Image antenna

When a radio antenna is mounted near a conductive surface such as the Earth or a flat metal plate or screen, the radio waves directed toward the surface reflect off it.

This second apparent source of radio waves is the image antenna.

Each charge and current in the real antenna has its counterpart in the image, and may also be considered as a source of radiation.

In order to form an image, the ground plane surface must generally have dimensions of at least a quarter-wavelength of the radio waves used.

This article incorporates public domain material from Federal Standard 1037C.