The service entrance grounding conductor required by the NEC is for safety, not
rf grounding, not lightning protection, only safety. Properly installed
grounding conductors are to prevent a fault current from burning up things
(including your house) or flowing through ones body.
A good RF ground system is bonded to the service entrance electrical ground rod
for the same reason. A good ground system made of several ground rods, copper
strap and radials and it will dissipate a strike, but it will not assure
complete safety from a strike. I know. I rebuilt many commercial radio
transmitters, STL, and microwave links (as well as a station) after a strike
and every station had tons more copper burried than any ham radio operator's
shack. Recently there was a series of articles on lightning protection in QST.
I have also run across some on the internet.
73,
Bill
AI4WM
--- On Mon, 10/6/08, Perry - K4PWO <k4pwo@comcast.net> wrote:
> From: Perry - K4PWO <k4pwo@comcast.net>
> Subject: Re: [TowerTalk] house entrance ground for RF ground?
> To: towertalk@contesting.com
> Date: Monday, October 6, 2008, 2:40 PM
> I should clarify that a perimeter ground system IS tied to
> the electrical
> panel ground at the panels ground rod, not in the panel.
> Most ground bus
> strips in panels are not well suited for the large currents
> induced by
> lightening strikes. I've seen many panels with a #6
> copper to the ground
> rod held by an acorn nut. If you connect the
> "shack" ground at the panel
> the induced current will flow from the higher potential
> ground and common to
> the hot sides of the line. Any surge protectors will shunt
> the current,
> until they are overwhelmed, raising the hot sides along
> with the
> common/ground. However, should the protectors fail, the
> common/ground
> system can go well above the hot sides and you will have
> equipment damage.
> Can a full on strike be averted, probably not... but the
> rule of thumb is
> prevent the induced current from entering the home if at
> all possible. Keep
> all ground connections direct, use largest conductors
> affordable, use
> cadwelds over acorn nuts, and do all bonding outside as
> close to the earth
> as possible. A station ground to electrical panel to
> ground rod is a daisy
> chain that invites the weak link to fail.
>
> 73 de Perry - K4PWO
>
> ----- Original Message -----
> From: "jim Jarvis"
> <jimjarvis@optonline.net>
> To: <towertalk@contesting.com>
> Cc: <gdslagel@yahoo.com>
> Sent: Monday, October 06, 2008 07:56 AM
> Subject: Re: [TowerTalk] house entrance ground for RF
> ground?
>
>
> >>>>
> >>>> My shack is on the first floor of the
> house and right above the
> >>>> electrical
> >>>> service entrance in the basement. For my
> station RF and DC
> >>>> ground, I'm
> >>>> thinking I'll run a 10' wire from
> the station down to the electrical
> >>>> entrance ground wire which, of course,
> runs right out to ground rods
> >>>> outside the house. Is there any problem
> with this or should I be
> >>>> running to a separate ground rod?
> >>>>
> >>>> Thanks for any opinions!
> >>>>
> >>>> Gary Slagel/N0SXX
> >>>> Hot Springs, SD
> >>>>
> >
> >
> > Gary,
> >
> > Jim Brown's comments were correct. The chap who
> said it was a bad
> > idea was
> > wrong. Sort of.
> >
> > You must get everything in the house as close to the
> same potential
> > as possible.
> > You say the shortest path to ground for you is to that
> ground rod
> > being used by the electrical
> > panel. Were it me, I would obtain copper strap, and
> run that down
> > there, and bond
> > it well to the rod. That's what Jim Brown said,
> basically.
> >
> > However, Perry said it was a bad idea... that you
> needed a separate
> > ground.
> > WRONG on separate. And wrong as well, in that the
> shortest path to
> > earth is the
> > best path...and the power ground rod appears to be the
> closest. So
> > a longer run to
> > another ground won't be better.
> >
> > But Perry's RIGHT, in that the power ground rod,
> by itself, is NOT
> > SUFFICIENT.
> > The power ground provides basic electrical safety, not
> lightning
> > protection.
> >
> > (Oh, it'll appear to be just fine... until and
> unless you get hit by
> > lightning. Then, you're
> > going to wonder what happened. And, you'll
> discover that you can't
> > have separate grounds,
> > just two marginal ones connected together by leaky
> earth. )
> >
> > You need a more robust system, to dissipate the
> current from a
> > strike, should you be
> > unfortunate enough to have one.
> >
> > I suggest you read back on threads on the reflector.
> This is
> > discussed ad nauseum, every year,
> > at least once.
> >
> > Multiple ground rods, connected with heavy cable (not
> coax braid) or
> > strap,
> > and with radials running away from the house are all a
> good idea.
> > Or, an array of radials coming
> > out from the power ground rod, each ending in another
> ground rod.
> >
> > Your site and aesthetics, and economics, will dictate
> what, and how
> > much, you ultimately do.
> > You might want to consider a ground system out by the
> antennas, as
> > well, if they're some distance
> > from the house.
> >
> >
> > n2ea
> >
> >
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
>
> _______________________________________________
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