HUGO GERNSBACK. Editor formerly BAD I1 G' C1[AF \/)(I

44, M,

ELECTRONICS -TELEVISN www.americanradiohistory.com PROJECTION TELEVISION IN ASSEMBLY FORM COMPLETE WITH RACK

20 "x26" PICTURE 36 RCA TUBES EASTMAN KODAK PRO- JECTION SCREEN f 1.9 BAUSCH & LOMB PROJECTION LENS 30 KV FLY -BACK POWER SUPPLY ANTENNA PICTURE & SOUND I.F. FACTORY WIRED G TUNED DUMONT INPUTUNER For realism, clarity, definition and TERMINAL HAS BIGGEST STOCK of BIG SCREEN Televiewing, the pictures BEST BUYS IN TELEVISION KITS, produced by this unit hove no equal' PARTS and ACCESSORIES! This TELEVISION ASSEMBLY KITS, com- screen is absolutely flat, pre- plete with all parts, tubes,. etc. with cluding curvature distortion anywhere factory wired and tuned R.F. and I.F. in the picture. Picture tones ore true sections. block, grey and white -high in bril- TA -10, 10" Model, net 229.50 liance, yet obsolutely glare -free! TA -12, 12" Model, net 259.50 TA -15, 15" Model, net Easy to assemble! Everything is sup- 349.50 plied, including prewired high voltage CHAMPION Models, some os above power supply, Dumont Inputuner, but with famous Dumont Inputuner. wired and pretuned 13 tube I.F. strip 10" Champion, net 273.10 for picture and sound, precision 12" Champion, net Bausch and Lomb f 1.9 projection 303.10 lens, Eastman Kodak projection screen, 15" Champion, net 393.10 mirror, 36 RCA tubes including 5TP4 DUMONT INPUTUNER-R.F. section projection tube, special dipole with which tunes continuously from 44 to WOOD -SIMULATED METAL reflector and 60 ft. coaxial lead -in, 216 Mc., complete with tubes and 12" heavy ENCLOSURE FOR ABOVE KIT duty RCA PM speaker, dial 58.65 push -pull 12 watts AT audio, rock and AVAILABLE picture frame os illustrated, Picture and Sound I.F. Strip- factory oll ports, wired SLIGHT E %TR. I (OsT wire, hardware, etc. Big to and aligned. With 13 matched easy- -fol- RCA tubes, your cost low manual of instructions qnd sche- 77.25 VISIT OUR TELEVISION DE- matic data prepared and edited by SARKES- TARZIAN -New 13 channel renowned John F. Rider, Publisher. R.F. tuner, complete with tubes 31.75 PARTMENT. SEE AND HEAR RCA -popular 13 channel R.F front The list price of the P -520 kit is only end, complete with tubes 44.10 ASSEMBLED TELEVISION KITS $1299.00, with adequate margins for Bausch G Lomb Television Projection IN OPERATION. Television Service -Dealers. Write us Lens, f 1.9, with mounting ring, for today for FREE! Write today for our Big, New special dealer price! use with 5TP4 tube. Net price 135.00 TELEVISION Kits & Ports CATALOG! TERMINAL RADIO CORP. 85 CORTLANDT STREET NEW YORK 7, N. Y. Phone: WOrth 4 -3311 Cable Address: TERMRADIO

www.americanradiohistory.com :1 hiRN RADIO IN SPARE TIME As part of my Course I send you the speaker, tubes, chassie, transformer, loop antenna, etc., to build this modern, powerful rpRACT/C/NO- Radio Receiver! In addition, I send ou parts to build many s= other real Radio circuits, like the Signal Generator, Radio Tester and Superheterodyne Receiver pictured below. You use this material to get practical Radio and - make EXTRAQtmoney fxing neighbors' Radios in spare time. Mail coupon below forire. Mlete information ! 1/ F

I

I SEND YOU BIG KITS OF PARTS You Build and Experiment Wich this MODERN RADIO AND MANY OTHER CIRCUITS

Do you want a giant-Pay Job iii LLB Future for I ralead Mee is Bright fast- growing Radio Industry -or your In Radio, Teler'lsi., Elechonics money -making Radio Shop? My own It probabh easier to F' >larit-J train -at -home method has helped hun- Radio now than es er before, because dreds of men with no precious expe- Radio Repair Business is iss,miog. Trap rience become qualified Radio Tech- Radio Technicians also and profitable m Mail Coupon and you'll get port unities in l'nl We, Aviation, Marine nicians. the Broadcasting, k. Think a Sample Lesson and my 64 -page book, ub1r work. d of eve,, "How to Be a Success in RADIO -Tele- greater opport nnit ies as public demand vision -Electronics," both FREE. See for Television. FYI, Elect node desires con- how you get practical Radio experience tinues to grow. Cut the farts on all these J. E. SMITH. President at home, building, testing Radio cir- opportunities. Send for FItli' books now. National Radio Institute cuits with 1í1G KITS OF PARTS I send! FM at Mat Nil Ca Dg Fer Yoe Sample "Get- May Winn Sou lid. EXTRA Mary Mail Coupon for Lesson, I TRAINED THESE MEN ting .ttrinainted With Itreeiler ert icing I Spn T.. MMRe Lomeli and my FREE 54-page It's packed 'a k Rakes fH A 's for 'file da, you enroll 1 start sending with facts about opportunities \ Nut Plis fuis EXTRA MONEY manuals. You learn n. Read the details about my Course. alrfig "I am Radio Rail in principles fro In my s-to- under had letters from men I trained. telling 41 ha.' Serviceman stand. illustrated lessons- I'R.\t'TI I'E what what they are doing, earning. See how eia on learn with parts I end -USE your quickie-, easily ton can for The knmHelge to make EXTRAs get starter!. o o Adams Ap- money fixing neighbors' Radios ligation. Just MAIL pliance Co. in spare time while still learn- COI'PoN NOV,' in an .. Am now ing: From here it's a short step envelope or paste 't get- on a penny postal. ting Ito a to ,enr i 'n fall-time Radio Shop or ttgood Radio joh! I. E. SMITH, Pres., Dept. eitX .s bonus and over - National Radio Institute. 1,onear. Bono tuu, W. A. ANGEL, Blytheaville, Arkansas. Stade Radio S,1w01. Washington 9. D. C Kiss MON( Meet .elle " I k n e w VETERANS n o t h i n g about Radio I en- when MR. J. E SMITH, President, Dept. $KX rolled. I am doing spare National Radio Institute, Washington 9, D. C. time work. I nie Lesson and 64 -page book. (Ni. have more than paid for Mail FREE Sample my Course and about salesman will call. Please write plainly.) $200 worth of equip- Age ment." - RAYMOND HOLTCAMP, Vandalia, Name.. -._ Illinois. Address...... My Course Includes in Training City Zone State TELEVISION ELECTRONICS Check if Veteran FREQUENCY MODULATION

www.americanradiohistory.com 4

Hugo Gernsback, Editor -in -Chief RADIO Fred Shunaman, Managing Editor M. Harvey Gernsback, Consulting Editor ELECTRONICS Robert F. Scott, W2PWG, Technical Editor formerly RADIO -CRAFT R. H. Dorf, W2QMI, Associate Editor I. Queen, W2OUX, Editorial Associate

In corporaleng Angie Pascale, Production Manager SHORT WAVE CRAFT TELEVISION NEWS Elmer Fuller, Shortwave Editor RADIO t TELEVISION Wm. Lyon McLaughlin,

Contents October 1948

Editorial (Page 21) Radio -Craft Becomes Radio- Electronics by Hugo Gernsback 21 DY.TV 40MF-450WVo Audio (Pages 22 -55) 40 MF -450 WV ° Ultra Loud Speaker Is Auto -Truck Size by Paul H. Thomsen 22 ' 85'C Modern NADE IN Microphones 25 USA. Interesting Amplifiers 26 Modern Crystal Phono Pickups Y9 Microgroove Phonograph Records by M. Harvey Gernsback 30 Electronic Organ Improved with FM by William K. Allan 32 New Trends in Loud Speakers 34 Four -Watt Portable for All- Around Use by Lyman E. Greenlee 36 A Synthetic Bass Note Circuit 37 Packaging and Unitizing Audio Equipment by Eric Leslie 38 A Sonic Analyzer (Cover Feature) 40 Radio Set and Service Review (Amplifier Co. of Americo Model 810) 42 Frequency Test Records by Richard H. Dorf 46 Phase Inversion Headaches by James R. Langharn 50 Calibrating Audio Oscillators by Richard D. Henry 52 New Magnetic Pickups by I. Queen 55

Television (Pages 60 -64) Cascode Preamp Reduces TV "Snow" by I. Queen 60 Television Sweep Circuits by Allan Lytel 62 Electronics (Pages 68-72) The Crystal Detector, Part IV by Jordan McQuay 68

Construction (Pages 75 -77) Binaural Ampiifier by Edwin Bohr 75

Foreign News (Pages 78 -80) European Report This year -the same as every year by Major Ralph W. Hallows 78 -Solar is first to give television Departments sen -ice men the most neededdevel- The Radio Month 10 Try This One 86 opments in electrolytic capacitors. Radio Business 16 Miscellany 87 New Devices 56 New Patents Keeping pace with the fast -mov- People 74 88 World -Wide Station List ing television Question Boa industry, SOLAR'S 81 by Elmer R. Fuller 90 Technotes 63 new Type DY -TV series dry elec- Communications 93 Radio- Electronic Circuits 84 Book Reviews 95 trolytic capacitors assure depend- able operation under the severest RADIO -ELECTRONICS, October, 1948, Volume XX. demands of modern television issue by No. I. l'uldisind niontlily the 25th Of month ... Itadcraft Publications. loc.. . preceding date of Eric \te.. F to G Streets. Philadelphia 32, l'a. Entered matter at Piet ()film, Springfield, SIass., under Art as second class permit high temperature delphia, Pa., Post of March 3, 1579. Application pending transfer opera- OM!, SUBSCRIPTION RATES: III 1'. S. to the Phila- Central American countries, and Canada, in U. S. possessions, Mexico. Foch and $3.511: 48.00 for two years: pg.m: for three years, tion with no sacrifice in long life countries $4.50 a year, $5.110 for single copies 30e. All other foreign two years. $11.00 for throe years- Allow one Ordering a change, please furnish an month for change of address. When address stencil impression trout a recent wrapper. or electrical characteristics. Inves- RADCRAFT PUBLICATIONS, INC. Hugo Contents Gernsback, l'res.; M. Harvey Gernsback, Vice -Pres.: Copyright. 1945, by Reds-raft Publications, Inc. G. Aliquo, Ser'y. tigate perluissimn of copyright milt,. Text and illustrations muet not be reproduced without SOLAR and you'll buy EDITORIAL and ADVERTISING OFFICES, 25 West Broadway, New York 7, N. Y. SOLAR next time ADVERTISING OFFICES: Chicago: 305 W. Washington Tel. 1tletor 2 -9690- BRANCH -every time! e2 $beet. Telephone Randolph 730:t. Mann ti Lexington ISIdg., 197Ú W..1 Grand Blvd. Telephone Madison Detroit: Frank holstein. Sonh hill St., Tel. Tucker 1793. 702C7. Los Angeles: Ralph W. Marker. 600 Write today for catalog. San Francisco: Ralph W. Harker, 582 Market St., Atlas Publishing Tel. Garfield 1 -2451. 1. Australia: Lon-don C Mefall's'Agency. 9 4Iz: thStreet, Melbourne. France: SOLAR CAPACITOR Paris 2e. Holland: Trilectron, Meernsteedsche, Itrentanoee 37 uAvenAvenue \tl'i)pera. SALES CORP. Mreef 124 Ileemstede. G : International Amerik le Street, Athens. So. Africa: Central News Agency, Itngt & News Agency. 17 NORTH BERGEN, NEW JERSEY Ltd., For. Itisslk & COMMIS!, loner Sts.. Johannesburg; g Stree Smith Street. Natal. Universal MiddleEast: teinm taky Middle Jolla Harrison rrburg nst Agency. Jalfa hoed Jerusalem.ue India::0 Gupta Co., Annita Bazar l'atrlka Lt., 14 Ananda Chatterjeo lane, Calcutta. (Distributors/

MEMBER AUDIT Ql Editorial and Executive BUREAU OF CIRCULATION Offices: (i TELEVISION ABC PAID CIRCULATION 6 MONTHS TO DEC. 31, 25 West Broadway, New York 7, N. Y. ABCtl 1947- 102.615a. (PunIlahers Statement) PRINTED FOR OCTOBER ISSUE - 150.000 E LE CT RO LYTICS RADIO -ELECTRONICS for

www.americanradiohistory.com Learn

TELEVISION, ELECTRONICS 4 OP METHOD HOME TRAINING

t Let NATIONAL SCHOOLS, of Los Angeles, a practical Technical Resident Trade School for almost 50 years, You receive all parts, in- in Radio cluding tubes, for build- train you for today's unlimited opportunities ing this fine, modern Superheterodyne Receiv- er. This and other alu. able standard equipment becomes your property. fREE aded w¿(t teli ya

Good Jobs Await the Trained Radio Technician Lessons t`t ; and You are needed in the great, modern Radio, Television and Elec- Instruction tronics industry! Trained Radio technicians are in constant and Interesting. growing demand at excellent pay -in Broadcasting, Communica- Material Are Up -to -date, Practical, tions, Television, Radar, Research Laboratories, Home Radio Schools Master Shop Method Home Study Service, etc. National National Schools Master Shop Method Home Training gives you course, with newly added lessons and equipment, can train you Television exciting basic and advanced instruction in all phases of Radio, in your spare time, right in your own home, for these made easy to understand by nu- by the remarkable and Electronics. Each lesson is opportunities. Our method has been proved and diagrams. All instruction material has -trained men all over the world. merous illustrations success of National Schools been developed and tested in our own shops and laboratories. the supervision of our own engineers and instructors. A under below. You Learn by Building Equipment with free sample lesson is yours upon request -use the coupon You Home Study and Standard Radio Parts We Send You Get This and Other Valuable Both Resident Training Y.,ir National Schools Course includes Lesson: not only basic theory. but practical Information in the Free Sample Offered t rainine its well-yon leant by doirgt. We send you complete standard equip- I. Basie Receiver Circuits and How They are ment of prufessiaual quality for build- Used. ing various experimental and test FOR units. You advance step by step until 2. Construction of the Antenna Circuit. APPROVED you are able to build the modern su- How Energy is Picked UI, by the Aerial. receiver shown above. 3. perheterodyne into Sound. which is yours to keep and enjoy. You 4. How Signal Currents are Converted VETERANS perform more than 100 experiments - a. How the Tuning Condenser Operates. build many types of circuits. signal Below Handles the Signal. Check Coupon generator. low Mower radio transmit- 0. How the R -F Transformer ter. audio oscillator, and other units. and other data. with diagrams and Illustrations. The Free Book.: shown above tell you more about it- -end for them today! NATIONAL SCHOOLS ! NEW PROFESSIONAL MULTITESTER LOS ANGELES 37, CALIFORNIA EST.19CL Now ACTION INCLUDED! MAIL OPPORTUNITY COUPON FOR QUICK National aebNs. Dept. SC -10, Paste on a aterd This versatile testing instrument is portable a: 4000 S. Figueroa. Lae Aseles 37. Cdil. and complete with test leads and batteries. F Simple to operate, accurate and dependable. IStatl aie FREE the books mentionedd in tout ad Including a sample aster or You will be able to quickly locate trouble sour course. I understand no salesman will cati oe me and adjust the most delicate circuits. You can use the Multitester at home or on ser- vice calls. It is designed to measure AC and NAME ell DC volts, current, resistance and decibels. g You will be proud to own and use this valuable professional instrument. ADDRESS

g s CITY ZONE STATE n

OCTOBER. I414$

www.americanradiohistory.com 6

CAPITOL RADIO ENGINEERING INSTITUTE

Pioneer in Radio Enrinevring Instruction- -Since 1927

Who Will Get the Better Job? The Serviceman Who Looks Ahead Will Get Ahead Don't play blind man's bluff with your future ! a "pre Are you, like -war model ". You must "re- tool" your tech- many other professional servicemen, nical knowledge in so wrapped up in order to keep pace. your present routine work that If you are wise, you will look you are losing sight of where you ahead and start will be tomor- now to increase your technical ability with the row? thorough, practical Look at the successful serviceman. technical training for which You'll find thousands of professional servicemen have en- that he's the fellow who looked and planned ahead. rolled with since Today, as a member CREI 1927. This is real, honest - of the great radio -electronic to- goodness practical engineering training that industry, you have opportunities that few men ever leads to better jobs presented by modern radio, enjoyed in the past. Your future success can electronics and television, be assured by the plans you and security in the make today. knowledge that you are capable of coping with The radio industry is expanding so fast, that it tough problems. is doubtful any serviceman can truthfully say he CREI courses are still available at pre- inflation has kept pace with all the major developments. Thousands prices and today give you more thorough instruc- of new men have joined the ranks of tion service per dollar than ever the radio industry creating new before -on con- competition for venient terms. It costs you nothing to read the in- you. New developments create demands for more teresting facts. Please write today. advanced technical ability. You can't afford to be VETERANS; CREI Training Is Available Under the "0.1." Bill! Send for and read our 24 -page booklet that explains our self- improvement program -our courses -and what we can do for you and your future. CREI courses are still available at pre -inflation prices and today give you more MAIL COUPON FOR FREE BOOKLET thorough instruction service per dollar than ever before- - on convenient terms. It costa you nothing to read the CAPITOL facts. Please write today. RADIO ENGINEERING INSTITUTE 16th and Path Road. N. W., Dept. RC- IO, Washington 10. D. C. Gentlemen: Please send your free booklet, "CREI training for your better job in Radio -Electronics," together with full details of your home -study training. I am attaching a brief resume of my experience, education and present position. Capitol Radio Check field of greatest interest: PRACTICAL RADIO- ELECTRONICS PRACTICAL TELEVISION BROADCASTING AERONAUTICAL RADIO ENGINEERING Engineering Institute RECEIVER SERVICING INDUSTRIAL ELECTRONICS An Accredited NAME Technical Institute STREET Dept. RC -10, 16th & Park Rd., N.W., Wash. 10, D.C. CITY ... ZONE STATE I AM ENTITLED TO TRAINING UNDER G. I. BILL. Brunch Offices: New York i7 170 Broadway .San Francisco 2 760 Market St. L RADIO -ELECTRONICS for

www.americanradiohistory.com Ì

HERE'S THE LEARN aMidete ikafiefir RADIO atI/0//

ß-.ant . -- ra. -- fr+ /_. I'LL TRAIN YOU AT HOME -BETTER -FASTER by Putting You to Work with Your Hands your In this picture I show you exactly what you'll get from me during Sprayberry Radio Training. This actual photograph speaks for itself! Sprayberry Radio Training COMPLETE start you with interesting, easily understood basic knowledge is really -I Manuals, profitable Busi- and I keep the mailman busy bringing you valuable Service ness Builders, extra helps and books -and 8 Big Kits of Actual Radio Equipment! My You get my personal help every step of the way. course is practical and down -to- earth. hands My method is BEST for you- because you train largely by working with your - building, testing, trouble- shooting with parts I supply. With these kits you build a powerful 6-tube superhet Radio, a big T6 -range test meter and perform over 175 other fascinating practical experiments. EARN WHILE LEARNING Radio, Electronics and Tele- 4 after you enroll I send you my famous Make Money In Shortly vision" that tells all about Sprayberry Training. com- BUSINESS BUILDERS that help you get and do You build this also send you a Sample Lesson, "How To plete 16 AC- neighborhood Radio Service jobs while I'll -range profitable Read Radio Diagrams and Symbols" -all FREE. DC meter set- These jobs pay well, and pave the way for test learning. You'll read many letters from successful Radio up. a Radio Service Business of your own. men I've trained -and you can decide for yourself All branches of Radio, Television and Electronics what Sprayberry Training holds in store for you. are booming! Trained men are needed NOW! I'll prepare you for your own profitable Radio Service a pay radio job in double quick LOW COST COMPLETE TRAINING I show you how to Business or big build this speaker time. You learn at home in spare time -you keep Sprayberry Training is surprisingly Low In Cost tester and many your present job while getting set for the future. -and if you desire, convenient monthly payments other instruments. My course is so perfectly planned -so easy to can be arranged. This is COMPLETE, Up -to -Date grasp and understand -you need no previous training -covering Radio Repairing, Television or experience of Radio or Electricity. and F.M., Industrial Electronics and many other You build, test and knowledge men trouble -shoot this Get the facts now -find out what Sprayberry Radio new developments. Sprayberry Trained know Radio. This is training that sticks s powerful 6 -tube su. Training can do for yew. Mail the coupon below really perhet Radio. and by return mail I'll rush my big book, "How To with you and makes money for you. SAMPLE LESSON FREE AND BIG CATALOG //fate COUPON %i See how quickly and easily you can get your start in Radio, Electronics, Television with Sprayberry FRANK L. SPRAYBERRY, President Training. Just fill out, clip and mail the coupon YBERRY ACADEMY OF RADIO, NOW for my big FREE book and FREE Sample 20108 Sprayberry Building, Pueblo, Colorado Read Lesson. No obligation. No salesman will call. Rush my "How To Make Money In Radio, Elec- then FREE copies of all the facts about Sprayberry Training - tronics and Television" and "How To Read Radio Diagrams and Symbols.' decide. Take the first step TODAY - rush the coupon to me. VETERANS: Approved for G. I. Training under NAME Public Laws 16 and 346. Check coupon and mail today for complete facts. ADDRESS AGE

SPRA ACADEMY OF RADIO CITY ZONE STATE Frank L. Sprayberry, President Check here if a Veteran ROOM 20100. BUILDING, PUEBLO, OCTOBER, 1948

www.americanradiohistory.com Ii

ALLIED'S NEW 1949 RADIO CATALOG

180 VALUE -PACKED PAGES .Seemd PI Cí pouf!

The Preferred Radio Buying Guide WORLD'S LARGEST STOCKS Everything in radio for everyone In Its ready for you -the new 1949 ALLIED Radio radio! ALLIED's huge stocks are the Catalog! world's largest, including complete Get the Radio Buying Guide that's the first choice of thou- lines of all leading makes of parts sands of expert service technicians, engineers, soundmen, and equipment. Get everything you Amateurs, builders and experimenters. The new ALLIED need from one dependable central- ized Catalog- Radio's largest and most complete- brings you source - ALLIED RADIO! 180 pages packed with the widest selections of the newest TELEVISION 8 HOME RADIOS and finest equipment, at today's lowest, money- saving prices! See ALLIED'S outstanding selection Here's everything in radio for everyone in radio: new Tele- of new Television sets, new table model vision and home receivers; radio -phonos with new Dual - radios, FM -AM combinations Speed Changers; packaged Sound Systems, with new Dual -Speed Automatic high -fidelity Changers. Save on these radio sound components and P. A. equipment; latest Amateur models -the choice of experts! receivers and station gear; test instruments; builders' kits; thousands of parts, tubes, tools, books -the world's largest AMATEUR STATION GEAR and finest stocks of nationally known equipment. Take ad- You'll find everything you need for vantage of ALLIED's speedy, expert shipment your shack in the new ALLIED Cat- and the alog. See all the latest releases in personal attention of seasoned old -time radio men. Get receivers, transmitters, parts, station the details, too, of radio's most liberal Time Payment Plan. equipment -the biggest and most Write today for your FREE copy of ALLIED's newest and complete listings in Ham radio! greatest Catalog -the preferred Radio Buying Guide! NEW SOUND EQUIPMENT Packaged, ready -to -use Sound Sys- LARGEST STOCKS QUICK, EXPERT SERVICE tems; amplifiers guaranteed for one full year; high -fidelity sound com- ponents; everything in speakers, Send for your FREE copy of mikes, P. A. accessories, intercom and recording equipment -head- Radio's Most Complete Catalog. quarters for Soundmen! Radio's Leading Use the coupon below - NOW! Buying Guide ....

ALLIED RADIO CORP. WORLD'S 833 W. Jackson Blvd., Dept. 2-I( 8 THE Chicago 7, Illinois

LARGEST Send FREE New 1949 ALLIED Catalog.

RADIO Name

SUPPLY Address

HOUSE ' City Zone State

RADIO -ELECTRONICS for

www.americanradiohistory.com New I. C. S. Course Simplifies Radio Training

THE BEGIN \ it IN RADIO no longer has to stumble quality tools and radio equipment supplied with over technical explanations - or sidestep involved the course. During his studies he assembles, wires theories - in acquiring the training he needs to and tests a modern 6 -tube, 2 -band receiver. become a successful repairman. Long before his last lesson, the average student These are carefully worked out for him in clear, is in a position to start making his training pay. And simple language in a new home -study course de- by the time he completes the course, he is well veloped by International Correspondence Schools. equipped - in knowledge, tools and radio parts - But the student doesn't stop here. He puts for a good job in radio or a profitable service principles and theory to work -using professional business of his own.

INTERNATIONAL Those who want to make good in Radio -who want a course that -to -date. extremely practical would do well to CORRESPONDENCE SCHOOLS is complete. up - mail this coupon. Do it Now! Cs Box 2881 -G, Scranton 9, Pa. Nance please send me full infor- Without cost or obligation Address mation on the courses before which I have marked X. City State RADIO SERVICING (with training equipment) Working Hours A.M. to P M. - Radio, General D Electrical Engineering Age _Occupation L Technician Radio, Operating Lighting Employed by Electronics Practical Electrician Practical Telephony !' Business Administration Special tuition rates to members of the Armed Forres. Enrollment under G.1. Bill and P.L. 16 Cj Telegraph Engineering Ei Salesmanship approved for IVarld IVar 11 Veterans. OCTOBER, 1948

www.americanradiohistory.com Radio Month NEW TV STUDIOS will be construct- TRANSISTORS may cause important ed by the American Broadcasting Com- changes in Army communications equip- pany in New York, Robert E. Kintner, ment, predicted Major General S. B. ABC vice -president announced last Atkin, Chief Signal Officer. The transis- month. The building to house the studios, tor (see last month's issue) will do most billed as the largest in the country, will of the things a vacuum tube will do but provide 2 million cubic feet of usable requires no filament battery. This could space. The principal studio will be 200 eliminate 25' S of the weight of portable feet long and 100 feet wide, with a 45- army equipment. Army tests are being g°1, foot ceiling. Soundproof carried translucent out to determine where the panels will divide the studio into smaller transistors could be used, and how far ones but, when not in use, will be they will prove practical. dropped by motor controls into slots built below ION the floor. may be / TELEVISION used by the De- partment of Agriculture to bring view- A NEW MAGNETRON which in- ers news and information of agricul- luccs so much heat that laboratory tural products, the Department an- workers become feverish and nearby nounced last month. The medium is the eggs and pencils explode was announced subject of a study under provisions of last month by General Electric. The new the Research and Marketing act. The tube operates at 1,000 mc. Its 50 -kw out- project will be conducted by the Agricul- put is said to be the greatest amount ture Department's radio service in co- of power ever produced at this ultra- operation with TV stations and net- high frequency. Water cooling is used. works. According to G -E scientist Dr. R. B. Nelson, experiments are still being car- NO TV NETWORK will conduct oper- ried on to determine how much power ations from coast to coast for at least can be developed at 1,000 mc. 5 years, predicted Sidney Strotz, NBC vice -president, last month. He explained that transmission costs be STRATOVISION service will be in- will prohibi- tive for at least augurated on a regular that length of time. He basis in Pitts- predicted, Spark Plugs are minia- burgh if an application too, that television station made last month operation ture broadcasting sta- for a channel is granted by the FCC. would continue to be a losing tions, send signals that proposition, financially, interfere with radio Westinghouse Radio Stations, Inc., filed for another two reception, distort tele- years, but after that a request for Channel 8 to be used by time would be a vision. The New Auto - profitable operation for all Lite "Resistor" Spark an airplane to broadcast TV signals concerned. Plug reduces this in- over a 250 -mile terference. -radius about Pittsburgh. Successful Stratovision demonstra- AN ELECTRONIC DETECTOR so tions (reported in RADIO -CRAFT recent- sensitive that it can find metal impur- i1'EH ly) show that major technical problems ities weighing less than one ten -billionth have been solved. The new service would of an ounce was disclosed last month by be the first link in a nationwide chain Westinghouse Research Laboratories. of airborne TV stations. The device can do a job in 5 to 15 min- utes that would take several days with AUTOLITE regular chemical methods. THE CANADIAN TAX of 25Y on William M. Hickman, physicist who radios and electrical products was re- developed the device, says it is a new moved last month. The excise levy, ac- application of the mass spectrometer, cording to manufacturers and dealers, widely used in separation of atomic reduced sales to a very low figure. The materials, detection of leaks in vacuum only tax now remaining on radios in systems, and analysis of materials in SPARK PLUG Canada is the 10% sales tax. synthetic rubber production. Here's How It RADIOTECHNICIANS hold the first "Town Meeting" Works to End of the 1948 -49 season in New York City on September 27, 28 Interference and 29, Harry Ehle, chairman of the The "Resistor" acts Town Meetings to dampen the spark Committee, announced plug radio signal to last month. an acceptable level' The meeting while still delivering will follow the general the full high voltage lines of the first Town Meeting of Radio discharge required to Technicians held in Philadelphia ignite the fuel. last January. Several modifications have Auto -Lite Ignition Engineers, working been worked out as a result of experi- with leading automotive manufacturers, ence gained at that meeting. have developed the new Auto-Lite "Re- The program will bring the techni- sistor" Spark Plug with this built -in cians who attend the meeting up- to -the- resistor that reduces spark plug inter- minute instructions and data on tele- ference.* Remember, the "Resistor" also vision servicing, as well as information helps deliver smoother idling, improved designed to make their lives easier as economy, longer electrode life. Dealers independent businessmen. are being supplied as rapidly as pos- The New York gathering sible. Write for Booklet M -1186 will be fol- for full information. lowed by a Town Meeting at the Hotel Bradford in Boston, November 15, 16 THE ELECTRIC AUTO -LITE COMPANY and 17, Toronto, Ontario Toledo 1, Ohio and by others in Atlanta in January, Los Angeles in March and 'Under 35mv /m from 540 k.c. to 150 m.c. at 50 ft. Chicago in April if present plans are Loading sample chamber of mass spectrometer Tune In "Suspense," carried Thursdays, 9:00 P. M., E. T. C85 out. in preparation for an analysis of metal vapor. RADIO- ELECTRONICS for

www.americanradiohistory.com The Radio Month 11 RADIO are being TECHNICAL ADVICE will be given RATS WIRED FOR and other used to measure the effects of electrical to government agencies Dr. Joseph A. Gen - groups by the Joint Technical Advisory PLEASE TEAR OUT brain stimulation, was an- mr gerelli of UCLA announced last month. Committee, formation of which The Committee, THIS ADV. AS REMINDER A small radio receiver, consisting of a nounced last month. miniature crystal rectifier and wire elec- which operates under the joint direction trodes, are placed within the rat's head of the IRE and the RMA, will report to ingenious operation. High -fre- Dr. E. B. Shackelford, IRE president, by an director quency pulses generated in the labora- and Dr. W. R. G. Baker, RMA tory are received, rectified and trans- of engineering. Members were appointed by an electrode to the proper part on the basis of professional standing mitted affilia- of the brain. The new method gives the irrespective of their commercial freedom of movement for observa- tions. The first chairman is Philip F. rat the IRE. tion in contrast to an older method of Siling of RCA, representing direct wiring. Vice -chairman is Donald G. Fink, Edi- tor of Electronics, representing the TELEPHONE RECORDING was au- RMA. thorized last month in Pennsylvania by One of the committee's first jobs was the State Public Utility Commission. the gathering of material on equip- tele- and propagation char- COVERING Subscribers will be provided by the ment availability TNEp phone company with a connector to acteristics for the u.h.f. spectrum, in CONSTRVcTIp which they may attach their automatic preparation for the September FCC SERVICI N voice recorders. According to the Utility hearings on TV allocations. TELEyI NG Commission's ruling, an "automatic re- connector tone signal" must be was inaugu- corder TAXICAB TELEVISION ELECTRÓÑIey E.D.ANOEASOk furnished with the connector. This de- rated last month by Charles de Lorne, S vice emits a brief tone signal every 15 a Chicago hack driver. Passengers say seconds to indicate that recording is in reception is fairly good with very little RADIO FACTS progress. Without such a warning, re- interference from other vehicles or AND FIGURES is illegal on public communica- the picture is a little 1001 633 Illus. cording buildings, though AUDELS RADIOMANS GUIDE- 914 Pones, tion lines. All customers will be required shaky over the bumps. orations, Photos, Wiring Diagrams, 38 Big Chapters. company from covering Radio Theory, Construction, Servicing, Includ- to release the telephone The set was installed by Motorola, ing Important Data on Developments In Television, responsibility for any libel or slander. The company Electronics and Frequency Modulation, Review. Inc., as a promotion stunt. Questions and Answers, Calculations á Testing. doesn't expect many cabbies to buy sets Highly Endorsed -Indispensable for Ready Reference ROCKET TRANSMITTERS capable (too expensive) but it hopes the public and Home Study. of sending scientific information from a in S4 COMPLETE PAY ONLY Si A MONTH will say: if television works so well Step up your own skill with the tarts and nguree of rocket 72 miles above the earth were better it your trade. Auricle Mechanics Gulden contain Prac- a moving car, think how much tical Inside Trade Information in A handy form. operated successfully last month at home! Fully Illustrated and Easy to Understand. Highly will show up at Endorsed. Check the book you want for 7 days' White Sands Proving Grounds, accord- Free Examination. ing to Science Service. The rocket was Send No Money. Nothing to Day Postman. FOOD STERILIZATION by means of travelling at a speed of more than 2,800 Imo- - -- CUT HERE - --'#9 '_'- X -ray generator was de- per hour. a million -volt miles last month in the Journal of The telemetering device used the scribed MAIL ORDER Applied Physics. The generator is capa- O N Aerobee system to transmit 24 different AUDEL, Publishers,49 W.23 St., Nió N of either X -rays or cath- books of continuous information to ble producing Mom sens me postpeld for FREE EXAMINATION kinds Il I decide to keep them l to ode rays. marked x below. further ground -based recorders. The system was ad al In 7 Days oon book ordered end electrons, rather mall Al monthly on eachbook until t have pas Mims evolved during the war by scientists of Acting as a source of -otherwise, I Will return them. and Johns Hopkins Univer- than as an X -ray machine, the genera- RADIOMANS GUIDE, 914 Pages . . . $4 Princeton . 1 of subjecting five ELECTRICIANS EXAMINATIONS. 250 Pages sities. tor is believed capable WIRING DIAGRAMS. 210 Pages 1 tons of food to the equivalent of a mil- ELECTRIC MOTOR GUIDE 1000 Pages . 4 24- ELECTRICAL DICTIONARY 9000 Terms 2 lion units of X -ray energy during a 425 Pgs. 2 ELECTRONIC MUSIC is due for ELECTRICAL POWER CALCULATIONS, hour Clay. Electrons were found to be HANDY BOOK OF ELECTRICITY. 1440 Pages 4 greater development and more artistic ELECTRONIC DEVICES 216 Pages 2 more effective than X -rays in vol. use, according to a statement made last much ELECTRIC LIBRARY, 12 vol., 7000 Pgs., $1.50 sterilizing food. Bacteria can be com- OIL BURNER GUIDE, 384 Pages . month by Edgar Varese, distinguished REFRIGERATION & Air Conditioning, 1280 Pis. killed with an ionizing close that Pages. composer. So far, says Mr. Varese, elec- pletely POWER PLANT ENGINEERS Guide,1500 raises the food's temperature only 2 PUMPS. Hydraulics &Air Compressors,1658 Pgs. tronic instruments have been made to WELDERS GUIDE. 400 Pages play the role of "freak ersatz ", trying degrees. BLUE PRINT READING, 416 Pages . . SHEET METAL WORKERS Handy Book. 388 Pgs. to imitate the sounds of conventional in- SHEET METAL PATTERN LAYOUTS. 1100 Pgs. broadcasts will . . struments. But ordinary instruments VOICE OF AMERICA AIRCRAFT WORKER. 240 Pages reach more European listeners because MATHEMATICS & CALCULAT IONS, 700 Pgs many years ago and it is Book 1600 Pages . . were perfected inaugurated last MACHINISTS Handy time that these tools of music were of additional relays MECHANICAL Dictionary, 968 Pages month by the BBC. The new service in- AUTOMOBILE GUIDE. 1700 Pages in step with other 400 Pages . . changed and improved BBC DIESEL ENGINE MANUAL, in our modern world. volves the use of five additional MARINE ENGINEERS Handy Book, 1280 Pages things . to increase BBC relays of MECHANICAL DRAWING GUIDE, 160 Pages Mr. Varese reports that electronic in- transmitters MECHANICAL DRAWING & DESIGN, 480 Pgs. to Pgs. have been officially adopted the American broadcasts from three MILLWRIGHTS & Mechanics Guide, 1200 struments . As with the old 3 -hour CARPENTERS & Builders Guides (4 vols.) hours daily. . in French schools. He has used them nine PLUMBERS á Steamfitters Guides (4 vols.) long-, me- (4 vols.) . . himself in compositions, not to imitate schedule, relays will include MASONS & Builders Guides and short -wave transmissions. MASTER PAINTER & DECORATOR, 320 Pgs. violins and flutes, but as completely new dium-, GARDENERS á GROWERS GUIDES (4 vols.) The new service is in addition to the ENGINEERS and Mechanics Guides and sounds, with music written 1 different . . . daily relay by the State Depart- Nos. 1, 2, 3. 4, 5, 6, 7 and 8 complete especially for them. 8 -hour Q Answers on Practical ENGINEERING Munich. EXAMINATIONS The composer predicts that the de- ment's own transmitters in U ENGINEERS & FIREMANS velopment of electronic music will do away with the interpreter -the musi- RADIO AND TV COURSES will be Neale by Columbia Uni- cian -whom he calls a "deforming prism offered this season Address between the composer and the listener." versity and NBC, according to a net- last month. Twenty - Occupation The hearer will press a button and the work announcement R.c.F electronic instrument will reproduce the seven courses will be included and 17 mu,teyedby music exactly as the composer conceived of the 21 instructors will be NBC staff it. members. OCTOBER. 1948

www.americanradiohistory.com 12

pRgy

NEW SERIES 16

SUPER DE LUXE AM-FM CHASSIS

30 DAYS TRIAL

Here is the last word in radio engineering ... a powerful, world - ranging, magnificently -toned radio that is unsurpassed for performance, selectivity, _ 7 sensitivity, and advanced engineering features. Uses fO these latest -type tubes, rectifier and tuning indicator: Nj three 7A7, three 7A4, two 7C5, one 7A6. one 7Q7, one 6BA6, one 6BE6, one one 6AL5, one 5U4, one 6U5. Comes com- 4 plete with satin stripe copper finish front panel attached, Magna- Tenna Loop Aerial and giant 141/2" Electro- Dynamic Panasonic Speaker. T O Requires only a q} few minutes to install, plug in and play. LOW FACTORY PRICES ... EASY TERMS ... 30 DAYS TRIAL. Send TODAY for FREE 1949 IO Midwest Radio Catalog of separate Chassis and beautiful Console and Table models. OUTSTANDING A Comp ete Line o IN ' and RADIO - FEATURES PHONOGRAPHS ... Available in SEPARATE Including the Exclusive Midwest CHASSIS Like the POWERFUL SERIES 16 AM -FM Model above in COMPLETE FLASH -O -MATI( or CONSOLES like this... Volume and Bond Indication Beautiful TELEVISION SYMPHONY GRAND Audio Switch -Over AM -FM Radio -Phonograph FIDEL -A -STAT with Color -Roy Tone Selection TELEVISION Audio Switch -Over NEW TRI -MAGNADYNE and Intermix AUTOMATIC Coil System

RECORD CHANGER ...Plus NO -DRIFT FM A Magnificent musical instrument and a masterpiece of cabinet design -the and many other features finest Midwest Radio in 29 years of manufacture. Offers world- ranging ra- dio reception and newest automatic Intermix Record Changing Phonograph. Uses Series 16 Super DcLuxe AM -FM Chassis. Giant 143.f" Panasonic Speak er; Tri- Magnadyne Coil System; Built - TILL IN COUPON AND MAIL TODAY In Loop Antenna. OR JUST Other luxurious con- SEND NAME AND ADDRESS sole and table model cabinets available ON k POSTCARD with Series 16, 12, and S chassis -on MIDWEST RADIO & TELEVISION CORP. Easy Terms and 30 Days Free Trial. Dept.382 909 Broadway, Cincinnati 2, Ohlo lam. snd your BUY DIRECT FROM FACTORY and SAVE! m nw FREE 1949 Catalog., NAME MIDWEST RADIO & TELEVISION CORP. ADDRESS Dept. 382 909 Broadway, CINCINNATI 2, OHIO CITY ZONE STATE .1 RADIO -ELECTRONICS for

www.americanradiohistory.com I:t

17 YEARS to Help YOU... Here's Our GREATEST Combination of Training Advantages IN LearnE a YOU ¡(((P EQUIPMENT

-.s Here's good news .. - BIG news ... our BIGGEST NEWS in 17 years. Now, AT HOME, you can get one of today's most effective combinations of Radio -Electronic training aids ... and you KEEP ALL EQUIPMENT. Mail coupon TODAY! Get FREE FACTS about D.T.I.'s amazing new home training. See how effec- tively D.T.I. prepares you to earn good money do interesting work ... enjoy a grand future in America's thrilling Radio- Television- Electronics fields.

. as one of your many "Learn -By- Doing" pro- jects to help you get valuable "on- the -job" experi- ence in ASSEMBLY ... WIRING ... SOLDERING ... A Jewel- Bearing, Self Powered ALIGNING...TESTING...and TROUBLE SHOOTING. T R MULTI -METER 1 You also receive HOME MOVIES 1 USE N the necessary parts G from which you con- a D. T. I. Exclusive! struct and keep this ... valuable, commercial - You also receive the loan type test meter, which of a 16 mm. Movie Projector help you earn while and many reels of instructive, can help you learn. "Learn -By- Seeing" film to you grasp basic points faster, Build O,r 180 It's like a teacher in your rim..nt. From Those easier. Exp. home, giving you an EXTRA RADIO PARTS advantage many say is worth D.T.I. sends you many the cost of the entire training. Radio -Electronic parts which you mount on bases with spring clip terminals for Modern CHICAGO LABORATORIES quick assembly . ideal for experimenting. Build If you prefer, you can get oll your prep- and operate 8 different aration in one of the notion's Rodio Receiver Circuits .. . outstanding new training ,Aeolt- :molt Rodio Telephone . . . PA laboratories. If you come l...i 1 r1 System ... Electric Eye ... to Chicago, living quar-

many fascinating will be found for you. .a' Isrohl and other ters llj projects. s.(111T'. MO ------rOererests Training, Inc. MAIL To MEE_ 2533 N. Ashland Ave., Dept. 1tl I'1n Effective EMPLOYMENT SERVICE heips you get started! Chicago 14, Illinois you can get the same Upon completing your training Send me complete details showing how I may make my effective employment service that has helped many D.T.I. 1 start in Radio -Electronics -Television. No obligation. graduates get started in the field. 1 Name Age Address Apt. DeFOREST'S TRAINING, Inc. 1 CHICAGO, ILLINOIS City Zone State If a discharged veteran Associated with the DeVry Corporation, 1 If under 16, check here. 11 for special information. LiJ of WWII, check here. Builders of Electronic and Movie Equipment. MINN MIMI MI MR

OCTOBER, 1948

www.americanradiohistory.com LO ICES

'*%45c:.,

RCA 15 -watt

DE LUXE AMPLIFIER MI -12295

You've never seen a .clue like this lar low output magnetic pickups. Phase distinctively styled RCA I5 -watt All - inversion and inverse feedback used to Purpose Amplifier. You can't beat it for obtain low distortion and uniform high fre- quality performance, compactness, quency response for various load condi- beauty, and simplicity of operation tions. Unique balanced tandem tone under all sorts of operating conditions. control circuit. Choke filtered power supply for minimum hum and uniform Electronically engineered to give top regulation. Large functionally designed performance. Frequency response (30 control knobs. Accessible output termi- 15 watt r.sh -pull Output to 15,000 - cycles). Two high impedance nal board and replaceable cartridge Noise -free electronic mixing microphone input - channels 116 db. gain type fuse conveniently located in rear. Switch for high -low power (RMA), each with individual volume Set of locking -type 3 pin Cannon plugs output requirements Under- control. Two hi- impedance phono chan- and receptacles for each microphone - writers- approved. nels, one for hi -level and one for low - input. Also available with 2 low imped- level pickups. Can be used with popu- ance inputs (250 ohms).

RCA 50 -watt De Luxe Hi- Impedance Amplifier MI -12293 Additional Unparalleled Complete with RCA Tubes Now only '197'° Amplifier Values RCA 30 -watt De Luxe Hi- Impedance Amplifier MI -12296 Complete with RCA Tubes Now only 'I 15 °° SOUND PRODUCTS RADIO CORPORATION of AMERICA ttPi ENGINEER /NG PRODUCTS DEPARTMENT, CAMDEN. N.J.

In Canada R C A VICTOR Company Limited, Montreal

RADIO -ELECTRONICS for

www.americanradiohistory.com or i because it's RCA... More profit because of these new values

RCA SPEAKER MI -12422 12 -inch high efficiency, Alnico V, Cone Type Mechanism. Special cone provides a selected listening characteristic -a result of thousands of listeners' tt RCA MOLDED SPEAKER BAFFLES yeas. over the past 10 7 5 O Molded Plasticized Fibre Baffle with at- years. 10-watt capacity. 15 tractive gray hammeroid finish and con- ohm voice coil. trasting grille cloth, 12 x 15" x 5t/2 ", sloping front, strong, moisture -resistant, and non -warping. Available Also available with for 5 ", 61/2" and 8" mecha- J5 matched I 0 -watt multi - nisms as M1.6378, M1.6379, tap line transformer as and MI -6380, respectively. Mt- 12421. Similar baffles for 5 ", 6t/2 ", 8 ", 10" and 12" mechanisms also available in molded Bakelite and wood. All prices shown are suggested list prices subject to normal dealer discounts. NEW BANTAM VELOCITY 12080-8 RCA VARACOUSTIC MICROPHONE MICROPHONE MI a MI- 6204 -C Smaller than pack of cigarettes. First h ree microphones in one. Here you have used at all 1948 the popular cardioid microphone (uni- political conven- directional) plus standard velocity micro- tions. Broadcast phone lbi- directional) plus standard These and many other quality. Built -in pressure microphone (non -directional) all profitable items of voice -music switch. in one general purpose unit. Variable 15 feet of cable. characteristic obtained by ingenious slider sound equipment are mechanism on rear of housing. Quality available through only in and performance found heretofore your RCA Sound Prod- more expensive polydirectiou.,l Br,,.,dcast Microphones. High ucts Distributor. sensitivity, shock mounted, high imped- ance. 30 feet of cable. MA /1 THIS COUPON FOR FREE CATALOG

MN NI u Es mum IIM MN ME IN MOM= =MIIINs RCA SOUND PRODUCTS (Dept. 111 -J) Radio Corporation of America Camden. N. J. BUY line of matched THE BEST 1 Please send me free copy of RCA's new Catalog on complete FOR LESS sound products and price list.

Name

Company

Type of Business_

84 pages of sound products- micro- Address phones, amplifiers, speakers, record- State ers, intercoms, portable P. A. and City - numerous other profitable items. Send for your FREE copy today.

OCTOBER, 1948

www.americanradiohistory.com 16! Iti1d11/. Business CLEARANCE SALE VIDEO CODE RELEASED ADMIRAL SALES AT PEAK The Association of Better Business In a mid -year statement STROMBERG CARLSON «-29 Amplifier to stockhold- Bureaus recently released its "Recom- ers, the Admiral Corporation and sub- In original cartons. mended Standards for the Advertising sidiaries of Chicago reported that sales Tops in tone qualify and Selling of Television Receivers." and earnings for the first six months Mike and phono in- Some of the high points follow: this year hit an all -time high. put. Includes tubes Sales were A television set or receiver shall be shown as $27,386,344 as against $21,- 2 - 6SJ7, I - 5Y3, understood as meaning one capable of 548,786 last I -6L6. year, an increase of $5,897,- receiving List $57.75 and reproducing televised pic- 558. Excluding sales to the government, Sala price 28.87 tures and nceompauyiug sound. If a set which in the first half of 1947 were or unit or attachment will reproduce $3,409,355 as against no sales in TOM THUMB CAMERA the RADIO television pictures only, without sound, similar period this year, Admiral civ- i7'""1 such fact shall be conspicuously stated. ilian -sales more The perfect outdoor than doubled with an com- Advertising shall clearly and conspic- increase of 51'S Net earnings were panion. Personal battery uously portable. Powerful 4 -tube indicate whether the price ad- $1,237,297 as against $854,456, an in- superhet. Built -in loop, hi- vertised for a television receiver in- crease of $328,841. Much of this gain gain pickup. Full vision cludes the cost of installation, antenna, was registered during the second quar- slide rule dial. Reflex -type or other equipment, or service necessary ter when earnings rose from $342,995 in camera. Uses standard 127 for reception of television. If an instal- 1947 to $706,887 this year, a jump of film. Compact unit 43/e" z lation charge is quoted in advertising, 106',, Acquisition by Admiral early in 41/4" z 93/4". the charge quoted shall be the total July of the electric -range manufactur- List $37.95 charge required of the purchaser for ing facilities of the Pressed Steel Car Sale price $22.97 assuring satisfactory reception on all Company, Inc., strengthened the com- channels within range, unless otherwise pany's line of products. ELECTRO -VOX Intercommunication staled. System Complete with sub When a statement such as "No Money station. Use as a Down" is used in advertising, in refer- telephone. C o n - ence to an installation payment plan, it G -E REPORTS GAINS illli verse from house to shall mean that the purchaser will not General Electric Company reported , garage. From sec - be required to make payment tion any until net income in the first six months of of house to after the merchandise been VIII other. Ready for has delivered 1948 amounting to $54,602,339, as com- and installed, and no payment be use, incl. 3 tubes. shall pared with $42,802,075 in the first half List required until the first due date speci- of 1947. Net sales billed set a pprice $1 0.97 new rec- fied in the sales contract. ord in both the first half and in the Claims as to performance Superior #770 Pocket Size Volt -Ohm shall be lim- second quarter. For the first half, sales Milliammeter ited to known facts, and to the practical totaled $772,761,792, a rise of 29% over Sensitivity - performance of such receivers under the $601,342,810 billed for the same pe- 1000 ohms per volt normal operating conditions, and to riod a year ago. Second -quarter sales Automatic zero adjustment those claims for which the advertiser amounted to $406,803,802, a 19% rise 6 A.C. VOLTAGE RANGES: would be willingly responsible to the over the comparable 1947 quarter. (8 15/30/150/300/1500/3000 VOLTS individual purchaser. 6 D.C. VOLTAGE RANGES: 0. 7.5/15/75/150.;750 1500 VOLTS When installation is performed by the 4 seller, the 4 D.C. CURRENT RANGES: responsibility- of providing 0- 1.5/15/150 MA 0.1.5 AMPS. acceptable television reception rests TV TUBE SALE INCREASE 2 RESISTANCE RANGES: with the seller, restricted only by quali- 0 -500 OHMS 0 -I MEGOHM Sales of radio and television equip- Latest type D'Arsonval meter. fications in advertising and selling state- ment, including electron tubes, ments, or totaled Streamlined plastic cabinet. Size-31/4" z 5 %B" as defined in the service con- $40,351,820 during the first quarter of z 21/4 ". Complete with batteries, test leads, tract or guarantee by the seller or the 1948, the Radio Manufacturers Associa- instructions and guaranty. manufacturer. tion reported recently. Almost half Net price only $13.90 of Whenever program material which is these sales, or $18,053,969, went to the to he televised from motion picture film, RADIO TUBES All U. S. Government, and $12,875,186 of new and guaranteed as distinct from direct televising, is re- 6B8, Kan the federal purchases were for radar -Rad S .19 114, unbranded $ .39 ferred to in RCA .19 3S4 unbranded advertising, such fact shall equipment. Production of cathode -ray 6C4, Natl. Union .22 ISS, RCA be 44 clearly and conspicuously disclosed. receiving tubes of the type used in TV RCA .32 6SH7, RCA .44 If any 6H6,35Z5, Std. brand .... 34 12J5, RCA .44 reference is made to picture sets showed the greatest gain over the BO, Std. brand .36 14A7, Sylvania .49 size of direct -view television receivers, 6.15, .36 1486, corresponding period of 1947. First - Sylvania Sylvania .49 the diameter of ILNS, Sylvania .39 1497, Sylvania .49 the television tube shall quarter output this year of 170,430 was 37 RCA .39 35Y4, Sylvania .49 be stated. It is recommended that the more 25Z6, Std. brand .39 50L6. Std. brand .... .55 than three times the production of size of the picture also be indicated by the first quarter of 1947 when 75003 VOLUME CONTROLS 51,214 approximate area by square inches or such tubes were manufactured. Of the 10K, 25K, 50K, 4meg, /smeg, Imeg, in the original dimensional measurements. factory packed cartons in bulk, known makes, Clare. 1948 quarterly output, 158,706 went to stat, Centralab, Sfackpole, etc . If the receiver is equipped with a set equipment manufacturers, 10,742 to without switch with switch built -in screen enlarger, that fact shall SALE PRICE users and distributors, 894 to the U.S. 19c each 29e each be conspicuously set forth. Any refer- Government, and 88 to export. Mention size shaft desired and we will ship the actual ence that is made to picture size of size the a or t to if receiver having a built -in enlarger shall also disclose the size of 6E, 12" PM SPEAKER, fain. 5) 6.8 oz meg. $5 95 the picture tube. 12" SPEAKER BAFFLE, walnut cabinet 4.65 CANADIAN SALES DOWN OUTPUT TRANSFORMER, matches SOL6 tube .29 Canada's radi,, set Manufacturers AC -DC CHOKE, 50 mils, 10 henrys .29 have recently been facing the biggest 103 -ASST CONDENSERS, .001 to .02 -600V 3.95 RCA -SYLVANIA PATENTS production slowdown that they have 100 -ASST SOCKETS, octal. !octal. min 3.95 Arrangements have been completed experienced, 100 -ASSORTED RESISTORS, watt ever but they saw one 1/2 1.29 recently by which Radio Corporation of bright light on their horizon: the fact America becomes a licensee under some SALE PRICES EFFECTIVE that two private broadcasters have ap- THIS MONTH ONLY two hundred radio and television tube plied for licenses Don't Delay, rush your order in now for television trans- patents of Sylvania Electric Products, mitting stations in Toronto and Mont- Inc. The license runs for seven years at real. The Canadian Broadcasting Corpo- BROOKS RADIO DIST. CORP. royalties of three -quarters of 1 %, but ration plans to review the applications 80 VESEY ST., (Dept. A) NEW YORK 7, N. Y. not exceeding $200,000 in any one year. this October. RADIO -ELECTRONICS for

www.americanradiohistory.com 17

Jobs worth Which $3000 to $7500 Better Pay are opening up Greater Security Do You right now for A Nice Home 1. FCC Licensed Want? Happy Vacations Radiomen A New Car and Travel How to Pass Commercial FCC Radio Operator LICE SE EXAMS TICKET I can train you to pass your FCC GET YOUR FCC License Exams in a few short weeks IN A FEW SHORT WEEKS if you've had any practical radio ex- Giet your license easily and quickly perience - amateur, Army. Navy, urtr and be ready for the $3110) t. radio servicing or other. My time - $7500 jobs that are open to ticket NEW WORLD tiruven training plan can help put on to holders. Cl RE training is the only OIL OF ELECTRONICS coo. too. the road success - planned course of coaching and anus Let me send you FREE the entire story training that leads directly to an ( sir() 1ivw last fill out the coupon and mail it. T rill send you. free of charge. at copy of "How FCC license. to I'as'o FCC License Exam.." plus a 'ample FC(' -typ,. Exam and Catalog A, IT'S EASY WITH CIRE desrrihi, oppo tunnies for you in Radio- COACHING AND Elect TRAINING Eliot. H. GUILFORD. ct,e President. Your FCC ticket is recog- nized in all radio fields as proof of your technical altil- ity. Employers often give preference to license holders, even though a license is not RADIO ELECTRONICS required for the jolt. Hold an CLEVELAND INSTITUTE OF FCC "ticket" and the job is RC -10 Terminal Tower, Cleveland 13, Ohio yours! I tan get mt' in a trten' >bmi neck+. S.ml I waa nt to kmm how fl booklet. "Hmv to Pas, FCC License Examinations" Ideas not rove exams for FREE and Catalog A. dust, lbìng tmatem. License), as e,II as ample FCC -type exam Look what these students say: .1ppm amities In Iladlo- 1:lertronics.s "Th ohs to this course, I now have a very good job in a local power pl:out's test department. I couldn't have obtained this job without the math and basic electrical theories in the first part of Section 1 of this course." Sind. No. 2893X12 NAME "I have been working for Police Radio Station W i'FS in Asheville for five months since getting my second,cbus ticket." Stud. No. 2858N12 ADRESS "You may be interested to know that I am employed at the local broadcast station. where I am a transmitter operator. I took and passed the FCC examinations last Feint a r y." Stud. No. 2754N12 CITY ZONE STATE B.T. Bill. CLEVELAND INSTITUTE OF RADIO ELECTRONICS Veterans check for enrollment Information under NO OBLIGATION -NO SALESMEN. RC-10 Terminal Tower Cleveland 13, Ohio Approved for Training under "G. I. Bill of R¡gilts" aaaa J OCTOBER, 1948

