Posted by
Don Wilhelm-4 on
Feb 04, 2010; 4:06am
URL: http://elecraft.85.s1.nabble.com/OT-Interesting-Accident-with-Homebrew-Vertical-tp4511024p4511591.html
Bob,
Indeed elevated radials *are* a part of the antenna (actually radials in
the ground are too). Elevated radials must be tuned (while buried
radials do not need to be). To do that properly, connect each one - one
at a time - and resonate it with the vertical element. When all have
been tuned, then they can be connected together.
To cancel the horizontal radiation component, the radials should be
oriented in opposing directions - any pair should be in a straight
line. 4 radials arranged 90 degrees apart is normally sufficient, and
in a pinch, 2 placed 180 degrees apart are sufficient.
It matters not whether the vertical part is fed from the center
conductor or the shield. The currents on the inside of the coax are
balanced (equal and opposite currents). The "magic" is to keep the
current off the outside of the coax shield, and that is what common mode
chokes (current baluns) should accomplish.
73,
Don W3FPR
Robert Fish wrote:
> I noticed
> that I had hooked up the shield of the coax to the vertical element and
> the center conductor to the radials. (I was experimenting with running
> 180 deg out of phase for end fire and forgot to change it back). I am
> not sure what that proves except that he radials really are half the
> antenna. Working Africa from here on the west coast with only 100 watts
> is pretty rare these days, so the backwards hookup is obviously working.
>
> I guess it makes sense that it shouldn't matter. What do you guys think?
>
>
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