Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere ; long waves may cover a part of the Earth very consistently, shorter waves can reflect off the ionosphere and travel around the world, and much shorter wavelengths bend or reflect very little and travel on a line of sight.

Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere ; long waves may cover a part of the Earth very consistently, shorter waves can reflect off the ionosphere and travel around the world, and much shorter wavelengths bend or reflect very little and travel on a line of sight.

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