File:Foxhole radio from WW2.jpg
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[編輯]描述Foxhole radio from WW2.jpg |
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 | |
來源 | 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. |
授權許可 (重用此檔案) |
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. |
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[編輯]Public domainPublic domainfalsefalse |
本作品在美國屬於公有領域,是因為該作品是在1929與1963年之間出版,沒有在該作品增加著作權聲明,且沒有進行著作權更新。除非此作品之作者已經過世一段時間,並達到公有領域所要求的條件,這類美國作品在其他不適用較短期限法則的國家或地區屬於有著作權狀態,如加拿大(作者過世後70年)、中國大陸(作者過世後50年,港澳除外)、德國(作者過世後70年)、墨西哥(作者過世後100年)、瑞士(作者過世後70年)與其他已簽署個別協議的國家。更多資訊請參考Commons:Hirtle chart。
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目前 | 2015年6月3日 (三) 07:26 | 529 × 487(88 KB) | Chetvorno(對話 | 貢獻) | User created page with UploadWizard |
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