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History of the manufacturer  


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Name: DeForest-Tubes    (USA)  
Abbreviation: deforesttu
Products: Model types Tube manufacturer

Lee de Forest (August 26, 1873 – June 30, 1961) was an American inventor, self-described "Father of Radio", and a pioneer in the development of sound-on-film recording used for motion pictures. He had over 180 patents, but also a tumultuous career—he boasted that he made, then lost four fortunes.

De Forest's most famous invention was the "grid Audion", which was the first successful three-element (triode) vacuum tube, the first device which could amplify electrical signals. He traced its inspiration to 1900, when, experimenting with a spark-gap transmitter, he briefly thought that the flickering of a nearby gas mantle's flame might be in response to electromagnetic pulses. With further tests he soon determined that the cause of the flame fluctuations actually was due to air pressure changes produced by the loud sound of the spark. Still, he was intrigued by the idea that properly configured; it might be possible to use a flame or something similar to detect radio signals.

Founded: 1901

Dr. Lee DeForest, in 1903 experminted with several varieties of  devices using the Bunsen Burner as the flame. He patented this as an “Oscillation-responsive device”  U.S. patent number  979275 A in 1905.

The Flame Detector experiments and patents proved little scientific use. However they served a useful purpose for the rationale for the development of the “Audion”.

After determining that an open flame was too susceptible to ambient air currents, de Forest investigated whether ionized gases, heated and enclosed in a partially evacuated glass tube, could be used instead. In 1905 to 1906 he developed various configurations of glass-tube devices, which he gave the general name of "Audions". The first Audions had only two electrodes, and on October 25, 1906,  de Forest filed a patent for diode vacuum tube detector, that was granted U.S. patent number 841387 on January 15, 1907. Subsequently a third "control" electrode was added, originally as a surrounding metal cylinder or a wire coiled around the outside of the glass tube. None of these initial designs worked particularly well. De Forest gave a presentation of his work to date to the October 26, 1906 New York meeting of the American Institute of Electrical Engineers, which was reprinted in two parts in late 1907 in the Scientific American Supplement.  He was insistent that a small amount of residual gas was necessary for the tubes to operate properly. However, he also admitted that "I have arrived as yet at no completely satisfactory theory as to the exact means by which the high-frequency oscillations affect so markedly the behaviour of an ionized gas."

De Forest grid Audion from 1906.

In late 1906, de Forest made a breakthrough when he reconfigured the control electrode, changing it from outside the glass to a zig-zag wire inside the tube, positioned in the centre between the cathode "filament" and the anode "plate" electrodes. He reportedly called the zig-zag control wire a "grid" due to its similarity to the "gridiron" lines on American football playing fields. Experiments conducted with his assistant, John V. L. Hogan, convinced him that he had discovered an important new radio detector, and he quickly prepared a patent application which was filed on January 29, 1907, and received U.S. patent number 879,532 on February 18, 1908.

[Source: and HRSA Radiowaves No. 44]


Further details for this manufacturer by the members (rmfiorg):

1/1947 Lee de Forest portrait in "Radio Craft" magazine 1907 - 1947.tbn_us_deforest_1947_leedeforest_portrait.jpg
Radio Retailing, February 1931tbn_deforest_tubes.jpg
Lee de Forest (August 26, 1873 – June 30, 1961) From Wikipedia.tbn_us_de_forest_photo.jpg
Radio Engineering October 1930tbn_de_forest_re130.png
Radio Engineering February 1929tbn_de_forest_re229.png
Radio Engineering March 1930tbn_de_forest_re330.png
Radio Engineering June 1930tbn_de_forest_re630.png
Radio Engineering July 1930tbn_de_forest_re730.png
Radio Engineering August 1930tbn_de_forest_re830.png
Radio News September 1930tbn_de_forest_re930.png
Radio Engineering October 1930tbn_de_forest_re1030.png
Radio Engineering November 1924tbn_de_forest_re1124.png
Radio Engineering November 1930tbn_de_forest_re1130.png
Radio Engineering December 1929tbn_de_forest_re1229.png
Electronics (Mc Graw-Hill) April 1930tbn_deforest_tubes_rear_cover_april_1930.jpg
QST April 1932tbn_de_forest_leeds_qst_april_1932.jpg
de Forest brochure 1925tbn_de_forest_brochure_c._1925.jpg
de Forest tubes - Joe Knight collection, USAtbn_de_forest_tubes_mid_1920_s_joe_knight_collection.jpg
Manufacturer documentationtbn_de_forest_training_manual_lesson_28_tubes.jpg


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