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Re: [TowerTalk] 80M antenna suggestion

To: Richard W.Harris <Richard_Harris@byu.edu>
Subject: Re: [TowerTalk] 80M antenna suggestion
From: Bill Coleman <aa4lr@arrl.net>
Date: Tue, 25 Oct 2005 20:08:13 -0400
List-post: <mailto:towertalk@contesting.com>
On Oct 24, 2005, at 10:59 PM, Richard W. Harris wrote:

> I have been looking at the following for 80M: a) inverted-V, b)  
> inverted-L, c) Delta loop  for 80M.  I can attach a 3-4 foot  
> standoff on my tower at the top of any of the sections to attach  
> any of these three antennas.  My question is do you  have any  
> suggestions as to which of the three antennas (or any other you  
> feel might be better) I might have the best luck with on this tower  
> for 80M?

I had a similar situation yours, except I had an 80m shunt feed on my  
15m tower, and needed something for 160m.

K9AY originally gave me this advice - run the shunt as high on the  
tower as possible, then build a matching network to suit. He even  
said he would help me with the matching networks - we could measure  
the impedance of the shunt and compute a suitable matching network.  
Then Gary moved away.

What I ended up doing was building a matching network for the shunt  
for 160m. On 80m, I had found a workable omega match by trial with a  
couple of big variable caps.

For 160m, it was clear I needed a wider matching range with an  
inductive component. I created an L network using a coil wound around  
a T200-2 toroid and a big cap. Using this I determined a Hi-Z network  
would work. A few trials later, and I built a bigger toroid using two  
stacked T200-2 cores and about 580-750 pf variable and fixed cap  
combination. I made my first EU QSO on 160m just this week. It works.

You've already done the hard part -- laying down all the radials.  
That 160m radial field will work great on 80m.


Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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