On 6/1/18 7:46 AM, Grant Saviers wrote:
Dan,
Correct, I measured the currents and wanted to see the pattern
distortion that resulted, after reading concerns about current asymmetry.
Previously, I modeled very simplified towers northwest of the vertical
(3 towers) affect on the pattern and found they were acting as
reflectors and shifting the pattern about 1.2db to favor the southeast.
The radial current asymmetry is a 0.4db influence in the opposite
azimuth. Luck.
Developing a model for the steel building 56' x 70' x 14' is easier now
with not yet tried tools in EZNEC 6. However, how to model a Ufer
perimeter foundation as the ground is tbd for me. Any advice?
I doubt you could adequately model a ground network (in the ground)
using a tool like NEC (even NEC 4). NEC assumes that the soil
properties are uniform (with some stuff like "cliffs" available), and
while NEC 4 will handle buried conductors, there's some fairly
idiosyncratic things about it.
Modeling a steel building is easy - do it like a car or ship - as a grid
of wires. The wire spacing/diameter should be chosen so that the
circumference of the wire is comparable to the spacing. (i.e. spacing =
2*pi*diameter) - big diameter wires are fine.
From a "interaction with antennas" standpoint, I'd do some experiments
with a "thinned grid" to see how much difference adding more wires makes.
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