[antennaware] vertical modelling

John Kaufmann john.w1fv@telocity.com
Mon, 18 Jun 2001 07:51:01 -0400

At 12:19 PM 6/18/01 +0200, Arie.Voors@ict.nl wrote:

>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
>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
>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
>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 ?

It sounds as if you are using MININEC to model your antenna. If this is the 
case, you will not get accurate results for the "elevated" radials.  NEC-2 
is more accurate for low elevated radials, although NEC-2 is not capable of 
modelling buried radials accurately.  NEC-4 can model buried radials.  One 
of the versions of EZNEC-PRO (http://eznec.com) can run NEC-4, but requires 
you to buy the license for NEC-4 separately and it's not cheap.  The EZNEC 
software and NEC-4 license will run over US$1000, I believe.  Perhaps there 
are EZNEC-PRO/NEC-4 users here who can comment.

73, John W1FV

FAQ on WWW:               http://www.contesting.com/FAQ/antennaware
Submissions:              antennaware@contesting.com
Administrative requests:  antennaware-REQUEST@contesting.com
Problems:                 owner-antennaware@contesting.com