switches (one having two individual moving arms and several contact posi- Over200 illustrations WHEN CHOOSING tions) as shown in Fig. 1 are recommended as 9x12 inches in size having the most desired features -quick action with fine accuracy. A RADIO SCHOOL Switches in series with shunts usually are not RCA Institutes. with Its reputation established by 25 years practical ; the action of the switch arms must servire. Is an institution recog- wipe and clean the joint in making and break- The Copy Ized as an Important factor ing single reason ú á 2 5e In the radio industry. -pole switches. The for this Whether elementary radio prin- is that the introduction of any amount of switch ON ALL ciples or advanced subjects. contact resistance in series with the shunt will 1á.Y4', sound applications or practical NEWSSTANDS radio engineering. RCA Insti- seriously effect the value of this unit. The per- i tutes is prepared to give you centage of error depends on the ohmic value of the instruction you need. the shunt. Taking arbitrarily a 100 ma. shunt Send remittance by check, money RESIDENT SCHOOLS NEW YORK AND CHICAGO for a 60 M. V. meter, its resistance is .606 ohms. with modern standard equipment order or U. S. Postage Stamps. Now adding a possible switch contact resist- EXTENSION COURSES FOR HOME STUDY Register letter if it contains Gash or currency. under convenient 'no obligation' plan ance of one tenth ohm (0.10) gives us a result- Illustrated Catalog on Request. ant total of .606 ohms, an approximate error of 10 per cent. Good switches with wiping, SHORT WAVE CRAFT R. C. A. INSTITUTES, Inc. pT S silver contacta and arms used with shunta whose 99R Hudson St. New York, N. Y. 75 Vatick St, New York -1154 Merchandise Mart, Chicago values do not run into amperes will make a very simple and inexpensive arrangement with a WALCO'S reasonable degree of accuracy. In using single - SOUND pole rotary switches in series with the shunt, be sure they are of the shorting type as there RECORDING INSTRUMENTS must not be an open break in traversing from Servicemen-Dealers-Technicians one contact to another, otherwise that inevitable Write for our latest catalog on Homo Recording "human l vse Apparatus. error" will effect your meter sooner or Official later. As noted in Fig. A, the contacta are FREENo obligations. Conant us about P. A. Radio anti Homo Record tag Inswllal ions. spaced an appreciable distance from the con- Service ELECTRICAL LABORATORIES CO.. Inc. necting lugs, keeping away heat, soldering flux, Manual York. 141 East 25th St. New N. V. etc. A good is never Cases.. rule to let rosin flux get Dnrvor, ' on switch contacts as it is nearly impossible to tell when it is all removed. with the exception 19331914 Mao Raeim, RUN YOUR A.C. RADIO that you will find your readings to be incorrect, Full 5.41, trou, and the meter needle erratic. by DIRECT CURRENT There's Fig. B plenty of SERVICING Operates AC Radios, am- transmitters, etc. MATERIAL in the 1934 Manual! plifiers. The rear view the fron 6 -32 or 110 DC. of meter with its associated Radio Service Men and others engaged in Sent on trial. current multipliers and selector switch. various branches of radio know the importance -- KATO ENGINEERING CO. of the GERNSBACK Manuals. and how much Mankato, Minn. U. 5. A. they depend on them for reliable information. AC generators $16.00. Light plants 699.00. Whether for public address work, receiver diagrams or tube information. the material needed is certain to be found in one of the volumes of the OFFICIAL RADIO SERVICE MANUAL. SILVERED, ETCHED Content* of the 1934 Manual in Brief Diagrams and service notes, more complete than ever be- DIALS fore in any manual. Voltage readings for practically all METAL sets. as an aid In checking tubes and wiring. All values Three types for models 301 -88.321 -54 and 199 of I.F. transformers used In superhetermlynes, with the manufacturers' own suggestions as to correct balancing. BUY THROUGH YOUR DEALER A complete compilation of tedio tube data. covering both New Catalogue No. 7 just for a post card old and new types. A cotnplete-llst of American broadcast stations Leuven, 410 E. 15th New York, N.Y. with their frequencies in kilocycles: extremely D. L. VAN St, useful In calibrating test oscillators and receivers. Free question and answer service. No theory: only service In- formation In quickly accessible form. A handy. easily - rnnsulled master index making It easy to find almost anything pertaining to service problems. Instantly. This index Includes all the diagrams published In all the previous GERNSBACK manuals. as well as the 1934 dia- I /SHUREI' MICROPHONES grams. A big convenience and time saver. NOW AVAILABLE AT YOUR JOBBER 400 PAGES (limned Undes Brush Development Ca Palentsj Over 2,000 Illustrations SHURE BROTHERS COMPANY 9 x Inches Microphone Headquarters Flexible Looseleaf Leatherette Cover 215 W. HURON ST. CHICAGO, U.S.A. Send remittance of $9.50 by check. money order or unused U. S. Postage Stamps. Register letter if it contains cash or stamps. MANUAL SENT POSTAGE PREPAID: Patronize RADIO -CRAFT advertisers GERNSBACK PUBLICATIONS. Inc. for merchandise of value. 99 Hudson Street. New York, N. Y.

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www.americanradiohistory.com 505 RADIO -CRAFT for FEBRUARY, 1935

Low Resistance Ranges The conventional resistance measurement is ac- range for a 1 milliarnp. meter generally A cepted to be 0 to 100,000 ohms using a 4% volt battery in series with a 4.000 -ohm fixed resistor, UNIVERSAL OUTPUT a 1,000 -ohm variable and the meter, the purpose of 1,000 -ohm resistor being to compensate for a.v1d INPUT-Audio any variation in the battery voltage. By the use of a 10 ma. shunt properly connected to TRANSFORMERS the meter. a range of 0 to 10,000 ohms will be obtained. The status of the meter now being MULTI -TAP OUTPUT 10 ma. or otherwise 100 ohms per volt, and The Universal primary and the tapped secondary, to ohms In 2 ohm steps. makes it possible having a 41/% volt battery. the series adjustable from 2 30 to feed practically any straight or push -pull output resistor of 1.000 ohms will amply take care of stage to any dynamic speaker. an adjustment for 460 ohms. The same action by using a 100 ma. shunt with a resultant UNIVERSAL INPUT AUDIO range of 0 to 1,000 ohms is obtainable with the can efficiently feed any straight or push -pull audio Cage on either A.C. or D.C. sets. 45 ohms. Fig. 1 shows variable resistor cut to Universal-Physically may be mounted on end or such a hookup as explained above including side. Slots In base allow wide range of adaptability just 2's cutting out the 4,000 -ohm resistor without redrilling panel. Overall dimensions: the means for Mtg. Centers: 13/4%54"4 to 19/10" or using the 10 and 100 ma. shunt. A 1 meg. when 2%'xß,4 'ot .. range can be had by using a 45 -volt midget Service Engineers should always have ene or more in their emergency stock. No. 3205 40,000-ohm fixed and 10.000-ohm vari- No. 1337 of each battery, of power- audio- Input-- Mlmnenl- line- mike- :mlateur -class in series with the meter but using a The above are typical of the GENERAL group able, all "It" transformers, chokes, auto -radio "It" units and vibrators. The most comprehensive line of replacement separate terminal post. This latter set -up units from one manufacturing source of supply- service engineers' every need. be All transformers are of high test silicon steel, all rolls are high vacuum Impregnated, removing all makes a good insulation test, in fact it will GENERAL any climatic conditions. near moisture. and assuring permanent dependable performance under so good that you will hardly be able to get GENERAL DUALITY assures set -owner satisfaction and dealer profit. the test leads before you will note considerable antics displayed by the meter band. "Multi - MAIL THIS TODAY /Tap" General Transformer Corporation. Current Supply Imektthea Guide, 504 S. Throop St., Chicago, Ill. A listing Send me without charge a copy of "Multi-Tap" 2114 models of radios which you can im- name of nearest distributor. Continuing with the circuit, Fig. 1, using with one of only five Guide with per- mediately service shunts for low ranges you should readily (5) "Multi -Tap" Power Transformers. Name .