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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