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A 5-tube superheterodyne receiver manufactured by Toshiba circa 1955 Superheterodyne transistor radio circuit circa 1975. A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency.
An important and widely used application of the heterodyne technique is in the superheterodyne receiver (superhet). In the typical superhet, the incoming radio frequency signal from the antenna is mixed (heterodyned) with a signal from a local oscillator (LO) to produce a lower fixed frequency signal called the intermediate frequency (IF
Block diagram of a superheterodyne receiver. The RF front end consists of the components on the left colored red. In a radio receiver circuit, the RF front end, short for radio frequency front end, is a generic term for all the circuitry between a receiver's antenna input up to and including the mixer stage. [1]
Image response (or more correctly, image response rejection ratio, or IMRR) is a measure of performance of a radio receiver that operates on the superheterodyne principle. [1] In such a radio receiver, a local oscillator (LO) is used to heterodyne or "beat" against the incoming radio frequency (RF), generating sum and difference frequencies.
For direct modulation these stages must be developed separately for each output RF (so called channel). On the other hand, in superheterodyne transmitters, only a single intermediate frequency signal is used, so only one type of stage for IF is developed. Thus, each stage is more reliable in superheterodyne. Also R&D is much easier for the ...
The heterodyne oscillator had to be retuned each time the receiver was tuned to a new station, but in modern superheterodyne receivers the BFO signal beats with the fixed intermediate frequency, so the beat frequency oscillator can be a fixed frequency. Armstrong later used Fessenden's heterodyne principle in his superheterodyne receiver (below).
The result was the RCA Radiola AR-812 and Radiola VIII Superheterodynes in 1924, the world's first consumer superheterodyne receivers. In 1924, these cost $224 and $475 respectively. [3] Up to 1930, RCA controlled the superheterodyne patent, and any radio manufacturer that wanted to build one had to pay royalties to RCA.
The name superheterodyne was a contraction of supersonic heterodyne, to distinguish it from receivers in which the heterodyne frequency was low enough to be directly audible, and which were used for receiving continuous wave (CW) Morse code transmissions (not speech or music).