Modulation helps to reduce the antenna size in wireless communication-Explain.

Explanation

Antenna is used at both transmitter and receiver end. Antenna height is an important parameter to be discussed. The height of the antenna must be a multiple of `(lambda)/(4)`,
`h=(lambda)/(4)`   ……(i)
where `lambda` is wavelength `(lambda-(c)/(v))`, is the velocity of light and v is the frequency of the signal to be transmitted
An example Let us consider two baseband signals. One signal is modulated and the other is not modulated. The frequency of the original baseband signal is taken as v = 10 kHz while the modulated signal is v = 1 MHz. The height of the antenna required to transmit the original baseband signal of frequency v = 10 kHz is
`h_(1)=(lambda)/(4)=(c)/(4v)=(3xx10^(8))/(4xx1xx10^(3))=7.5km` ……(2)
The height of the antenna required to transmit the modulated signal of frequency v=MH is
`h_(2)=(lambda)/(4)=(c)/(4v)=(3xx10^(8))/(4xx1xx10^(6))=75m`......(3)
Comparing equations (2) and (3), we can infer that it is practically feasible to co antenna of height 75 m while the one with 7.5 km is not possible. It clearly modulated signals reduce the antenna height and are required for long distance transmission