Radio Broadcast (May 1928-Apr 1929)

©C1B ZZSdl WILLIS KINGSLEY WING .... Editor KEITH HENNEY . Director of the Laboratory HOWARD E. RHODES . . Technical Editor EDGAR H. FELIX . . . Contributing Editor RADIO B ROADCAST ENGINEERING THE LABORATORY* SERVICING VOL. XIV. NO. 6 Contents for April, 1929 Frontispiece The Serviceman s Responsibility 366 New Uses for Power Amplifiers Fred H. Canfield 367 The Condenser-Type Loud Speaker Joseph Morgan 369 The March of Radio An Editorial Interpretation 372 A Well-Balanced Radio Commis Regulation of Allocations At sion tempted Congress Considers Commission's In the World of Broadcasting Record Amateur and Commercial Radio More Discussion on Frequency Control The Routine of Testing Receivers John S. Dunham 375 Strays from the Laboratory Keith Henney 377 Vacuum-Tube Fuses "Phantom" Power Tubes Output Versus Amplification Novel Dynamic Baffle Causes of Winter Static Life of a.c. Radio Tubes Experiments With Pentodes Amateur Intermediates The Real Size of the Radio Market ----- 379 The Experimenter's Armchair Robert S. Kruse 380 Grid-Leak Power Detection Frederick Emmons Terman 382 Sound Motion Pictures ---- Carl Dreher 385 Production Testing With Oscillators Richard F. Shea 387 Rook Reviews ------ Edgar H. Felix 388 The Serviceman's Corner - - - - 389 Practical Radio Service Records John S. Dunham 392 Characteristics of Power Rectifiers Roger Wise 393 "Radio Rroadcast's" Home-Study Sheets 397 No. 19. Fundamental Radio Theory No. 20. Inductance Standards Real Versus Apparent Selectivity Kenneth W. Jarvis 399 Rroadcast Engineering ----- Carl Dreher 402 "Radio Rroadcast's" Set Data Sheets ---- 403 The Day-Fan 8-AC Power Set The King Model H Receiver The Freshman 2N-12 Receiver The Bosch Model 28 Receiver An Examination for Radio Servicemen J. R. V. Meacham 405 In The Radio Marketplace 406 Radio Rroadcast Laboratory Information Sheets Howard E. Rhodes 412 No. 273. Neutralizing R. F. Circuits No. 276. Simple Two-Way TeleNo. 274. Bucking Coils for Dy phone Set namic Loud Speakers No. 267. Simple Two-Way TeleNo. 275. Obtaining Grid Bias phone Set The contents of this magazine is indexed in The Readers' Guide to Periodical Literature, which is on file at all public libraries among other things SO MANY of you have said so many nice things about the March issue that there was some wonder in the editorial offices about the possibilities of compliments — and what is more to the point, real use and appreciation — on this number. But on examining the contents, which can be found not far to the left, we are just as proud to launch this issue as we were the preceding one. Mr. Morgan's story on the condenser loud speaker packs all the available information into three interesting pages, beginning on page 369. Mr. Dunham's article on page 375 gives dealers and servicemen an interesting outline of set testing routine which is practical down to the last period. The figures on set and tube sales for the last two years, compiled by the Editor should prove interesting and useful reading for everyone in the industry. And then, Mr. Kruse makes his bow as conductor of the new experimenter's section, Prof. Terman has a corking article on "power" detection, Mr. Jarvis puts a new angle on the selectivity question which is by no means a theoretical one, Roger Wise writes of characteristics of filament rectifiers, and there are our regular departments, all of them unusually interesting. WE OWE a general apology for an error which crept into Mr. Kruse's article in the March issue which described the work of the Radio Frequency Laboratories. The caption under Fig. 1 should have read: "A model set using screen grid tetrodes." The caption under Fig. 2 should have made clear that the device shown was used for checking the design of single stages which are placed in the central compartment. T^HE May issue will contain the third of Prof. Terman's -*■ articles in his series on "Detection" and will deal with the principles of C-bias detection. In addition there is an interesting article on self-shielded coils, a discussion of audio-transformer measurements by J. Kelley Johnson, and many special articles of interest to radio dealers and servicemen. The latest addition to our new news section, "The Radio Marketplace," the Radio Dealer's Notebook, is continued with more practical data. Incidentally, the welcome given this feature by radio dealers has been most encouraging. Dealers who have not seen this feature are referred to page 407 of this issue and to page 332 of our March number. The service side of radio sales — the relation is written in that way intentionally — will not be neglected in our May number: an address given by the Editor at the Federated Radio Trades Association convention in Buffalo will be printed for the first time. That article, "The Inseparability of Sales and Service" emphasizes a division of the dealer's business that has had all too little attention. — Willis Kevgsley Wing. TERMS: $4.00 a year; single copies 35 cents All rights reserved. Copyright, 1929, in the United States, Newfoundland, Great Britain. Canada, and other countries by MAGAZINES Country Life DOUBLED AY. DORAN & COMPANY, INC., Garden City, New York Radio Broadcast Short Stories Le Petit Journal El Eco West World's Work . . . The American Home BOOK SHOPS (Books of all Publishers) . . . New York: <Lord & Taylor, James McCreery & Company. Pennsylvania Terminal, 166 West 32nd St., 848 Madison Ave., 51 East 44th Street, 420, 526, and 819 Lexington Avenue, Grajjd Central Terminal, 10 Wall Street> Chicago: <75 East Adams Street> St. Louis: <223 N. 8th St. and 4914 Maryland Ave. > Cleveland: <Higbee Company > Springfield, Mass: < Meekins, Packard & Wheat. OFFICES . . . Garden City, N. Y. New York: 244 Madison Avenue. Boston: Park Square Building. Chicago: Peoples Gas Building. Santa Barbara, Cal. London: Wm. Heinemann, Ltd. Toronto: Doubleday, Doran & Gundy, Ltd. OFFICERS . . . F. N. Doubleday, Chairman of the Board; Nelson Doubleday, President; S. A. Everitt, Vice-President; George H. Doran, Vice-President; Russell Doubleday Secretary; John J. Hessian, Treasurer; Lillian A. Comstock, Asst'l Secretary; L. J. McNaughton, Asst't Treasurer • april, 1929 page 364 #