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Image: First vacuum tube AM radio transmitter

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First_vacuum_tube_AM_radio_transmitter.jpg ‎(448 × 360 pixels, file size: 45 KB, MIME type: image/jpeg)

Description: Apparently the first commercial AM Audion vacuum tube radio transmitter, built in 1914 by Lee De Forest who invented the Audion (triode) in 1906, from a short announcement in Electrical World magazine. It was not the first AM (sound) transmitter; short-lived technologies like the Poulsen arc and Alexanderson alternator| had been transmitting sound since 1906. But the vacuum tube feedback oscillator, invented in 1912 by Edwin Armstrong, replaced them, and has remained the key technology used in radio transmitters to the present day.
Title: First vacuum tube AM radio transmitter
Credit: Downloaded 25 September 2013 from "High-Frequency Oscillating Transmitter for Wireless Telephony", Wireless World, Vol. 66, 18 July 1914, p. 144 on Thomas H. White's Early United States Radio History website
Author: Lee De Forest
Usage Terms: Public domain
License: Public domain
Attribution Required?: No

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