[Amps] Isolation Transformer

[Jim Carr]

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 at yahoo.com>
To: <dhallam at rapidsys.com>; "AMPS List" <amps at contesting.com>; "Jim Carr" 
<n7fcf at 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 at 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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