Part of the confusion here is that a made-to-order commercial radio
room is usually going to be a single room inside a shelter, built on a
concrete slab, and the problem is protecting everyone's stuff inside
the shelter.
The main thrust of the answer is tying everything going out/coming in
to a single point ground panel.
Since it is a single room building, the SPGP is also how everything
gets to the outside. EVERYTHING. Power, telephone, radio leads,
EVERYTHING. It's got all the suppression gear mounted to it, a very
short thick ground lead to the external ground system, which includes
the power company ground.
Now what happens when you take this very successful strategy and try
to export it to a residential situation?
Well, if your radio room is next to where the power and telephone come
in, and it is feasible and acceptable to route the outside ham wiring
to the same place, then you have the maximum system available to your
residence. Just do it.
What if you don't. Then what do you do?
You extend the system so that no aspect of the commercial radio room
SPGP is lost in your house. Consider my house as a kind of worst case
for purposes of demonstrating the principle.
Unfortunately, when you do, you have to duplicate some provisions to
accomplish the same thing.
In my case I have power and tel to the front of the house. I have ham
radio and two different remote power feeds to the back of the house. I
have a shack over the garage at a distance from either of the two.
Going around the house IS OUT OF THE QUESTION. (No, don't ask...)
This means to fully protect my situation, I have to have THREE SPGP's.
One at the ground in the front for power and tel, one at the ground in
the back for power feeds and ham radio, and one at the shack, for
EVERYTHING that comes into the computer and radio rooms.
The SPGP's are connected by heavy conductors, in what is essentially a
thick copper triangle.
All elements going through a given SPGP are suppressored at that
point.
This means that circuits going through two SPGP's go through two
suppression points. Power goes through suppression on all three
points.
Consider the Polyphaser writings what you do when you are lucky enough
to have all three of my suppression points at the same place.
Once you get the idea, it's pretty simple.
73, Guy.
----- Original Message -----
From: "KC2TN" <kc2tn@comcast.net>
To: "'Bill Hider (N3RR)'" <n3rr@erols.com>; "'Guy Olinger, K2AV'"
<k2av@contesting.com>; "'Jon Ogden'" <na9d@speakeasy.net>; "'Tower
Talk (mail list)'" <towertalk@contesting.com>
Sent: Thursday, September 19, 2002 10:53 PM
Subject: RE: [Towertalk] Box forSPG and Lightning protectors
> There's another series of Articles by Ron Block in QST in the
> June, July and August 2002 issues.
>
> When reading article's by Ron Block (or Polyphaser articles) the SPG
> refers to the single point as the "ONE and ONLY point in the radio
room"
> where ground connections should be made to. The point to which he
refers
> is the SPGP (single point ground panel). This SPGP is what is
connected
> to the outside ground system. "The goal is to make the ground path
leading
> away from the SPGP more desirable than any other path."
>
> Joe
>
>
>
> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com]On Behalf Of KC2TN
> Sent: Thursday, September 19, 2002 10:25 PM
> To: 'Bill Hider (N3RR)'; 'Guy Olinger, K2AV'; 'Jon Ogden'; 'Tower
Talk
> (mail list)'
> Subject: RE: [Towertalk] Box forSPG and Lightning protectors
>
>
> I guess the confusion comes from what is called the "Single Point
Ground".
>
> In my mind when I started to research this stuff and to sort out all
of the
> various
> opinions and implementations was to fundamentally understand what a
"Single"
> point
> was. Now it appears as though there can be "TWO" SPG's??
>
> I may be caught up in semantics but to the uneducated this can be
confusing.
>
> What Ron Block was stating in his article was to establish the SPG
in the
> Shack
> with all protectors mounted there and assure this SPG is connected
to
> the outside ground system with a suitably sized connection.
>
> ALL of Polyphaser's examples show the bulkhead in the equipment room
with
> connections to the outside ground system.
>
>
> BTW...Sorry but the article's I was referring to by Ron and Roger
Block
> from Polyphaser were in "73" magazine not QST
>
> I am by no means an expert on this stuff, just trying to understand
it!
> I've seen so much over the last 6 months it's hard to sort out
what's
> right. But the really "wrong" opinions really stand out now. So I
> understand when & why Bill says NO! NO! NO! sometimes.
>
> Joe - KC2TN
>
> -----Original Message-----
> From: Bill Hider (N3RR) [mailto:n3rr@erols.com]
> Sent: Thursday, September 19, 2002 9:48 PM
> To: Guy Olinger, K2AV; kc2tn@comcast.net; 'Jon Ogden'; 'Tower Talk
(mail
> list)'
> Subject: Re: [Towertalk] Box forSPG and Lightning protectors
>
>
> Guy has it right.
