Know your antinodes before you cut the wire.
A browser tool for end-fed wire antennas (EFHW and random wire) that shows where along the ham bands a given wire length's feedpoint will land on a voltage antinode (good match) vs. a current antinode/node (poor match) — so you can pick a length, or a switched-length scheme, before you're standing in a field with a NanoVNA.
Offline-first PWA, no backend, no login, no framework. Static HTML/CSS/JS.
See docs/spec.md for the full design spec.
Open dangernode.html directly in any browser — no
build step, no dependencies, no server required. It's a single
self-contained file (see CLAUDE.md for why), so it's also the only file
you need if you're copying it onto a phone for offline field use.
Core physics module (inlined in dangernode.html's own <script> — see
CLAUDE.md for why) plus the full v1
UI — tabs, a Settings tab (global VF), the live SVG antinode/node chart
with vertical danger-zone shading, wire-length/tolerance sliders (each
paired with a synced number input), band toggle chips, Quick Check,
Suggest Lengths, counterpoise reference, unit conversion, localStorage
persistence — are implemented, covered by tests/unit-physics.html
(27/27 passing). See CLAUDE.md for the current-status detail
and docs/spec.md for the full spec.
MIT — see LICENSE.