Ulu I 110 K\I Hugo Gernsback

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%Mt ei;sch RADIO TELEVISION NEWS

Jet.E,,on. ULU I 110 K\I HUGO GERNSBACK. Editor formerly RADIO CRAFT

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AUG 1949

IMPROVE YOUR TELEVISION PICTURE

SI I TFIFVISION NFWS 30(.

u. S. and ATEST IN RADIO - ELECTRONICS - TELEVISION CANADA TSE FUTURE HOLDS GREAT PROMISE

Neither chance nor mere good fortune BELL Telephone Laboratories lead the new capital needed to meet the service ahead. has brought this nation the finest tele- world in improving communication opportunities and responsibilities phone service in the world. The service devices and techniques. There is a tremendous amount of Americans enjoy in such abundance is to be clone in the near future and Western Electric Company provides work directly thc product of their own imag- the System's technical and human re- Bell operating companies with tele- ination, enterprise and common sense. the sources to do it have never been better. phone equipment of the highest qual- bil- Our physical equipment is the best in The people of America have put ity at reasonable prices, and can always of their savings into history, though still heavily loaded. and lions of dollars be counted on in emergencies to de- building their telephone system. They we have many new and improved facili- liver the goods whenever and wherever plant. Em- have learned more and more ways to use ties to incorporate in the needed. courteous. the telephone to advantage, and have ployees are competent and The long- standing Bell System policy continuously encouraged invention and The operating telephone companies of making promotions from the ranks initiative to find new paths toward new and the parent company work together assures the continuing vigor of the horizons. one place may so that improvements in organization. They have made the rendering of spread quickly to others. Because all telephone service a public trust; at the units of the System have thc same serv- same time, they have given the tele- ice goals, great benefits flow to the Wren these assets, with the traditional phone companies, under regulation. the public. spirit of service to get the message freedom and resources they must have through, and with confidence that the Similarly, the financial good health to do their job as well as possible. American people understand the need of the Bell System over a period of many for maintaining on a sound financial years has been to the advantage of the basis the essential public services per- IN Tltls climate of freedom and re- public no less than the stockholders and formed by the Bell System, we look sponsibility, the Bell System has pro- employees. forward to providing a service better vided service of steadily increasing value and more valuable in the future than It is equally essential and in the pub- to more and more people. Our policy, at any time in the past. We pledge our lic that telephone rates and often stated, is to give the best possible interest utmost efforts to that end. service at the lowest cost consistent with earnings now and in the future he ade- LEROY A. WILSON, President financial safety and fair treatment of quate to continue to pay good wages, Telepi anti Telegraph Company. employees. We are organized as we are protect the billions of dollars of savings American the E'4s A ,,unt I:pnrlJ in order to carry that policy out. invested in the System, and attract the (Frow

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Same coupon entiies you to FREE "superhet" circuits work, three rea- lesson, "Getting Acquainted With sons why tubes fail, locating defects, Receiver Servicing.' Discloses short- repairing loudspeaker. Over SO pic cuts Radio repairmen use. Tells how tures, diagrams. FREE. send coupon ! See for you/sell how /train you atiíome -to BE A RADIO-TELEVISION TECHNICIAN Want a good -pay job in the fast -growing RADIO - TELEVISION Industry? Want a money- making Radio - You Build This MODERN RADIO with Parts I Send Television shop of your own ? Here's your Complete, powerful Radio receiver brings opportunity. I've trained hundreds of men to in local and distant stations. NRI gives be Radio Technicians . MEN WITH NO you ALL the Radio parts ... speaker, PREVIOUS EXPERIENCE. My tested and chassis, trans- proved train -at -home method makes learning sockets, easy. You learn Radio -Television principles ¡former, from illustrated lessons. You get practi- loop antenna, cal experience building, testing, experimenting with MANY KITS OF PARTS I send. All equipment yours to keep. MAKE EXTRA MONEY IN SPARE TIME The day you .u roll. 1 start wending SPECIAL BOOKLETS that show you how to make EXTRA MONEY fixing neighbors' Radios in spare time. From here its a short step to your own shop, or a good -pay Radio- Television servicing job. Or get into Police, Aviation. Marine Radio, Broadcasting. Radio Manufactur- ing or Public Address work. And think of getting in on the ground floor of the booming Television Industry. Trained men are already in demand . . . new stations are going on the air, manufacturers are building over 1011,000 sets a month, more and more homes are getting sets. The man who prepares now will reap rich rewards. SEE WHAT N.R.I. CAN DO FOR YOU Act now ! Send for my DOUBLE FREE OFFER. Coupon en- I Also bt titles you to actual lesson. "GETTING ACQUAINTED WITH RECEIVER SERVICING," absolutely free. Over 811 pictures and diagrams! You also get my 114-page book. "IItiW TO BE A SUCCESS IN RADIO and TELEVISION -ELECTRONICS." Tells Send You Many more about YOUR opportunities, details of my l'ourse. how quickly, easily you can get started. Send commin in envelope or paste on penny postal. J. E. SMITH, President, Dept. 9HX. National Radio Other RADIO KITS Institute, Pioneer Home Study Radio School, Washington 9. D. C. I TRAINED THESE MEN Has Own Radio Business Extra Cash In Spare Time MR. J. E. SMITH. President, Dept. 9HX "Now have two Radio "Earned enough spare National Radio Institute. Washington 9, D. C. shops, servicing about time cash to pay for 200 sets a month. Have my Course by time I Mail me FREE Sample Lesson and 64 -page book about how to win Eill largest sery ic e estaMb- graduated. NRI train- success in Radio and Television- Electronics. (No salesman will call. lishment in S. E. is - ing is tops! " -ALEX- Please write plainly.) souri. " -ARLEY STU- ANDER KISH. Car- , DYVIN, DeSoto. Mo. . teret, New Jersey. Name Age

GET THIS Address S TRAINING UNDER City Zone. State

G. I. BILL I VETERAN L ;]('heck If Veteran APPROVED FOR TRAINI \ NI/ER C. 1. RILE. 4 Hugo Gernsback, Editor -in -Chief these RADIO - Fred Shunaman, Managing Editor You Caafíylateh Ic1.1:/: i It/l\II:S M. Harvey Gernsback, Consulting Editor 1O!iiIffif/e:I ra/ues/ formerly RADIO -CRAFT Robert F. Scott, W2PWG, Technical Editor Plate Load R. H. Dorf, W2QMI, Associate Editor SNORT WAVE CRAFT TELEVISION NEWS RELAY RADIO IS TELEVISION I. Queen, W2OUX, Editorial Associate i''/ mon-ohm coil. SPST nor- 1[ Trademark reg,alered U. H. Patent Ornee ) mall- open contacts. Extra Angie Pascale, Production Manager sensitive and used for many Circulation Manager Business Manager Wm. Lyon McLaughlin, applications. 1%). high. 114' G. Aliquo Charles K. Brett ` wide, lek' mtg. rtes. Tech. Illustration Director . >I t 1'.,nn $1.19 Soles Managers John J. Lamson, Lee Robinson Silver Mica Button Condensers Contents August, 1949 Editorial (Page 17) Squeezing the Service Technician by the Editors 17

Television News ( Pages 18-31) Improve Your Television Picture (Cover Feature) by Allan Lytel 18 Booster Uses Standard Tuner by Matthew Mandl 22 New All Channel TV Antenna 24 kw- Trouble Shooting Television Sets by Irving Dlugatch 25 E F G The Tronspole Variotenna, Part 1 by Hugo Gernsback 28 Television Queries Answered by Dove Gnessin 30 $7.50 per 100 (all one type) Electronics (Pages 32 -37) MA-3538 ((:1 rit mod M.1 MA -3591 IDI 311 mmf Al Spectrometer Measures Mass of Chemical Ions by Jerry S. Adams 32 MA.3531 IF) 53 mmf M t Electronics in Medicine, Port X, Electron Microscope...by Eugene J. Thompson 34 MA -3503 (AI 75 mmf MA MA -3532 III) 75 mmf 1l \ Experimenting with Ultra -Violet Roys by Ernest J. Schultz 37 MA -3504 IA I 200 mmr V s MA -3519 IF) 250 mmf r: I Construction (Pages 38 -40) A High -Fidelity Tuner -Amplifier, Port II by M. Harvey Gernsback 38 #18 2- conductor Wire & Drum New Design (Page 41) Used for running 111- volt AI' lines, extension speak etc. Full 175 feel of highest qualit> s silo New Devices Exhibited at Chicago Parts Show 41 tough, weather-resistant insulation. 'omplsete r n Jill handy drum for mooting uvo r -, ra_ I.Imtii.I Audio (Pages 42.45) quantity 12.39 Improved Phono Amplifier by John S. Carroll 42 Notes on Sound Recording by Richard H. Dorf 43 BRAND NEW Frequency Bridge for Audio by K. E. Forsberg 44 METERS »d ur Model :nn' r for Theory and Engineering (Pages 46-47) ll-round ham and fret Microwaves, Part IV by C. W. Palmer 46 appllrations. 10 ma DC basic movement. a I.. il- meter flange: 2.4' body. Amateur (Pages 48 -49) I4,' deep. Stock up on Mobile 10 -Meter Rig Puts out 20 Watts on Phone..by A. B. Kaufman, W6YOV 48 these nor they tear. MA 2i),) 1, Servicing (Pages 50 -58) $1.95 each Manufacturers versus Service Technicians by Hugo Gernsback 50 Why Pick on Rodio Technicians? by Lyman E. Greenlee 52 Training for Radio by Jules L. Hornung 53 Iron Core FM and AM Fundamentals of Rodio Servicing, Part VI, Reactance, Impedance and Phase IF TRANSFORMERS by John T. Frye 55

Highly rmi l rot for I ur tim :n.l replacement. Foreign News (Page 59) 111.4 Wuulbie Iron cores provide high selectivity and gain. Only 24'21 .1" square; shade lug mounting.nting. European Report by Major Ralph W. Hollows 59 MA -2.298 lo 111' IF Transformer . . 49e ea. Test Instruments (Page 60) MA -2039 455 HI' IF Transformer ..35e ea. Laboratory Square -Wove Generator by John E. Pitts 60 Departments INTERCOM TRANSFORMER SET One transformer to match voire coil to grid. another The Radio Month 8 Question Box 70 for SOL6 and similar output tubes. Both of these tine Rodio Business 14 Technotes 71 mens l'1.1'S a momentary DI'DT spring return push - button + u'h for leas than value ut one transformer New Devices 63 Miscellany 72 alone' These are hall. strap-mounting transformers. Radio- Electronic Circuits 64 People 74 ONLY 98e FOR ALL THREE UNITS! New Patents 66 Communications 76 Try This Or 68 Book Reviews 81 GRILLE CLOTH ON THE COVER: Robert Witherspoon tunes the transmission line with o Never before at our lea price: Highest ua lit y. golden-tone grille cloth. styled to y J capacitive slider while Joan MocClay adjusts the television harmonize with ail cabinet deal Gen s17aa r emus 50. 0ldih. per yard receiver. Decorations by John Wonamaker. Miss Mac - Clay's dress by Frances Sider. Kodachrome by Avery Slack. 4 This Month's Specials! August, 1949. Volume XX, No. Published monthly. Office: Erie Ave., RADIO -ELECTRONICS. II. Publication TI7 Microphone and plug; used; g .. 79t 1- to ti Streets. Philadelphia 32. Pa. Entered as second class matter Scptember 2 1048, at the post office at 25 mh Iron core 11F choke; 100 MA 1, .. 19e S. and Philadelphia, Pa., under the Act of March 3. Taro. SUBSCRIPTION RATES: In C.C I anada, In I. 14. 55 mmf butterfly condenser 32e possessions. Mexico. Smith and Central American countries. $3.50; í8.u0 for two fears: $8.00 for three yeah; 50 nil butterfly condenser ...... 29e angle coptes 30e. All other foreign countries $4.50 a year. $8.00 for two years, s11.00 for three years. Allow one Mercury switch; flexible IB' leads 29e month for change of address. When ordering change please furnish an address stencil Impres.lon from a recent wrapper. Brand new tC, Jark Box RADCRAFT PUBLICATIONS, INC. Hugo Gemeback, Pres.: M. Hrvey Gernsback. Vire -Pros. Alo,Album. See',. slid, 5u 11, 11; LLnk I.akelir kr :uni .. 15t Contents Copyright. 1949, by Radcraft Publications. Inc. Text and Illustrations must not be reproduced without permission r copyright owners. EDITORIAL and ADVETISING OFFICES, 25 West Broadway. New York 7. N. Y. Tel. REctor 5.9000. BRANCH ORDER FROM THIS AD! ADVERTISING OFFICES: Chicago: 308 W. Washington Street. Telephone RAndolph 8.7383. Loa Angeles: Ralph W. Harker. 1127 Wilshire Blvd., Tel. MA 81271. San Francisco: Ralph W. Harker, 582 Market St. Tel. Oarfleld l -2481. Send 25,l. deposit aim order. l'as balance plus pus loge FOREIGN AGENTS: Great Britain: Atlas Publishing and Distrltuting Co.. Ltd., 18 Hrlde Lane. Fleet 8t.. Lon on lielivery. Gel your n on 3114- America's select don E.C.4 Australia: McGill's Atene,, 179 Elizaheth Street. Melbourne. France: Brentano's, 37 Avenue de ['Opera, mailing list and get first crack at latest. greatest cal - Paria 2e. Holland: Trlleclron, Ileemnteedsche, Dreef 124 Ileemstede. Greets: International Bonk A News Agency, 17 radio parts. electronic nl.inment. tithes. e Amerltls Street. Athena. S. Airiest: Central News Agency. Ltd.. Cor. Itlaslk & Commissioner Su.. Johanneshnrg; Send llorders to Desk BC -89. Minimum order $2.50. 112 Long Street, Capelown; 389 Smith Street, Durban. Sud. Pnlveraal Book Agency. 70 Harrison Street, Johannes- burg. Middle Last: Slrlmatzky fiddle Feet Agency. Jena Howl. Jerusalem. India: swill Gupta IDistributoml t----_ ----a ----r !o., Armit Bazar Palette Lt.. 14 Ananda Chatteries lane. Calcutta. Broadway News Centre. Post Rag #5557. DEdar. Bombay #14. K. L. Kannappa Modeller. 30 General Patters Bead. Mount Road, Madre, 2. Paklataa: Paradise Book Stall, Opp. Regal Cinema. Preedy St.. Karachi 3. MIDAMERICA CO.Inc

IVSTORE WAREHOUSE Editorial and Executive Offices: MC 2412 S. Michigan Ave. 2307 5. Archer Ave. AUDIT MURRAY CIRCULATION 16. inn. 25 West Broadway, New York 7, N. Y. OF Chsaeo 16, III. Camas* RADIO -ELECTRONICS for TELEVISION, ELECTRONICS 4 HOME TR

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CITY...... Zone STATE . .. GET THE DETAILS -SEND THE COUPON Check here It Veteran of World Wer II AUGUST, 1949 li fit Another radio service dealer thanks FRS?"' PAYS' Sylvania Campaigns Tf E OM THE for big rise OFir FO,Q /E in business E MA/L1/G S ENr/RTRQEI y0/ sE,QI//CE/,.

OSRES YOUR pp pORTu Hti t

Increase your Business with Sylvania's Fall Campaign - BEY=S- READY NOW! RADIO SHOP CHIEF HEEPER.UPPER OF YOUR RADIO "ylvania's September, October, November, .tnd December campaigns are available now. I lere's what you receive: ARCADIA. FLORIDA MODERN LODVHDET 4 Postal Cord Mailings - one for each month. 4 Window Displays - one for each month. march 9. 1949 4 Window Streamers - one for each month. 8 Newspaper Ad Mats - two for each month. Hammond -Morgan, Inc. Radio Spot Announcements -several for each month. R 9 South Terry Street A 8- 12 Orlando, Florida and -inch decals for window, door and truck.

1 o Gentlemen: Tied up directly with Sylvania's national advertising, these campaigns will boost your E Last month your representative showed me his display matter X on the Sylvania Direct Mail Advertising campaign for February, husiness. You pay only the postage on the P March and April. E cards you mail. Sylvania gives you every- R thing else free. \X'rite for full details imme- T I placed an order for the series of direct mail cards and received them about two weeks later. diately, or see your Sylvania distributor. T R I mailed the first group of cards out on the morning of Feb - A ruary 26th about 8 o'clock. Before 2 PP I had a call for service as the result of the mailinv11J Later the same afternoon I had a N couple come in to look over new radios. E They had received my card D regarding repairs and decided that instead of having their set re- SYLVAN paired, they would come and what IA in see I had in new radios. They a are at this time about decided on buying a set retailing for 499.95 Y plus an FM antenna installation. N have read the statements A I of other servicemen over the country about their business increasing 30% and the C T upward as result of this ELEC[RI 1 Sylvania advertising, but I believe the results I have obtained are RA DIO TUBES; CATHODE RAT TUBES ELECTRONIC DEVICES FLUORESCENT LAMPS. o above anything I have yet heard about. The first day I had made FIXTURES. WIRING DEVICES, SIGN TUBING. EIGHT BULBS; PHOEOLAMPS N enough profit from the mailing to pay for the entire three months A the l. service, and prospects are that the other two months mailings r will bring other business. Sylvania Electric Products Inc. R Advertising Department R -1708 A I thought perhaps you would be interested in the results I had Emporium, Pa. D with this series, and can tell you I now that I hope to increase rep Gentlemen: Please send me full details on your 1 mailing list on the next series, and I think I will stick to this September, October, November, and December O form of advertising as long as it is available at such a very low cost. Service Dealer Campaigns. Yours very truly, N Name S T BENNY'S RADIO SHOP

1 Company T U Address T B. McGehee E City Zone e. C ADORERS SYSTEMS a[n ROAIR SERVICE ON ANT MRE OR MODEL RADIO HOME RECORDING APPARAT DA State.

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MICROGROOVE reproducing equip- ITS HERE! JOHN BALLANTYNE, chairman of ment has been installed by 652 AM the board of Philco Corp., died on June stations in the U. S., according to a 10th while making a commencement report last month by Robert J. Clark- EVERYTHING IN TELEVISION address at Meadowbrook School in son, general manager of Columbia Pennsylvania, where his 13- year -old Transcriptions, who conducted a sur- son was a member of the graduating vey. Another 185 plan to install the VIDEO class. Ballantyne was president of necessary pickups in the next few Philco from 1943 to 1948, after which months. In addition to the standard LP pressings, Columbia offers to program HAND producers a transcription service in which microgroove records take the BOOK place of the traditional 16 -inch, 33%- r.p.m., 15- minute -per -side transcrip- Over 900 tions. Because of the close groove spac- pages... 800 illustrations ing, more than 20 minutes can be recorded on each face of a 12 -inch record, resulting in a considerable money saving. In addition, technical characteristics are standardized.

bound in LICENSE with amateur call handsome PLATES Dupont letter., instead of the usual meaningless Fabrikoid numbers and letters are now available to automobile -owning Florida hams, due CONTENTS -IN 14 to a bill which took effect on July 1. Television: Past, Pres Installing Television In recognition of nt & Future. Receivers. the valuable work done Fundamentals of elec- Servicing Television by amateurs in emergencies, State Sen- tronic Television. Recei The Television Station. ator Lloyd F. Boyle, himself a ham, The Television Television Test (MAW Receiver. ment. introduced the bill in the legislature; Television Antenna Building Television was signed Systems. Receiver. it by the governor on May Creating a Television Date Section. 12. Each man Show. wanting a call- letter Descriptions of Modern Television Terms. license plate must apply to the Motor Bibliography. he became chairman of the board of Television Receivers. directors, acting only in an advisory Vehicle Commissioner and pay an extra $5.00 capacity. A native of Philadelphia, he $1 fee. THE was a graduate of the University of Pennsylvania. He became treasurer of RADAR STATIONS will be built in RADIO DATA BOOK Philco in 1940 and vice -president in the Bahamas by the United States, as W. F. BOYCE and J. J. ROCHE charge of operations a year later. He part of its Florida- based, 3,000 -mile THE ONLY RADIO HAND- was 49 years old at the time of his guided missile range, the Defense De- BOOK OF ITS KIND! demise. OVER 900 PAGES ... 12 SEC- partment announced last month. The TIONS, EACH A COMPLETE agreement was concluded with Great COVERAGE OF ONE RADIO DR. WILLIAM W. HANSEN. a pro- SUBJECT. fessor of physics at Stanford Univer- Britain and the Bahamas governments. CONTENTS: sity who helped develop radar, died on The department will conduct extensive I. The 150 basic circuits 8. Charts, graphs and May 23 at the age of 39. tests on guided missiles, beginning, it in Radio curves hopes, in July, 1951. The radar stations 2. Complete test equip- 9. Cades. symbols and As early as 1937 Dr. Hansen was ment data standards will be needed to track the paths of 3. Testing. measuring working on the use of radar for mili- and alignment 10. 50 tested circuits de the missiles. 4. All about antennas signed tor optimum tary purposes. He was recently elected 5. Sound systems performance 6. Recording II. Dictionary of radio to the National Academy of Sciences 7. Complete tube manual and electronic terms and was awarded the Liebmann Memo- TWENTY -FIFTH ANNIVERSARY of $5.00 rial Prize for outstanding work in the Radio Manufacturers Association radio engineering. is being celebrated this year. The or- THE RADIO AND ganization's Silver Anniversary Con- vention was held in Chicago on May TELEVISION LIBRARY LICENSING BILL introduced in the 19. concurrently with the Radio Parts Comprising THE VIDEO Illinois legislature, requiring all per- HAND BOOK and THE RA- Show. DIO DATA BOOK outlined sons servicing radios and TV sets to above. undergo a training course and exami- This is the biggest book value in 1949 RADIO FALL MEETING for- Rrecord! A complete b brary on nation (see report this section of adio and Video in a handsome July issue) was defeated last month. merly known as the Rochester Fall slip case complete only The Radio Manufacturers Association Meeting, will be held October 31st, $9.00 and the Television Installation Service November 1st and 2nd at Hotel Syra- And don't forget to get this month's copy of Association of Chicago were instrumen- cuse, Syracuse, N. Y. according to an announcement by Virgil M. Graham, AND tal in having the bill killed in com- RADIO DISTRIBUTION mittee. chairman of the Radio Fall Meeting MAINTENANCE Committee and director of technical re- the complete trade journal devoted to soles and INTERNATIONAL TV EXHIBIT and lations for Sylvania Electric Products service of Radio, Video. Audio. convention will be held in September Inc. The Meeting will be sponsored by Single copies 25e, $3.00 per year. $5.00 2 years. in Milan, Italy, under the auspices of the Engineering Department of Radio the Italian government. The exhibit, Manufacturers Association for its All products of to take place at the Arts Palace in members and members of the Institute BOLAND & BOYCE, INC., Montclair 3, N. J. Milan, will show equipment made by of Radio Engineers. Officers of Fall are available at your European firms; United States com- Meeting Committee in addition to Mr. panies invited to participate are RCA, W. DISTRIBUTOR'S COUNTERS Graham, include R. Ferrell of The LOCAL Du Mont, Philco, GE, Raytheon, and General Co., vice get your copies TODAY! Electric -chairman Westinghouse. The convention will and treasurer, and R. A. Hackbush of meet at Como, about 45 miles from Stromberg Carlson of Canada, Ltd., Milan. secretary. RADIO- ELECTRONICS for s 'I'he Radio Month 9 FCC celebrated the 15th anniversary Bickford, and A. Flaconer, Jr., of the of its creation on June 19th; on that Mayo Clinic. It has been tried so far date 15 years ago the Communication on 60 patients. A machine standing at Act was signed. On July 1, 1934, the one side of the anesthetist takes con- old Federal Radio Commission was tinuous records of the patient's heart Absolutely No Knowledge of Radio abolished and 11 days later the FCC and brain waveforms. Preliminary Necessary, You Need No Additional Parts. organized. About 125 of trials indicate the technique is The was formally that PROGRESSIVE RADIO KIT is the Only Com- the present staff members, including equally useful with any type of anes- plete Kit. Operates on 110-120 Volts AC /DC Commissioners Hyde, Walker, and thetic. Contains everything r need. Instruction book. metal chasms. tubes. Istors a all other nee- Sterling, were with the Commission misery radio parts Thee 3S -page Instruet,en Rook w ,t- en by expert radio ...rooters ana eng.neers teaches weather you to Duda radios in nal The tit.- when it was organized. RADAR aided all- operations its are designed to rov,ee e ceuent performance. of the first annual re- of the Berlin air -lift, Dr. H. R. Ait . fifteen ,rcuits constructed. including Comparisons Skifter, tl . . 1 audio amplifier and 3 transmitters. SPECIAL OFFER-Electrical and Radio Tester nt ebse- port and present figures indicate how president of Airborne Instrument Lab- lulely FREE with each Progressive Radio Kit. Plus FREE Membership in the Progressive Radio Club. En- radio has grown since 1934. At that oratory, Inc., revealed last month. A titles you to free expert advice ana consulubon service time there were 51,000 radio stations new type of radar made by the com- with li radiotethnitians. ORDER YOUR KIT NOW! of all kinds, 600 broadcasters, 45,000 pany, the Moving Target Indicator VACUUM TUBE VOLTMETER KIT hams, less than 2,000 ship stations, (MTI), shows only objects in motion, A professional piece of test equipment you need for FM and Tt'. Attractive steel about 700 aeronautical licenses, 250 simplifying the work of the operator. ease. FREE: Book on Ad- police transmitters and no fire stations. The principal bad -weather flying prob- ranted Servicing Techniques. In contrast, recent figures show lem was traffic control, since ships nearly 150,000 total stations (in addi- would be likely to collide with each 5" OSCILLOSCOPE KIT tion to more than 200,000 associated other. The MTI radar permitted the AMFM TELEVISION an absolute tist- for txlay'x radio- mobile units), 4,000 broadcast authori- maximum number of aircraft to oper- man. Input Impedance: t Min. and 511 zations of all kinds, 80,000 amateur ate by keeping track of the position of Mudd. Tllxs- 2 -sJ7. 2-11'3. 1.554. I .5ItP1. FRF.e:: Bonk on Ca- $39.95 calls, 20,000 shipboard stations, 27,000 each and telling pilots how to proceed thmte Ray Oselllo -rope air service licenses (and over 100,- to avoid collisions. VOLT -OHM -MI LL !AMMETER 000 aircraft radio telephone authoriza- KIT tions), more than 4,600 police stations, LICENSING of radio service shops is simple to instruct. Inexpensive in Los to an but accurate. FREE: Book on and 100 municipal fire department sys- legal Angeles, according Elementary Radio tems. Individual licensed operators opinion furnished by City Attorney ..r hg ... $14.95 (holders of commercial tickets) have Ray L. Chesebro last month to the City increased from the 1934 number of Council, reported in the Loa Angeles SIGNAL TRACER KIT 5,500 to almost 375,000. Times. Radio repair, says Chesebro, an Invaluable aid In trouble- shnnling FREE. Iia,k on Radb. The grand total of all authorizations falls into the same category as auto- Text Instruments. n $21.95 outstanding, including both operators mobile repair shops and used car lots, and but mobile land which already operate under revocable r -105 TELEVISION KITS stations, excluding Factory'built and aligned 13 stations, has passed the 700,000 mark, permits issued by the Police Commis- channel Tuner -1g Tube KR- sion. The Council, in asking for the 7" Kit 559.50 testifying to the tremendous importance Complete net of tubes. in, biding of radio in present -day America. opinion, was seeking to stop general Cathode Ray Tube. $41.58 unethical and fraudulent practices in F-aetny -built and aligned 13 channel Tuner. 10' KIt, less tubes $82.99 TELEVISION PROGRAMS are not the radio repair business. Complete net of tubev. including Cathode worth the phosphor they're projected liar Tube $55.80 Cabinet for T. or 10' ...... $24.50 on, was, in effect, the comment made NATIONAL NETWORK of radiotele- FREE: Television nervnln_ Gm< last month by Lloyd Espenschied, one phone stations for mobile service to the of the inventors of the co -axial cable general public was announced last PROGRESSIVE AMPLIFIER KIT which makes large -scale television pos- month by the National Mobile Radio II il \Inpll hi ìuiiId sible. "I wouldn't give a damn for any- System. Operators of local systems tau selenium re( l :: thing I've seen," commented the 60- which handle messages for private Book on Amplifier- 516.00 year -old inventor, as reported by the automobiles and trucks have banded to- TV SWEEP GENERATOR KIT $28.95 New York Herald Tribune. "It's the gether in a nation -wide network oper- Rangopa .. ,tr same as sound broadcasting- perme- on the same channels. Subscrib- SIGNAL GENERATOR KIT $18.95 ating 150 Kc. -34 M ated with commercialism from begin- ers in any area served by an affiliate 35 Me. -100 '.. RF SIGNAL TRACER PROBE KIT $5.50 ning to end. We in the United States will be able to send messages from their 20 cycles -2 -1534 spa. ought to be ashamed. The British have automobiles or trucks to any point in ECONOMY AMPLIFIER KIT...... 55.95 Simple to huai "mete with live tubas. done a far better cultural job in both the country. Present stations, many of FRFV .n Amplifiers. sound which by telephone answer- S TUBE AC-DC SUPERHET KIT...... 514.25 and television broadcasting." are owned Complete and cabinet. Mr. Espenschied and Herman A. ing services, are experimental and have Fne,:F;: Iinek Receivers. 6 TUBE AC-DC 2 -BAND SUPERHET KIT.S17.45 Affel, research engineers in the Bell served subscribers locally for some time. Complete with tubes and cabinet. Telephone Laboratories, devised the By August the network will be in op- FREE: Hook oo Amateur Radio Building. 7 TUBE AC -DC FM RECEIVER KIT $29.95 co -axial cable in 1929 to satisfy the eration between Boston and Washing- Co mp lete ',an t w and eabinet. urgent demand for more telephone ton, so that a traveler at almost any MEP: T,levi.i.ut and FM Servicing Moles. 4 TUBE SUPERHET PORTABLE KIT $12.95 circuits. point along the route will have continu- tom plite with tube. and cabinet: leas lallerlea. FREE: Book on Dual ous contact with one or another of the Radio Clrculto. AUTOMATIC BIKE BRAIN WAVES can be used by an stations. Messages will be transmitted RADIO anesthetist during an operation to warn between cities by the station operators, Can be mounted on a bi- if the patient is approaching death, it using stations themselves for re- cycle. or carried as a per- the sonal portable radio. Sup- was disclosed last month. According to laying, though regular long- distance Plied nith all bicycle mounting hard, are and a Mayo Clinic team at the Atlantic telephone calls will be made when neces- telescopic antenna. Anti- theft feature. City meeting of the AMA, continuous sary. 1.e. batteries 517.47 records of the electrical activity of the AUTOMATIC CAR RADIO brain and heart give warning of danger TRANSISTOR TETRODES are the lì tubes supelhet. Three gang condenser, fits all ar asv In- two minutes earlier than the breathing latest development in germanium crys- stallalion mount ing bracken and pulse rates which W. included. List price the anesthetist tal amplifiers, Rowland Haegele of 5x1.9; NOW ONLY 527.97 ordinarily observes. When the regular the Physics Laboratories of Sylvania Also 5 Tube Ruperhet Only 525.97 waves suddenly flatten out almost to a Electric Products, Inc., announced last Deduct 2% if full payment accompanies order. C.O.D. orders accepted in U.S.A. straight line, it is time to stop the month to a Princeton conference. The concerning the above anesthetic mixture and turn on the tetrodes, said Haegele, provide a high mertchandise. tend for our FREE oxygen. degree of isolation in mixer service so PROGRESSIVE ELECTRONICS CO. The new life -saving technique was that signals on one emitter are not Dept. RE -28 497 Union Avenue developed by Drs. R. F. Courtin, R. G. picked up by the other. Brooklyn 11, New York AUGUST, 1949 111 le(a44.t TEST CHECKER KI eathhii_ TUBE ÿ r.. .e i.wt:.9^ k .¡, '7estwted 1. Measures each element individually. 5. Checks every tube element. 2. Has gear driven roller chart. 6. Uses latest type lever switches. 3. Has lever switching for speed. 7. Uses beautiful shatterproof full view meter. 4. Complete range of filament voltages. S. Large size 1l "x14 "x4" complete.

Check the features and you will realize that this Heathkit has all the features you want. Speed - simplicity - beauty - protection against obsolescence. The most modern type of tester - measures each element - beautiful Bad -Good scale, high quality meter - the best of parts - rugged oversize 110 V. 60 cycle power transformer - finest of Mallory switches - Centralab controls - quality wood cabinet - complete set of sockets for all type tubes including blank spare for future types - fast action gear driven roller chart uses brass gears to quickly locate and set up any type tube. Simplified switching cuts necessary time to minimum and saves valuable service time. Short and open element check. No matter what arrangement of tube elements, the Heathkit flexible switching arrangement easily handles it. Order your Heathkit Tube Checker today. See for yourself that Heath again saves you '3 and yet retains all the quality - this tube checker will pay itself a SHIPPING for to few weeks - better build it now. Complete with detail instructions - all parts - cabinet - roller chart -ready WT. 15 LBS s295O to wire up and operate. hew r eal4 TELEVISION ALIGNMENT GENERATOR KIT

Everything you want in a television alignment generator. A wide band sweep generator covering all FM and TV frequencies -a marker indicator - AM modulation for RF alignment variable - calibrated sweep width (1 -30 Mc. - mechanical driven inductive sweep. Husky 110 V. 60 cycle power transformer operated - step type output attenuator with 10,000 to 1 range - high output on all ranges - band switching for each range - vernier driven main calibrated dial with over 45 inches of calibrations - vernier driven calibrated indicator marker tuning. Large grey crackle cabinet 16 -1/8" x 10 -5/8" x 7.3/16". Phase control for single trace adjustment. Uses four high frequency triodes plus 5Y3 rectifier - split stator tuning condensers for greater efficiency and accuracy at high frequencies - this Heathkit is complete and adequate for every alignment need and is supplied with every part - cabinet - calibrated panel - all coils and condensers wound. calibrated and adjusted. Tubes, transformer, test leads - every part with instruction manual for assembly and use. Actually three instruments in one- TV sweep generator - TV AM generator and TV marker indicator. Also covers FM band. 53950

qleaddit eecttitleet SINE AND SQUARE WAVE hew AUDIO GENERATOR KIT FM TUNER KIT CONDENSER CHECKER KIT $1475 s1950 a $345? CABINET ELSE TO BUY EXTRA

ELSE TO BUY A truly fine FM Tuner with the coils ready Experimenters and servicemen working with a wound. all alignment completed -all that Bridge type circuit Power factor scale square wave for the first time invariably wonder is necessary is wiring and it's ready to play Magic eye indicator Measures resistance why it was not introduced before. The charac- - uses super regenerative circuit - 110 V. 110 V transformer Measures leakage teristics of an amplifier can be determined in 60 cycle transformer operated - two gang operated Checks paper -mica- seconds compared to several hours of tedious tuning condenser - slide rule calibrated All scales on panel eledrolytics plotting using older methods. Stage by stage, dial - two tubes - complete instructions Checks all types of condensers, paper -mica. amplifier testing is as easy as signal tracing. including pictorial enable even beginners electrolytic- ceramic over a range of .00001 MFD The low distortion (less than 1%) and linear to build successfully. to 1000 MFD. All on readable scales that are output ( one db.) make this Heathkit equal The circuit uses twin triode and is ex- read direct from the panel. NO CHARTS OR or superior to factory built equipment selling for tremely powerful - pulls in stations far MULTIPLIERS NECESSARY. A condenser three or four times its price. The circuit is the beyond normal expectations. Shipping Wt., checker anyone can read without a college popular RC tuning circuit using a four gang 4 pounds. education. A leakage test and polarizing voltage variable condenser. Three ranges 20.200. 200- Beautiful mahogany cabinet for FM for 20 to 500 volts provided. Measures power 2.000. 2,000- 20,000 cycles are provided by Tuner (shown above) extra $3.75 factor of electrolytic between 0c/ and 50%. selector switch. Either sine or square waves 110 V. 60 cycle transformer operated complete instantly available at slide switch. All com- with rectifier and magic eye tubes, cabinet, cali- ponents are of highest quality, cased 110 V. brated panel, test leads and all other parts. 60 cycle power transformer. Mallory F.P. filter eatkket TOOL KIT Clear detailed instructions for assembly and condensers. 5 tubes, calibrated 2 color panel. use. Why guess at the quality and capacity of grey crackle aluminum cabinet. The detailed Now a complete tool kit to assemble your a condenser when you can know for less than a instructions make assembly an interesting and twenty dollar bill. Shipping Wt., 7 lbs. instructive few hours. Shipping Wt., 13 lbs. Heathkit. Consists of Krauter diagonal cut tens and pointed nose 10000 V H.V. Test Prebe kit RF Crystal Test Probe Kit assembly pliers, Xce- No. 309. Kit to assem- lite screwdriver, 60 No. 310. Extends ble. RF probe extends Watt 110 V. solder- range of any 11 meg- VTVM range to 100 ing iron and supply ohm VTVM to 3,000 MC. Complete with of solder. Shipping and 10,000 Volt ranges. 1N54 crystal. Shipping Wt., 2 lbs. Complete A necessity for television. Ship. wc, 1 lb. weight, 1 lb. $6.50 kit.... $5.95 ...... _ _.. _. $4.50

* ... BENTON HARBOR 20, MICHIGAN

R A D I O - E L E C T R O N I C S f o r H EQUIPMENT and accessories

?gear,'eatic¡¢ct rc eat!`kit 5 "OSCILLOSCOPE KIT '7eatuze4 BATTERY ELIMINATOR KIT Instant switching to plates or amplifier from front panel. Now a bench 6 Volt power supply kit Sweep generator supplying riable for all auto radio testing. Supplies 5 - sweep 15 cycles to 30,000 cycles. a All on 7 1 Volts at 10 Amperes continuous or controls front panel. Cased electrostaticly shielded 110 V. 15 Amperes intermittent. A well filtered 60 cycle power transformer. rugged power supply uses heavy duty AC test voltage on front panel. selenium rectifier, choke input filter External synchronization post on front panel. with 4,000 MFD of electrolytic filter. Deflection sensitivity .65 V. per inch 0.15 Volt meter indicates output. Out- full gain. put variable in eight steps. Excellent for Frequency response ._ 20 °s from 50 cycles to 50 Kc. demonstrating auto radios. Ideal for Input impedance 1 Megohm and 50 MMF. servicing - can be lowered to find The Heathkit 5" Oscilloscope fulfills every sticky vibrators or stepped up to equiva- S22:0 servicing need. The husky cased power transformer supplies 1100 Volts negative and lent of generator overload - easily con- SHIPPING WT. 18 L85. 350 Volts positive. Tubes supplied are two strutted in less than two hours. Com- 7 4dé,e^ ELSE 6517 amplifiers, 884 sweep generator, two plete in every respect. `^"`i ro suv 5Y3 rectifiers, and 'BPI CR. tube. Grey crackle aluminum cabinet and beautiful grey and maroon panel. Chassis especially de- 1949 MODEL signed for easy assembly. An oscilloscope provides endless sources $3950 of experimentation in radio, electronics, .iesle 4 VACUUM TUBE medicine and scientific research. Detailed instructions make assembly fun Zee Klt and instructive. Shipping \C't., 24 lbs. VOLTMETER KIT Express only. ELSE TO BUY ' eatuzed

New 200 on Meter. ?leu.' eatkt(it SIGNAL TRACER AND 24 Ranges. New Accessory H.V. Probe makes UNIVERSAL TEST SPEAKER KIT Heathkit a kilovoltmeter. (Extra) The popular Heathkit signal tracer has now New Accessory RF Probe extends range been combined with a universal test speaker to 100 megacycles. (Extra) at no increase in price. The same high quality tracer follows signal from antenna A new V -2 VTVM with Model Heathkit to speaker locates intermittents de- new 200 microampere meter. four ad- - - fective parts quicker saves valuable serv- ditional ranges scale linear ranges - - full ice time -gives greater income per service on both AC and DC of 0 -3 V.. 10 V., hour. Works equally well on broadcast 30 V.. 100 V.. 300 V. and 1,000 V. - FM or TV receivers. The test speaker has Accessory probe listed elsewhere in ad assortment of switching ranges to match voltage range to and 10,000 extends 3,000 push pull or single output impedance. Also volts D.C. New model has greater sen- $1950 tests microphones, pickups PA systems sitivity, and accuracy the - stability -still comes complete- cabinet 110 V. 60 highest quality features shatterproof - - - cycle power transformer tubes, test probe, plastic full view meter face automatic itot441.9 - - all parts and detailed instructions for as- meter protection, push electronic pull ELSE TO BUY sembly and use. Shipping Wt., 8 lbs. voltmeter circuit, linear scales - db. scale- ohmmeter measures 1 /10 ohm to I billion ohms with internal battery - isolated DC test prod for dynamic meas- featfiecr ELECTRONIC SWITCH KIT urements It megohm input resistance - DOUBLES THE UTILITY OF ANY SCOPE on DC - AC uses electronic rectification $Z45ó An electronic switch used with 6H6 tube. All these features and with any still the amazing price of only $24.50. oscilloscope provides two separately Comes complete with cabinet - panel - three tubes - new Mallory controllable traces on the screen. Each switches - test prods and leads. 15. ceramic divider resistors and all trace is controlled independently and other parts. Complete instruction manual for assembly and use. Better the position of the traces may be start your laboratory with this precision instrument. Ship. Wt., 8 lbs. varied. The input and output traces of an amplifier may be observed one beside the other or one directly over the other illustrating perfectly any change occurring in the amplifier. Dis- tortion - phase shift and other defects show up instantly. 110 Volt 60 cycle transformer operated. Uses 5 RF SIGNAL tubes (1 6X5, 2 6SN7's, 2 6S17's). Has individual gain controls, position- GENERATOR KIT ing control, and coarse and fine sweep- ing rate controls. The cabinet and panel match all other Heathkits. Every part supplied including detailed in- $3452 structions for assembly and use. Ship- $1950 ping Wt., 11 lbs.

e. , ei i e: 3 - T U B E A L L W A V E

ELSE BUY R A D I O K I T An ideal way to learn radio. This kit is complete ready to assemble, with tubes Every shop needs a good signal generator. The Heathkit fulfills every and all other parts. servicing need, fundamentals Operates from 110 V. AC. Simple, clear detailed from 150 Kc. to 30 megacycles with instructions strong harmonics over 100 megacycles covering the new television make this a good radio training course. Covers regular broadcasts and short wave bands. and FM bands. 1 1 U V. 60 cycle transformer operated power supply. Plug -in coils. Regenerative 400 cycle audio available for modulation or audio testing. Uses circuit. Operates loud speaker. Shipping 3 lbs. 6SN7 as RF oscillator and audio amplifier. Complete kit has every Wt., part necessary and detailed blueprints and instructions enable the HS30 Headphones per set $1.00 builder to assemble it in a few hours. Large easy to read calibration. 21/2" Permanent Magnet Loudspeaker 1.95 Convenient size-9" x 6" x 4'., ". Shipping Wt.. 412 lbs. Mahogany Cabinet 2.95

. BENTON HARBOR 20, AUGUST, 1949 12

TV Offers YOU Good Pay, Security and Bright Future CRfl On- the -Job Training Can Give You the Technical Ability to Step Ahead of Competition and Get the Better Job You Want GET IN and get ahead in Television! You can make your every field- aeronautical radio, UHF, wide band operation own opportunity if you start preparing now. No need to are based on TV techniques. Your CREI training becotttes tell you how fast Television is expanding-or, of the number important no matter in what direction you are heading.) ou of jobs being created. One of industry's leaders predicts: will find CREI training basic and helpful right from the start. 1 Million Persons in TV within 4 Years! He estimates 12 You will learn about and understand such subjects as: Optics, Million TV sets by 1953 -40 Million by 1958. Pulse Techniques, Deflection Circuits; RF, IF, AF and Video Amplifiers; FM; Receiving Antennas; Power Sup- If your future is in radio, you must get in Television. plies; Cathode Ray, Iconoscope, Image Orthicon and CREI offers the very training you need to go after -and Projection Tubes; UHF Techniques, Television Test good job. Equip- get -a TV ment, etc. CREI can show you the way with convenient spare-time Don't wait another day. Television won't wait for you. In study at home that gives you the up -to -date technical back- all our 22 years of association with professional radiomen ground you must have for Television. CREI courses are de- we know that the man who acts promptly is the man who signed to give you a thorough grounding in basic principles succeeds. and take you step -by -step through the more advanced subjects of TV and its related fields. It must be remembered FREE SAMPLE LESSON that all new electronic developments have their roots in past Now. see for yourself! Mail the coupon for free sample lesson and see how interesting It Is to study at home and improve your income technique. The basic theory of TV finds application in through ability the CREI way. THE ORTHICON AND IMAGE ORTHICON" This lesson describes the development of the small. 3 -Inch Image VETERANS: CREI TRAINING AVAILABLE UNDER G.I. BILL. orthicon tube: theory and operation of the orthicon; image orthicon; specific features. FOR MOST VETERANS JULY 25, 1951 IS THE DEADLINE - ACT NOW ! MAIL COUPON FOR FREE BOOKLET If you have had professional or amateur radio experience anti want to make more money, let to CAPITOL RADIO ENGINEERING INSTITUTE prove to you we have the training you need to lith A Put RNI. N. W., Deft. I 48-11, Washiness II. D. C. qualify for a better radio job. To help us answer Gentlemen: Please mail me FREE SAMPLE LESSON and your intelligently your inquiry -please slate briefly your 12 -pg. booklet. "Your Future in the New World of Electronics." background of experience, education and present plus full details of your home -study training. I am attaching a position. brief resume of my experience. education and present position. (.'heck field of greatest interest: D PRACTICAL TELEVISION ENGINEERING PRACTICAL RADIO ENGINEERING D TELEVISION, FM & ADVANCED AM Capitol Radio AERONAUTICAL RADIO ENGINEER- SERVICING ING D ADVANCED ELECTRONICS COMMU BROADCAST RADIO ENGINEERING NICATIONS Engineering Institute (AM, FM, TV) D RADIO.ELECTRONICS IN INDUSTRY NAME An Accredited Technical Institute Founded in 1927 s'rREET - _..- ...._...... Dept.14$-A, 16th and Park Road, N. W., Washington 10, D. C. CITY ZONE STATE I AM ENTITLED TO TRAINING UNDER G. I. BILL. Branch Offices: New York (7) 170 Broadway San Francisco (2) 760 Market St. RADIO -ELECTRONICS fo 13

THIS BOOK WILL HELP YOU SAVE TIME, WORK, EARN MORE!

- - ^.:..-

YOU SHOWS SYLVANIA TO Only $ßóo

EXPLAINS THESE AND RADIOS MANY MORE

SERVICE 1 AM and FM receiver alignment 2. Locating hum 3. Signal tracing and trouble shooting AN 4. Finding receiver faults from oscil- WITH loscope patterns S. Checking AVC action 6. Voltage gain measurement 7. Auto radio vibrator tests 8. Checking peak current in rectifiers OSCILLOSCOPE" 9. Impedance measurement filter capacitors and gives You step 10. Checking - book that in many others! a big, complete the oscilloscope Keré s for using audio am- -step instructions radio receivers, bY servicing testing and 'scope and transmitters. of circuits, circuit SYNNIA plifiers 90 illustrations more than The set-up arrangements oscilloscope pasterns ove 50 ELECIRIC eTexplain p testing FLUORESCENT LAMPS, FIXTURES. WIRING DEVICES, SIGN applications. TUBING: LIGHT BULBS: PHOTOLAMPS; RADIO TUBES; CATHODE RAT TUBES; ELECTRONIC DEVICES r- alp Sylvania Electric Products Inc. Advertising Dept. R -2916 * Get this big 72 -page book! Emporium, Pa. Gentlemen: Send me "How To Service Radios with an * More than 90 pictures t1tlógr8tBB1R Oscilloscope." Enclosed is $1.00. Name

Address * Written in easy -to- follow servicemen's language! City Zone State I- AUGUST, 1949 Radio IiUsilIcss The laacent Engineering Corp. of New 5th Annual Pacific Electronic Exhibit WHERE TO BUY IT . York, N. Y., specialists and con- for August 30, 31, September 1 in San WHOLESALE RADIO sultants in electronics, have recently Francisco. been appointed as consulting engineers Spokesmen for the West Coast group of Baltimore by the Plessey International Limited of said the Exhibit will be held in con- Ilford Essex, England. This company is junction with the 1949 Western Re- Unbeatable T. V. Reception one of the largest manufacturers of gional Convention of the I.R.E. Both For the strongest, sharpest. brightest possible television, picture in any location. electronic, mechanical and groups will center their activities in other equipment in the British Isles. San SNYDER LAZY XX Francisco's mammoth Civic Audi- T.V. ANTENNA torium. The QUICK TO International Telephone & Telegraph joint meetings of the Electronic INSTALL l:orp. has announced the formation Industry and the I.R.E. will follow by of four Just unfold, Capehart- Farnsworth Corp. as a wholly - days the Annual National Conven- tighten and erect. owned subsidiary to acquire the assets tion of the American Institute of Elec- surnm ndvd fr trical Engineers, also scheduled for San fringe areas.as 1<.otlal` arMet vu rad of Farnsworth Television & Radio Lazy X ail eha-t Is plus FM Francisco. Over-all height II ft. erected C0111- Corp., as approved Farnsworth I by hurtw tlf ;1r !,/o.,,..!:,h1':iai ;`1 $19.88 stockholders. 1.' ,.. utni:h , [ . ml1;!.1>I1.1 i T\-2. Allen B. Du Mont Laboratories, Inc. of NEW LOW PRICE! HALLICRAFTERS At a meeting of directors of Capehart- Passaic, N. J., announces the publica- Farnsworth Corp., ELLERY W. STONE tion of a four page " Dealergram," lat- MODEL S -38 Model S-:Oh, shown Irings was elected President and DAVID R. est dealer aid especially prepared for outstanding reception HULL, moderaterice. Standarda Ianl Executive Vice President. franchised Du Mont dealers and dis - ndre Winsthree short wave I Is. 0allt -b, P.M. The following officers were also elect- tributors, according to HENRY R. GEYE- speaker.`aker It to s AMr rent Pal 5.10 kr. `il' ed: PHILO T. FARNSWORTH, Vice Prest- LIN, advertising manager of the tele- 0111% rectifier... dent; HENRY C. ROEMER, Vice Presi- vision receiver sales division. We have complete line of Hallleralters Receivers. dent; WILLIAM CLAUSEN, Vice Presi- The Dealergram, which consists of dent; P. H. HARTMANN, Application Engineered for T.V. -FM Treasurer; W. four pages of video news items of in- F. HOEPPNER, Comptroller; and CHES- Wide Range Sweep Signal Generator terest to dealers and distributors, cur- TER H. WICGIN, Secretary and Assist- rent promotional ideas and sales Precision Series E -400 helps, ant Treasurer. EDWIN NICHOLAS, insert rt adng 2 In A. is profusely illustrated and will be 4H11 Me.' 2 1 ranges tu 2.10 Mr. 2811-4M) Mr. lianas harmu- former President of Farnsworth Tel- mailed to Du Mont dealers and :Orally tl distrib- calibrated. Narrow ami wide I OJ sweep. 0.1 Me. evision and Radio Corp., will act as utors each month. The first mailing of ui . Mo.`stWon- Range phasing Assistant to the President. the Dealergram includes Crystal Marker'Calilí,rral rl Os. an explana- i ilnnr hum -In. 4 rotary se- tory lected r 1,11 sock.ets ('nn,. letter and an application blank 1Irte with s test rabies. In..; which will Mr andd 2 Me. r c. le Ilvtron Radio & Electronics Corp. has enable dealers to have the 'Ïtsee icalÌS" sales -aid sent to '2.1-x3 n-51247 0 been producing TV picture tubes since their employees. February of PRECISION 5" SCOPE this year in steadily in- Model ES 500 S149.50 creasing quantities. Shipments are now being made to a broadly representative F. hania Electric Products, Inc. an- LOW PRICES ON QUALITY GUDEMAN group of leading manufacturers of TV nounces that a full line of television ALUMINUM CAN FP TYPE receivers -as well as to Hytron dis- sets bearing the Sylvania name will CONDENSERS tributors. be placed on the market this fall, ac- 30.30 mfd, 150 V 59: cording to DON G. MITCHELL, presi- 50-50 mid. 150 V 65c dent of the company. 20.20.20 Intd, 150 V 65r Stewart- Warner Corp. of Chicago had 40.40.40 mfd, 150 V 75.. a net profit for the first quarter of Sets are expected to be available on 50-30 mfd, 150 V. 25 -25 V 75.. 1949 of $404,292, equal to 31 cents October 1. Initially, the line will feature 10 -inch and 121/2-inch table models, BUILD YOUR OWN AND SAVE! per share of $5 par value common stock, JAMES S. consolettes, and console combinations NEW! SIGNAL GENERATOR KIT KNOWLSON, board chairman and president, with three -speed record changer, AM EICO MODEL 320 K told the annual meeting of stockholders. The com- and FM radio, and also a 16 -inch con - pany had a net profit of $902,094, or solette. si l,. In making the announcement, Mr. inipIta withilh fumlamen. 70 cents per share for the period ended 4ill ryelc Mitchell stated that Sylvania had de- type Ldto March 31, 1948. First quarter sales in sebe- layed entrance into the television set i 1. a-x 1949 were $14,706,155 and in 1948 were tubes. $17,338,552. market until an extensive program of $19.95 field and laboratory engineering re- HIGH PRECISION VACUUM TUBE search in the direction of simplification, Philco Corporation, Philadelphia, re- VOLTMETER KIT. Model 221 K $23.95 clarity of picture and minimum main- ports that the sales in the first quarter tenance, Top Auto Reception at Low Cost of 1949 were $53,006,000 had developed sufficient experi- as compared ence to assure quality performance. SNYDER AUTO RADIO AERIALS with $58,661,000 in the first quarter a SIde -Cowl Mounts year ago. Net income in first MAINLINER C -3D $1.88 the quarter of this year was $915,000 and was equivalent, Television Manufacturers Association New deluxe malet. 3 has started a project t Inne extend tu IIh. I'hrnmo after preferred dividends, to 49 cents aimed at estab- rare ball and rhmon, lishing standard service agreements and r;qped IS :1k Kiln' 'lJIl - per common share on the 1,678,779 IIF W,I practises for television sets, according BIG BOY C -4D $2a6 ; hylene shares outstanding on March 31, 1949. 4 heavy duly .rrilI,e 3 to MICHAEL L. KAPLAN, President of L`'raft 1. In the first quarter a year ago, net tending fa 9e. ,throne static :Omen nt- TMA and of Sightmaster Corp. A sur- h 11 and chrome raapcd iingeelwlth income totaled $1,959,000 after tax - Bakelite Insulators. vey eluded. paid reserves of $600.000 for inventory of service organizations and dealers who service sets will be WRITE FOR FREE MONTHLY "FYI" BULLETIN and $185,000 for future research and the first action Phone MUlberry 2134 to establish a universal contract for the ADDRESS ORDERS TO DEPT. QR -83 development work. This was equivalent to $1.16 per benefit of the public and the industry. common share on the 1,- After this accumulated 607,576 shares outstanding at the end data has been WHOLESALE of 1948, after preferred dividends. sifted, TMA expects to be able to RADIO PARTS formulate a standardized service 'con- Iry CO., Inc. tract under which service organizations 311 W. Boltimore St. The West Coast Electronic Manufac- will be expected to meet certain quali- BALTIMORE 1, MD. turers Association, San Francisco, Cali- fications as to experience, backgrôìund, fornia, announces the scheduling of the technical ability and reputation. RADIO -ELECTRONICS fors li &ebCIftCL

AMEICA'S FOREMOST TV ANTENNA

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ONE ANTENNA - ONE LEAD IN

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AN ANTENNA OF PROVEN QUALITY The Welin Circle "X" television antenna has extremely high signal strength and it eliminates the necessity of having rotors, it is quickly assembled, easily installed, structurally sound, has less vibration, no reflectors to align, requires only one lead - in, and is perfectly matched to 72, 150 and 300 ohm receiver input circuits. $25óö Dealers can reduce their service recalls by using the Welin Circle "X ". It provides a satisfied customer on first installation. The Welin Circle "X" has been field tested and WRITE FOR CONFIDENTIAL has proven far superior to other antennas. In addi- DISTRIBUTOR AND tion to outdoor service the Welin Circle "X" has DEALER DISCOUNTS given outstanding reception when installed in attics 30 -40 miles from the transmitting station.

