File:Foxhole radio from WW2.jpg

Foxhole_radio_from_WW2.jpg (529 × 487像素,文件大小:88 KB,MIME类型:image/jpeg


摘要

描述
English: A "foxhole radio" receiver from World War 2. Not allowed powered radio receivers, which could give away their position to the enemy by the signal radiated by their local oscillator, American soldiers in World War 2 constructed their own homemade "crystal" radios so they could listen to news and music. The tuning coil (cylinder) was attached to a long wire antenna and ground. For a detector, this used a graphite pencil lead attached to the point of a safety pin, pressing against a "blue" steel razor blade. The graphite point touching the semiconducting oxide coating of the razor blade formed a crude point contact semiconductor diode which rectified the radio signal from the coil, extracting the audio signal from the radio frequency carrier wave, which was listened to with the earphones. The operator dragged the pencil lead across on the razor blade's surface until a sensitive spot was found and the station was heard, which required a lot of patience. The source says this foxhole radio belonged to Leutenant M. L. Rupert and was used on the Italian front.
日期
来源 Retrieved February 10, 2010 from John W. Campbell Jr., "Radio detectors and how they work" in Popular Science magazine, Popular Science Publishing Co., New York, Vol. 145, No. 4, October 1944, p. 209 on Google Books
作者 John W. Campbell Jr.
授权
(二次使用本文件)
This 1944 issue of Popular Science magazine would have the copyright renewed in 1972. 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 1971, 1972, and 1973 show no renewal entries for Popular Science. Therefore the copyright was not renewed and it is in the public domain.

许可协议

Public domain
本作品属于公有领域,因为其是于1929~1963年之间在美国出版,且无论其是否具有著作权声明,它并未进行著作权更新。更多信息请参考Commons:Hirtle chart/zh著作权更新日志。请注意该作品在其他对美国作品不适用较短期限法则的司法管辖区仍然受著作权保护(基于作者的逝世日期),如加拿大(作者过世后70年)、中国大陆(作者过世后50年,不包括香港和澳门)、德国(作者过世后70年)、墨西哥(作者过世后100年)、瑞士(作者过世后70年)及其他有本地条约的国家。

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Foxhole radio from World War 2

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