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Question 20330
JEE Physics · Hard

Principles of Communication: Communication System MCQ

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Communication SystemHardQuestion 20330

Question

In a superheterodyne AM receiver, the intermediate frequency (IF) is typically 455 kHz. If the receiver is tuned to 1000 kHz, the local oscillator frequency is:
  1. A
    455 kHz
  2. B
    545 kHz
  3. C
    1455 kHz
    Correct
  4. D
    1000 kHz

Correct answer

1455 kHz

Explanation

fLO = fRF + fIF = 1000 + 455 = 1455 kHz (high-side injection, standard for AM receivers). The mixer produces |fLO − fRF| = 455 kHz IF regardless of which station is tuned. The image frequency = fLO + fIF = 1910 kHz must be rejected by the RF preselector filter.

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