DIVISION CONTINENTAL COPPER & STEEL INDUSTRIES, INC. 500 MARKET STREET PERTH AMBOY, N. J.

AUGUST. 1949 Ili

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Squeezing the Service Technician

. New legislation threatens the telerision service contractors . . .

By THE EDITORS

THE radio service technician's bed has never been Why are present service contract rates so low? There strewn with roses; and of late the situation has been are three main reasons. First, it is in the dealer's interest worsening to such an extent that it threatens to get to make the price for installation and service as low as entirely out of hand. possible, since he does not intend to do this work himself. Latest development comes from New York State, where But because of the novelty of the business, would -be con- the Attorney General's office may take action which could tractors had no means of knowing what their costs would strike a mortal blow to the independent television installa- be, and in many cases were sold these "suicide" contracts. tion and maintenance man. The proposition is to declare Probably the greatest single cause of loss -producing that television service contracts come under the existing contracts is the "sour" television model. We have had these insurance laws, and that all organizations handling service models since the beginning of broadcast radio. Every should therefore be licensed under the State insurance law. manufacturer makes such a set occasionally, and the This means that firms taking television service contracts complications of television render the chances of putting would have to prove they were financially stable, and on the market a model with latent defects that much would have to put a required sum of money into a trust greater. Such a model may call for twice as many service fund to insure that television set owners would get the calls as the average televiser, and the maintenance tech- service they are entitled to under their contracts. nician who has contracts for a large number of them is The real cause, of course, is that television maintenance slated for certain economic destruction. contracts have been set at a price which has made it im- The nature of the contract itself it partly to blame. possible for the service contractor to carry them out. His Only a term of service, with no restriction on the number costs have been so much higher than the contract fees of calla, is usually specified. The customer therefore feels that he has been forced into bankruptcy, in many cases it good business to call up the service technician any time watching the savings of a lifetime disappear with the if something out of the ordinary appears on the screen. funds he received for his television contracts. Many maintenance men report that half their calls are Tragic as this has been for the service technician who of the "nuisance" variety, in which nothing is actually has been forced to close up his business, the customer has wrong with the set, and the customer requires only an been hurt as well. He has paid his money for a year's serv- explanation of what he has seen. ice. Three months after the contract is signed, his receiver How can we remove these causes? may develop a fault. He finds that the company with which Obviously THE UNLIMITED MAINTENANCE CON- he signed the contract is no longer in existence. The dealer TRACT MUST GO! The manufacturer must be respon- who sold him the television set and contracted for its in- sible for calls due to defects in his receiver. All calls - stallation through an intermediary service firm is not after the manufacturers' guarantee period -should be paid interested in his plight. Neither is the manufacturer of the for by the customer. An ideal installation and maintenance set, in spite of the fact that one of his models may have contract would call for a fixed fee for installation and a been the cause of the customer's dilemma and the con- specified number of calls during the "work -in" period of tractor's bankruptcy. the receiver. All calls thereafter would be paid for at As we go to press no final decision has been taken by a stated rate per call. This system would prevent the main- New York State on this proposal, and it is hoped that no tenance technician from going bankrupt. unfavorable decision will be made. New York State is by For -make no mistake about it-the small two- or three - far the country's biggest television market, and if such man shop is the most efficient service organization ever an adverse action were taken in that state, many other devised. We went through this same children's disease in states would certainly follow the example. the infancy of broadcast radio in the early '20's. More The New York State Insurance Department contacted than one manufacturer wished to assure good repairs many of the larger television manufacturers in an en- by "factory service" and sets were shipped back to the deavor to have the makers themselves guarantee the ser- factory when they broke down. But it was soon found that vice contracts. With the exception of several large tele- factory repair departments could not break even without vision set makers who have their own service setups, the charging from three to five times as much as would the manufacturers declined to have anything to do with the local repairman for an equivalent job. proposition. They insisted that maintenance was the deal- The final answer -for manufacturer, dealer, service ers' and distributors' job and felt that if the manufactur- technician and set owner -is not a system that will add ers were made responsible they might become involved in to the expense of television maintenance by sqeezing the lawsuits and other difficulties. smaller service technicians and installation firms out of What then is wrong with the entire setup? How can business, but common sense that will take the "gimmicks" the trouble be cured? The main difficulty is obviously that out of the present setup and thereby make it possible for the rates paid for television installation and maintenance them to stay on the job. are so low as to drive the service concerns out of business. Far -seeing television manufacturers cannot fail to be The cure is obviously to remove this trouble, not to make impressed with this situation. We are faced with a shrink- the present difficulty an excuse to channel television ser- ing economy in this country and the public cannot be placed vicing, installation, and maintenance into the hands of in a position where it hesitates to buy television receivers. large concerns who -given a near -monopoly on the busi- for fear of having to pay twice for television servicing. ness -can then raise the contract rate to a figure that Neither can the manufacturer profit from a system that will assure them a profit under the most unfavorable cir- would result in fewer and fewer technicians being left in cumstances. This will react into higher cost to the custo- the field to service the growing number of sets. It is up mer, and eventually the manufacturer and dealer will to them to help the service technicians stay in business pay for it in the form of fewer television set sales. if they do not want to lose money in the end. AUGUST. 1949 18 Television NcWa Cover Feature Improve Your TELEVISION PICTURE

Without knowing a thing about radio. ou can better Four reception. A 'show -to- do-it" for non-technical TV set owners

By ALLAN LYTEL

When you adjust the rear -panel controls, have someone hold a mirror so you can see how adjustments are affecting the picture. Large mirror is best.

IF YOU drive a car, you probably feel set is much more critical for two good If the installation is a professional fully capable of telling when the gas reasons. one or if the antenna might damage tank is empty, of filling your tires First, the very short waves used for someone or something if it falls down, with air to the right pressure, and television transmission won't travel better not move it. Probably your serv- of putting antifreeze in the radiator around corners -they travel in straight ice technician has installed it right. when winter comes along -even though lines, though they will bounce off flat Whether or not you relocate the an- you're no mechanic. Despite the fact surfaces. That means that for best re- tenna, you may be able to improve re- that you may not know a resistor from ception the antenna should be placed ception by turning it a bit. Usually an inductor, there are certain improve- where radiation from the transmitter you'll do best by having it broadside to ments you can make on your television can reach it directly, without obstruc- the station, as illustrated in Fig. 1. But installation, too. tions or detours. that not always being true, try other But wait a minute! Put down that Second, a little noise on your radio positions as well. screwdriver and that pair of pliers. It's doesn't bother the ear much; but on Eliminating ghosts definitely not a good idea to go barging television the noise (interference or into the set's innards- that's work for static) makes little spots, lines, "rain" There's nothing mysterious about your professional television service and "snow," dance all over the screen, television ghosts. If you get them, it's technician. There are dangerous high and -as you may know from experience voltages inside that back cover. There -eyes won't stand much of that with- are also delicate adjustments, disturb- out complaining. LOOKING DOWN ON ANTENNA ing any one of which might put your If you have put up your own an- set out of commission. But there are tenna, the first thing to do is find out plenty of improvements you can make whether it is in the right place. Moving without taking the back cover off the the antenna a few feet in any direction set. can make all the difference in the Your first area of operation might world. So try moving it around, with a very well be your roof if you have an friend watching the TV screen to tell outdoor antenna. Your regular radio you when the picture is best. You may T1 has probably been doing very well with have to turn down the CONTRAST control a built -in antenna; but your television if you get much of an improvement. Fig. I- Antenna is broadside to the station. RADIO -ELECTRONICS for Television News because your antenna is picking up two signals from the some station. Take a look at Fig. 2. The transmitting antenna squirts out energy in all directions. The energy your antenna picks up should be that going along path A- the shortest and most direct route. But suppose some of the energy going in another direction (path B) hits a building, as the drawing shows. It bounces off the building just as light rays reflect from a mirror. (Angle of incidence is equal to angle of reflec- tion.) The reflected energy also reaches your antenna. But because it has traveled over a longer total distance than the direct ray of path A, it arrives a little later. Thus, you have two signals from the same station! The picture on your screen is "paint- ed" by a spot of light that moves across and up and down the screen very fast. At each point on the screen it varies in brightness to give the right shading to that part of the picture. And the amount of brightness at each instant is dictated by the signal it receives at If your picture is bad, get to work! The show the genuine and ghost images. that instant from the station. this better arrows Now, let us say that the signal of two parallel wires embedded in a tough, Strip the plastic away from the first TVSTATION flexible plastic, is known as ribbon line couple of inches of your piece of line, YOUR ANTENNA one of an- PATH A - or Twin -Lead or some similar name. It and fasten each wire to the 4 is usually about % inch wide, and tech- tenna posts of the receiver. You'll need nicians generally call it "300 -ohm" line a screwdriver because the antenna posts because of its electrical characteristics. are usually screw terminals, to which If that's what your installation has, it's the line from the antenna is already at- \PATIi B /PATH B time to go to work. tached. When you tighten up the two Take the tinfoil from a package of screws again, you should have both the cigarettes, tear off about half, and original antenna line and the end of the wrap it around the ribbon line a few new piece of the line in place. Fig. 3 3U'LDING inches away from your receiver. Keep illustrates the scheme. Be sure to get it in place with a paper clip. The photo one bared wire from each of the two Fig. 2- Dual -path reception can cause ghosts. will give you the idea. lines securely under the head of each path A tells the spot to make your Slide the foil slowly along the line screw. screen black in the center of the picture and await from the set, watching the Now, starting at the free end of the of a man's vest. Then the signal of JIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIII I IIIIN I I11111111IIIIIIIIIIIIIIIIIIIIIIIIIIII I11111111111IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII path B comes along a fraction of a second later with the sanee command. TO THE SERVICE TECHNICIAN By time the spot of has that light Written primarily for the nontechnical television set owner, this article moved over into the whiteness of a light- colored wall. But the path -B sig- is also intended to aid the television service technician. The technician's nal tells the spot to go black -and it time is valuable; presenting a copy of the article to each owner he visits does. Result: you see two dark areas will help save him unnecessary trips and stave off time -wasting queries. (two vests) where there should have For this reason, RADIO -ELECTRONICS has prepared reprints of the entire article (with been only one! The second vest, to the the exception of this special announcement, which will not be included). The cost of the right of the first, is the ghost. reprints is low enough to allow the technician to hand one to each of his customers. The problem is to eliminate the sig- Postpaid prices are: nal of path B. If your antenna is of a Single copies...... IOQ each =_ very directional type -that is, it rejects Lots of 6 7y2Ç each Lofs of 25 5{` each all energy not approaching it directly Lots of 12 6 each Lots of 50 4Ç each p. -you'll probably have little trouble. Orders may be sent to Order Department, RADIO -ELECTRONICS, 25 West Broadway, If you do get ghosts, try revolving the New York 7, N. Y. antenna while a friend watches the 11111111111111111 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 11111111111 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I screen. You'll very likely be able to find screen. You should have your most dif- new section of line, hold the razor blade one position at which ghosts will be at ficult -to- receive station tuned in, with across the plastic ribbon and dig it in a minimum for all or most stations. If the CONTRAST control turned down until until the metal contacts both wires. there is no such position, you'll proba- you can barely see the picture. You will Watch the screen. The picture may im- bly have to get a more directional an- notice that with the tinfoil at a certain prove or get worse. Try this razor - tenna. spot, the picture gets worse, and that blade trick at intervals of an inch or There's no way to predict in advance at another spot it brightens up. Leave so all the way up to the antenna ter - whether you'll have ghosts; they are the tinfoil at the place at which the mgnals. You will find at least one point not caused by the set itself. They are picture improved. Check all the other where the contact will improve the pic- entirely an antenna problem- therefore stations to make sure you didn't make ture. Cut the line at that point, bare experiment until you're satisfied. them worse. If all is well, you've scored the wires, and twist them together to a point! make the improvement permanent. Better results downstairs If reception still isn't good on your While this will probably improve only After you've finished with the an- worst channel, take the tinfoil off. At one station, it isn't very likely to make tenna itself, pay attention to the wire your radio store buy 3 or 4 feet of 300- others worse; therefore you will have or line connecting it to the set. ohm ribbon line. Make sure you have gained something again. If two stations The connecting line, usually made of an old razor blade handy. are bad, go through the procedure sep- AUGUST. 1949 20I Tcicvisiou News

Bible. This is quite a critical adjustment. Another good way is to try and find a channel with FM or similar interference. Try the channels not used by stations in your location. Turn the CON- TRAST control up and watch for a "tweed" (as in men's suits) pattern. If you can find one, adjust the FOCUS control until every detail of the tweed pattern is crystal -clear. The optimum adjustment can be found very quickly. If there aren't any test patterns and you can't find tweeds, tune in a program. Adjust the FOCUS control until you can see individual horizontal lines of light across the screen. You'll have to look closely on most sets, and you may have trouble seeing the lines at all on 7 -inch and smaller tubes. Using a 'This photo shows the strip tinfoil wrapped around the line held in place with a clip. of and test pattern is by far the best method of the three mentioned. arately for each one, and then use a and parts age, some of the adjustments There are two more controls you can switching arrangement like that shown need changing; you can often do it adjust if your set has a 7 -inch tube or in Fig. 4. You can buy the double -pole, yourself, without bothering the service smaller. These are VERTICAL CENTERING double -throw knife switch at a hard- technician. and HORIZONTAL CENTERING. If the pic- ware or ten -cent store. When you want But please read on before you touch ture is too far over to one side of the to watch programs on station A, throw anything! One wrong move, and the mask or too high or low, these controls the switch to contact the line adjusted picture may be standing on its ear. Go will move it to the right place. Adjust- for that station; ditto for station B. slowly! ment is very easy -just watch the im- When watching stations needing no im- Item No. 1 is to get a good -sized mir- age and twirl the control shafts. provement, leave the switch entirely ror if you have one. A hand mirror will Once again a warning: The other open. You can screw the base of the do if you can't find a bigger one. After controls on the rear of the set interact; switch to the back of the receiver cab- moving the set out so you can get be- that is, adjusting one affects the func- inet. hind it, prop the mirror on a chair in tions of another. One twist of a shaft There's one more thing to check in front of the screen. If you can't do that, and you're likely to spend the rest of the antenna department. Notice how get someone to hold the mirror for you, the evening trying to get a good pic- the ribbon line comes down from the as the personable young lady is doing ture. roof. Is it securely anchored all the in the photograph. way so it can't whip about in the wind? If there isn't much light behind the Light filters and enlargers If not, move it yourself and see set, use a flashlight to read the control There have been rumors that watch- ANTENNA POSTS ON RAZOR BLADE HELD IN HAND markings. Usually these are stamped ing is RECEIVER -__ CONTACTING LEADS in the metal of the chassis and are hard television bad for the eyes. If to read; be sure that the control you your receiver works well and you treat are adjusting is the one you want. it right, the rumors are -just rumors. For instance, locate First adjust the FOCUS control. (It don't the set where may be either on the rear or the front direct light can fall either on it or on of your set.) There your eyes. If it's under a window or TO ANTENNA are just three ways to do it right. Take your choice. there's a lamp beside it, your eyes will NEW PIECE OF LINE If there is a test pattern on (any have to withstand quite a change of illumination when you look away from Fig. 3 -Add piece of line and test with blade. channel will do, but choose the one that normally gives you the the picture to the comparatively bright whether there's any effect on the pic- best picture) tune it in and fix the front-panel con- sunlight or lamp. ture. If there is, anchor the line firmly trols watching If light falls on the screen, the glass intervals along way if possible, as usual. Now, the im- at the age carefully in the mirror, slowly will reflect it, along with the light from and at least at top and bottom. Don't ro- the picture itself. Effectively tate the FOCUS control until the black that re- use nails or screws; your radio service lines near duces the contrast -"washes out" the shop has special the apex of the bottom ver- insulators. tical wedge are clearest and most picture. So, for best television viewing, keep the room dark except for a little Adjusting controls sharply defined. Fig. 5 is a photo of a perfect test pattern and the arrow light that doesn't shine on your face or You don't have to be an engineer to shows you the area to be watched. Make on the screen. adjust a television set's controls cor- the adjustment very precise Keeping the room entirely dark is rectly, will help. You -so that but a few tips your eye can separate the black lines hard on the eyes, too. When you look use the front -panel controls more often away from the screen, your eyes have to a point as near the center as nos - than those on the rear, and you've prob- to adjust from reasonably bright light ably tamed them so they'll perform as ANTENNA TERMINALS OF SET (the picture) to utter darkness, a scheduled. r VERY SHORT CONNECTING WIRES change that's too sharp, according to The little, knobless controls on the medical men, to be healthy. rear, though, have probably affected Ago Picture-tube filters are sold to "in- you in one of two ways if you're a more crease contrast " -you've probably seen or less average set owner. Either you've the ads. Some of them are simply left them strictly alone or you've be- tinted, transparent plastic. The light come so curious that you twiddled them from the picture itself passes through all and then were unable to do anything the filter once and is dimmed to some but call your repairman. Of the two, LINE FOR STATION A extent. But any external light reflected the first reaction is the safest, but LINE FOR STATION B from the screen passes through the fil- there's no reason why you can't go ter twice -once on its way to the screen around back and adjust at least some and once from the screen to your eye. of the controls to get a better picture. As you can see, the reflected light is As your set "breaks in" and the tubes Fig. 4-A switch selects desired tuning line. cut down twice as much as that from RADIO- ELECTRONICS for Television News ll

the picture. As a result, daylight or You may have heard that American If you're still not satisfied, try rais- room lights falling on the screen don't television stations transmit with a defi- ing the antenna as high as possible. nition of 525 lines. What happened to Some owners in outlying districts have the difference between 525 and the 485 even used telephone poles (bought their we mentioned above? The answer is own, not climbed up existing ones) or that the time that might be occupied by tall metal towers. This matter of re- the missing 40 lines is taken up with ception in fringe areas, as these loca- "sync pulses ". These are electronic in- tions are called, requires considerable structions which tell the receiver what study and is best handled by a profes- ro do to keep the moving light spot in sional technician. step with that at the transmitter. With- If you are located where the signal out them-no image! is weak, but still strong enough to give you some picture, a booster will often in Out the country help. These are little amplifiers contain - Television stations usually have a ing one or two vacuum tubes, that any maximum useful range of about 40 set owner can install himself. Con - miles because of the technical charac- nected between the antenna line and teristics of the wavelengths on which the receiver, they increase the strength Fig. 5 -Watch outl ned area when focusing. they transmit. Sometimes they'll reach of the signal before it reaches the re- farther, sometimes not the full 40 miles. ceiver. Even where some stations come tend to wash out the picture so much. But if you live more than 25 to 30 miles in well, there may be others which per - Polaroid filters are a little different. from a station, you're likely to have a form badly; a booster may help with They are tinted, too, and act like the little trouble getting a perfect picture, the bad ones and can be switched off others; but in addition, they have the one without "snow" effect. when you are watching a strong sta- same properties of cutting down re- The best way to proceed if an ordi- tion. flected glare as do the Polaroid glasses nary installation doesn't get the results Improving your television set pays while a car. you may have used driving you want is to use a special antenna, off in better pictures and more satisfy - Apparently reflected light is polarized one that's very directional. These an- ing entertainment. much more than direct light; the po- tennas not only suppress static arriving But remember this always: your tele- larized filter removes most of the polar- from directions other than that in which vision receiver is a delicate instrument, ized reflections. the antenna is pointed, but also provide and it's immensely complex. Leave its Some viewers like filters and some a gain -they receive energy and send it insides strictly alone; if something goes don't-it's a matter of individual pref- to your receiver much more efficiently wrong that hasn't been wrong before, erence. They undoubtedly do prevent than the simpler antennas. cull your television service teelunician! eyestrain to some extent by removing the glare from overly bright screens, but you can do the same thing by turn- TELEVISION TUBES LOSE BRILLIANCE ing down the BRIGHTNESS control. If your set has a 20-inch viewing EACH new television set any of our change in brilliancy with age is ex- tube like the Du Mont on this month's neighbors installed seemed to be ponential. After a very short time - cover, you probably aren't worrying better than anything we had seen up to approximately 50 to 100 hours -there about getting a bigger picture. But if the time. Such bright pictures! But is a sharp drop in brilliance. The drop you have a smaller one, you may want after noting this three or four times, we is then gradual, usually taking about an enlarging lens. Available in many began to wonder. Television can't be 1.000 hours to reach 50Ç4 efficiency. sizes and styles, most of them are improving that fast! Could it be that This means that the light for the same either solid or liquid -filled plastic. Un- new sets give a brighter image, and wattage impinging on the screen would fortunately, you can't get too far off that the older ones dim down so grad- decrease as described above. We use toward the side without getting picture ually that one doesn't notice it? the words 'screen burning' to describe distortion with a lens; but since a big- Radio tubes wear out, and the cath- this." ger picture will allow you to sit farther ode -ray tube should be no exception. The exponential, or "die- away" curve away from the screen, you can usually But does it lose its brilliancy gradually, below gives a rough indication of how get more or less directly in front of drop sharply and then level off, or run much brilliance your tube will lose in the set all the people who want to at practically full brilliancy through a given number of hours. It cannot be watch. most of its useful life and then drop taken as an exact picture, as other fac- There's an important limitation to off sharply? tors affect the tube life, and of course the size of your picture. Remember that A letter to H. D. Suesholtz, general the brightness control will be used to a television picture is not a solid "pho- manager of Transvision, brought the offset the effects of less screen bril- tograph" but an optical illusion. It's information : liance. But it does give a fair over -all made up of 485 horizontal lines of light "The screen efficiency decreases as idea of how the tube declines with in- from top to bottom of the picture. If the tube is used. The curve showing creasing age. the tube is small, the lines must be loo crammed in; they are so close together

you can hardly see them. With even a 90 very large picture -the number of lines remains the same; the lines are now far enough apart to be seen. Whatever 80 the size of your screen, you have to get PERCENTAGE far enough away from it so that the SCREEN 70 lines blend together and the eye is BRILLIANCE fooled into thinking it sees a solid picture. Therefore, with a big screen, be 60 sure your room is large enough to allow you to get back from the set a sufficient distance. The distance will vary 50 according to the condition of your eyes and your preferences. Watch a picture 400 500 1000 1500 of the size you want at your dealer's T ME IN USE (HOURS) store to get the information you need. This curve shows how maximum brilliance of the C -R tube decreases with hours of use. AUGUST, 1949 22 Television News Booster Uses standard Tuner

Ready -Made Front End Makes For Efficient Operation By MATTHEW MANDL*

TELEVISION booster consists of one or two stages of r.f. amplification with the output so designed that it will match the input of the TV receiver. While it is not difficult to wire an r.f. stage, the wide band of frequencies which must be covered in television makes the tuning system critical. The channel - selector section is the most troublesome because the high frequencies to which it must tune make necessary a number of precautions for even average performance. Assembly and wiring of such a tuning circuit demands constant attention to stray capacitance, lead inductance, and skin effect, for all con- tribute to high losses and poor efficiency. When, at the same time, a 6 -mc bandpass with a good signal -to -noise ratio is required, the problems become even more complex. For these reasons most homemade boosters fail to give satisfactory results- particularly on the higher- frequency channels. These difficulties can be greatly reduced by using a commercially built tuner as the foundation unit for the booster. Such tuners have been care- is at right of tuning drum. This is the booster made from the Philco front end. Power supply fully engineered for the TV frequen- ANT INrUTS +245V cies, are fairly high in efficiency, and make bandswitching simpler. Any good 4700,f 6.214 tt--1. AFC tuning section can be used, and many

RI LO types are available from TV kit manu- - 6J6 11- facturers. 2214 - 2214 470140 0SC-AFC Often a defective tuner which has 2 6 been replaced by a new one during serv- .05C 22µ f 6 5 icing can be salvaged for use. Tuners 1 frequently develop defects in only one or two channels, and thus can be uti- TUNING DRUM lized for booster construction, because a booster is not needed for all channels. Jc310 Essentially, a commercial tuner con- nóµf 220 sists of three sections: the r.f. ampli- ti 560 fier, the mixer, and the local oscillator. H3.3 These into one unified µµf are combined 30On LINES - 6AG5 assembly, small in size, with the tubes BALANCED TO ONO 6AG5 mounted on top. Such a device already RF AMP 1400 MIXER TO IFS has all the components, except for the power supply, necessary for construct-

10µy1 ing a booster. If we eliminate the local 5614 E oscillator and convert the mixer to an impedance- matching device. we have an loCn 2 0006 470µµf excellent r.f. amplifier, pretuned and 66 desit*ned for easy channel selection. 470µ6.t--- Three things are necessary. First, d -I disconnect from the oscillator the tun- °l l --Atvv ing coil which is coupled to the mixer. 4 Oµµf 100 1.470044f I14 PLUG-IN COILS -4t The oscillator tuning coil need not be removed, but should he open so that it AVC 6AG5 6J6 +245V r will not affect the tuning of the unit. MIXER RF 05C Second, convert the mixer tube to an 31 14 41 13 3f 14 impedance-matching device; cathode and plate circuits must be changed 6.3V fun T470»10 slightly as outlined later. The final step Television Instructor Technical Institute Temple University Fig. I- Original circuit of the Philco television tuner. Coils may be had for any channels. RADIO -ELECTRONICS for Television News 123 is assembly of a small power supply 6A G5 for the device. NOT USED A booster of this type was built using a Philco turret tuner. The Philco turret ó 1 has two rotary drums, each with eight to slots into which coils are plugged. One drum receives the antenna-r.f.-input Ca10T coils, and the other the mixer -oscillator 1 HI , - coils. Fig. 1 shows the original tuner 4 circuit. Fig. 2 is a schematic of the -0?O I booster, showing the changes made in LO I i TO AN' B- the tuner. The power supply is given . in Fig. 3. A comparison of the original and modified circuits shows that only IST 6A65 2ND 6AG5 two changes were made: the 6J6 oscil- C312 3 4 4 3 RFC T0 6.3v later-a.f.c. tube was eliminated, and the TUNINT, DRUM 1 6AG5 mixer was changed to an im- 470µ0t device for a 300 -ohm pedance- matching Fig. 2- Circuit of booster. Oscillator- a.f.c. tube was removed and miser made output stage. receiver input. two With the oscillator eliminated, 15H /20NA tuned circuits are still present -the in- 5Y3-GT NFUSEP +2nv put to the r.f. amplifiers, and the in- 5v 6K terstage circuit between the two 6AG5 B B tuner are z TO tubes. Plug -in coils for this BOOSTER available for any TV channels, and 43K 8 eight different stations can be made t 1 the drum. As with available by rotating 300 - 300Y /25MA other tuning units, coils are pretuned at the factory and need little adjust- 6.3V TO ALL FILS ment. If coils should be found too far off frequency, adjustments can be made by changing the spacing of the turns Fig. 3 -The booster diagrammed above is slightly. Tracking capacitors, present powered by the simple supply shown here. in all types of tuners, can also be employed when necessary to get peak per- Final construction job appears in the photo. formance. The Philco tuner has provisions for high- and low -band antenna inputs, ANT using 300 -ohm transmission lines. Two 4.7K antennas, with separate transmission lines, can be employed. Each will be 11 12 13 switched in automatically as the drum REANPL is rotated. If the double antenna sys- 2 tem is not desired, a single antenna 5 and lead -in can be used by shorting 1.5415 across the two terminals, as indicated LINK COUPLING 66 by the dotted lines in Fig. 2. +130V CONY Constructional details Since the modified tuner comprises the entire booster, additional chassis space is needed for the power supply. With the Philco tuner, the chassis used is 5% x 9 x 1 inches. The Philco tuner measures 4!.2 x 5% inches, and this 4.5-6.5V much of the chassis top is left open. ,-". The tuner is bolted to the chassis, over TO CONTRAST the open section, as the photos illus- IK CONT trate. The chassis is made of wood; 4.7pur .0015 the tuner framework is metal and pro- SHIELD 4 vides adequate shielding. A strip of Plexiglas, Lucite, or other low-loss material should be used for the input and output connections. In the Fig. 4- Circuit of the tuner appearing in RCA, Admiral, Emerson. and other receiver models. tuner illustrated, bolts and nuts were used for terminal connectors, though iature type 6X4. Almost any small former used. The type 47 pilot bulb acts low-loss jacks or other plug -in devices power transformer will do, because the as a fuse and protects the rectifier tube can also be employed. Connectors with current drain of any commercial r.f. and transformer. large surface areas should be avoided, tuner will not exceed 20 ma. The volt- With some commercial tuners, the re- however, because the capacitance ef- age for the booster circuit, however, moval of tl.e oscillator tube will suffice, fect between them becomes quite pro- should be no higher than 245; and if and this should be tried first before dis- nounced for the upper -channel fre- the output of the supply is greater than connecting the oscillator coil. If the un- quencies. this under load, a voltage divider sys- used oscillator coil does not seriously The power supply is a conventional tem like that shown in Fig. 3 may be affect tuning, no further changes need full -wave rectifier type. A 5T4 was used. be made except to the mixer output. used, but any standard rectifier tube The resistance of the bleeder will de- With the booster described, all oscilla- will be satisfactory, including the min - pend on the particular power trans- tor wiring was removed to make a

AUGUST, I 9 4 9 211 Television News

ANT stage is below 1. The reason is that 6J6 (3) single tube boosters have to match the 270)1µt low receiver impedance (300 ohms) in ( I their plate circuits, substantially reduc- RF AMP 150 I ing gain. Use a common ground for booster and TV receiver to assure balance 150 150 throughout. When operating the boost- 470y)1f er, a 300 -ohm transmission line is used

1.5µN1 27040 from its output to the input terminals .015 TO TV RCVR INPUT of the receiver. It should be as short as possible to avoid stray fields. For the 150 T470)1i yf high channels, the antenna transmission line may have to be tuned by shorted stubs attached to the input

1.51( terminals. Tinfoil, wrapped around the 8+135V line, can also be used for tuning. Slide 4.1µµf it up and down the line until the picture is best. Other tuners lend themselves just as readily to booster construction, with identical changes. Fig. 4 shows a typical tuner which TUBE REMOVED FROM SOCKET has been used in several receivers. It was originally the RCA 630TS receiver tuner, and subsequently was used by RCA in 1948 models, 8TS30 Fig. S -Tuner of Fig. 4 may be revamped as above for booster. series. The Admiral 30A1 -B chassis neater job. Take care not to open cir- output and receiver. Balance is attained also employed identical tuners, as did cuits unintentionally, because some by using an unbypassed cathode resis- Emerson in model 571, and other man- ground or B -plus returns may be term- tor against the plate -load impedance. ufacturers. Removal of the coupling inated at the oscillator -tube socket. Since the circuit is degenerative, gain link between the mixer and oscillator The mixer tube is used in a circuit is less than 1. This double -tube booster and a change in the plate circuit of the whose primary function is to make an is much better than a single -tube boost- mixer, as shown in Fig. 5, converts this impedance match between the booster er, even though the gain of the second tuner into another high -gain booster. New All-Channel TV Antenna ATELEVISION receiving antenna of trum with a gain of approximately of the rods are mechanically and elec- entirely new design was announced 1.9 over a half -wave dipole. At the trically connected to the junctions of recently by Continental Copper & Steel lower -band frequencies, the pattern is the circle segments so that they are Industries, Inc., New York. Called the wide and bidirectional, about the same 90 degrees apart on the ring. Welin Circle X, it consists of a circu- as that of a dipole. At the higher The impedance of the feed point is lar tube with four radial rods, the frequencies, the rear lobe becomes con- approximately 150 ohms, though it whole forming a shallow cone. siderably smaller than the front one. varies somewhat over the range. In The single antenna is said to be ef- Because a complete investigation of ordinary installations, 300 -ohm line is fective over the entire television spec- the validity of the design principles has used, with a minimum impedance mis- not been completed at this writing, lit- match (and standing -wave ratio) of 2, tle can be said of the engineering basis though neither is much greater than for the antenna. It has been found, this at any frequency. For critical in- however, that despite the broad angle stallations where signal is low or noise of signal acceptance, it is remarkably level high, matching stubs and trans- effective in suppressing ghosts. A slight formers of the ordinary type reduce reorientation to one side or the other the mismatch. diminishes ghost reception, apparently For optimum results, the antenna because of certain phase. relations be- should be placed in a space loop and tween the direct and reflected signals the bottom of the ring should be at reaching the circular outer ring; can- least 5 feet above the ground beneath it. cellation seems to take place. Inter- estingly, it has been found that a slight reorientation in the vertical sense - tilting the assembly so that it points upward about 7 degrees -also diminishes ghosts to a large degree in some cases. The photo and diagram show how the antenna is constructed. The outer circle is composed of four segments, each % wavelength at 135 mc. The 135 -mc frequency was chosen as the median of all the television channels. Each of the radial rods is "z wavelength. The inner ends of the rods are fastened and connected as the diagram indicates, adjacent pairs going to the two ends of The Circle X resembles shallow skeleton cone. the transmission line. The outer ends The drawing shows dimensions and connections. RADIO -ELECTRONICS for Television News 125

A standard signal generator with 400 -cycle modulation and an output meter are necessities.

Trouble- Shooting Television Sets

Sweep generato- and scope are optional. By IRVING DLUGATCH

MANY an old -timer in radio 2. Whether it is self- excited or re- Required equipment servicing has turned green ceives an external signal; with envy on seeing the "com- 3. The frequency; The foregoing is the general method any problem. Tele- plete service laboratory" un- 4. How it is supplied with its oper- of solving servicing veiled by his newest competitor. Yet ating power. vision, even with its multiplicity of cir- half the servicing the skilled radio Let's see how the four facts are used cuits, does not introduce any further technician does is with no other test in practice. Suppose a device is de- difficulties. Signal tracing is used in all equipment than his eyes, ears, nose, scribed as a three -stage amplifier sup- its possible variations. To do a good job and fingers. That's possible because he plying a 15,750 -cycle sawtooth wave to of signal tracing, you need: knows his basic theory and has spent its output terminals. It is receiving d.c. 1. Output indicator: Any a.c. meter with a in with years of postgraduate study in the Col- potentials from a conventional full - capacitor series the hot lege of Experience. wave rectifier power supply. There is, lead. Since a high -resistance voltmeter Television doesn't differ from sound however, no sawtooth voltage at the and a wide -range ohmmeter are needed ti radio in this respect. It is even simpler output. Now let us proceed to put it for checking parts, a combination in- to service in some respects because the into condition. strument, such as the Superior TV -20, eyes can be used to better advantage. We know the frequency is 15,750 cy- Precision 85, Electronic Measurements The kinescope tube is a piece of cles per second; we know we 120, or Radio City Products 450C, is test therefore, recommended. equipment wired right into the receiver. need an a.f. voltmeter to trace the sig- Many may have been frightened nal. Since we dealing an am- 2. Signal source: Should provide are with modulated away from video work by the ballyhoo plifier the signal must be coming from r.f. up to at least 30 me on over special test equipment supposedly some external source. The fundamentals and a 400 -cycle audio meter will signal. needed. Emphatically, special television determine if the signal is arriving at An attenuator for the 400 -cycle note is very test equipment has a place in every the input terminals. If no signal is desirable. If it can go as high as 200 television shop. The purpose of this ar- present, the amplifier is not at fault. If or 300 mc, it can be used in ticle is to demonstrate that a large per- the signal is coming in, we would next for work the r.f. sections. The Simp- son 340 or Jackson 640 centage of television servicing can be check the power supply. If it is O.K., are typical. done with a good volt -ohm -milliameter we need only trace the signal from and a signal generator. stage to stage. The trouble can be lo- Optional equipment Servicing any electronic circuit is calized in short order and the defective The following test instruments are simplified if we know: component found with the ohmmeter or highly desirable, if available, but are 1. What it is designed to do; voltmeter. not absolutely required. AUGUST, 1949 261 Television News

1. Oscilloscope: Usefulness greatly Checking and signal tracing G.E., etc.), the i.f. is always 4.5 mc. increased by provision for feeding video Also, tracing should be carried to the signal to grid of cathode -ray tube. Du Our test equipment is assembled. We video amplifiers where the sound is ob- Mont's 164E or similar instruments can understand our instruments. Now what? tained. A very common complaint with be converted by adding a tip jack as Certainly not an immediate probing in- these receivers -a buzzing sound heard shown in the drawing. to the "innards" of the television re- with the audio -is due to video getting 2. Sweep generator: Should have ceiver. That must wait until we have into the audio system. Provided the variable sweep width and cover a full used our senses to determine the sec- fault is not with the transmitter, the range of radio and intermediate fre- tion of the receiver at fault. trouble can be eliminated by carefully quencies. Inclusion of a phaser is also So much has been written in the past aligning the picture i.f., sound i.f., and desirable. RCA WR -59A, Hickock 610A, on the "test- pattern- examination" type sound discriminator. If the discrimin- and Triplett 3434 are examples of such of trouble shooting that I shall not take ator and limiters (if used) are working an instrument. the space to repeat such information. properly, they will reject the amplitude- 3. A number of selected, plainly What follows is an outline of the meth- modulated video signal. In the picture marked capacitors and resistors for ods to be followed after this step in the section, the response curve should be quick substitution. localizing of troubles within a suspect- such that the sound carrier is down to The true expert soon learns not to ed section of the receiver. (See "Serv- about 10% of the level of the picture trust the calibration of any instrument, icing Televisers," page 50, and "Tele- carrier. regardless of its original cost. The sig- vision Trouble Chart," page 54, of the Misalignment of the r.f. circuits or nal generator should be calibrated at January, 1948, issue; also "Using TV mismatch in the antenna system may regular intervals. This can be done for Test Pattern" in the November, 1948, cause the buzz by changing the ratio the sound r.f. and i.f. carriers by using issue.) between the level of the sound and pic- a television receiver that is operating ture carriers. normally. Feed in the signal from the JACK ON FRONT PANEL Audio amplifiers and detectors: Inject generator while the set is properly 3AP I 400 -cycle note using speaker as output tuned. When C-R T the 400 -cycle note is heard indicator. For tracing distortion, use with TO SWEEP OSC C 19 the television sound, we have the 2 an actual signal and listen with signal correct frequency to be used for align- SOuUf O70K tracer or headphones. ment purposes. 1200V The picture carriers do Picture i.f. not need precise amplifiers: Connect out- calibration (for rea- put meter of video sons to be noted later). at plate output am- BREAK EXISTING CONNECTION AT X AND INSERT plifier. Inject Next, our meters' SWITCH modulated picture i.f. accuracies are to signal at the grids of the i.f. tubes, be questioned. Fortunately, A Z- modulation jock added to scope is useful. precise re- beginning with the last i.f. stage first sistance and voltage readings are in most cases Since misalignment of circuits is a and moving toward the antenna. The unnecessary and in many last position for injecting cases foolish. This is obvious very common complaint in television the picture when we i.f. will be the remember that most work, let us begin with converter grid. The con- parts tolerances verter usually being part of are 20 %. In addition, we will often Alignment procedure: The service- a compact be tuner, it may be more convenient to tracing signals that are not sine waves. man does not need to go through the The results complete alignment of all circuits in a feed the i.f. signal directly to the re- obtained then with most in- ceiver's struments are so mystifying television receiver. Normally, a re- antenna terminals. Make sure that spe- there is no trap at cial interpretation is required. ceiver brought in for repairs requires this point to prevent Most a.c. the i.f. from getting meters used in television servicing are only a "touching up" such as might be through. Inci- calibrated for done with an AM broadcast set. Be- dentally, always remember that the car- r.m.s. measurements of rier frequency sine waves (the rectifier -type actually cause of the broadness of the picture is not passed at maximum gain in the i.f. amplifiers. A reads average values but is i.f., it rarely requires any realignment. lower corrected to frequency will give greater output. read r.m.s.). When, for example, a saw - A satisfactory picture can be received tooth wave -of much lower effective even if the alignment of the individual If the trouble is due to i.f. oscilla- value than a sine wave with the same circuits varies a bit from the normal. tion, it will be indicated by decrease in peak voltage -is measured, the reading The oscillator and sound i.f. may re- d.c. output at detector load when signal is bound quire realignment from time to time to generator is removed and suspected i.f. to be low. Where a.c. and d.c. grid are combined, the d.c. component may keep the sound with the picture. grounded. be measured with a d.c. meter and the Suppose that, using the standard Video amplifiers and detectors: Sig- combined voltage with an a.c. meter. test -pattern- examination and localiza- nal tracing by injecting 400 -cycle sig- Subtracting the d.c. from the reading tion methods, we have localized or par- nal. This will give about six dark, hori- of the a.c. meter will show the amount tially localized a number of troubles. zontal bars on the raster. (See "AM of a.c. in the circuit. We would then perform the following Generator Useful for Television" on Despite the claims of manufacturers, signal tracing tests: page 47 of the July, 1949, issue of very few a.c. voltmeters are reasonably R.f. amplifier and converter: Signal RADIO -ELECTRONICS.) The darkness of accurate above a few thousand cycles. injection tracing method using mod- the bars will depend on the signal am- Such things as rectifier characteristics ulated sound r.f. carrier frequency with plitude and the gain of the stages being and meter coil inductance limit the fre- receiver's speaker as an indicator. If tested. An output meter will also be quency range. Only with special probes the signal generator cannot tune high satisfactory. For distortion, investigate can these effects be overcome. The enough, use a signal tracer with a good peaking coils and capacitors. Defective probes still can't offset error which fol- v.h.f. probe and high gain to follow coupling capacitors and plate load re- lows any attempt to measure anything received signal from a television sta- sistors are also common causes of this but a sine wave. tion. Don't forget to check oscillator complaint. Oscilloscopes are not immune to these grid voltage and contacts on channel Sync circuits: Signal tracing by in- faults. At high frequencies, their am- selector. jecting audio -frequency signals. Meas- plifiers may distort the wave being ex- Sound i.f. amplifiers: Signal tracing ure output at grid -leak- biased clipper amined or so attenuate it that the in- with signal generator and output me- tubes with d.c. high- resistance volt- strument is worthless. Again a special ter. D.c. output meter is connected meter or note whether raster locks in probe will permit the use of an oscillo- across detector load. An a.c. meter at with injected signal. A high -gain signal scope at these frequencies. The oscil- the plates of the audio amplifiers or tracer may be used. Oscilloscope may loscope makes it possible to measure the speaker can be used, also. The sig- be used to compare waveforms with peak -to-peak values; and, for this rea- nal generator should be tuned to the manufacturers' data. (Sync clipper son, it can be used to compare accu- sound i.f. tubes usually have the plates and rately voltages of different wave shapes. In receivers using intercarrier sound screens, or both, operating at very low This is all we need for signal tracing. (Motorola, Hallicrafters, Videola, new voltages with zero bias.) RADIO -ELECTRONICS fo Television News 1Y7

Horizontal deflection circuit: Here much to speed servicing, and are in- television trouble shooting, as far as the signal is being supplied by the hori- dispensable in certain jobs. these techniques are applicable. Tele- zontal oscillator. The signal can be In conclusion, note that this article vision theory must be digested so thor- traced with a tracer, output meter, or is not intended to be a complete serv- oughly that the individual will be able oscilloscope. The oscilloscope is best icing manual. It is an outline of the to develop these simple facts into his but not absolutely essential. It requires signal -tracing techniques to be used in own streamlined methods. accurate waveform photographs for comparison. With the signal tracer, the 15,750 -cycle signal may not be audible to some persons. A good compromise is the output meter giving a relative New French TV Test Pattern reading. A correctly operating discharge tube THE NEW French television test As with most test patterns, the finer and multivibrator tubes have a plate pattern illustrated here is more com- ends of the wedges are at the center of potential of approximately 10^/,, of the plex than the usual American one. the screen because the cathode -ray- low -voltage supply. Considerable varia- It is designed to produce usable and ac- beam spot is always best concentrated tion will be found, but if the plate curate performance information, re- (smallest) at the center. The circle en- voltage exceeds 30% the waveshape gardless of the technical standards of closes the area of best definition, ap- may be incorrect. If it approaches the the TV system. proximately 2/5 of the image height. To supply voltage in value, the pulse is not The chessboard edges are suitable for observe definition outside this favored present. Magnetic deflection output very exact framing. The aspect ratio area, 16 groups of vertical bars are tubes are usually operated at cutoff. is almost the same as the American provided. These are similar in function Do not attempt to measure the plate 4 to 3, 4 to 2.91. to the bars of the wedges and are cali- in voltage of horiz al tput tubes and Vertical definition wedges are pro- brated the same way. damping tubes in magnetic deflection vided, as on American patterns, but Modulation percentage may be measured with an oscilloscope. The heavy A high -voltage pulse is they are calibrated differently. Instead receivers. pres- black with white notches provide ent, snaking voltage measurement dan- of being marked in terms of the band- bars width a signal easily evaluated on the scope. gerous. necessary for resolution at each point, the figures indicate the number The horizontal extensions on the black Miscellaneous: All oscillators, regard- of bars (counting both black and white) bars make lag clearly apparent. less of type, develop a high negative which would appear across an entire Contrast range may be estimated voltage on their grids in normal opera- line. Thus, the bottom of the left verti- with the fan -shaped half -tone wedges. tion. Sync discriminators can be serv- cal wedge is labeled 175, meaning that The half -tone dots actually are part of iced exactly like any FM detector. Al- if the alternate black and white "fence the pattern, not added for reproduction ways check the balance of push -pull pickets" were extended to fill the entire purposes in this magazine. The five output tubes, if used. Damping tubes width of the picture with the same steps ranging from black to white are common causes of distorted pic- spacing as at the "175" point, 175 of should be clearly distinguishable on the tures. them would appear. This system allows receiver's screen. Two large half -tone Vertical deflection circuit: Generally the pattern to be used with TV systems areas were provided in separate places the same as for horizontal deflection of any standards -specifically (for the to eliminate errors due to spots on the circuits. purposes of Radiodiffusion Française) tube. the is the High voltage supply: For flyback sys- with both 440- and 819 -line transmis- Ordinarily linearity test sions. Two vertical wedges perfection of the large circle. Note that tems, listen for 15,750 -cycle whistle au- are provided for a wider range of values, and two all the wedges are drawn as radii of dible when horizontal oscillator is optical illusions horizontal horizontal wedges (calibrated in the the circle to eliminate operating. Check sweep cir- same manner) are provided, the right which otherwise would make the circle cuit as described previously. For r.f. one having finer lines for use with the appear imperfect at all times and hin- oscillator system, test oscillator tube, 819 -line transmissions. der accurate judgment. measure oscillator grid bias with d.c. high- resistance voltmeter and see if rectifier is lit. Test by measuring resistance of bleeder resistors. Voltage may be measured directly with a d.c. voltmeter having 1111111111 I I I I I I I I 11111111 1111111111 sufficient range or 400 300 using a special multiplier. 300 4 00 Make sure ion 1 IIIIIIIIIIIII RADIODIFFUSION IIIIIIIIIIIII 111!'111111 11111 positioning of trap 0 0 500 FRANCAISE 500 700 magnet is not the cause of a dark screen. A defective kinescope is also to TELEVISION be suspected. A 10BP4 needs not less

than 7,000 volts for adequate bright- 1111111111 1111111 RON IIIIIIIIIIII ness. With excessive ripple, make sure 175 400 two 900 500 7,80 deflection yoke is properly grounding 300 400 500 outside coating of kinescope. Check filter capacitors by substitution. 7 em.-- Low- voltage supply: Most supplies deliver 300 to 400 volts. The usual voltage and resistance checks will uncover most 300

faults. Capacitors are best tested by 50 ? substitution. Selenium rectifiers can be 400 1 tested with an ohmmeter. They should have a minimum back -to- forward re- 500 700 sistance ratio of 1,000 to 1. IIIII IIIIIIII IIINbBiNVI Now that we have gone completely 300 400 through the receiver, a review will 300 show that no special test 280 IIIIIIII IIIIIIIIII equipment E was required in most cases. Obviously, M E sweep generators, signal calibrators, and other elaborate instruments can do French test pattern is suitable for use with any system. Variety of markings aids Testing. AUGUST, 1949 Television News Ylt I THE T1IANSPOL[ VARIOTENNA

. . to unusual indoor antenna with neu features has

recent I. been e ols ed . . .

