Phase 1 preview

HF propagation, computed on your device

ITU-R P.533 compiled to WebAssembly. Nothing is computed on a server, your location never leaves the browser, and once loaded it works offline.

Tools

Path planner Pick two points, get 24 hours × nine bands of SNR margin. Computes live in this browser in about a third of a second. live engine · ~11 MB first load Reach map Where a station can be heard, with day/night overlay. Add receivers to draw circuits and read each one's usable band range. precomputed · pan & zoom Style guide Every design token in all three themes. The reskin test: one token file drives the whole app. design system

What is real here, and what is not.

Predictions come from the ITU's own reference implementation and are verified numerically identical to a native build of it. Distances, bearings, MUF and the diurnal behaviour all check out against reality.

The engine's reliability output is a known open defect — it reads zero for every circuit tested and ignores the required-SNR input — so nothing here displays it. What you see is SNR margin, which is verified responsive.

The A-score described in the design docs does not exist yet. It is meant to be a calibrated probability, and calibrating it depends on resolving that defect first.

Reach maps are precomputed for three sample sites at 100 W into isotropic antennas — deliberately pessimistic. The station control applies a real transmit advantage on top.

Why it is built this way

On-device compute means our cost does not scale with users, so this can stay free without a funding story.
No server in Phase 1 at all — a scheduled job publishes static files and the browser does the rest.
Offline by construction, which matters for the emergency and field work this is aimed at, where there is no signal.
Nothing hides uncertainty: data age, model limits, and known defects are shown rather than smoothed over.