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Author Topic: Help with earthing please  (Read 2425 times)
G6ZBB
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Posts: 1




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« on: December 04, 2015, 12:59:57 PM »

Hi Guys,

I am just sorting out a new station earth and would like your opinion as to this proposal:

My plan is to sink 3m of 22mm diameter copper tube into the soil just outside my shack window, the soil is clay in structure. I will then lead some 70mm2 (sorry I can't seem to indicate square millimetres properly) up the outside of the house to the 1st floor radio room. This should be no longer than about 8.5m in total from the end of the tube to the end of the earth, so it should not form any part of a wavelength between 10m and 160m frequencies.

That's fairly straightforward to do, but I have read that I should also connect the existing utilities earth to the ground point to remove possible potential differences.

The utilities earth is on the opposite side of the house, so the shortest route would be up from the ground to underneath the kitchen roof, along the kitchen and up the side of the house, over the roof and down to the earth tube. I don't like this idea much as I feel the wire might possibly pick up RF from the dipole or long wire antenna which will be mounted some 12ft above the roof line.

As this is not an RF ground but just for potential matching I was wondering what gauge of stranded wire I should use? I was thinking perhaps 10 or 16mm2, but this might be over or under kill.

Can I please take advantage of your experience and ask if you think if I am going about this the right way, what you think of my potential matching proposal and what gauge of wire would be appropriate for that purpose?

Thanks for your help.

Regards,

Dave
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WB4SPT
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Posts: 276




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« Reply #1 on: December 08, 2015, 07:33:52 AM »

Hi Dave;   I have sunk 5 ground rods in my latest residence, which is also packed clay.  I really can't imagine that job with tubing.   It takes quite a pounding to drive these.  I feel that plumbing tubing, even the hardened copper will deform.  Ground rods over here are typically steel with copper cladding. 

2nd point.  The bonding to the service entrance is primary.  Best to use strap, second best to use stranded, worst to use braid.   The connection to the shack is not needed or desired.  This heavy conductor is used to direct kiloAmps away from the radios and house.  You can see the flaw in running large conductors TO the inside of the building.
There have been a lot of recent threads that explain this clearly.  Cheers. 
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WB4SPT
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« Reply #2 on: December 08, 2015, 09:38:58 AM »


The utilities earth is on the opposite side of the house, so the shortest route would be up from the ground to underneath the kitchen roof, along the kitchen and up the side of the house, over the roof and down to the earth tube. I don't like this idea much as I feel the wire might possibly pick up RF from the dipole or long wire antenna which will be mounted some 12ft above the roof line.


To this point, I would recommend keeping the bonding conductor to service entrance at or below grade, even if it is not as direct.   This way, with bare conductors you do gain some additional "earthing".  Best to distribute some ground rods along the way.  There have been some reports of building damage due to  lightning steam/whatever, so some folks recommend at least a meter distance from the structure.  I've also heard to follow the drip line of the roof to increase soil conductivity.  You will hear lots of things!  Shocked
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K8AC
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Posts: 1569




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« Reply #3 on: December 09, 2015, 06:04:33 AM »

Dave - be wary of advice you get here.  Check out this link: http://www.w8ji.com/station_ground.htm

W8JI is a prominent engineer here in the USA and his advice is solid. 

73, Floyd - K8AC
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KD0REQ
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Posts: 1629




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« Reply #4 on: Today at 10:09:46 AM »

you will also find broadcast-grade advice over on polyphaser.com.  the masterful grounding job W8JI details on his shacks is right up there with a tower farm of broadcast stations, although I doubt his towers are 8-inch tubing like the Shoreview antenna farm.
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