Jeff,
If you still have your AEA analyzer handy, place a 200
ohm carbon resistor between the output screw terminals
of the balun (I assume you are using the KLM 4:1 ferrite
balun and not the coax balun). With the 200 ohm resistor
installed input VSWR of the balun (measured at the SO-239)
should be better than 1.5:1 from 5 to 30 MHz if everything
is working properly. If you disconnect the resistor, you
should get a very poor VSWR reading. I didn't check the DC
resistance on mine, but I suspect that it should look like
a short circuit between input and ground (I am not familiar
with the internal design).
It wouldn't surprise me if the balun is at fault. I seem to
recall from my previous inquiries on this balun that some
users had trouble with the screw terminals loosening up,
and the internal connections breaking loose. This sort of
problem would be consistent with the symptoms you report.
If you need a balun in a hurry (to get up and running for SS),
the manual for the KLM describes a half-wave coax design that
you can make yourself in a couple hours with 50 or so feet of
RG-8. You might also try Jay Terleski, WX0B at Array Solutions.
He makes a real good 4:1 balun in a small NEMA enclosure
that should give you lots of good service.
Hope this is helpful.
Mike, W4EF...............
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From: Jeff Singer[SMTP:k2kv@reallybig.com]
Sent: Sunday, October 31, 1999 12:45 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Need help with KLM problem
Hi all,
After some months of non-use, we got on the air yesterday only to discover
that my KLM 40M4 is having problems, for the first time.
With an AEA Analyzer, the SWR is reading around 6.6:1. After tilting over
the tower, we pulled the coax and tested it without a problem, so it's not
the coax. Everything else looks fine mechanically, though we did take a few
minutes to clean and reseat the balun connectors. Once we did this, we put
the AEA meter to the antenna (while still tilted over) and all looked close
to perfect! Then, we put it all together again and brought the tower back up
to vertical. Unfotunately, and much to our surprise, once everything was in
normal position again we had the same 6.6 SWR!
So, now we need some advise from those with more experience, for example:
What kind of reading should we get with an ohmmeter from the shack end of
the coax, with the antenna connected as usual?
How should the balun read if NOT connected to anything?
We removed several element tips when tilting over the tower, and they were
all moist with penetrox, so I don't believe there is a continuity problem
with the elements. The phasing straps are under so much pressure, it would
be hard to suspect contact problems here. Also, we just replaced the straps
this past spring, when the others snapped due to a heavy snow-related
problem. The new straps are no longer flat. KLM now uses aluminum tubes with
flattened ends.
We'd really appreciate some helpful direction here, as we're anxious to get
this back to normal before the upcoming Sweepstakes!
Thanks very much in advance,
73 de Jeff K2KV
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