File:UHF Barkhausen-Kurz Lecher line transmitter 1933.jpg
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DescriptionUHF Barkhausen-Kurz Lecher line transmitter 1933.jpg |
English: Experimental UHF radio transmitter using two type 932 tubes in a push-pull Barkhausen-Kurz oscillator, constructed by James Millen in 1933. During the 1930s the frontier in radio research was the UHF wavelengths. Ordinary vacuum tube feedback oscillators would not reach these frequencies due to electrode capacitance and inductance. The Barkhausen-Kurz oscillator, the first transit time oscillator, was the first circuit which could produce power at UHF frequencies. It used a specially designed triode tube in which the electrons, instead of moving from cathode to plate, oscillated back and forth between cathode and plate through the grid, which was biased at a high voltage. The transmitter uses two coupled Lecher lines (parallel wire transmission lines) as the tank resonator. The dipole antenna (right) in front of the parabolic reflector, is fed by another parallel line. Millen is using another Lecher line to measure the output frequency. This transmitter radiated 5 W at 300-400 MHz. |
Date | |
Source | Retrieved March 21, 2014 from James Millen, "Experimental 3/4 Meter Transmitters and Receivers" in Short Wave Craft, Popular Book Corp., New York, Vol. 3, No. 11, March 1933, p. 648, fig. 3 on American Radio History] website |
Author | James Millen |
Permission (Reusing this file) |
This 1933 issue of Short Wave Craft magazine would have the copyright renewed in 1961. 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 1960, 1961 and 1962 show no renewal entries for Short Wave Craft. Therefore the magazine's copyright was not renewed and it is in the public domain. |
Other versions | UHF Barkhausen-Kurz Lecher line transmitter 1933 closeup.jpg |
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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.
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