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Explain how modulation reduces height of antenna and avoid mixing of signals.
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Modulation reduces antenna height: For the transmission of radio signals, the antenna height must be multiple of λ/4 ,where λ is the wavelength . λ = c /f

where c : is the velocity of light

f: is the frequency of the signal to be transmitted

The minimum antenna height required to transmit a baseband signal of f = 10 kHz is calculated as follows :

image

The antenna of this height is practically impossible to install.

Now, let us consider a modulated signal at f = 1 MHz. The minimum antenna height is given by,

image

This antenna can be easily installed practically. Thus, modulation reduces the height of the antenna.

Avoids mixing of signals: If the baseband sound signals are transmitted without using the modulation by more than one transmitter, then all the signals will be in the same frequency range i.e. 0 to 20 kHz . Therefore, all the signals get mixed together and a receiver cannot separate them from each other . Hence, if each baseband sound signal is used to modulate a different carrier then they will occupy different slots in the frequency domain (different channels). Thus, modulation avoids mixing of signals.

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