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 :
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,
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.