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

### Explanation of question 4

A 145.5MHz carrier is frequency modulated by a 2kHz sinusoidal voltage and the frequency swing is 6kHz. The modulation index is

1. 3
2. 1.5
3. 0.67
4. 0.33

The answer is :- 2 Modulation index = . Frequency swing of carrier = 6 kHz, so, frequency deviation of carrier = 3 kHz, i.e. half of swing. Thus, the modulation index = 1.5, i.e. there is a swing of 6 kHz, 2000 times per second.

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