Radio broadcast .. (1922-30)

WILLIS KINGSLEY WING .... Editor KEITH HENNEY . Director of the Laboratory HOWARD E. RHODES . . Technical Editor EDGAR H. FELIX . . . Contributing Editor RADIO BROADCAST ENGINEERING -THE LABORATORY- SERVICING VOL. XIV. NO. 6 Contents for April, 1929 Frontispiece - - - The Serviceman s Responsibility New Uses for Power Amplifiers - - Fred H. Canfield The Condenser-Type Loud Speaker Joseph Morgan The March of Radio - - An Editorial Interpretation A Well-Ilalunced Radio Commis- sion Congress Considers Commission's Record More Discussion on Frequency Control Regulation of Allocations At- tempted In the World of Broadcasting Amateur and Commercial Radio The Routine of Testing Receivers - John S. Dunham Strays from the Laboratory - - - Keith Henney Vacuum-Tube Fuses Output Versus Amplification Causes of Winter Static Experiments With Pentodes 'Phantom" Power Tubes Novel Dynamic Baffle Life of a.c. Radio Tubes Amateur Intermediates The Real Size of the Radio Market The Experimenter's Armchair - - Grid-Leak Power Detection Frederick Sound Motion Pictures - - - - Production Testing With Oscillators Book Reviews ------- The Serviceman's Corner - - - - Practical Radio Service Records - - Characteristics of Power Rectifiers - Robert S. Kruse Emmons Terman Carl Dreher Richard F. Shea Edgar H. Felix John S. Dunham Roger Wise "Radio Broadcast's" Home-Study Sheets No. 19. Fundamental Radio Theory No. 20. Inductance Standards Real Versus Apparent Selectivity Broadcast Engineering - - - - Kenneth W. Jarvis Carl Dreher "Radio Broadcast's" Set Data Sheets - The Day-Fan 8-AC Power Set The Freshman 2N-12 Receiver The King Model H Receiver The Bosch Model 28 Receiver An Examination for Radio Servicemen J. B. V. Meacham In The Radio Marketplace Radio Broadcast Laboratory Information Sheets Howard E. Rhodes No. 273. Neutralizing R. F. Circuits No. 274. Bucking Coils for Dy- namic Loud Sneakers No. 275. Obtaining Grid Bias No. 276. Simple Two-Way Tele- phone Set No. 267. Simple Two-Way Tele- phone Set The contents of this magazine is indexed in The Readers' Guide to Periodical Literature, which is on file at all public libraries 366 367 369 372 375 377 379 380 382 385 387 388 389 392 393 397 399 402 403 405 406 412 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 prac- tical 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 cork- ing 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 fila- ment 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. THE 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 interest- ing article on self-shielded coils, a discussion of audio-trans- former 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 practi- cal 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 con- vention in Buffalo will be printed for the first time. That article, "The Inseparability of Sales and Service" emphasi/rs a division of the dealer's business that has had all too little attention. — WILLIS KINGSLEY 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 DOUBLEDAY, DOR AN & COMPANY, INC., Garden City, New York MAGAZINES . . . COUNTRY LIFE . . . WORLD'S WORK . . . THE AMERICAN HOME . . . RADIO BROADCAST . . . SHORT STORIES . . . LE PETIT JOURNAL ... EL Eco . . WEST BOOK SHOPS (Books of all Publishers) . . . NEW YORK: < LORD & TAYLOR, JAMES McCREERY & COMPANY. 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