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[Antennaware] Fw: Topband vertical matching.

To: <>
Subject: [Antennaware] Fw: Topband vertical matching.
From: "K9AY" <>
Date: Tue, 17 Aug 2010 10:57:59 -0500
List-post: <">>
Oops .. sent this from the wrong 'return address' first time.

> Dave,
> I started working on problems like this before compuer modeling, so I have 
> the habit of separating the antenna analysis and the matching network 
> design. L- T- and Pi-networks are very easy to design on a good Smith 
> chart program, or just mathematically using one of the matching programs.
> Although it's nice to have it all-in-one at times, the "modular" approach 
> makes it easy to examine alternate matching schemes -- for example, when 
> you want to compare several configurations to maximize VSWR bandwidth of a 
> fixed-tuned network. Also, some of the virtual structures required to 
> accommodate shunt components can violate NEC design rules and give 
> erroneous results.
> BTW, I usually match inverted-Ls with a shunt capacitor (8 or 10 
> inexpensive high voltage discs), and a slightly long antenna to provide 
> phantom inductance. I find capacitors easy to adjust by adding or removing 
> small values, and very easy to weatherproof in a small plastic box.
> 73, Gary
> K9AY
>> For the last few years I have just been matching my topband vertical
>> or inverted L antennas by using a 1:4 UNUN
>> I have just seen the following article by Jay at Array Solutions..
>> where he resonates the antenna at 1.9MHz which gives a capacitive
>> reactance at 1.83 (which becomes a phantom part of the L-network) the
>> other part being a real inductance to earth.  I like the look of this
>> arrangement because of its simplicity and the fact that there is a DC
>> connection to ground.
>> I would like to try and model this directly in EZNEC, but not quite
>> sure how to define the load components and the source in this case.
>> 1) Can I just specify a load of L+R (where R is the simulated earth
>> loss)  and the source in the lowest segment?
>> 2) Should I put the L+R in the lowest segment and the source in the
>> next segment up?
>> 3) Or is there a better way?
>> I would appreciate any advice from anyone with a bit more experience
>> than I have.
>> 73,
>> Dave, G3UEG
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