communication-systems Question 37

Question: Q. 4. (i) Explain any two factors which justify the need of modulating a low frequency signal.

(ii) Write two advantages of frequency modulation over amplitude modulation.

R [2016- Delhi Set-I, II, III]

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Solution:

Ans. (i) A low frequency signal is modulated for the following purposes:

(a) It reduces the wavelength of transmitted signal, and the minimum height of antenna for effective communtication is λ/4. Therefore height of antenna becomes practically achievable.

(b) Power radiated into the space by an antenna is inversely proportional to λ2. Therefore, the power eares and signal can (ii) (a) High efficiency (b) (c) Maximum use

1+1 of transmitted power

1 Bx(t)+Cx(t)2

In amplitude modulation, the amplitude of a carrier wave is made to vary, with time, in the same way as the modulating signal varies with time.

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