I think these lessons Hank explained so well aren't just for KT-34
variants or tribanders. In WV I had a stack of Force 12 C-3Es, with a
Force 12 2-element short 40 above the top one. Performance on 15 was
much degraded from that before the 40m antenna was added, until I turned
the 40 90 degrees to the stack, at which point all 3 antennas played
much better.
73, Pete N4ZR
Check out the new Reverse Beacon Network
web server at<http://beta.reversebeacon.net>.
For spots, please use your favorite
"retail" DX cluster.
On 6/3/2022 3:16 PM, hp via TowerTalk wrote:
I do not have a 36XA but have a KT34 rebuilt to latest M2 specs and mechanics.
It had never been quite right on 15 so when I rebuilt I spent a LOT of time on
what was going on on 15.SWR was always taking off below 21025 and F/B was lousy
in CW portion. Long story short - problem was the 15 meter cap tubes were
slightly
oversize ID and the 3/8 tubing was undersize by a few mils on each such that you
could not get the capacitance you needed . So after I resolved that - I could
get
good swr and F/B over the band . Look up N6MW on the internet he has published
a lot o
of what both he and I and others did on KT34 15 meter problems.
Now to interaction.
I was doing the work on a tripod on roof peak about 30 feet under a 40M1L
rotatable dipole.
I would get everything just fine (running F/B with a friend about 2miles north
of me. )
Then I would finalize everything and recheck next night and it had gone to
hell. I was using
the 40M1L at night and was not attention to where it was left.What was
happening is that
the F/B and low end SWR were massively affected by the coupling to the 40M1L
dipole some 30 feet higher .
I could move F/B 100khz -150khz by changing orientation of the two antennas. (I
suspect that one might
be able to "open" the dipole and reduce the coupling but with the dipole in
line with the KT34 boom
it was not an issue )
Once I nulled the remote 15M sig on the dipole (end on to the signal) then
adjusted the KT34 15M traps - everything
was solid and would stay just fine. My signal source buddy and my Grandson
armstrong rotator who both thought I was
crazy as hell were relieved.
See Bill N6MW comments on KT34 he and I were working on same issues at the time
and has other data
Hank K7HP
Message: 1
Date: Thu, 2 Jun 2022 14:14:59 -0600
From: Steve London<n2icarrl@gmail.com>
To:towertalk@contesting.com
Subject: [TowerTalk] Why does KT34XA/KT36XA stink on 15 ?
Message-ID:
<CAB7zQ=386x5CB2ymYN1iRy7qrM3Bj1W4+KkX2ySrO40XLNjx0g@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
I know I'm not the first one to observe this...
I have a KT36XA on one tower, and reference monobanders for 10, 15 and 20
on other towers. On 10 and 20, the XA always performs within a few dB of
the monobanders (sometimes, even better than the monobanders). On 15, the
XA is always down about 6 dB from the monobander. This is consistent
regardless of distance, direction, skip length, etc. Even the "band noise"
is down by this amount. The SWR on all 3 bands is reasonable. Long ago, I
also measured the resonant frequency of each element. See
http://www.kkn.net/~n2ic/kt36xa.xls . There is a 40 meter beam about 30
feet above it, but the 15 meter SWR does not change when either the XA or
40 is rotated, so I don't think there is significant interaction.
What did KLM/M2 do wrong on 15 ?
Before you tell me your KT36XA works great on 15, what are you comparing it
with ?
73,
Steve, N2IC
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