Electronics and Communication Engineering - Radio Receivers - Discussion

Discussion :: Radio Receivers - Section 1 (Q.No.26)

26. 

In a superheterodyne receiver, the IF is 455 kHz. If it is tuned to 1200 kHz, the image frequency will be

[A]. 1655 kHz
[B]. 2110 kHz
[C]. 745 kHz
[D]. 910 kHz

Answer: Option B

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).


Hamsa said: (Mar 4, 2015)  
Explain this?

Pigs said: (Oct 11, 2016)  
Elaborate this answer.

Pinky said: (Jun 20, 2020)  
Sfi(image frqency) = si(tuned or input signal) + 2 * (intermediate frequency).
Sfi = 1200+2*(455).
Sfi = 2110.

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