I recently rebuilt mine to a KT36XA also but did not experience the SWR
problems on 15. I can send a graph of a before and after comparison if you
like.
The only thing I recall about 15 meters is with the 15M capacitor tubes
being of the wrong size in some shipments due to an out of spec tube supply.
I found this in the archives:
To: "Towertalk Reflector" <towertalk@contesting.com>
Subject: Re: [TowerTalk] C31-XR versus KT36XA
From: "Ward Silver" <hwardsil@centurytel.net>
Reply-to: Ward Silver <hwardsil@centurytel.net>
Date: Tue, 16 Sep 2003 20:49:48 -0700
List-post: <mailto:towertalk@contesting.com>
A slight clarification on the exact problem with the KT34XA...
When we started presenting data, as Steve said, several other XA owners came
up and said, "Mine acts JUST LIKE THAT and nobody has ever been able to
explain why or fix it!" Other guys (the majority) couldn't repeat the
behavior and had never observed it. At Dayton in 2000, I was having dinner
with some DL hams (can't remember exactly who, apologies DL hams) and they
said, "You know, DL2? figured it out."
To make a long and mysterious story short, KLM received and used an
out-of-spec shipment of tubing for the 15-meter capacitor sections. The
capacitance is formed by the OD of the inner tube and the ID of the outer
tube. The outer tube had the right OD, but the wrong wall thickness (too
thick) and so the ID was too small and the resulting capacitance too large
and the resulting frequency of minimum SWR too low. (Follow me through that
sentence?)
The specified wall thickness for the outer tube was not the common value for
tubing of that OD. Somebody either ordered or shipped the common (too-thick)
tubing and KLM's QC didn't catch it. The difference wasn't enough to
prevent the plastic end caps from going in - it was just a few thousandths
of an inch too thick - so the problem went unsolved for years.
If you have an XA that tunes up too low on 15-meters, contact M2 because
they have a retrofit kit that will fix it up. The suspect antennas seemed
to also have blue end caps on the tuning capacitor tubing, but it's not a
one-to-one relationship.
Most of the credit goes to the DL guys for having the smarts to make the
right measurements and deduce what had happened. We published the data and
caused the connection between cause and effect to become known. And THAT,
my friends, is why publishing your test data is so important. That is
SCIENCE, even if it is applied science. As Isaac Asimov said
(approximately), "Breakthroughs in science never start with 'Eureka!' They
start with 'Hmmm, that's funny...'"
73, Ward N0AX
73 and gud luk with your rebuild, mine works great!
Joe - KC2TN
"If you're sure of everything,
and it still doesn't work,
one of the things you're sure of is wrong!"
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of smith.l@mchsi.com
Sent: Monday, March 07, 2005 8:41 PM
To: towertalk@contesting.com
Subject: [TowerTalk] KT43XA/KT36XA Rebuild
I recently completed rebuilding and upgrading my old KT34XA to a KT36XA and
have
encountered a problem that I need help with. This is the 5th time I have
updated
this antenna since I got it in 1980 and mechanically it is much better than
previous versions.
My problem is with the SWR on 15 meters. It is 1.8:1 across the band while
20M
and 10M are virtually flat from end to end. SWR was checked on sawhorses and
I
figured it would improve on top of the tower. I was wrong-it remained 1.8:1.
We
lowered it back down and remeasured everything, rechecked all elements,
etc.,
and found nothing out of whack. It is assembled correctly and all elements
are
oriented properly.
Does anyone have any experience with this? I am sure it has to be something
simple that I am overlooking but if any of you could point me in the right
direction it will be appreciated.
Thanks.
Larry Smith, N4FD
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
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http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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