Radio spectrum the earth (ground waves), shorter waves can reflect off the ionosphere and return to earth beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon. To prevent interference between different users, the artificial generation and use of radio waves is strictly regulated by law, coordinated by an international body called the International Telecommunications Union (ITU), which defines radio waves as "electromagnetic waves of frequencies arbitrarily lower than 3 000 GHz, propagated in space without artificial guide".[1] The radio spectrum is
Coast earth station Earth station (article 1.63) Coast earth station Coast earth station, also called the coast earth radio station is – according to "article 1.76" of the International Telecommunication Union´s (ITU) ITU Radio Regulations (RR) – defined as «"An earth station in the fixed-satellite service or, in some cases, in the maritime mobile-satellite service, located at a specified fixed point on land to provide a feeder link for the maritime mobile-satellite service".» Each "radio station" shall be classified by the "service" in which it operates permanently or temporarily. In accordance with "ITU Radio Regulations" (article 1) this type of "radio station" might