Numerical Electromagnetics Code

The Numerical Electromagnetics Code, or NEC, is a popular antenna modeling system for wire and surface antennas. It was originally written in FORTRAN in the 1970s by Gerald Burke and Andrew Poggio of the Lawrence Livermore National Laboratory. The code was made publicly available for general use and has subsequently been distributed for many computer platforms from mainframes to PCs.

NEC is widely used for modeling antenna designs, particularly for common designs like television and radio antennas, shortwave and ham radio, and similar examples. Examples of practically any common antenna type can be found in NEC format on the internet. While highly adaptable, NEC has its limits, and other systems are commonly used for very large or complex antennas or special cases like microwave antennas.

By far the most common version is NEC-2, the last to be released in fully public form. There is a wide and varied market of applications that embed the NEC-2 code within frameworks to simplify or automate common tasks. Later versions, NEC-3 and NEC-4, are available only as compiled binaries and after signing a license agreement and have not been nearly as popular. Versions using the same underlying methods but based on entirely new code are also available, including MININEC.

NEC traces its history to an earlier program, BRACT, which was used to analyze antennas consisting of many thin wires in free space. It was useful for modeling certain common types of antennas used on aircraft or spacecraft or other examples where the ground was far enough away that it did not affect the signals. BRACT was developed in the early 1970s by MBAssociates for the US Air Force's Space and Missile Systems Center. MBAssociates, named after the founding partners of Bob Mainhardt and Art Biehl, are better known for the development of the Gyrojet rocket gun.

BRACT's success led to a second contract with MBAssociates, this time by the Naval Research Laboratory and USAF Rome Air Development Center, to adapt the BRACT code to consider the effect of the ground. This produced the Antenna Modeling Program, or AMP, which was extensively modified to support disk-based files, simplify the input and output to make it easier to use, and extensively documented. A follow-up, AMP2, added calculations for extended surfaces like reflectors.

...
Wikipedia