Antenna grounding

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KC0QNB

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Ok guys I did a quick search and found three links I felt a need to share, I will just post them here, as far as further technical, data don't ask me I am not anywhere near an expert on the subject.
http://www.sgcworld.com/Publications/Articles/lightning1.pdf
http://sgcworld.com/Publications/Articles/lightning2.pdf
http://sgcworld.com/Publications/Articles/lightning3.pdf
I have also seen reference to National Electric Code (NEC) 810
One more link, I linked this from mikeholt.com
http://www.mikeholt.com/newsletters.php?action=display&letterID=220
scroll down the page and click the link that says click here, or the image of article 810.
I also encourage interested people to take a look at http://www.polyphaser.com
and see if they offer downloadable data concerning this subject.
I have done this much the rest is up to you. Please post anything you find here.
to the moderators, I haven't found a sticky or wiki on this subject...yet perhaps one should be made. If there is a sticky wiki, (sorry) let me know.
73 Ryan
 

cberk01964

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I'm getting ready to put up a Diamond discone. I concerned about a ground. I'm using a tripod mount, so running the ground wire straight down is not a option. I was fiquring to follow down the side of the roof with the least amount of arch/turn, then down the side and to the pole. Does this sound acceptible. What grounding system are others using?
 

KC0QNB

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Gothenburg, NE
I'm getting ready to put up a Diamond discone. I concerned about a ground. I'm using a tripod mount, so running the ground wire straight down is not a option. I was fiquring to follow down the side of the roof with the least amount of arch/turn, then down the side and to the pole. Does this sound acceptible. What grounding system are others using?
Like I stated I am not even close to being an expert, of course a straight line would be better, I have mine coming from the center of the roof and by the most direct route, straight down the slope of the roof, over the edge between the gutter and the eave then down to the ground rod, I used #6 thhn (insulated wire) because that is what I had on hand, and an 8 foot copper coated steel ground rod (standard variety). Be sure you have the area located for underground surprises, before you drive the ground rod it that is your plan. There is some good additional info here. click the free tech pubs tab
 
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jon_k

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I think the best question is this. My antenna is not mounted where the electrical service comes in to the house.

I'd like to bond all of this.

Where can I:

A) Find a strap and run kit for the 17 foot mounted antenna pole/mast.
B) Find a kit that can be run underground and/or along the ground to the electrical service to bond the ground for the house to the antenna? (It's about 50 feet.)
 

KC0QNB

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I think the best question is this. My antenna is not mounted where the electrical service comes in to the house.

I'd like to bond all of this.

Where can I:

A) Find a strap and run kit for the 17 foot mounted antenna pole/mast.
B) Find a kit that can be run underground and/or along the ground to the electrical service to bond the ground for the house to the antenna? (It's about 50 feet.)
You got a shovel and a lot of cash for copper wire? your best bet is a separate ground rod for the antenna, for now then when you can run a wire around the foundation and tie the two together, I am guessing here, read the stuff I posted in my original post and the "here" link in my 2nd previous post, I am sure all the answers are there somewhere.
 

jon_k

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You got a shovel and a lot of cash for copper wire? your best bet is a separate ground rod for the antenna, for now then when you can run a wire around the foundation and tie the two together, I am guessing here, read the stuff I posted in my original post and the "here" link in my 2nd previous post, I am sure all the answers are there somewhere.
I'll read the links.

Problem with two separate rods is due to things I've read elsewhere.

You have a ground rod for the antenna -- and a ground rod for your electrical box, and you will end up having varying voltage potential between rods. Note your radios become the common link via COAX ground to the HOUSE ground.

A lightning strike comes, and creates varying degrees of potential. Chances are, either the antenna will want to equal out at the service panel -- or the service panel will want to equal out with antenna ground. Either way, the current will be moving through your radio!

Sure, won't burn your house down but will destroy everything you've got. This happens because the current grounds in ripples in the ground like radio waves. The ground location of service panel may have a 1,000,000 volt difference potential than the antenna site when hit by lightning. The current is going to go to the potential area.

This can be made worse if soil resistance differs between two points. The voltage will always want to travel upline to the ground rod in least-resistant soil. Bonded grounds based on my understanding are the most important factor. Without them you might as well not even ground anything.
 

