Produced by Roger Frank, Robert Cicconetti and the Online Distributed Proofreading Team at https://www.pgdp.net [Transcriber's Note: An underscore character "_" is used around text to signify italics in the _original_ text, as illustrated. It also is used to signify a subscript, used frequently in technical descriptions. For example _E_{C}_ would have been originally typeset as a capital E followed by a smaller C subscript, and both would have been in an italic typeface.] [Illustration: Pl. I.--One of the Lines of Towers at Radio Central (Courtesy of Radio Corporation of America).] LETTERS OF A RADIO-ENGINEER TO HIS SON BY JOHN MILLS Engineering Department, Western Electric Company, Inc., Author of "Radio-Communication," "The Realities of Modern Science," and "Within the Atom" NEW YORK HARCOURT, BRACE AND COMPANY COPYRIGHT, 1922, BY HARCOURT, BRACE AND COMPANY, INC. PRINTED IN THE U. S. A. BY THE QUINN & BODEN COMPANY RAHWAY, N. J. TO J. M., Jr. CONTENTS 1 Electricity and Matter 3 2 Why a Copper Wire Will Conduct Electricity 9 3 How a Battery Works 16 4 The Batteries in Your Radio Set 27 5 Getting Electrons from a Heated Wire 34 6 The Audion 40 7 How to Measure an Electron Stream 48 8 Electron-Moving-Forces 57 9 The Audion-Characteristic 66 10 Condensers and Coils 77 11 A "C-W" Transmitter 86 12 Inductance and Capacity 96 13 Tuning 112 14 Why and How to Use a Detector 124 15 Radio-Telephony 140 16 The Human Voice 152 17 Grid Batteries and Grid Condensers for Detectors 165 18 Amplifiers and the Regenerative Circuit 176 19 The Audion Amplifier and Its Connections 187 20 Telephone Receivers and Other Electromagnetic Devices 199 21 Your Receiving Set and How to Experiment 211 22 High-Powered Radio-Telephone Transmitters 230 23 Amplification at Intermediate Frequencies 242 24 By Wire and by Radio 251 Index 263 LIST OF PLATES I One of the Lines of Towers at Radio Central Frontispiece II Bird's-Eye View of Radio Central 10