Radio Broadcast (Nov. 1925-Apr 1926)

712 RADIO BROADCAST ADVERTISER -its in A receiving set is no better than its tubes. With other parts and connections right a set may be as good as its tubes — no set can be better. That's why you want CECO Tubes. They stand up and deliver. With them your set works at its maximum. Clarity of tone, rich volume, long life — CECO has them all to a superlative degree. Our charted tests (results confirmed by laboratories of national reputation) PROVE CECO TUBE SUPERIORITY^— whether used as detectors, audio or radio frequency amplifiers. CECO Tubes make a Good Receiver BETTER. Try them and you'll BUY them always — for results. Now Ready! CECO Tubes with new type Long PRONG BASES. Also, Power Amplifier Tubes, E (Dry Cell Type), F (Storage Battery), for last stage of Audio Frequency. Dealers write giving jobber's name. _ C. E. Mfg. Co., Inc. m 702 Eddy Street, Providence, R. I. TUBES RADIO PANELS OF GENUINE BAKELITE Cut, drilled and engraved to order. Send rough sketch for estimate. Our New Catalog on Panels, Tubes and Rods — all of genuine Bakelite — mailed on request. STARRETT MFG. CO. * 521 S. Green Street Chicago, 111. RADIO FANS, a one-year's subscription to Radio Broadcast will cost you four dollars, two years six dollars. Consider this expenditure as being a necessary investment on your part for the future development of your own knowledge of Radio. To Roberts Knockout Fans Do you know that we have published two books on the Roberts Knockout Receivers? One is a treatise containing all the articles printed, and the other is just one article with complete blue prints on how to build this wonderful receiver. Price one dollar each. Write to Booklet Dept., Radio Broadcast, Garden City, N. Y. R343. Elfctron Tube Receiving Sets. Receivers. QST. Jan. 1926, pp. 17-20. Reflex. "A New Reflex Circuit", L. W. Hatry. A reflex circuit using good high primary-impedance audiotransformers and proper bypass condensers, is described. Distortion is prevented also by reflexing through a radio frequency tube with a shunt rather than a series audio frequency connection. The method and circuit arrangement in a two and three-tube set are discussed in some detail. R344.3 Transmitting Sets. Transmitters. QST. Jan. 1926, pp. 21-25. Crystal Controlled. "Practical Crystal Controlled Transmitters". A description of crystal controlled transmitters operating from a d.c. as well as a. c. source of supply is submitted. Complete constructional details of the crystal controlling station at 4 xe are given. It operates from a d. c. source using an ux-210 and three 204-A tubes. The a. c. crystal controlled set described operates, with two ux 210 and two 203-A tubes. Method of mounting the crystals and certain precautions are necessary in handling them, according to the author. R402. Short Waves Short-Wave QST. Jan. 1926. p. 28. Transmitters. "Getting Down Below Five Meters", H. Lyman. Several circuit diagrams with constants of transmitters suitable for the very high frequency bands used by amateurs, are given. R007. Regulations Conference, QST. Jan. 1926, pp. 33-36. Fourth National. "The Fourth National Radio Conference", K. B. Warner. A survey of the transactions and recommendations made by the various committees at the Fourth National Radio Conference, is given. Several changes in the allocation of frequencies were proposed, including amateur phone operation on the 3500-3600 kc band (85.7-83.3 meters). Broadcasting conditions are to be placed on a higher plane than heretofore, through elimination of some of the stations and adoption of new regulations govering their operation. The new frequency assignments from 550 kilocycles up (545 meters down) are also published in this summary. R610. Equipment; Station Description. Stations. Radio. Jan 1926, pp. 10-1 1. Portable. "The Radio Detective". A car, completely equipped with necessary transmitter and receivers for use in connection with the radio supervisor's work in the 8th district, is described and illustrated. A Kolster direction finder, short and long-wave receivers of various types, a 50-watt transmitter, and equipment for giving license examinations anywhere, make this portable radio station a modern radio supervisor's office on wheels. The diagram of the field strength measuring set is shown, and constants of the circuit given. R343. Electron Tube Receiving Sets. Receiver, Radio. Jan. 1926, pp. I2ff. L C Modified "An Exceptional Four-Tube Receiver". E. E. Turner. A four tube receiver, r. f. stage, regenerative detector, and two stages of audio amplification, is described. The wiring diagram shows several unique features, which are also taken up in the general discussion. Among these is the method of controlling oscillations in the regenerative circuit. Data on coil construction and panel layout, serve as a guide to building the set. An ABC eliminator may be used with the set, the wiring diagram of the complete circuit being shown. This set is a modification of the LC circuit described in the October, 1025, issue of Radio. R531.2. Station Call Letters Stations. Radio. Jan. 1926, p. 22. Sbort-waie. "Short-Wave Stations". A complete list of short-wave stations both, limited commercial and general public, operating in the United States, is given. There are forty-six in all. The inclusion of class, frequency, wavelength, owner, power, and call, makes this table a most complete reference guide. R376.3 Loud Speaking Reproducers. Loud Speakers, Radio. Jan. 1926, pp. 24ft. Hornless. "Hornless Types of Loud Speakers", Dr. J. P. Minton. The author enters into a detailed discussion concerning the general types of loud speakers now used. The new cone type speakers make use of large vibrating surfaces. Flat surfaces may be used to obtain good sound vibrations over a large frequency range, but shaping such surfaces into the form of a cone gives greater rigidity and less natural resonance, at the same time rendering also better acoustic radiation. Three types of driving units jhave been employed in the commercial cone speakers; electro-dynamic, balanced armature, and bipolar unit. These are discussed in detail. R383. Resistors. Resistors, Radio. Jan. 1926, pp. 25ft. Vacuum Tube. "Vacuum Tube Resistors", G. F. Lampkin. Vacuum tubes, in addition to being used as detectors, amplifiers, and oscillators, may be used as variable resistors to very good advantage. As such they have several advantages not found in grid leaks or regular resistances. They are especially good as a grid leaks in an oscillator to control keying and phone transmission. Data on actual tests made with 201-A and 202 tubes, and information concerning their uses as grid leak resisters, are given. R148. Modulation. Modulation, Radio. Jan. 1926, pp. 31-32. Methods. "Speech Modulation Methods", Lieut. J. B. Dow. Three methods of speech modulation, the variable absorption method, grid voltage variation method, and the plate power variation method, are taken up. Several circuits, including the Meissner and a combination Heissing and Colpitts, are shown, and an account of their performances discussed in some detail. R343. Electron Tube Receiving Sets Receivers. Radio. Jan. 1926, p. 33. Short-rVaoc. "A Good Short-wave Receiver", F. C. Jones.1 For use on the very high frequency stations, a receiver must be capable of sharp yet not too sensitive tuning. Herein is described a two-tube receiver operating on the capacity feedback principle, the tube capacity being large enough for this purpose, Oscillations are controlled by _ means of a runedplate circuit. Construction;;! data and circuit diagram are given. 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