Write two factors justifying the need of modulating a signal.
A carrier wave of peak voltage `12 V` is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75% ?

Explanation

Modulation of a signal is necessary to
transmit a signal in the audio frequency range over a long
distance on account of (i) suitable size of the
antenna, (ii) suitable effective power radiated by
the antenna ,
(iii) avoiding mixing up of signals from different
transmitters.
here, `A_c = 12 V, A_m = ?`
`mu = 75% = 0.75`
As ` mu = A_m/A_c`
`:. A_m = muA_c = 0.75 xx 12 = 9V. `