Fessenden was a child prodigy, learning Greek, Latin and French. He turned to science and later worked as chief chemist for Thomas Edison during the 1880s, then briefly for Westinghouse. He formed his own company with millionaire backers and developed his most remarkable invention, the modulation of radio waves. On Christmas Eve, 1906, ships off the Atlantic coast with Fessenden-designed equipment received the first radio broadcast. Fessenden eventually held 500 patents.
Fessenden's technology--the "heterodyne principle"--has remained fundamental to radio to this day, allowing reception and transmission on the same aerial without interference. A continuous signal was sent, but with the amplitude of the waves varied or "modulated" in a way that followed sound waves. A receiving device could then sort out these variations and reconvert them into sound. He won Scientific American's Gold Medal in 1929 for the fathometer, which could determine the depth of water under a ship's keel.
Sources: Right against the world, by J.F. McEvoy in The Beaver, June-July 1990, p. 43; Asimov's Biographical Encyc. of Science & Tech.; NRC Hall of Fame
© 1996 Softshell Small Systems Software Design Inc.