-. in using the 10 ma. as well as the ceive that Address hundred ma. shunt in ohmmeter form, you have General Transformer Corporation a variable current supply from zero to 100 ma., 504 S. Throop SI., Chicago, Ill. City State controlled by the 1,000-ohm variable resistor. (zero adjustor). This is very handy for many purposes, such as furnishing current for testing other meters in series or determining the milli- volt drops or internal resistance, the sensitivity vets, G/44- v of relaya and for many other purposes. In explaining the following method of test- O N Z /N P er resistance, consider that p ing for internal NIVERJAL Af-UC AMPLIFIER only 1 milliampere meters are being used, ex- cepting the above mentioned power supply unit. PORTAMP-a new sensation in Portably en- Access to a meter having a 60 M. V. drop Poseer Amplifiers, designed by skillful his gineers of LEOTONE Laboratories. This fine port- must be obtained in case the reader or able P. A. System delivers the "punch" required friends do not have one handy. for operation In auditoriums and outdoor advertising work .. always clear audible reproduction. It features a 77 tube In the first stage which feeds Into 43 power pentode. The rectifier Is a 2525 $1S95 Scale Shunt- Comparison arranged for universal operation on 90 -125 volts, A.C. or D.C. A "mike" transformer is built -in. This meter should be new or nearly so, Old "PORTAMP" Kit including Brown Monaco Leath- WIT OF PART/ are apt to be slightly out, especially erette carrying case, American "EL" double- button instruments ARC - W/REO -rEfTEO due to dull or microphone, microphone transformer. kit of along the center of the scale, TURI'S tubes and speaker. COMPLETE...... $18.95 95 worn pivots, etc. This meter we will designate Wired and Tented $21.95 $i21 as the standard, and the meter to calibrated or tested to be called the unknown. Connect both the standard and the unknown meters in parallel, LEOTONE RADIO CO. 630e Sta NewYork,NY positive to positive and negative to negative. Set the power supply to the 10 ma. position. Short the ohm circuit test leads and adjust the OPERATING NOTES variable until the power supply meter 1,000 -ohm (Continued from page 482) reads 2 ma. Now make contact with the test leads to the unknown meter terminal posts and times complete cut -off. Trouble was due to the again adjust the 1,000 -ohm variable at the power 0.6-ohm balancing resistor in the 182s' filament supply until the unknown meter reads full scale. supply intermittently breaking contact. A per- The reading obtained on the standard (using manent repair was effected by soldering lead X2 (see 3, below) to (a), and then con- 0 -50 scale) will be the correct milli -volt drop of Fig. point the unknown meter. necting (a) to (b) by a bus and soldering at (b). thus eliminating resistor (ab) entirely. It is a wire -wound potentiometer. Set has now been Scale Series- Comparison in operation for over a year with no complaints. JOHN MUKHLKE, As previously explained. any change in the current consumption of the meter affects the milli -volt drop. Before any reasonable calculation to determine the internal resistance of a The greaten handy radio eetalug yet issued by aro Mail order Or. meter can be obtained the current at full scale geniutlon. It contains the most INFORMATION BUREAU venetile line-up of e handi.e must be known. To find this connect the stand- catalog Sedan; ard and the unknown in series, negative ter- (Continued from page 483) world, all price. are onpeti. e; third. t book is handy ürfiptkaoRADwO minals to positive and etc., and adjust the cur- later. in and easily Me into ïtn, ment which necessitate readjustment It ó``uapr;. rent supply until full scale reading is obtained is better to do the aligning work with the set on one of the two instruments. If both meters Thosaadi el.lte e at Lewes Tien in its operating condition. Some of the m nufseturen n read alike the internal resistance will be equal (A.3) When aligning a set, the grid side of canto, are American Radio Hard. LOWEST WHOLESALE as recorded above Aeme, Acetates, Brandes, PRICES to the milli -volt drop in the the oscillator should be clipped onto the grid Bruno lab.. Rud. Centralab. Gonna, alite mentioned parallel test. And should the un- tint. Eh , Electric Soldering, Ev- Aerials, amplifiers, . wire, without removing the tube or any other erted, nrand, Flechthlln. G-erk .rule,condeneen. uall t of known test one division (on 60 division scale) part from the set. The idea is to maintain en! Industries. Gen Wm e.. ' onverters, speaker, bark, Ilammnrlund, Jackson, bares, phonograph.. short. low it is obvious that the internal resistance is the receiver in as nearly the condition en- Kenyon. Lynch. Ohmic, Ox- wan receivers. recording nnu,p. ford. Minn, Radio City. Read tranAerm- 2 per cent hgher than the milli -volt reading countered when it is operating, as possible. rite. Rider. Roh. Shun. Signal, Set. ltubes, transmitters end taken in the parallel test. can be no differences introduced Thordaeon. Trimm. Triplett testing equipment. Then ii nev there Tobe.. uni `mal Microphone, Upco ol. en t t The schematic layout is shown for the 1 ma. by subsequent changes. .na many a hen. a men n. A.C.-D.C. universal rectified meter having its If it is found that the grid -dip is at a dif- Write For Your Coq Today! 5 -volt A.C. resistor connected internally, the ferent point on moving the dial in one direc- YOU WILL ADMIT THAT THIS RADIO CATALOG Is D.C. aide generally being 50 ohms internal. tion than that in the other, the coupling be- THE HANDIEST BOOK YOU EVER RECEIVED (60 M. V.) This same hookup can be used tween the oscillator and the tuned circuit is with the 1 ma. D.C. meter, as there will be no evidently too close, which causes an inter- TRY-MO RADIO COMPANY A.C. connection nor will there be any 400 -ohm locking of the circuits. The coupling should 85CORTLANDT ST. NEW YORK,NY. to the lead from the 4,960 -ohm be loosened by reducing the capacity of the shunt connecting Please address correspondence to Dept. C resistor, shown by the dotted lines. coupling condensers. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 506 RADIO -CRAFT for FEBRUARY, 1935 "CONTRACTED SPEECH" ON THE NEW YORK - LONDON RADIOPHONE (Continued from. page 462) it to its original intensity range after it has traversed the transmission medium. One device which accomplishes this improvement in signal - to-noise ratio without overloading the circuit equipment is called the compandor. The name is a combination of "compressor" and "expander," 0 other radio book is comparable to suggesting the new 1935 the functional operations of the two OFFICIAL RADIO component parts of the apparatus. SERVICE MANUAL. In contents, in The advantages to be gained by Complete Directory'~ style of printing, in grade of paper, in compressing and expanding the speech volume range can be illustrations, there has never been pub- seen from lished such a comprehensive volume. Figs. IA and B. Figure IA shows a Radio Receivers one -directional speech transmission circuit '. 1934 -1935 The 1935 Manual contains over a thou- sisting con- sand pages is of a transmitter, a gain control, an am- -yet it only 1t%a inches plifier, a long line or radio thick because it is printed on a special channel, another Guide gain control, another amplifier, and a receiver. Radio Service Bible stock which is an exceptionally The Full good stock, yet one gain controls are so linked together that of the thinnest and when either one is set most durable papers. This 1935 Man- at maximum the other ual is the most is at minimum. The range of gain of the authentic and elaborate gain control and associated service guide ever used in the radio in- amplifier at the transmitter is from 15 db. to zero, and at the dustry. Service Men and dealers who receiver use 1935 from minus 16 db. to zero. this Manual are astonished Now, suppose speech by finding in it such a wealth currents varying in in- of profitable tensity between 0 db. and minus 30 db. are corn- service information ing from the transmitter. which has never been published be- If the gain controls fore. are set in position 1, the speech will be amplified SET SERVICING 15 db., and the weak sounds will enter the Service information found in the noisy circuit at minus 15 db. intensity, 10 db. 1935 Manual cover. all typa of Contents of the 1935 Manual above radio receivers. Over the noise level. But the strong sounds of The material is 1,000 pages full of diagrams and essential information of speech extremely valuable to Dealen manufactured receivers -only data of real use in will be 15 db. above the overload point and Service Men. On man,' servicing is of amplifier diagrams included. This new Manual is really portable since it will be A, and consequently will be dis- appear voltage read- torted. ings of tubes. socket connec- extremely thin and light as well. Volume V continues where Intensity ranges assumed to illustrate tions, transformer data, align- the preceding manual left off. Many circuits of old sets are this condition are shown graphically in section ment details, and other service included. Service Men notes. know every set has certain weak A, Fig. 1B. points which are really the cause of trouble. Wherever the If the gain PUBLIC ADDRESS information could be obtained, controls are set in position 2, The these weaknesses with their shown by pages on P. A. Installation cures are printed right with the circuits. This is an entirely the dotted lines, the speech will en- will be helpful to Service Men new and valuable counter no gain, and amplifier A