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Re: [TowerTalk] Inverted L Tuning Question

To: "Tom Osborne" <w7why@verizon.net>
Subject: Re: [TowerTalk] Inverted L Tuning Question
From: "Dennis Vernacchia" <n6ki73@gmail.com>
Date: Thu, 4 Dec 2008 18:22:55 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
The issue with teh AM BC Strong Signal interference is addressed in
the Nov/DEC NCJ
( National Contest Journal ) magazine article
..and article uses exact same antenna analyzer as Dick is using  !
73, Dennsi N6KI

On Thu, Dec 4, 2008 at 6:09 PM, Tom Osborne <w7why@verizon.net> wrote:

> Hi Dick
>
> You can get some screwy readings if there is a BC station nearby.  I can't
> even use my analyzer here on my 160 inverted L because of RF from the
> local.
> I have to use the SWR bridge in the shack.  73
> Tom W7WHy
>
>
>
> > Hi Guys,
> >
> > I'm trying to set up a 160-m. Inverted L for ARRL-160 this weekend but am
> > having an interesting tuning problem.  All thoughts appreciated!
> >
> > The Inverted L is made up of #12 stranded copper wire 136' in total
> > length:
> > 82' vertical and 54' horizontal.  The vertical wire is spaced 6' from a
> > 88'
> > self-supporting tower with a Cushcraft XM-240 mounted on top.  (XM-240
> > elements
> > are not grounded)   Initial radial system is  2- 135' radials laying on
> > the
> > ground- not much but two similar radials worked pretty well on my 60'
> > tower last
> > year as the towers are 150' from a salt water river.
> >
> > Placing the Antenna Analyzer (AIM 4170) at the base of the Inverted L
> gets
> > the following measurements:
> >
> > 1) With the coax braid connected to the tower base which has two 8'
> ground
> > rods: lowest SWR is 3.9 at 1.776 Mhz and Z = 79.
> >
> > 2) With coax braid only connected to the two radials (and not the tower
> > base): lowest SWR is 1.62 at 1.614 Mhz and Z = 81.
> >
> > It was my understanding that the coax braid should be connected to both
> > the
> > radials and the base of the towers gnd system, but as you can see the the
> > minimum SWR and resonant freq. go crazy when I do.
> >
> > Any recommendations what I can do to get it working before tmw night?
> >
> > 73,
> > Dick- K9OM
>
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