> I couldn't have said it better.
> And my shack has all of what Guy says here.
> The SPG in the shack is a consolidation point (panel) for all of the
> equipment grounds in the shack and connects them to the outside SPG
and its
> associated ground grid..
>
> Also, Guy's comments on the disconnection of equipment are what I've
been
> saying on this reflector for years.
>
> Bill, N3RR
>
>
> ----- Original Message -----
> From: "Guy Olinger, K2AV" <k2av@contesting.com>
> To: <kc2tn@comcast.net>; "'Jon Ogden'" <na9d@speakeasy.net>; "'Tower
Talk
> (mail list)'" <towertalk@contesting.com>
> Sent: Thursday, September 19, 2002 9:10 PM
> Subject: Re: [Towertalk] Box forSPG and Lightning protectors
>
>
> > What is being proposed is a common grounding point within the
shack,
> > which is a good idea. THIS IS SEPARATE from the single point
common
> > ground where everything comes into the house.
> >
> > If your shack is right next to the SPG, well good. If your shack
is at
> > a distance, like on an upper floor or in the "bonus room" over the
> > garage, then ground everything (this includes phone lines, cat5,
etc)
> > in the shack to a common point in the shack, including a healthy
> > safety ground run to the ground at the SPG, and whatever you may
be
> > using to effect an RF ground.
> >
> > What the second (shack) common grounding point does is to keep all
the
> > potentials in the shack to a common level if a strike occurs, and
gets
> > inside somehow. A close strike can saturate the ground field and
then
> > things start to rise. You want them all to rise together.
> >
> > You want to avoid lightning coming into your shack on one
conductor
> > and using some piece of equipment as a path to another conductor
to
> > leave your shack and go to something less saturated with charge.
> >
> > In these situations, phone lines and such can be the enemy because
> > they are a way OUT of the house to a less saturated place.
> >
> > About the disconnects, listen long enough, and you will hear
stories
> > of lightning jumping across open spaces of some several feet to
> > continue its path to neutral ground.
> >
> > A disconnect point not grounded on the lightning side of the
> > disconnect can be just about useless. It takes BOTH. And the
ground
> > has to be a good one.
> >
> > 73
> >
> > ----- Original Message -----
> > From: "KC2TN" <kc2tn@comcast.net>
> > To: "'Jon Ogden'" <na9d@speakeasy.net>; "'Tower Talk (mail list)'"
> > <towertalk@contesting.com>
> > Sent: Thursday, September 19, 2002 6:03 PM
> > Subject: RE: [Towertalk] Box forSPG and Lightning protectors
> >
> >
> > > Not to disagree with Bill because he's been a BIG help to a lot
of
> > us here
> > > on this reflector (ME included) regarding station protection.
> > >
> > > BUT...
> > >
> > > I was confused about where to put my SPGP also ..My original
design
> > had it
> > > right outside the shack in an enclosure
> > > but I changed the design after reading the Ron and Roger Block
QST
> > > "Lightning Protection" series "What Your Mother Never told you!.
> > >
> > > In that article there was this excerpt:
> > >
> > > "...As we'll detail later on, the primary ground system is
> > represented
> > > by a set of copper-clad ground rods, interconnected below grade,
> > with bare
> > > copper radials. Also fundamental to a good protection scheme is
the
> > creation
> > > of a single point ground WITHIN the ham shack. This single point
> > ground will
> > > be used to MOUNT ALL of the I/O protection equipment and to
provide
> > a ground
> > > for all of the equipment cabinets at the station's operating
> > position. This
> > > INTERIOR single point ground is CONNECTED to the external ground
> > system
> > > (composed of those radials and ground rods) by the lowest
impedance
> > copper
> > > strap that you can manage. The tower ground system outside and
the
> > single
> > > point ground system inside must be solidly interconnected with a
low
> > > impedance metallic strap, so that your coax cable's shield is
not
> > the only
> > > interconnection conductor between these two ground points.
Keeping
> > as much
> > > of the lightning's energy off of the coax shield as possible is
> > essential to
> > > minimizing damage from a direct hit. For larger strikes, it's
best
> > to
> > > incorporate a grounding kit prior to the protector, to save your
> > expensive
> > > coax connectors from arcing damage. An effective (good quality)
> > coaxial
> > > in-line protector can then be used to handle smaller strike
currents
> > that
> > > may be tempted to travel down the cable itself."
