Skip propagation is a form of radio propagation that allows radio waves to travel long distances by bouncing off the ionosphere. The ionosphere is a layer of the Earth’s atmosphere that is ionized by solar radiation, and it is located between 50 and 600 kilometers above the Earth’s surface.
When a radio wave is transmitted, it can travel in a straight line (line-of-sight) until it reaches the ionosphere. At this point, some of the energy in the wave is reflected back to the Earth’s surface, while some of it is absorbed by the ionosphere. The energy that is reflected back to the Earth’s surface can travel much farther than the normal line-of-sight range, depending on the ionosphere conditions.
This is known as skip propagation, and it can be used to communicate over long distances, even across continents, with relatively low-power radio equipment. CB radios, which operate on the 11-meter band, are able to take advantage of skip propagation to communicate over longer distances than their normal line-of-sight range.
However, skip propagation is highly dependent on the ionosphere conditions, which can vary greatly depending on the time of day, season, solar activity, and other factors. This means that communication using skip propagation can be unpredictable and unreliable, and it is not guaranteed to work all the time.