Effective Length

(of an antenna), a parameter of wire antennas that characterizes the antenna’s efficiency in transmitting and receiving electromagnetic waves. The effective length for a receiving antenna is defined as the ratio of the electromotive force at the receiver input to the intensity of the electric field incident on the antenna; for a transmitting antenna, it is defined as the length in free space of a conductor with a uniform and inphase current distribution along its entire length that generates the same field intensity in the direction of maximum radiation as a real antenna under conditions of equal current amplitudes in the conductor and the real antenna. The effective antenna length is numerically identical in transmission and reception.