Name: | DeForest-Tubes (USA) |
Abbreviation: | deforesttu |
Products: | Model types Tube manufacturer |
Summary: |
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 |
History: |
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: en.wikipedia.org/wiki/Lee_de_Forest and HRSA Radiowaves No. 44] |
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