[TowerTalk] KT34XA Measured Behavior

[Ward Silver]

As the Cheif Measurer and Report Writer for the tribander tests, I thought
I should stick my two cents in...

We were also puzzled by the measurements.  KLM, which was in the final
stages of life support at that time, was mute on the subject.  Because the
antenna had been shown to work at W7TSQ's QTH and because the antenna did
work in some segment of all bands measured, we went ahead with the data.
We also pointed out that it behaved strangely on 15.  All reasonable to
do.

Then an interesting thing happened...

When I gave our talk - people started coming up to me and saying things
like, "My KT34XA acts JUST LIKE THAT!"  They had tried everything you can
think of to fix it and had essentially given up.  The factory had been
completely unhelpful. There were no answers.  Others said, "Baloney - mine
is perfect!"  Everyone had, to the best of their knowledge, assembled it
per specification to the tenth of an inch.  What in the wide world of
sports was a-goin' on here?

Then another chance conversation with DL2FBU (I think) and others at
Dayton. Turns out that a batch of these strange XA's had turned up in
Europe, as well, and the Germans had traced it to improper tubing
thicknesses in the 15-meter capacitor sections.  Too-thick tubing
increases the capacitance between the inner and outer sections, lowering
the tuning point of the elements sufficiently to cause the observed
behavior.  Trouble was, nobody at the factory would 'fess up to this, even
after the company went belly up. 

To make a long story less long, a very subtle shift in a critical element
was inadvertently made in a batch of XA's.  Everything can be assembled
EXACTLY by the book and the results will be as shown in our report - it
has NOTHING to do with attention to detail.  If you have one of these
antennas, you will have to replace the improper tubing with material of
the correct wall thickness to restore order.

I have spoken to Mike Stahl of M2 about it and am writing a short article
that will, hopefully, alert owners of the mutant XA's to the problem.  He
is deciding what to do about offering a kit to fix the old XA's, although
it will likely wind up being cheapest to just offer a 34-to-36 conversion
kit. 

This was exactly the effect desired for creating a publishing a protocol
and test data.  Along with a discussion of testing and relative behavior,
anomalous performance could also be identified and discussed.  Perhaps
with the publication of the article and M2 offering a conversion kit, we
can help owners of the defective XA's get their money's worth on 15 and be
happy.

73, Ward N0AX

> 
> Well, I saw the numbers they came up with on 15 and they were ridiculously
> poor, especially the F/B.  It doesnt take a test range to figure out that
> something was amiss.
> 
> While the 34's are tough to assemble correctly, I've now built (actually
> rebuilt since all of them were bought used) 3 of them and have had not real
> trouble from any of them...and they worked just fine the first time out with
> no adjustments necessary.  While I did a lot of new things to my latest XA,
> even my earliest attempt is still working just fine.
> 
> As with any complex/intricate project, you must pay absolute attention to
> detail to obtain success.
> 
> 73, TY K3MM


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