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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