Radio broadcast .. (1922-30)

"I've been in the Radio game fifteen years and it's by far the best book Fve ever seen on Radio." Radio Telegraphy and Telephony" By RUDOLPH L. DUNCAN Director, Radio Institute of America And CHARLES E. DREW Instructor in Radio, and in charge Electrical Division, Radio Institute of America A Complete Handbook for Radio Students, Operators, Amateurs, Inspectors, and Engineers. This new book contains most of the in- formation that anyone seriously inter- ested in Radio would want to know. Subjects never be/ore treated in a Radio book are covered here in a thorough, simple, and lucid manner. 26 Chapters: Introduction to Radio; Magnetism—The Electron Theory; The Production of Electromotive Force; Electromagnetic Induction; Motor-Gen- erators—Starters; Curve Diagrams; Stor- age Batteries and Charging Circuits; Meters; Alternating Current and Fre- quencies ; Condensers — Electrostatic Capacity—Capacity Measurements; Vac- uum Tubes; Receiving Circuits; Alter- nating Current Operated Receivers and A-C Tubes; Telephone Receivers—Loudspeaker Re- producing Units; Commercial Receivers; Rectifier Devices—Rectifier Circuits—Voltage Divider Re- sistors—Filter Circuits; High Voltage Condensers; Antennae or Aerials; Resonance; Commercial Broadcast and Telegraph Transmitters; Commer- cial Tube Transmitters; Short Wave Transmitters and Receivers; Spark Transmitters; The Arc Transmitter; Direction Finders—Radio Compass; Radio Telephone Broadcast Transmitter Equip- ment; Appendix. "Radio Telegraphy and Telephony" was published in May. You \yill find in this book the most recent information on current prin- ciples, methods, and equipment. Over 900 pages for $7.50. You may have it on approval for 10 days—but as one radio expert wrote us, "Ten minutes, not ten days, should be suffi- cient to convince any real radio man that he needs 'Radio Telegraphy and Telephony.' " A Wiley Book ON APPROVAL COUPON JOHN WILEY AND SONS, Inc. 440 Fourth Ave., New York City Gentlemen:— Please send me for examination Radio Telegraphy and Telephony." Within ten days after its receipt I will send you $7.50 or return the book. l_ Name Address.... Reference . • 10-29 LIKE A SHIP without \ " RUDDER the "control" is gone . . . not powerless . . . but rudderless ... no longer does she re- spond to the helmsman. Your radio without a good resistance device, like the CENTRALAB resistance, doesn't respond to the slightest touch of the "helmsman." You steer your way through the ether by fits and starts . . . augmenting the "static storms" by internal "self-inflicted" noises. Better be sure that your radio is "Centra- lab" equipped. This shows the exclusive rocking disc construction of Ontralab volume control, "it" is the resist* ance. Contact disc *'D" has only a rocking action on the resistance. Pressure arm "P" together with fhftft and bushing is full; Insulated. "Volume Control Voltage Controls & Their Uses" is the title of an interesting pamphlet that is yours for the asking. This la the action of the usual wirewound con- trol after it has been in use for some time . . . like dragging a stickover a cobblestone pavement. CENTRAL RADIO 20 Keefe Ave. LABORATORIES Milwaukee, Wis. The tailor uses the lame principle as OntraUh. He does not want to ruin the garment by placing the iron on it BO he places a cloth in between. Centralab controls cannot ruin the resistance because the rocking disc is in between the pres- sure arm and the resistance. ELECTRAD PERFORMANCE Builds Sales T The Perfect Volume Control u. s. Pau. 1034103 1034104 and Pats, r.-n.l. You can sell and recommend the Super-TONATROL because it will stand up under heavy loads. Labor- atory tests approximating ten years average use prove its remarkable last- ing quality. New type resistance element fused to an enameled metal plate. Pure silver contact. Easily dis- sipates 5 watts. Metal cover for rapid heat radiation. List price, $2. 40 to $3. 50 EIECTRAD BUILT BETTER CONDENSERS AND RESISTORS Pyrohm Resistors Accurate — Unchanging "DEDUCED sensitivity, low volume, •*•*• distortion and poor tone quality are the inevitable results of using inaccurate resistors which do not maintain their proper resistance values. To be assured of satisfactory op- eration in power supply units and power amplifiers, be sure to specify and use—Aerovox Pyrohm resistors of the proper resistance values and current carrying capacities. These units are made of the best grade of resistance wire wound on a refractory tube, and protected by a porcelain enamel against moisture, oxidation and mechanical injury. Send Cor Catalog Complete specifications of all Aerovox Pyrohm resistors are con- tained in a complete catalog which will be sent free of charge on request. The Research Worker contains, each month, valuable in- formation on radio design. It will be sent free on request. AEROVOX WIRELESS CORE PRODUCTS THAT ENDURE' 312 • « OCTOBER 1929