KC0QNB

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Good point, I posted the links so everyone could read them, they have to decide what is the best thing to do. Here is another link Jon, if your information is from other sources, than mine post links on this thread. Ok here is another link I just found there is a paragraph in here that states one should never consider using a non-conductive structure for antenna support? I knew that using pvc pipe for a mast was a bad idea now I can back up my position.
 
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jim202

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The best information provided here is the tail end of the Mike Holt link on the NEC 810
grounding information. The other 3 links have useful information, with again the best
is in the third link.

There was one statement given by Ron in his articles that bothers me. He states to bury
the ground wires only at a shallow depth. I would take offense to this as it is contrary
to a number of sources including the NEC articles. The NEC states to place the wires
at a depth of 30 inches or below the frost line if it greater. The reason for this is the
step potential that can develop from a buried wire. You see and hear all the time to
not stand under a tree in an electrical storm. If the tree gets struck, it will have a high
voltage induced into to the soil. As you get further away from the tree, this voltage is
reduced. This is called the step potential.

If you dig far enough into lightning strikes, you will find articles on how some cows in
a field were killed and some cows survived a strike to a tree they were around. What
has been found is that the cows that were facing away or toward the tree were killed.
The cows that were facing at right angles to the tree survived. What the research
has found was the cows that were facing towards or away from the tree, had their feet
spaced further apart to get a higher step voltage induced into their bodies. The ones
that were facing at a right angle to the tree had their feet at the same step potential
and survived.

Bottom line is to place the ground wire at a depth to reduce the step potential to
people that may be walking in the vicinity of the ground wire and a strike on the
protected structure takes place. This is also why in the NEC that it states to
ground both metal fence posts on both sides of a gate. To also run two ground
wires parallel to the fence gate opening between the post and have them spaced
about 18 inches away from both sides of the fence. This way the soil where you
stand to open the gate will be at the same potential as the gate and fence.

Tying the tower, antenna support or what ever you want to call it to the electrical
ground of the power service entrance is also trying to place both of these items
at the same potential. It is all about personal safety and electricity.

Having spent the last 15 years building cellular communication sites, you get a good
understanding for a grounding system. No one item by itself will do the job. It
takes putting all the items together to provide a good protection. This means
tying the electrical power, the telephone cables, the antenna cables, the tower,
the antenna cable ice bridge or cable tray, the shelter and the fence around it
all together in a commonly bonded system. Surge protectors on the electrical
power, telephone cables and the antenna cables are all part of this system.
If done correctly, you should be able to take a direct hit on the tower and your
communications system will stay playing. I have seen this happen a number
of times where a tower took a direct hit from lightning while I was there.
The tower steams a little in the rain, but the cell calls still keep connected.

Jim



Ok guys I did a quick search and found three links I felt a need to share, I will just post them here, as far as further technical, data don't ask me I am not anywhere near an expert on the subject.
http://www.sgcworld.com/Publications/Articles/lightning1.pdf
http://sgcworld.com/Publications/Articles/lightning2.pdf
http://sgcworld.com/Publications/Articles/lightning3.pdf
I have also seen reference to National Electric Code (NEC) 810
One more link, I linked this from mikeholt.com
http://www.mikeholt.com/newsletters.php?action=display&letterID=220
scroll down the page and click the link that says click here, or the image of article 810.
I also encourage interested people to take a look at http://www.polyphaser.com
and see if they offer downloadable data concerning this subject.
I have done this much the rest is up to you. Please post anything you find here.
to the moderators, I haven't found a sticky or wiki on this subject...yet perhaps one should be made. If there is a sticky wiki, (sorry) let me know.
73 Ryan
 

KC0QNB

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Location
Gothenburg, NE
Thanks Jim, you are right the code requires current carrying conductors to be buries at least 30" below the surface, the ground bonding wire is not a current carrying conductor, technically, I will look into it further, or I guess you can, find the location in the code or other source where it references what you stated, if you can find it, post a link here in this thread, I started this thread for this very purpose, to get input from other folks that need the info.
tnx Ryan
Edit: I did a quick check on the net and found a few links that may be of interest, the first link I clicked was from lightning Mike, I browsed the article briefly, I will re read it later.
 
