Hi Pete,
If your C3 is between the EF-240S and the guy wires, was the C3 not suspect?
Sounds like it was cleared of potential interference with the 240S but I am
wondering how you did that.
Joe
K4AW
-----Original Message-----
From: Pete Smith [mailto:n4zr@contesting.com]
Sent: Thursday, July 25, 2002 8:55 AM
To: towertalk@contesting.com; Force12Talk@qth.com
Subject: [Force 12 Talk] Re: [Towertalk] C31XR & guy wire detuning
At 08:12 AM 7/25/02 -0400, K7LXC@aol.com wrote:
>In a message dated 7/23/02 12:50:44 PM Pacific Daylight Time,
>jskatz@sk.sympatico.ca writes:
>
> > I want to break the 54' sections into two segments each. My question:
> >
> > What should the lengths of these two sections be to minimize their
> > interaction with the C31XR?
>
> There are 2 things at work - the antenna and the guy wires. First, you
>need to see if it's a guy problem by keying the radio into the antenna and
>then turn it while you watch the swr. If the swr varies as it turns, then
>it's guy wire interaction. If it doesn't change, you've got an antenna
>problem.
Steve, I think that's too simple. If the SWR doesn't change when it turns,
it MAY not be a guy wire problem, but you can't be sure because not all
destructive interaction affects SWR,and the placement of the guy wires may
be such that their effect is more or less independent of antenna rotation.
As an example, my F12 EF-240S is at 104 feet, above a C-3E and 9 feet above
the tops of the uppermost guy wires, which were grounded at the bottom but
insulated from the tower. Rotating it showed no SWR variation, but the
antenna was an indifferent performer. Then, in order to accommodate a
tribander stack, I replaced the top guys with Phillystran, and the antenna
clearly and strikingly "woke up." Since the guy wire change was the only
change in the near field or in the antenna itself, I think the inference is
clear.
73, Pete N4ZR
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