www.americanradiohistory.com 18

DYNAMOTORS t RAND wild ID head and Voltage Input Output Radio iulp, ', 725A magnetron A Type M m a e. -.\B klystrons lierai Volts Amps Volts Amps Set Priee h,..,; 11124 tr. rar-n P1. Regulator dncuphxr, It supply. blower. BO 77KM 14 411 1000 .350 BC 191 $20.(10., prase. \Ifg. 1:. \ ,r }' afmr. Pk 1wr o l: 45 KW aim. In- 11. unLN Put: 115l, 400 e)'. Modulator pulse duration .5 to 2 PE 73 26 19 ])11111 .330 1[C 373 24.505 1:1 ail 138 DM 21 14 3.3 235 ,11911 BC 312 3.45LN Ìrone.uÌ in I71alx 5 N'1i 11 , KKK IMunwilh7:1. tw72.lompl. pkg. r DM 2ICX 26 1.6 235 .119)1 Be 312 3.455 . . 5210.00 Complete l'kg.awn aborC, less t13rt DM 25 12 2.3 2511 .1150 RC 367 2.49L5 m,.lulatr 5150.00 DM K V:\. 16 Pi . 28R 28 1.2.5. 275 .1171) It(' 316 5.75 talus its f.11oo iug D M 33 28 7 510 .250 itt' 456 5,11)5 A COMPLETE LINE -MICROWAVE EQUIPMENT IN STOCK: components: D M 42 14 96 515 .1111 SCR 506 6.3OLN 1OCM. 3CM, 1.2CM. SENO FOR MICROWAVE Regulator Transform- 11130 .051) er: Ray' het. l X- 2/8 PE 55 9515_ Prl: 92 -136 CO ey, 1 í'11. Sec: 200,580 r, 12 25 500 .100 SCR 215 5.25L5 COAX CABLE PE 55 12 25 2511 1160 52 5.26 amps. 4000 t' rms test. RC 36 3.955 RG II'l', olui Imp artuns sI S .51 /11. PE 101 C 13/26 411)1 ItG 21 Filter Reactor' .150 by, 5 amps, 41100 y test, 12.6/ .135 S('R 515 5.255 1', twill man. 125 ultra lamp. aim/red-8 .50 /fl. Raytheon UN 9547. 6.3 81111 .020 110 20 U. 59 ohs) lmp pulse ral,le. Corona min. start- 9 41' 1.12 ing voltage 17 Transformer: l'ri: Ilul c - mps: See: 115 r KV S .50 /1t. BD AR 93 28 3.25 375 .150 RC 35,1", 70 ohm non, armored amps. Size: 12" Si 20" n 29". Net nt. approx. 210 4.955 S .50 /ft. 23350 2 1.75 .1173 lb:. Entire unit is 28.5 AI'S -1 3.505 enclosed In grey metal cabinet 35X0458 28 1.2 250 .060 3.595 sy it II utmmt lug facilities. New. as shown $99.50 ZA .0515 12/24 4/2 500 .051) 3,955 COAX CONNECTORS 8.19 pack 12 9.4 275 .110 Mark II 9.955 8318 $35 UG 21.0 $85 VOLTAGE REG. "Translat" Amertran Type "Rit" 2 Eta 5011 .1150 831ßP $35 UG 86'U ...... 5.95 'N -New. 1 Load. Input 90.130 r 50/60 CY Out out 115r 540.00 N-Like Ness'. 831AP $35 up 254'U $75 SELSYNS--115 r. GO cy Sizes TRANSTAT VOLTAGE REG. EVA. 0 Tao $7.75 pr. 831HHP $15 Il.3 -113 nti cr amedell UT 255/U $85 11111 amps male to type "5'' male adapter $1.25 ITE Circuit Breaker, 115 annps, 600e $15.00 STEP DOWN TRANSFORMER: l'ri: 140.220 Ill) volts GREAT THERMISTORS VARISTORS 60 eyriees_ 3 KVA. Sec. 115 r. 25011 volt Insulation. TUBE VALUES Size 12'x1_ sl" (5.95 ea,) 1.95 ea. 01-A 8 .45 530 11-1673:42 (Bead) PLATE TRANSFORMER: tari: 117 T. 60 cy, See. 17.060 1A3 .70 D-16,176 I. at 144 531 Ì5.00 D-170396 (Beadl I)-1711225 ma, with choke. Oil immersed. Size 26 "620 "x I B24 4.85 Ameriran ir. 532 3.95 D-1611382 (Button) 1/.1138087 $65.00 IH5 .55 559 4.00 Fil. Transformer: D-166226 1 Button) I)-11121 Prl: 220 r.a.r.. 60 ey: .05KVA. S I 14 .69 562 5 te t.. 31000 T test $90.00 D-I679I8 ITnba) It-1.1631 $24.50 1T4 .69 615 .89 FII. Trans. UX -6899. 60 Prl: 115 V. ey, See: ToTwo -V. 2C21 .69 703-A 7.00 5.5 Anus lefts. 29KV Test $24.50 2C22 .69 R.F. COILS Plate Transformer: 704-A .75 tart: 111,2:0 r.a.c., 50 -60 ry. See: 2121-A 25.00 705-A 3CP /16 -7, 11F mil Ass's', 30.411 e. for rerr FMR- 21.000 v, tao ma. 2.85 13V $120.00 2122 15.00 707-8 20.00 $ .59 2.126 15.M 14Y 100 2C539.5.1306/C3, Antenna Coil, 3.8 to 6.5 mc, iron 2127 15.09 715-B core for BC 1306 rm. 5 12.00 -117, .45 TRANSFORMERS 2131 25.00 7208Y 50.00 2220300 22.5 to 25 une. for Adcock antenna ekt of 2132 15.00 phasing box. For radio beacon equipment 720CV 25.00 3C3020, AC 163 $1.25 (All Primaries -115 V, 60 Cy.) 2138 25.00 721-A 3.60 RF Antenna coil, 3750 to 5850 ke. i'/0 BC 1 11.\ -5055: 525 ref 75 ma, 5 2139 25.00 r 2 atop. 6.5 c lì ainp. 723-A/B 7.75 S .35 2155 25.00 7248 I. 51.0. mil. 1800 to 2250 ke. $3.13 1.75 allias Idug-in, 9/o :5084: 500 yet 250 ma, 6.3 a 3131 25.00 724-D Xmtr 32 -RA 1.5 amp 4.95 2.50 51,0, $1.85 x5083: 6.3 r .6 amp et, apamp 1.85 2X2/879 .69 725-A 25.00 tail. 1980 to 1841) lie, p,o Collins Xnitr =5067: 6.3 vet 1 3A4 .65 amp, 6.3 vet 7 amp 2.75 726-A 10.00 1: s $1.85 r - 1:1' =5102 1080 rot 55 ma, 6.3 r 1.2 anti. 6.3 r 1.2 amp 3.45 3BPI 2.25 800 2.25 , o coll. bands A, B, C. IIetr BC 6.3 3C24 :5103: r 1 amp, 6.3 r 1 amp. 0:1 r 1 snip 2.35 .60 801-A 1.10 .45 :5104: 600 r 450 ma no et 4.95 3C30 ,70 804 9.95 I: .r I , 11V amp. coil. 9 -12 mc. Collin 325 :5108: 50 or 5 306 Xorn' 40 r 200 ma. ' 2.4 amp,, ú r 1.2 amp 2.50 .79 811 1.95 $1.75 3CP1/SI 261900- 4/1.3. IRE :5110: YOU r 42 ma, 390 r 1 42 ma, 55 r 125 ma, 3.50 814 4.95 amp coil. 1KN', 11. 850 -18,0(10 kc, 45 r 35 ma 3021-A 1.50 815 2.50 3.1 S1lrhrni by 3.755 3DPI 2C1528, 9. BFO coil $2.95 :5123: 6.3 vet 5 amp, 6.:1 Vet 1 amp 2.55 2.25 836 1.15 for Super Pro Rees -Ive,' $ .65 :5127 6.3 cot 3.2 amp. 6.3 vet l aft) 2.25 3EPI 2.95 837 1.9:1 3FP7 1.20 843 .59 XMTR InuUNIfN1GIIUN;TS 3GPI 3.50 860 15.00 BC 375: TT'-9 12.5 mc): Tl:-22 400 CYCLE TRANSFORMERS .79 861 40.00 I;150-650 krl; TI' 26 (:'ru.,n0 kel. }sell SBPI BC 610: $2.25 HV PLATE XFMR: Pri: 115 r. 400 ey See: KC. 1.20 874 1.95 Tl- 48 (2.5-3 tina; Tl' 53 I8-12 mc). 1::.5 5BP4 4.95 876 Each 3.3 11E :52.1652 $11.50 4.95 51,75 5C PI 3.75 889R BC 223 AX: TU 17 D- 163253: l'r1: Ill y, 400 rs. Soc: 2.5 v. 5 amp, 5 78.50 (2-3 me): TU 18 CI-1.5 me) 2 ins 5FP7 3.50 1005 30 Each ,,r 51P2 $1.95 PLATE XFMR: I1 1613 .95 Prl: 115 r. 400 er. See: 98mí r 5130 6000 r C` 32 ma de 39.50 1619 .21 BC 1287 XMTR -RCVR :12033. $12.50 6AC7 1.00 1624 XNITR consists Plate Xfmr: Pri: 115 r. 800 ey. See: 4.500 et. .85 of tuned line pulse oseillalor on 154.186 259 ma. 6AK5 .69 1629 .35 l'an he modified lu operate on $4.50 6C4 or. stork lee or CVC, and put KS 9445. Par. Xfmr: Pri: 115 r. .58 1961 5.00 on the armateur 2 -meter hand. RCVS,, 400-2100 es. Sty: 502 6G 2.00 het wi.lh is it super - ' t . 120 Ma. it 8012 3.95 2 stages of RE and 5 top: 5 2 tap 616 stagger -tuned I.F. stages PLATE XFMR; 115 1.00 9002 .65 111 tors. Plenty Of omits in -hassis Pri: r. 40 0-2401) er. See: 45nf3. 6K7 .55 for asiditional com- 6 ma 9004 .47 ponents and changes. Csed but in excellent condition. :7143. tari: 115 See: 6L6GA 1.00 9006 .47 100 q'. 6.3 V. 7 amp. 3.3 V. 6,5 6SC7 l'ntnplet° 527.50 amp: 6.3 v. 1.3 amp. .70 CEG 72 1.95 with p,ts er supply for operation from KS 9584. Pri: 52.50 6SL7 1.00 EF 50 .79 rra eyele, 115 r, 100 ey. See: 5000 r. 2911 ma 6V6GT $42.56 111 imp. .79 E-1148 .75 PLATE $15.00 7C4 1.00 F-127 20.00 XFMR: Pri: 115 v. 380.26110 elw. See: 22nu c 350 va 7E5 1.00 FC 258A 165.00 AND PASS FILTER SS 7E6 ,72 FC 271 :70473. PLATE 40.00 peaked 1 a( 700 XFMR: Pri: 115 T, 400 ey. See: 1150 -0- 11.'5o3í Minable). 40 IOY .60 GL 562 75.00 Rich-to-high impedance.n ma i 1 iifle l i into phone $1.75 12A6 .35 GL 623 75.00 mnnrt or r ter. fits an 01(51. Sew, 12GP7 14.95 GL 697 75.00 whit circuit a diagram $2.25 12K8Y .65 ML 100 60.00 INVERTERS 12SF7 PE 206 -A: Mont: ,49 OK 59 45.00 28 l'UC o :18 ants. Output: 80 volts 12SR7 .72 0K 60 45.00 IS .am soil-amps. gal ryeles. Dynamic mike and Leland. Nets, complete 15R 1.40 61 headset \ high ua with nelnsed relay, 0K 55.00 emeient unit. used qliU'. niter, instruction Amok $12.50 2807 .75 DK 62 in B -19 tant \tat rs. Mike and PE 218: Input: 25 -28 VDC 92 55.00 "immOlete phones r amps Output: 115 30 (Spie) .70 RCA 932' .65 $2.75 ohs (n` 1500 rolt -amps. :160 It -15 headsets: 8000 -500 cycles. Poor physical 35L6 ,89 VR 91 1.00 ohms impedanee. rubber eushiam. Intl good running Croises is1111 O' condition $15.00 3525 .66 VR 130 1.25 cord andnd plug PI. 55 New 51.95 HEADBANDS: 1111.1. 45 (Spec) ,59 'VR 135 1.25 1L11-4. 1(It -30. Here $ 25 ea. POWER 50L6 .79 VR 137 1.25 CHOKES 39'44 .49 VR 150.30 .75 MICROPHONE T`EMENTSII Siring. Choke: 4.5 to 6 by: .2 lo I snip. 35'51 carbon transmitter element 113 510.95 .72 VU 120 1.00 L, TSIS -E. hy, 2 inni' $1.45 l'y. .33 amp 211 .75 VU '101.1 -A 8.5 hy, 7.50 134 1.00 S .75 ea. 125 ma 1.50 Dual 2.5 hy. 130 227A 3.85 Element for nirrupliono T -2 I. 30 25 by, nla 1.25 WL532 4.75 dun resistance, $ .95 ea. .l lis'. 12 hnp. 46 225 8.80 WN 150 3.00 6 hy, 150 ma 1.50 ohms 16.00 250R 7.95 WT 260 INSTRUCTION Dual 7 5.00 MANUALS by, 75 ma, I l Dual .5 I,;, 361) 268-A 20.00 }With \BO 312, BC 342 hy, 60 ma .95 Cavity: Cavity ma 1.65 hy. 40 ma 355-A 19.50 Only-$5.00 Sl'II 281 $1.52 Dual 2 hy. 31_ $1.25 Mark I1 100 irr .75 Muts 417A 22.50 'Photocell. '%A l7(IPt .75 $ .75 .116 hy, .15 '. 6- :Wit 5118 1.00 amp 4.50 hy. t hC 612 1.00 .01 10', 2.5 atop 75 ,'X -3.2 .75 1.50 Dual l'_ IT ms.. 2 45 VIBRATORS SPECIALS' TR 1210, 12 ide, 5 pin 51.20 Sel. Reetiher Input: 115 var. 60 eye. OAK V-66671. Oul: 120 vale, 1.66 21 -32 Vic. 7 pin 1.15 EE -89A REPEATER ups. Full \Vase Bridge. F. T. & II. :1)1611 51aí. Tspe 1:.5310, 12 59.95 cor, 5 pin 1. Fart rid, range Sel. Rectifier Input: 30 vac, 6O CY. 51:d. Type . . amp. 06211.1. Of hold I, Out: 21 roc, 12 vile, 4 1110 1.15 as t:i -:s ills In 25 toiles. ohm'. Full wave., bridge, GE :31'10 Ì.50 Itad iaait T1í2, 6 r. M. 6 -Plut im,'ned in a Ill, I, special 1.40 Ness'. o11ó spire 1111E -I, EC11O RANGING REC'EIVEI : Mfrs. inbe and i nslrnel mon taanoII. h'.. DRIVER m- filial. it les In all tapes available. standard type b:drtr ire. .... _...... 521..50 dacater SaOUI signal transmission and reception huit U it II S'vngu of 200 to 600 yds. and freq. rango of l0 lu 27 k HAND GENERATORS ew, with batten' bus. less proloctor $85.00 GN 35 Or: :e0 SONAR SOUND DETECTOR: r. Oita nis, 8 s', 2.5 anus less Underwater de(ertor with hand era ,,I udcrolihwo $ BEAM MECHANISM units encased in rubber sheath. \Girl UN 15: (1 11r. ,110 III t. 100 ma. 6 T. 3 amt. less ä3m1 Th.: m,.1 t +rwer(,nl. a- $12.50 crank , tly offered for MN52H Azimuth control box for aircraft mho Coln - $5.50 Iwan rotation. fÌÓ: I ratio Inass $1.25 turned by 24 ode Ti,,,,,' t hat ARC -3 Airborne adio series replacement relays. Types wit 12 vac. rmryele type . 's - ' .51, '5313. 57.528. 55531, 55585, 55458, ea, CROSS POINTER INDICATOR n',rrocket oofor ea.' ewm tEne o 5.60 Fisse holder. GI' type EL-1 rn its In witshaft. 914.1.. ti t .,- r X $1.00 l 111 Am Recording 50 h monistlin g faei rtyne Film ft. lengths bulb Moans' tr nght it I 11.111111. biUnler,I,ttf ngdrte .. "'seal $ 35 ea. In tray. L. r to 12 ear step 5,.,,' , Modulation Trans. ARC :9460. 807's Plates used in 11., farmer push pull tu stn so 111.1 st 111 is' r6 2 007's In peralle' $1.65 nennt. Nerv $2.50

All merchandise guaranteed. Mail orders promptly filled. All prices, F.O.R. New York City. 131 -C. Send Money Order or Check. Shipping charges sent C.O.D. PHONE Liberty St. DIGBY New York 7, N.Y. COMMUNICATIONS EQUIPMENT CO. 9 -4124

RADIO -ELECTRONICS for

www.americanradiohistory.com i!

7ñousandsSwlíMpy,

Thousands of Radio Service Technicians are right! They've found the way to quicker, easier, more profitable servicing. Join these thousands of successful money- making Servicemen who have switched to PHOTOFACT Service Data. Learn for yourself how this accurate, easy -to -use, practical data saves you time, makes your 100% work easier, helps you earn more. PHOTOFACT gives you The Amazing useful service data -every photograph, every diagram, every hit of it to to information helps you do a complete job. You owe yourself Radio Industry RED BOOK to PHOTOFACT. There'll he a big difference in the time you switch Parts Buyer's Guide save and the bigger profits you'll earn every single working day. Replacement NOW-stop wasteful hunting through doz- ens of incomplete parts manuals. The RED PHOTOFACT VOLUMES BOOK tells you what you need to know The Preferred Service Data about replacement parts for approximately 17,000 sets made from 1938 to 1948. In- rcceiser Sers lee Data right 'Bring your file of pust-s'ar complete, accurate listings of all 9 Here's the most accurate and complete cludes up to July, 1948! components just radio data ever compiled- preferred and used daily by major replacement -not thousands of Radio Service Technicians. Includes: Ex- one. Lists correct replacement parts made views clusive Standard Notation Schematics; photo by 17 leading manufacturers -not just one. keyed to parts lists and alignment data; complete parts proper alignment, stage gain. Covers original parts numbers, listings and proper replacements; instal- circuit voltage and resistance analysis; coil resistances; replacement numbers and valuable changer service data, etc. Order Volume 4 today notes on: Capacitors, Transformers, record only lation -keep your Photo(act library up -to- date -it's the Controls, IF Coils (including Peak Fre- Service Data that meets your actual needs! Radio quencies), Speakers, Vibrators, Phono- 1948 to July 1, 1948 Vol. 4. Covers models from Jan. 1, Cartridges. Plus -Tube and Dial Light Vol. 3. Covers models from July I, 1947 to Jan. I, 1948 Your lu data for each receiver, and Battery re- $1839 Vol. 2. Covers models from Jan. 1. 1947 to July 1, 1947 Each Volume, placement data. Get all the right answers In Deluxe Binder Vol. 1. Covers all post -war models up to Jan. 1, 1947 in the RED BOOK. 440 pages, $395 8'/s x 11; sewed binding. ONLY., 1947 Record Changer Manual Nothing like it! Complete, accurate FREE Cumulative index data on over 40 post -war models. Exclusive expploded views, photos Send for the FREE Cumulative Index to from all anales. Gives full change PHOTOFACT Folders covering id/post- cycle data, information on adjust- war receivers up to the present. You'll hints and kinks, com- want this valuable reference guide to ments, service and plete parts lists. PLUS-for the first the Radio Service Data preferred time complete data on leading used by thousands. Helps you find the Wire,- Ribbon, Tape and Paper Disc Foldersour Get this Recorders! 400 pages; hard cover; Jobber orQwri elf for it today. opens flat. Order now! s495 ONLY BOOST YOUR EARNING POWER! Receiver Tube Placement Guide Subscribe Regularly to Mail This Order Fern where to replace each to HOWARD W. SAMS Si CO., INC. Shows you exactly PHOTOFACT Folder Sets St, Indianapolis 7, Indiane tube in 5500 radio models, covering 2924 E. Washington Each tube lay. Here's the most accurate and com- 1938 to 1947 receivers. ever compiled by a clear, accurate plete Radio Data - for S enclosed. out is illustrated two sets per My (check) (money order) diagram. Saves time -eliminates risky issued regularly 192 pages, com. month. Keeps you right up- to -the- BOOK. $3.95 per copy hit- andmiss methods. receiver pro- Send the RED plc rely indexed. $125 minute on all current duction. Packed with extra help - Send PHOTOFACT Volumes in DeLuxe Binder: ONLY data on Auto- full PHOTOFACT 4. Vol. 3. 2. ['Vol. 1 (S18.39 each ). matic Record Changers -com- Vol Vol. munications receivers -amplifier, Automatic Record Changer Manual, $3.95. Dial Cord Stringing Guide -plus new PHOTOFACT Tele- uniform Tube Placement Guide, $1.25. The hook that shows you the one right vision Folders -exclusive, Here, in one coverage of popular Television Dial Cord Stringing Guide, $1.00. way to string a dial cord. best by ac- handy pocket -sized book, are all avail. Models, data proved Send FREE Photofact Cumulative Index. over tual service clinic experience. Sub- able dial cord diagrams covering today. for 2300 receivers, 1938 through 1946. scribe at your Jobber regular monthly issues. $150 Makes dial cord restringing 00 Name lobs quick and simple. ONLY.. ;1 PER SET, ONLY

Address 8 CO., INC. HOWARD W. SAMS City Starr INDIANAPOLIS 7, INDIANA

OCTOBER, 1 9 4 8

www.americanradiohistory.com Ì'/

Are you Building a Business ... or Burning your Bridges?

Would you patronize a dentist who filled your teeth with plaster of Paris?

Would you trust your children's lives to a doctor who prescribed cut -rate pills?

Your business, too, is built on cus- pared with your investment in your tomer confidence! And your reputa- reputation. tion is too valuable to risk with That's why we say -YOUR CUS- inferior or unknown products. The TOMERS AND YOUR REPUTA- cost of the parts you use in the aver- TION CAN AFFORD ONLY THE age repair job is insignificant corn- BEST! ... SPRAGUE.

KOOLOHM CAPACITORS pR.RouE RESISTORS

U. S. rai. Ua. SPRAGUE PRODUCTS COMPANY, North Adams, Mass, JOBBING DISTRIBUTING ORGANIZATION fOR PRODUCTS OF SPRAGUE ELECTRIC CO.

SPRAGUE h Reap ::w4Y0u 're Rio le" and The superiority of the new Sprague type TM High- Tempera. ture Molded Paper Capacitors didn't happen by chance. You can use this better unit in your work today only because of more than four years of intensive research and one of the largest retooling programs in Sprague's history. That's why we can say "The First Truly Practical Molded Paper Tubulars are Sprague TM's" -and it is also the reason you can use them on any job with confidence and pride. Highly Heat Resistant Conservatively Rated Moisture Resistant Small in Size Non -inflammable Mechanically Rugged Completely Insulated

RADIO -ELECTRONICS for

www.americanradiohistory.com Editorial I 21 RADIO CRAFT Becomes After 20 years. RADIO ILAI11O- CRAFT takes clew HUMP r:l.n: tBoNKS By HUGO GERNSBACK

were asked to vote for the one they FOR some time past it has been apparent that the titles. Our readers and which appealed most to them. On the blank title of RADIO -CRAFT no longer reflects the editorial preferred finally was a space for first, second, and third choice. Readers content of the magazine. When the publishers was was to be made, it was felt were asked also to suggest a title of their own which decided that a change -three titles listed. that, since the magazine first and last belongs to its not included in the list of twenty readers, if any change was to be made they should have The first voting blanks were received on March 29. The a say in any contemplated new title. final ones on April 26. The first day's votes totalled 77G, ELECTRONICS. Subsequent re- Accordingly, a letter was addressed to a representa- the choice being RADIO- scattered through the turns did not affect this choice in any particular, RADIO - tive group of RADIO -CRAFT readers first day until Union. The following is an ELECTRONICS keeping the lead from the forty -eight states of the the twenty - letter which the writer addressed to the final ballot was received. Only seven of excerpt from that runners up to RADIO -ELEC- subscribers last March: three suggested titles were TRONICS. These follow : 2. RADIO SCIENCE, 3. RADIO - "When in 1929 I started the magazine, the name TRONICS, 4. RADIONICS, 5. RADIOVISION, 6. RADIO WORLD, RADIO -CRAFT was a 'natural.' At that period, radio was and 7. RADIOTELEVISION. amateur radio, etc. mostly constructional set building, The vote for first choice came out as 58.8% in favor have changed -so -a craft, in other words. But times of RADIO -ELECTRONICS. The balance was broken up and has radio and so has RADIO- CRAFT. scattered among the seven runner -up titles. "The name today is a misnomer. On the cover since of the returns were most enthusi- Its A large percentage 1943 we print our slogan: 'Radio- Electronics in All astic about the title RADIO- ELECTRONICS; again these let- Phases,' and we wish to keep up with that definition. ters out-pulled all other recommendations. the magazine Indeed, the have great future plans for - may we take the occasion to express our more departments, fully At this point more pages, color pages, many most sincere thanks to that great legion of our readers, to justify our slogan. who took the trouble to vote for the new title, as well as "But the present name does not reflect the slogan. the hundreds who wrote long, constructive letters and Many technical readers, engineers, the radio industry, their reasons for voting their particular title. advertisers, new readers -all have the impression that You will no doubt have noted that the change from or a set - RADIO -CRAFT is still only a 'How -to- make -it', RADIO-CRAFT' to RADIO -ELECTRONICS was not sudden. It builder's magazine, because the title says so! Hence the took four months to make the change. Beginning with absolute necessity for change in name. the July issue the words "RADIO -ELECTRONICS" were fear then on "'Well,' you may ask, 'why don't we go ahead and tm'ed underneath the old masthead, which from The answer is: We don't know which name kept increasing in emphasis while the old title RADIO - change it issue the to choose! We have a list of names, many of which CRAFT kept shrinking until with the present title RADIO - sound good to us -but how do they sound to you, the change is complete. We believe that the new of the magazine reader? We are too close to the picture to judge, and ELECTRONICS expresses the contents title. besides we build the magazine, but we are not its read- more accurately titan could any other ers. No magazine staff ever is competent to take a de- Radio -Electronics is a tremendous force in our pres- tached view of its product. . ent civilization. Yet, the radio- electronic age has only be- No man can tell "So we come to you and ask for your help in choosing gun-it is still in its merest infancy. discoveries still to be a new name for your magazine -a name that will fit the wonders still ahead and the the magazine better than the present one. made in the radio -electronics field. will to grow "We here at RADIO -CRAFT feel that we do not have RADIO- ELECTRONICS magazine continue to change the name of your magazine without apace with the advance of its art-I,: will chronicle from the right over the first asking the advice of a representative cross section month to month the latest advances from all bring these ad- of our readers, particularly our older readers." world as fast as the printed word can a sheet listing twenty -three vances to you. . To the letter was attached OCTOBER, 194E

www.americanradiohistory.com 221 AIIiI1ill Ultra Loud Speaker Is Auto - Truck Size

U ills a flood ampli- fier. this unit can be heard two miles

By PAUL H. THOMSEN

sary for added strength. Considerable care was taken to make sure each shingle nail was driven into solid wood, for a loose nail might cause rattles or flexing. To avoid chipping, nails were never driven in near the edge of the Masonite. One of the first and most important requirements of this mobile loudspeaker is that the roof of the trailer be abso- lutely waterproof. Any rotten lumber on the trailer must be replaced. If the roof leaks, it won't be long before boards will become loose and distorted; nails will not hold fast in rotten lumber. Clear the trailer of all cabinets, par- titions, and doors. Leave the housing over the wheel wells and leave the heat- er if one is provided and if it does not Occupying the entire trailer front end, this horn is limited only by the power feeding it. fall within the projector area. The following quantities of clear white pine will be needed to build the THE loud speaker is the most inef- 6,000 cycles since the projectors have mobile loudspeaker: ficient unit of a public address sys- exponential characteristics. Quantity Length Size tem. It is possible, however, to de- The next problem was to select some (Feet) sign a more efficient loud speaker type of construction which would not ex- 1 12 2 x 4 by using a suitable air -coupling system ceed the weight- carrying limit of the 1 8 1 x 6 consisting of a horn or baffle. trailer. The designer chose the air- 1 12 1 x 12 The complete loud speaker is composed plane -rib structural method of obtain- 60 8 1 x of (a) the diaphragm, 4 (b) the driving ing rigidity with minimum weight. The 10 10 1 x 4 unit and (c) the section which is least rib structure had to be of sufficient considered by most PA men, the air - strength to prevent vibration at its own coupling system. resonant frequency. For mobile operation the weight and Tests indicated that '- inch -thick physical size of a loud speaker are very tempered. Masonite would be satisfac- important. All these factors affecting tory when reinforced with ribbing over the final results were considered in the its entire length. Clear white pine lum- construction of this mobile loud speaker ber was selected for the ribbing because system, designed and built by the writer. of its low weight and because it is easy There is a practical limit for ease of to work into shape. portability to the size of loud speaker The problem of securing these white projectors. In this system the size was pine ribs in place was solved by using limited to the tow end and right side of shingle nails, which, with the proper an ElCar 18-foot house trailer, as shown amount of lumber, give sufficient above. The lower frequency limit is strength and insure maintenance of the TOP VIER approximately FILLIPS ,usus rower 35 cycles; excellent high - shape of the projectors. Wood screws FA/TI- SU-SPEAKER UNIT IIOURTIRL RACK frequency projection is obtained up to and bolts were used only where neces- Fig. I -Floor plan of triple speaker system. RADIO -ELECTRONICS for

www.americanradiohistory.com Audio 23

the wooden mounting the floor and left wall of the trailer. Material below will also be required: Fig. 2 shows should be com- for all six loud speakers. Ea, h pair Then all floor markings 10 sheets r -inch tempered Masonite, rack of speakers is mounted on a piece of pleted. 4 x 10 feet clearly that the ribs are long clear white pine lumber cut to the di- Fig. 1 shows 7,000 shingle nails, about 1 inch closer near the speaker mounting rack No. 10 blued wood mensions shown in Fig. 3. These three 3 dozen 1%-inch the two than at the trailer walls. This is because screws pieces are then mounted on pine shown in Fig. 4. the diaphragm of the speaker places pieces of white in this area Prior to their installation within the more pressure on the walls trailer, all these pieces are screwed to- of the projector. The ribbing is positioned every 6 inches up to the 30 -inch rib. The ribbing in this area may be 2 x 2's or 1 x 4's sides facing the projector 5.ve. with the thin wall. Seldom were more than two or three nails used to hold each of these members in place. However, it is most important that each nail be of sufficient MOLES FOR strength. At a.wre000 SCADS; IS' size and length to insure SPACED 2 "APART this stage of construction each member or vertical rib should withstand a hori- zontal pull of at least 100 lbs. without showing a tendency to break loose. The vertical and top ribs are essen- tially the same, but it was desirable to Fig. 2 -How the six speakers are mounted. use a separation of 6 inches for the rib- bing on the bottom surfaces. This in- 6 blued wood 1 gross % -inch No. sured adequate strength for supporting screws

12 12 square yards of canvas CAIN INCHES i6- 2 5/e' 6 Rola type G12 or equivalent 12 -inch, 20 loudspeaker units eA1124IECEs -watt ore e' 140. 1 quart quick drying enamel 5 lbs. window putty 1 Fig. 4- Speaker board top and bottom pieces. wall of the trailer speaker boards. Remove the inner Fig. 3- Detail of one of the builder during the carefully within the projector area and several boys and the study of all bracing so gether for maximum strength. The six construction and painting. make a careful of this mobile loud- that all of it which can be used will be speaker -cone openings are covered with The designer ± on a screening to prevent speaker found that a tolerance of left in position. Park the trailer ordinary window a dis- wall of the from damaging the cones. This 1/32 inch was permissilèle up to level plane, and remove the anything loud speak- which the projectors are screening is tacked on. tance of 18 inches from the trailer through mounting board. This could be in- to extend. Use a saw and do not cut into It is suggested that you do not install er creased to r/s inch at 36 inches. Where the canvas top. See Fig. 1 for the floor the speaker units until you have com- re- carpenter work on the possible, a tolerance r/s inch was plan and the size of the opening pleted all the Beyond provide vertical sup- entire installation. However, the speak- held at 48 inches and CO inches. quired. Be sure to contour was modified as ports for the roof of the trailer. This er mounting rack may be screwed to this limit the will give you easy access to the section of the trailer where you will do most of your work. Point X in Fig. 1 is the point where you should drive a nail from which all measurements should be made. With paint, mark all the dimensions on the floor exactly to scale. The speaker -unit mounting rack should be outlined on the floor and then the two outer walls of the projector. These dimensions are fixed and can be used as the working edges. Next draw the floor lines of the inner vertical walls (A and B) of the two out- side projectors. Remember that the di- mensions given are the final values after the r -inch Masonite has been added over the ribbed structure. The openings for the speaker cones are 10 inches. The contours of the fillers A and B should be roughly drawn, using the approximate maximum filler thickness of 71/4 inches as a starter. A line should he drawn from Point X to the right front corner of the trailer. This line will be the center line for the center projector. From this line all points can be found for the left and right vertical walls of the center projec- tor. Two 2 x 4 vertical roof supports should now be installed to carry the full weight of the roof of the trailer at this construction details and framing excellently. corner. Fig. 5 -This top view of the horns shows the OCTOBER, 1948

www.americanradiohistory.com Audio 24 I-

rapidly as the Masonite would permit upper and lower surfaces will fall. How- The space between without cracking to fill the opening in the pairs of loud ever, the horizontal center line on each speaker units is the trailer, as shown in the photographs. side effectively removed, in of the three projectors should be so far as the load on the diaphragm Remem.rer that the sound pressure on drawn in first is the surfaces to give a working line. concerned, by placing a filler of two of the projector is great- Since you have now covered the est near the loud hori- sheets of tempered Masonite between speaker mounting zontal center lines on all of the vertical two or, preferably, board. For that reason extreme care was ribbing, three 11 -inch wedges it becomes necessary to draw made 1 taken to fit the pieces properly. of -inch clear white pine and then This this line on the inside surfaces of the nailing all the pieces together three projectors. and to From this line draw a 1 x 10 -inch crosspiece 2 inches wide, as again the upper and lower surface lines shown in Fig. 7. on the tempered Masonite. Make them Previously it was clear. pointed out that a Now proceed to nail, above the up- tolerance of only ± 1/32 inch was per line and per- below the lower line, a 1 x 4 missible. It is equally important to seal white pine side mounting rail. If, due the corners of the projector to the near the curvature of the side walls, you diaphragm of the loud speaker where cannot fit the 1 x 4 close to the side wall there are L great pressures. Regular win- CONES 'ALL.c M1cINO BOARD through its entire length, cut it into dow putty or plastic wood may be used DiM.INiNCntS t01AL (MUNCH FROM shorter pieces SOURCE (see Fig. 5). However, when the Masonite is dry. be sure that each piece is securely The last job is installing the loud Fig. 6- Sidewall plan of the projector horns. nailed to the vertical ribbing. It will be speakers. All the voice coils are con- necessary to curve the lower close fitting requires well -seasoned edge of nected in parallel, and the fields are so wood the upper mounting rail and the connected and careful nailing. Clamps were used upper that all voice coils operate during edge of the lower mounting rail to keep in phase. the nailing of the vertical ribs. within the tolerances It was found very convenient specified. The amplifier equipment was mounted to use a in the rear piece of steel about 1 of the trailer. Bear in mind x 2 x 5 inches as the a back stop when nailing into sections importance of balancing the weight of ribbing that appeared to on the trailer for ease of handling and be springy. greater safety. 1 The gasoline- driven gen- Fitting the Mosonite bin' erator was placed in rear center to re- .1 After the vertical ribbing duce the weight placed on the tow ball is finished, 11' of the car. The the vertical sheets of 1,k -inch tempered operating table, pream- Fig 7-Construction detail of filler wedges. plifier and equalizer Masonite may be fitted in place. For con- rack and turntable venience were placed along one side of the trail- in handling, the pieces nearest To the upper and lower side mounting er, with the loud speaker mounting board the main amplifier on the other should rails are toe -nailed horizontal 1 x 4 side. be not more than 30 inches long. The white pine supports. portion A minimum of 4 The photograph below for the vertical panel contact- nails was used at the ends of shows the audio ing the loud the pieces. equipment within the trailer speaker mounting board The inner edges of the pieces were as viewed should be screwed on. Use through the rear window. The 4- channel s, -inch No. 6 shaped to follow the contours of the top preamplifier, blued wood screws for additional and bottom surfaces. the Tonalizer or equalizer, strength. The screws are placed in clear- the 8 -day clock, turntable (recorder) all As in the case of the vertical panels, are in ance holes spaced about 1 inch back of the microphone which is apart. small sheets of Masonite were shaped located The vertical streets of Masonite are at to fit on the operating table. The large in place to form the upper and power amplifier least 4 inches above and below the esti- lower surfaces of the projectors. is located on the left. mated upper and To pre- The monitor loud speaker can lower horizontal sur- vent rain from running down the top, be seen faces of the projector (see Fig. in the upper left partition above one of 6). Pen- a 2 -inch strip of canvas is hung over the the projectors. cil marks should be placed on the verti- upper edge of the outer wall cal ribbing of the trail- approximately where the er. Amplifier equipment The power amplifier for this PA sys- tem should be able to deliver at least 100 watts of audio frequency over the frequency range of 30 to 6,000 cycles with relatively low total harmonic dis- tortion. Tests indicate that distortion should be less than 5',- at full power output. The equipment illustrated is capable of delivering 230 watts, class AB operation. The full significance of the expression "Mobile Loudspeaker" will strike you when you get your first stationary PA job. Then and only then will you realize you need about 500 feet of microphone cable to permit placement of this speak- er, not up on a telephone pole, but out in the lot several hundred feet away from the gathering. The relatively high projector efficiency along with good fre- quency response will insure not only adequate coverage of the immediate gathering but of several complete blocks. The designer would like to suggest a 500-ohm T -pad on a 75 -foot cable as a remote volume control. This permits anyone to monitor the volume from out- side the walls of the trailer, more or less Inside the truck. The 230 -watt amplifier is at left, the turntable and preamps at right. as it is heard by the audience. RADIO -ELECTRONICS for

www.americanradiohistory.com Audio

i. - - 1,4 " 7. 4- ""4: .146 et ,;41,,*.

-.

Fc

This cardioid, Turner Model 77, has a frontto-rear discrimination of IS db. the This is Astatic's Velvet Voice crystal 640AA con- unit, evadable as model 200 with flat of Western Electris response or 241 mainly for speech work. denser Mike

The Stephens C-I is a new condenser mic- rophone that phase-modulates a crystal oscillator. Response extends from one- half cycle in 24 hours upward to 15 kc.

.

Amperites R90 ribbon will not boom or Astatic's Cardinal (crystal or dynamic) .blast. Its range is 40 to 14.000 cycles. ,or be lifted from stand for hand use

44111111111, ,

6. a*

O. s Ill

The new RCA Bantam velocity microphone shown beside its full-size fore-runner at left has the same output level and an 80 to 8,000-cycle frequency response. The exploded view above shows how the magnet is an integral part of the case.

OCTOBER, 1948

www.americanradiohistory.com 26 Audio lnleresling Amplifiers

The Bell Model 2122 at left has three phono Inputs. Two for magnetic units have the required bass equalization. The Fisher amplifier fright) has the Scott Dynamic Noise Suppressor. Electron -ray tubes show the action.

RCA M1.4297 voltage' Knight 20 -watt amplifier is made up of unit b- low has phono input e group of one -chan only, audio ;s flat nel subassembly units. through- out thn whop range.

";; . i ;, ' RCA's portable SR.1SA system in '.4 dudes a 15 -watt amplifier with I microphone input and 2 channels for phonograph pickups. The car- rying case for the amplifier has mike, stand, and cable. A loud- speaker is mounted in case cover.

Lafayette - Concord Bi <,. A 2.131 ,s built especially for high. fidelity hcm- , wo offh. use. FM amplifier, e,

The picture above shoe. Wud mphfier with both power chassis installed- Op, in parallel, they furnish 90

RADIO -ELECTRONICS for

www.americanradiohistory.com Audio 27 A convenient table lists 10 important features of 18 modern amplifiers. The text explains how to use the ratings.

increase gives vital not fidelity. Most manufacturers do not Bass attenuation will usually THE accompanying table and understandability of statistics on a representative group give intermodulation ratings, so they the clarity were from the table. In general, speech. of commercially available ampli- omitted have variable are an amplifier with low harmonic dis- All amplifiers which fiers. A number of varied types controls should have presented, phonograph amplifiers for tortion is likely to have comparatively equalizers or tone some mark on each equalizer dial to in- the home, high -power PA units, and little intermodulation. re- an amplifier for PA work, dicate the proper setting for flat two - chassis preamplifier- power -ampli- In choosing most man- the frequency response and distortion sponse. Information from the fier combinations. not mention this point selecting an amplifier, the purpose may or may not be important. Where ufacturers did In some of the amplifiers do have dots it is to be used should be the unit is to be used only for voice it but for which zero marks to indicate the flat set- kept in mind. That will insure that the is uneconomical to purchase a high - or quality of the unit chosen is high enough quality system. The same may hold true and -what can be just as important - when it is to be used only for back- that extra money is not spent for a ground music, as in a restaurant or higher -quality amplifier than necessary. hotel lobby. Volume controls are often For phonographs in homes the pickup turned down in these locations so that a.v.c. to be used (and the loudspeaker) should the music is not too obtrusive, or be considered. If an inexpensive crystal may be used. is the customer's choice or if he intends Where live music is to be amplified to buy a limited -range speaker, there high fidelity is usually demanded. Here a is little point in paying for an amplifier distortionless reproduction through flat to 20,000 cycles. If, on the other flat amplifier is much preferred. But hand, the buyer is a discriminating lis- the loudspeakers in use may be a limit- tener who is willing to spend enough ing factor, so much so that it may not money to get a wide -range dual loud- pay to spend any extra money necessary The Brook amplifier features separate preamp. magnetic for response beyond 8,000 or 10,000 cy- speaker system and a modern point is not marked, not saddle himself cles. On the whole, a serviceman who tings. When this pickup, he should run in the .shop, using an with an amplifier that droops at the rents PA systems to various organiza- a frequency have a high -quality audio oscillator and an output meter high end of the audio band. Pay atten- tions will do well to resistor, ratings, unit, since quality will be needed in connected across a dummy load tion to the harmonic distortion owner of the unit to though moderate amounts of many applications. will enable the too. Even his own indicators. Spots of cod- distortion may not be obvious to the ear, Because of the well -deserved popu- make modern magnetic pickups, ing paint or red nail polish are con- auditory fatigue, a condition which larity of easily in be many of the amplifiers listed have input venient, and may be purchased makes the higher tones appear to needed. a period channels especially designed for them. the very small quantities unpleasant, will set in after of amplifiers have par- is worth These inputs have a higher gain than Several the of listening. No exact figure interesting features. In the in judging how much auditory normal phono channels and some have ticularly anything past most smaller amplifiers (with out- fatigue will occur because different per- the necessary 6 -db -per- octave bass boost Some of the units which put power under 25 watts) were de- sons will he affected differently. In any equalization. were not use an have magnetic pickup inputs are the signed for small PA jobs and case, for high -quality results, Recently, much more at- amplifier with the lowest possible distor- Bell 2122, Altex A -323B, Newcomb of high quality. HLP -14, Fisher, Concord 2 -131, and the tention has been paid to the phonograph tion rating. Amplifiers with living -room- Harmonic distortion is a percentage Masco MA -25EX. Almost all of these enthusiast. fixed bass equalization or size outputs are being made to the high- figure which indicates how much har- have either Brook a variable controls. est standards. One of these is the monic energy will be developed when supply and power pure sine -wave tone is fed into the am- The table indicates what type of 10C3. The power results from non- equalization control is available with amplifier are on one chassis which may plifier. The distortion away in a cabinet or a closet. linearities such as tubes which do not each amplifier. The buyer of a unit for be hidden portion almost any use other than in a broad- The smaller unit contains the preampli- operate entirely on the straight controls. It is attractively of curves, grid recti- casting station will do well to look for fiers and all their characteristic to be placed at some convenient fication, and unsymmetrical operation Kass and treble boost and cut controls. designed dis- While a permanent flat response might spot in the living room. The low -im- of push -pull stages. Some harmonic can present, largely be- appear to be most desirable for high pedance line between the two units tortion is always reasonable length: Incidental- cause nothing in life is ever perfect. fidelity, there is no denying that most be of any not ly, intermodulation ratings are given A total of 5r; is usually defined as the microphones and loudspeakers are high -fidelity amplifiers, linear. In addition, the room in which on the Brook amplifier. The maker's maximum for show 1.69'4 at the full but lower values are preferred. the sound is heard may be unsuitable. data sheets only of dis- If, for instance, it has smooth unbroken 30 -watt output, an extremely low figure. Intermodulation is another type Brook's from nonlinearities. It oc- walls, high tones will bounce around and Whether or not this is due to tortion arising of only low -mu triodes curs when two input sine waves produce may be very unpleasant to the ear. The policy using of beat frequencies. only reasonable thing to do is to attenu- throughout is a matter to be thrashed sum and difference the two schools who hold Beats will not be produced unless there ate the highs. High- frequency cut also out between the amplifier. If they helps to reduce acoustic feedback and is (a) that all multigrid tubes distort and is nonlinearity in tubes need not dis- are, the effect is one of creating new necessary in matching the curves of (b) that multigrid itself and most records for playback. tort. tones within the amplifier most respected high -fidel- them to the speaker along with Bass boost is necessary too, in play- One of the feeding is the Altec Lansing the original sounds. This is certainly ing records with a magnetic pickup. ity amplifiers OCTOBER, 19413

www.americanradiohistory.com 281

A -323B. Though the circuit is fairly built -in volume expanders. The Knight switch, as does the Newcomb HLP -14. standard, Altec claims that its special 20 -watt unit is one of these. The maker output transformers This is in additión to variable tone con- make a good deal states that, contrary to the practice in trols. The switch has positions for rec- of the difference. The unit is being of- most amplifiers, the degree of expansion ords with various fered now as amounts of surface a kit which includes the in the Knight is not affected by the set- noise. No curves are given but presum- power and output transformers, the ting of the volume control. This may be equalization ably the switched equalizer affords prop- coil, and a punched chassis a great convenience to listeners who er compensation for the record charac- and complete set of schematic and pic- turn down the gain momentarily to hear teristic torial diagrams. plus some extra high cut in the the doorbell or answer a question and "noisy" positions. In addition The RCA SP -15A to the 14- is a complete por- find that the expansion control has to watt amplifier listed in the table, New- table system. The microphone, a desk be reset. comb offers stand, and the a similar amplifier with 30 amplifier all fit into spe- Among the amplifiers listed which fall watts output, the KXLP -30. cially built pockets in the case and the into the high-power class are the ACA- speaker The Fisher amplifier incorporates the is mounted in the cover. The 58D (52 watts) and the Ward Airline famous H. H. higher -power amplifiers Scott Dynamic Noise Sup- are not usually 45- and 90-watt jobs. The latter consists pressor. Various refinements are added, small or light enough to fit into a ease, of either two or three separate units such as separate electron -ray tubes to so must be carried separately. in a single metal cabinet. The preampli- indicate action of the gates, and two - The serviceman who goes on many fier and one 45 -watt power amplifier chassis construction. portable PA jobs Three inputs can will find it useful to are furnished for the 45 -watt system. be accommodated but only one make (or have a carpenter at a time. make) a To double the output power a second The desired one is selected by a panel special case for PA equipment. Ingenu- 45 -watt chassis is added. Each power switch. There ity in making specially -shaped are five controls associ- compart- stage uses six 6V6 -GT's in push -pull ated with one form of tone control or ments and brackets for the various ac- parallel. Two photos show how the pre- cessories another, enough to give any listener free will pay off in convenience. amplifier and power chassis are mount- rein in is neither suiting the musical balance to It pleasant nor impressive to ed. The preamplifier terminates in 600 his tastes. arrive on location entangled in miles of ohms and a volume -indicator meter con- The Masco 25 -watt loose cable and carrying several amplifiers are of- objects nected across this appears on the front fered with (MA -25HF) or without in each hand, pockets bulging with more panel. equipment. (MA -25EX) a built -in expander. The Very few amplifiers provide various same features Some of the amplifiers are offered in 12 -watt offered have steps of fixed equalization selected by a units, MA -12HF and 12EX. AUDIO AMPLIFIERS

Mfr. L Power Harm. Output Output Frequency Phono Inputs Mic. Inputs Equalizers Remarks Model output dist. imped. stone response No. Gain Na. Gain (type) I watts) ( %) (ohms/ (cycles/ (db) (db) Alter A -323 -B 15 2 2.5 -24 p -p 6L6 -G 20- '0,000 117 use h -gain boss boost avail. in db 1 77 phono input treble cut kit form Amp. Co. of Am. 52 5 2 -500 p -p -par 30- 15,000 1 79 3 124 bass and 58D 6L6 -G (4) +1 db 1 107 treble cut Audar BMP -25 20 5 4, 8 p -p 6L6-G 1 50- 14,000 65 1 110 treble cut operates on ±2.5 db 117 v o.c. or 6 v. d.c. Bell 2122 10 3 3.4 -18 p- p686 -GT 30- 15,000 4 60 -80 0 boss and treble no mixers

±0.75 db - cut and boost Bogen PH -10 10 5 3.2, 8 p -p 6V6 40- 15,000 1 72 0 bass and treble +1 db boost and cut Brook 10C3 30 1.3 1.5 -500 p -p 2A3 20- 20,000 I 100 0 bass, treble separate +0.5 db 3 80 preomp chassis

Fisher I 20 8, 16 p -7C5 r 20-20,000 bass and treble dynamic noise db cut and boost suppressor Knight 20 2 4 -500 p -p 6L6 -G 20- 20,000 1 78 0 bass and treble (Allied 93 -103) built -in +1 db cut and boost expander Lafayette- 10 2 2 -500 p -p 6V6 30- 20,000 1 1 bass and treble Concord 2 -131 ±1 db cut and boost Lafayette- 60 5 4 -15 807 p-p 30- 12,000 1 85 2 120 step -type Concord +2 db Masco MA -25EX 25 5 4 -500 p -p 6L6 -G 1 30- 20,000 90 1 120 bass and treble +1 built -in db 1 60 cut and boost expander 1 70 1 75 Newcomb HLP -14 14 5 3 -500 p -p 6V6 30- 15,000 1 90 0 boss boost treble automotic bass ±1 db I 109 cut and boost compensation RCA MI -4297 40 2.5 4 -250 p -p -Par 30- 10,000 0 2 111.5 bass cut 2 more inputs (voltage amp) 6L6 +1 db with MI -4288 may be added (power amp)

RCA SP -15A 15 5 4 -250 p-p 6V6 50- 10,000 1 75 I 114 high cut portable 1 100 and boost Rek -O -Kut R -5A 9 5 8 -500 6K6 15,000 p -p 50- 2 76 I 125 treble boost for ±1 db and cut recording Setehell Carlson 25 0.5 p -500 -p6L6 60- 10,000 1 87 4 138 PA -722 treble and tone control for +1.5 db bass cut each channel Stark 20 5 4 -500 p -p 6L6 1 50- 12,000 78 2 120 treble cut db Cabinet-top +2 phono oval(. Ward 45 2 1.4 -600 p -p -por 50- 15,000 2 74 4 110 6V6 (6) ±7 bass and treble 90 -watt db cut and boost model avail. RADIO -ELECTRONICS for

www.americanradiohistory.com All 10 =9 Modern Crystal Phono Pickups Crystal pickups are still most popular Judging from the literature circulated by manufacturers, few crystal pickups CRYSTAL pickups are still by far Shockproof Nylon needles will be avail- today use the old standard steel needles. the most popular for home phono- able with .001 -inch points. Buyers of Some, such as the RCA Silent Sapphire, graphs, probably because they these should heed Duotone'swarning that have permanent sapphire or special al- are inexpensive and have high the new needle -point radius is not the loy- tipped needles built into the cart- the only requisite for playing Microgrooves. ridge, but most offer cartridges with output. In higher-priced equipment special magnetic types are gradually replacing The low needle pressure and the 33 1/3- replaceable needles of their own since magnetic output is r.p.m. turntable are essential. In view of design. Many of these have "knee crystals but, so low, a preamplifier usually must be add- modern research it is doubtful, too, action," meaning that they are bent whether any pickup using a conven- that they have enough vertical com- tional chuck to hold removable needles pliance to eliminate any noise that will afford the best fidelity. would result from vertical irregularities The Rochelle salt crystal is affected in the record surface. Unfortunately, by humidity, and its life may be short- this usually adds some lateral compliance ened for that cause, especially in damp as well, adding slightly to the droop in climates. A newer development, the P -N, the high- frequency response. The knee or ammonium dihydrogen phosphate action does a great deal, however, to- crystal is more durable. The P-N crys- ward reducing needle talk, direct acous- tal is not damaged by high tempera- tic radiation of record modulation, and tures or humidity. Crystals have been noise. demonstrated after immersion in boiling Many of the new crystals are water. equipped with needle guards. These usu- Another new development is a ceramic ally take the form of small spring -metal crystal material composed of titanates extensions or knobs on the lower surface of barium and other minerals. These are of the cartridge case. When the knee - the high -dielectric ceramics used in action needle hits the record too hard, it up shock. The ceramic crystal pickup made by Sonotone. small capacitors. Not all the properties yields and the guard takes the One maker, Webster Electric, has rede- for this ed, making the replacement job more signed the cartridge mounting is - than just a few minutes with a screw- purpose. The entire cartridge spring driver. clipped into a special pivoted mounting Most crystal types differ only in the screwed to the arm. Its normal position The frequency is at an angle to the record surface, as shape of the cartridge. is response of the usual crystal gives me- the drawing shows. When the pickup dium to low fidelity because of an abrupt dropped accidentally or is in any way cutoff between 4,000 and 6,000 cycles subjected to a pressure greater than 2.5 and a number of peaks and valleys in ounces, the front end of the cartridge the response curve. Theoretically, an tips up and the small projection acting ideal crystal has smooth response from as the guard rests on the record. (See ordinary records, tapering off smoothly drawing.) in the upper register. The taper can be Despite guards and knee- action removed with simple RC networks. The needles it is (still) a good idea to handle gen'ly. Brush PL -20 is a good example of this Electro -Voice Torque -Drive uses lever action. pickups type of crystal. Its cost, however, is far One of the most useful features of greater than that of the ordinary type of the titanate compounds have been recent pickups is a simple change in the of crystal pickup. fully explored as yet; therefore it is method of connecting cartridges electri- High -fidelity crystals, however, are difficult to predict the possibilities of the cally. Formerly the leads had to be sol- new new material. Advantages claimed by making a comeback. The Columbia MOUNTING LP (long -playing) Microgroove records manufacturers of the new type pickup SPRING CLIP are made with a frequency curve that are low needle pressure, elimination of approaches the ideal crystal character- needle talk and wider frequency re- istic closely. The first available record sponse. player for playing the Microgrooves was The cartridge is much smaller than made by Philco in collaboration with the Rochelle -salt type. This is said to Columbia engineers and uses a crystal permit a mechanical construction which pickup. Claims for the player (which causes less distortion, as well as lending also is sold under the Columbia label) itself to better design of the pickup arm. DISC GUARD state that the pickup will reproduce the Electro -Voice has developed a "torque Webster cartridge has unique mounting. Microgrooves ideally. Probably an R -C drive" crystal pickup. Its stylus is compensation network is included. coupled to a harness arrangement dered directly to terminals. It was no Astatic also produces a crystal pick- which, by lever action, distorts the crys- difficult trick to overheat a crystal with up (FL -33) for Microgrooves. Like the tal. (See illustration.) The harness is the soldering iron and damage it per- Philco unit, the arm is constructed for built so that vertical stylus movement manently. Today virtually all pickups stable operation with only 6 grams produces no output, eliminating one have plain round pins projecting from needle pressure. The crystal gives ap- source of surface noise. The lever action the rear. Small lugs are furnished sepa- proximately 0.5 volt output, even with multiplies the torque imparted to it by rately, to which the leads are soldered. the smaller modulation present on the the moving stylus so that lateral com- The lugs are then slipped over the pins. new records. Another maker of Micro- pliance is much increased. The response Danger of heat damage is eliminated groove pickups is Shure with its 900MG. curve furnished shows a fairly smooth and the serviceman's job is made much The Duotone Company has recently constant -amplitude response to 10,000 easier because he does not have to work announced that their Star Sapphire and cycles. in a tight place with his soldering iron. OCTOBER, 1948

www.americanradiohistory.com :101 Audio

Microgroove aph Records

Technical characteristics of Columbia's new high -fidelity long -playing recording system

By M. HARVEY GERNSBACK

ASIGNIFICANT advance in certain fidelity limitations in conven- a much shorter distance and its undula- commercial phonograph rec- tional wide -groove recording. Fig. 3 is tions are much sharper and its bends ords was made when Columbia a schematic drawing of a disc surface. more acute. announced its long -playing When the disc revolves under the cut- Fig. 4 is an enlarged Microgroove picture of each r e c o r d s late in June ting stylus at a constant rotational of these grooves. Notice that for AA' (RADIO-CRAFT, August, 1948). Up to 50 speed, the stylus will take the same the width of the groove is fairly constant minutes of music may be recorded on a amount of time to travel from A to A' single 12 -inch Microgroove record, com- if it is near the outer edge of the disc, pared with only 8 or 9 minutes on a as from B to B' if it is near the center, standard 12 -inch disc. . each of these distances representing the The new records differ from conven- same fraction of a revolution. However, tional ones in two major respects: First, the actual linear distance traveled from they are recorded at 33 1/3 r.p.m. B to B' -with the cutter near the disc (standard b r o a dc a s t transcription center -is much smaller than that speed) instead of 78 r.p.m. Second, the traveled from A to A', when the stylus number of grooves per inch is from 224 is near the edge. to 300, compared with about 90 in con- The drawing is much out of scale, but ventional records. This means that the assume that the stylus travels each of groove width is approximately one -third these distances in 1/5000 second. If the that of ordinary phonograph records. tone being recorded is 5,000 cycles, the That is shown clearly in the two photo- stylus will trace out one cycle in each micrographs Figs. 1 and 2. Fig. 1 shows case, as the drawing shows. Notice that a microscopic enlargement of a section the one -cycle groove of AA' takes up a Fig. 3 -Pinch Effect cause near disc center. of the new disc, compared with an ordi- comparatively long distance and its un- nary disc in Fig. 2. dulations are fairly gradual. But at BB' at all points. A reproducing needle of Recording at 33 1/3 r.n.m. introduces the same cycle will have to be traced in the proper size and shape will fit nicely into this groove and reproduce its vari- ations faithfully. But for BB' the steep- er bends of the engraved wave cause the LAND+ groove width at points X to be percepti- FLAND bly narrower than normal due to the shape of the cutting stylus. Because of this, the playback needle will be forced up out of the groove somewhat; it will not track properly, and the output vol- GROOVE: ume of the pickup will be decreased. +GROOVE Distortion may also be introduced be- cause the needle will move vertically as well as horizontally. This pinch effect will occur to some MIW11. ....1 extent no matter ----. what the frequency. In practice pinch effect is not bothersome at frequencies Fig. I, left; Fig. 2, right- Photomicrographs of ordinary and Microgroove record section. much below 1,000 cycles. If the playback Owing fo variations in records, the ratio is nearer 2:1 than the more usual 3:1. needle point is a little larger than opti- RADIO- ELECTRONICS for

www.americanradiohistory.com I31

which gives anything previously heard on records. mum, it will attenuate frequencies even ords are pressed on Vinylite low no needle scratch. The two requirements, namely lower than this. The actual attenuation practically -inch stylus tip The lack of needle scratch or back- needle pressure and .001 due to translation loss in playback mean that ordinary pickups and pickup and ground noise is aided by the phenome- radius, varies with the particular the tone arms cannot be used with the new in Fig. 5 are typical. nally light needle pressure used in needle. Curves com- records, although some professional - a diameter of about 8 inches phono pickup. The light pressure, Under discs, results type arms and cartridges can be modi- 33 1 /3- r.p.m. recordings) bined with use of Vinylite (in ordinary record reproduc- fied to do the job. And the 33 1/3-r.p.m. the translation loss is so great that little in essentially noiseless small With such a low noise level, it is turntable speed means that only a correction is possible; but from 8 to tion. enthusiasts will have begins not necessary to boost the level of low- number of record about 13 inches, where the effect suitable turntables. Consequently, a to be noticeable, diameter equalizers are of phono cartridges, re- whole new group used, when recording, to correct the arms, motors, and complete record play- sponse. These high -boost equalizers raise now B ers has been developed and is the amplitude of high frequencies fed to the market. In general, there as the coming on the cutter, the boost increasing are two types of players. One, an auxil- stylus travels inward on the disc. iary unit for those who already own a Because of translation phonograph, consists of a 33 1/3-r.p.m. loss, high -fidelity, 331/3- turntable and special pickup. The unit r.p.m.recordings (of nor- plays only Microgroove records. The mal groove width) are A diameters of user continues to use his old phono- rarely made at recording graph for old -style records. The second less than 8 inches. Fig. 4- Grooves of same frequency at different featured in new which can be type of player unit, The frequency range disc diameters. radio -phono combinations, has two sep- successfully recorded and played back disc volume sounds during recording. In- arate pickups, one for ordinary and without attenuation on a lateral -cut records. The turn- speed of record stead, the volume level is set once and one for Microgroove depends on four factors: desir- table is a two-speed device. Generally rotation, modulation index (ratio of left alone. This is a particularly fully modulated groove width to un- FREQUENCY, CPS modulated groove width), diameter of 5678100 z o "do o yw ._ .. - - - -'-I record at the innermost recording DB. groove, and stylus tip radius. Decreas- 3.5" maxi- o ing the tip radius increases the J'11 2.5" mum frequency which can be recorded, 5 while decreasing turntable speed de- a 0.5" creases the maximum frequency (for - 10 given recording diameter and modula- records, -15 tion index). In Microgroove II 8.5" turntable speed is reduced from 78 to q0i 331/3 r.p.m., a ratio of about 1 to 2.3. 2 But stylus tip radius is reduced by a 6.5" the relationship -2 factor of 1 to 3. Though Fig. 5- Playback loss at various diameters. between the two is not a direct one, the more than com- in recording symphonic the unit is an automatic record changer reduced stylus radius able advantage manual rec- pensates for the speed reduction. Hence, and operatic music, where much of the for 78- r.p.m. records and a innermost diameter of the effect comes from the wide vari- ord player for the 331/3 r.p.m. discs. even at the music's two -speed Microgroove records (5% inches) fre- ations in volume. Columbia points out For those who already own of distortion quency response and lack C PS 1 r.p.m. recording VELOCITY DB is superior to old 33 /3- IK 10K at its innermost diameter, according to 20 100 Dr. Peter Goldmark, director of engi- at neering research and development +20 CBS and in charge of development of the records. Curve A in Fig. 6 shows the recording used. It follows very characteristic +10 closely the standard NAB characteristic B (used in broadcast transcription work A and in many standard records), except at frequencies below 100 cycles. These more o low frequencies are emphasized A than in the NAB curve. This reduces turntable rumble problems in low -cost record players, because the amount of bass boost needed is reduced. The rec- 10 ords will reproduce almost perfectly without equalization when p l a y e d through a high -grade crystal pickup fitted with a .001 -inch radius stylus. The -20 arm and pickup must be designed to track with a pressure of 1/5 ounce. Because of the fine grooves, the max- imum groove amplitude must be much curve (B) of stal pickup. smaller than in conventional recording. Fig. 6-Microgroove recording curve (A) vs. constant ampli ude This means lower -level recording. Ac- are special pickups, level claimed by Columbia that no compression is used during re- turntables, there tual output both of the crystal and magnetic types. for these records is 4 db lower than con- cording. Listening tests on two Micro- confirmed this. ventional records. However, this lower groove recordings have Figs. 8, 4. 6 are from Gernsback Library Book, level is not too important since the rec- The dynamic range is much wider than "Practical Disc Recording." OCTOBER, 1948

www.americanradiohistory.com This chassis holds the electronic heart of the organ, the FM oscillator and the discriminator. The tuning capacitor is mounted on rubber.

