About This Propagation Page
All data depicted on this page resides on external web pages. This page pulls multiple resources together onto a single page. This page will self-refresh every 15 minutes. Clicking on a graph, map or chart will open the web page with the original source data. The NVIS World Map data from Australia is updated hourly while the foF2 Critical Frequency Plot from Austin is updated every 15 minutes.
For a point to point propagation prediction that depicts probabilities for each band and allows for determining the best frequency and best time to make a long distance HF contact, please see VOACAP Online.
To create a coverage prediction map for any given band, use VOACAP based coverage prediction.
Please note that VOACAP may not produce an accurate prediction for NVIS or ground-wave propagation modes.
If you do not know how to use the data depicted on this page, please view the HF NVIS Frequency Band Selection article that can be found under the Resources menu, or by clicking here.
Maximum Usable Frequency (MUF) Map
|Key For Above Map|
|RED||Contour lines indicate X-Rays reach a level that is capable of producing short wave fade-outs on sun lit paths.|
|GREEN||Green bands indicate radio auroral zones, where radio signals will experience fading, multi-path and absorption.|
|GRAY||Regions that indicate where the sun is rising or setting, to 12° below the horizon (i.e. gray-line). Improved propagation is possible due to the loss of ionization in the D-region, while ionization remains longer in the F-region, allowing for longer propagation.|
The MUF for any 3,000 kilometer (1,864 mile) 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 (2,485 mile) paths, multiply the given contoured MUF values by 1.1. The MUF for the given 4,000 km (2,485 mile) path is then determined at the midpoint of the desired path.
For longer path lengths, divide the path into equal 3,000 km (1,864 mile) or 4,000 km (2,485 mile) segments and compute the MUFs corresponding to the two midpoints that are 1,500 km (932 mile) or 2,000 km (1,242 mile) from each end of the path. Then select the lower of these two MUFs.
Note that the critical frequency (CF), which is appropriate for good NVIS communications, is approximately 1/3 of the maximum usable frequency (MUF). The critical frequency (CF) is indicated at the foF2 entry at the top left of the Austin digisonde image immediately above.