Definitions:

Antenna Factor (or correction factor) is defined as the ratio of the incident Electromagnetic Field to the output voltage from the antenna and the output connector.

NOTE: The antenna factor varies with frequency.

Gain The ratio of the signal received or transmitted by a given antenna as compared to an isotropic or dipole antenna.

NOTE: Antenna gain can only be achieved by making an antenna directional, that is, with better performance in one direction than in others.

A relationship can be derived for the Antenna Factor in terms of the antenna’s gain and the frequency of operation. If the incident field is part of a propagating wave, the power density S of the wave is given by: .

Its crucial to note that the preceding two relationships only hold for propagating plane waves (far field conditions), and are polarization matched to the fields. The impedance mismatch between the antenna and receiver is included in the Antenna Factor.

NOTE: For antennas which are not defined by a physicalarea, such as monopoles and dipoles consisting of thin rod conductors, the effective length is used to measure the ratio between E and V.