Think of this page as a “quick-look” HF propagation compass. It won’t replace a full ionospheric model — but it’s perfect for deciding which band is worth calling right now, and whether conditions are calm or cranky.
The idea is simple: SFI and Sunspots are the “engine power” that can lift the ionosphere, while K and A describe geomagnetic disturbance — the part where the engine still runs, but the road turns into potholes. Click any KPI tile to open a 7-day trend chart plus a short “what it means” note.
How to read the KPIs
- Solar Flux (SFI) & Sunspots (SSN): Higher values usually mean stronger EUV radiation, which can increase ionization. That often helps higher HF bands like 20/17/15/12/10 m open more reliably. If SFI/SSN are low, those bands can feel “quiet” or close earlier.
- K-Index & A-Index: These describe geomagnetic activity. When they rise, absorption and instability increase — signals can get weaker, noisier, or “fluttery”. As a rule of thumb: K ≥ 4 means conditions are getting disturbed, and polar routes are often the first to suffer.
- Solar Wind: High wind speed alone isn’t everything, but it’s a strong “storm ingredient”. Sustained fast wind can push K/A upward (especially when the magnetic field turns southward), which can temporarily degrade HF and make VHF modes more/less interesting depending on the setup.
- foF2 (MHz): The F-layer’s vertical critical frequency — basically the ionosphere’s “ceiling” straight up. It’s useful for judging low-band behavior and NVIS potential. Expect strong day/night variation: foF2 is commonly lower at night.
- MUF (≈3000 km): The highest usable frequency for a longer hop around ~3000 km. A rough approximation often used is MUF ≈ 3 × foF2. If MUF sits above 14 MHz, 20 m is usually in play; above 21 MHz, 15 m has a better chance of being lively.
Practical “what should I do now?”
- High SFI/SSN + low K/A: try higher bands first (20 → 15 → 10 m).
- Rising K/A: expect rougher paths; drop lower (40/60/80 m) or use robust digital modes.
- MUF near a band edge: timing matters — the band may open/close within hours.
Source: hamqsl.com (stored locally). If foF2/MUF aren’t available in the feed, this page may estimate them from SFI using a simple heuristic. Use the trends as guidance — not gospel. HF still enjoys improvising.