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Re: [TowerTalk] Question about ground

Subject: Re: [TowerTalk] Question about ground
From: Jim Lux <>
Date: Sun, 09 Sep 2012 17:01:00 -0700
List-post: <">>
On 9/9/12 3:54 PM, Matt Fearnow wrote:
Hey all I'm relatively new. I'm running a ground for my ground rounds
for antenna coax junction.  I have to go from my electrical service
panel ground rod about 80'.

80 feet?  Do you actually need to run a separate ground bonding wire?  I
assume you have some sort of grounding at the antenna to which the
shields are bonded.  Then you have a grounding electrode at the house,
to which the shields are bonded. I'm not sure you need a bonding wire, if everything is buried. However, I will say that I pull a green wire ground along with 120VAC to receptacles out in the yard, and some of the runs are 80 feet long: but I don't have a separate grounding electrode out there.

The purpose of a bonding wire is to make sure that "ground" is at the
same potential at both ends.  In this case, you don't really care if the
"ground" is different out in the field than at the house.  What you care
about is that center conductor and shield and all the other wires, at
the house, go up and down together.

Are there other wires you're running out there in addition to the coax (e.g. rotator, weather station, relay controls)?

2 questions 1) how deep should trenching be?

Is it required to "meet code"? Are your coax in conduit? Is it going to be under concrete? Deep enough so it doesn't get dug up accidentally. Rigid metal conduit and concrete can be buried less deep than bare cables (because an accidental shovel hit won't cause problems)

In California, in general:
24" for direct burial
6" for rigid or intermediate metal conduit
18" for non metallic raceway (plastic conduit, flexible or not)
12" for a 20 Amp or less branch circuit protected by GFCI (e.g an extension cord plugged into a GFCI outlet) 6" for irrigation/landscape light <30V if it's type UF or in a cable or conduit.

If it's in a trench with at least 2" concrete somewhere above, you can go 6" shallower (except for the two 6"ers)

Under a street, road, alley, private driveway, etc. for non-residential, at least 24" for all
Residential driveways 12 or 18" depending.

What I do is rent a trencher, which usually cuts a more than 2 foot deep hole, and put it that deep. If I need to come shallower (rocks, etc.), I put cheap concrete bricks over the top of plastic conduit.. I backfill to about 1 foot deep, then lay a plastic colored ribbon over it and complete the backfill. Hopefully, if someone is digging with a shovel, they won't make it too deep on the first plunge, and they'll see the ribbon, or hit the bricks.

2) does brick dust used
as a natural stone mulch, will that affect the ground wire?  Some
areas it is only 1-3" others it seems to be 4-5" deep of brick

I don't know. It's basically fired clay, so I would think it's not much different than rock or soil. Is it particularly alkaline or acidic, or likely to react with the copper?

Thank you in advance for guidance.

Matt Fearnow 73 - Matt - W9SIG


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