(a) Describe briefly three factors which justify the need for modulation of audio frequency signals over long distances in communication.
(b) Draw the waveforms of
(i) carrier wave, (ii) a modulating signal and
(iii) amplitude modulated wave
(a) (i) Modulating is done due to the size of the antenna should be comparable to the wavelength of the signal.
(ii) effective power radiated is proportional to would be small for audio frequency signal.
(iii) To avoid mixing up of signals.