Many antenna programs have a method for placing a simple transmission
line in the model.
EZNEC, for instance will allow you to define a very short wire (like
one inch) place it just about anywhere at a distance from the antenna
wire parts, and define a transmission line (including substituting a
specified length for the actual distance). You then place a source on
the short wire and you can run impedances on it. Great for coming up
with tuned feeder multiband solutions.
This presumes that you can drop a balanced feedline directly down, or
in a way that it's equally influenced by both halves of the antenna.
What model(s) are you using?
----- Original Message -----
From: "David Gould" <david.gould@btinternet.com>
To: <antennaware@contesting.com>
Sent: Sunday, March 13, 2005 2:03 PM
Subject: [Antennaware] Modelling transmission lines.
>I have been modelling verticals and dipoles for some time, but am not
>very
> knowledgeable on transmission lines. I wondered if anyone could
> explain
> how to add a transmission line or had a file that was similar to
> what I
> want to do.
>
> I am trying to model a 160m inverted V dipole with the centre at
> 75ft with
> 75ft of open wire feeder (eg 450 or 600ohm) coming down to ground
> level. I
> am trying to find what impedances the atu will have to deal with at
> ground
> level. (I know what the impedances are at the dipole centre 75ft
> up.)
>
> Any help would be much appreciated.
>
> 73,
> Dave G3UEG
>
>
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