Live ionosonde data · Estimate
Best band right now
Enter your location and a target. This estimates the highest frequency the F2 layer will carry on that path right now, from the latest ionosonde readings, and says which bands that leaves open. It's an estimate of the MUF only: it does not model absorption, noise or the lowest usable frequency.
Path
Estimated MUF estimate
Map
Bands estimate
Each band's lower edge is compared with the MUF. Under MUF: at or below the estimated basic MUF, so the F2 layer can support it. Marginal: above the basic MUF but within the ITU operational-MUF allowance, so it may work. Above MUF: above even that. A band under the MUF can still be dead from absorption (worst on the low bands in daylight), noise, or because nobody is on.
For a full prediction with power, antennas, LUF and reliability, run the path in VOACAP Online .
How it works
Data. Ionosondes measure the F2 layer's critical frequency (foF2) and MUF(3000)F2, the highest frequency that one F2 hop of 3000 km can use. KC2G collects the latest readings from GIRO and INGV for its MUF map and republishes them every 15 minutes; this page reads that list and KC2G's contour lines. The readings are typically 5–20 minutes old when KC2G publishes them; each one's age is shown. Readings older than 3 hours are ignored.
Control points. Following ITU-R P.533-14 Table 1a, the ionosphere is sampled at the path mid-point for paths up to dmax (the longest single F2 hop, at most 4000 km). Longer paths use two points, half a hop in from each end, and the lower result wins. Above 9000 km the hop count follows P.533 §5.3 (hops of 4000 km or less, at least 3° elevation).
Interpolation (our simplification). At each control point, foF2 and MUF(3000)F2 are each a weighted average of the 4 nearest ionosondes, weighted by 1/distance². This is not how KC2G draws its map (it uses a physical model fitted to the data), and it can be badly wrong far from any ionosonde or across the day/night line. Coverage is rated good if every control point has an ionosonde within 1000 km, sparse within 2500 km, else poor. Those thresholds are ours, not from a standard.
MUF. The basic MUF for the hop is P.533 eq. (3) with M(3000)F2 = MUF(3000)/foF2, using the ordinary-wave form (P.1240-2 §3.1: the gyrofrequency term dropped). foE isn't in the live data, so the calculation runs for both limits of x = foF2/foE and keeps the lower MUF. The operational MUF can be higher than the basic MUF; P.1240-2 Table 1 gives a ratio of 1.10–1.20 by day and 1.20–1.30 at night for ≤ 30 dBW EIRP. That range is the “marginal” zone. All of this applies monthly-median relations to a single live reading.
Not modeled: the lowest usable frequency (LUF), D-layer absorption, noise, E-layer and sporadic-E modes, F1 modes, long path, geomagnetic storms and polar-cap absorption (see band conditions), and your power and antennas. On 160–40 m the MUF is rarely the limit; absorption is (P.533 eq. 20: it grows as the sun climbs and falls steeply with frequency).
- Recommendation ITU-R P.533-14 (08/2019), HF propagation prediction method: Table 1, eqs. (2)–(6), (13), (29), (30).
- Recommendation ITU-R P.1240-2 (07/2015), basic MUF, operational MUF and ray-path prediction: §3.1, Table 1.
- NOAA Global Monitoring Laboratory, “General Solar Position Calculations” (sun above the horizon = zenith < 90.833°).
- Ionosonde data: prop.kc2g.com (Andrew Rodland KC2G; funded by WWROF), from the Lowell Global Ionospheric Radio Observatory (GIRO) and INGV eSWua, and the observatories that run the ionosondes.
- Band edges: 47 CFR 97.301 (this site's band plan data).