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Summary
| Description |
English: The first varactor parametric amplifier, invented at Bell Labs in the late 1950s. Using 4 varactor diodes, it achieved 10 dB gain at 400 MHz. Parametric amplifiers are used as extremely low noise microwave amplifier stages in radio telescopes, spacecraft communication antennas, and military communications. The input microwave signal is amplified in a semiconductor varactor diode by applying a "pump" microwave signal at another frequency from a local oscillator. |
| Date | |
| Source | Retrieved October 19, 2014 from Radio-Electronic Engineering magazine, Ziff-Davis Publishing Co., New York, Vol. 29, No. 11, November 1958 , p. 24 on http://www.americanradiohistory.com |
| Author | Unknown author |
| Permission (Reusing this file) |
This image is from an advertisement for American Telephone and Telegraph Co. without a copyright notice published in a 1958 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
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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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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 21:26, 16 February 2015 | | 1,064 × 1,010 (178 KB) | Chetvorno | User created page with UploadWizard |
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