On 2/11/2020 1:17 PM, jimlux wrote:
On 2/11/20 11:30 AM, Jim Brown wrote:
On 2/10/2020 8:41 PM, Grant Saviers wrote:
I think 4sq vs 2L beam tradeoff depends on the beam height vs ground
conductivity and thus the 4sq gain/pattern.
Yes. Several years ago, I did a modeling study of horizontal and
vertical antennas vs height and ground conductivity. It's here.
http://k9yc.com/Multi-Station.pdf
N6BT (original Force 12 designer/owner) recently published the results
of a ground-breaking study he did of verticals and terrain. Tom is a
very smart engineer.
https://ncjweb.com/features/mayjun19feat.pdf
I wonder what you'd get if you modeled the vertical as slanted (relative
to vertical) using NEC, as if you had a vertical antenna on a sloping
surface.
You're not going to be able to model things like a cliff, or a slope
down to the beach with NEC, but a 12 degree downslope should be modelable.
I think a lot of the handwaving about vertical pol and models is because
for H-pol, the ground is pretty much a mirror and the incidence angle
isn't super important, nor is the precise soil properties. But for a
V-pol it really depends, and it's highly angle dependent. That's what
Dean N6BV says is why HFTA is Hpol only - it was too complex to add in
the Vpol calculations.
I suspect that these days, one could build an equivalent of HFTA that
handles both pols and a terrain model (such as that for RadioMobile for
VHF and up). However, you're still stuck with the significant
variability in soil properties.
Yes. I talked to Dean about doing that about ten years ago. He responded
that he'd recently contracted Parkinson's, so no longer felt up to the
task. I've since encouraged several others who I thought might have the
engineering chops to do something for vertical polarization, but so far,
none have taken the bait. One of the problems is likely to be data for
soil conductivity, which a colleague told me is considered valuable (and
thus costly) because of its usefulness in prospecting for oil and
various minerals. That was 10 years ago, so that may have changed.
73, Jim K9YC
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