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Define the term 'amplitude modulation'. Explain any twofactors which justify the needfor modulating a low frequency base-band signal. |
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Answer» Solution :AmplitudeModulation : It is process in which the amplitudeof the highfrequency carrier wave changein accordance with the instantaneousvalue of MODULATING signal . Factor Justifying the need of Modulation: (i) Effective power radiatedby antenna : As `P alpha 1/(lambda^(2))`,for good transmission , l must befrequency signal . `v = 15 KHz`, `lambda = c/v = (3 xx 10^(8))/(15 xx 10^(3)) = 20000 m` `rArr ` length of antenna should be `= (lambda)/(4) = 5000 m`, which is practically impossible. If transmission frequency is raisedto 1 MHz, then `lambda = c/v= (3xx 10^(8))/(10^(6)) = 300 m` and length of antenna `= lambda/4 = 75m`, which is reasonable. THUS there is need ofconvertinginformation contained in original LOW frequency base-band signal to high frequency setting transmission. |
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