AntennaKNoBs

New in v0.114.0

A SimNEC station on any antenna. Model the antenna in EZNEC, AutoEZ or NEC, and the feed system (coax, measured choke and unun S-parameters, a tuner) in SimNEC: read_ssn_station reads just the station chain from the .ssn and hangs it on any antenna, a .nec deck’s or a builder’s, in a short design. On a real SimNEC station it reproduces SimNEC’s own generator-side trace to 3e-15. See a SimNEC station on any antenna.

Coax as SimNEC, TLDetails and AutoEZ solve it. A SimNEC cable is now AC6LA’s Johnson line (momwire 0.88.0), with the skin-effect inductance and k0 included. It matches AC6LA’s own T-Line Model worked example to machine precision.

Hand-written SimNEC scripts read as a script. Statements, comments, constants, conditions, loops and functions are evaluated rather than pattern-matched, and anything still unread refuses by line number.

NEC-5 decks with several sources on one knot open as NEC-5 reads them, one source of their summed voltage. A feed at a junction knot (an EFHW’s feed at the end of its wire) now exports to SimNEC, written as SimNEC writes it.

The whole pitch, in one line

antennaknobs describes an antenna as Python code — a small parametric builder, its geometry computed from named knobs — then lets you explore it two ways: drive it from a script (sweep, optimize, compare, export a NEC deck), or open it in a browser and turn the knobs live, watching the radiation pattern, SWR, and impedance respond as you drag. Most antenna tools are a static formula calculator or a desktop app you have to install; this is neither.

See it in action

A live modeling session, end to end: a 10 m Moxon built from knobs, tuned by dragging, and read out in real time.

And the other half of the story — writing an antenna as code: a full tutorial building a parameterized single-wire dipole from an empty file to knobs turning in the workbench.

Antennas as Python code

Describe an antenna once as a small parametric builder — geometry computed from named knobs — then sweep, optimize, compare, or open it in the browser. Most tools make you hand-place every coordinate.

Multi-basis MoM

Sinusoidal and B-spline bases in one engine, cross-validating each other — basis quality that otherwise costs four figures in commercial tools.

Fast on big arrays

H-matrix / ACA acceleration with GMRES, where every free NEC tool is dense O(N²). Demonstrated O(N log N) on a 2142-segment Yagi.

Cross-checked physics

A NEC-2 reference engine runs alongside the in-house solver — and a licensed NEC-5 can join as a third — so you get a built-in accuracy check most tools lack.

No platform lock-in

A web UI by default — works anywhere a browser does, while the competition is Windows/Linux/macOS desktop-only or a GUI-less library.

Start here

What is antennaknobs? The tool, who it's for, and how the pieces fit.

Quickstart pip install, then a resonant dipole in ten lines of Python.

Many ways to express geometry The same delta loop, one knob-set, built four different ways — pick the one that fits how you think.

The solver & accuracy Bases, H-matrix acceleration, and how it's validated.