Absolute Gain of an antenna

An antenna is a transducer which is designed to transmit or receive electromagnetic waves. These Electromagnetic waves are formed when an electric field combines with a magnetic field. The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave. Absolute Gain is expressed in dB. The above figure shows general electronics symbols of Antenna and a Dipole Antenna.

..
..

The absolute gain of an antenna, for a given direction and polarization, is defined as ratio of                                       

(a) the strength that would be wanted at the input part of an ideal isotropic radiator to

(b) the strength provided to the antenna.

Examples of absolute gain are full-load gain and no load gain