OK, so what happens if we modify the N3OX approach. I have a Hy-Gain AV640
as my only antenna, and have it mounted on a 20', foldover "tower." See,
there's a tower to this. SEriously, 4" diameter up to 11', big hinge, and
2.5" diamtere above that...will hold a small yagi.
The AV640 is roughly 3/8 wave, using stubs off the main main support similar
to a Hy Tower.
What happens if we take the N3OX approach, but put two, or possibly three
wires going up the outside of the fiberglass, one the full 60' length, one
perhaps at 3/4 wave for 20 meters, and one perhaps 3/4 wave at 10 meters,
and tune the shortest for 10-15, the next for 17 - 30, and the longest for
40 - 160?
Am I as nuts as I think (due to interaction between the vertical wires?) or
is there some logic here? It seems to work with the AV640 even though the
stub is shorter than and next to the main tubing. As an alternative,
perhaps grounding the other two wires that are not in use would help.
Thoughts?
Art, K0RO
----- Original Message -----
From: "Rob Atkinson" <ranchorobbo@gmail.com>
To: <towertalk@contesting.com>
Sent: Thursday, November 20, 2008 11:49 AM
Subject: Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type,
> I've wondered before what the deal is with 43 foot verticals. By
> that I mean, it seems suddenly I started seeing 43 feet mentioned all
> over the place for an "all band vertical." Is 43 feet some magic
> length? How was this determined and who originated this idea? I
> figured maybe it was something that had been in the handbooks for
> years and I never knew about it.
>
> Anyway, having a bizarre feedpoint Z isn't necessarily a bad thing by
> itself. It just means you need a matching network at the feedpoint to
> tune the antenna to 50 ohm unbalanced feed. What's bad is having a
> vertical so tall in wavelength that you wind up with all or most of
> your RF going off in one or more high angle lobes. That starts to
> happen when length begins to get beyond around 200 degrees or 5/8
> wave. There are all these little high angle lobes that gradually
> multiply and get bigger as you go up in frequency. You have to figure
> out how high you can go in frequency with 43 feet before that happens.
>
> Don't be persuaded by big signal reports on some 100 w. operation with
> no radials. The right band for the distance with good conditions
> and enough power can do wonders. 20 over S9 with 100 watts when
> everyone else on the band is running 1.5 kw and is less than S9...now
> that's an antenna!
>
> 73,
>
> rob / k5uj
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