I have had very bad luck with the big W2DU current balun.
Three years ago I bought four of them for different wire antennas that I
slung from trees.
Two of them have already busted.
1. One had an intermittent short. Would check ok with ohmeter on ground
and not
work in the air. After much scratching of my head, I discovered that the
short developed
only when I had a pl259 attached. Upon opening, I discovered that the
shield was not
dressed well and when the pl259 was attached, it pushed the center pin a
little into
the connector and shorted the center and shield. Very irritating.
2. This occured a couple of weeks ago. I have a 2 element relay switched
40m wire beam.
It suddenlys stopped working. With so many working parts, I did not suspect
the balun.
Checked the relay, etc., to find that it was fine. Eventually worked may
way up the
feed line to find that the balun was busted. It had an open circuit. I cut
it open to find
a clean fracture of the center conductor and a near fracture of the shield.
Fatigue is my
guess. I think that there is a design fault. The beaded teflon cable is
not well supported
in the inside. The only support consists of the soldered joints. The 50
ohm teflon thin
coax has a thin stiff (20 or 22 swg) solid center conductor and I guess
that the swaying
of the wire beam (one year old) flexed the choke assembly in the balun
enough to cause
a fatigue fracture. (BTW, unlike the first one, the shield in this unit was
dressed fine.)
Changing the balun was a bit of work. My wire beams are supported by four
ropes in trees, and are
over structures. It was a pain to get it down to work on and again get it
back up. Changing a
balun on a yagi installed on a tower and mast, with driven element near one
end of boom seems
even worse. Ugh.
I recently put up the Force 12 C3SS tribander and used their balun. It is
extremely well built.
Some special features:
1. It has a rubber o-ring at the so239 to seal with the pl259
2. It is vaccuum potted with silicone. Absolutely nothing shakes on the
inside.
3. They claim that instead of using a bulkead mount so239 (as w2du does),
they use
a crimp on so239 to crimp the shield.
It seemed really well built. (And I though that the W2DU's were well built
when I
bought them.)
Time will tell.
Regards,
Rajiv, N2RD
----- Original Message -----
From: <W4nf@aol.com>
To: <towertalk@contesting.com>
Sent: Monday, September 20, 1999 12:09 PM
Subject: [TowerTalk] Balun for 40-2CD
>
> I read several posts that stated they used the W2DU beam balun on the
40-2CD.
> I was wondering what experiences people have had with this type balun. I
> have always just used a coax wound balun on all my yagis as I have looked
at
> baluns as an additional point of failure of an antenna system. Where I
have
> never had a coax wound balun fail I have been involved at several times
where
> the balun was the failed part on the system.
>
> Your comments are appreciated. Thanks, Jack W4NF
>
> BTW I bought W6QHS's book on yagis and plan on strengthening the 40-2CD to
> the 100 MPH spec 40-2CD+. Someone mentioned W9RE having a kit for this.
> Anyone know the cost and how to get a hold of him.
>
> --
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
> Search: http://www.contesting.com/km9p/search.htm
>
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|