By WILLIAM K. ALLAN

reactance of S should be low compared to the total shunt resistance of R and the tube's grid resistor in parallel. Since capacitive reactance increases with de- creasing frequency, the low- frequency response drops off. Fig. 2 is the system described in the Merrill article. It shows how the string vibration can be used to frequency -mod- ulate a carrier. The tube is connected as an r.f. oscillator, tuned by Cl and the coil. Across Cl are the series capacitors 'C2 and S, again our string (or reed) and pickup screw. When the string vibrates, the capaci- tance of S changes at an audio rate. The changing capacitance causes the oscil- lator frequency to vary at the same rate, in effect giving frequency modulation. If the r.f. signal is picked up on an FM receiver, the string tone will appear in Electronic the loudspeaker. Organ In Fig. 2 Cl tunes the oscillator to its resting frequency. C2 is adjusted so that the vibrating string will produce the de- sired FM deviation. If C2 is large with respect to the capacitance of S, the ef- fect of variations in S will be large, and Improved With FM vice versa. An electronic reed organ The principle illustrated in Fig. 2 was AN OLD and well -known method to have a low impedance at audio fre- used by the writer to build an electronic of amplifying the sound of quencies, these changes of voltage ap- reed organ. Instead of the piano strings, string or reed instruments is pear on the tube's grid and vary its the vibrating parts are organ reeds. In shown in Fig. 1. Several ar- contrast to the d.c. electrostatic system ticles illustrating the method have ap- AF OUT of Fig. 1, no high polarizing voltage is peared in RADIO-CRAFT. Among them are needed at the pickup screws. The insu- "Tone- Controlled Electronic Piano" by lation resistance between pickup screws Bretsfelder, January, 1938 and "Elec- and ground need not be high, so humid- tronic Organ" by Allan, April, 1941. ity and stray dust particles will have "Non -Radio Uses for FM" by Merrill. no effect. The unit has SCREW outstanding or- April, 1942, described a different system gan tone and full bass response. It is so which was used to build the FM organ S simple and satisfactory that electronic described in this article. music enthusiasts will be able to build B+ The non -FM principle is simple. A PIANO STRING it without difficulty. polarizing battery B is in series with If the amplification factor of a triode Fig. I -Older pianos used polarizing voltage. a resistor R and variable capacitor S, is 20, grid voltage changes are 20 times which consists of a piano string and output. The reader more effective than plate voltage a metal will recognize the screw placed very close to it. principle of the condenser microphone. (In an organ, TO FM RCVR the screw head is placed A separate screw is placed near each f- close to the vibrating reed.) When the string of the piano string vibrates, (or reed of the or- -9+ the capacitance between gan) and all are connected in parallel string and screw head varies at the rate to the amplifier input, of vibration. usually by wind- ing a single turn of a steel wire once Since the amount of charge on the around each screw. capacitor Output tends to be varies with its capacitance, low, as the total capacitance change electrons move from the battery to the caused string by the vibration of any one as its capacitance increases, and string is small compared with the total in the opposite direction as decreases. shunt capacitance of all the other screws Current flowing through the resistor R and strings. The hum problem is often causes a voltage drop across it, which serious, and the high polarizing in turn voltage causes the voltage at C to vary may be dangerous. Insulation DIANO STRING at the must be string's rate of vibration. Since excellent-a great problem in humid C is a blocking condenser large enough weather. For good output, capacitive Fig. 2 -One method of using FM for piano. RADIO -ELECTRONICS for

www.americanradiohistory.com Audio I33

is connected as a Foster - Pull out a reed. Insert the rounded changes in varying plate current. If the The 6H6 in the Seeley discriminator. L3 is identical to end of the tool and, with a knife plate circuit is tuned by the pickup line of the reed in Ll, placed with axis parallel to it and slot, mark the center screws instead of the grid circuit (as red cell. Also spaced about 21/2 inches away. (See on the outside top of the Fig. 2), 60 -cycle hum is reduced by the on the factor. photograph at head of this article.) A mark across the end of the tool tube's amplification reed cell the position of a .001 -µf condenser midget variable condenser resonates L3 outside top of the The reactance of the reed. Remove the tool is about 88 ohms. At 60 cycles to the oscillator frequency. It must be of the tip at 1800 kc and place the reed on top of its cell be- it is 30,000 times greater. Employing mounted on sponge rubber because it is to motion of any kind. It must side the center line with its tip against such a condenser in series with the pick- sensitive punch be carefully tuned for best tonal output. the end mark. With a center 6C 5 6H6 R.f. bypass condensers of about 100 nark a point about one -fifth the length PAM MOD OSO .00025 LI L3 DISCRIM from the free TO AI AMPL µµf can be placed across each of the of the reed tongue back 5 5^e h audio load resistors if nec- end of the reed tongue. .06 100,000 -ohm cessary. Choose a brass machine screw about the same diameter as the width of the 2.5Mn 1001% Constructing the organ reed tongue and, with a drill slightly The constructor will be well advised smaller than the screw, bore a hole .002 an old reed or- the top of the reed cell. Turn B+ to obtain a manual from through C2/.5 gan. These can often be had for almost the screw into the wood so that it cuts I nothing at auctions or second -hand fur- its own thread as it goes. After blowing niture stores. Choose a C to C reed or- out any sawdust replace the reed in its REEDS a case, in C4:.0001 gan, usually found in piano preference to an F to F, in case pedals are ever added. Remove the manual, the pallet open- Fig. 3- Aufhor's circuit needs no shielding. taking care not to get ing rods separated from their proper up electrodes and the inductance they keys. Remove the swell shutters and tune reduces the hum level over 44 db. hinged stop -control covers. By combining these two hum- reduc- Fig. 4 shows the tools necessary for ing devices (patent applied for) an or- placing the pickup screws properly over gan can be built with no shielding. To the reeds. A tool similar to that invented appreciate what this means, the reader by Victor R. Mumma is made by grind- should have tried to adjust a conven- ing one end of an 8 -inch length of / x tional electrostatic organ in which the Fig. 6- Second reed action on the top manual. shielding had to be removed and re- change and trial cell. Repeat this process with all the placed between each bass reeds will use of the result, and for good measure he other reeds. The 19 machine screws and the should have touched ground while try- about No. -20 at 300 volts! treble reeds about 6 -32 screws. ing to pull a reed polarized to ground of a reed or- Join all the reeds together The change in the tone flattened shielding gan is remarkable. The organ may be them by tucking notes being braid underneath the ends of the reeds played like a piano, the bass protrude from their cells. struck so staccato that no audible sound where they the electric To guard against intermittent connec- is produced except when of his The output sounds like a tions the writer soldered each pickup is on. strip. A short piece deep diaphone organ pipe. reeds to the ground of flexible wire to permit removal would Fig. 3 is the circuit. The 6C5 is con- probably have been better than solder- nected as a shunt -fed Hartley oscilla- to a ground bus in case the and ing directly tor, L1 being the center -tapped grid instrument is to be tuned. plate coil. An r.f. coil from an old Vic- tor t.r.f. receiver, chosen because it was Operating adjustments wound in grooves and center -tapped, When all connections are made and is about 1'/2 inches in diameter with the tubes are heated, make sure the os- about 48 turns each side of center tap, cillator is operating. It should light a the total winding being 11/2 inches long. neon lamp held in the hand and touched The grid leak and condenser are 47,000 to the plate terminal, and the signal ohms and 250 µµf, respectively. Cl is the Fig. 5- Suction source is rotating impeller. should come in strongly at about 1800 .002 -µµf plate bypass condenser. Rl and receiver. The standard test and kc on a radio C2 form a decoupling network. They re- '/s -inch iron to the thickness, width, for negative voltage across the grid leak duce the output to a point where neigh- end curvature of the longest reed. With be made if a meter is available. of may also bors can't pick up organ music too loud- a hacksaw cut a slot down the middle The output of the discriminator may be ly at 1800 kc on an all -wave receiver. C3 the opposite end, wide enough to insert an amplifier or the phono iron connected to is the all- important hum -reducing .001- a knife blade. Finally, bend the in a radio. The volume control can lies jack µf condenser in series with the pickup into a U so the tip of the slotted end be operated by the swells. A movie or screws which are placed over the exactly over the tip of the rounded end broadcast attenuator stands up better grounded reed tongues. as in the center of Fig. 4. than a receiver volume control. Tune the discriminator condenser (C9 in Fig. 3) slowly and carefully while a bass reed is sounding. You will know when you hit resonance because with Rl shorted out, a 5,000- ohms -per -volt meter shows a change from +15 to -15 volts across the 100,000 -ohm discriminator load resistors as the condenser passes through resonance! If the oscillator's harmonics happen to heterodyne with the harmonics of any (Continued on page 34) Fig. 4- Pickup screws are installed with these tools. The one in the center is home -made. OCTOBER, 948

www.americanradiohistory.com 34 Audio New Trends in Loud Speakers New- developments in on old componeul

enough to fill a room with sound at less P -52HF with a It. 5 db response from than a watt of excitation. 40- 12,000 A typical Brociner- Klipsch speaker system. cycles. Actual response ex- Prices for standard speakers are low tends upward to 16,000 and down to 30. enough to keep them from adding great- The crossover frequency is 800 cycles. LOUD SPEAKERS have come a ly to the total equipment bill. long way Special Horizontal sound distribution angle for since the days of the dual -unit systems run higher, in some the high frequencies first metal horn types. is 80 degrees; ver- Today cases overshadowing the cost of the am- tical coverage is 40 degrees. These there are high -fidelity speakers plifier an- and microphones. But even so, the gles are provided by the 8 -cell tweeter which reproduce the whole range of figures are lower hearing, than for theatre sys- horn. The woofer is a 15 -inch cone high -power projectors which tems which, for some years, were the speaker will service large auditoriums, with a 4s._ -lb. Alnico V magnet. and an only two -way speakers available. Another very interesting two -way air- column unit that can be heard over Very few two-way systems a distance are of- speaker (the Klipsch) is an improve- of 10 miles. All this in addi- fered to the consumer with separately ment tion to the many standard on the old folded or re- entrant units in sizes mounted woofer and tweeter. One of horns. The front of speaker from 2 to 12 inches, with this is a efficiency these is made 1w Stephens. This is the (Continued on facing page)

CORNER

TOP VIEW OF SPEAKER CHAMBER SIDE VIEW

Construction of Klipsch speaker. Low -frequency sound comes from the vertical side slots. the Altec -Lansing Model 604B duplex speaker.

(Continued front pag.e 33) lytic condenser cans for couplings. strong local with leather nuts acts as pallet opening radio station, dress the wire The writer discarded the keys which rods. connecting the screws nearer to ground came with the reed organ and used a The bottom of the wind chest to shift the oscillator frequency, and standard pipe -organ was cov- retune manual which has ered by a sheet of tempered Masonite or the discriminator. Any two pieces slightly wider keys. Just back of of metal making intermittent the Presdwood, and an Amperite magnetic contact ivory -covered portion of each key a hole contact mike was with each other near the pickup screws was placed on this Presd- drilled, and a 1/4 -inch x 20 round- wood sounding board, (for example, octave -coupler rods) will head machine inside the wind screw was threaded from chest under the top treble reeds. Weight create noise and must be avoided by all the top half down through means. this hole in was added on top of the mike until the the key. The pallet opening rods had bass response A suction source was made extended to the bottom of from the their upper ends in the bottom of this the manual. This required impeller wheel of a junked airplane hole a shoe- polish so that turning the machine screw can lid filled with melted lead, supercharger as shown in Fig. 5. An 8- gave precise except adjustment for opening of for the inch square opening for the to-9- inch -diameter fan is used for a the reed pallet without changing mike 3.950 r.p.m. the cable. The result is a lovely contrasting motor, and a 16 -to -18 -inch level of the keys. Fig. 6 shows how a sec- fan for a 1,725 reed tone obtained without danger of r.p.m. motor. With this ond reed action was added on the top feedback type of blower the wind chest if felt is placed over the out- with mov- pipe -organ manual by inverting the reed side but not touching able side is not required, regulation action and operating the Presdwood. being its pallet opening If some of the direct sound from the automatic; but the suction line rods from the ends of extensions behind from the blower reeds escapes to blend with that from should be large enough the pivot point or fulcrum on the rear the speakers. and short enough to prevent a very pleasant effect, re- a serious of each of the pipe -organ keys. The sembling a pressure drop on a heavy string stop. is obtained. In chord. News- ends of these extensions are slanted fact organists have print cardboard tube cores convey declared these stops the toward the center to allow for the differ- to be among the most pipe suction, with old triple 8 -pf wet electro- -organ -like ence in key widths. Bronze welding rod electronic tones they have ever heard. RADIO -ELECTRONICS for

www.americanradiohistory.com Audio -I 35 solid piece of wood. The sound from est on the horn's axis. Frequency re- the low- frequency unit is emitted from sponse is especially designed for best two vertical slots that run the full speech intelligibility, extending from length of the cabinet, which is placed in 250 -5,000 cycles with the 4',,i -foot horn. a corner so that the walls of the room The MI -6269A is an interesting RCA form part of the horn. A wide-angle development. Much of the distortion in tweeter on the cabinet top supplies the speakers is caused by resonance of the is highs. ' cone and by its stiffness. Some of this Most high -quality reproducers are of remedied by the new method of mount- to the co -axial type, with the tweeter as- ing the cone. Instead of cementing it sembly built into the woofer. Space is the circular edge of the metal frame, saved by this arrangement without im- the designer has attached a flexible portant sacrifice of frequency range. paper skirt to the cone's edge and fas- Usually the tweeter unit is a separate tened the other end of the skirt to the metal -diaphragm driver with multi - frame. An iron ring guard protects the cellular horns to disperse the sound over cone from damage. Since the entire cone wide vertical and horizontal angles. can move instead of only the inner part, The Altec- Lansing 604B is an excel- the frequency range is increased as lent example of this. As the photograph much as an octave over response with with- conventional cone mounting. shows, the high -frequency horn is Accordion -type speaker, an RCA development. A speaker of remarkable appearance, in the large cone. A separate small case Cone floats freely on a flexible -paper rim. contains the electrical network which di- pictures of which have just been re- vides the audio band into high fre- ceived from Italy, is referred to as an quencies, channelled to the tweeter only, expansion loudspeaker. Although the and lows, which go to the cone speaker manufacturer neglected to give any de- only. The assembly can be mounted in a tails of its operation, it would appear to standard bass -reflex cabinet with no have a horizontal moving coil in the pot more difficulty than a standard single magnet at the base and a stylus run- speaker. It is designed to cover a spec- ning to the top of the globular or ellip- on trum from 30 to 15,000 cycles. soidal "cone." Audio signals acting horn, the the voice coil would then lengthen and Because of the multicellular vertical axis of the globe, of coverage for the high fre- shorten the angle it to expand and contract at its quencies is 60 degrees horizontally and causing equator. The manufacturer claims - 40 degrees vertically. This is an impor- propaga- point because treble sounds tend to with apparent justice -equal tant tion over an angle of 360 degrees, and travel in straight lines. With ordinary the listener must stand prac- further claims advantages over speakers, the in reproducing novelty -the expansion speaker. It right in front of the unit to hear standard cone speaker An Italian tically is claimed to be completely omnidirectional. the full range. With the multicellular high frequencies. horns it is usually possible to place the speaker in the room at some point where almost all of the area will be covered. LO`rPE eaÁR s4is Jensen was probably the first manu- facturer to make coaxial speakers for COIL CONNECTIONS home use. The Jensen JHP -52 is a 15- inch cone speaker with a small cone OUOSPEAKLR UNR AML -2O speaker mounted at its center on a spider support. The angle of sound dis- yg ADJUSTING SCREW is much like that tribution in the Jensen HEATER CONNEC TVA in a single speaker, requiring the lis- yERTICA tener to be on the axis for best results. ADJUST MICROPHONE The Jensen system is much less expen- 4ORZONTA TYPE DB- HI P sive than those using multicellular a 50- 12,000 -cycle fre- horns. It covers COIL CASSE quency range. LOUDSPEAKER STAND VOICE One of the most interesting speaker is air type, AIR MOSf developments the compressed MICROPHONE STA I built on an entirely different principle TYPE 10- 3667E from most units. Air is pumped to the o CUP speaker horn by a compressor at con- AIR FILTER, The airstream is modu- stant pressure. A C POWER CABLE lated by two slotted grids, one movable and one stationary. A small armature is attached to the movable grid. The out- AMPLIFIER TYPE 2H -24' put of a 20 -watt amplifier is connected to the voice coil, which moves in accord- ance with the audio impulses and pushes the movable grid in and out. The pres- sure of the air emerging from the speak- er horn is varied by the movements of the grid, much as the air from the lungs 12 VOLT BATTERY is controlled by the human vocal cords. FILTER DRANCOCR com- The sound output of one typical GASOLINE ENGINE pressed -air system is equivalent to that GENERATOR- COMPRESSOR TYPE GG -14-24 of an ordinary 500 -watt PA system, is sup- though only 20 watts of audio The compressed -air speaker works like the hu- plied. The signal, despite the horn, is man voice, with lungs, larynx and vocal cords. strong in all directions, though strong- OCTOBER, 1948

www.americanradiohistory.com 36j Stability due to in- verse feedback and gain of more than 100 decibels in a 1,2 pound amplifier

Four -Watt Portable

For All -Around Use By LYMAN E. GREENLEE

THIS little amplifier can be built stability. Another factor contributing easily and cheaply and has The resistance values given will be cor- many to stability is the short leads. It is neces- rect for a power uses. It is suitable for a small PA transformer having a sary to shield the input to the 6SJ7 and 700 -volt center -tapped secondary. system, as a recording amplifier, also For to the 6F8 -G. A tube shield will be lower- voltage transformers it will be or as a musical instrument amplifier. required for the 6F8 -G. The model shown in the photographs necessary to reduce the value of Rl. All grounds should be brought to a Check the bias voltage until a resistor was built on a 5 x 91/2 x 3 -inch chassis common bus which is connected to the is found which will give 12.5 to 15 volts. which just fits a 12 x 12 x 7 -inch port- chassis at the 6SJ7 socket. The 6V6 and able speaker case, leaving IIeasurements of bias voltage should room for a 6F8 -G tubes are slightly overbiased for be made with 5 -inch speaker. The completed unit a v.t.v.m. connected be- increased stability. Actually, 250 ohms tween the 6V6 grid and ground with weight 151, lbs. This includes every- and 2,500 ohms would normally be used thing except the microphone input to the amplifier shorted, and also and stand. in place of 300 ohms and 3,000 ohms across The frequency response is very good, Cl. respectively. In some cases it will be The use of fixed bias permits a larger hum level is unusually low, over -all desirable to omit the 25 -µf condenser stability is excellent, undistorted power output and enables and still the cost across the 6V6 bias resistor, or to the amplifier of construction remains extremely small to drive a 12 -inch speaker. decrease its value to 10 µf. This will of The improvement in tone quality is so for an amplifier with a gain of over course depend somewhat on the use to 100 db. The model used noticeable that it is well worth the extra a 6SJ7, 6F8 -G, which the amplifier is to be put. For cost involved. 6V6, and 6X5, but equivalent tube Owing to the high values types use as a speech amplifier, the condenser of resistance used in the bias bleed3r may be substituted. A 7C7 may be used may be left out entirely. in place circuit, the unbalanced load on the pow- of the 6SJ7 or 6J7, a 6SN7 or The method of obtaining 7N7 may a fixed bias er transformer is slight, and the selen- be substituted for the 6F8 -G, for the 6V6 is rather unique. It uses ium a 7C5 for 6V6, a rectifier is operated well below its the and a 7Y4 or 6X5 -G selenium rectifier connected to one side maximum voltage for the 6X5 rectifier. If a suitable rating. It is im- pow- of the power transformer secondary. portant to use good electrolytics having er transformer is available, an 80 or equivalent rectifier may be used with 6SJ7 .002-.00s 8F8-G 8V6 identical results. H- j4a 6 3 6 The diagram is shown in 1. 4708 Fig. This IMCG C2A5 MIKE .001 3 circuit, originally consisting of a 6SJ7 5 IOOK ZR and 6V6, was later modified use 4 1=5KaII to a 6F8 and 6V6. Since neither of these ar- 11- 6 rangements gave sufficient gain, the 47K 6SJ7 was restored. R2 3.3MEG 470K This circuit is very stable, yet filter- ing has been reduced to a minimum. 2508 2W 6 450V 501,50V, 10 E 250 25/35V Note that the 6SJ7 is operated with CI cathode grounded, giving greater sta- 120K 306/5 RI POMA 10K SA bility and less hum. A small bias cell R4 25K /10W /ww was originally used, but it was removed TOOV CT 3 5 with a resulting improvement in per- 10MA formance. Note also the absence of by- SW ON vC < ® II pass condensers in the 6F8 -G cathode 7 10- 117V AC ál T.os 10 e2 circuits, and the feedback arrangement < ! 7 to the 6F8 -G output- section cathode. ¿450V. = Using inverse feedback greatly en- PL 6.3V.34 FILS hances the performance and improves Fig. I -The schematic. Break in plats circuit of 6FB -G is for alternate connection of Fig. 3. RADIO -ELECTRONICS for

www.americanradiohistory.com audio :17

it might be undesirable for some appli- cations. In the upper position of the potentiometer arm the high frequencies are accentuated by the low reactance of the .005 -µf condenser across the 100,000 - ohm resistor which is in parallel; while in the ground position, the high notes are effectively bypassed by the .005-pi condenser. The power transformer's high -voltage winding should have a current- carrying capacity of at least 60 ma, and the heat- er winding should supply 3 amps. The 2,500 -ohm speaker field used as a filter choke gave 250 volts for the 6V6, but a field of 1,500 ohms or even less might be more suitable. It may be desirable to reduce the value of the decoupling resistor R4 from 25,000 to 15,000 ohms. The value of this resistor will depend partly on the amount of leakage across the 8 -µf filter condenser, and in some cases the voltage drop across 25,000 page. Bottom view of the portable amplifier shown in the two photographs on preceding ohms will be excessive. details are resistor to 1 meg- No definite constructional low leakage; otherwise the bias voltage cessive, reduce this by ohm. The size of the 6SJ7 plate coupling given, other than those revealed will probably be too low. the photographs. Actually, it is possible If a phonograph input is to be used, capacitor will affect the bass response. the to use a smaller chassis as there is the pickup should be coupled to the Unless it is desired to accentuate Better the bass, it can be left at .002 pi. plenty of vacant space available. 6F8 -G input rather than through be secured by using a The .005 -of condenser across the out- results would 6SJ7; otherwise the gain will be exces- baffle system, overloading. The put transformer cuts down the ten- larger speaker and better sive, with resultant a system would add to the is to use a dency to squeal and gives a more nor- but such hest method of coupling weight and decrease the portability of potentiometer with a grounded center mal response with the 5 -inch speaker. used, it may be the unit. tap, as this permits fading from micro- If a larger speaker is direc- desirable to omit this capacitor. For most applications, a good .002 3 be used. This 6SJ7 R -C2 is an ordinary tone control. tional microphone should t - I 2 E Alternative tone compensation is shown is especially important if speaker and be in the in Fig. 3. This circuit, connected at microphone are to operated .002 same room. v--o-1 point X in Fig. 1, permits attenuation of a with other than a 4 -ohm 6F8 -G both bass and treble frequencies. There If speaker PHONO - 3.3e is used, it may be necessary is a loss in gain with this equalizer, and voice coil Fig. 2 -Fader for a phonograph input. to insert a voltage divider to reduce the 61/6- a divider may phone to phonograph pickup. Fig. 2 amount of feedback. Such 4,700 in shows such a connection. Nothing is consist of two -ohm resistors voice coil with their heard when the fader arm is at center. .05 IOON .05 series across the mid -point connected to the 6F8 -G cath- Input resistance R2 in the grid circuit 500n loot( side of the voice coil must be of the 6SJ7 is shown as 3.3 megohms. ode. One .005 TONE grounded. This connection will provide This value may vary from 1 to 5 meg- divider suitable for 6 -12 -ohm ohms, depending on the response and TO 9 AS LONN a voltage sensitivity wanted. If the gain is ex- Fig. 3- Circuit for better tone compensation. voice cotla.

_1 Ng/it/se/it. /t a N X .Vote Circuit MANY music lovers object to small 12SK7 35L6 -GT (105, 175, 245, 315, etc.) will be pro- duced. The coupling condenser C4 is rel- radios and phonographs because 2ND AUDIO 41.01 OUTPUT 22N most of them lack good low- frequency atively small to attentuate the 35 -cycle response. The low notes are lacking be- fundamental so it won't overload the cause small speakers and inadequate speaker. baffles must necessarily be used in small The human ear is a nonlinear device cabinets. Adding tone controls to ac- that produces harmonics of notes it centuate bass is not the solution because hears. If the ear hears notes harmoni- excessive low- frequency power overloads cally related to some low note, it re -cre- the speaker and causes boominess and ates the fundamental that would have distortion. A novel circuit used in the produced them. This synthetic bass cir- Sonora Model RCU -208 produces the ef- cuit takes advantage of this effect. The fects of bass notes synthetically. The ear hears low notes that are not pro- a.f. circuit of this receiver is shown in duced by the speaker. the diagram. Negative feedback between the screen Low notes are boosted by the low -pass grid of the 12SK7 and the voice coil low- positive feedback network Rl, R2, R3 ers the dynamic plate resistance of the and Cl. Positive feedback increases the 35L6 and reduces the effect of changing nonlinearity of the tube to which it is Diagram of the Sonora synthetic bass circuit. output impedance. Hum from the posi- applied. This increases the odd har- tive supply is reduced by feeding it to monic content. Assume that a strong speaker would be greatly overloaded or the screen grid of the 12SK7 through 35 -cycle note is passed through the cir- the note would not be reproduced be- C2 and C3. Values for these capacitors cuit with the tone switch Si closed. This cause of the inadequacy of the speaker. are chosen so the hum voltage bucks out removes the feedback, and either the With Si open, odd harmonics of 35 cycles the hum on the plate. OCTOBER, 1948

www.americanradiohistory.com Audio Packaging and Unitizing Audio Equipment

By ERIC LESLIE

evident trend. One large television man- ufacturer (Admiral) is featuring equip- ment which can be bought a piece at a time as the purchaser's finances permit. Unitization and packaging have re- cently been receiving considerable at- tention in the sound field. A number of amplifier manufacturers are now pro- ducing equipment which can be in- creased in size by units from a very small to an extremely large amplifier. At least two unitized types of "contain- ers" have been featured recently -one in the industrial field by RCA, the other in home sound equipment by Jensen. The RCA unit -built console is made for industrial plants, large schools, hos- pitals, hotels and similar establish- ments. In its simplest form it is the sound control panel with a bank of 16 zone switches (permitting paging to 16 speakers) shown in Photo 1. A two -unit console, almost exactly similar in ap- The console below pearance, provides a dual- channel con- in use at a large trol panel with paging facilities to 64 industrial p l a n t. zones. In the third step addition of a record -transcription pedestal makes pos- sible distribution of speech and phono- graph music and in the fourth, shown AS the technical problems in any early television receivers was no doubt in Photo 2, a second transcrintion pedes- type of radio equipment are the reason for neglect of the cabinet- tal and a radio solved, tuner provide facilities designers and manufac- s neglect which caused some women to for fading music in and out, turers find as well as it possible to pay refuse to have a receiver in the house. supplying live speech and radio pro- more attention to the manner of pack- Together with cabinet appearance, aging un- grams to 128 zones. and to the container itself. The itization is becoming an increasingly A number of amplifiers are adapted early radio receiver was an aesthetic atrocity -today it may be the finest piece of furniture in the room. Preoc- cupation with technical problems in

Photo Simplest form of the I- RCA console. Photo 2 -This console provides two turntables, an all -wave radio and wide paging facilities. RADIO -ELECTRONICS for

www.americanradiohistory.com Audi* I39

Hybrid equipment employed A notable feature of both the above systems is that while they are designed to work with the manufacturer's own equipment, they may be used equally well with apparatus the purchaser al- ready has on hand. Another manufac- turer (Lafayette- Concord) has gone a step further in its unitized sound equipment designed for industrial plants. One of the company's standard Lafayette- Concord amplifiers is in- stalled in the lower part of the assembly of Photo 5, while a Browning FM -AM tuner in the top section supplies FM and AM music for distribution. The micro- phone is for paging. Photo 4-The other units of the Customode. A number of other interesting uniti- zation and packaging experiments are being put forward. In some cases uni- tized chassis are seen. This method of construction was first brought to public attention during the war with the Har- vey unitized radio (RADIO -CRAFT, No- vember 1943). Each stage of that radio was a separate unit. A number of units Photo 3 -The Jensen reproducer cabinet. were strung side by side on bus wires to the unit -built system, though they to make up a receiver. may not necessarily have been designed In some of the modern amplifiers, to work with it. For example MI -4288 such as the Ward illustrated elsewhere and MI -4297 described in the table on in this issue additional chassis are page 28 may be used in many installa- placed behind each other. One or several tions. There is space in the pedestals for of these can be placed behind the same pre -amplifiers, and for a number of spe- panel, as on certain RCA and Airline cial effects generators (time signal, amplifiers. Amplifiers can be built up to electronic siren, fire signal) which are higher powers, additional pre -amps add- available if required. ed, or defective sections removed for servicing, with a facility impossible in The Jensen Customode more rigid equipment. As competition may The Jensen equipment consists of four for the sound market increases, we of totally new basic wooden cabinets. One of these - expect to see a number reproducer (Photo 3) is designs in the direction of better and the bass reflex and unitiza- designed to accommodate the manufac- more versatile packaging Photo 5 -A hybrid system for industrial use. turer's 15-inch loudspeaker units. It may tion. be used in either a vertical or horizontal position. It is 36 inches in one dimen- sion, 24 in the other. All Customode units are 18 inches deep. The other basic units (shown in Photo 4) are an open-front record cabinet with three shelves, and two utility cabinets, with hinged fronts. One of these is 24 inches long, the other 18, and both are 12 inches high. They provide sufficient space for re- ceivers, record players, recorders, am- plifiers and any other equipment the high -fidelity enthusiast, experimenter or apartment -bound amateur may require. Photo 5 is a composite which uses all the units -record cabinet at left, repro- ducer in center, small cabinets at right and medium cabinet above. Innumerable other arrangements could be built up from the basic units. An almost limit- less number of combinations is indeed possible with these cabinets. The sim- plicity of design will also doubtless start many a home constructor on the road to a neat and unitized layout of his own equipment in simple home -built cabinets. Doors hinge at the side on the small cabinet, drop down on the large one (to form an operating table if required). Motorboard and slide assemblies may be used instead of doors for cabinets in- tended to hold phonographs or record- ers. Illustration of one unitized -cabinet combination. Possible variations are almost unlimited. OCTOBER, 1948

www.americanradiohistory.com Audio 4 0 I Cover Feature A Sonic Analyzer :fn instrument which brings panoram- ic analysis to the audio spectrum

number of receivers standing by on a other audio measurements and particu- single frequency. larly in vibration analysis. They are also used for monitoring In the Model AP -1 analyzer, a block and designing industrial r.f. equipment, diagram of which is shown in Fig. 2, the are used in laboratories for analyzing output of the equipment under test is oscillations, pulsed signals, modulation fed into an a.f. amplifier. Its output, in characteristics of FM and AM systems, turn, is swept by an oscillator which designing and maintaining mobile trans- beats with any audio -frequency signals PANORAMIC analysis of radio -fre- mitters and receivers especially for FM, which appear to produce a sum fre- quency signals became familiar telemetering, radar studies, and by quency of 100 kc, which is applied to a during the last war. A receiver was broadcast stations for observing char- very sharply -tuned 100 -kc i.f. amplifier. electronically or mechanically tuned acteristics of their transmitters con- The i.f. output is detected, amplified continuously over a given band of fre- tinuously. through a video amplifier and applied to quencies and its output fed into the ver- the vertical plates of the cathode-ray tical amplifier of a cathode -ray oscillo- Panoramic audio analysis tube, whose horizontal sweep is kept in scope. A signal on any part of the band synchronism with the local oscillator, being covered would cause a pip to ap- To further increase the usefulness of thus permitting the face of the tube to pear on the oscilloscope trace. By syn- the system, the manufacturers of the be marked off horizontally in fre- chronizing the horizontal sweep of the panoramic analyzer conceived the idea quencies. oscilloscope with the tuning apparatus, of extending the method to cover the audio range. The frequency scale on the tube is The result was the Pan- logarithmic, and the sweeping oramic Sonic Analyzer shown oscillator on our also scans logarithmically. Since front cover. This instrument sweeps the the range ability to separate individual frequency from 40 to 20,000 cycles once per components (the resolution second, showing an audio of the in- signal of any strument) depends on the relationship frequency within the range as a pip on between the horizontal the instantaneous rate of scan base. Fig. 1 shows how it and the selectivity of the intermediate is used for analyzing an amplifier which frequency stages, is fed a signal means is provided to at 1.5 kc. The second, vary the i.f. selectivity continuously. I I third and fourth harmonics appear, and Selectivity is greater at the lower fre- I are measured on the screen at 4, 1.25 quencies -where frequency components and 0.5r,á respectively. These measure- ments may be close together in terms of cycles are on the log (left -hand) scale -and decreases with increasing of the cathode-ray screen. fre- quency. Perfect synchronization is ob- Fig. I-A I.5- kilocycle wave and harmonics. The value of such an instrument in tained by having the selectivity controls, checking audio amplifiers is obvious. the local sweeping oscillator and the the pip's position on the oscilloscope Not only may harmonic distortion be cathode -ray tube horizontal deflection could be made to indicate its exact fre- instantly spotted and measured, but controlled by the same sawtooth genera- quency. intermodulation distortion shows up im- tor. Numerous panoramic analyzers were mediately. It also has applications in The balanced modulator shown direct- used by the military to cover the whole usable radio- frequency e-e spectrum. Not IOOKC %TAL FILTER AND AMPL. only did they indicate the presence of 40ß0K CPS I enemy transmitters the instant they BAL. MOO IOOKC AMP. DETECTOR opened up, but also intercepted many a distress messages. Due to makeshift equipment and inexperienced operators, ISKIP MC. these were often well off the regular dis- LIN VIDEO AMP. REACEMOO. SE ECTIV. VOLT. CALIBRATION tress bands on which constant watch CONI SELECTOR was kept, and the panoramic analyzer i was entirely responsible for many res- 'ISOLATING AMA. cues which would never have been made C.RS. without its help. VOLT./ F REQ. STANDARD SCALE SAWTOOTH GEN In times of peace, the panoramic an- SELECTOR AND AMPL. alyzer is used by amateurs, who can sur- INPUT VOLTAGE RANGE SELECTOR 1 MULTIPLIER vey a whole band continuously with it, I I and by commercial stations who can sub- stitute one panoramic analyzer for a Fig. 2 -Block diagram of the Panoramic Sonic Analyzer's main chassis (upper section in photo). RADIO -ELECTRONICS for

www.americanradiohistory.com Audio I41

Right -Upper chassis of the Son:c Analyzer. Above -The lower chassis contains the intermodulation measuring equipment and power supply.

amplifier eliminates produce a pip reaching to the 0.5 point sired level and switching equipment to ly after the first a.f. fre- spurious modulation products and keeps on the cathode -ray tube linear scale, measure each of the interacting the local oscillator frequency out of the with the scale selector set at 50 my and quencies. at X10,000. (Full scale While the instrument is intended i .f. the multiplier such Two voltage scales are provided on output would be 500 volts in this case.) mainly for measuring distortion in the cathode -ray tube -the left gradu- Measurements as low as 50 microvolts types of audio equipment as amplifiers, aids, etc., it may ated in a two -decade log scale and the are possible. Smaller measurements can radio receivers, hearing right graduated linearly. Input voltages be made by using a highly linear am- also be used to investigate rectifier hum, are measured with the scale selector plifier between source and analyzer. power system harmonics, high -fre- and input multiplier (third and sixth Special equipment is provided in the quency vibration and for Fourier an- knobs from left, respectively). The scale lower chassis of the sonic analyzer for alyses of square, rectangular, sawtooth selector has seven positions ranging use in measuring intermodulation dis- and other types of waveforms. A variety immediately from 0.5 to 50 millivolts, and the multi- tortion. This consists roughly of am- of possible applications will plier has five positions from X1 to plifiers, attenuators and a demodulator suggest themselves to :_the practical 10.000. Thus a 250 -volt signal would to bring the input frequencies to a de- sound man.

AIDS Bureau of Standards laboratory NEW DEVICE MEASURES GAIN OF HEARING setup to determine the gain of hearing aids. An echoless room is usually used to compare the THREADED TO FIT 2.7/8 SPAR volume of sound picked up by 27/32 MEW 3/4 the hearing -aid microphone ii with the volume supplied by the _/ earphone after amplification. Mal=ial,G more Method shown gives pre- cise measurements. The aid's j microphone is fitted into one end of a sealed cavity to which sound is applied by a loud- speaker. The cavity, shown in inset, appears in the photo at lower left. The hearing aid's earphone is fitted to another sealed cavity. Sound pressure in each is measured and recorded for each frequency, on tape of right. The amount by which sound pressure in the earphone cavity exceeds that in the microphone cavity gives an in- dication of the hearing aid's net gain. Evaluation of the elec- trical gain of the amplifier is easily made with an ordinary meter, but no account is taken of the acoustic efficiency of the microphone and earphone. The new method of measurement gives information on over -all performance.

OCTOBER. 1948

www.americanradiohistory.com 42 Audio Radio Set and .Serriee Review

Amplifiermplifiei Co. of A niteriivi .lode/ RIO

inch wide, only 1/69 inch less than the terial recorded on one track cannot be usual single track. There is 1/32 inch heard when the other track is played spacing between the two. back. Due to the slightly reduced width No alteration is made to the tape. The of each track from the usual size, out- two tracks are created by the position- put in playback is about 1 db less than ing and construction of the record -play- usual. Erasure of one track does not back head and the erase heads. These affect the other. Records made on the are shown in Fig. 2, a top view of the Twin -Trax (if made in one direction tape -handling chassis. One erase head only) may be played back on any ma- is positioned at each side of center. The chine equipped to handle Scotch tape at right -hand erase head is mounted slight- 71/.:: inches per second. ly higher than the left one, so that it erases only the upper portion of the Excellent quality tape or track 1. The left erase head, set The twin -track feature and the re- % inch lower, takes care of track 2. duction in size of each track do not seem The single record- playback head at to affect tone quality. Frequency runs the center is used for both tracks. When showed that response, from amplifier in- the lever at right is placed in the FOR- put to playback- channel output, varied Model 810 Twin -Trax Magnetape Recorder. WARD position, the tape runs from the no more than 3 db from 70 to 9,000 right reel to the left. The record -play- cycles. What is more important, listen- TWO separate half-hour recordings back head rises so as to magnetize (or ing tests made with a 12-inch, high -qual- or a single one -hour record may be be magnetized by) track 1 only. If the ity speaker showed a most satisfactory made on a single 1,225 -foot strip of user has set the amplifier controls for standard of performance. Using both Scotch recording tape with the new recording, the lever also switches in the high -fidelity FM channels and live per- Twin -Trax Magnetape recorder, made right -hand erase head, obliterating any formers, a large number of varied se- by Amplifier Corporation of America, previous recording on track 1. lections was recorded- popular and New York. The recorder is furnished When the lever is set at REVERSE classical music, male and female speech, either as a complete unit with case, the tape runs in the other direction and even dog harks. The latter were so life- the record- playback head is lowered 143 like that a dog in the room where the inch to coincide with track 2. When re- tapes were played back spent consider- cording, the left erase head is energized able energy trying to find the owner of to obliterate previous sounds on track 2. the full -throated bay within the speaker Despite the close spacing of the cabinet. Though no distortion measure- tracks, tests show that, unless too high ments were made, reproduction was ex- a recording level is used, program ma- tremely clean and noise level very low.

su Fig. I -How the two tracks are positioned. 5 -watt, 10 -tube, high- fidelity amplifier, and oval loudspeaker, or as a mech- anism for which the purchaser may sup- ply his own amplifier. The tape- handling chassis is by far the most interesting portion of the re- corder. It is the first of its kind on the market. The tape is run through the machine in one direction and a half hour's ma- terial is recorded. Then the mechanism automatically reverses, and the tape runs in the other direction while a sec- HU ORWARD ond half -hour recording is made. Prob- ably the most important feature of the unit is the resulting economy. A stand- , ard half-hour reel of tape may be used STOP for a full hour. 2?_ OP.J Fig. 1 shows how the is tape used P:_ 1 REVERSE twice. As the name of the recorder im- i plies, the tape provides two recording MOVABLE ERASE HEAD RECORD ERASE'HEAD REVERSE tracks. The width of the recording MOUNT TRACK 2 PLAYBACK TRACK I CONTACTOR on (REVERSE) HEAD (FORWARD) the standard 1k -inch tape is 7/64 inch with most recorders. In the Twin -Trax the tape utilizes two tracks, each 3/32 Fig. 2-Top view of the recording chassis, design of which permits very easy tape- threading. RADIO -ELECTRONICS for

www.americanradiohistory.com Audio

Auditory fatigue, which is probably the best measure for small amounts of dis- tortion, was not apparent even after several hours of listening. The driving mechanism, consisting of a single motor and four rubber -tired drive wheels under the chassis, normally drives the capstan at a sufficiently con- stant speed to eliminate wow or notice- able variation in speed. The unit tested, however, did wow slightly toward the end of the forward run. This was traced to a small amount of oil which had dripped on the rubber tires of the drive wheels. Cleaning them with a small amount of carbon tetrachloride removed the wow. Normally, excessive lubricat- ing oil is not used in the factory and a cup is provided to catch any leakage. The cup itself may possibly leak (as it evidently did in the tested unit) due to shipping and handling. Some wow may also be caused if the tape reels are slightly low or high so that the tape does not wind evenly. A small, easily loosened setscrew beneath each drive shaft permits height adjust- ment.

Con record one hour be used The twin -track feature may Fig. 3- Another view of the tape- handling mechanism, with protecting hoods in place. to record a continuous one-hour pro- gram. The reverse contactor, indicated against which the tape rubs. Its center do not touch. Near the end of the tape in Fig. 2, is an insulated guide post is divided into two metal contacts which the user may paste a small strip of con- I2SC7 6SN7 6E5 12SJ7 Rl6 C22 ; L R26 R16 6SN7 6V6 RI4 R15 12 (4 RECORD R24 R26 CI7

P25 R 29 RADIO RI R2

6 (I6

R13 R32 R4 C24 MIKE

RECORD -----T 53 C26 R37 RP R P R P S f H r o R40 II7VAC PLAY R ( 32 -m r 6.3VAC ` / t

P2 ¡ r14 SOLENOID CONTACTOR Y, 52 // EAT AMP Moron, L----J 1 //

3 C21 Pil0T5 L OUT TRANS -_ R42 R43 /600A i

5W ON TREBLE CONI R39 Ru R45 EN o STOP C37 3.2. 6.3Y R44 REVERSE R56 117VAC p TREBLE 5Y3-G CH EKT L------C30 C26.r SPAR BÓOoLINE 6 \B 3 I11VVC TO S3 C29 C3 R47 54 P4 SPAR

BASS Fig. 4

RI4TOA,F2.2CA,R34011.R4-1.511,R51MEG,R6-HAG, RT-25011,R6-270K,R7-40K, RIO-IMEG,RII-S0OA,R12-500N,R13-IA, R14-100M,R15-2505,W6-250A,R17-IA, 50A,R19-270A,R20-10K,R21-IMEG,R222A, R3625A, R39-2S11/20W, R40-10K, R41-10A, 1123-SOA, P14-50A, R25.500A,R26IMEG,R27-100A,R26-27A,R29.100A,R30.250A,R31-250 / IOR, R32-275, R33-10011, R34-50K, R35-I11, R3G-10K, R37-7.5K/20W, R42270A,R43-2AB,R44- DREG, M620A,R46-10K,R47-IMEG,R46-5K,R49-IN, R50100(,R51-1001C,R52-50011,R53-2511,R54-50011,R55-200/10W, R56- 25. C20-.05, C21-.0005, C22-.000I, (1-.0005, C2-10/450V, C3-.I, C4-.I, C5-.00025, C6-.002, C7-.I, C6-.I, C9.01, CIO-.001, CII-.t, Cl2-25, C13-.00y CI4-.01, CISDI, (16-.001, 07-001, C16.1, C19-A01, C34-.1, C35-10/450V, C36:00025, C2310/450V, C24-!0/4501, C25-10/450V, C26-VALUE DETERMINED BY HEAD, C27-.0002, C26:002, C29-10/4509, C30-10/4509, C31ro006, C32.10/450V, C33-.t, C37-.3, C3650/25V, C39-.I, ALL CORDS 400V UNLESS OTHERWISE NOTED RPH-RECORD PLAYBACK HEAD EN-ERASE MEAD OCTOBER, 1948

www.americanradiohistory.com 44J ducting tape -Scotch cellulose gummed around various heads and guides simpli- It is then equalized by a fixed tape backed with metal network, foil. When the fies operation considerably. C9 and 10 and R19, 20, and 21 foil shorts the contacts, (manu- a solenoid is When the left lever is placed at facturer's part numbers). The output of actuated. The solenoid is shown at the SHUTTLE and the right lever shifted into lower the second triode of the 6SN7 feeds the left in Fig. 3. Its plunger travels FORWARD or REVERSE, the capstan no head. to the A 6E5 electron -ray tube mounted right, pushing a long metal bar longer controls tape speed. Rate of on the control panel (not which trips the forward- shown in the reverse lever travel in either direction is, therefore, early model) is used as a recording -level into REVERSE. The tape immediately much increased -four times, in fact. Al- monitor. For professional users S5 is changes direction and track 2 comes into though twin -track operation normally provided for connection to a vacuum - use. Reversal time is about 1/5 second, leaves the tape rewound at the end of tube VU meter. The socket furnishes all and disturbance to the program is slight. a one -hour session, the high shuttling necessary power. speed is very useful for rewinding when The supersonic bias and erase signal Shuttling difficulties less than an hour has been recorded or (approximately 50 kc) is generated by for skipping a portion of the tape to a 6SN7 and a 6V6. Erase voltage During the tests, the solenoid some- play is fed times back only selected parts. A com- to the erase heads through a plug and failed to throw the lever into RE- plete rewind at the shuttling VERSE, leaving it, speed takes socket, P3 and S3, respectively. Bias is instead, at STOP. The 71/2 minutes. maker stated that this was due to superimposed on the audio signal by mal- The operator simple positioning of the small rubber cap on should not shift from capacitive coupling to the head the right end of the solenoid SHUTTLE to RECORD PLAY while the tape through C21. In the diagram all com- plunger, is running and that, if the trouble seems likely to at high speed. It is perfectly ponents which are parts of the tape - recur in production models, a permissible, however, to shift from the handling chassis are enclosed in dashed firmer low mounting for the cap will be to the high speed without stopping boxes. devised. the motor. The shuttling lever at the left in Fig. The playback channel has a gain of 2 is used for high -speed rewind and for The amplifier about 120 db. The high gain is the prin- threading the tape. All three heads cipal reason for using d.c. on the first are two on movable mounts. When the lever is The complete recorder is shown in tube heaters. After passing through placed in the SHUTTLE position, the the photo at the head of the article. The the right half of the 12SC7, the signal heads snap back out of the way (down- photo is that of a pre- production model, is fed to the 6V6 output tubes through a standard ward in the picture). The tape is then and the panel lettering has been 6SL7 phase inverter. Output put in place merely by dropping it into changed slightly. is 5 watts to a 6 x 9 -inch oval speaker. the slot between the hoods (Fig. 3), The schematic diagram appears in As the diagram shows, connections which places it automatically between Fig. 4. Except for the 12SJ7 preampli- are provided for an external 600 -ohm the heads and the capstan and guides. fier (note d.c. filament heating of this speaker. No 600 -ohm wires are attached The lever is then placed in the RECORD and the 12SC7), two separate channels to P4, so the owner must install them. PLAY position. This pushes the erase are provided for recording and play- A phone jack allows plugging in an ex- heads against the tape and locks it back. ternal .I -ohm PM speaker. tightly between the record-playback In recording, the microphone or head and tuner the capstan, so that tape speed signal is amplified by the 12SJ7, the Equalization system will be controlled only by the capstan. left half (on the diagram) of the Both fixed and variable The lack of any need for threading tape equalizers are 12SC7, and the left triode of the 6SN7. incorporated in the playback channel. Fixed components are C5, 6, and 26, and R8, 9, 10. C27, 28, and 31, and R42, 43, and 45 are parts of the variable equalizers. The controls are R44 (treble) and R47 (bass). The positions of these controls for flat output are marked on the front panel with red dots. A connector is furnished for feeding the output of the playback channel to an external amplifier. This is useful for dubbing tape recordings onto discs or for feeding PA systems. A maximum of about 3 volts is available. To avoid increasing the over -all height of the recorder, the amplifier, shown in Fig. 5, is mounted under the tape chassis with tubes on the rear apron. This also keeps the tubes cooler and makes replacement easy. Buyers of the tape- handling chassis are furnished with an instruction book which describes the necessary amplify- ing equipment and shows how to connect the heads to existing amplifiers, as well as giving the necessary instructions and cautions on the actual manipulation of the mechanism. The tape-handling mechanism is like- ly to become very popular with experi- menters and sound men who already have elaborate amplifying equipment. There is tremendous enthusiasm for magnetic -and especially tape- record- ing, but the difficulty of building the 3 ____w 8 precision recording and playback head has deterred most serious workers from Fig. 5-The amplifier is specially constructed to fit under the tape -pulling chassis. constructing recorders of their own. RADIO -ELECTRONICS for

www.americanradiohistory.com DON'T BE A" PRE -WAR MODEL!

MAKE MORE MONEY -ENJOY SECURITY with CREI'S Brand -New 1003/4 Practical "On -the -Job" Course

1&vs1Iø)v W1I

Be Left Behind For Every Serviceman Who Realizes He Must Keep Pace - or handle all types Going Now With this soon have the technical knowledge nece- -ary to Don't Put it Off! Get of good paying Television and FM servicing business. Will Equip cont- "Down -to- Earth" Course that It costs you nothing but a few minutes time to get the You to Forge Ahead in the Servicing Field plete details of what we offer and what it can do for you. The next twelve months will produce some of the greatest op- portunities that have ever been offered to alert men in the CREI EQUIPS YOU TO INSTALL AND SERVICE Servicing Field. ALL TYPES OF TELEVISION AND FM RECEIVERS It is the year for you to make the big decis . Either you are in the industry, going to catch up with the new developments Now ... with the help of of the "top third" now en- or you are going to be passed by. this new CREI streamlined gaged in service work to profitable are so great, that over a two -year Service course you can move enter the ultim to We think your opportunities and FM we have been developing this brand -new. practical ahead to unlimited oppor- field of television period service. course. It is written for today's servicemen to meet today's tunities in your chosen field. installation and problems and opportunities. CREI has again taken the This can be your big year! waste another day. made to lead by offering a course so Don't CREI knows what you need, and every effort has been CREI has the answer, to your If you are now en- entirely new that for the first keep this course practical and to the point. year future security in this new work, you will be able to understand nd time in our twenty -one gaged in servicing - course. Write today been reviewed and checked history we can offer a down servicing apply each lesson. This course has for complete information. service experts who know what you most know to -earth course of training by qualified In offering The cost is popular. The to get ahead in this booming field. for servicemen. this course at a popular price, terms- are easy. The infor- Every lesson can he helpful in your daily work- -you will CREI is enabling thousands mation is free. Write today. MAIL Radio Service Division of CAPITOL RADIO ENGINEERING INSTITUTE Washington 10, D. C. TODAY 16th 6 Park Road. N. W., Dept. S ial. Gentlemen: CAPITOL RADIO Please send me complete details of your new home study emirs, in Television and FM Servicing. I am attaching a brief resume of my experience, education and present position. ENGINEERING INSTITUTE NAME_ An Accredited Technical Institute STREET Wash. 10, D.C. CITY ZONE. STATE Dept. 5108, 16th & Park Rd., N.W., I. I All ENTITLED TO TRAINING UNDER G. PILL. Branch Offices: New York 7) 170 Broadway - San Francisco 2 760 Market St. OCTOBER, 1948

www.americanradiohistory.com -16 Audio

Frequency Test Records

Tone discs are an indispensable tool for the audio enthusiast and the serviceman. Pickups cannot be equalized without them, and other uses are many

By RICHARD H. DORF

Output of pickup from Clarkston sweep record shows flat response (above) and dip (below). ting the amplifier gain control to some On this record, the change convenient begins to take reference level on the meter place at 800 cycles and 11/2 connected is db down to its output. In all cases, the at 500 cycles. Below 500 cycles the curve amplifier used should be flat and the drops at 6 db per octave. speaker should be replaced with a Another RCA record, the 12 -5 dummy -25, will load resistor. You can bridge be very useful for owners of headphones across a 33 1/3- the resistor to listen r.p.m. turntable. Made of Vinylite, it be- to the record. gins with a combined 400- and 4,000 - After the 1,000 -cycle tone, frequencies cycle tone for intermodulation from tests. 10,000 down to 50 cycles are given. Constant- frequency tones are then given At each of the selected frequencies from 12,000 to 30 cycles. (there are 18 of them) a voice identifies No information is available on the the tone to be given, then the tone is condition of present pressings recorded of the for several seconds. Jotting RCA discs. Since the 12 -5 -25 down the is a fairly output -meter readings gives new recording, it is probably in good the performance of the pickup -amplifier condition. HOW good is your phonograph combination. If the amplifier is flat, the pickup? How well does it per- readings will give the curve of the pick- London Gramophone form? How correct is the equal- up. An excellent set of discs is made by izer you have bought or built Because of the age of the masters to go with the London Gramophone Corporation. it? You can find the answers from which these Columbia records are The album to these questions with very little is No. LA -32. Three records trou- pressed, the 10003 -M is not flat at the are included plus the best ble and expense by using standard fre- high frequencies. stroboscope Tests of several recent we have seen. The stroboscope is cali- quency records. At least one of these samples show that response begins discs should to brated for 78 and 33 1/3 r.p.m. and for be in the record library of drop off at about 2,000 cycles and 50 every audio enthusiast. is and 60 cycles. There are only two Radio service- down 9 db at 10 kc. About the same bands on each side. men who are called on The disc is 10 inches to install and effect is present with the 10004 -M. Co- in diameter and the stroboscope repair changers and hi -fi phono bands systems lumbia is understood to be preparing a are in white against a black are missing a good bet, too, if they don't new set background. of test discs, including at least The first record has a constantly keep a tone record in the shop. one which can be used to calibrate pick- varying tone from 14,000 to 10 Phonograph pickups are not easy to ups for the new cycles, calibrate Microgroove records. recorded with the same characteristic with ordinary equipment. To Most discs cannot be used for this pur- as is check an amplifier, employed on standard London rec- all you have to do is pose because the grooves are too wide ords and Decca connect an audio oscillator ffrr discs. A playback to the input for the 1 -mil- radius needle. system can be equalized and a voltmeter to the output perfectly for and start the high -quality British discs twisting dials. But you can't check pick- RCA Victor records with this ups without a frequency record unless RCA makes a number of test records, you use expensive 100 custom-built labora- some of which contain no modulation. D! tory equipment. These have lead -in grooves, a few nor- o 9NIINNINIIMIIIIMEISNBIIIp Five firms make the test discs which mal grooves, and an eccentric lead -out are most easily available in this country. groove. They are used for testing the m Each company SL7III1N1 makes several different action of record IS I'N11117/1111BN1111NRIN11 -changers and juke I records, each designed for a special pur- boxes. There are also records with a few nil s ss ,j. sos 1:INII pose. To choose the proper one for your odd -frequency tones, used for special own ap- I needs, note the description of each plications. mAllmep `" `" smu record carefully and check the informa- Probably the most useful RCA Fig. I- Curves show how pickup types differ. tion record against your own problems. at present is the 12 -5 -5. This disc con- tains a continuously varying record. Columbia frequency records tone, be- All that is necessary is to play ginning with 10,000 cycles at the outside the frequency record, adjusting equali- Probably two of the most often used and ending with 30 cycles on zation tone the inside. until the amplifier shows flat out- records are the Columbia 10003 -M Buzzer signals are insertéd at a number put throughout and 10004 the range. American -M. The curve of the 10004 -M of points to mark the frequencies. The manufacturers might is the same as take a hint from curve 1 in Fig. 1. The disc is flat above 800 cycles (except for the British, both on standardization curve of the 10003 of -M is similar, except a slight dip at about 8,000). The cross- the characteristic and on issuing fre- that the turnover is moved down to 300 over frequency is 500 cycles. Like most quency records cycles. Both for it. This British these records begin with a records, the bend in the curve is not as standard is shown in Fig. 1,000 -cycle tone. 2. This is useful for set- sharp as in Fig. 1, but more gradual. The second disc has the same low -fre- RADIO- ELECTRONICS for

www.americanradiohistory.com 47

a MONEY BACK GUARANTEE- We believe units offered for sale by mail order should be sold check the design, calibration and value only on a "Money- Back -If- Not -Satisfied" basis. We carefully to a return for credit or of all items advertised by us and unhesitatingly offer all merchandise subject _refund. You, the customer, are the sole judge as to value of the item or items you have purchased. Accurate Pocket -Size THE NEW MODEL 670 The New Model 770 - An VOLT -OHM MILLIAMMETER SUPER METER (Sensitivity: 1000 ohms per volt) SUPER METER. A l'n,10 n all, n Features: ST¡p" x VOLT - OHM - MILLIAMMETER Compact -measures 314g" x 21/4" plus Uses latest design 2'; accurate 1 Mil. INDUCTANCENDI Ta nRd ADECIBEL D'Arsonval type meter. Same zero ad- MEASUREMENTS. justment holds for broth resistance ranges. is not necessary to readjust when 7 I I-1 It D.C. VOLTS: O to :3 ` range to 150u 75.0. A.C. VOLTS: uwitehing from one resistance enother. This is an important time -sav- ing feature never before included in a D.C. CURRENT: n 1'. 1 -. I. l'.o . : V.O.M. in this price range. Housed in n 00/ 1. 0 to I -, An., RESISTANCE: round- cornered, molded case. Beautiful 11 CA- 100.01111 Mmis, to 10 Megnhms. letters to 4 NMI. black etched panel. Depressed PACITY: .001 to .2 ?pfd.. .1 - (Quality test for eleetrolyties.1 REACT- filled with permanent white. insures long ANCE: 700 to 27.000 Ohms: 13,000 Ohms life even with constant use. to 3 Menelaus. Specifications: 6 A.C. VOLTAGE RANGES: -31111, its. INDUCTANCE: 1.73 to 70 Henries: 35 u 1 5 /3 0 /15 0 1300 /3unn to 0.000 Beadles. 6 D.C. VOLTAGE RANGES: 0- 7'¢/15!75/ +38, I-m 7311/15011 volt, DECIBELS: --I0 to +18. +10 to / D.C. CURRENT RANGES: 0- 11z/15 /150 +30 In +:3R. ]la. 0-l'2 Amps. 0 -1 The model 670 comes housed in a rugged. 2 RESISTANCE RANGES: 0.500 ohms. cracklefnlshed steel b- Slegohm. eet complete with test The Model 770 comes complete leads and operating in- $2840 with self-contained batteries, 390s7 and all operating structions. Size 5'/0" X NET test leads N[T 71.2" s 3 ". Instructions. The New Model 450 THE NEW MODEL 777 TUBE TESTER 20,000 OHMS PER VOLT!! Speedy ope nrl ì1,n -o. unit b. the newly designed rotary ,elector switch which replaces the TUBE & SET TESTER usual snap, toggle, or lever Tube Tt vier Specifications: action switches. *'Tests all tubes including Now Miniatures, etc. Also Pilot Lights. * Tests by the well -established emission method for tube quality, on the scale of the meter. * New type line voltage. SPECIFICATIONS directly read lobes up to 117 volts. V.O.M. Specification: `Tests all D.C. VOLTS: gat 20.000 Ohms Teals shorts and leakages up to lobes. Tests Per Volt', 0 to 7.5/15,75/110,730 / 3 31eyohms In all 1.500 Volts. lank plates In '(,sets. Net type line vollace tadju, ter. Tr -u A.C. VOLTS: (At 10.000 Ohms as iisle indisi dual sections suet . Per Volt). in to 15,30,130'300/ trlles. pentodes. etc.. in multi- 1á0n.::.01111 Volts. purpose tubes. Nuise Test deferl- udrodn ,nie tubes noise dur t.. D.C. CURRENT: 0 to 1.5/15/ faulty rlenanls and s lane Internal 150 Ma. 0 to 1.5 Amperes. conncetions. rses a 41/2' soma, RESISTANCE: 0 to 5.000/50,- rugged ruder. W'o'ks on Ou to 000/500.000 Ohms. 0 to 50 Slog - 123 suies 00 eyeles A.M. [211111. EXTRA ICE -Move Model 777 Pe ate on 90.120 an extremely be ondeeeee volts SO cycles ' A.C. Housed Leakage Checker. AI laaaton type beautiful 'land- rubbed Cabinet. .11atorincorpdrat- Complete with test IeaES,tubes. Coon d detailed $( 9 Cages $3950 will 1detetale operating x even when the Ire- t.on e 1iá. the perNET 131 7- S ". NET minuté. The Model 88 COMBINATION The Model S -35 a POWERFUL -A SIGNAL GENERATOR REFLEX PROJECTOR AND COMPLETE WITH WESTERN ELECTRIC SIGNAL TRACER BUILT -IN DRIVER UNIT Signal Generator Specifications: CONSEItVATIVELY RATED AT 35 WATTS -WIL1. EASILY Frequency Range: 150 Kilo- HANDLE UP T11 53 WATTS WITHOUT BLASTING cycles to 50 Megacycles. The blast- is gattge alumi11t1111 In the ni in trumpet section r10.01etely eliminates R.F. Signal Frequency kept Wass of the ing and blaring. New plastic diaphrtcm osenuules Ihr tesnlant peaks completely constant at all out- changes whereas the 11d type: also it Is absolutely snipe rr'loins to attOoSpherle put levels. Modulation is ac- old type Was subject to atmospheric cor- ac- usltal Complete uralt unconditionally complished by Grid -blocking guaranteed for mie Year. tion which is equally effective for alignment of amplitude and Specifications frequency modulation as well as POWER (CONSERVATIVE) - 35 for television receivers. R.F. ob- -312 FT.; tainable separately or modu- WATTS: AIR COLUMN lated by the Audio Frequency. DISPERSION -8C: POWER (PEAK) -55 WATTS: BELL DIAMETER - Signal Tracer Speeineatlons: -15": IMPEDANCE ---8 ohms: FRE- I'se5 the new Sylvania IN34 Ger- QUENCY RANGE -130 to 5000 manium crystal Diode which tsmt- bintd with a eslatanee- capacity . mile: C.P.S. PROJECTION - ,ork provides I a tre- FINISH Attractive eyclei ange 300 two tone - crystalline. cycles to ran Nrg -tI' 3111 The Model S -35 Comes $2885 $2850 The Model 88 comes complete with all ttest leads and operating Complete with Built -In $ NET NET Driver Unit. ONLY Instructions. ONLY 2Or; DEPOSIT REQUIRED ON ALL C.O.D. ORDERS PARK PLNCY. GENERAL ELECTRONIC DISTRIBUTING CO. NEW YORK0798

