Earth grounding - materials and effectiveness.

Channel Hopper

Channel Hopper

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Driving a long copper stake into damp ground is a given of course, but this is to be done in a field near a main road, and there is the opportunity to put more than one of them in. Possibly up to four in each corner to capitalise on the possibility of VLF testing.

I have a few galvanised steel scaffold pipes of between two and three metres long and the ground is certainly soft enough (London clay) to knock them down with a sledgehammer.

So , is a galvanised pole good enough to work as a grounding rod and for VLF is it a case that the deeper the burial the better?

Thanks in advance.
 
Terryl

Terryl

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No the galvanizing will corrode with constant contact with the ground and it will not conduct as you expect.

Do as I did, I used a 6 point ground system, (you can do 4) one ground rod as a center point, this is the main ground, then connect with 1/4 inch copper tubing buried 12 to 18 inches down out to 10 to 20 meters to the other ground rods.(in a square or circle as needed, with the main in the center)

We used this all the time for VLF and LF frequency setups, also good for poor ground conductivity problems, the longer the ground radials the better the ground counter poise.

On one setup we had to use 16 radials at 40 meters each for a good ground, as the soil was 90% sand.

On one VLF setup we used a copper grid, 1 meter on center, in a field 16 acres square, that cost a bit in copper. Most AM radio stations use the same thing, they have a very large ground grid.
 
Channel Hopper

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The trouble with copper is the possibility it will not be there next time owing to theft ( it's also near a railway.)

I could always grind off the galvanising at the lower extremes of the poles , the water table has been found to be just under 2m down as well so the poles will be continuously in a damp environment. I expect the field and the need to experiment there will have a life expectancy of no more than five years at best.
 
Terryl

Terryl

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If they (the thieves) don't see you do it, they won't know it's there. Also the deeper the better, can you rent a trenching tool called a "Ditch Witch" makes life a hole lot easier....:)...Get it...Hole....

On some AM radio sites we put some concrete pads over the ground grid, a 4x8 foot concrete pad 4 inches thick needs a back hoe to move it.

In my case I used copper tubing, I drilled some holes in it, and when needed I pump salt brine through it, keeps the old ground system working, it's been there for 14 years.

My ground here at the ranch is very poor as to conductivity, it is loam about 6 to 12 inches or so, then shale, then granite, we also get some mighty big lighting storms, so I need the best ground system as I can get. When I planted some fruit trees I had to dig a big hole with a back hoe, then make up a nice plug of dirt.
 
Channel Hopper

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I have a digging thing, but it is for a four to six inch diameter post, far too large for what is needed on site.


Anyhow I'm going to have a go at home since the garden is large enough for at least a 10 yard gap between the two spikes, in most directions, though I will start with an East/West line (for no reason other than Sweden having its Grimton demonstration in a couple of weeks time).

There are a number of trees though so I will have to experiment with smaller holes for roots and debris from the original house build.

I found this document online that provides the depth and frequencies for various soil consistencies, though it does not mention ideal distance between spikes. I am hoping to go just below 2m with what I have, possibly close enough to the water table.

I've also found a suitable substitute for copper in the shed, a couple of brass curtain rods that come complete with screw terminals. Using these means I don't need to drive anything greater into the ground than 2 inches in diameter, I have plenty of scaffold pole, steel gazebo posts and a lump hammer, plus some hilti style drills that are a yard or so long to cut through anything that gets in the way.

Will take pictures of progress.
 

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Channel Hopper

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Hmmmm, hit gravel at about 24 inches a few metres from the conservatory, will fill hole with water and start on the other one near the back of the garden.
 
Terryl

Terryl

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Hummmm...Gravel, not good.

Are you going to be transmitting on VLF or is this just for reception?

If transmitting then the spacing between ground points should be at least a 1/4 wave, and setup in what ever direction you want most of your signal to go.

