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Re: [TowerTalk] Question about ground

To: Jim Lux <>
Subject: Re: [TowerTalk] Question about ground
From: Matt Fearnow <>
Date: Sun, 9 Sep 2012 21:01:10 -0400
List-post: <">>
On Sun, Sep 9, 2012 at 8:01 PM, Jim Lux <> wrote:

> 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.
Well the electrical service comes in to the back of the house.  I need to
go from there to the side and up to the front to where the entrance into
the basement where my shack will be.  A few years ago, an engineer (now SK)
had advised me to tie all grounds together, from the electrical, to the
"tower", to the cable shields, to the ground plate in the house for the
gear.  IIRC, was to allow all points to have equal paths to ground.  Else
if not, if current came in from the eletrical panel, through the gear, and
out through their ground (if that was the shortest path)

> 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)?

Possibly in the future.  This termination is for the junction plate at the
house for the "Antenna(s)" coming into the shack, with arrestors.

>  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)

Ok, thanks, No Code requirements.

> 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
>> stone.
> 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?
Thats true, brick is fired clay.  PH is relatively neutral.  I guess then
the question is, what do the hard clay area's (VA comes to mind) do they
need to do anything special for grounds?

Thanks again I am really learning a lot just by sitting back and reading
all of your posts on this list.


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