11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111

By HUGO GERNSBACK

l'arL J.

Final model of the transpole variotenna for TV reception.

TELEVISION has brought in its Fig. 1 shows the connections of the near the top, makes that section rotat- wake a number of problems which antenna itself. For better understand- able through a 180 -degree arc. The in- have to do not so much with engi- ing of the connection, a simplified dia- side rotor loop is controlled by a lucite neering as with living conditions. gram is shown in Fig. 2. Note that con- handle "H". The loop assembly is It is admitted that the outdoor an- nection is made, not in the orthodox mounted on a cylindrical wooden base. tenna is at the present time the most manner as in the dipole, but front oppo- A shorting switch (see Fig. 3) is efficient. Unfortunately, it cannot al- site ends. For some reason, not per- mounted on the base, also. ways be used -particularly in our fectly understood, this arrangement It was found that in actual operation larger cities. works best in such an inductive loop. all types of ghosts and snow can easily Many landlords of apartment houses I termed this connection "transpole," be eliminated in New York City under do not allow antennas on the roof and a contraction of the terms transposed frequently even the house owner does and pole. not wish to disfigure his roof with an By providing a switch which is used unsightly antenna. That is the reason to short the open ends, as shown in Fig. for window and indoor antennas. 2, snow and ghosts usually can be elimi- I have had the problem under con- nated effectively. When in use, the an- sideration for a long time during which tenna is oriented by revolving it on its many indoor antennas were tested. It base. Each station has its own best soon became apparent that on account position. of the peculiar problems arising from A far more efficient antenna is the wave reflections indoors, a better device double -loop inductive antenna with a was needed than had been proposed so revolving inside rotor shown above. far. The idea of an inductive coupled This antenna is larger, the inside loop antenna soon occurred to me and a num- measuring 15% inches diameter; the ber of models were built. The two types outside 17 inches diameter. The two shown here are the evolution of this loops come to about s/z inch from each idea. The smaller one which only other. I call it a Variotennra. measures 11 inches across proved quite The connection diagram of this loop satisfactory on fairly strong signals. is shown in Fig. 3. It will be noted that It is composed of four 3 -inch brass or it, too, is connected as a transpole. nickel ribbons wound concentrically, In this loop, aluminum rod % -inch with lucite spacers on top and bottom diameter was used with a center lucite to keep the loops about 1/4 inch apart. supporting rod and lucite insulation A strong inductive effect is built up for the bottom of the loops. A simple between the convolutions. horizontal splitting of the lucite rod, An early model of the antenna had fined loops. RADIO- ELECTRONICS for Television News 129 the most unfavorable conditions in steel M. Noll, television instructors at Tem- other as two high -band antennas. While apartment houses. All six local chan- ple University, for test. it may appear to you that all this is nels were well received without any Here are their findings as reported highly conjectural, I believe that it trouble. In some cases it is necessary to by Matthew Mandl: would be difficult for anyone to give a revolve the base for best reception, then "I tried the antenna out on my Ad- true analysis of the actual performance rotate the inside loop for clearest pic- miral TV receiver in Trenton. Channel characteristics because the antenna ture. On some of the channels it may 3 from Philadelphia carne in fairly well performance for certain angles of the be necessary to use the switch, but this -though with some snow. (My set is, loops is never the same in any two posi- is required only in locations where of course, on the ground floor and I tions in the room. the reception is particularly poor. had the antenna standing on the re- "Within a room the reflections would It was found advisable to use one or ceiver.) I found the antenna worked have too short a path to be visible in best with the 300 ohm line connected the form of ghosts on the screen. By to terminals 1 and 2, with 4 and 3 rotating the two loops, therefore, a open, and the two sections at right condition can be encountered where angles to each other. each loop picks up (independently) a WOOD BASE "Channel 6 (from Philadelphia) separate signal from a different re- carne in with same picture quality as flected angle. If the loops and the an- 3, although I found the two loops tenna position are so regulated that INSULATION worked best at about a 45- degree angle, the two reflections are in phase, the with terminais 3 and 4 open. antenna would be capable of feeding a "Channel 10 (Philadelphia) came in signal to the receiver far in excess of with same picture quality as channels a single antenna capable of only one 3 and 6, with both loops in the same orientation. This factor, combined with plane. Connecting 3 and 4 seemed to the circular configuration of the two make a slight improvement-though elements, means that advantage is also not too pronounced. taken of any vertical components pres- "Tentatively, my theory on its oper- ent in the room. ation would be as follows: On the low - frequency channels, inductive (mag- "Since, however, so many reflections netic) linkage evidently occurs between and polarization changes are encoun- the two loops, effectively giving them tered indoors, the very versatile arrange- the required length for resonance. The ment of your antenna is bound to give fact that each loop can be swung at an better performance because it can be angle independent of the other, means adjusted to take advantage of multiple 300 OHM TWIN - LEAD that full advantage can be taken of reflections." the many reflections existing within a of will be room. Noll and I have found that cor- Another new type antenna SWITCH described by the author in an early issue. ANT. TEfMINA.S rect orientation of an indoor antenna rarely corresponds with true orienta- Directions for building a simplified Fig. l- Connections of the fixed -loop trans- Transpole Variotenna will also be inset. tion such as would be found outdoors. pole television antenna. Construction "On the high frequency channels, the given. capacitive reactance between the two ANTENNA LOOPS loops becomes low and affords coupling. This, then, unifies the two loops and they act as a short antenna for the high channels. "Gain for this antenna seemed to be I on. iderably higher than an ordinary folded dipole -though we would like to check this some more. "Because of the many reflections indoors, however, we are at a loss when Fig. 2- Simpler diagram expia ns unit above. we endeavor to theorize on your particular antenna. Positioning the an- two lead -in metal sliders to balance the tenna in different parts of a room, for transmission line effectively to the re- instance, requires a change in the angle ceiver. Once this is done the sliders are of the two circular elements. As soon no longer touched and are clamped into as we think we have some answers in position. one particular location in the room, we ANTENNA S SWITCH Surprisingly enough, on some sta- must revise theory when we move the TERMINALS tions even the displacement of only ', antenna -for better reception is usu- of an inch of the rotor loop may make ally secured by a complete change of the difference between a good and a angle between the two loops. As men- Fig. 3 -The antenna with the rotating inside poor picture. This is not true of all tioned in my previous letter, the ca- loop is connected as this diagram indicates. channels, but some stations may prove pacity between the two antennas with quite critical, depending upon location. both in the same plane, and the inter- TERM. This antenna is not at the present acting magnetic fields, probably com- INNER LOOP 4 time made commercially and is pre- bine to make the L and C resonant at sented here merely as a contribution the low TV channels. Because the C- is believed L is Q of antenna to the art. It that as tele- ratio large, the the SWITCH vision receivers evolve, some such an- would be low, resulting in a broad TERM o"- O tenna, that is, one of the variotenna bandwidth and greater coverage. 3 OUTER LOOP 2 variety, will probably be incorporated "I have found that better results on in future television sets. the high channels are procured when Early last Spring I dispatched two loops are angled, and it is our a the TO TWIN-LEAD sample of the two -loop type variotenna belief that in this position the two to Messrs. Matthew Mandl and Edward act more or less independently of each Fig. 4- Diagram of above with loops extended.

AUGUST, I 9 4 9 :i1 /I Television Sews Television Querfes Answered

IN MY work as a Question Box en- I am reproducing below a number of gineer for RADIO -ELECTRONICS, I them. Though the selections may not have been struck by the broad be of the greatest general interest yet thinking evidenced in many of the they seemed most interesting to me. questions about the new subject of tele- If RADIO- ELECTRONICS readers have vision. Unlike queries on other subjects, any other points they would like cleared which are invariably highly practical, up, let me hear about them. If they many television queries have no imme- are important enough and numerous diate practical purpose behind them, enough, we will have another article but are made in the search for greater like this one. If not, they will simply knowledge. be discarded (not returned to the By DAVE GNESSIN As the answers to these questions writer). Thus the worst that can hap- may help other readers to understand pen to your query is that it may re- some of the points which occur to many, main unanswered.

embodied in FCC regulations. Thus you beam -bender element of the ion trap. Ion Traps may take your receiver with you from Loosen the clamp bolts if any, and ad- ? Two television sets in my town look coast to coast, sure that everywhere just the beam bender first for raster almost exactly alike; but one has the (almost everywhere, anyway!) you can and then for brightest picture. The ele- usual ion trap consisting of two coils plug into 117 -volt a.c. and have your ment will probably resemble one of the on the neck of the cathode -ray tube TV receiver working normally. three types shown in the drawings of near the base, while the other doesn't. If you are interested in the possible Fig. 2. Yet they both work fine. They are combinations for scanning other than 7 -inch tubes. How does the second one those now used, note Fig. 1. Then figure work without the ion trap ? -L. AL, out how many different ways the scan- Vertical Black Line Marion, Ohio. ning function might have operated. .' / hare a Philco TV model 48- 100Û, A. Up to a diameter of 7 inches, electro- diagram of which I enclose. On the face statically deflected tubes work satisfac- No Raster of my picture I get a vertical black line. torily for television. They need no ion ? Maybe it sounds silly, but I was My adjustments are correct. I've gone traps since ions respond readily to elec- so careful doing it I was sure 1 couldn't over all the component parts of the set trostatic deflection and do not burn a harm anything. I opened up the C -R without finding a failure. IVhat do I do brown spot in the center of the screen. tube assembly of my new television set von' to get rid of the black line ? -L.M., Some 7 -inch tubes, however, use elec- to examine it. Then I carefully reas- Baltimore, Maryland. tromagnetic deflection, as do all the sembled it in rebat I thought was ex- larger sizes. These electromagnetically actly the sanie manner as it was orig- A. Checking with the company, I find deflected tubes require ion traps or inally. The tubes light up-I have they've discontinued the 0.1 -µf screen - beam benders to prevent the brown spot sound, but the screen is as dead as the grid bypass capacitor C on the GBG(i -G from forming. proverbial duck. What did I spoil? The horizontal output tube, because of com- It may also be that the second set you set uses a 10ßP4. -D.R., Columbus, plaints such as yours. Simply remove describe uses an ion trap of the newer Ohio. that capacitor and leave it off to clear PM type. Such a trap consists of two up your trouble. See Fig. 3 for its ex- small permanent magnets in an assem- A. Don't be alarmed. The symptoms act position in the circuit of the re- bly which clamps or slides over the base you describe indicate a misadjusted ceiver. neck of the C -R tube. Fig. 2 shows three C0111111011 ion traps. Interlaced Scanning ., Wind's the reason f,, .vvunrirrg sideways? Couldn't up -and -down scanning have been used as well -or for that matter- inside -out or outside -in or some other scheme ? -P.C., New Ro- chelle, New York.

A. You're quite correct. We use inter- Fig. I -These examples show three of the many scanning schemes which might have been used. laced scanning of 525 lines. In Europe they use a different number of lines. Nor do they all interlace. But remem- ..--PERM.BAR ION TRAP COILS ON CLAMP ber that every separate system of scan- RETAINING RING MAGNETS OVER NECK OF TUBE ning needs a receiver constructed for NECK OF C -R TUBE that particular system. We could scan right to left, up- and -down, or even spirally.

The manufacturers have agreed on SPRING CLIPS 4 TUBE BASE NECK OF C-R TUBE a uniform system of scanning for all PERMANENT MAGNET IN SOCKET TV transmitters and receivers in use RING in the United States. This system is Fig. 2 -Three types of beam benders or ion traps. The first two utilize permanent magnets. RADIO -ELECTRONICS for Television News 31

an implied warning against fooling at the left side of the screen the picture TO HV around with viewing tubes! is folded; a man walking to the left HORIZ OUT appears to be walking into himself. I 8F3G8-G Power Supply hate to change anything since the rest TO HORIZ SWEEP OSC Dual of the picture is O.K. -L.R., Chicago, ID IORIZ DAMPER 100 5 ? My Phileo 49- 1278 has a very odd Ill. power supply. It uses two low- voltage 3 2 .. .1 3.9N you probably rectifier tubes, a 51'4 -C and a 7Z4. Their A. With a large screen in nor do their use magnetic deflection. Check your outputs are not parallel, set 100 voltages add. lhhy this odd combina- horizontal scanning circuit. If your damper tube (prob- tion of rectifiers ? -R.F., Zanesville, uses a horizontal ably a diode), your fault is probably B +325 V Ohio. there. -I1, -grid Fig. 3- Remove 0.1 screen capacitor. A. In the first place, the large current demand of this television set requires Replacing Picture more output than one rectifier tube Stub Technique Tube (such as a 5U4) can supply. The rea- ? I used the stub technique recom- son for making the second rectifier a mended by RADIO -ELECTRONICS to elim- 9 Is there some standard, safe, rec- small cathode -type 7Z4 is a sound one. inate interference from the TI' an- ommended way to remove and replace Examination of the circuit diagram re- tenna (or lead -in). The open -ended picture tubes in TV sets? It's the most veals an extensive bypassing system, stub required is several feet long and fragile part of the set and probably re- centered mostly about the screen -grid consequently unsightly. Coiling it to get quires special care. -A.F., Centralia, circuits. In the r.f. and video i.f. sec- it out of the way disturbs its trap ac- Ill. tions these capacitors are very critical. tion. What do you recommend that I A. Reasonable care, avoiding scratch- A synthetic dielectric was used for the do to solve the problem ? -A.B., New ing the screen face or abusing the thin close tolerances required. This per- York City. glass neck would suffice. However, here formed excellently for the specific ap- is a step -by -step recommended proce- plication, but had a comparatively low - A. There is a general rule covering dure: voltage rating (about 50 volts above cases of this sort. The open -ended rib- stul) is cut to half the CAUTION: First ground H.V. Anode working voltage). bon -line trap cap to frame of bracket of tube, and B. plus to the chassis ground for double 4- NEW --. 5U4-G (2) OLD safety. 7Z4 PRIB 1. Disconnect the deflection - cable socket, picture -tube socket, and high - voltage connection. 2. Remove beam bender (ion trap) attached to and any other miscellany 20 TO FOCUS COIL tube. 30 clean 3. Prepare in advance crepe or iMEG B+400V(APPROX) newspaper on top of a table to receive the tube. 4. Loosen tube mounting nuts and support brackets, meanwhile support- 5U4-G F 40s 1900.1.10 ing tube. CAUTION: Asoid touching the coating on the outside of tube. Fig. 4-Old Philco design used two similar rectifier tubes. New circuit appears at right. 5. Without forcing or applying un- due pressure, carefully remove tube, In early designs two 5U4's were used wavelength of the signal concerned. support brackets, and mounting as as rectifiers. Since they are filament - The identical trap action takes place single unit from cabinet, laying on pre- type tubes, they heat instantly, provid- when the stub is shorted at the end of pared paper or crepe, tube face down. ing full output voltage throughout the a quarter -wave section. Thus, all you (Before completing this step first make set. The other tubes, being cathode need do is cut your trap stub exactly sure all wiring is disengaged and types, were still cold, hence drawing no in half. Then, instead of leaving the clear.) Since the face of the tube has current yet. This forced the full recti- end of the stub open, short it. You now the greatest thickness and weight, it is fier voltage to all elements, regardless have the sanie effect, plus an extra stub advisable to place the tube face on the of resistance step -down. Those valuable of ribbon -line for your trouble. What- palm of the hand while carrying it, for TV capacitors, carefully built for this ever the unsightly effect of the original safety. Don't ca. ry by the neck. application, popped like so much corn stub, you've reduced it by half. This is 6. Loosen picture -tube clamp screw at the overload. a 100% improvement in the appear- which fits around the rim of the tube This new technique uses the 7Z4 ance. If the result is still unsightly, face. cathode -type rectifier for the screen cir- perhaps you'd better formulate another 7. Finally, lift the entire assembly cuits. Thus, by the time the 7Z4 pro- question. See Fig. 5 for a comparison off the tube, leaving the tube face down duces voltage, the other tubes are heated between the two stubs -the open half - on the paper. and ready to receive it. The 5U4 uses wave and the shorted quarter -wave. To replace the tube just reverse the its heavy current for the audio and steps described above. output stages. The division of rectifier RIBBON TRANSMISSION LINE . OPEN ENO The men who best understand tele- output avoids damage to components, vision tubes -the professionals in tele- and makes for satisfactory steadiness vision stations and assembly men in of operation. factories-handle them with goggles See Fig. 4 for comparison between and gloves. They know exactly what old and new rectifier setups described they are doing. In following their ex- 2 above. ample, you will not only be insuring ANT POST k. 4,/ SHORTED END yourself against that day when a tube .. _ ...... may implode in your hands; you will Folding Over very large k- ; -1 be advertising to the set owner that you ? My television set has a know what you are doing-and issuing screen. The picture is fine except that Fig. 5-Thue fwo stubs have the same effect. AUGUST, 1949 :32 Electronics

Liquids and Jases >

spectrometer-is produced. This is the reason for the name mass spectrometer. A practical model In actual practice, it is more convenient to collect only one of the devi- ated beams at a time. A collector with a slotted shield ahead of it is used, rather than the broad plate of Fig. 1. Since the acceleration of the ions can be controlled by varying the electric field (the force causing them to move in a straight line) and their curvature by varying the magnetic field, an adjustment of voltage or magnetic field strength can be made which will permit a particle of any given mass to pass through the slit and to the col- ¡'u ntos cnnrr.nU Yrorrss if histru men rs lector plate. Rear of commercial mass spectrometer. Note curved tube and vacuum pump. The practical instrument is shown very well in Fig. 2, a cross section of a spectrometer tube. Gas from the sample bottle circulates in the chamber, where it is ionized by bombardment from the electron gun, electrons from which enter through a hole in one of Spectrometer Measures the field- forming plates. These are maintained by the bleeder at such voltages as to accelerate the particles and start them down the analyzer tube. The magnet, which applies the field to curve Mass of Chemical Ions the beam, is not shown. The particles which are of the correct mass to pass through the slit are caught on the collector plate and give up their charges, which are registered on the grid of the electrometer tube and made By JERRY S. ADAMS to give an indication on the recording galvanometer as shown. Field voltage or magnetic intensity, or both, being varied in synchronism with the progress of the record, a continuous spectrum may be obtained. Both the presence of ions of different masses and the THE mass relative num- spectrometer is today into the sample bottle at low pressure. ber of ions in each of such beams may one of the most useful electronic The particles of gas are ionized by bom- thus be recorded automatically. tools in the experimental labora- bardment from a more or less standard tory and in large -scale industrial electron gun, and the ions are accele- Uses of mass spectrometry processing plants. Used to analyze and rated in a beam by the field- forming Applications of the mass control the quality of chemical spectrometer com- plates. fall into the following general fields: pounds simultaneously, it is especially A magnetic field at right angles to I. Rapid and accurate analysis of valuable for detecting very small quan- beam the tends to curve the ion path liquids and gases which may contain a tities of impurities and for analyzing into a semicircle. Ions of less mass are, dozen or very small more components; samples. of course, more easily swayed from 2. Determination The principle of the of the kinetic forces mass spectrome- their path than those of greater mass. in and mechanism of chemical reac- ter is as simple as that of the ordinary Therefore, after having traveled a short vacuum tions; tube. Fig. 1 is a rough and distance, these ions will have separated 3. Identification simplified of chemical processes drawing illustrating the proc- from the heavier ones. Collected on a which occur in metabolism. ess rather than the equipment. The photographic plate, as in Fig. 1, a spec- In the first of these applications, sam- material to be analyzed must be in the trum of ionic weights- similar to that ples of as little as form of gas or vapor, .001 cubic centimeter and is introduced produced by a beam of light in a light in volume can be used as test specimens. RADIO- ELECTRONICS for Electronics 33

The energy of the bombarding electrons to ionize 1.1001D SAMPLES SAMPLE BOTTLE PHOTOGRAPHIC PLATE is made sufficiently high and TO PUMP fragmentate the molecules, so that ions of several different masses can be formed and the compound identified in to the FIELD-FORMING PLATES PATHS OF IONS OF DIFFERENT a manner analogous fingerprint Il MASS BREAAOFF method of identifying a criminal. - "MAGNETIC FIELD One of the major problems in the Fig.I chemical industry has been the analysis of small impurities in intermediate METERING VOEUME ÍCORDING OSCILLOGRAPH NLE" 30TT-E DC AMP. products. With the mass spectrometer GAS SAMPLESt RECORD ELECTROMETER 1_0F MIRROR this work is fairly simple. For example, INIZATiON ;1AMBE0. GALV I as little as .00:3',', diethylbenzene has FIELD-FORMING PLATES been detected in ethylbenzene during 500 - 3000v LAMP have to be of con- VARIABLE . of tests that proved siderable importance to the rubber industry. These tests could not have been made without the mass spectrometer. BLEEDER In the analyses of hydrocarbons ELECTRON GUN (compounds comprising hydrogen, car- ANALYZER TUBE bon monoxide, nitrogen, etc., with one Fg.2 to five carbon atoms), the mass spectrometer has been used with particular Fig. I- Diagram shows method by which ions of differing mass are separated in spectrometer. efficiency because it obviates the need Fig. 2 -The complete apparatus consists of the tube plus pumping and recording equipment. for preliminary fractionation, permit- ting analyses to be completed in 30 minutes, whereas about 8 hours would otherwise be required. This should facilitate the improvement of numerous petroleum products. In compounds with as many as six isomeric octanes, the mass spectrometer has analyzed fractionated cuts of alky- lates and paved the road leF:ding to improvements in aviation gasoline. In the analysis of gases in thermionic vacuum tubes, samples amounting to only .001 cubic centimeter have been detected. In pure scientific research, the mass spectrometer has proved of particular value in studies of the kinetics and mechanism of reactions. Its application to this field has followed two different The analysis tube itself. The sample is injected into the transverse tube at the far right. lines: In the first, small samples are withdrawn from the reaction chamber must be made. In one series of experi- (one containing easily identified heavy during the reaction and analyzed. In ments, dimethylether and acetaldehyde isotopes) to a biological reaction either the second, heavy isotope tracer tech- were decomposed with heat and con- in an intact animal or in an isolated niques are employed. tinuous analysis was made of the con- tissue or extract, then to isolate the The fact that the mass spectrometer sequent gases -enabling scientists to products and determine their heavy - is capable of analyzing comparatively ascertain the nature of this reaction isotope content. In one sequence of ex- small particles permits withdrawal and for the first time. periments, rats were fed a labeled amino analysis of samples throughout the acid for a period of several days. The course of a chemical reaction at inter- Tracer methods acid was labeled by synthesis with an vals ranging from 2 to 10 minutes, heavy- isotope tracer techniques have excess of heavy isotope of nitrogen, so depending on the types of analysis that also made the mass spectrometer use- that the body components of the rats ful in metabolism studies- particularly could be dissected and analyzed for with regard to intermediary metabolism labeled atoms with a mass spectrometer (that is, the mechanism of the break- at the end of the test interval. As a down and synthesis of proteins, fats, result of this unprecedented work, it and carbohydrates and their introcon- was learned that the absorption of food version, as well as the effects of vita- products in a living body is a very mins and hormones thereon). extensive succession of chemical reac- The usual procedure in isotope -tracer tions -not a simple mixing process, as work is to submit a labeled subtance was previously supposed.

NEW LONG -LIFE RECTIFIERS

Rectifier tubes for X -ray service with age tubes. It was thought, however, up

I i fe expectancy 50 times as long as pre - to less than a decade ago, that 5,000 y iously used types was announced by volts was the maximum. During the war Z. J. Atlee of the Dunlee Corporation, 35,000 volts was used and the new tubes Chicago. The new tubes have filaments raise the ceiling to over 100,000. Be- made of a thorium- tungsten alloy. cause of the much lower work function They have a possible use in televi- of thorium on tungsten (2.63 volts) sion. than of pure tungsten (4.52 volts) Thorium- tungsten filaments have long much more efficient emission is obtained Operating positron of the mass spectrometer. life and are commonly used in low -volt- and at a lower temperature. AUGUST. 1949 Electronics Electronics in Medicine Dart 1- E letetron utitroxteopes gire a magnii'ieation of 100,000 times By EUGENE J. THOMPSON

THE story is told that the great clearly a need for an instrument which It was also found that any particu- German physician and bacteriolo- would extend the limits of human late body (specific minute particle), gist, Robert Koch, discouraged and vision. such as an electron, in motion, had a virtually penniless, spent his last The first steps in this direction were characteristic wavelength. Thus, if the remaining funds to buy a microscope. made about 20 years ago when it was velocity V of an electron is expressed It was indeed a fortunate purchase, discovered that a stream of electrons in electron volts, its wavelength in both for him and the whole of human- passing through an axially symmetric cm is ]. =10-8 V 150, A. with ity, because it he made the dis- electric or magnetic field could be fo- Practically speaking, a stream of coveries which brought him fame and cused much as a glass lens focuses electrons traveling under a potential the everlasting gratitude of his fellow light (Fig. 1). difference of 60 kv has a characteristic men -discovery of the bacteria that cause tuberculosis, cholera, and other diseases. However, despite the magnifi- cent medical achievements this instrument has made possible, it has many -- SOURCE OF ILLUMINATION - -_ limitations. - Electrons Light For example, a large group of diseases-infantile paralysis, smallpox, influenza, and many others -are caused CONDENSER LENS _ -_. by viruses, deadly killers so small that Magnetic Glass they cannot be seen with the finest optical microscope. Hence, there was SPECIMEN STAGE

OPTICAL LENS MAGNETIC LENS OBJECTIVE LENS DOUGHNUT-SHAPED COILI CROSS SECTIONI SPECIMEN (- SPECIMEN % Magnetic Gloss

PROJECTOR LENS Magnetic, Gloss ÇNSS FIELD FOCUSED ELECTRON IMAGE STREAM RCA ELECTRON MICROSCOPE LIGHT MICROSCOPE MAGE Fig. I- Magnetic field focuses electron beam. Fig. 2 -The electron microscope accomplishes electronically the ¡ob of the light microscope. 5R4GY(2) 6L6(2) LIGHT MICROSCOPE ELECTRON MICROSCOPE - RI x22 VI

125 1125 I I X58 C5 X61C9 T3 4 6 125 125 5116 R115 A 47 47 +370V R G OUT TO VAC INTERLOCK 874 V11 SCR THROUGH R201. KI CONTACT N °4 F7 X26oC D C13 .1 SPECIMEN 3A _ X60 C6 X63 CIO J2D6C D BOK 826-K J20-K T32-2 L2 125 ...125 o o o s r/ TO HV REG V22 ETC TB2o6 7 R3 2 R62 OBJ REG V23 x19 V4 f \ x591 C7 X64101 i i SEC 3YEL R8 PROD REG VIN THROUGHI 75K2 R 26 125 125 T4.= 6.3v A 55 TO COND SUPPLY R21 ARM

RI .8 L4 L5 6B0K X240 J16 2 x26-E x2i V6 R4 0 o 0 0 J18.0 x71-2 J20-E 6SF5 220K 572 IMEG TO PROJ REG PLATE V14 T82-3 a 7

X26 9 R2 50K -A. REG ON S 04 METER S.4 J20 i--- TB2 5 ' I U2 6.3V I( SEC ' e'e BLK 1 T4 Fiq. 3 (left) -O eration of two microscopes. RED Fig. 4 -a (above), 4 -b (p. 35). 4 -c (p. 36(- Complete schematic diagram of the RCA VR-150/0D3 12 12 type EMU-1 microscope. RADIO- ELECTRONICS for Electronics 35

VALVE INTERLOCK OPEN ONLY WHEN VALVES ARE IN "OPERATE" POSITION

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óa ¢ r AUGUST, 1949 36 Blectroaics wavelength of 5 X 10''° cm, which is into a parallel beam and directed on er than a 60 -cycle design. This feature about .00001 times that of light. the specimen to be magnified by the makes it possible to use a relatively It is not possible to detect objects or condenser lens, L1. The image of the small, low-loss resonance coil which re- details whose dimensions are much specimen then falls on the objective quires very little power to excite it. smaller than the wavelength of the lens L2, which focuses and magnifies Also, for a given permissible ripple illumination used, so the magnification it, producing an enlarged image, I1. value, smaller capacitors can be em- obtainable with optical microscopes is Part of this enlarged image is further ployed. The speed of regulation at r.f. relatively slight (about 2,000 times). magnified by the projector lens, L3. frequencies is not the problem it is Because the wavelength of high -speed In the electron microscope the source with a regulator operating on the low - electrons is only a hundred -thousandth of illumination is a hot cathode which voltage side of a slow 60 -cycle recti- that of light waves, it should be pos- emits electrons. An anode with a small fier. In addition to this, it is a simple sible, theoretically, to get electronic hole in the center gives these electrons matter to shield stray r.f. fields. magnification up to 200,000,000 times. a high velocity, and a doughnut- shaped The actual circuit is shown in Fig. 4. In practice, the maximum enlargement coil Ll produces a field which bends and a block diagram in Fig. 5. Refer- is 100,000 times, which is still 50 times the paths of the electrons into a paral- that of any light microscope. lel beam directed on the specimen. The The electron microscope operates electron rays pass through the speci- FIL. OSC. much like a transmission -type light men and are affected in varying degree I I COAXCO-AX LINE I microscope. As shown in Figs. 2 and 3, depending on the composition of the DRIVER . -1 DC MOO.AMPL. --I FIL.TRANS. in the light microscope the source of specimen. Those which pass through OSE I TO MICROSCOPE illumination is a lamp (and mirror), are brought to a focus by the field of the light rays from which are formed the coil L2 and form an enlarged im- 1 RECTIFIER, age Il. The electron rays which form DOUBLER& a section of this image are in turn FILTER magnified by the field of coil L3, and RELAY CONTACTS NORMALLY OPEN caused to form a further enlarged Fig. 5 -Block diagram of 60 -kv power supply. 2 Al image I2. It will be noted that the T03.5 3 RELAY coils Ll, L2, and L3 act like the lenses ring to the latter, the high- voltage S10 %24-I HOOD in the optical microscope, and are re- rectifier is essentially a high -Q reso- INTERLOCK JM-I ferred to as magnetic lenses. nant network consisting of Lx and Cx 183.6 J168 C+370Y The I2 in REG OUT image the electron micro- which is in series resonance with re- %24-D X716 scope is formed by an electron beam spect to the driving oscillator, but par- JIB-D TO GUN FIL R70 ARM which itself is not, of course, visible. allel- resonant when viewed from the J2-C NOTE A- ALL PRI TRANS PWR LINE A fluorescent screen, therefore, is high -voltage rectifiers. Cx represents X70-C CONNECTIONS ARE SHOWN placed so that the beam falling on it the sum of the rectifier and stray ca- produces S6 HVIt %io-A T a visible image. Photographs pacitances. The resonant impedance of J16-N are made by allowing the electron beam b J2-A %24-N the high -voltage coil and the Q of the to fall directly on a photographic plate. circuit determine the amount of excit- T4 J20-P Four basic systems comprise the elec- ing power required from the oscillator TB2-8o T82-9 826-P tron microscope. The schematic dia- because of the small load. J20-Mo gram is shown at Fig. 4. The optical sys- The requirements of high Q and max- 126-M0 CONTROL tern has already been described, and CIRCUIT imum impedance demand careful coil T2 the control system is essentially a design and frequency selection. The Q T3 F1 switching and metering network. The of the circuit is about 200 and the X74 vacuum system consists X24-7 124-A T53-A of an oil dif- operating frequency 32 kc. Under these fusion pump, a forepump, and an elec- conditions the required exciting power Jle-T JIe-A T9 tronic valving arrangement. Its pur- is around 150 watts; the maximum J2-8 012 -D X24- pose is to pump the air out of the area load is approximately 30 watts. 170 -0 I 470 -D Je -G through which the electron stream must The high- frequency oscillator is con- 54 53 PANEL LIGHTS J2.4 pass, so that an electron leaving the trolled by the resonant circuit to main- MAIN PWR Y 1-- ON X70 F filament will travel the length of the tain the proper driving frequency, and instrument with a minimum likelihood the amplitude of the current from the A I % 4 «70-E of striking a molecule of air. This re- oscillator controls the power -supply A2 X S J2-E quires a vacuum of about .00001 mm output voltage. The oscillator current JIB-H of mercury. A3 X 6 is dependent on the screen voltage ap- X 24-H The chief electronic features of in- plied to the oscillator output tubes. T83-4 A4 X 7 TB3-I0 terest are contained in the power sys- R27 Thus, controlling the screen voltage tern. Two power supplies are used. A 600n EA PANEL LIGHTS SIB I RH DOOR governs both the amplitude and con- RH DOOR INTERLOCK NTERLOCK high- voltage, 60-kv unit is used to ac- stancy of the output voltage.

SI7 LH DOOR celerate the electron stream. Its high The rectifier employed is a voltage ilLM INTERLOCK DOOR INTERLOCK side is attached to the anode and run doubler which does not require a tuned 153.3 83-9 at ground potential, while the negative transformer, because the circuit is such TO DIFF leg is connected to the cathode, at that one side of the high-voltage coil PUMP CIRC -60 kv with respect to ground. A low - can be grounded. For this reason a voltage supply is used to power the simple resonant circuit is permissible. XIO F2 FI tubes and the magnetic -lens coils. Be- A tuned filter is used to eliminate I5O ISA cause the speed of the electron stream high- frequency ripple from the high - 183.2 TB3-I and the current flowing through the voltage output. The low- frequency dis- lens coils are the critical factors in turbances are corrected by comparing focusing the instrument, both supplies a -___..___I_ _ FI_M portion of the input voltage with a VOLTAGE FORE be PUMP must very stable. For satisfactory standard voltage and regulating the operation, regulation must be: oscillator screen with a d.c. amplifier. TO 117V 604, LINE Over -all microscope voltage .015% The voltage regulation is better than J29 Objective lens coil current .005% .002 %. I 513 ROOM LIGHT Projection lens coil current .068% The lens -coil current is also regu- TO CUSTOMER o 1 CONTROL SW Condenser lens coil current 0.1% lated. ROOM LIGHTS The current variation is less 3 The problem of getting a highly reg- than .002% for the objective lens coil, AUXILIARY LIGHT CONTROL ulated 60 -kv power supply in a small .004% for the projector-lens coil, and Fig. 4 -c -The microscope control circuits. space was solved by using an r.f. rath- .02% for the condenser lens coil. RADIO -ELECTRONICS for Electronics 37 Experimenting with

Ultra - Violet Rays

By ERNEST J. SCHULTZ

These pictures thaw how the ultra -violet -ray MANY interesting experiments made from part of a discarded photo- can be performed with the graphic ferrotype plate. For best re- powerful ultra -violet rays ob- sults a reflector is essential to avoid tainable with the simple ap- wasting the rays. A highly polished ^Á_ paratus described here. One use of the chrome reflector is the most effective. device is a "heatless" suntan which can The reflector is mounted, with adjust- be realized with short exposures of able brackets, on the 11 x 7 x 2 -inch only 2 or 3 minutes daily for several chassis. If desired, the actual lamp as- days. Study of the weird characteristic sembly may be made independent of colors of fluorescent materials and ex- the power and oscillator chassis, pro- amination of stamps and documents vided the leads are kept to a reasonable under "black" light are other very in- length. No particular precautions need teresting applications of the ultra-vio- be observed in the wiring, and the lay- let ray. out is not critical. A variety of con- There are many other intriguing struction methods could be employed tube and its reflector are fitted to the met- uses. For instance the germ- killing ef- for the job. fect of the rays can be employed in The germicidal lamp gives rich out- sterilizing materials or areas. Goods put throughout the violet end of the that would normally perish rapidly spectrum and up. Peaks of output oc- maintain their freshness under the pro- cur between 2,500 and 3,000 Angstrom tective glare of the ultra -violet gen- units. The lower peaks have the germ - erator. killing powers, whereas the rays of fre- The circuit employed is an adapta- quencies about 2,900A tan and burn the tion of the "Furedy" circuit and uti- skin. rf lizes r.f. energy to power the ultra- Be very careful when using ultra- violet -ray tube. In operation it parallels violet rays. Overexposure causes pain- a commercially available lamp, but is ful burns of eyes and skin. p more powerful. The tube used is a 15- watt G -E fluorescent Germicidal bulb. No heat accompanies the ultra -violet The tube life (barring breakage) is al- rays; therefore, you cannot depend on most endless as the filaments are not your sense of feeling to warn you when al chassis. Though parts are few (see under used, and there is no chance of burnout you are getting an overdose. with the r.f. supply. The r.f. oscillator Determine your sensitivity by making is a 6B4 -G, and the rectifier an 80. trial exposures starting at not more than Other tubes, such as a triode -connected l or two minutes daily and increasing be 6L6, can of course substituted with the exposure gradually till you get the equally good results. desired tan. The oscillator is an ultraudion operating in the 11 -meter diathermy band The exposure, of course, varies in- with a coil Ll of 11 turns of No. 20 versely as the square of the distance bare tinned wire, wound on a 1 -inch from the source. polystyrene form, the turns being Goggles are indispensable when ex- spread to cover I% inches. The tube is pe ' 'sting with ultra -violet rays. capacitively coupled to the ends of this coil, with the two leads shown in the Almost any glass (colored or clear) i schematic. One is wound tightly round will serve to protect the eyes. The rays the glass at one end (L2). About three will not penetrate ordinary glass with- chassis) large base has mechanical solidify. turns will be sufficient. The other lead out great loss in intensity. The rays is to filament simply attached a prong will not penetrate clothing, so the ex- d (L uv 1 80, 5Y3, ETC at the other end of the tube. Blocking perimenter need protect only uncovered L2 / 250 capacitors of -µµf capacitance are parts of his body, such as his eyes, face, 00025 MICA_1 w/ installed to keep d.c. off the leads for and hands, if working under the lights LI 200V safety's sake. for long periods. 00 50MAL The two r.f. chokes are standard 2.5- The ultra -violet generator produces IAVAC .00025 2.SMH mh chokes. Shortwave types could be profuse amounts of ozone, and the lamp 2RV used but apparently are not necessary. can be used where deodorizing as well e 600V The tube UV is a G -E 15 -watt Germi- as germ killing is required. For the ex- 2.5 T cidal lamp, as stated before. perimentally inclined constructor, mak- 225 /2W í6.3V The ultra -violet tube is mounted with ing one of these generators will open two conventional fluorescent sockets up new fields of adventure in invisible 684-G,6L6 TRIODE ,ETC screwed to a metal mount made slightly radiation with moderate expenditure longer than the tube. The reflector is and not a great deal of work. Be sure to adjust oscillator to II -meter band. AUGUST, 1949 38 Construction

A High- Fidelity Tutier-Atiiplilier Part II-Amplifier has taco types of

equalization, three feedback loops. By M. HARVEY GERNSBACK

THOSE of you who last month read 68,000 -ohm resistor in this loop de- boost capacitors to start the boost at a Part I of this story probably com- termine the maximum amount of boost higher frequency, giving greater boost mented to yourselves, after look- and the frequency at which it starts. at the low frequencies. The values we ing at the photos and schematic, Potentiometer Rl in shunt with the use are the result of listening tests "He's using two tubes and two ger- .02 -pf capacitor controls the amount of with a wide -range loudspeaker (a manium diodes for the r.f. end, but the bass boost. Although this bass -boost Stephens P52 -HF). We found that photos show an awful lot of other tubes circuit alone will give considerable raising the frequency at which the and parts. What is he using them for ?" boost, it is augmented by a second bass - boost starts caused tubby reproduction A glance at Fig. 1 should answer that boost circuit at the grid of the first like that of a juke box. If you like question. It shows the wide -range audio 7A4. This is made up of the 22,000 - that, fine; but then there's no sense amplifier. ohm resistor, the .04 -pf capacitor, and building yourself a wide -range system Let's leave the two -stage phono pre- R2 between the 200,000 -ohm tap on the like this. amplifier (the 6SL7 -GT) until later volume control and ground. The fixed Fig. 2 shows the maximum value of and discuss the main amplifier first. resistor- capacitor combination deter- bass boost obtainable and the bass cut As Fig. 1 shows, it consists of six tri- mines the frequency at which boost obtained with Si open. Adjustment of ode stages, resistance -coupled. The starts. R2 determines the amount of R1 -R2 will give intermediate first amounts three stages (the two 7A4's, and boost and it is ganged with RI. The use of bass boost. As the curve shows, half of the first 6SN7 -GT) are single - of a potentiometer gives a smooth, boost starts at about 800 cycles but ended. The two sections of the first stepless adjustment of bass boost. doesn't really begin to climb until about 6SN7 -GT are direct- coupled. The sec- For bass cutting (useful when listen- 250 cycles. Below this frequency ond section the is a kangaroo phase splitter ing to speech on stations having a tend- rise is at the rate of about 6.5 per feeding -pull the push second 6SN 7 -.. T. ency to boominess) Sl, an ordinary octave. Maximum boost occurs at 20 This in turn drives the 10.5 -watt output power switch on the back of the dual cycles where it is 21.4 db. Bass cut push -pull stage of triode -connected, control R1 -R2, opens when the bass - starts at about 350 cycles and reaches -A class 807's. boost control is turned off. With Si a maximum of 14 db at 20 cycles. open, a .01 -pf capacitor Negative Feedback Loops is placed in Treble boosting is handled by shunt- series with the 0.1-pi unit, coupling ing small capacitors of .025 and .015 The colored lines in Fig. 1 indicate the plate of the second 7A4 to the fol- pf across the 2,200 -ohm cathode re- two separate negative feedback loops lowing 6SN7 -GT grid circuit. This pro- sistor of the first 7A4, thus bypassing in the main amplifier (there's a vides third effective bass cutting. the negative feedback in loop 1 high one in at the phono preamplifier). Loop 1, Reduce the size of the .01 -pf capacitor frequencies. The treble switch S2 -b around the two 7A4's, is for bass boost- for greater bass cut. Likewise, decrease does this in positions 1 and 2. Treble ing. The .02 -pf capacitor and the the values of the .02- and .04 -pf bass- cutting is accomplished in positions 4, 5. and 6 of S2. A two -section, resistance - capacitance network from the plate circuit of the second 7A4 to ground SELECTOR VOL. RI, R2, SI 6SN7=GTS S.D. ADJ. causes the high- frequency rolloff to SWITCH 7A4 CONI. have a steeper slope than with a single section. The two sections can be traced from the two 4,700 -ohm resistors in series in the output of the 7A4. The bypassing capacitors are connected to contacts 5 and 6 of the two -gang switch S2. Fig. 2 shows the amount of treble boost and cut which this arrangement gives. The boost position is used only on broadcasts where the program material lacks highs. It is very effective. The tone -control stages are based on the design used by Lincoln Walsh in the Brook amplifier. Following the tone -control stages there is a 100,000 -ohm screwdriver - adjusted potentiometer to set the overall maximum gain. The following four stages are included in negative feedback loop 2. You have probably noted the absence of cathode -bypass capacitors within loop 2. This is deliberate. Because of the large amount of negative feedback used (20 db), phase shift at very low and very high frequencies (which Same photo as last month -but minus veil -shows placement of ports in the amplifier section. could cause negative feedback to turn RADIO -ELECTRONICS for Construction 139 GAN5E0 BASS BOOST 68K .02 1 1 1005 +430V FM 6SN7-GT 6SN7-GT j RI4J I aff rrr:3ACK t 4 .05 1 K / IMEG ST ÈOÓ4to TREBLE .01 Ó5 SELECTOR REE .1 - Sw NOTE 7A42 17A4 4 4 / AM I VC) I 4.7K 4.7K 5 410K 6 5 OA o / f I -..01 Á05T 6 PH EG I6r'¡'' 1 . 470 R3 o 22K SI 0 1 --..w/Vb 9 I6r20n 470K 25 0 1-0 I 'M EG 47N 7 BASSCUT SPKR 7 470K 3eAo+S2-b 6 47K 3 r-IF SW r i o 2.2V 50,25v 2.2 47K 2 j-1 .04 22K A5 ( .1 45 I1 ZX Á7ó

IS 15 T Ts 11- 1/+ 45)V 450V i250MA 2 2MEG 33NS 12214

20 4._1----4"... 15Ta5ov -^K 8 +420V B- 13+ 440v 54

- 0120W FEEDBACK LOOP N'2 a 5 o . '. 7. IOK /20W 420V RI -R2 -SI GANGED PHONO PICKUP

ISK _.a 20 GANGED TO SELECTOR SW NOTE VC-500K VOL. CONT. WITH 200K L MK TAPS I IOOK NOT USED)

s '--11-- B +250V TO AM TUNER FIL PINS - 7A4: I -8; 6517 L 65147: 7 -8 L2K325v 3.6K 470K L 2.2 MEG RESISTORS I /2W - OTHERS IW UNLESS NOTED CAPACITORS 600V UNLESS NOTED

2A3's cause less hum trouble than the meter from one 807 to the other so 684 -G's but require a separate 2.5 -volt that plate current can be accurately filament transformer. If 6A5 -G's are balanced by R4 at 48 ma on each out- available, they can be used, with proper put tube. adjustment of plate and grid voltages. The 100 -ohm units in series with the We tried using a 6AS7 -G but gave it screens limit screen dis >ipation to a up because of the difficulty of driving safe value. it to full output with a resistance - The output transformer is a critical coupled driver stage. It just requires component. It must be good or you will too much input. get into oscillation trouble with the The two 100 -ohm Fig. Complete schematic of the amplifier. resistors and R4 large amount of negative feedback em- I- in The three feedback loons are shown in color. the grid circuit of the 807's are for ployed. It must be a true high -fidelity bias balance. R5 adjusts the total plate unit with less than 1 -db variation from current on the 807's (about 96 ma with 20- 20,000 cycles. into positive feedback) must be Primary inductance kept no signal). A 100-ma meter is as small as possible. Cathode capacitors con- must be high and leakage reactance nected in place of the meter jumper in low. There are a number of trans- could cause too much phase shift at the cathode low circuit to measure indi- formers on the market which will meet frequencies. The loss of gain is of vidual 807 plate no importance. current. S3 switches these specifications. Cheaper trans- The first stage in the loop is merely a voltage amplifier (one half of a 6SN7 - GT) feeding the phase splitter (the TUNING VOLUME other half 6SN7 -GT). Direct coupling is used to eliminate one more source of TREBLE 7A4 BASS SELECTOR phase shift. With direct coupling and 6SN7 -GT F M INPUT low -value load resistors in the phase - 65L7 -GT splitting circuit, balance is good within 807'5 less than 1 db over the whole audible CATHODE CURRENT range. R5 The second 6SN7 -GT is a conventional push -pull stage feeding the push - PHONO R3, SIG INPUT pull 807's. R3 in the plate circuit of BALANCE this 6SN7-GT is a balance control to 6075 equalize the signal voltages on the BALANCE 807's. To adjust, disconnect the nega- R4 tive feedback, feed an audio tone of METER about 1,000 cycles to the amplifier, and SOCKET adjust for equal signal level the at METER grids of the two 807's. Use a scope sW or v.t.v.m. The output stage is unusual in the use of 807's as triodes. With the plate voltage specified, output at the secondary of the output transformer is about 10.5 watts at the grid- current point. We FEEDBACK used 807's because they are avail- OUTPUT SPEAKER 807s FUSE SW, S4 6075 PHONO able at low cost in the surplus market SOCKET EQUALIZER and, more important, being cathode - type tubes they generate little hum. We gave up 6B4 -G's because of this; The II x 17 x 3 -inch chassis holds the push -pull 807 amplifier in addition to t.r.f. tuner. AUGUST. 1949 Cuoatructieo 40 I

