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 due to :
(i) Size of the antenna .
(ii) Effective power radiated by an antenna.
(iii) Mixing up of signals from different transmitters .
Numerical : Here `" " A_(c) = 12 V , A_(m) = ?`
Modulation index `" " mu_(c) = 75% = 0.75`
Since , `mu_(a) = (A_(m))/(A_(C)) implies 0.75 = (A_(m))/(12) therefore A_(m) = 0.75 xx 12 = 9.00 = 9V.`