HF band conditions
Updated 10 Nov 04:26 UTC. This page reloads itself every ten minutes.
- Solar flux (SFI)
- 129
- Planetary K index
- 1.7
- X-ray flux
- C1.6
- Radio blackout
- R0
- Geomagnetic storm
- G0
| Band | Daytime | Night |
|---|---|---|
| 160 m | Poor | Good |
| 80 m | Poor | Good |
| 60 m | Fair | Good |
| 40 m | Fair | Good |
| 30 m | Good | Good |
| 20 m | Good | Fair |
| 17 m | Good | Poor |
| 15 m | Good | Poor |
| 12 m | Good | Poor |
| 10 m | Fair | Poor |
How to read this
Good means the band should support long-distance contacts on a typical path. Fair means it is workable but patchy. Poor means unlikely to open. Daytime and night refer to the path, not to when you read this page.
Where the numbers come from
The readings come from NOAA's Space Weather Prediction Center and refresh every ten minutes:
- Solar flux (10.7 cm, SFI) drives the maximum usable frequency. Higher flux means the upper bands open more often.
- Planetary K index measures geomagnetic disturbance. At 5 or more (a G1 storm) the ratings drop a step; at 7 or more everything is Poor.
- X-ray flux from the GOES satellite shows solar flares. An M-class flare (R1) degrades the daylight side for a while; an X-class flare can black it out.
The band ratings are a rule of thumb built from those numbers: a maximum usable frequency of about 16.5 MHz at SFI 70 rising 0.25 MHz per flux point, half that after dark, with the low bands penalised by daytime absorption. It does not know the season, your location or the exact path, so treat it as a quick guide. For a full prediction use a tool such as VOACAP.
VHF and UHF (6 m and up) depend on line of sight and the weather rather than the sun, so they are not rated here.