OCTOBER, 1948

www.americanradiohistory.com 481 Audio

quency characteristic (turnover at 300 when a frequency-modulated oscillator cycles) but are played with a good pickup or one the high end is flat. Again is used. The amplifier output cannot be equalized to give flat output the highest tone recorded is 14,000 over the measured directly but must be fed to the range, the recorded tones can be used in cycles, which is higher than anything on vertical plates of an oscilloscope. The place of the American test records. test oscillator. Tests made with pattern, for a flat pickup and amplifier, For testing amplifiers it is possible the London frequency album, is to using an similar to that at the head of this use a pickup which does not have a flat equalized G -E pickup, showed that the article. The lower figure shows the inclusion pat- response, but some method of controlling of 14,000 cycles was no mere tern when there is a dip at about 5,000 the amplitude gesture. Both of the tone will have to be the optical pattern and cycles and a peak at 3,000. The entire used. This is not the pickup tests showed always a good idea, that the 14,000 - frequency range can be observed at once since if the pickup is very cycle tone was not only present, deficient in but and the effect of any adjustments in the the high range, so much pre- amplifica- actually was slightly higher in level playback system can be than seen without tion may have to be used that noise will the rest of the treble band. necessity for making a laborious run spoil the measurements. The third disc has the same curve as through the whole band. Marker pulses the second Servicemen who find themselves con- but instead of a continuous are placed at 1,000, 3,000, 5,000, 7,000 fronted with variation in defective changers will find frequency, a number of con- an investment in 10 e0 11 1011 one of the special test stant tones are used. The same 2011 range is records well worth while. Some of these, covered but the lowest frequency is 30 mentioned cycles instead .s earlier, are available from of 10. RCA. They will test the entire operation The London records o are pressed in of the changer mechanism in a few sec- the same smooth material (with high onds. shellac content and little abrasive) as Space does not permit a discussion London musical discs. The surface noise here is so of the underlying principles of low that the level of even the high- making records. For that est- frequency tones can easily be reason, the judged reader may wonder why the low -fre- on an output meter. The album is an quency section (below turnover) is outstanding one in every respect. 2 re- It is corded at lower level than the rest of too bad that there is not one disc -3 with the range. That this is true is illustrated a 500 -cycle turnover (for equalizing for 35 by the "Christmas- tree" light American records) but the higher -fre- pattern Fig. photograph. The width of the light quency sections of at least two of the 2- British discs are recorded this way. discs bands seen when a record is held so that are eminently suited for equalizing a single a system for any purpose. and 10,000 cycles so that each part of light source is reflected from the pattern may readily be identified. it indicates the volume level of each of Universal D61B The patterns show not only frequency the tones recorded. A full explanation response of of this appears in the writer's book, The only the system, but also har- disc, as far as we know, monic Pracliral Disc Recording ( made distortion and transient response. Radcraft at present by the Universal Micro- Publications) now just off the press. phone Company is the D61B. This is evi- Using the discs One last word of consolation for those dently intended primarily for the who In using a frequency record (and in have had unhappy results with fre- serviceman, though at least the high - quency records. frequency selecting one, too) the technician must Aging of the masters section is useful to anyone. have and wear of any particular pressing The D61B is pressed a good idea of the results he wants in a very quiet to get. The desired result, may make results erratic. If your pickup plastic, probably Vinylite. It is compar- the equalized frequency curve -will be the same, response seems to have small peaks and atively new, so can be expected to be in no valleys matter what type of pickup is used, in the range, especially if the good condition. The sample tested shows highs roll off, don't throw away the (both light pattern though the equalizer circuits used to ob- and pickup tests) tain them will vary. cartridge. Most laboratories roll their some very slight dropoff at the high own tone discs (when they frequencies. Almost always, the bass band (up to use them at This is not sufficient even all) indicating that the best audio engi- to be measurable about 1,000 cycles) should be adjusted in many cases. The for flat output. neers are reluctant to accept findings frequencies above a -cycle The trick here is to 500 turnover choose a record with based on pressings as entirely conclu- are recorded flat. The tone is a continu- the proper turn- over frequency. For playing most Amer- sive. However, a good collection of test ously varying one, with voice announce- records will give very usable ments ican -made discs choose one with a 500 - results, at each 1,000 -cycle mark. Top cycle especially if the discs are used to check tone is 10 kc. turnover; for foreign ones a 300 - cycle one each other. The average of the curves The low- frequency section is more suitable. For the Brit- of the ish high -fidelity records the first record given by two or more similar discs will D61B has been recorded in 2 hands on prove to he accurate enough for almost the usual constant of the London frequency album is best. -amplitude basis. The All that need anyon. first band, 50 to 200 be clone is to equalize for cycles, was made at flat response over the entire a level 7 db lower than the next, which range. is 200 The high -frequency band is something to 500 cycles. This, in turn, is 7 of a problem. -1,000 db lower in level than the rest Some high -frequency pre - I-I 000 of the emphasis is used in all musical records. -8,000 disc. Just why this was done is not The known. The literature accompanying exact amount is not standardized. -7,000 the However, probably the best compromise -6,000 record gives the output voltages of 14 American, Astatic, is to adjust for the NAB curve, which -5,000 and Shure crystal slopes downward, beginning pickups at 400 and 1,000 cycles. This at about } -4,000 enables 1,000 cycles, to -16 db at 10 kc. Ameri- --3,000 the serviceman to spot a bad one can without too much trouble. makers do not lay claim to any -2,000 frequencies higher than this. -,000 Clarkston sweep- frequency Since the best records to use for this Z,F purpose are recorded with a flat high One of the most interesting test rec- end, the proper equalization will =-::(250 ords have made is the Clarkstan Sweep -Fre- been obtained when the pickup output is quency Transcription, available for both flat below 1,000 cycles and has the indi- S0 33 1/3 - and 78 r.p.m. turntables. It has cated dropoff above 1,000. a tone which varies between 60 and 10,- Frequency records are valuable to 000 cycles at a rate of 20 times per sec- sound men who do not own an audio test ond. The effect is very similar to that generator. If the records, particularly obtained in visual receiver alignment those with a series of constant tones, Fig. 3- Velocity indicated by light pattern. RADIO- ELECTRONICS for

www.americanradiohistory.com 19

.r-".. -ra,4.9--- [A. FAYETTI-C

3 Great ELECTRO Mail Centers To Speed Orders

29 Years of Service -500.000 Satisfied Customers

HUGE MERGER PAYING OFF FOR RADIO MEN! Just 30 days ago we broke th e news about the sensational Here's aspirin for those high MAGIC price headache's. Bargains are Lafayette- Concord merger. And ever since, cheers have been around for smart shoppers., RADIO-MIKE still k. in from value -wise radio men all over the world! at a fete samples wires, Ig Take a look Without like the deal because from our stocks: lets you broadcast These fellows tore taken through your own it means even better service, even SPECIAL radio. Simply New Versatile Hi -Fi Amplifier! lower prices - and they know it! turn on radio and NEW YORK: Lafayette- Concord is now the tune to any clear radio supply organization in BUY! channel between Lafayette- largest Concord engi- the world, bar none. Does that put 1250 and 1700 KC, Frank talk into the mike, neer, any butter on your bread? Mister, VACUUM MJ (.es- and you'll hear ter announces just ask your wife why she likes to through your own radio up to 75 feet o amazing A & P, at Woolworth's. TUBE away. For home, office, restaurants, nurs- shop at the se m. It eries. Uses 45 V. miniature "B" battery élue at R. H. Macy, and she'll tell you. ' It de- VOLTMETER and flashlight cell. No. 22548R, pays to do business with the top 10 wattsliners with tube & battery.... 15.9s7 8O you KIT complete at less than organization. You get what distortion want. You get it right away. You BEST BUY! the entire sure of a 445- square meter. 0.500 microamps dc. over get it for less. And you're of 40 to DC input resistance of circuit, 11 mega- range square deal! Check these 5 impor- 12" SPEAKER 15,000 e. Vari- ohms. AC input resistance 6.5 megohms. tant points: 1. GREATER VALUE; in 5 ranges. able bass and Ranges: .1 to 1000 megohms Alnico V Permanent STOCKS; and DC voltage on linear scales. 0-3; treble controls. 2. COMPLETE AC Magnet Dynamic Separate high 3. DELIVERY; 4. EN- 30; 100; 300; 1,000 volts. Tubes: 1 -6SN7, FASTEST Speaker. 1- voice coil or mike, 5. voltmeter circuit. 1 -6H6 bal- gain channel for G. E. pickup HELP; and OLD bridge type 6 -8 ohm impe- GINEERING linear diode as rectifier. Precision with and low gain channel for tuner. The am- You get anced dance. 14.18W, capa- use with the TIME RELIABILITY. 17, accuracy. Output meter scale plifier is also designed for resistors, city. Dust proof con- foundation unit. more than a full measure of each is calibrated for 600 ohm circuit and based Webster 79 wire recorder struction. Ideal for is being made up when you head your orders to on reference level of 1 mw. Rectifier poster A complete package complete with rase. fine FM reception, which includes the amplifier, Webster Lafayette- Concord. supply. 6 "x9 "x5 ". Kit public address work, roll- tubes, battery and instructions ready for foundation unit and a high frequency etc. An unbeatable The rolloff control with 6 posi- HAVE YOU SENT FOR YOURS? assembly. 110 V., 50-80 cycles. AC. so rush your off control. value, limited quantity, tions for the G.E. variable reluctance or No. 24540R 29.95 Pickering cartridge permits switching from No. 5B7010R si.7r mike to pickup. Write for info on how to PLAY RECORDS BY adapt this nod ipment to your needs. RUGGED SELENIUM RECTIFIER REMOTE CONTROL THRU RADIO May be used to re- NEWS ON THE TV FRONT Supplies sufficient place 117E6,117E3, to plu rec- 0Y4, and other rec- At the start of 194K there were 17 TV ords through radio tifier tubes and stations on the air. Today there are 31 receiver at full socket in AC -DC and many new ones are scheduled to open volume in other battery type port- fast, right across the country. A few of rooms, without able radios, inter - these are: Birmingham, Ala.; Phoenix, wired connections. coma, etc. Peak in- Ariz.; San Diego, Calif.; Ames, Iowa; Oscillator fre- verse V. 380 V.: Peoria, Ill.; New Orleans, La.; Lansing, quency variable 100 milliamps max. IIA" square x 11/16' Mich.; Syracuse, N. Y.; Nashville, Tenn.; between 1350 to high. Replaces both tube and socket. These liallas, Tex.; Atlanta, Ga.; Jacksonville, 1700 KC by means miniature rectifiers are extremely rugged Fla.; Indianapolis, Ind.; Portland, Ore.; of screw driver ad- and long lasting. Order a half down. Salt Lake City, Utah; Omaha, Neb.; and tnrdverlLcoRe8880Biu ., justment of trim- 75 Louisville, Ky. ming condenser. No. 10560R for enough, 4" Here's the opportunity of a lifetime Small room to make a buck se, into any' stand- servicemen. There's x 4" x metal c to go are turning out sets No. 24531R, in TV. Manufacturers ard record player ße49 they can, and their service or- ...... :::,....fREE complete kit, less tube as fast as ganizations 'e frantically trying to find 111nr 9 be fooled. No. 117N7 -GT tube 62.34 men to install i the sets. But don't TV is a lot trickier than radio. if you figure on being a TV man in your com- budging with bargains - up. 1R0 pages munity, now is the time to smarten plus everything in famous brands. As starter you might look over the new of Hi -Fi, Lafayette- Concord TV bulletin. It will Complete coverage TV, and Test give you a quick picture of equipment Bam, AM & FM Radios, P.A. available and how much they Ports, Tools, etc. Rush belons-. Equipment. a lt'sef n.,` Jut clip the coupon It, rem pm' n,. for. wmur.Pere catalog. RUSH THIS COUPON AT ONCE FOR YOUR FREE CATALOG

11 -8 STROMBERG- CARLSON SHOP IN PERSON Lafayette,Concord Dept. York 13 AT ANT ONE Of 100 Sixth Avenue. New MAIL NOW! FM DIPOLE ANTENNA 7 DYNATENNA WR OUTLETS: 901 W. Jackson Blvd.. Chicago Peachtree St., Atlanta 3 Casera all FM bands. Heavy mounting 265 bracket with swivel base permits cantenna Maw YORK TV -FM ANTENNA best reception from any 100 Siso, avenue 13 CHANNEL to be turned for Please rush Free catalog No. 99 me. Arrays use hairpin type direction. Slide -in trombone type arms are 542 E. Rd., Covers 44 -216 Bea 5 tem- in megacycles. mm dipole and reflector elements. ft. calibrated and marked Please send Free television bulletin. pered aluminum mast, Low and high fre- Arms and mast of light, seamless, heat - CHICAGO sections rotable for treated aluminum tubing. Easy to handle, attached order. quency 901 W. Jackson Blvd. 1 enclose S -- Please fill of direction of yet tough enough to withstand winds, ice, - maximum signal regardless 229 W. Madison St. Shipping charges extra. stations. Each section may be oriented to snow. Complete with hardware, six feet of eliminate ghosts, images and interference. 300 ohm low -loss twin lead -in wire. ATLANTA adjustable Peachtree SI. Ceramic insulation. All angle 265 NAME bass mount. Complete with instructions. 5/39578R - Each, singly..__., 14.95 No. 21983R '9.71 Each, in lots of 3 14.45 110 redorai St. ADDRESS LAFAYETTE - CO N CO R L:::::.6 CITY .. ZONE OCTOBER, 1948

www.americanradiohistory.com JOI redi Phase Inversion Headaches

By JAMES R. LANGHAM

didn't. Just a suspicion that something else is better has always set us off on a test. This time the tubes aged and before long our tap was in the wrong place. I had by this time become aware of the floating inverter shown in Fig. 2. This is a sort of self -balancing inverter. The signal applied to the grid of the inverter tube is the difference between the volt- age on the output tube grids. The books say the value of R is not at all critical -just make it big. Well, we tried it. And it worked as the books say. There is a constant differ- ence, though, between the signal on one grid and that on the other. This differ- ence grows less as you increase R, but with any given output tubes there is a limit to how large R can be. If you go past that limit (and we tried that too), you start popping output tubes one after the other, and 6A5 -G's aren't cheap. The result was a steady 21/2 -db difference in Langharn gets out the iron again to try another phase inverter. Hope springs eternal ... levels to the grids. We tried beating that by juggling the sizes of the two 6A5 -G W¡LEN you come right down fooling around grid resistors, but that was just beat- with audio we believed ing our heads to cases, the best phase in- what the transformer companies said against the wall. So we verter is a transformer. Of about went back to Old Standard. their products. We'd look at the About course, transformers have curves they published and wish that time somebody showed me we could the split -load type of inverter illustrated faults: they are expensive if they're afford to get one of those lovely inter - worth their salt; when they are cheap, stage or output in Fig. 3. That looked fine to me, and I transformers. We ac- lost no time putting they don't give equal amplitudes to both tually did save up and buy one that it in the amplifier. grids or they don't pass all the frequen- looked lovely and for which even lovelier 6J5i172 65N7 cies or they pick up hum or introduce things were claimed. It wasn't until 6A5-0 ( 2) too much distortion. about a year later that we discovered Way back when the XYL and I began this beautiful interstage gave one grid about '7 db more signal than the other, 6J5/v2 65N7 6A5-G(21 and that the frequency band -instead of being within 1 db from 20 cycles to 20 kc -was within 1 db only between 80 and 9,000 cycles. Later I got a job in a laboratory where I was required to test a bunch of transformers, and I was amazed to dis- cover that all the big -name jobs ran 8.15 OR I/2 6SN7 circles around their specifications. All CORDS 600V the companies have their high -fidelity Fig. 2 -R should be large for models; and they all publish curves that best balancing. look as though they were drawn with a The plate load of the tube is split, and straightedge but the average guy has no half put between facilities cathode and ground. for checking them. My advice Ingenious as heck. And what's more it to anyone buying a transformer is: Find worked. I balanced a technical the resistors care- school or laboratory where fully and got equal results at both grids. you can check the thing and then send At 1,000 cycles, that is. it back to the ALTERNATE ARRANGEMENT factory with a letter and a We had it in there a week or so be- FOR SMOOTHER CONTROL curve. They'll be very nice and send you fore the XYL complained. a good "It doesn't one then -maybe. They did us. sound so hot on the high notes," she said. So, what with one thing and another, I cocked an ear. "Sounds okay to nie." the XYL and I decided we'd use a tube She insisted, though, and I ran a to invert our phase. The first circuit we curve. Around 5,000 cycles I was getting tried was the old standard kind, you a good 5 -db difference, and, because at know, where you tap off the grid resistor that time I was running the finals in of the following stage to feed the second AB instead of strict class A, it showed triode (pentodes should work as well). up. Oh, it works. Don't get me wrong. If This one is drawn in Fig. 1. you're running a PA system and you Fig. I -Old Standard phase -inverter circuit. This should have satisfied us but it don't care about anything high up on RADIO -ELECTRONICS for

www.americanradiohistory.com You 1 l the scale, why sure, go ahead and use it. it won't make a bit of difference. SIGNAL GENERATOR satisfac- can run your feedback voltage to the I MÖDFI 300 It'll drive your other 6L6 very don't distortion won't be no- bottom grid very nicely (if you torily and the can run a cor- ticeable. But for your home rig where run too much), and you really clean for the plastic rective feedback (to assist in balancing you want it output - records and FM and the really good AM the output tubes) from the joint back to the tube cathodes to the common screen or stations, lay off it. Go on inverter. We did. common cathode of the phase Old Standard. can be worked with to know another This circuit also During the war I got but bear in mind that you have of inverter, the cathode -coupled, triodes, type no screen signals to help along the in- shown in Fig. 4. This is an ingenious inversion, and it may be version. way to handle We hitched this up and used it very to follow if you're not fa- The Model 300 Signal Generator b,.nnr< lineertlp a little hard we try to Spe- successfully so long as didn't selection of tour a. ,r'atrll' al lcn 1 tregne11l'ies. miliar with it. Bear in mind that a tube crystal pnxili,mll n ex an y standard ts-O' much feedback around the out- cial ..lal standard whether a signal is applied put too lal to adapt the model laml:tun lo a tryst al freq. doesn't know When we got a better or TELEVISION MARKER OW'ILI..\TGI1. Four put transformer. ycle audio modulation. hl ..r.nit. Supplies between a grid and a grounded cathode Hundred 90'1 output and tried to run over 8 (lb feed- 156 Kr. In1 Kr, 900 Kr. and 15911 Kr. to voyer a grounded grid. Now of all rerehrrs manufactured. Work- equally scell trill. or a cathode and The feedback probe. in the back, we got into trouble. AI' -1)1' SIS. Complete With Intuit. :till .ultplll then, imagine a signal coming grid can't Nothing else to buy. )sales 'tuu $16.95 Net voltage applied to the bottom Model :Inn -K Complets, Kit & appear so easily on the top grid because Instructions 14.85 6A5-G421 sounds 6+ 230.300V OR 664-G/2A3/2A3-9 the top grid isn't grounded. That silly, but, if you'll think about it a min- RANGE MASTER" 56k .02 see what I mean. The signal ute, you'll MODEL IO appears between grid and cathode be- 58oK cause the cathode goes positive and the grid can't. If the grid can go positive, it will; and then you no longer have 560 your inversion. That, plus the fact that we wanted to drive our 6A5G's with low mu triodes (to avoid Miller effect) made us discard I still say CONOS 600v this particular inverter; but it's one of the nicest inverters I ever saw. Without feedback and with Miller Fig. 3 -Split -load inverter uses single tube. effect and all, we got near- perfect in- to 12 kc. That This signal will appear version all the way up. The 9 -in -I Service Instrument top control grid. these 28 ranges: - as well as was where Miller effect was knocking Covers on both cathode and screen (1) ('Al'tCITV 1501 -.I, 01 -1. 1.111 Mil. fault. u ib11 amps. both cathode and screen us and that wasn't the inverter's (2) A.C. t'C55ENTu. .110. -i. because 5aó dis. plate (31 A.C. VOLTAGE 1 lu Inn sup, any output tubes with less 100 latu colts. unbypassed resistances to With 6L6's or 141 D.C. VOLTA(7I: Ill Inn have large, 1111i milliamps. it'll go on up (01 D.C. CURRENT 1 In 1001 (or B- plus). These voltages will grid- cathode capacitance (al RESISTANCE 0 tu 111.0nn 11111.11110 1 tnettWtm. ground 21' 171 Special Ilielt ranee titi to oV Altar, modulate the electron stream in the bot- ) Sensitive 6A5-G (2 ill:11`1Illni let's take it 91 OSCILLOSCOPE C.ALI Iü ATOR lli tom pentode. Okay? Now Ier,d ILMS Volts from A.1 . line. '- 6SJ7(2) col $28.95 top grid goes positive, Model 10 -1' Portable 1111ustrat slowly. As the Slalel Illm Faxed 28.95 Net up and 01 Bench 23.50 Net the current in the top tube goes 5la.el III Net -i Model 10 -K. Complete Kit & 10x1 ntrlian 17.95 the IR drop in the cathode resistance Test Leads .111 goes up. The cathodes of both tubes go IuEG to- positive, since they are connected R positive, the " MULTI- TESTER " gether. If the cathodes are 12A MODEL 30 other end of the common cathode resis- IMEG tor -the grounded end -must be nega- tive with respect to the cathode. The .01 bottom grid is grounded for audio. Being at the same potential as the bottom of must also the cathode resistor, this grid CONDO 600V with respect to its cathode. works well. be negative Fig. 4- Cathode- coupled inverter Since modulating a tube is just the process of placing an audio voltage be- into the supersonic regions with tween its grid and cathode, the bottom trouble at all. tube is modulated. Its signal is opposite We went back to Old Standard, but in phase to that of the top tube. this time we included a refinement. WI \.C. Vols; u -12 21/12'. 25. 1250 V. on front panel r.uu The size of the cathode resistance is have a decibel meter the n.0. Vou; o -:v lu 315 lao 10110 V The high- A switch pushes 11.1'. ('IITrent II.I Ino a very important factor here. that reads the output. ileeisl:Wre 11- l0.0u0 100.000 I Ale:t. Glints. on on, n. ,.; h.Is hots minus Ill to plus 57 1)11. better the inversion. Typical meter over to read the signal SI 5.95 Net er it is, the the 315 l illu't ralr, ll %loir! 13.95 Net values of the resistors are shown in Fig. output grid and then the other. We have It , . I

www.americanradiohistory.com 52I AMMO

IIIII ea-ednater49 //laded lad V

., Showing how the old oscil- loscope can be used for fre- quencies higher than usually is considered to be possible

By RICHARD D. HENRY

for about 15 minutes. Connect the oscil- lator output to the vertical input of the scope and the 60 -cycle test terminal of the scope to the horizontal input. If your scope doesn't have a 60 -cycle test terminal, grab a 6.3 -volt filament trans- former and hook the secondary to the frizontal input. Now follow this procedure for call- , ating at each frequency. As you get the stationary pattern mentioned in each case, mark your oscillator dial (I used a National ACN, which is extreme - handy for this purpose) very care- fully so that you can reset the pointer Calibration sef exactly at the mark. After making -up. Our author is making a careful pin -prick mark through each the dial pointer. mark you can note on the dial in very light pencil the frequency. Afterward IWONDER whether most radiomen the screen, know the great brainwave hit me. you can do a fancy pen- and -ink job. that you can calibrate an audio The scope could For oscillator over actually be used to cali- 60 cycles. Open up both oscillo- its entire range with brate all the way up the range! scope gain an oscilloscope only. Not just With controls (and the oscillator up to great accuracy, too (if the 60 -cycle a.c. output control) and adjust for a proper- perhaps 600 cycles -I mean all the way line frequency to 15,000! is accurate) and without ly sized and centered pattern. All you using a microscope to count have to After building and writing loops on the do is keep it in the center of the about the screen. It's easy, it's fun, and screen so you audio oscillator of which you it even can see the edges. The os- may have works. cilloscope sawtooth sweep read on page 28 of the August RADIO oscillator is - Very likely, most of you know the not used yet so switch to horizontal CRAFT, I cast about for some way to cal- method. in- ibrate Maybe everyone knew it but put so that the 60 -cycle test voltage will the thing. My wife (believe it or me. But just not) had read somewhere in case you're in my class, actuate the horizontal deflection plates. about using a I'll give you a step -by step procedure. Now slowly adjust the oscillator's scope for the purpose. So had I. But I fre- So get out that oscillator you built three quency control until an O recalled that you had to have a appears on cali- years ago and never calibrated, and the screen. The O brated oscillator to compare with get may be lopsided but the hold of an oscilloscope. If you or your all you have to do is new one. Most of the boys I adjust the oscillator hang out friends don't have one or your until the O stops with just whistle through their front radio moving. It should look club doesn't keep one in the shack, your something like one of the patterns teeth when they want an audio tone; local serviceman in not one had an oscillator. can probably be talked Fig. 1. Mark your dial 60 cycles. out of his for an hour or so, or For 30 cycles. One did have a scope, though, and maybe Adjust the oscillator he over a Sunday. Since this method gives for a figure -eight pattern like told me cheerfully that you could use greater accuracy that in the line frequency than comparison with Fig. 2, with two loops at the sides and over about a 10 -1 another oscillator, you needn't one at top and range, as far, that is, as 600 bother bottom. cycles. him for his audio generator, even if he For 40 cycles. Adjust Lissajous' patterns, you know, where has for a pattern one. with 3 loops at the sides and 2 you count loops. This I had heard before The only at top but 600 cycles thing you have to worry and bottom. See Fig. 3. as a top limit wasn't much about is the use. accuracy of your 60 -cycle For 300 cycles. Adjust for 5 loops at line frequency. If you live in a top and bottom Well, last week I got a scope large and just one at each anyhow, city, generally it's all right. In certain side of figure. This mainly because that was the only item I areas is a very important could served by waterpower, there may adjustment and much patience may get the feminine half of the part- be some doubt. be nership to okay. If your electric clock necessary to get the pattern to stand Pretty pictures. keeps time within a few So there I sat seconds a week, still. Make the mark very carefully on at the bench lining the as checked with the radio, the oscillator oscillator up to 600 cycles. (Incidentally, don't worry. dial. the sine -wave pattern is very nice, in The low frequencies The balance of the range case you built the unit.) Idly sitting, twisting Start off by turning on both the scope Now remove the 60-cycle test voltage the scope knobs and watching and the oscillator and letting them cook from the input to the horizontal ampli- RADIO- ELECTRONICS for

www.americanradiohistory.com 53

it on the basis Order a model 247. Disregard the unbelievably low price and compare A CHALLENGE appearance, quality and performance to any other Tube Tester '(ANY MAKE, ANY 15 day return it to us for full PRICE). If you are not completely satisfied with the model 217 after a trial, necessary. refund -no explanation and incorporates new The model 247 is not surplus nor is it a hashed over pre -war model. It is newly designed one today! advances in Tube Tester design. Read the description below and order The New Model 247 TUBE TESTER Checks octals. loctals. bantam jr. peanuts, television miniatures, magic eye, hearing aids. thyratrons. the new type H. F. miniatures, etc. Features: of .. A newly designed element selector switch reduces the possibility obsolescence to an absolute minimum. of multi -purpose e When checking Diode, Triode and Pentode sections can be tested individually. A special isolating circuit tubes. sections envelope. comes complete ONLY allows each section to be tested as if it were in a separate Model 247 method of checking for with new speed - read o The Model 247 provides a super sensitive between any and all of the chart. Comes housed in shorts and leakages up to 5 Megohms - rubbed terminals. handsome, hand we believe, is the fact that sloped for ° One of the most im;'artant improvements, oak cabinet S 90 action snap switches are all numbered in exact slip - on the 4 position fast- bench use. A the standard R.M.A. numbering system. Thus, if the portable hinged cover is accordance with element terminating in pin No. 7 of a tube is under test, button included for outside use. NET No. 7 is ttse,l f or that test. Size: l0'í" c .ìo'4.. x THE MODEL 650 - AN A.C. OPERATED SIGNAL GENERATOR RANGE: 100 KILOCYCLES TO 105 MEGACYCLES "RI: obtainable .(pastel) or dulated b) the \udio Freyuenr. Audio Modulating Frequency --I00 0rtes pure sine ware -le,- than ' di-torsion. 'Attenuation- -a-aep ladder hype of attenuator IT pad). *U -es a Hartley Excited O.eillatar with a Buffer Amplifier. *Tube.: 65 a- R.F. O- cillator: (i' \7 as modulated buffer and Mixer; 6SL7 as audio oscillator and rectifier.

Model 650 comes complete with coaxial cable, test leads and instruction -. Hou-ed iu heJ\, gunge grey crystalline $ 95{,/¡ cabinet with beautiful t..o t.we etched front panel. Size 9t" x l0 x 6 ". NET PRICE: The New Model 670 SUPER METER INDUCT- A Combination VOLT- OII\lMILLF\ \(METER plus C-\I'.\ClT1 REACTANCE. ANCE and DECIBEL ME \'UREMENTS. 0 15/30/150/300/1500 /3000. D. C. VOLTS: 0 to 7.5 15 73 rot'. 750'150017500. -A. C. VOLTS to C. CURRENT. 0 to 1.5/15/150 Volts.- OUTPUT VOLTS: 0 to 15 :Hl 150 :300 15003000. - -D. RESISTAN('F:: o to 500 100.000 ohms. 0 to 10 Megohms.- -CAPACITY: Ma.; 0 to 1.5 Amps.- REA('TAN('l' Inn to 27.000 .001 to .2 Mfd.. 1 to 4 Mfd. Quality test for electrolyticsl,- Ohms; 13.000 Ohms 3 Megohms.- to 70 Henries: 35 to 8.000 Henries. DEt'IBELS:DECIBELS: -10 -1S, - 10 to --38. -30 to 58. THE MODEL 670 COMES HOUSED IN A RUGGED, CRACKLE- FINISHED STEEL CABINET COMPLETE WITH TEST LEADS NET AND OPERATING INSTRUCTIONS. SIZE 3 c 7'.." c 3" Available for Immediate Shipment From Stock -20'; Deposit Required on All C.O.D. Orders

DEF TN ST. MOSS ELECTRONIC DISTRIBUTING CO. EW YORK 7 N YN

OCTOBER. 1948

www.americanradiohistory.com JI MIMI)

CALIBRATING AUDIO OSCILLATORS SUPER VALUES ((',,,t,n,ed f,'en, /suit 52) i fier and switch to the internal generator. sweep wave pattern appears. Again it is a from MID -AMERICA! good idea to For 50 advance the horizontal cycles, With the oscillator dial gain control to spread Stromberg -Carlson DYNATENNA accurately set at the the pattern, 300 -cycle mark, ad- rather than to try to count the waves. just the coarse and fine sweep tuning For frequencies controls on above 8,000 cycles. 'I his famous -mke the scope until a pattern of At FM m i t t i n g station. i l l us- this point it becomes very hard to antenna has been ad- exactly six sine waves appears. t rated instructions Care- stop the pattern if the 500 -cycle di- vertised and sold for and all necessary fully set the fine tuning control until visions mans rimes the low are maintained. Generally 1,000- hardware. A s. - the pattern stands still. The price 5111) -AMERICA synchronic- cycle points sufficient. \ driver is only c tool are For each de- asks! Covers both FM needed for assembly. bands. Delvers FM Uynatenna is seam - !LOOP reception at 2 its best. ' less, heat- treated, Complete with 60 ft. of all aluminum . . , 300 -ohm twin lead -in. will withstand Line is standard ap- severest weather. proved flat -type. solid dielectric with weather - resisting insulation. $495 Mounts anywhere easily ... ertically or each horizontally to match 54.45 Fig. l- Single loop at 60 cycles. each Fig. 3 -40 cycles. polarization of a n s Fig. 2 -30 cycles. t r - In lots of 3 my control should be set at its off posi- sired tion. Just for safety, frequency marking above 8,000 switch to the exter- cycles, set the nal sync position to oscillator dial at half the be sure there is no desired frequency, tune sync voltage applied to the sawtooth the scope for a oscillator- single sine wave, then tune the oscillator Now tune the oscillator down for l,elow the two waves. This latter point will be 60 -cycle mark until just one the desired frequency. ire wave appears. Tune until this -[ands After the calibration PERMEABILITY still, then mark your dial 50 is complete, it TUNER yeles. will not hurt matters to check the mark- Build a really 1101' 5 Or ti -tub,. Takes place of old-=t'le AC -UC superhet receiver! ings. That can be done coil.: gang eondenser, of and antenna For loo to 1000 as many ways regular 133 K(: in termediate frequency. cycles. Starting with as you Complete with permeabilty tuned MA -2167 the want. It is a good idea because 4' x toeiliator coil. single sine wave 2,6' x - at 50 cycles, 2','; ! a ,diameter dial drum. Com- slowly the sweep plete wit h diagram+ for hui 41 24 advance oscillator in the scope may lding 5 and ti tube sets. 1 the oscillator dial until Order MA -21e. Loop Antenna two sine drift slightly between . 1Se %[raves appear. settings. Order MA -2114 Drilled, punched Chassie This is the 100 -cycle . . , , ife mark. To calibrate To check, just remember that if' the at 50 -cycle intervals scope's up to 1,000 cycles, adjust the oscillator sweep oscillator is tuned so that BANTAM dial for motionless the screen shows one sine wave at 1- WATTER sine wave patterns. setting any The frequency of the oscillator of the audio generator, any mul- will, in tiple of the BCR- 746 -A tuning unit each case, be 50 times the number frequency used to get the used as foundation for of single wave will Bantam I- watter de- sine waves that appear. You can easily be indicated by the scribed in Jan. 1948 OST. number of waves appearing, Makes tiny -rystal- count the waves (if there aren't too controlled CW 'Emitter. many of Measures only 3 -', ' long, them) by counting the peaks 2', high. 1',' wide. quires only volts Re- at top or bottom of the pattern. AUDIO OSCILLATOR volts 1' A", 30 to 90 When B ". Draws S to 15 ma 20 waves appear This R -C audio under load. Supplied leas24e you will have reached test oscillator, orig- crystl. 1S4 tube and plug - 1,000 cycles. inally described in In coil MA- 907... It is not really necessary Sylvania News, has or even a good idea to count cycles above a range of 50 to 5,000 cycles. It is tuned SPECIAL AUDIO about eight (new glasses are expen- by the dual 1- megohm potentiometer. TRANSFORMERS sive). Just keep R2 is provided to Exceptionally high- quality universal going each time until vary the wave form lip 12' output transformer for to speakers. Rated 12 the of the at watts. Matches any single, next sine pattern appears. You will output. By using an oscilloscope, pushpull or parallel tubes to ti -6 ohm voice coded leads. 2' coil. color know the builder high with Vi" mounting centers forinstalla that that is 50 cycles higher than can produce a sine wave with Lion on chassis or speaker. Complete with inst e the less than [ions for matching tube impedances. MA-1201110 last one. Open up the horizontal gain 5r; distortion, or produce tones Hermetically sealed 200 ohm control to spread the pattern rich in harmonics. Single 3000 -ohm to 4 -ohm and make CTto50,000 ohm grid. Use as voice microphone transformer, coil output for 501.6, the wave -shape easier to see. Varying R2 will 35L6. etc. 1r6' high on 251 change slightly the line -to-grid, etc. 313 Lan¿ mounting centers. frequency al'fzlly', MA -1262 120 MA 1,000 to 2,000 cycles. as well as the wave form. -1256 490 If you want to Calibration calibrate this range in 100 -cycle steps, should be done after the setting of R2 has been Heavy Duty Noise Filters set the oscillator accurately at 100 determined. Rated on 10 cycles. snips, 11: -volt AC. Measures only Adjust the sweep tuning The frequency range can be Install right in amplifiers, l' /T'á'square, controls varied where receivers and other equipment on the scope by changing line noises must be kept at a minimum: for a single sine wave- Now the values of R3 and R4. tionally -known manufacturer. Na- Ter/ MA -2164 . a77 start at 1,000 cycles with a 10 -wave Filter for mobile power supplies. 10N/55MA Has Rated 10 amps, 6 -30 VDC. pattern- Turn up additional 2 mfd. IOU VDC condenser. the horizontal gain to 4.7K/IOW T square. MA -2165. 2' high. ter/ spread Jac77T the pattern nicely, then tune slowly and at each place where the sine - SPEAKER SPECIALS wave pattern appears and stops, mark. All with Heavy ALNICO 5 Slugs To check the 2,000 -cycle point, set the 3' 2' PM MA-2062 .. 51.39 4x6 oscillator at 1,000 Oval PM MA -2187 51.39 cycles and tune the FRED CONI .0035 5' PM MA -2011 .. 51.39 6- PM MA- 2189... 51.95 scope sweep for a stationary single sine wave. Then 4.7K ORDER tune the oscillator for two DUAL POT FROM THIS sine IME6 Qu,mtitie+ are limited, AD! waves. Mark 2,000 cycles. There so get your order inn w! Minimum order shipped, ò2.5u. Send 25'1, should Get on deposit, balance C. O. D, now be 9 marks between 1,000 MID -AMERICA's mailing list to receive GAIN BULLETINS that list BIG BAR- and 2,000 cycles. parts, electronic latest, greatest buys in radio equipment. Send orders to Desk 11C -108. For 2,000 to 8,000 cycles. To mark the dial at 500 -cycle intervals, set the oscil- lator at 500 cycles, tune the scope for a 2412 S. Michigan Avenue single sine wave, then proceed to tune the oscillator, beginning at 2,000 cycles Chicago 16, III. and making a mark each time a sine- RADIO -ELECTRONICS for

www.americanradiohistory.com Audie 55

New Magnetic PICKUPS

By I. QUEEN The Clarkstan No. 201 RV wide range pickup.

pickups Microgroove recordings. The stylus is ture in its Magneto- Induction MI pick- SEVERAL phonograph exist in the cartridge were discussed in the September, a whole diamond with a .001 -inch tip ups. No air gaps radius. The cartridge will track with so that dust particles and metal filings 1947, issue. Of these types, the The pre- reluctance) only 5 grams of pressure. are automatically excluded. magnetic (or variable stylus may be replaced at wide popularity. It is a The Lear MP -103 uses a retractable cious -metal has attained MI -2 is housed in a mu- rugged unit, unaffected by moisture or stylus. No damage results to the stylus the factory. or record, even when the stylus is acci- metal shield for maximum protection temperature and capable of high fidelity. of two from many dentally dropped. A felt pad is built against hum. There is a choice Magnetics are now available by Astatic. EA -1, equipped manufacturers. In some cases the manu- around the stylus to clean away dust preamplifiers particles as the record moves. The model for bass boost only, may be installed facturers also recommend their own pre- Model A -172 preamplifier is recommended with inside an amplifier or radio set. amplifiers and equalizers. adds adjust- pickups have this unit. EA -2 is self -powered and Most good magnetic roll -off and choice of turn- practically linear response throughout Model MP -203 (also by Lear) may be able treble their range, but all require bass boost used with either lateral or vertical over frequency. or recordings. Frequency response is ap- The General Electric IRM -6C was one (6 db per octave below 500 cycles variable reluctance pick- crossover frequency is used). proximately the same with either type. of the earliest whatever ups. was described in the September, Many music lovers prefer adjustable A combined preamplifier and equalizer It may be unit, PE -210, is recommended for this 1947, issue of RADIO -CRAFT, together treble response so that highs recommended for noisy records. In any ease, pickup. with the preamplifier reduced on it. The new IRM -8C is similar but uses a roll -off must be used to compensate for The Jensen model J -9 Magtronic pick- most up uses a sapphire stylus fastened into a diamond stylus. Thee-Gray Research the recorded characteristic of which for pickup normally droops an aluminum shank with hot cement. and Development Company, discs. The G -E has been furnishing selected somewhat toward the high end (between Although the jewel may be removed and some time and a re- replaced by applying heat, it is best done diamond -pointed G -E cartridges to go 5 and 10 db down at 10 kc), has announced that into the case of the Clark- at the factory. The excellent response with the Gray arm, sistor is built will furnish a slightly modified stan to provide a roll -off. up to 14 kc is attained with a load of they of 22,000 ohms resistance and .001 -uf cartridge with a .001- inch -radius dia- The table lists the characteristics point and increased lateral corn - magnetic cartridges, the most important capacitance in parallel. This is the min- mond which should be used. pliance for playing Microgroove records. being the frequency range. All those imum load in Where Like the Lear MP -103, the Jensen Audak's R -61 pickup is available shown have excellent response. impedances running from is or greater, the J -9 has a retractable stylus and is pro- a variety of the output voltage .05 ohms. The jewel needle is re- pickup may be connected directly to the vided with a felt pad around it. 5 -2,500 microphone input of a high -gain ampli- Astatic has included an unusual fea- placeable. fier. The amplifier must, of course, be In choosing the properly equalized. Output Min. needle a diamond has Unusual pressure List stylus, remember that Manufacturer Stylus Frequency (volts at price about ten times the life of a sapphire. and Model material range 11.000c.p.s.) feature (grams) A sapphire is also more easily damaged. $25 with sapphire sapphire RV pickup cartridge Clarkstan or 30- 14.000 .06 needle is 15 The Clarkstan the armature $45 with accommodates a removable stylus. No RV diamond diamond re- (replaceable) tools need be used to remove and $25 with D -120M uses sapphire place it. Extra sapphire needles are diamond 40- 10,000 .07 handy 18 Pickering mounting $60 with available. Styli with tips of different 120 -M S -1 20M uses diamond radius may be had, including a .001 - sapphire Microgroove rec- Lear stylus is inch unit for playing retractable 17 $12 ords. This manufacturer does not make NIP -103 sapphire 50-10.000 .08 a but recommends any .08 on plays either preamplifier, vertical rec. vertical In many Lear 26 175 standard unit if it is necessary. MP -203 sapphire 5044,000 .04 on or lateral cases the RV may be connected directly lateral recordings to a high -gain amplifier. sapphire is a compact 50- 14.000 .08 stylus is 19 812 The Pickering cartridge Jensen (replaceable) retractable version of the Pickering professional JO at factory) pickup, which comes complete with arm. no air gap is arms Astatic precious 50- 12,000 .1 used. MU 30 17.50 It is easily adapted to most pickup M l-2 metal metal shield by the special "keystone clip" mounting IRM -tiC Electric into which it slides. The stylus is fixed Gen. flexible $7 n5 IRM -liC. sapphire 50- 10,000 .022 IRM-SC be replaced at -8C diamond jewel 23 to the cartridge, but may IRS1 mounting 139.50 the factory. A model 125 -H preamplifier 120 -M. .085 (high - is recommended for the 1343.90 Pickering has intro- Audak jewel 5040,000 impedance 23 Very recently R-61 (replaceable) model) duced a model D -140S cartridge for OCTOBER. 1948

www.americanradiohistory.com 561 New 1 evices

PHONO PREAMPLIFIER FILM RECORDER ELECTRONIC KEY WIRE RECORDER Collins Audio Products Co., Inc., Frederick Hart & Co., Inc., Electric Eye Equipment Co., Premier Electronic Laboratories, Westfield, N. J. Poughkeepsie, N. Y. Danville, III. New York, N. Y. The I -A amplifier is used with GE, The Hartron Model VRF -3 is a sound - The Mon -Key electronic monitor Pickering, and similar magnetic, low - recording and The Wiresonic has a built -in radio machine which uses trans- sending key automatically makes level phonograph pickups. It provides parent film as the recording prop- receiveer and a turntable and pickup for the proper medium. erly spaced dots and dashes, and pro. standard bass equalization for this The film, an endless 62 -foot loop, is duces Frequencies pickup. a tone for monitoring purposes. from 40 to 10ä000 type of run under a recording head, the stylus cycles are reproduced The entire preamplifier, including Pressing the paddle left or right gives by the amplifier, which the of which embosses 120 parallel tracks. dots or dashes correctly timed as two micro- tubes, is enclosed within a small metal Four hours of continuous for any recording are speed from eight to 40 shield can, at the bottom of which is possible. w.p.m. The mechanism uses no weights an octal tube base. The unit is plugged A voice and is ad. -operated relay arrangement ¡usted with two thumbnuts. into an octal tube socket which can be is available to start or stop the unit The key controls a multivibrator; provided on almost any amplifier automatically, and a track dot locator en- and dash contacts switch in appropriate ables the user to listen to one track timing networks. (through headphones) The multivibrator while another drives a keying tube which track is being embossed. A actuates a transformer relay having two sets of contacts. for telephone recording is built in. and One set keys the transmitter: the other a self -contained loudspeaker, as well as keys connections an a.f. monitoring oscillator feed- for an external speaker are ing a 2 -inch provided. A foot PM speaker. The unit control and head- operates fr -m 117 v"It phones are available for stenographic ii-. or d.c. phone inputs and one low -gain channnl. transcribing purposes. A push -pull, 10 -watt output stage is in- BROADCAST cluded. There are separate bass and treble tone controls. An 8 -inch speaker MICROPHONES is mounted in the cover. Electro- Voice, Inc., Buchanan, Mich. NBFM MODULATOR Models 645 and 650 are high- fidelity Bee -Bee Electronic Co. dynamic microphones designed for FM Los Angeles, Calif. and AM broadcast stations. Flat re- Bee -Bee sponse extends from Model 500 is a reactance - chassis. Leads from the input lack of 40 to 15,000 cycles type narrow-band for the 650, and from 50 to 15,000 FM modulator de- the amplifier and from the power sup - cycles for the 645. Output stgned for converting any transmitter ply can easily be wired to the socket. of the latter is slight with pentode 8- supply requirements ly lower. or triode crystal oscil- are 250 volts at lator or v.f.o, to FM 2 ma. Both models are shock -mounted to operation. A co- reduce vibration effects. axial cable connects the output from The preamplifier is especially useful A recessed the unit to where impedance- changing rotary switch the transmitter. The input uninterrupted operation is im- al- is for a high- impedance portant, as lows instant selection of 50 or 250 microphone. in broadcast stations and ohms. The modulator operates wired music studios. If the from a sep- unit be- arate b.3 -volt filament and 150.180.volt comes defective, it is simply pulled out plate supply. and a good one plugged in. An adapt- RECORD SAVER er (jumper) plug is available to recon- Penlee nect the amplifier input directly to the Mfg. Co., TELEPHONE PICKUP first regular stage when a crystal pickup Dubuque, Iowa Mid -America is to be used. Mfg. Co., Inc. Say A,Disc is a circular piece of very St. Louis, Mo. thin vi ylite of the same diameter as the ordinary record label. Constant This device consists of a high- imped playing of record, once pickup coil enclosed in a flat RECORDING a especially on covered case CHASSIS changers, enlarges its center hole, with simulated leather- The Rek -O -Kut Company, which makes the music "wow" or waver case is placed under the telephone instrument, which should Long Island City, N. Y. in pitch. The Say -A -Disc has a hole of be of the new- exactly the proper size. When er type (bell in base). The assembly includes it is Coil the M -12 over- cemented to a record, the turntable output can be fed to the grid head cutting mechanism and the TR -12 center -pin passes of an amplifier for listening or record- dual -speed turntable. through the hole in the small disc, which takes the place ing. of the original hole in the record. model,ode), made for use with the Soundscriber, is also TRANSCRIPTION available, PLAYER Bell Sound Systems, Inc. HIGH -VOLTAGE METER Columbus, Ohio Spellman Television Model Co., Inc., 2079 consists of a two -speed New York, phono turntable, crystal pickup, am- N. Y. Voltages The mechanism plifier, and 8 -inch loudspeaker, all in up to 30,000 may be mees- is enclosed to prevent a single carrying case. Frequency ured with this meter, which dust and record chip from the re- is intended fouling sponse of the amplifier is flat principally for servicing projection gears. An automatic safety feature within SOUND -LEVEL METER I db from 60 to 10,000 cycles. A television receivers. A 4 -inch scale is raises the cutter when it reaches the in- provided side of the disc, Herman Hosmer Scott, Inc., for easy reading. The panel preventing damage to is of bakelite and the record and stylus. The mechanism, cabinet of oak. Cambridge, Mass. The meter draws only 20 available separately, is adjustable pa. to fit Utilizing subminiature tubes almost any 12 -inch turntable. and new circuit techniques, -410 The turntable 12 the type -A sound - inches in diameter, level meter SPEAKER is lathe- turned Irom cast represents the first light, GRILLE aluminum. The -Size chassis is pocket instrument of its kind. This Wright, Inc. cross- ribbed for extra new strength. Rim instrument features improved sta- drive is used, the neo- bility and St. Paul, Minn. prene drivers contacting the inside dependability, simplicity of rim Model 10 of the table. operation, and accuracy, in addition to -P flush -mounting grille is a the advantages resulting from its small circular piece of I8 -gauge steel with size and weight. grillwork as shown. It is made for mounting speakers up to IO inches in SQUARE -WAVE diameter flush with walls or in the backs of automobiles. The disc is 10 GENERATOR inches in diameter and is not furnished General Electric Co., Inc. with speaker cloth or mounting holes. microphone input is provided Syracuse, N. so that Y. the unit may be used as a small PA The YGL -I square -wave generator has system. Power output is S watts with 5% six overlapping frequency ranges, giv. distortion. A combination bass -boost ing coverage from S to 125,000 cycles. and treble -attenuation tone control is It delivers a rectangular -wave output included. voltage with a 25% negative pulse and a rise time for the leading edge of 0.3 microsecond. D.C. POWER SUPPLIES Radio Products Sales, Inc. Los Angeles, Calif. RPS power conversion units furnish The sound -level meter covers the low -voltage. high -current d.c. for op- range from 34 to 140 db above the erating surplus equipment. Almost standard any ASA reference level. It in- piece of equipment can be powered WARNING DECALS cludes all three standard ASA weight- by one of the units, various models ing of Allied Radio Corp., characteristics to duplicate the which furnish 14 volts at 2 to 40 response am- of the ear at various levels peres and 28 volts at 1.8 to 40 Chicago, III. and am- has a two -speed meter. There is peres. Decals reading "DANGER provision for using extension cable, -HIGH Each unit contains a selenium rec- VOLTAGE!" are printed in two colors optional types of microphones, vibra- tifier and a transformer for operation and may The self- contained power supply is tion pickups, etc., and be attached to any equipment electronically controlled analyzers or fil- from 117 -volt a.c. No modification or having exposed high-voltage terminals. to minimize ters. The unit is 101/2 inches long. N/z rewiring of the the effect of any line- surplus equipment is The decals are 2% x 4 inches voltage variations. inches in diameter, and weighs only necessary. Motor tuning in size. Output may be synchronized to an mechanisms, They may be obtained without charge ex. slightly over 2 pounds including bat- usually disabled by the normal ternal source. - con by writing to C. W. Bailey, W9JJD, at teries. versions, remain in operation. Allied. RA DIO- ELECTRONICS for

www.americanradiohistory.com J Ì

A sensational buy. New in original overseas sealed packages. Complete with War Dept. Technicol Bulletin. An ideal phone for co cation work, well suited for use in noisy locations, Brand new . 3 0-3, DC voltmeter vehicles. MIN were originally used in armored 2" round case. Meter has 450 ohms 8000 ohm impedence 128 ohm ear- sistonce 150 ohms per volt'. Add phone units with built in matching 15e each to cover postage and hand. transformers. Add 30e to cover postage ling.' and handling.

1300' Rubber Tbes! Radio I .95 3 CP 'Ind. Screen'

, Ind. Screen .95 Covered Wire 3 DP 1.A eampayas 3FP7.A 135 3 HP 7 1.45 .add 25c each to cover R5 or 433G. /ARN7 postage and handling' either of these Radio ONLY) 5óo Receivers 1.75 Compost New 4 conductor 16 gouge 5 FP 7 with tubes. 1.95 Icomplete rubber ered cable. Color 5 CP 1 Now deal for convection coded. U ed by United States 5 BP 1 2.45 2.45 for home reception. Government os Field Telephone 5 HP 1 A real Used but good. Cable. 1300 feet on steel reel. .add 35c each to caver buy or only S F.O.B. Our warehouse Shipped postage end handling' motor freight or express shipping tsss Shipped express col. / charges collect. 2.65 leer 7 BP 3.25 r' 7 CP I .add 40c each to postage and handling'

9 GP 7 3.50 LOOP AtarNlY 'Shipped express, charges collect'

A BUY 3 PHANTOM

1 std primarily on aircraft & Marine ADF S> stems. Loop LP-21.A contains an rive- ANTENNA iris motor and selsyn. 7 hese loops hase ht-en rentosed from salsagc aircraft. hut arc guaranlved to he in excellent working 1 sundown. 1 Lrpped fft !repress (o /lee, A transmitting antenna, for use approximately 450 MC. Complete with beam rotor, plenty of power. Ori. Electric Extension Ideal for standard coos con- Western g,nally designed for 24 volt DC operation, but CW 23098. nector. A eather Control Box, Type 110 volts AC. Complete plate. easily converted, proof unit. 'Add Complete with mounting instructions included. Excellent for other 4 25c to cover hand. cartons. Coo- All new in original uses too. Brend n surplus, quaronted. rains one 50000 ohm reostae, 1 ling and postage' Add 40e euch to cover postage and hondl'nq' toggle switch, onee phone jack, one microphone jock, one test key, and one n indicator lamp. Add 20e to e cover postage and handling. 500' Sß)95 NME1RS 99sf A 13AR6AlN! 3 CONDUCTOR(, Westinghouse, Oxygen Flow TELEPHONE WIRE Indicator . MK Il. New in origi- volt meter Brand ne. toes D.C. nal cartons, 49c, add I5c to 3 Braided 2 3/4" conductor eixir.'`.01111111( 0 to 9 volts in 2" case with coer postage and handling. insulated copper & steel etc .. . telephone wire. It is Flange made of copper for con - Brend new Bowen D.C. e ductivity, and steel for 0 to 100 amp scales .600Anmter All merchandise subject to prior strength. Worth at least ant with 100 am: shunt eck .99c sale, minimum order $2.00, No 3c per ft. Vet due to an same case es volt meter C.O.D. orders accepted. Michi- exceptional buy, we can to cover postage at less Add 20c each . it than gan residents must add 3 State now offer and headline IC a ft. soles tax Shipped Ecprese Collect

6532 McNICHOLS ROAD DETROIT 12, MICHIGAN

tLANIMMIS&vertEAST c1&5ü/Sur

OCTOBER, 1948

www.americanradiohistory.com 58

* Save 2/3 the cost. KIT * Gain valuable knowl- SWITCH edge. ANY SCOPE sieettileirELECTRONICTHE UTILITY OF * Achieve better work- manship. UBLES traces controllable o separately Learn many new appli- on any scope. * dividuol inputs traces, locate cations. the input and output See both immediately. shift, etc., Ideal training for use. distortion, phase positioning * controls and Individual gain rate con- and fine sweeping Heathkits are regular control. Coarse Heathkit matches factory quality test trols. Complete punched,othformttd metal parts are equipment unassembled 5 tubes, All with tubes, Complete but with all forming, and cadmium plated. inst blueprints and punching, parts, detailed calibrating 13 lbs. and printing Shipping Wt, already completed.

THE NEW HEATHKIT VACUUM TUBE VOLTMETER KIT HEATHKIT The most essential tool a radio man can have, now within the reach of his pocketbook. The Heath- CONDENSER CHECKER KIT kit VTVM is equal in quality to instruments selling for $75.00 or more. Features 500 microamp meter, transformer A

* * * DEPT. C ... BENTON HARBOR, MICHIGAN RADIO -ELECTRONICS for

www.americanradiohistory.com TEST EQUIPMENT

THE BASIC FM SERVICE INSTRUMENT TELEVISIOf -r * 5 tube Circuit large cy transformer. * calibrated dial. Supplies either Variable RF or FM. * phasing control. * Variable sweep Sweep width * output for scope. 0 to App, 10 No bond Mc. * switching necessary * Uses new miniature At the HF tubes. lowest cost service possible, anyone FM and can now Heath television kit sweep receivers. T generator kit o and operates wi sendsc. covers all e l necessary this fr kit puts any organization assembling share the i i position of the to Every partprofits FM and TV two supplied - grey color calibrated crackle cabinet, punched, panel, formed and metal parts plete plated. a detailed instructions tubes, use Shipping for assembly weight 6 lbs. tend

H E A T H K I T HIGH FIDELITY 3 -TUBE KIT E AMPLIFIER HEATHKIT ALL -WAVE RADIO I N T E R P H O N 110 -volt AC operation SYSTEM KIT high fidelity 2 -WAY CALL Build this An ideal way to learn S8.75 and save two - amplifier radio. This kit is complete Ideal call and com- thirds of the cost. Push to assemble, with 1619 ready system pull output using tubes and oll other parts. type honicationmes, offices, factoriesfor, tubes (military from AC. Simple, Operates Makes ex- 61.6's), two amplifier clear detailed instructions stores, etc. stages using a dual make this o good radio cellent electronic baby and a triode (6SN7), training course. Covers reg- watcher, easy to as- inverter give this phase ular broadcasts and short semble with every part amplifier a linear repro- selling for ten times wave bands. Plug -in coils. supplied including tim- duction equal to amplifiers Regenerative circuit. Oper. supplied; punched and formed - instructions. Distance this price. Every part ates loud speaker. ple chassis, transformers (including quality output to up to 1.5 mile. Oper- $14.50 and complete Add postage for 3 lbs. 3 -8 ohm voice coil), tubes, controls, ates from 110 V. A.C. postone 20 lbs. S1.00 instructions. Add for HS 30 Headphones per set 3 tubes, one master and one remote speaker. 12" PM speakers for above 56.9S 2' 2" permanent magnet loudspeaker 51.95 Shipping Weight 5 pounds

NEW 1948 HEATHKIT 5" OSCILLOSCOPE KIT newer servicing technique in FM and televs,on at A necessity for the two color a price you can afford. The Heathkit is complete, beautiful ports punched, formed and plated and every part panel, all metal interesting supplied. A pleasant evening's work and you have the most piece of laboratory equipment available. vertical and Check the features - large S" 5BP1 tube, compensated using 6SJ7's, 15 cycle to 30 M cycle sweep gener- horizontal amplifiers gives 1100 ator using 884 gas triode, 110V 60 cycle power transformer volts negative and 350 volts positive. 26 Convenient size 812" x 13" high, 17" deep, weight only pounds. with test voltage and ext. syn post. All controls on front panel weight Complete with oil tubes and detailed instructions. Shipping 35 pounds. Order today while surplus tubes make the price possible.

110 V. A.C. TRANSMITTER 110 V. A.C. MILITARY RECEIVER POWER SUPPLY KIT for SUPPLY KIT For BC -645, 223, 522, 274N's, etc. Ideal POWER powering military transmitters. Supplies 500 to 600 Volts at 150 to 200 MA plate, 6.3 Ideal way to convert military sets. Sup- C.T. at 4 Amps, 6.3 at 4 Amps and 12V at plies 24 Volts for filament - no wiring 4 Amps. Can be combined to supply 3 -6 -9- changes inside radio. Also supplies 250 V. 12 or 24 Volts at 4 Amperes. Kit supplied voltage of 50-60 MA. Connec- complete with husky 110V 60 cycle power D.C. plate rectifier. oil filled con- tions direct to dynamotor input. Complete transformer, 5U4 densers, cased choke, punched chassis, and with all ports and detailed all other parts, including detailed instruc- instructions. Ship. Wt., 6 lbs. $ 5.95 $14.50 tions. Complete - nothing else to buy. 7tie HEATH CO mil P..IVY HARBOR, MICHIGAN >t ~ DEPT. C ... BENTON OCTOBER, 1948

www.americanradiohistory.com GO Television Gascode Preamp Reduces TV'Snow"

Top view of preamp. 6AK5 is in foreground. By I. QUEEN

AT TV frequencies the useful may not be sufficient. The local stations The cascode, described in the Proceed- transmission range is limited may be picked up, but they are usually ings of the IRE, June, 1948, has several to approximately line -of- sight. accompanied by noise or "snow." unusual characteristics. The TV total gain transmitters are located in The r.f. preamplifier described here and internal noise is due to the first tube populated centers to provide maximum has been found really effective. It is only. The 6AK5 is coverage. connected as a triode About eight or ten miles from capable of really appreciable amplifica- for that reason. The 6J6 merely stabi- a station the signal strength begins to tion, not merely a slight theoretical gain lizes the system and contributes practi- drop off rapidly, leaving fringe areas which shows up only on a sensitive cally nothing where to either noise level or average reception is only fair or meter. Designed for TV channels 2 gain. poor. In thèse areas a preamplifier can through 6, it can also be used on the 88- The experimental model (Fig. 2) was provide much- improved picture and 108-mc FM band. At reasonable dis- built with its own power supply sound. Besides for con- giving extra gain it re- tances from the transmitter a small wire venience. If power can be duces interference taken from such as often results is sufficient to give satisfactory recep- the TV set, the unit can be made even from direct pickup by the i.f. channel. tion when the preamplifier is added. Fig. more compact. There other are instances where pre - 1 is the schematic. Two tubes are used in The coils, except L2, were found to be amplification is necessary. Apartment - a single stage of amplification. The cir- noncritical. For L2 a National house type AR- owners sometimes do not allow cuit is called a "cascode." The 6AK5 has 5, a permeance- tuned, high -Q coil, was roof antennas, but an indoor antenna its cathode grounded, the 6J6 its grid. used. For television frequencies the core is screwed almost all the way in. For 10µµt FM it is ANT s 1 2 brought out. SW 5W4 6AK5 6 L4 - LI is 21/2 turns of push -back wire 117VAC L around L2. L3 and L4 are wound on '%- inch TO RC R polystyrene rod with No. 22 wire, 11 turns for L3 and 14 for L4. RFC con - SV 100 76J6 .01 sists of 15 turns of No. 22 wound over a 6.3V SK 10 i 100 -ohm insulated resistor. The 20 -µµf tuning capacitor across L2 is a six -plate 6i45-0" 100V o miniature air condenser. The preamplifier was designed for use Fig. I- Schematic of preamp. 6AK5 is triode- cornet ed. 6L6 isolation stages give no gain. with 300 -ohm twin -lead conductors. Ex- periments showed that the tightly coupled 21/2-turn coil Ll worked best in the antenna circuit. However, gain was very low when the same thing was tried in the output circuit. Capacitive coupling proved best. It is not necessary to use r.f. chokes in the filament circuits. They were tried, but no improvement was noted. Both tubes were operated with 100 volts on the plates. A noticeable gain increase is obtained when the voltage is raised to approximately 135. However, it is better to use the lower value un- less maximum gain is essential. No hum was noticed in either picture or sound even when the power- supply filter was shorted out. The band pass is very wide. We were unable to notice any loss of detail on any of the local patterns (channels 2, 4, 5). The variable condenser is not criti- cal, but there is a definite tuning effect from one station to the next. There is no evidence of self -oscillation when parts are laid out as shown and leads are made as short as possible. The pre- amp was stable even when the antenna was disconnected. Here are some actual results obtained. Fig. 2- Underchassis view. Coil at lower right corner is L2. Twin lead is on output strip. Low signal strength which was just RADIO -ELECTRONICS for

www.americanradiohistory.com Telerishm 61 short of producing any picture at all was increased to produce a fairly good image. A weak picture was increased to very good. Since this unit introduces so little noise of its own, it can also be used where there is already enough signal the TV set level but too much noise. If igOiewl gain is reduced by the amount of gain that the preamplifier adds, the same picture will appear, but with practically no "snow." This assumes that most of the "snow" is due to the input circuit of TV set. the NEW Television Kits, and Equipment Advances in TV Reception and Servicing! INDOOR TV ANTENNA Important television more enjoyable, more profitable! The problem of installing adequate Transvision makes receiving antennas is denying television reception to many would -be set owners, particularly those in large apartment buildings and housing developments. In many instances, landlords will not per- mit tenants to install TV antennas on buildings or grounds.

New .. FIELD STRENGTH METER Model 11 BL TV /FM KIT Cabinets. momponeures the most extensivenlinlilulstrúd quakylisted ti reonlaiea only le TRANSVISION Components and special equipment. a heading values. See your distributor. stream- An under -the -rug television re- wilatiy° few of Trarurlsitnl's PM Radio; receives all channels: indoor 115 sa. in. picture: complete NET S799.00 in MODEL IOB L, TV/FM lilt, givra ceiving antenna described recently cabinet N NET f 24.95 lined 180 visibility design a satisfactory Roto -Table for Model 10111., gives full cabinet with Bolo-Table; streamlined Electronics may provide TV Kit. gives 60 sol. in. picture; cottsolelte NET 29.95 problem in many MODEL 7CL, ET $189.00$I solution to the antenna it is e. table model can he sup - 7BL. same as -CL. except that head -in tire. (Models 7C1, and 7ma may be MODEL antenna. 60 ft. instances. The antenna shown .111 Itltlpilo cabinets, f of copper or tubes, an`d cut out of a thin sheet STRENGTH ETER ... made from % -inch copper strips riveted NEW ... TRANSVIS ÁONTFINELD IMPROVES actual isetal (3h and soldered together. This antenna is advantages. including-III Measures Antennalorlen- t use a elev'ision illmitthe combinations . . . consisting ils actual' picture'' signalslmeasiitai of various antenna and lead -in a high -gain, end -fire array Measures horses or gain . Ihmat be domo exactly . UI . 16) la CHANNEL SELECTOR Vaal oscillator) cal l bra" to a checking rem -elver eradiation lis ie, of elements which connect I Useful for Weighs tbs.... three signals of this unit Amplitudes. Interfering case . Initial coat 300 -ohm line through matching stubs. ousedl`in` attract metal carryingeatT NET $99.50 and it is i Inaanau,ana. complete with tuba The array is highly sensitive, n.msvislat Field strength ?toter. Model FSM1. said to be sufficiently directive to dis- criminate against ghosts. Several of these units can be paralleled to improve the performance.

