Arie,
I have access to NEC4 and it indeed does handle the buried and elevated
radials properly. I also have an interest in shortened verticals. If you
would like
to send me a NEC input file or even better an EZnec input file I will be
happy
to model it for you. The NEC4 code cannot be shared but I am willing to
run
the problem.
Incidentally the results you cite seem reasonable based upon my
experience
with inverted L designs.
73 Jerry
On Mon, 18 Jun 2001 12:19:39 +0200 Arie.Voors@ict.nl writes:
>
>
>
> For a periode of time now I am trying to modell a vertical with a
> two spoke top
> hat (80 m dipole) and a radial ground screen.
>
> The actual (burried) ground screen consists of about 20-30 copper
> wires with
> lengths between 1/8 and 1/4 wavelengt;
> some without, but mostly with one or two copper ground stake pipes
> (5 meters
> long).
>
> The measured impedance is about 45 + j 400 ohms.
>
> The modelled antenna, using a 20 radial ground screen elevated 20 cm
> above
> ground, gives me an impedance of 22 +j 150 ohms
>
> I can not beleave that my ground (screen) has such a 'big' impedance
> of about 23
> ohms.
>
> My modelling of antenna systems, not using a ground screen, works
> very well.
>
> The question is, is it possible with nec-2 to model such a vertical
> antenna
> system
> by using a ground plane elevated above ground, or do I have to use
> nec-4 ?
>
> Is it possible for 'normal' people, not connected to any official
> company or so,
> to get a PC based nec-4 executable ?
>
> Another question is, if there are people who have succecfully
> modelled a
> vertikal antenna with
> a burried ground screen using nec-2 ?
>
> If so, is it possible for me to recieve a copy of this model ?
>
> Thanks in advance,
>
> Arie.
>
>
>
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