Make the fan-dipole summary and tuning chart per-band - #13
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A fan dipole is multiband by leg, but the summary and build sheet treated it
as a single-band antenna at the operating frequency.
Summary: the "Other bands" line ran the harmonic-match scan, which the coupled
fan legs miss, so a multiband antenna read as "not a close match on other
bands". A fan dipole now gets a per-leg report instead — fan_dipole_legs_report
solves at each leg's own design frequency, and the summary lists every band the
antenna covers with its SWR ("Bands covered — one dipole leg per band").
Build sheet: the tuning chart was one whole-antenna table from the summed leg
length, meaningless for a fan. A fan dipole now gets a per-band tuning table
(BandTuningRow) — each leg's length and the trim that shifts its band ~1% —
and the overall chart is suppressed. Templates render whichever applies.
Tests cover the per-leg report, the summary's "Bands covered" section, the
per-band tuning table replacing the overall chart, and that non-fan antennas
keep the overall chart. Suite 521 -> 526.
Note: the per-leg SWRs surface that the modelled legs interact strongly at
their default half-wave lengths (some bands read high until trimmed) — a
fan-dipole geometry-fidelity matter, separate from this presentation fix.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The fan geometry used a fixed 30° azimuth fan, so the spacing between adjacent leg ends was an uncontrolled by-product of angle × leg length — and came out backwards: the legs closest in frequency (nearly the same length) ended up closest together, maximising the coupling that detunes them. Replace it with a controlled end spacing — the distance between adjacent leg ends, which is what a spreader actually sets. FanDipoleModel gains end_spacing_m (default 0.3 m); leg_end_offsets_m centres the legs and steps their ends by that much, and the card builder fans each leg to put its end at that perpendicular offset (a longer leg takes a shallower angle). The model rejects a spacing too large for the shortest leg. A "Leg-end spacing" field on the fan-dipole input drives it (auto-saved and unit-aware like the other length inputs). Widening it measurably reduces the inter-leg coupling on most bands; perfect multiband still needs per-leg trimming (the per-band tuning chart), since a leg can also be a harmonic on another leg's band. Tests: the end offsets step by the spacing, the deck's leg ends match, an over-large spacing is rejected, and the field round-trips through the form. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Problem (reported)
For a fan dipole, the summary and build sheet only described the antenna at the single operating frequency:
Fix — per-band for a fan dipole
fan_dipole_legs_report) that solves at each leg's own design frequency, and the summary lists every band the antenna covers with its SWR — "Bands covered — one dipole leg per band; trim each leg to tune its own band."BandTuningRow) — each leg's length and the trim that shifts its band ~1% — replaces the meaningless overall chart (which is suppressed for a fan). Templates render whichever applies.Tests
+5: the per-leg report covers every leg band; the summary's "Bands covered" section (no more "not a close match"); the per-band tuning table replacing the overall chart; non-fan antennas keep the overall chart. Suite 521 → 526, green locally.
Honest note (separate follow-up)
The per-leg SWRs surface that the modelled fan legs interact strongly at their default half-wave lengths — with several closely-spaced legs in the 30° fan sharing one feed, some bands read high SWR until trimmed (and trimming alone may not fully fix coupling). That's a fan-dipole geometry-fidelity matter (wider/separated legs, drooping, per-leg trim), distinct from this presentation fix. Happy to take it on next if you'd like — the summary now makes the effect visible, which is the right first step.
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