[R-390] Grounds

[Dave Maples]

All: Also remember that ground rings, rods, etc., do NOT last forever.  If
you put in a ground system years ago, there's a good chance it's no longer
there, particularly if you are in acidic soil.

Cecil is also correct...it just takes one bad install to wreck the train.
Fortunately, most techs that are worthy of the name don't let crazy folks
install into "their" sites in a willy-nilly fashion.

Dave Maples

-----Original Message-----
From: Cecil Acuff [mailto:chacuff at cableone.net]
Sent: Sunday, August 02, 2009 9:36 PM
To: Bruce Ussery; Dave Maples; R-390 at mailman.qth.net
Subject: Re: [R-390] Grounds


Bruce that usually means someone didn't follow good technique in grounding
the equipment and racks inside the building.  Routing of DC power wiring and
signal carrying cables etc...

It doesn't take but one guy that comes in and installs something that's not
up to standard and it undoes all the work (not to mention the money spent)
of others.

We usually call for a grounding audit after a site has been hit in that way.
Especially with all the exterior grounding work that sounds like has been
done at the site.  It usually uncovers something that needs rerouting and
grounding improvements within the building.

Certainly there needs to be a central point ground system in the building
for a good start.

Cecil
----- Original Message -----
From: "Bruce Ussery" <twc9198764412 at earthlink.net>
To: "Dave Maples" <dsmaples at comcast.net>; <R-390 at mailman.qth.net>
Sent: Sunday, August 02, 2009 4:59 PM
Subject: Re: [R-390] Grounds


> For a while I got back into the RF world as my daily job, working for the
> NC
> State Highway Patrol's VIPER microwave network group. (VIPER = Voice
> Interoperability Plan for Emergency Responders.) This lets anyone with the
> proper radio reach anyone else in his group statewide, when in range of
> any
> of around 200 towers. The new sites we installed went into nice pre-fab
> buildings with pretty impressive grounding systems. Lots of wide copper
> strips where the feedlines enter the building, lots of Polyphaser devices,
> surge protector boxes on the AC mains and generator circuits- all done
> pretty much like Dave described for larger buildings.
> Even with all this effort lightening still causes damage routinely, mostly
> to the "mux shelf", a box full of circuit boards that basically sorts out
> all the signals going into, or coming out of the microwave; the generator
> controls, and the UPS box. The Alcatel microwave and Motorola trunking
> radios generally survived. Experience helps I imagine.
> Thanks to all for the good information.
>
> Bruce
> WA4ZLK
>
> ----- Original Message -----
> From: "Dave Maples" <dsmaples at comcast.net>
> To: "rbethman" <rbethman at comcast.net>; <R-390 at mailman.qth.net>
> Sent: Sunday, August 02, 2009 3:56 PM
> Subject: Re: [R-390] Grounds
>
>
> All: The NEC is correct in this case.  All the grounds need to be
> connected
> together with large-gauge wire, so that any surge current (whether direct
> or
> induced) cannot set up a large potential difference between the ground
> systems.
>
> In the commercial world we bond power and telco grounds together, and then
> bond that to a ground ring around the building.  The ground ring around
> the
> building is bonded to a ground ring around the tower (if any), and the
> tower
> legs are bonded to the tower ground ring.  Three ground rods at the tower,
> one ground rod at each corner of the building and more if the corners are
> more than 15' apart, and all bonded to the appropriate ring.  Each coaxial
> cable shield conductor is bonded to the ground ring around the building at
> the point of entry into the building, and lightning protection is bonded
> to
> the ground ring around the building.  Each telco and power entry or exit
> has
> a suitable surge protector on it.  Inside the building, equipment grounds
> are bonded to the bonding point for the power, telco, and coax shield
> grounds.
>
> This is a large condensation of guidance we received from both Polyphaser
> and equipment vendors.
>
> Hope this helps.
>
> Dave WB4FUR
> : http://www.qsl.net/donate.html
>
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