VLF frequency's are quite large in the wavelength department as you know, so a ground system that would work well for most VLF signals would be a ground grid, the bigger the better.

If you have any AM radio stations near by, go take a look, they are out in a large field, this is for two reasons, one, in case the tower (or towers, the active antenna it self) comes down, and two, for the ground screen, this screen is usually buried 12 to 16 inches down, on 12x12 inch centers.

This ground screen is usually #8 copper, and is quite an attraction to copper theft as it covers several acres, and is quite costly to replace, this is why most AM stations around here cove them up with concrete pads or large rocks.

I use to hat going out to the transmit site with a reported loss of power, most were just small adgustments, the others were a coroner's call to remove the junky's body after we got it free from the tower and ground grid, supprizing on how many never read the BIG signs saying to not touch the active tower due to the very high voltage.
 
Channel Hopper

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I could just get a 1/4 wave, on the 160m band at a diagonal in the back garden (though I could drive a stake out the front to be certain).

A mental calculation of 10kHz is in the region of 20 miles so unless I rob a bank or win the lottery and move, I doubt it

This is receive only, at my own property, the field mentioned earlier is a testing area for the local ham club (though there are sheep next door :confused ). They would be carrying out transmitting and at a ground distance of about ten miles, I could have a go at picking up the signals.
 
Channel Hopper

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Just looked at the following link (Odd that plain iron isn't mentioned)


I might settle for a couple of aluminium aerial masts that are doing not a lot on the roof. If I put a horizontal rod through them then I can clean off the corrosion by a 90 degree twist each time I pour salt water down the middle.
 
Channel Hopper

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Or bite the bullet for two lengths of copper piping.


To be honest Im not sure the metal really does make much difference in the greater scheme of things, so long as it is securely fastened into the ground with enough contact area that is saline/conductive, other factors (soil permitivity, tree roots, other natural shielding within the topography, localised forms of interference) will have somewhat more impact on the reception.
 
Channel Hopper

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Hit a root at 35 inches, drilled through that, then into ground glass and ceramic at 38.

Hole in soak again but will try another part of the garden tomorrow
 
Terryl

Terryl

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My Satellite Setup
OpenBox X5 on a 1 meter motorized dish.
And now a 10 foot "C" band dish.

Custom built PC
My Location
Deep in the Boonies in the central Sierra Nevada mountains of California.
I could just get a 1/4 wave, on the 160m band at a diagonal in the back garden (though I could drive a stake out the front to be certain).

A mental calculation of 10kHz is in the region of 20 miles so unless I rob a bank or win the lottery and move, I doubt it

This is receive only, at my own property, the field mentioned earlier is a testing area for the local ham club (though there are sheep next door :confused ). They would be carrying out transmitting and at a ground distance of about ten miles, I could have a go at picking up the signals.
The larger the conductors diameter the shorter it would need to be, (also the wider the bandwith of the ground radial) at one site we used 4 foot by 4 foot copper plated steel plates, only had to do 4 acres that way.


Dig the whole place up and lay down some aluminum window screen, then bury it.
 
Terryl

Terryl

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Messages
2,353
My Satellite Setup
OpenBox X5 on a 1 meter motorized dish.
And now a 10 foot "C" band dish.

Custom built PC
My Location
Deep in the Boonies in the central Sierra Nevada mountains of California.
Hit a root at 35 inches, drilled through that, then into ground glass and ceramic at 38.

Hole in soak again but will try another part of the garden tomorrow
Ground glass???? Watch out you don't hit something left over from WII.
 
Channel Hopper

Channel Hopper

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The garden appears to be littered with man made items at different depths.

I dug two more holes yesterday afternoon, the second is underneath the largest tree and is currently at 40" before hitting debris, though it looks like natural stones. Today's rain should soften up the soil for a better chance on Thursday.

I had a look around online for a 2" auger with extensions, or something similar but nobody seems to supply them.

I might get one of these


and build my own addition tubes.
 
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