will and P. A. specialists. Such addition to the Manual. All the latest re- just trans- prominent features ceivers are included -all -wave sets, short -wave sets, mit the strong speech currents without as class A radio auto- overload- amplifiers--single and sets, midget and cigar -box sets, etc., as well as P.A. ing, but the weak speech currents will be 5 db. dualdl channelo l ayetems-atten u- amplifiers and equipment, and commercial servicing instruments. below the noise level as atore n and m ers- uoerpower heard at the receiver. stages- The cumulative index is even more complete than before; Transmission under preamplifiers and other including cross- reference to sets sold this condition is shown in commercial devices for P. A. under different names section B, Fig. 113. work are included. and type numbers. Volume V includes resistance data; socket layouts; I.F. data; and voltage data. But if the setting of the gain control is varied ALL -WAVE RECEIVERS Tube data on latest continuously Information relative to short- tubes. Free question and answer service -as included in between position 1 for weakest wave rs have found their our last three manuals. speech currents and position 2 for strongest way into the 1935 Manual. For speech currents, these standard manufactured and proportionally between nets, wherever possible, these positions for intermediate currents, no te aignin details for as av e OVER 1,000 PAGES overloading will occur, and the received speech ands are ncluded in addition will to the service material listed for Over 3,000 Illustrations. Flexible, loose -leaf leather- be at least 10 db. above the noise level at other sets. ette covers. Size 9x12" -yet only 11/4" thick all values of signal intensity. Transmission con- AUTO -RADIO RECEIVERS ditions on the noisy circuit with such a system All available service information of operation are shown in section C, Fig. 1B. auto-radio se n, has been GERNSBACK PUBLICATIONS, Inc. As the gain alincluded. From thin data controls operate slowly and simul- one Service Men could derive 99 Hudson Street New York, taneously in opposite senses, there is no effect sufficient knowledge to venture N.Y. on speech quality in a specialty field -that of or intensity variations as servicing only auto -radios. MAIL COUPO N TODAY! heard in the receiver. MIS Simplified schematics of the compressor and GERNSBACK PUBLICATIONS the expander are shown in Fig. 2A and B. Each Inc., 99 Hudson St., New York, N.Y. consists of a voice channel, and Enclosed find a branch cir- my remittance of $7.00 for which send me, POSTAGE PREPAID, One cuit which controls the gain or loss in the voice Copy of the 1935 OFFICIAL RADIO SERVICE MANUAL. [Send remittance by check channel. or money order; or register letter if it contains cash, currency or unused U.S. Postage stamps.] The " Vario- Losser" The voice channel of the compressor contains NAME a "vario- losser," an amplifier, and a high -pass filter. The vario-losser is made up of a pair of three- electrode vacuum ADDRESS tubes with their plate circuits bridged across a section of the voice channel which has an impedance high compared to the impedances of the tubes. CITY STATE The voice-chan- RC -2 -36 nel gain is dependent on the voltage applied by the branch circuit to the grids of the vario- losser tubes, which are biased normally to operate near their cut-off point. The branch circuit of the compressor contains an amplifier, a linear rectifier, and a low -pass filter. It picks off part of the output of the p$IRATE voice channel, rectifies the speech voltage linear- 11101116S ly, filters out the speech -frequency components of the rectified voltage, and applies the resulting For March ADVENTURES envelope voltage to the grids of the vario-losser A BOOK- tubes. When the input voltage to the compressor LENGTH NOVEL MAGAZINE increases, the grid biasing voltage applied by "Pirate Vengeance For February the branch circuit also increases and thus tends A COMPLETE NOVEL to cause a decrease in the gain of the voice chan- By CAPTAIN DINGLE "The War nel. Proper adjustment of the gain of the Gang" branch circuit amplifier insures that this de- A Flaming Tale of Buccaneer Days By LEONARD H. NASON Also Short crease will be so related to the increase in input Stories of Modern Pirates An Action Story with all the Mystery and voltage that the output intensity range of the by Capt. J. Winchcombe- Taylor Danger of the Great War compressor will be only half the input intensity George Also Short Stories by Capt. Dingle, P. H. Allan Moffatt and others MacArthur, Francis Rotch range. The cut-off point of the low -pass filter A GERNSBACK PUBLICATION A GERNSBACK PUBLICATION in the branch circuit is made lower than that 15c The Copy -On All Newsstands I5c The Copy -On All Newsstands of the high -pass filter in the voice channel in order to prevent regeneration. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 507 RADIO -CRAFT for FEBRUARY, 1935 The "Vario- Repeater The voice channel of the expander (Fig. 2B) contains a "vario-repeater" and an amplifier. The vario- repeater is a push -pull amplifier so connected that the plate circuits of the tubes are effectively in series with a transformer whose input impedance is low compared to the impe- are biased to a is the dance of the tubes. The tubes EVERYDAY SCIENCE AND MECHANICS the cutoff, so that when no voltage Samt scientific - taetnaeal - meclanlnal - point near magazine In the field. Up-to-the- circuit is applied to their grids. constructional Downs from the branch minute wi h news flash.. of ecientifle events. afford so little gain that the loss through of oonetruetional articles and many popular expert. they to sell offsetting the ment,. Ideas from which you can make things the vario-repeater is high, just A HOST OF INTER. initial gain in the compressor. When a positive ESTING SUBJECTS COVERED: - circuit to the Woodworking- Photography -Magic - potential is added by the branch Patents and Inventione-Book Reviewr- initial negative bias, the series plate impedance Metal -work inI- Chemistry - Engineer- of the tubes decreases, and the loss decreases in ing -Micro Electrical Experi- in the ments -Household Help.-Astronomy the same manner that the gain decreases -Prise Contest. --and other cabjecia compressor. Both the incoming speech and the copy today! branch circuit output are applied to the grid cir- Get your the rela- On all newsstands cuits of the vario- repeater tubes. But tive magnitudes of the voltages applied to the l OC grids from these two sources are such that only the copy the branch circuit output can cause any appreciable variation in vario- repeater gain. This by using a step -down trans- Over 150 Illustrations condition is obtained former at the input of the vario- repeater and a step -up transformer at the input of the branch circuit. So youuroaffo/!e/i? The branch circuit of the expander performs were you on the night of the function of picking off a portion of the "Where applying the October 13th ?" Silent ... silent speech current at the input, and Here's a tip, Most Amazing' demodulated and filtered speech -voltage fluctua- as a door knob.... tions to the grid circuit of the vario- repeater. Inspector ... call a good service- The variation in gain of the vario- repeater, ex- man and have him bring along pressed in db., equals the variation in input to some Centralabs ... chances are TYPEWRITER the expander for expansion which will offset the all your Super- Iodyne needs compression previously accomplished. The circuit that's rectifier and a to make it tell all it knows. contains an amplifier, a linear of Centralab BARGAIN low -pass filter. It applies an opposing grid For a mere handful bias to the vario- repeater, which is high when Radiohm Replacement EVER the speech current received is strong, and pro- parts will service almost portionally lower when the current is weak, every known make of OFFERED thereby causing a higher gain in the vario -re- make it for weak radio . And peater for strong speech sounds than perk better than before. ones. Thus the expander undoes what has been The new compressor. y. y Rain. Sr.p rr Mse done by the ube..,s.bee4she patented Commercial operation of the compandor on :....raa+:s..+wah, RADIOHM the long -wave radio circuit to London has yielded encouraging results. Soon after the compandor was placed in operation, it was found that un- conditions 'satisfactory service could / der most be given with static 5 db. stronger than the old commercial limit. Because of the improve- Division of Globe Union Mtg. Co. ment in signal -to-noise ratio due to the corn - MILWAUKEE WIS. pandor. it is usually possible to deliver at least without fail- RADIOHMS- RESISTORS NEW 6 db. more volume to the subscriber ure of the voice -operated switching devices at MOTOR RADIO SUPPRESSORS \\. the terminals, a factor of great importance when REMINGTON long extension circuits are involved.

