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Ionospheric effects on propagation

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Barry
Ionospheric effects on propagation

As electromagnetic waves, and in this case, radio signals travel, they interact with objects and the media in which they travel. As they do this the radio signals can be reflected, refracted or diffracted. These interactions cause the radio signals to change direction, and to reach areas which would not be possible if the radio signals travelled in a direct line.

The ionosphere is a particularly important region with regards to radio signal propagation and radio communications in general. Its properties govern the ways in which radio communications, particularly in the HF radio communications bands take place.

The ionosphere is a region of the upper atmosphere where there are large concentrations of free ions and electrons. While the ions give the ionosphere its name, but it is the free electrons that affect the radio waves and radio communications. In particular the ionosphere is widely known for affecting signals on the short wave radio bands where it "reflects" signals enabling these radio communications signals to be heard over vast distances. Radio stations have long used the properties of the ionosphere to enable them to provide worldwide radio communications coverage. Although today, satellites are widely used, HF radio communications using the ionosphere still plays a major role in providing worldwide radio coverage.

The ionosphere extends over more than one of the meteorological areas, encompassing the mesosphere and the thermosphere, it is an area that is characterised by the existence of positive ions (and more importantly for radio signals free electrons) and it is from the existence of the ions that it gains its name.

The information above was taken from the website linked below. It is an informative site that gives some good basic info on radio wave propagation in the ionosphere. It's a great place to begin your study on this subject so lets talk about it Thursday night.

http://www.radio-electronics.com/info/propagation/ionospheric/ionosphere.php

Since Sloar activity affects ionisation directly, you may want to look at another article on the same site at:

http://www.radio-electronics.com/info/propagation/ionospheric/radio-propagation-prediction-solar-indices.php

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