The local oscillator of a broadcast receiver is tuned to a frequency higher than the incoming frequency

Electronics and Communication Engineering (ECE) : Radio Receivers - Quiz(MCQ)

To permit easier tracking

To allow adequate frequency coverage without switching

To help the image frequency rejection

Because otherwise an intermediate frequency could not be produced

Correct Answer : Option (B) : To allow adequate frequency coverage without switching

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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

745 kHz

910 kHz

1655 kHz

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).