F.M., A.M. and S.S.B. transmitters

Explanation of question 8

A double-sideband AM transmitter has a carrier frequency of 14.3MHz and the highest audio modulating frequency is 3kHz. The bandwidth will be

  1. 14 - 14.6MHz
  2. 14.294 - 14.306MHz
  3. 14.297 - 14.303MHz
  4. 14.2985 - 14.3015MHz

The answer is :- 3 Bandwidth = highest frequency-lowest frequency = (14.3 MHz + 3kHz) - (14.3 MHz - 3k Hz) = 6 kHz, i.e. from 14.297 MHz to 14.303 MHz The bandwidth will always be twice the highest audio modulating frequency.

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