Editing Skywave (section)

{{Short description|Propagation of radio waves beyond the radio horizon}}
{{For|the company|SkyWave Mobile Communications}}

[[Image:Skywave.jpg|right|thumb|250px|Radio waves (black) [[Reflection (physics)|reflecting]] off the [[ionosphere]] (red) during skywave propagation. Line altitude in this image is significantly exaggerated and not to scale.]]

In [[radio communication]], '''skywave''' or '''skip''' refers to the [[Radio propagation|propagation]] of [[radio waves]] [[Reflection (physics)|reflected]] or [[refraction|refracted]] back toward Earth from the [[ionosphere]], an [[Ionization|electrically charged]] layer of the upper [[Atmosphere of Earth|atmosphere]].  Since it is not limited by the curvature of the Earth,  skywave propagation can be used to communicate beyond the [[horizon]], at intercontinental distances.  It is mostly used in the [[shortwave]] [[frequency]] bands.

As a result of skywave propagation, a signal from a distant [[AM broadcasting]] station, a [[shortwave radio|shortwave]] station, or &ndash; during [[sporadic E propagation]] conditions (principally during the summer months in both hemispheres) &ndash; a distant [[VHF]] [[TV/FM DX|FM or TV station]] can sometimes be received as clearly as local stations.  Most long-distance shortwave ([[high frequency]]) radio communication &ndash; between 3 and 30&nbsp;MHz &ndash; is a result of skywave propagation. Since the early 1920s [[amateur radio|amateur radio operators]] (or "hams"), limited to lower transmitter power than [[Broadcasting|broadcast stations]], have taken advantage of skywave for long-distance (or "[[DX communication|DX]]") communication.

Skywave propagation is distinct from [[line-of-sight propagation]], in which radio waves travel in a straight line, and from [[non-line-of-sight propagation]].