The PSK Automatic Propagation Reporter automatically gathers reception records of PSK activity.

Some links to site with the basics of HF bands and propagation.

• HF Ham Bands and Frequencies (electronics-notes.com)
  • a overview or summary about the HF ham bands or amateur radio frequencies, the frequency allocations and their properties.

WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter".

WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station's callsign, grid locator, and transmitter power in dBm. The program can decode signals with S/N as low as -28 dB in a 2500 Hz bandwidth.
The WSPR protocol compresses the information in the message into 50 binary digits.

WSPR characteristics:

Understanding Solar Indices

• Understanding Solar Indices (ARRL pdf)

VOACAP

VOACAP (Voice of America Coverage Analysis Program) is free