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Question
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.
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Solution
Three important factors which justify the need of modulating a message signal:
(i) Size of antenna or aerial: For communication within the effective length of the antennas, the transmitting frequencies should be high, so modulation is required.
(ii) Effective power which is radiated by antenna: Since the power radiated from a linear antenna is inversely proportional to the square of the transmitting wavelength. As high powers are needed for good transmission so, higher frequency is required which can be achieved by modulation.
(iii) The interference of signals from different transmitters: To avoid the interference of the signals there is need of high frequency which can be achieved by the modulation.
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