File:De Forest 1909 arc radiotelephone.jpg
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English: An early experimental two-way AM radiotelephone set developed in 1907-09 by Lee De Forest. This was before the development of amplifying vacuum tubes and the device used an arc converter, a high voltage electric arc in an alcohol flame attached to a tuned circuit, to generate radio waves. The receiver (box on left side) used an early version of his Audion tube detector. This was a civilian version of the radiotelephone sets which De Forest installed on the U.S. Navy "great white fleet" which were tested during their historic around-the-world cruise in 1907-1909. The naval version of the device transmitted at longwave frequencies of around 40 kHz and had a limited range of about 5 miles. Apparently, neither the civilian nor the military version of this device was a commercial success; the Navy found it deficient and junked it after the voyage. De Forest describes it in his autobiography: "The transmitter consisted of a handsome mahogony box containing two pancakes [flat inductively coupled output coils] primary and secondary, mounted so the coupling between the two could be varied. The little carbon arc with the alcohol lamp was mounted on a bracket on the righthand side of the cabinet [not visible], The microphones... were mounted on a standard telephone arm projecting from the front. Two special carbon microphones, one on either side of the tapered mouthpiece, were mounted on an arm in such a manner as the voice waves acted on both diaphragms. The two carbon buttons were connected in series, in the earth connection between the secondary pancake and the ground" - Mike Adams 2011 Lee De Forest, King of Radio, Television and Film, p. 113-114 |
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| Source | Retrieved 13 October 2013 from Samuel Shelbourne Robison, D. W. Todd, S. C. Hooper 1918 Robison's Manual of Radio Telegraphy and Telephony, 4th Ed., U.S. Naval Institute, Annapolis, Maryland, p. 127, fig. 62D on Google Books |
| Author | Samuel Shelbourne Robison |
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This work is in the public domain in the United States because it is a work prepared by an officer or employee of the United States Government as part of that person’s official duties under the terms of Title 17, Chapter 1, Section 105 of the US Code.
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| This file has been identified as being free of known restrictions under copyright law, including all related and neighboring rights. | ||
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| current | 22:05, 13 October 2013 | | 1,340 × 1,888 (484 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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