131/2 MILLION VIDEO SETS BY'52 Television is already giving radio some serious competition -and promises more -for, "ready or not," it has start- ed to roll and "is not holding up for anyone." So says the advertising agency of Lennen & Mitchell, Inc., of New York, in a study recently completed on "Cur- New... REMOTE CONTROL UNIT rent Television Facilities, Programs, and New... ALL-CHANNEL BOOSTER Audience." Television, the agency states, -CHANNEL TELEVISION BOOSTER TRANSYISION ALL areas. o areas which the status of a To achieve television reception In .weak signal engineers toward Tra svision .n is fast heading of range of certain broadcast stations. /el;wlvi.. TELEVISION out booster. It inwmas.s signal strength l'h $6,000,000,000-a -year i n d u s t r y, four have designne.l this c evisionchanneÜn 13 television channels. Tunes all 133Ì ontiinuo s M1 lllll gain 1M used whh t`y S -S LIST 939.93 times the size of radio. gain W upper television channels.` Model Lennen & Mitchell estimate that the TRANSVISION REMOTE CONTROL UNIT ... possible the tuning of a televi cost of developing television will run to This remarkable unit makes set n Shen vinin ., as far as 90 feet. Turns iver ' distante the television years set off. Ideal for installations where $800,000,000 in the next several is a high gain. allchannel mit receiver isIs Inaccessible. Tuner unit .. rtwmvs r9tauta _ _ for stations and sets alone. This does not 50 mlcro -volt sensitivity. LIST s4v.tw Model 47.00 which the indus- out cabinet include program costs, line r e bum' try hopes advertisers will assume. NEW 8 -PAGE CATALOG nhp° 7,L iiaélt°le t » 't v.:1r above or te to Eighty million dollars of the N.Y. _=- total represents the cost of constructing TRANSVISION, INC. Dept. R.C. New Rochelle, IN CALIF.: Hollywood 46 allocated number of stations per- Tranavision of California. 5572 Santa Morves lyd., the all prices fair traded. mitted by the Federal Communications All prices See higher west of Mississippi; Commission. OCTOBER, 1948

www.americanradiohistory.com 62 Televisivo Television Sweep Circuits Part I -Basie theory of the multivibrator oscil- lator and its application in television receivers By ALLAN LYTEL*

THE sweep circuits of the modern the relative values of the two time con- television receiver are time constant to assure that this ocil- of vital im- stants. An unbalanced circuit is used in lator will lock portance, but they are not in with the sync signals. difficult commercial applications because the This is the "hold" control. to service or to understand. They function of the multivibrator is to act as A modified version, the cathode - are of two main types, the multivibrator a switch for the charging condenser. and the blocking-tube coupled multivibrator, is used in a great oscillator. The oscillator is used either at the many receivers where The most common type of multivibra- a common cathode vertical frequency of 60 c.p.s. or at the resistance assists in tor is illustrated in Fig. 1. the coupling be- This is essen- horizontal frequency of 15,750 c.p.s. tween tubes. Fig. tially two stages of resistance -coupled Values 4 shows the rear- for horizontal operation are rangement of the circuit as used for given; those for vertical operation are horizontal sweep in the Belmont in parentheses. 22AX- 22. The action of this circuit is very Synchronization much the same as that of the standard multivibrator of Fig. 1. A signal derived from the synchroniz- ing pulses of the television .005(.051 .001 (.01) signal is usu- ally applied to the multivibrator to keep O -0 BIAS (2.2MEG1 (I.IMEG1 it in step. This keeps the sweep voltage, EGI -CUTOFF developed by the multivibrator, synchro- Fig. l-a--Basic circuit of the multivibrator. nized with the video signal so the pic- ture will be steady. Without an applied -0 BIAS ESYNC EGI sync signal (when no 0 VOLTS -- -- CUTOFF BIAS station is being 1 ; received), the oscillator will continue to Fig. 3- Effect of superimposed sync signal. I- I operate and sweep I- ISO BIAS the electron beam - - EG2 ------CUTOFF BIAS across the tube face. This will prevent a Other multivibrators, although not in t I spot from being burned in 1 1 1 1 I t the tube face current use, are also of interest. The coating. EPI direct- coupled multivibrator appears in The sync signals or triggers are ap- Fig. 5. This circuit uses direct coupling

I I 0 plied to B+ the grid of V1, causing the between grid and plate, a C -bias source, EP2 multivibrator to remain in step with the and an input trigger. Two input pulses io entire television system. This action are required to obtain one output pulse. Fig. f -b -Plate and grid voltage wave forms. may be followed by looking at the wave The circuit has two stable conditions of forms in Fig. 3 where the multivibrator operation: either V1 is conducting and amplification, each stage being R -C- is caused to follow the sync signals. V2 is at cutoff, or V2 is conducting and coupled to the other. Fig. 1 is an illus- Normal operation of the multivibrator VI is at cutoff. No other condition is tration of the free -running multivibra- is indicated for the first two cycles with possible; and, if one condition is dis- tor, which gets its name from the fact turbed, the circuit immediately changes that no LONG RC input signal is required to begin 0 BIAS to the other. The fundamental multivi- oscillations. No two tubes or parts can EGI CUTOFF brator action applies here, and a trigger ever be exactly of matched, hence when this 1 SHORT RC proper polarity either starts or stops circuit is first placed in operation one I the tube from conducting. The wave I tube conducts more heavily than the I forms illustrate that V2 is conducting other. If we assume that Vl conducts 0 BIAS and its plate voltage is low; hence a pos- more heavily, its plate voltage will be CUTOFF itive trigger will affect VI, but not V2. lowered. This places a negative voltage I A negative trigger will affect V2, but on the grid of V2. V2 will then conduct B+ not VI. less and its plate voltage will rise, coup- ling a positive grid voltage to VI. The EPI ; OVOLTS +300V action occurs very quickly and VI is at J I j- .-B+ HORIZ.SIZE saturation while V2 is at cutoff, an un- EP2 stable VOA .01 condition for the circuit. 0 VOLTS When C2 discharges through R2, V2 2 Fig. -Wave forms in an unbalanced circuit. .0015 is no longer at cutoff. It begins to con- duct, 4-I and the circuit reverses itself so the oscillator synching after that. A INPUT V1 cuts off and V2 conducts heavily. capacitor is SYNC placed between the V2 plate 4.71% The frequency is determined by the and ground to develop a sweep voltage .00 132R time constants of the circuit. If this is for the cathode ray tube. a balanced circuit in which Cl equals C2 The sweep and the have and retrace dif- Rl equals R2, Fig. 1 -b will show the ferent time durations so the circuit must wave forms. If that is not true, as with be unbalanced -C2 -R2 must not Fig. 4 Typical cathode- coupled multivi brator. the be the values given, the outputs will be un- same as Cl -R1. Since the sweep time is When VI balanced, as may conducts, the entire circuit be seen from Fig. 2. to be longer than the retrace, C2 -R2 is flips to the other state. The degree of unbalance depends This conduction upon made about ten times the value of Cl- reduces the plate voltage of VI and the R1. R2, Temple University Technical Institute, Phila- in the grid circuit of V2, is grid voltage of V2, which is a continu - delphia, Pa. made variable and is used to vary the (Continued on page 64) RADIO -ELECTRONICS for

www.americanradiohistory.com 6e3

IN RADIO & TELEVISION TWO GREAT BOOKS ... COVERING EVERYTHING COMPLETE TELEVISION EVERYTHING IN RADIO AND THE MOST MANUAL ELECTRONICS IN ONE BOOK! THE RADIO THE VIDEO BOOK HANDBOOK DATA 768 pages ... 14 sections, cover- in television . the only radio handbook of its ing every phase over 800 illustrations . . . hand- kind ... 1148 pages . . . 12 sec- a radio sub- somely bound in Du Pont Fabri- tions, each covering letters. ject more completely than any koid with red and silver How Television Works. Basic . . . through other book! advanced. How to Design and Engineer Television. to Troubleshoot and Repair Television. Used by Engineers. Servicemen. Designers. How Technicians.. Draftsmen. Operators. Safety procedures. Latoratory Research How to Select and Install a Television Antenna. Inspectors. Amateurs. Experimenters. Show. Consultants. Broadcast Tech - How to Create a Television Development. How to Build an Operating Television Receiver. instructions. Police. Fire. FlorestryMandand Raillroad Complete Marine. Select a Television Receiver. Communications. How to and everyone in radio and electronics PAST, PRESENT AND FUTURE SECTION I. TELEVISION, and de- can use this book! find an a count of the inventions, discoveries Here you will television. velopments that led to the n present system of I. 150 BASIC CIRCUITS SECTION ref- OF ELECTRONIC TELEVISION Each circuit properly classified and clearly labeled for instant SECTION 2. FUNDAMENTALS electronic of electronics a explanation of the complete erence! Every basic operating unit in the entire field In this chapter, simplified of rvcryoae in radio 150 circuits -completely il- television system is given. for the convenience CONTROL- lustrated- -ALI, in this one section! SECTION 3. THE TELEVISION STATION- PICK- UP- 2. TEST EQUIPMENT TRANSMISSION SECTION step -by -step volt. current and ohmmeters, tube checkers. condenser operation and piece of equipment is taken in a All types of signal gen- Each white on black meters. inductance mttens, bridge measuring devices. RF presentation. illustrated with photographs, schematics, signal tracers. distortion analyzers, and graphs, and simplified line drawings. erators, AF signal generators. meters. scope patterns test speakers, oscilloscopes, square -wave generators, frequency SECTION 4. THE TELEVISION RECEIVER and illustrated. completely de- field strength and tuning meten are explained stage is individually studied and its function Each all the other stages. AND MEASURING scribed as a unit and in relation to SECTION 3. TESTING ANTENNA SYSTEMS ta use test equipment and make every kind of measurement SECTION 5. TELEVISION How book. the various receivers and locales are ex- in radio. This sectie n alone is worth the price of the entire The proper n:utenna for plained. SECTION 4. ANTENNAS TELEVISION SHOW trans- SECTION 6. CREATING A This section presents complete information on all antennas. and Production showing various types Programming with technical mitting and receiving. Completely illustrated, In television programming is tightly interwoven of antennas, their construction und wave patterns. operation-the studies TELEVISION 11tly SECTION 5. SOUND SYSTEMS SECTION 7.n DESCRIPTIONS a OF MODERN com- The planning, velection of equipment and the assembling and RECEIVERS of varions components in complete PA installations. Every variations-Design- Mechanical Features bining Circuit type of receiver On type of unit used is described and analyzed in detail. This section includes a circuit diagram of every- SECTION 6. RECORDING the market today. recording found SECTION 8. INSTALLING TELEVISION RECEIVERS This section is the only complete description of disc surveys, equipment re- Here all phases of recording are Every '.step is covered . . . pre installation in any radio manual oa the market. the antenna, laying transmission lines, -both home and commercial. quired, locating and erecting covered- locating the receiver in the building. SECTION 7. TUBE MANUAL TELEVISION RECEIVERS of all SECTION 9. SERVICING The only uncommercial tube manual giving complete listing -Interpreting Test Patterns -Alignment- Repair tube base illustrated along- Troubleshooting how- to -do -it transmitting and receiving tubes with each This in another section devoted to detailed. procedure, side the description. this time on servicing the receiver. TEST EQUIPMENT. HOW TO USE SECTIONS 8 & 9. CHARTS, FORMULAS, CODES, GRAPHS, SECTION 10. TELEVISION HOW TO BUY IT SYMBOLS was expressly designed to sections are found all data and and information Section 10 of the VIDEO HANDBOOK Here in these two can save you as much as Il0(10.10 in useful to anyone in radio and electronics. give you this information- it purchasing test equipment. 10. 50 TESTED CIRCUITS RECEIVER SECTION I I. BUILDING A TELEVISION a SECTION 0$ all equipment built in radio & electronics is covered here in complete plans, diagrams, photographs of com- ; of and descrip- Included here are section presenting the typical circuit with parts lists and assembly by far the most useful collection of cir- ponents needed tions of each type. This is SECTION t 12 SECTION nn over presented. nhmographs, sym- cuits Here are compiled all the graphs. charts. curves. SECTION II. DICTIONARY OF ELECTRONIC TERMS bols, formulas and rules dictionary will explain every radio term -any word used in TERMS This and titles used in radio. A complete dictionary of words. terms, phrases SECTION 12. BIBLIOGRAPHY television. valuable list of books for anyone desiring SECTION 14. BIBLIOGRAPHY Here is n unique and complete list of literature on telev is inn issued to date. further details on any subject in Radio. This is the mo.t ADVANCE SALE 12 complete books in one only NOW! Less than 42c per book! 5.00! ORDER $5.00

RC ] 0 Mail This Coupon to Your Jobber Today -or Direct to: sell- J. These books are best BOLAND & BOYCE, 460 Bloomfield Ave., Montclair, N. ers in the radio and tele- Send me 1 VIDEO HANDBOOK send me I RADIO DATA BOOK Make sure you 1 enclose $5.00 ($5.50 Foreign) vision field. I enclose $5.00 ($5.50 Foreign) enclose and will pay postman $1.00 copies order and will pay postman $4.00 I $1.00 get your ... I enclose $1.00 nn delivery tin O. S. only) (in IT. S. only) now! Use this coupon to on delivery order either one or both NAM E books get them both, - ADDRESS you'll profit by the valu- CITY ZONE able information they con- STATE tain! BOLAND 8 BOYCE INC., PUBLISHERS 6

OCTOBER, I 9 4 8

www.americanradiohistory.com Television

FREE"WN/LE THEY LAST! TELEVISION SWEEP CIRCUITS (Continued from Wiring diagram for 5 tube ACDC set. These excel- page 62) lent diagrams won't last long -so .end for your free copy today: MILWAUKEE ing action AUTOMATIC RECORD CHANGER until V1 is conducting and V2 is at cutoff. According to the wave forms, there must be two of these trig- - only S13.95 gers- negative or positive -to obtain \\\ one single square -wave output since this circuit remains in a given condition af- n ter the trigger impulse is removed.

, , \ ,, ;'1ß There are therefore two triggers re- quired at the input for a single square- wave output. VOLUME CONTROL Bargains The pulse amplitude required for positive triggering is somewhat greater SaLi.41,1, .1,1,11,,,j brand. than for negative triggering. This dif- a -7 Art 001(10 tonal value! All ference in triggering amplitude is not Maud new. great enough for the circuit to discrimi- I, Ana \,t'. with switch, 3- shaft nate between negative and positive syn- n 14mts V.1'- with switch. 3 shaft r.uuh ohms VA'. withu.itch. 1- ,haft In11.11rltl ohms V.1'. with awilcll, I- ,haft n .Jun, V.C. null switch. P ,hart- Tapped - ^ ^!. I I, : V.0 with switch. r ,haft -- Tapped I ; V.C. with switch. 3- elwtt- Tapped . VAC. wills switch, 3 ,haft-Tappe.l only 44c ea.

OIL FILLED CONDENSERS Standard Brand. Upright T' r, Stand -Off Insulators Fig. 7- Double- tracker for an oscilloscope. 4 MI6. 600 VDC s .45 o %Ifd. 600 \DC .69 Another interesting multivibrator 7 MId, 606 VDI' .74 ... "- is s \ItlL 6011 VIN .79 the single -shot type of Fig. 6 which uses to \Ir.L 6110 vine 89 a positive grid return. A + =EC voltage divider 8 Mfd 1000 l'lw 1.90 -" R1 -R2 is used to keep a positive poten- Fig. 5 -a -The direct- coupled multivibrator. tial on the grid of VI, and a positive SPEAKER Specials grid return produces a positive potential (Too quality. precision -built speakers at absolute on the grid of V2. V2 is minimum rust., Epll - -8+ the normally conducting ,- 1 tube, and V1 is cut off be- P.U... Is I, .thlicn V S .99 ea. 11 o VOLTS :- t'.51. 17 oz. -111110 V 1 I 1 -I. 1.15 -I I cause of the bias across R3, bias due to Iv P.M.--1 oz Moico V .99 -9+ Evt the ,- 1.06 P.M. Soc.'. . 1.89 total plate currents for both tubes. s. .M. -1 ea Alnico P .99 0 O VOLTS This multivibrator 1 will . -1.47 oolcaz. .l - V its produce a single - I- I' -3IM -2.15 or Alulto V 1,55 EIN' L k square -wave oz 1 k L output for a single input !t I',M. -6.1 Ahdn. V 2.75 i< o +- 1'.116 -0..9 In. Alnle V 3.69 zE trigger. PC 1451--6.9 oz Alnico V 4.39 EMI r _° Iv..tlnìro r r r r r r 12 l'.. -3.S t- 4.95 12- P.31M. -6.9 Iv. Alowo V 5.95 Fig. S -b-Two impulses produce a full wave. Electronic switch '- P.11.- 21 rn .!intro 3 with 6V6 P.1'. Output $7.95 complete Among the many uses of the multi- linonsie 1;911 chronization signals. Limiters or clip- ' ohms field with at 6 vibrator P.P. Output 3.95 complete pers are usually used ahead of the is the electronic switch shown " Rohm. it 1190 I4Ims field wills 616 in Figure 7. P.P. Output multivibrator to remove the unwanted This is used to present two 6.95 r omplete pictures on Dynamic 10110 ohms field 5.95 pulses that might otherwise cause er- an oscilloscope at the same ratic and unstable operation. time. At the heart of this device is a IF TRANSFORMERS free -running multivibrator V1 -V2. V3 B+ and V4 are squarer tubes used to clip . Iir' IF Tra11.. ,, itorPor 32e ea. the ends of the outputs of the multi - 61' IF Tr:ui>- vibrator. t^iw,r all h .1 V r 7 p 39e ea. Al idcct Size I16 KC IM Tra n,- Common cathode resistances thing Iupnr A IIIt o are used 49e ea. for V3 and V5 and for V4 and V6 to couple the squarer tubes to the amplifier MICROPHONE CABLE E IN tubes V5 and VG. When V3 conducts. A P C 0 t I G H the heavy plate current causes a large 93 IR drop in the cathode resistance, which .s 19 Strands Shit -r is l'latrd 'Ein.r1. 1: Dw,hi, S. - a great enough bias to cut off V5. illa l'clltilorr Acetate, l' -1 inn Stith )hri,rne Prom, During this time V4 is TI Ialtuent. Fig. 6 -a -The single -shot type multivibrator. not conducting, 11 -Black Braid. E. Salt and Pepper Itruid. 0( and therefore V6 has only the bias due F-IAul.l Tit i.1.1 Coppor, 4 SII -ansia #36 It & S. Q- t -- -, ., II -mu Rubber Jark-t. to its own plate current. This means I:Iaok C0% it,' 0 VOLTS that either V5 or V6, but not both, may only 4c per foot I i I I be conducting at any one time. ER3 The output voltage is fed to the signal ' O VOLTS MINIMUM (MISER $1.00 circuits of the test 'scope so that the wilt:\ Illtl ikli1 I,, .Ilptuit ' I t for all C.O.D. I two input signals may be 1_, _I seen. Actually $hl . Ire.. B+ - will be relunllyd! Ii. I first one signal and then the second ap- - will lie ,hipped r o ' VOLTS pears, but the rate of switching is so r I, I:. V 1 1 O t V,,,k I I I I I rapid that the two signals appear to III + be I¡¡I present at the same time. This is a use- Ep20 ; ful method of comparing wave 7IVCOAJ1110.. OVOLTS forms in I I alignment procedures and t-' Ì iI_B+ may also be g Dept. A, 73 West Broadway - - -CUTOFF used to compare two signals coming - - - 1 New York 7. I N. Y. BEEKMAN 3 -6433 from two different antennas in radar Fig. 6-b--Wave forms of multivibrator above. receivers. RADIO -ELECTRONICS for

www.americanradiohistory.com 65

RADE INOoeEs-r<1°P AA /' TUBE ADS THE SENCO ` VALUES!Here's the final answer to your tube problem. Again we've gone the limit - cutting off IN SUPER every bit of overhead expense that unnec- essarily adds to your cost. Result: lowest prices CARTONED of INDIVIDUALLY on the market today! So why not take advantage ALL these tremendous savings now. sm-- DEts_- IIl1 BRAND ONLY EW SENCO CAN OFFER 1 Lots of rase l Type 10 Lots of rREMEND OvS Each Eachac SAaiNCSeI OZ4 Trpn 10 Lotsis of 69c E ach Each 1A3 Typc 10 LLots 45 6AL5 '/ Each 1A5GT 39c 49 38 Each -4. f G 59 6AU6 raY,/ 6U6 IA7GT 49 49 39 49 TYP` Eech Each G 55 6AV6 6U7G 39 106 45 39 35 32L7GT 75 687 (f 6VSG 25 34 52 48 1E7 68 55 49 ^ 99 68G6G 6V6GT 1_ 59 IH4 89 89 G 45 49 35 51 69 59 6BE6 99 6XSGT 4452 32 I H5GT 52 38 G 49 39 GT/G G 59 6B)6 49 7A4 4 39 IH6 49 49 53 35W 74 6C4 59 25 7A7 43 35Y4 43 40 1J6 69 Il / 80 6C5GT 29 40 iL4 72 786 4459 3549 - 35Z3 43 49 45 4-7/ 6C5MG 40 35 7F7 1LA4 36ZSGT/G 43 6C6 7)7 49 44 39 1LH4 49 39 - 45 32 35 69 59 6C8G 7N7 54 49 37 29 INNS 69 37 29 44 45 606 49 7X7 49 t, 38 39 IN5GT 6F5 45 45 G 59 49 e XXFM1 39 44 39 1R5 55 45 44 25 19 55 6F6GT 7 Y4 35 41 155 49 45 39 44 49 55 6F7 12A6 35 42 45 IT4 59 39 29 47 69 6F7 VT70 49 !2A8G7 25 43 41 ITSGT 55 49 39 35 54 47 59 q9 6H 6GT G 12AT6 28 45 6JSGT 45 50 45 49 39 36 30 j1 G 45 12AT7 45Z5GT 1V5 6J6 69 45 39 59 ,cri/ 126A6 59 47 59 49 2A3 6J8 49 12BE6 50 45 49 39 80 72 50A 5 2A5 50 45 60 55 2A6 43 35 27 5085 45 6J7GT S9 49 12H6GT 50L6GT 42 32 2A7 49 --` 6K6GT/G 38 12JSGT 39 34 50 45 2X2 39 45 25 50Y6GT 879 35 6K7G 12J7G7 19 50 4$ 3A 29 50 45 4 49 39 6K7GT/G 49 41 I2K7GT 39 57 55 45 45 58 3Q5 SS g9 6K8G 5 39 12K8Y 39 45 39 3S4 35 45 55 6L6G 79 69 12Q7GT 25 59 39 45 (-¡ 45 65 12SA7GT 71A 59 SU4G 6N4 84 78 G 40 32 29 79 69 !25F7 3 75 39 5W4GT 39 34 \14JIl 6Q7G7 38 I2SC7 S0 39 47 1634 49 76 5X4G 39 6R7 39 125G7 39 45 5Y3G 77 49 42 35 6R7GT 55 45 125)761 37 78 35 27 5Y3GT 49 ' ;.5! 49 G 40 33 65A7 49 i 12SK7GT G 80 49 39 SY4G 39 6SA7GT 12517 35 38 5Z3 G 44 83 40 6587 37 11SQ7GT 43 48 49 39 55 G 40 83V 52 5Z4 59 65D7G7 39 -s I25R7 32 69 6A6 34 84 6Z4 79 69 6SF5 14A7 32 49 39 6A7 61 49 39 J 35 85 65G7 1486 65 55 89 49 45 6A8GT 44 39 59 49SO 39 + 6SH7GT 49 99V 49 46 6A87/1853 40 32 49 46 65J7GT 39 99X 35 25 6AC5 69 _ / 6SK 44 37 69 59 59 7GT,G 49 GT/G !17Z6GT 25 6AC7/1 +' 6SL7GT 49 39 G 89 60 49 1828 76 6AG7/6AK7 g9 6SN7GT 47 ;;;;GT/G 49 45 99 89 47 45 1131 6AH6 49 65Q7GT/G 26 39 39 29 44 37 45 1644 29 6AK$ 74 6SD7 27 32 19 69 39 49 6557 30 44 59 49 59 32 49 80 75

I V I D E N MINIMUM D OF THE MONTH lENCOAADIOrNc. ORDER $1.00 WHEN ORDERING- 25% deposit Send Ship- 885 Broadway, all C.O.D. THYRATRON, Dept. A, 73 West ments. Include suffi- TRIODE TYpE cient postage-excess York 7, N. Y. will be efer ded SPECIAL New without postage. will be expressge TELEPHONE -BEEKMAN 3 -6498 collect. Allshipped prices 29c EACH York City.

OCTOBER, 1 9 4 B

www.americanradiohistory.com 66 m. War Surplus Bargains Sold As Used Unless Otherwise Specified!

VOLUME CONTROLS PRICE RESISTORS -CARBON 1 megohm, carbon, 1" shaft $ .35 100 ohms, 1/2 watt $3.00 per hundred 1000 ohms, carbon, screw -driver shaft .35 120 ohms, 1; 2 watt 3.00 per hundred 20 ohms, wire -wound, 1" shaft .35 220 ohms, 1/4 watt 3.00 per hundred 500,000 ohms, carbon, 2" shaft .35 270 ohms, 1 watt 3.00 per hundred 1000 ohms, wire -wound, 2" shaft .35 470 ohms, 1 watt 3.00 per hundred 6000 ohms, with switch, carbon, 1" shaft .40 480 ohms, 1, watt 3.00 per hundred Dual 25,000 ea., wire- wound, 1" shaft .35 1200 ohms, 1,,2 watt 3.00 per hundred Triple 25,000- 50,000 -20,000, carbon, 1" 6800 ohms, 2 watt 3.00 per hundred shaft .70 12,000 ohms, 2 watt 3.00 per hundred 21,000 ohms, 1/4 watt 3.00 per hundred RESISTORS 56,000 ohms, 1/4 watt 3.00 per hundred WIREWOUND 85,000 ohms, 1/4 watt 3.00 per hundred

1 50,000 ohms, 1 watt 3.00 per hundred 3 ohms, 20 watt .10 270,000 ohms, 1/2 watt. 3.00 per hundred 2500 ohms, 20 watt .10 830,000 ohms, 1/4 watt. 3.00 per hundred 1/2 ohm, 20 watt .10 1,200,000 ohms, 12 watt 3.00 per hundred 11269 ohms, 100 watt (has 5 taps) .35 5,600,000 ohms, 1:1 watt 3.00 per hundred CONDENSERS PRICE

.5 mfd. 600 V., Oil, x 1 1/4" 3/4" x 2" $ .20 .5 mfd. 400 V., paper, 1" dia. x 21/4" .25 5.2 mfd. 50 V., Chicago Ind. Cond. Corp., Oil, 1 x 21/2 x 3" .25 4 mfd. 600 V., GE Pyronol, 1" x 21/2" x 3" .50 2 mfd. 600 V., Aerovox Oil, 1" x 1" x 3 1/2" 1.25 8 mfd. 600 V., Chgo. Ind. Cond. Corp., Oil, 1" x 4" x 5" 1.50 1 mfd. 4000 V., C -D, Oil, 2" x 4" x 7" 4.00 .02 mfd. 600 V., mica .05 4 mfd. 1000 V., Oil, C -D or Aerovox, 1" x 2" x 7" 2.50 30 mfd. 330 V. AC, GE pyranol 3.00 2 mfd. 1000 V., C -D, Oil, Single hole mounting, 1 1 2" dia. x 41/ 1.75 4 mfd. 600 V., C -D, 11/2" 2 x 4" ", single hole mounting 1.25 140 mfd., variable, padder screwdriver adjustable .25 7 -17 mmfd., variable tuning, 5 plate, 2" shaft, 1/4" dia. .25 1 mfd. 400 V., paper, Aerovox .15 14 mfd. 50 V., paper .15 1 mfd. 1500 V., paper .20 05 mfd. 400 V., paper .15 Telephone LINCOLN 8328 LIP MICROPHONE PRICES F.O.B. INDIANAPOLIS TYPE 813 TUBES Made by Western Electric, TERMS: CASH WITH ORDER Navy type CW- 51071, with $5.95 each instruction sheet, brand new AMERICAN SURPLUS Type 813 tube sockets PRICE $1.50 PRODUCTS CO. NEW PRICE 50c

INDIANAPOLIS IND

RADIO -ELECTRONICS for

www.americanradiohistory.com r67 TURBO AMPLIFIERS WILLARD LEAD ACID CELLS

Used for parts- shipped com- plete with the following tubes; 7 C5's 2 $3.00 6 V. (New) (Dry- charged) NAVY CRV -46151 AIRCRAFT 1 7 Y4 electro- 6 V. metal carrying case) (Add 1 7 F7 (In RADIO RECEIVER lyte specific gravity 1.265) $4.00 PRICE - Carton of 10 - $7.50 Drugstore) $ Four bands including broadc;;st (195- 9,050 KC). Circuit is six -tube super- heterodyne with mechanical hand change or remote operated electrical band BL- SELENIUM RECTIFIER TYPE 23751 change. Remote band change and tuning the much needed 110 V. DC controls included, making this set readily A must for the radio man for at .75 adaptable to mobile ham use. Powered source. 110 -120 V. AC input, 110 -135 V. DC output requirements. from self- contained 24 V. DC dynamotor. amp. Connect in parallel for highest current The sets are complete Size 3%x2%xl% inches. and remote con- $ 1,65 ea. with tubes $2950 PRICE-New trols. No cables or plugs. Including case

BOX REMOTE CONTROLLED COIN INSERT AND SPEAKER Made by Personal Music Corp., Newark, N. .1. Model F 24 Volt operated. fusel Weight 6!:, lbs. Size 4''¡ x 7'. x 51/,' high Sloping front P M Speaker 5" size Has 2 Pilot Lights for illumination Finished in chrome metal and grill with red plastic Accepts I to 6 nickels Each 5c coin gives about two phono records of music Should he mounted on a flat base Has Hayden Mfg. Co. timer Luck i" in top. (with key.) Easily removable coin box, size 6" x r_ llle'ßd"

3 4 µRequires ires from power unit A beautiful piece of equipment that could be built to house coin operated radio Worth several times 1111.11. ask- $4.95 OPEN VIEW ing price. Price brand new...

TUNING HEAD CRV -23253 PILOT'S CONTROL BOX, TYPE CRV -23254 RECEIVER Used with ('RV -46151 Receiv, r for remote control of volume, Has bands, as off, on switch Used with CRV -46151 Receiver for vernier tuning. selection of any One of six frequency -1600, or .eleetiou of C.W. and M.C.W. and M.V.C. or A.V.C. Black beveled dial with hairline cursor. Bands are 200560,,560 about 280 'H ish. Size 2 "x2'z "x5" high. -4450, 4450 -9050 Kcs. Each band spread over 1600 tuning shaft Brand new $1.50 each degrees of dial edge. Has provision for flexible direct drive on any tuning shaft. Black ARGON BULBS or can be adapted for finish. Size 5 "x3 "x2" overall. ideal for R.F. indication, night crackle $1.50 each Brand new, Box of ten $1.75 Brand new

PHONE LINCOLN 8328

PRICES F.O.B. INDIANAPOLIS RECTIGON FIELD TELEPHONE WIRE TERMS: CASH WITH ORDER WESTINGHOUSE BATTERY CHARGER BULB ,ti :nuli, i =iiand and weath- 3 ndutor, Style 260416. 6 ampere rating. For replace- erproofed. Idea for intercommunication ment in most chargers or for building systems, telephones, seisyn mdi, :.t r . Ilse power supply to use on D.C. operated equip- it inside or out of doors. ment. new, $4.25 Brand new $1.90 each 525 Foot roll, brand 537 N. CAPITOL AVE. INDIANAPOLIS, IND.

OCTOBER, 1948

www.americanradiohistory.com 68 I Blectrics The Crystal Detector Part /"- I'iivifiitx and Techniques Using Germanium I'r,yxtiir/ Diodes By JORDAN McQUAY

MODERN crystal rectifiers are minais well above ground potential when greater adaptable than 400,000 ohms for each crys- to many practical desired. tal when measured at volts. uses. They can be valuable -10 in Another important characteristic of FM receivers originally designed to almost any circuit where low- germanium crystal diodes is their re- power rectification operate only in the 42 -50 -mc band can is required. markably long life. For instance, the be converted for reception Most practical are the germanium in the 88- type 1N34 is rated for service in ex- 108-mc band with tubeless crystal con- types of crystal diodes which give superi- cess of 5,000 continuous hours. verters or performance now being marketed. These con- at frequencies up to sev- A few types of silicon crystal diodes, verters use germanium eral hundred megacycles crystal diodes with low values designed originally for microwave oper- and require no power of load resistance. Known for operation. as types ation and obtainable through war sur- They are connected between the antenna plus channels, can be used at lower fre- and the input of old style receivers. quencies. They must be operated at very low power and invariably suffer from Television uses reduced operational efficiency. Germa- Crystal diodes can perform at least nium crystals are desirable for most two important practical functions in modern tele- applications. vision receivers. They can be used for Crystal detectors detection in the discriminator stage of the sound circuit and for low -power d.c. Using germanium crystal diodes to de- restoration of the picture signal. tect the i.f. output signal of conventional Except for band -width requirements, PLASTIC CAT WHISKER PLASTIC superheterodynes is satisfactory up the discriminator of a television set is to several Fig. I- Cutaway view of IN34, crystal diode hundred megacycles. At high- similar to that of an FM receiver. For having many radio and television applications. er frequencies, silicon crystals are pref- television, ±25 -kc deviation is required; erable. for FM, 1N34, 1N35, 1N38, ±75 kc. and 1N39, they are A single crystal diode can be used as A pair fast becoming important circuit of matched type 1N35 ger- ele- a half -wave detector as shown in Fig. 2. manium crystals is used for detecting ments. Full -wave rectification In requires two television sound signals just as in FM addition to improving performance, crystal diodes (Fig. 3) of the same type, receivers. germanium crystal diodes permit sim- preferably with the same characteris- Crystal diodes are plification of many radio, television, and used in clamping tics. circuits as d.c. restorers whenever the electronic control circuits. They are A.v.c. voltage suitable can be supplied by a input voltage does not exceed the nor- for use as second detectors and separate crystal diode arrangement, as mal rating of as d.c. restorers the germanium rectifier. in television receivers, shown in rig. 4. Crystal A provides a Type 1N34 is limited to approximately as modulators and demodulators, and negative voltage for a.v.c. as action; crys- 60 volts; type 1N38 will accommodate low-frequency oscillators, voltage tal B functions as the second detector, voltages regulators, and polarizing up to approximately 100 volts. devices. Oth- For signals of greater er applications include volume amplitude, any limiters sTALS number of additional crystal diodes and clamping circuits, square -wave clip- (preferably pers, radio testing instruments, of the same type) can be meter ISK AUDIO OUT connected in series. rectifiers, volume IF TRANS expanders and com- A typical pressors, rectifier o clamping circuit is shown bridges or varistors, in Fig. 5. It uses and a variety of other functions. Fig. 3 -Full -wave detector in superheterodyne a single crystal diode set using two connected between the Contained in tiny cartridges germanium crystal rectifiers. output of the (Fig. 1), final video amplifier and the grid input crystal rectifiers require no heater sup- but is connected with opposite polarity of the picture tube. Some form of d.c. ply. They are affected less by tempera- to that of crystal A to balance the load ture, humidity, and age than other types on the final i.f. stage of the receiver of dry rectjfiers. a They resist shock and Both crystals should be of the same IF IN r.000l vibration 4 as well as or better than con- type, but need not be perfectly matched. 0 5Oupf AUDIO ventional vacuum IF TRANS OUT tubes. Crystal diodes also are used in the 27OKT second detector or discriminator stage IF TRANS RTAL of FM A receivers, replacing the usual %TALS o .I t - diode vacuum tubes. Since the AVC IF IN Á 27K .}. 25µµt AUDIO OUTPUT discrim- o inator has a balanced output, the two Fig. 4- Superheterodyne circuit using separate Fig. 2- Typical circuit of germanium diode germanium crystal diodes used for full - crystal diodes for defection and for a.v.c. as a half -wave detector in a superheterodyne. wave rectification must have almost identical operating characteristics. restoration Electrical is necessary at this point be- features include small Ideal for this purpose is the type cause a video amplifier is an a.c. ampli- shunt capacitance (less 1 than µµf), low 1N35, consisting of two 1N34 diodes fier and there is no d.c. component in the forward resistance, high back resist- which are selected with great care video ance, at output signal. The needed d.c. com- and the ability to work into a the time of manufacture so that their ponent represents the average illumina- low resistive load with reasonable ef- resistances are matched within 10'Z of tion of ficiency. the original scene, and, unless it The lack of a heater removes their average value in the forward di- is restored, proper scene illumination one common cause noise of and hum rection when measured at 1 volt. The on the picture tube cannot be main- and permits connection of both ter- reverse or blocking resistance must be tained. RADIO -ELECTRONICS for

www.americanradiohistory.com Electronics I69

The high back resistance of a ger- manium rectifier can be put to good use in many types of pulse- shaping circuits, since the crystal diode effectively sup- plies its own load resistance under most operating conditions. Thus, germanium diodes can also be used in electronic con- trol devices. They offer a considerable advantage over any type of diode vacuum tube used in the same applica- tions. As a limiter, the crystal diode can be inserted in any circuit to remove un- desired peaks. For example, when an electronic device requires a negative trigger pulse without positive over- shoots, the undesired overshoots can easily be eliminated by connecting a crystal diode across the input of the trigger circuit. Testing and servicing Crystal diodes are very useful in radio and electronic maintenance. A crystal diode can be used as the rectifying unit for a vacuum -tube volt- meter, permitting the compact construc- tion of a practical, multipurpose a.f. -r.f. probe (Fig.6). Vacuum -tube voltmeters are essential- ly d.c. indicating devices, and require some kind of rectifier for a.c. measure- ments. Long leads introduce capacitive effects and are objectionable, and the rectifying unit should be installed in the test probe. A small diode vacuum tube could be used, but a germanium crystal is far more practical. It requires no pow- Fig. 6- Compact crystal probe for use with a v.t.v.m. is built in a small penlight case. er and is free from the contact poten- being must also be being adjusted and fixed during manu- effects normal to most diode vacuum the apparatus tested tial grounded to the voltmeter by an addi- facture for optimum operation. is also smaller, mak- tubes. The crystal tional wire and clip. Although lacking in both sensitivity ing a more compact probe. diode employed in and selectivity, these tubeless receivers maximum rating of a The single crystal The current this circuit is adequate only for meas- provide fairly reliable local reception, crystal diode is considerably higher of less than approximately with excellent fidelity. than that for diode vacuum tubes. uring signals 50 volts. To increase the voltage range Any of several circuits can be used. Probes using crystal diodes have high of the probe, it is necessary only to con- Fig. 8 shows a typical one. The tuning input impedance and low capacitance, nect a sufficient number of crystals in condenser has a maximum capacitance which reduce loading and detuning. series across the input. Two 1N34's per- of 365 µµf. The frequency response of a germani- up to about 100 The coil is wound on a cardboard diode zero to well mit a.c. measurements um crystal is flat from volts. or bakelite tube about 5 or 6 inches long over 100 mc, making it ideal for signal When connected to high -resistance with a diameter of 2 or 3 inches. Use tracing and a.c. voltage measurements. headphones, the probe can also be used No. 22 covered wire, and close -wind 90 Every 10 PIX SIGNAL for signal tracing, locating spurious to 140 turns on the coil form. or 15 turns bring out a tap by twisting TO GRID OF CRT oscillations or noise, and localizing dis- 4701( tortion. the wire, staggering the spacing so that a clip on the end of the antenna wire Crystal receivers can be attached easily to any tap. Then XIAE I IMEO Inexpensive tubeless radio receivers scrape off the covering from each ex- 7 can be constructed for local broadcast - posed tap to permit good contact. band AM reception using any type of The receiver will require a long an- Fig. 5- Crystal diode used as clamper for d.c. tenna erected as high as possible and a restoration in video stage of a TV receiver. good ground connection. Volume is va- A basic circuit for a crystal is shown ried by changing the tap to which the in Fig. 7. The capacitor is used to iso- antenna clip is attached. No battery or late the probe from d.c. components other power source is necessary. present in the circuit being investigated. Ham The entire probe may be built into a applications small penlight flashlight case. One side A simple device for determining the field strength or radiation pattern of a of the capacitor is soldered to a short Fig. 7- Crystal probe circuit. Omit the 22 -meg length of sharpened No. 8 wire; the oth- resistor if the v.t.v.m. has an internal shunt. ham transmitter can be constructed er side is connected to the mounted around the crystal rectifier, requiring crystal. A flexible shielded lead is used crystal diode as a detector. Here is a only a resonant dipole and a microam- to connect the rectified output to the in- modern parallel to the crystal- and -cat- meter. These components are connected put of the vacuum -tube voltmeter or sig- whisker era of the early days of radio. in what is effectively a closed series cir- nal tracer. The frame of the penlight But the problem of finding the most cuit (Fig. 9). case must be grounded to the voltmeter sensitive spot on the detecting crystal is Since only relative readings are usual- via the wire shielding. The chassis of now eliminated, modern crystal diodes (Continued on page 70) OCTOBER, 1948

www.americanradiohistory.com 70 l Electronics locksmithing and key making PRACTICAL THE CRYSTAL DETECTOR UP -'O -DATE COURSE (Continued front page 69) How to pick locks, de -code, make master -keys, install, service. etc. New self -instruction lessons Iy desired, for every handyman, home- accurate calibration is un - cuit (Fig. 10). The owner, value of R varies carpenter, mechanic, necessary. The crystal diode and the re - service station operator, Rx- considerably, depending upon the mag- ft shop, hardware dealer, ceiving dipole must be mounted rigidly gunsmith, cycle shop. nitudes of the voltage and current. Any Good steady money -making trade! in a fixed position with respect to each type of germanium diode is capable of 53 EASY ILLUSTRATED LESSONS other. During field measurements, the handling Igo, Full $loes, an average current up {J'rL\ price only nothina_more crystal to about fir must not be jarred or shaken. 40 ma with a transient surge current, In the vicinity of very- high -power for some +M - n NELSON -HALL CO.- types, of 500 ma. 1139 5. Wabash transmitters, Ave., Chicago S, 111, it may be necessary to in- An important sert advantage of crystal a small limiting resistor R (1 to 10 diodes when used as voltage watch and clock repairing ohms) in the series regulators circuit to obtain on- is their ability to return to normal after LEARN AT HOME - scale readings. the application of IN YOUR excessive voltages. SPARE TIME Using a stub dipole of appropriate When four crystal Prepare now for a happy future size, the diodes of the same of prosperity. security. Fascinat- same crystal- microammeter ar- type are arranged in a ing high -grade occupation for rangement bridge network men of almost any age or physi- can be used to explore the (Fig. 11), the circuit functions cal condition. You can earn while electric as a you field distribution inside cavity very effective learn. resonators voltage rectifier. Action PRACTICAL COURSE INMOROL- and wave guides. of the bridge network oar. How -to -do -it lessons for is conventional. beginner, as well as those al- If a pick -up coil is substituted for It accepts ready in the trade. Thorough waves of any shape as long clif- instruction training t the resonant dipole, the ocks. arrangement as the voltage does not exceed the rating Coritnlinswisat,ealtÌ,hesf can be used to indicate eloful photos, drawings, diagrams, charts, etc. Orel 64.95 resonance in of the germanium diode or refund employed. In Mel guaranteed. u.h.f. oscillator stages Ì verßiá g'. r.,nl lea Sattsfacaon and transmission this case the network of four type -1N34 diodes accepts any wave form not ex- practical RADIO servicing ceeding 10 volts peak -to -peak value. SELF -INSTRUCTION COURSE One important advantage in using Teaches you. the Practical elle of ra repair, adjustment,stment, opera- crystals for bridge rectification is tion. alteration, trouble-shooting. No that previous knowledge necessary. Pre- the conducting pare own- resistance is much lower or rain sftruthe big industrial r.`'`..A than when (conics Geld` Simplified lessons. In- using vacuum tubes or any cluding' mathematics. review other lions, prattlem ,, ,evert Ilp. ñ.,Iatnr Only unilateral devices. When a plat. Money-back 'guar :direr. $3.95, r, nn bridge 1?, r network is used in connection with a.g.c. or impulse REAL ESTATE BUSINESS circuits, reflex action is much faster with crystal diodes The f.nmolntln of nil . Iss land! than with any Train yourself for career this other booming profession. Here Is the in. type of rectifying element. formation you need on how to get and now to get ahead in realal Crystal -diode bridge networks can be estate. Includes tnstnmtions in ap- praisat. Valuations. management. in- Fig. Germanium crystal utilized to a great tvestments. prao feel real eat operating. I,nv east lousing, 6- receiver for local extent in ring mod- he law ltonnrea estated transactions including legal forms, broadcasts. The fixed ulators, etc.. many other subjects successful crystal simplifies tuning. carrier- suppression modulators, state man an Strictly pinto -date. Complete, and similar modulation éëiówss.9s: sey-e.ak guarantee. Use Nu -Risk coupon systems. circuits. The pick -up coil should have Such networks impose strict require- enough turns to insure on -scale meter ments on the four germanium crystals. iiort- eat MAftiemq/ic readings; usually two or three turns are The diodes must be selected with great Di4rp w,rn care; their resistance Prvcf:co/ MechonicsSinP/.; ed adequate. When used with high -power (in the forward equipment, it may be necessary direction) must be balanced within Re a "master mind." Learn how to Juggle again figures, do nang tricks with numbers. to insert the 2.5'; when measured at 1.5 volts, Add long columns limiting resistor R in series and of hg rts this light- in addition, ning.uulck, hart-cut way. Multiply 4 fig- ozoi with the microammeter. the forward resistances of ures by figures without old -fashioned mwtipliation, Here are speedy. Impllfied Crystal diodes can be used in place systems used by sage izards." expert accountants, engineers. Only $1.49. of diode vacuum tubes or other unilat- 100 APPROX includes illustrations, problems, coupon below, answers. Man eral or nonlinear components in fre- VARYING INPUT VOLTAGE quency meters, modulation meters, and REGULATED OUTPUT VOLTAGE COMPLETE BLUEPRINT READIND COURSE other indicating devices. Other functions Interesting, of crystal diodes -such as limiting, o leesóns forn'buïbuilders. mechanics, electricians.elet-tricians. plumbers, welders, r clamping, and voltage regulation Fig. Ipenters, automotive & aviation -often I0- Voltage regulator circuit. Germanium etc. 24 volumes ainclude can be applied over 600 actual blueprints. diagrams, to amateur rigs. Crystal crystal is used. R is the limiting resistance. tnvnve teman. Can rums. Unusual Iranai,, for any man. ete. rectifiers are particularly useful in port- only $6.95, postpaid. Satisfacton lormrefund. Coupon below.below, each pair of crystal diodes must be BUILD IT YOURSELF matched He a practical handyman. have time and within 1.5 ohms. money with these profess i01151 Tricks. ofthe- Trade. Carpentrry made easy! This is a long and costly procedure course one handy vollulme complete full for the average user of photographs, diagrams. Teaches crystal diodes. Iwork lmf, paint mg A decorating. R SMALL It led to the upholstering, power tools. c liner malt- development of the varistor, etc. Full n rice o > 51.98. oneyback aupo,, today) Guarantee. a single unit enclosed in a metal tube ICRO- AMMETER envelope, containing a complete bridge Mail This No -Risk Coupon -Quick Action! Fig. 9- Crystal rectifier circuit for measuring I the field strength of the amateur transmitter. AC I NELSON -NALL Co., INPUT UP TO 10Y 250K 1139 S. Wabash Ave., Dept. K -31, ANY WAVE FORM Chicago B. III. I able or mobile work since they require Ple:me r.,, i nie e Items I am that checking below. It no power for operation. material will DC OUTPUT I Iwithin l0 days and you Iwill t I :till Immediate refund, without question or null.L,. Its characteristic relatively high back I 1 ) Watch A Clock Repairing 54.95 I conductance upon breakdown aking 3.95 makes the I ( ) Practical l Radio Servvicing crystal diode useful as a voltage regu- Fig. II- Germanium crystals i bridge recti- ( ) Real Estate Business 6.95 I ( ) short -Cut Mathematics 1,49 lator, and excellent voltage control can fier. Low conducting resistance is its feature. Course 6.95 I ( ) Build It vtiding 1.98 be maintained with none of the disad- I House agement 1.6e I ( ) Jewelers' E ncyclopedia 1.95 vantages of gas- discharging Sell Life I aaaaa nee tubes. The network of four germanium diodes, i 1 1 Complet Shorthand Course 1.956.95 I crystal is most effective when used to matched and balanced at the time of I enclose e in full payment. Ship postpaid. regulate voltages between 20 and 60 manufacture. The varistor is I: Ship COD for a...... plus postage and COD chargea. I extremely Volts. versatile and destined for wide use in I The crystal is connected, with a lim- a variety of future modulation and de- iting IAddreeo I resistor R, in a simple control cir- modulation circuits. 6IIMM=MIMIR11= MOM =11M1=1J RADIO -ELECTRONICS for

www.americanradiohistory.com ïI

Correspondence from service technicians and distributors suggests that many may be con- MODEL 911 fused by the question, "What instruments do I TV, FM SWEEP GENERATOR. really need to service TV and FM receivers ?" 2 thru 226 mc.; electronic sweep adjustable 0 to 10 mc.; high output adjustable 0 to 'í volt. Separate 1 mc. and THERE IS NO NEED FOR CONFUSION! The 5 mc. precision crystal marker oscillators to insure correct TV video i.f. curve shape and width; phasing control and answers are simple and direct . . . the new 60-- sine -wave 'scope TV sweep voltage; 120-- saw -tooth service techniques easy to master when pic- FM 'scope sweep voltage. All this, yet only $78.50 net. torially presented. Only one new instrument must be added - some older instruments be replaced with new models for efficient and designed for efficient TV and FM servicing, the profitable TV and FM servicing. new Silver Model 911 Sweep Generator takes all confusion out of TV and FM alignment. THE ONE NEW INSTRUMENT needed is Model 911, a wide -range sweep generator for visual REPLACEMENT OF OBSOLETE instruments with alignment. If you get the one the set makers the new "VOMAX ", the famous 906 FM -AM themselves seem to favor you are naturally Signal Generator, adding new "SPARX" AM, best equipped. Equally important, 911 comes to FM, TV Signal Tracer, will really pay off in you with new pictorial instructions. Specially TV -FM service profits.

MODEL 900 -A "VOMAX ". The new " VOMAX" MODEL 906 FM -AM SIGNAL GENERATOR. MODEL 905 -A "SPARX ". Combining signal - tracer and universal test speaker, 905 -A is is the truly universal v.t.v.m. - makes TV, fM Similarly the choice of the big engineering free usual tracer and AM measurements accurately - at highest laboratories plus thousands of service tech- amazingly sensitive yet of with r.f. -a.f. switching; meter resistance. Giant meter, non -breakable nicians, 906 stands out as maximum value. 90 hum. Vacuum -tube prod PM speak- glass; 45 ranges; new single probe for o.c., kc. thru 210 mc. in 8 ranges, -±1% accuracy; high -gain high -fidelity amplifier; 6" transformer gives wide d.c., a.f., ri., volts, ohms, db. and current less than 1/2 microvolt, including strays to over er; 18 -watt output impedonces. Two essential instru- measurements. Advancing far beyond its prede- 1 volt v.t.v.m.- metered output; multiple shield- choice of is the finest 37 years of cessor, the overwhelming choice of experts, ing; adjustable 0 to 100% amplitude modula- ments in one, 905 -A "VOMAX" equips you with the world's newest tion; adjustable 0 to 1,000 kc. FM sweep. Net prize -winning rodio engineering experience $44.50 net. and finest meter for only $68.50 net. price only $116.50. con design - value far exceeding r 1 iiace ftdaCQld for new catalog OVER 37 YEARS OF RADIO ENGINEERING ACHIEVEMENT of LCETI - Laboratory Caliber Electronic Test Instruments . . . quality and prices which amaze even the experts. EXECUTIVE OFFICES: 1240 MAIN ST.. HARTFORD 3. CONN.

F A C T O R Y OFFICE: 1 2 4 9 MAIN ST.. HARTFORD 3. CONN

OCTOBER. 1948

www.americanradiohistory.com '7')

RADIOMEN'S HEADQUARTERS WORLD WIDE f MAIL ORDER SERVICE ! ! GENERAL ELECTRIC 150 WATT TRANSMITTER Cost the Government $1800.00 Cost to You -BRAND NEW -$67.50 This Is the famous transmitter used in C.B. Arany Isnube,s and construction have tiren primed ground station +. dining the tsar. Its design and in service, under all kinds et vrnditionv, all ,.ter the world. The entire In covered by meus+ of ping -tuning omits which frequent-v linge are included. Fart, timing has its own oscillator and power alnpol5er coils and rondrners, and antenna timing circuits-all designed antis-yin hequenry' range. to operate at top efficiency within its Transmitter and accessories are tinish'd in black crackle, and the meter, and RF ammeter are mounted on the niilliatttneter, toll front panel. Here are the specifications: FREQUENCY RANGE: 200 500 KC and Ir.00 to 12,9011 Kt'. (Will operate On lu and meter to furnished1. 20 band with slight modification for which diagrams are OSCILLATOR: Selfexcited. therms, compensated, and hand trlihrated. POWER AMPLIFIER: ised class "C" stage, using 211 tune equipped Neutral- and with antenna coupling circuit which matchs. practically any length antenna. MOOt'LATOR: Class "B" -uses twu 211 tubes. l'OA'Ell St'l'l'LY: Supplied complete euh tildM furnishes llgut5' at :into MA, from either tlynaluutor 12 of 24 rolls. t'ou.pletc ilNtluctiiins are /wnished to operate set Ilium 110V A('. S12F. 21'4 t23g9W. .shipping Total wu. 300 lbs., o plete with all fillies. rdynanlotor power supply. se n tantra[ Imlt +. antenna Huang unit and the essential plugs. NOTE: Price incases to $100.00 efletive Oct. L 1946 GENERAL ELECTRIC RT -1248 15 -TUBE TRANSMITTER -RECEIVER BRAND NEW BC -221 FREQUENCY METERS Taaalrlg POWCN -130 watts, on any ono instantly 500 Mc. selecteselected. easily pre -adjusted frequencies from 435 to Transmitter uses 5 tubes including aeW'Western Electric 316 A as final. Receiver uses 10 tunes In- with calibrating Crystal and eluding 1)55'a. a nest detector and illator, and formers. plus 3 -7H7's as t?'s with lug tunet 40 Mc. IF trans- a -7Hw. 7En's and 7F7,. In addition It contains n relays designed to operate any sort of calibration charts. A Precision equipment when tuated by received signal from a similar set elsewhere. Originally designed fpenalor 12 volt operation. power supply no included, is frequency standard that is use- unit for 110 It cinch for any experimenter to connect this AC. using arty supply capable of 00 DC at 185 i MA. The Ideal unit for use In mobile n stationary , the ful for innumerable applica- in Cituena Radio Telephone Rand where no license i ry. instructions and dlakrams supplied for running the nT -124$ transmitter on or reception. either code voice ,r AM or FM transmission tions for laboratory technician, for use as mobile public address cyst em. on 80 to 110 Mc.' as an FM broadcast receiver.:min. Iransmitlre receiver, s an Amateur Teievielon transmitter oro receiver for remote service man. amateur, and ex- trC:rsimilirot relay hookups, for Geiger-Mueller counter applications. It sell for only or two for 553.90. if desired for marine or mobile the ynamotor which will work on either 12 or DC and supply perimenter at the give away all power for the set is only $15.00 additional. price of only $75.00.

1949 MODEL MUTUAL CONDUCTANCE TUBE TESTER""" ne" 9 pun socket to hand, $49.95 No futurefutu tube detelopments possibility of good tub, rt. :1 /1 1K "Bad" or had tubes reading "Good" as in dynamic conductance or other ordinary emission testers. Attractive testers panel and case equal to any on the market in appearance...Large 4 Sy" meter... Calibrated mtcromho scale :ta well as a Bad -Good scale . .. Front panel fuse... Individual sockets for all tube base types -voltages front .75 volts to 117 volts and tested complete :witching flexibility allow all present and future tubes to be regardless of location of element. on tube base... Indicates gas content and detects shorts or opens on each individual section of all Metal. octal and miniature tubes including cold as well cathode. magic eye and voltage regulator tube. as all ballast resistors. Name of the nationally kn reading "Good" as on dynamic rondartance tester. or other Model °C"-Sloping front counter case $49.95 Model "P "- Handsome hand -rubbed portable cule 54.95 Built -in roll chart with either of above $5.110 extra. RTI711 Brand New 12 Tube, 110 Volt Receiver -Indi- cator- TERRIFIC VALUE Oscilloscope complete with all tubes and power - supply. Has telescoping hood over scope tubes, which PORTABLE ELECTRIC is equipped with a detachable calibrated screen. Has DRILL centering and amplitude controls and two video (Sold at Ins than setablished factory price so we cannot mention brand name.) Inputs. A natural for television $39.95 Only $19.95 equipped with ,4" Jacobs Geared Chuck and Key. Not an intermittent duty drill, but a tall size lugged tool. SELENIUM RECTIFIERS. All types are rated at Most convenient type switch. natural grip handle, and balance like a six- shooter. 130 V.A.C. Ito not assort to make quantity. Precision mit seai:s -- turbine type tooling blower- -extra long brushes. No stalling under heaviest 75 MA .70 pressure because of powerful 110 Volt AC -DC motor and 10 for 6.511 50 for $31.00 multiple ball thrust bearing. 100 MA .75 10 for 7.00 50 for 32.50 Other, bearina.s self- aligning lifetime -lubricating Chrysler OIRte 150 MA .80 10 for 7.50 50 for 35.00 Made for toughest year-in and year -out service In Plant or on construction lobs, 200 MA 1.05 10 10.00 for 50 for 47.50 Amnzitlg pei'petllal factory guarantee assures you of lifetime of trouble-free Ilse. 260 MA 1.25 10 12.00 for 50 for 57.50 deposit on l'.O.U.'s. Full refund if returned prepaid within Orr days.

CONDENSERS -PAPER TUBULAR Gon N'V -uni. .012. .005 HEAT GUN --8e: 01. .0.5 -9c: .1 -l0e: .2r -23c. LYTICS: 05 35e- ELECTRO- amid 2u0, -20e: Hhufd 'tar - 20c: ::un,)d LsOV --23g: Streamlined pistol gitp heat Burl in vivid red housing. 20 /20mfd 1.10- - 35c: 30/20 Isar -46c: iii ltd 15uv -43c: anlfd that 475í -.34c: delirrrs s powerful 20 Cubic Ft. per minute blast of hot 16mfd :Ifni -65c: OIL CONDENSERS: Ontd 600r 49e: 2nlfd 6O0 --29c: ::X. air at 160 Fahrenheit. ordinary blowers have small fan hued GiOc- -29c. motor, but this has a lilelinie- lubricated AC-DC motor of SPEAKERS -These 1.51 the rugged tar-auto cleaner speakers are the lined that aie Wad- type. that produces A hurricane able. All have o either luaty rsize Millet/ V magnet,. of hot or cn1.1 air. Perfect for blowing out dirt or 31y" dust from radio chassis. drying out ignition systems, warm- 51.15 6 for $6.60 4" $1.15 6 for ing rap carburetors, quick'dry'ing paint, thawing pill radia- 5" $6.60 51.10 . Ir. tor $9.50 tors or water pipes etc. Warning:- away' -Keep this troni 6' 51.50 6 for $8.70 Noll/ wife. Or she will he using it to thy her hair because 7' (Car Radio Sise).. .. $4.50 6 for $21.59 it will do it in halt the tins, tit her Oofinary hair dryer. S" 10 or. sass $3.95. 6 for $20.50 to say nothing of her using it to diy stockings or Nothing. of delutst the refrigerator instantly. 6" 21 or. .... 54.9$ .. 6 for Only le" $26.50 $12.93. Satidat'tion guaranteed or money rinmded a letiiined prepaid within 5 das- 21 oa. $5.50 6 for S30.00 12' 21 ea. $7.95. 6 for $42.00

$595 Takes Both SCR -274N COMMAND SET The greatest radio equipment value in history BIG BARGAINS A mountain of valuable equipment that includes 3 re- ceivers that use plug -in coils, and consequently can be I. ALUMINUM GEAR BOX Isaky7 that con - Islas two vowel t ill undo, and ! changed to any frequencies desired without conversion. mulched grs bains. e:2 g a all seising Also included are two Tuning Boxes; 1 in r Irani Sy to inrlrs in diameter. This Control Antenna unit:: am caddy r led to rota;r a beau: an. `` Coupling Box; four 28V. Dynamotors (easily converted to feoua chi` n lar use .$3.00 IAr dyw,Ì!t.ïl 2. SENSATIONAL (FASCINATING. AMAZ- 110V. operation); two 40 -Watt Transmitters including ING SE LSY NS. (Nand new velnyms made by crystals, and Preamplifier and Modulator. 29 tubes sup- G. E. Co. Twd el aelhel est walk pedeetly un Iln\Urll'. of plied in oll. Only a limited quantity available, so get' one the aloft of seism and all of het t iration'oiineete I your order in fast. Removed from unused in to it still rotate exactly as loans deglev, in 'n +rT aircraft and the saine dlrrrllin, b i l l o w i n g oar ,iliglt as it guaranteed electrical condition. A super value at $34.95, the units we r rIled logethel by Shafting instead of wiles. This is cur ehAbrl roll including crank type tuning knobs for receivers. Twist Ihr shaft of lie mains rr fil Ira.- Don of colilti on many vi.lnrnnls. 1'seful lot indicating the direction "I , a'h7 sane, rnlaling directional antennas, i. , niu- Dolling innumerable upi al amts Iron: a dis- PE -109 32 -Volt Direct Power tance. with Current Plant Ctaf pleteinstrir° lions. l'r matched ale I1,, 1 I he Pair 54.95 51 - nw,i pmul e- In ram m- of the rue 4, hat Iell ignnle 21- J!l' Dc for oprAlton. The price of this power plant is l only 55'r $79.95. also supply . cnrr that 'll supply 1111s .SC trim] the ab"t, toll, or a ft inn dray 32V 1)Cs soope for $12.95. t- NOTE: Each of the PE -109 power we Cable Address: BUFRAD plants that sell has been actually run and tested for output by us before shipment. Above price is FOB Bufalo, BUFFALO RADIO SUPPLY, 219 -221 Genesee St., Dept.RC-I0 BUFFALO 3, N. Y. RADIO -ELECTRONICS for

www.americanradiohistory.com 73

RADIOMEN'S HEADQUARTERS -}- WORLD WIDE MAIL ORDER SERVICE ! ! TO MOST BUFFALO RADIO SUPPLY, ONE OF AMERICA'S LARGEST ELECTRONIC DISTRIBUTORS, IS IN A POSITION SUPPLY THOSE OF ITS AFFILIATES. OF THE REQUIREMENTS OF FOREIGN PURCHASERS, DIRECTLY FROM ITS GIGANTIC STOCKS OR PURCHASING COMMISSIONS EXPORT INQUIRIES ARE SOLICITED BOTH FROM EXPORT HOUSES AND FROM FOREIGN GOVT. A OF DELAY BY CONTACT- HERE AND ABROAD. EXPENSE CAN BE REDUCED AND REQUIREMENTS FILLED WITH MINIMUM ING BUFFALO RADIO SUPPLY INITIALLY.

