Sorry for the delay Jim, I've been on vacation.
The KT-34XA is constructed so that the coaxial capacitor sections are
oriented to the front on some elements and to the rear on the other
elements. Going from the reflector to the last director, they should be
oriented rear-front-rear-front-rear. The XA pictured in the Antenna Book
article has all the capacitor sections to the front.
I pointed that out just to show how easy it is to make a mistake when
building an XA. I just wondered if the same mistake might have been made on
the XA used in Steve's and Ward's tribander report. I wonder if they have
photos? I also wondered if they ever confirmed whether or not the XA used
in the report was one of those that had the defective tubing.
73 - Bryan W4WMT
-----Original Message-----
From: Jim White, K4OJ [mailto:k4oj@tampabay.rr.com]
Sent: Friday, September 19, 2003 9:37 AM
To: bryanr@bometals.com
Subject: Re: [TowerTalk] C31-XR versus KT36XA
I am looking st the picture - how are those backwards?
Thanks,
Jim
Bryan Rambo wrote:
Ward, thanks for your careful explanation below. And again, I didn't mean
to imply that you had botched data in the tribander report. Sorry for not
being more precise with my words :-(
I wonder if it was ever confirmed that the KT34-XA used in the report was
indeed one of the units with defective tubing? The reason I ask is that
it
is very easy to put one of those antennas together wrong. As evidence of
that, look in the ARRL Antenna Book (editions 17,18,19) in chapter 22 and
take a gander at the KT34-XA depicted there. Three of the elements are
mounted backward on the boom!!!
73 - Bryan W4WMT
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Ward Silver
Sent: Tuesday, September 16, 2003 11:50 PM
To: Towertalk Reflector
Subject: Re: [TowerTalk] C31-XR versus KT36XA
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
----- Original Message -----
From: <K7LXC@aol.com>
To: <bryanr@bometals.com>; <towertalk@contesting.com>
Cc: <hwardsil@centurytel.net>
Sent: Tuesday, September 16, 2003 8:26 PM
Subject: Re: [TowerTalk] C31-XR versus KT36XA
In a message dated 9/14/03 9:36:16 AM Pacific Daylight Time,
bryanr@bometals.com writes:
I'm glad you brought up the business about Steve & Ward's (otherwise
excellent) tribander report. It's a real shame that the ONE antenna
that
got botched was the XA.
Actually several other XA owners told us that theirs were identical to
the test antenna.
FYI any XA that came out of KLM once they moved to Washington State
was
suspect since they made wholesale aluminum substitutions that created
problems.
They couldn't get the parts from their suppliers because they didn't pay
them
so they shipped anything they had in stock that was close.
It sure would have been interesting to see
how the XA stacks up to the more recent designs
Sure. Get us a KT36XA and we'll be happy to include it in our next
round
of tests.
Cheers,
Steve K7LXC
TOWER TECH
Champion Radio Products
_______________________________________________
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.
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_______________________________________________
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.
_______________________________________________
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