DB formers may be used only if the amount The phonograph preamplifier need +20 of feedback is appreciably reduced. not be included if the builder has no Quality will of course suffer in that use for it. Just omit everything on the +15 case. The transformer we used (Chi- lower level of Fig. 1 and use a two - +10 POS I cago Transformer Co. BO -6) has a position (FM -AM) selector switch. +5 will tertiary winding (terminals 4 -5 -6) for The 6SL7 -GT preamplifier circuit 0 use if feedback is applied directly to equalize a low -level, w'de -range mag- -5 the cathodes of the power tubes. Don't netic pickup for varied recording char- 50 00 500 1000 5000 101(14K use this winding. acteristics. CYCLES The output winding is 16 -20 ohms, Fig. 3 shows ti-e response for dif- DB with an 8 -ohm tap. Feedback is taken ferent positions of S5 when using a IllftOe11f1f1Me111 off the 16 -20 -ohm terminal and goes Pickering 120M cartridge. The nine +IDIIi11P052-5 111111 1111111 back to one cathode of the first GSN7- positions provide proper equalization +5ii11111RNI11111 1111111 GT, through S4 and one of five re- for practically all U.S. and foreign Mi9111 sistors selected by S4. This switch records manufactured since electrical 011111 15111 varies the amount of feedback from recording was adopted. The bass and _511111 111111 o'a:r411 none (position 1) to 20 db (position 6) treble tone controls in the main ampli- 11111111 111111 PPO54G!Oi in six steps. The amounts of feedback fier augment these nine positions. 101I111111111 ilÌi:, in positions 2 through 5 are 2, 8.6 db; Feedback loop 3 provides the pre- ca- _2011111 111111 11iii11 3, 12.4 db; 4, 14.9 db; 5, 17.7 db. These amplifier equalization. The three SO 100 500 1000 5000 IOR141 measurements were made at 1000 cycles pacitors selected by S5 -b are in series CYCLES with the P52 -HF speaker as load. The with the feedback line and, with the whole circuit within feedback loop 2 47,000-ohm series resistor, set the DB is based on a design by D. T. N. Wil- crossover frequency at which bass 1111111i liamson in Wireless World (London). boost starts. +5 10=1;11111111 You may be surprised at the use of The six capacitors which are bridged íi111 \2!!11111UK11 feedback with triode class -A output across the 47,000 -ohm resistor by S5 -a 011111 11i111iS \í!íía1 tubes. The difference between triodes increase the amount of negative feed- 1 0 1 1 1 1 1 11111111 ;N with and without the feedback has to back at the higher frequencies, effec- O 1 1 1 be heard to be appreciated. We have tively causing high-frequency rolloff. 1 5 1 1 1 1 1 1 1 1 1 M checked input- output linearity at vari- S5 -a selects the proper capacitor for _2011111 1111111 11111111 ous levels with no rolloff. In positions 1, 2, An An sm win 5000 MR 141 output feedback and the desired CYC ES with varying amounts of feedback up to and 6 there is no rolloff. The 2.2- 20 db, using an oscilloscope and a.f. megohm resistors connected to various Fig. 3 -Phono curves suit almost any record. oscillator. The linearity curve is prac- switch points in the amplifier are tically a straight line with full feed- switch -click suppressors. S5 is mounted back and bends rapidly as feedback is on the chassis deck. A flexible shaft Adjustments reduced. connects it to the front panel. An amplifier employing a large Another advantage of the large amount of feedback (such as in loop 2) amount of feedback (even with triodes) Construction is a tricky thing to get working prop- is greatly increased loudspeaker damp- erly. If you plan to use the full 20-db ing. Electrical output measured at the The layout of stages is shown in the feedback, a scope (or v.t.v.m.) and a.f. speaker terminals is flat within 0.5 db two photos. The unsymmetrical ar- oscillator covering the full audio range from 20- 20,000 cycles. This is with a rangement was dictated by the tuning is almost a necessity. Without these speaker load. capacitor and coils for the AM tuner aids you may have unsuspected positive With feedback there is no dif- and by a desire to keep leads to the feedback at a supersonic frequency, ference in frequency response when front -panel controls as short as pos- which will cause baffling distortion and measured with resistive or speaker sible. even birdies in nearby broadcast re- load. Take away the feedback and re- All ground returns are brought to a ceivers. sponse with the resistive load is still common bus rather than to chassis. The In our amplifier, for example, with a good; but with a speaker load, it varies bus is grounded to chassis at a point resistor load on the output the ampli- as much as 5 db over the range. The near the first audio stage. The outside fier is perfectly stable at all settings peaks coincide with speaker resonance foil of paper capacitors (curved plates of the screwdriver- adjusted potenti- points. The measured internal imped- on schematic) should be connected as ometer. But with the Stephens speaker ance of the amplifier at the 16 -ohm the schematic shows to keep stray - connected, and the speaker's tweeter output (with 20 -db feedback) is 0.66 capacitance effects low. The cable con- volume control full on, oscillation re- ohm. The net result of all this is very necting the chassis to the separate sults unless the screwdriver- adjusted fine response to transients, which shows power supply chassis (see Part I in potentiometer is set at least 15,000 up particularly well with music. the July issue) should have heavy fila- ohms away from full on or off. Differ- ment wire -No. 12 at ent output transformers and speakers DB least. We used paral- will have distinct effects. If you don't 1G. +20 lel pairs of No. have the necessary test equipment SS BOOST ;MAXI After the amplifier available, plan to use less feedback. + is it completed, may Adjustment of R3, R4, . and R5 has be necessary to re- POS 2 been covered. The screwdriver -adjusted +5 verse the plate leads potentiometer is set at about 50% of FIAT Il51111111Pr/- to the output trans- full rotation (note the caution about 0 former if you are get- this control mentioned above). The 5 111/Tr\011 ting positive, instead feedback -control switch S4 is set for -Io ` 111 of negative, feedback the level of feedback desired and left -15 in loop 2. If it is easi- alone. In fact it may be omitted en- er, it is also effec- 20 tirely by wiring in permanently one of tive to reverse the the feedback resistors. Note that the -25 secondary leads at values of these resistors must be -30 the transformer ter- changed experimentally when a differ- 20 50 100 500 1000 10,000 20,000 minals. Use shorting- CYCLES ent output transformer is used or feed- POSITIONS I -6 REFER TO S2 type switch sections back is taken off a winding having an Fig. 2- Responses obtained with the main equalizer controls. for S2, S4, and S5. impedance other than 16-20 ohms. RADIO -ELECTRONICS for New Design

EVERY year the radio parts distributors of the nation, manufacturers' representatives, and others New Devices Exhibited intimately interested in radio components gather at the Stevens Hotel in Chicago for the National Radio Parts Show, at which practically all the important manufacturers of radio components exhibit their latest and newest at Chicago Parts Show items to prospective customers. Unlike some of the displays occasionally seen at the IRE show, almost everything exhibited is practical, down -to- earth stuff ready for sale and delivery refused admission because he had no be distorted (and thus to produce a to the distributor of repair parts or to antennas in his intended display. voltage) in direct proportion to the the manufacturer of radio and televi- The other startling innovation was amplitude of the reed's swing. Placing sion receivers and other electronic de- exhibited by Sprague. Since the dawn a pickup on the little platform at the vices. Yet products of great technical of the art, capacitor makers have top of the assembly naturally cramps involun- its style, and the voltage interest often do appear. Some of these battled the inductive effects drops accord- items, kept carefully under tarily introduced into their products, ing to the stiffness of the stylus. Thus are new where the read wraps to get the jump on a competitor. especially rolled foil is used. output as on the meter indi- Yet is sound compliance Others may be components which have there a reason for the cates the or bendability of been in use for some months, but whose capacitor - with - added - inductance. For the stylus assembly being tested. A any given frequency, there is a series chart (individually calibrated for each combination of inductance and capaci- instrument) interprets the meter read- tance which has a much lower impe- ings in microcentimeters per dyne of dance than the capacitance alone. Mod- applied pressure. ern radio receivers require a great deal The compliance meter was a working of bypassing of the 455 -kc i.f. signal. A model for practical use and was not one capacitor -inductor combination tuned to of the items exhibited for sale at the 455 kc is much more effective than an Electro-Voice booth. It is nonetheless a untuned capacitor of the same value. valuable contribution to the art of re- The Sprague 0.2 -µf resonant capacitor cording and reproducing sound.

has only 1/111 the impedance of an ordi- An important development in the Sprague bypass capacitor resonates at 456 kc. nary 0.2 -µf capacitor at 455 kc. There- printed -circuit field was signaled by fore this 0.2 -uf resonant unit is as ef- Centralab engineers, who told of the in- technical importance has escaped both fective as a standard 2.0 -µf capacitor creasing tendency to combine printed the manufacturer's own publicity de- at its correct working frequency. and ordinary wired components in partment and the reporters of the ra- In the sound field, Electro -Voice has standard radios or televisers. The Cen- dio press. produced an interesting compliance we- tralab Couplate and similar units are The Chicago show this year was no well known, and a new unit, an inte- exception. There were several outstand- grating device for television receivers ing items, including a rotating televi- which replaces six standard compo- sion antenna that doesn't rotate and a nents, was exhibited. People have an bypass capacitor with an inductance unfortunate habit of thinking in terms deliberately inserted in series with it. L of pure printed or pure wired circuits, The paradoxical antenna is known as it appears. The future may show that the Square Root Quad -loop. Once seen, in many cases it will be more efficient its principle is recognized as that used and economical to use both printed and long ago in the Bellini -Tosi direction wired components in the same piece of finder. One wonders (without detract- equipment. ing from the genius of the designer) Users of the glorious but extinct why somebody didn't think of it sooner! Electro -Voice compliance meter rates pickups. Baldwin phones will be interested in Two special dipoles are (. unted the new dynamic headphones exhibited crosswise to each other (one, for ex- ter for measuring the stiffness of by Permoflux. The phone is built with ample, is directional. north- south; the phonograph styli. Higher fidelity and a voice coil and pot magnet like a small other, east -west). Leads from each of less record wear result from the use of loudspeaker. Developed for applications these antennas are brought into a phas- high -compliance styli, and this instru- where flat frequency response is essen- ing box, from which a single 300 -ohm ment measures them for that quality. tial, the new phones are still a hit ex- line goes to the set. A knob on the box A vertical reed (see drawing) is sub- pensive for general use, but might be is turned to bring in the best picture jected to an alternating magnetic field interesting to a high -fidelity enthusi- from any given direction. from a coil surrounding it; the field ast. The acoustic frequency- response While the manufacturer is reticent makes the reed vibrate. A piezoelectric curve shown was made in a 6- cubic- about the contents of his box, he admits ceramic element is mounted at the free centimeter coupler with 1 mw of power freely that it contains a pair of crossed end of the reed. Its inertia causes it to available. coils with a revolving pickup loop between them. One admires the ingenuity RESPONSE IN DB (ZERO DB =.000204 DYNES PER CM2 ) 120 that adapted the Bellini -Tosi idea to PLATFORM FOR STYLUS frequencies in the 200 -mc range and us VOLTMETER sympathizes with the designer's deci- uo sion not to tell anybody how he did it- CERAMIC until, at least, a few of his competitors 105 CSTAL) have paid for the privilege of taking loo the little box apart. 95 REED EXCITING The Square -Root was by no means COIL 90 AC the only antenna at the show. It was Loo 3 4 5 6 0 9 1000 2 3 4 5 6 7 09 the Show of the Antenna, with even a C PS rumor that one manufacturer had been Frequency response curve of he Permoflh, phones, left, and diagram of compliance meter. AUGUST, 1949 Improved Phono Amplifier

A design for a cheap, yet good amplifier for a table -model phonograph By JOHN S. CARROLL

THE amplifier described here is the ode would seem to be adequate for the back in the output stage, it will be final one of a series designed to input tube. However, large amounts of necessary to start with signals as high determine how much table -model feedback may increase this requirement as 1 volt to secure sufficient driving record players can be improved by as much as 5 to 10 times, making voltage on the grid of the output tube. without excessive increase in cost. a high -mu tube necessary. Then the distortion developed in the The simplest amplifier used in such In the past, such feedback amplifiers driver stage will be intolerable. This is phonographs consists of a rectifier and have used a resistor between the plates the reason why so many small a.c:d.c. a small beam -power tube, occasionally of the input and output tubes as feed- amplifiers have such poor tonal quality, combined as in a 70L7 or 117N7, some- back path. This places the feedback even with feedback. times as individual tubes such as the voltage on the grid of the output tube The solution shown in the schematic 35Z5 or 35W4 and 50B5 or 50L6. These by way of the coupling capacitor. While is to run the feedback loop to the input "one -lungers" are capable of power out- that system reduces distortion in the of the first stage. It then reduces dis- puts between 1 and 2 watts, but require high output from the phono pickup. 1486 a2 c 35A5 These small beam tubes actually re- z=z.se,.- quire a peak signal of 7.5 volts to de- 2 Iól 2 velop full output. The average high - output crystal pickup generates an --f.01 SPRR 35Z3 average signal of 3 to 4 volts, and 450n/50MA 470K 120K 7 reaches a peak value of 7.5 volts only t a 2 270k on very high -level in the usual 1w passages 50 50 50 e InVAC/OC record. In general, then, such record 160 1W 30/30V 10 V21.----4-1 players suffer from inadequate power output and excessive distortion, the lat- 1486 35A5 250 ter running as high as 11% of the total e 1 e 1 low harmonics. The logical solution is inverse feed- Feedback is applied from plate of the second stage fo cathode of first through C and R2. back: this would reduce distortion without loss of output power. But the output stage greatly, it fails to take tortion and flattens the frequency re- cost of feedback is higher signal volt- into account conditions in the input sponse in the input stage as well as the age, which is not available in these stage. power tube. Polarity of the feedback is single -tube record- player amplifiers. A Given a plate supply of 100 volts, a such that the connection is made to the driver stage is a necessity if feedback typical high -mu triode will put out 7.25 cathode of the input tube; obviously, is to be applied. volts of signal with an input of 0.13 to develop any a.f. feedback voltage at The better -quality crystal pickups volt. This, however, is the maximum - this point, the bias resistor must not put out about 1 volt of signal; since signal condition for the tube, and is be bypassed. Thus, some additional de- 7.5 volts will drive the output tube accompanied by 4.6%r harmonic distor- generation is introduced in the input under normal conditions, a low-mu tri- tion. If there is a great deal of feed- stage, further improving its characteristics. In addition, the polarity of the feedback voltage is such that it adds to the bias of the tube on positive signal peaks, and subtracts from the bias on negative peaks. Thus, it acts as an automatic bias control, avoiding grid current on positive peaks, and cutoff on negative peaks. The effect of the feedback on the characteristics of the power stage is unchanged; it lowers the effective plate resistance of the output tube, avoiding high- frequency peaks and improving the speaker damping. Constructional details The photographs show the prototype amplifier as constructed for test purposes. Lock -in tubes were used in this model, but either octal or miniature types will serve as well. No high -mu single triode was available in the 0.150 - The chassis looks typical of those in inexpensive instruments but performance is excellent. amp series with lock -in base. The 14B6 RADIO -ELECTRONICS for Audio 143

-a duo -diode, high -mu triode -was chosen instead, and the diode plates connected to cathode at the socket. The feedback loop consists of Rl, R2, and C. The latter is simply a blocking capacitor, intended to keep the d.c. plate voltage of the :35A5 off the cathode of the 14B6. Having no other function, its size is not critical, except that it should not be reduced below the value given. If it is too small, feedback will be reduced at the lower frequencies, causing an over -all bass boost which may overload the speaker. R1 and R2 act as a voltage divider and put a specified percentage of the output signal voltage on the cathode of the 14B6 (essentially the same as putting it on the grid with reversed polarity). The value of Rl is set by the bias requirements of the 14B6, leaving The few components, if wired point to point as in commercial models, make unit inexpensive. R2 the only variable to be determined. The calculated value (180,000 ohms) level is attained without such usual Since this unit was entirely experi- proved satisfactory. However, the gimmicks as hum -bucking speaker fields mental, the chassis was used as ground, over -all gain of the amplifier can be or hum -cancelling networks. and a capacitor was inserted in the adjusted at this point. Increasing the The amplifier was constructed on an chassis side of the input circuit to keep value of R2 increases the gain, and odd chassis which happened to be avail- the pickup arm isolated from the a.c. vice versa. It is easy to determine a able. Circuits were simplified consider- line. In commercial construction, all value for this resistor by trial and ably with an FP type of tubular capa- ground points would be brought to a error. citor containing all filter condensers central tie lug, and grounded to chassis Since the over -all feedback results in and the cathode bypass in one can. All through a .01 -µf capacitor. The ground- a considerably flatter and wider fre- other resistors and capacitors are ed side of the pickup could then be con- quency response, plate -supply filtering mounted on a terminal board. Commer- nected directly to chassis, and the ca- is made considerably better than usual. cially, this probably would not be done; pacitor eliminated. It would be neces- This is more for the sake of improved the point -to -point method, using the sary to mount the can -type electrolytic transient response than for hum reduc- pigtails of the components as wiring, is condensers on an insulating wafer, to tion (feedback reduces the hum to a probably cheaper and just as good if avoid grounding to the chassis through large extent). Remarkably low hum not better. the can.

\ O1 eS on Sound Ijerordiig THE other night I went to a meeting By RICHARD H. DORF rent through the coil as you can with- of the New York Section of the IRE out burning it up. According to Dr. to hear two lectures on tape recording. magnetize the heads. The frequency of Hare, it's about right when you spit on One of the speakers was Dr. D. G. C. the oscillator and its amplitude -within it and it sizzles. If you take this literal- Hare, a physicist who has spent some limits -don't seem to be too important. ly, be sure you have a couple of extra time developing a new broadcast -qual- In fact, if they are critical, you can be fuses and a tube of Unguentine handy ity tape recorder. pretty sure the waveform is bad. So . but anything for better sound Dr. Hare's talk on the subject of take a look at yours on a good oscillo- quality! noise contained some highly interesting scope. information for those interested in There isn't much you can do about New discs arrive magnetic recording from any stand- it, but turning off the audio at the peak Having become an enthusiastic mi- point. of a wave will also leave the recording crogroove fan since the long -playing One of the problems is keeping noise head "permed " -permanently magne- records bowed in, I jumped at the a reasonable number of db below pro- tized. Funny thing, though, that speech chance to try some of the new RCA 7- gram level. Apparently no one is quite waves, which are mostly either positive inch, 45- r.p.m. discs when samples ar- sure of all the causes of noise; but or negative, not equally both, have no rived. I have a Garrard 201V motor through the cut -and -try procedure, effect. Why? Dunno. which is governor- controlled from 78 which every radioman has developed One more tip. Dr. Hare said he has right down to 33, so setting it at 45 since his radio infancy, certain infor- taken a brand -new tape and carefully was simple. If you want to try it, just mation has been obtained. kept it clear of everything before mak- count revolutions until you get a little Probably the prime difficulty arises ing the first recording. Then he found over 11 in 15 seconds, then trim up the from magnetization of the recording, that running it once through the erase adjustment while matching the music playback, or erase head. How many head before making a recording les- to a piano. owners of tape machines can honestly sened noise. The center -hole problem was solved say they have never had a slightly mag- Demagnetizing a head is quite a for about $2.00. A machinist made up netized screwdriver somewhere near chore, it appears. Air-wound coils with an aluminum washer approximately one of the heads? Most screwdrivers 60 -cycle a.c. running through them are 5'1,; inch thick. The outer diameter become magnetized at some time during used in about the same method as for equals the inner diameter of the disc their careers; working on a tape re- demagnetizing a watch. Details weren't hole (about 1% inches), and there is a corder with one may raise the noise given, but you place the coil around center hole in the washer to fit the level by as much as 15 db! the head, then lift it off. The number of standard turntable center pin (about The bias -erase oscillator is another times you have to do it will vary with 14 inch). Furnishing the machinist prime factor. If it hasn't a perfect the quantity of perm the head has; but with a sample disc and a turntable is a sine-wave output, the distortion will if there's much magnetism, it may take good way to get the dimensions ac- result in a d.c. component which will all day! Shoot as much 60 -cycle cur- curate. AUGUST, 1949 441 11114114)

Frequency Bridge For Audio

Theory, construction, and calibration data By K. E. FORSBERG for a Wien frequency- measuring bridge

BUILDING an audio oscillator is purely resistive, and two resistive and Fig. 2 -a as 02. Because of the com- not a difficult feat-many excel- capacitive. ponent values and the frequency, it is, lent designs have been published The phase shift in an R -C circuit in this case, equal to 01. in RADIO -ELECTRONICS and other varies with the proportion of R to X,,. Observe the result. EeC is now in magazines. But calibration, once the Since X, varies with frequency for any phase with E, , the generator voltage. unit is built, is quite another matter, value of capacitance, phase shift varies Since the voltage across any section of especially if no one in the vicinity has with frequency for any given combina- a well -calibrated generator and an oscil- tion of R and C. And in the Wien loscope. bridge of Fig. 1, R in the reactive arms 'AC The solution may well be an audio - is variable. As a result, R1 -Cl and R2- frequency meter. Such a frequency C2 can be made to give any desired EAc is 52 meter valuable for other purposes as degree of phase shift at any frequency. 'U "i well -for instance, as an interpolation EAC EBC Rl and R2, two potentiometers of a b device for heterodyne radio- frequency the same resistance mounted on a single meters or for harmonic -distortion meas- shaft, vary approximately in unison. Fig. 2- Vectors show how the null is reached. urements on audio amplifiers. But because -C1 is Rl a series network R3 is always in phase with the signal For an a.f. meter to be really valu- and R2 -C2 a parallel, the phase shifts source, headphones connected between able, it must be accurate; to be econom- of the two vary oppositely when the ical it should be made from standard point B and the arm of R3 will have potentiometer shaft is turned. With in -phase voltages at its terminals. All parts. The one described here contains both Rl and R2 fully shorted, for ex- only 10 parts -no vacuum tubes. The that is necessary to obtain a perfect ample, arm AB is wholly capacitive, null is to adjust the principal investment required is a bit giving arm of R3 so that maximum phase shift, while the amount of voltage appearing be- of headwork. No standard component arm BC is out, no shorted causing phase tween it and point C is the same as is 100% accurate; therefore, to make shift. On the other hand, with all resist- that between B and C. the frequency meter tell the real truth, ance in the circuit, phase shift in the values and calibration must be obtained Suppose now that the frequency is AB arm is minimum (because there is raised, but Rl and R2 are left at by experiments and calculations. a their maximum of resistance), while that present settings. The net reactance be- in arm BC is maximum (because most tween A and C is changed, and so is of the impedance B between and C is the reactance between B and C. As a capacitive reactance). result, the phase shifts in AC and BC The voltage of the signal source is are reduced, as Fig. 2 -b indicates. impressed across the series combination still leads E,,. (though not as much), of Rl -Cl and R2 -C2. Because the net but the shift in BC is too great. Eec impedance from A to C is always at now falls behind Es,. (lags it) because least somewhat capacitive, the current of the new values of 01 and 02. The Iw leads the applied voltage Es,. by voltage across the headphones now has some angle between zero and 90 degrees. an in -phase and an out -of -phase com- Fig. 2 -a is a vector diagram showing ponent; while the in -phase voltage can this. Es,. is represented by the line at be balanced out by adjustment of R3, zero degrees. Since vectors revolve there is no way of nulling the out -of- counterclockwise, the I line represents phase voltage and a signal will be the current, leading E,, by an amount heard. el. The basic formulas for the phase The current passing through R2 -C2 shifts will be found in many textbooks, is IA , leading the generator voltage by although this explanation is very hard 01. This current causes a voltage drop to find. The null frequency is En across R2 -C2. Since arm BC is 1 capacitive, the voltage drop EeC lags f - the current which caused it by a Fig. I -Basic Wien frequency bridge ci cuit. I, cer- 6.28,/R1 X R2 X Cl X C2 tain number of degrees, depending on The instrument is a Wien bridge, of the values of R2, C2, and the fre- Construction which 1 is Fig. the basic circuit. A quency (assumed to be constant Fig. 3 is a schematic of a practical variable- frequency signal source is throughout this explanation). The lag Wien bridge having three frequency connected to a bridge, two arms of of the voltage drop Ee behind the cur- ranges: 20 -200; 200 -2,000; and 2,000- which (the two sections of R3) are rent Ia which caused it is shown in 20,000 cycles. RI and R2 are the sec - RADIO- ELECTRONICS for Audio 145

tions of a dual potentiometer with log- Solve also for K and K,., using the Connect an audio oscillator (it need arithmic taper. Wire the potentiome- values of capacitance in the circuit not be calibrated) to the bridge and ters so that the resistance- rotation when the switch is on bands B and C. adjust it so that a null is secured above curve will be like that of Fig. 4 -a, 2. Decide on the first frequency for 200 cycles. Note the frequency from the which will give a frequency curve as which the bridge is to be calibrated, calibration just made, then switch to then substitute it for f in tl'e formula band B. Readjust the bridge for null on K this frequency, mark the dial, and R 500K measure RI and R2. Then VR1 X R2 = -. f K= f\/R1 X R2, CI C' C5 The K to be used is that for the band where f is the frequency to which the .02 1002 1.0002 being calibrated. oscillator is set. Calibrate range B as A E C If the frequency is 20 cycles, for ex- before, to a point ,above 2,000 cycles. - ample, and K, is 7,950,000, Then follow the same procedure to find SIG IN C 2 50K ß/R1 X R2 = 7,950,000/20 = 397,500. K,.. I y 500 3. Find a setting for R1-R2 at which To use the bridge, feed in a signal and adjust first R1 -R2 and then R3 for DO NOT \ /R1 X R2 = 397,500. En C GND TO A If both sections of the potentiometer va- sharpest null. Readjust both controls as CASE ried exactly equally and the resistances often as necessary to get a complete C2 .4002 C. 60002 1 at any setting were the same, the value null. Then read the frequency directly DET of either would be sufficient. Since com- from the dial. mercial dual units do vary somewhat, While headphones are usually satis- Fig. 3- Schematic of a practical Wien bridge. this geometric mean (square root of factory, a sensitive a.c. v.t.v.m: gives the is more exact null indications. Depending shown. If wired backward, in Fig. product) necessary, as it was as with on the voltage fed to the bridge, an 4 -b, the frequency calibrations will the capacitors. Using a good ohm- be meter, find ordinary a.c. voltmeter might also be very crowded at one end of the scale. a setting at which one resistance is slightly above and used. - The capacitors should be mica or the other a little below value high -quality paper units. A metal case the desired of 397; If well calibrated and carefully is useful for preventing stray capaci- 500 ohms; then make trial calculations handled, this Wien bridge is an ex- tance, but don't ground the jack frames and vary the settings slightly until the tremely accurate frequency-measuring to it. The dial scale should provide last equation above is satisfied. Mark device. for the dial with 270 degrees of rotation; a piece of scale the frequency at the One useful application not concerned polar graph paper will provide equally setting found. with measurements is in receiving c.w. spaced divisions. 4. Go through steps 2 and 3 for each signals on crowded amateur bands. It is frequency to be used on each band. very difficult to copy when a strong in- Calibration It is possible to find the values foì terfering note is very close to the de- K without having a capacitance The bridge. sired one in frequency. The bridge may easiest way to calibrate the Apply 60 -cycle line voltage to the input bridge is to feed a signal into it from be connected to the output of the re- terminals of the bridge through a step - ceiver and the headphones used as the down isolation transformer. Adjust Rl- FREQUENCY "detector." Adjusting the two controls R2 and y RES ISTANCE R3 for sharpest null, and mark will then balance out the interfering á RESISTANCE the scale. Measure the resistance of R1 t note while allowing the desired one to 2 and R2. Then come through. A single- frequency a.f. j F REDUE NCY K, = ß'R1 x R2. amplifier may be constructed by insert- Calibrate range A as in steps 2 and ing the bridge in a feedback loop so ROTATION- ROTATION ---0 3, extending the calibration to as high that all frequencies but one are fed a b a frequency (above 200 cycles) as pos- back 100 %. Many other uses will occur Fig. 4- Correct curve for RI, R2 is as above. sible. to the experimenter. a calibrated generator. But, if the bridge is to be used to calibrate a generator, that is impossible. Some calculations and measurements will then do the trick. With the capacitors given in Fig. 3 for each range, null frequency depends only on the resistances of R1 and R2. If these two resistances and the ca- pacitances of each pair of capacitors (C1 -C2, C3 -C4, C5 -C6) were equal and as stated, a simple table of resistance vs. frequency could be given. In the actual unit, they will not be equal nor will they be known exactly. The procedure is as follows: 1. With a good capacitance bridge, measure the capacitance (including strays) actually in the circuit between the switch arm and the other end of each capacitor; note the results. Then solve the following formula for K (the range multiplying factor) for range A (20 -200 cycles) : K, = 1 /6.2SVC1 x C2. Sump RI, 4 bu: . rr,., If, for example, the measured capa- LIIm,L,. 11;.r. citances of Cl and C2 are exactly .02 each (an unlikely case), then K,= l/6.28\/.02X 10'X.02X10.' = 7,950,000. "Junior won't monkey with those knobs -he hates baths!" AUGUST, 1949 46 Theory 81111 Engineering MICROR'_1VES

Part 11' -11ou %% Guides are joined By C. W. PALMER and tuned for lowest possible loss

branch line and would introduce losses in the main waveguide path. Sometimes it is desirable to have a variable reactance in a waveguide setup to permit balancing out undesired reflections. In such cases tuning screws -small cylindrical posts projecting into the broad face of the guide as shown in Fig. 4 -are used. These screws provide capacitive reactance which varies with the penetration of the post into the guide. A single screw may be sufficient, but usually three screws are provided at quarter -wavelength intervals along the guide. 0e3fonmy Budd l'hoto Sometimes it is desired to insert in a Fig. I -In bending waveguides, use is made of either the E or the H bend. Both appear here. waveguide a device that will either pass a desired mode (modes of propagation SO far we have learned how wave - .02 decibel for such a section to several were discussed in Part I) and no other, guides are used to transfer mi- decibels, with a corresponding increase or reflect completely the power in a crowave radio power from an in the standing -wave ratio. certain mode. Resonant diaphragms or oscillator or transmitter to an Fortunately such discontinuities can windows are used for this purpose. A antenna, and from the antenna to the be taken care of by introducing into the thin rectangular ring of the proper di- receiver's amplifying and detecting cir- guide obstacles that produce reflec- mensions placed across the inside of cuits. tions which cancel the unwanted ones. the rectangular waveguide and sepa- We have learned that the familiar The matching devices most commonly rated from it by insulation will reflect, radio quantities - inductance, capaci- used are diaphragms and tuning for example, all the T E0,1 mode trans- tance, impedance, reactance, and re- screws. The diaphragm, or window as mitted through the guide. sistance -are found in r.f. plumbing, it is sometimes called, is an aperture of If a thin metal diaphragm across the but that their appearance is entirely thin metal placed across the waveguide. guide is provided with an opening of new. And since we are dealing with Such a window introduces either induc- the proper size, all the power in the wave propagation instead of conduction tive or capacitive reactance depending T E0,1 mode will be transmitted. of r.f. currents as in low- frequency ra- on the direction of the slit. Resonant slits in the waveguide dia- dio, we must learn a new set of rules. Fig. 2 shows inductive and capacitive phragms are also useful for passing In this part of the microwave series windows. For an inductive window the waves of low power and rejecting those we will attempt to express those rules edges of the slit are parallel to, and for of higher power. The slit is so narrow in a form that will help the radio man the capacitive window perpendicular that breakdowns occur, and the res- to understand better the do's and don'ts to, the electric field. Usually these win- onant condition is temporarily removed. of r.f. plumbing. dows are soldered in place and are not A device of this sort is useful for pre- One of the most important things to variable. Where large amounts of pow- venting the direct power of a trans- learn in using waveguides is to avoid mitter from reaching and damaging a discontinuities or changes in the inter- receiver connected to the same antenna nal mechanical shape of the guide from system, during transmit periods, while one section or piece of apparatus to an- allowing incoming radio waves to be other when joining them together in a received normally. In a radar system "circuit." a special form of such a device is called Look at Fig. 1 as an example. It a TR or ATR box, and will be discussed shows two types of L bends used ex- in detail later. tensively in r.f. plumbing. The first is INDUCTIVE WINDOW CAPACITIVE WINDOW known as an E bend, and the second is Fig. 2 -The inductive and capacitive windows. A microwave primer called an H bend. It is easy to remember which is the E and which the H er are to be carried in the waveguides, It is frequently necessary to use long bend if you think of the E as the "easy" inductive windows are preferred be- stretches of waveguides, and it is very and the H as the "hard" bend (if it cause the capacitance type breaks unusual for them to proceed in a were possible just to bend a piece of down, causing arcing and loss of power. straight line. Bent and twisted sections straight guide to make a right -angle Several examples of the use of fixed with the bends in both E and H planes, turn, which it isn't). windows in waveguide circuits are tees for branch lines, etc., must be used In manufacturing these bends, devia- shown in Fig. 3, which shows E and H to fit the needs of the individual in- tion from the inside dimensions of the tees used for branching or splitting the stallation. straight section by even a few thou- waves into two paths. The windows in In using these lengths with tee's, L's, sandths of an inch in the bent portion these tees balance out reflections that etc., certain rules must be observed to will increase the loss from a nominal would otherwise be introduced by the obtain the desired results. These are RADIO -ELECTRONICS for Theory 81111 Engineering i47 summarized here in the following eight Joints in waveguides electrical contact at all points around items. Sections of waveguide may be soldered the edge with the inside of the guide, 1. A shorted end of waveguide (as together end to end. If the sections line or behavior will be erratic as the the side arm of a tee or a stub) an odd up and reflections plunger is moved and power may leak number touch, losses and of quarter wavelengths long introduced by the joints are negligible. past the termination. reflects an "opening" where it joins an- However, for maintenance purposes Better results are obtained with a cup other waveguide. Waves in the main and to make waveguide apparatus use- contact as shown in Fig. 6. Contact is arm would travel into such a side arm able in more than one installation, it well main as as traveling through the has become common usage to terminate arm. waveguides with flanges on the ends 2. A shorted end of waveguide any which are soldered to the and half re- guide number of wavelengths long machined flat on the ends.'These flanges flects a "solid wall" where it joins are bolted together. Experience has another waveguide. in Waves the main shown that this type of joint can be arm of a tee would travel through with- made better than even the average out such a side arm for this entering soldered guide-to -guide joint if care is reason. taken to make uniform contact. 3. A -wave quarter section of wave- To reduce further the possibility guide opposite impedances its of has at losses due to waveguide joints, it is ends (if impedance is high at one end, considered good practice to use the CUP BLOCK \ it is low as in ordi- at the other) just "choke flange" joint, butting a choke of co and Fig. 6 -The cup -type plunger reduces losses. nary types -axial parallel flange always against a flat one. transmission line. summarizes (This The principle on which this choke made with the inside walls of the guide rules 1 2.) and flange works can be readily understood a quarter wavelength from the plunger, from waveguide Rule No. 2 above. See where the flow of current in the walls MATCHING DIAPHRAGMS Fig. 5. This shows a cross -section view of the guide is zero. Losses in this type of a choke -to -flat joint. The slot left by of termination can be held to as little the junction of the two waveguide sec- .08 db. tions is a half wavelength long at the An improved termination is the choke E - PLANE H- PLANE optimum frequency of operation of the plunger which uses the same principle Fig. 3- Windows used in waveguide branch. waveguide, which means that the side as the choke coupling. As shown in Fig. cavity A reflects a "solid wall" to the 7, no mechanical contact with the in- 4. The Q of a waveguide is a func- side walls of the waveguide is made at tion of frequency and also depends on FLAT FLANGE CHOKE FLANGE the front surface of the plunger. Con- of volume to inside of the ratio area tact is made at B where the current is the guide. Q's of 25,000 are not un- zero. Choke plungers have losses in the in waveguides common and resonant neighborhood of .02 db. cavities. 5. The characteristic impedance dif- Dielectric in waveguides fers with different modes of operation. In a rectangular waveguide the im- :-CAE C -F, AT JOINT The fact that the introduction of pedance is proportional to the narrow Fig. 5-The choke flange, perfect connector. a dielectric inside waveguide will de- or b dimension of the guide. It varies crease the "cutoff" wavelength has been from about 475 ohms to zero as the b main guide so that there can be neither used practically in a so- called "line dimension is reduced. leakage of r.f. nor dicontinuity to cause stretcher." This device introduces con- 6. The wavelength in a hollow wave- reflections in the main guide path. trolled amounts of dielectric into the guide (as measured in a slotted wave- In addition to the above, the point B guide to tune it. guide section) is always greater than where contact is actually made between The effect of an ideal dielectric in a the wavelength of the same wave in the two waveguide sections is at a waveguide is to increase its apparent air, due to the multiple reflections from point of zero current, and perfect elec- the walls of the guide. trical contact need not be made between 7. Sections of open and closed wave- the two sections as is necessary in join- guides may be used as switching cir- ing two flat flanges. cuits by applying the principles of Such choke couplings are frequently Rules 1 and 2 above. used as "wobbly" or nonrigid connections between waveguide sections. They A B are used, for example, at the junction CHOKE TYPE ADJUSTABLE WAVE GUIDE SHORT of an antenna where it is desired to shift or rotate the final section of guide Fig. 7- Improved plunger uses choke circuit. to orient the antenna for peak response. size. It also lowers the impedance in As a rigid connection the loss in a all but one TM (transverse magnetic) choke -flange joint is in the order of .02 mode. The losses of a guide filled with db, compared to about .05 db for a well - solid or liquid dielectric are higher than made contact joint. The nonrigid con- for an air -filled or gas -filled guide. nection mentioned, with a gap of about is slight. wavelength However, the effect II between the choke and An exception to the above and a Fig. 4- Tuning screws for varying reactance. flat flange, has a leakage of about .3 db. point of caution to the experimenter in 8. Standing waves in waveguides are Plungers for shorting bars microwaves is the effect of water. Small checked in a manner similar to that amounts of water condensed on the used ;or co -axial lines. A section of In terminating side arms as described inside of a waveguide may introduce waveguide with a narrow slot parallel in the rules above, it is sometimes de- losses up to % decibel per foot of to the axis of the guide is used. A probe sirable to make movable shorting plates waveguide. This is caused, not only by with a crystal detector or a small fuse or plungers so that the lines can be the large dielectric loss characteristic (!JOO ampere) heated to almost the tuned exactly to a desired quarter- or of water at high frequencies, but also blowing point by direct current is used half -wavelength point. by the high dielectric constant of water. to detect the presence of standing Plungers can be either solid blocks, This is why some waveguide installa- waves as with a slotted co -axial line at cup terminations, or choke terminations are pressurized or charged with lower frequencies. tions. The solid blocks must make good an inert gas. AUGUST. 1949 1111 Amnteur

óV^Om°oc Ro° PE 03 tk . . e 1010 ie irixo-tixt o-tix b.p W D FAN . KA out Ats

W[IEN vacation time comes tures of both methods of frequency acceptable. No protective bias was in- along, why leave ham radio control. cluded as this was thought unneces- at home? Plenty of fun may The transmitter requires four tubes, sary for the low -power tubes involved. be had and some excellent and only two tuning controls. The crys- Depending upon the power supply contacts made while mobiling in the tal- buffer -stage tuning control may be used with the transmitter, it is possible high Sierras or other vacation spots. set to the mid -frequency of the "rub- to overload heavily and burn out the The low -power, 10- meter, mobile ber" crystal and left there. It is nec- final tube if its plate circuit is not in transmitter described was designed and essary only to touch up the tuning on resonance. The use of protective cath- built with this in mind. With all bands the final tank when shifting frequency. ode bias, however, would lower the open for mobile operation, 10 meters The r.f. section of the transmitter over -all efficiency, which on this low - was still selected over all other avail- is unusually simple in design, as the power job is not desirable. Momentary able bands, with 75 meters the only schematic shows. The crystal and buf- overloads will not cause tube failure, other one considered. Both bands are fer stages are combined in one tube. and 6L6's are comparatively cheap. good for dx, but 75 is much more A 40 -meter crystal is connected as a The antenna may be link -coupled to crowded than 10. Seventy- five -meter Pierce oscillator, using the screen grid the 25 -watt commercial tank coil, or it mobile, if really mobile, would require of the 6AG7. The plate circuit of the may be directly tapped on the coil (as a loading coil to resonate the short whip 6AG7 is tuned to 20 meters. The r.f. in the diagram) where a quarter - antennas available, causing low radia- is coupled to the final grid capacitively. wavelength whip is used. As 25 -watt tion efficiency. But where short skip or An unusual feature here is the use tank coils do not usually come with 75 variable -inductance tuning. Taking ground -wave range is a necessity, of .0002 /IKV MICA 2.51.11 6L6 meters wins. The other bands, such as advantage of the already high distrib- PA AL 6 meters, were not considered, as their uted wire and output capacitance, no 6AG7 range with low -power equipment is capacitor, fixed or variable, is required 40M XTAL insufficient for the tourist ham. across the buffer tank coil L1. Instead, e w The first major decision in design using a National XR -50 coil form, a .000 was whether to go FM or AM. The coil was wound which resonates in the wt600V choice of FM meant far less drain on correct range and whose resonance can 66K .006 the power supply. At the same time, be varied by moving the iron core in modu- or out. This occurred with a winding SEE TEXT 2.SMH more tubes might be required for METER lation. Then, too, where AM receivers of No. 29 enamel close -wound to a 600V WARNING-SEE TEXT were being used on the receiving end, length of 1/4 inch. This gives an excel- L -C and very good doubling / 6L6 MOD TRANS QRM would knock the lower -power sig- lent ratio 2 -BK nal out easily. Therefore, AM was se- efficiency. Mechanically and electrically FIL PINS 2-7 - V lected. it simplifies the transmitter. Despite Frequency control was the next ma- the high L -C ratio, at these frequencies 6C5 issue. Crystal control was prefer- the tuning of the stage is not sharp. jor SPEECH AMPL able from several viewpoints. A major The final stage consists of a conven- 2250 disadvantage was inability to shift fre- tional r.f. amplifier which doubles to 10 CARBON MIKE 25 quency to avoid QRM. A v.f.o. would meters. It receives all its bias from a ID 8+500V have allowed this, but was impractical grid -leak. As a doubling operation II 50V because of the cost and the problems of takes place in this stage, it is desirable insuring drift-free operation under mo- to have as high a bias as possible to C- .001 / I KV OR LARGER was facilitate harmonic generation. The SID L- 25w,10M COIL bile conditions. The solution the W TI - SB MIKE TO GRID use of a variable- frequency or "rubber" grid leak selected was 68,000 ohms, but crystal. It gives some of the best fea- a value of 50,000 to 100,000 ohms is Doubler coil LI is wound on slug -tuned form. RADIO -ELECTRONICS for Amateur 149 variable links, and because there are The bias resistor of the 6L6 was in- heaters must be on as long as the rig constructional difficulties in making a creased to a high value which, in paris on standby. The transmitter is then link hold still under mobile conditions, allel with the microphone button and put on the air by applying voltage to directly feeding the antenna may be transformer, supplies the correct bias the dynamotor. A simplified schematic advisable. When this is done, always to the tube and current to the micro- of the PE -103 dynamotor is shown. The place a mica coupling capacitor in se- phone. This has several desirable fea- control and output leads terminate in ries with the antenna lead. Failure to tures besides simplicity. It makes pos- a Cannon type P8 -41 connector. ( A do this places the power- supply high sible a.c. operation of the transmitter Cannon type P8 -24 plug fits this con- d.c. voltage on the antenna, and a dan- for portable or home operation. The nector.) gerous shock may occur to an innocent modulator 6L6 is automatically biased The dynamotor starts when the cir- bystander. FCC regulations forbid di- to very low plate current when the cuit through pin No. 4 is grounded rect coupling. microphone is off, conserving the power through a push -to -talk switch on the Both methods of coupling have dis- supply. Of course, where a push -to- microphone. The PE -103 may be used advantages. A varying link will ampli- without modification if the positive side tude- modulate the carrier. With the 6 -12V ITCH SECTION of the vehicular storage battery is tapped antenna connection, harmonics grounded. If the negative side of the may be radiated, and a swaying whip, battery is grounded, the 6 -volt control to its change of capacitance, may circuit must be altered. Disconnect the due 6 -12VDC cause detuning of the transmitter and INPUT hot side of the control relay, 3E6, from consequent amplitude modulation. The the negative side of the low-voltage in- choice is yours! put circuit and connect it to the positive There is one important mechanical side as shown by the broken line on the detail in the final stage. The tuning diagram. capacitor must have both rotor and In most of these units, the high -volt- stator above ground. age lead terminates at pin No. 8 and To keep the transmitter compact, 6 volts for controlling an antenna jack -and -plug metering with an ex- change -over relay at pin No. 3 on the ternal meter is used. The plates of the NOTE- GROUNDED PEN LEAD AT X AND CONNECT AS connector. However, PE -103's bearing buffer and final must be monitored SHOWN WITH BOKEN LINE serial numbers between 4711 and 9500 when the transmitter is tuned. The Simplified schematic of the PE -103 dynamotor. may have connections to pins 3 and S meter jacks have been put in the plate reversed. Be sure to check your dyna- leads. This places high voltage on the talk microphone also controls the power motor before connecting it. jack frames, which must be isolated input to all stages, this is of little At 500 volts input and 60 ma final from the chassis with fiber washers. advantage. plate current, input power is 30 watts. Here the meter will indicate true plate Assuming 70', efficiency, power out- current. For safety it may be advisable The power supply put is 21 watts. The input power may be varied from 15 to a maximum of to place the jacks in the cathode cir- An excellent power supply is an cuits as per conventional design. Of about 40 watts. With the modulator Army surplus PE -103 dynamotor, ob- shown, input power should run approx- course, grid and screen current must tainable for less than $10, which has be subtracted for a true plate- current imately 15 to 20 watts to allow a high built -in circuit -breaker protection and degree of modulation. indication in this case. will operate from either a 6- or 12 -volt (Mr. Kaufman's last communication Construction details are not too im- battery. The output is rated at 500 portant, and each amateur will have to us was fairly recent, which indicates volts at 160 ma. The unloaded voltage that he is still alive, even with two jack his own ideas, depending upon avail- may reach 650, so it should not be op- able chassis and boxes. frames and a capacitor shaft, both 500 erated until the transmitter filaments volts above ground, on his front panel. are warm. This will save the 600 -volt MATERIALS FOR TRANSMITTER Despite the author's apparent good luck bypass capacitors. Resisters: 1 -270, 1 -1,000 1 -47,000, 1-68.000. 1- in never having accidentally brushed 270.000 ohms, y1 watt; 1-510 ohms, 1 watt; I-4 000 It is also possible to operate the ohms, 10 watts; I -2,250 ohms, 25 watts. hand across any of these gadgets his 1 dynamotor while connected for 12 volts Capacitors: I -50, I -200 Ind. mica; -.006, 1 -.015, on I 1-0.1 cf. 600 volts. 1 -10 Ist, 50 volts, while his feet were firmly planted input, on a 6 -volt supply. In this case -.01, paper; the ground, we cannot recommend that electrolytic; 1 -35 laid, variable. the output is 250 -300 volts and may Transformers: I- single- button carbon microphone readers depend on the same good for- be used directly on all of the transmit- to grid; I- modulation, 5,000 -ohm primary. 8,000 -ohm tune. Mount the final tuning capacitor ter tubes with the 2,250 -ohm protective secondary. on the chassis with standoff insulators Tubes: I -5A G7. I-6C5. 2-6L6. dropping resistor for the modulator Miscall : 1-40 -meter crystal (variable -fre- and use an insulated shaft. Place the and crystal stages removed. quency); 1- Notional XR -50 coil form; 2-shorting, between the cathode of I- non -shorting phone jocks; I -PE-103 Dynamotor; metering jacks Cathode -type tubes are used, so their cabinet, chassis, hardware. each tube and ground, with the frame of each jack grounded. You will have a better chance of remaining healthy enough to read the meters. -Editor) Plate power should never be applied until the tube filaments have come up to operating temperature, primarily to protect the capacitors. Where a dynamotor power supply is used, regulation is poor and excessive voltage may be applied to the capacitors until the transmitter loads up the supply and lowers its output voltage.

The modulator The speech amplifier and modulator are of standard design, a 6L6 driven by a 6C5. Rather than use the 6 -volt car -battery circuit (too much hash) or a dry -cell supply for the carbon microphone, a special circuit was employed. This is the underside of the transmitter chassis. Final tank tuning capacitor is at left. AUGUST. 1949 501 Scrridnfl Manufacturers Versus Service Technicians

IT has been a matter of growing con- By HUGO GERNSBACK one thing to tnanafticture a set, but a cern to us that for over two decades totally different thing to service it. now the radio service technician Why not tell radio service technicians from a local newspaper, advertising a new tele- has not been recognized by the radio vision model by the . . Radio Company. The that they will be paid for every worth- customer asked me what I knew about the set. I set industry. During this period thou- while suggestion submitted? . . . had, of course. seen the ad in the paper that same sands of letters from radio technicians day, but I was forced to admit I knew nothing But no radio technician will put him- have passed across my desk complain- about the new receiver and could give no in- self out to send in sugestions to a ing of the lack of recognition by the furmatiun . . manufacturer, knowing that he will not manufacturers. be paid for his necessary labor- indeed It is true, perhaps, that during the J Il 111111111111111111111111111111111111111111111111L' he does not know whether his sugges- first decade the old so- called "radio tions will be welcome or not. However, servicemen" had only themselves to . . . The rodio service tech- E his experience is invaluable, and should blame for this treatment because their nician is still of odds with E not be lost to the manufacturer. business methods left much to be de- My sired. = the radio set industry . . . _ final letter to the manufacturers During the last decade, however, this (Letter #10) was sent to the radia- television (manufacturers early in J condition changed for the better, yet :i111111:1111111111111111111111111111111111111111111 F. recognition was not forthcoming. Even I thought it worthwhile to reprint. here, the entire substance of that letter: at this moment-although a number of . . .Instead of taking the trade, and forward -looking manufacturers are be- particularly the technicians in the field, .For a period of over ten weeks ginning to work intensely with the into their confidence, the manufac- we have addressed to you a series of radio technicians -more than half of turers are doing everything to antag- letters stating the service technician's the industry is not only indifferent onize these men, thus losing not only viewpoint in his relations with the toward them, but actually hostile. good will but actual stiles. . . radio set manufacturer. This is our Recognizing this condition -as this final letter. magazine has done for over 20 years - From Letter #4....FROM NOW ON I recently took it upon myself to do EVERY YEAR WILL REQUIRE something about this state of affairs. MORE AND MORE SERVICING OF Several months ago I began to ad- TELEVISERS. Television sets -being dress a series of ten weekly letters to far more complex than sound radio sets the heads of the entire radio -television -are bound to get out of order quicker set manufacturing industry. In these than the average radio. During the next letters I set forth, in no uncertain few years -unless the number of new terms, the service technician's case. service technicians coming into the in- This correspondence resulted in a great dustry increases greatly-it is easy to We believe we are well qualified to deal of attention in the trade; I re- foresee that there will be chaos due to represent the service technician, since, ceived many letters from the manufac- the inability of maintenance techni- for over 20 years, a major portion of turers -large and small. cians to make repairs and do servicing our magazine has been devoted to the The ten letters are much too lengthy in a reasonable time. If present condi- radio servicing field. Here is a short to reproduce in full here, so I will limit tions prevail in 1952, conceivably it resume' of the highlights contained in myself and give certain highlights as may take months before a customer's the previous nine letters. follows: television set can be repaired. The set 1. Over 75,000 service technicians -who manufacturers fully realize the situ- routinely go into the homes of your From Letter #1....We think it ation, but so far they have made no set users -can create either good will would be a big surprise to many manu- effective attempt to remedy it. . . or ill will for you and your product. facturers, if it were generally known, 2. For nearly 20 years the radio re- how many buyers are actually in- From Letter #6-Taken from a ceiver industry -and now the television fluenced by the advice of a radio tech- television set manufacturer's letter to industry-has done practically nothing nician, the serviceman. After all, he us. to obtain the good will and full co- is supposed to "know," and the family . I think that you could take another look at operation of the service technician. the extent to which the servicemen are being which is in the market to buy a TV penalized due to the fact that they are not re- 3. You have not taken the service set will listen to him.. . ceiving technical information on new models in technician into your confidence. advance. This particular could be the sub- point 4. You have continuously made the From Letter trouble ject of long discussion : but, generally speaking. #2....The great the average. first -class serviceman in this industry today with set manufacturers, both serious mistake of placing the service can readily absorb the features of any new model technician in the same position as the television and radio, is that there is within a short time, provided he has the technical data which is released along with any new buying public. practically no cooperation with No TECHNICAL infor- the model ..." mation on your new reaches technician. Letters by the independ- sets these ....Today's common habit of many technicians until long after it lias been ent technician addressed to manufac- is the set manufacturers to publicize announced to the public. This has turers for servicing information, for new receiver to the home set buyer caused justifiable information on various etc., resentment and in- parts, while instruction and alignment manu- creasing ill will. meet with little cooperation. He is fre- als for the service technician are still 5. You have never thought it worth- quently not even answered. on the press. Put in the po- yourself while to sell the service technician on sition of the radio technician when this your new product -before advertising F Letter #3 -Parts of a reader's happens-and it happens nearly all the letter to RADIO- ELECTRONICS. it to the public -so that when a pros- time. It causes bitter resentment.. . pect asks him about it he can The other day when I visited one of my discuss customers he showed me a full -page advertisement From Letter #8....Remember, it is it intelligently. (Continued on page 52) RADIO- ELECTRONICS for Servicing

TO THE SERVICE TECHNICIAN

BUILT -IN MAGNIFIER The 10 -inch tube of the Model OXOOY is equipped with a lens actually sealed on at the factory. Experience has shown that a large number of television users use and approve the imperfect magnifiers that are mounted ahead of the lens, and which cannot give optimum results, due to light losses from the rear surface. astigmatism, etc. The OXOOY magnifier lens brings the picture up larger than that obtainable from a standard 15 -inch tube, yet gives full picture visibility over more than 135 degrees without distortion. Light loss is small. That is because the lens is factory sealed to the front of the tube, which actually forms its rear face. Thus there is no intersurf ace to reflect the light. The close mounting, plus design factors engineered by the VIDEON research department, is responsible for the wide angle

G RAL view. This feature alone is a A ERISTICS mendously important sellin' point. b tubes: 28 Tube: 10 -inch Reception on the n 10- Loudspeaker: 12 -inch inch OXOOY i atti lis- RUM. SHEATH Video bandwidth: 4.5 me Overall gain: See Service tinguisha fro stand- M onuol r Frequency range: All and in tel et the television channels: stand- XO ite priced in the J ard FM band Al i(ANGE w uxT BRIDGED -T I. F. AMPLIFIER Most revolutionary feature of the Model OXOOY is the Bridged -T video i I. section. This section employs 6J egulated triodes in the well -known grounded -grid amplifié Power Supply cathode varies in voltage at the signal freq and second grid is grounded). Thus we e w not characteristic of the triode, and ue e g grid Special -the excellent isolation b ee inpu n ou ut circuits Lens that characterize the -ntod t ility ven better than

that of a pentode stea the more common two - coil i. f. tr sform. - een stages, the Bridged -T circuit shown is This provides a wide bondpass of 4.25 mc. in es a number of technical difficulties hitherto ex Fenced with two-coil coupled circuits. Briefly, a straighter. ided curve with less loss of gain is possible with this circuit. A total gain of 55 is realized over the whole video i. I. amplifier.

