Question

Explain any two factors that justify the need of modulating a low-frequency signal.

Answer 1

Following are the factors that justify the need of modulating a low-frequency signal:-
(1) Size of the antenna: An antenna is required for both transmission and reception of the signal whose size (at least λ/4) should be comparable to the wavelength of the signal so that time variation of the signal can be properly sensed by the antenna. For a low-frequency signal, the wavelength is large, and an antenna of such a large required height is practically impossible to construct and operate. Thus, the need for high-frequency transmission arises.
(2) Mixing up of signals from various transmitters: When many transmitters are transmitting information signals simultaneously, they get mixed up and the information is lost. This gives rise to the need for high-frequency transmission and allotment of a band of frequencies to each transmitter to avoid mixing of signals.
(3) Higher energy: High-frequency signals have higher energy, and therefore, even after loss due to attenuation, the signals can be carried over long distances.