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Radio Receivers - Engineering

Q1:

The selectivity of most receivers is determined largely by

A sensitivity

B characteristics of IF section

C antenna direction

D all of the above

ANS:B - characteristics of IF section

A signal (image) can interfere with a superheterodyne receiver if fits the following equation.

Image = Signal +/- 2 x I.F.

Which says that a signal has the capacity to interfere with a superhet receiver if its frequency is equal to the signal frequency (1200 kHz in our question) plus or minus twice the IF (450 kHz in our question).

So one possible image is: 1200 + ( 2 x 450 ) = 2100 kHz (possible).

And the other: 1200 - ( 2 x 450 ) = 300 kHz (not likely).