necbol 1.0.0

A plain language Python wrapper for NEC

NECBOL

NECBOL is a Python library that provides a geometry-first interface for building antenna models using the NEC (Numerical Electromagnetics Code) engine.

I wrote it primarily for my own use for the reasons below, but I think it's good enough now to share so that other people can make use of it.

• Not having to think about splitting wires into three-way junctions when I need to join one wire to another (e.g. feeding a hentenna)
• Being able to view the geometry easily & in the same way whether it's in free space at Z=0 or 10m above a specified ground
• Being able to re-use components easily (almost in the style of copy, paste, rotate, move, connect)
• Being able to comment out entire components like loops, helices etc with one or two comment symbols
• Being able to add and remove 'environment' components like dielectric slabs and conductive sheets, cylinders etc
• Creating a core "NEC runner" to which I can add:
  • code to optimise/sweep any parameter set based on any target parameter (gain, VSWR, segment current, feedline common mode current ....)
  • bespoke plotting such as delta (B minus A) and resolving into custom polarisation definitions
  • whatever else I think of

Features

• Component-based antenna construction: Easily create antennas using predefined components.
• Flexible length units: Specify antenna dimensions in mm, m, cm, ft or in as needed.
• Automatic wire joining: Automatically connects wires that intersect, simplifying model creation.
• Flexible connector placement: Add connectors between specific points on different objects.
• Configurable simulation parameters: Set frequency, ground type, and pattern observation points.
• Current component library: Helix, circular arc/loop, rectangular loop, straight wire, straight connector
• Easy to place: feedpoint, series RLC load(s), prarallel RLC load(s) specified in ohms, uH and pF
• Optimiser: Optimise VSWR and / or Gain in a specified direction
• More coming soon: See next steps/future plans below.
• Extensible design: It's written in Python, so you can use the core and add your own code
• Example files: Simple dipole, Hentenna with reflector with example parameter sweep, Circular version of Skeleton Slot Cube with Optimiser code

⚠️ Note: NECBOL is a very new project, and my first released using pip. Code comments are work in progress, and I have yet to decide how to add a user guide.

🛠 Installation

Install using pip: pip install necbol

Open and modify the example scripts to suit your needs. Tip: Look inside necbol/geometry_builder.py to see which antenna components and modification methods are currently available.

User Guide

See the file minimal_example_dipole_with_detailed_comments.py in the examples folder for a minimal explanation of how to use this framework. Browse the other examples as needed, and see the comments in the nec_lib/*.py files which are currently being written.

Next steps / future plans

• add more geometry elements
• optimiser
  • polarisation purity
  • current on a certain segment
  • feedline current (needs a feedline object tagged)
  • stretch / warp / sheer the 3D geometry
• Add gamma feeds? Does this need a component? Look at adding squalo maybe.
  • this links to adding models for feedline and common mode current minimisation in optimiser.
• Wireframe viewer
  • arrow pointing to specified gain direction
  • arrow pointing to max gain direction (with dBi & maybe F/B)
• Clutter / environment objects
  • dielectric slab (for brick walls, GRP panels etc)
  • other antennas
• Automated A/B compares
  • Over ground vs free space
  • With / without specified feature
• Advanced graphing:
  • A minus B graphs