Home / Propagation / 2 m and 70 cm tropo map
Light areas are regions where the atmosphere bends the wave more than usual. The brighter it is, the further the signal can travel beyond the normal radio horizon. The dark background is ordinary atmosphere — range as you’d expect day to day.
A duct is a channel in which the wave bounces between layers and travels hundreds of kilometres instead of escaping into space. Then on 2 m you can hear stations that normally aren’t there.
The mere existence of a duct isn’t enough — it has to be sufficiently thick relative to the wavelength. The required thickness increases with wavelength, so 70 cm fits into ducts that are too thin for 2 m.
That’s why there are days when 70 cm lights up while 2 m stays quiet. The other way round — almost never.
Vertical atmospheric profile (temperature, humidity, height) from NOAA’s GFS model, at six pressure levels from 1000 to 850 hPa, on a 0.5° grid — 486 points over Poland and neighbouring countries.
From this, radio refractivity is computed according to ITU‑R P.453, and from that the tropospheric ducts. Recalculated every three hours, with a forecast up to two days ahead.
Sporadic E — an ionospheric phenomenon, not tropospheric. It appears on 2 m rarely, but can open the band over thousands of kilometres. It can’t be computed from meteorological data.
Aurora and meteor scatter have their own rules too. This map shows tropo only — but properly calculated.
A frank note on the limitations: the model has a vertical resolution of about 200 m, while real ducts can be thinner and sharper. The map tends to underestimate rather than overestimate — if it shows marginal conditions on 2 m, it may be better out in the field. Treat it as a guide to when it’s worth listening, not as an oracle. The best test is still a radio switched on.
Meteorological data: Open-Meteo (GFS / NOAA model, CC-BY 4.0 licence). Country borders: Natural Earth (public domain). Method: ITU-R P.453 — tropospheric radio refractivity. Computed and plotted on this server, with no third-party maps embedded.
SFI, K index and HF band status — solar and geomagnetic data updated continuously.
