Radio Digest (July 1924-Apr 1925)

' ' RADIO DIGES T— Illustrated April 4, 1925 Questions and Answers Winding a Conpler nn. ! havo n horn upler that does not wort I. l would lik. to get .i lltllr Information on the proper way ind It. Th. aperiodic primary and the ndary are wound on a tube ^'i Inches ire and the tickler on a tube .i J Inches long, the primary haa 80 turns and Is I Hilary ! ', Inches. The ndar) has S8 turns and the tickler -•■ turns. Thi lary Is shunted p] ■ condensi • i'; • -■ I will tune to about 475 meters, I want to rewind colls bo tbey will tune from 800 win you please tell me ■ t-..|>. r numbers of turns for the colls. l w.mt to u*' number 88 wire. length you wish to r having the aperiodic primary t h<>wing number of turns is correct. Sta turns on the primary, 40 turns on the secondary, and about 20 turns on the tickler. With a .0005 condenser you will no trouble covering the range. Tuning to Hlgrher "Waves ( 12878) SDG, QrayvlUe, TH. i have a Freshman Masterpiece. It is loud and i gel distance and volume, but I am unable to get any station with a wave length higher than 4.84 meters, and as I Uke tO get KSD and KVW, I would lik, to and some way to bring the tuning capacity of my set up to -<^ meters. I can tune in the lowest, t thought maybe a condenser across the aerial and set would do it. hut it did not help. .\. — in answer to your quest ion, we wish to advise that a small lixed condenser across each one of. the tuning condensers will help you tune, to the higher waves. Crystal in B. D. 125 (12459) CGD, Coin, Iowa. Will R. D. 125 tuned Radio frequency diagramed in the December 20, 1924 issue work successfully and be selective? I have made one but the crystal only works a short time then it quits. I leave it for a day or two then maybe it will work lor a short time and then quit. The crystal worked good in a small set at any i inic. The three coils and three condensers arc equally divided on the panel and was wired as directed. I havo traced each wire time and again to make sure. Is it possible for parallel wires to have any effect on it? A. — The trouble in your case is most probably not the crystal but the battery. The battery in all probability is run down and when allowed to stand for a while it picks up again but soon after dies when put to use again. Double Antenna (12890) LT, Mound, La. I have substituted a double wire antenna for my single. My signals now come in almost too strong at times and it is harder to tune out interference. Can I install a single wire beneath the double, and on the same poles, with separate lead-in, so I may use either one giving best results under different weather conditions, without the one not in use interfering with the other. If so, how far beneath the double should the single wire be run? A. — It is possible to put up another antenna, below the one you now have at a distance of 3 or 4 feet. If the signals come in too strong use less amplification. A. F. TUBE COUPLINGS Tie ( < 'ontlnui d from page 80 ) form of coupling now general use is resistance pllng, the outstanding superiority of which is the quality -Of the output. It is of a transformer that It cannot equally amplify all frequencies and certain frequencies are passed more hut where two stages of Radio frequency amplification arc used, or with a superheterodyne or reflex, I he use of more than three stages of resistance coupling is not i,, I.,' recommended. It can be done, but complications are likely to follow. Figure :; shows three stages of resistance coupled amplification with the necessary jacks for plugging in the phones after either the first or second stage. ©B 90V© "5U2V©Pigure 4 efficiently than are others. While remarkable strides have been made in the perng of audio transformers they are Mill not perfect and the chief claim of the resistance coupled method is the perfect reproduction secured. A resistance coupled amplifier can be adjusted to a point at which there is no distortion of any audible frequency and all frequencies are p.iss.-d equally well. There is less amplification per tube where the resistance coupling is used, but to offset this slight ■lvantage there is the purity of reproduction and the fact that there is less I: battery current draw. As to actual •. three stages of resistance coupling • just about the same as two stages of transformer coupling, both as to initial tment and upkeep. In figure 2 Is a circuit using one stage of transformer coupling and two stages of I coupling. This is a very ilar arrangement which gives excelquallty with a very low amount of distortion. Th. question will at once come up In the reader's mind that if there is no distortion In resistance coupling, how many st; be used efficiently. It will be found that four stages can be I behind a regenerative detector, and behind a circuit using one stage of Radio frequency amplification and a detector, Ranlf Radio Coniole. BanJf ManufacturI Veddi r St., Chicago. ZELLERS RADIO LOO BOOK, 25 Cents, mpany, Hooper, Nebraska, SPECIALIZED RADIO DEALERS — Vou k.