Audion and Vacuum-Tube Receiver Development (1907-1916)

Topics: Radio, Lee De Forest, Vacuum tube Pages: 2 (627 words) Published: July 29, 2008
LEE DEFOREST AND THE EARLY AUDIONS

In 1906 Lee DeForest announced the development of the first three-element vacuum-tube detector in The Audion: A New Receiver for Wireless Telegraphy, from the Scientific American Supplement. The original Audion was capable of slightly amplifying received signals, but at this stage could not be used for more advanced applications, such as radio transmitters. The inefficient design of the original Audion meant it was initially of little value to radio, and due to its high cost and short life it was rarely used. In fact, in the 1909 edition of Operator's Wireless Telegraph and Telephone Hand-book, Victor H. Laughter's review of the Audion, while noting how sensitive the device was as a receiver, also stated "it is doubtful if it will ever come into wide use, owing to the difficulty in manufacture and short life". The Audion did have a strong allure for teenage experimenters, however. Its imperfect evacuation meant that, like a neon tube, it often glowed an enchanting blue or violet when in use, with the shade varying in response changes in signal strength. And then the filament would burn out. Years later, in the September, 1926 issue of Radio Broadcast magazine, Carl Dreher reminisced in Memoirs of a Radio Engineer about the enticing but frustrating early devices -- "Flung into deepest despair by the demise of a beloved tube, or the failure of a new one which never worked at all, the audion speculator would save up his pennies and plunge again."

PRACTICAL REFINEMENT

Eventually vacuum-tube design was improved enough to make them more than novelties. Beginning in 1912, various researchers discovered that, properly constructed according to scientific and engineering principles, vacuum tubes could be employed in electrical circuits that made radio receivers and amplifiers thousands of times more powerful, and could also be used to make compact and efficient radio transmitters, which for the first time made radio...
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