AGILE Modeled WWV Maximum Usable Frequencies

The maximum usable frequency (MUF) for the paths from WWV are calculated from the foF2 value modeled for the WWV-to-receiver path midpoint (blue trace) based on a single-hop geometry. This geometrical MUF (black trace) may underestimate the actual MUF during the day due to E-region refraction.

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.