Roy Lewallen wrote in
:

I'd appreciate and welcome reports from anyone who finds a significant
difference in insulated wire results between EZNEC and NEC-4, in the
region where both should be accurate (typical wire insulation values).


Roy,

My comment is not intended to impune EZNEC in any way. I don't know how
EZNEC v4 models insulation, and cannot comment on it.

I have read a description on Cebik's page about modelling the effects of
insulation by loading all segments with a constant value of L which
apparently makes a insulated wire half wave dipole model in NEC2
calibrate well with NEC4' IS model. It would seem that the amount of the
inductance was chosen empirically, a curve was fitted to the experimental
model data. It occurs to me that the results depend to an extent on the
current distribution on the conductor, and might be different for a small
loop where the current is almost uniform.

The reason for the study is to be prepared to fend off criticism from
opponents (the BPL industry, the FCC etc) who might criticise performance
modelled on bare wire when everyone wants to make the loops from
insulated wire. I can defend a NEC4 IS model, but if there are questions
about the accuracy of LD loading of a small loop based on empirical data
from half wave dipoles, I am in a weaker position and possibly worse than
NEC2 models of bare wire.

Modelling the insulation is probably splitting hairs. If I address that,
the next question will be over using stranded wire vs single core.

Owen