Radio Propagation

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F2 Critical Frequency

F2-layer critical frequencies:  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).  Use to determine best band for Near Vertical Incidence Skywave (NVIS) propagation. More on NVIS: WB5UDE KV5R WA6UBE

recent high-resolution map of F2-layer critical frequencies


Maximum Usable Frequency

Maximum Usable Frequencies (MUFs) for 3,000 kilometer (default) radio signal paths: 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.

recent high-resolution map of Maximum Usable Frequencies

More on Propagation

Voice of America Point-to-Point Propagation Predictor

Collection of Current Data; ARRL Bulletins; ARRL; eHam; Wikipedia; G0KYA E-book


Digital Modes

WB8NUT's web site on digital modes

KB9UKD's digital modes samples