Principles of Communication: Frequency Modulation MCQ

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Frequency ModulationHardQuestion 20261

Question

Commercial FM radio has a channel bandwidth of 200 kHz. The maximum frequency deviation Δf allowed is 75 kHz. Using Carson's rule, the maximum audio frequency that can be transmitted is:

A
12.5 kHz
B
15 kHz
Correct
C
25 kHz
D
75 kHz

Correct answer

15 kHz

Explanation

Carson's rule: BW = 2(Δf + f_m). So 200 = 2(75 + f_m) → 100 = 75 + f_m → f_m = 15 kHz. This is why FM has better audio quality — it covers the full audible range (20 Hz – 15 kHz vs. 4.5 kHz for AM voice).

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