File:Armstrong FM radio station W2XMN Alpine NJ 1940.jpg

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Summary

Description	English: First broadcast FM radio station W2XMN built by Edwin Armstrong in 1938 in Alpine, New Jersey, USA. The insets show a portion of the transmitter, and a map of Armstrong's network of FM stations in 1940.
Date	November 1940
Source	Retrieved October 3, 2015 from E. W. Murtfeldt, "What are the facts about FM?" in Popular Science magazine, Popular Science Publishing Co., New York, Vol. 137, No. 5, November 1940, p. 73 on Google Books
Author	E. W. Murtfeldt
Permission (Reusing this file)	This 1940 issue of Popular Science magazine would have the copyright renewed in 1968. 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 1967, 1968, and 1969 show no renewal entries for Popular Science. Therefore the copyright was not renewed and it is in the public domain.

Licensing

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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