AM Super Heterodyne Radio Receiver - Elementary Electronics - IEB
AM Super Heterodyne Radio Receiver
In this type of radio receiver the selected radio frequency is converted to a fixed lower value,
called intermediate frequency(IF). This is achieved by a special electronic circuit called mixer
circuit. This is a local oscillator in the radio receiver it self. This oscillator produce high
frequency waves. There is a local oscillator in the radio frequency. The selected radio frequency
is mixed with the high frequency wave by the mixer circuit.
In this process beat are produced and the mixer produce of a frequency equal to the difference between local oscillation and radio wave frequency. As explained later, the circuit is so design that oscillation always produce a frequency 455 KHz above the selected radio frequency.
Therefore, the mixer will always produce and intermediate frequency of 455KHz regardless of
the station to which the receiver is turned.
For instance, if 600KHz station is tuned, then local oscillation will produce a frequency of 1055KHz.
Consequently,the output from the mixer will have a frequency of 455KHz.
The production of fixed intermediate frequency is the salient feature of Super-heterodyne
circuit. At this fixed intermediate frequency. The amplifier circuits operate with maximum
stability, selectivity and sensitivity.
As the conversion of incoming radio frequency to the intermediate frequency is achived by
radio frequency. Therefore this circuit called Super-heterodyne circuit.
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