Grounding Help
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jim202
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Grounding is an art all by itself. If you ask 10 people how to do it, you will probably end up with about 15 answers. How many of them are correct will depend on what they said.
Having said that, there is a finite science to grounding. The starting place will depend on what the soil is like where you live. If you have sandy soil, your best bet is to move to another location. But if your stuck there, expect to have to drive several real long ground rods into the soil.
Now here we start getting into the science of the grounding rods. There is a finite amount of reaction around each ground rod. It will depend on how long the ground rod is as to how much influence there is between the ground rod and the soil. The point to remember is the cone of influence around the ground rod radius is equal to it's length. In other words, if you have an 8 foot ground rod, the cone will extend out 8 feet from the rod center point. So in order to get the max effect, we don't want to place the rods so close that this cone of influence runs into the next ground rod's cone of influence. So the best spacing is to plant the rods no closer than trice their length. This way you will be able to obtain the lowest resistance of each ground rod.
The next point to keep in mind is that you want the lowest resistance as you can get for the connection between the rod and the wire you use to connect them together. In order to get this and not have any corrosion take place to lower the effectiveness of your grounding, you will need to make the connection with an exothermic weld or use a high compression joint. The wire size will depend on your pocket book, but the use of some silver plated number 2 solid wire is a good starting point.
You might want to check with your homeowners insurance company and see what kind of guidelines they have on grounding an antenna structure. The national electrical code also has a nice section on grounding that you should review.
Now that you have opened up the proverbial can of worms on your simple quest for information on how to ground your simple antenna and radio. have a good day.c
Hope I haven't turned you away from the hobby, but there is more to grounding than the average person has ever thought about it. I have spent some 45 plus years in the public safety communications area and have been building cellular sites for about 18 of those years. Grounding does not come easy or cheap. It is an education all it's own.
ka5lqj
Member
jim202 jim202
Member
Quote: "So the best spacing is to plant the rods no closer than trice their length. This way you will be able to obtain the lowest resistance of each ground rod."
Hi Jim,
Not to poke fun, but I know what twice is...2 and thrice is 3, what's "trice", 2½?
Good information though.
73,
Don/KA5LQJ
Member
Quote: "So the best spacing is to plant the rods no closer than trice their length. This way you will be able to obtain the lowest resistance of each ground rod."
Hi Jim,
Not to poke fun, but I know what twice is...2 and thrice is 3, what's "trice", 2½?
Good information though.
73,
Don/KA5LQJ
ka5lqj
Member
Now,
I've found two other effective ways of grounding as well. I use a minimum of bare # 4 solid. Make the run from the radio to the outside and the ground rod as minimal as possible. I take a Coke bottle, 20 oz, fill it with tap water and start the hole with the rod. After a few good jabs in the ground to open it up, I remove the rod and pour enough water to fill the hole, and replace the rod, jabbing again deeper. When it starts to bog down, I remove the rod and fill the hole with water. I do this until the rod is about six inches exposed, the rest in the ground. I put on the wire clamp device and hook the # 4 in and tighten down REAL tight.
After that is completed, I dig a 4 inch wide, 12 inch deep ring around the ground rod about 12 inches away from the rod, emptying the ditch of soil. I fill it with Rock (ice cream) salt and wet the trench down good. I got out everyday and refill the trench with water. Eventually, the rock salt starts to melt
and in combination with the water, lowers the soil resistivity, but, this may kill your grass or flowers near the rod. So I came up with an alternate plan.
# 2. > Do all of the above, except the trench. Take a 2nd copper-clad rod, and drive it in, but instead, put it completely out. Now, take a piece of 3/8" pvc, cap one end and drill 1/8th" holes from the bottom up, 5 feet. Fill with rock salt and insert the pvc in the 2 made hole. Now fill it with water and when it goes down, refill it. If you could fit a ½" or larger pvc with holes, you could add a screw-on water hose connection, hook up the hose and just let it "drip" for a long time. ;-)
I've found two other effective ways of grounding as well. I use a minimum of bare # 4 solid. Make the run from the radio to the outside and the ground rod as minimal as possible. I take a Coke bottle, 20 oz, fill it with tap water and start the hole with the rod. After a few good jabs in the ground to open it up, I remove the rod and pour enough water to fill the hole, and replace the rod, jabbing again deeper. When it starts to bog down, I remove the rod and fill the hole with water. I do this until the rod is about six inches exposed, the rest in the ground. I put on the wire clamp device and hook the # 4 in and tighten down REAL tight.
After that is completed, I dig a 4 inch wide, 12 inch deep ring around the ground rod about 12 inches away from the rod, emptying the ditch of soil. I fill it with Rock (ice cream) salt and wet the trench down good. I got out everyday and refill the trench with water. Eventually, the rock salt starts to melt
and in combination with the water, lowers the soil resistivity, but, this may kill your grass or flowers near the rod. So I came up with an alternate plan.
