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[TowerTalk] modeling LPDAs

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Subject: [TowerTalk] modeling LPDAs
From: DavidC" < (DavidC)
Date: Sun, 26 Dec 1999 21:49:22 -0500
You will want to visit L.B. Cebik's site:
There is little left to be said about modeling after you plow
through all that he shares there!  ;-)

- 73, DavidC  K1YP

> Anyone have any experience to share modeling LPDAs?
> I'm trying to model my T10 using NEC4WIN, and I'm having 
> what looks like ill-formed matrix problems. Granted, there are 
> a LOT of segments - LPDAs have a lot of 'wires' since 
> the boom is hot - I have 39 wires @ 4-10 segments each.
> When I graph any quantity (gain, f/b, swr) over a frequency 
> range, I get mostly smooth curves, but every so often 
> I get a very sharp spike off the chart. (This is in free space)
> I've tried twiddling everything, from wire size to 
> # of segments, etc. Also the feed impedances don't seem right.
> The azimuth pattern _does_ look good, and apart from the
> sharp spikes the average numbers for gain, f/b, swr look good.
> Have I hit on a limitation of NEC4WIN? Past a point, the
> results don't change as I increase the # of segments, so I
> don't think it's a resolution problem....  
> Tnx & 73
> Len K1NU

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