PORTABLE only Fig. 2 The compressing (A) and expanding (B) units of FIRST TIME! Remington's the "compandor" system. new purchase plan now lets you buy a genuine latest model Remington Port- able No. 6 direct from the factory for only 100 a day. Not used or rebuilt. Not incomplete. A beau- GUARANTEED RADIO SERVICE tiful brand new regulation Remington Portable. Standard 4-row keyboard, standard width carriage, margin release on keyboard, back spacer, auto. REQUIRES THE BEST matto ribbon reverse: every essential feature found in standard typewriters With your machine we send you free a 19-page course REPAIR PARTS! ashial NIGH in typewritinSoo nyo es PASS itooh dash oh letersquioker pen and ink. You also get a hand- FILTER FREESusome, sturdy carrying case free. Typewriting Course BIG PRICE REDUCTION The low terms Condensers now make it possibleib for o yto buyb thison genuine completele Roemington Portable for only 10o a day. But we Are Best! cannot guarantee present prices long. Higher wage scales, rising cost of ma- terials, everything points to higher © Identical in every prices. So we say, "Act now .. while our liberal offer still holds good!" detail. FREE Don't Risk One Cent Carrying You Plainly marked Try this typewriter in your homo or VARIO- REPEATER. ofce n our 10-day FREE TRIAL for capacity, volt- OFFER. Then. if you do not agree that it is the finest portable at any age, part number, price, return it at our expense. Yon make and model don't even risk shipping eh Don't wait. Mail coupon nosyw. It's the best radio they are for. you've complete vmachine for soowlittle money. So act NOW' Attractive, workmanlike appear- CLIP COUPON NOW ance Remington Rand Inc., Dept. 189 -2 Buffalo, N.Y. TOBE condensers -like the one il- pop- Please tell me how I can buy a new Rem- lustrated -are available for all ington Portable typewriter for only loo a day. ular receivers. Also enclose your new catalog. Name Tobe Deutschmann Corporation Address CANTON MASSACHUSETTS City State Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 508 RADIO -CRAFT for FEBRUARY, 1935 RADIO MONTH IN REVIEW (Continued from page 455) Modern Testing Instruments New York City) and at the end of that year, cars were continually added to the force as the number of calls increased. This is shown in that give Accurate Measurements, the accompanying chart. But since the end of 1932, no cars have been added, although the number of calls have been steadily on the up- Longer Service and swing. This means that the cara in service are Lower -Priced are being taxed further and further to keep up with the calls, especially during certain hours of the evening and night. The tendency is to increase more and more the speed with Service men and dealers highly praised the which the vehicles travel to the scenes of the DEPENDABLE Model 408 Multitester -and it deserved crimes or suspected crimes. praise. But the new improved Model 403 -A Obviously, there is a limit DEPENDABLE" MULTITESTER to such an increase MULTITESTER insures and equally obvious is the fact that only even greater satisfaction at less cost. Em- a cer- bodying every feature tain number of prowl cars can be controlled MODEL 403 -A of the former model, from the central No. 403 -A is more compact, having been de- transmitters. s Certainly something should be done to Model 501 ANALYZERaUNIT to the prevent described belowtrument any further increase in the casualties caused by 2,000 ohms per volt. Accuracy within 2 per cent in D'ARSONVAL the cars and type moving coil meter. one very practical suggestion 3 -range 0- 2,000,000 ohmmeter; 4 -range which has been put 0 -5 -50- 250 -750 voltmeter; 0 -500 microammeter. forth as a solution is to subdivide the calls into COMPLETE, ready to operate "emergency" and "reg- $13"NKT ular" calls. Thus, if a crime is reported, every KIT $10.65 second counts, and the radio car with its con- tinual contact with police headquarters is successful in reducing the interval to a minimum. But, on the other hand, many calls are simply A new efficient analyz- when Mrs. er unit combining many DEPENDABLE Jones hears a cat on the neighbor's prominent features: roof or a slightly ossified citizen acts "suspici- 2000 ohm per volt sen- ous" and makes Mrs. Brown nervous. Speed in sitivity -Self contained ANALYZER these cases is not nearly so important -the cars 3 range ohmmeter- can travel at normal, sane, speeds. NO external batteries CA MODEL 14 The idea then, is to divide either the calla or required-Eliminates 54 the cars, referring to charts or both, into two classifications -one and fussing with connect- to answer emergency ing plugs- Protection against obsolescence calls, where time is known to be a vital -Entire metering system is independent of factor -the other to answer all circuit switching -Free Reference Point other calls. This or some similar arrangement testing -Instantly makes all Point to Point should be successful in reducing the present, measurements between ANY TWO POINTS. unnecessary loss of life. Model No. 5413 Analyzer -Ohmmeter: 0 -2000: 0- 200,000; and 0- 2,000,000- Voltmeter: 0 -5; 0 -50; 0 -250; and 0- 750-Microammeter: 0 -50-2000 0- 500- Milliammeter: ohms per volt; 8y4" meter; 2% accuracy. 5 -TUBE S COMPLETE, ready to operate. -W BAND SPREAD KIT $21.50 $2495NET KIT SET Model No. 5414 -Same as above (Continued from page meter: with additional Mllllam- 478) Ranges 0 -50; 0 -250. Bakelite rase: meter 3ÿs-; that it can be used separately 2% sentries. All shunts and multipliers Individually from the receiver calibrated to within 2%. Model 5414, itself. The method of connection ready to operate COMPLETE, permits the 528.95 amplifier to be used with either a pickup or KIT $24.50 with an external receiver or input circuit.. aaasn..., wa-y, List Just connect the new "DEPENDABLE" of Parts (Essentials Only) DEPENDABLE Model 501 ANALYZER UNIT to the One I.C.A. metal chassis; meter of your obsolete analyzer -or One I.C.A. metal better still, to the 'DEPEND- front panel complete with ANALYZER UNIT ABLE" 403 -A MULTITESTER. and escutcheons; you have a tnalern. tes tent analyzer One I.C.A. metal mounting plate for rear MODEL without expensive investment. of chassis; 501 Model 501 Analyzer Unit combines all the Iollowing features: (it Enulpped Two I.C.A. large brackets with G ft. for supporting V- 10 -wire analyzer able. ., ''Sure Pull Out'' adaMCrs, panel to chassis; separate chassis -ground wire with insulated lamp. enre (2) Free Refer - One Point testing between any two elements. including chassis or I.C.A. condenser mounting shelf; ground. (31 Instantaneous selector switches -no reference charts One I.C.A. bracket no fussing with jacks and Ixods. (4) Current measurements through automatic - for mounting small 5- come obsolete. series Jacks. (5) Will not be- plate (6) R.M.A..tandard numbering at socket and llresi t terminals. condensers: Compact, light, handsome. Includes Adapters, Leads for Current Two 'umparnnent. Testing. Open face, with tool and adapter coil shield cans complete with 6 -prong sockets; COMPLETE, ready to operate Two I.C.A. sets of 6 KIT NET -prong coils: green $9.25 O9 16 -38 meters. brown 35 F.O.B. -75 meters, black 73- We Issue Balance every 137 meters, red 136 -200 meters; No Catalog tnter, y be paid on delivery. DEEDUCT 2% IF FULLrAMOUNT One General Transformer power transformer: One General Transformer 200 -ohm filter GRENPARK COMPANY choke: 101 Hudson St. One Sprague or Dept. RC New York, N. Y. Cornell -Dubilier 6 -6 -6mL filter condenser in cardboard case, C17, C19: C18, One Sprague or Cornell- Dubilier 5 -5 mf- dual bypass condenser in cardboard case, C21: C20, One I.C.A. binding post strip (assembled Know Thyself! Stirring Stories of with binding post); well Two I.C.A. marked tip jack strips; Illustrated 'This new monthly f Two I.C.A. 31/2 in. dial scales; magazine la also your Future Science Two own doctor. WHAT I.C.A. split drive pulley assemblies for AILS tuning dials; Here, each month, IN011MEDCIEtes you can Two Sprague or Cornell and advises you revel in the wonders of sci- -Dubilier condensers, thoroughly- Written ence and imagination .001 -mf. (brown and red spot). C7, C8; for you through by doctor,. masterful tales by the world's One Electrad or I.R.C. 1 meg. resistor Non- technical y e t leading authors of science - (brown, black and green), RS; authoritative for all fiction. laymen. Many Besides many - Two Electrad ana- ing stories thrill or I.R.C. resistors, % -meg, tomical Illustrations. in each issue, you will find (green, black and several interesting departments, yellow), R9, R12; Special "Science including Two Electrad or I.R.C. resistors,1 Offer! Questions and Answers" and /10 meg., "The Science Fiction League" (brown, black and yellow), R5, R8; Maariks -the voice One Electrad $11 of a world -wide orsanization. or I.R.C. resistor, 14 meg 18 fo SPECIAL OFFER (an U.S.A. only) -One (red, green and yellow), R6; year for $2.00. Send check or money One engraved 4 -prong socket: Send 25e for order. sample copy WONDER STORIES