On 10/28/19 11:18 AM, K9MA wrote:
The reason the parasitic elements are isolated from the boom is that the
boom would detune them. AFAIK, no one has figured out a way to model
elements shorted to a boom, and experimentally tuning an antenna is
expensive.
Virtually all modeling codes based on NEC will handle an element
connected to the boom. I model antennas on complex structures
(spacecraft) using NEC, and that's significantly more complex than a
right angle connection of a boom and elements.
The entire high performance VHF/UHF antenna world makes heavy use of
models, and they don't have any problems.
I'd be interested in the source of your assertion - It is true that some
modeling codes, back when, (we're talking MiniNEC days) didn't do such
a hot job with right angle connections.
And, it can be tedious to model mounting hardware, various and sundry
plates, etc. And modeling traps is a whole issue in itself, if only
because the RF properties of the trap often aren't real well defined,
and are difficult to fixture for a measurement.
But overall, I don't think that NEC would have any problems with this.
And, of course, you could also use another finite element code than NEC
- there's a whole bunch of them that are better adapted to modeling
"structures" made of lots of solid surfaces. For NEC you have to create
grids to represent structures and there's definitely an *art* to doing
that in a practical sense.
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