VOACAP


VOACAP is a radio propagation model that uses empirical data to predict the point-to-point path loss and coverage of a given transceiver if given as inputs: two antennas, solar weather, and time/date. Written in Fortran it was originally designed for Voice of America.
Some movies on the coverage during daytime can be found here.

Simulating HF propagation conditions

Currently versions based on the original source tree exist for Windows, Linux and OSX. The program core uses text files for I/O and a bunch of wrappers now exist.
Besides commercial visualization tools, there are also Open Source implementations with GUI:
For immediate results, VOACAP provides a web interface for both the coverage and the prediction.