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Re: [TowerTalk] Modeling Rohn 25G in K6STI's AO

To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Modeling Rohn 25G in K6STI's AO
From: Mark - N5OT <r-emails@n5ot.com>
Date: Mon, 25 Oct 2021 09:33:02 -0500
List-post: <mailto:towertalk@contesting.com>
Gawd I got so educated over the weekend.  That was great.

I put up 50 feet of tower, a 12 foot mast, and two 70' long top load wires.  Tuned out the SWR at the shack with a matching network.  Stations heard me well, I thought.  Worked Great Britain from Oklahoma, etc.  More data for the cruncher.

I still think traps are elegant, but the most practical solution at N5OT is to keep it simple and put up a different vertical for 80 meters in another part of the yard.

Thanks everybody for all the great comments.

73 - Mark N5OT


On 10/24/2021 1:50 PM, Dan Maguire wrote:
Hi Mark,

Those models are some of the most complex I've ever created. I'm not sure I could do it again if my life depended on it!

Dan
On Sunday, October 24, 2021, 04:38:31 AM PDT, Mark - N5OT <r-emails@n5ot.com> wrote:


Thanks, Dan.  I got buried in your content for about an hour and it was excellent.

Mark

On 10/23/2021 9:38 PM, Dan Maguire wrote:
Jim Brown wrote:
I've seen a simple equation for modeling a straight triangular tower in NEC. As 
I recall, the diameter worked out to be around 0.65 the width of a side. This 
would account for modeling it as a radiator.
The image just below "Wire Geometry" on pagehttps://ac6la.com/aecollection8.html  
<https://ac6la.com/aecollection8.html>shows the equivalent diameter for Rohn 25G according to:a) Section 9.1 of Leeson's 
"Physical Design of Yagi Antennas"   EquivDia = SQRT(Area / PI) + Perimeter / (2*PI) = 9.55 inchesb) Wikipedia 
pagehttps://en.wikipedia.org/wiki/Antenna_equivalent_radius  <https://en.wikipedia.org/wiki/Antenna_equivalent_radius>    
EquivDia = 2 * (LegDia/2 * FaceWidth^2)^(1/3) = 8.58 inchesI'm afraid I don't know which is "more correct".Dan, 
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