[Top] [All Lists]

[TowerTalk] KT34XA cracked insulators

To: <>
Subject: [TowerTalk] KT34XA cracked insulators
From: (
Date: Mon, 5 May 1997 10:24:03 -0400
One thing to watch out for on these blue insulators is voids on the inside
surface which contacts the 3/8" tube.  I've found a significant number of
new ones to have pockets which could allow a lot of water into the cap tube
assy.  I've yet to see any cracked green or blue insulators on any of the
used KT34XA's I've bought.  However, it seems silly not to replace them if
you are going to rebuild the antenna anyway.  I double check all tube
lengths, as KLM tends to be a little sloppy.  I debur all the tubes prior
to assembly, and use a rubber mallet to make sure they get on all the way.
Once you have slid them onto the 3/8" tube, double check the distance
between the two end caps to make sure that they have not slid partway off
the tube.  Another thing I did with my last one which had some corrosion
and damage to the inner 3/8" tubes was replace them all with new 6061T6
tube with a .058 wall instead of the .03? wall that they use.

Regarding poor connections on KLM beams in general, I make sure I use
conductive grease on ALL clamp joints and on all but the cap tube clamps,
use #6 SS sheet metal screws through the clamp joint to lock everything
together.  (Of course, you should
be sure that everything is assembled and working properly before doing
this!)  On the olderKLMs, the clamp straps are a little thinner stock, and
it seems they tend to stretch over time, so when you take it down, you'll
notice some of the joints will be very loose.  Combine this with some
normal corrosion and you'll have a lot of fairly unreliable and inefficient
connections.  So, I also recommend replacing the straps that loop around
the cap tubes with new ones.  Total rebuild list of materials is:  1
KT34X/XA update kit (which includes new cap tubes and cap insulators,
penetrox, and new clamps for the 10 meter element, as well as modification
instructions for older KT34's with weep holes on the OUTSIDE tube and the
latest dimensional drawing), 20 cap tube straps,  and about 100 #6 SS sheet
metal screws 1/4" to 3/8" long(not available from KLM), in addition to any
other repair parts.  The update kits are about $50 US.

One other thing they've changed is the balun.  There are 2 baluns out there
and the better one is heavier.  If the label is still on yours, KLM should
be able to tell from the date which you have.  Otherwise you'd have to
weigh it or something.  Lastly, the balun spring clamp mounts tend to rust
easily and is usually trashed after a few years.  KLM will probably just
send you a new one free of charge if you complain about it.  I sprayed my
last one with some cold galv. spray to give it some added protection.

These antennas ARE a LOT of work! hi!

73, Tyler K3MM on 05/05/97 08:59:26 AM

cc:    (bcc: Tyler G Stewart/BENN/CEC)
Subject:  [TowerTalk] KT34XA cracked insulators

Hi Folks.

I rebuilt an XA last summer. It had only been up 2-3 years, so I was
not expecting to have to replace the capacitor caps. But when I got it
down, I found several were cracked.

Here's an excerpt from a previous post containing relevant info:

Initial visual inspection showed 7 out of 40 of the blue capacitor caps
were cracked. I also did DC resistance measurements of the traps and
found that most traps had a total series resistance of 30-50 mOhms
(milliohms). Two of the traps had resistances of 200-300 mOhms. I traced
the high resistance to the large end of the most outboard shorting
strap (15 meter section).

I called KLM and spoke to Bruce about the caps. He said they should have
lasted 10 years in normal UV exposure, and that there were only 3
for their premature failure. These were (1) installation with a hammer;
(2) installation using oils as lubricant; or (3) bad lot of plastic.
I told him I hadn't used (1) or (2), and he very kindly sent me a
replacement set for NO CHARGE, to replace the set I had bought for the
prior rebuild. I'd call that great service from an antenna maker!

I rebuilt the antenna using the new caps. Bruce told me that the best way
to install the caps was to warm them up in hot water. This is a great tip!
They went on really easily once they were warm.

Hope this helps...

-Tony, K1KP,

FAQ on WWW:     
Administrative requests:

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>