Means of signal propagation
From Megawiki
Amateur radio operators employ various means to get their signals from one point to another.
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Direct Line of Sight
The simplest form of propagation is direct line of site. Radio waves travel much as light does and line of sight communications refers to a direct path of communication. Line of sight communications are limited by the surrounding terrain and by the curvature of the Earth.
Signal Refraction
Ionization of the upper atmosphere can refract a signal back towards the Earth. This method is the most common employed by hams for world wide communication.
Signal Reflection
Radio waves can be reflected off of some surfaces which may include buildings; airplanes; mountains; moisture; thermal layers of the atmosphere; an aurora; the Earth; or even the Moon.
Signal Repeating
To help extend range, signals can be received by a station and retransmitted automatically. Such a device is simply called a repeater. Repeaters are usually located on the top of a mountain; a tall building or they may also be installed on satellites to enable communication over a very large area.
See also
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