Three engraved 6 -prong sockets POPULAR 99R Hudson St. New York, One engraved 5 -prong socket; MEDICINE N. Y. A GERNSBACK PUBLICATION One Hammarlund dual tuning condenser, 140 '7New York, Nt. Y. mmf. each section, CI, C2; Two Hammarlund 5 -plate midget band - On All Newaatand spread condensers; Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 509 RADIO -CRAFT for FEBRUARY, 1935 One Hammarlund shaft coupling for above; One Hammarlund 15 -plate midget trimmer condenser, CS; Air Conditioning Electrad or I.R.C. 2000 -ohm regener- One is America's Next Great Industry ation control, R1; One Electrad or I.R.C. .5 -meg. combination electricians. radio service men and other THE idea of volume control and switch, R2; mechanically inclined men servicing Air Conditioning bypass con. and Refrigeration Units is sell -evident and the thought One Sprague or Cornell -Dubilier has occurred to some untold thousands ever since air condenser in metal can, 1 mt., C22; ditioning equipment has been Installed in public auditori Sprague or Cornell -Dubilier condensers, ums. theatres, studios, department stores, office buildings Four and manufacturing plants. The tremendously broad possi- .1 -mf., C10, C11. C12, C15; bilities in this new industry are bound to give employment Three Sprague or Cornell -Dubilier con- and success to men far -sighted enough to see its advance- C14, ment and development. densers, .02-mf.. 400 V., C13, C23; One Sprague or Cornell -Dubilier grid con- Well -known Engineer Edits Manual denser, 100 mmf., C6; The OFFICIAL AIR CONDITIONING SERVICE One Sprague or Cornell- Dnbilier antenna L. K. Wright. an expert and a MANUAL is edited by condenser, 100 mmf., C9 ; Mote on air conditioning and refrigeration. aideleate leading authority In this Air Conditioning Service Manual nearly every Two Electrad or I.R.C. resistors, 50,000 every modern installation and indi R14, page is Illustrated: all ohms. (green. black and orange), R16; vidual part carefully explained; diagrams furnished of I.R.C. 25,000 ohms, known equipment; special care given to the servicing and One Electrad or resistor, end. The tools needed are illustrated and ex- and orange). R7; installation after (red, green plainer; there are plenb of charts and page page One Electrad or I.R.C. resistor, 10,000 ohms, of service data. (brown, black and orange), R13; CONTENTS IN BRIEF One Electrad or I.R.C. resistor, 5,000 ohms, with the History of Air Conditioning; Fundamental Laws; Meth- (green, black and red), R4; ods of Refrigeration: Ejector System of Refrigeration; One Electrad or I.R.C. resistor, 6,200 ohms, Compression System of Refrigeration: Refrigerants; Lu- RCA WORLD -WIDE ANTENNA bricating Oils: Liquid Throttle Devices: Servicing Ex (blue, red and red), Rio; pension and Float Valves; Servicing Refrigerating Sys- Two Electrad or I.R.C. resistors, 400 ohms, tems; Control Devices; Thermodynamics of Air Condition- (yellow, black and brown). R11, R15; ing: Weather in the United States.: The Field of Air Free your short -wave reception from ;s One Electrad or I.R.C. wire-wound resistor, Conditioning: Es. the interfering noises of street cars, I Complete Air Conditioning Systems 2,500 ohms, 5 W.; billeting Requirements for the Home, Small Store. Res- automobiles and electric motors with a Sprague or Cornell -Dubilier bypass con- taurant: Layout of Duet Systems; Starting Up System: One double-doublet an- Operating and Servicing Air Conditioning Systems: Air denser, .02 -mf., 600 V., C16; this scientific, Filtration. Ventilating and Noise Eliminating Devices; tenna system! Attractive appearance Portable Electric Humidifiers and Room Coolers; Auto- matic Humidifiers: Air Conditioning Units (or Radiator - easily installed! Price $6.00, plus Systems and Warm Air Systems; Central Conditioning installation. Units, etc. Ask your dealer or service en- 9x12 Inches BROADCAST ARTISTS RE- gineer for a Certified Installation, or 352 Pages write for the FREE booklet: "An- Illustrations CORD PROGRAMS tenna Facts" to RCA Parts Divi- 600 sion,Dept. C.,Camden,New Jersey. (Continued from page 463) Flexible, Loose -Leaf Leatherette Cover ered discs at either 78.2 r.p.m. or 3335 r.p.m. Records up to 16 ins. can be accommodated by WORLD WIDE the large rim drive constant -speed turntables may Su- A COPY shown in Fig. B. A full 15- minute program be cut on one side of the 16 in. discs. Head- /1N I_FNNA phones are used for monitoring, as well as a indicator. The complete A (Send remittance by check, money order nr unused visual volume level y1II U.S. Stamps. Register letter if it contains stamps switching arrangement enables the tuner, piezo or currency.) crystal pickup, magnetic pickup, 200-ohm line INC. or microphone pre -amplifier to be easily switched GERNSBACK PUBLICATIONS, output is conveniently Street New York. N. Y. into the amplifier. The 99R Hudson switched to either cutting head. the 10-ohm voice coil of the dynamic speaker or to a 500-ohm transmission line. All these switches and con- CLASSIFIED ADVERTISEMENTS trols are mounted conveniently in front of the operator. A. C. GENERATOR Every part making up this complete recording so that the re- LOW -COST CHANGES device bas been carefully chosen 10 PRACTICAL AND perfect as possible for converting Dodge 12 -V., Ford T, A., Chevrolet sults may be as nearly Delco 6 -V. generators into 100 -500 watt capacity commercial grade recordings. A.C. generators. or into 32 -110 V., D.C. motor or generator. Dodge Is 500 -W. self- exciter. All in one book illustrated with complete simplified instructions and drawings for only $1. Autopower, 410 S. Hoyne Ave., Chicago. WEBSTER CHICAGO WHAM'S PROGRAMS ELECTRICAL SUPPLIES PRE -AMPLIFIER INSULATION, WIRE, VARNISHES, SUP- LIGHT LAMPS PLIES, etc. Send 3c stamp for bulletin. Auto - A 2 stage 60 DB unit completely self - power, 410 Hoyne Ave., Chicago. (Continued from page 471) contained exceptionally high gain from monitoring ... PATENT ATTORNEYS disconnecting the loudspeaker and very low hum level ... extra fiat circuits does not suffice to stop radio programs frequency characteristics. This new PATENTS -REASONABLE TERMS. BOOK and from filling the ears of the radio operators. unit is adapted advice free. L. F. Randolph, Dept. 562, Wash- Every radiator, screen door and bed spring is WEBSTER- CHICAGO ington. D.C. source "Uncle Wiggler" stories for use either with Dynamic ribbon or a potential of im- PATENT INVENTIONS IS MY SPECIALTY and night club revelry beneath the antenna Crystal microphone with an output through 28 years; Sterling Buck, Registered towers. Every loose metallic connection is apt pedance of 200 Ohms. Patent Attorney 7780, 629 F, Washington, D. C. to produce a tiny arc, and once started, the arc It is a completely self -contained Pre - (Free Booklet -R). will reproduce every syllable of the unseen Amplifier and power unit in one. And To get a good night's sleep, according RADIO energy. is no auxiliary equipment to buy. it is necessary to tie a ground there to the operators, Of high enough quality for Broadcast WORLD WIDE ALL. WAVE RADIOS -FIVE wire on every coat hanger and door knob. Send for Special Bulletin Models. World's cheapest No -cost sample. 20th Station use. Century Co., B -2493, Kansas City, Mo. of details and prices. BLUEPRINT, DATA, 18 CRYSTAL SETS- WEBSTER COMPANY Tubeless; 1860 Miles; selective: speaker. 25c W. Lake St., Chicago, DI. coin. Setbuilders list free. Modern Radiolabs, THE 3830 151 -B Liberty. San Francisco. 30 YEARS IN RADIO REPAIRS- MICROPHONES, METERS, BROAD - BUSINESS Devices, Instru- casting Equipment, Electronic Last month Readrite Meter Works celebrated LEARN RADIO Prompt repair service. Low prices. in the Last Three yews ments. 30th Hugo Gernsback wired 200 graduates Plated Estimates on request. Sound Engineering Cor- their anniversary. At the oldest. largest and best equipped privately owned poration, 2208 Kinzie, Chicago. them as follows: radio operating school In the East. Western Electric and RCA tube transmitters; 200 licensed graduates placed in RADIO INSTRUCTION HEARTY CONGRATULATIONS ON YOUR past three years in broadcasting. shipping. police radio, THIRTIETH MAY YOU AL- aviation, service work. etc. Course prepares for all U.S. ANNIVERSARY Government Telegraph and Telephone licenses. Send for RADIO ENGINEERING, BROADCASTING, WAYS RIGHT THE FUTURE AND New classes every six weeks Marine READ 40 -page catalog. Investigate. aviation and police radio. Servicing, ANALYZER CORRECTLY SO WHEN BIG from Sept. 10th. Open aII year around. Telegraphy taught thoroughly. All RADIO SCHOOL 1S Boylston St., BOSTON and Morse FORTUNE COMES ALONG METER BUT MASS. expenses low. Catalog free. Dodge's Institute, R. F. Trop. Treas. -EST. 1899 -G. R. Entwistle, Pres. Pine St., Valparaiso, Indiana. DONT TESTER STOP TAKE HER OHM One of America's leading Radio Schools Please Say That You Saw It in RAnio -CatPT

