Principles of Communication: Communication System MCQ

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Communication SystemHardQuestion 20262

Question

In a superheterodyne receiver, the purpose of the local oscillator and mixer is to:

A
Amplify the received signal
B
Convert any received frequency to a fixed intermediate frequency (IF)
Correct
C
Generate the carrier for transmission
D
Digitise the incoming signal

Correct answer

Convert any received frequency to a fixed intermediate frequency (IF)

Explanation

The mixer beats the incoming signal (f_RF) with the local oscillator (f_LO) to produce IF = f_RF − f_LO (typically 455 kHz for AM, 10.7 MHz for FM). The fixed IF allows sharp, optimised filtering regardless of the tuned station.

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