Re: NEC-LIST:Modeling a conductive surface in NEC2

Hi Jerry

You can model any surface using wire segments that are about a 1/10 of a
wavelength in length.
I don't think that the diameter of the wires would be of such importance in
such a case as long as they satisfy the general rules for NEC with regards
to Segment length to radius ratios etc.
This same technique of modeling surfaces by a wire mesh can even be used to
model very complex structures such as aircraft, boats, cars etc.

If you are looking for a easy to use, professional program to quickly model
this problem, why don't you try using SuperNEC. It has a full 3D graphical
interface so you won't have to write any text .nec files, and a really great
output interface for plotting 3D radiation patterns, smith chart plots etc
etc. It also has a number of predefined structure and antenna assemblies
such as wire mesh plates, cylinders, spheres, yagi's, helices, lpda's etc
etc. With the antenna assemblies, by changing your model frequency in
SuperNEC, the assemblies are automatically re-segmented so that your model
remains valid. Another great feature of this product is the structure
checker which checks your model to see that all the nec rules to produce
accurate results have been followed.
I am sure that these features of SuperNEC will considerably reduce the time
taken to model your specific problem.

You can download SuperNEC from www.supernec.com and get a 30day evaluation
license file for running the software.

Regards
Brandon Orchard
----- Original Message -----
From: "Jerry Flanders" <jeflanders_at_comcast.net>
To: <nec-list_at_gweep.ca>
Sent: Friday, September 27, 2002 11:42 PM
Subject: NEC-LIST:Modeling a conductive surface in NEC2

> I am trying to evaluate a few ideas for a replacement antenna for my ham
> radio club's 2 Meter repeater.
>
> The new antenna will be mounted on one of our city's water tanks. I would
> like to take into account the effect of this nearby reflective surface in
> the model calculations.
>
> I understand NEC2 cannot model the surface, but that I can simulate the
> surface with a wire grid. I need help with some specifics on the grid
> structure.
>
> I have a copy of Arie's "Build" to actually generate a grid of the right
> size and shape, but I don't know what mesh size (size of the openings) is
> appropriate. If I use too large a mesh opening, I suspect it would not
> represent a plane surface accurately, but if I just use an
> arbitrarily fine mesh, I will cripple this 384MB computer. Is there a
rule
> of thumb for adequate mesh "pore" sizes in terms of wavelength?
>
> I could also use advice on what diameter "wire" to use for the grid, and
> what conductivity, if conductivity is important. I assume it is a steel
tank.
>
> Anybody?
>
> Jerry Flanders
>
> W4UK
> --
> The NEC-List mailing list <nec-list_at_gweep.ca>
> http://www.gweep.ca/mailman/listinfo.cgi/nec-list

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