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 $\lambda / 4$. Therefore height of antenna becomes practically achievable.
(b) Power radiated into the space by an antenna is inversely proportional to $\lambda^{2}$. Therefore, the power eares and signal can (ii) (a) High efficiency (b) (c) Maximum use
$1+1$ of transmitted power
1 $\mathrm{Bx}(t)+\mathrm{Cx}(t)^{2}$
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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