File:Round radiotelephone set.jpg
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Summary[edit]
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English: One of the first vacuum tube AM radio transmitters, a two way radiotelephone set sold by the Marconi Wireless Telegraph Co. designed by their chief engineer, Henry J. Round in 1914. It used a prototype triode vacuum tube designed by Round. It was designed for shipboard use. The large tube on the frame was the transmitting tube, while the small one was for the receiver circuit. The transmitter used an Armstrong type (tickler) oscillator circuit with the carbon microphone directly in the antenna lead, modulating the RF antenna current. The input plate power was 5 to 10 W at a plate voltage of 500 V. The set was guaranteed to have a 30 mi (50 km) range when used with a 100 ft (30 m) high, 200 ft long (60 m) wire antenna, but could be pushed to have an antenna current of 1 A which would give a 100 mi (160 km) range. See also "Marconi's Wireless Telephone", The Wireless Age, Vol. 2, No. 7, April 1915, p. 489 |
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| Source | Downloaded 3 September 2013 from John Ambrose Fleming (1919) The Thermionic Valve and its Developments in Radiotelegraphy and Telephony, The Wireless Press, Ltd., New York, p. 216, fig. 126 on Google Books |
| Author | Credited in caption to Henry J. Round |
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This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
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This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the rule of the shorter term for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See Wikipedia:Public domain and Wikipedia:Copyrights for more details.
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
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| current | 13:53, 1 October 2013 | | 1,728 × 1,128 (268 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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