Re: NEC-LIST: NEC-2 ver NEC-4 ver MININEC

Peter,

NEC and MININEC are two different cores with different algorithms.
NEC has two well-known versions, -2 and -4, although -3 is used by a
number of folks. MININEC 3.13 is the public domain version of the
core, but Rockway and Logan have developed a more recent version with
many upgraded and new capabilities--it is proprietary from EM
Scientific.

The differences in the calculating cores yield different limitations
for NEC-2 (the subject of the book) and MININEC 3.13. The limitations
of NEC-2 are partially, but not completely, corrected in NEC-4. For
example, NEC-4 handles tapered diameter elements with much greater
accuracy than NEC-2. However, MININEC 3.13 shows no significant
inaccuracies with most tapered diameter element schedules.

Some of the limitations of NEC (-2/-4) have been documented in an
article I did for QEX a couple of years ago, with some detailed
tracking of conditions vs. model results. It is not a standard folded
dipole that gives NEC various degrees of difficulty--if both wires are
the same diameter and spacing meets NEC minimums, results are
accurate. However, if the wires have different diameters, errors will
occur relative to both MININEC 3.13 results and standard folded dipole
calculations (and MININEC results coincide quite closely with those
standard calculations). Some of these difficulties are reflected in
the gain averaging test, which is available on some commercial
implementations of NEC-2, such as NEC-Win Plus. The degree of error
tends to vary with the diameter differential and spacing.

MININEC 3.13 also has limitations which NEC-2/-4 do not have. Again,
they result not from "stripping down," but from basic differences in
the algorithms of calculation.

I hope this brief note is useful.

Regards,

L. B. Cebik
Received on Mon May 01 2000 - 04:18:56 EDT