During these times of poor propagation, browsing the web you can find pretty useful and interactive tools to try to predict the probability and the reliability of NVIS (Near Vertical Incidence Skywave) single hop paths, representative of common tactical military HF communications scenarios, as well as of thousands of kilometers (DX) paths, more suitable for strategic back haul links scenarios.
VOACAP Online can be
used for NVIS and DX paths. The diagrams show for each hour the
propability and reliability of links required by users:
http://www.voacap.com/prediction.html
http://www.voacap.com/prediction.html
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| VOACAP diagram related to Italy - Far East links |
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| analysis for the requested link Italy-Swaziland |
For who loves to listen exploiting the NVIS propagation, these URLs provide near real-time high-resolution maps of F2-layer critical frequencies (foF2) which correspond to the maximum radio frequency that can be reflected by the F2-region of the ionosphere at vertical incidence, that is when the signal is transmitted straight up into the ionosphere (NVIS): just choose the location that you are interested from a quite extensive list.
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| today foF2 statistics form Roquetes (Spain) |
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| foF2 real-time plot from Brisbane (Australia) |
If you are more interested in NVIS, well, this pdf document is a good starting point.
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