Using this Map

 

This is a highly informative map that can be used by amateur and professional radio communicators to determine maximum usable frequencies for any world-wide path at the indicated UTC (Zulu) time.

RED contour lines will appear superimposed on the MUF map if x-rays reach levels capable of producing short wave fadeouts on sunlit paths. When this occurs, the red contour lines represent the highest frequency (in MHz) that may be absorbed by the enhanced solar flare x-rays. Use this information together with our new X-ray Absorption Map to determine what frequencies and paths may avoid affects of radio signal absorption during x-ray flares.

The MUF for any 3,000 kilometer path can be determined by finding the midpoint (or half-way point) of the path and examining the MUF at that midpoint on the map by finding the labelled MUF contour value. All contours are given in MHz.

For 4,000 kilometer paths, multiply the given contoured MUF values by 1.1. The MUF for the given 4,000 km path is then determined at the midpoint of the desired path.

For longer path lengths, divide the path into equal 3,000 or 4,000 km segments and compute the MUFs corresponding to the two midpoints that are 1,500 or 2,000 km from each end of the path. Then select the lower of these two MUFs.