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Receiver Noise |
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Noise, Receiver
the electrical fluctuations that occur mainly in the input circuits (for example, amplifiers and filters) of radio-receiving apparatus (seeFLUCTUATIONS, ELECTRICAL). When combined with noises from external sources, such as atmospheric noise, terrestrial noise, and cosmic noise, a total noise is produced that acts as a natural threshold of the sensitivity of the radio receiver. The quantitative characteristic of receiver-noise intensity is its noise temperature. For example, until the 1950’s, the input devices used in superhigh-frequency radio receivers had noise temperatures of more than 2000°K, which was many times higher than the noise temperatures of the external sources. Subsequently, low-noise, superhigh-frequency amplifying devices were invented, such as tunnel diodes, parametric amplifiers, and quantum mechanical amplifiers, which made it possible to lower the receiver-noise temperatures, respectively, to values of the order of 300°, 30°, and 3 K, thereby improving the sensitivity of superhigh-frequency radio receivers by about 10 to 50 times. REFERENCEAinbinder, 1. M. Shumy radiopriemnikov. Moscow, 1974.I. M. AINBINDER Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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