Re: [TowerTalk] Grounding control cable/Rotator control box

["Tower (K8RI)" <tower@rogerhalstead.com>]

Just a point of interest here and I've only seen it once.
All coax comes into the house through underground PVC conduit. The coax is 
grounded to the tower and to the bulkhead for the Polyphasers.  These are 
all tied into a common ground using #2 bare copper with 8' ground rods about 
every 16 feet.  This run is part of a network consisting of over 600 feet of 
bare #2 and over 30 8' ground rods.
There is about a 10' run for each coax from the Polyphasers to the rigs 
and/or antenna switches.

> If you have a Polyphaser installed at the bulkhead entrance to the shack,
> the chance of this happening is extremely small.  With the arrestor in 
> place
> we are talking hundreds or thousands of volts rather than millions or
> billions inside the shack.  This is not necessarily true if the arrestor is
> located at the base of the tower rather than entrance to shack.

Earlier this summer I had the coax from the 440 array disconnected from the 
antenna switch.  The cable was laying on the desk top which is about 6 
inches under the switch.  As all the cables go through that grounnded 
bulkhead I really didn't pay much attention when a storm appeared to brewing 
up

This computer and my chair are about 4 feet from the switch.

There was a bright flash and very loud bang as an arc flased from the coax 
to the antenna switch.  That is over  a 6" arc.  The Polyphaser is fine so I 
can only conclude this was from induced voltage in the ground.  Everything 
else in here was tied to ground.

There was no damage to any of the rigs.  My cat-5 network did shut down and 
reboot, but came up running fine.

> A better solution is to ground the center conductor (along with shield) to
> common ground system that has low inductance to an outside single point
> ground system.

Certainly the safest.
Any one ever see what snow static with an ungrounded vertical does at the 
shack end of the coax? <:-))  It's far more potent than the mags on my 6 
cylinder Continental engine.


Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com


Keith NM5G

-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Joe - WDØM
Sent: Monday, September 13, 2004 9:06 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Grounding control cable/Rotator control box

Here's a web site to consider, when it comes to disconnecting coaxial cables
from equipment:

http://www.polyphaser.com/ppc_PEN1016.asp

The quote pertaining, is toward the bottom/middle of the page, and reads
thusly:

"Just a word to those who tell us that they are safe from lightning because
they always disconnect the coax from their equipment. When asked what they
do with the disconnected line(s), they usually respond that it is placed on
the floor. Now if you stop and think about the last few thousand feet that
the lightning has jumped, you can see the fallacy of their thinking. In
fact, they made it worse since arcing involves ignition temperature plasmas
inside your house. True, the radio may still work, if it survives the house
fire. Throwing the coax out the window is not a solution, especially if the
coax has already entered the house from the antenna or the antenna is roof
mounted without a ground path. Grounding switches will not last long with
direct hits unless other good ground paths are provided. Grounding the
antenna line and not disconnecting the coax shield can still allow strike
energy to be shared with the equipment The shield connects to the chassis
and if a single point ground is not present with power/telephone protectors,
the equipment will be damaged. "

73,
Joe
WDØM




At 08:00 AM 9/13/2004, Dale L Martin wrote:


> On Sun, 12 Sep 2004 22:14:42 -0600
>  "Noel" <yaesurig@msn.com> wrote:
> > Had a pretty good lightening storm here this evening and decided to
> > disconnect my coax cables after I heard that familiar ticking sound
> > that told me there was static charge buildup on the coax.
>
>
> hmmm....
>
> I learned this lesson a few years ago:
>
> There are three sounds that help to remind me to disconnect cables:
> 1.  The sound of distant and approaching thunder 2.  The click the
> light switch as I leave the radio room 3.  The click of my bedside
> table lamp at night 4.  The starting of my car engine in the garage
>
> 73,
> dale, kg5u
>
>
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with
> any questions and ask for Sherman, W2FLA.
>
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_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.

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_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any 
questions and ask for Sherman, W2FLA.

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_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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