# 2. > Do all of the above, except the trench. Take a 2nd copper-clad rod, and drive it in, but instead, put it completely out. Now, take a piece of 3/8" pvc, cap one end and drill 1/8th" holes from the bottom up, 5 feet. Fill with rock salt and insert the pvc in the 2 made hole. Now fill it with water and when it goes down, refill it. If you could fit a ½" or larger pvc with holes, you could add a screw-on water hose connection, hook up the hose and just let it "drip" for a long time. ;-)
bitpicker1
Member
Grounding Opinions Wanted
Hi all,
I'm working on my technician license as I type. While doing that I'm trying to plan my installation based on a couple prerequisites. Antenna locations are already preset. It's a long story so I won't go into that.
Basically, one location is on the peak of the house at the west end. The other is just above the gutter on the east end.
The station will be in the basement near the center of the home.
I've read a lot about grounding and like it was earlier mentioned, everyone has "their" way. So I'll give you my plans an see what you have to say.
My soil is clay.
1) An 8' grounding rod will be placed at the base of each antenna.
2) A grounding rod will be place outside of the basement window near where the equipment will be. (10' - 15' run)
3) I'm planning on using #8 solid copper wire.
4) This is what I'm not too sure about. I'm planning on linking all three rods together so that everything is on the same grounding system.
All comments and suggestions will be appreciated.
Thanks for your help.
Ken
Hi all,
I'm working on my technician license as I type. While doing that I'm trying to plan my installation based on a couple prerequisites. Antenna locations are already preset. It's a long story so I won't go into that.
Basically, one location is on the peak of the house at the west end. The other is just above the gutter on the east end.
The station will be in the basement near the center of the home.
I've read a lot about grounding and like it was earlier mentioned, everyone has "their" way. So I'll give you my plans an see what you have to say.
My soil is clay.
1) An 8' grounding rod will be placed at the base of each antenna.
2) A grounding rod will be place outside of the basement window near where the equipment will be. (10' - 15' run)
3) I'm planning on using #8 solid copper wire.
4) This is what I'm not too sure about. I'm planning on linking all three rods together so that everything is on the same grounding system.
All comments and suggestions will be appreciated.
Thanks for your help.
Ken
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ka5lqj
Member
Ken,
Sounds like a "plan" to me.
It's too bad we don't have a machine that would dig an 8 foot deep, 2" wide trench. You could drive
your ground rods, then cut the trench in at least 4 directions, 8' long and tie copper pipes to the
grounding rod. This should give you more of a "grounding grid".
OR, you could dig out an one foot deep hole, 1/4 wavelength out and lay copper wire for a "grid".
There are all sorts of possibilities
Sounds like a "plan" to me.
It's too bad we don't have a machine that would dig an 8 foot deep, 2" wide trench. You could drive
your ground rods, then cut the trench in at least 4 directions, 8' long and tie copper pipes to the
grounding rod. This should give you more of a "grounding grid".
OR, you could dig out an one foot deep hole, 1/4 wavelength out and lay copper wire for a "grid".
There are all sorts of possibilities
W2PMX
Member
To answer the OP's question, any expert will tell you that all grounds should meet at one common point. (It's called unipotential - everything at the same voltage.) If you can keep everything at the same voltage, whether that voltage is ground or 10 million volts above ground is irrelevant. Ever see birds sitting on a 316KV line? The entire bird is 316KV above ground, so there's no current flowing through it. Voltage isn't dangerous, the current it causes to flow is, and if everything is at the same. voltage, no current flows.
Ok.. Ken,
Take a look at what Jim wrote above.. he knows what he is talking about.
As far as what you have shown, the buried wire should be bare. Typically, 4/0 is used for grounding and 2/0 is used for stub ups, but that is massive overkill for a home system. In addition, all connections are cad welded.. way too expensive for the home system. Ground rods are margnially effective due to their small diameter. Remember, more copper in contract with mother earth, better connection. I won't even begin to discuss modeling soil layers and their effect.
With all that said, it is important for you to understand something else that is far more important than anything else. Once this ground system is installed, you should to sure to make ONE connection from the incoming utility ground to your newly installed house ground. In addition, make ONE connection from each component to the ground bus and then one connection to the ground system. This will eliminate circulating ground currents. The really big one, though, is to understand that single connection between your incoming utility and the ground system. If you don't do that, there is a very strong possibility that a nearby lightning strike will take out a lot of electrical devices, or worse. Remember, that lightning, flowing thru earth is a current and the earth is a resistance, creating a voltage drop. If this happens across the two separate ground points, a VERY high voltage can be developed. Single point grounding is very important to a successful installation. I recommend FIPS-94 as a reference and the IEEE green book.
Bob
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