Radio Broadcast (Nov 1926-Apr 1927)

430 RADIO BROADCAST ADVERTISER There's money for you in RADIO Wonderful opportunity for ambitious men to win success in this fastgrowing profession The Radio industry is expanding so rapidly that trained men are at a premium. There is a constant, urgent demand for operators — factory superintendents — engineers — service men — designers — salesmen. There is no better way for you to succeed in this fascinating business than to study the Radio Course of the International Correspondence Schools. This course is new and complete. It was written by practical authorities in this field. It is endorsed by leading radio experts and radio manufacturers. Mr. R. E. Thompson, president of the R. E. Thompson Manufacturing Company (makers of the famous Thompson Neutrodyne Radio Set), says: "I was once a student of the International Correspondence Schools myself and I am familiar ■with your methods and texts. I recommend them to any young man who is sincerely seeking to improve himself in position and salary." Quincy J. Workman, of Scranton, Penna., writes that he has "nearly doubled his salary" since he took up the I. C. S. Radio Course. He is now manager of the Radio Department in a large store. This same course enabled John M. Paynter, of the U. S. Lighthouse Service, Charleston, S. C, to get a position as Radio Operator and Ship's Electrician. Scores of other men in radio factories, laboratories and stores report similar progress. You, too, can get in on the ground floor if you act quickly. But don't delay too long. Mark and mail the coupon today and let us tell you all about the I. C. S. Radio Course and what it can do for you. Mail the Coupon for Free Booklet ~l International Correspondence Schools Box 8297-F, Scranton, Penna. Without cost or obligation, please send me I all the facts about the new I. C. S. course in | RADIO 1 I Name.. Street Address.. City ..State.. Bradjptstab \ PERFECT FILAMENT CONTROL 'l Provides complete J noiseless filament control for all radio tubes V withoutchangeof con 5 nections. Metal parts ■" are nickel plated. One ■» hole mounting. Sell „■ contained switch opens ^ battery circuit when V desired. i ■™ Electric Controlling Apparatus mm 278 Greenfield Avenue Milwaukee, Wis. % ^8en-Brar%r Co. R156. Transformers Transformers and Chokes. Wireless World (London). Sept. 29, 1926. Pp. 455-458. "Magnetic Circuits of Choke Coils and Transformers," S. O. Pearson. In designing choke coils and transformers for radio circuits, it is important to keep in mind that in many parts of these circuits the coil must carry both d.c. and a.c, says the writer. If the d.c. component saturates the iron, practically no choking effect is produced by the coil. The principle is outlined diagrammatically by curves showing the variation of cuirent taking place in the anode circuit and the magnetic flux density. The use of air gaps is supposed to greatly increase the magnetizing current, but, at the same time, reduces the effective inductance of the coil. R113.6 Reflection in Loud Speakers. Loud Speaker Wireless World (London). Oct. 13, 1926. Reflection. Pp. 506-508. "Acoustic Reflection," N. W. McLachlan. The discussion concerns the effect of resonance when loud speakers are located in rooms where echos occur. The reflections produced will determine the proper placing of loud speakers for best results on the low as welt as the high frequencies. R005. Executive: Administrative. Problems of Radio Broadcast. Dec. 1926. Radio Industry. Pp. 144-145 "What the Future Holds for the Radio Industry," F. Strother. In discussing the problems of the radio industry, comparison is made between two companies — the National Cash Register Company and the Radio Corporation of America; the former with one aim. one purpose, the latter with a variety of purposes. The RCA is called an artificial organization, because it lacks the natural foundations of a business enterprise, i.e., a purely commercial origin, singleness of purpose, and positiveness of control. The importance of commercial skill, inventive talent, or manufacturing skill, is considered as valuable as the possession of patents. The final analysis is sketched as resolving itself into a problem of "the survival of the fittest." R115. Meteorological. Weather and Radio. Radio Broadcast. Dec, 1926. Pp. 152-153. "How a Low Barometer Affects Radio," E. Van Cleef. A theory is presented explaining the relation between static formation and atmospheric circulation. In addition to the points discussed by the author in Radio Broadcast, May 1925, pp. 90, the following is added: Reception is accompanied by static when transmission crosses any part of a warm humid "low" or when transmission crosses an area adjacent to an intensely developed humid "low" whose surface temperatures are above the freezing point. If the precipitation throughout the "low" is rain, static will be pronounced, while if it be snow or ice, little static will