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Question
Explain any two factors that justify the need of modulating a low-frequency signal.
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Solution
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.
RELATED QUESTIONS
Write two advantages of frequency modulation over amplitude modulation.
Define amplitude modulation in a communication system.
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- m > 1, will result in interference between carrier frequency and message frequency, resulting into distortion.
- m > 1 will result in overlapping of both side bands resulting into loss of information.
- m > 1 will result in change in phase between carrier signal and message signal.
- m > 1 indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.
Why is a AM signal likely to be more noisy than a FM signal upon transmission through a channel?
An amplitude modulated wave is as shown in figure. Calculate
- the percentage modulation
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- peak value of information voltage.
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