File:Lecher wires and oscillator 1932.png
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[edit]DescriptionLecher wires and oscillator 1932.png |
English: A Lecher line demonstration kit used to measure the frequency of a vacuum tube UHF oscillator, from a 1932 radio magazine. The Lecher line, invented by Ernst Lecher in 1888, was widely used to measure the frequency of short wave UHF transmitters during the 1930s. It consists of a pair of parallel wires that serve as a length of balanced transmission line which is short-circuit terminated by the metal plate (right). Radio frequency currents applied by the triode oscillator (left) form standing waves along the line. At multiples of a half-wavelength (λ/2) the voltage goes to zero, a point called a node. This is indicated by a light bulb on the oscillator across the input to the line. To measure the wavelength λ of the radio waves, the shorting plate is slid up the line until the light goes out. Then the distance between the shorting plate and the oscillator feeders is λ/2. Once the wavelength is determined, the frequency can be calculated by f = c / λ where c is the speed of light. Caption: Lecher wire demonstration apparatus with lamp for indicating the point of resonance |
Date | |
Source | Retrieved March 26, 2014 from D. L. Barr, "Demonstrating Short Waves" in Short Wave Craft magazine, Popular Book Corp., New York, Vol. 3, No. 3, July 1932, p. 153 on American Radio History website |
Author | D. L. Barr |
Permission (Reusing this file) |
This 1932 issue of Short Wave Craft magazine would have the copyright renewed in 1960. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. [1] Search of the Renewals for Periodicals for 1959, 1960 and 1961 show no renewal entries for Radio News. Therefore the magazine's copyright was not renewed and it is in the public domain. |
Licensing
[edit]Public domainPublic domainfalsefalse |
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. العربية ∙ Deutsch ∙ English ∙ español ∙ français ∙ galego ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ português ∙ português do Brasil ∙ русский ∙ sicilianu ∙ slovenščina ∙ українська ∙ 简体中文 ∙ 繁體中文 ∙ +/− |
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File change date and time | 11:57, 26 March 2014 |