[TowerTalk] Fw: pesky N's (Another N connector failure)

[n4kg@juno.com]

--------- Forwarded message ----------
From: Glenn Rattmann <k6na@cts.com>
To: k6ll@juno.com
Cc: n4kg@juno.com
Date: Mon, 16 Oct 2000 18:20:30 -0700
Subject: pesky N's

Friends,

Well... the perfect record for the 16 year old, home-made, full size,
three
element 40m beam is intact after all.  When I got up there I found that
the
"broken wire" visible through field glasses from ground was in fact just
the tail of a black tie-wrap sticking up.    All the wires at the balun
and
hairpin area were sound.  Since I was there, I did unbolt all the lugs,
cleaned them up and applied new NoAl-Ox.  Puzzled, I figured that there
must be some underground damage to the hardline-- Arrggghhh.  But, on the
way down I remembered there was a junction between the hardline and the
RG-213 jumper up to the beam.  The splice is about ten feet down from the
top.  Hmmmm... better take a look.  Nice putty-and-tape job, still looks
good, but....

Sure enough, when I peeled open the splice, there was the failure.  The
center pins from both the RG-213 female N, and the hardline male N, were
completely carbonized-- just not there anymore.  Nothing but black
powder.
I can say these connectors were assembled to proper specs with great care
many years ago, so it was not a marginal connection initially.

There was absolutely no evidence of water ingress.  Therefore I surmise
there could be two possible ways this joint failed.  One is some level of
damage from a past lightning strike; not too likely since I have never
had
a hit that I know of, and lightning is very rare in San Diego County--
like
maybe once per year.  The other more likely scenario is that the
hardline's
center conductor just migrated downward, relative to the shield, due to
variable temperatures and gravity.  When the joint became marginal,
eventually it became a spark plug for a while until it was totally
frapped
(I run 1300 Watts out).  If so, this would be the THIRD time that a
"migrating" center pin of a type N connector has disabled one of my
systems, but only the first failure involving a hardline connector.

It will take a couple hours up on the tower to fix this problem properly.
Luckily, the failure did not preclude guest op K6LL from apparently
winning
the recent CQP, in spite of making only 86 QSOs on 40 before the antenna
went dead.  Crafty ol' Dave just figured out how to squeeze the missing
QSOs out of the other bands, instead (you only need the mults once, not
on
each band-- whew).

--Glenn K6NA

(Tom-- this might be of interest to Towertalk, where I am not presently
subscribed.)

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