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  1. #1

    Default Need a grounding solution

    Was fortunate to inherit a nice ham radio spot on top of a small mountain. Just moved in a couple years ago. Brought my tower and antennas etc with me. Really excited to be out in the woods miles from civilization on a nice high property.

    BUT I can NOT find get a good spot for a ground rod. The bottom 2 acres of my property has a house surrounded on all four sides with the lawn and forest, and the back three acres are dense forest.

    No matter WHERE I probe the ground, I can not get any kind of rod more than about 15 inches into the ground. For 100 feet in any direction from the house there is only a foot or so of soil that is covering the mountain bedrock. It's solid rock everywhere.

    When the house was built in the 60's they worked for 7 days blasting out a big enough hole in mountaintop rock so my Dad could have a full basement. I was there when they did the work. The result was a huge hole with a house foundation sitting in the bottom with only about 3 or 4 feet around the house foundation before it was solid rock. Special footing drains and deep channels were blasted through the bedrock and the footing drains routed the water collected from around the foundation to drain through those channels a few hundred feet from the foundation.

    We used to laugh after they cleaned out the hole saying that Dad now had the makings of a great Olympic sized swimming pool. Heck he could probably just fill it up with water as is. <grin>

    I tested the soil immediately around the perimeter of the foundation. The foundation top is about 18 inches above the soil. I was able to drive a ground rod down in the space between the foundation and the surrounding solid rock but at about 4 feet I hit the bottom of the hole which is of course solid rock.

    So my problem of course is trying to provide a good ground for some kind of antenna structure ideally away from the house. I have my old tower which used to sit on a large concrete pad about 6 x 4 x 4 or more feet deep. But here I don't have anywhere near enough soil to build a solid base for a tower. (was thinking about drilling into the bedrock and putting in some stout anchor bolts to hold down a tower base plate) That's another whole problem.

    But how do I ground the tower or even some kind of tripod mounted mast with only an average of 15 inches of soil ?? I've been told I can drive rods in a angle to get them buried somewhat. But soil depth is so small it would be almost like they would be horizontal. That being said, I've also looked at burying a couple of 8 to 10 foot ground rods in deep horizontal trenches. But they say best depth should be at least 30 inches or so ?? I only have on average 15 that I can find available in any 10 foot lengths anywhere on the 2 acres.

    Any of you guys ever run into a problem like this? Oh and for some reason this area seems to be a lightning magnet ... Lots of huge lightning all around us all the time. Dad used to say maybe the mountain bedrock we are sitting on, has a high iron content? <grin> In any case .. I'm keen to get a good ground system in place .. help

    - Rich WA1TRY

  2. #2

    Join Date
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    FN31id
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    Driving ground rods at an angle, even a steep one, is about all that you can do. And, best not disturb the soil by digging a trench. But, you can only do what you can do. Maybe a few more rods 20' or so apart will help. Think about a single point ground outside of the house and tie to the power company ground. This is all per the NEC tho it is easy to find many ham lightning experts preaching otherwise. There has been a great thread

    In the end, figure out a way to easily disconnect the antenna coax cables and ground the ends.

    Here is the tail end of a grounding thread on the repeater builder forum. Note that the lightning dissapater are smoke and mirrors is one conclusion. And, lightning cannot be eliminated but can only be dissapated. So the idea of a ground loop around your tower with a radials leading off in different directions would be good for your hill top tower. One of the references shows a buried ground mat. Money and time ... that's all!
    -Jeff NE1U

  3. #3

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    Thanks Jeff,

    "Money and time ... that's all" ... Yeah .. at 73 years old living on a small pension and SS, I'm afraid "money and time" are the things I have little control over. <sigh>

    Thanks for the insight and advice. I've amassed a considerable library of ham radio technical publications over the years .. one of them the most recent ARRL publication about Grounding and Bonding was pretty good. And my experience has always been that there are a lot of "smoke and mirrors" solutions out there. Although only a ham since the 70's I've been an avid electronics and radio enthusiast since the 50's when I started doing some SWL dxing and listening to the old time ham bands.

    I'm in the midst of applying some of your ideas .. Have already fashioned an external "box" to the foundation wall facilitating the feed through of various cables and control lines etc. Have the box and all the lines grounded and a 6 foot ground there. Not ideal and will probably try more properly spaced short rods in that area available around the foundation where the soil is about 6ft.

    Still working on burying a #6 or larger ground wire around the house perimeter to the main AC ground which unfortunately is all the way around the house opposite of the panel feed through panel. And sadly to get from from that panel to the house AC ground I'm going to have to tear up (or go around) a ground mounted deck.

