☰ HF Propagation menu

Propagation Tools and Converters

Free online tools for radio amateurs: convert the main space weather indices, find sunrise, sunset and gray line times for any grid locator, and see how HF conditions respond to the Sun.

SFI to Sunspot Number ConverterConvert solar flux (F10.7) to sunspot number and back.Kp to A-Index ConverterKp, ap and A-index conversion with the full table and G-scale.Solar Flare X-Ray Class ConverterFlare class to W/m² and the NOAA radio blackout scale.Sunrise, Sunset and Gray Line by Grid LocatorSunrise, sunset and gray line windows for any Maidenhead locator.HF Propagation What-If SimulatorMove the sliders and watch HF band conditions change.

Which tool do I need?

Use the sunrise and sunset calculator to plan low-band DX around the gray line. Use the what-if simulator to learn how flux, Kp and flares move the bands. The three converters translate between the units used in reports, spots and forecasts: flux and sunspots, Kp and A-index, and flare class and X-ray flux.

All calculations run in your browser; nothing you type is sent to any server. For current values, see the live data.

Data: NOAA Space Weather Prediction Center, NASA SDO. Band conditions are estimates computed by Map For HAM and are indicative only. Methodology and credits · Data feeds · Widgets