[TowerTalk] C31XR / CC 402CD Question

[David Jones]

Dave,
Your posting raised a somewhat related experience I am having right now and
I would love your input.
I have a tribander/40m dipole (cut 7.060) yagi at about 52ft, along with
Inv-V for 80m (cut 3.550) about 6ft beneath it (and a 160 Inv-L at that same
level, but not part of this concern).  That's four antennas all switched
with an Ameritron RCS-8 (5 feed switchbox).

I tried to put up another dipole for 80m (3.790) another 4ft or so below the
first - way too much interaction with both the original 80m and the 40m (in
fact the original 40m shows interaction as you swing it around on the
rotator, I presume with the 80m dipole?).
So I then tried to cut the dipole down to 40m (7.225) - still a problem with
interaction.
It's now a 30m dipole much lower on the tiny tower, and not causing a
problem (I can see).

My questions (after all this):
1) Does the setup of the RCS-8 play a role in causing (or hopefully
eliminating) interaction.  I believe it comes from the factory with "open"
positions for the unused antennas.  Would shorted unused antennas cure the
problem?
2) As you suggested, is there a way to "play" with the length of the feed
after the switchbox to help lower any interaction and spikes in Swr as it
rotates?
Thanks for any input!

----- Original Message -----
From: "Dave Hachadorian" <k6ll@juno.com>
To: <towertalk@contesting.com>
Sent: Tuesday, April 24, 2001 5:04 AM
Subject: Re: [TowerTalk] C31XR / CC 402CD Question


>
>
> On Sun, 22 Apr 2001 23:05:42 -0400 "Guy Olinger, K2AV"
> <k2av@contesting.com> writes:
>
> > Get your tribander of choice and prepare to possibly
> > operate
> > them at right angles, where the 402CD has been reported to work
> > well.
>
> The 40-2CD works well aligned with a nearby tribander. Mine is
> only 6 feet above the tribander. The loading coils in the 40-2CD
> elements move the third harmonic resonance to about 18 Mhz. In fact,
> the 40-2CD makes a very good 17 meter antenna, with a deep null off
> the sides, and swr ~ 2.
>
> The only thing you need to worry about on the 40-2CD, and probably
> any close-spaced beam, is the random length of feedline dangling
> off the driven element of the 40, while the tribander is being used.
> This feedline can shift the resonance of the 40 driven element into
> the higher ham bands. A good way to test for this effect is to
> repeatedly short, then open, the 40 meter feedline, while observing
> swr on the tribander to see if it changes. If it does change,
> experimentally change the length of the 40 feedline.
>
> Dave Hachadorian, K6LL
> Yuma, AZ
> K6LL@juno.com
>
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David Jones
djones449@home.com



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