How do you model wire antennas with NEC and 4nec2?

The Numerical Electromagnetics Code (NEC) is a method-of-moments program for thin-wire antennas developed at Lawrence Livermore National Laboratory; the public-domain NEC-2 was documented by Burke and Poggio in 1981.^[1] 4nec2 is a free Windows front end that wraps NEC-2 (and NEC-4 where licensed) with geometry editing, pattern plots, sweeps and an optimizer, widely used for Yagis, verticals, loops and arrays.^[2]

What segmentation rules apply?

Segments should typically be no longer than about λ/10, with λ/20 or finer near feeds and sharp bends; segment length should be large compared with wire radius for the thin-wire kernel (NEC’s extended kernel relaxes this); connected wires should have similar segment lengths at junctions; and wires should not overlap or intersect except at segment ends.^[1]

How does NEC model ground?

Options include free space, perfect ground via images, a reflection-coefficient approximation for real ground, and the more accurate Sommerfeld–Norton method for antennas close to lossy ground. NEC-2 cannot model wires buried in ground; NEC-4 can.^[1]

What can NEC not do well?

Dielectric-loaded structures, printed antennas on substrates and closely spaced wires of different radii push it beyond its assumptions. For such structures, use openEMS or a 3D solver. The average gain test (AGT), in which a lossless model in free space should give an average gain of 1 (0 dB), is a useful check of model validity.^[1][2]

Frequently asked questions

See also

• Method of moments
• Yagi-Uda
• Simulation overview
• openEMS

References

Online sources accessed October 21, 2026; printed works cited by edition. See all sources.

1. “Numerical Electromagnetics Code (NEC) — Method of Moments, Tech. Rep. UCID-18834”. G. J. Burke and A. J. Poggio, Lawrence Livermore Laboratory. January 1981.
2. “4nec2: NEC-2/NEC-4 based antenna modeling and optimizing tool for Windows”. A. Voors. freeware.