> > >
> > > After conferring with Ron over lunch (he lives close by) we
decided
> > it was
> > > best to move the SPGP inside the shack
> > > to allow easier bonding of all the protection components,
including
> > an AC
> > > protector, to one plate. The plate was then
> > > connected to the EXTERIOR ground system via 2 6" copper straps.
The
> > reason
> > > for the two straps was to equal the total
> > > cross section of cable(s) entering (11") with the ground leaving
> > (12") to
> > > attach to the exterior ground system.
> > > This keeps all voltages rising and falling together with zero
> > current flow.
> > >
> > > My exterior ground system consists of 2" strap cadwelded to 4
legs
> > of
> > > radials off the tower consisting of
> > > 4 8' 5/8" ground rods 16' apart on each leg and also a perimeter
> > ground
> > > connected to the AC panel all tied
> > > to the SPGP via the 2 6" straps.
> > >
> > > I should mention that my tower is only 10 feet from the shack
and
> > > Electromagnetic Pulse protection is near impossible
> > > given the proximity of the tower. Unless I wanted to encase my
shack
> > in
> > > copper $$$$.
> > >
> > > BTW...This whole system did not come cheap! But the idea is to
keep
> > the
> > > energy in the ground field and most of it
> > > outside the house. Also, Ron's SPGP is in his closet next to his
> > station.
> > >
> > >
> > > Joe - KC2TN
> > >
> > > -----Original Message-----
> > > From: towertalk-admin@contesting.com
> > > [mailto:towertalk-admin@contesting.com]On Behalf Of Jon Ogden
> > > Sent: Thursday, September 19, 2002 4:25 PM
> > > To: Bill Hider (N3RR); Tower Talk (mail list)
> > > Subject: Re: [Towertalk] Box forSPG and Lightning protectors
> > >
> > >
> > > on 9/19/02 2:23 PM, Bill Hider (N3RR) at n3rr@erols.com wrote:
> > >
> > > > As I read some of the comments/questions about covering the
> > lightning
> > > > protection boxes, I'm wondering if consideration was taken
into
> > account
> > > for
> > > > a Single Point Ground (SPG)??
> > > >
> > > > If the lightning protectors are just laying around on the
ground,
> > > presumably
> > > > near the ground rod, and then coax or control cables are just
run
> > into the
> > > > house without a SPG, what's wrong with this picture? If
that's
> > the
> > > > scenario, you're missing a couple layers of protection.
> > >
> > > But if the lightning protectors are all tied into the same
ground
> > rod, isn't
> > > that the same as the SPG?
> > > >
> > > > First of all, a SPG box provides the common ground point
ensuring
> > no
> > > > difference in potential even in the face of lightning.
> > > > Secondly, a SPG box made of metal, rather than plastic,
provides a
> > Faraday
> > > > shield for all wires passing through the metal SPG box. A
plastic
> > box
> > > does
> > > > not.
> > > > Third, a steel box, rather than aluminum, provides a magnetic
> > shield
> > > against
> > > > magnetic fields (produced by lightning strikes) inducing
currents
> > into
> > > your
> > > > cables then entering the house.
> > > >
> > > Yes, but the box only shields the stuff inside the box. What
about
> > all of
> > > the coax that is run inside the house that is not shielded by
any
> > metal? I
> > > fail to see how a metal box that encloses other metal boxes is
going
> > to do
> > > much.
> > >
> > > 73,
> > >
> > > Jon
> > > NA9D
> > >
> > > -------------------------------------
> > > Jon Ogden
> > > NA9D (ex: KE9NA)
> > >
> > > Life Member: ARRL, NRA
> > > Member: AMSAT, DXCC
> > >
> > > http://www.qsl.net/ke9na
> > >
> > > "A life lived in fear is a life half lived."
> > >
> > > _______________________________________________
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> > >
> > >
> > > _______________________________________________
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> > http://www.mscomputer.com
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> > > _______________________________________________
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> >
> >
> > _______________________________________________
> > Self Supporting Towers, Wireless Weather Stations, see web site:
> http://www.mscomputer.com
> > Call 888-333-9041 to place your order, mention you saw this ad and
take an
> additional 5 percent off
> > any weather station price.
> > _______________________________________________
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> >
>
>
>
> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site:
> http://www.mscomputer.com
> Call 888-333-9041 to place your order, mention you saw this ad and
take an
> additional 5 percent off
> any weather station price.
> _______________________________________________
> Towertalk mailing list
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> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site:
http://www.mscomputer.com
> Call 888-333-9041 to place your order, mention you saw this ad and
take an additional 5 percent off
> any weather station price.
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