occur. A comparison of the weather conditions for the 1925 season and the 1926 season, when considered with the points mentioned, explains why reception was betterin 1925. R343. Electron-Tube Receiving Set. Receiver, Radio Broadcast. Dec., 1926. Pp. 169-173. Single-Tube. "A Single-Tube Receiver That Won't Radiate," Zeh Bouck. A single-tube three-circuit regenerative receiver, nonoscillating, is presented, using the King Equamatic system. In the author's opinion, the following are the requirements for a good beginner's receiver: (a). Easily wired and mechanically simple, (b). Inexpensive to construct, (c). Nonoscillating, (d). Should be good enough to keep. Construction and operation details are given for a receiver which fulfills these conditions. R384.3. Frequency Meters. Frequency Meters. Bureau of Standards. Letter Circular LC 180. "Specifications for Frequency Indicator, Type B, for Use in Radio Transmitting Stations." This circular letter describes in detail the construction of a frequency indicator for use in broadcast transmitting stations, whose frequency falls between the values of 550 and 1500 kilocycles. It consists of a simple capacity and inductance circuit with a thermo-galvanometer coupled inductively to it through one turn. The specifications are very detailed and complete for constructing a precision instrument. R351. Simple Oscillators. Oscillators. Bureau of Standards. Letter Circular LC 1S6. Pie^o. "Specifications for Portable Piezo Oscillator, Bureau of Standards Type N-." A portable piezo-electric oscillator, consisting of a simple electron tube with inductance, shunted by a variable capacity, in the plate circuit, with provision for the crystal in the grid circuit, is described. Together with the drawings, this information is complete concerning construction and operation of a valuable laboratory instrument. R134. Detector Action. Detector Proc. I. R. E. Oct. 1926. Pp. 649-662. Action. "Theory of Detection in a High-Vacuum Thermionic Tube," L. P. Smith. In this paper some new ideas have been presented regarding the detector action by means of the high-vacuum tube in connection with a grid leak and condenser, which show the function of the grid leak and condenser as well as their proper values for best detection. It has been shown that three main sources of distortion exist with this method of detection. They may be briefly stated as follows: Two sources from the curvature of the grid characteristic; one of these is frequency distortion due to the harmonics produced, and the other an amplitude distortion arising from the fact that the rectified grid current does not vary linearly with the input voltage. The remaining distortion is produced by the grid leak and the condenser. R114. Strays. Strays. Proc. I. R. E. Oct., 1926. Pp. 663-673. "Long-Distance Radio Receiving Measurements and Atmospheric Disturbances at the Bureau of Standards in 1925," L. W. Austin. The article presents a resum£ of the long-distance measurements of long-wave stations made by the Bureau of Standards. Conclusions are drawn regarding the possible explanations of the results. Phasatrol A true balancing device for radio frequency amplifiers PHASATROLS are the latest achievement in radio frequency amplification and can be installed in any radio frequency set in a few minutes — no technical knowledge or skill is necessary. PHASATROLS simplify tuning, stop radio frequency oscillations and distor* tion, enable your tubes to work at maximum efficiency and prevent them from radiating interference to your neighbors. At your dealers or write direct. Write for hook-up circular Price, $2.75 Dept. 25, 428 Broadway, New York, N.Y. ELECTRAD This is a good lime to subscribe for RADIO BROADCAST Through your dealer or direct, by the year only $4.00 DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK Automatic Power Control No more plugging in sockets and turningswitches every time you use your set — no more tinkering with them every time you turn off the set. The Yaxley Automatic Power Control takes care of your B eliminator or trickle charger or both. You know that when you turn on your set, the trickle charger is off, the B eliminator is on. When you turn off your set the Power Control turns off the B eliminator and turns on the trickle charger. No. 444 Series type — for sets having tubes with a current draw equal to or greater than 6 U. V.199 types of tubes. Each, $5.00 Radio Convenience Outlets Install a Yaxley Radio Convenience Outlet for loud speaker and phone connections in every room. Consists of a wall plate and a wall socket jack with screw terminals. Fits any standard switch box. Easily wired. Wiring diagrams in each package. No. 135 Radio Convenience Outlet Each, $1.00. Also makers of the famous AirCooled Hheost at. Jacks, Jack Switches, Cable Connector, Plugs, etc. At your dealer's. If he cannot supply you send his name with your order to YAXLEY MFG. CO. Dept. B 9 So. Clinton St., Chicago, 111.