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

For modulating a message signal, the main three factors are:

1. Size of antenna or aerial: For communication the transmitting frequencies should be high.
2. Effective power which is radiated by antenna: Modulation is required to get high frequency signals.
3. The interference of signals from different transmitters: To avoid the interference of the signals there is a need of high frequency which can be achieved by the modulation.