Friday, 1 February 2013

Refraction


Refraction

Radio waves are refracted (or bent) when they propagate through the atmosphere.
The refraction is caused by changes in the speed of the signal with altitude
or by other spatial changes in the atmospheric conditions. Normally, the speed
of the signal increases with altitude, causing radio waves to bend downward.
However, on occasion, weather conditions may lead to variations in speed with
height that differ significantly from the typical variations. This may result in a situation
in which only a fraction or no part of the line-of-sight wave reaches the
receiving antenna.

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