www.americanradiohistory.com 510 RADIO -CRAFT for FEBRUARY, 1935 r- WELLWORTH CHICAGO., TRADING COMPANY 6e0 W. WASHINGTON BLVD. I Electrical PORTABLE SPRAYER Outfit WESTINGHOUSE POWER GENERATOR 1 Manufactured for U. S. Signal Corps 2 SPECIFICATIONS: s HOUSING -Aluminum (Diameter-6%a in. ' 7_ _ M PLETE Length -54 in.) I I SHAFT -2 3/16 tn. (driving end) Diameter 9/16 in. (the end is threaded for a distance of t In.) I I BASE -Cast Iron (Length -7% in. Height 1 9/16 in. Width 4% in.) I I OUTPUT -200 Watt 110 volts AC (speed .1:100 R.P.M.) STATORS -Two pairs (two North and two I I South) ROTOR tooth I -12 inductor. ups and Installing explanations. I Built-in commutator. We Rotor turns in also include a set of four re- balibearinga. placement carbon brushes. I I With each Generator we supply FREE a set of diagram -blue prints and I instructions There Are Over 25 I showing twenty-five different uses. technical Information, electrical Hook- Applications Some of which are: I I A.C. Dynamo Internal Mix Spray lighting from eight I to ten 20 Watt 110 Colts lamps. I Gun Supplied with the Short Wave Transmitter Portable E I o c r i e supplying Mounted on base with three ballbearing t Heavy Duty Metal Cutting Lathe 110 Volts AC' for operating I I rollers. Shipping weight at complete Sprayer. "Ham" transmitter. outfit, 55 lbs. Operating 110 V. AC 60 Cycla Ra- I dio Receiver in I)C districta. Public Address This is the outfit for all -around spraying work wherever Systems. current is available. Camp Lighting. etc., etc. You can spray paint, varnish, duro, enamel, lacquer, insecticides, etc., with lt. Simply insert plug into electric socket and Furthermore the following uses this marvelous machine is ready. are explained: Outfit equipped complete with Internal Mix Spray Gun, with quart aluminum Raw to obtain cup, round or fan spray, i I1.P. heavy duty motor, 110 -volt, 60 -cycle AC. air electrical power: from a Windmill, filter, Kellogg Air -Cooled Compressor, 1 %xl 54, 15 feet of hose, cord Waterpower, and plug. LENGTH: 20 in. Automobile, Motorcycle, Bicycle, 1VlDTH OF BASE: 4 1n. Price of Complete Outfit with Gun, $27.50 Footpedalt or Handerank; how 11E10111' OVERALL: 9 in. to operate AC Radio Internal MU Spray Gun alone SPEED: Two -step sets from 32 S 7.50 pulley. V. DC farm light systems. etc., Filter Tank alone FINISH: Raked -on GRAY ENAMEL. etc. 4.25 COMPLETE with Compound Slide rest Kellogg Air -cooled compressor alone Generator, as de- 7.50 having Swivel base and tool holder. scribed. including four Price of complete Large oversized bronze hearings. Accu- outfit without motor 20.00 replacement c a r b o n 90 rately planed bed, machined face plate. brushes, Blue -print Hollow Spindle. 5 In. awing. Stand- / C and instructions ard Morse tapers; 13 in. be- Ony WELLWORTH TRADING CO. Shipping weight 18 lbs. RC -235, tween enters. Shipping (Replacement carbon 560 West Washington Blvd., Chicago, III. weight: 26 lbs. b r u s h e s $695 bought separate $1.50 per net of I enclose $ for which please send me the following: $3.50 extra for chuck four. Set f instructions bought (4 Jawed. 3 In. diem.) less chuck separate $1.00.1 ORDER FROM THIS PAGE SINCE WE DO NOT PUBLISH ANY CATALOGI Remit by check or money order for full amount of each collect, item -shipped by esprer, if no money for P.P. enclosed. No C.O.D. Money refunded if not satisfied. City State __.- ....._..._....._..__ All Merchandise Offered in This Ad Is Absolutely New and Unused ------I AGENTS WANTED! A LOW -COST 30 -W. P.A. 16 MM. SOUND CAMERA MOTION PICTURE SOUND (Continued from page 479) Most fascinating AMPLIFIER field awaits live Radio Serv- area covered with each type lens. For ice Men -quick, eure (Continued from 478) focusing profits page of a special lens, a critical focuser ASK FOR FREE can be CATALOGS 12,000 cycles is substantially flat. Careful place- fitted into the camera, giving a wider range of S.O.S. CORPORATION ment of parts and adequate filtering combine to precision in focusing. 1600 Broadway New York. N. Y. produce a unit which, as a whole, is The possibilities of this amateur sound camera Cable Address: "Sanaund" New York entirely \ stable and quiet, hum being conspicuous by its are almost unlimited. It is possible to make absence. permanent records -news reels of vacations, An output transformer has been incorpor- special happenings such as parties, outings, etc. ated in the amplifier having a 16 -ohm second- You can make "travelogs" with your own de- ary. This winding may be used to feed the scriptions and notations added in sound. You voice coil of one standard speaker, or if desired, can make your own "Hollywood sound produc- SEXOLOGY the voice coils of additional speakers con- tions" with your friends. You can make per- The Magazine of Sex Science. For.me.t educational .ex r nected in series or parallel arrangements. manent records of your children's voices as well Mae. 9e .et. plain Eneli.h. Instructive and enlightening-not - as r.e book- talna no offensive matter. Know thyself All article The inclusion of this transformer eliminates their appearance -in fact you can do almost written by doctors. Each issueissu contains 25 important .ex article. 6 loss anything that is possible muatratioa. doctors answer your ea .ion any of high frequencies due to the ca- with the professional FiinsSend 15e for sample or $1.00 for 8 months suóúrlp pacity of the high impedance platea, if these sound cameras used in the large studios. Hen. SEXOLOGY. 95R Hudson Street, New York City were brought out to an external transformer. Technically, the circuit consiste of a 57 tube feeding a 66 working into a 2A6 used as When It's Needed in a Hurry! a triode with plate and screen -grid tied together. This stage drives four 46s hooked up Servicemen-Amateurs-Experimenters in series parallel, the incorporation of filter N.R.I. RESIDENCE- CORRE- Depend on resistors in the grids eliminating the need for BURSTEIN -APPLEBEE CO. careful SPONDENCE SCHOOL America's Livest Radio House matching. A 6Z3 heavy duty rectifier in America's Handiest Ship- completes the tube complement. ping Point. The use of 45s was decided upon after 20 YEARS OLD 1012-A McGee St. Pages numerous tests with practically every type of From a humble start 20 years ago, when the kanaaa City, Me. Wte power tube applicable t e copy. to this circuit. Their National Radio Institute (then known as the low cost, common usage and uniform char- National Radio School) first opened its doers to acteristics especially in series parallel circuits, the original 4 students, this institution, under decided the issue. The grids are overbiased the guidance of I. E. Smith, its President, has to create a Factory Prices-New 1935 Release condition approximating class A -B advanced to a point where a staff of approxi- prime, the amplifier operating in class A with mately 125 trained and specialized employes are RADIO-Short-Wave-KITS its resulting fine tone quality, for small in- needed to keep abreast with the large task of put voltages, and as a class B system at teaching radio FREE CATALOG 30 high by mail and in the resident school signal levels, making possible the large 30 W. at Washington, D.C. RADIO CITY LABS. output. This school has contributed hundreds of trained Suite 1222.30 Rockefeller Plaza Fixed bias was ruled out, as aside from the men to the industry, many of whom hold key New York, N.Y. fact that an additional tube is essential, nec- positions in radio. Over 4,000 graduates of i essitating extra parts, extensive laboratory N.R.I. are members of the alumni association, tests using this amplifier in fixed and self and incidently this is the only home study school bias, class you enjoy reading interesting scientific A and class B arrangements have in existence which has its own active alumni IFarticles. yet not too technical, you should toy failed to show any marked superiority with association. a copy of the current issue of EVERYDAY this system at full power output. The power The courses today include instruction in prac- SCIENCE AND MECHANICS-on all news - consumption is 110 W. at an A.C. line voltage tically every branch of radio including elec- stands -10c a copy. of 115. tronics, television and short waves. Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 511 RADIO -CRAFT for FEBRUARY, 1935 of the usual tong- nickel ribbon filament in place I LATEST RADIO EQUIP- sten wire, and extra element supports that provide increased rigidity and minimum micro - D YNA TEST MENT phonics. Short-wave fans may find this tube a "hum -dinger" on circuits now specifying 30s or (Continued front page 473) 864s. Try it and see. A NEW SPEAKER (649) "PYRANOL- INSULATED Al2 IN., 6s/4 lb. reproducer of wide -range frequency response type has been developed CONDENSERS (640) for de luxe sets. Its large size enables it to THESE condensers are treated and filled with respond readily to wide variations in audio pyranol," a non -inflammable, non -explosive power without overloading. Field coil resistance liquid dielectric (patented). Cases are hermetic- and output transformer characteristics are op- ally sealed to exclude dirt, air and moisture, and tional. Voice coil, 2.8 ohms at. 400 cycles. are lacquer -finished for durability. Very small; use these units in your next high -voltage P.A. A HIGH -FIDELITY RECEIVER (650) job, or amateur transmitter. VARIABLE selectivity, plus a new speaker assembly, in a brand -new set model, bring MERCURY -RECTIFIER CHARGER a rather outstanding degree of reception to those music- lovers who must have concert -hall fidelity (64 I ) of reproduction. Where super -sharp tuning is THE addition of radio, windshield wipers and not necessary to prevent interference, broad - defrosters, etc., have placed an unusual drain ANEW DYNAMIC TEST frequency tuning results (in these sets) in re- on the automobile battery for which the genera- production of all overtones. The use of two tor, with ordinary driving, cannot. compensate. SPEAKER SENSATION! response to harm both the speakers is responsible for faithful To step up the generator may Always the first with the latest items for all audio frequencies from 50 to 10.000 cycles. generator and battery. The new mercury- rectifier servicemen, Radolek presents the most es- A special labyrinthal sound arrangement projects charger, a 110 -V. A.C., 6 -A. unit, will quickly sential new piece of test equipment for the program from the front of cabinet only, pre- replace the energy taken from the battery and radio servicemen, The Dynateat Speaker. venting disturbing overlapping of tones from tapers off as the battery approaches full charge. liken the ease of in the A special 6t/4" speaker with e. multi - rear of cabinet. The makers Use this unit while the car is parked tapped field coil which will match any set adjustment from 10 kc. selectivity to wide -range garage. requiring between 250 and 11,000 ohms as frequency reception necessary for high -fidelity, the field circuit. Plain or tapped field cir- to operation of the familiar tone control. Radio - cuits available. output, 30 W. COMPACT P.A. ORDER SYSTEM phono. and all -wave operation; Two special transformers match the voice (642) coil of the Dynatest Speaker to any tube NEWEST IN VOLTAGE AMPLIFIERS or output transformer. Three rugged RESTAURANTS, hotel kitchens, office set -ups switches select the correct speaker circuits. (635) all can use this new remote talking set to chassis to your shop for re- Co.) advantage. "Ord -O -Pam" perhaps is the simp- String any (RCA Victor for pair-the Dynatest Speaker will match its lest and most effective apparatus yet devised in black fabricoid covered for applications where low energy messages. It is circuit! Supplied to be amplified. giving amplified one -way case, 12" x 12" x 6 ". Easy to connect. DESIGNEDlevel voice frequencies are only to press a buttol, and talk in a now. List into standard power amplifier necessary Order your Dynatest Speaker Made to operate normal manner. The message is reproduced in only $22.50 less Radolek's discount to the units, it is well suited to take the output from a coupon below for further photo- a loud, clear voice, easily understood at a dis- Trade. Fill in the velocity microphone, phono, pickup, or at the remote point. information and the latest Radolek Profit is about tance from the loudspeaker electric cell transformer. Amplification Available in A.C., D.C., and A.C.-D.C., models. Guide. 80 db., while output level is approximately plus 20 db. THE RADOLEK CO. 584 W. Randolph St., Chicago "EXACT DUPLICATES" FOR PUNC- RADOLEK COMPANY TURED ELECTROLYTICS (636) 584 W. Randolph St., Chicago, Ill. Corp.) RADIO -CRAFT INDEX (651) (Aerovox send me your radio literature. the July Please available -a complete line of electrolytic By Subjects, Issues and Authors, ( ) I am a radio serviceman, 1929 to June 1932 issues of RADIO -CRAFT are NOWcondensers to replace "duds" in all standard ( ) Radio dealer, indexed and cross- indexed, in a publication you sets. Voltage ratings are in excess of ( types of may ottain for only 25c (stamps or cash). Write ) Experimenter, ratings where those particular use School manufacturers' to us for this valuable 24 page reference; Its ( ) Student at parts have been notorious for breaking down. will save you time and money! A bulletin lists the many types. Name ANALYZER MODERNING KIT (637) Address (Radio City Products Co.) city State OBSOLETE analyzers need no longer be scrapped because they do not test the latest A NEW PORTABLE P.A. 7 -prong tubes nor latest circuits. This kit adapts the old outfit to the latest tubes and set AMPLIFIER cable includes individual models. The 10 -wire from page 477) ground chassis lead with insulated clamp ter- (Continued minal; individual control -grid with insulated and a 500,000 -ohm volume control across the Truly a Pioneer! clamp terminal; spare lead for future use (you secondary of the input transformer gives a fine This modern all -wave receiver features every can't keep analyzers absolutely up- to-date with- adjustment of volume, and helps maintain a con- conceivable improvement known in radio to- out some changes!) "Sure grip and pull out" stant output of the microphone at all frequencies. day-it is a receiver that you will be proud adapters and a bakelite 7 -prong socket requiring The filter consists of a double 8 -8 mf. 175 V. to own. no mounting are standard equipment. Five condenser. The negative goes directly to the The "Ma- receiver for the truly critical adapters are furnished. metal chassis, and the positive is filtered with listener! a standard 500 -ohm A.C.-D.C. choke. A 41/2 V. LOW- DRAIN, MULTI -RANGE METER battery for the button currents for the micro- in the amplifier. (638) phone is also contained AS T U R D Y, accurate 1,000- ohm -per volt meter designed to give current, voltage and resistance readings over an exceedingly wide range has come to our attention. Used with an external 45 V. battery, the reading possibilities are as follows: D.C. -I, 50 to 500 ma.; D.C. -E, 10 to 100 and 100 to 1.000 V.: A.C., 10, 100 and 1,000 V.: D.C.-R, 0 to 1,000, 0 -1 meg., 0-10 mega. Resistances values from r/z ohm to 10 mega. One switch suffices for all tests.

There in no finer all- NON -MICROPHONIC "99" TUBE wave receiver built (639) today, Write for Complete Details on this (Hygrade -Sylvania Corp.) Modern All -Wave Receiver AGREAT favorite with builders of battery drain, Pioneer Sound Laboratory radio sets because of its low current York, N.Y. the "99" has been frowned upon for its excessive 135 Liberty St., New tendency toward "microphones." This new tube makes use of a sturdy long-life oxide-coated Please Say That You Saw It in RADIO -CRAFT

www.americanradiohistory.com 512 RADIO -CRAFT for FEBRUARY, 1935 ALL -WAVE RECEIVER 15 to 2,700 Meters HERE la a TRULY ALL- \'AVE receiver; all -wave in the strletast tente of the word. has Now Only It the enormous range of from 15 way up to 2700 meters. Just consider what this means. 15 meters approaches the ultra short wavelengths; from there the range of the set continues on up through the amateur bands, television bands, police and airplane banda $12.64 right into the regular broadcast band and from there further up into the upper channel of foreign speech and muslo broadcast bands; this, mind you, all with a 4 -tube miniature receiver. That is why we say It is an "all- waver" in the strictest tense of the word. with Tubes Not only that but the receiver will work from any source of electricity whatever, storage batteries, be it an electric supply main, 32 volt faros lighting plans. or what have you. The special adapters listed below will adapt this 321 -V receiver to any and all of these electrical sources. The receiver uses only the very latest type of tubes which is a dual pentode triode tube (ac- such as 6F7. tually 2 tubes in one), a 43 power output No. 321 -V Universal All -Wave Receiver Including Tubes But Less Coils, 110 volt tube, a 77 high -gain tube and a 25Z5 A.C. -D.C. Operation. List Price 321.50. Works from ANY rectifier. YOUR PRICE $12.64 No. 322 Set of 4 Plug -la Cella A series of 7 colla are used to cover the YOUR PRICE (15 to 200 meters) List Pries $4.00. sje3s ELECTRIC tremendous reception range. No. 323 SOURCE Set of 3 Plug -In Cells (200 to 2700 Meters) List Dynamic speaker, built -1n antenna and YOUR PRICE Price $3.00. _ 51476 provision for phonograph pickup. The re- No. 324 All Electric Auto Adapter With List Suppressers, for useu inn automobiles owrr boats. Including Batteries ceiver consumes as little as 40 watts on Price $12.50. YOURPRICE ...... _...._....._...... _. 