Absolute Gain

In simple language, absolute gain measures how much a device improves the power of a signal. The absolute gain of an antenna, for a given direction and polarization, is the ratio of (a) the power that would be required at the input of an ideal isotropic radiator to (b) the power actually supplied to the given antenna, to produce the same radiation intensity in the far-field region. If no direction is given, the absolute gain of an antenna corresponds to the direction of maximum effective radiated power. Absolute gain is usually expressed in dB.