Propagation MUF Map

Propagation (MUF map)

A world map of the MUF — the maximum usable frequency — built from the ionosonde network, with a verdict per band on the path between you and any point you click.

What the numbers are, and are not

The MUF is a median: the frequency the path carries on about half the days, not a guarantee for today. That is why the band OpsLog shows is the highest one below 85% of the MUF rather than the MUF itself.

And it is the ionosphere only. No antenna, no power, no noise. A path can be open on 10 m and still unworkable with a low dipole, because 5000 km asks for a takeoff angle of a few degrees.

Pale areas on the map are where no ionosonde has reported nearby, so the value there is extrapolated.

The window on a path

Two layers decide it:

• the F2 layer sets the top — the highest frequency that comes back instead of going through;
• D-layer absorption sets the bottom — the lowest frequency that survives the trip.

A percentage is shown where the top is genuinely in doubt. Below the MUF, a band is judged open, marginal or absorbed, and that verdict takes account of band and distance: a short path survives far more loss than a long one, and a high band far more than a low one. It assumes an ordinary station — a hundred watts and a wire. Hover a band for the figures.

The absorption readout is a comparison, not a threshold: so many dB of D-layer absorption on this path, against the dB an ordinary station survives on this band over this distance.

The skip zone

When a high band shows as skip, that is a statement about geometry, not about the contact. The F2 layer carries the band — it would reflect it for a station further away — but not at the angle a path this short asks for, so the signal goes through the layer instead of coming back.

Short contacts on the high bands still happen every day: sporadic E, side scatter, and simply because FT8 hears far below what a voice contact needs. None of that is modelled here, so nothing is claimed about it.

See also

• Maps and Antennas — the great-circle map and the beam lobe.
• DX Cluster and Spots — band openings detected from real reports rather than predicted.