(a)Describe briefly three factors which justify the need for modulation of audio frequency signals over long distances in communication .(b)Draw the waveforms of (i) carrier wave , (ii) a modualating signal and, (iii) amplitude modulated wave.

(a)Describe briefly three factors which justify the need for modulatio

1.	(a)Describe briefly three factors which justify the need for modulation of audio frequency signals over long distances in communication .(b)Draw the waveforms of (i) carrier wave , (ii) a modualating signal and, (iii) amplitude modulated wave.
Answer» Solution :(a)(i) For efficient transmission and reception , the size of the antenna should be atleast`(lambda)/(4)`, where`lambda` is wavelength of the signal to be transmitted . Due to thisrequirement , an audio signal of15kHz rquires an antenna of 5 km height , which is not feasible. (ii) The effective power radiated by a linear antenna isdriectly PROPORTIONAL to the square of the frequency of signal being transmitted . HENCE , for audiofrequencies the power radiated and consequently thetransmission range is extremely SMALL . (iii)All audio waves are CONTAINED within a small range of frequency from 20Hzto 20kHz .If these waves are transmission is made at high frequency , different channels can be allotted different frequencies and mix up of channels will be AVOIDED. (b)

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(a)Describe briefly three factors which justify the need for modulation of audio frequency signals over long distances in communication .(b)Draw the waveforms of (i) carrier wave , (ii) a modualating signal and, (iii) amplitude modulated wave.

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