Hi Gange
I have been following this thread, But have become confused. if in my situation
my tower is 200 feet from the shack, My shack RF ground is 60 feet from the
service ground. I have a ground at the tower. reading the post i will according
to the NEC run a ground from the tower to the service. with ground radials for
my vertical my yard will have a maze of copper/aluminum wire.Then if i install
a RF ground every 16 feet on the tower to service ground, will this bond all
my RF grounds to the service?
But then should my tower get struck by lightning will it run the house ground
and blow everything with a mains ground?
Another point, my HF radio is 12v so do i need to bond this to the service? or
will my shack RF ground suffice.
My amp is 240 has a separate service and RF ground but not bonded.
Just asking.
Dave kg4uxr
----- Forwarded Message ----
From: Gary Schafer <garyschafer@comcast.net>
To: Jim Carr <n7fcf@hctc.com>; Glen Zook <gzook@yahoo.com>;
dhallam@rapidsys.com; AMPS List <amps@contesting.com>
Sent: Mon, December 14, 2009 2:54:53 PM
Subject: Re: [Amps] Isolation Transformer
We have heard this story from you before and it is a dangerous one.
If you had 103 volts difference between two grounds then there was a problem
with the device or the grounding system. NO question about it.
All grounds on the premise are required to be bonded together so that there
is never a difference in potential between any item that is supposed to be
grounded.
Yes tower ground rods ARE required to be bonded to the building ground rods
which ARE required to be bonded to the electrical entrance ground system.
Not only is the safety ground there to clear a fault it is also there to
ensure all equipment enclosures remain at the same potential.
No it is not safe to do as you suggest and use an isolation transformer to
run your transceiver which is connected to a separate ground rod of its own
which is not tied into the main electrical ground system.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On Behalf Of Jim Carr
> Sent: Monday, December 14, 2009 2:04 PM
> To: Glen Zook; dhallam@rapidsys.com; AMPS List
> Subject: Re: [Amps] Isolation Transformer
>
> At least two rods driven 8ft into the ground composed of either
> galvanized
> steel or coper 5/8" in dialmeter or a 3/4" galvanized pipe.
> Spaced no closer than 6 ft apart, grounded to the service main grounded
> conductor with copper wire maximum size #6 AWG Bonded to the building
> steel
> Metalic water pipes and the foundation re-bar with in the case of a
> 200amp
> service #4 AWG copper or aluminum wire of the same ampacity. That is not
> the
> equipment ground which comes under bonding.
> Ground rods at the antenna tower bonded to the equipment serve a
> different
> purpose. As a ground reference for the antenna and lightning protection.
> The
> NEC does require grounding of a radio tower, but that is for receiving
> towers not transmitting. Whether a tower is grounded or not is relative
> to
> how it is used and fed. You would hardly want to directly ground a base
> loaded tower. I have seen cell towers with 10ft ground rods at each
> corner
> of the building and each corner of the tower base bonded to the tower
> and
> the service main. But it isn't required by the code. The NEC also
> requires a
> UL or CSA approved lightening protector on the feed line. Try finding
> one
> for ladder line. A good idea? Yes but as I remember again only required
> on
> receiving antenna's.
> The beauty of the isolation transformer is that it isolates the building
> ground and the transceiver / antenna ground system's from each other.
> Also
> NEC also states that the building equipment ground is not to carry
> anything
> but the fault current of a short. If you tie a seperate ground rod to
> the
> rig and a equipment back to the panel, that equipment ground will carry
> a
> current provided by the difference in potential between the service
> ground
> rods and the remote one at the rig. So you would need to run a #6 copper
> wire back from the remote rod to the service rods. I burned the gimlet
> off
> of a 3/4 ship bit when I touched it to a grounded cast iron soil pipe. I
> was
> a hundred feet out from the temporary service I was plugged into/ There
> was
> nothing wrong with the drill or the service. It was the difference in
> potential between two ground's 100 ft apart. It measured 103volts.
> Personally I'd isolate it and enjoy the safety.
> Jim
> N7FCF
>
> ----- Original Message -----
> From: "Glen Zook" <gzook@yahoo.com>
> To: <dhallam@rapidsys.com>; "AMPS List" <amps@contesting.com>; "Jim
> Carr"
> <n7fcf@hctc.com>
> Sent: Monday, December 14, 2009 7:51 AM
> Subject: Re: [Amps] Isolation Transformer
>
>
> > No!
> >
> > NFPA NEC (National Electrical Code) specifically states that all
> ground
> > rods must be connected together. Now there are practical situations,
> like
> > when the r.f. ground, lightning ground, and electrical ground are
> widely
> > separated that makes tying them together extremely difficult, if not a
> > practical impossibility. However, whenever possible NFPA NEC should
> > definitely be followed.
> >
> > Glen, K9STH
> >
> > Website: http://k9sth.com
> >
> >
> > --- On Sun, 12/13/09, Jim Carr <n7fcf@hctc.com> wrote:
> >
> > The purpose of the ground wire in a 120v/240v branch circuit is to
> blow
> > the fuse if a hot wire touches the metal cabinet. The RF grounding
> system
> > is a horse of another color and usually has it's own ground rod
> seperate
> > from the service main.
> >
> >
> >
>
>
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