[TowerTalk] klm kt34 baluns

[Michael Tope]

Hi Mark,

Our club has just finished rebuilding a KLM KT-34XA and KLM 40M4
yagi. The general consensus among the work crew was that it probably
would have been better to throw the antennas away and buy new ones.
Removing all the dirt and corrosion on all the electromechanical joints
in these two KLM antennas was an incredibly time consuming job. Like
you, we found a number of joints which, despite the presence of the KLM
anti-seize compound, were very difficult to get apart. In one case I
actually broke an element on the 40M4 and had to buy a replacement.
When rebuilding the antennas, I started out using No-Alox (grey stuff
loaded with zinc) to coat the joints, but later switched to Silicon high
vacuum grease on the advice of Eric, N7CL. This will be a good experiment
if I happen to be around when the antennas come down again (I hope it isn't
for a least ten years), as the antennas are put together about half with
No-Alox and the other half with SHVG.

By the way, you should be aware that M-squared Antenna company
is introducing a rebuild kit for the KT-34XA (should be out sometime this
summer). I am told that the kit will include machined replacements for the
shorting straps used on the XA as well as new center insulators. If you can
wait for it to come out its probably worth your while. I had to shim all of
the
shorting strap joints on the XA and 40M4 with Aluminum shim stock and
in some cases install SS sheet metal screws to get them tight. This was a
helluva
lot work. When I corresponed with Mike Stahl, K6MYC at M-squared (Mike
designed the KT-34XA), he said that that the rebuild kit will also come with
a set of computer optimized dimensions which allegedly will squeeze an extra
dB or so of gain out of the XA (the original XA dimension were arrived at
emperically).

As far as the baluns go, I ran some tests on the two that came off the XA
and
the 40M4. When I ran the two baluns back-to-back at the output of an Alpha
78
running 1.5KW, the baluns showed reasonable self heating (not any more than
the
RG-8X coax I was using) - probably good enough for RTTY duty at 1.5 KW.
When I put them on an HP network analyzer and terminated them with a
200 ohm resistor, they each showed a good VSWR (<1.3:1) down to about
5 MHz. According to the parts list (the markings are worn off), this is the
B3641
3-60 MHz 4:1 balun (I don't know if this is the the heavy one or the light
one
you were speaking of).

Good luck!

Mike, W4EF..........................I


----- Original Message -----
From: Mark Sihlanick <n2qt@pipeline.com>
To: <towertalk@contesting.com>
Sent: Sunday, April 23, 2000 2:35 PM
Subject: [TowerTalk] klm kt34 baluns


>
> I've got a kt34a and a kt34xa I'm refurbing.  The klm supplied baluns
while
> identical in appearance have a significant weight difference, 8.5 oz vs 14
> ozs.  Being the inquisitive sort what makes the difference?  Also what is
> the groups opinion on these baluns vs some other replacement?
>
>
> Also the klm antennas have got to be the hardest ones to refurb of the
> major manufacturers.  The antioxidant stuff used makes the joints just
> about impossible to separate and it seems to attack the aluminum.  This is
> the copper colored stuff.  Mosley antennas for comparison still telescope
> apart easily with the gray stuff used on them..
>
>
> Mark n2qt
> (still yet to buy a new hf antenna)
>
>
>
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