First HF prediction building block. GIRO publishes MUFD — the F2-layer
maximum usable frequency at the 3000 km reference distance — directly
from station measurements, already calibrated against CCIR M(3000)F2
climatology. Rather than recomputing MUF from scratch (which would
require the ~2 MB CCIR coefficient tables), this module treats the
measured MUFD as the anchor and scales it to the actual path distance
using a thin-layer secant-of-incidence ratio.
That keeps the measurement calibration (~3.3× foF2 at our fixture, vs
~5.1× from a naive thin-layer formula) and only uses the thin-layer
math for the relative distance correction.
* adjust_mufd/2 — scales MUFD(3000) to an arbitrary hop distance.
At D=3000 it's a no-op; shorter paths get lower MUF (near-vertical),
longer paths within the single-hop window get higher MUF.
* fot/1 — standard 0.85 × MUF Frequency of Optimum Traffic.
* hf_score/2 — 0-100 band-vs-MUF score with 5-tier curve:
100 (≤ 0.75×MUF) / 80 (FOT) / 50 (≤ MUF) / 20 (fringe) / 0 (dead).
Limitations are in the moduledoc: single-hop only, nearest-station
bias, no LUF/D-layer absorption, no Kp geomagnetic storm modeling.
Those are separate commits once this has bake time.
Not yet wired into PathLive — follow-up commit will add HF bands to
BandConfig and wire the panel.
Graham McIntire
6d69989599