The monopole antennas are commonly used for the medium wave radio broadcasting. They also find application in walkie-talkies, other hand sets and cars.
A monopole antenna is vertically mounted above the ground and is excited at the base as shown in Fig.
A monopole antenna is equivalent to a dipole as shown in the above Figure.
The radiation characteristics of a monopole antenna and a dipole of double its length are identical except the radiation resistance and the radiated power.
Since the monopole antenna radiates only in half space (above the ground), it radiates half the power compared to the corresponding dipole and consequently has the radiation resistance half of that of the corresponding dipole.
The monopole antennas find applications at low frequencies where the wavelengths become excessively long.
This antenna is also suited for medium wave transmission, because for that wavelength the earth behaves like a good conductor and therefore supports only vertical polarization.
The monopole antenna naturally provides vertically polarized waves and an isotropic radiation pattern on the ground which is most suited for broadcasting applications.