SOS EMERGENCY TRANSMITTER SOS BUFRAD CAR RADIO ANTENNAS This is the fatuous Gibson Gal Transmitter that All of our car radio antennas are made of triple plated Adm iraity saved so many lires during the war. lt is used as a Brass Tubing. complete with low loss shielded antenna leads and distress rail transmitter on boats and airplanes. The the world to high quality flltings. Gibson Girl N the easiest transmitter in 3 66 ". Your price or experience necessary. No SIDE ('OWL -BR -I. sections extend to -single operate. No instruction in lots of 12 -51.35 ea. external power supply required for operation. It is unite -$1.50: extend merely necessary to turn the crank on the top of the SKYSCRAPER -BR -2 has 4 heavy duty sections that transmitter and power is generated and the distress 98 ". This super -aerial must be seen to be fully appreciated. signal is automatically sent out on the international Your price -single units -$2.45; in lots of 12 -$2.25 ea. distress frequency. Brand New Gibson Girl trans- TILT ANGLE-BR -3. may he adjusted to all body contours, 3 mitter complete with tubes $9.95 sections extend to 66 ". Single unit price -51.50; 12 lot price - $1.25 ea. Antenna Kit for Gibson Girl transmitter. This kit of the Gib- VERSATILE--BR -4, single hole fender or top cowl mounting was designed to improle the effectiveness to with all body contours. 4 sections son Girl Transmitter by increasing the range several may be adjusted conform ea. 300 of special antenna extend to 56 ". Single unit pi-ire- $2.90; 12 lot price -$2.75 times. The kit includes feet 3 sec- wire. two balloons for raising the antenna in aim THE MONARCH -BR.S. single hole top yowl mounting. rather, two hydrogen generators to inflate the bal- tions extend to 56 ". Single unit price -$1.90; 12 lot price - loons. a special box kite for antenna erection In $1.75 ea. windy weather, and searchlight. powered by the OUR ANTENNAS AND COMPARING, crank onerated generator in the transmitter. l'nory AFTER SEEING plete kii $9.95 YOU WILL NEVER BUY ANY OTHER MAKE! RENDIX SCR 622-Very high Frequency Voice Transmitter - 156 MC. Thin job was good enough for the Joint Receiver -100 to flew. INSTANTLY, Anywhere!! Command to make it standard equipment In everything that COMPRESSED AIR even though each set coat the Gov't 92500.00. Crystal Controlled and Amplitude Modulated -HIGH TRANSMITTER OUTPUT and 3 Microvolt Receiver Sensitivity gave gond communication Portable Air Compressor and up to 180 miles at high altitudes. Receiver has ten tubes and storage tank. Ruggedly built two 832's. Furnished corn - lu- transmitter has seven tubes. including best matez ials usine lifetime unit, 4 crystals, and the spe- c nnea- piete with 17 tubes. remote control bricated ball- beating on cial wide band VHF antenna that was designed for this set. ing roil and oil Impregnated main from unused aircraft and are guaranteed o be in perfect bearing on shaft. l'nnsual design These sets have been removed variable valve Doubla. condition. We include free parla and diagrams for the conversion to -continuously forever eliminates receiver. the most common finit in ah frequency coverage" in the 622 la also rompressow. PATENTED mn tine The SCR 522 complete with 24 volt dynamotor sells for ..olv $37.95. The SCR air intake system increases effi- available with a brand new 12 volt dynamotor for only $42.95. ciency tremendously mer other compressors so that air output is much greater than that trou larger compressors powered by STEATITE VARIABLE CONDENSERS 3500 beat t -r moors. Will deliver approximate) ru. inches of air per minute at maintained pressure of Ideal for high -frequency applications in receivers and low power transmitter stages. 30 lbs., or will inflate a 90 Go. truck tire in less titan Cumes STANDARD "" DIA. SHAFTS SCREW DRIVER ADJUSTMENT one minute. IO 5.35 --IO for 52.90 -100 for $23.011 thong fnger Ì adjustment all nssettingofg output mmf 5.20 -10 for $1.50 -100 for $16.00 value, which will 'automaticalli be 15 mmf $.37 for 52.90 -110 for $23.00 pressure at any -10 Works from any ,4 11.P. motor. l'seful 25 mmf $.35 -10 for $2.90 -1181 for $23.011 $.20 -10 for $1.80 -100 for $16.00 maintained. for $15.451 for spraying paints or lacquers, disinfectants, inset' 35 mmf $.40 -l0 for $340-110 $.20 -10 for 51.80 -100 for $16.00 ticides, annealing or brazing with natural gas. inflal- 50 mmf $.411 -10 for $3.70 -110 for $30.00 for tg tires. etc. l'Ore $14.50 postage prepaid anywhere mmf $.50 -IO for $4.411 -110 for $38.00 $.25-10 for $2.30 -100 $20.00 in the U. S. Efficient. completely adjustable syphon liai mmf $.55 -10 for $4.50 -100 for $39.00 $.25 -10 for 52.30 -100 for $20.00 type spray gun romplete with 12 ft. of 100 lb: tested for $64.00 with container. 1411 mmf $.80 -10 for $7.411 -110 $.30 -10 for $2.70 -100 for $25.00 hose available for only $7.75 .pint 160 mmf $1.00 -10 for $8,50-100 for $70.011 also prepaid. 25% required on all C.O.D. orders. mmf $1.60 for $12.50 -100 for $100.00 $.40 -10 for $3.60 -100 for $32.00 for free catalogs of radio parts and surplus 140-,140 -10 Senti condensera. rotor has two ball bearings and a t1(" shaft. items. or steps Butterfly AUTO-TRANSFORMERS-Steps up 110v. 15 mmf. per section $.50 -10 for 94.50 -100 for $40.00 down 2201 to 1101- $1.95. -10 for $5.50 -100 for $50.00 6.3v. 20 Amps. -$1.98: l'nitersal0 30 mmf. per rection $.60 FIL. TRANSF.: 30 50 mmf. per section $.70 -10 for $6.50 -100 for $60.00 Output Trans. lt Watt -89e: Is watt- $1.29: Watt -- $1.69. AUDIO TRANSFORMERS: S. l'Iate to 'Manufacturera and distributors write for prices on larger quantities. 9. Grid. 3:1 -79e: S. Plate to l'.l'. Grids -79t: 250,000 VARIABLE CONDENSERS IN STOCK. lleaty Duty Class Alt or B. P.l'. Inputs -$1.49: WE HAVE OVER sets -69e: MIKE TRANS- Miriget Output tor AC-DC to FORMER for T -17 Shure mmrnphone. .ilollar RT constats of a three stage. rageai. 68J7'a and or mike to FILTER CHOKES: 200, 300. 400, 500 ohm light duty -1579 =r ITC ouncer type- $2.00. Stancor SR Dlt 250 ma, sn 6E6 output stage high gain. Iluh fidelity antplifl line or grid -$1.95. 75 with 60 cycle. 110V power supply on the saute I:1tsx 110V. m g oule for3111.5. Navy, ffully s hi POWER TRANSFORMERS halt -shell type. oh, 14% chassis, which is protected by substantial steel Specify either 2.5 oho' 125 ma -25e tu 25 for $4.25: " Meissner type Idec- 60 cy. Centettapped 11V autdu, Choke- condenser combina- cover mer tubes and parts. Made by Western of t w: lapped Otter chokes --25e: or 6.3V filament when size speaker field when trie with typical equality components such as husky -650V. 1, ,IA. 5V & 2.5 or lion. ivied to replace any For 4 -5 tube sets PM --79e. power years 6.3V f1A9 Installing speaker "SI'r.ATTl vloualy intended too gise of trouble-free serv- Ni & 2.5 or SPLATTER CHOKES- These TuVprd ll For 5 -6 tube .sets- 650V. ) 5- `V tiffe ice with no more need for repairs than telephone. 1 are l IIi;mul,lnütsln 6.3V .75 CHOS" Disconnecting one wire each. from the special input 'r & 2.5 latnrhl, entolome objection de For 6 -7 tube sets -675V, ^>I.v. or scm, Si. do. output filtea, 1011 result In as hielt fidelity 1.90 DC resistance 50 Mums. Our part No. and with tubes. 6.3V dise U, amplifier as be obtained. sets -700V. 7 ^'i t. & 6.3 or SELENIUM RECTIFIERS -Dry n For 7 -8 tube suitable for &naevi o diagram and c parts ll t Included-$14.95. two 2.35 1.2 log, maximum, 7 sol t 3 12.5 for supplying filament soure- 7 A. r,x' & to At', 1655 Il tube crystal contr011ed superbes re- For -ö tube sets-700V. 3.60 rsmverting DC ureters to Al' appli,ati041 ar RT. - F7cle1 radirxs, - ceiver for 24 -28V DC operation. Beautiful chassie aigri mn w hr s ,l lox' &aient rltargers 90e. 7 For 8 -9 tube sets-700V. :mV.w. 5V -3A. 2.5V- and cabinet. Uses latest tube U'pes Including 3.5A. 2.5- 10.5.4 2.85 30 MC IF miniature UAJS'x. Tubes and schematic supplinl. 2.85 AMPLIFIIER PLATE t COILS -Slog For 9 -Il tube sets -700V. 'V & 6.3V -4A 30 MC VIDEO Only a few available at $14.95 For 9 -15 tube sets -600V. 150MA, 5V & 8.3V 2.95 tuned -251. SET SCOOP. Product of a fa- SOLDER 1000 CYCLE AUDIO FILTERS RADIO audio filters as mous aircraft radio manufacturer who KESTER ROSIN CORE SOLDER of Navy PD52010 -1 low pass mentioned in the "Peaked Audio" article in has abandoned the manufacture of table NAVY instrument grade in 1 /16" di- num- June CQ, and designated by the above model radios because of the flood of ameter. Made from virgin lead and tin are the exact electrical and physical ber, 5 genuine and water -white rosin to the highest equivalent of commercial audio filter units government orders. All in ply possible specifications, and guaranteed selling for $35.00 wholesale. They are in- mahogany cabinets, both regular and "Radio to contain at least 40% pure tin. You finitely better than the surplus bleached. 6 -tube models have tone con- Filters" being sold for reducing know how you cursed wartime solder Range trol. Original list price given first-then mud on your iron in a QRM, and at 2 KC off resonance for ex- that turned to -1 is Sensational discounts. will bright and ample, a 2 section filter using PD52010 your cost. minute. This solder stay twice the selectivity available you capable of $34.95 -$16.97 clean on your iron longer than any thru the use of the Q5 -er (the BC453 sec- Model 565, Mah. or blonde, have previously used. Have your own tion of the 274N which has provided the Model 6618, Mah. or blonde, stockpile against possible imminent amateur's previous highest standard of in- $44.95 -$20.97 SPECIAL hostilities. 20 lb. spool -$11.95. Smaller terference elimination). EXTRA $21 -97 PD52010 -1 with diagram. ...$5.00 Model 663, Mah. or blonde, $46.95- l tantities per lb. - -75c. -NAVY BUFFALO 3, N. Y. BUFFALO RADIO SUPPLY, 219 -221 G.:nesee St., Dept. RC -I0 OCTOBER, 1948

www.americanradiohistory.com 7I People BRENGLE SHIFTS FIRMS Ralph T. Brengle, president of the National Association of Relay Manufac- A turers, has recently announced that, ef- MPERI fective TE July 1, 1948, he will devote his Studio Microphones full time to Potter & Brumfield, Chicago, manufacturer of industrial relays. at P.A. Mr. Brengle is a Prices substantial stock- Very \s= holder a n d officer of Potter & Brum- Ideal for BROADCASTING field, and for sev- RECORDING eral years has PUBLIC ADDRESS handled their na- tional sales and ad- "The ultimate in microphone quality," says Evan vertising. He has Rushing, sound engineer of the Hotel New Yorker. discontinued his operations as Shout right into the new Amperite Ralph T. Brengle Microphone -or stand 2 feet away - Sales Co., manufac- reproduction is always perfect. turers representative, and has turned pi ï this phase of his business Models over to the The only type microphone that is not newly formed Lund -Hansen Co., who RBLG -200 will affected by any climatic conditions. ohms continue to represent Potter & RBHG -Hi -imp. Brumfield and other lines formerly Guaranteed to withstand han- more "knock- List $42.00 dled by Mr. Brengle in the Chicago area. ing around" than any other type mike. GUSTAFSON G ETS MEDAL Special Write for Special Introductory Offer,'. -j G. E. Gustafson, Zenith Radio Corpo- Offer: and 4 -page illustrated folder. ration's vice -president in charge of engi- neering,recently received the President's Medal of Merit for his contribution to victory in World War II. The medal AMPERITE O/n1 'Kontak" Mikes was presented an InC. Model SKH, list $12.00 at a P y luncheon sponsored 561 BROADWAY NEW YORK 12, N. Y. Model KKH, list $18.00 by the Chicago As- In Canada: Atlas Radio Corp., Ltd., 560 King St. W., Toronto sociation of Com- merce a n d Indus- try. The Medal of AMPLIFIER AND KEYER SELSYN TRANSMITTER Merit is the highest TG -I9 AND AUTOMATIC KEYER And .., 5 award given civil- it, II _pad watt. This do. ketr , i Id' rd ludo INDICATOR is p hases. Photo ians by tall aetuale,l by l ink tape lm tr,linf: the Presi- easily tan be er 'erred to a . \Pau .namplifier. 110 Volt tin yd. I,peta dent of the Don. Conies with two Wei',. two rSJ7 's. tu, ,.SC', United one 51'ID output u nd trans.. 4. 8. and 15 old. 1..... i States. It was be used as phono motor. rr", presented to Gustafson Used (Tested) $19.95 (f.x, for his war work as chief of Zenith's enerneering research, which helped INTERPHONE make possible that company's successful production AMPLIFIER BC of war material, including -347 the V -T fuse. Ideal as Hill,. It :ant position Indicator. for Hain, Tele- rm,s' Airclaft T3 /WI l'ses OFS Ision or Commercial use. Complete Willi 1 -X2 nee Tube. Contains two 121 \lid>;et Inch indicator, Autneyu Trans. 12 Gn llixh Fidelity 11TC Volt ryrlo transformer. ouster [tans- Id wiring instrnrtiols. R. W. METZ N- ER DIES forme::: l'n"xPs". Input 2110 Price: NEW 7.95 uhm In single or push-P011 Cr11, General Electric Company has Ilutput 2110 uhul hIn iugle er an- Push-Pull Plate: plus - 11.151, 1.T.1. University of bladed, rouant t eted. Aunt. 7G -311. bight. and Minnesota with a degree Prices: witch s I -0 Ft. roll hom=511 nIn metai llboxu g I" 1':rl f $1.25 rag al r..b,a in electrical T 50 Ft. rolls for hail batteries and reading vwlnloro go engineering, comes to Turn- ...... $2.00 underin d load. Price: NEW $2.95 er with a wide range of experience in ADDRESS DEPT. RC Prices F.O.B., Lima, electro- Ohio 25% DEPOSIT On C.O.D. Orders acoustic engineering. As head of the Turner engineering staff, his atten- 132 T tion will be devoted mainly to research FAIR RADIO SALES LIMA,SOUTH and product development of micro- óg ó. phones and electronic equipment. RADIO -ELECTRONICS for

www.americanradiohistory.com Construction It's Mutual Help! linaural Amplifier Give Us Your Order and We'll Give Low Prices on Your Radio By EDWIN BOHR and Electronic Requirements! Here are Only a Few Specials! In Fig. 1, a top view of a pair of ears --> Our 3 -Item Special! E- the and a sound source, the path from I- Standard -Phono Motor-9" Turntable source to the right ear is shorter than 2- Crystal- Pickup -incl. HDWE. that from the source to the other ear. 3- Covered record Player Base- 13E81/4a The intensity of sound in the right ear, 31/2 with cut -out for Motor will be slightly greater. De- SPECIAL, ALL 3 for S 4.50 therefore, 42.50 pending on the difference of levels in the In Lots of 10 plot the posi- Over 100 Assorted Resistors cars, we subconsciously I1.15 '/e to 2 Watts tion of the source. In Lots of 25 2 1.I15 When there is some echo, the echoed 501.6 Output Transformers. ea. .32 varying in- In Lots of 25 7.50 sounds reach our ears with 12Sß7 Sealed Carton Tubes .30 tensities. None of the echoes (in an 100 or More 27.00 470 ohm -10W. Resistors .07 average room) is as loud as the direct 40 ohmIOW. Resistor. Lots of 100 5.00 8 Ft. GE Approved Rubber Lino Cord. each sound even though all the echoes added 12.00 orig- Lots of 100 together may be much louder. The All Merchandise Guaranteed This amplifier has two identical channels. still takes place, and New and Standard Brands inal triangulation Refund in 10 Days if Returned Prepaid echo only gives naturalness to the Send 20° Deposit With Order the C.O.D. Merchandise F.O.B. N.V.C. of the sound we hear does sound, because we are used to it. Balance MOST WOrth 4 -1368 not come from the source of The ordinary electronic audio system the sound straight to our has only one "ear," the microphone. The ALMO ELECTRONICS INC. ears. In an ordinary living single microphone picks up sounds from 135 Liberty St. New York 6. N. Y. Alton over 90' - of the sound bounces all directions within its range with near- OUR ONLY BRANCH several times from the walls, floor, ceil- ing, and furniture before we hear it! SOUND SOME *Make Your Own Because we are used to this echoing it sounds natural to us. Unless it is very RECORDS bad, as it might be in a large marble - with RISCO 3 -way Home Recorder walled chamber (a railroad station for we can still tell from which instance), in Sound direction a sound is coming. Our two "Snapshots on inches apart. 1 ver 10 minutes recording ears are spaced several UI" rccurd at dual peed We unconsciously calculate the intensity l.. min. at single speed. of the sound coming to each ear from EARS High fidelity the direction of sounds. the various directions and, because we Fig. I -How we know record player used to the echoes, our brain is able Uses are the di- professional to focus attention on the sound we want ly equal efficiency. Even though recorder sound source to micro- to hear. The process is very much like rect path from An auxiliary P.A. that which surveyors call triangulation. phone may give louder amplifier out- amplifier Ready to operate with 6- spk, crystal mike. Ideal for music lessons. parties. your child's cute sayings- Speeches. Churches. $49.50 Attractive portable Case $5 EXTRA FOR SEND FOR l'O \Il'I.F.TF: DETAILS DUAL SPEED Make your own Record Library! Copy your friends records and Save Money RECORDISC RECORDING BLANKS We Sell Retail Steel Styli Cut. tuna Needle, 3 Base 6k2 in. It In. lO ln. for 79c. Tungsten Bond 9c 15e 21c tipped. 5.000 Playback Needle. Aluminum 1Re 24e 36c $3.00 25Áo on COD orders -ORDER FROM THIS AD RISCO ELECTRONICS WHOLESALE DISTRIBUTORS 25 West Broadway, N. Y. 1, N. Y. GREYLOCK A Dependable Name in RADIO TUBES GT. Glass, and Minialule All Tubes Individually Boxed. 12SÁ7. 125K7. 12507, SOLO. 12AT6. 2sas. 128E6. 35W4. 5085 each 39c IRS. 155. 174. 354. 304. OAKS. BACS. S ACO, GREG. GRAS, 6AU6. 611.16, 6Xa. 11723.. each 49c lJL7, 70L7. 117L7 h 59c All Tubes carry RMA 90 -Day Guarantee s PM SPEAKERS Alnico No. S ace Alnico NO. S caen $í_191.29

TERMS: Net COD. He orner accented for less than 55.00 WRITE FOR BARGAIN CATALOG C -10 GREYLOCK ELECTRONIC SUPPLY CO. chassis may be seen from this photograph. Placement of parts under the 30 Church Street New York 7, N. Y.

OCTOBER, 1948

www.americanradiohistory.com 76 Construction speaker is still not natural because it has been picked up and comes out from only one point (the speaker), even though the source may be a large sym- phony orchestra spread over a wide stage. It is possible to make a sound system which is actually binaural. That is, it ABSOLUTELY NO KNOWLEDGE OF RADIO NECESSARY gives the same effect as hearing with YOU NEED NO ADDITIONAL PARTS! both ears. It does this by using two THE PROGRESSI VE RADIO KIT is the ONLY COMPLETE KIT microphones, placed approximately Operates on 110 -120 volts AC/ employed m the DC,, Contains these circuits. The circuits e designed everythingerything you toe provide excellentox performance. Altogether, same distance as ction otherMnet- circuitspits are fifteen apart a person's ears Chassis, Tubes. Condensers. Resist,r all tructed, including 11 receivers. 1 audio radio parts. The 36 -page Instruction rand 3 transmitters. The sets start with simple (Fig. 2). Each microphone tecaryten by Rook writ- feeds a sep- expert radio instructors and engineers teaches you complex. gra.uatl óg áw m build adios in and finish with several examples Of radio set. arate venal manner.. The first cir- usingu amplifier and the output of each cuit built isi a three tubes plus rectifier. simple one -tube detectors. . Eacñ succeeding incorporates n PROGRESSIVE arrangementstcentst of de. RADIO KIT . . ONLY $14.75 amplifier is fed to a single earphone. lectors. RF and AF amplifiers. This kit for aa , g the principles of .need transmitter and When one of lifer design. It is used neyt' SPECIAL FREE OFFER these earphones is worn radio schools and Electrical and Radio Testers nt All commonly-used each absolutely FREE with against including grid plate Progressive Radio Kit. PLUS FREE membership in each of the listener's ears, the The aend detfnite.impedanee. Progressive Radio transmitters are designed with Hartley Club. Entitles you to free expert an - oscillators, and Arm. vice and consultation service with licensed radio sound he hears is truly binaural because nodulaton.'lBoth ans. Write for further tech. tubeandq sstaclenlum rectification information or ORDER your KIT each ear is effectively placed just where WE PAY POSTAGE ON PREPAID ORDERS C.O.D. ORDERS SHIPPED COLLECT the corresponding microphone is located. RECHARGE your AUTO BATTERY RCHESTRAuI \ with the NEW AUTO RADIO so MINE -rMIHEE WITH BUILT -IN BATTERY CHARGER PAT. PENDING ALSO BUILT -IN POWERIZER FOR ELECTRIC SHAVER SENSATIONAL FEATURES Powerful 6 -Tube radio 3 Gang Condenser Extra R.F. Stage (for increased Sensitivity/ Large P.M. Speaker Single LIST PRICE Compact Unit Easily Installed Charoes ONLY Through Radio 3497 Simply Plug Radio Coed into 117 v.A.C. electric Outlet Makes $49.95 Winter Starting Sure For Electric Shaver Just Plug Shaver into Radio Extension Cord. Automatic AUTO RADIO Fig. 2- Binaural sound and audio equipment. in A number -hops car radios, now at a 111,1 Iiiw to üt! SIX -I - d t =nl iii t,rodyne, of interesting effects ought with steady, full -toned reception M.,unlinc brackets inrludi-d fill' easy in. to result. Wearing the headphones stallalion in your car. Don't miss this big bargain! and unable to see the room in Six Tube Superheterodyne Three Gang Condenser $27.97 which the Powerful Long Distance Reception Fits All Cars, Only microphones are placed, the listener Easy Installation Mounting Brackets Included. LIST PRICE 539.95 ought to be able to tell whether voices and music come from the left or the TOM THUMB BIKE PORTABLE RADIO right. If a person walks across the room, TELESCOPIC ANTENNA POWERFUL RECEPTION speaking all the time, the headphone - EASY MOUNTING BEAUTIFULLY FINISHED METAL CASE wearer ought to be able to "follow" the Can be mounted on bicycle or ca rried as a ersonal portable radio. Sup- speaker in his path from one side of the lied complete with all bicycle mounting hardware and telescopic an- tenna. Simple mounting -quickly detachable. Whip antenna. room to the other. dial. vernier tuning, full size alnico -6 slide rule flashlight' cells and standard 5759 on n ease It "S" battery. Attached handles for We decided to find out carrying a regular portable. Light weight e. beautifully how well this in finished. Mounting bracket features anti -theft locking device. Size 7r.tonex x 31,a. Weight 3 lbs. 3 oz. theory reduces to practice. Fig. 3 shows the amplifier used. ONLY $17.47 LIST PRICE $24.95 Actu- ally there are two completely separate Send for Your FREE DEALERS catalog and amplifiers here, both built on the same ATTENTION RADIOMEN !! Price Today! List chassis. Each has its own input and out- RADIO KIT'S AMPLIFIER KITS FM ('OIL & CONDENSER KITS RESISTOR KITS put. However, CONDENSER KITS RADIO TOOL KITS FM -AM CHASSIS SPEAKERS RADIO the gain controls are PARTS PORTABLE RADIOS CAMERA -RADIOS TUBES AUTO RADIOS HOME ganged so that the gain of both ampli- RADIOS TELEVISION SETS TELEVISION CABINETS TEST EQUIPMENT TUNERS FM fiers will always be very nearly the same. Ganged 1- megohm potentiometers PROGRESSIVE should not be hard to find as they are ELECTRONICS CO. stock items. They do not have to be used, DEPT. RC -18 497 UNION AVE. BROOKLYN 11, N. Y. though, since ordinary single controls will give the same results if they are put, the echoes become very annoying domed enough to kill interfering noises, provided with dial scales because the single ear cannot so that they perform But the sound coming from the loud - can be set to the same points by hand. the triangulation necessary to focus its 7C7(4) attention on a particular spot. As a re- 7C5 (2) sult, echoes, air noises, clocks ticking, footsteps, and all sorts of noises become .05 very obtrusive in the loudspeaker. They may even drown out the desired sound or make it unintelligible. They sound 705 unnatural at the very least. The effect can be simulated in a noisy location by stopping up one ear and noting the ap- parent increase in background noise and the difficulty of understanding speech from any distance. To overcome this, broadcast and re- cording studios are acoustically treated to deaden a large part of the echo. Sound -absorbent material is placed on the walls and ceiling, and echo is re- Fig. 3- Schematic of amplifier. Any two amplifiers may be used if they are identical. RADIO -ELECTRONICS for

www.americanradiohistory.com Construction 77

No construction details are given, as any exactly similar pair of amplifiers may be used. FULL 13 CHANNEL The two microphones should be iden- tical. Use the same length of cable for both to reduce output and high -fre- TV-FM COVERAGE! quency response by the same amounts (if at all). The higher the fidelity of the whole system the better, but both ßt1 gene... channels must be the same in every de- tail. NEW JFD The power supply was built on a sep- arate chassis to minimize inductive hum Sukcz- bcacyt NI -LO pickup. Almost any audio chokes can be Array used. Do not put loudspeakers on the Duo -Orienting amplifier outputs, as the binaural effect is best with headphones. The two microphones were placed in a room about 15 x 20 feet. They were spaced about 8 inches apart. The lis- FEATURES! tener wearing the headphones was in a Folded Dipole with separate room. In the room with ill. 4 JFD All -Angle Steel Mount - Reflector were a ing Bracket for erection of microphone two people holding masts anywhere. conversation and a radio was playing No. TA115 softly. 4 Corrosion -proof 71/7' mast. mc. First, just one microphone was con- 4 Frequency Range 44.216 and nected. As expected, the sound seemed 4.2 DB gain. to come from a deserted armory, the 4 Minimized ghost effects. pro - RECOMMENDED usual effect with single -channel systems 4 U -Bolt Clamp securely attaches array to mast, is off mike. vides unlimited spacing of bays and allows them to For use with Hallicrafter, Philco, when the sound source 'way Emer- was to under- be oriented independently. RCA, Stromberq- Carlson, The conversation hard son, Admiral, Crosley, Dumont, Rotolock insulator insures stand, and the rustles of cloth and the Unbreakable polystyrene DeWald, Motorola, Teletone, insulation. hiss of air movement were very ob- high frequency Fada, Garod and other television hardware bag. trusive. 4 Lightning -fast assembly time - no sets. Now we connected both microphones. Write for the New JFD 16 -poge Super -Beam Catalog, No. 7810S. Immediately the background noise seemed to lessen. The voices could be clearly. We could sense that understood Ft. Hamilton Pkwy. Brooklyn 19, N. Y. the voices came from one direction alto 4112 the music from a different point. The phones used were magnetics and P we thought higher -fidelity phones might improve results. So we connected in a AUXILIARY pair of crystal units. The results were very much improved. The higher -fre- quency sounds, whose reflection as echoes are much more efficient, were SPEAKER heard and more realism and sense of Control distribution ut sound with suppl r me n t a ry direction were felt. The sound was nat- speakers connected to radio. TV receiver. phono- in a different sort of way from graph or P -A amplifier. ural Ideal for homes, bars- grills, hospitals, fairs, and better sound where you want it. the usual "high -fidelity" reproduction. etc., for more Size: 5" sr a 3" deep. sense of "presence," as if Fully enclosed unbreakable cast -aluminum case. Open back. $5.75. Cloud back. $6.95. There was a volume control. Best 4- P.M. speaker. Fully Money refunded if not fully Built -in As guaranteed. the listener were actually in the same Simple to install -directions with each shiument. sanisAro.. speakers have been connected to standard radio many as 8 glossy Also available in vertical waterproof model for room as the sound. This is impossible TV ceiver without alterations. ' In 7 beautiful or Blue. Nile Green. outdoor theatre use. with L -pad vlume control colors -Ivory.' Red, Mahogany. Light details on re- with single- channel systems because the otherwise specified. speakers will and waterproof speaker. Full Gray and White. Unless quest. directional distribution of the sound be shipped in Ivory. cannot be transmitted. TARRYTOWN METALCRAFT CORP., 84 Chestnut St., Tarrytown, N.Y. It is very possible that binaural trans- mission will be introduced to the public d before very long. Experiments have been carried out in England with two microphones, two transmitters, and two receivers. In the United States experi- ments of the McClatchy Broadcasting Company have definitely shown that audiences prefer double -channel repro- duction. In June of this year, Marvin Camras of the Armour Research Foundation demonstrated binaural reproduction be- $$-ft tells HOW - in fore the New York Section of the IRE. simple, direct language. He used a specially built dual -channel New 9th edition now off the press. magnetic recorder which carries two 100 pages of valuable information. separate sound tracks at the same time. The output of each one is fed into a sep- Available from all leading radio parts and arate loudspeaker, and the two speak- equipment distributors or directly from factory ers are located at a distance from each at only 40e per copy. other. Horace Harding Blvd., Elmhurst 4, N. Y. PRECISION APPARATUS COMPANY, Inc 92 -27 OCTOBER. 1948

www.americanradiohistory.com 78 Foreign News European Report By Major Ralph W. Hallows

RADIO -ELECTRONICS LONDON CORRESPONDENT

. For easier, better work, and carries a stylus of tungsten carbide. and more profits A non -flaking carbide on down -to -earth electri- -many times harder than sapphire -is used. As the cal jobs -new handbook moving parts gives hundreds have less than one twen- of useful tieth the weight of an facts, data, and ordinary needle, methods, record wear is very light. This pickup in handy form, at low price has an excellent response of only from about 30 $2.50 to 15,000 cycles a second. The musical quality is certainly there -but so, alas, Just Out! is the surface noise! ELECTRICIANS' Phonograph and broadcasting So much use is made of recordings for broadcasting and so important have POCKET the phonograph and other instruments become for this purpose, that the BBC COMPANION HE British has for some time now had one of the By Benjamin Goldberg gramophone country's leading research and develop- ment departments in the Formerly Electrical Inspector, .0 cur York Clty or radiogram- recording field, headed by M. J. L. Pulling. 375 pages 4h/g x 7, hundreds of ophone (radio- The stand- illustrations, chaffs, diagrams, and fables gram, for short), ard maintained is a high one: at all Here, at your Iingertlps is a romptchensite mien- called in frequencies between 50 and 8,000 cycles lion of the important farts. figures and 410 the eke- America Vivian needs to know the relative about modern eietrieal 1 In k. the phonograph or radio- levels at the output The Elect i('taut.' phonograph, of a Pocket Companion a rs lyour is a reproducing chain question..: gilt, needed informal ion based " um the Na- considerably more important pro- must be within plus tional Elertrie.d custe and Underwriters' requirements; vider of home or minus 2 db of those upplies diagrams' hills what to dn. It tt''ra the en- entertainment in Britain at the input t. range of tublrrls Rom than of the recording Imams. in the United States. The main chain; noise of all kinds meters and fr..' SAVE TIME -WORK introduced to lighting. wlring. reason, I fancy, is that our folk have by both chains must be at and literally hundreds of MORE EFFICIENTLY a least 55 db below others. much smaller choice of radio pro- peak signal level. In addition. It coo- - Wlth ielplul tlata, I and Many bins : clear explanation of tabuik- grams. Even if you live in or ingenious improvements have on subjects like near Lon- eleetrital fundamentals and thesethen. been made. nalhe"ud don and have a reasonably good radio The discs normally used are ie.. The author Is Electrical Fundamen- a mart lead rlretrirlun of tals receiver, your available of 171/4 -inch diameter and run at either broad programs dur- rxperienee and has Meanings of Terms ing the daytime, when 78 or 33 1/3 r.p.m. It is not always a le msal rhoiee of the Commonly Used In continental sta- real- obi helpful prarUral nn Electrical Work tions on the 500 ized that the track speed Electricians' -1500 -kc waveband don't of the record ial -and the price is Tools notch Methods of Work usually provide worthwhile sets the upper limit of the a.f.'s that can less than that of oth- Electric reception, er handbooks Meters be reproduced. while small- Transformer Connection are not generally more than three. The With a disc revolving at .01.1 Moro CVncerlieni. The Schemes BBC a constant rate, track speed l rlre,riri :ms' l'oket turn' Electric Motors offers two, called the Home Pro- decreases as press nos all tables, Typical Control Schemes gram and the Light Program, and you the cutter moves inward. In fact, if a dial anl, large. for AC Starters Lighting and signal may be reproducer were designed to give Lily lead . .b. Four lif- able to pull in Luxembourg. It's a de- lrlent unlexr'. Circuits xi,. quirk Insulation Resistance only natural that this In any selection can't fact need In Testing TUNGSTEN CARBIDE STYLUS your wok. Electrical Equipment please everyone; but if you have a Troubles radiogram BRIDGE PIECE Illumination Values -forgive me, a radio- phono- Residence Wiring Sys- graph -and a good selection tems of records, MAGNET POLE HOW Electrical Symbols and there's no need to shed any tears over Abbreviations TO Electrical Formulas and that problem, unhappy as it may be. Their Applications Electrical Code Tables. REPAIR Diagrams and Ex- The phonograph pickup < amples ELECTRIC MOTORS Standards for Electrical Naturally we pay a lilt RUBBER PRESSURE PAD Materials. Equipment of attention by and Installations to pickups. The chief aims of inventors RIBBON , Also published - Hill. Roscn- Domestic Heating Sys. Murray tem are to reduce needle hnrg's ELECTRIC MO Controls scratch to a mini- Safety Cautions anti TOR REPAIR fully mum and to Fig. I- Details of new Brierly ribbon pickup. Ih arar Emergency s obtain the maximum (dainty F i t fre- of all Aid . .. and many quency mw rewinding more response. The two are hardly sired response near the kinds uf motora. ata, start of the 5O I compatible, motor ro ntrols, since the better the upper grooves, the upper a.f. limit halfway to pages, 000 (Rostra- a.f. response ¡7,',;L: ni Try TEN DAYS' of the pickup, the more is the center would be a whole octave 11 slay, at our h surface noise brought out. Still, several lower. TRIAL recent tests before audiences with There are several ways out of this ill Books. trained 23: musical ears seem to show that difficulty. One is to use only a small S.s N. Y. reproduction with plenty of top and a band near the send me books outside edge of a large checked below for DJ days' exam- good ination val approval. In ln days, deal of needle scratch is far more disc for recording. The books plus I will pay for drawback here a few rents portage. or relurn then] post - acceptable than that with not very much is even (Postage paid on cash orders: same return that large- diameter records privilege. Books sent an of anproral In U. S. aoly.I either. made in this way have only 2 to 3 ELECTRICIANS' POCKET t'ONII'.tN1uN. $1.10 A novel ribbon pickup was demon- I.I.FaTltlt' minutes playing time for the best re- \IOTUIt REPAIR. $5 IYi.:,u outside strated by its inventor, J. H. Brierley, sults. to an important London musical society Another is known as automatic radius last month. The construction is shown compensation. A frequency discrimina- in Fig. 1. The ribbon is a U- shaped tor network with several variable ele- piece of foil lying parallel to CIt3, Zone. St the ments is used. As the recording head plane of the lines of force of the mag- travels over the disc a progressive vari- Ocrupalian netic field. The bridge piece, of light ation takes place, giving more and more plastic material, is cemented to the foil pre -emphasis to the upper frequencies RADIO -ELECTRONICS for

www.americanradiohistory.com I 7s

NATIONALLYY T A rS TUBES' ADVERTISED BRANDS ! PURPOSE RCA - Kenrad - Sylvania - Tung -Sol - National Union - Raytheon - Philco - Hytron SPECIAL All new tubes. 100 °° guaranteed. Individually boned. TUBES TYPE PRICE RADIO TYPE PRICE TYPE PRICE TYPE PRICE TYPE PRICE PRICE TYPE 305GT 6N5 $0.80 fiU6GT ....50.65 7C6 30.85 32L7GT ...51:96 sp,.Clol 01A 50.45 ....i0.0 5U7G .54 7C7 .65 33 .811 3S4 .65 6N7 .80 Ray Purpose 0Z4 3V6GT .65 7E6 .65 .96 Cathode .65 5R4GY .... 1.15 6P5GT ...... 34 A3 1..6515 1V7G .65 7E7 .80 35A5 .65 .95 A4P 1.15 514 1.15 6P7G S .45 607 .65 iW7G .80 7F7 .80 35L6GT 3API .S2.95 10Y .. 3.95 A5GT .... .54 5U4G A5 7G7 .46 ... .96 5V4G .80 6R7G .54 ìXSGT .... .96 35W4 2.95 3822 6Y6G .80 7H7 .80 35Y4 .65 ... 3'L .65 5W4GT ... .65 6S7G .96 38PI C61 Á7GT .... .80 6 Y7 .80 717 .96 35Z5GT ... .45 3'" 84P 1.15 5X4G .54 6S8GT .... . 3.95 4B24 ..... 6SA7GT ... .54 eZ5 1.15 7L7 .80 36 5CP7 . . 9.95 g5 .96 5Y3GT .... .40 1.15 7N7 .54 531 5Y4G .45 6S87Y .... .80 6Z7G .80 37 3.95 1.95 CS .65 ZY5G .65 7Q7 .65 38 .65 717A .96 5Z3 .54 6SC7 .65 .... 5FP7 . .85 C6 .65 A4 .65 7V7 .96 39 .80 .80 6SD7GT ... 3.95 864 C7G .96 524 A5 .65 7W7 .96 40 7BP7 ...... 11.95 1.15 6A3 .96 6SF5 .54 725A 5.95 05G 6SF7 .65 A6 .65 7X7 .96 41 .51 4.95 ... D7G .96 6A4/LA ... .96 7Y4 .54 9LP7 . .. 730A 1.95 6A5G 1.15 6SG7 ...... 65 A7 .65 .65 42 215A ... 08G 1.15 6SH7GT ... .65 A8 .65 724 .65 43 8.95 ESGP .... 1.15 6A6 .80 5; I2GP7 .. 6A7 .65 6617GT ... .54 84 .65 2A .45 45 E7G 1.15 6SK7GT ... .54 B5 .65 2A5 1.15 4523 ...... 54 14G ...... 0 6A8 .65 .65 2A6 .96 .54 6A87 .96 6SC7GT ... .80 B6 4525GT ... FSG . 80 65N7GT ... .80 rB7 .65 2A7 .96 46 F6 1.15 6A C7 ...... 96 .80 .80 6SQ7GT ... .54 788 .65 2A8GT ... .65 47 F] 1.15 6A06 2A H7 .80 .65 6AE5GT .. .65 66H7 .54 7C4 .96 .... 48 G4G SUS 6C5 .. .65 7C5 .65 2AT6 .... .65 50 1.15 GSG .80 6AF5G .... .96 .80 .90 28A6 .... .65 50A5 G6G ...... 80 6AF6 G .... .96 .85 6A G5 .96 50E15 H4G .65 2FSGT ... .54 50L6GT ... .54 HSGT .... .54 6A G7 .96 .80 .80 2H6 .54 50X6GT ... H6G .96 6A K5 215GT .45 53 .80 6A L5 .65 ... SPEAKERS 16G .96 21(8 .80 56 .54 6A16 .54 eP _ L4 65 ..... 2SA7GT .65 57 .65 684G .96 - ' .. $1.25 LA4 .96 58 .65 L84 .96 687 .96 1.15 4,. 2615 .54 70L7GT PM Speaker...... LC5 ...... ° .65 71A 1 .96 6134 .St.54 26F7 .25 LC6 .96 2SG7 .65 75 ...... 54 Speaker LDS .96 6C5 :55 ...... 6C6 'SH7 .65 76 54 LH4 ...... 96 2S17GT .65 77 .54 .96 6C80 .. LNS .Si S 2SK7GT .. .54 78 .54 1.98 N5GT 65 ' 79 .80 605 .65 { 2SL7GT .. .80 6" pM Speaker...... N6G 2SN7GT .80 .45 '65 6FSGT .54 .,. J .. 0 GT KJ .54 81 1.15 ' 2S07GT .. Ñ4 . 6F6 .65 .80 6F6GT 2SR7 .65 82 ...... RS .65 23 .80 .80 6F7 .96 .96 6F8G .96 i47 .80 83V S.5 .65 ELECTRIC PORTABLE 486 .80 84/664 T4 .fiS 4N7 .96 85 55 TSG 6H6GT .... 54 PHONOGRAPH .65 .50 V .65 615GT .... Leath,! 4H7 .80 817L7GT .. 1.15 A3 .96 6 15G 50 1.15 96 litlrr. 25L6GT ... .54 1I7N7Gt .. A4G I.IS 6J6 ruler h.r I. .. 1.15 617GT .... .65 2525 .54 I17P7GT 2A5 .65 Speaker. It¡In .1; 96 25Z6GT ... .54 11723 °A6 .80 618G Self .tart lug . .80 6K6GT .50 peed. 2fi .54 117Z6GT 287 80 .... Size J. I..' s. .80 .54 fidelity pickup. 2647 1.15 VR90 2 X2/879 1.15 61(7 1.14 £20.75. .45 .80 61(8 .80 frire 27 VRI5 .... 344 .65 NET PRICE .65 V R 150 .. .. 6LSG .80 30 3137/71291 . .96 LOTS OF THREE 31 .80 9001 .80 106/1299 .. .96 32 .96 FM-1000 .. 1.15 304 .65 6L7G A .80 1313 FRANKLIN-EILIS CO. RChaa9Ph7S11nó±

is a perceptible 2, making a third -hand record- hand recordings. There as it approaches the center of the disc. from No. and by about ing. You can continue the process as difference at fifth -hand Another method is now under develop- the record becomes unac- the per- long as you like. Some while ago I was eighth -hand ment which would seem to give This is good proof that the sys- be pro- given a very interesting demonstration ceptable. fect answer-if only it could is effective, for any distortion or form at reason- of what happens if you do. You have to tem duced in troublefree dif- frequency discrimination introduced by What is wanted is a means listen pretty hard to notice much able cost. -hand and third- (Cm/tin/fed on following. page) of rotating flat disc records at constant ference between first track speed instead of at constant angu- lar velocity. Several methods have been suggested; but all so far have been too complicated or too expensive. One way out of that difficulty would be to use cylindrical records of the original Edi- son type. The trouble is that they are too fragile and need too much storage space. "Second- hand" recordings All disc recorders and reproducers used by the BBC consist of dual units. When a long program is being recorded the turntables of both units revolve, though as a rule only one disc is being cut. Monitoring is perfect, for follow- ing just behind the recording head is a reproducing head which can be brought into action by a pushbutton switch. It is also possible by using another switch to make the reproducing head on re- corder No. 1 feed the cutter on recorder No. 2. And, having made what we may call a second -hand record on recorder No. 2, a most interesting experiment can be made. The original piece comes to an end. Put a new disc on recorder No. 1 and re- can "tap in" or find any desired point on a recording. record on this the second -hand record Fig. 2 -With this device the operator OCTOBER. 1948

www.americanradiohistory.com uo Foreign News

EUROPEAN REPORT TUNERS (Continued front page 79) progressive stages multiplies rather IF... than adds. AM Tapping in there is something in this FM It is issue often required to "tap in" on a that you would like For Your Favorite Amplifier. A disc, that is, to complete line of start playing at a par- to own or see demonstrat- AM, FM and AM- ticular point between the beginning FM Tuner chassis. Distinctive in and ed... styling. the end of the record. The BBC calls Outstanding in perform- this groove- ance. Features include built -in locating. A clever piece of phono pre -amp. For the ultimate in apparatus has been developed which en- listening pleasure choose tuner ables the exact point required to be WRITE units backed by twenty years of found with absolute precision. The re- electronic research and manufac- producer has a tracking turing experience. rod placed to: The West Coast tangential to the turntable. Over this rod Headquarters for SOUND Write for literature. moves the carriage with a straight arm supporting the pick -up. Above the EQU I PMENT or . .. The SARGENT - RAYMENT Co. tracking rod is a vernier scale, show- 212 Ninth St., Oakland 7, Cal. ing the exact position of the carriage and the pick -up. A switch operates a VISIT lever mechanism, enabling the stylus to WANTED be lowered onto the record or raised our Sound Demonstration from it at will. RADIO SERVICE MEN The readings on the vernier scale at Rooms. which the desired Experienced men with cars for part -time passage begins and work on AC -DC receivers. ends having been noted, it is a simple Some traveling matter required. Must be bondable. Pleasant work to play just the excerpt required. with good compensation. Need men in or The apparatus is illustrated in Fig. 2. near Davenport, Iowa, Chicago, Indian- You'll see the idea at once and it may KIERULFF apolis, Buffalo, Rochester, N. Y., Pittsburgh, interest and amuse you to evolve Philadelphia, Washington, some- D. C., Baltimore, thing on the same lines for your own Md., and Boston, Mass. phonograph. Address box number 01 c/o Radio- Electronics Radar shipping control COMPANY 25 W. Broadway New York 7, N. Y. A remarkable system of radar slip- ping control (the first 820 -30 W. Olympic of the kind in Blvd. the world) has just been brought into Los Angeles 15, Calif. SUPER -MITE RADIO action at Liverpool. This is one of Eng- Richmond 70271 land's most important seaports. It lies SUPER -MITE FEATURES! PACKS AMAZING some distance upstream World's most powerful min- POWER! from the mouth iature radio. of the estuary of the River Mersey Uses War -Born midget and, electronic tubes. $399 as veterans who were there during the Coast -wide reception ob- tained. war may remember, there are dense fogs Powered by midget hen- during ingaid battery. " the colder part of the year. Miles Picture diagram for radio s upon miles of beginners. docks are situated on both banks of the river at Liverpool and Brilliant red chassis. chrome and blck streamlined bto elite Birkenhead and there is always kua ds. heavy Conpletekitready to as shown Only traffic, 33.99 each. not only up and down stream, STEADY PROFITS set not ailable elsewhere at 10 times this npricé but also by the cross -river ferries. Many ELECTRONIC RESEARCH LABS. accidents have occurred in the past and Your Own 1216 Park Row Bldg., Dept. RC. New York City 7 shipping has suffered heavy delays in Business thick weather. The radar equipment is of the scanning with PHONO -AMP beam type, with PPI Q tube display. Five PPI tubes are used. WITH TUBES.. $4.89 The first gives CORADIO PHONO -OSC a small -scale picture The Coin Phnuo or Mike Inp ut of the whole estuary Place IMPLEE and its approaches these specially t builtaradios that over play I or 2 'Viril TITBE.. $4.49 a range of 20 miles. The next hours for 25c in the thou- --WRITE three sands of available hotel FOR LITERATURE give large -scale rooms, tour- FM TUNER KIT pictures of the same ist courts, etc. They yield immediate profits and steady Ama Perform- area in three sections. The fifth income. Install Otto..11 tube expterimtnt l F`Iptuner. enables Coradio the finest full instructions. chazilag an extra -large Limited made. $2.95 -scale picture of any capital required. Send for SIGNAL GENERATOR small part further informaHon. 956 ke of the area to be obtained at Write today. -465 ke- -600 kt -1400 Ice. Fully Guaranteed CORADIO with tubes. - will. Ships do not receive orders from Coin Operated Radio InsunocAC DC Complete $9.95 the controller Dept. B. SIGNAL TRACER at the radar station, for 212 eroa..way, Phone:BEekmon BUM -In . pkr. .W PC. Highly sensitive $10.95 the connin - and navigation of 3- 0038 -9 injector cl rcuit. ('on, ilete with tubes a ship 5" dynamic must always be the NEW YORK 7 N. Y. spkr. New 500 ohm field. torn cones .30 responsibility of DISTRIUTORS the ca "tain or the pilot in charge. But S23 YORK Knickerbocker Ave., rooklyn 21. N. Y. indications and warnings are sent out continually by radio and a navigator PEN- OSCIL -LITE can ascertain at any time not only the Elements of MAGNETIC exact position of his own vessel, Extremely convenient test oscillator but servicing; alignment for all radio 32 powered Small . Self TAPE RECORDING also the positions of other vessels Range from 700 cle a audio and and megacycles Output to cost FACT - of danger points. The apparatus was i900nformation. Used by Sgnal Corps Writee foe 999 Applications in- PACKED stalled during by A. the summer so that it GENERAL TEST EQUIPMENT PAGES C. SHANEY might be checked and adjusted and 38 Argyle Ave. Buffalo its 9, N. Y. Only 25c AMPLIFIER CORP. of AMERICA operators thoroughly trained under con- -10 398 Broadway New York 13, N. Y. ditions of good visibility. RADIO- ELECTRONICS for

www.americanradiohistory.com question Box 181 AX- FM -AM DETECTOR Development Co. Models AX -171, 178, AX -180 or equivalent. Be sure that can handle the l WaHt to experiment with the FM- the model you select in the patent re- power you develop in the generator. AM detector described Con- page 64 of the November 1947 There are three output terminals. viewed on any two of issue of RADIO- CRAFT. Can you supply nect the transducer across use depend on the experimental circuit constants ? I.E.G., them. The ones you - of the trans- Oceana, Va. type and operating limits ducer. A. Here is the circuit with constants amplifier has been added. A 6SF5 a.f. COLOR ORGAN included on the 'diagram. It may be to with the cath- necessary experiment I saw a device that the resistor in the plate Some year's ago ode choke and sound to colors that changed circuit of the 6SQ7. converted with the frequency and amplitude of FM the sound. Can you supply a circuit 6SF5 AM one of these 1_410/450v showing how I may make IMEG 27011 AF OUT l 1 .0001 devices to connect to the output of nay 6SQ7ETC rt radio or phono amplifier ? -J.F.C., Los RF IN 2 Tti Angeles, Calif.

0001 A. The device shown was originally 20/25V 1941 issue of described in the January a Communisations-type $26950 Electronics. It is designed so that col- Broadcast aver (slightly 540 KC to 110 MC Higher Wett ored lamps respond to changes in fre- of Rockies) amplitude. The lamps may 0011 quency and 10/450V be concealed behind a frosted glass or 200µH For discriminating listeners on ADJ.TO plastic panel or in frosted tubes. The ar- 4.2 MC 2211 all wave bands (FM /AM) ...who 0 +250V rangement is left to the ingenuity of the AVC TO PREVIOUS builder. appreciate the thrill of superior per- S AGES a two -channel with high -fidelity audio CORDS 600V UNLESS NOTED The device is fed by formance ... power amplifier. Lamps, 1, 2, and 3 re- ... who want a few extra controls GENERATOR B, C, SUPERSONIC spond to frequency, and A, and but not too many. D to amplitude. Lamps 1, 2, and 3 are Please show a circuit of a 4u -watt connected across 234 volts a.c., devel- supersonic generator. I want to apply oped by T3, through Rl, R2, and R3. An "S W L" version of our famous vibrations of various frequencies to a These resistors limit the current so the SX -42. Two stages RF. three stages What type laboratory flask or beaker. lamps will not light. The filaments of IF amplification - 14 tubes plus tiansdneer do you recommend ? -A.M.H., the V1, V2, and V3 are connected across Rectifier and Voltage Regulator. See Kekaha, Hawaii. 5 of through resonant cir- -ohm tap Ti local Hallicrafters dealer. cuits. The tubes are connected so their it at your A. This supersonic generator will de- internal plate resistance shunts the velop up to 40 watts at 25 kc. You can dropping resistors. When the impedance change the frequency by varying L, Cl, in the filament circuits is low, the fila- on Ll for stable the hallicrafters or both. Adjust the taps ments heat and the plate resistance FIFTH AVENUE A crystal transducer is 4401 W. oscillations. drops so that the tube passes enough CHICAGO 24, ILLINOIS recommended over the magnetostriction current to light the lamp in series with type because of its wider frequency range. This may be one of the Brush 600 (2) .5 /211V in TWIN -TRAX TAPE RECORDERS 4BIG Recording Dollar LOAD Make Your Go Twice as Far A LI B the 2MH C gf XTAL TRANSDUCER

5/111V .5/2KV 7.5V PORTABLE FOUNDATION CHASSIS STANDARD LONG -PLAY 6.5A 0 300 MA DC ALL TWIN.TRAX Recorders actually cut tape standard one- hour -play model; an ingeni- the costs in half! The only Recorder line operat- ous two -piece portable that divides .5 /400V a compact 500-750VDC ing on the revolutionary principle of using weight for easy carrying; and two isolated and independent sound tracks long- playing model providing four continu- fidelity. All can on standard I/4" wide tape. Records on one ous playing hours at high panel mounting. The 10H /200MA 900v ,HIVS track during forward tape travel and on the be adapted for rack laboratory. other track during reverse; rewinding thus ideal, line for use in the home, MAIN station, recording studio, etc. SW eliminated. Tape reversal is automatic and broadcast Recorder until instantaneous. Mechanically and electrically. You can't afford to buy any technical these recorders embody every design ad- you have sent for and read full TWIN - vance in the recording field. specifications of the revolutionary There's a model available for everyone! A TRAX Recorder! NOTE - 6., r -,,,, i.,r ". 1,.,, i 7., iF,. If.._hda: T,,... ..L CI -.02/2.54V 2 FUSES 900V AMPLIFIER CORP. OF AMERICA .I /600V (2) 398 -10 Broadway, New York 13, N. Y. II7VAC .2115/3AOR MOREe-4 OCTOBER, 1948

www.americanradiohistory.com 9ucstiou. 11hux it. Ll is a low- inductance choke con - series across volts sisting of 235 developed by T3. about 1,000 turns of No. 26 A will glow because of its lower enameled wire on wat- an adjustable lam- tage, but B will be dark. We're inated or powdered The plate re- GILDING -iron core. L2 is sistance of V4 is in parallel with made the same as A. Ll, but using only 800 When the voltage across the secondary turns. Vary the number of turns and of T2 is high enough to heat V4, it position of the cores to get the most passes current pleasing to lamps B and bypasses the LILY! effect. A. V5 and V6 are across The amplitude- taps of lower sensitive lamps are impedance than V4; therefore connected in pairs, higher A, B, C, and D, each output is required to light them letter representing two so they lamps. With no will pass current to C and D. signal input, lamps A and B are in

6L8(2) 1 TRANSLUCENT CYLINDERS OVER LAMPS

Zi4.5Kn TI 4 L1 A B C D 3 2 I D C B A o IO .1/600 °iY1-- AUDIO INPUT 164 1.5K /50W R3 J/lC' 1 .4.1 /600V T2 A - V4 v5 V6 NEW, IMPROVED 500 VI TO V6 71-A

{. --231V 4 T3 Model 7 -B -1, O:SW 250/2W 250V 112 AUTOTRANS engineered -/i 117 V }4 . 100W SW 5V/ 3A 300/20W ® LAMP COLORS -A -RED, 8 -BLUE, C- GREEN, DYELLOW 1 7VAC 6 _tee 20 40',150V I GREEN, 2- BLUE,3 -RED to meet YOUR o 350V needs! LAMP RATINGS- $. 150MA *-1 A 7.5W,8-10W,C-ISW,D-I5W¡I- 2-3 -15W EACH 4 2 450V G 350V -A- AMPLITUDE CHANNEL FREQUENCY Carefully engineered, 5U4 -G -F- CHANNEL and manu- ALL LAMPS 117V

factured of the finest materials, PL 6.3V TO 61.6 FILS the ESPEY Model 7 -B -1 is spe- cifically designed to meet the most exacting requirements for a replacement chassis, and will STROBOSCOPE lend itself to any type of installa- I would like a circuit to amplify the A. Some types of ticking of a watch telephone relays can tion. This model is drift- compen- and convert each tick follow 10 pulses per second. However, to a light pulse. The watch ticks about sated, AM FM, with 10 tubes the circuit shown does not require a re- .15o tiares per minute. Can this be done lay to operate. plus rectifier. Supplied with a relay and The R4350 strobotron complete, strobotron?-E.C., gives a blue -white light and operates Leamington, Ont. at ready to operate. a maximum rat of about 15 flashes per 5R4-GY IK/sw Send to DEPT. +800V -15V I0K7IOW R4350 C -10 TODAY for 117VAC 5V 00K IOW 20K 5W 2 IKV FREE LITERATURE $ 300V 0A5 SW 6 700V 7 42K 3W ó 70MA r? 3/1KV +90V IOMEG 2 20 MEG ,E S Pe, T MANUFACTURING COMPANY iNC. RI K 5(--\ 4 wes tA16,1 Y2,e RYRERr -NtW YORK. 21.5. Y. 6.3V TO 6$L7 .025 +4.5V .011600 1/3 I.SKV "ESTABLISHED - 1928" T 910 20 IIT

450VV - 156V IGNITION TRANS RADIO MADE EASY! 66V- 0KV INST. PEAK TRIGGER GRID VOLTS 240 150K A JRI Trainer ! r- WATE- --1 second. The circuit shows a contact -type A NEW APPROACH to radio itr LE crystal microphone as a pickup device. Is a 3I FD repairiu. ,I can be LEARNED .05 600V grlri eI e g into. ..i.lt I .I /í00 The ticks are amplified and used to Nell n fo The it oper- oven. Prepare yourself for a o Discover f 6SL7 ate the 0A5 trigger tube. Place the II E\ t TO , LEA IIN by this NEW 31FTIOi.irep rloL ,I 2 E the Jill Home Troller Sndfor XTAL MIKE watch close to the diaphragm of the TOI/AY. $ 2.00 postpaid or Plus 15016 c.o.d. charge. Satisfaction guaranteed. CONTACT TYPE 6 3 microphone and inclose both in a hous- OUTPUT THE JRI TRAINERS LHI 2 MEG ing that excludes outside noises and P. 0. Bon 2091, Dept. 100, Chicago 9, III. vibrations.

