Near-Real-Time MUF Map
Weather and Radio Propagation Forecasting Course. We are accepting enrollments for this class NOW. The next class will
commence on 16 June 2003.
The following image is a recent high-resolution map of
Maximum Usable Frequencies (MUFs) for 3,000 kilometer
radio signal paths. It is also a map showing the current location of the
auroral ovals, the sunrise/sunset terminator and the regions of the world where
the sun is 12 degrees below the horizon (which estimates the gray-line corridor
where HF propagation is usually enhanced). This is map is similar to the
plethora of constructable maps that is produced by PROPLAB-PRO
Version 2.0, a very powerful
radio propagation software package for IBM or compatible computers, ideal for
amateur or professional radio communicators. Instructions on how to use this
map follow below.
(This map is updated every 5 minutes.)
Click on PROPLAB-PRO Version 2.0 for additional map samples.
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
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.
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.
The map shows the radio auroral zones as green bands near the
northern and southern poles. The area within the green bands is known as the
auroral zone. Radio signals passing through these auroral zones will experience
increased signal degradation in the form of fading, multipathing and
radio auroral zones are typically displaced equatorward from the optical auroral zones (or the regions
where visible auroral activity can be seen with the eye).
great-circle signal path from the Eastern United States to Tokyo Japan is shown
along with the distance of the path (in km) and the great-circle bearing from
the U.S. to Tokyo (in degrees from north).
this signal path crosses through the green lines indicating the position and
width of the radio auroral zones, propagation will be less stable and degraded
compared to if the signal never crossed through the auroral zones. Using your
mouse, PROPLAB-PRO will let you plot the great-circle paths and azimuths
between any two points while this display is
The yellow Sun symbol near the equator indicates the
location where the Sun is directly overhead.
The regions of the world where the Sun is exactly rising or setting is
known as the Grayline
and is shown as the solid gray-colored line that is closest to the Sun
The second solid gray-colored line defines the regions
of the world where the Sun is exactly 12 degrees below the horizon. This line
defines the end of evening
twilight. Everything inside of this second line is experiencing
The area between the two lines (shaded a lighter shade
than the night-time sector) is known as the grayline and has special significance to
radio communicators. Signals which travel inside
the grayline region often experience significant improvements in propagation
because of the loss of ionization in the D-region as the Sun sets. However,
because the higher F-regions of the ionosphere remain strongly ionized for
longer periods of time, signals with higher frequencies are able to travel to
greater distances with less attenuation when they are within the
The great-circle path from the eastern U.S. to Japan is also
shown with the accompanying distance (in kilometers) and bearing (clockwise
from north). Notice how this path may occassionally pass into the influential
auroral zones if geomagnetic activity increases or during the
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