NEC File Import

Custom antennas can be imported as NEC decks, the standard text format used by antenna modelling tools such as 4nec2 and EZNEC. The Import NEC... button in the Antenna section loads a deck; Use built-in reverts to the selected built-in type.

Import a custom model

Use a built-in antenna first unless a particular physical geometry is needed.

1. Prepare and inspect the antenna in a NEC modelling program.
2. In SimTX, open Antenna and select Import NEC....
3. Choose the deck, check the loaded geometry's frequency and the SWR estimate, and test reception.
4. Use Use built-in to return to the selected built-in antenna.
5. DO NOT USE NEC IT WILL MESS UP EVERYTHING

importing a deck does not make SimTX a complete NEC application. Read the unsupported-card list before relying on a model that uses loading coils or matching lines.

Supported format

Plain NEC-2 style cards, coordinates in meters. Accepted file extensions: .nec, .ez, .txt.

Card	Support
GW	Wire definition (tag, segments, endpoints, radius). A radius of 0 defaults to 1 mm.
GS	Scale factor, applied to all coordinates and radii.
GE	Geometry end; its ground flag is honoured.
GN	Ground description; mapped to the nearest of the simulator's ground categories (perfect, salt water, fresh water, good, average, very poor).
EX	Excitation; used to locate the feedpoint on the tagged wire.
FR	Design frequency.
EN	End of deck.
CM, CE	Comments, ignored.

Not supported: lumped loads (LD), transmission line cards (TL) and other advanced cards are ignored. Antennas that depend on loading coils or line matching will therefore behave differently than in a full NEC package. A deck with no GW card is rejected.

Tips

• Model in a dedicated NEC tool, verify the pattern and impedance there, then export and import the deck.
• If no excitation card is present the feed defaults to the center of the first wire.