I don't have an answer for you, but since you asked such a general
question I'll generalize it a bit more and suggest you do a search on:
measuring antennas with drones
I read one such article a few weeks back and thought it a neat idea,
but for the one I read it was evident they were only checking
near-field and had more work to do to even get that right.
Having an antenna range, a UAV/drone, and appropriate data collection
/ data reduction could simplify a lot of this in the future. Should be
much cheaper to do too. Reading more articles should give you a
feeling for what the state-of-the-art currently is. I don't have a
handle on that yet having only read one article.
Good luck in your quest.
On Thu, Oct 1, 2020 at 10:39 AM K9MA <k9ma@sdellington.us> wrote:
>
> A somewhat more general question:
>
> There is a whole bunch of trapless tribanders available now, all based
> on modeling. How well do the predictions of NEC4 models for these
> antennas really agree with actual test results? Antenna testing is
> expensive, and I know at least one vendor admits to not testing at all,
> relying entirely on the model results. I have a couple of such
> commercial antennas, and I'm not convinced they really perform as the
> model suggests. I've done some pattern measurements for one of them
> under almost exactly the same conditions for which I measured the
> pattern of my old TH7. The TH7 looked consistently better and the TH7
> patterns looked a lot like those published by HyGain, which were
> certainly based on antenna range measurements.
>
> The tuning of yagi parasitic elements is quite critical, so probably
> requires much better model accuracy than, say, a dipole. For example,
> AFAIK all these model-based tribanders have isolated parasitic elements,
> because the effect of the boom can't be modeled easily. The parasitic
> elements of the old trapped tribanders could be connected the boom,
> because they were initially tuned empirically.
>
> Does anyone know of any measurements made to verify model results for
> this sort of antenna? (Even on a scaled VHF/UHF model?)
>
> 73,
> Scott K9MA
>
>
> On 10/1/2020 7:59 AM, Steve London wrote:
> > Jim Lux wrote:
> >
> > but does the model actually show much difference? One can get way down
> > in the weeds with this - put a tapered segment in that's 1 cm long,
> > etc. But if the wavelength is 20 meters, a 1 cm transition is 0.0005
> > wavelength. I'd worry more about numerical instability than model
> > accuracy at that point.
> >
> > --------------------
> >
> > I have been going through the same exercise with a homebrew 15 meter
> > beam. Can models like N6BV's YW be trusted for segments that are a
> > small fraction of a wavelength ? What about the Leeson
> > equations/spreadsheet for converting to an equivalent,
> > single-diameter, cylindrical element ?
> >
> > Some examples from my modeling:
> >
> > - The 1/2" wide, 0.1" thick, 3.5" long, aluminum straps that connects
> > together the parasitic element halves ?
> >
> > - The 3" long swaging sections ?
> >
> > 73,
> > Steve, N2IC
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
>
> _______________________________________________
>
>
>
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--
Curt, WE7U http://xastir.org http://www.sarguydigital.com
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