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Radio Receivers - Engineering

Q1:

In a broadcast superheterodynes receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 100. If the intermediate frequency is 455 kHz. The rejection ratio at 25 MHz will be

A 1.116

B 1.386

C 2.116

D 2.386

ANS:A - 1.116

fsi = fs+2IF.
fsi = 25*2*0.455,
fsi = 25.91MHz.

ρ=fsi/fs - fs/fsi.
ρ= 25.91/25 - 25/25.91,
ρ= 0.0715.

α= √1+(100)^2+(0.0715)^2.
α= √1+10000+0.0051,
α= √52,
α= 7.22.