NEW POWERFUL ELECTRIC MOTOR Question Box queries For Rotating Hans. FM. Television will be answered by mail and those of general inttrr.t will be Antennas; Barb -cue Spits. Min. K`,- printed in the magazine. RR Turntables. Telescopes. A fee of 51.00 will be charged for questions requiring no Operates on 110V AC. 60 -Cps. research or schematics. I Requires only 12MFD Cndsr.) Write for estimates on questions requiring diagrams or con- Appr. RPM í -H 1-Torque-No ïs siderable Free Swing research. Be sure to give full specifications and details on the application. Quiet Easy to Mount W,te Full Due to the nominal fees charged Instructlonr tr POSTPAID IN r for this work, it must be handled as a spare -time cgc CONT. USA ; proposition. Therefore ALVARADIO, Dept. RC rapid service is impossible. Six to 8 weeks is required to draw 907 -4 - 5. Alvarado. Loa Angeles 6. Cal. up answers involving large schematics or research. RADIO -ELECTRONICS for

www.americanradiohistory.com Tcchnotcs

. CHECKING OSCILLATORS Another receiver can be used to find /itt. )2adict Serviceman out whether the local oscillator in an FOR YOU EVERY WEEK apparently dead receiver is operating. ADDITIONAL SSSS Tune the good receiver to a frequency equal to the dead receiver's i.f. plus 550 ELECTRICAL APPLIANCES kc and the dead receiver to about 550 kc. REPAIR MODEL 40 A beat note should be heard in the good WITH THE AID OF THE NEW receiver. The sets may have to be coupled fairly closely if the dead one is UTILITY TESTER well shielded. It may be necessary to use A NEW KIND OF INSTRUMENT FOR TESTING capacitive coupling between the oscilla- ALL ELECTRICAL CIRCUITS AND tor and the antenna of the good set. A APPLIANCES SUCH AS- 2 -turn gimmick around the oscillator 'RANGES "WASHERS 'VACUUM CLEANERS or anode may be used to couple to 'SHAVERS *FANS 'AIR CONDITIONERS grid REFRIGERATORS the antenna. 'HEATERS *MOTORS THOMAS P. MOTTLEY, 'IRONERS 'TOASTERS 'SUN LAMPS *WASHING MACHINES ALL TYPE MOTORS Ocean Grove, N. J. FROM FRACTIONAL H.P. TO 2 H.P. THE MODEL 40 UTILITY TESTER Will test Thermostats under ACTUAL WORKING WESTINGHOUSE MODEL H -I26 CONDITIONS: Will measure the ACTUAL CUR- .... RENT CONSUMPTION of any appliance either THE UNIT IS IN OPERA- The set went on and off intermittently. A.C. or D. C. WHILE ap- coil is TION- reading will be direct in amperes -the One lead of the speaker voice pliance or utility may be plugged directly into grounded to an eyelet on the speaker front panel receptacle -a special pair of insu- lated clip -end leads is provided for motors : In- frame. Remove this lead and solder it corporates an ultra -sensitive direct- reading re- directly to the speaker frame. sistance range which will accurately measure all resistances down to a frac- FLoYD D. GOFF, appliance and utility tion of an ohm; Will test bulbs. fuses. condensers. Black Mountain, N. C. field coils, etc.; Is ideal trouble shooter as it will instantly locate opens, shorts and grounds ; Will locate cause of failure in three way heat control switches; will indicate when one aide of an ap- pliance or motor connected to line under test is .. PHILCO PORTABLE MODEL 250 grounded "; Will indicate excessive leakage be- Hum on battery and a.c. operation tween a motor and a line: Will indicate when a Tester comes three motor is running erratically due U. an sometimes be traced to the grounded The Mosel 40 alility ( phase whether the volt- housed in a rugged crackle finished `Tlt a "blown" fuse; Will indicate with portable ver. if the current is side of the volume control which is con- steelst cabinet age is 110 Volta or 220 Volts. es andcoper A.C. or D.C. and if the frequency is 25 cycles aticompleteinstructions-on on is-only nected to the A -minus lug through a or 60 cycles. 1,000 -ohm resistor. The hum is caused Dept. R.C. by a poor ground connection. Simply N CO. NEWA YORK tighten the nut on the volume control. GENERAL ELECTRONIC DISTRIBUTING BENNIE ONDRAK, Idaho Falls, Idaho If to STRIP .. OUTPUT TRANSFORMERS "It's Fun I had several output transformers that I could not identify. I used an a.c. WIRE- voltmeter with 0 -10- and 0 -150 voltage ranges to determine the turns ratio and from this was able to find the impedance Slays 2pQedy ratio. The characteristics of the trans - former were found by the following with the method: Check the transformer for shorts and grounds. Apply a known a.c. voltage to the high -resistance winding, and meas- peedeX ure the voltage developed across the secondary. The turns ratio is the ratio of the. voltages. The impedance ratio equals the square of the turns ratio, Primary impedance WIRE STRIPPERS (turns ratio)' Strip :300 ohm Twin F.M. and Televi- Secondary impedance sion lines so we can find the best plate -load re- Strip all types wires sizes 8 to 30 sistance to match the secondary imped- G -C announces a new television and F.M. ance. tool for 300 ohm twin line. It will easily For example, a transformer develops strip both wires at the same time. Just 5 volts in the secondary with 125 volts place the wire between the jaws and on the primary. The turns ratio is 125/5 squeeze -insulation will come off instant- the wire. A great time- or 25:1. The primary impedance is the ly without moving NET product of the turns ratio squared and saver on installations. No. 733 -H Regular Twin Line the secondary impedance or 625:1 Net PRICE will Strippers ...... $3.60 (25x25/1x1). This transformer No. 744 -H Automatic Twin Line ONLY match the 3 -ohm voice coil most effici- Strippers .$4.80 Net ently to a 1,875 -ohm source, (1,875/3- Other models available for all size wires -write for catalog Dept. D or see your Distributor. 625/1). Tubes designed to work into a (DISTRIBUTORS. WRITE FOR DETAILS) $3.60 2,000 -ohm load, such as 25L6's and 11naut fir furor/ by 50L6's, will work effectively. GENERAL. CEMENT MFG. CO. ul.,Ine FRANK SORENSEN, VIUDI. I. ROCKFORD. ILL. U.S.A. Brooklyn, N. Y. OCTOBER, 1948

www.americanradiohistory.com 8 I Radio-Electronic :i.rcuits -- TECHNICAL CODE OSCILLATOR and a 6.3 -volt battery can he used for i KOs This simple code oscillator can be portable or mobile operation. used by itself, or in conjunction with The 6C4 is used both as transmitting OIL- FILLED TRANSMITTING another unit just like it for 2 -way com- and receiving CONDENSERS oscillator. When receiving, MICAS munication or code practice. the plate- current variations appear as .05 515'D 10110V 60.35. .1116I05 21110V $0.15 The circuit is .05 509V .14 .011905 3MInV .35 that of an ordinary re- a varying voltage across the mike trans- .1 25011V .75 .0000.5 50161V .85 laxation oscillator using a neon former .1 7500V 1.65 .1100067 2511UV .20 lamp. secondary and the sound, am- 2x.1 71100V 4.10 .00007 ^500V .20 .12 plified by the 6AQ5, is heard in 15009V 7.95 .0025 2501V .25 .tI5 IOOK TO OTHER OSC the .25 1an11V . .001125 50161V .85 phones. 411161V ' .'- 2.15 .0105 2uo0V .25 .25 6000V 3.75 .00072 5000V .85 When transmitting, 1ox.25 610V 1.05 .0008 50011V .85 the oscillator re- 601V .28 .0001 25o11V .25 ceives its II7VAC 1 NEON PHONES plate voltage through T, which 0 11100V .40 .1011 15000V .85 --1 .5 20110V .75 .0r2 200V .20 acts as a Heising modulation choke. The .75 41111V .30 .01r2 31100V .85 .85 I microphone is 6011V .35 .1103 °511IIV .30 energized by voltage tak- 1.0 10011V .45 .1013 3000V .65 en from the 6AQ5 2.0 200V .20 .104 25011V .35 cathode resistor. T is 2.0 I found that the GE sn0\' .40 .1Nrs 10110T.V .15 type NE -2 lamp an audio output transformer, of which ".0 10110V .60 .1615 30001 .65 worked best. 4.0 600V .60 .006 20011V .35 only the primary is used. If several 4.0 1200V .15 If two oscillators are used, they ^A 20VAC 1 .55 .I11 1200T.V .15 transformers are in the junk box select 11.0 1010V 1.45 should be connected together as 6,11 4011V .85 the dia- the one which works best. An audio A.0 1001V 1.75 TUBES- CHOKEPOTS gram indicates. choke can 10.0 600V 1.00 also be used. 30.0 90VAC Tnb,s -6V6 Metal 60.89 Connect the free end of 1.40 Tubes -12K8 Metal .29 the head- Adjust 30.0 330VAC 3.75 phones the coupling between the an- Choke -- I11051.5 - I1111. to a good ground. It may be .50 011,0 1.59 tenna and the oscillator plate coils for Pots: 0K 50K .19 necessary to reverse the line 21.0 Electrolytic. -100K plug to ob- best results when 25V .40 Dual. 54 Meg tain receiving. 100.0 25V .50 250K -50K' .30 oscillation. Change the value of the .0025 -µf capacitor if a different tone FRED W. CREED, VE3BUC, SHIELDED WIRE 222 50 Ft. for .65 is desired. Toronto, Canada RESISTOR KIT Assorted t_ &1 W 100 for 1.49 JOHN V. MULLENDORE, BATHTUB KIT 9x 1 5 05, ETC. 10 for .58 Boonsboro, CONDENSER KIT .01- .00001...100 for 2.99 Md. CRYSTAL PICKUP CONNECTION MICAS .01, .002, .005, ETC. All Values .09 'l'he phono and microphone inputs on .01 150V PAPER (MIDGET) ...60 for 1.00 my amplifier are both 500 0.1 600V PAPER 8 for 1.00 HIGH -FREQUENCY ohms. I want- TUNER ed to connect a crystal pickup. Here is a simple method of making Connecting a crystal $2.00 min. order F.O.B.. N.Y.C. Add postage a high -frequency tuned circuit. It can be pickup through s0°, deposit. balance C.O.D. with all orders. a transformer, even one with a Manufacturers inquiries Invited. Send for Flyer. used when the original coil consists of 100,000 - Prices are subject to change without notice. just one or two turns of wire. ohm primary, would have destroyed the Make a loop of a strip of sheet copper, low- frequency response, to say nothing the width of the strip to be determined of other frequencies where a resonance TECHNICAL RADIO PARTS CO. between the capacitive crystal and the 265 Greenwich St. Dept. inductive transformer might have creat- RC -5 N.Y. 7. N.Y. ed large peaks. The small 1 -tube amplifier shown in EXCITER MACHINE SCREW the diagram was the solution. The 6C5 ',NUT is used as an ordinary resistance-cou- EXCITING BARGAIN SOLDERED TO LOOP pled amplifier. The output, instead of 25 to 40 WATTS being taken from the plate, is taken from a small resistor R in series with 10 to 80 METERS FOUNDATION KIT experimentally. Make a disc of the same the 47,000 -ohm equivalent of the follow- sheet copper to fit inside the loop. Solder a nut to the loop, as shown in the diagram, and fasten a screw to the disc. Now the disc can be turned within E : .,c red around the BC -610 series of plug -in the loop, varying the inductance of the tununq units. Described In the I Ith edition Radio coil over a wide range. Handbook. Completed exciter uses 6AG7 crystal or electron coupled Oscillator, 6L6 buffer- doubler R. A. CUNNINGHAM, and 807 amplifier. Kit includes four tuning units lillustroted of right above with cover removed), Newport, Ky. special 51/4" aluminum relay rock panel, socket for plug -in units and special hardware, together with full instructions and diagrams for assem- ing grid resistor. R is equal to the im- bling complete exciter. 2 -METER TRANSCEIVER No. 31A28, FU -40 Foundation, Spec. $957 , 97 pedance of the amplifier input, 500 ohms The transceiver shown in the diagram in this case. PARTS KIT. Everything needed to complete ex- can be fitted citer except tubes and power supply. Includes into a very small space. Since the output arrangement acts as all mica condensors, resistors, RF chokes, sockets, Power may be taken from a receiver or a voltage meter switch, 0 -200 mo meter, key jock, and divider, output voltage is less miscellaneous parts. amplifier or a pair of 90 -volt batteries than the tube input voltage. However, No. 31A28A, Special Per Kit, Each 9.37 DID YOU GET IT? THE BIG B -A 1948 Catalog No. 481 - to 2T N°I2 Everything in Rodio and Electronics. Write 6C4 6AQ5 if you have not receicved it. FREE on request. J /5 HI IMP PHONES M.005 SB CARBON

7 .05 MIKE TRANS BURSTi7A- APPLBEE 4TH 12 1012.14 WOE( SFREET. Y VHF CH 1001( KANSAS CITY 6. MISSOURI ,005 I TELEVISION RECEIVER -$1.00 T.0001 I Wive instructions for building your own television r. 16 pages -11 "x l7" of pletures, pictorial .. . dal !tied schencuirs. 17"x22" nmlplete sc,Onaticb il iagt loi & rhassi, layout. Also booklet of 1l i cornent instructions. voltage & resistance tables and trouble- 4.7K 270K shooting hints.-A11 for $1.00. 6C4 6405 .001 CERTIFIED TELEVISION LABORATORIES 1 4 Dept. C, 5507 -13th Ave., Brooklyn 19. N. Y. o6.3V RADIO -ELECTRONICS for

www.americanradiohistory.com Radio-Electronic Circuits 83 the amplifier input transformer steps it up so that a normal phono channel gives the proper gain. If higher output is Are YOU Fixing Radios wanted, use a plate -to -line transformer. LEARN RADIO The 6C5 is mounted inside the phono- this New, EASY Way? graph case. A cable brings filament and LEARN FAST . . . plate voltages to it from the main am- LEARN RIGHT . . . plifier. REMARKABLE ARMAND BRISSAC, NEW FEILER AT A PRICE YOU Ford -do -Lae, Mich. 4 "STETHOSCOPE' CAN AFFORD

1 -TUBE AMPLIFIER Method Guaranteed A. A. Ghirtvdi, Here is a 1 -tube phonograph amplifier Toughest with sufficient output for comfortable to Lick Easy- fo- u',derstand listening if a high -output crystal pickup Jobs! BASIC TRAINING 1,- 11 hl-fashloned j SENSATIONAL -NEW! why FM & TELEVISION seesiring IurllunO and CATHODE - RAY FOR BEGINNERS STETHOSCOPE Thou-? only 589.95. Get man- servicing ability? (Used by U.S. Army & Navy) ual for full stet... of radio servicemen II1010E COIL ex- The best training costs the least! S ualsin no Rh little terlenee -are already Ding radios this remarkable. Actually. Ghirnrdi's famous 972 - 'automatic- way. It's as Simple as A.B.C. because page RADIO PHYSICS COURSE Stethoscope Servicing is the n weal. ost basic book has given more Iiadio- all repairs. Stetho- "ethos! yet devised lm simplify Electronic beginners their start cope is goal anl..d to speed -up and lilt- Only 55 Servicing be book course lime y servicing ability or your money will than any other or flooded. You owe II IO yourself Io lind ut how ever published. Contains complete RADIO ran begin lashing in. Hlethasclpes m come its basic training to fit you for a side viably of prices from £9. 81 In £59.9 There'sTher s career in any phase of Radio - PHYSICS InSnlao. sh. In meet every peed. Dolt delay-send Electronics work. Over 300 pages COURSE Nqo s t,.í.51. make Basic Electricity easy to Get This FREE New learn. Other subjects include 31i Course. i is used. No tone control was found neces- Radio Transmission; Broadcast one giant book. Technical Manual Today. Stations: Receiving Units: Vac- sary, but if one is desired, a capacitor '.The Inside Story" mlains tal- uum Tubes; Inc1,1-We; Amplification: Photoelectric Cells; This 1 S11crt V,IS,n- a Loyd of :ln b.tfir sutu.rls. If broken into resistor may be nabie Iiillls and Iiv . and 1- megohm variable Illustrated 25-page Illil- 14-a+4511'titans I .old 11lln' you'd regard this bid complete - placed in series between the amplifier d eal Mania' leu, the Inside Sour book a banain a ' lflier 7,01 illustrations. 11f an amazing new servicing e111- Use coupon. Read it t, .I.tysr at our risk! grid and common negative. 1sl- alsonta Ilnlalllss tanal'Ie C. AICHNER, JR., Ithns 11151 kinks (Or lat cet' Tali,, A Complete Course in HARRY uay ml slant1 pr c str Erie, Pa. handling only manual FREE. RADIO- ELECTRONIC DON'T DELAY-GET YOUR MANUAL TODAY 1 A NO -LOSS EQUALIZER FEILER ENGINEERING CO.. Dept. IORC8 SERVICING 945 George St.. Chicago 14, 111. Learn professional service When an R -C equalizer is added to an rush n ml "T'bn Inside Story." I on- loss re- Clineerloso Stante to ncoverl handling. work at home! existing amplifier, its insertion Sandy n for a maid job as a duces the over -all gain of the circuit. Name Radio Faectronie servlee repair ex- pert! Its easy Io learn front nllir- Often the amplifier does not have suf- Address anlCs 1390yyge, pro(usely Illus- trated S1015Eí1N RADIO 51:ItV- 6SN7 lily II'ING dark That tacts you only .01 £"e nenplen e. Covers all phases of o--1 Only $5 the mot k. Explains senice test in- struments and when, where nd .1 .05 t50yr 2 E MODERN RADIO why to use cash type. Even tells how In 1,115141 your own. Tells hose to OUT SERVICING I0W,1,1,.situa all kinds of radios. an- ITRIO SURPLUS SPECIALS! Sir sils. test components, Learn to be a Service alyze' (heir EG 11 it( adjust - IN at home moka all IY'pes repairs. Expert - etc. ex- 2W - prnts, installations. Even ORDER NOW -BY MAIL! without an instructor! lains lam to snarl a stuvessful radio 0005 '1:..11 D.4ND5E'r5 sz.95= Servira bosun.. M ,lay Saving Combination offer. -10 UNITS. New 2.50 20k TI- TUNING 1151 :I0 CONTIDN. BOX. New 2.00 IL %NI ;F: FILTERS. New. 1,TC Navy 'Nile CUTS SERVICE TIME with rout mid ping 2.95 .49# +250V AItC -5 JACK 11115 IN HALF OUT OF BC348 ACCESSORIES }Whether you repo it todi'n profes- ' - The equalizer controls both treble and bass. 1T411. ASSF:\IIILIE9, Complete- s ally or luny- work with them ANT.. I1F, Dl -T. New, Each ..51.29rr as11)-, r, I, l ra r d l's RADIO ficient reserve voltage gain. I.F. TR,LNS. 912 KC .49= l' 11(11' BLEHIIOOT l 1t'S IIAND- l'ILLNK TUNING KNOB .39c :.IIIK rvan salt- )'out lilac 4114111514111S This equalizer, described originally in I1L -42A REEL SIOTOR & GEAR HON.... 1.95 ing almost :my job! .lust look Al RCIt5FT OUNSIGIIT NOISE FILTEIt .. .29= o the make and n1 nel of the radio The Review of Scientific Instruments, L1 .98n ant to tux. Rook foyers tmumon 0YE- ANI1 -11-1 DEAL/PHONES. -Z by ,nbl.' i In m'er 151111 receivers with- 111:191 -A PLUGS, New. 15e each or ..7 for 1.00= can be added to audio amplifiers -1 urers. Tells what to do G I.-RU RECEIVER COILS. 2- llend .59 mutar 1:1ní' do it. Over 300 As shown in the 3.95 to out reducing the gain. AN -51t DIPOLE & REFLECTOR sisthaml'illy page's enntain charts. data. Only $5 TELEPHONE' 8.95 moles. etc.. th'.tt graph, it provides up to 20 db of boost F:E -S FIELD ' Informations RADIO AIRCIUFT KNIFE SWITCH, Hvy. Dtv.. ill 10111 Y'w save time, do better or attenuation in the bass and treble t11DT .69 a lt i repairing any radio ever TROUBLESHOOTER'S DI'DT .49 ade. 744 big, manual -size pages. HANDBOOK channels. Both channels are controlled New 2.95 W. sells sit., 4 I1,+ Use coupon. .CPS -13 11YNAN1OTORS. book! with logarithmic potentiometers so that Used, but good condition V Price Includes Postage . ,. WL.., ring Offer! NOT study% Let R A D I O TROUBLESHOOTER'S CALIF. common +20 , BUYERS ALVARAD I O s n' 'Oe° HANDBOOK save you time on ADDSALES Dept. RC -5. 907 S. Alvarado .5041.., SAVE service lobs! Let MODERN RADIO SERV- sale C.O.D. you truly +10 TAX: Los Angeles 8. Cahforn,a ICING train for professional adioelectronic service work. Get both big MONEY! books for special prim of only $8.50 for the D5 0 two. Use coupon. 10 EASY TO LEARN CODE 20 Dept. RC -108. Murray Rill Books. Inc.. or increase Weed 20 50 100 200 500 IK 26 5K 1011 20V. It is t 11 to learn 232 Madison Ave.. New York 16. N. Y. an luatructograpll Code Teacher. ERE() CPS th prac- ^. Enclosed find $...... for 11mka Checked: or :l send Affords the quickest and most Ì will be. C.O.D. i1 l'. V.A. onli, and pay postman this shows maximum possible tone variations. tical method yet developed. For amount lulus postage. eve.. Graph sinners or advanced I t u dent I. uncles-stood return ifterll'u r .lu t Available tapes from beginner's satisfactory n itnce will 1,o refunded. r is flat when con- menage, on all the equalizer response alphabet to typical C RADIO PHYSICS COURSE SS 155.50 foreign) 5 to 40 WPM. nd,iecn. Speed range MODERN RADIO SERVICING SS 155.50 foreign) trol shafts are at mid- points in their Always ready -no QRM. n RADIO TROULESHOOTER'S HANDBOOK S5 (S5.30 insertion loss foreign) arcs. At these settings, the ENDORSED BY THOUSANDS! MONEY- SAVING COMBINATION of each channel is 20 db. The losses are The Distrurtopraoh Code Teacher literally takes the plate of an per - Handbook for only 59`50 a f or Ned two ($10.50 for- compensated by 20 -db triode amplifiers instructor and enables anyone to eign) ltor-earn and mast de without fur- following each network. ther sslslance.e Thousands of successfulu one ton have mired the mode" with the lnetnaetoerafll System. Name Insert the equalizer at a point in the Write today for convenient rental and purchase plans. amplifier where the input signal does Address not exceed 5 volts. This prevents over- INSTRUCTOGRAPH COMPANY city k ynnc Slate loading at maximum boost. 4701 Sheridan Rd.. Degt RC, Chicago 40, III. OCTOBER, 1948

www.americanradiohistory.com 86 -Try This One Nere s e ADJUSTING TV SETS When I go to a customer's home to Radio - SENSATIONAL Buy adjust a television receiver I carry a Television - Electronic mirror with me. Most of the adjustments COMBINATION are on the rear of the set. I have an Parts & Equipment Specials assistant hold the mirror as INTERCOM & RADIO the sketch TELEVISION-CATHODE RAY HIGH indicates so I can see the face of the VOLTAGE A REAL MONEY 2000 volt D.C. Power Supply 'Customers Say MAKER FOR YOU For an unbelievahly low price. we can supply MIRROR HELD AT PROPER ANGLE a completely filtered television or cathode ray "Intercom alone is worth -- _ -- 20011 volt D.C. power supply. Why bother with bulky and dangerous 60 your low price. R_ cycle supplies or ex- pensive R.F. power supplies when you can You get free o Pit SCREEN' REAR purchase a complete 2000 volt U.C. unit (not a kit). ready to plug into the 110 volt A.C. 6 tube radio in power line. The ridiculously low price has been REAR CONTROLS made possible this deal plus by a fortunate purchase of high quality components. These units are brand real utility!" picture tube. This not only speeds up new, completely tested and guaranteed. the installation process but also makes Price $7.95 Intercom Master Intercom for more accurate adjustments than the 4000.6000 VOLT TELEVISION SUPPLY imbibition Similar to the Shlon, Including 6-Tube Radio usual method of going around unit above. but has a much to the higher U.C. output voltage suitable for use Combines o top -quality 6 tube superhel receiver, front of the set after each trial setting with the new 7" and IO" television tubes. plus office or home intercom system in handsome of the controls. PRICE $12.50 walnut- r cabinets. Hi- Amplification 3 tube RADIO NOISE FILTERS intercom permits instant communication between H. L. FRAZIER, Eliminates radio extremely noisy radio reception due to -master and up to 4 remote sub -stations. Any Jersey City, N. J. power line disturbances caused by lights. refrigerators. remote station can coil the master while radio is washing machines. vacuum cleaners. elevators, oll playing; call con be returned to any remote station. burners. diathermy machines. etc. Operates on 110 volts AC or DC. F ilters out man -made noises in the broadcast. short. wave. and ultra -high frequency bands. It's handsome-Ws easy to install -It's easy to use! LINE -VOLTAGE CONTROL Designed for all radios. appliances, and electrical Price Includes Radio equipment consuming up to 1300 watts 112 amperes) Master, I Remote, 50' wire Poor line -voltage regulation is a com- at 120 volts AC or DC. Original retail price was mon evil in rural sections. Here is an Housed in a metal ease I sa" x 3" x 710- complete $94.50 with 4 remotes. Buy with male and female line connectors. from RSE and SAVE OVER economical and effective way to compen- PRICE ONLY $1.95 50%. sate for the drop in voltage which usu- Industrial Type Radio Noise Filter -Will handle up Brand new $2995 to 50 amperes. Housed in shielded case 3gá' a 3? ',' x -only 400 avail- ally 250 able. occurs at night. ". Edra Rummies -5395 PRICE $3.95 T CONTROLLED VOLTAGE OUTLET EASILY ASSEMBLED RADIO KITS MIDGET I.F. TRANSFORMERS 5 Tube AC -DC superhet kit furnished in a Back again -by popular demand! brown plastic cabinet of 4 3.15V artistic design. cab- RSE scores again with inet size (9 "x5 "x6 ") a new and bener 117VAC á I. F.! 400.500 KC range Variable condenser tuned; with 2 double tuned -114' square x g g 3.15V 3' high-ceramic based mica trimmers o - used 1 1 high gain iron cores -pep up old receivers, Tubes I2SA7, - í2S(17, I - 12SK7, 4 49 i ideal for new construction now I - 3525 and I 50L6 -and avail- lac "t". s able in either input or output types -for PRICE $11.95 5fantlartl tubes peak performance! Individually boxed Connect a 6.3 -volt filament transform- 6 TUBE 3 WAY PORTABLE in the colgrfwl RSE carton. List price $2.10. KIT LRI- input; LR2-- output; er as shown in the diagram. The sec- For operation on 110 volt A(' or I)C and ondary should be battery- Specify Type. rated at 1.2 amperes Superheterodyne circuit Matched Eggog Crate or higher Each and should be center -tapped. Full vision dial Doxen Rotating the selector switch will give High gain loop 36e 69c $3.95 Cabinet of Blue Aeroplane cloth finish. $29.00 three different voltages, the line voltage size 13x9')4x7" and two higher values. If Tubes used 1A7, 1H5, 3Q5, 117Z6 and the other 2 - IN5 VOLUME values are lower the NUt including tube. than line voltage PRICE $13.75 Eatra for reverse the connections to the secondary. kit tubes 53.75 CONTROLS 6 TUBE, 2 BAND SUPERHET KIT Our own private brand-made by RICHARD L. PARMENTER, Bands covered BC 550 -1600 KC and 6.18 MC a nationally known manufacturer. Power supply 105 -125V AC. DC The Middleboro, Mass. Full is o n dial kind that net for $1.09. Noise -free carbon con- Variable condenser tuned, with two double tuned struction,same standard shaft and bushing. Individually I. F.'s boxed in our colorfulcartoncarrying the RSE equalityseal Walnut veneer55KC cabinetbinet of approval. Complete with switch, SPEAKER full range of sizes. PROTECTION r PRI CE $15.75 10 M ohms 100 M ohms Speakers are very readily damaged 15 M ohms 250 M ohms each A 25 M ohms 500 M ohms 59c while being carried from customers' SCIENTIFICALLY DESIGNED 50 M ohms 1 Meg ohms PHONO SCRATCH per 10 homes to the shop and back. To prevent FILTER 2 Meg ohms Resonated at approximately 4500 cycles effectively 500 M Knurled Shoff asstd. 5 tearing the cone, I carry a 13 -inch- reducing objectionable needle scratch without alter- 50 ing the brilliancy 500 M ohms less switch, 39c each, of reproduction. 100 for $35.00 square sheet of heavy cardboard and Contains a HI -0 SERIES resonated circuit. Tested four screws by means of an audio oscillator and an oscilloscope and nuts with washers. The to give 22 db. attenuation with very low signal loss. cardboard is fastened Attenuation may be regulated by means of a SPECIAL TUBES to the front of the MINIATURE gain control. speaker by passing EASY TO ATTACH "The All- American Five" the screws through Just two wires Here they to clip on. Compact $ 1 L5 are -the fastest mavi's the cardboard and the speaker mount - Price P V ever mode -at RSE's long discount. Brand new, tested top -grades with ing holes. The washers are used under THREE TUBE PHONO AMPLIFIER regular RMA guarantee. Individu- the screwheads to prevent An assembled un it ready for installation using tone ally boxed the screws and volume control and six feet of rubber $2.95 in a -appealing from pulling cord Cartons: Know your supplier-his through the cardboard. Not Tubes) reputation. With Shoot us an order to- The few seconds necessary to attach Complete (Set of cTublesg $3.95 day -watch your profits zoom to- morrow! the cardboard to a speaker will often PHONO OSCILLATOR Wireless phono oscillator transmits recording for 12S A70T ...65 12S K 7GT ...65 12S07 GT ...59 save costly cone replacements. crystal pick -ups or voice from carbon mike through 35250T... .49 5016GT. radio without wires. Can also be used as an tercomm ...65 ROBERT M. BOSCH, by using "All -American Kit ", one each of above .. $2.98 P.M. speaker as mike. Price Philadelphia, Pa. (excluding tubes) 1$2.95 With Complete Set of Tubes $3.95 ORDER INSTRUCTIONS SPECIAL! SPECIAL! Minimum order -52.00. 25% de- Mammoth posit with order required for assortment of radio and electronic all DIAL SLIPPING parts, not less C.O.D. shipments. Be sure to include than TEN POUNDS of new Demand This When I get a receiver in which transformers, chokes, condensers, resistors. Seal of Qualify sufficient postage- excess will be the switches. coils, wire, refunded. Orders received without dial hardware, etc. A super- cord slips on the tuning shaft, I buy for experimenters, service- postage will be shipped men. and amateurs express collect. All prices first remove the cord. After wrapping for only $1.25 F.O.B. Detroit. two thicknesses of rubber tape around Satisfaction guaranteed on all merchandise. the shaft, stretching the All prices F.O.B. New York City tape fairly WRITE FOR FREE CATALOGUE tight, I restring the cord -and go on to the next repair. It's a sure cure! RADIO DEALERS SUPPLY CO. JOSEPH A. DESBIENS, 135 Liberty St. New York, 85 SEEDEN AVE. DETROIT 1, MICH. Fall River, Mass. N. Y. RADIO -ELECTRONICS for

www.americanradiohistory.com Miscellany I 87 ago aÒ10 TI)lrtp-jflbf Pfal'S BUYS ! FOR 31n 5nnebarl; tJubllratlon9 4 TERRIFIC HUGO GERNSBACK LEO og VALUES! Founder SAVE s'rl)(K UP NOW at up to i condi- Modern Electric, 190E 8ll off list. Perfect Most Electrical Experimenter 1913 ON tion, unsealed cartons. Radio News 1919 types in stock -ALL GUAR- Science & Invention 1920 TUBES! ANTEED FOR 90 DAYS! -Craft 1929 Radio an. 37, 30, 77, 84. 85. Rt), 5114. Short -Wave Craft 1930 01111. OK?. 01,7 39c of America 1908 or ,:x7 Wireless Association 0A4. r 1 t. 71. 70. 75, 51'4. 5Y3, 51-4, 1A7. 1LY5, - - r:FS aLS. 0.15. (MO, 111,0. have 788. Y Some of the larger libraries in the country still 11sK7. an7. 7A7, 49c miles of ELECTRICAL EXPERIMENTER on Ole for nterested readers. Ntïer xg.x2ls", ttiaó ^ $ .911 TUBE GT size 41,í^ mi. x 3va^) EXPERIMENTER, p"r t"'1 1.25 In ELECTRICAL CARTONS \Ie,liun, I ,'a^ x,,. x 4, j') 14-r 100 1.49 P lain white n Per IOa 1.79 October, 1914 LarR, - 1 x 5, Condenser Rotary Adjustable Variable W I R E RECORD.PLAYEACK SWEEP H EAD -Precision built. Triple - by Frank H. Broome FM and TELEVISION Coll (record, playback, e 4-pin plug-in type. Moulded The Colin -Jeance System of Radiote- 534.95 haeRte housing (II 4. x t^ SIGNAL GENERATOR 'Cl, accurately "1"' grooved lephony for maximumm fidelity C s n i Accurate! -Aligns FM and television receiv- llcity. An Experimental Wireless Telephone ers. Frequency range 2 -227 MC. Output mod- tit pp- $6.95 Onmodulated. High frequency insu- plientions by Shney ulated or WIRE HEAD SOCKET- l'olorlzed, moulded bake- Paul lation throughout, built -in power line filter in, Fully sit imbed .38 A Neat Lead -in Insulator and special Midline capacity tuning condenser. L we Easy to operate -use it to adjust to new TV by H. Clifford Bullard to Here's a POWER CONTROL UNIT -25 watt - channels. AC only. Exceptional opportunity 3511 o11n, nce,rlat mud. eath- A Non -Inductive Potentiometer purchase instrument of this kind direct from Terrific r'4.n,,l metal e 431.1 sol x3 ^i. manufacturer at a tremendous saving! ' " stil., e bronze pointer by Clifford G. Burr Item ... ó111,b. Shoe.' 114. 4 Ib .. .911 How to Make a Variable Condenser 'OUNCER" OUTPUT TRANSFORM- ER .1." 1 3 111,11 2000 ohm tapota by Edgar Felix .I..p1.le Ill. :In' to ,1. Fxrel. AM I11:.:' u...1 ,II II lens; ,r-e e tubes .49 "Aeroplane Wireless" 12 for 5.00 The Lieben -Reisz Gas Relay vs. the SIGNAL UNIVERSAL AUTO SUPPRESSORS for s,ork plug o Audion GENER- . .07 18 for 1.OÓ Ilrnnd preelsion by Eugen Reisz SOMETHING nitwcocontaining: r." ATOR mnd0iniature, 3I meg. cul: choke 12500 INCLUDES KITCHEN SINK r ohms DCI; resistors, Mirk ;41,_ $32.50 HEARING AID condenser, etc. All SUB- on 1 ^Iketlt, chassis .21 -49 ASSEMBLY Onlr "'" $1.49 Kl', MC. 8 IIF hands. Frequency coverage 100 71 r stable terminal internal mod- ulator. RP ttnuaor.t Ca, Isoe follower out- RECEIVED YOURS RHEOSTAT put tube. At' only. t An indispensable service shop YET? but ruurent. SPECIALS!! All famous makes: " shafts. "RECORDING COM- ohms. PONENTS 6 ACCES- s- tt - 250 SORIES" 9 6 for 1.98 39e "NEARING AID 6 MINIATURE PARTS" 9 .ill watt - 15 ohms. 98e ALNICO MAGNETS g 6 for 5.00 "RADIO 6 FLEC 100 watt 75 duns. TRONIC C O M P O- - NENTS" ea. 2.49 Rr a CRYSTAL MICROPHONE. Sensitive din - phmgm 1ype. pall size lia." O.D.. to the - This unique televiser is able fo appeal ^ deep; ideal) for REGULAR or CON SPEAKER. taste, as well as the sight and hearing of the 2 -WAY TACT MIKE or s PILLOW IbJlncr shark -mid. metal frame. Less looker -in. Everything is here but the bathtub. .95 INTERCOM SYSTEM sl 4.95 1...,.. ea. ALNuC,1 MAGNET, I SI'FRIa1FNTAL KIT AID Rar. .Do SIMPLE HEARING Master and .., n . .., rfill Has 4" l'?I

l'nll.. .11'U1'. . (Fcrmerly priced at $37.50) lots of 6- S12.95 LEOTONE'S "JUMBO RADIO PARTS DYNAMOTOR KIT" S5.95 BIGGER & BETTER THAN EVER! ! Yes. the NEW "JUMBO RADIO PARTS KIT" of - Out- HAS PROVEN ITS VALUE to hundreds of Radio aril men -17 FULL POUNDS of new & dismantled 4lntput radio & electronic parts -COILS. TRANSFORM- ERS. WIRE, SPEAKER REPAIR PARTS. RE- KEY. HARDWARE. 41111 MA SISTORS. CONDENSERS. oillenl. In- etc.. etc. All these and MUCH MORE $2.95 12 21 for only P Sall.. 1)C'r Typo (Shipping weight 21 lbs.) Pb: 133A5; pow- er sup for ply RCA VICTOR POWER TRANSFORMERS for models ßl`223. 45. r,2 or 75. Unshielded. _sling. wt. 7 11,... It-32. 55.95 110V. AC MOTOR. Approx. 1750 RPM. Shaded polo. frn,4. 11.P. pole( perst in for Record ('layer.. OhlIL Racked by ECA with RMA Guarantee 3 III" .haft. Overall: 2 t x- -s x 1. - Sh1 .. n . - 11 s - 1.29 Deposit Req. On all COD'S find check (or money order) I] in full Min. Order 52.00. 2006 Enclosed PLEASE ADD SUFFICIENT POSTAGE . . EXCESS 20 °. deposit. bal. COD for the following: REFUNDED Send mo FREE ECA Bargain Bulletin FM Sig. Generator $34.95 E Dynamotor 35.95 AM Sig. Generator $32.50 J Intercom $14.95

Name Address

City Zone.... State OF CONES AND FIELD COILS Originally made for King George IV, and now MAKERS STREET NEW YORK 7. N.Y. demonstrated by Donna Meinzer of Zenith's 65.67 DEY ELECTRONIC CORP. OF AMERICA -5 hearing aid division, this 24 karat gold instru- WORTH 2- 0264 ment was the most advanced modern hearing 353 W. 48th St. New York 19, N. Y. 12000 SO FT OF RADIO FARTS aid of 1829. It is strictly non -electronic. OCTOBER, 1948

www.americanradiohistory.com 88 New Patents- HARMONIC GENERATOR EVERY Patent No. 2,443,094 SERVICEMAN Wendell L. Carlson and Hugh L. Donley, Princeton, N. J. (assigned to Radio Corp. of America) CAN These inventors use a nonlinear ceramic con- denser to generate r.f. harmonics. The element may be 80'; barium titanate oxide and 20% strontium titanate oxide. This dielectric is coated with metal electrodes. The unit may be about 1.5 mils thick and 5 mils in diameter. Such a con- denser has almost no resistive component so TEST EQUIPMENT NON-LINEAR TITANATE CONO

INPUT THE NEW MODEL 770 - OUTPUT An Accurate Pocket -Size VOLT -OHM MILLIAMMETER (SENSITIVITY: 1000 ONMS PER VOLT) Features: there is negligible power loss. Its nonlinear I'UUNaet- Ineasnl es semi,' x Sib- x 2% . transmission produces l'.es latest harmonics. design 2,, aerorate 1 Mil. D' ,trsunval type The ceramic mSmeter. capacitor is used to couple two ame zero adj tisunent holds for both resistance ranges. resonant circuits. The input is tuned to the It is mnr necessary In m adjust when switching from one fundamental, and the raidanl'e entice In another. output to the desired This is an hnnn'taft time- harmonic. A saving feature never before included in :, V.O.M.t in this battery and bypass condenser are prier l :nllgr. also connected between the circuits. The capaci- (finned in ruund-rrrurremi. Molded c tance varies with the voltage lIent.tiful black etched panel. Depressed letters filled across the ceramic with permanent wldle, ounces lungii fe even null ton- unit. When the d.c. bias is set to zero, only odd harmonics can be Specifications: a A.C. VOLTAGE RANGES: 0.15 30 150 generated because both 30 00 volts. halves of the wave are affected equally. With the e D.C. VOLTAGE RANGES: O-Ta -a 15 75 150 750 1500 volts. application of d.c. bias, the r.f. current becomes D.C.D CURRENT RANGES: 150 Ma. 0nm. Amps. nonsymmetrical and even harmonics 2 RESISTANCE RANGES:Ra NDE S: 0.500O -SOO ohm. O -1 MeeoN m. are gen- erated. The bias may be set to optimum for the The Model 770 comes lest lea with desired harmonic. self-contained batteries, test leads and

all operating I instruction N ET We m a oufacture a" a complete mine of radio test equipment. PHASE SHIFT IA PD. BY Write Dept. RC -10 for FREE catalog today! Patent No. 2,442,097 SUPERIOR Stuart W. Seeley, Roslyn Heights, N. Y. INSTRUMENTS CO. (assigned to Radio Corp. of America) 227 Fulton St., New York 7, N. Y. Out -of -phase current:: into a goniometer coil system are generated by this system. The two coils L in Fig. 1 are fixed and at right angles at your regular jobber to each other. Currents through tbem must be L

L2 d1 000aL 0 1 Collins c.4nnounces: O Fig. I -Coils L are fixed. L2 may be rotated. COLLINS CUSTOM 90 degrees out of phase. The movable coil L2 COMPONENTS is coupled to the others. When it is rotated, there is more coupling to one fixed coil and less to A complete high fidelity radio receiving system from antenna the other. to loud The bridge circuit in Fig. 2 is the general speaker matched by engineers. schematic of this invention. The two fixed, similar goniometer coils are shown as L and their internal resistance as RI. The two con- FM densers C are equal and the resistors R are also AM TV PHONO entail. Calculation - shows that, under these con- Matched units -May be purchased separately as or a complete ACIN II package- Add -a -unit system

THE COMPLETE SYSTEM COMPRISES: I. New, improved Collins 19 tube FM /AM tuner with Bass and treble tone controls, FM squelch, Pickup equalizer tube. 2. High fidelity amplifier (12 watts, triode output) Fig. 2- Bridge shows theory of the invention. 3. Record Changer (intermix, with G.E. cartridge) 4. 12" P.M. speaker (wide range) Bitions, ambient temperature variation may 5. Antenna system (for FM and TV) change the Q of the coils, but does not affect the 6. Transcription player (dual- speed, precision arm) phase of currents through L. This is very im- 7. Television chassis portant in precise systems such as shoran and (12" and 15" screen) loran. Write for interesting brochure describing this wonderful equipment. very finest radio receiving Learn how you may obtain the equipment -all from one source. No more hap- hazard purchasing ekes of equipment with matching problems. of different COLLINS CUSTOM COMPONENTS are matched at the PULSE TIMING factory for top -notch, efficient operation. You will save money too. Patent No. 2,442,769 David E. Kenyon, Smithtown, N. Y. COLLINS AUDIO PRODUCTS CO., INC. (assigned to Sperry Corp.) P. O. BOX 368 'Phone Pulses controlled by an R -C circuit are not WE -2 -4390 WESTFIELD, N. J. as reliable as those controlled by a tuned circuit containing inductance and capacitance. However, RADIO -ELECTRONICS for

www.americanradiohistory.com New Patents 89 accurate timing can be provided by coupling a dune multivibrator to a resonant circuit as is here. V1 and V2 in Fig. I are the multivibrator Crystal stage Most Efficient tubes. They feed into a cathode- follower Lightest V3 which includes the parallel tuned circuit L -CI. This controls the multivibrator input. Re- of V3. sistor R is used only to limit plate current Pickup Cartridge Ever Conceived! Initially VI conducts beoause it has no

A

OZ. SIZE WEIGHS ONLY ACTUAL 5

time pulses. Fig. I -The LC circuit serves to

grid bias. The largo VI plate current produces a negative pulse through C2 at the V2 grid, cutting off this tube. VI, in turn, conducts. A short time later ishown as tl in Fig. 21 con- V2 denser C2 has discharged enough to permit to conduct and to cut off V3. At this instant positive pulse with a fiat top appears at ter- minal A. At the same time a differentiated pulse may be taken from B. The abrupt drop in V3's current induces a :urge negative voltage across 1, -C1 and therefore :oases VI to cut off. The tuned circuit tends to seillate at its resonant frequency. After a half -cycle. however, the VI grid returns to zero and starts to go positive. This places a low -re- TORQUE A{0 vOLTAGI B{0 NEW SERIES 12 ti t2 13 14 TIME Fig. 2- Pulses which appear at the terminals. DRIVE sistance shunt (grid -cathode circuit of the tube, eroes the tuned circuit and damps out oscilla - tions. As VI conducts, V2 cuts off und VI con- ducts. At this time It2 in Fig. 21 the flat -topped pulse ends. OF RECORD GROOVE TO CRYSTAL C2 is dis- BETTER COUPLING After a definite interval, condenser amazing improvement charged enough tu permit V2 to conduct again. Exclusive Electro -Voice development now brings cycle repeats opens This is time t3. Now the previous in record playing ... outmodes existing crystal pickup cartridges ... itself. Fully tested and proved ... the fiat -topped is gov- up vast new replacement opportunities. The duration of the pulses a more rugged cartridge for erned by a tuned circuit and all pulses acre new Series 12 TORQUE DRIVE provides is and coin - exactly the same. Duration between pulses everyday use in home phonographs, booth demonstrators, contro led by the discharge time required for the operated machines. Assures finer reproduction, less surface noise, less capaci or C2. needle talk, less record wear, longer record life, more needle plays! 3 BASIC MODELS REPLACE OVER 100 STANDARD TYPES Comes in low. medium and high voltage outputs to provide universal Speeds servicing, steps up your profit. Installation is simple. replacement. -tip Each cartridge is furnished with replaceable Osmium -tip or Sapphire long -life whisker needle. It is available individually or in kits. List price, $7.50 Series 12 with Osmium -tip needle List price, $8.50 Series 12 with Sapphire-tip needle New MICROGROOVE Model L -14 ,tsk your E -V Distributor. or send now for TORQUE DRIVE Crystal Cortridge now Bulletins 141 and 142 available -at some price. New Model 20 MAGNETIC Pickup ELECTRO- VOICE, INC., BUCHANAN, MICH. Cartridge also available for REGULAR MICROGROOVE records. Uses match- Export: 13 East 40th St., New York 16, U.S.A. or Cables: Arlob ing Transfilter.

S app's? cd by E. R. u nolaaar. Walla Walla, Wash. ANOTHER FIRST BY "Don't mind me Lady -I'll have this radio fixed SIcretracc, _. In a jiffy." 1 OCTOBER, 1948

www.americanradiohistory.com 90 World-Wide ,'Station List

Edited By ELMER R. FULLER

WELL, fellas, you asked for it, world shortwave stations that can be and here it is. I've got a job found in no other volume in as complete to do, a BIG job, and I need a form. It is to be printed twice a year MONEY SAVING PRICES your help to put it over. In and the third edition will be published On all Public Address and Inter- the future, this department will be pub- in November. communicating Equipment lished in two installments. Then we will SEAC, in Colombo, Ceylon, is now be- NEW! skip one issue, in which the FM station ing heard weekdays from 2330 to 0130 WEBSTER. list will appear. The station list will on 15.120 mc. Other programs are heard CHICAGO thus be printed complete in two issues on 9.520 and 17.730 mc, 3:1 I :1 Itl' \I Recoil' but we do not Changer for new Colum- instead of three as in the past. Now have the schedule of bia type microgroove these transmissions wog playing records. then, here is what we have to do: show from Ceylon. Willi base. Similar in that the readers of this magazine appearance to Model 55. really The Danish station is now being heard Model No. 133 - want this department, that they are on 15.165 me from 0900 to 1100, EST, grer $38.75 reading Pria .. it, enjoying it, and wish to see and reports of reception will be very For 33 it not 1/3 and 78 11PML only continued, but enlarged to much appreciated. They may be sent With automatic stop. its pre -war Similar to Slo.iel 130. status. Many of you will direct to the station at Rosenornsalle 22, Plays new and Old type remember this recants.verts. Model No. 256. department when it was Copenhagen, Denmark. Reports will be called "On Pria .. $34.60 the Ham Bands" and will answered by letter from the director of remember the features of Model 246. Similar to that era. Well, the shortwave department. Model 236 above but we are going to put those same features The le, alplegal le slip. State of Israel is being heard Your back into print again. I $29.85 CHOCK FULL OF BUYS: have been look- very well on the east coast several times ing over some of the station lists of each day. The present schedule is from those days, and the old ideas are gradu- 2155 to 2245; 2400 to 0015; RADIONIC EQUIPMENT COMPANY 0330 to ally taking shape again. Several of them 0500; 0600 to 0615; and 0930 to 1345. 170 NASSAU ST., NEW YORK 7, N.Y. will be put into use in future issues. The frequency Tribune Theatre Entrance in use is 6.840 mc. Tel. WOrth Pictures? Yes, we 2 -0421 Coble "CHANSLOR" /A.. '. want pictures of lis- If you want a really neat card tening posts, to put rare verification cards, and in your collection, listen for ZQP on RADIONIC the like. Here is where EQUIPMENT CO.. Dept. 1010 your help comes 3.910 mc from 1000 to 1200. The an- 170 Nassau in. Street. New Yak 7. N. Y. Send reports on your shortwave ac- nouncements are in English on Mondays Send at once ;;our free catalogs, supplements and bar- tivities, and any information you and gain lists as published- listing products of leading may Saturdays. The quarter -hour time manufacturers of radio- electrmle parts and equipment have on schedules and frequencies. If interval is the beating of African drums. NAME you have good up -to -date photos of lis- Other frequencies used are 7.220 mega- tening posts, P.O. BOX or MEET good verification cards cycles and 9.700 mc. send them to us and we will give the Let's hear from you, TOWN STATE and give us the N. wr,m = sender full credit if they are used, and help we need to put this department ======m1 will in see that they are safely returned to the number one spot of RADIO -ELEC- the lender, if he informs us that they TRONICS. My boss tells me that I are if can UNUSUAL OFFER desired. supply any really good material he can Recently we received a new book find space to publish it. This removes which was published recently in Den- the war -imposed barrier of lack of Basic 'Scope Kits! mark. It is known as "The World -Radio space, and gives us a wide-open Handbook chal- Use for oscilloscopes-modulation monitors - for Listeners." This is the lenge. So, you can see, your editor is television repeaters- experimental jobs best book Buy complete of its kind that I have ever in need of help from the readers, and at special savings or any item: seen, separately at thew rrain pr ires and I heartily recommend it to all here's hoping that they make good for of our readers. It 3" TUBE KIT gives information on him -Hi! HERE.'S N II VT YOU Free. Station GET Location and Schedule Free. Station Location and Schedule 1-Pou'rr 't 23ÚY 50 -70 cps .iit i'r . -__; c. I.:dna, 2.3V/ 2.500 WWV WASHINGTON. D. C.: U. S. Bureau 4.810 HJBB CUCUTA. COLOMBIA: 1700 2200 1.75A. L.I(- 63. ,, IIV 3.\ $5.25 of Standards; eont iuuiusly 4.820 XEJG 3.310 YVIRO GUADALAJARA. MEXICO; 22000o to 2- Filter Chokes: 8 lly. 1101115 $1.23 ea 2.50 TRUJILLO, VENEZUELA; 1700 to 2100 2130 4.820 HJED 1 -fond. 25.23n,í,1. 2000V D(' CALI, COLOMBIA; 1900 to 2200 oil filled 1.25 3.340 VUD3 DELHI INDIA: 1201 to 1245 3-Conti. 4mfd. 600V D(' oil filled 60e ea. 1.60 3.370 YVIRT MARACAIBO, VENEZUELA; 1730 to 1- 31t1' -1 Cathode ray tube 2.50 3230 3.380 YV5RY CARACAS. VENEZUELA; 111130 1- Dlheptal socket to for 3BP -1 .35 ' 111 3.390 YV4RK MARACAY, VENEZUELA: 1X110 to $13.65 J I 3.390 COLOMBO. CEYLON: 11730 to 1200 Yours Complete at ONLY $9.95 3.400 YVSRW CARACAS, VENEZUELA; 0530 to -2:111 3.420 YV2RC MERIDA, VENEZUELA; 18110 to 2130 5" TUBE KIT 3.440 YVIRU MARACAIBO, VENEZUELA: 1900 t9 21:11) 1 Power Tram tic : -ITT. l'ri -113 oiv 3.460 YV4RP VALENCIA. 33 -65epr See- 12011V 2ui1. 2.3\', 1.73.(, VENEZUELA: 1730 to 11.4V /.6A, n,{\' /u,\ 21 311 $5.50 3.480 YV4RQ PUERTA CABALLO. VENEZUELA; 1 -L.Y. Pincer Transformer: l'r1 -115 /230V i7011 In 21311 .3- li3rps. ? e -TORV CT /llama. 11.5V.'4. \ 4.75 3.480 ZQI JAMAICA, BRIT. WEST INDIES: 2-PlIter Chokes: 8 IEy Il11nla. $1.23 c Pow to 2200 2.50 3.490 YV3RS 1 -Coed. 25.23mfd, 2000V DC BARQUISIMETO, VENEZUELA; 1030 oil filled 1.25 u 21911 3 -Cond. 4mfd, 000V DC oil filled. Coo ca. 1.80 3.500 YV5RX CARACAS. VENEZUELA; 0:130 m 1 -5CP -1 Cathode ray tubo 141111; 1530 tu 2311 3.50 3.510 YV6RC 1 Market BARQUISIMETO. VENEZUELA; 18011 for 5CP -1 .35 to 2130 1-Clip for 5CP -1 third anode .25 3.530 YV5RS CARACAS, VENEZUELA; 0330 to $19.90 3.910 20P LUSAKA. SOUTHERN RHODESIA: Polo tu 121111 COMPLETE ONLY $14.50 4.040 PONTA DEL CADA, AZORES; 1700 to 1:1011 4.100 HCJB QUITO. ECUADOR, 181111 to 22311 SCOOP PACKAGE 4.700 201 KINGSTON. JAMAICA: 16311 to 1830 4.750 YVIRV MARACAIBO. VENEZUELA: 0530 to ill(P -1 Cathode Bay Tidies Neu- hi 21:0 original cartons $9.60 A BUY at 4.770 YVIRY CORO. VENEZUELA; 1000 to 2130 minimum order -69.60. 26ee deposit with order 4.780 SINGAPORE, 0343 0 for MALAYA: to all C.O.D. shipments. 6e sure to include 1111111: 2930 to 111311 sunicient postage -excess will be refunded. without Orders . 7.780 YV4RO VALENCIA. VENEZUELA: 16311 ostage ill be shipped express collect. to Aredn prices F.O.B. N. Y. City. 21:10 4.780 HJAB BARRANQUILLA, COLOMBIA; 171)0 to 2 S. KLEINMAN 4.790 BANDOENG. NETHERLAND EAST Suggested by Arthur Traufïer INDIES: 11731) to 110111) 96 Gold St. New York 7. N. Y. Council Bluffs, Iowa 4.810 TWIRL MARACAIBO. VENEZUELA; 0530 to -230 "The Unfinished Symphony." RADIO -ELECTRONICS for

www.americanradiohistory.com World Wi.Ic Station List 91

4.830 Y'V2RN SAN CHRISTORAL, VENEZUELA: 1100 to 2130 OPPORTUNITY AD-LETSI 4.840 YVIRZ VOLERA. VENEZUELA: 1630 to 21 r a word for ONLY IS THE COST!, BOGOTA, COLOMBIA: 1900 to 2- Advertisem,:. -. Iioo Lost 25c $89.50 4.850 HJCA and must be 4.860 PRC5 BELEM. BRAZIL: Imllll to 07011: o: each innerttol. address initials 2690 except SII.. included at the .,he,e rate. Cash should accompany to 1100; 1539 to by an lays ail classified gdvertisemena unless placed 0600 . accredited advertising agency. No advertisement for 4.880 HJFH ARMENIA, COLOMBIA; discount 2200 less than ten words accepted. Ten percent Issues. Objec- 4.890 H1CH BOGOTA. COLOMBIA: 1800 to 22' s issues. twenty percent for twelve 0430 to li i or misleading advertisements riot accepted. 4.900 ZOH COLOMBO. CEYLON: tionable reach 4.920 CR7BU LOURENCO MARQUES. MOZAM Advertisements for November,mbe948. issue, must 16. 11 1330 to 1600; Sundays. lib DOI s : BIQUE: N. to 1300 Radio- Electrania, 25 W. Broadway. New York 7, Y. 4.920 YVSRN CARACAS. VENEZUELA; 0600 t.. 22311 06110 to AT 4.920 HJAP CARTAGENA. COLOMBIA; 26 YEARS EXPERIENCE RADIO REPAIRING 13011; 1700 to 2200 I've perfected simple system you an fol- 0645 to 1115; your fingertips. repair 4.940 HJCW BOGOTA, COLOMBIA; low step by step. No formulas or alculatlons. Cuts 10011 to 2315 minimum. Teal price $2.00 postpaid or COD. 1000 to 1400; tittle to 4.950 HMO BOGOTA. COLOMBIA; Slate' -hack guarantee. Roos Radio 14613 -T Grandriver, 17011 to 231/0 Detroit 27. Michigan. 4.960 HJAE CARTAGENA. COLOMBIA; 1600 to 2230 SERVICEMEN. BEGINNERS MAKE CARACAS. VENEZUELA; 0530 to RADIOMEN. - We 4.970 YV5RM more money, easily. quickly. $250 weekly possible. 02'111 -31L VENEZUELA: show you Merit 4.990 YV3RN BARQUISIMETO. Avenue, Springfield Gardena 13. New u218York 11130 to 2230 132nd 5.000 WWV WASHINGTON. D. C.: U. S. Bureau day and RADIO AS A HOBBY ('AN PAY ITS WAY. AND of Standards: rorulnuausly Argenthte, Box 57C, night yours t Write: Federal Grand 5.810 MOSCOW. U.S.S.R.; schedule on- Kansas CityoWri for the SENSATIONAL -NEW- IMPROVED known 1800 to COMPLETE BRAND NEW 5.840 PZH5 PARAMARIBO. SURINAM; THROAT MICROPHONE SASCO. 0 INCH 21143 T -311-S. 50c or 3 for $1. Merchandise list free. Calif. 5.870 HRN T IoGUC1 GA3Ppto, HONDURAS: 10838 Ventura. North Hollywood. 1000; 0300 2343 DETAILED 5.880 IRK CAPETOWN, SOUTH AFRICA: TELEVISION: BUILD YOUR OWN. 0411 KIT Los Angeles 1, TELEVISION In 0130: 11(10 to 1600 plans 81.00. Teleprint, 8341 E. 74th St.. 5.980 ANDORRA; 011011 to 08311: 1300 to 1900 Calif. less tubes 5.890 MOSCOW U.S.S.R.; 0800 to 1645 2330 and 5.890 OAX42 LIMA. PERU: 1630 to YOU CAN a Complete with 13 channel tuner, all parts 5.910 OZX4V LIMA. PERU. 1800 to 2400 receivers thtsigo 1nalats generator. tti easy step.hy -step following instructions and 5.950 HH2S PORT -AU- PRINCE. HAITI: 0600 to Mol:eylack guarantee. Chas. Gates. Pecos 2, Texas. to 2130 $1. schematics. 0813: 11110 to 1300: 1730 COMPLETE THEORY MOSCOW. U.S.S.R., 2300 to 1000 AMATEUR RADIO LICENSES. less tubes 5.950 RVIS for radio examinations. Home $89.50 5.970 HVJ VATICAN CITY; 1000 to 1100 preparation IIInstitute. ARGENTINA: 18011 sidentincourses.. all tubes $149.53 5.960 LRSI BUENOS AIRES. New York City. See our ad on !'age 94. Kit complete with to 2300 101 West 63rd St.. Cost of cabinet $25.00 6.000 IFV GEORGETOWN. BRITISH GUIANA. GROUP OF MIEN. GRADUATES OF WEI.L- SELECTED new TUNER 11343 to 0745: 0943 to 1145: 1415 knrown trade seheoh desire employment In Radio Field. Using radio servicing. instal- and factory aligned EforTthe television tu 1945 Will travel anywhere. Qualified in Installs this unit MONTREAL. CANADA' 0700 to 231: instruments, circuit operation. etc. Contact spectrum. The kit builder merely 6.000 CFCX lation, test makes three connections. Contains 6.000 HPSK COLON. PANAMA: 11730 to 2300 Placement Dept.. Eastern Technical School. 888 Purchase Into hit chassis and 6.010 ZRH JOHANNESBURG. SOUTH AFRICA: Street. New Bedford. Mass. an oscillator andanti compact. Usng newnnI.Fr coils whichhiche Pro- 2113 to 01311; 091111 to 11110 FOREIGN. DOMESTIC, small Sound NOVA SCOTIA: 0530 to MAGAZINES tltMK DATED)- vide maximum gain and picture definition. 6.010 CJCX SYDNEY. Books. booklets, subscriptions. pin -ups, etc. Cata- F.51. for complete listen- 22110 arts. New reception is high quality log loi (refunded). Cicerone's. 883 First Ave., 6.070 COLOMBO. CEYLON; 1930 to 1200 ing pleasure. 0700 to 0800; York 17. N. Y. 6.020 !MX BOGOTA. COLOMBIA: SAME TELEVISION complete Ism 14110 to WE R1:PAIR ALt. TYPES OF ELECTRICALINSTRU- I compete with all 90 MEXICO; 0700 to 11100 tube checkers d analyzers. Hazelnut Instrument 6.020 XEUW VERA CRUZ. menls Liberty Street. New 6.020 FZI BRAZZAVILLE. EQUA- Co. 1 Electric Laboratory). FROM STOCK TORIAL AFRICA: 1120Q to 18: Yrk, Ter 17 Li IMMEDIATE DELIVERY Illlin to 01311 436 BOWEN 6.020 PGD HILVERSUM. NETHERLANDS: 1743 LANCASTER, AI.LWINE & ROM 1sIF.L. to 2330; Tues.. 0300 to 04x,0; Wed. Washington 5, D.C. Registered Patent Attorneys. Building. and & Sat.. 10:10 to 12110: 1600 to 1730 PlaGice before United States Patent Office. Validity un- Booklet and 6.030 MOSCOW. U.S.S.R.; schedule infrngement Ineestlgations and Opinions. The New known form 'Evidence of Conception" forwarded upon request. B -45 0100 Model 6.030 CFYP CALGARY. CANADA: 0730 to 18011 to IN Battery 6.030 HP58 PANAMA CITY. PANAMA: BRITISH RADIO DEVELOPMENTS. EXPERTS Operated 1111311 Britain parethese 6.040 RANGOON. BURMA: 0913 to 1015 cés.l fully explainemd by leadinga leehntcialns in- 6.040 COBF HAVANA, CUBA: 0000 to _:300 cluded regul try in foremost British radio monthly. PRAC- SIGNAL 6.040 XETW TAMPICO. MEXICO: 0745 to 111145 TICAL WIRELESS. Features include constructional de- 6.040 WRUS BOSTON. MASSACHUSETTS: 100 tails. help and advice columns. and much of unique in- t. 2" 10 both amateur and serviceman expert. Read every' 0230 terest to GENERATOR 6.060 TETUAN. SPANISH MOROCCO; wh ro by enthusiasts who wish to "keen head" in Inter- to 0:101: 1330 to 1500 trade or amateur DX field. Rush order nor. For AMI. 0430 to 1005 national only for servicing 6.060 KNBA DIXON. CALIFORNIA; anneal subscription mailed direct from London. andsend FM and relevisi'n . 2301 to 0030 s 111111 LONDON. ENGLAND; Newmes, Ltd., il'W.FO, 342 t 6.070 GRR 0030 $2.011 to George Receivers. R.1' s CFRX TORONTO. CANADA: 0600 to New 17. 4 6.070 0300 Avenue. Volk Ree ever D 6.080 CKFX VANCOUVER. CANADA' 0930 to Kilocycles i 6.080 Munich III 0645 .O9Ó IO BUENOS AIRES.RES. ARGENTINA; In a1 font 11, l p 221111 1_ to town i 11010 to 0030; 1400 B "T" BOOKS "ith 6.090 LUXEMBOURG: IIl Mlc. to 50 Mc. Ilannmla ,. - to 1630 test lead. setf-rnntained bat 0730 to 1941; shielded $27.75 6.090 CBFW MONTREAL. CANADA; teries and instructions. NET 211110 lo 2100 FREE to 2150 6.090 ZVB7 SAO PAULO. BRAZIL: 1600 6.100 VUD3 DELHI. INDIA: 1200 to 1245 6.100 WARSAW. POLAND: 1100 to 1800 BRAZIL: 0900 to 1200; 6.100 PRE9 FORTALEZA. The New Model TC -50 1600 1900 INDEX to 6.110 GSL LONDON. (ENGLAND: 2300 to 0215: Gompkfc 1615 to TUBE PANAMA: 0630 to Need d 6.120 HP5H PAN AMA CITY. Most O/fe^ AND SET MEXICO; 1500 to 6.130 XEUZ MEXICO CITY. RADIO 0700 to TESTER 6.130 CHNX HALIOFAX. NOVA SCOTIA: DIAGRAMS 2400 /a)a.rb" A romplete laboratory. 6.130 COCO HAVANA. CUBA: 07(10 to dSewk0v COLOMBIA: 1100 to all purpose 6.140 H1DE MEDELLIN. trument hisversate 231111 tube ENGLAND: 1515 to 1000; tile combination 6.150 GRW LONDON. and set tester will ac- 20011 to up- 2200 to 03110 curately test all 6.150 CKRO WINNIPEG. CANADA: g n e d IRAN: 0930 to 1400: 2230 lo -date d e s i 6.150 EOB TEHERAN, The multi - Io 2315 tubes. COSTA RICA: 2130 to meter :action affords 6.150 TIRH SAN 10SE. many necessary mea 'Nun IOW urements for every- 6.150 CS2WD LISBON. PORTUGAL; 1330 to 1800 0700 to 09011 day's service wait. 6.160 HJCD BOGOTA. COLOMBIA: , t- CANADA; 0900 to 0200 The Now Model TC -50 Tube d S, Tester 6.160 CBRX VANCOUVER. a.C.V.. U.C.M.A.. HHCM PORT AU PRINCE. HAITI: 0300 to of Radio -Electronics. No strinnn, not h. bines ven instrumenta, D.C.V.. 6.160 FREE to every reader Meter, Decibel Meter a l Tube Tesler. 0930: 11011 10 1410' 1700 to 2145 to buy. How to tse Diagrams" gives hints, sugna. Ohms, sOutput ing servicing. 2%. Reading( GOOD HER3 BERNE. SWITZERLAND; 0245 to short efts on the use of diagrams ill radio Full cale accuracy to limitell 6.160 will tell you Just what models are In- for taOng tubes. Obsolescence reduced 11713; 1200 to 1700: 2030 to 2230 The 26.page INDEX Radio Diagrams" and BAD scalo charts COLOMBIA: 1000 to lino: cluded In SUPREME "5tost. Often -Needed to absolute minimum. Simple and quirk reading 6.200 HJCT BOGGOTA manuals. If you need a circuit at any time, the INDEX Mullhneter section affords most pop- will tell y,,u here to get it. Get both lamés In 2 -1n -I for tube testing. BOLIVAR. VENEZUELA; FREE. just send 2c stamp for postage. ular ryday's measurements. 6.200 YV6RD CIUDAD volume Set. Tester operates on 90 -120 1700 to 22311 Modell w Tl' -511 Tube and Volta 60 cycles A.C. Horsed in a sturdy beautiful 6.200 FK8AA NOoUMEA, NEWtnCIALEDONIA; 02011 SUPREME PUBLICATIONS Ch áó '23`íií`. Complete with test - cabinet. 0 portable. hand rubbed in- leads. tube charts and all detailed. operating 6.230 HRD2 LAIlOCCEIBOA. 1200 to OHONDURAS; Sstructions. loe 8"x 101/2" xa NET $39.50 6.330 COCW HAVANA. CUBA: 0600 to 2400 STOCK 6.240 HJCF BOGOTA. COLOMBIA; 1700 to 2300 IMMEDIATE DELIVERY FROM DOMINICANDOO 6.240 HIIN CIUDAD It's nearly read, ..the new, bigger. bet- REPUBLIC:UJIL0 . Catalog of ter-than-ever Walter All orders filled same day received 6.280 HCJB QUITO. ECUADOR: 18011 to 22400 d and ec (or 1949 free 6.310 HIIZ CIUDAD DOMINICAN F. ..priority" delivery, eserve your TRUJILÓOu of this helpful. nformati ^e buying ELECTRONIC s guide now. Simply write: ' 1949 Catalog' 6.360 HRPI SAN PEEDRO. SULLA.o HONDURAS: rd. Sign your name and ryYla1iEUpvlitcul gpermoon..d to -- INSTRUMENT CO. CSX LISBON, PORTGAL: 1230 6.370 Y, 7, N. Y. 6.450 CORI SANTA CLARA. CUBA 0630 tto 2400 WALTER ASHE RADIO CO. Dept. RC9 42 WARREN ST. N. (Continued on following page) 1125 PINE ST. ST. LOUIS 1, MO. OCTOBER, 1948

