Effective area

From Glossary of Meteorology

effective area

  1. (Also called effective aperture.) In antenna design, the ratio of the received power available at the terminals of an antenna to the power per unit area in the incident wave.

    For all antennas, effective area A is related to gain G at a given wavelength λ by the equation
    The effective area of an ideal antenna is equal to its physical area S. In practice, A/S for microwave antennas is always less than 1, a representative value for paraboloids being 0.6.
    See aperture.