[Top] [All Lists]

[TowerTalk] grounding

To: <>
Subject: [TowerTalk] grounding
From: (Billy Cox)
Date: Tue May 27 02:36:47 2003
>It would be very interesting to know what measures you had in place when
>you took the hits, and how the damaging voltages got into the shack.  Can
>you elaborate a bit, Billy?  My problem is that I can't "do it right" (2nd
>floor shack) and need to assess whether I can improve what I AM doing.

Hi Pete,

For many years I did like most ... had all the station on a 'power strip'
or two ... unplugged it from the wall ... and disconnected the coax(es),
and hoped that the rusty old 8' ground rod would be enough. <DUMB!>

Even doing that ... I'd see arc/burn marks sometimes on things like the
SWR bridges or the remote antenna switches would arc inside. Most of
the time I wear headphones due to some hearing issues, and for all I
know such damage could have occurred WHILE I was operating! Not so
smart ... that's the other problem ... what if a storm blows in while you
are operating ... I think I was VERY lucky several times out here. All you
have to do is be 60 seconds too late, or forget to unplug 1 piece ... and
you may lose more than you ever imagined. I played it too close too many
times I felt.

Sometimes I think the path IN was via the AC lines in the house, others
via the control lines or coax ... which disconnected <and I thought was
grounded> still allowed the 'bad stuff'(tm) to enter into the station.

In '95 when the BIG ZAP hit ... the main coax feed <pre S02R daze>
was disconnected and laying behind the main desk. I was sitting here
reading a QST ... and like the old joke, before you can say something
about it ... it's all over, other than the ozone smell ... and in this case
the carpet under the desk smoldering. The insurance agent that came
out, still swears we took multiple 'hits' that day. Could be ... the main
tower had flash marks on it's top ... both telephone boxes were blown
off the wall. The Beverage coaxes were burned and BLACK inside ...
I am still not 100% where it started, but once the path to the ground in
the shack was made ... it was all over. The IC765's ground traces were
GONE on many of it's boards. The heat pump compressor welded,
and so forth. <Thanks goodness my xYL is a ham, otherwise ...>

Pete, I would do two things there ... considering the 2nd story shack.

Try to keep as much of the surges/etc. out at your tower, which is a bit
away from your house as I recall. And try to keep ALL grounds at the
same potential. Being on the 2nd floor you probably are not going
to be able to establish the perfect system, but you should be able to
have it all rise and fall as to potential differences at the same time.

That's what one of the packet node ops here did, and his problems
seemed to finally go away. With the node, there was no way to unplug
and disconnect ... and that then exposed the rest of his 2nd story shack.

When he finally had all the grounds together, even though they were
probably not at a very low impedance ... there now was no longer any
differences in the potentials during times of surges and such ... his
tower is 100' and at it's base is where he first line of defense went.
<grounding the coax shields, ground rods, control lines protected, etc.>

Hope this helps!

73 Billy AA4NU

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