Intermediate frequency
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An intermediate frequency (IF) is a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. It is the beat frequency between the signal and the local oscillator in a radio detection system. IF is also the name of a stage in a superheterodyne receiver. It is where an incoming signal is amplified before final detection is done. There may be several such stages in a superhet radio receiver.
Widely used IF frequencies are 10.7MHz (FM Radio), 455kHz (AM Radio) and 44KHz (television reception).
Other common IF frequencies are 240MHz (Cellular/WLAN), 140MHz (Cellular/WLAN), 70MHz (Cellular), and various frequencies in the range 35-45MHz (TV).de:Zwischenfrequenz es:Frecuencia intermedia sv:Mellanfrekvens