TRAP TRIMMER 2uµf1 3 -3Dµµ! 6J6

PLATE COIL GRIDCOIL 51µµ

5 TO WG 6 COUPLING NINON COIL 6J6 Vernier 3.9n Tuner d+ 100 100 (CONTRAST) Off -on TO BIAS Volume Brightness Contrast TUNING SYSTEM Technicians have reported some instability in the pushbutton circuits of the OXOOU and OXOOV which tended VIDEON CORPORATION to drift after some months of use. New -type ceramic capaci- 00000 Tele- Boulevard, Radioland, U. S. A. tors reduce this possibility to a minimum in the OXOOY, Please and any traces of it are eliminated entirely by a vernier send service data on your Model OXOOY. capacitor which may be adjusted by the user to bring in Also please send advertising information on Model each station perfectly after it is tuned with the pushbutton. OXOOY. This vernier may be used on all channels, though in prac- I am interested in receiving further information on your tice it is likely to be used only to "sharpen up" the models weakest stations. Name For complete servicing information, mail coupon to: Company Name THE VIDEON CORPORATION Address Radioland, U. S. A. City Zone State Mate' o, for the above ad courtesy Snaider Television, Televisio i Assembly Co., The Hallicrofters Co. and Transv:sion, Inc. AUGUST, 9 4 9 Servicing '2 Why Pick on Radio Technicians?

By LYMAN E. GREENLEE

RECENTLY another wave of "in- and charges 75c he is a good guy. To- License regulations will not make an vestigations" sponsored by individ- morrow he may spend two hours on honest man out of a dishonest one, and uals and sundry organizations of the same type of set cooked up in a in many cases will make it easier for various kinds has been supposedly different way. Is he going to charge the chiseler to operate and harder for producing statistics to prove conclusive- 75( for that two hours of labor? the honest newcomer to get a start. ly that most radio repairmen are out to A fundamental point overlooked or Check with any service where licensing "gyp" the public. Two things about ignored by the unfair survey is: Is the is required. Radio repairing has always these investigations should make all radioman entitled to pay for his time? been a pretty tough racket and some of legitimate radio repairmen fighting mad. Is he entitled to a fair hourly wage for the boys have been driven to practices First, the methods used have been de- time spent in checking a set in addition which are actually unethical though cidedly unfair. Second, why pick on the to the actual time spent fixing it? If they were not gypping or overcharging. radioman? What about refrigeration he is not (and the surveys seem to as- I refer to "installing" imaginary com- service, auto mechanics, watch repair- sume just that) it's just about time we ponents instead of itemizing the charge men, washing machine servicemen and all quit servicing radios for labor, where it belongs. Strange as others who do repairing for the public? We all remember several sets from it may seem, the public has some radio- Most of the surveys are based on the past experience. One was an a.c. -d.c. men educated into believing their labor planted "fault" in an otherwise normal midget that could have been fixed in isn't worth anything! radio. So the repairman slaves for a five minutes, if you knew just what to Organizations couple of hours on screwy job do, four or five hours to find of repairmen can help some but it took clean up the planted just to test him out. He charges the trouble. Acid solder had been used situation wherever and whenever it is necessary. maybe as much as $5.00 for his time and and was causing enough high -resistance Maybe they could also help to clean a to make the receiver up the situation is classed immediately as thief and leakage to ground in other fields! chiseler and gyp artist! Maybe a 14- go dead in damp weather. Probably year -old kid cord/ fix it in five minutes some other repairman had used acid But the best way is to clean up your -if he was lucky, was a smart kid, and solder, but that didn't help the matter. own situation -to watch your own rep- if he knew there was a planted "gim- You can seldom charge full price for utation and improve it by your manner mick." So could the service technician, your time on these gh jobs; but you of dealing with the customers. Every IF he were lucky. If he finds the fault certainly can't do them "for free" if repairman should have a standard immediately in one of the doctored sets you want to keep on eating occasionally. schedule of charges and an open and aboveboard method of doing business. This will do more than any other one MANUFACTURERS VERSUS SERVICE TECHNICIANS thing to defeat the charges of rack- eteering hurled against the industry. (Continued front page 50) 1. Be frank and honest with every customer. Tell him what was wrong, WHAT "S THE REMEDY? to the public through newspaper or what you had to do, and how long it took, whenever We have gone to considerable ex- magazine advertising. such an explanation is sur- If you will read the sample advertise- necessary or desirable. If it took two pense through industry research, hours locate veys and personal interviews, to pro- ment carefully, you will note that it to an obscure fault, say so vide manufacturers with the necessary gives all the salient technical points and justify your charge. data and information to remedy the of the new product. YOU ARE NOW 2. Always make out an itemized bill above situation. The answer is simple TAKING THE SERVICE TECHNI- listing labor and parts separately plus in principle. To us it is amazing that CIAN INTO YOUR CONFIDENCE. any special charges such as sales tax. it has not been done before. In our Consequently, you will immediately Give the customer a copy and keep one opinion there is only one way to ob- have over 75,000 experienced technical for your file. Have established list prices tain the good will and confidence of salesmen rooting for you, instead of for everything you sell, including your the service technician, namely by talk- openly expressing their ignorance - time. Stick to your schedule, but if ing to him in the language which he and even their disapproval of your you make a mistake, admit it and don't understands through the proper media product -when the prospect asks ques- charge the customer for it. -the technical trade press. tions about it. There is no reason 3. Give a standard guarantee, and if We are attaching a sample advertise- why this plan should not be adopted a job goes wrong within the guarantee ment designed to sell your product in by every manufacturer of radio and period, fix it without quibble or question. receivers. an intelligent manner to service tech- television It is bound to earn Keep accurate records of what was nicians. The advertisement which we biz dividends for you and the respect found wrong with each job, but remem- of the service technician.... (End of have prepared is merely a suggestion ber that sometimes it pays to fix a set of what should and must be done to get letter). free even if the customer is wrong. the technicians on your side. We have here reproduced for our An advertisement of the type shown, readers the sample advertisement. No 4. Don't advertise "free" service. There when placed in the technical trade press advertisement of this type has ever is no such thing, never was and never BEFORE the new receiver or allied appeared in the technical press in this will be! product is introduced to the public, country. 5. Avoid repair estimates if possible. will do wonders for you. The cost is We would very much like to have They cost you time and money. Handle small and wholly out of proportion to the service technician's reaction to this these situations by saying: "Mrs. Jones, the good will of the more than 75,000 article. As many of your letters prob- if this job runs more than $5.00, I will service technicians that you will earn ably will be submitted to the manu- call you and give you an estimate." with this message. Remember please, facturers. I trust that all of you will It takes more of your time to fool with that the advertisement should always lind the lime to comment fully on the repair estimates than it does to repair appear before the receiver is introduced all. P. radios. RADIOELECTRONICS for Servicing Training For Radio

A training program of real acalue is possible By JULES L. HORNUNG* only when the student possesses the

WITH all expectations of a high -paying job, John Doe necessary qualifications graduates from the Ready Radio & Television School. He is really amazed at his own knowl- field! edge of the Just six months ago, Jules L. H g. well -known author of books on radio he had never seen the inside of a radio communications. was educated of Columbia, Bowdoin. and the Massachusetts Institute is . of Technology. He an or television set. educator of long standing, having been o radio in- Armed with his diploma, he begins structor at New York University from 1929 to 1932 and shops manufac- chief instructor of the radio division of the New York a tour of service and YMCA Trade & Technical Schools from 1916 to 1941. During turing plants. In the first two places he the wor he was Commondant, Novo! Training School (Radar) at M.I.T., where he received special commenda- is turned down cold. At a third place, tions from the Chief of Naval Personnel and the Secretary the owner tells him frankly that he of the Novy, as well as an honorary professorship of electrical engineering fram M.I.T. He now holds o com- doesn't know enough; at the fourth mission os commander, USNR. place, he is hired, only to be fired two On the practical side, Mr. Hornung was chief engineer of WGBS from 1926 to 1928. His best known books are weeks later. It is quite natural for John Practical Rodio Communication and Rodio Operating Doe to register bitterness. There is no Questions and Answers (both written in collaboration with for Arthur R. Nilson), and nis latest work Rodar Primer. At greater disappointment the gradu- present he is nead of the rodio- electronics deportment, ate student in any trade than to find Walter Hervey Junior College. New York City, o YMCA that he is not equipped to take a job in affiliate. He presents here on ideo of what the radio school graduate may expect to find after his course is the profession he has chosen, or that finished, and the requirements for o rodio trainee. he cannot live up to the requirements of the job. The first reaction of John Doe is usually to blast the training program of they had acquired little training and a received, but mostly to his own short- the school. On this point, he might be vast number of promises. Their unsat- comings. Perhaps he did not study him- right. Following World War II, a horde isfactory training programs have in self and his possibilities prior to enter- of radio and television schools opened many cases damaged the quality of ing school. Coupled with the weakness to take advantage of the GI Bill of their work in radio and television of the Ready School training, the lack Rights. Many of these schools have not servicing. of proper self -analysis may be the survived simply because the various However, John Doe might consider downfall of John Doe. John Does awoke to the sad truth that the fact that his failure to succeed in In analyzing the progress of a stu- radio- electronics may have been due, dent in a radio -electronics school and Chairman, Radio- Eloctronies Division. Walter on Hervey Junior College. New York. N. Y. not to the specialized schooling he has later the job, it has been found that many of the problems encountered are a direct result of failure to consider interests and aptitudes prior to training. If a student is more interested in tinkering with automobiles than radio and electricity, no school in the world can turn him into a successful radio craftsman. The young man who plans to be a technician and later run his own repair shop should ask himself these questions: A. Do I have a definite interest or flair for radio -electronics and allied mechanical work? B. Do I have the background in elementary mathematics and general science to understand properly the elements with which I will be working in electronics? C. Do I have a reasonable degree of mechanical aptitude or "feel" for handling tools? D. Do I have the personality to cope with the general public? E. Am I willing to enter the business from the bottom floor, as a learner, upon graduation from school rather than expecting a top -paying job at once? Small grcups allow individual instruction in complex procedures such as TV -set alignment. If the service- technician -to -be cannot

AUGUST, 1 9 4 9 54 Servicing w answer these questions affirmatively, he quirement than the pure academic pre- faculty and administration. In the case should immediately cross radio -elec- requisites and accomplishments is gen- of the "mismatched" student, it poses tronics off his list. No amount of train- erally overlooked. How well is the stu- a problem which is not easy. When it ing can fit him for a successful and dent suited in terms of personal char- is clear that the student cannot achieve useful career in the servicing end of acter? He must view his temperament, his goal, it is obligatory for the school the business. There are always excep- personality, integrity, ethics -in- essence, to advise that he drop the course. How- tions to this rule, but in general the and ability to get along with people. above pattern represents a fairly ac- These are of vital importance to the curate cross section of the require- employer. They are also qualities which ments. ensure the young engineer the maxi- It will be easy to arrive at the an- mum opportunity for success. These swers to A and E. However, B, C, and factors are of such major importance D call for some amount of further ex- that many leaders in industry consider planation. academic ability and mechanical ac- Requirements of B would include the complishments only a fraction of mathematics and general science neces- the engineer's required characteristics. sary to obtain a high school diploma. After the young man has analyzed That means at least one year of gen- himself properly and affirmed his de- eral mathematics and one year of gen- sire to enter the field, the next problem eral science, or its direct equivalent. lies in the selection of a school. The Many high schools also require a year student interested in servicing would of algebra. The prospective technician be wise to carefully consider at least should not tackle the present field six well -known schools before making without a high school education, or its a decision. A school is best judged by equivalent in science, physics, and its reputation within the industry. If mathematics, at least. the industry has received an unusually The requirements of C are compara- large number of poorly trained stu- tively easy to analyze. If the student dents from a certain school, it will not finds himself at loss in making small be any secret. The school will be black- mechanical repairs at home (light sock- balled by the people who are its great- ets, wiring, etc.), or if he dislikes work- est asset. Photos courtesy YMCA Trade á Terhnieal Schools. ing with tools, he had better steer away The student may obtain information New York The same rea- from various sources vocational from radio -electronics. -a Instructor points out final soning would apply if he had consider- guidance counselor, a Veteran's Admin- set adjustments. able trouble figuring out the circuit of istration counselor, or someone already the family electric iron. employed in a responsible position in ever, there are degrees of mismatch. The answer to D is harder. Personal- the industry. He should examine the Some of these can be cleared up by ity poses a great problem in all phases school's curriculum and test its offer- extra effort on the part of the student of business and industry. However, the ings against what he desires to learn. and the faculty. If the engineering stu- technician will many times deal direct- On the engineering level, the student dent cannot meet the necessary mathe- ly with the consumer of his product. must realize that it will be a long haul, matical requirements because of lack That means facing an occasional irate financially and scholastically. Choosing of previous training, he should be and altogether unreasonable customer. a college which will offer the necessary coached or advised to undertake sepa- If the technician cannot damper his elements to fit him for a career will not rate courses in his work. For the clear- temper, keep smiling, and admit that he be an easy task. Once again, counseling, ly mismatched student there is no bet- isn't infallible, he will not only antag- reputation within industry, and cur- ter solution than frank advice and onize his trade but may eventually lose riculum of study must be considered at ultimate dropping from the rolls of the his business. He must have the patience length. school. to cope with people who know little of In the selection of the radio- electron- The greatest test of any training his repair problems; he must be willing ics educational program, certain basic program in radio -electronics and asso- to offer service even at an occasional factors should be observed. The student ciated fields begins when the student is personal sacrifice of time. If he has the might well consider the following be- employed on his first job. This is where type of personality that will let him fore making up his mind: all his study and training meet the acid treat each customer as a friend and not 1. Reputation of school, test. If it has been good, the student a dollar -mark, he has little to worry 2. Curriculum, can cope adequately with the problems about. 3. Admission policies, his job presents. If it has been bad, he 4. Cost of training against values to will find himself in the predicament of The prospective engineer be obtained from it, John Doe. For the young man who plans to be- 5. Reputation of faculty, In choosing a school or program of come an engineer, the same prerequi- 6. Guidance and counseling program study, the young man planning to en- sites hold true but their scope increases available, ter the field of radioelectronics must tremendously. An engineering student 7. Placement bureau, realize that the entire industry is de- embarking on a career in radio -elec- 8. Absence of mass -production tac- veloping at a breath -taking speed. All tronics must have particular capabili- tics; comparative individuality in in- phases are becoming more complex in ties to face the rigid requirements of struction. mechanical operation, and the demands the field. The would -be engineer's high school of industry are increasing daily. It is To be successful, the engineering stu- background should definitely include alno longer enough to be able to tinker dent must possess an inherent liking gebra, chemistry, physics, and if pos- with a radio or television set; anyone for and aptitude in mathematics, phys- sible. calculus. In other words, he in the field must be able to know how ics, and English. These subjects are the should purposely load his course elec- it works, why it works, and what will building blocks for a good engineer. tives with as much science and math make it work better. He must be pre- One might question the necessity of as he can carry. His college work in pared to keep up with new develop- English, but it must be remembered these subjects will be increasingly eas- ments in the field and increase his that an engineer must be able to put ier in direct comparison to the amount knowledge continuously from year to his thoughts and ideas into clear and of preparation which he took in high year. This new era of electronics is one concise written words and to read writ- school. full of demand and great promise. The ten explanations. Once the student has entered a repu- right young man, properly trained and Perhaps an even more important re- table institution, the onus lies on the well qualified, will go far. RADIO -ELECTRONICS for Servicial 55

Part VI- Reactance, impedance, and phase By JOHN T. FRYE we find that WE ARE now nearly ready to a thermometer -controlled pen making Following the chart, splice inductance and ca- a continuous track. Any point on the voltage and current in this direction pacitance together into that voltage curve on the chart will tell you again rise to a maximum in 1/240 sec- blissful state known as "the just what the voltage is at that instant ond from the time they started, and in tuned circuit." But before the actual -the curve is simply a combination of another 1/240 second are also back to wedding takes place, we ought to make all those instantaneous voltages. zero. Total time 1 /60 second, and we sure that the union can withstand any No, alternating current really does are back at the end of the circle (or and all strains that may be placed upon not wiggle as the chart might lead you cycle-it's the Greek word for circle) it. It is true that we have observed to believe. What happens is that cur- and ready to start all over again. how both an inductance and a capaci- rent from the alternator starts to flow This is all to tell you what you prob- tance behave under the influence of a through the resistor, starting with very ably don't need to be convinced of- direct current, but do we know what low (zero, to be exact) voltage and that the voltage across the resistor and they will do when an a.c. voltage starts current. Both current and voltage rise the current through it are exactly in pushing and tugging at them? Perhaps until, at the end of 1 240 second, we phase, and that when the voltage is it would be well to investigate this have maximums of 170 volts (dashed maximum or minimum, so is the cur- angle before we bestow our blessing on line) and 2% amperes (solid line). rent; and both reverse precisely in step. the marriage. But when the resistor is replaced by You cannot penetrate very far into either an inductor or capacitor, this the a.c. woods without having a clear harmonious state of affairs no longer understanding of phase; so we may as prevails. A phase shift takes place, and well get that straight right now. Phase the current reaches a maximum value simply means comparative time of oc- at a different time from that at which currence as applied to actions, changes, the voltage is highest. Let us see why. or events. If two things happen to- Fig. 2 shows what happens when an gether, we say they are in phase. If one inductance is placed across the output happens first, we say that it has a lead- of an a.c. generator. The dashed line ing phase. The thing that happens sec- shows the voltage applied to the coil. ond is said to have a lagging phase Chief actors -inductor, capacitor, resistor. You will recall from our discussion of with respect to the first. self- induction (read it again if you Consider the case of you and your (The exact quantities are unimpor- don't) that the changing current one -and -only doing a dance step. If the tant; in many radio circuits we have through the coil produces a counter - feet of both are in phase, her foot alternating currents of some hundreds e.m.f. (voltage) very nearly equal to moves back at the same instant your of volts at only a few milliamperes, the applied voltage but directly op- foot moves forward. If your foot has a and in some welding circuits there may posed to it. This induced voltage is leading phase, it will move forward be- be hundreds of amperes with only a shown by the dotted line. Notice that fore hers is out of the way, and you few volts. In most a.c. diagrams, volt- when the applied voltage is positive (or will probably step on her toes and be age and current curves are arbitrarily for a.c. it might be better to say "in told you are a poor dancer. If your foot drawn the same height -see Figs. 2 one direction ") this induced voltage is has a lagging phase, she is doing the and 3. The only reason we didn't do it negative ("in the other direction ") and leading, and you are going to be a hen- here is that the two curves would then vice versa. pecked man! be on top of each other, and you could- Remember that this induced e.m.f. is As applied to electricity, phase usu- n't tell them apart. Neither is the fre- produced by the expanding or contract- ally means a comparison between sim- quency important; we have used 60 ing lines of force cutting the turns of ilar changes in two or more different cycles because it's common, but the the inductor. Further recall (or re- voltages or between a single voltage story would be equally true at radio read) that these lines of force are in and its accompanying current. For ex- frequencies.) motion only when the current is chang- ample, Fig. 1 shows what happens when But now- because of the way an al- ing value. Still further, the induced an a.c. voltage is applied across a pure ternator is built -our voltage and cur- voltage is highest when the movement resistance. Don't be surprised if you rent start to drop, and at the end of of the lines of force -and consequently don't see it; Fig. 1 has probably balled 1'120 second there is no voltage across the rate of change of current-is fast- up more students than anv other -dia- the resistor and no current flowing est. Keeping all of this in mind (yes, gram in the science of radio! It's sup- through it. Then the current starts to I know it's a neat trick), where would posed to show the life history of a cycle flow through the resistor in the oppo- you say the rate of change of current of alternating current. In our figure, site direction. Our clever mathemati- on Fig. 2 is the greatest? the least? having chosen the standard 60-cycle cians represent these volts and amps in The solid line represents the current current, our has line is laid off in frac- the reverse direction by just drawing flow. The rate of change is highest tions of a 1/60 second. This makes it a the voltage and amperage curves in when this line is most nearest vertical; time chart, just like the rolls that re- the opposite direction to the first ones. least, when it is horizontal. As you sus- cord the temperature for a day, with Neat, eh? pected all along -but can now see on AUGUST, 1949 561 Servicing

the diagram -the rate of current wire, against the applied voltage, to work with microfarads, simply mul- change is least when the current itself through the generator, and on to the tiply the numerator by a million, thus: is maximum. It is at these maximum - other plate. They keep right on flowing 1,000,000 current points that the induced voltage in increasing number while the applied X, - -sustained only by a changing current voltage falls to zero and starts to build (6.28) (60) (1) -is zero. On the other hand, the rate up in the opposite direction; but the and you find that the answer is approx- of change is greatest at the point where current again begins to droop as the imately 2,654 ohms. the current is just starting to reverse other plate nears its maximum charge. When you recall that an inductance its direction or cross the zero line; and Thus we see that the current through is stubbornly opposed to any change in this is the point of maximum induced the circuit is maximum when the ap- the amount of current flowing through voltage. plied voltage is minimum and is at its it, and also remember that the current when the voltage is VOLTS AMPS OR MA minimum applied in an a.c. circuit is changing almost 200 i4 highest. Since the electrons have to continuously, it should be easy to see 150 3 flow onto the plate of the condenser inductance, too, is . 1.4- , TAGE that an going to offer .4.164.- i 2 before its voltage can rise, it is easy to more than a little opposition to the 0 i see why the current through a pure flow of a.c. 0 capacitance leads the applied e.m.f. by RESISTO The amount of this opposition in- 50 90 electrical degrees. creases when either the inductance or aIRRENT 10o You have noticed that a capacitor, the frequency of the applied voltage is 150 which says a firm "No!" to the passage increased. Since the induced or oppos- I 4. 200 of d.c. after it has once become charged, ing voltage increases with the amount 0 1/240 1/120 3/240 I/60 coy , SECONDS seems to murmur a "Maybe" or of inductance encountered, it is not even "Yes" to the knocking of a.c.? hard to understand why a greater in- Fig. I -E and I in a resistance are in phase. While the electrons do not actually pass ductance will offer more opposition to In experimenting with an induction through the dielectric material, their the flow of current. The induced volt- coil, we found that the current reached rushing back and forth through the age also depends on the speed with a steady value a split second after the connecting circuit from one plate to which the expanding and contracting voltage was applied. We can see from another creates an alternating current lines of force cut the wire; and since our diagram that the current peaks in that circuit just as if the capacitor an increase in frequency means that are separated from both the induced were replaced by a resistor. the lines have to speed up in order to and the applied voltage peaks by a We say "resistor" instead of "short go through their expanding- contracting quarter of a cycle. Since we know that circuit," for the capacitor does offer routine more often in the same space we must apply the voltage first, we can some opposition, depending on its ca- of time, no great brain is required to see that in a pure inductance the cur- grasp why an increase in frequency rent lags the applied voltage by a quar- VOLTAGE OR AMPS stirs up more 'opposition to current ter of a cycle. .(APPLIED VOLTAGE flow. The armature of an a.c. generator This resistance which an inductance has to make one complete revolution or CURRENT presents to the flow of a.c. is called in- turn through 360 degrees to produce ductive reactance. It has the symbol

one complete cycle of voltage. The angle INDUCTOR X,, is measured in ohms, and is found through which INDUCED by the formula: this armature has - VOLTAGE ter turned from the starting point is indi- 1/240 I/ 20 3/240 I/60 X, = 6.28 f L, cated in degrees along the time axis. SECONDS in which f is again the frequency in This is all there is to "degrees," as cycles per second, L is the inductance Fig. 2 -Phase relations in inductive circuit. applied to phase lead or lag or other in henries, and the 6.28 is 2Tr, the a.c. terms. It is convenient to divide pacitance and the frequency of the ap- same ancient mathematical pastry we the cycle (remember, it's a circle) into plied a.c., to the passage of current. As had served up in capacitive reactance. 360 degrees and refer to fractions of a the capacitance is increased, more elec- If we want to know the reactance of a cycle in degrees instead of saying -as trons must be moved to charge it each 10 -henry choke to a 60 -cycle voltage, we did, clumsily-1/240 second, etc. time; therefore, the current that is simply substitute in the formula: Every quarter of a cycle is seen to oc- composed of the movement of these XI = (2) X (3.1416) X (60) X (10). cupy 90 degrees. Do you see why we say electrons is increased just as if the and we find the answer: just under that, in a pure inductance, changes in equivalent resistance represented by 3,770 ohms. current lag changes in applied voltage the capacitor were lowered. If the fre- To review a little while we catch our by 00 electrical degrees? quency of the applied voltage is in- breath: Resistance is the opposition Fig. 3 shows what happens when an creased, the electrons have to make a.c. generator is connected across a more trips back and forth between the ...... \rvOLTAGE capacitor. The dashed line again repre- plates in a given length of time, and / ' sents the value and polarity of the ap- more electron trips mean more total i plied e.m.f. with respect to time. As the current just as if the equivalent resis- CURREN voltage first starts to rise in the "posi- tance were lowered again. tive" direction, the electrons are easily This "equivalent resistance" offered 0 CAPACITOR I pushed onto one of the plates of the by a capacitor to the passage of a.c. is 90 160 20 360 capacitive reactance, has the DEGR ES i capacitor and rush on at their maxi- called mum rate, for they encounter little re- symbol X,., is measured in ohms just Fig. 3- Current leads in capacitive circuit. sistance. But as this plate acquires like resistance, and for any given ca- more charge, its voltage rises (note pacitor can be found by the formula: offered to the flow of a steady direct dashed line) and begins to repel the 1 current; Reactance is a specialized electrons the generator is trying to X, - form of opposition that a.c. runs into. force upon it. The movement of elec- 6.28 f C Reactance comes in two flavors: ca- trons, which makes up the current in in which f is the frequency in cycles, pacitive or inductive, according to wire circuits, slows down and finally C is the capacitance in farads, and 6.28 whether the current leads or lags the stops when the applied e.m.f. and the is 2a (your old friend of grammar - voltage. While all three impede the electron charge have reached their school days, 3.1416). If you want to flow of current, they are not at all maximum values (at 90 °, or one -quar- know the. reactance of a 1 -µf capacitor alike. Resistance uses up power and ter of a cycle). Then, as the applied at 60 cycles, you simply substitute in dissipates it in the form of heat. Reac- voltage starts to decrease, the packed the formula, not forgetting to change tance transforms electric current into electrons begin to flow back into the microfarads to farads. Or if you want a magnetic field in an inductance or an RADIO -ELECTRONICS for e)7 Save Up to 22% at ALLIED on these famous Hallicrafters models

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ALLIED RADIO CORP., Dept. 2-E1-9 833 W. Jackson Blvd., Chicago 7, Illinois FREE Radio's Leading Send FREE ALLIED Catalog CATALOG FREE 9 Enter order for Hallicrafters Model Buying Enclosed $ Full Payment Guide d Part Payment (Bal. C.O.D.) Send ALLIED Easy Payment an order blank. Used by thousands of expert radio O details men. Get every buying advantage at ALLIED: widest selections-money- Name saving prices- speedy, expert shipment-personal attention -complete Address satisfaction on every order. Send today for your latest ALLIED Catalog. City Zone State Í se f.JGUST, 1949 Servicing

electrostatic field in a capacitor for a portion of a cycle and then returns YOU'LL HIT THE JACK POT .. . this stored energy as an electric current during the remainder of the cycle. WITH QUAM Adjust -a -Cone SPEAKERS With pure reactance in the circuit - There's a jack -pot of satisfied customers waiting for never actually found in practice -the the serviceman who uses Quam Adjust -A -Cone energy is just swapped back and forth / Speakers. Here' s why! from one form to another without any 3PCKpOT. First, there's the unsurpassed performance and effi- loss of power. In a purely reactive cir- ciency of Quam Adjust -A -Cone Speakers. They will cuit, there is a 90- degree phase shift in moke any receiver sound as good or better than it did with the original equipment. one direction or the other from the in- phase condition of a purely resistive Second, you can be sure of trouble-free service. With the construction of the Quam Adjust -A -Cone circuit. The more resistance we have Speaker, because it permits accurate centering of the in comparison to the reactance, the voice coil alter assembly, a rubbing voice coil is fewer are the degrees of phase shift practically unheard of. (the closer together are current and Third. By replacing a defective speaker with a Quom voltage maximums or minimums). Adjust -A -Cone, the serviceman makes a larger mar- Capacitive and inductive reactances gin of profit, ensures a satis- have factory job and a satisfied exactly the opposite effect on customer. phase, and can be combined just like positive negative You can hit the jackpot with and numbers. In a cir- Quom Speakers. cuit containing both, the effective reactance is found simply by subtracting the smaller reactance from the larger QUAM -NICHOLS CO. and giving it the name of larger. 521 E. 33rd Place, Chicago 16, Illinois the For example, in a circuit containing 15 MAIL THIS COUPON Please send GUAM Catalog. ohms of capacitive reactance and 10 FOR FREE CATALOG Name Address ohms of inductive reactance, we just City State take 10 from 15 and say that the circuit has 5 ohms of capacitive reactance. In addition to reactance, all actual circuits have some resistance; and we have a special word to describe this total opposition to a.c. That word is psi impedance, represented by the symbol Z, and it means "reactance and resistance." The two are somewhat like fractions and decimals in that you cannot add them directly. You have to extract the square root of the sum of SubStltution their squares, which gives us the form- Signo t to receive ula for finding impedance: Z = R- + (X1, X1) . S SS tells HOW - in Suppose, for example, -we have a cir- simple, direct language. cuit containing 4 ohms of resistance, New 9th edition now off the press. 10 ohms of capacitive reactance, and 7 100 pages of valuable information. ohms of inductive reactance (total reactance 10 7, or 3 ohms capacitive). parts and - Available from all leading radio Substituting these values in the equipment distributors or directly from factory formula: at only 40c per copy. Z =V42+ (10 -7)' =x/16 4-9= PRECISION APPARATUS COMPANY, Inc. 92 -27 Horace Harding Blvd., Elmhurst 4, N. T. V 25 = 5 ohms. But here it is the end of the chapter, and the union of capacitance and inductance into a tuned circuit -like the FM-AM marriage of Little Abner and Daisy CUSTOM 32,001 FREE Resistors' Mae -has been repeatedly postponed. CHASSIS These nuptials will take place in the very next chapter! Each KIt e0.11.005 the :,lent of 33.11011 i 4 watt re.i.tors. ENGINEERS -REPAIRMEN- AMATEURS: Now is the time to learn PRINTED -CIRCUIT METHODS. Most radio and TV makers already are designing printed circuits for their products. Let our 521 Kit be your laboratory. MANUFACTURERS: A dab or two of conducting or resistance paint on your present products may eliminate components and labor -save you Pen- nies or dimes on every unit. Use one of our S21 Kits to discover where. Write us about your quantity needs. stating characteristics required. The MICROPAINT KITS provide a complete printed- circuit paint laboratory for you, includ- 13 TUBE, HI- FIDELITY CHASSIS ing instructions. The S21 12- Wide, 105- Deep, 7. Nigh Kit, $7.27, contains silver Manufacturer over-run-made for the famous Ansley and copper conducting paints; low, medium, and Consoles-complete high resistance points; lacquer; and solvent. All tsinlues 2 B\Be PP for power soutput. driivven by a balanced phase inverter circuit sisn¢¢ f are designed for brush application on nearly pu SW. FM any insulator. Draw separate components or band. 8.8 MC-I08 MC. land dS401eKC -17000 KC. Response: 50.10,000 Ifs 13 db down,: 105.125 lt. complete working circuits. The paints air -dry A.C. Underwriters App. Reg. List $10000. rapidly. The Manual "Design and Repair of Write for full specs. You be the Judge of this line chests -10 day my back guarantee. $50 Printed Circuits" is included free with each Kit. 25,i deposit, 1,1:01 c C.O.D. aemeiete SALCO Electronic Distributors Inc, MICROCIRCUITS CO. 373 -Broadway, ---- Brooklyn I1. N. Y. Dept. 2J New Buffalo, Michigan RADIO -ELECTRONICS for Foreign News iN European Report By Major Ralph W. Ilallotis

RADIO -ELECTRONICS LONDON CORRESPONDENT

What the televiewer wants British prices for televisers- remember I'm speaking of sound-and -vision sets I was very interested in the data with at least 10 -inch C -R tubes -seem produced not long ago by the American to be a great deal less than yours. Were firm, Audience Research, Inc., on what I intending to go out to-morrow to buy Americans want in the way of tele- a TV receiver of the kind mentioned, IN Roumania visers and in comparing these with the I'd find two or three types below the they're talking yearnings, the earnings, the likes, and $200 mark and quite a wide selection seriously of the dislikes of potential televiewers in at under $300. For $750 I could buy loudspeaker re- Britain. There's no doubt at all about a good- looking combination all -wave ception from a what our ordinary man and woman re- radio -phonograph -televiser with a 12- plain crystal set. gard as essential in a televiser. First inch- diameter cathode -ray viewing tube No tubes, no transistors; in fact no and foremost, they simply won't have and all the trimmings. amplification at all. Just a straight- any set which gives a picture with an forward, common crystal detector of area less than 65 square inches. And The war on interference the fixed type, connected on one side that means a 10 -inch C -R tube. At one to the antenna and on the other to the time or another this manufacturer or You may recall that I've told you loudspeaker. When I said talking seri- that has tried to popularize a low - already how we in Britain are tackling ously I meant that no less formidable priced set using a 4 -inch, 6 -inch, or the problem of man -made interference a publication than the Bulletin of the 8 -inch C -R tube and the result has in- with radio and television reception by Roumanian National Technological Re- variably been something very like a making it illegal to operate an unsup- search Institute has published an ar- complete flop. Even if a televiser gives pressed factory machine, domestic elec- ticle in which Mr. Matei Marinesco the clearest of images of smaller size trical appliance, or automobile. In gives accounts of both his investigation than about 65 square inches, the ordi- Switzerland they're dealing with some of the theory of electromagnetic and nary viewer just won't have it in the of the main causes of interference in other reproducing instruments and of house. another way. Switzerland is, in pro- the promising results claimed to have Next, our folk won't buy the televiser portion to its size and its population, been obtained already in his efforts to that does not also reproduce the ac- perhaps the most completely electrified evolve a practical crystal- detector- companying sounds. The main reason country in the world today. Thanks to loudspeaker receiver. ofor this is that few indeed of our do- its vast resources of waterpower, even It all began like this. Feeling that mestic radio receivers can tune in the small villages and outlying farms have the radio receiver incorporating tubes sound channel of the television broad- electric mains supplies. No steam loco- and needing "juice" either from electric casts. motive runs on its railways and it has mains or from relatively expensive bat- Price seems to be a secondary con- a vast mileage of electric street -car teries could never become really popu- sideration. So long as its cost is not systems. Some of the street cars oper- lar in its country districts, where there outrageously high, a good televiser sells ate over interurban systems of consid- is little money to spare, the Roumanian rather more quickly than its makers erable extent. With cheap electric pow- Radio Company announced a competi- can produce it. That is due to some er available everywhere you can tion, with large money prizes, for gen- extent to prevailing conditions. We are imagine that radio listeners (there are uine "people's receivers ". The condi- still on short commons as regards food no televiewers yet) complain bitterly tions were, briefly, that sets should and our shops (owing to the urgent of the effects of man -made static. They contain no tubes, that they should necessity of exporting all we can in have to pay for licenses to use radios operate loudspeakers and that they order to pay our way) are still not too and they're not a bit pleased when a should provide a sound intensity of 30 well stocked with consumer goods. fine selection of "noises offstage" makes phons in a room with a content of 50 Hence, there aren't many things on a classical concert sound like a feature cubic meters for an input of 100 milli- which people can spend what money program concerning a large boiler fac- volts. they have left after paying living ex- tory. Getting down to the job, Mr. Marin- penses and taxes. Televisers can be The license fees are collected by the esco decided that the big snag was not bought on the installment system and, government Posts and Telegraphs De- the crystal detector, but the loud- provided the installments are within partment, which has recently decided speaker. Those which most of us use their means, people buy them in large to spend a considerable percentage of are, he finds, sadly inefficient devices, quantities. this income on static suppression at since the ratio of power output to From the A. R. I. report I see that source. To accomplish this will cer- power input works out at between 2 televiser prices are, on the average, tainly cost a tidy sum, for, to take and 6,/,. Devise a loudspeaker with an round about the $400 mark in the U.S. transport alone, both the railways and output -input ratio of 80% or a bit more (The A. R. I. report is based on U.S. the street car systems use overhead and the trick should be done. Mr. Mar- TV prices in effect last fall.Editor) conducting wires with spring- loaded inesco claims to have evolved loud- Now, that does surprise me. On ordin- sweep contactors on locomotives and speakers with efficiencies up to 85'; ary broadcast radios American prices cars. At every joint in the overhead over fairly wide bands of frequencies, are far below British. A small 4 -tube wires the travelling contactors are in conjunction with which a simple radio receiver costs at least twice as liable to jump, producing sparks and crystal set fulfils most of the conditions much here as it does in the States. radiation of the kind which shock - laid down for the competition. Well, (I'm leaving purchase tax out of con- excites antennas over a considerable here's hoping! What with the transis- sideration, since it varies from time area. The problem is a pretty big one, tor and the super -efficient loudspeaker, to time and has, in any event, nothing you'll agree, and the Swiss are to be the amplifying tube may have to look to do with the efficiency or otherwise congratulated on getting down to it in to its laurels. of mass- production methods). But this practical way. AUGUST, 1949 Test Instruments Laboratory Square Wave Generator

Square waves at frequencies up to 50 kc may be produced with this instrument plus an a.f. generator

By JOHN E. PITTS

Quarter -view photo shows where the principal parts and controls are placed.

r1../ be coupled to the IN terminals to pro- rk, 6SJ7 fZJ 6SJ7 - 7C5 n 7C5 u waves as high as 50 kc. 225V (51(/ W 5 6.2N/2W 25/I1,V (2) -240v (2) u duce square zov OUT 5 R5 (1.s600V 240V C2 2 The voltage available from the 6SF5 --oHl be varied by the OUT 3 terminals may 500 when 60 -cycle input R2 R6 IOW potentiometer using 20K y R19 DUAL or from the IN or OUT potentiometers, or 3.5V R4 R13 audio RI 2 _ÿ15V 510K 500n both, when using an external OS< f 60rv R9 RI4 C4 IN SI K I1W 240K 3K /2W oscillator as the signal source. ó R3 l oOUT RIO I i 2 510 IW 750 -I8 v 40 GND The instrument was designed for R1 R8 75V RII 450v Ne., L1h HA low RIB mounting in a relay rack, but it can 510/IW 2.4K/2W ION /IOW readily be modified for portable use by building it in one of the amplifier -type 6) 6.3V PILOT LAMP (C3 .25/IKV covered chassis. +250v The was built on a 10 x 17- L6.3V/2.5A- 65F5.65.P FILS generator inch chassis with a 10% x 19 -inch 7.5K /IOW panel. It begins with one voltage ampli- 5V /2A L 12H fier, a 6SF5, acting as a partial limiter. T2 75MA ALL VOLTAGES SHOWN WITH RESPECT TO CHASSIS WITH SI The 6SF5 is capacitance -coupled to a C5 ON 60ív AND OUT POT FULL ON 6SJ7 whose plate circuit the square II7VAC 30=525v -in wave appears. This tube is direct - FIL PINS- 6SF5:7 -6 i 55J7:2-7; 7C5:1 -6 S2 coupled to another 6SJ7 amplifier, which in turn is capacitance -coupled to Bottom power supply gives negative voltage. 300-0-300V/10MA push -pull 7C5's, which are direct - coupled to the push -pull 7C5 output (e 6JV/2.SA-1C5FILS BUILT to supply the need for a stage. TI 5Y3 L2= source of variable - frequency, The output of a variable audio oscil-

5V /2A 12H square -wave voltage to be used in lator may be connected to the IN ter- SOMA testing audio amplifiers and radio- minals and the input to the square - phone transmitters, this laboratory - wave generator varied by potentiometer C8+ is IC6 type, square -wave generator will furn- Rl when the input selector switch ish approximately 50 volts of square - thrown to osC. With the switch thrown -38OV wave output from either its 60 -cycle to the 60-CYCLE position, the input is 400-0-400V/125MA 20/ 25V EACH internal source or from a variable - connected internally to one of the 6.3- frequency audio oscillator which may volt filament windings. The input from RADIO -ELECTRONICS for fi l

:T",,,0 TELEVISION SIGNAL GENERATOR Enables alignment of television I.F. and front ends without the use of an oscilloscope Gen- The Model TV -30 represents a radical departure in the design of Television Signal erators. Unlike the "sweep" type of Generator which requires the use of an Oscilloscope and extensive technical knowledge including pattern interpretation, etc., the TV -30 is a self - contained unit which permits alignment of Television Receivers by the use of exactly the same methods employed in the past to align Broadcast and Short -Wave Receivers. FEATURES: Built -in modulator may be used to modulate the R.F. Frequency also to localize the couse of trouble in the audio circuits of T.V. Receivers. Double shielding of oscillatory stability and reduces radiation to absolute minimum. Provision made for circuit assures fre- external modulation by A.F. or R.F. source to provide frequency modulation. All I.F. on the Vernier quencies and 2 to 13 channel frequencies are calibrated direct in Megacycles dial. Markers for the Video and Audio carriers within their respective channels are also calibrated on the dial. Linear calibrations throughout are achieved by the use of a Straight Line Frequency Variable Condenser together with o permeability trimmed coil. Stability assured by cathode follower buffer tube and double shielding of component parts. SPECIFICATIONS: Frequency Ranee: 4 Bands -No Switching. I8 -32 Mc. 35-65 Mc. 54-98 Me. 150 -250 Mc. Model TV -30 comes corn- Audio Modulating Frequency: 400 cycles (Sine Wave). Otte with shielded coaxial 1995 Attenuator: 4 position, ladder type with constant im- lead and all operating in- pedanee control for fine adjustment. striations. Measures 67s7-u Tubes Used: 6C4 as Cathode follower and modulated buffer. 6C4 as R.F. Oscillator 6SN7 as Audio Oscillator and power rectifier.

THE NEW MODEL 670 The New Model 770 - An Accurate Pocket -Size SUPER METER SUPER METER. A Combination VOLT -OHM MILLIAMMETER VOLT - OHM - MILLIAMMETER plus CAPACITY REACTANCE. (Sensitivity: 1000 ohms per volt) INDUCTANCE and DECIBEL Features: MEASUREMENTS. Compact-measures 34," x 5T/g" x design 2% accurate 1 Mil. D.C. VOLTS: 0 to 7.5/15/75/150/T.iu Uses latest 7,00. A.C. VOLTS: 0 to 15 /:01 D'Arsonval type meter. Same zero ad- 0 1500/3000 Volts. O U T P U T justment holds for both resistance ranges. VOLTS: 0 to 15/30/150/300/1500 /3000_ It is not necessary to readjust when U.C. CURRENT: e to 1.5 /15,150 n switching from one resistance range to 1.5 Amps. RESISTANCE: 0 to Sop/ timesav- 11111.0011 ohms. 0 to ln Megohms. CA- another. This is an important is PACITY: .001 to .2 Mfd.. .1 to 4 31íd. ing feature never before included in ,e uality test for electrolytlrs.i REACT - V.O.M. in this price range. Housed in ANCE: 700 to 27.000 Ohms: 13.000 Ohms round -cornered, molded case. Beautiful iu 3 Megohms. black etched panel. Depressed letters 70 Henries: 35 INDUCTANCE: 1.75 to filled with permanent white, insures long - to 0.000 Henries. life even with constant use. DECIBELS: -10 to +18. +10 to +30. Specifications: 6 A.C. VOLTAGE RANGES: +30 to +58. 0.15,30, 150 3110,1500/3000 volts. The model 670 comes housed in a rug ted. 6 D.C. VOLTAGE RANGES: 0 -754/15/75/ cast 150 7 '0/15011 roll.. ¡net'oat complete with test Q,eo 4 D.C. CURRENT RANGES: 0 -154 /15/150 leads and operating in. Ma. 0-I'-_ imp 0 -1 striations. Size 51/2" s 2 RESISTANCE RANGES: 0 -500 Ohms. NET 7'/z' r 3 ". Mncohm The Model 770 tomes complete Si with sell -contained batteries. g7 247 test leads and all operating THE NEW MODEL mstruetitns 390NET The Model 88 - A COMBINATION TUBE TESTER SIGNAL GENERATOR Check oetals, tonals. bantam Jr. magic television miniatures. AND magic the, hearing amis, thyn- lrona, the new type H.F. minl- lares, etc. TRACER . Features: SIGNAL - A newly designed element se- Signal Generator Specifications: S lector switch reduces the possibility of obsolescence to an Frequency Range: 150 Kilo- absolute minimum. cycles to 50 Megacycles. The When checking Diode. Triode is kept sections of multi- R.F. Signal Frequency `V -_ and Pentode completely constant at all out- purpose .aAS special i is ac- ? individually. put levels. Modulation - isolating circuit allows each complished by Grid -blocking ac- section to be tested as if It tion which is equally effective were In a separate envelope. for of amplitude and The Model 247 provides a su- alignment per- sensitive method of check- frequency modulation as well as ing for shorts and leakages up for television receivers. R.F. ob- to 5 Megohms between any tainable separately or modu- and all of the terminals. lated by the Audio Frequency. One of the most important improvements. we believe. is Signal Tracer Specifications: the 4- position the new Sylvania 1N34 Ger- Model 247 comes complete with new the fact that I'ses fast- action snap switches are manium crystal Diode which com- speed -read chart. Comes housed in hand- an eumbethe ndar accord. bined with resistance-calmeilY net- some hand -rubbed oak cabinet sloped for all n with the standard R.M.A. work provides (re- bench use. A slip-on port- numbering system. Thus, If anenry range of 300 able hinged cover is indi- the element terminating in cycles to 50 ?Iegaryrl"s 85 90 a Is under outside Ilse. Sizes VB pin No. 7 of tube ated for L NET test. button No. 71s used for mes complete with all test leads and operat¡no NET + y+ IPy4" x 8"y s 5". ONLY that test. I rtl i_m. ONLY 2O9 DEPOSIT REQUIRED ON ALL C.O.D. ORDERS MONEY BACK GUARANTEE -We believe units offered for sale by mail order should be sold only on a "Money -Eack -If- Not -Satisfied" basis. We carefully check the design, calibration and value of all items adver- tised by .is and unhesitatingly offer all merchandise subject to a return for credit or refund. You, the customer, are the sole judge as to value of the item or items you have purchased.

