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
>
>
_______________________________________________
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