Owen Duffy wrote in news:Xns98FAA23A9BF6nonenowhere@
61.9.191.5:

Roy Lewallen wrote in
:

The EZNEC insulation modeling method is basically similar to that used
by NEC-4, but different. The accuracy is comparable. Both programs
(EZNEC and NEC-4) are accurate only for thin layers of material with
relatively low conductivity and permittivity, i.e., like typical wire
insulation. But since the typical change in effective wire length is
only on the order of 3% or so, high accuracy isn't required.

I believe I recall your mentioning a multi-turn loop in an earlier
posting. The insulation feature in these programs doesn't model the
effect of insulation between wires, which might be an important factor
for a multi-turn loop. It only models the effect of the insulation on
the wire's self impedance. So use with care.


Thanks Roy.

My interest is in small single turn untuned loops loaded with 50 ohms.
IMHO, the accuracy of modelling practical multi turn loops becomes an
issue because of the distributed capacitance and possibly proximity
effect.

A small test was done recently where one of my loop designs with
Antenna
Factor predicted by an NEC2 model was compared on BPL emission
measurement over a range of HF frequencies with a calibrated R&S active
loop, and the median of the difference was around 0.5dB from memory,
InterQuartileRange was less than 1dB... so that provides some
confidence
that the models are sound.

I think I recall responding to someone else's post about peformance of
multiturn loops.

When I make loops (usually out of LMR400), I use my antenna analyzer to
get them to resonate properly and to match them. I really don't care
what the insulation is doing because the analyzer will tell me anyway.

BTW, a 1-turn LMR400 loop is about as good as an 80m hamstick, but a
whole lot more narrow!


--
Dave Oldridge+
ICQ 1800667