Stampa:Hertz micrometer resonator.png
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Taqsira
| Deskrizzjoni |
English: Resonator antenna that German physicist Heinrich Hertz used as a radio wave detector in his first experiments that demonstrated the existence of radio waves. It consists of a helix of brass wire in the shape of a ring, with a spark gap between the ends. It probably functioned as a quarter wave antenna. When the radio waves produced by his spark gap transmitter were at the resonant frequency of the loop of wire, it produced a high voltage between the ends of the wire, which jumped across a tiny spark gap. The spark gap (bottom of loop) was a micrometer with which he could measure the length of the spark, to get an estimate of the field strength of the waves. |
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| Sors | Retrieved December 30, 2014 from Rollo Appleyard, "Pioneers of Electrical Communication 5: Heinrich Rudolf Hertz" in Electrical Communication magazine, International Standard Electric Corp., New York, Vol. 6, No. 2, October 1927, p. 70, fig. 9 on http://www.americanradiohistory.com |
| Awtur | Rollo Appleyard |
| Permess (Użu mill-ġdid tal-fajl) |
This 1927 issue of Electrical Communication magazine would have the copyright renewed in 1955. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1954, 1955, and 1956 show no renewal entries for Electrical Communication. Therefore the magazine's copyright was not renewed and it is in the public domain. |
Liċenzja
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This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
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