Radio Digest (Oct 1923-July 1924)

RADIO DIGEST — Illustrated February 9, I he Interference Problem in Radio By E. F. McDonald, Jr., President of the National Association of Broadcasters IN ANALYZING the Radio interference situation at the present time, it should tys be remembered that while -:ing is of paramount importance to millions of people throughout the coun•e are other phases of the Radio stry which must be considered and a which depend much of the commerce he world. Trans-Atlantic and ship-to.dio traffic are of vital impor The work of the serious Radio experiiso of the highest value in hering the advancement of the Radio In order that the broadcast listener may get the most out of his receiver, a thorough knowledge of the causes of the interference which he occasionally experiences, together with the various means available for their reduction or eliminais essential. Two Most Frequent Causes of Trouble There are, of course, various types of interference occasioned by different causes. The two most annoying at the present time are telegraph code interferences from ship and shore stations working on low wave lengths of around 450 meters, and the reradiation of receivers of improper design or improperly operated by unskilled users. It is to the interest of all participating in the Radio industry to assist in correcting these conditions as well as the other causes of interference. The National Association of Broadcasters have conferred with Secretary of Commerce Herbert Hoover on the subject of ship interference, and through his efforts and co-operation are arranging for international regulations providing for the carg on of ship-to-shore traffic on wave lengths outside the broadcasting band. This article, therefore, deals only with the interference created by re-radiation from Radio receivers. Legislation Cannot End Bad Conditions It is a popular fallacy that all that is necessary to put a stop to any undesirable condition is the passing of legislation. Unfortunately this idea has occasionally taken root and grown into something that constitutes a real menace at the heart of our American civilization. There is nothing more detrimental to the morale of a nation than the adoption of legislation which is obviously impossible of enforce ment and which, through the ease with which it may be ignored, teaches wholesale disrespect not only for the law but the authorities that make laws. We have, at the present time, no better example of an "iron-clad" law which, so far at least, has been impossible to enforce, and which has possibly worked a greater evil than that which it was designed to eliminate — than the prohibition amendment. Patriotism Only Successful Porce in War During the war the navy department undertook through its intelligence service to prohibit the use of transmitting and receiving apparatus throughout the country. The prohibition on' transmitting was comparatively easy to enforce, but, notwithstanding every effort to eliminate reception, in the final analysis it came down simply and squarely to reliance on the loyalty and patriotism of the individuals which go to make up our great nation. Obviously the individuals who really desired to use Radio for ulterior purposes had no such sense of loyalty, and as a consequence, to a great extent, all that was accomplished was the prohibition of the use of receivers in the hands of those who would not use them in any case to the disadvantage of the country, whereas it was practically impossible to stop the use of such apparatus in the hands of those intent on serving their own ends. Adopted Legislation Could Not Be Enforced For these reasons, the adoption of legislation prohibiting the use of receivers which feed back energy into the antenna is obviously absurd. The adoption of an act of this kind would be comparatively easy, but the enforcement would require a greater force of officers and special agents than we have at the present time attempting to enforce prohibition. Certainly our government cannot afford such an expenditure even if it were possible to completely eliminate re-radiation by such means. It should be remembered that, in the first place, the locating of the offending receivers which feed back into antennae would be comparatively difficult, and even were they located, it would be a simple matter for the user of a set of this kind to disconnect the tickler coil, or whatever means was used to feed back the energy, while the inspector was present, and at This symbol of Quality is your protection. UV-201-A Radiotron UV-201-A is a highpower vacuum tube which, while suitable for a detector, is intended primarily to be used as an amplifier, at either radio or audio frequency. It is famous for volume, for clearness and for economy of service — drawing but .25 ampere. Radio Corporation of America Sales Offices — Dept. 312 233 Broadway, New York 10 South LaSalle St., 45'3 California St. Chicago, 111. San Francisco, Cal. Price $5.00 Be sure that every vacuum tube you buy is marked RADIOTRON. Radiotrons BEG. U S. PAT OFF. Standard Merchandise Only S. HAMMER RADIO CO. 303 ATKINS AVE. BROOKLYN, N. All Sales on a MONEY BACK GUARANTEE Anything and Everything in Radio $54.00 BLUE PRINT FOR THE IMPROVED COCKADAY 4 CIRCUIT RECEIVER $1.50 A 5 TUBE NEUTRODYNE set with Genuine Facte parts, wired complete in Mahogany tSC ftft Cabinet without tubes or batteries <pOD.