NEC Versions
There are at least four versions of NEC, with NEC-2 emerging in 1981 and NEC-4 appearing in 1992. NEC-2 is the highest version of the code within the public domain without license. NEC-4 remains proprietary with the Lawrence Livermore National Laboratory and the University of California.
NEC-4 currently requires a separate license for use. The licensing details are available from Lawrence Livermore National Laboratory here.
MININEC was a version first written in BASIC for home computers. It first emerged in 1982 on the Apple II computer. MININEC computational engines are now written in FORTRAN to improve speed. MININEC is an independent implementation of the method of moments. The basic algorithms are based upon the advice of Professor Wilton at the University of Mississippi (now with the University of Houston).
MININEC suffers from some known flaws compared to NEC, the best known being that resonant frequencies may be slightly in error. However, MININEC handles different wire diameters better than NEC2 and probably NEC4; this includes different diameter parallel wires, different diameter wires joined at an angle, and tapered diameter antenna elements. Placing sources at an intersection of two wires is a problem for NEC2 but not MININEC. MININEC converges more slowly (requires more segments) when wires join at an angle, when wire segments of significantly different length are adjacent, and has a weaker ground model.
Read more about this topic: Numerical Electromagnetics Code
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