AGILE Modeled WWV Maximum Usable Frequencies

The maximum usable frequency (MUF) for paths from WWV to selected locations is calculated from the model ionosphere using the secant law and a single-hop path. The F region MUF (blue trace) is based on the model foF2 value (green trace) and height of the peak density. The E region MUF (red trace) is the maximum frequency supported in the 90-120 km range (which may not have a well-defined peak.) The overall MUF is the greatest of the E and F region MUFs. Note that the geometrical MUF generally overestimates the actual MUF due to refraction effects.

Received signal levels at 2.5, 5, 10, 15, and 20 MHz are indicated on the plot, with darker squares corresponding to stronger signals. The lower frequencies (2.5 and 5 MHz) are typically absorbed during the day by the D-region. Propagation well above the expected MUF (i.e., 20 MHz) usually indicates sporadic E.