Towertalk
[Top] [All Lists]

Re: [TowerTalk] 80 meter antenna advice. (NY6DX)

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 80 meter antenna advice. (NY6DX)
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 11 Feb 2020 13:59:37 -0800
List-post: <mailto:towertalk@contesting.com>
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
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>