88 PARK PN. YE GENERAL ELECTRONIC DISTRIBUTING CO. NEW YORK

AUGUST 19 4 0 62 Test Instruments

OVER 85 BARGAINS EVERYTHING BRAND NEW MONEY BACK GUARANTEE ONE POUND ROSIN SOLDER S .49 S 3.95 SOLDERING IRON, 100 wafts 1.97 S 37.95 TOM THUMB CAMERA & RADIO 17.97 PERSONAL PORTABLE BATTERY, 67'/V 1.44 RCA TELEVISION TUNER, with 3 -6J6 29.75 POWER TRANSFORMER, =630 type 11.97 PUNCHED CHASSIS PAN, =630 type 5.45 TELEVISION ANTENNA, hi & to freq 6.95 TELEVISION INDOOR V- ANTENNA 3.97 TWIN LEAD -IN, 300 ohms, 100 feet 1.79 TWIN LEAD -IN, 300 ohms, 500 feet 6.45 COAXIAL CABLE, RG59U, 100 feet 4.35 COAXIAL CABLE, RG59U, 500 feet 18.95 TELEVISION 10" NO -GLARE FILTER .79 6AG5, 6AK5, 6AL5, 6J6 each .79 OUTPUT TRANSFORMER, push -pull .37 OUTPUT TRANSFORMER, 16V6) .39 FILAMENT TRANSFORMER, 2' /V, 10 amp .69 CHASSIS PAN, 8 mounted sockets .39 CHASSIS PAN, popular radio type .19 A.C. -D.C. CHOKE, 50ma, 10hy .17 I.F. TRANSFORMER, 456kc .39 OSCILLATOR COIL, 456kc .09 VARIABLE CONDENSER, 420 162 .69 VARIABLE CONDENSER, FM, 88 to 108mc .89 RESISTANCE CORD, 150 ohms .39 ASIATIC PICK -UP, long playing 2.95 R 13,14,15,16 WEBSTER CRYSTAL, fits most arms 1.45 TOGGLE SWITCHES, SPST .14 TOGGLE SWITCHES, DPST .22 ANTENNA HANK, 15 ft. on handy spool .09 The 10 X I7 -inch chassis provides plenty of space 100 -ASST. CONDENSERS, .001 to .02 3.95 for the components, allows neat wiring. 100 -ASST. RESISTORS, ' watt 1.50 100 -ASST. KNOBS, screw & push on 2.95 100 -ASST. SOCKETS, loci, oct, min 2.95 either of these 100 -ASST. PILOT two sources goes to the Capacitors C2 and C3 should be LIGHTS, 47, 49, 51 4.95 grid of 6SF5 100- PEANUT TUBE CARTONS .75 the through R2, a limiting at least of the voltage rating (1,000) 100 -GT TUBE CARTONS resistor .95 in the tube's grid circuit. This specified, as they have the combined 100 -SMALL G CARTONS 1.25 produces partial clipping the input. 100 -LARGE at voltages (about 640) of both power G TUBE CARTONS 1.45 The output produces a wave of the supplies 3 INCH PM SPEAKER, Alnico 5 .84 and the peak plate voltage of 4 INCH PM shape shown above 6SF5 SPEAKER, Alnico 5 .97 the plate lead the 6SJ7 cathode follower stage across 5 INCH PM SPEAKER, Alnico 5 1.07 in the schematic diagram. their terminals. 6 INCH PM SPEAKER, Alnico 5 1.29 The 6SF5 output voltage is capaci- 8 INCH PM SPEAKER, Alnico 5 2.95 It was felt best not to ground one of AUTO VIBRATOR, 4 prong, non tance- coupled to the first 6SJ7 which 6.3 synchro . .97 the -volt heater windings, since the AUTO WHIP ANTENNA, further limits and squares side mount 1.69 off the wave cathodes of all the 7C5's are at a high TUBULAR CONDENSER, 5 mfd -25V .09 tops. The mutual coupling resistor R9 TUBULAR d.c. potential above ground. Were one CONDENSER, 10 mfd -35V .12 in the first 6SJ7 plate and second 6SJ7 TUBULAR CONDENSER, 10 mfd -50V of the tubes to develop a cathode .14 grid direct couples -to- TUBULAR CONDENSER, 40 30 -150V .29 the two tubes for heater leak with the minimum frequency heater circuit at discrimination. The ground potential, one of the rectifier VOLUME CONTROLS second 6SJ7 is used as a phase inverter tubes would be destroyed if the primary of a modified cathode -follower type to LESS fuse should not blow. SWITCH, 25M, 100M, 1 meg, ..Each .14 provide WITH the proper drive for a push -pull SWITCH, 50M, 200M, ' 1 meg. Each. .29 stage. The phase inverter One of the photos shows a front is capaci- quarter view tance- coupled through C2 C3 of the completed instru- ROUND CHASSIS PUNCHES and to ment and the other, push -pull 7C5's which are direct -coupled an underneath Cut socket holes, etc. in a ¡iffy. view, shows placement of parts. In the - i's" to another pair of push -pull 7C5's in Vi" 11 16 the output stage. latter photo the input circuit is at the - 1 1l /e" 11/4- 11 64 1 3 16" To present a relatively right and the output stage in the mid- Each 1.95 constant volt- dle with all electrolytics age drop across the first stage of the and the power RADIO supplies toward the left. TUBES direct- coupled 7C5's, the stage is shunt- Though the frequency response 1R4 SYLVANIA .19 ed by R16 so the voltage applied of an 6C4 NATIONAL UNION .19 to the output stage will not depend amplifier may measure up to snuff, the 26 CUNNINGHAM .19 wholly on the plate resistance of the waveform of the input voltage may not 11135 SYLVANIA .37 driving stage. In order that the output be reproduced accurately in the output. 76 PHILCO .29 This is due to non -uniform 12SR7 KENRAD .29 stage may have its plate circuit re- phase shift 1R5 UNBRANDED .29 turned directly to ground potential, the between stages; different frequencies 12K8 RCA .29 last two stages are shifted by different amounts. 35W4 HYTRON are operated from a .34 power supply whose positive A square wave may be fed to in- 5085 ARCTURUS .34 terminal the 35Z5 KENRAD .39 is grounded, thus putting the grid cir- put of the amplifier. Since it is rich in 80 CUNNINGHAM .39 cuit of the first 7C5's approximately (odd) harmonics, the output waveform 5T4 RCA .49 390 volts negative with as observed on a scope 6K7 RCA respect to the will be square .49 chassis. only if the phase shift in 6F5 STANDARD BRAND .49 the amplifier 40 12SF7 RCA .49 A -pf capacitor C4 is connected be- is uniform and if the frequency re- 50L6 KENRAD .5S tween the output cathodes and ground. sponse is wide. It tests both at once. 1LC6 SYLVANIA .69 117Z3 It must be mounted on an insulated The instrument has proved TUNGSOL .69 itself ex- 1LE3 mounting plate. Since one TUNGSOL .69 of the power tremely useful in adjusting and testing 25A6 STANDARD BRAND .69 supplies is operated in an inverted man- various types of amplifiers, and also as ner, the cans of capacitors C4, C6, C7, the timing base for an electronic and C8 are all hot with BROOKS respect to chas- switch. The time and money spent in its RADIO DIST. CORP. sis, and, if exposed, must be adequately construction have been more than re- 80 VESEY ST., DEPT. A, NEW YORK 7, N. Y. protected from accidental contact. paid by the usefulness of the equipment. RADIO -ELECTRONICS for New I evicts 63

SOLDERING PLIERS V.H.F. VOLTMETER conductors. The new tubular 300 -ohm Twin -Lead made especially for recep- SWEEP GENERATOR KIT Durst Mfg. Co., Sylvania Electric Products, Inc. tion (like the tubular transmitting lines Radio Kits Co., North Hollywood, Calif. New York, N. Y. introduced by the company last year) has New York, N. Y. A new method of so derinq radio The Polymeter Type 221 is a vacuum - the conductors separated mainly Model SW5 is a parts is introduced by these pliers. The tube voltmeter with essentially flot re- by the enclosed air space within the kit of ports for building a 2- 226 -mc test for two arms of the tool are 'insulated from sponse from 20 cycles to 300 mc and tube. Thus dirt collecting on the out- generator serv- each other and connected to a low - usable up to 500 mc. A special sub- side of the tube does not lie between voltage, high -current transformer. The miniature tube used in the r.f. probe the conductors and has little effect on wires or parts to be joined are held by provides high input impedance and electrical characteristics. Additional the pliers. and the foot switch is pressed very low capacitance. Vacuum -tube features are lower wind resistance and for on instant. The comoonents and the rectification is used throughout. Six greater strength. solder are heated enough by the high scales give d.c. ranges of 3 and 1,000 current to melt the solder and form a volts, which can be multiplied by 10 PORTABLE METERS solid joint. with a 10 -kv accessory probe. A.c. volt- Weston Electrical age ranges are the some as those for Instrument Corp., d.c.: r.f. up to 300 volts may be meas- Newark 5, N. J. ured. Resistance and current ranges are The model 901 series of a.c. and d.c. included. voltmeters, ammeters, milliammeters, and microammeters features instruments with easily seen scales and efficient shielding. Unbreakable windows icing AM, FM, or TV sets. Either AM extend the full width of the meter and or FM output is available, with a max- curve around each side to reduce imum FM sweep width of 10 mc. Sweep shadows. The units have hand -cali- and phasing are variable: a sweep -sync brated mirror scales and knife -edge output is provided for an oscilloscope. pointers. Basic accuracy is within 0.5 %. Instruments using rectifiers for reading a.c. have an accuracy of 1.5% of full ABOVE -CHASSIS The pliers remain coo' at oll times as scale. RESISTOR does the work, except at the point of contact. Less solder is used and sur- Clarostat Mfg. Co., Inc. rounding ports -capoc tor wax, plastic Dover, N. H. spaghetti, and so on -ire not dam- The Standee is a new -type vertical aged. The pliers may zlso be used as power resistor for above -chassis mount. an ordinary tool. saving time ordinarily ing. needed for changing ools for solder- Basically, the Standee comprises a ing. wire winding on Fiberglas core. bent in hairpin form with a mica separator CIRCUIT -BREAKER PLUG ANTI -STATIC between the legs, placed in a ceramic tube filled with cold -setting inorganic Hopax Electric Inc., COMPOUND New York, N. Y. Merle Chemical Co, Providing protection ectrical de. Chicago, Ill. vices and to power w this plug contains an interesting circuit breaker. Plastic phonograph records, such as the The power cord from on electric motor vinylite long playing discs, accumu- or other device is conr ected to it, and late a static electric charge which at- it is then inserted in a line socket os is tracts dust and lint, making the playback noisy. Anti -Static Compound No. CAPACITANCE 79 is a liquid chemical which eliminates the charge. Applied in small quantities COMPARATOR with a tintless cloth to either side of a vinylite disc, it dries quickly and (as Clippard Instrument Laboratory, confirmed in tests by the editors) does Inc., not harm the record. After application Cincinnati, Ohio of the liquid, the discs have no appar- Model PC -4 capacitance comparofor ent charge; they remain unusually is an accurate production -line test in- clean and noiseless. strument designed to aid in selecting The liquid should be applied with a dampened cloth, using a circular mo- cement, and provided with bottom ter- tion following the grooves. About I50 minals and mounting bracket. The lugs records can be treated (one side each) are locked into the tube wall in addi- with a 4 -ounce bottle of Anti -Static. tion to being sealed in cement. By having this power resistor mounted MINIATURE RESISTORS above the chassis, the problem of heat dissipation is neatly solved. Wilkor Products, Inc., Standees are available in the stand- an ordinory o.c, plug. When the device Cleveland, Ohio ard 19/32 -inch diameter, in heights of shorts or overloads and draws too much Carbofilm resistors are available in li /zt 2, 21/2, and 3 inches, ith power ratings of 10, 15, 20, andw 25 watts, current, a small lever, which ordinarily sizes from 1/4 to I waft and resistances respectively. Maximum rests between the prongs springs up from 20 ohms to 5 megohms. The small- resistance val- and pushes the plug o it of the socket. est resistor is 1/16 inch in diameter and ues ore 6.000, 9,000, 12,000, and 15.000 ohms, respectively. The breaker is reset by lifting the lever, only % inch long. Isuloted units may pushing it bock between the prongs, be had. and reinserting the pl iq in the socket. SCOPE LENS Designed primarily for fractional - horsepower motors. tht Alit should be and grading capacitors. It may be used Allen B. Du Mont Laboratories, usable for electronic a to pment as well. by non -technical personnel to obtain Inc., Ratings up to 10 omoeres are ovoil- results within 0.2 %. The range of the Clifton, N. J. reading is IO tuf to 1,000 pf. The meter able. The new Type 2542 oscillographic is a 4 -inch direct- current D'Arsonval projection lens, fine. is a two -element, svm VERSATILE BINDING metrical, objective lens with a relative aperture of f/3.3 and focal POST DUAL -POINT PICKUP a length of Superior Electric Co., Electra- Voice, Inc., Bristol, Conn. Buchanan, Mich. The 5 -Way binding host is intended 'The Twits is o torque -drive crystal for general radio is if should be phonograph pickup with two tips on the especially suitable for 's-st and measur- stylus shank- One hos a I -mil radius ing equipment. Five rffterent methods for microgroove records and the other to of connection it orr possible: spade TUBULAR 3 mils for standard discs. Either is lugs, wire (sine up to No. 121 through TWIN -LEAD placed in position by tilting the car- American Phenolic Corp., Chicago, Ill. Amphenol's Twin -Lead was one of the first of the ribbon type dual transmission lines. The flot line undergoes changes in characteristics, however, when moisture or dirt collects on the 7.7 Inches. It projects an oscilloscope surface of the insulating material, since pattern up to 3 inches square from 8 all the plastic lies directly between the to 30 feet, resulting in a picture as large as 12 feet square. Axial light transmission of the system is about the center hole. wire looped oround 85 %. An the lens shaft, clip leads (there is enough shaft advantage of is the sin plicity with which for this when head is turned to end it may be mounted on any oscilloscope equipped with a position), and stondari l -inch banana plugs. bezel similar to that supplied with Du fridge in its special holder, which may The hexagonal- shaped Mont instruments. (This bezel may be head being be installed in almost any standard hod separately.) captive, it cannot get lost. The posts The lens is slipped arm. The arm should be lightened for into the bezel and a clamp knob on are furnished in red and black, with 6 o -gram stylus force. Output is I volt the lens is rotated. The lens is designed 30- ampere capacity and a 1.000 -work- at 1,000 cycles ing -volt rating. from the RD90 test primarily for use in lectures and dem- record. onstrotions. AUGUST, 1949 ß 1 1 Hadio-Electronic :ircuits- LAFAYETTE AMPLIFIER CONTROL UNIT SHOWCASE TEST EQUIPMENT Many lovers of high -fidelity recorded the two BOOST positions, a capacitor is AT ROCK BOTTOM music go to considerable trouble and inserted in series with the 15,000 -ohm expense to develop reproducing equip- resistor, making the output impedance PRICES ment meeting their needs. All too fre- of the smaller leg of the voltage divider quently, the joy of owning and operat- (and therefore the output voltage) in- Limited quantity. Showcase display models ing such equipment is marred by the crease as the frequency decreases. In of popular type quality test equipment in fact that the amplifier chassis just either CUT position, a capacitor is in- small quantities. Brand new merchandise ... doesn't harmonize with most household serted in series with R1, increasing the current models. ORDER NOW ... at these furnishings and is too bulky to be hid- impedance of the larger section of the SLASHED PRICES! den in a convenient bookcase or radio voltage divider as the frequency de- SUPREME 576 SIGNAL GENERATOR cabinet. An amplifier is seldom mounted creases. The output voltage available RF Rangers: ó2.2u5 KC; (,50 -2050 KC; 2050.6500 in a closet or an attic because the opera- across the smaller section decreases as KC; 6,520.5 MC fundamentals. Audio: 40 cycles- - voltage output continuously variable. RF carrier mod- tor wants it close at hand where he can well. ulated at approx. 50r/, at 400 cycles. I10125V., control the volume and tone at will. The TREBLE control is a single- section, 50160- cycle. 91,2 x 8!a a ' ". AC't: 15 lbs. o K21667 Was $67.57 Nc.. $47.77 -H 20/450V t518 8+250-300V SUPREME 561 AF -RF OSCILLATOR 5 types of signal output; variable audio 15- 15,000 50µµ1 TREBLE 651_7-GT '55 .1 eye. Unmodulated RF 65 KC -20.5 MC. Variable audio II « o 6J5, 2 5 .05 1.005 .OS modulated output 10410 , I ; frequency modulated 90051 30uut RF. 1511 a IO2 x 81/4. Wt: 33 lbs. x,Al VA O REI PU -io K21717 Was $133.87 Now $91.77 30uuf TUNER Ap TRIPLETT MODEL 3212 çPU LOAD 4)0x .0001 COUNTER TUEE TESTER RES Sockets for 4. 5, 6. 7 -prong large and small, 8 -prong II octal and !octal, 5 -prong bantam, - -prong miniature 3.64 2.2, J.20 5 and sub- miniature. Full range filament voltages: T25V 0-. 7511. 211. 411 .512(2.5(3.31516.$17.5112 -6(251321501 f-o 70/85/95/100/110. 51/2" BAD and GOOD color coded .003 scale. Neon indicator short test. Illumnated toll chart. ' RI 2008 R2 5 110 60 -cycle AC. 15 x 113+ it 6 15 lbs. -V ". Wt: 3908 K21518 Was $62.23 Now $47.77 ItTAL PU TRIPLETT 2432 SIGNAL GENERATOR 104003 .041,l 6 hands: 75 K(: -50 MC. 30'4 internal modulation at Owl cy. 400-cycle audio signal at panel jacks. Excel- ® uNER T T T lent stability and accuracy. Tubes: 6SJ7, 6,15, 65(T. FLAT1 RCUTI7 Rr-4 BOOST J VR. 150.30. 115 -V.. 50/60-cycle power supply. 10 a -Ml1r III x 614". \\'t: 16 lbs. FIL PINS - 6SL7- GT:7- 8i6J5:2 -1 R3 2008 72nC0-AxCABLETOAMPL K21507 Was $66.15 Nov $44.77 This amplifier control unit, with its five -position wafer switch. When this TRIPLETT MODEL 2400 volume and equalizer controls, is on a control is in any BOOST position, a small VOLT-OH M -MILLIAMMETER 10 x 4 x 23 -inch chassis that can be capacitor shunts the highs directly to DC sensitivity: 5(1110 ohms;\'. Ranges: DC V. 0 -1(11 mounted in the cabinet of a large rec- the output terminal rather than going 56125 (11500110(10: DC amts (1 -111; DC ma: 0 -11101 501250; DC micro amps 0-250: AC V. 0-I0/50/250/ ord player. Suggested by a circuit in through the R1 -R2 voltage divider. In 50011000 at 100(1 ohms/V; AC amps (1- .511(5110: Radio and Hobbies (Australia), it con- the CUT position, highs are attenuated Resist: 0- 100(114(1,000 ohms, 0 -4(40 melts; DB-10 to

-29, -43, -49, -55. Portable case 1 X 10 x S'4 shits of a 6SL7 -GT compensated pre- by a 100- or 500 -µµf capacitor across \\'t: 14 Ihs. amplifier for variable -reluctance mag- the output terminal. K21506 Wos $48.51 Now $36.77 netic pickups and a straight 6J5 The apparent input capacitance of JACKSON MODEL 643 amplifier designed with a gain of ap- the 6J5 (due to Miller effect) might be VOLT -OHM -MILLIAMMETER proximately 14 to compensate for the sufficiently high to cause high- frequency I I -key. push button selector. Volts AC and DC: 01101 losses in its plate equalizer circuits. losses when the treble control is in the 1001250150011000(5000; -10 to -14. 10 to 34, 30 to 54 db. DC MA 01111(1110(11250: 0-10 amps; 0-30001 Separate high -level input channels center or flat position. This can be com- 300.00013 mtgs. DC sensitivity: 3000 ohms/V. are provided for crystal pickup (with pensated by connecting a 30 -µµf air Portable steel case 8,2 x 81.2 x 6 ". \Vt: 8 lbs. With sel(- contained battery & test leads. compensation) and radio tuner. trimmer to the center position and ad- The BASS control is a two- circuit, justing it to about half capacitance to K21759 Was $44.75 New $32.77 five -position switch. When is in the give just enough high boost to flatten Jackson 642. same as above except 0 -1(1(1 micrnamp this meter. and 0000013f )0,0011/ 30 megs. DC sensitivity: middle position, the low -frequency re- the response curve. The 200,000 -ohm 20,000 ohms/V. sponse of the equalizer is flat. Low, resistor R3 prevents interaction be- K21653 Was $58.31 Ncw $42.77 middle, and high frequencies appear tween the equalizer sections. SUPREME 565 VTVM across R1 and R2 in series. Approxi- Operating voltages may be taken Ranges: Oil /2.5/10/50/250/500; AC IX. 0)112.511 mately 114 of the available voltage is from the amplifier, from a tuner, or 250; DC input resistance 411-80 melts; AC 20-4(1 megs. Input capacity 9 mm(d. Probe includes hi. taken from the junction of the two from a small power supply. frequency diode. Portable case 911,1,; x 45ir x resistors and applied to the 72 -ohm co- The control unit is connected to the Weight: 11 lbs. axial output cable through a 200,000 - amplifier through the shortest possible K21411 W' -:' $62.23 Now $39.77 ohm resistor. The output and input length of 72 -ohm co -axial cable ter- JACKSON MODEL 637 voltage are approximately equal be- minated with a 1-megohm resistor. This DYNAMIC OUTPUT SET TESTER cause the loss in the voltage divider 1- megohm resistor is the grid resistor ranges, lu luncti.n,s: push-button selection. Fila- compensates for the gain in the 6J5. or volume control at the input of the ment voltages . -5 to 115. Neon leakage test. Checks ballast tubes and cu ndenscr s. AC & DC V. ranges: When the BASS control is in either of amplifier. 111(11(0125015t0(I00f125(0; -u1 to -54 db. DC MA 0/1 //10/1011/.1a0 : 11 -10 amps: Ohms: (1131(1(01400.11110 / Su megs. Portable oak case 141a a 133a x 6 ". With LINEAR S -METER sel Ls ont aine) ahmm, ter battery and probes. \\'t: 18 us. A number of communications receiv- Only two resistors and a 1 -ma meter K ?1440 ti' $95.55 New $69.77 ers lack S- meters, making it practically are required for the S -meter circuit Mail Orders Only impossible for the operator to give ac- shown. Rl is the normal cathode re- curate comparative signal- strength resistor in a typical i.f. amplifier con- ports. A simple linear S -meter that can trolled by a.v.c. voltage. R2 and R3 are LAFAYETTE RADIO be added to almost any superheterodyne the resistors which must be added to RADIO WIRE TELEVISION, INC. receiver having one or more i.f. stages the circuit. Measure the voltage drop Dept. JH -9 en the a.v.c. line was described in Short across Rl when no signal is being re- 100 6th Avenue New York, N. Y. Ware Magazine, ceived. Adjust the potentiometer so the RADIO -ELECTRONICS for Radio-Electronic Circuits 65

voltage between its arm and ground is NEW FOR equal to that across Rl. When this ad- POLICE CALLS IMPROVED PR7 M * is made, the meter will read * NA TAXI CABS justment MODEL LIC zero. An incoming signal will reduce AND OTHERS the cathode current, thereby decreasing Tunes 152 -162 Megacycles the drop across Rl. This makes A nega- F. M. Superheterodyne, 115 Volts, tive with respect to B, and some cur- Tubes- 12AT7, 121 6B1 6, 1978. 355,8 35W4. $3995 2 stages high gain 10.7 Megacycle I.F.'s. Ra- rent will flow through the meter, mak- tio detector. Plastic cabinet 101/2x63/4x6 deep. Schematic and instructions. Shipping Slightly IF AMPL weight 7 lbs. higher Sensitivity 10 Microvolts or better. Selectiv- West Coast Bt 150V ity 250 K.C.'s or better. Excise Tax Reception expectancy with attached antenna Included from 50 Watt transmitter 3 miles, much farther from transmitter of more power or F.O.B. R2 308 outside antenna. Indianapolis Ready to plug in and use; 28 Watts power 510.00 with consumption. order, 0-IMA B ached SEE YOUR DEALER FIRST OR WRITE rest C.O.D. R3 500 APPROX DELUXE CA -2 COAXIAL RADIO APPARATUS CORP. ANTENNA 303 FOUNTAIN SQ. THEATER BLDG. FOR BEST RECEPTION -LIST INDIANAPOLIS 3, INDIANA ing it read upward. Sensitivity can be controlled by adjusting the arm of FT -237 MOUNTING -For BC -601 and 603's. and for the potentiometer. Values on the dia- SUMMER SPECIALS: 11C -589 and 683's. Prices: feed -$7.00; New ....$9.95 ON -45 GENERATOR only. Used LOG gram are for an i.f. stage using a 6K7, MP -22 MAST BASE Slouuting kith LEG and SEAT ASSY. 1' /Haim Gen. 2.75 action and wonting bracket voltage t spring CRANKS }' /Iland Generators, ea. .75 6SK7, or similar tube. The for Insulated at top to receive MS -53 Mai l below. the bleeder should be taken from a 150 - Section listed Mast Base 311' - 22 SELSYN TRANSMITTER & only ... _ _ 52.95 INDICATOR SYSTEM Ideal as radio beam position Indi- volt point in the receiver. MAST SECTIONS -For above MP -22 cator for Hain. Television. or r Base. steel, copper coated, ('am tubular mercial use. Completeplete with 5 Inch palmed In 3 foot +renons. Bottom sec- 1 -82 Indicator. Autosyn Trans.. 12 tion be used NOISE LIMITER 3le4-53 ran 10 make any CO UNUSUAL Volt cycle Transformer, 1 Wir- length. SIS -52 -1146 -Lt for laper. ing instructions. Price The plate and the maximum Screw -in IYpe. Any section current -frire N I :N' $7.95 signal level of a pentode are controlled 501 Ea. PL- 118 I'1.1'G f /1 -82 SI.00 TELESCOPING STEEL ANTENNA by the screen -grid voltage. This action i Three sections 94 long. Telescoped 40'. DYNAMOTOR -t'ee your electric Size: is to S.. Price 51.50 shaver In vuur car: Dynamotor will is used in a novel noise limiter described supply 110 Volt 100 MA from 0 VIII' and will operate mon types of in The Short Wave Listener (London). COMMAND TRANS. AND RECEIVER TRANS- AC-DI' shavers. Normal FORMERS operation -110 Y.A.C. 60 CYCLE INPUT 12 VUC input: 220 Volt 100 SIA output 51.95 The circuit shows a 6B8 as a combina- Output: eeo.o.000 V.A.C. at 250 MA. 12 V.A.C. at 3 source, mos.; 12 V.A.C. at 3 amps. & 5 V.A.C. at 3 amps. tion second detector, a.v.c. and : IIEH -I06 $6.90 DYNAMOTORS: first a.f. amplifier. Output: 250.0 -250 V.A.C. at 60 MA. 24 Y.A.C at 6 INPUT: OUTPUT: STOCK No.: PRICE: amps.: 6.3 V.A.C. at .6 amps. :I0:11 -1n9 .. $3.00 9 V. DC 450 V. 60 MA I) 9450 53.95 12 V. DC 220 V. 100 MA D 402 3.95 8+250V MOTORS 12 V. DC 940 V. 200 MA D 901 '7.95 6 or 12 Volt AC -DC Heavy Duty reversible Motor with 28 V. UC F/SCR 522 l'E 94 7.95 5/16'' a 7/16' shaft. Price: New $2.95 12/24 V. DC F/No. 19 MARK H P/S a3 9.50 6 Volt AC -DC Motor -Ideal for auto Alno, modele. etc. 13/26 V. DC F/BC-645 l'E 101 2.95 Shaft 4- x ?4'. Used -Tented $1.50 12/24 V. DC 500 V. 50 MA D 0515 2.95 Model Motor -12 Volt AC -DC 54 double end shaft Motor. 28 V. DC F/Comm. Re- Size: 21/2° L. z 254 W. x 154 H. Price $1.50 ceivers DM 32 1.95 14 V. DC 230 V. 100 MA DM 20 3.95 110 Volt 60 cycle, Ball Bearing Motor. spores. 3500 12/24 V. DC 990 V. 200 MA- R1'5I. 1'2.5 11.1'. Shaft: z and 220 V. 100 3/16' %. Motor size: 654 MA L. x 4' I1. Concerted 3) 104 9.95 13pe. Price $2.95 28 V. Hand Tool Motor -12 Volt At' -DC -5600 RPM. L. DC 400 Cycle Inverter MG-149F 3% fRernnditlnnedl 14.95 x P.' I)la. with aplined shaft s/. D. z 34 L. tarier $2.95 211GI SELSYN MOTORS-WITH CAPS: Can be used as position indicator for antennas; 110 Volt 60 BLOWER -110 Volt 60 cycle. Intake. rwle. 4 2' outlet. Ap- with instructions. Normally operates from 57.5 Volts 400 prox. 100 cu. ft. dis. Motor size: x 3'-1750 RPM. 3 cycle. frire per pair $3.00; Price-Caps only, ea. .. 50e Price. Pew. 58.95. PrIre -Motor only $3.95 SELSYN :C.7ß248 -115 Volt AC 60 cycle. Size V 314' MISCELLANEOUS: 5147. l'an be used to turn small antennas or for position Coaxial Cable -125 Oil SI Cotton covered -50 Ft... $1.00 Indicator ,Valens. PrIre per Pair $5.95 Coaxial Cable -72 01151 Rubber r sere l -8 Ft... .50 Cable }'t -4 Cond. Ruh. covered. shielded 50 2.00 TRANSFORMERS -110 Volt 60 Cycle covered Primaries: The screen voltage is supplied by a Wire-2 Cond. Rub. :14 stranded -20 Ft 1.00 Sec. 24 Volt 2 amp. .52.25 FL -6 FILTER 12000 CPS 1.75 See. 14 -14 or 28 Volt 7% or 15 amp.. . 4.95 voltage divider consisting of a 240,000 - -17 ...... Tr or 3 for BC.223- PrIre. New 4.50 Sec. 12 Volt 1 amp 1.50 Cable for RC -2'23 w /l'L40 earh end . ... 1.75 ohm resistor and a 500,000 -ohm potenti- Ser. 24 Volt 1 amp...... 1.95 Cable for BC-375 w /PL -6I each end 1.75 2e .5 2.5D 1.50 ometer. This control can be adjusted to Cable for Tr'S }31/61F'7, 63E10, or 65Fl3 2.95 Sec. 36 \V.A.C. -. A. 2.95 L1' -LIA Loop-l'Are. Lased 3.95 0 VCT- 60 SIA 6.3 5 5 \.. 3 amp. 2.45 a point at which noise cannot exceed Pings for LI' -21 Loop -1I. -112 or IT..I I' 1.00 71a1 VTT- 00 MA 6.3 V. 4 atop..amp., 5 V. 3 amp 2.95 CU -365 Cord for LP -21 Loop .. 1.50 s00 VTI' -2n0 SIA the signal level. 6.3 V. 6 amp.. 5 V. 3 amp... 4.75 Address Dept. RE Prices-F.O.B., Limo, O No 25% This circuit can be applied to other Deposit on C.O.D.'s Minimum Order $200 tubes similar to the 6B8 and to sets with 132 SOUTH MAIN ST. a pentode first a.f. amplifier. FAIR RADIO SALES LIMA, OHIO

WHERE RADIOMEN MEET, EAT and SLEEP l',sit the FAMOUS FIESTA LOUNGE OT.E L RAND Renowned for Fine Food Atlantic City's Hotel of Distinction The Ideal Hotel for Rest and Relaxation Beautiful Rooms Solt Water Baths Gloss inclosed Sun Porches Open Sun Decks atop Delightful Cuisine Garage on premises. Moderate Rote Schedule. OPEN ALL YEAR Exclusive Pennsylvania Ave. and Boardwalk AUGUST, 1949 661 NCw Patents BANDWIDTH CONTROL pose. The circuit shown here gives faithful integration and far more output thar is possible Patent No. 2,464,125 with the more simple R -C networks. Harold G. Fisher and Eugene O. Keizer, Because of a relatively large value for R, the Princeton, N. J. output current through capacitor C is nearly E /R, (assigned to Radio Corp. of America) that is, practically independent of frequency and output impedance. The voltage across C is the Described here in connection with an i.f. am- integrated response of the input voltage. plifier, this electronic control varies bandwidth A resistance- capacitance network is added at the out- of an amplifier while maintaining a flat response. put. This makes possible a grounded output which The reactance tube is connected as an artificial is convenient as well as extending the range of inductance to couple two i.f. stages. the integration. HIGH -EFFICIENCY MULTIVIBRATOR Patent No. 2,465,249 Cyril E. McClellan, Catonsville, Md. (assigned to Westinghouse Elec. Corp.) A conventional multivibrator is a very ineffi- IF AMPL cient device. An input signal causes one tube to conduct and . blocks the other. At the end of IF AMPL the short pulse the first tube returns to cutoff. and the second passes current until the next pulse is applied. Usually this interval is much greater than the TG duration of the signal. The second tube contributes no useful power ; yet it conducts al- 1 most continuously. 5+ This patented improved multivibrator also uses W I T H T H I S M O D E R N two tubes, but both conduct only during the exist- EFFECT OF COMPENSATION .0 ence of the input signal. Then both go back to L ALONE EFFECT SERVICE UNIT OF their normally blocked condition. C Battery B biases both tubes to TELEVISION and FM radio present unlimited cutoff. A positive BRAND WIDTH CONI input pulse unblocks the left -hand tube, allowing opportunity for service PROFIT . . . your current to flow FRED through the windings of T to the profits and service require the best equip. cathode. As the abrupt flow passes through R. the ment ... SER -V -LUX. When the bandwidth control (see figure) is set %$Custom built instruments avail- near the grounded end, the gm of the reactance is able for oll types of service ...or, tube high. This results in a higher Ip for a given Eg and is equivalent to a lower effective L unit can be supplied with blank and more loading across this effective inductance. panel. The lower inductance increases the coupling be- Write for bulletin D tween stages. but the double -hump response does not appear because of the added loading. SERVELUX The bandwidth variation is also accompanied MANUFACTURING CO. by a change in mid -frequency. As the value of L 391h and Buchanan A.e. is decreased, more of the higher frequencies are GRAND RAPIDS, MICH. passed. making the center frequency higher. To compensate for this undesired condition. the gm of the following i.f. tube (of which the grid is shown) is also controlled. As the bandwidth potentiometer is set near the grounded end, the gm of the i.f. tube is increased. Due to Miller s effect, the capacitance C voltage drop is transmitted through C to both input of the tube rises thus restoring the mid -band frequency to normal. control grids. This voltage being positive, both As the potentiometer is rotated to the negative tubes are saturated. When this condition is RADIONIC terminal, bandwidth is decreased, loading reduced reached, capacitor C begins to charge; a negative riarldl t16 Rada rtAtse s%dUACCLaAr S'KlJQ Ito maintain the flat response), and the input charge collects on the grid and both tubes are capacitance to the following tube is less, thus quickly blocked, ending the cycle until the next maintaining the center- frequency value. signal arrives. Transformer T accentuates and sharpens the BIG pulse currents. INTEGRATING CIRCUIT sq. in. 61 Potent No. 2,463,553 WIDE -BAND AMPLIFIER Raymond C. Olesen, Altadena, Calif. T.V. Set Patent No. (assigned to Consolidated Engineering Corp.) 2,460,907 Alfred C. Schroeder, Feasterville, Pa. $169.50 Integrating systems are pulse -shapers used in (assigned to Radio Corp. of America) television receivers and various pulse circuits. In An this circuit one is used to convert a voltage pro- excellent i.f. or r.f. amplifier, this 6.16 21 tubes Incl. 10" tube. RCA lic. picture portional to velocity into one that is proportional amplifier is especially effective as a first stage Notionally Known Nome. TERMS: 20% to amplitude. because of its low noise factor. dep.: Bal. COD; FOB Warehouse. The first triode is a cathode follower. The FEEDBACK LOOP second triode is used as a grounded grid stage. EQUIPMENT This arrangement is slightly different from the RADIONIC 1F- "cascade" which has the first stage connected with its cathode grounded (RADIO -ELECTRONICS, Tribune Theater Entrance October, 1948). The advantage of the cathode

170E Nassau Street t t New York 7. N. Y. follower is that the input capacitance (Ci in WOrth 2 -0421 :: Open daily 9 to s-- Saturday 9 -5 dotted lines) is reduced by feedback. This increases the gain bandwidth product of the ampli- TODAY fier. An r.f. choke couples the stages. This choke, MAIL ! ! with the distributed cathode -to-ground capaci- E 0Et a A aTs o e l tance (Cg), forms a resonant circuit. thereby F Unbeaten improving gain and signal -to -noise ratio. The out- GTT CASIoBs B+ S ot 11 Prtce. t tos Sound or seismic waves are conveniently de- TeerWp ,- 1,.y. 1 CO ¡, N. Y. ¡ tected by a magnetic type of instrument which R-- EQUIPMEeu rK t may consist of a fixed electromagnet with a wind- Street. T gareain RF OR IF -,.m,tofilC ing at the poles. The coil support is made so Nassau Part, STAGE Sets, heavy that it cannot follow the motion of the ,1-,01. eltpO t rush 1aYtt electromagnet. Therefore a sound or seismic wave Accessories. will cause the electromagnet to vibrate, but the Catalog it 1 Tusess4 ...... coil remains relatively stationary. This results in ...... an induced voltage in the coil. Its output is pro- NAME ...... , E..... wave. ADDRESS...... _ -- portional to the velocity of the Often the required response must be propor- ...... - iv tional to the amplitude instead of velocity. An s CITY . , ' integrating system can also be used for this pur- RADIO -ELECTRONICS for New Patents 167

put transformer, tuned by Co to the center of the REMOTE -CONTROLLED passhand, is shunted by a resistor to lower its SELSYN Q for wider band response. Patent No. 2,462,117 The total amplification is nearly equal to that Ward C. Mikkelson and Jacob Anches, of a high -gain pentode stage. Stability, band- United States Army width, and noise factor are better. (may be used by the U.S. Government without royalty payment) CRYSTAL OSCILLATOR This is a telemetering system for transmitting to the modulator of a standard radiotelephone Patent No. 2,459,842 data by radio from one Selsyn to another- transmitter. George T. Royden, S. Orange, N. J. The output of any Selsyn is composed of three At the receiving end, the audio signals are sepa- (assigned to Federal Tel. & Radio Corp.) a.c. voltages, the amplitudes of which vary with rated by resonant circuits and are rectified and In this two -stage oscillator the plate of the the instantaneous position of the stator. In this filtered. The respective d.c. signals control sepa- second tube feeds back to the tank L along two paths (A and B). A feels to the first grid. This XMITTER RER. AND FRIER is positive feedback because the second plate and the first grid are in I hose. Path It feeds back 1 voltage which is out of phase. The negative feedback is made greater to keep the circuit from I17VAC RECT.AND FILTER OD, --4 XMITTER oscillating. A crystal is connected in the negative-feedback path to form the equivalent of a high -Q series resonant circuit which bypasses the negative. REMAND FILTER

PATH A 1 IADIO OSC. AlIaOOSC.I 1 u RECEIVER RESONANT CRC. r--I RECt.AND FILTER AMPL 1

- RCVR RESONANT CRC. REC.AND FILTER

IIHI RESONANTCRC. REC.AND FILTER AMPL 1+ I117V/60NOSC.1

PATH El feedba k voltage to the cathode. Therefore, at the crystal frequency, there is no negative feed- system the Selsyn output voltages are rectified, rate outputs from a 60 -cycle oscillator. These back and the circuit oscillates only at this fre- filtered, and used to control separate audio oscil- three a.c. voltages are proportional to those quency. lators. As an example, these may generate 60, obtained from the Selsyn at the transmitter. After The crystal stabilizes the circuit and compen- 120, and 240 cycles, respectively. The amplitude amplification, they are fed to the second Selsyn sates for temperature and load variations. Tank of each will depend upon the Selsyn output which which will assume the same angular position as L is tuned approximately to the crystal freuency. controls it. Each of these audio voltages is fed the first.

FISHPOLE ANT. For Your Mobile Rig! .. FILTERS & 7,ucadrvl (,.ax ter_ HiGain LINE DIE 100 Amp W /2x5 MFD 511V , I L L. Or Dlrul.E. 11 iF're,l tonal 74" wnln d,alÌÌV Pt ó11d 12^ Dyn filled cond. 110 VAC. DC $1.98 An^enna. wf AT5 /ANI(. FILTER DUAL 1 KW Ma y Use ;. /w gack. Mike 49 Clean p your 11CI A TV1. Ease 11 3 for flange. F^r M W:: BAND PASS FILTER 49D11T uee.lew: 51.29 e Xfmr Mount. Uses 4 -.0112 Condensera L -DNAND :0473. Sharp band pass a: 1011 , .. S4. 25 3 for 61.39 1`1.259 for above 3Sc peaked UTC/ Su Fe F. w /,bmg. and cond. Complete.. Bandwidtll: 650 cycler at 20 db. down Flee, twdg. nuns peak. 111211-hr high Impedance. Ca0 600CTS. 000 METER 4K.V.. 0-1MA MOVE ohms tapped Roller smith T.D.Ñ. w /External Itcsis TRANSFORMERS be plugged into 'phone output of reteint S0a150 Rand. 31/2- rd. bake. case. for total results. Cute out 01111 o hms. Fully Pria $7.95a J AND New, with circuit diagram 52x00 Shielded. He FLEXIBLE SHAFT CHOKES Std.... 59c lIC4mÌ M. h nvYttiml 'lm' p rcable 1159 60 cy. INPUT * ** SPECIALS * ** 1 olio:. {4.S0 á3.95 Equip. Conservatively ¡Wed ELECTROLYTIC CONDENSERS D.T. TYPE TUBULAR. PRONG MOUNT. LUG TERM. ROTARY BEAM COUPLER FILAMENT TRANSFORMERS 18e so. 10 For $1.75 ale Coupler: 3000 Rotation: 1 Turn Coupling Link. Case i'eieo $2.95 5Y /6A, 53.25 2.SVCT /6.5A 33.25 MCD. VOLT M.D. VOLT Matir Mount on Side, o. 1.35 404-40 ISO I...3VCT% A, 0.3C7 /2A 2.45 4o 200 iO4-20 130 Kit Lugs- 6,11au Radio Trie. 1D0 For 31.00 1-50147- 0.3VCT /IA, 6.3V( T 7A 300 Kit Lups -Large Radio Type. 100 For 1.00 2x0.:19/1A. 2.75 20 Kit Trimmer Condenaerc -Wax used ae S ple kit of $1.93; 8V /1 . A 2.75 ] 10 3000 15123- 6.3V('T /SA. 6.3V/1A 20,10 150 10 200 famous cmwlenser Cu. Some list for 52.50 ea. 3.25 Special. 1011 Pea .95 1:5127-8.3vCT /3.2 A. 0.3VCT /IA 2.25 30.30 450 1.50 1 6.59/8A. 5V /3A. 40}40 25 40 Kit Ferrule Res,. -Ideal for Experimenters. 10 For F'-2.59/.75A.7414- 0.5 /.6A 3.95 K it Rotary Swdehes- Includes 2 and 3 gang. 10 For 2.95 2x2.5VCr /1I.5A, $3.25; 6V//2.5A 7 40 400 40 1SÓ 1.95 :.3VCT /7A. 6.3VCT /5A. SVCT /BA, 386.39/.6, 6..3 3.95 SO 200 40/20 150 Kit Volume Controls -50 to 2 es. 10 Far 1.38A-63V/2.5A. 2.2.59/7A 3.25 2.10 150 Kit iatntob C Single Duals and Tholes. 1112- 282.5VCT/6.5A, 2.5V /0.SA 2x20 25 2x40 150 F., 1r 1.00 4.25 304-15 150 Pea. New, unused .95 kit,t Fuse and ferrule Clips. 20 For...... 1.00 PLATE TRANSFORMERS Kit Coil and Choke -10 R.F. eons .90 assorted and 1.00 1'410- 8OOVCT /4OMA, 700VCT /500MA 56.50 29e ea. 10 Fer $2.75 Kit Cod Forms-Tnd'd H.F. 50 For .;!.OV /SOMA. $4.99: 709'1A 2.25 210 300 15 -15/20 250/2S Kit Power Rneostats-25 and 50 watt. 0 For 3.9 ''113- 310VCr /150MA. I5.,1CT /15MA 3.00 225 I5 10 -10/20 Kit Vitreous WW Ress. -20 For 1.00 42- 600VCT /0100A 25IV('T /.077A 2.95 20/30 350/25 3x10 150/20 1.485- 102(1VCT:40OMA, HE. In 11.95 20/30 250 3xs 6494- 2.2009 /350MA, 2.209/.01A 1.95 2s30 15050 1 525 2.150V /94OMA. 54.50; 24dVCT1830MA 30.20 150 15 450 POWER SUPPLIES 3.95 30/20 350'25 10 450 10/60/100 450 100 /50 20 529 COMBINATION TRANSFORMERS 15 -I5 /20 350 25 80 150 BASIC KITS 780V /600MA. 0.3/2, 53.95; 825VCT /19OMA, 15 -15/40 15025 40i204-20 150 SVCT /3 25 -25/10 25 350 40,20 150/25 S aa,e d S. TV pwr. Supply Trans. 53.95 20-20/10 50,400 25 200/25 3 contains 111- 21t30OV %CSiiA, 53V' I SSMA. 43V /3.55iÁ 0 1 ONO V /55MA. 6.39/1.2A. 0.3/1.2A. 2 -.1 MFO 48(1VCT 3.9S 40 30 2500V. 2x2 Tube. Socket. 1- 100000 ohm Steals. ItiO8- /1 SOMA. 59 3A. 6.3V /6,25A $4.2` 2x20 150 10 !31- 585VCT /AOMA, 5V /:JA, 6.3V /OA 3.95 50/100 330,100 /SO /'rice ...... $7.95 . 20 20 00 25 10.10 -10 25/150 -150 Basic S. a .). TV Power Supply ntalna Trans. 055- 525VCT /75)4A, 5V /2A. 6.3/1.8. 1OV /2A 4.45 10 -20'20 350 25 16 'I 102- IOBOVCT /SSMA, 0.3/1.2. 6.3V/1.2A 3.95 450 23011/4MA, 2.5/2A. 2 -IMFD 7500 Pyr., 2x2 I1VCT /I55MA, 6.3VCT 10 -15.20 350 25 20 350 Socket. 8.95 /5A. 5VCT /3A 3.95 15 250 B as,cl'15 1ewe. Sup ($00-2x1 1 OVCT /.OI A. 039 / t A. 2.5VCT /7A Walt P y contain. Tram. n.3VCT /IOA. 05V- 100V -40V.I .50 6t111VCT /.155MA. 6.3V /5A. 5V /3A. 2-7MFD 00ÚW. SVCT. I 8,69.6.39./.1A 6.25 SVCT /3A, 580VCT /.04A. MFD. VOLT PRICE MFD. PR Dual Choke. 1007 200MA. 5T4 Tube. Socket. 0.3/1.25A $2.95: 40V /.OIA. VOLT ICE prim 5.75 . 25 - - . 1.95 310/10 490 9.69 290 20 300 SO S .79 TI Ú0- 112OVCT /77OMA. 500VT /.o82Á. NV. INS 12.50 3x10'20 400 25 .69 150-20 6 25.50 .9 B asic I)SO Supptyn C570- 24V /0OOMA, 770V /.0035. 2.SV /3A. 80 40 150 400. 50 1.10 120-60.20 150/25 .49 Watt Am liDUalr.i co ains. Trais' T37A-2300V /.0I14Á. 11V. INC. .25 60 7MD 000V, 5T4 Tube. Socket. Price 10.75 2.5/2.A. HT. INS...... 7.95 2x80 250 .85 3x20 50 .69 ('300- 64OVCT /.OSOA. 5VCT.3A. 0.3VCT /3.2A 3.95 ISO -SO -2S 1S0 .49 3.20/20 450.25 .39 1510M COMPONENTS 20-10 50 450 50 .49 20-8 25 50 25 9 2x2200 400 25 .59 0-20 20 450 25 .69 Transformer -3000 V /IMA. 72OVCT /200MA. 0.49/ FILTER CHOKES 40 -20.20 400 25 .59 40.10.10 450 .98 .:A. .4V .6A. 5V 3A. 1.259/3A. Full Power 40 -40:25 00 25 .59 40 40 25 475 400 'SO .S9 Packet for 5" and 7- Scope Supply. Special 6.95 2511Y /65MA. 00; 1 SI tti; SOMA.... . $2.50 40 -10.50 450.150 .89 40 20 25 50 50 .89 wing 15.29119, I50MA. 53.25; 8.5HY /125y1A 1.50 40_40 -10 450 .69 40 40 16 Transformer- MI /00V /5MA for 10- and 154 $10.95 Dual 7111' /75MA. IIUY /65MA 450 400 350 .8n Deflection Yoke for n 12- Scope Tube. 1.85 40-30 -10 450 .89 4x20 1 .10 Fully 7111Y'140MA. $1.60: Dual ' HY /1011MA .75 50 cased. Ray 20A...... 3.95 Duet 3.15 -30 300 .69 2x30 -15'20 400'25 .59 2.SITY /13011A. 51.25: 116HY/150MA .25 3.30 20.10 450 1.10 30 -15 -10 20450'25 .89 Deflection Yoke -Same as atwve Pnlleo - - - - - . 3.95 I ffl' /2.5A. 61.45: .3509 350MA 7.25 Focus Coil for above WE D- 164915 .25 Dual :511Y /38OMA. $1.00; 511Y /40MA... .55 mocking Oscillator Trans, -15000 cy. Horizontal /17MÁ. SEND FOR LIST OF MANY OTHERS Ratio. 2:1 Freed ...... 85 100v /20MA. SAM SHY/200MA 1.65 Stocking Oscillator Tram. -0318 l':1 :1 1.50 2.11-11. /200MA. 51.20: 2x2 211Y /.55A .... 9.95 MU Kf4CATa0N m N'Nq BlockinqY O.cillator Trans.-TUma Ratio 2 1 1.75 2511v.7511A. U pulse Tran . -Rae Ix A002 2:1:1 1.79 $1.10: 2011v'300mA 7.95Ì,1A" iá1 ïiiiirlf DT.wr sweep [ 0 Ir E PM A N -fr NEY9TORK7. 1V y 80ry4t Cooke -311Y :í551A 250 ohms. 2 for. .75 WRITE FOR LISTS OF 91014 MANY OTHERS u5 OMPANTY .. ..a ,.,:A!é,,Lr,w .." WRITE FOR FLYER OF OTHER BUYS

