Radio Broadcast (May 1928-Apr 1929)

RADIO BROADCAST ADVERTISER .5? BOOK REVIEWS (Continued from page 56) Practical Radio Telegraphy — Nilson and Hornung are out of date. This fact, as well as the long experience of the authors in the training of radio operators, justifies the appearance of the present volume. The treatment begins with the physical fundamentals of the art, the first seven chapters being devoted to such topics as magnetism, motors and armatures, and characteristics of alternating current circuits. The treatment is nowhere skimpy; in the chapter on armatures, for example, the elements of armature winding are fully described. Wherever physical principles are expressed the atomic theory is used. Occasionally the phraseology is a little dubious, as in the discussion of dielectric breakdown on page 107, where the authors tell us that "a ruptured insulator might be defined as a material in which the electrons have been extended beyond their limit, or, in other words, the electrons have been strained beyond the elastic limit of the atomic structure. ..." A strained electron might tax the conceptual powers of greater intellects than those of average young men studying to become brass pounders on the high seas. But the explanations are in the main clear and scientific; the one which has been quoted is not a fair example. Photographs and practical illustrations of apparatus have been secured from manufacturers and communication companies. Spark, vacuum tube, and arc transmitters for marine use, commercial receivers, and the radio compass, .are thoroughly described. Questions at the end of each chapter may be used by the student to test his knowledge. Most of the chapters are written to the length of a normal assignment in a radio school. The printing is first-rate, with the exception of a comical error in the running head of Chapter XXI. The book includes an index. It is written for readers who lack preparation in elementary electricity, mathematics, and chemistry, gives them what they need of such prerequisites, carries them through the technique of radio marine telegraphy, and fills the need for a reference book for finished operators. — Carl Dreher. In sending the coupon below, make sure that your name and address are included and are plainly written. USE THIS BOOKLET COUPON Radio Broadcast Service Department Radio Broadcast. Garden City, N. Y. Please send me fat no expense) the following booklets indicated by numbers in the published list above: Name. Address. (Number) (Street) (City) (State) ORDER BY NUMBER ONLY This coupon must accompany every request. RB 5-28 THREE TIMES! The new UX 250 Power Amplifier Tube is capable of supplying the speaker three times the undistorted energy as that of a UX 210 tube. Results — great volumewith unsurpassed quality. This tube, however, requires equipment especially designed for it. The General Radio Company have developed a complete line of transformers and filters particularly Type 587-A Power Speaker Filter adapted for USe With tlllS This instrument thoroughly insulates the speaker tube. Folders describing amfrom the high voltage and current of the last stage plifier units and component tube. It is equipped with a heavv dutv choke that •!, , •„ ■ , 1 1 . apparatus will be sent on will pass 100 milliamperes without undue satura rr tion and suitable condensers. Price, $10.00. request. 30 State St., Cambridge, Mass. Radio 274 Brannan St., San Francisco, Calif. i\E¥NCH / Resistors for receiving, transmitting, and power supply work. ARTHUR H LYNCH, Inc., 1775 Broadway, N. T. C the Code -Hi ^v're'ess or Morse — at home with the Jag] ^J^^^HSSSs^^i.J Teleplex Automatic ('ode Instructor. *^W>lUft No better method for self-instruction exists. Quick — Easy — Thorough. Endorsed by U. S. Navy. The only instrument that Reproduces actual sending — messages, kadiogiams, etc. Any speed. Complete Course nished. Thirty times as many words as any other instrument. Avail yourself of the Teleplex for a quick mastery of the code, write for booklet Kit. TELEPLEX CO., 7« Corthmdl St., New York. 200,000 Ohms Two hundred thousand ohms is quite a lot of resistance in wire wound form and of a type unaffected by temperature changes to High RelmncV ViltmeUr build into a voltmeter. Still, that is the actual amount used in the Jewell high resistance B-eliminator voltmeter, to establish a high resistance of 800 ohms per volt. For the set owner who demands the best from his receiver, this instrument will provide the maximum flexibility in home testing. Besides its adaptability for making B-eliminator voltage adjustments, the Pattern No. 116 may be used for general test purposes as well. The movement of Pattern No. 116 is a sensitive, D'Arsonval moving coil type, having silvered movement parts. The scale is silver etched with plain black characters and the pointer is provided with a zero adjuster. Ask your dealer about it or write us for descriptive circular No. 1 103. Jewell Electrical Instrument Company 1650 Walnut Street, Chicago "28 Years Making Good Instruments"