Medium frequency travel longer distances via skywave propagation, in which radio waves radiated at an angle into the sky are reflected (actually refracted) back to Earth by layers of charged particles (ions) in the ionosphere, the E and F layers. However at certain times the D layer (at a lower altitude than the refractive E and F layers) can be electronically noisy and absorb MF radio waves, interfering with skywave propagation. This happens when the ionosphere is heavily ionised, such as during the day, in summer and especially at times of high solar activity, At night, especially in winter months and at
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