\J\J List AMSCO PRODUCTS Our P rice $71.00 AMPLEX KIT i56.50 1.80 11 Plate Variable Condenser 1.65 2.30 17 Plate Variable Condenser 2.05 2.50 23 Plate Variable Condenser 2.25 3.50 43 Plate Variable Condenser 3.00 4.00 11 Plate Vernier with Bakelite Dial 3.50 4.50 23 Plate Vernier with Baktlite Dial 3.95 5.50 26 Plate Vernier with 4-in. Bakelite Dial 4.75 5.00 43 Plate Vernier with Bal<elite Dial 4.45 1.00 6 Ohm Rheostat with knob 85 1.25 30 Ohm Rheostat with knob 1. 10 1.25 6 Ohm Rheostat with dial 1. 10 1.50 30 Ohm Rheostat with dial 1.35 1.50 400 Ohm Potentiometer with knob 1.39 1.75 400 Ohm Potentiometer with dial 1.55 2 inch Bakellto Dials 40 3 ine! 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List Our Price S 2.25 Filkostat $ 1.90 2.00 Bradleystat 1.75 2.00 Bradleyleak 1.75 PHONES $ 5.00 Tumey 3000 Ohms $ 2.75 12.00 Western Electric 10.50 6.00 Brandes 4.75 12.00 Baldwin 7.95 7. 00 Federal 4.95 6.00 Potter Precision 4.15 TRANSFORMERS $ 7.00 Federal No. 65 $ 5.45 5.00 Acme 3.85 5.00 AU-American 3.85 7.00 Amertran 5.75 5.50 Thordarson 4.50 mo Duplex Pushpull, pair 10.50 5.00 Akraoy 3.95 5.00 Modem 3.95 5.00 F.rla 4.25 5.00 Amplex 4.25 BATTERIES $ 5.50 45 Large Ereready or Cyclone $ 4.25 2.75 45 Small Eveready or Cyclone 2.45 2.75 22^4 Large Ereready or Cyclone 2.45 1.50 22% Small Eveready or Cyclone 1-35 CONDENSERS $ 2.00 Signal 11 plate $ 1.40 2.50 Signal 23 plate 1.60 2.75 Signal 43 plate 1.05 ■-. imiral 11 plate 1.45 2 75 Admiral 23 plate 1.65 .Imiral 13 plate 1.80 fi.00 ITammarlund Vernier 11 plate 4.95 8.50 llammarlund Vernier 23 plate 5.65 7.0© Hammarlund Vender 43 plate 6.25 4.50 U. S. Tor.l Vernier 11 plate 3.50 r. S. Tool Vernier 23 plate 3.75 5. T>i) D. S. Tool Vernier « plate 4.25 ALL MAIL ORDERS SHIPPED PROMPTLY. Orders over $5.00 will be shipped prepaid. Money orders or C.O.D. Write tor Price List. Not insured unless insurance charge? included. tach it the moment he left. The enforcement of any such act would also be rendered extremely difficult because of the statutes prohibiting the entrance of private dwellings without proper search warrants. The Solution to the Problem Granting that the feed back from receiving sets is harmful and that preventive legislation, if not impossible, at least is impractical, what is to be done? Obviously the solution to the problem is constructive action on the part of the Radio manufacturer. At the present time the laboratories of eight of the largest manufacturers of receiving apparatus are at work night and day on the production of a simple device to be connected ahead of receivers feeding back, which will not allow the passing of this energy out to the antenna. Such a device, when developed and perfected, will be put on the market by the manufacturers, according to an agreement among them, at practically actual cost, so that the users of all types of sets will have the benefit of the device without undue expense. It is not fair or reasonable to expect the users of feed back receivers to junk and throw away apparatus representing the investment of many hundreds of thousands of dollars, when by the addition of some simple device the re-radiation can be entirely removed and reception improved. The public will not be hard to persuade to use a device which will cost little and which will not only through reciprocity eventually eliminate all feed back howls, (Continued on page 30) SUPER VALUES NEW COCKADAY FOUR CIRCUIT RECEIVER ALL PARTS As specified by Mr. COCKADAY LIST PRICE, $75.00 pS $59.00 Solid Mahogany Cabinet for above set, $7.50 Extra GENUINE FOR 5 TUBE SET Fada-Hazeltine Neutrodyne Parts List Price $65.60 Our Price $50.15 You Save $15.45 by Buying Through Us RESISTANCES — Genuine P. L. Original Lavite 48,000 OHMS $1.00 100,000 OHMS $1.00 We Are Prepared to Supply Dealers. Write for Our Proposition. We Have Just Received a New Shipment of Our Price THE NEW MODEL D. N. K. & K. PHONES $ft 50 MADE IN GERMANY ^ WE GIVE A 20% DISCOUNT On All Standard Radio Apparatus Not Listed Above ALL MAIL ORDERS SHIPPED PROMPTLY. SEND MONEY ORDER. INCLUDING POSTAGE. The BADIO MAIL ORDER HOUSE— Known for Low Prices. Write for Our Cataloj B HAN Es-ZENER 3 WEST 29th STREET, NEW YORK CITY WEIGHS ONLY, 802 We THE PHONE IT TOOK A SOLID TO DES1 arantee A *200,000.00 COMPANY stands squarely back of the guarantee on everu Scicn tific headset SEND NO MONEY? Sfi&ISRo Order TODAY a.ooo ohms bu Postcard and Pay Postman on arrival LOUD SPEAKER UNIT*!*5 295 POST* PAID The Scientific Headset to be the greatest value on the market. Try it for five days. If not satisfactory send it back and your* money0 will be refunded immediately. Circular0 oa request. Dealers wanted. THE SCIENTIFIC ELECTRIC WORKS 98 Brookline Ave. dept. w. BOSTON, MASS, Agents for New York and Vicinity— AMBASSADOR SALES CO.. 74 Cortlandt St., Phone CortUndt C29C k