In a radio receiver, the local oscillator is tuned to a frequency

A)
equal to incoming frequency
B)
lower than the incoming frequency
C)
higher than the incoming frequency
D)
None of the above

Correct Answer : Option (C) :   higher than the incoming frequency

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In a superheterodyne receiver, the IF is 455 kHz. If it is tuned to 1200 kHz, the image frequency will be
A)
745 kHz
B)
910 kHz
C)
1655 kHz
D)
2110 kHz

Correct Answer :   2110 kHz

Explanation : 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 (455 kHz in our question).

So one possible image is : 1200 + ( 2 x 455 ) = 2110 kHz (possible).

And the other: 1200 - ( 2 x 455 ) = 290 kHz (not likely).

The selectivity of most receivers is determined largely by
A)
sensitivity
B)
antenna direction
C)
characteristics of IF section
D)
All of the above

Correct Answer :   characteristics of IF section

As compared to tuned radio frequency receivers which of the following is the advantage of using superheterodyne receivers?
A)
Stability
B)
Noise suppression
C)
High gain and better sensitivity
D)
Better selectivity at high frequencies

Correct Answer :   High gain and better sensitivity

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