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# Antenna Size

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 λ/4.

ANTENNA SIZE

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 λ/4.

where λ is wavelength ( λ= c/υ ), c is the velocity of light and ν 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 ν = 10 kHz while the modulated signal is ν = 1 MHz.

The height of the antenna required to transmit the original baseband signal of frequency ν = 10 kHz is

The height of the antenna required to transmit the modulated signal of frequency ν = 1 MHz is

Comparing equations (10.2) and (10.3), we can infer that it is practically feasible to construct an antenna of height 75 m while the one with 7.5 km is not possible. It clearly manifests that modulated signals reduce the antenna height and are required for long distance transmission.

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12th Physics : UNIT 10b : Communication Systems : Antenna Size |