[TowerTalk] elevated verticals....radial config.

[Jim Lux]

At 11:26 AM 6/13/2005, Tom Rauch wrote:
>You also have to watch the feedline and mounting very
>carefully. When you use less than 10 radials feedline
>currents start to be an issue. When you use two radials it
>is a big problem.
>73, Tom W8JI
Tom's got a very good point. As far as coupling to the feedline goes, it's 
much like just another radial, that happens to go off at some odd angle, 
and typically at some non-tuned length.  You could adequately model it as 
just another wire hooked to the other radials, but in the position 
comparable to the feedline would have.

   As you're modeling, try this experiment.. Model 2, 3, or 4 
radials.  Move the end of one radial 2 or 3 feet (while keeping the length 
same).  See how much the pattern (and/or the feedpoint Z) changes.

This is where modeling is really, really useful.  You don't expect to get 
gnat's eyelash precision from the model, but you can pretty quickly figure 
out how sensitive a design is to such mechanical tolerance or interference 
issues.

For instance, if you've got a vertical mounted on your eaves, you could 
just model the rain gutters as a single wire.  Then look at the difference 
as you move the wire around (or break it up), and you'll see if the gutters 
are "significant" in the overall scheme of things.





>----- Original Message -----
>From: "Terry Conboy" <n6ry at arrl.net>
>To: <jimjarvis at ieee.org>; <towertalk at contesting.com>
>
> > According to modeling in EZNEC, as long as the two radials
>are symmetrical
> > (180 degrees apart, same slope), the azimuth and elevation
>patterns are
> > very uniform, and the horizontal radiation cancels quite
>well in the far field.