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Re: [TowerTalk] AV640 too many resonances.

To: "R. Kevin Stover" <>
Subject: Re: [TowerTalk] AV640 too many resonances.
From: K8RI on TT <>
Date: Mon, 11 Apr 2011 13:59:26 -0400
List-post: <">>
On 4/11/2011 8:17 AM, R. Kevin Stover wrote:

Most of this is Yes and no ...
The web page gives a more accurate chronology of the antenna for most of 
its life.

When first installed this vertical worked great and the SWR for each 
band was very close to 1:1 and it covered all of each band with less 
than a 1.5:1 with the exception of 40 and 10.  Even 40 was less than 2:1 
at the extremes.
It was very easy to set each band resonance to what I wanted and there 
is no interaction between bands.

The antenna has been moved around a lot, from the first temporary mast 
where the original frequencies were set, to a 32' tower which was later 
increased to 40'. Slight changes were noticed as some of the bands would 
shift up or down a little with the moves.   A 40 meter, half wave, 
center fed, sloping dipole passed within about 40 feet of the AV640 at 
about 10-15' above the base caused the greatest change which was on 40 only.

I even ran a KW  into it on 6-meters from the little Tokyo Hy-power 
1.5-Kfx even though the literature says it's good for 200 watts. I 
believe later manuals state 300 watts.  A call to Hy-Gain telling them I 
was running a KW PEP brought and answer that it should be fine.

THEN Paper Wasps got in through the drain hole.
(Watch out for line wrap) A good many of the wasps were killed at the 
feed point connection and "wasp goo" leaked through the coax connector 
and into the connector on the coax requiring both to be replaced.  The 
circuit board had to be removed and thoroughly cleaned.  The choke and 
compensation cap had to be replaced as well.Replacing those put it back 
in good operation at least on 40 and 6 meters. I didn't try it on the 
other bands, but it worked well for several months. I had sold the amp 
so it never had more than a 100 watts into it on six after the bugs.

The previous time I had it down I waterproofed all the connections.

   I took the antenna down last fall and it had been laying on sawhorses 
until about 2 weeks ago.
BTW it is guyed at roughly the 2/3rds point using 3/16" Dacron rope to a 
Lexan ring.

> Is the vertical at or near the same hight it was?

Pretty much and at the same location where it was initially set up.

> Is the vertical in the same environment from a nearby structures point
> of view? Elevated verticals can get a little twitchy. Once you get one
> dialed in at a particular location or hight, then move it, they usually
> take some adjustment.

Nothing close at this point and it's well above any metal.

> I moved a Hustler 5-BTV from one side of my roof to the other, a 5 foot
> elevation change and much closer to an 60' tall Sycamore tree, used the
> same tuned radials, and had to basically rebuild the antenna from
> scratch, adjusting tubing lengths etc..., to get it working where it
> did before.

The AV640 does not use radials, but rather a counterpoise consisting a a 
group of spring steel wires about 4' long.
Moving it in the past has only had minor effects. It also uses stubs and 
capacity hats so it's like a group of monoband verticals on one feedline.


Roger (K8RI)



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