Gray Line Map -

   This maps shows the current areas of daylight and darkness in real time.           [Back ]
Grey Line Map
The Sun's position is marked with: Sun    The Moon's position is marked with: Moon

The grey line is a band around the Earth that separates daylight from darkness. Propagation along the grey line is very efficient. One major reason for this is that the D layer, which absorbs HF signals, disappears rapidly on the sunset side of the grey line, and it has not yet built upon the sunrise side. Ham radio operators and shortwave listeners can optimize long distance communications to various areas of the world by monitoring this band as it moves around the globe.

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