File:Audion receiver.jpg

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|description={{en|1=An early audion [[:en:radio receiver|radio receiver]] built by the inventor of the [[:en:audion|audion]] vacuum tube, [[:en:Lee De Forest|Lee De Forest]], around 1914. The audion, the first [[:en:triode|triode]], was the first electronic tube that was able to [[:en:amplification|amplify]]. Although invented in 1906, the amplifying ability of the audion was not recognized until 1910-1912, so this was one of the first amplifying radio receivers. It appears in a paper by De Forest demonstrating to his fellow engineers that the audion was not just a radio detector but also had the ability to amplify a signal. }}

 
|description={{en|1=An early audion [[:en:radio receiver|radio receiver]] built by the inventor of the [[:en:audion|audion]] vacuum tube, [[:en:Lee De Forest|Lee De Forest]], around 1914. The audion, the first [[:en:triode|triode]], was the first electronic tube that was able to [[:en:amplification|amplify]]. Although invented in 1906, the amplifying ability of the audion was not recognized until 1910-1912, so this was one of the first amplifying radio receivers. It appears in a paper by De Forest demonstrating to his fellow engineers that the audion was not just a radio detector but also had the ability to amplify a signal. }}

 

 

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This device was not a complete receiver, only a detector and two stage audio amplifier; in use it was connected to the output of a "tuner" section which selected the station to be received. The two audion tubes are visible, mounted upside down, as audions usually were, so that their delicate filaments did not sag under their own weight and touch the grid. The upper center knob controlled the filament current; the lower multipoint switch the plate voltage. The gain of these primitive tubes was low; the source claims power gains of up to 5. Inadequate evacuation left considerable residual air in the audion which ionized, causing erratic operation and shortening the life of the filament.
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This device was not a complete receiver, only a detector and two stage audio amplifier; in use it was connected to the output of a "tuner" section which selected the station to be received. The two audion tubes are visible, mounted upside down, as audions usually were, so that their delicate filaments did not sag under their own weight and touch the grid. The upper center knob controlled the filament current; the lower multipoint switch the plate voltage. The gain of these primitive tubes was low; the source claims power gains of up to 5. Inadequate evacuation left considerable residual air in the audion which ionized, causing erratic operation and shortening the life of the filament. Alterations to image: removed aliasing artifacts (diagonal stripes) from scanning of halftone image using Gimp FFT filter.
 
|date=Prior to March 1914
 
|date=Prior to March 1914
 
|source=Downloaded [[03-26-2013]] from [http://books.google.com/books?id=uEASAAAAIAAJ&pg=PA18 Lee De Forest ''The Audion - Detector and Amplifier'' in ''Proc. of the Inst. of Radio Engineers'' ( Institute of Radio Engineers, NY) Vol. 2, No. 1, March 1914, p.18, fig. 4] on Google Books
 
|source=Downloaded [[03-26-2013]] from [http://books.google.com/books?id=uEASAAAAIAAJ&pg=PA18 Lee De Forest ''The Audion - Detector and Amplifier'' in ''Proc. of the Inst. of Radio Engineers'' ( Institute of Radio Engineers, NY) Vol. 2, No. 1, March 1914, p.18, fig. 4] on Google Books

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