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
>
>
>
> _______________________________________________
>
>
>
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