Ground (surface) wave

Ground wave (also called surface wave) propagation is the mode in which a radio wave from a transmitting antenna travels near the surface of the Earth so as to reach a nearby receiving antenna. In this mode the wave hugs close to the ground and follows the Earth's own curved surface as it travels from transmitter to receiver, rather than travelling in a perfectly straight line through the air above.

Because the wave stays so close to the ground, it induces electric currents in the ground itself, and it steadily loses energy to the ground through this absorption process. As a result, a ground wave's signal cannot be transmitted over large distances -- this mode is suitable only for local broadcasting over relatively short ranges. It is used specifically for radio waves of frequency less than 2 MHz, in what is called the medium frequency band. Because TV and FM signals operate at much higher (very high) frequencies, groun …