What is the need of Super heterodyne tuning in AM
receivers?? Q - factor problem also arise at RF amplifier
tuner also???
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Answer / sattar
TRF (tuned radio frequency) receiver is a popular type of
Am receiver as it is cheap and simplest.But it has tendency
to oscillate at higher frequency ,and its selectivity is
less and BW variation takes place during tuning.So,SHR
(super heterodyne rec) is used.
In SHR,the incoming Rf freq. is mixed with a local
oscillator freq.(LO) to generate a supersonic intermediate
frequency((IF) ) such that IF=LO-RF.This IF is independent
of RF charecteristics and hence gives uniform SELECTIVITY
and SENSITIVITY.
The RF amplifier provides image frequency rejection of SHR
amplifier and its Q-factor can be increased by using
GANGLED CAPACITORS at input and output.
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