AUGUST, 1949 Try This One

INDOOR FM-TV ANTENNA 11 An adjustable indoor antenna for i6THE BARGAIN CORNER MOULDED BAKELITE CONDENSERS- notch be - TELEVISION TV and FM reception can con- assortment f 00001 to .25 odd.. 200.0Ú0W\' Sies mold: pigtail leads. Shpg. wt. 2 lbs. $2.49 structed, as shown in the photographs, KIT lie' 10 ASSTD. .. SETS of surplus an- WAFER SOCKETS-4 to prong. kit of 12 asst!..25 from a pair collapsible KNOBS Selected Bakelite & Wood; including PARTS tennas and two brass ball- and -socket set -screw, poshsn & push -button types. Kit of 2.7 asstd. 98 fittings. Each half of the dipole is made MICA PADDERS & TRIMMERS -Includes mul- ACCESSORIES liVle & ulic base Upes. Kit of 1", 69 from an antenna adjustable from 10 to VOLUME & TONE CONTROLS -Wire wound & . I.49 WRITE FOR FREE CATALOG 18 39 inches. The dipole is 81 inches over- carbon. leso switches. Kit of 111 asstd. HERE ARE SOME OF THE SPECIALS all when extended; 24 inches when telescoped. It can be adjusted to cover W -IIOB ARMY FIELD WIRE-Twts 11 p.úr. TRANSFORMER only in 300 -460 TELEVISION all frequencies between channels 4 and rather- proof. Acail. rolls rte. ft. ea. Rhpg. wt. 1 lbs. /Ire ft. a STEAL AT 2.1. Pri. 115 Volts 60 Cycles Sec. 2500 Volts @ T -30V THROAT MIKE with runner cord & 13. Fully extended, it gives good results NOW ONLY 1.90 2 ma.: 6.3 Volts @ .6A.: 2.5 Volts @ I.75A BRAND NEW! on all low-band TV channels. 8 for 1.9 Small site -brand new PRICE $3.85 plug.THROAT MIKE CORD & SWITCH lI lt- 08A1 . s'y ft. rubber cord. 1.1.11M & JK -48 lark, 490: 6 for 2.49 SPECIAL! TELEVISION I.F. RADIO HARDWARE TREASURE -A FULL POUND of Screws.s. Nuts. Washers. TRANSFORMER Logs. etc. All in HANDY SELF-SEALING MINCED -LID METAL CAN. Slips. wt. 2 is a transformer consisting .a77LIaá. Here shielded lbs. .. _...... of 2 slug tuned coils, 4 ceramic con- !!SPECIAL!! -11/4 VOLT BATTERIES -Std. 2 pin osoket. Volts & Amps. GUARANTEED! Intl! cur- densers, 3 mica condensers and two re- rently dated/. 37k'x2ht' sq. PKGE. OF 5 sistors resonating at 21 -29 MC. May be (dtpg. wt. 8 Ins.t ONLY ... 590 RADIO NOISE FILTER- l'reclsion engineered. ivy. converted to Television Video or Audio LF, duty, capacitive -Inductive type. REMOVES INTER- Transformers or disassembled for use in FERENCE FROM MOTORS, SHAVERS. LAMPS, ETC. Shock- proof. Bakelite rase. c':i, -Y3% : shoe. the TVRF section. Housed in regular I.F. wt. 2 lbs. -Special ...... $2.95 can. Rush your orders! Price $1,15 BENDIX AMPLIFIER (Line of SiShtt -A "TREAS- URY OF PARTS. Contain..: power trans.. b oil 5 TUBE AC /DC SUPERHET KIT condensers, 3 au Bos, socket, eta. etc.. worth many lines the price. Black crackle case 7''x544'x4'. Shpg Beautiful Catalin cabinet with complete t. S Ihs.- REDUCED TO 8í75 CABINET DRAW SLIDES -ter CONSOLE CHANG- parts and instructions fo quickly and easily ERS. RECORDERS. TRANSMITTER RACKS. make up a sensitive 5 tube AC /DC super- DRAWERS OF EVERY TYPE. Smooth hall -hearing action: steel & alum lnum construction. Shpt. wt. 2 lbs. heterodyne broadcast radio. Plenty of vol- per pr. ume with good tone quality is assured by extension 113' overalls $1.89 pr. 11' extension 11 overall/ 1.98 pr. the beam power output stage and the PM 12'4 extension 116'.4 overall, 2.19 pr. 2.75 pr. Dynamic speaker. }Ivy. duty. all- steel. 12'4'/18'i' - - All material including tubes are furnished up for less than half the cost of the built "FACTORY SPEAKER REPAIRS SINCE 1927' radio. Nothing else to buy. Tubes used .i all CODa are, 1- 12SA7, I- 12SK7, 1- 12507, 1 -50L6, RADIO CO. I -35Z5. Powerfully sensitive built -in loop 6 Dey et.eetY included. Price including all tubes and o NE Catalin cabinet. $11.95 Loo 3 WAY PORTABLE KIT The antennas used are commonly GOVERNMENT SURPLUS! 5 Tubes plus rectifier provides high sensi- available on the surplus market. How- tivity and excellent tone, even in remote WORLD'S LOWEST PRICE not col- areas. Beautiful 2 -tone brown leatherette ever, if these are obtainable, covered cabinet with plastic front grill- lapsible automobile antennas can be work and slide -rule dial. Light and com- used. The ball-and -socket fittings, pur- pact- operates from 110 Volts AC /DC or chased from a hardware supply house, batteries. Superheterodyne circuit -built in are similar to those used on some types loop. Tubes used: I -IR5; 2 -1T4; 1 -IS5; of casement windows. We used hard- I -354, plus reef. Complete with all parts wood for the base. Any insulating ma- COMES COMPLETE WITH and diagrams, less tubes and batteries. EDGERTON terial will work just as well. The un- FLASH TUBES Extra set of 5 matched tubes, 53.75 4 for derside of the base should be covered & REFLECTORS Price $13.75 EASY TO with a layer of felt or fitted with small CONVERT INTO rubber feet. A 2 -WAY PHOTO Model NFRD -Radio Noise Filter FLASH UNIT If it doesn't work, send it back!! EUGENE JACONETTI, OPERATES ON 110V. AC & 12V BATTERY We absolutely guarantee that our model Brooklyn, N. Y. Brand new at a fraction of origina cost. Contains NFRD will eliminate all line noises when finest component parts available. All necessary indu. Aft r to radios, television parts and complete instructions properly connected TV -FM INSTALLATION NOTE conversion, works on 110V AC or CC Q. sets, motors, electric refrigerators, electric 12V battery by a flick of a switch. two shavers, vibrators, oil burners, transmitters It is not always possible to provide Immediate delivery on all mail orders COMPLETE and all other sources of interference. This adequate support for ribbon -type trans- CINEX, INC., 165 W. 46th St., N. Y. 19, N. Y., D.pt. REO unit will carry up to 12 amperes or 11/4 mission line running to FM and TV KW of power and may be used right at antennas. Consequently, the line whips the source of interference or at the radio. in the wind and causes a type of flutter Small size only 3" x 11/2" each $1.95 interference that affects TV pictures HEADQUARTERS FOR INDUSTRIAL TUBES x 71/2 ", very low priced at and weak FM signals. Furthermore, SPECIAL! SPECIAL! the continued strain on the transmis- AND CAPACITORS IN QUANTITIES 1000 Klystrons 500,000 other Mammoth assortment of radio and elec- sion line is likely to cause it to snap 5000 Magnetrons, tubes. Write for our Bulletin and Prices. tronic parts, not less than TEN POUNDS off at the antenna. These troubles are of such items as transformers, chokes, con- particularly common in installations LIBERTY ELECTRONICS densers, resistors, switches, coils, wire, where the unsupported line crosses wide 135 Liberty Sf., New York 6. N. Y. hardware, eft. A superbuy for experi- areas or hangs from the roof of a menters, servicemen, and ama- tall building. $1. LL25 teurs for only You can minimize trouble from this RECEIVER on all merchandise. source by stretching a heavy cord TELEVISION -SI.00 Satisfaction guaranteed own All prices F.0 B New York City complete instructions for building your television across the area and wrapping the line receiver. 18 pages- 11'x1T of pictures. pictorial dia- WRITE FOR FREE CATALOGUE TB The cord prevents the line grams. clarified schemed -a. 17'x22' complete schematic around it. diagram & chassis layout. Also booklet of alignment from swaying and takes the strain that Instructions. voltage & resistance tables and trouble- shooting hints. -All for $1.00. RADIO DEALERS SUPPLY CO. would normally be placed on it. CERTIFIED TELEVISION LABORATORIES 154 Greenwich St. New York 6, N. Y. JACK ROTHSTEIN, Dept. C. 5507 -13th Ave.. Brooklyn 19. N. Y. Eatontown, N. J. RADIO- ELECTRONICS for Try This One 0 69 ELECTROLYTIC TESTER A foolproof method of testing electrolytic capacitors for hum -dissipating qualities is provided by this circuit. The 117Z3 supplies the necessary power R. S. E. to check electrolytics at voltage ratings 3 inch of 150, 50, and 25. Because the 40 -ttf input filter capacitor does not supply TELEVISION SCOPE sufficient filtering action, a hum will be OZ 4's heard in the phones. To check the elec- (No Limit) Features: trolytic in question, place it from the WIDE BAND VER- Fresh RK and RCA. correct voltage point to the top of the TICAL RESPONSE fuse and plug in the phones. Keep the Standard commercial grade, not JAN's. FLAT TO 750kc .o6/600v BUY 12 DOWN 3db 11723 58C get 1 free AT lmc E C H IR 75R 20R .0/600V A VOLTAGE GAIN 0R EGG CRATE OF 100 $490° OF 20 AT 5mc l t AR -3 ',PHONES The R.S.E., AR -3 Scope has been built by $l/6h 25 .005 .1 VIBRATORS Ross Armstrong to our rigid specifications. It's o a complete unit that embodies standard hori- MALLORY universal standard zontal amplifier and sweep circuits with volume control all the way down until 4 prong, non -syn- es n normal sensitivity. the electrolytic connections are made or chronous. Can size ` i i It's different because of the extreme vertical else an 1% " x 31/4 annoying click jars your ear- EACH amplifier response. Check the featured drums. the hum diminishes ca- If the BUY 12 get 1 free specifications against others. For TV use wide pacitor is good; if not, discard it. All band response if necessary. ground returns for the electrolytics un- EGG CRATE $10900 The case is 8' high x 5' wide x 14' long, der test are made through Mr ampere of 100 i attractively finished in "hammered" opal- fuse for protection against completely escent blue enamel. Operates on PRICE shorted capacitors. RADIART 363U1 standard 110 volts -60 cycles JOSEPH SCIORTINO, AERIALS (discontinued model) 3 section -40 watts. Tubes, 311P1-6ÁC7 $4995 Waterbury, Conn. 63" top cowl, universal -6S17- 6X5 -SY3 -884. In- included. mount, 48" lead. Former $241 structions Complete specifications upon request. Solis- F. O. B. SOLDERING RIBBON LINE list $6.75. The polyethylene insulation on rib- EACH faction or your money back. DETROIT bon -type transmission line melts easily BUY 10 get 1 free making it difficult to solder joints. You $21500 per 100 PUSHBACK won't have this trouble if you wrap several layers of Scotch tape around the insulation where the connection is GENERATOR CONDENSERS WIRE to be made. The tape prevents the insulation from breaking down or creep- By one of the big 3 BELOW MILL PRICES! ing. 2,000,000 feet -tinned copper -oil 1st class, WM. GAMBONEY, .5 mfd 200 double cotton serve, waxed finish. Chicago, Ill. 15c VDC, 6" lead E A C H Available solid or stranded TV ANTENNA MATCHING STUB BUY 12 get one free 100 22 gauge (6 colors) per 1000 $3.98 A 300 -ohm TV transmission line can $12.00 per be matched easily with this method. 20 gauge (6 colors) per 1000 $4.98 Cut a 48 -inch length of 300 -ohm line ORDER INSTRUCTIONS, 18 gauge (brown) per 1000 $6.49 and short one end. Attach the open end Minimum order - $2.00. 25% deposit to the receiver with order required for oll C.O.D. ship- antenna terminals across ments. Be sure to include sufficient post- the transmission line from the antenna. age- excess will be refunded. Orders Roll up received without postog will be the stub until the picture shipped express collect. All prices Demand ihir brightens, then hold the coil in place F.0.5. Detroit. Seal of Quality SUPPLY & with tape or a rubber band. Run your KHVIV hand along the antenna lead -in while ENGINEERING CO., Inc. watching the picture. If the picture is DON'T WAIT ORDER TODAY 85 SEEDEN AVE. DETROIT 1, MICH. affected while so doing, add or subtract turns from the coiled stub until the picture remains unchanged. MILTON M. SCHUMAN, Be a "Forty-Niner" in '49 THE "FORTY -NINER" Ball imore, Md. GEIGER COUNTER PISTOL GRIP Several of the "instant- heating" soldering irons are equipped with pistol grips. Any ordinary iron can be fitted with one. Cut the grip from a block of wood to fit the hand. Use a coping saw and a file. Curve the top to fit the iron, then 11 WNW, bend a strip of light metal to fit over the J:! original handle. The Lightweight uranium detector. Detects beta and gamma rays. metal strip and a few bolts are Equipped with 36 inch search probe. Contains two 671/2 volt Minimal batteries in the used to clamp the pistol grip to the wll -known type of relaxation oscillator supply. !Oe ! 0 Weight 454 lbs. complete; sise 4"4".6". Beautifully finished case with handle. Price $89 i iron. Complete with four tubes, including Geiger tube, batteries, search probe and ear -phone. ROBERT L. HYMAN, THE FORTY -NINER CO., 5245 Grand River, Detroit 8, Mich. Kansas City, Mo. AUGUST. 1949 70 I IPIicsti011 Ii11x

ALL -WAVE RECEIVER ? Do you hart a circuit of a small, Question Box inquiries are answered by mail. Those of general portable, all -wave superheterodyne re- on this page. A fee of $1.00 is charged for ceiver suitable for phone and c.w. re- interest are printed ception? I do not want one with a loop questions requiring no research or schematics. Write for esti- antenna if it can be avoided.- E.P..I., mates on questions requiring research or schematics. Be sure to give full East Peoria, Ill. specifications and details. Due to nominal fees charged for this work, A. A four -tube, all -wave superhet was it must be handled as a part -time proposition. Therefore rapid service is interfer- used in the battery-powered impossible. Six to eight weeks is required to draw up answers involving ence locator described on page 46 of the September, 1947, issue of RADIO - large drawings or research. CRAFT. Commercial coils are used in this set that tunes from 560 kc to 18 mc. Additional coils can be added to would like to be able to use several 40- What size speakers are required. and ? Ely, TO 114 PLATE 2ND DET IN SET meter crystals that I have. -E.W.F., how shall I connect them -J.M., 1S5 ? Berkeley, Calif. Minn.

6 4 a perfect match be- enough drive for the A. Maintaining 0+ 2 A. More than amplifier and speakers at all will be supplied by this tween the push -pull 3C24's times, this speaker control system is µ A 10 -ma meter is used to meter AI exciter. designed around a heavy -duty. four - R1 and R2 are shunts to 1500K each stage. seven -position wafer switch. This of meter to 100 gang, increase the range the 1,000 -ohm resistors I N.0001 switch and the two TO1T4 GRID RETURN and 200 ma, respectively. Connect the can be mounted in a small box that can r' -*A+ meter in series with a 1%-volt battery ...12 pm/ APPROX 8F0 rheostat. be attached to the amplifier. The and a 200 -ohm wire -wound are the line -to- IG4-GT rheostat for full -scale de- speaker transformers i Adjust the voice coil type with 500- and 1,000 -ohm 470K flection. Connect different lengths of T 2 primary taps and with secondary taps i lAl l No. 28 or 30 enamel wire across the BFO CONT impedance of the voice 471( 1 to match the 1 0001 until it reads 1 ma for meter terminals coils. The speakers in the dining room BF0 TRANS S RI and 0.5 ma for R2. When the cor- I I should each be rated at 15 watts or 1 °, of wire have been found, 1 rect lengths more, and the others at 25. 2-7 I wind them around a pair of 1 -watt re- 47K I sistors having a value of 5,000 ohms or TERMINAL STRIP more. r ------, DINING R00M121 TRANS OFFo 807 should not I Grid current for the ON - -- 4 ma; therefore vary the setting AMPL ONBFO SW B+ A+ exceed of the 50 -µµf variable coupling capaci- fSEC I is not overdriven. Drive range to 36 mc if tor so the 807 increase the tuning for the 3C24's is controlled with the 10 reception. A two - you desire -meter variable link in the exciter output. gang, 35 -µµf capacitor can be connect- six to The oscillator plate coil has about ed across the main tuning capacitor wire spaced to bandspread tuning. turns of No. 18 enamel provide inches on a 1%-inch plug -in form. For reliable c.w. reception, a b.f.o. 1% A 50 -watt coil with variable link is used is needed, a of a suitable one circuit in the plate circuit of the 807. If a coil shown. A standard 455 -kc b.f.o. being type is not available, then use a can be used, or one can of this transformer -tapped coil with swinging link made from a standard 455 -kc i.f. center be in the grid circuit of the final amplifier. transformer tuned about 8 kc higher or lower than the i.f. in the set. Note that a switch inserted in the a.v.c. line SPEAKER CONTROL SYSTEM is keeps it open when the b.f.o. turned ? A 2.5 -watt amplifier is to be in- on. This prevents the b.f.o. from over- stalled in a hotel. Two speakers are to loading the detector and reducing the be used in a dining room, one in the sensitivity of the set. lounge, and another in a garden about 600 feet away. Please show a foolproof EXCITER FOR TU -10 -11 FINAL method of switching the speakers to ? Please print a. circuit of an exciter use any or all of them at will. Both for driving the TU-10-B 10 -meter dining -room speakers are to be used transmitter described in the November, simultaneously. The amplifier has 4 -, 1948, issue of RADIO- ELECTRONICS. I 8 -, 16 -, 250 -, and 500 -ohm output taps.

7C5 607 C^SMALL BOX ION COIL 2 500 The switch positions are: OM COIL 47/ W 50144f 1 -All ON; 40M XTALS OFF, and dining .005 OUT TO 36241 2- Lounge garden MICA 40uid 40K .00SMICA room ON; _T_ _T_ 3- Garden OFF, lounge and dining .005 .005.7 IOW 5W' -MICA room ON; T1100K1 Dining room oN, garden and 47 4- ISO IV/ 5W +300V lounge OFF; KEY JACK lounge oN, dining 20K 5- Garden and 100W room OFF; a' r A F B D G 6- Garden ON; lounge and dining room OFF; FILS- 7c5:1 -B; 007:1 -5 +500-600v 7- Lounge ON; garden and dining 10MA room OFF. RADIO -ELECTRONICS for Tecóuar'tes I71 .. PHONO FOR 3 -WAY SETS The conventiona, method of connecting a record player consists of providing a switch to transfer the high end of the volume control from the i.f. output to the phono jack, while, at the same time, an extra set of contacts grounds the i.f. output. However, when this method is used with three -way portables, hum and oscillation often result, particularly when the receiver is used on a.c. This effect, caused by EQUIPMENT :AND COMPONENTS lengthening of critical leads, is espe- For Better TV Performance and Lower Installation Costs cially bad when the chassis is isolated from the common negative in the a.c. Eliminate the Variables in Television Installation with position. the Transvision FIELD STRENGTH METER 2ND DET, 1ST A F Improves Inslallar s: . Sums 1!,., the Work! !

Has numerous features and advantages, including-I I I Measures actual picture signal strength !FT . .. (21 Permits actual picture signal measurements without the use of a complete television set. * * * * * * * * * * * * * * * * * * * * * * * ** * * H+ * * PHDNf1JACA ..01 *

min CHASSIS * The circuit snow,' has been used suc- * cessfully to overcome this difficulty. No * switch is used, and the radio is tuned * off stations when records are being * played. The phono jack is permanently * connected to the high end of the volume * control through an isolating network, 13) Antenna orientation can be done exactly which consists of a 100,000 -ohm re- 141 Measures losses or gain of various * antenna and lead -in combinations . . . (5) * sistor and a .01 -tif capacitor in series. Useful for checking receiver re- radiation (local * TRANSVISION Leads marked A and B should be as oscillator) (61 12 CHANNEL SELECTOR * short as possible. The output of a (7) Amplitudes of interfering signals can * TELEVISION and FM crys- be checked . (8) Weighs only 5 lbs.. * tal pickup is sufficient to override com- 191 Individually calibrated ... (10) Housed * SWEEP SIGNAL GENERATOR in attractive metal carrying case ... (11) Initial pletely * Complete frequency coverage 0 interstation noise in these re- cost of this unit is covered after only 3 or 4 from -227 MC with no band switching ceivers. installations .. (12) Operates on 110V 60 * . . . Sweep width Cycles. AC. * from 0.12 MC completely variable. . . . Ac. As there is seldom sufficient room to * curately calibrated built -in marker generator. mount the phono jack on the chassis, NEW LOW PRICE *Model SG Net 579.50 it may be soldered to the end of a short Model FSM -1, r let,' with tubes Net S79.50 * length of insulated shielded wire such * * * * * * * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * * * * * * * ** as lapel mike cable. This may be folded TRANSVISION IS NOW inside the case when not in use; all TRANSVISION ALL -CHANNEL * metal parts of the jack should then be TELEVISION BOOSTER * EXCLUSIVE DISTRIBUTOR OF covered with an insulating material. * DU MONT TV .'FM K. R. KNOWLTON, * Toronto, * INPUTUNER Ont. * * .. CABINET REPAIR * * Plastic radio cabinets are sometimes * * marred by the chemical action of carbon * tetrachloride and other chemicals which * fall on them. They can usually be re- * stored to good condition by rubbing the * marred surface with fine * steel wool * soaked in light machine oil. * PETER * WALTNER, * Hollywood, Calif. * * .... BYPASSING BAD TUBE Model B -1 List $32.50 * Model IT -1, with tubes List $59.t5 Every once in a while a customer All Transvislcn Prices ore for traded; sub;ect to change without notice. brings in a set with a bad r.f. tube for Prices 5% higher west of the Mississippi. which I have no replacement on hand. When the customer is in a hurry for his TRANSVISION, INC. Dept. RE, NEW ROCHELLE, N.Y. receiver, I remove the tube and connect a 500 -It tf capacitor between the grid Please ship the following Transvision Products THROUGH YOUR NEAREST and plate connections on the socket, by- LOCAL OUTLET Rf:-8 passing the tube. As soon as I can get a replacement tube, of course, I install it and remove the capacitor. Most re- I am enclosing 10% DEPOSIT in the amount of ...... balance C.O.D. ( ceivers will work nearly as well without 1 I went to get into the Television Business. SEND ME DETAILS OF YOUR DEALER PLAN. the r.f. tube as with it, at least in my Name City and Zone ... location. (please print) P. J. LOMBARD, JR. Address Winnebago, Nebr. State AUGUST, 1949 Aliscellrny

erators' examinations are given at intervals of not more than 3 months; or who, according to a physician's certificate, has a disability which prevents RADIO TUBES AT ROCK BOTTOM PRICES! him from appearing for examination; or a member of the Army, Navy, Air duties AM, FM, TV Tubes -c. RCA, Etc Force, or Coast Guard whose 341 KEN RADS, 49 make it impossible to appear for ex- 163 1R5 766 Best Brands ONLY 1A7GT 155 7E6 amination at the appointed time and 1H 5GT 1T4 10 each OZ4 6D6 7G7 each 1N5GT 1U4 12A O1A 608 7H7 place. 6J6 3A4 12A8GT 1LA4 6F5 7L7 The applicant would be granted a 6AG5 394 12AT6 40 1LA6 6F7 7N7 36 39 44 OAKS 5Ú4G 12646 46 1LB4 6F8G 7T7 Novice Class license upon passing a 1 LC5 43 6A L5 5V4 128E6 47 6H6 101' code test and written examination. The 6AQ5 5Y3GT 12F5 50 11E3 6J7 12A 56 will of receiving and 6AV6 6A3 12H6 70L7GT 1LH4 6K7 12A7 57 code test consist 6A8GT 12K7GT 71A 1 LN5 6SD7GT 12J5GT 58 sending plain language messages in In- 6606 77 6BG6G 6ÁT6 12SA7GT 81 LP5GT 6SF5 1297 Morse Code at a speed of 6BH6 68A6 12SH7GT 112A 1Q5GT 6SG7 125E7 78 ternational 6BJ6 68E6 12SJ7GT 117Z3 1T5GT 6507 125G7 81 not less than 5 words per minute. Each 6S8GT 6C4 12SK7GT 35W4 1V 657G 125R7 89 2A5 112 character will be formed at a speed of 65N7GT 6C5GT 12SN7GT 50135 6T7G 1223 6557 6F6GT 12SQ7GT 1A4 2A7 6U7 14N7 117Z6GT 7.8 w.p.m. and spacing between then 678 6G6 12SR7 1A6 3LF4 6W7G 2050 182 increased so the overall speed is 5 6Z7G 6K6GT 14X7 165 5X4 7A4 2051 183 12AU7 6P5GT 20 106 6A3 7A7 24A 482 w.p.m. The written examination will 12AT7 6SA7GT 25L6GT 1C7G 6B8 786 30 483 6C6 7E7 35 51 VR150 include questions on rules and regula- 12AX7 65D7GT 25Z6GT 105G tions essential to the beginners' oper- 12BA7 65J7GT 32L7GT 107 PM SPEAKERS 1258 6SL7GT 35 1DBGT ation and elementary radio theory 1978 6SK7GT 3565 1F4 10 or more Price 2C34 6597GT 35C5 1F5G ea. ea. necessary for understanding these 2E24 6U7GT 35W4 1G6GT 5* elf 1194 rules. 4A6G 6V6GT 24A 1H4G 4* 95e 51.05 01A 6X4 38 1H6GT 3* 950 1.05 The license would permit the holder 1L4 6X5GT 39 44 1J6G 2" 9St 1.05 to operate c.w. in the 3,700- 3.750, 4o $1.44 1.5e 14,100- 14,150 28,000- 28,500 -kc bands and phone and c.w. in the 145 -147 -mc 50L6- 35Z5- 12SK7- 12597 -12547 3 54.1 R 5.155.1 T4 band. Plate power input to the final ALL AMERICAN FIVE BATTERY TUBE SPECIAL amplifier is limited to 75 watts. This 5 tubes for- 51.95 4 tubes for- $1.29 license would not be available to holders or former holders of commer- Minimum order 55.00. Add Sr per tube fo orders of less than 100. Tubes may be assorted in mixed cial licenses issued on the basis of a price ategories All shipments FOB Chicago. 25 °° deposit with order, balance C.O.D. ALL MER. technical examination. CHANDISE BRAND NEW and individually boxed. Foreign inquiries invited. The Technician Class license would entitle the holder to all amateur privi- CONCERT MASTER RADIO TUBE COMPANY 1802 Winnecago 40, III. leges in amateur bands above 220 mc. The examination for this license will consist of a code test (same as for Novice Class) and examinations on BOOKLET FOR SET OWNERS radiotelephone and radiotelegraph theory and amateur rules and regulations. the first effective effort The booklet, published by Sprague POSSIBLY The present Class A, B, and C li- by a manufacturer to cooperate with for free distribution by the radio serv- censes would be called Advanced Class, the service technician in building up ice technician to his customers, is avail- General Class, and Conditional Class good will with his customers appears in able to any bona -fide service shop respectively. Under the proposed the form of a booklet entitled Your through all Sprague distributors. Space amendments, Advanced Class ( Class Money's Worth in Good Radio and Tele- is provided on the back cover for the A) licenses would not be issued after vision Service, issued by the Sprague technician's own imprint, thereby mak- December 31, 1950. Commencing Janu- Products Company, North Adams, ing it a valuable advertising piece for ary 1, 1951, valid Advanced Class li- Mass. the individual service shop. The radio- censes would be renewed only as Gen- The 5 x 71/2 -inch pamphlet of 16 man would be well advised to mail one eral Class (Class B) licenses. The pages has a beautifully designed cover of these booklets to each of his custom- present Class A privileges would be which impels the recipient to look in- ers. It is the best piece of publicity he granted only to amateurs qualifying side, where the story of modern radio has received since the advent of broad- for the new proposed Amateur Extra repair is told in language admirably casting. Class license. Qualifications for this new suited to the intelligent, but nontech- license include a 20- w.p.m. code test and nical, set owner. Beginning with an il- FCC AMATEUR PROPOSALS a written examination in advanced lustration of a 1924 radio, it shows on radiotelephone theory including tech- the next two pages an all -band receiver I April 21st, the FCC released niques for operating in bands assigned and a televiser, and describes the high Oa document outlining proposed for narrow -band emissions. degree of technical skill and large amendments to the rules governing Many amateurs will no doubt wel- amount of precision equipment needed amateur radio service. The amend- come adoption of the proposals for lim- to maintain and repair such complex ments are based on proposals submitted iting bandwidth of phone signals be- modern home electronic equipment. by the American Radio Relay League, cause they will put an end to the A picture of a large test bench, cap- the National Amateur Radio Council, splatter and spill -over all too common tioned "The Modern Service Shop Needs Inc., and the Society of American Radio on some of the bands. Phone operators This Sort of Equipment," covers the Amateurs of Washington, D. C. will gain 50 kc (3,800 to 3,850) in the two center pages; the next two detail Radio constructors and experiment- 75 -meter band; provided that the max- and itemize the manuals, test appara- ers who are not amateur operators will imum bandwidth does not exceed 3 tus, tools, and other equipment re- be interested in the proposals for new kc. A 6 -kc bandwidth limitation will quired in a modern repair shop. novice and technician amateur licenses. be effective on the 3,800 to 4.000 and The extensive and thorough training To be eligible for a Novice Class 14,200 to 14,300 -kc bands and in the necessary to today's service technician license, the applicant must be a citizen 29,650 to 29,700 kc sector of the 10- is pointed out clearly, and the low com- of the United States whose actual resi- meter band. Ten and 20 -kc bandwidths parative cost of his services is driven dence, address and proposed station are are pe- mitted in the 28,500 to 28 650 - home at various points throughout the more than 125 miles air line from the kc and 50.1 to 54.0 -mc bands respec- book. nearest point where amateur radio op- tively. RADIO -ELECTRONICS for Miscellany I7.; - . Mel al Ladders Da ugerous By W. OTIS FITCHETT*

IN ADDITION to the best-known haz- as a "short- circuiting" material. Elec- ards of using extension ladders, a t) icity rushes to ground at every op- How SENCO new one has been added. It is the dan- portunity, and always seeks the best ger of possible electrocution while using available conductor when doing so. SAVES YOUR MONEY one of those postwar, all -metal exten- A wooden ladder made of, say, dried sion ladders. Newspaper dispatches re- Poplar, has a resistivity in ohms per cently described the accidental death cubic centimeter of 5 X 1011. This is in New York of two television mechan- approximately 1.8 million trillion times Some Types at less than TUBES! manufacturing ics when their metal extension ladder the value listed for aluminum, in the cost. came in contact with a 13,200 -volt direction of safety. AL1. liltt S'rI NEW GUARANTEED! IMMEDIATE DELIVERY! INDIVIDUALLY overhead electric transmission wire. The time of ('.ARTONED: greatest shock danger Special Discount: DEDI'IT .r., arum earl. tube mkt, This is direct evidence of the extreme comes when, while standing on the 011t11110 21 or loure assorted tubes. danger of handling metal ladders, flag- ground, a human being permits a metal 19e Each 678 6SL7GT 1688 poles, or 6U6GT 6SN7GT D6 awning brackets in the vicinity h.dder to come into contact with a high - 39:44 6V6GT 6SS7GT 6F8G of exposed electric wires. Metal 57AS 6X5GT 6V5 6(8 gutters voltage conductor (any voltage above 1644 2AN7GT 6Y6G 6L5G and downspouts are also rightly ap- 50 may be considered "high" in V99 2AÚ6 7A4 /XXL 6(66 this X99 26117 7A5 667G proached with suspicion if adjacent to discussion 1. At such a time the exact 217GT 7A6 6SV7 29e Each 2(761 706 6776 electrical conductors. In the past, most specific resistivity of the metal would 20761 7C6 7A7 2A7 2SA7GT 7E5/1201 7138 ladder accidents have been due to loose 2X2 be of no importance. A thoroughly wet 2SF5 7E7 7C5 rungs -with the superstitious souls, of wooden 2X4 2SK7GT 7F8 767 ladder might prove equally haz- 6C8G 2SL7GT 7H7 12806 course, maintaining that the greatest ardous. 6 F7/VT70 2SN7GT 7K7 I2C8 6F71V1 26070T 12A111 14136 ladder hazard of all is to walk careless - Now, here are two rules for ladder 6 6R7GT 4138 12BA6 19 ly G 4C7 12E1E6 2050 under one. safety: 66SRU7 978 12817GT 2051 Three kinds of extension 12A6 4A 223 ladders are 1. If there are live high - voltage wires 12A8GT 25Z661 14F7 59e Each 12F5GT generally available at the present time, around do not use any kind of metal 27 5A6G 12116 30 25B6G 024 aluminum, magnesium, and kiln -dried Ladder. 26 32 25L6GT 11.M 36 35/51 595 ILC6 wood. Since aluminum is an excellent 2. Where wooden ladders are em- 35L6GT 2807 'LDS electrical conductor, its 39e Each 35W4 321767 ILE3 danger when ployed, store them indoors so they don't IA3 3525 33 ILH4 used in close proximity to electric power get wet. 1F4 35266 34 ILNS IU4 47 3524GT 11466 lines will readily be recognized. How- IU5 5085 43 IT4 IV 55 46 4A6 ever, magnesium is a relatively poor 2A6 57 501601 5V4G 76 56 613E6 conductor nears S1:Igo 3A4 of electricity, and might, itaDio E)írtp-Jríbe 5U4G 78 59 68666 therefore, be thought safer. Actually, 5W4 80 11723 68111, 31n 43ernsbark publications 5X46 85 604 606 the resistivities of the two metals are 5Y3G 50e Each Irith SY3GT shield) as shown below at 20° C, expressed in HUGO GERNSBACK SMIG 45e Each IA5GT 6A FSG IA6 6h86 ohms per cubic centimeter (copper be- 6AH6 6U5 665 185/25S IA7GT 6W4 ing the Founder 5AT6 114 IC7G standard, its figure is included SBA6 6W6 Modern Elletrin 1900 IP5GT 1076 : 58E6 6Y3 for comparison) Electric.' Experimenter 1918 IRS 1F4 12A 6C5GT 11146 Radio News 1910 IS4 14A7 Copper: 5C6 1.724 X 10-6 Selene & Iawatlea 1920 ISS INSGT (F60 IT5GT IH6G 1407 Aluminum: 2.828 X 10-6 Television 1927 5H6GT 22 Radio -Craft 1928 67 70L7GT S17GT 2B6 IR4 Magnesium: 4.6 X 10'6 Short -Wave Craft 1930 í(66T 483 Television News 1931 387 3D6 From these figures it will be seen Wireless Association SK7G 69e Each N Amerlea 1009 (1(70T 6ÁL57 3LF4 that magnesium definitely has not suffi- SNI 6ÁN5 3V4 6AC7 1852 SSA7GT 61316 5Z3 I17Z66T cient current -carrying ability to qualify borne al the larier libraries in the try still hay iSD7GT 6D7 5Z4 topics al ELECTRICAL EXPERIMENTER on Ole for iSF5GT 6F5GT 6A3 89e Each as a useful electric conductor; but, hav- interested readers. 5517 6666 6A6 ing less than twice the iSK7GT 6P5GT 6A87 IB3GT 8016 resistivity of I6670T 6R7GT 6AN5 6166 aluminum, it can be equally dangerous AUGUST 1915 ELECTRICAL Hard 10 let tubes: Our t i l l s ? , rk Is r nslau US b1 gus ly.:uld.d. It 1 0 tub` I. lint (isard. writ, 1 General Electric Co. EXPERIMENTER Television, or the Projection of Pictured TUBULAR OUTPUT ELECTROLYTICS TRANS- over a Wire, by H. Winfield Secor FORMERS AT BARGAIN PRICES Submarine "Wireless" Signaling SENCO buyer IU Si?,?, (v 1505', 30 Mpl. cores thru with An Interview with Guglielmo Marconi, fe great savings for x 2 M/d. ® 150V.... 3 39 you! by Samuel Cohen 41 x 411 5141. w 150V.... 40 x 50 51111. (ú 150V.... 41 MI5 ..39c Ea. How to Build an Electric Writing Ma- 511 x all Mfd. 0 1511V.... 40 501.6 Push Pall N I. x a11 Mfd, p 150V.... 2 39e E:a chine x 311 x 2n M01. 4e 1511V 46 81'6 Push full or Telautograph, by Homer lb N 51111. 60 450V.... 0 ]i N51111.Fi4:OV .... .42 490 I(:1 Vanderbilt 111 x 10 51111. Fl 45115'.... .42 211 x 20 51I11. .15n5'.... .47 A New 100 -Watt Wireless Telephone 1 M61. fr. 1'.11\' 29 .32 FRESH STOCK New 11,E -2 KW. Radiophone Arc Gen- 0 MN. G. 1:11v 34 OF 4 Mrtl. F isul' 35 CARTRIDGES 111 M01. 61 50V 39 erator lp Mfa. .. 4505' 40 Webster Up -to 411 Mfd. M 4505' ...... 7 N7 $1.19 -date Wireless Set of the SS. 32 x 16 MM. 6d 4505'.... 49 10 x l u x 105101.Mrd. 4J 450V. PN88 Shure "Olympic" 1011 MN. ,00 50a' 49 Crystal 1.69 A Novel Idea for Wireless Telephones Wireless Relays and Amplifiers RADIO MEN WHO KNOW.. SAVE AT SENCO! Min mm Order $2.50: Send 3'1 delNl.lt An Improved 13 ha ali Electrolytic Detector, 111.1u sh0unrnu. Include .nmrient pnaaxr Isaiah Rosin b, retundrd. llydlrs without puslaae tul` I. Anti -Hum Stunt for Radio Receivers, .!Nit.] Io1,11 rn11rr1. .\II turirrs E'.tl.1t. Nis 101k by Urban McMiller WRITE FOR FREE A Cheap but Efficient Carborundum "SENCO SPECIALS OF THE MONTH BULLETIN'- Detector, by H. J. Andrews A Simple Galena Detector, by Harold Pruden 1:lENCO RADJOIN C. An Alloy for Radio Crystals, by Lloyd Dept. L. 73 West Broadway Stratton New York 7, N. Y. Tel. BEekman 3-6498 AUGUST, 1949 71 People Hi-riot-11 sassed Swope has joined the Radio Corporation of America as ad- SIGNAL GENERATOR KIT viser and consultant. His work will not require his full time, and he will con- EICO tinue his independent practice with other organizations. Mr. Swope recently TDUTE MODEL resigned from the Columbia Broadcast- 320K ing System, Inc., of which he had been a director and member of the executive committee, since 1932. aÁÓio I9e95 Drs. C. H. Townes and P. Kusch of Complete Columbia University have been ap- In this magazine you will find an pointed consultants to the Microwave Build your own signal generator. kit exhaustive panorama of French ra- E.co comas Standards Laboratory of the National complete with on parts and easy-to -follow in- dio in all its phases and a complete structions. Hartly oscillator range of 150 Kc to Bureau of Standards, where they will 100 Mc: Colpitts audio- oscillator -gives pure 400 be available for consultation on mi- report of the radio industry of cycle sine wove voltage. Perfect for aligning crowave absorption spectroscopy and France. TOUTE LA RADIO is the standard broadcast receivers. In kit form. com- atomic beam equipment for use as fre- principal French radio magazine. plete. $19.95. Foctory wired and tested. $29.95 quency and time standards. Write for FREE Broadcaster newspaper We will send a sample copy to all radio Fred R. Lack of New York, vice- presi- specialists, industrialists. importers, and 10% radio dealers, if you will make your re- Phone dent of Western Electric Company, has Cash Lo been elected president of the Armed quest on your letterhead. Please address: with 3 -9255 Forces Communications Association. Orders Cove Globe Mr. Lack, a member of the Industry TOUTE LA RADIO Advisory Committee for the Armed 509 ARCH ST., PHILA., PENN. Services and 9 Rue Jacob Paris 6, France SIXTH & ORANGE. WILMINGTON. DEL. during since World War 6205 MARKET ST.. W. PHILA., PA. II, succeeds Brigadier General David Sarnoff, chairman of the board of Radio Corporation of America, who has served GREYLOCK as president of the Association since ARE RADIO TUBE BARGAINS! its formation in 1946. WE GT, Glass and Miniature Types LOOKING ISS ..1V4 GT I2SK7 ` 6S! 1 341/2w 114 EATS GSK7GT 128417 Dr. Elmer C. Larsen has been appointed iO4 6BAG GS07GT 2526GT ( each in 3a4 buss t2SA7 25L6GT 100 lots chief engineer of the Tungsten and SPECIAL OFFERI All above types may be pur. Chemical Division of Sylvania Electric FOR TIMES! chased in 100 Also lots of assorted. available YOU in smaller quantities at 39r each. Products, Inc., it WHAT HAVE GOT! nAK5 6BG6G 69e was announced by Interested In small or large quantities of all 49 tmypes of Transmitting, Recels - bib 5 ° °' 163.8016 89e John B. Merrill, di- Industrial. and 2E24 $1.89 g Tubes. All tubes in individual cartons vision manager. Dr. TERMS: Net C.U.D.. F.U.B. NYC. MINIMUM Larsen will assume Send your list to: ORDER 55.00. Write for Bargain Catalog C8 direction of the en- MOHAWK ELECTRONICS CO. Greylock Electronics Supply Co. gineering and sci- 160 GREENWICH ST., NEW YORK 6. N. Y. 30 1 Street Lurch Ne. 1 eel. 7. N. 1. entific program for improved production and process Check these Prices! control of tungsten and chemical prod- SELENIUM ucts. RECTIFIERS 115 VOLTS J. Gilman Reid has been appointed chief Kor Radio & Trlru.i of the Engineering Electronics Labora- planation. 1//uy lots of lots tory of the National Bureau of Stand- guaranteed of 10. each 100. each ards, where he will direct research on 75 MA .56 .50 electronic instrumentation, 100 MA .64 .56 miniaturi- 150 MA .72 zation, printed 66 -circuit processes and TRAIN QUICKLY! 200 MA .89 78 techniques, electronic circuit compo- 250 MA 1.16 .88 OLDEST, nents, and electronic standards. BEST EQUIPPED OPAD -GREEN COMPANY One of the senior scientists in the SCHOOL of ITS KIND in U.S. 71 Warren St.. N Y. 7, N. Y. B Eckman 3.7385.6 Bureau's radio proximity fuze program .2 oppo hugtil.j 4:4de. during World War II, Mr. Reid has Come to the Great Shops of COYNE in Chicago during our 50th Anniversary Vearl Get quick, practical conducted research on electronic in- training in RADIO -TELEVISION or ELECTRIC- ATTENTION Amateurs- ITY. G I Approved. struments, Finance plan for non -veterans. Experimenters-Inventors special controls for isotope Mall Coupon Today for complete details. separation, auxiliary instruments for NOT "HOME- STUDY" COURSES! Cut your cost on radio supplies and equipment mass spectrographs, heat transfer, and You learn on real. full -size equipment. not by mall. in half. Clip coupon today. Finest staff of trained instructors to help you get ready quickly for a better job, a fine future. Hundreds "hard In gel se;;r surplus thermal conductivity. it big iltUts uloug with Ili best in standard brand FREE BOOKS Coycoupon fon theruELEC- mini] UI -all at great savings to you. Let TRICITY or RADIO -TELEVISION. Both books us know your partieubtr requirements. IM- sent FREE if you wish. No obligation; no salesman Paul W. Erickson has been appointed will call. 11 El 1 ATE 1 11':1.1 VERY. Act NOW! manufacturing superintendent for the PLEASE PUT MY NAME ON YOUR MAILING LIST FOR SPECIAL BULLETINS. Electronics Division D. W. COGNE. Pees. of Sylvania Elec- COYNE Electrical& Radio School. Dept.a941H NAME tric Products, Inc., Boston, Mass., ac- 500 S. Paulin Street, Chicago 12. Illinois ADDRESS ZONE cording to an announcement by J. J. Send FREE BOOT. and full details on: CITY. STATE RADIO- TELEVISION Sutherland, general manager. He was ELECTRICITY NAME NIAGARA RADIO SUPPLY CORP. formerly supervisor of production engineering and then general ADDRESS 160 Greenwich St., New York City 6, N. Y. foreman in charge of microwave tubes. CITY STATE RADIO -ELECTRONICS for People lei Leonard C. Welling has joined the JEWEL RADIO AND TELEVISION CORP., New York, as General Sales Manager. Mr. Welling is THE COMPLETE 2 TUBE RADIO backed by over 20 HERE IT IS years of experience BUILT INTO A HAT! in the industry. Formerly associated with Emerson. Mr. Welling was also one of the principal owners of the French Sonora Covers entire broadcast band within Radio company in 20 mile radius Paris. Set weighs 5 ozs.; hat, 7 ozs. ir Conceals in lining 'ii" thick Emil J. Maginot has been appointed sales manager in charge of Distributor Absolutely mobile, no extra aerial needed Sales for the NATIONAL UNION RADIO Volume 8 tone equal fo many portables CORP. of Newark. N. J. as announced Regulation waterproof sun helmet... 95 COMPLETE WITH by Kenneth C. Meinken, President. adjustable size p u, led tom BATTERY PACK Maginot has served National Union successively as Director of Sales Engi- ACCLAIMED FROM CO ASTTOCOAST 000¡/rr Bklyn neering and Manager of Advertising Here's the two-tube 8 Halsey St., M r r Wm 3 and Sales Promotion. topper that's got the (

INDIA STARTS RADIO CLUBS Dear Editor: eÇ We are pleased to announce the formation of the Amateur Radio Club of GE\S3A[ India and the Short -Wave League of India, with headquarters at Mhow in Central India and a QSL bureau at L BtA3Y Bombay -P. 0. Box No. 6666. Each of these books supplies usable information No. 29 -HANDY KINKS and SHORT CUTS. A cart-tally ...tiled compilation of time s Kinks on Antennas -Power Supplier -'rest quipmen -Servicing -in the Shop - Phonographs and Amplifiers- lolls and Transformers - Miscellaneous Subject,. 50e each. No. 30- UNUSUAL PATENTED mine in new n of unusual circuits, many a result of wartime of to anyone Interested in 1eelectUrolrs Cold rol Circuit:- -Detectors and Amplifiers- Power Supplies -M isrellaneaus Cir- cuits - Foreign Circuits. 50e each. No. 31 -RADIO QUESTIONS AND ANSWERS. Answers to mors requently asked quest inns. Clear circuit diagram.. Amplifiers -He- o ivers - Transmitters - Meters and Test Equipment- Interphones- Power Supplies- Phonograph Amplifiers- o P. 4. Systems. 50e each. in e0 No. 32- ADVANCED SERVICE This is the first time the history of TECHNIQUE. An up -to -date col- of this lection of information for the ad- our country that an organization VITAL vanced serviceman: Visual Align- kind has been established. The ARCI ment-Tracking Probleme-Negative Feedback -Tone Control ClrettlIs- looks after the interests of all transmit- Adding Microphones to Sels -Merch- ing Loudspeakers - Remote Joke ting amateurs, and the SWL takes care linxes- Servicing Record Changers A FOR TV SERVICING -Hum Elimination -FSI Servicing. of shortwave listeners. combined 50e each. A new and highly important book! Gives a complete understand- journal for members of both organiza- No. 33- AMPLIFIER BUILDER'S ing of working principles behind oscilloscope operation. and how GUIDE. Invaluable for the designer tions, QRZ, is published monthly. to use the instrument effectively. Clearly written with single and builder of audio equipment. are be- purpose -to help you use and understand the oscilloscope. No man Tells how to build a wide variety cf The headquarters stations servicing television receivers can afford to he without this knowl- amplifiers with power outputs ng- lieved to be the best -equipped amateur edge. Invaluable for anyone who uses the oscilloscope. Ing from 8 to 30 watts. Detaileda design information on. Push -Pull - stations in Southeast Asia. The calls l'hase Inverslon -Bass and Treble ALL ANGLES COVERED Boosters- Volume Expanders - Re of the ARCI and SWL stations are sistance Coupling - Internal Feed- respectively. Chapter I- Direct Current ono Alterno,!ng Current. Visual observa back. 50e each. VU2ARCI and VU2SWL, lion and measurement of vorying voltages and currents on the No. 34 - RADIO -ELECTRONIC Both are very active on 7, 14, and 28 cathode-roy tube. Chapter 2 -How beom from electron "gun" CIRCUITS. An extensive collection projects image voltage variations fluorescent of circuit diagrams. with brief. to- mc. of current and onto the -point descriptions of each. in- screen, and how beom is deflected by electrostatic and electromag- cluding: Intercommunications ' We are enclosing a photograph of the netic means. Chapter 3 -How signol deflects electron beam vert, terns - Power Supplies - Balancing of VU2ARCI. colly in c -r tube and sweep voltage deflects beom horizontally. Role Circuits -V. T. Voltmeters-Ampll- main operating position of the saw -tooth oscillator-the gas discharge tube -the multi - fiers- Receivers-ITono Amplifiers- MAJ. B. M. CHAKRAVARTI, PRESIDENT, Rave Electronic Be- vibrator- synchronization -locking. Chapter 4 -The cathode -ray tube Short Adaptor.- lays. 50e each. Mhow, Central India -accelerating and focussing power supplies -the sweep generotor- RADIO the No. 35 - AMATEUR horizontal and vertical amplifiers- controls on oscilloscope-how B UILDER'S GUIDE. For the "haul" to operate a 'scope. Chapter 5- Aligning TV i.f. channels -TV front - who builds his man. Practical. down- end alignment -Alignment of i.f. amplifiers in AM and FM sets. Use to. earth It tells how to Bond: A of signol generators-id. alignment of o.c: d.c. receivers- bandpass Meter Band Aeon, Tube Set-- Minia- alignment -aligning the discriminator -the ratio detector-rd. align. ture Communications Receivers - ment FM Lang Lines Transmitter- Iteglnner's of AM and receivers. Chapter 6 -Audio output measure- Transmitter Preselectnr Rotary GEIGER COUNTERS ment-voltage gain -power output -audio response curve plotting - - - Beam Aerial -Power Supplies -and HAMS! BE FIRST AGAIN! BUILD YOUR OWN! peak a.c. measurements. Checking sow -tooth amplifiers-magnetic otter ham gear. 50e each. check deflection circuits -synchronizing pulses. Ham transmitter measure- No. 36 -RADIO TEST INSTRU Find radium. trace water mains, prospect, ments -over and under -modulation. Locating hum -incorrect adjust B ENTS. A Stt'ST for every radio local contamination, assay ores. ment of vibrator power supplies. Phase shift in audio amplifiers. man. This latest trunk on building BETA COUNTER! lest equipment places emphasis on SENSATIONAL practical construction of: Signal 30 MG,CM1 WALLS Tracers -Capacity Meters- Porlahle ....$7.50 112 PAGES 103 ILLUSTRATIONS and Bench Multi- checker- Signal D Send Beta counter Generators-Tube Checkers - Elec- D Send complete parts kit and diagram ...$48.50 Voltmeters many others. tronic -and $90.00 50e each. O Send assembled 5.5 pound portable No. 37- ELEMENTARY RADIO O Send IIOVAC quantitative lab. model $150.00 Only 75c SERVICING. For the radio man who knows little about servicing. O Send detailed information Check O COD See your jobber today or send for THE CATHODE -RAY How to get .trred. and even noire AEC Bulletins omlloole OSCILLOSCOPE along with other titles in the GERNSBACK important how to keep going: Plan- LIBRARY. ning the Service Shop-Equipping the Shop -Systematic Circuit Cheeks COUNTERS -Signal Tracing Methods- Servicing COSMIC the Midget - Soldering - Servicing 112 Cornell Ave. Swarthmore, Pa. Vnlnme Controls-Bow to Service MAIL THIS COUPON NOW Speakers. 50e each. No. 38 -HOW TO BUILD RADIO RECEIVERS. This book contains 10 OTHER BOOKS Iswmrlent varlet' of sets to appeal D No. 29 -Handy Kinks and Short Cuts. 50c O No. 32- Advanced Serv- n every radio ran. McIntire: Shoo- i ce Technique, Wave. Broadcast. Portable. A. t'. O No. 30- Unusual Patented Circuits. 50o ce Operated. Miniature and Standard TO LEARN CODE Receivers. Complete roll-winding EASY No. 31 -Radio Questions and Answers. 50e O No. 33-A nip! t e r data is fnrn i shed 50e each. II Is eaa7 to learn or Ineream steed Builder's No. DISC RE- Instrperograph ('ode Teacher. Guide. 50e 39- PRACTICAL with an CORDING. Whether you're inter- Anords the quickest and most prat - RADCRAFT PUBLICATIONS Inc., ONO. 34- RadioElee- ested in amateur or professional re- tiral method yet developed. For be- Avail. Dept. 89. 25 West Broadway, tronic Circuits. f ding. you'll find this hunk by ginners or advanced tudents. 11. from beginner's alphabet 7, N. Rlrhard Dorf Invaluahe. It not able tapes New York Y. only tells how to make success- typical messages on all subjects No. Amateur Radio you to 'end me the hooks checked. postpaid. O 35- ful records. but in addition each Speed range 5 to 40 WPM. Aimai, r s important recording component is wady QRM. 40 50e -no NO. CATHODE -RAY Guide.) given a full chapter. explaining its 75c OSCILLOSCOPE. D No. 36-Radio Test In- purpose. and what features to hook ENDORSED BY THOUSANDS! when buying. Without waste of strumente. 50e for The Ins tructograph Code Teacher I enclose $ words. It gels right down to business literally takes the D No. 37- Elementary Ra- on the first page. It tells you what boinstrutor ela. anyoneyn to dio Servieing codedble without fur. Your Name mu need to make good words and learn and 50e do by using any 'rIre equip- ther sealatance. Thousands of successful operators bare IPrint rlear17l how to it the System. D No. 38 -How to Build ment- -from the implest to the most W-acquiredtoday for ronvenret teetal and "purrcchas plane. Address Radio Receiv- expensive -depending on your pur- t ers. 50e pose and pocketbook. You will find Jobber's Name all the practical phases of recording O No. 39- Practical Disc covered as welt as the underlying INSTRUCTOGRAPH COMPANY Address Recording. 75e . principles. 75e each. 4701 Sheridan Rd.. Dort. RC. Chicago 40. Ill. RADIO -ELECTRONICS for I:ommuuicntious I77 HAM LIKES U.H.F. ARTICLE Dear Editor: I have just finished reading Part I of "Microwaves" by C. W. Palmer in the . \pril issue of your magazine. This is a very fine article. By using NEW GIANT the elementary and practical approach as Mr. 161" PICUBETURE Palmer has done, more interest will be T awakened in the u.h.f., especially among hams. Most hams are not grad- Immense ISI square -inch uate engineers; w Ir metal -glass but armed with some tube ... clear. steady. bright knowledge of microwaves pictures... Synchronized and with sound and picture than child their natural enthusiasm for radio, can tune on Iectl Long Distance FM Circuit.. they will proceed to make history in Big oni Eleaker Dynamic - ---' the upper bands, just as they Panasonic Speaker ... Avail. g have able to beautiful consoles or from 200 complete meters down, chasm. (not a EASY TERMS Jobbers: Write for Price Information kit). Buy direct at Low Fac- PETER N. SAVESKIE, W2JFE tory Prices. with Low Down Payment and Long Easy Stately / stand, N. 1'.

