File:Dipole radar altimeter antenna.jpg
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Dipole_radar_altimeter_antenna.jpg (771 × 474 像素,檔案大小:81 KB,MIME 類型:image/jpeg)
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[編輯]描述Dipole radar altimeter antenna.jpg |
English: A dipole antenna of a radar altimeter from an advertisement in a 1947 radio magazine. It was mounted on the bottom surface of an aircraft and transmitted radio waves which reflected from the ground. The altitude of the aircraft was calculated from the time it took the radio waves to return. This is a half-wave dipole; composed of two symmetrical elements each 1/4 wavelength long, insulated from each other with the white insulator. It is mounted 1/4 wavelength below the aircraft's body, so the aircraft's aluminum skin functioned as a reflecting surface to reinforce the outgoing wavefront. It is made of painted brass tubing, and was mounted parallel to the airstream to reduce air drag. The text gave no information about the operating frequency, but if the antenna is roughly 20 cm, long as it appears to be, the wavelength is around 40 cm so the operating frequency was in the UHF range, around 700 MHz. A coaxial cable feedline attached to the connector, bottom. |
日期 | |
來源 | Retrieved June 15, 2014 from Tele-Tech magazine, Caldwell-Clements Inc., Bristol, Connecticut, Vol. 6, No. 5, May 1947, p. 7 on American Radio History website |
作者 | 未知Unknown author |
授權許可 (重用此檔案) |
This image is from an advertisement without a copyright notice published in a 1947 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. |
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[編輯]Public domainPublic domainfalsefalse |
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本作品在美國屬於公有領域,因為其於1929至1977年(包括)間在美國出版,且沒有著作權聲明。更多詳細資訊,請參閱共享資源:赫特圖表,以及就出版的公共藝術品的詳細說明。請注意美國的作品在不適用較短期限法則的管轄區可能仍然受版權保護(基於作者的逝世日期),例如加拿大(作者逝世後50年)、中國大陸(作者逝世後50年,不包括香港和澳門)、德國(作者逝世後70年)、墨西哥(作者逝世後100年) 、瑞士(作者逝世後70年)及其他有本地條約的國家。
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目前 | 2014年6月17日 (二) 18:49 | ![]() | 771 × 474(81 KB) | Chetvorno(對話 | 貢獻) | User created page with UploadWizard |
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