Communication Systems - Engineering

Q1:

A 300 Hz sound wave of intensity 20 dB is transmitted by a 1500 kHz radio wave by frequency modulation. It is seen that instantaneous frequency varies between 1500.2 kHz and 1499.8 kHz, 300 times a second. If the intensity of sound wave is 100 dB.

A The instantaneous frequency variations will be between 1500.2 and 1499.8 kHz, 1500 times a second

B The instantaneous frequency variations will be between 1501 and 1499 kHz, 1500 times a second

C The instantaneous frequency variations will be between 1501 and 1499 kHz, 300 times a second

D The instantaneous frequency variations will be between 1501 and 1499 kHz, 60 times a second

ANS:C - The instantaneous frequency variations will be between 1501 and 1499 kHz, 300 times a second

Since, the intensity of audio wave has been increased five times, the instantaneous frequency variation is also increased five times.