Re: NEC-LIST: Average gain test and diagnosing the source of the problem

Good day Michael,

I have some limited experience in modeling antennas on boxes and cars.
Without looking up my work, I think I got APG values within 5 % of target.
In those cases I used C++ code to generate the wire lists. My grids were as
uniform as possible with respect to wire length and radius. I observed the
equal-area rule for the wires. The antennas are modeled with the same
segment density as the supporting surface. In general, the APG value
improved with mesh density, but if there is a big difference between the
mesh wire radius and antenna wire radius at a junction, this will cause a
problem. I used square mesh cells except in cases where two surfaces meet
at a non-right angle, e.g. the side and back panels of a hatchback. In that
case I used a triangle at the top of the join and sloping quadrilaterals
going down the panel's sloping edges. Segment center alignment in parallel
wires seems to be important in general, but sometimes it can't be done while
keeping the body shape.

Good luck,
Doug Miron

"wilfam" <wilfam_at_technet2000.com.au> writes:

problem

Hi,

If the average gain test shows that your model has a problem then what is
the best way to identify the cause of the problem ?

There is some great information available about this test but not many
examples of "issues" and how they were identified and resolved.

I'm keen to learn.

My particular interest is antennas on wire grid models. I have looked at a
number of great papers that describe wire grid guidelines.

I have a model (source unknown) that had its square wire-grid
"triangulated". In an effort to make the model fit the guidelines I set
about progressively removing the "triangulating wires" in an attempt to be
more compliant with the guidelines. The only trouble was that the average
gain test results got progressively worse.

I have a colleague that is building a different model from scratch. As he
is building the model his gain test results are also getting worse...but he
is unsure why.

We appear to be missing a piece of the puzzle.

I'd appreciate your help.

Thanks,

Michael.

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