10 volts and 80 watts on 220 volts. The _. _.. _ ». _...... `S .3S receiver is housed in a steel cabinet, burl - 220 volt AC -DC adapter-YOUR PRICE walnut finish. Measures 8% wide, 6" 50.88 high, 3%" deep. Ship. wt., 12 lbs. 32 volt farm light adapter-YOUR PRICE....._...._. $6.00 FREE Radio and Short Wave An AMAZING VALUE! Treatise 108 Pages 4 -TUBE 1500 Illus. AC -DC RECEIVER E nclo s e five cents (coin) for 200 TO 550 METERS -BROADCAST Postage. Treatise HERE is one case where sent by return price does not follow quality I for although the price - P 'nt n m is down, the quality is TERMS and address clear- 1 -25Z5, up. Uses ,'ñt,vu tuutvell 1 -38, 1 -36 and 1 -39 -44 -and yet with ly on request. tubes in these simple Send money 387 brings stations which for their distance and order. certi- completely revised ami enlarged. this new clarity will I931 edition contains ills amaze the most skeptical broadcast listener. fied check or solid pages of use Has a built -in antenna and requires no ground. NI radio Intormatl n. diagrams. Illustrations. You can nEW V. S. ratio kinks and I take it anywhere -any place where 110 volts re live radio merchandise. or D.C., 25 a ith er A.C. stamps. C.O. PARTIAL OF the Fonda Now $ .95 or 60 cycles, is available. D. shipments mental P2-FunPrinciples a RadioHal for the The set measures wide only if 20% Chapter entai Circuits antitort Usettec of Tubes-lieTubes sinning Six -Volt Halter 16 ,Iba. List Price $23.50. yModel reinittanceac Sett for Two .' 381. 4 companies -Vol[ Public Addres OnlOnly Tube A.C. Broadcast Receiver, Complete with or- Systems-Howallow to Build };bort 10 Tubes. List Price der. If sent -teas Trans $23.60. via and Hr-He- NOTHING ELSE YOUR PRICE 810.955 parcel re 1 ver Model past Include Tube 387 5 -Tube AC -DC Broadcast Receiver. charges; Chart IWRITE TO BUY YOUR PRICE with Tubas ex- lori SocketSockeel ('Prs Today - 812.95 cels refunded. rections etc « Radio Trading Co., 97 Hudson St., New York City READERS - Index Send for your FREE supply to Advertisers These handy post cards will make it A Midwest Radio Corp Inside Back Cover Aerovox Corporation..._..__.... 492 N easy for you to answer any of the ads. Allied Radio Corp Back Cover National Amperite Corporation 498 Radio Institute 451 which appear in RADIO- CRAFT, and National Union Radio Corp 491 B without cutting any valuable articles or Bud Speaker Co 490 P Burgess Pioneer Sound Lab 511 data which you may Battery Co 485 Popular Book Corp wish to save. Burstein- Applebee Co 504 510 Popular Medicine 508 C R Capital Radio Research Labs 500 Radio Circular Co 494 Central Radio Labs 507 Radio City Labs - Clough -Brengle Co 510 503 Radio City Products Co 501 Coast to Coast Radio Corp 602 Radio Trading Co Columbia Sound i 512 System (Postal) 498 Radio Training Assoc. of America 452 Continental Carbon, Inc 502 Radolek Gentlemen: Cornell -Dubilier Corp Company - 511 503 RCA Institutes 504 Coyne Electrical School 449 RCA Victor Co I noticed 509 in the __..__ issue of D Readrite Meter Works 489 RADIO -CRAFT Remington your advertisement, and Delta Radio Co 498 Rand Inc I 507 would Tobe Deutschmann Corp.._ 488, 496, 507 appreciate your sending me complete information S. O. S. Corporations and literature. As e E 51.0 Electrad, Inc 487 Sexology Magazine. 510 constant reader of RADIO -CRAFT, I with Electrical Labs. Co 504 Sears, Roebuck & Co 600 fo keep the copies of my magazine intact. Shallcross Mfg. Co 494 and I am faking Shure Brothers Company 504 this means of inquiry. Franklin Transformer Mfg. Co _. 501 Solar Mfg. Company rather than mutilate Freed Radio 500 my copy by clipping Company 494 Speed Radio Tube Company 504 the coupon or cutting ouf the adver- G F. L. Sprayberry School 488 tisement. General Transformer Corp...... --...... ---- 505 Supreme Instrumenta Corp 495 Goldentone Radio Company 496 T Iama- Grenpark Company _..._.._..__ 508 Triplett Elect. Instr. Co 499 H Try -Mo Radio Co., Inc 505 RDealer Short Wave Service Hammarlund Mfg. Co ..._.._..__.. 493 U Man Experimenter Hygrade Sylvania Corp 497 Public Address Uncle Dave's Radio Shack - . 498 RJobber Universal Microphone Co. 500 Engineer Manufacturer - Insuline Corp. 490 Professional Set of America_...._.._.. V Radio D. L. Van Leuven Builder Engineer Labs 504 Kato Engineering Co .. . 504 w Name The Ken -Rad Corp. Inc ...... _.._ __ 602 The Webster Company 509 L Wellworth Trading Co 510 Address L & L Electric Co ___ 502 Wright- DeCoster, Inc 492 Leotone Radio Co _ 505 .- (While every precaution is taken to insure C,ty State M accuracy, we cannot guarantee against the McGraw -Hill Book Co _. 496 possibility of an occasional change or omis- Mass. Radio School 509 sion in the preparations of this index.)

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30 Days LE Trial BEFORE you buy ally radio write for the new FItEL; 1935-36 Midwest "Fifteenth Anniversary" catalog and see for yourself the many reasons why 110,000 satisfied customers bought their radios direct from the Midwest Laboratories and saved from 3 to ;./2". Why pay more than the direct -to -you laboratory price? "arena to we.td -wide on You, too, can make a positive saving of from 30';;, to 50% by buying R this more economical tvay. Learn why Midwest outperforms sets cost- Vineland, ing up to 1200.00 and more. Never before You saa- MIDWEST so much radio for so little ira, Con. money! Midwest gives you triple protection with: One -Year I have Guar- received- On,y Midwest Gives You Multi-function Dial antee, Foreign Reception Guarantee, Money -Back Guarantee. many foreign sta- This dial was designed in keeping with tion, in- SO ADVANCED 1935 FEATURES equalled world the trend of the times, yet is not an airplane -wide broadcasts... GInd i ng England, France, Germany, Spain SE.Loa- dial! It is a many -purpose dial that per- Many exclusive features include: domEAO, forms many functions. Now, Midwest guar- Micro- Tenuator... Fidel-A- Stat... Italy, Russia, Australia, etc. Send Madrid. A friend. head of today for money- saving a radio department in a antees that inexperienced persons can se- Separate Audio Generator...Cera - facts! store. said he would rather Only Mid- buy a Midwest than the cure good foreign reception. Send for FREE mie Coil Forms, etc. SENSATIONAL HIGH FIDELITY RECEPTION west covers a tuning range of 9 to make he sells. Charles R. miniature of actual rotating dial which This bigger. better. more powerful, clearer- Ingraham. clearly shows these outstanding advantages: 2400 meters (33 Megacycles to 125 toned, super selective, I0 -tube radio gives enabling you to easily and you absolute realism- assures you of life- Peruvian Praises 1. Dial calibrated in Kilocycles, Megacycles KC)- Foreign Reception M in even low - like, crystal -clear tone -unlike anything and successfully tune you have ever experienced before. You will Safford, 2. Call letters of American Broadcast Stations powered foreign stations up to hear one more octave Arizona - printed on dial and illuminated; -overtones -that I Cos real - cannot be brought in with ordinary ra- 3. Slow Smooth -Acting Tuning; 12,000 miles away with crystal thrill to -Fast, reception. dios. Now. hear every u.ten to 4. Station Group Locator; clear, loud -speaker instrument, every my Mid- 5. Simplified Tuning Guide Lights; voice. every shade and west, to -O -Band All 5 Wave Bands enable you to hear a 6. Automatic Select Indicator; -1 inflection of speech. enjoy today's finest High Fidelity 7. Illuminated Pointer Indicator; I frvoiceom afar 8. Silent Shadow Tuning -Improvement on American programs. In addition, off la d Meter Tuning; you get Canadian, police, amateur, Take advantage of tay: "This fe the voice of 9. Centralized Tuning. the amazing 30- he Pacific, V'K2 N1E. in commercial, air plane and ship day FREE trial Sydney. Australia," or, and derive new delight "We take you now to New Style Camellias broadcasts MIe,.W.i+- ..,Yi offer. Send for Westminster Abbey, ".. The Midwest 36- and new excitement from un- FREE catalog. [a Franklin a. John page catalog pie-DEAL P. O. Boa 244. tures a complete DIRECT WITH LABORATORIES Increasing costs are sure to result in higher line of beautiful, Br- radio prices soon. Buy before the big ad FOR. tistic de luxe con- vance...NOW...while you can take advan- AMAZING 3O°DAY FREE TRIAL sole and chassis in rage e[ Midwest's sensational values...no middlemen's profits to pay. You can order- dP TO OFFER AND NEW 1935 CATALOG' four colors. Write yourw1935-36 High Fidelity radio from new MIDWEST RADIO CORP., User- Agents for new of 0 FREE Mid catalog with as much certainty Dept. Cincinnati, Ohio. Make Easy satisfaction as if you were to select it in our n 920, catalog today! laboratories. save to Without obligation on my part send Extra Money catalog. Midwest long -range great whetn y oo p 3wa°y...you get 30 days your new RICE 1035-30 Check Here oub this olar E Miniature Dial. and com- radiosDante FRE trial.. as litt a as $S.00 down puts a Mid- for [n FRE.plete detail. of your liberal 30-day fo El as; eI11 west radio in your home. Satisfaction guaranteed FREE trial offer. This is NOT anordir. low as .. 2 !WI or moneyE back. Write for new FREE catalog today. MIDWEST RADIO CORP. Name Address DEPT. S. 920 - CINCINNATI, OHIO, U. A. Town State Established 1920 Cable Address Miraco All Codes 1sgve'reassgitinr;cvl:r.ehtxtIiwr

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ALLIED RADIO CORPORATION 833 W. JACKSON BLVD., CHICAGO, Dept. D. Please send me: THE 1935 ALLIED CATALOG. AIIíedRadio Cl A complete Parts List for the circuit described In: CORPO A T I O N Address BLVD., Chicago,lll. 833 W.JACKSON City State t