    Quick question .. That grounding wire around the house .. does it have to be all buried? I think I can push it under the 20 feet or so of deck above ground. The main AC for the house and it's ground is only a few feet past that deck. I can get a surrounding ground around the perimeter of house buried but can't get past that deck on the side of the house, or the front porch because they are large and built almost directly on the ground. Maybe I can only run the perimeter ground around one side of the house and bring it above ground to snake it under the deck? I wonder about how to handle that perimeter ground as far as routing / buried or not?

    At my old QTH the first thing I did after our new house was built was to install a crank up fold over 40 foot tower. (over 40 years ago) I paid a lot of attention to grounding etc. and always subscribed to what I believed was that a properly grounded tower will not stop a direct lightning strike BUT will reduce that chance greatly by providing a "cone of protection" and bleed off and dissipate the build up of potential so it reduces the chance of a direct strike. In later years I've come to read less and less about that "cone of protection" and modern day so called experts don't discuss it much. (or maybe I'm just reading the wrong stuff ?? <grin>

    I should note that in my 40 years at the old QTH neighbors a few hundred yards from my house had been hit either directly or indirectly by lightning strikes. One guy 3 houses away had TV antenna strapped to his fireplace chimney that was totally destroyed. The chimney and that part of the house was obliterated. Several other homes in my neighborhood over those 40 years had serious lighting damage. I "never had a problem" even though I had the tallest structure in the area (40 foot tower with 15 addition feet of mast and assorted yagi antennas the highest at the top (close to 60 feet up) So I can only go by my real world experience with proper grounding and a good "cone of protection". Or maybe there was some luck involved .. <grin>

    Interesting idea here was to get a ground down as far as possible and then bend it over so the remaining length was buried as far as possible. Maybe better than a fully horizontal buried ground ?

    I'm going to experiment and see how steep of an angle I can drive a few 8 foot rods horizontally at the antenna site.

    Also considering a "patch panel" type of thing on the inside wall of the foundation where I can disconnect or ground the incoming coaxes and rotor lines.

    Anyway, thanks for the ideas .. I'm looking forward to hearing more ...
    Last edited by Rich A; Sat 29th Jun 2019 at 18:25.

  4. #4

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    Also you can bend the rod 90 deg. as far as you can (15” in your case) and bury the rest.

  5. #5

    Default

    Quote Originally Posted by AC5PS View Post
    Also you can bend the rod 90 deg. as far as you can (15 in your case) and bury the rest.
    Thanks for that .. maybe that would be better than a fully horizontal bar .. Getting maybe 20 inches or so as a vertical component might be an advantage and give me an improved ground over just a straight horizontal bar.

    I'm now doing some more "extensive" probing (foot by foot) all over the back area of the yard where I hope to install the antenna support structure. I've got a bunch of those fiberglass 4 foot poles that are used to mark the edges of driveways for snow plowing. They actually can be driven in the ground quite deep if you are careful. After they are down more than about 18 inches, then it gets hard to pull them out but they are working out fine where I can use them as driven probes to "map out" how deep the soil is over a 20 foot or so square area.

    So far .. it's not looking good. Mostly around 12 inches to bedrock with only a couple small areas that are good to about 20 inches within the 20 foot square I'm testing so far. Am now thinking about possibly moving the antenna site back into the 3 acres of forest behind my back yard. It's just a little lower (by maybe 10 feet) than where my house is which is the highest point for a mile or more in all directions.

    I may find the soil depth there to be greater. But that would move the "antenna farm area" about 700 feet from the house. Hard line ?? Already looking at problems involving Rotor cable and coax length. I'll have to trek out into the woods when the weather clears and see what the soil depth looks like there. My dream ham radio spot is becoming a real nightmare.

  6. #6

    Join Date
    Nov 2016
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    FN31id
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    Hi Rich, my property has a shelf 4' down and I used a hammer drill. New building up the street had a jack hammer on a tractor to chip out the rock for a partial basement. I hammered the 8' rods down as far as possible & cut off. That cutting was not easy with a reciprocating saw. The rest were knocked in at as steep of an angle that would bury the entire rod and was so much easier.

    Part of me says, find a local ham club and be up front with your ulterior motives. LOL I am from The Middle of No Where, Illinois and CT has more clubs than the Central IL has hams. So investigate what you can tap into locally. If any of the clubs meet on Saturday AMs, bring donuts. Don't ask, just bring 'em. Learn how to schmooze. People will appreciate it and laugh.
    -Jeff NE1U

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