www.americanradiohistory.com 92 World-Wide nation List,

Free. l REVOLUTIONARY SOLDERING IRON Station Location and Schedule 6.510 CP40 COCHAHAMBA, '01 BOLIVIA; 1930 to 6.620 TG2 GUATEMALA CITY. GUATEMALA; 1811l1 Io 23110 6.700 YNDS MANAGUA, NICARAGUA: 0810 to So/detron 11011; 1700 11 2130 6.770 CP49 LA PAZ. ).ark Its Pat. Pend.d. BOLIVIA; 171111 to 0900; 11011 In 12110; 1930 In 21(1(1 8.770 For Easier, Better Soidering -' SINGAPORE, MALAYA: 0331/ to 1200 on 8.850 YNOW Any Joob. MANAGUA. NICARAGUA; 1800 to Weighs only 3 ozs., yet can do the 211111 job of a 200 watt iron. 6.910 YNOW Heats up in twenty seconds MANAGUA. NICARAGUA; 1300 to from a cold start; saves time. 2.81(1 6.980 Fingertip control; permits soldering without MOSCOW. U.S.S.R.. 1600 to 1745; fatigue. 2311 to 2345 6.980 FO8AA PAPEETE. TAHITI: Tuesday's and Friday.. 22011 to 211(0 7.010 XPSA KWE1YANG, CHINA; 23:10 to 0030; 04311 to istmi 7.100 BISSAU. PORTUGUESE GUIANA; 1:115 to 1730 7.120 GRM LONDON. ENGLAND: > ' a 1143 to 1215; Ready ,..1E for attachment 7.130 VQ6MI HARGEISAla and A.operation on BR TISH3{1SOMALI- LAND; Mott to 1030: 1200 50 -60 - 7.150 XGOY CHUNGKING. to 1300 through transformer s. -- CHINA: 0530 to 0730; supplied -- 1145 to 0945: with iron, or 7.180 KWS4 10110 to 1045 5 -e volt A.C. or D.C. VIENNA. AUSTRIA; 2345 to 2030 without transformer Urom an automobile 7.220 JCKW JERUSALEM, PALESTINE; Overall size 9/, X 15/18 battery). 2330 to ": ship. wt. approx. 4 lbs. 161111 7.220 SINGAPORE. MALAYA: 2330 Ideal for fine precision work in 7.250 PJCI to 0130 "hard -to- reach" places. WILLEMSTAD. CURACAO; 11311 t0 Readily interchangeable tip- heads; no 12311: 1030 10 2130 cleaning or filing. 7.250 Munich 41 MUNICH. GERMANY; Retains heat with switch 7.260 GSU 1100 to 1700 off up to I minute; efficient. LONDON, ENGLAND: 2.115 to 2330; Bakelite 2341 to 0130: handle. cork covering, for comfortable 7.280 JLW 1000 to 1700 cool grip., TOKYO. JAPAN: 03011 to 09110; 1600 PRICE, including transformer to 1800: 2.110 to 11230 and Tip -Head "A," $13.95 7.290 VUD3 DELHI. 5,4 higher west INDIA; orino to 1100; 1730 of Mississippi; fair traded. lu 1H25: 2100 to 2.1011 7.290 ZOY ACCRA. GOLD Ask your distributor, or for further 7.300 COAST; 1045 to 1310 information Write MOSCOW. U.S.S.R.; 1:100 to 1800; to: 1815 l0 2110 TRANSVISION, INC., 7.310 YEN SAN SALVADOR. Dept. RC, NEW ROCHELLE, SALVADOR; 1300 In Calif.: Transrlaioll of C.d.. S..72 N. Y. lu 1500; 1900 to 300 Santa 3lo1Hra Ithv1.. Hollywood 7.380 HEK3 96 BERNE. SWITZERLAND; 1000 to 1115; 1511 to 13:19 7.570 EA143 SANTA CRUZ. CANARY ISLANDS: 0731 to 18900: 1230 7.850 ZAA to 17111 TUBE TIRANA. ALBANIA: 1300 SPECIALS 7.8::0 SUX CAIRO. to 1630 AC EGYPT; 1400 to 1920 -DC eve - 10IAGT, 3323GT. 122547. 7.950 ALICANTE. Miniature 8ve- K7. J6I ;T..51.90 SPAIN: 011111 to 1000: -:0111. 3155 '4, 12ÁT6. I in1 b, 1801 ít.\6. BF4.... 1.90 8.030 F TWO JUMBO ASSORTMENTS X E BEIRUT. LEBANON: 0191 903.íL5. 2O* -5110. 10 ea. * 1515 to 0115; 3514, I SA7. K7. UT. 100 tubes. t1 Noe; 1131 to 10110 411- 3.1 \1'4. 30 -5085. 10 ea. 12. \T6. BA6. 8.700 COCO HAVANA. Either of the 111i6. 100 tubes. 8.720 CUBA: 0700 to 2330 above specials at only COIK CAMAGUEY. CUBA: 2001 Every tube new $34.00 8.830 COCA to 01)30 and perfect. Guaranteed 100^/e. HAVANA. CUBA: 1530 to 0030 8, -letti um recli tiers 1n051.í --len 8.950 GONG SANTIAGO, Postage extra. for 97,20 9.030 CUBA; 0600 to 2300 No. IO Y Tubes 20% deposit on C.O.D. orders. COBZ HAVANA. CUBA; 0700 49c ".20 9.080 CNR3 to 0100 RABAT. MOROCCO; 0110 to 0500; No. 1626 Tubes CORPORATION 1311 10 1900 49e 892 Communipaw 9.160 CR6RB No. 1625 Ave. Jersey City 4, New BENGUELA. ANGOLA: 1330 Tubes 49e Jersey 9.180 HEF4 BERNE. SWITZERLAND to 1430 CRYSTAL PICKERS 9.210 HI2G CIUDAD TRUJILLO. REPUBLIC; DOMINICAN List 0530 to 0830; 1300 to $6.50, our price $1.95 COUPON 15311; 1700 -OF- THE -MONTH 9.230 COBA McClintock Meters TUBES ST0. HAVANA. CUBA1A1800I to 1200: 1730 TUBES STO or 35W4....10 for S3.90 to 2330 0 -500 TURFS 12SQ7T or 12A76....10 for 9.270 COCX MA 3" square $1.95 STO 501.007 4.90 HAVANA. CUBA; 0700 to me;( Thousands SAPPHIRE PHONO 0115...10 for 5.90 9.330 SOFIA. of other bargains STD. BRAND NEEDLES 1.101 52.501...10 for 5.50 BULGARIA; 2301 to 0100; Vol. Controls -.5 Meg. 05311 to 0700: Writ, for our bulletin No. C -911 STO. BRAND -40.40 W.SW.. IO for .40 1100 to 1330; 14011 to Y PASS CONDENSERSMED 150V 10 for 5.40 1515 800[ -.005 or .01 MED 9.340 HBL GENEVA, 100 for SWITZERLAND; 1300 to C hination 6.90 1311 #L/n4 SOUND EQUIPMENTCO. Kit -All Above Items Only 9.370 EAQ MADRID. WITH 537.50 SPAIN; 1330 to 1600: 911.913 Jefferson Ave., TOLEDO 2,OHIO THIS COUPON -ORDER AT ONCE I630 to 2200 RADIOS -4 lobe Superhet. (Nat. 9.380 COBC HAVANA. RADIOS -5 tube Known) 8.95 9.380 CUBA; 0700 to 2400 Superhet. 'Nat. Known, 13.95 OTC LEOPOLDVILLE. BELGIAN Write for Monthly GO: own CON- Coupons and Bulletin 9.420 Write for FREE specifications on these RADIO GRADE.[ YUGOSLAVIA; 01(0000 to DISTRIBUTING CO. 12311; PASADENA 1$, CAL, 11130 to 0815: 111110 to 1045; GOVT SURPLUS JAN -INSPECTED 1111 U, 1121 - TUBES 9.440 FZI BRAZZAVILLE. FRENCH TORIAL EQUA. RCA 1630 UHF AFRICA: 0000 to 0130; - ORBITAL beam amplifier 1100 to 2020 9.460 TAP tremendous possibilities, high ampl. AWÓr ANKARA. TURKEY: 1000 to I81S; factor. 6.3 volts. Smallest "POCKET TALKIE "! Sun.. Slim.. Thurs.. 12GP7 954 304TH 9.470 CR6RA 1330 to 1545 for as low as 59.95 LOUANDA, ANGOLA: 0113 Io 0230; 9LP7 864 393A 00311 to 0741; 5CPI ItE.ALIA' WORKS- -talk and hear 9.480 1400 to 1530 5AP4 2 -10 miles MOSCOW. U.S.S.R.: 2.19 559 37113 or Hl °re -FITS IN 9.500 XEWW to 0200 5API 2X2A YOUR L'OC'KET! Uses flashlight MEXICO CITY. MEXICO: 080n to 3824 1131111 4APIO HYI110 434A batteries. ABOUT SIZE OF 9.500 PACKS 01X2 LAHTI. FINLAND; 0109 made CIGARETTES! Wt. 1 LB. to 0130; All tu for V.S. Ot In 0741: 1000 AOmótivoly during the war, Lune Mixed. SEND ONLY S1.00 eh k ' pals 9.510 11.62 to 1600 Inred to qua buver.s.' Some tithes as 'rah r,;.¡7. TOKYO. JAPAN: 0300 to 0830 low s the ' o1 l-,..1. Limar photos. picture CAT 9.520 VLW7 in stork. a nen -Rad :11,4TH tubes with 1x0'1, 5 price PERTH. AUSTRALIA: 0530 to 1030; DETAILEDDSUCH CAT00 1:a OTHER bum to 1900 3-tubePRODUCTS et A8: (i1.00 rcfumMtlrefunded can parts 9.520 ZRG GOULD GREEN 3 -í111q M,aketPocket rtler. JOHANNESBURG, SOUTH 107 W. Radio Dash AFRICA: Broad..., Now York City 13 Cigar Vacation Car Transmitter 091111 to 1045 Transmitter Ra,llo Garage Door Openers 9.520 OZF :1-luha COPENHAGEN. DENMARK; 1145 F.Iec no11r IHUrClnr Alarms Hearing Aids: to 1111 MOTOR INDUSTRIES CO., Dept. RW -9, Kearney, Neb. 9.520 SEAC COLOMBO. CEYLON: * POLICALARM 9.530 WGEO 1980 to 1200 SCHENECTADY. NEW YORK; 191(0 to 2"_30 F. M. RADIO 9.530 SSU STOCKHOLM, SWEDEN: 2000 to RECEIVER "1(111 9.540 VLR MELBOURNE. AUSTRALIA; 0800 Get Started in to 0915: 0930 Radio to 1001: 1245 to 1415 $399' 9.540 LK( 10 ''HOW- OSLO. NORWAY; 0:100 to 0315; 0500 T0.0 -IT" BOOKS to 0711: 11100 to 17111) Excise tax Included. 9.540 Munich 11 Get a d rnuod:. Inn in radio by MUNICH. GERMANY: 1190 to 1700 ru. 9.540 C1CA . Indianapolis of these IOe timely text boon, EDMONTON. CANADA; 0815 to 0200 Eachh clearly written. pmhlselyillus. 9.550 PRAGUE, CZECHOSLOVAKIA: $10 cash, rest C.O.D. trated, contains over words.ords. 1215 You'll be amazed In 1230; 1715 to 13311: 140n to 1430; Slightly higher west information 1115 to 15110: 1515 to 1530: 1600 to 101,1,5. Excellent forl reference-ideal 1630: IO of Rockies. technical 9.550 XETT Your loony MEXICO CITY. j1MEXICO; 0700 to TUNES bock If not l librd?. 111" 152 -162 MEGACYCLES 9.550 PARIS. FRANCE: 0000 to 0130; 0715 6 -tube superheterodyne, ready to operate. Veneer 5 BOOKS for 50c Io 1915 cabinet 9.560 91/z x 61/4 x 51/4 deep, wt. 6 lbs. Schematic 10 BOOKS for KOMSOMOLSK. U.S.S.R.: 2100 to inside back cover, $1.00 2110 warranty outside. 2 stages high 9.570 KWID SAN FRANCISCO. gain 10.7 megacycle Sent to You CALIFORNIA; I. F.'s. Guaranteed reception J Postpaid (711(1 In 11(1(1) from local No. 1 -How To Make Four tionary (Leaning s) 9.570 WRUW BOSTON. F.M. transmitters with attached antenna Doerle Short Wave Sets No. 6 -Now To Have rrFun MASSACHUSETTS; 2000 NoM In 221111 -police, cabs, others. Ready to plug in and use. The st Popular AMWave 1 No. 7-HowHow To Read Radio 9.570 KWIX SAN FRANCISCO. CALIFORNIA; 115 volts, A.C. -D.C. Power consumed 28 watts. and 2 Tube Receivers Diagrams 2211 to 0:113 No. C 9.580 CSC SOME CHOICE DEALERSHIPS for3 LONDON. ENGLAND; 1330 to 1345; OPEN ... WRITE Beginner. No. 9- Simple Ex- 1,730 No. 4 -All About Aerials primsots to 1130; 1600 to 1615: 1815 to No. S- Beginners' Radio Die- 211.'11 No. 10-Television 9.580 VLH3 RADIO Remit by cheek or oney order- rrgieter letter If you MELBOURNE. AUSTRALIA; 0345 to APPARATUS CO. á rash or st amp.. 0830; Sal.. 0245 to 0901; Sun., 0330 729 N. BANCROFI ST. to 0838 INDIANAPOLIS I, IND. RADIOO PUBLICATIONS 9.590 VUD5 DELHI. 25A West B'way, INDIA: 0900 to 1230 New York (7) 9.590 WLWO CINCINNATI. OHIO; 1530 to 1700 RADIO -ELECTRONICS. "-err

www.americanradiohistory.com 93 :11111 iii upuiications ESPERANTO A WORLD NEED Dear Editor: FOR FINER FM -AM RECEPTION I have just read Glenn R. Turner's letter in the June issue of RADIO -CRAFT THIS TUNER-AMPLIFIER COMBINATION and I think he has the right idea on Esperanto. Americans don't feel the need for an international language because English is spoken all over America. Hence the poor response when Hugo Gernsback proposed Esperanto over station WRNY. But here in Europe the situation is very different. You tune your radio and hear half a dozen different languages from stations only a few miles away. People get annoyed about it. When Radio Budapest first started broadcasting in Esperanto about 12,0011 letters came in, all enthusiastic. Now over a dozen European stations have Esperanto programs, in addition to at least one Brazilian station. When the distance between continents has been reduced to almost nothing by technology, as that between European countries has been, Esperanto will be- NO come a must. The introduction and en- couragement of Esperanto might well DRIFT become radio's most effective contribu- TUNER tion to the cause of peace. ANTHONY A. MÜNNICH, Budapest, Hungary WITH NO GIMMICKS, PLEASE REVOLUTIONARY pear Editor: I have seen several articles telling: AUTOMATIC how servicemen have been "tested" with FREQUENCY a solution "gimmicked" sets. I offer CONTROL! which will determine the honesty of a repairman. It will stop the complaints about impossible faults that a trained see. man would not normally inputs. Polished chrome chassis. F e a t u r e s audio Use sets which are perfect in every FM -AM TUNER RC -8 Audio cable, escutcheon, decals, anten- automatic- frequency control, most revo- installation instruc- there is one blown - -- nae, and detailed respect except that lutionary development in FM design tions furnished. out tube. This is a common trouble and entirely eliminates drift and multiple complain. tuning responses. Nine shielded minia- RC-2 the repairman could not ture tubes plus rectifier include double HI- FIDELITY AMPLIFIER RF stage in both FM High impedance input; 12 watts output If the customer is told that he had a limiter and tuned 500 with impaired and AM. Low -impedance loop, enabling at 1% distortion. Taps: 4, 6, 8, 15, 'pyrolienated helical flexibility in mounting, provides low - ohms. 65 db gain, including inverse which ruined all the reception. Rear socket pro- feedback. Uniforms frequency response cross- modulation noise AM 8 watts vides easy access to 6.3 -volt AC and from 20 tò 20,000 cycles up to tubes" and is handed a bill for $19.75, well -filtered 100 -volt DC output. Hum 65 db below rated output. exceptionally 5Y3. he will have a good excuse to get out for supplying external pre -amplifiers, Tubes: 6)5, . 6SN7, (2) 6V6, If the bill is for one additional pilot lights, etc. Controls Durable polished chrome chassis. his shootin' irons. include separate bass, treble and switch tube plus a small service charge, he positions for phonograph and television Writs tor Descriptive Circular "1" ad Preen. will have no complaint. DOYLE STRANDLUND, Homestead, Mont. The RADIO CRAFTSMEN, Inc. CHICAGO 5. ILL. (Replacing a bad tube would not in- 1341 5. MICHIGAN AVENUE, volve any real repair work. How about inserting a faulty power -supply filter capacitor instead ? -Editor) pEREECT 500 FORMULAS TO SUCCESS dollar firm,. ,larhd MANY million h nM1 a .i n[le frnila. f ''r '' E.I. CO. CUSTOMER IhSO nard a hig once. aloe OLD ho., as. le.. -tried and tested flaking recipes na nroee+ses nor TEpS flaking thinga all at the ridi" Ucur Editor: AMpEIfICA>elsüwi III"1 Iy low prive ui 25,11. FOS POSTASE v, npl,nrlunily to win. a Reading the article on "The Crystal `I Ib bm fe,r I,!iIa.a caritas ¢aná'wilh undreamed of rrofta Detector" in the June issue and seeing ampurill ß CORP. of AMICA v orgnn,e m New York 13, N. Y. a rut 1908 Electro Importing Com- 398 -10 Broadway seh.dn expenses to the tonne. Or the old 1rk.ünp put them De- ut cost, as nitwit as pany ad for the Electro Universal IIMO,_,. I had Duo paving o,Il many dollars in tector Stand, I remembered that profit lo m r ta one ud dehIer, mu,when ran mate the bought one of these stands through same thing y ïorro es ts. I SPEAKER RECONING "V .t,eif fou follow our of Hugo Gernsback's magazines when s.mpi e ivnstruion t ALL WORK GUARANTEED 66 PAGES. 3200 WORDS IN TEXT was a boy of 12. to. 7"-81.95 15" -$4.00 Send for 500 FORMULAS AND RECIPES" 3" -51.40 e now all! be asked I have kept up with the Gernsback 8 2.20 4x6- 1.90 Sold Dont t "- 1.411 "- for anotherE or ater. 2.20 back guarantee. all through the years, and 5 1.50 l0 "- 2.70 557- magazines "- 2.50 6 1.65 12 "- 3.00 6x9- PIANS COMPANY still read them regularly. "- NATIONAL N. New York 23. N. Y. OXFORD RECONING SERVICE P. 0. BOX 28 R. STATION C. E. JONES, Selby Ave. St. Paul. Minn. Springfield, Mo. 1039 OCTOBER. 1948

www.americanradiohistory.com !1 I

Hollywood Make Good in at Experts Help Cou RADIO -TELEVISION Home RADIO SCH OL Direst from Hollywood, DIRECTORY nerve-center of broadcasting. Tele- . Radio ,d untler ctivities. conies R -T -a's - proven na tested home training. time team. home Her. at last -easy to instruction that quickly ins:dines you for steady. good.pay Jobs or your own Radio business. kits radio parts 10 boy given et n extra charge. Get full de. tails , t n Sund postal for Become .,aie a .d in Itaillo- Television. FREE BOOK "Itow MA, RADIO TRAINING ASS'N OF AMERICA. Dept. 5620 RCa Hollywood Blvd. Hollywood 28, Catit

CORRESPONDENCE COURSES IN RADIO and ELECTRICAL ENGINEERING TELEVISION TECeHNICIAN ELECTRICAL ENGINEERING;,e yf1eari2; Prepare ;;,,Ll`. yoourself at Low Co.. for tyre fume.. Modem course. mplifiW anyone can denund euickly. Z In dia O ENGINEERING publicEats "nedomo, wort. Trains you to be s uper-eereiee tube technicien. Serrinm.. I vacuum- 18 oomDletfonádan needed DadÌy. Dlpions, on IN MONTHS! postcard for Rw tCopl :ofy' WRITE °nom P ont posa, es. $is C.0"r.. Here is the opportunity you Lincoln Engineeringp g ' School, have been waiting for. Now you can get in on Bex931C11a. Lincoln 2. Nebo. the ground floor of the nation's fastest growing industry- TELEVISION. RADIO and TELEVISION LOOK AT THIS RECORD - In 1946 only 6,500 Thorough Training in All television sets were manufactured - in 1947 this Technical Phases skyrocketed to 175,000 APPROVED FOR VETERANS - already in the first four COURSES DADS- EVENINs W months of 1948 over 160,000 RCA sets have been pro- SERVICE GRADUATES ARE IN DEMAND duced. This means hundreds For Free Catalog Write Dept. RC -4e of new jobs are being 6 to 12 Months created every month. Practical Electricity RCA INSTI TUTES, Ince Welding A Service of Radio Corporation of America MSOE Refrigeration NOW ADDS TELEVISION The 350 WEST ITH STREET NEW YORK 14, - Milwaukee Heating N. Y. School of Engineering now provides complete, prac- TECHNICIAN tical, technical training in television as well as Radio in its 12 to 24 Months laboratories. This is not just a serviceman's Electrotechnics course. The special Radio and Television 18 month's residence course in- Electronics TELEVISION 1948!! cludes complete training in radio as well as Refrigeration, Heating Train at an Institute that pi d television and Air Conditioning - qualifies you for a successful career as a techni- in TELEVISION TRAINING sinter 1938. cian in all phases, AM, FM, PROFESSIONAL Morning, Afternoon or Evening Ses- TV Receivers and Trans- sions in laboratory and theoretical in- mitters 36 Months struction, under guidance and Radio Communications, Electrical of experts, Engineering covering all phases of Radio, Fre- This Technician Course Prepares You Bachelor of Science quency For Any Of These lobs: Degree Modulation, Television, lead Radio Servicing - AM and FM Taxicab transmitters to opportunities in Industry, Broad. TV receiver servicing operating Major in Machinery or casting and receiver servicing Electronics or own Business. Licensed by Broadcast Station Operating Railroad N. Y. State. Appeared for Veterans. Electronic transmitters operating Parts Sales and receiver servicing ENROLL NOW FOR NEW CLASSES Rodio and TV sales Supervising Radio and testing in radio Visit, Writs or Phone and TV manufacturing and TV manufacturing Terms start January, Police transmitters operating and Shop managing receiver servicing April, July. RADIO- TELEVISION El ical Engineering 7 INSTITUTE î Bachelor oIScience Degree MILWAUKEE SCHOOL OF ENGINEERING, 480 Lexington Ave., N.Y. 17 (46th St.) N. Broadway and E. Stole, Milwaukee, PLaza 3-4585 2 in 2 additional years Wis. blocks from Grand Central Without obligation end free booklet Building" "Career Majoring in ELECTRONICS and more s details on coursa in Radio and Television MILWAUPcLE- or Course. - Name Age liCHÛAL of ENGINEERING Address A Technical Institute founded 1903" City State Be 'they" man. Lea how Dept. RC 1048 toe , N. Broadway, Milwaukee, Wis. areceive messagese In encode by telegraph ,á radio. commerce needs thousands of n or Jon,. Good pay. adventure, In- teresting work. Learn at home quickly famous Candler System. Qual- throughify for Amateur or Commercial FREE Li- Dept.a.t.. YSTEM GCO. WANTED Box 028. Denver 1. Colo., U.S.A. Men and Women to Fill RADIO TOP COURSES SOUND RECORDING SCHOOL RADIO JOBS t its. Preparatory, Service, Broad- Iterlal, in :, td ai AM- FM- Television square ,il.nana. cast, Television, Marine Op- , cuclaturo and intermotlulation analyzer. If you are Ir. other equipment. and h. r, il, a future. why not join the 61111,11. erating, Aeronautical, Fre- the Don Complete recording 5111,110 as imilating broadcast. &load of Radio Arts win Martin motion aeir ,.full)' employed in the quency Modulation, Radar. picture and vmmerc,d sounds rfcording. under tho dlreo- radin industry. The demand is great timi id D. M. 'rren:aine. personnel for qualified radio in .t3I- F5l- Trlevistnn. Classes forming for fall term 1. be Train now to Oct. nouncer, script writer. disk Jockey, news- HOLLYWOOD SOUND INSTITUTE, Inc. caster, or radio technician. Entrance exam Sept. 20. ('ornplete day and night 1040 -C No. Kenmore Hollywood 27. classy . . Calif. , the latest egnipmrnt. Free placement Veterans. Literatur,.. service. Approved for retriait. Write for tree booklet. COMMERCIAL RADIO INSTITUTE Don Martin School of Radio Arts (Founded 1920) 1655 North 8 West Biddle Street. Baltimore I, Md. Cherokee St. Hollywood 28. Calif. .LEARN RAD10! IN ttNI,I' In 31(iNTIIS PREPARE FOR A GOOD JOB! IO COMMERCIAL RADIO RADIO OPERATOR (CODE) //RADIO OPERATING CODE BROADCAST ENGINEER RADIO SERVICING ELECTRONICS TECHNICIAN and RADIO SERVICE COURSES F.M. TELEVISION RADIO SERVICEMAN REFRIGERATION FM and TELEVISION SERVICING Television Servicing -I5 Months Write for Catalog and Picture Brochure i AMERICAN RADIO INSTITUTE Y.M.C.A. TRADE & TECHNICAL 101 West 63rd St.. New York 23. New York Veterans get $130.00 Equipment SCHOOLS SEND FOR 15 W. 63rd St. (N'r B'way) New York City Approved Under C! Bill of Rights FREE LITERATURE Licensed by New York State BALTIMORE TECHNICAL INSTITUTE 1425 Eutaw Place, Dept. C. Baltimore 17, Md._ RADIO -ELECTRONICS for

www.americanradiohistory.com Book Reviews 193 AUDIO AMPLIFIERS. FM TUNERS AND INTERCOMS. Compiled and published by How Modern Design ard W. Sams & Co. Regular Photofact size, 33s pages. Price $3.95. from This specialized volume of Photofact BUILD KITS WALL BAFFLE data on all amplifiers. YOU CAN MAKE MODERN RADIOS folders includes Largo size and 5'111' YOURSELF! I it'll tl ll'g FM tuners, and intercom systems which AND TEST SETS st'is rut' Lin d. n. ny maslmite Bild since HOBBYISTS of speak - have been covered by Photofacts IDEAL FOR SCHOOLS AND I all weight, volume is bound 12" Top. I-" the end of the war. The VACUUM TUBE Wire. .S' Bottom and 1l l ill. ylaaer Ballte in paper covers and includes 102 post- VOLTMETER raker unultipg ., I, d. war models produced by 29 makers. KIT 012 65N7 bridge type volt- Model 1215W Increasing importance of audio am- meter Natural Masonite Fin for the 0 -500 m ps DC. ish. List $16.00 plifiers was given as the reason u tmmet Model 1215WS Óu1^ sqa er0 Ivory or Brown Wrinkle. before the war primarily ohm circuit, 1 mini. edition. Sold wan"tita level. List $18.50 installations, amplifiers are now For frequency FM for PA l ighI of cus- DC. 6.5 megolirns A,' being used widely as the heart ninput i.l:mre. sys- l1n to 111011 n gnhm' 1 Streamlined tom- assembled home entertainment 5 Dranges. Linear AC - 0CV Its -IUU " vil,.. CABINET tems, in conjunction with FM tuners, scales. ßa11 balanced UNIVERSAL linear Iliade AC rectifier. !di and in modernization jobs. I í precision sistor. 6x11x5 ". Probe for high The volume also includes complete 1, frequency FM and TV Ideal for sound instal- v ilati at extra cost. lations where an at- material on the Webster Models 79 and Wil' complete instructions. LIRICST P E $29.95 tractive baffle and 80 wire recorders. good tone quality 2 -BAND RECEIVER sought. Dimensional KIT S6X Characteristics . . Plus Natural Repro- * 6 -tube THE ARCHITECTS MANUAL OF ENGI- * Equipped for 110 duction . Sturd. NEERED SOUND SYSTEMS. Issued by Archi- volts AC or DC construction, in cor- tectural Relations. Sound Equipment Section. This 2-I:41141 ter ner type design. com- leather covers, 288 pages, 91/4 x cot ers the f BIBS bining heavy masonite RCA. Simulated ranges: SSO kr. -1600 inches. Price $5.00. , and wood. Ili", kr.. Ii I -nw ipl.,, As indicates, this volume is With mbr title I the ,1. stool. '. read. Model 6K Natural Masonite ..5 8.00 List reference work iliac 12'x12"+8' ' intended to be a general Ivory or Brown . 10.00 T.1'r Model SKS 12'x12'58" ' $17.95 Model 8K 14'515'59" Natural Masonite .. 10.00 for architects who deal with_ sound_in- cuti l "59" Ivory or Brown .. 13.50 ' Model 815 14"x15 Masonite. 14.00 an lie.,... stallations. As such, it is essentially 1'Iw :,Il many other umvlrls Model IORS17,17,10"0" "Ivory o Natural.. Masonite 18.00 ' electronic tar Model 12K 18"520"510" Brown. 18.50 acoustical, rather than an Chicago. Ill. Model 12K5 18"520"510^ Ivory or Net CONCORD RADIO CORPORATION. Reducers for any of above baffles. each treatise, filling a gap which has existed RADIO WIRE IN . New Above models patented and patents pending OLSON RADIO WAREHIOUSE.WAREHOUSE. Akron,k Ohio for a long time. COMPANY. Va. MISSION RADIO. San Antonio. Texas Pressure Controlled Acoustics is not, at present, an exact OFFENBACH AND REIMUS, S Francisco. Cal. electronics, local jobber. write directly LOUDSPEAKER ENCLOSURES science to the same extent as II not available at your lI. to us. so the book necessarily appears sketchy. Write for Catalog K 11.411...1 '.1ó111r1 IrLlrces the 1111ilnate III hill.. But there is at least some information range, high level 50111141 of RADIO KITS COMPANY reproduction. Anti -Ferd- on almost every conceivable type 120 Cedar Street, New York 6, N. Y. back characteristics , sound installation. In addition to the tribute 10 wulcual Ihnut- aspects, the text goes into elec- andcabasigeularLl Trlang de- acoustic sign and small space re- wiring, types of quirements oller numer- trical requirements - installation ous practical amplifier units, loudspeakers. methods. Finished In at - over half the pages are de- tractive leatherette and Slightly TEST -AID constructed of heavy ply - and diagrams of h,axi. voted to floor plans -AID FOR RADIO -TELE SETS i setups. With each group of plans FIRST typical ONLY a set of sample specifications is pre- sented.- R.H.D.

APPLIED PHYSICS: Electronics. Optics, $1595 R. Metallurgy. Edited by C. G. Suits, George COMPLETE Harrison. and Louis Jordan. Published by Little. Brown and Co. 6 x 8y: inches. 456 pages. Price $6.00. WRITE FOR of a called "Sci- CATALOG This book, one series SHEET CELL COVER 194 LOWER ence in World War II" devotes AND RESIS- MASTER BAFFLES REMOVED REMOVED QUICKLY FAULTY CONDENSERS List to electronics. A history of the TORS FAST SERVICING Model 6V 10^x1O^x5. Ivory or Brown.. $10.00 pages Model 8V 15'515"x9^ Ivory or Brown.. 17.50 SUBSTITUTES 11 DIFFERENT VALUES OF CAP. OR Model 10V 17 "x17"58 Ivory or Brown 20.00 ' work of the National Defense Research Somme to 40med 50. 4' orr Brown.. 22.50 ' RES. WITH SET IN OPERATION Model 12V 20'x20'530^ Ivory in 600 WVDC -27 ohms to 5 meg. Above models Patented Patents pending U.S.. Committee, it describes the work done Canadaand t CHECKS CONDENSER LEAKAGE ON DIRECT CURRENT by Division 13 (Electrical Communica- FROM OWN PWR SUP. SUPPLIED New Super Sector tions), Division 15 (Radio Co- ordina- OUTPUT INDICATOR FOR ALIGNMENT -CONTINUITY on Propaga- CHECKS LOUDSPEAKER CABINET tion), and the Committee PROVIDES 100 VOLTS AT 100 MA FOR EXPERIMENTS. especially -AA tion. Much of the material, These are only a few of many s Off the dealing with radar countermeas- that TtIssees, , IID. dealer h:mr writeyous TTE5TT - ures, has appeared in various publica- direct. 'tl/Srw IB I_"' in a 111,1.1 11 a,.,,,u -. V", and is here brought together e o n - tions, . l . r a k , Veit' slimly STREET. BKLYN, N.Y. plysnUod to refer to. 256 E.98th na c t ìot of 'wavy form easy nl finished ill Irons i The section on Optics has some infor- Brown Leatherette. Excel- lath arOnstie qualities and mation on infra -red and ultra -violet ant:mine enough for the is interesting finest Installations. light, and sound, which Size 20"120"56" (specify point of view. and 25B8 Tubes!! celer). List ...$15.00 from the communications 12B8 Reducers for 8" or Id" 011:16 tube. and Composed of adapter, 1 -0.1T6 tube. 1- speakers. Net .30 +0h0Ì the Patent 2 miniature r Acoustic Design ',115' tube. and (tile re baise will Applied For. / 1221lxsockets. to ¡my l- A-11_/0 ENGINEERING fit into the 17ÌS1 or 25118 socket. Nulling rlsr discounts to Jobbers. Dealers h and R works. Kold of Usual ices San unit L r mplele. lust plug in an cera . All er mndrle: S2.19 Complete Radio Engineering Monet I, awk t tutee 1211K or 2511K unit Francises, CaliforniarNosC.O.D.. n th g. Course. Bachelor of Science De- e. n , 1,.,, gree. Courses also in Civil, Elec. - - - TUBE SPECIAL: a,coranti.a: 4(77.1.0-d+..,c1.o Engi- trice!, Mechanical, Chemical, Aeronautical 32L7 -$1.09 Accounting, 701.7 - S .79 - neering: Business Administration. 25138 unit & 70L7(.T- 3.19 successful. 65th I SSrB,pR:A:aL..a. Secretarial Science. Graduates 2 12118 unit & 321,7(4T- 3.49 Jan., March, June. Write for year. Enter Sept., 3597 MISSION STREET a ta lop. COMMERCIAL RADIO San Franristo. California TRI -STATE COLLEGE esoOOLACe1 elÌDIIAIp11 36 BRATTLE STREET, BOSTON 0. MASSACHUSETTS OCTOBER, 1948

www.americanradiohistory.com 9(b

i Index to Advertisers WE'VE MOVED Allied Radio Corporation Almo 8 RADIO Electronics, Inc. 75 TUBES More Alvaradio Supply Space- Better Service Co. 82, American Surplus Products 85 Co. 66,, 67 For immediate shipment 3 TUBE PHONO Am perite Co., Inc. Amplifier Corporation 74 of America 80, 81, 93 AMPLIFIER Walter Ashe Radio Co. 91 R.M.A. Guaranteed Audel Publishers Bell Telephone 11 Labs. Inside Back Cover Individually Sealed Cartons Boland & Boyce Publishers, Inc. 63 $1.95 Bradshaw Instruments Company GT Types Miniature Brooks 51 Types Radio Distributing Co. 16 Buffalo Radio Supply 6K6GT .40 72, 73 1S5 .50 COMPLETELY WIRED, Burstein -Applebee Company 84 VOLUME Capitol Radio Engineering 6K5GT AND TONE CONTROLS Institute 6, 45 .46 1T4 .55 Certified Television Laboratories 84 Set of 3 tubes; 50L6, 35Z5, 12A6 $1.10 Cleveland Institute of Radio 17 Output trans, 5016 6V6GT 1 .35 Collins Audio Products .46 R5 .55 Co., Inc. 88 's Meg. vol. control with sw. .35 Commercial Radio 1" speaker ,95 95 6SA7GT .46 3S4 pm Communications Equipment Co. .55 pm speaker 1.15 Coradio Co. 18 80 6" pm speaker 1.55 Coyne Electrical School 6SJ7GT .46 6BÁ6 96, 97 .50 6,1" pm speaker L39 Custom Craft Mfg. Co. 8" pm speaker 2..19 DeForest's Training Institute 95 6SK7GT 13 .46 6B E6 .50 Webster pickups L79 The Electric Auto -Lite Company Asiatic ('artridges L 711A, L -26A 1.49 Electronic Corp. of America 10 6SQ7GT 87 .46 6ÁT6 .42 Alliance motor & Turntable 2.50 Electronic Research, Inc. 80 VM X400 INTERMIX CHANGER 21.95 Electro -Voice Manufacturing Co. . 89 6X5GT .40 12BA6 .50 (I.E. Reluctance Cartridge 4.54 Espey Mfq, Co.. Inc. Phono Pre -Amplifier complete with Fair Radio Sales 82 74 12SA7GT .46 tubes 4.95 Feiler Engineering Company 12BE6 .50 Phono Oscillator complete ... 85 with tubes Franklin -Ellis . 4.52 79 12SQ7GT Oscillator Coil. 12SA7 .15 General Cement Mfg. Co. .46 12AT6 .42 General 83 AlI Electronic Distributing Co. 47, prices F.O.B. N.Y.C. -on C.O.D. 25?o Deposit. General Test Equipment 83 12SK7GT 80 .46 35W4 .42 Write for tre., caca o

www.americanradiohistory.com IIooic Itcvicwa I97

ENGINEERING PRINCIPLES, eludes dipoles, single wire types, loop ELECTRONIC -Hall, to your problems in by John D. Ryder. Published by Prentice antennas, parallel -wire arrays, rhom- Answers Inc. 6% x 91/4 inches, 398 pages. Price $6.65. bics, V- shaped antennas, parabolas, THEORY AND DESIGN Written by a professor of electrical cones, horns, and wave "lenses ". The engineering who has specialized in elec- radiation resistance of antennas is con- OF FM EQUIPMENT tronic tubes, this book will prove valu- sidered at length. The author then in studying and reso- Here is thorough treatment able to anyone interested delves into wave conductors hich relates basic prncI. the action of the various types of tubes. nant devices, properties of transmission pies with best practical methods of design. It covers fundamentals of which Tubes covered include the cathode -ray lines, and fundamental properties In a detailed chapter tri- brings out important relations indicators, diode rectifiers, vacuum wave guides and cavity resonators. between amplitude, frequency tubes, amplifiers for are devoted to and phase modulation, and lays odes, multi -element Several chapters the basis of treatments avail- OV` small and large signals, gas diodes, screening and shielding; oscillator de- able to the design engineer. From such a starting point, this gas -control tubes, photoelectric cells, the sign; impedance of mixer, diode, and intensive book goes I., to practi- cir- cal applications in a::ciliary ap- cyclotron, and the mass spectrograph. amplifier tubes; antenna entrance paratus of FM nttwcrks, trans- with the explana- amplification, feedback, m itters. receivers and aerials The author begins cuits, wide -band . shows use of numerical cal- fundamental particles (the of single- and multi -grid mix- ¡illations and design formulas tion of the operation equipment now in use. various types of atoms), electron bal- ers, and frequency drift and control. in listics as applied to vacuum tubes, and The noise of single and multi -grid FREQUENCY the actions taking place in such tubes stages receives considerable attention. de- MODULATION as the cathode -ray type. The necessary Equivalent networks and wide -band ey August Hund. Consulting. anglnerr mathematics is included, together with tection, microphonics, the selection of i 375 pages, 6a9. 113 illustrations. 54.50 curves and diagrams so that the reader tubes, FM receivers, impulse receivers, easily. among the This hook shows you how mathematical for- is enabled to follow the material and radar receivers are mulas are applied to engineering solutions by The section on thermal and field emis- topics covered. using tables and curves -gives you explanations is very refreshing and includes 409 directly in the illustrations so that figures can he sion of electrons A lengthy bibliography used without re- reading the text . . helpful in- makes the subject much clearer than references from 47 publications. - formation for employing special design formulas of textbooks on the subject. Ref- in connection with hand width characteristics many H. W.S. networks . testing methods useful in design- erences are given so the reader can ing and maintaining FM receivers. sub- delve more deeply into the various Here's practical information on formulas for jects discussed if he desires further in- BASIC MATHEMATICS FOR RADIO, by G small modulation index, wave propagation in the E.E. Published by Prentice-Hall, Inc present -day FM hand, time constants in FM net- formation.-H.W.S. F. Maedel, alignment of FM 5 z 9% inches. 339 pages. Price $4.75. works, FM signal generators. is necessary for under- receivers, feeders used in FM systems, transmit- Mathematics antennas, etc. standing electronic phenomena but most ter ULTRA- AND EXTREME -SHORTWAVE RE- mathematics books give generalized in- 10 DAYS FREE EXAMINATION CEPTION, by M. J. O. Strutt. Published by Co., Inc. 400 pages, 5% z 8% including much material not D. Van Nostrand formation r INC. inches. Price $7.50. and therefore McG RAW -HILL BOOK COMPANY. useful to the radio man, 330 West 42nd Street. N.Y.C. 18 Modulation are not particularly interesting to him. Send nic a ropy of Hood's Frequency design of re- 1 This book covers the for l0 day's' examination on approval. In Ill days arithmetic or re- and antennas for use in the h.f., This text begins with basic will lem it $LCg, plus a few rents postage, ceivers The tain Ille euuk postpold. u.h.f., and s.h.f. (micro -wave) and ends with complex numbers. v.h.f., several years teach- regions. It embraces the frequencies, author, who spent Name to radio students, has from 6 to 30,000 megacycles (fifty me- ing mathematics Address in wavelength). kept his treatment strictly within the ters to one centimeter City and State Basic data is given for designing radio lines of usefulness in radio. equipment throughout this en- Exercise problems and step -by -step Position receiving solutions are tire range. explanations of their Company RC-w-as plentifully throughout the SAVE!aWe pay postagoe and packinrcluhá1rgeesvr you The opening chapters deal with the spotted send ...... and pages. The reader is carried through polarization, reflection, absorption, stages .... e..s.1 refraction of radio waves; ionospheric the work in logically planned man -made, atmospheric, so that any intelligent person can use RADIOMEN! ELECTRICIANS! disturbances; home study. The and interstellar noise; and various the text for unaided Get this Valuable Book of modulation. language is clear and no assumptions forms about previous One chapter discusses noise generated are made by the author R E E on the reader's part. in tubes, resistances, networks, and knowledge Explain, 414., for Merely Examining Mathematics is never a painless sub- Latest resonant circuits, and presents mathe- set: Coyne's NEW Pay- Raising of noise and the ject except to those especially interested matical definitions make noise -figure of electronic tubes. in it but this book will at least 6t their use easily under- i The section on antennas for the numbers and looks pr! ,.if Ihr in- standable.- R.H.D. ll ere's a l'ItA1 °rlr.tl, , l of radio higher frequencies is up -to -date and press! Gives you "kilo. hots" on eyer'Ihiug in Radio today, Basic principles to newest in Televi- sion and F.11.--how construct, Install, service. Latest trouble- shooting methods. 11100 illustrations, o'er 1500 pages. ideal for reference or hone train- ing. To prove how valunhle these great lundis fall he r o you, Coyne will give you a FREE copy of our r. helpful "1511 New Radio Diagrams Explained" for looking over the 5 Vol. Set. OFFER 1.1MITl1) ro ACT NOW We will send you 5 vol set AP- a PLIED PRACTICAL RADIO for 7 days FIIEK ex- mrinatiol, together with Radio Diagrams, La* set or $3 v o'er for 7 days. If you Ilke it send $15 rash, After 7 lays and $3 monthly until $18.75 is paid. If you don't want the set. owe et. t art urn It and you ñER NOTHING. Either way Yon keep Diagrams Rook Free. SEND NO MONEY! Cou- pon asks to see links tree mill get your gift look 4.4 FREE f.r doing it! Send Ma,gN BOOK ro5ngm NOWT ' Division COUPON Educ-.tl on al Book Publishing COYNE ELECTRICAL & RAD10 SCHOOL. Dept. 78 -TI 12. I 500 South Paulina St.. Chicago Illinois ' y1 DI:. Send nit'. p,00niald. l'oyne's new - olun1e set. ..ry, "tPPI.1ED PRACTICAL RADIO" I for 7 Days FRED a TRIAL per your Mrer. Also end. absolutely FREE, as a gift. _....._ "150 New Radio Diagrams Explained" I NAME AGE by: E. R. Donohue. Walla Walla, Wash. Suggested I ADDRESS out of my mouth!" "No, you kids have not found a gold mine, and get that thing LTOWN ZONE STATE J

OCTOBER, 1948 (Printed in U.S.A.)

www.americanradiohistory.com 91

Whether you require large quantities of relays for production runs or single units for laboratory or amateur work, Wells can make immediate delivery RELAYS and save you a substantial part of the cost. Our capable engineering staff is prepared to offer assistance in the selection of correct types to suit FOR EVERY PURPOSE your exact requirements. } Each relay is brand new, standard make, inspected, Over a Million in Stock! individually boxed and fully guaranteed. The following list represents only a tiny portion of our relay stock. STANDARD DC TELEPHONE RELAYS Write or wire us for information on Stock Operating Cod Net types not shown. No. Voltage Resistance Contacts Manufacturer R101 Each 2411 1500. DPST (NO) Auto. Elec. 11.102 24V 400. $1.35 SPOT Auto. Elec. 1.10 R -103 24V DUAL-1000 3PST NO) Auto. Elec. 1.35 R.105 24V 600. 3PST NO) CUTLER HAMMER P.106 Clare 1.20 24V 1300. 3PST NC) Clare HEAVY R -152 12V 1.25 DUTY CONTACTORS 50 DPDT -SPST ENO) Guardian 1.10 R 153 12V 200. SPOT SPST NO) Stromberg 1.25 R -154 12V 200. SPST NO. Clare R -155 1.20 SENSITIVE 12V 100. SPST .4NOINCI Auto. Elec. Stock Operating Coil R -158 1.15 DC Net 6V 50 IPST NO1 RELAYS No. Voltage Stromberg 1.10 Resistance Contacts Manufacturer Each R -159 6V 50 DPST NO) R -178 24V DC Stromberg 1.10 100 SPST(NO)100A. 6 41H34A R -160 6V R -179 $3.85 12 3PDT 3PST r 6V DC 6.5 NO) Auto. Elec. 1.05 SPST(NO) SOA. 6 411183A 3.00 R -161 6V 10 3PST R -180 12V DC 25 2NC1N0) Auto Elec .90 $P$TINO) 50A. 60411308 3.25 R -121 150V 5000 R -181 24V 2PST' NO)SPOT Clare 1.65 DC 65 SPST (NO) 100A. 6 41H8B 2.123 150V Stock Operating H -232 3.65 6300 SPST NO) Clare 175 24V 55 SPST(NO) 50A. Metal R -602 150V Resistance Contacts H -233 Cased 3.25 6500 3PST -NO) Clue Manufacturer Each 6V 15 SPST NO) R-51S 24V 1.75 R-218 4.6V 1800 SPDT 50A. Metal Cased 3.15 750 SPST .NO) Clare Korman 220C $1.95 H-235 24V 70. SPST.NO1100A. R -517 1.25 R-220 75V 5000 Type B6 3.85 12V 250 DPST (NO) Clare SPDT Allied Cont. R -519 250V 1.20 R-221 18.2411 5000 SPST (NO) 14000. SPDT Auto. Elec. Allied Cont. 1.15 DIRECT 8.520 1.95 R-174 250V 5000 OPST CURRENT AIRCRAFT CONTACTORS 250V 14000 DPDT R.B.M. INO) G.M. 1,85 R -521 2.10 R-175 350V 11000 DPDT-DPST(NO) Stock Operating Coil 32V 1000. DPDT Kellogg G.M. 2.95 Net R -166 120 R-176 24V 250 No. Voltage 24V DUAL-200 DPDT-SPST (NO) DPST (NO) G.M. 1.50 Resistance Contacts Manufacturer Each Stromberg 1.59 R-177 24V 300 4PD7 R-182 28V 80 24V DUAL-200 /PST I NO) G.M. 1.65 SPST(NO)25A Guardian Aulo. Elec. 1.20 R-600 8-12V 5000 R-183 24V $1.85 H -210 250.350V 40000 SPOT S-DunnKS 2.10 60 SPST 010) 50 A. Allen DPST NO) A oto. Elec. 2.95 R-507 Bradley 2.75 H-241 48V 650 24-48V 1000 SPDTDPST (NC) Guardian Type SPDT-SPST I NO) Clare 1.25 1.15 R-184 28V B6A 50 SPST (NO) 100A. General TYPE IS DC TELEPHONE R-185 Elec. 2.95 RELAYS 24V 100 SPST(NO)50A. Leach 5055ECR Stock Oparating Coil R-186 24V 2.75 Net 132 SPST(NO)50 A. Leach 7220-3.243.50 No Voltage Resistance TYPE BO DC RELAYS R-187 24V Coolants Manufacturer Each 100 SPSTINO)50 A. Allen Bradley R -109 24 -48V 4000. Stock Operating Coil R-188 $4V 2.95 SPOT Auto. Elec. 51.50 Net 200 SPST'NO)75 A. Allied R -110 24.32V No. Voltage Resistance H-234 Cont. 2:95 3500 SPOT Auto. Elec Contacts Manufacturer Each 14V 45 SPST NO) 30 A. R -112 90.12011 1.50 R-169 24V 250 1.65 6500 SPST (NC) Auto. Elec. 1.75 SPST (NO) Allied Cont. $1.95 R-114 24V R-171 24V 230 500 4PST i NO) Auto. Elec 1.30 DPDT Allied Cont. 2.15 ANTENNA CHANGEOVER R -603 24V 400 R-172 5 -BV 30 DPDT -SPST RELAYS DPST IND) Auto. Elec 1.25 (NO) Allied Cont. 1.70 Stock 11-238 24V R-173 2.6V 5 Operating 150 DPDTSPST (NC) P.B.M.' 1.25 SPST (NO) Allied Cont. 1.25 Net 11-239 24V 180 R-529 24.48V 1000 DPDT Voltage Resistance Coolants Manufacturer DPST i NO) Auto flc 1.25 Allied Cont. 2.50 R-192 Each 6-12V DC 44 2PDT 10 AMP Allied -PBS R -23I $1.35 I2VDC 100. DPD7 6 AMP G. E. R -256 1.95 TYPE el DC RELAYS 24-32V DC - SPDT -DPST (NC) Guardian 1.45 Stock Operating RSOI 110 AC 4 IKW Coil NO DPDT (IKW) G. E. 2.45 No Voltage Resistance Contacts ß -507 12.32V DC 100 -SPST Manufacturer ach SPDT G E. -500 W 1.95 R-204 12V 65 DPST (NO) R205 Allied Cont. $1.15 24V 760 DPDT Allied Cool COMBINATION PUSH R-224 12V 1.25 BUTTON AND 75 SPST (NO) Allied Cont 1.15 REMOTE RELAY SEALED DC N -237 27V 230 DPDT Allied TELEPHONE Cont 1.25 i Stock RELAYS Operating Coil Net Stock No Voltage Resistance Contacts Manufacturer Each Volageg Resistance Contacts Manufacturer H -244 1224 V DC Dual-60 SPDT R -125 24V Each CR2791R106C8 $1.65 300. DPDT Clare HEAVY DUTY KEYING RELAYS R 126 90-120V 2000 $2.75 DPDT Clare 3 Stock Operating Coil ADJUSTABLE R -504 24.70V 2800 00 Net TIME DELAY RELAY SPOT G(-C103C25 3.00 No. Voltage Resistance Contacts Manufacturer Stock Operating R240 Each Coil Net V TYPE DC 28V DC ISO r TELEPHONE RELAYS SPST NO) 10A Guard. 36471 $1.05 No. Voltage Resistance Contacts Manufacturer Stock Operating Coil P244 75V AC 265 SPST (NO) 20A i 11246 AC Each Leach 1327 1.75 115 SPST (NO) or R W. No Voltage Resistance Net R 206 24V DC 150 SPDT -3 Cramer Contacts Manufacturer AMP Pse -KL 1.20 INC) 10 AMPS R -164 Each R.207 24V 1.120 Sec $8.95 24.32V 1000 SPST 'N0; DC 210 4PDT-3 AMP P &B -KI. 1.10 R -512 W E $1.20 R -219 50V DC 24 -48V 3500 DPDT 1500 DPST (NO) ISA PAR -SP 1.25 DC MECHANICAL ACTION R -513 12 -24V R -217 115 AC 600 SPOT-10 RELAYS 300 DPDTDPST INC) W E AMP SI. Dunn 1XAX2.25 R -5I4 4 -6V 1.20 R -525 24V DC Stock Operating Coil SPOT 200 DPDT -10 AMP Guard 34464 1.25 Net 41-526 6V 1.05 R -508 110 AC 600 No. Voltage Resistance Contacts 35 DPDTSPST INC SPDT -6 AMP Guam/ 37189 1.95 R245 Manufacturer Each R -506 24 V DC 300 DPST (NO) 6A 12V 25 4' lever G.M. INO; W E .95 $095 1.05 R -510 24 V DC R -527 6-12V 200. 200 3PDT -10 AMP Guard. 516983 1.05 2' Lever .95 AC- STANDARD TELEPHONE R-604 24 V DC RELAYS 200 SPST 010) 30A. St. Dunn-B2A 1.75 Stock Operating Coil H -608 115 AC No Voltage Net SPST (NO) 20A St. Dann1HXX2.25 TYPE C.M.S. RELAY Resistance Contacts Manufacturer R -620 12V DC 35 3PST R-212 90.135V Each (NO) 10A GuardBK2 1.05 Sto ck Operating Coil NONE Clare $0.95 R223 28V DC 150 SPST (NO) 40A. Price Net R -213 5.8V Bros. 1.35 N o. Voltage Resistance Contacts Manufacturer DPST i NO Clare 14230 12 -24V DC 80. DPST (NO) Each R -605 24V 10A. 1.20 R -5 11 24V DC 200 MICRO -SW 3PST NO Auto H -231 24V 230. DPST (NO) Clare $2.45 R -606 24V Elec 1.95 5A. R.B.M 1.15 - DPST A NITINC) Auto. SPST (NO) R -607 24V - Elec. .95 SPST iNO. Auto Elec. .95 DC CURRENT REGULATOR DC -TYPE 76 ROTARY RELAYS St ock Operating Coil Stock Operating Coil No Net Net Voltage Resistance Contacts Manufacturer No. Voltage Resistance Contacts Each Manufacturer Each R5 09 6.12V DC 40 SPST NC R -197 9.16V G. E. $0.85 DIRECT CURRENT 70 DPDT Price Bros. $1.65 R -198 9 -I6V 125 6PST 13140) LATCH AND RESET MIDGET RELAYS ( RELAY C) SPOT Price Bros. 1 65 R.199 Stock Operating 24-32V 250 SPDT DPST (NC) Price Bros. 165 Coil Net R200 24.32V 275 No. Voltage Resistance Stock 3PDT-SPST (NC) Price Bros. 1.65 Contacts Manufacturer Each Operating Coil R-201 R -500 12V DC 24.32V 250 I 10. DPDT NO. Voltage Net DPST NO) SPDT -10 AMP St. Dunn- Resistance Contacts Manuf acture, R -1J2 24V Each 165 CX -31908 52.85 300 DPDT Clare R.601 9.14V 60. R -133 24V $1.20 3PS)T (NO) Price Bros. 1.65 300 NONE Clare R -134 24V .60 DC- ROTARY STEP RELAY 250 4PDT Clare R -135 NV 1.20 Stock Operating 300 SPST iNC) Clare Coil Net R -137 1.15 No. Voltage 24V 300 SPOT Clare Resistance Contacts Manufacturer Each 19-138 24V 1.15 R-621 6.12V 3o0 4PST (NO) Clare 30 3 POLE R -139 2411 1.15 200 4PDT 23 POSITION W. E. R Clare 1.15 $10.95 140 24V 280 SPDT R.B.M. R 1.15 DIRECT 141 24V 280 3PST (NO) R.B.M. CURRENT DC- RACHET RELAY R -142 24V 1.15 400 DPDT Allied Cont. KEYING RELAYS Stock Opeuting R -143 24V 280 1.20 Coil Net SPST i NO PALM. No. Voltage 8.144 24V 1.15 Resistance Contacts Manufacturer Each 250 SPST (NO) R R-145 Allied Cont. 1.15 Stock Operating Coil i -230 5.8V 2 SPOT.DPSI 24V 300 DPST .110) Net T110) Guardian $2.15 Allied Cont. 1.15 No. Voltage Resistance Contacts R-146 12V 126 DPST Manufacturer Each IINOI r. INC) 8.190 R 147 Clare 1.10 12V 65 DPDT IO AMP Advance 9 -14V 75 SPDT Guardian Elec. R.148 12V 1.05 100 DPDT SPST INC) Pnce Bros. R -191 28V 8.119 6 -8V 1.10 125 DPDT 10 AMP Guardian A $1.20 45 SPST (NC) Clare 1,00 R -192 12V 1.20 Special Sample Engineering Offer R -150 6V 30 44 3PDT 10 AMP Allied Cont. Se ST ;NO) E -Z Elec. 95 R-522 2-6V 2. Type 1.35 Any ten relays SPST (NO) R B.M. R -193 5.8V listed (one of each type) R 523 90.125V 6500 .65 II DPDT 10 AMP DPDT Clare 1.90 SPST with the h 222 12V 100 Type 1.05 exception of Stock Nos. R -621 DPST (NO) P 6 B R -194 24V 26S N -242 24 -32V 95 DPST i NO) 'DAMP ch1027 300 DPDT F.B.M. and R -246 -only $ 10.00. N 243 24.32V 1.20 Type 300 4PDT R -195 1054SNW1.25 R.B.M. 120 6V 32 DPDT 3 AMP 8.196 G.(.Co. 1.15 12V 50 DPDT 10 AMP SPST (NC) Guardian 1.15 R -242 ORDER DIRECTLY 24V 170 SPOT 2 AMP Leach FROM THIS AD OR THROUGH YOUR Type12530(W1.25 H -236 5.8V LOCAL PARTS JOBBER 18.5 SPDT 10 AMP Leach -KFM 1.05 Manufacturers: Write For Quantity Prices. /WELgsf ¡Distributors: Write For The SALES, INC: New Wells Jobber Manual. 320 N. LA SALLE ST., DEPT. -Y, CHICAGO 10, ILL. RADIO-ELECTRONICS for OCTOBER 1 9 4 8

www.americanradiohistory.com I l!

nu

rl I rl

"s"'

.1 *1,'t1141,,`.3 vr -.---""K.--`

Switches in small offices do a distant operator's bidding.

IT TALKS WITH FINGERS

For those who want to talk, Bell Labora- tories scientists developed the telephone. For those who prefer the typewritten message, they developed TWX - Teletypewriter Exchange Service. Fingers on a keyboard send your message to be typed by one or scores of other tele- typewriters selected at your request from the 21,000 instruments connected to the Bell System's nationwide TWX network. As in telephone service, your TWX con- nection is set up through switching systems, manual or mechanical, as best may serve. And over long distances your message travels economically with many others on the same pair of wires. All these technics are prod- ucts of Bell Telephone Laboratories research in the telephone art. TWX is today a vital link in the nation's BELL TELEPHONE LABORATORIES chain of communication. And year by year EXPLORING AND INVENTING, DEVISING AND it benefits from the steady growth of the PERFECTING FOR CONTINUED IMPROVEMENTS telephone system which carries it. AND ECONOMIES IN TELEPHONE SERVICE.

www.americanradiohistory.com MALLORY Mdgetro1

The .l;r Volumes Control with BIG A dvv.ieages

I lriaTLI The small size of the Mallory Midgetrol lets you service portables, auto radios and small AC -DC receivers which Mark require 15/ls" controls.

Simple The unique shaft design of the Mallory Midgetrol saves nstallati installation time with all types of knobs.

Electrical characteristics let you use the Mallory Midge - F'Simplel trol tOCliil to replace It/s" as well as 15/16" controls. Stocks are further reduced because no special shafts are needed.

The Mallory Midgetrol is quietest by actual tests -and tests prove it stays quiet, too. In addition, it has nine big features that are all new.

NEW SIZE NEW SHAFT NEW SWITCH NEW CONTACT NEW DESIGN NEW EXTENSION NEW ELEMENT NEW TERMINAL NEW TWO -POINT SUSPENSION

It's the NEW Standard in Carbon Controls. See your Mallory Distributor. a CAPAC T . RS ... CONTROLS ...VIBRATORS , , SWITCHES... i ESISTORS... RECTIFIERS.. VIP RA PACK* POWER SUPPLIES... FILTER CH,

P. R MALLORY & CO., Inc

www.americanradiohistory.com