Terms . and on 30 Days Trial! Send for 32.page. 4 color catalog today. CENTRAL ORGANIZATION NEW FACTORY AUTHORIZED TELEKITS SERVICE IN Dear Editor: TELEVISION AREAS Much had been said and printed pro IO -B S82.99 and con about licensing radio, television 7.B S59.50 and electronics technicians. I think MIDWEST everybody will agree that organization RADIOS is better than licensing. The main difficulty is Sparkling new Telekll IO B has 52 inch screen. with new long distance that existing Brand new compact lay -out has video tube FM Circuit and new organizations are few and mostly of a anted on chassis. Big illustrated easy to- follow 3-Speed Phonograph. local nature. What is needed is a na- instruction book guides you step by step through tionwide easy assembly. No special knowledge of television Semi This organization that will be rec- is required. All you need is o soldering iron, MIDWEST RADIO & TELEVISION COUPON CORP. ognized the pliers, and screw driver. 10 -B Kit can be used Dept. country over. This will give on It Pmt x351,909 in cas.ey. Cincinnati 1.0111a with 121/2, 15, 16 -inch tubes. Telekit 10.0, rural and small -town Tube Cord for Deese send am your now DM 1950 Catalog. technicians a $52.99. kit, including 100P4 and oll other NEW 1950 chance to benefit from such an organi- tubes, $55.80. 10.0 Telekit cabinet, $15.95 to FREE NAME zation. $24.50. Telekit Guarantee includes free factory - service. 4 Color ADDRESS 32 Pogo -__ Here is a solution to the problem. Write for catalog listing 10 -1 and 7 -B Telekits. MID W IST What organization New 7.11 Telekit for 7.inch tube. $59.50. Tube CITY ZONE STATE has more influence CATALOG kit, including 704, $39.58. 7 -0 cabinet, $15.95 a and contact with the service technicians to $24.50. than RADIO -ELECTRONICS? Who has been INSTRUMENT pioneering on the advantages of organ- NEW! KITS izing more than your publication? You of new low ba rgain have a golden opportunity to further prices! the industry this way: 5" OSCILLOSCOPE Set up an organizing committee and & STETHOSCOPE print Model TS -7K $44.50 application blanks in every issue FOR TELEVISION, of RADIO -ELECTRONICS, requiring appli- FM & AM Ittun quality laboratory cants to be engaged in some form of rIal llosrope plus she. Note simple clean lay out for easy assembly of v u tracer: 2 h,ntru- electronic servicing. As soon fur as there new Telekit 10 -B. Features 2 sound I. F. stages, lienDesigned frleTVf ' alle is a sufficient enrollment anew pre -built, pre -aligned tuner that includes FM alignment elect officers o AM stage of R. F. for distance servicing. jJack and make RADIO -ELECTRONICS reception. Easyto.od- probe listed below. Per. official lust horizontal lock circuits. Beautiful new model ml t a signal tracing headquarters cabinets 7 throe h and communications cen- for -0 and 10.8 are heavily constructed pl nex Of pat. of hand rubbed walnut. tern. These extra fee ter. Set the membership dues high lures in addition tu conventional son, enough to cover the cost of high gi 05 expenses, V, loch, idtddlfler3 With such as wall plaque and response D membership plate with all tube.Cu cards. Print including 3' ('II tnhe questionnaires regarding Less probe ml head - fair eelcaaen 15s hourly wages or service charges 13 x 1 e . on the rs'7.K..robe Kí154.25 various repair jobs. Have mem- TS7.factery built.59.95 bers CHANNEL TS 7P. factory built submit their opinions on the sub- DELUXE SIGNAL TRACER 3.29 ject TUNER Model TS-3K $22.75 and the other problems we are confronted with. all fad, WI!,f`trlts w l,,,ules $19.95 Inrls-ml ,4, hours. iGivex you k:`ow how' tougher I believe a step like this must be jobs. Easy t use b1 exert taken to secure a large enough organi- Locates valises. of failing. clis,1, sels, etc. zation to gain recognition from the am bo for ' connecting your manufacturers and the public. NEW 13 CHANNEL TUNER is a small compact reading on up11F and audio. unit with stage of R.F. Tunes TV and AC , Iatxted. ',eel case Mx all ZFM 12x11-. With 4s ulves, pod.. James M. Pelley channels. Mode to conform with Telekit or any guide. Cher TV net having video I.F. of 25.75 Mc. Modelodel 75,3 I (No address given) built 534.95 Complete with tubes, Drs wired, pre- aligned; TS -IK, Ileglnners only three connections to make. See your job- Sig. We would he inclined ber, or write to us for information. Your cost, Fact. built 9.35 TS'9C, Crystal to agree with $19.95. 151N141 Profs- XII 4.50 75Trace,Poc you -had we not already tried it! Dur- Write for catalog of Telekit antennas, boosters, Sil'' 20 43 Fart. built Faro. built 28.95 7.50 ing 1931 we television kits, tuners, television parts and tubes. ORDER front organized the Official Radio your lubber. If he tramai stpPly. mall Service Men's Association (ORSMA). FEILER ENGINEERING CO., Dept. 8RC9 Despite considerable work and a large 945 George Street, Chicago 14, III. amount of money spent on organiza- rill im instrument. .lbxld .... tion, publicity, certificates, booklets, TELE IT lapel buttons, etc., it did not prove a NAM,: success. SANDERS ELECTRONICS CO. AVIATION BLDG., 3240 N.W. 27th AVE AM di,:FN. But we learned one thing. An organi- (Continued on page 79) MIAMI 42, FLORIDA AUGUST, 1949 78

RADIO SCHOOL DIRECTORY

Become an ELECTRICAL ENGINEER JOBS IN TELEVISION MAJOR IN YOUNG MEN 16 TO 60 ELECTRONICS There Is a lob Opening for Every Qualified Trained Television Technician WE CAN TRAIN YOU Free Employment Service

Visit Our Modern Laboratories and Class Rooms

APPROVED UNDER C.I. BILL OF RIGHTS B. S. DEGREE...IN 36 MONTHS AMERICAN RADIO INSTITUTE Make one of the most important decisions of your New York Buffalo, N. Y. Syracuse, N. Y. life -today! Capitalize on your electronic inter- 2010 B'way (68 St.) 640 Main St. 131 Shonnard St. ests- decide to become an Electrical Engineer. RADIO -TELEVISION TECHNICIAN "Teaching Radio Since 1935" valuable year by earning Choose, also, to save a To young men interested specifically in radio Degree here in 36 your Bachelor of Science and television: Prepare here for a career in months of intensive study. field which business leaders pre- television-the FILL THAT JOB WITH A This 46- year -old, non -profit Technical Institute dict will be among America's top ten industries offers a world -famous course in Electrical Engi- by 1951. In 18 months you become a Radio - C.T.I. TRAINED MAN! neering with a major in Electronics. You follow Television Technician, ready for positions in re- which is Solve your man -power shortage by employing well - an industry -guided program constantly ceiver and transmitting testing, servicing, sales. trained, dependable young men who have been attuned to current developments. It presents a supervision and production. trained by Commercial Trades Institute. Our grad- in the basic sciences , uates have completed an lilt, nsive course in Radio solid background of this school's trig curriculum. Mathematics, Economics and Because or Television Servicing. Their training has been Chemistry, Physics, the Bachelor of Science degree in Electrical practical -in well- equipped shops under expert subjects , plus 19 tech- Electrical Engineering .. Engineering (Electronics major) may be earned supervision. They've learned to do excellent work. nical specialty courses in Engineering Electronics, To enable you to evaluate the efficiency of C.T.I. in 24 additional months. four courses in Electronic Design. training. we'll be glad to send you an outline of including the course. You'll find the subject matter extensive. Practical, military or academic training will be complete, Marmot.. for advanced credit. We probably have men who hail from your vicinity. evaluated A SPECIAL PREPARATORY PROGRAM is offered but most of our graduates will travel anywhere for for men lacking high school diplomas. a good opportunity. We cordially invite employers ELECTRONIC TECHNICIAN to write us for detailed information on available men. No employment fees.) Address: At the end of the first year of study of the Elec- TRAIN in modern, well -equipped laboratories, Placement Manager. Dept. P108 -8 trical Engineering course, the student is qualified shops and classrooms. Faculty of 85 specialists - 30,000 graduates. as an Electronic Technician. over 1500 students and COMMERCIAL TRADES INSTITUTE V-MILWAUt.£E- 1400 W. Greenleaf Ave., Chicago 26, III. of FALL TERM OPENS OCT. 3 5CHL ENGINEERING ri,- Founded 1903 Complete Radio Engineering by Oscar Werwath Course. Bachelor of Science De- Electrical Engineering 36 months gree. Courses also in Civil, Else- - Electronics Major Send Coupon for trical, Mechanical, Chemical, Aeronautical Engi- free 48 -page Pic- neering: Business Administration, Accounting. Electronic Technician 12 months torial Bulletin "Your Secretarial Science. Graduates successful. 66th Radio -Television Technician IB months Career" and 110- year. Enter Sept., Jan., March, June. Write for page Catalog. catalog. aII TRI -STATE COLLEGE ANGOLA ova MILWAUKEE SCHOOL OF ENGINEERING OWQh E. Milwaukee, Wis. Make Your Career Dept. RE -849, N. Broadway end State, I Without obligation send me the Bulletin, Your Career," and your catalog. I am interested in course. I RADIO and TV In nn other Industry does the future hold hrigbler NAME AGE I financial promise and security than in AM and FM Radio. Television. These fields need and want men I trained as announcers. script writers. dise jockeys. and ADDRESS radio technicians. It will pay you to Investigate the lion Martin School of Radio Ans, established In 1937. I Complete day and night classes . . the latest equIp- ...STATE ( ) Veteran of World War Il - ent . . and a staff of 30 nationally known In- Min WM RIM WM MIR structors. Over 97% of the combination men graduates are placed on jobs immediately through the free idaremem service. ADprosed for veterans. FREE-Write for Free Booklet "YourFuture In Radio."

Don Martin School of Radio Arts RADIO -TELEVISION LEARN RADIO! Iú55 Na. Chrakee. Hollywood, Calif. H Udson 23281 Save school time and money with WRTI Specialized PREPARE FOR A GOOD JOBI Training. Qualify for high - income technical career, in only ten months under practical engineerinstructors. COMMERCIAL OPERATOR (CODE) Practical daily lecture -laboratory training provides the RADIO SERVICEMAN skills necessary to hold down responsible positions. TELEVISION SERVICING Become an FCC -licensed commercial Radio Operator: or. an FM- Radio -Television Technician. W'RTI grad- BROADCAST ENGINEER ile "key" man. Learn how to send and receive in vole by teleerann uates employed world -wide. Approved for veterans: non- V.A. Furnishes Books and Tools and radio.Commerce needs thou Sand of veterans accepted. Send for free 11111-t rated booklet. t for jobs. ( a,,.I pay , adventure. no SEND FOR FREE LITERATURE teresii,g wk. Lea at home quirk,, through (fatuous Candler System. Qual- WESTERN RADIOTELEVISION INSTITUTE ify for Amateur or Commercial BALTIMORE TECHNICAL INSTITUTE rise. Write for F'IRF.F. ROOK. 341 -A West 18th St., Los Angeles 15, California 1425 Place. Dept. C. Baltimore 17, Md. CANDLER SYSTEM CO. Eutaw Debt. 3 -J. toy 025. Denver 1. (ola..1..s.A. RADIO -ELECTRONICS for 4 C01111111inicationc 79 zation of this type cannot be run by r ELECTRICAL TRAINING mail order. Seventy -five percent of the 25 WATT I radio technician's problems are P.P. 6L6 HI GAIN I Intensive 32 Weeks' residence course in funda- local. AMPLIFIER KIT mentals of industrial electrical engineering. in- Take the matter of fair charges for in- A wonderful bur' )Lake cluding radio, electronics. Prepares for technician, stance. It would be impossible to set up an amplifier aorlh engineering ::ides. Approved for veteran training. $50 to you. l'un et nul 66th year. Enter Sept. 6, Jan. 9. Catal e. these on a national scale, for a tech- enough tor audl tonum R atfn g I:,wl pr.ple. Separately run- ELECTRICAL SCHOOL nician in one area would starve to 1 oiled 31ike & Phono inputs. All BLISS 754E TANOMA AVENUE parts, Incl. drilled chassis. bard WASHINGTON 12, D. C. death on what would be exorbitant bare. Roller. circuit diagram. Ge. charges for another part of the country. Loss nitra Ship. wt. 12 lis. Besides the difference in problems, a PRICES NET F.O.B. OUR PLANT. national organization finds it hard to keep in contact with the members and promote local activity. As a result, he Giversa RADIO ENGINEERING 365J Canal N. Y. 13; Co finds himself merely a name on a mem- 1 5f., WAlker 5-9642 FM- Television- Broadcast bership roll. Such an organization gets Police Radio. Marine Radio. Radio Servicing, Avla- no recognition from the manufacturers tIon Radio and Mlles High mobile applications. Thorough training in all branches of Radio aid Elec- nor the public. It just adds another wall PEN -OSCIL -LITE tronics. Modem labors t orles and equipment. Old es- Extremely convenient test oscillator tor all radio tablished school. Ample housing facilities. 7 acre plaque to the display of certificates, servicing; alignment Small as a pen Self campus. Small classe.. enrollments limited. Our bonds and diplomas many radiomen powered Range from 700 cycles audio to over graduates are in demand. Write for catalog. 600 megacycles u.h.f. Output from zero to 125 Approved for Veterans already have on walls, v. Low in coat Used by Signal Corps their and to Write for Information. VALPARAISO TECHNICAL INSTITUTE which few people pay any attention. Dept. C VALPARAISO. INDIANA GENERAL TEST EQUIPMENT The only organization worth any- 38 Argyle Ave. 9, N. Y. 4 Buffalo thing is one in which radio technicians join to work together for objectives they could not easily obtain separately. OPPORTUNITY AD -LETS A,lsertiseutems In this Section cost 25c a it., For this the local organization is ideal. each insertion. Name, address and initials mu.l If you have a local problem, talk it Included at the above rate. Cash should aceompair. all arnsilied advertisements unless pieced by RADIO over with other local men and form a accredited advertising agency. No advertisement for less then ten words accepted. Ten percent discount group of five men or more to do some- sit issues. twenty percent tor twelve issues. Obtec COURSES tlnlable nr misleading advertisements not ercepted thing about it. No town is too small. Advertisements for September, 1949, Issue, most reach Preparatory Mathematics, Serv- In some Western organizations, mem- us not later than July 24. 1949. loom electronics. 2a w. Broadway, New York 7. N. Y. Ice, Broadcast, Television, Ma- bers come 30 miles to meetings. Draw a rine Operating, Aeronautical, 30- circle around your shop and count Frequency Modulation. Radar. "RADIOBUILDER ". 3 ISSUES 25e. SAMPLE FREE. the radio technicians inside it! Lals.ratories, 578 -B, San Carlos, Castel ans lapel la 11: loll tim Oct. 1st California. If your problem is low returns, agree Enlfase. Rae, fegt 1911 WE REPAIR AI.L TYPES OF ELECTRICAL INSTRI'. not to cut rates -or each other's meats. tube cheaters and analyzers. Ilotleton Instrument Veterans. Literature. Co. (Electric Steter Laboratory,. 1411 Liberty Street. New throats. If bad publicity, send your York. N. Y. Telephone -ItA relay 7-4239. COMMERCIAL RADIO INSTITUTE 1920) chairman and secretary round to the Mound. 24 VOLT AIRCRAFT BATTERIES. NEW 11 AMP AT 36 81001e Street. Baltimore West I, Md. local paper -or broadcast station, if hr. rte. Dry ehntged 914.50 ea. less 25% in Into of four. No C.O.D.'s please. Security Parachute Co., Oakland Air- you have one. Do people complain of port. Oakland. Calif. dishonest repair? Offer the services of BARGAINS: NEV%' AND RECONDITIONED HALM- your organization to investigate such crafters. National. Collins. Hammarlund, Sleiasner, RME. other receivers. tuners. television receivers. transmitters. cases, and to testify where dishonest etc. Wholesale prises. Ternis. Shipped on trial. Liberal trade -in allowance. Write. Henry Radio. Butler. Missouri work is found and the customer is will- and 112411 west Olympic. Los Angeles. California. ing to prosecute. I ELEVISION TECHNICAL CAREER Arrange technical HERMAN LEWIS GORDON. REGISTERED PATENT As Television gain. momentuni, rapidly. meetings with outside talent. Increase Attorney. Patent Investigations and Opinions. Warner constantly. It arose to properly-trained t. üulldmg, Washington, D.C. nicians careers with e future In Indu,. business with educational campaigns Itn,edraMP., or own Business. MAGAZINES 1 BACK DATES)-FOREIGN. DOMI:STII'. to the public. Your organization will be arts. Books. booklets, Train at an Institute that pi d subscription.. pm -ups, etc. Catalog. a success as long as you work and keep 10c (refunded). Cicerone's, 863 First Ave.. New York in TELEVISION TRAINING since 1938. 17. N. Y. )horning, Alteen.. or Evening Sessions in it working. laboratory and theoretical Instruction, un- BARGAIN HUNTING? RADIO SERVICEMEN WRITE. der guidance of reverts, covering all Rhum Some things cannot be well done by a Sensational catalog. Ilen,hew Radio Supply, 3619 Troost. .d Radio, Fregi,r,,ry Modulation, Tele- Kansas City 3. Missouri. vision. 'dta,ee,' by N. Y. State. Free local organization. Top -notch speakers 'lavement Service. Approved for Veterans. of the radio field are willing to address ASIATI:111 RADIO LICENSES. COMPLETE THEORY ENROLL FOR preparation for passing amateur radio examination. Home NOW NEW CLASSES study and resident coons. American Visit, Write or Phone you if a series of meetings can be ar- Radio Institute. ranged. State laws come up -such as 101 west 63rd SI.. New York City. See our ad on Page 78. RADIO- TELEVISION the proposed one to LANCASTER. ALLWINF. Q ROMMEL. 436 BOWEN permit erection of Building. Washington 5. D.C. Registered Patent Attorneys. roof antennas for television-at which Practice before United State. Patent Oree. Validity and INSTITUTE infringement Investigation. and Opinions. Booklet and the radio technician should be heard. forni 'Evidence of Conception" forwarded upon request. 480 Lexington Ave., N.Y. 17 (46th St.) For Plaza 3-4585 2 blocks from Grand Central these purposes the State Federa- 27 years experience radio repairing. Simplified system. tion is perfectly adapted. Both Penn- No calculations. No formula. Total price 42.00 potimld or COD. Slmneyback guarantee. Ross Radio. 14615 Grand - sylvania and New York now have such river. Detroit 27. Mich. federations, and other will states fol- RADIOMEN, AUDIO SERVICEMEN, BEGINNERS - MAKE ENGINEERING SCHOOL low as radio technicians' organizations eeeee money. Casi ly. qulekly. $250 weekly possible. We A practical Audio Fn etorerinqq In Sound show you how. Information free. Merit Products. 216 -32L menials: DISC. FILM and YACNtTIC Recording: Trans- increase in number. 132nd Avenue. Springfield Gardens 13, New York. mission M meldsells. Monitoring and ?Menlo. Lab- oratorieso contain Sets, Osrlllators. liar. A national federation to handle manic Analyser. mammon seta. Intermodulatton Ana - in- yzer, and iner ruimnet. Recording Studio Ima. ALUMINUM TIRING, ETC. BEAMS FOR AMATEURS. Iatlne Broadcast. Motion Picture and Commercial Sound terstate problems will be the next step. TV. FM. Write for lists. Willard Radclirt, Fostoria, Ohlo. Recording. N. M. Tremein, Pm: Director. Approved for veterans and Foreign Visa. Such a national federation -built up HOLLYWOOD SOUND INSTITUTE. 101 RADIO REPAIRING TIPS IBOOKLETI. SEND lee. the democratic way through local and 30 cents U.S. Itadlo. 135 E. 28 St.. New York 16, N. Y. 1040 -E North Kenmore Nollywoed 27, Calif. state associations, and handling only the business they For sate, 300 seta: wireless sets. Canadian. 19 MK and I1. cannot -can be suc- export parked. 193 wireless seta. American. B -19. In cessful. crtes. 108 wireless nets. Canadian. 19 MK. 11 basic stations. In crates. Export packed sets are complete with RADIO Remember, no organization can "do antennaea and spare toises: American sets are leas an- and TELEVISION tennae.+ and sisare tubes: basic Canadian sets are repacked Thorough Training in All something for you," but you can often with 1 set of nominees. Foil Canada. $32. Ameo lira,., Technical Phases do more for yourself through an or- 428 Broome St.. New York. APPROVED FOR VETERANS DAYS -EVENINGS W ganization than without it. We hope to PHOTOFLASH TUBES SYLVANIA R4330. BRAND New $10.00. Quantities of Ten $8.00. lararone. 1218 Leland RCA GRADUATES ARE IN DEMAND hear in your next letter Ave.. Bronx 60. N. For Free that you and Y. Catano9 Weile Dept. CC -49 your colleagues have formed a local RCA INSTITUTES, Inc. TELEPHONE DIALS. USED. AUTOMATIC ELECTRIC A Service of Radio Corporation of America Electronic Technicians Association. AK-I1 $3.25. N -E Type -1 Rebuilt $2.25, Readjusted $1.25. 330 - WEST ITH STREET NEW YORK 14, N. Y. All dials postpaid in I'S. Klasel Electric Products. 431 -C Editor Sherman, Galion, Ohio. AUGUST, 1949 RO

Index to Advertisers

Allied Radio Corporation 57 Almo 74 American Merrilei Company 75 UNITED'S Amplifier Corporation of America Si Bell Telephone Laboratories, Inc. Inside Front Cover Boland & Boyce, Inc. ... 8 Brooks Radio Distributing Company 62 Buffalo Rodio Supply SUMMER VALUES!!!! Capitol Rodio Engineering Institute 12 Certified Television Laboratories 68 Cinex, Inc. 68 BC454 RECEIVER. 3 to 6 Me. Like new 54.50. Condensers, Assorted Voltages - Cleveland Institute of Radio 16 No. 4 Tube. S1fd. to .1 Sl:d luu Lu 7 Mc. Used. Paper .0003 BC458 TRANSMITTER. 5.3 to good $1.95. Communications Equipment Company 67 t uudi t ism $7.95. So. 5 Oil paper. .002 Mfd. to 1 Sifd. 50 for $2.19. Concert Master Radio Tube Company 72 27414 TRANSMITTER RACKS. Single IFT- 234-A). Double ,FT-226A1 New. either Doe -89e. No. 6 Auto. Gen. and Distr. types. 50 for $1.69. Cosmic Counters 76 No. 7 Mica, ins. 37 Slmf. to .1 Slfd. 100 for $1.95. 74 ARRI RECEIVER. A beautifully bulls TILE. Job. Coyne Electrical School Nn. S Mira Xnttg. .0002 Slfd. to .01 Slfd. 10 for its the 234 to 219 Ur. band. A "natural" tor conversion DeForest's Training, Inc. 7 to Is. meters.... Excellent condition. with lollies and $1.19. antenna relay bus. Approx. shpg. wt. 8 Its. -$7.95. No. 9 Ceramics. 1.0 to 1000 Mint. 100 for $1.95. Fair Radio Sales 65 No. 4 15 77 V.H.F. TRANS. -REC. Similar to BC -966 1.F.F. H 10 Trimmers. 1. 2, 3 and sections. for $1.00. Feiler Engineering Company tubes. with dynamotor. gear train. relays and many Nu. 11 Filters. Tub., F. I'., cartridge, etc. 10 for 51.95. The Forty-Niner Company 69 nhrr Operates In the of 2110 Mc. useful parts. vicinity Nn. 12 Air Pad. All types. Ceramic ins. 10 for 51.19. Shim. Ill. approx. 4n Lbs. Express only. Like new- General Electronic D' 'buti ng Company ... .. 61 $9.75. Transformers General Test Equipment Company 79 BC -702A RADAR TRANSMITTER. Airborne. Uses No. I:! Power: 40 to 190 Nie. 5 and 8.3 V. Fil. asst Gernsback Library Series 76 -It.t:. L. =7 tubes In coaxial line B.F. system. 4- of 5 for $8.95. . 74 2X2 rectifiers In power supply. Fur 115 V. (a 400 l'y,'. Nn. H Output. P.P. Singles. 3 to 15 W. 10 asst Greylock Electronic Supply Company limy' I:v.,pti.ni.I experimenters item or patio $3.95. Heath Company 10, 11 an 1.6,. Express wily. Sew - $12.95. Used. No. 15 ('blokes. 40 to 180 Ma. Asst Induct. 10 for it $9.95. Instructogra ph Company 76 $4.45. ASD, RADAR TRANSMITTER. Navy. Operates in International Resistance Company Back Cover Tube Sockets, All new u NI. region. Uses 4 type 15 -e: tubes in P.P. Lafayette- Concord 64 tuallel lone line R.F. 1 -151{ Rectifier. Completely Nu. IO 4 to 8 l'in, Inc. min. 25 atoll 89e. .Melded In black wrinkled case. High quality parts. Leotone Radio Corporation 68 Terminal Strips 115 V. 9110 Cy', Fhpg. wt. approx. 40 Lbs. Express Liberty Electronics 68 .rely. Like Ness -$12.50. No. 17 At.wted sties and sizes. 50 for 89e. Microcircuits Company .. 58 RELAY SELECTOR UNIT. BC -685A. Consists of Hardware Assortments two tndir (dual band pass filters. 4511 1.yrks and 700 Mid -America Company 4 No. 18 Solder lugs. All sizes and types. 3 Lbs. for cycles. each uses 3 2S LOOT and 1 -12116 tubes. Com- $1.29. Midwest Radio Co. 77 ponents include 14 telephone type relays. ?Ills and 5110 ohm roils. one 25 position 4 circuit mt.O' relay with No. 19 Screws, Nuts, Washers. etc. 3 Lbs. for 51.29. Mohawk Electronics Company 74 12 ohm salt. band -pass transtormer, networks. re- No. 20 Alum. Rivets. All sizes and types. 3 Lbs. for Murray Hill Books, Inc. 75 sistors. rnndenoers. etc.. rte. Panel controls are miss- $1.29. ing. Heavy gauge chassis and panel. size: 8°1" X National Company Inside Back Cover 11ay" X Is ". Metal hood encloses entire unit. Shpg. Insulators. Ceramic approx. 55 Express only. Like new, less tubes, National Radio Institute 3 t. lbs. No. 21 Studs, Spacer., Feedthrus, etc. 50 for $1.79. Including diagram -514.95. National Schools 5 TRANSCEIVER TRANSFORMERS. Input for single 1 52) Niagara Radio Supply 74 button mike and single plate, to single grid. Shielded. KITS LISTED - $35.00 Lug terminals. New -79e. Opad -Green Company 74 Adlets 79 BK22 ROTARY RELAYS. As used with 269 series METERS, 2' ROUND CASE. ALL NEW Opportunity compass units. Like new condition-$1.95. Precision Apparatus Company 58 Tull.. ti.t M -299 ADAPTER. for SCI(- 522 Progressive Electronics Company 9 MICROPHONE -79c. lal Ovum. u 150. 51.49. VOLUME CONTROL ASSORTMENT. A selection of Utl N'stghse., 2 scales 0 -3.5. 0 -140, $1.85. Guam Nichols Company 58 various rapes of carbon and wi resound c tntrols. All Amps.. D.C. new and clean. A SI'l'ER VALUE'!" DON'T MISS IT!!!: 15 for 98e. (cl Gruen, 0.1.5, $1.59. Id) G.E., F.S. -5 Ma. 0 -50 scale. Less Slit.. $1.49. CONDENSER SPECIALS (el Trip. F.S. -10 Ma. 0 -50 scale, $1.49. 4.0 Mfd. 900 V.D.C. Square upright can -29e. Amps. R.F. RADIO SCHOOL DIRECTORY 40 + 40 Mfd. 250 V.U.C. Round upright can-55e- (fl G.E. 0 -6 With Thermocouple. $1.69. (Pages 78 -79) 1 Slfd. loon V.U.C. Small Rect. can. 8 for $1.00. (gl G.E. 0.8 With Thermocouple. $1.69. 2 Mid. 800 V.D.C. Round can. 8 for $1.00. M llliampe. American Radio Institute 900 Slyd. 200 V.D.C. Sealed round can, with mounting (h) Weston, =507- F.S. -1.2 U.C. 0 -100 scale. Technical Institute bracket- 81.05. $1.69. Baltimore (1) Readrite. so. 0 -10 Volts DC. Black Fin.. $0.59. Bliss Electrical School OUNCE! TRANSFORMER W- 226262 -4 Candler System Company FENWAL THERMOSWITCHES AS' Output. l'rl. Impedance: 10.000 Olmts. Sec. Im Commercial Radio Institute 40(111 250 c priais: Ohms, tapped al Ohms. Metal S -17. 115 V. 10 Amps. Set at 275 degrees. 44y D. X 75 51w. 400 Cyr. . IV I.g. N r O.D. Overall. 10% at 414 L. Asbestos covered shielded leads. Variable from Commercial Trades Institute 20 ^r at 75 Mw. la 250 Cyr. Response: 250 tu 2500 -100° to +400° F. at 90° per turn. New 95e. Cye. ± Glass sealed. ea. Don Martin School of Radio Arts 3 Dlt New-95e, 5.15. Same as S 17 except for 5 Amps. rating. New, 79e. Hollywood Sound Institute OUNCE! TRANSFORMER 1t7254S02 Milwaukee School of Engineering G.E. 5 DYS3AR31 Dynamotor l'rl. Impe,lain e: 5000 Ohms. Sec. Impedance: 250 RCA Institutes Olnns. Size: 1N' Lx. S r Overall. Uiagraut on case. 12 V.U.C. at 6.9 Amps. Input: 5110 V.D.C. at 85 Sla. I lernal 'cal ly sealed. New -89e, ea. output. Shoo. Wt. -05í Lbs. New -$2.95. Radio -Television Institute Tri-State College POWER AMPLIFIER AND POWER SUPPLY HOOKUP WIRE Valparaiso Technical Institute For morale radin -phono combination. Tomes: 1 -ISQ7; Assorted sizes and colors. Fabrics. Plastic. Rubber Western Radio -Television Institute 1 -4.15; P.P. OVO; 1 --51'3 or 5%4 Rect. 12 Walls and Glass Insulation. Solid and Stranded. 500 Ft. output. Power Soppy delivers 3511 V.U.C. at ISO Ma. assortment -92.39. Size: u" N 7 6 -9 Ohms to spkr. All outlets built -in, for phono motor, pick -up. speaker and input. ILaut i HOOKUP WIRE fully both. Brand new. less tubes. Shpg. WI AP- l prey. 17 Lbs. Express only. A GREAT iii -1 Duly New rut wire. I.engths from 3' to 20' L. In various $7.95. sizes and types of Insulation. Our selection of 3 Lbs. Only $1.00. Radio Apparatus Corporation 65 LAST SHIPMENT, JUST ARRIVED!! Radio City Products Company. Inc. 75 BETTER THAN EVER REFOREIIII V.H.F. TRANS- CEIVER (SCR -522) (AN) NOWIIII Radio Dealers Supply 68 01115 a sew ,.I (Luse ia.pal,r set, nett At 0ús st- OUR ELECTRONIC PACKAGED!! Radionic Equipment Company 66 Ira'rlise Irrite. Our u clean u and in over- Chock full of new and different parts and assemblies. 69 all condition. DON'T n ORDER NOW SbpO. Radio Supply It Engineering Company WAIT!! 10 Lbs. of good usable material for only $1.29. GET WI..xpprox. 60 Lbs. Express only. With tubes. $39.95. '1)1'115 NOW!!!! Solco Electrical Distributors 58 Senco Radio, Inc. 73 RADIO PARTS KITS Quantities are limned -Order now. Minimum order - charge 66 Re store. Assorted Values. 82.00. There will be a 25e packing for all orders Servelus Manufacturing Company under $2.00. 25% deposit required. balance C.O.D. All Hotel Strand 65 No. 1 Cartan. Non -ins. .W. to 2N'. 100 for $5e. orders shipped F.O.B. Chicago. Illinois. Any orders 13 No. 2 Carbon. Ins. % W. to 2 W. 100 for $1.69. rrretved without shipping instructions will be shipped Sylvania Electric Products 6 No. :I W.W. Enameled 5 W. to 50 W. 25 for $1.95. Hallway Express. Telekit 77 Toute La Radio 74 Transvision 71 SURPLUS MATERIALS United Surplus Materials 00 UNITED Universal General Corporation 79 S. St. Chicago 6, III. Welin 15 314 Halsted Wells Sales, Inc. 82 Wholesale Radio Parts Company, Inc. 14 RADIOELECTRONICS for f Book Reviews 81 THE A.R.R.L. ANTENNA HOOK (5th Edition - 1919), by the Headquarters Staff of the American includes operating instructions, a de- Radio Relay League. Published by The American tailed explantion of how it works, lubri- Radio Relay League, Inc.. West Hartford, ('onn. cating procedure, and a list of usual x 9% inches, 266 pages plus index and catalog section. Price. $1.00. troubles and their solutions. As in all the Photofact publications, photos and Though written especially for radio drawings are plentiful. In this manual, amateurs, this edition can be consid- each mechanism is pictured at least once ered a textbook on antennas and be in operating position; and at least two used by students, experimenters, and under -chassis photos, with numbered professional engineers. arrows for every part, are furnished. Its first five chapters are devoted en- An exploded -view drawing shows in de- tirely to antenna theory and design tail how each unit is constructed. Parts problems, and sufficient data is pro- lists are furnished,- R.H,D. vided to permit the reader to design an antenna to his own specifications. Chapters six through ten give full de- INTRODUCTORY RADIO THEORY AND SERV- tails on constructing specific types of ICING by H. J. Hicks. published b. McGraw -Hill Book Co., Inc., New York. 6! s x 9' ALL antennas for a inches, 393 But Azele4. the various amateur pages. Price $1. bands. By following the directions in these chapters, the reader can erect No electronic knowledge on the part many different antenna systems with- of the reader, nor any mathematical TWIN-TRAX out resorting to the design data in the training other than the ability to add, "The Tope Recorder foregoing chapters. subtract, multiply, divide, and square the Engineers are Buying" The remaining chapters cover the is assumed by this text. mechanics of antennas and include de- As an introduction to radio -and that When it comes to high fidelity sound tails on is the expressed purpose, according equipment, it's the specifications that count constructing and raising masts, to with the title in a engineers. And that's why they're buy- rotary beam mechanisms, and orienting -it turns creditable job. ing antennas. The explanations are certainly easy Twin -Trax - the popular -priced tape -R.F.S. to recorder with professional specifications. follow, as far as they go. There are Extended frequency response, wide very many diagrams dynamic of practical cir- range, low hum level, easy operation, trouble - cuits and a large quantity of do -it free performance! And two AUTOMATIC RECORD tracks means CHANGER SERVICE projects. twice the MANUAL, VOL. 2, published by Howard W. Sams. Servicing is definitely stressed, playing time on standard tape Inc., Indianapolis. Ind. Kb_ x I I inches. Price $6.75. the author pointing out possible troubles reels, with tape costs cut in half -a saving at every opportunity. Separate chapters you don't have to be an engineer to This manual describes 45 record on FM and television are provided. appreciate. changers and magnetic recorders, and All in all, a good introduction for the Write today for technical literature and a certificate accompanying the book professional factory discounts. en- novice -easy to read and as informa- I,aea,a titles the buyer to a supplement on the tive as befits its purpose -a well calcu- RCA 45- r.p.m. unit when it is issued. lated encourager for more advanced AMPLIFIER CORP. OF AMERICA The data on each changer or recorder study.-R.H.D. 398-10 Broadway New York 13. N. Y.

BUFFALO RADIO SUPPLY, ONE OF AMERICA'S LARGEST ELECTRONIC DISTRIBUTORS, IS IN OF FOREIGN PURCHASERS, A POSITION TO SUPPLY MOST OF THE REQUIREMENTS DIRECTLY FROM ITS GIGANTIC STOCKS OR THOSE OF ITS AFFILIATES. EXPORT INQUIRIES EXPORT HOUSES AND FROM FOREIGN ARE SOLICITED BOTH FROM GOVT. PURCHASING COMMISSIONS HERE AND ABROAD. EXPENSE CAN BE REDUCED AND REQUIREMENTS FILLED WITH A MINIMUM OF DELAY BY CONTACTING BUFFALO RADIO SUPPLY INITIALLY. $12.95 TAKE ALL BIG "SO" RADAR SET SENSATIONAL VALUE IN COMPRESSED AIR "SO" RADAR SET, complete with n rubes AC -DC POCKET TESTER THREE BARGAINS Iodine picture tube. This Plan-Position -nr TiIbi analyzer. featuring sensitive re- -indicator Oscilloscope has a self- contained INSTANTLY. ANYWHERE!! HOME WORKSHOP AT pulsion type meter housed In a bakelite BARGAIN park designed to run irom the 110 V. power PRICE. At-ciliate and I,rreise 2 speed case. represents the culmination or 15 yeah supply on I.5T or l'T boats. It provides 5. rhievement portable Air Com- guarauleed hubby ¿aloe. the essential diameter picture adjustable at in the instrument field by will to an $0. large company machine for the hone urksuop. SttWy 40, 4 or 2 mile circle with specializing in electronic test pressor and storage the bait at the equipment. enough for light preductim, work or renter, slowing location of landt other ships. tank. Ruggedly built I5rl,rY atandby service. Supplied Willi or any obstruction. so that navigation can Speelflrations of the AC -DC Model 17' of belling tor connectingnecting to any be carried out in With darkness or densest Volt -Ohmmi lliameter: of best materials ,mailable electric moor or power take- fog with as much safely as In brightest sun- AC Volts-o.!i, 511, 125, 250 IWC Volts using lifetime lubri- off. Also included in this unbelievable light. Your coat $39.95. -0.25. 50, 125. 250 offer are such accessurses as a 'h- drill Milliamperes AC -0 to 50 cated ball- bearing on chuck with specially bardet tool steel DC Milliamperes ed 'RM. SPEAKERS" - - . - jams, a 4 electric furnace thigh speed 0 to 50 connecting rod and Latest type PM Speaker én Ohms grinding wheel- a Klon buMug wheel tall Full Scale - oil impregnated main with a large suppiY of Miffing con, cabinet. This Ots1eakrm 100,000 pound, and a 47 steel wire seratt+ case match on munication . Ohms Center Seale - bearing on shaft. Un- brush. Your cost Sole export rec ivers, na i n a.ldltln 5400 $6.00. make perfect mirrrnm usual design forever agetit. Distributor inquiries invited. te tat tuna. Our prit e CRparlly- ALUMINUM GEAR BOX ISMO7 that $4.30. Including output A .05 to 15 Mrd. eliminates valve contains two powerful electric motors 34.99 Total frire, prepaid trouble, the most corn - and two notched gear trains. 62 gears SPEARERStTher,e'PM. anywhere in the l' 'i in all varying in available. All sÌ avec heavy t ,rversi e 57.00, Similar In' ri,tu fault Are from k to 4 th IM V magnets in air compressors. Inches In diameter. Tlds 111111 is read- )jeter. 'acklna the AI' ily converted to 34 sa is.... s for 56.60 ranges of PATENTED unique air intake system rotate a beam antenna 4_ SI.15.... 6 for 56.60 operated m other similar .$5.00 3 $1.10....10 for $9.50 above, $5.50 prepaid. increases efficiency tremendously over SENSATIONALI FASCINATING. 6 $1.50.... s Ion $8.70 other AMAZING 6.54. Oval . 2.10.... 6 for S10.80 compressors so that air output SELSY NS. brand new 77 salons made by O. (oar Radio Side) 54.50.... 6 for $21.50 1:, l' o. Two or Inure e- lo oz... 53.95.... 6 for $20.50 is much greater than that from larger connectedcted together work s. 1949 MODEL perfectly e 21 0 .5s4.93.... s for 526.50 compressors powered 110 VAC. Any rotation of the shaft of 10 21 oz... 55,50.... 6 for 530.00 MUTUAL CONDUCTANCE by heavier mo- one selsyn and all others emu crest to 12 21 05..5793.... 6 for 542.00 tors. Will deliver amor. 3500 cu. in. it will rotate exactly as many degrees AUTOTRANSFORMER -Steps p Ito, or TUBE TESTER, $52.95 In the same direction following tine, steps duwu to 1I0e- $1.95. Atlra'fiw air per min. at maintained pressure tingly as the PH.. TRANSF.: 0.3v, 3 Amps. -51.35: if units were connected Unl . Large i'_- vie of 30 lbs., or will inflate a 90 lb. together by shafting instead of eersal output Trans. a watt -a9c; la Watt wires. $1.29: 3u Watt- - Calibrated utirrodm scale -ers _-3+ This Is 51.69. AUDIO - truck in Toss than 1 true whether you twist the shaft FORMER: s. Plate to N. Grid. S. as well as Hail-Goo! scale tire min. Com- of the master unit fraction of a to revo- Grids-75e; Heavy Duty Flout panel fuse . 090..: o l plete with 100 lb. gauge, fingertip ad- lution or manyby revolutions. t'aeful for AR or Ii P.P. ts$.49; midget AC -DC sets 1.1101.1 so-kets for Indicating u -6e; MIKE TRANSFORMER allows setting tie direction of weather for T -17 Suture Irmpbnne, tills base I)'hies- toit., justment of output sane, rotating direct tenet antennas. or similar t 1.TC mincer sype_53.00. tanrn SB sur DB mike from .75 v. Io 117 y :hi pressure at any value. which will controlling Innumerable operations from ine tir grid- SI.96. comp. switching flesh hihr, ' n dblanee. Com - POW -Half -shell type. automatically be allow all present and future , maintained. Works plete with dia- 110V, 60 cy. Cenertanped HV winding. ttit tlt Specify either 2.5 or 0.3V filament when tithes In be tested regai d. ^f irt from any 14 HP. motor. Useful for grant in- nlering. less of location of elements structions. Per For 4.5 tune eta -650V, 4OMA. 15V onn tube base spraying paints or lacquers. disin- notched a 2.5 or it 3P ... Indicates gas content ail pair $4.95 71.49 shorn or ,,V'ns on each Individna r 6 t 1 -610V fectants, insecticides, annealing rut In 41MA 'S' s'Ilou of all AUDIO AMPLIFIER-- Brand new flua a 2.5 or 6.5v 1.75 ¡octal. octal and miniature Fur 2 tube nues h1ehuli ne roll cathode. an, brazing with natural inflating stage triode amplifier hating 2 of the Valu- V...... , S6M. 5\' mage ere gas. a 2.5 .3V..... 1.90 niag, teculatnr Rubes as well as all loll Ire and eat ee murer trpe alalln Dion- For T -a x .SV tires. etc. Price $14.50 postage pre- Loir Is- i00 \'. :tiMA. last. 3launractlrer name withheld because o formers that sell }10.011 a 0.:1 nr lwr 2.5x' . fer piece. .. 2.35 price offer. paid NealNeat xlfunhlmnm rase. follyfh1IY rnrinxed Ilarg- Fnr T -a 'wise errs- Tnih \', 1D \1A, SV rial anywhere in U.S. Efficient ad n.f1 _, Cswrlrah.. . Model "C" Sloping est dimension 6 inches) lerfect for roe 3.80 front counter justable syphon type spray com- Infer- he .- nnç: t1ih:11A. $52.95 gun Ilene)'shim, pb,mn anililer, 9A. 2.5v-3.5A. mike ampli- 2' , .S \. 2.itt Model "P" -- handsome hand- plete with 12 ft. of 100 lb. tested or signal a,npllflPr Fnr ) -11 1 e. Inn \. 5. Irxrrr for Itst irir sA a rubbed portable rise 57.95 radio 'setssets. A srnsatinn:d bargain at mil' 50 2.63 hose for only $7.75 with n,r 9-15''' nhLp otx_Dónv. l5nif,.5á- 11,1111 -In oil r50 with ruiner of pint con- ... . 33.40 r, A n.3v zss above 5.00 extra tainer, also prepaid. BUFFALO RADIO SUPPLY, 219 -221 Genesee St., Dept.RE-MBUFFALO 3, N. Y. AUGUST, 1949 82

TRANSMITTING

RECEIVING !v INDUSTRIAL

SPECIAL PURPOSE .R

DELIVERY Check this list for exceptional values in magnetrons, IMMEDIATE cathode ray tubes, voltage regulators, transmitting tubes -also neon. AT THE LOWEST PRICES pilot and flashlight bulbs. These are brand new, standard make tubes. Order enough for IN OUR HISTORY! future needs directly from this ad or through your local parts jobber. Type Price Type Price Type Price Type Price 52.45 S0.45 10Y VT -25 $0.45 7078 523.25 872A 014 710A 2.15 874 2.15 1822 4.35 1246 .25 12K8 .65 713A 1.55 878 2.15 1N21 Xfal Diode .65 2.20 .80 12SF7 .70 714AY 9.95 930 e 1N216 " 7.95 954 .50 1N23 " .80 12SH7 .40 RK715B 1N23A" .85 12SK7 .60 717A .90 955 .55 .85 12517 GT .70 721A 3.95 956 .55 1N27 " 4.65 957 .55 1R4 1294 .65 12567 .40 724A .95 12x825 2 amp. Tungar 2.25 7248 4.25 991 (NE16) .30 165 725A 19.95 1005 .35 155 .95 13 -4 Ballast .35 1.10 15R 1.40 726A 19.95 1148 .40 1521 730A 11.95 1201 .75 1T4 .95 FG -17 2.85 .35 REL -21 3.25 801 .60 1616 1.25 2C26 1619 .55 2C26A .45 23D4 Ballast .45 801A .75 .55 25Z6 GT .55 803 6.95 1624 1.25 2C34 804 9.95 1625 .45 2J21A 11.45 28D7 .40 2J22 9.85 30 VT.67 (For Walkie .75 805 5.45 1626 .45 8.45 33 VT -33 Talkies) .75 808 1.75 1629 .45 2J26 809 1635 .95 2J27 14.45 RK -34 .45 2.75 2J31 9.95 34 .35 810 7.95 2051 .95 14.85 39 44 .35 811 2.35 7193 .35 2J32 813 2.55 2J33 19.95 45 Spec. .55 7.85 8011 13.85 46 .80 814 3.75 8012 4.25 2J37 3.35 2J38 12.95 EF50 VT250 .45 815 2.85 8020 14.95 CEO 72 1.50 826 .49 8025 7.50 2J48 829 9001 .70 2X2 879 .65 72 3624 1.75 3.25 .35 VR -75 .90 8306 3.95 9002 .45 3A4 .65 3A5 1.05 76 .55 837 1.75 9003 3.85 VR78 .65 838 3.25 9004 .45 3ÁP1 CRT .45 3622 2.95 80 .45 841 .55 9006 FG 843 .55 3824 1.75 -81A 3.95 USE 83 851 32.50 NEON BULBS FOR RADIO 311P1 CRT 3.75 .85 1.95 83V .95 WL -860 2.55 NE-2 $0.06 3CP1 -S1 .06 3C24 24G .47 89Y .40 861 32.50 NE -15 .65 VR -90 .70 864 .55 NE -16 .24 3D6 1299 .06 CRT 2.95 VR -92 .65 865 2.55 NE -20 3FP7 .24 CRT 2.95 100R 3.25 866A 1.30 NE -21 3HP7 .24 3GP1 CRT 3.75 FG -105 9.95 869 26.50 NE48 305 .90 VR -105 .85 8698 28.95 NE -51 .06 REL -5 17.95 VÚ111 .65 5AP1 CRT 3.95 11723 .55 58P1 CRT 2.95 VT-127 English .25 5CP1 CRT 3.85 VT -127A 2.95 Pilot and Flashlight Bulbs 5GP1 CRT 6.55 VR -150 .55 VT -158 9.85 5J23 14.25 Stock No. Maxda No. Volts Watts Bulb Base Price 5J29 14.25 205 21.90 6 -8 3CP 05.6 DC Bay $0.07 5Y3G .40 2058 1.95 350.40 64 .90 211 (VT -4 -C) .65 350 -31 57 12 -16 1.5CP 04'2 Min. Bay .08 6A6 S -6 Cand. Scr. .13 6AB7 .95 215A 1.95 350.42 Spec. 12 6 .90 231D 1.30 350-20 1446 12 .2 amp. G -31/2 Min. Scr. .07 6AC7 1-3'a Min. Bay .06 6AK6 .80 2828 4.25 350 -14 49 2 .06 120 3 S -6 Can. Bay .11 687 .95 304TH 5.95 350.15 356 PR -10 6 .5 amp. B3,2 Min. Flung .05 66E6 .65 304TL 1.75 348 -22 .45 307A 4.25 350.19 Prol. Bulb 120 500W 1-20 Med. Pf 1.45 6C4 T -2 Tel. Base .18 6C6 .75 316A .75 LB -17C 24 .035A 19.75 3508 2.55 LB -58A 110 7W C -7 Cand. Scr. .17 6C21 Min. Bay .07 606 .60 371B .85 LB -57A 53 12.16V 1CP 6E5 .70 388A 4.95 L8-100A Airplane .50 417A 19.95 Headlight 24v 239W A19 Med. Pf .38 6H6 953 .22 6J5 GT .50 434A 7.45 16.101 323 3 (AIRCRAFT) T1'2 .90 446A 1.55 LB-101A LM -60 115V 250W T -20 Med. Pf .40 6J6 DC Bay .14 6N7 GT .80 450TH 19.95 LB -102 1195 12.16 50CP RP -11 110V 100W T -8 DC Pf .33 6R7G .80 GL -471A 2.75 LB -102A CC -13 1491 2.4 .8 DC Bay .14 6SF5 .65 527 11.25 LB-1028 amp. .70 WL -530 17.50 (Airplane type) 6507 Bay .14 65H7 .40 WL -531 17.50 LB-102C 3D2 28 DC 532A 1832 3.55 LB -104 313 28 .17 amp. T -3'2 Min. Bay .11 6SJ7 GT .65 Mk. Bay .12 6SK7 GT .65 GL -559 3.75 LB-105 1816 13V .33A -.11 1-2 Tel. Base .18 651.7 GT .65 KU610 7.45 L8-106 12A 12 .09 HY -615 1.20 LB -107 24 -A2 WE 24 .75 .105 1-2 Tel. Base .18 6SN7 GT .80 Med. Scr. .22 6507 GT .60 7008 9.95 LB -108 5.14 Argon 105 2'2 Watt 7A4 .65 700C 9.95 LB -109 S Telephone Type Neon T -2 .17 7A7 .65 700D 9.95 350.18 1477 24 17 T -3 Min. Scr. .16 7C4 1203 .40 702A 2.95 7C7 .65 703A 4.85 7E6 .65 705A 2.65 10(,i DISCOUNT ON ORDERS OF $100. OR OVER 7F7 .75 707A 19.50 7H7 .75 7N7 .75 707 .65 10 YT -25A .40 Manufacturers: We carry thousands of electronic parts in stock. Send us your request for quotations.

Distributors: Our standard jobber gemenf applies. Order WELLS directly from this ad. SALES, INC. 320 N. LA SALLE ST., DEPT. -Y, CHICAGO 10, ILL. (present-Ill

Latest flyback high voltage supply gives clear, bright pictures even in fringe areas Automatic frequency control locks picture in place Two flanking speakers do justice to FM sound Front -of -panel focus control Coil tuned switching assures equivalent of separate, high -Q circuits for each channel Automatic gain control 3 -stage by other 37 me IF minimizes picture interference caused radio services Double -tuned RF bandpass circuits improve selectivity and image ratio. Automatic Station Selector and fine tuning control.

Features a big 10 -inch picture tube - most popular size of all - in a genuine mahogany cabinet handsomely styled in the spirit of tomorrow ... yet only $26950 COMPANY, Inc. SLIGHTLY HIGHER WEST NATIONAL OF THE ROCKIES U S E T T S M A L D E N , M A S S A C H 8 NEW IRC RESISTOR AND CONTROL ...all in sturdy metal ASSORTMENTS

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Here's a full family of 8 IRC kits and cabinets tailored to your individual requirements. Each of these new resistor and control assortments comes to you in a beautiful all -metal cabinet at absolutely no extra cost -you pay only the regular price of the merchandise. You'll want several of these attractive kits. They provide an efficient way to stock parts, add to the appearance of your shop - and save your time in unnecessary buying trips. All ranges have been carefully selected after a detailed analysis of AM, FM and TV requirements. See these new kits at your IRC VOLUME Distributor's, or write today for CONTROL CABINET free catalog bulletin. International Resistance Co., 401 N. Broad St., Philadelphia 8, Pa. In Canada: Inter- national Resistance Co., Ltd., Toronto, Licensee. INTERNATIONAL RESISTANCE CO.

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