1.

Write one factor which justifies the need of modulation fortransmission of a signal.

Answer»

In fact there are many factors justifying the need of modulation.Mainly we perform modulation in order to make baseband (message) signal compatible with the channel. Few of the factors are:

Size of the antenna

Most of the signals of our interest are of low frequency(information signals). Now we know that frequency and wavelength hold an inverse relation. So a low frequency signal will have larger values of wavelength

Now,Size of an antenna is given by the relation

Antenna size = wavelength/4 ,which will a large value

And now we don’t want a low frequency and end up with a huge antenna.Having an antenna of such large dimension is impractical. Hence we modulate baseband signal with a high frequency carrier.

2.Interference of signals from various transmitters

In order to avoid the interference of signal from different transmitters,high frequency is required which can only be achieved by modulating the base band(message signal).



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