[TowerTalk] C31XR
K7LXC@aol.com
K7LXC@aol.com
Fri, 1 Sep 2000 08:07:06 EDT
In a message dated 08/31/2000 10:03:05 PM Pacific Daylight Time, ve3tu@rac.ca
writes:
> I will be purchasing a c31xr for a new installation. I have
> talked to couple of hams with this antenna up at 70 and 80 feet and they
> said that the resonant point or should I say the lowest swr point on 15m
> was a little low in frequency and the low swr point on 20m was a little
> high in frequency. My question is has anyone played with the tuning to
> move the low swr points and did you have any success? I would like to
> know if the tuning follows the typical tuning of a dipole.
My experience with 4 or 5 of these antennas has been with 15M re-tuning.
WB9Z posted his similar experience awhile back; I think he cut 1/2-inch off
of the 15M driven element and that took care of his problem (you might be
able to find his comments in the TowerTalk archives @ www.contesting.com). I
think I took 1/4-inch off of the latest one I installed and everything was
where we wanted it. I was going to take 1/4-inch off each end but after I cut
one side and checked it - everything was FB. You can see how critical the
length is.
BTW I did this on the tower by rotating the boom so that the elements
were vertical and the bottom ones were easily accessible from the tower. I
did one side and then was going to rotate the boom 180 degrees to do the
other side which turned out to be not necessary.
The moral of the story is to get the antenna installed and then use your
antenna analyzer to check it out. While I wasn't happy with the SWR curves of
the first one I installed on the tower, it was fine at the end of the coax in
the shack; the owner was a CW operator so he was only concerned about the SWR
in that portion of the bands.
Cheers, Steve K7LXC
Tower Tech
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