Radio propagation

Radio propagation is a term used to explain how radio waves behave when they are transmitted, or are propagated from one point on the Earth to another.

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In free space, all electromagnetic waves (radio, X-rays, visual, etc) obey the inverse-square law which states that an electromagnetic wave's strength is proportional to 1/(x2), where x is the distance from the source. Doubling the distance from a transmitter means the strength is reduced to a quarter, and so on.

Related Topics:
Electromagnetic wave - Inverse-square law

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Radio propagation on Earth is not only affected by the inverse-square model, but by a number of other factors determined by its path from point to point. This path can be a direct line of sight path or an over-the-horizon (see also radio horizon) path aided by reflection from the ionosphere. A variety of phenomena make radio propagation more complex.

Related Topics:
Inverse-square - Line of sight - Horizon - Radio horizon - Reflection - Ionosphere

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Since radio propagation is somewhat unpredictable, such services as emergency locator transmitters, in-flight communication with ocean-crossing aircraft, and some television broadcasting have been moved to satellite transmitters. A satellite link, though expensive, can offer highly predictable and stable coverage of a given area.

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