-.p up your sales all summer. Write dio Laboratory, C 10. Lake go. Salesmen calling on radio dealers wanted di line. The Thoria Tube Compat D," Middle Hen to build radio acta in spare time. Lambert, B01-B Kaufman BIdg., wii hlta, K A REAL FIXED DETECTOR For REFLEX and CRYSTAL SETS or Operates »> a ir,.';l irt In |ti«lf. Standi Reflex Voltage, laiU tndaflnJ 1 doe* •wa» with txrthcrtome catwhliker and hunting ( ,r II • Tou can depend on 11 being; alwayi "Hot." Get ■r distance reception on CKVKTAL SET. Hare A n than •n Tubes. Oet a I. I know the Joy of 'teptlon. Packed In t.-.i with {tracked and Untrue(Inns p: . '>. Every one guaranteed. Dialtrt Write for Diic&unti TOWNER RADIO MFG. CO. 2620-A Victor St. Kaniai City, Mo. Push Pull When powerful local signals are being received, and either of the above methods are used, it frequently happens that the last tube cannot handle the volume of energy delivered to it, which brought about the use of push pull amplification. While two tubes are used in such a unit they act as one stage and both halves of the cycle are utilized. Since the energy is great, and high plate potentials are always applied to such a unit, a C battery is essential to biasing of the grids. The amount of amplification from a stage of FOLDING Box-Type Loop, Bakelite Winding supports, non-kinkable wire and 3 taps. A new convenient size, 23 Inches high. Shipped prepaid for $6.75. Perry Radio Service, 815 Lake Ave., Racine, Wis. PATENTS Write for my free Guide Books "How to Obtain a Patent" and "Invention and Industry" and "Record of Invention" blank before disclosing inventions. Send model or sketch of your invention for instructions. Promptness assured. No charge for above information. Clarence A. O'Brien, Registered Patent Lawyer, 2009 Security Bank Building, directly across street from Patent Office, Washington, D. C. GO into the RADIO BUSINESS We specialize in Equipping New Dealers with entire stock — ADVICE FREE. Send, for Our Radio CATALOG & BARGAIN LISTS Wholesale Only MANHATTAN RADIO CO. 112 Trinity Place New York City M ,', -Q ,\\V ' idcastlnf k\ VV -.1 I t,i»--.'.' station* of North Amer | V-' __-riiJI''a lndcxi-d by Wavo I Oo 720 St citron* *m PC5T PAID lengths. Dial Readings, Mil, Frequencies and fall Letter-:. Nettling to wrlto but your dial settings. Gives dial positions for station: you bare been unable to get. SelfIndexing. 86 paces, 7x1(1 Inches, with beautifully hound c postpaid. Stamps taken. THE RADEX PRESS 222 Euclid Arcade Annex Cleveland, 0. push pull is not apt to be as great as is to be obtained from a single stage using a 5 to 1 transformer, since the ratio of push pull transformers is usually about 2 to 1 or 2Vz to 1. However, the reproduction will be far clearer and there will be considerable amplification because of the 2 to 1 ratio and the amplification constant of the tubes, which may be anywhere from 5 to 10. clearness, is shown in figure 5. Making use of four tubes, it is a combination of transformer coupling, resistance coupling and push pull amplification, giving a high amplification for the first tube, a little less, but one without distortion for the second tube and the ability to handle volume on the last two tubes. This amplifier, if built in a separate cabinet with input terminals at one end 0"eT 135V© "ei'90v.© Figure 5 Figure 4 shows an excellent audio frequency amplifying system, which will give exceptional reproduction and is capable of handling a very great volume of energy. This is the best means known of getting pure reproduction without resorting to the use of resistance coupled amplification. The ideal amplifier is naturally one that will give the greatest amount of signal strength compatible with good quality and clearness. The nearest approach to such an amplifier, and one which is the best possible compromise between volume and Specialized Radio Dealers YOU CAN KEEP UP YOUR SALES ADD SUMMER Write to the DRAY RADIO LABORATORY 6 E. Dake St., Room 507 CHICAGO idio Tubes Exchanged Send us your old tube— any make — any condition—and we will send you a Brand New J Guaranteed Tube, of whatever type you require, for $1.75. All ship -, _ __. inents by insured Parcel A T /O Post C. O. D. Send no money J —order today ■"■ D-R-C RADIO CO. C.O.D. 327 S. LaSalle St Chicago, Ml. T^l^ T^T,The very latest up-to-date radio wall HK H M map 28 by 34 Inches. Shows call 1% I i I j letters, locations, lengths, and kilocycles of all radio broadcasting stations, U. S., Canada, and Mexico, relay divisions and radio districts. Also a scale for measuring distance. This wonderful map postage paid, ABSOLUTELY FREE. Merely send us a list of stores in your city which handle radio apparatus. Be sure and give the street address, and if you know the manager's name, give It also. DO IT TODAY before this offer is withdrawn. OZARKA, Inc. 808 Washington Blvd., Chicago, 111. and output jack at the other, would be ideal for use after any type of receiver from a one tube regenerative to a six tube super-heterodyne. $10.00 IS ENOUGH Tou can get programs 400 to 1,000 miles away on Lambert Crystal Sets, and you don't need tubes or batteries. 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Art Mache Co. 347 W, Austin Ave. Chicago No. 807 — Complete with owerful sensitive unit. Crystal black $20.00 When a storage battery fails to take a charge, it is an indication that it needs to be overhauled ac a battery station.