Live from NOAA SWPC
Band conditions
The numbers that drive HF propagation, straight from NOAA's Space Weather Prediction Center, with what they mean on the air. Refreshes every 5 minutes.
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Planetary K-index · last 7 days
NOAA space weather scales
R = radio blackouts (X-ray flares, daylight side, HF absorbed). S = solar radiation storms (polar-path HF absorption). G = geomagnetic storms (HF degraded, especially high-latitude paths; aurora on VHF). Forecast days show NOAA's probability of R1–R2 (minor) and R3+ (major) events, and S1+.
Reading the numbers
Solar flux (SFI) tracks how much the ionosphere is being ionized. Higher means higher usable frequencies. As a rough ham rule of thumb, not an official scale: under 70, the high bands (15–10 m) are mostly closed; 70–100, fair, with 20 m and below doing the work; 100–150, good, with 15–10 m opening; over 150, excellent upper-HF and 6 m F2 is possible.
K-index measures geomagnetic disturbance over 3 hours (0–9). Low is good for HF. At Kp 5 and up NOAA calls it a storm (G1+), and HF gets noisy and absorbed, worst on polar and high-latitude paths. A-index is the daily average of that disturbance (under 10 is quiet).
X-ray class (A, B, C, M, X, each 10× the last) is the Sun's current X-ray output. M- and X-class flares cause sudden HF blackouts on the sunlit side of Earth that can last from minutes to hours (NOAA R scale: M1 = R1, X1 = R3).
Data: NOAA Space Weather Prediction Center, services.swpc.noaa.gov (public, US government). NOAA's Kp and A values are estimates; the definitive Kp comes from GFZ Potsdam. For a measured MUF map, see prop.kc2g.com.