File:Tuned RF power amplifier.jpg

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Summary

DescriptionTuned RF power amplifier.jpg	English: A tuned RF amplifier module for a radio transmitter, from an advertisement in a 1938 radio magazine. This consists of two power triode tubes and a tank circuit consisting of a high Q coil (top) and a variable capacitor (center). The promotional copy said it was usable up to 27 MHz.
Date	May 1938
Source	Retrieved March 12, 2014 from Radio News magazine, Ziff-Davis Publishing Co., Chicago, Vol. 20, No. 11, May 1938, p. 31 American Radio History website
Author	Unknown authorUnknown author
Permission (Reusing this file)	This image is from an advertisement without a copyright notice published in a 1938 magazine. In the United States, advertisements published in collective works (magazines and newspapers) are not covered by the copyright notice for the entire collective work. (See U.S. Copyright Office Circular 3, "Copyright Notice", page 3, "Contributions to Collective Works".) Since the advertisement was published before 1978 without a copyright notice, it falls into the public domain.

Licensing

This work is in the public domain in the United States because it was published in the United States between 1929 and 1977, inclusive, without a copyright notice. For further explanation, see Commons:Hirtle chart as well as a detailed definition of "publication" for public art. 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 (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.

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