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Author Topic: Ground in shallow soil?  (Read 1572 times)
KD4KSX
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Posts: 5




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« on: March 15, 2002, 09:52:40 AM »

Hi,all.

I am trying to set up a decent ground for my HF station. (/ae, yay!) I can't drive the classic 8' stake straight down, because my lot is 8-18 inches of soil on a solid 'pan' of limestone bedrock.

I can run a short gnd lead out of the shack, but the earth area is between the driveway and the house (about 3' wide strip.)

I _really_ don't want to dig up the driveway for a radial system.

Would 2 8' stakes, driven in horizontally at a shallow angle (-5 to -10 deg, as deep as I can get them), connected at center to station gnd, work well as a ground in this situation? (picture a shallow inverted-vee antenna underground...)

Other suggestions/cautions are welcome...
Also, should I bond this to the gnd buss in my electrical service box, or just to my equipment chassis?
Tnx es 73
--Bob
KD4KSX/AE
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WB2WIK
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Posts: 20565




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« Reply #1 on: March 15, 2002, 06:54:08 PM »

You didn't say why you want a ground.  In many (most) cases, there's no grounding requirement for a safe, efficient ham station.  Unless you've identified an actual need, I'd forget about it.

However, you might have a look to see where the electric utility company grounded your service panel.  Possibly they were successful in driving in the 8' ground rod required by code in most places, and you can attach to that!

I know some places I've lived the ground was so solid that to install an 8' ground rod I had to rent an 8' drill auger and very large electric drill, and literally (not to mention slowly and carefully) drill 8' into the ground in order to make way for the rod.  I've seen utility companies do this, too.

73 de Steve, WB2WIK/6
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KD4KSX
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Posts: 5




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« Reply #2 on: March 16, 2002, 10:56:10 AM »

Steve,
Thanks for the reply.

I think my ground is inadequate because I can't get my antenna to tune properly (g5rv/2), I'm creating TVI, and when I touch the chassis of my tuner, the signal I receive changes level (touchy). I haven't gotten bitten by rf yet, but I'll wager it's just a matter of time...

Attaching to the power co gnd would require about a 20 ft run. Too long?

As far as the original question, would a shallow horizontal gnd work ok?

Tnx es 73,
--Bob Spaulding
KD4KSX/AE
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KL7IPV
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Posts: 984




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« Reply #3 on: March 16, 2002, 11:53:00 PM »

I am not sure even running 2 foot stakes would help if the soil is actually rock just 2 feet away. You might consider using a 4"X4" grid like is used in making a concrete slab. Place the grid below the surface level as deep as you can in the space that you can. You can either drive your own heavy ground rods near the edges of the grid or tie the grid to the power ground. The only problem I really have with what you have said is the ground potential. It would seem to me the ground that you have available is no better or worse than the power company used. So REALLY, how good is theirs? I would call the power company and ask them to come out and measure the grounds they are using. You may also want to measure the resistance between where your radio is located and the power ground for both continuity and low resistance. If they have a really good ground and the resistance between it and your radio is good, then I would wonder why you are having such problems as you state. Have you checked ALL the connections between the station ground and all the equipment for tightness? Have you got all the connection points clean and not acting like rectifiers to generate the RF troubles you're having? Are your inter-equipment ground wires not a length that make them act as radiators on the frequencies you use? Is the TVI on a TV that uses rabbit ear antennas, outside antennas or cable? Can you cure the TVI with high pass filtering? I think you have your work cut out for you . Good luck. I would be interested to know what the power company measured to their ground and how deep their ground rod is to accomplish it.
73
Frank
KL7IPV
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KD4KSX
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Posts: 5




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« Reply #4 on: March 17, 2002, 10:30:08 AM »

Frank,
Yes, the building gnd is questionable. Oddly enough, I work for the power co (computer geek, not a gnd wizard Smiley ) I think I'll wander down to the Test Section and have them check the situation out.

I drove one 8 ft rod horizontally, as deep as I could get it, along the top of the bedrock (I tried vertical first, got _almost_ 1 ft down before hitting bedrock) and ran an awg 6 lead into the station to a proper ground bus (also part of the problem), then solidly tied the equipment to the buss, and got a significant improvement in reception and noise.

I haven't had time to check out tx/tvi yet, but I'll post results as they come in.

Tnx es 73,
--Bob Spaulding
KD4KSX/AE
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WB9WHE
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Posts: 56




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« Reply #5 on: March 18, 2002, 05:03:40 PM »

Getting a good ground in shallow soil is not as hard as pople would have you believe.

First, measure the available space and depth. Suppose you have a 3' wide X 10' long by 2' deep space outside the window. Go to Home Depot, Loew's or your hardware store. Look at the shiny copper colored water pipe.  Buy about 25 feet of 3/4" AND 4 elbows, ONE "T" connector and ONE end cap.

CAREFULLY dig a rectangular 3" wide, 9' X 2'  long trench (a 9' x 2' rectangle with a 3" wide trench for the pipe), 6-18" deep, keeping the pipe away from all buried structures (do you know where the gas, electric, water, sewer, phone and CATV lines are?? DO not put this ground near any of these, especially anything electrical or conductive) so that you have about 20-22' of linear pipe shaped in a rectangle 6-18" deep. Insert the "T" close to the house, and run the pipe up, from the rectangle, to the wire (be sure to use at least a #4) and connect the pipe to the wire with 2 pipe clamps, don't forget a drip loop. Solder all joints. Place the endcap on the vertical pipe that connects with the station ground.

Burry the pipe. Stomp on the earth. Totally saturate the area with the hose every day for the next 3-4 days so that the earth washes back into the trench, comming in good contact with the pipe.

Now, you have both a DC and RF ground. Be sure that nobody ever uses the area for anything like a garden!!!!!!!!!!

Then, E mail me and let me know how it works!
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K9KJM
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Posts: 2416




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« Reply #6 on: May 17, 2002, 01:34:44 AM »

The suggestion by WB9WHE to use copper pipe is a good one. I have even gone so far as to "dope" the soil around such a buried pipe, (or drill lots of little holes in the pipe and fill it) with copper sulphate, rock salt or something similar........  Depending upon how close this would be to the surface, this might not be good for plants in the area........    BOND ALL grounds/ systems together!   Rather than lay 8 foot ground rods at an angle, just cut them into shorter lengths...... Rule of thumb is twice the distace apart as depth (2 foot deep rods should be spaced about 4 feet apart, etc) Bond all this stuff together. The more copper buried, the better! Copper "strap" is also a great material to use. It can be sometimes bought for a reasonable price from upscale roofers, who use it for roof flashing.......    2" to 6" wide is nice..... Use silver solder for any underground joints. The stuff used in the refridgeration trade....       Good Luck!
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K5OO
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Posts: 7




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« Reply #7 on: September 25, 2002, 01:20:39 PM »

Run radials of wire. Makes better RF and DC ground that one rod anyway. Currents will divide and coverage will exponentually multiply at rf vs. one conductor. The idea is to make a "screen" rather than a wire. Bury it in as much soil as you can ,run as many as you can, run as far as you can. You've done about all you could after this. A rod in a bedrock it not much ground anyway.
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