The ionosphere can be considered as a mirror which reflects the radio waves, as does the ground. Thus a large area of the globe can be covered from a single point.

The reflection is affected by several factors:
Day/night;
Seasonal changes;
Number of sunspots (by an eleven year cycle).

Rule-of-Thumb
Short distance – Low frequency
Long Distance – High frequency

Darkness – Low frequency
Daylight – High frequency

To give a theoretical presentation of which frequencies that will work from various points, we issue an updated Radio Propagation Forecast every 3 months.

This Forecast sheet is available as a downloadable PDF-file - in order to facilitate reproduction and distribution among crews.
A click on the image to the right, will open the PDF-file for viewing and/or printout. If you prefer to save the PDF-file on your hard-disk for future use - please rightclick on the imagelink and choose "save target as...".