Write three important factors which justify the need of modulating a message signal. Show diagrammatically how an amplitude modulate wave is obtained when a modulating signal is superimposed on a carrier wave.

Solution

Three factors for the need of modulating a message signal:

a) Size of the antenna or aerial should be $straight lambda$ /4.

b) Effective power radiated by an antenna should be close to $Error converting from MathML to accessible text.$
c) Interference of signals from different transmitters. Inorder to avoid the interference of the signals, high frequency is required which can be acquired by modulation.