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OceanaRadio

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Virginia Beach, VA
Some notes on grounds, burying, bonding, and roof attachments...

Desert locations have no effective earth grounding unless they drill to the water-table, and in very few cases is that specified or required. Bonding and surge-protection devices alone can protect a structure and it's equipment, however there are special designs there that may not be of interest here.

Burying is specified below frost-level for an important reason: when soil freezes it contracts into honeycomb shapes and dries to a resistance that renders it useless for dissipation of lightning energy.

Before someone asks how much lightning occurs in Canada in the wintertime (none?), understand that once a soil layer has been subject to freezing, it tends to remain honey-combed and dry well into the summer thunderstorm season. 30" is a rather abitrary depth that doesn't cover all frost-levels, but does reach into a layer of soil that usually retains more moisture than a few inches sub-surface. It is not specified anywhere I have noticed to bury a lightning protection bonding conductor at 30". Sub-surface so it is not a trip-hazard should be a consideration, and with ground rods along its length (if greater than 20'). If a bonding conductor is short and not a trip-hazard, there is no reason to bury it.

Now a Ground ring for instance has in its design a current-disspating feature as well as the current-equalization achieved by the continuous bonding. When we say "equi-potential" is the goal of good bonding practices this is true, but this only works at DC-voltages. Lightning is so rapid that it develops RF energy into the hundreds of megahertz. To these frequencies, any conductor over about 20' in length is felt as an open circuit and can effectively dissapear as the primary transmission line. However when the bonding leg includes deep-buried ground rods at least every 20' along it's length, then equalization currents can both disspiate and provide some equi-potential benefit to the entire system. In parts of Florida there may be no freeze issues, however the soil (even sand) has a higher moisture content and therefore lower resistance when at least 8' deep ground rods are used. Chemical-treatment of the soil around ground rods, locating a ground rod next to the condensate-drain of AC equipment, and other locations with always-moist soil are examples of good planning for an effective ground system. When proper bonding is applied to a good ground system, and proper surge protection is provided for the electrical systems and equipment in a structure, a good lightning protection system is achieved.

Now, to the member who wants to get his roof-mounted antenna mast-ground down to earth in the shortest direction, that may not be the most efficient. Even a single roof-mast should have a bonding conductor that runs in opposite directions along the entire roof ridge-line, then drops straight down to at least one 8' ground rod at both ends of the structure. Any antenna masts along the middle of the roof would bond to this roof-ridge bonding conductor. The more masts you add, the more lightning air-terminals you have just added as protection to the entire structure.

The 45-degree "cone of protection" provided by an air terminal (lightning rod, or mast in this case) has a caveat: Beyond about 20' in any direction, any object or sharp-corner of a roof can be subject to a side-flash from lightning even if within the 45-degree 'shade' of the air terminal. Beyond about 50' in any direction, any object or sharp corner can be attached directly by one of the return-strokes of lighting or a side-flash from other point of attachment. If your entire roof-ridge has a bonding conductor traversing it (even without other masts or air terminals), there is still limited protection from damage resulting from an attachment or side-flash elsewhere along the roof.

If a home is not subject to a direct-attachment from lightning, and only a single mast at the edge of a roof is used, perhaps a single down-conductor to a single ground rod is sufficient. This would amount to protection from a low-energy side-flash for instance. However since you will never have enough antennas no matter how many you put up, they may as well help protect your home too ;-)

Jack
 

KC0QNB

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Thanks Jack, I never heard of the roof ridge line conductor, but it seems reasonable, and is worth considering, I have a question however, how does one dissipate the potential for a "side-flash"? If you look an any roof and there are "air terminals" (masts and antennas) and the mast is mounted away from the edges and you add a ground rod at either end, there will be a sharp turn of conductor actually, at least two the one coming down from the mast then going horizontally along the ridge line then another sharp turn back down to the ground rod. From what I have read so far in my research it has been stated many times to avoid sharp turns in the lightning dissipating conductor, how do we over come any sharp corners?
 

jim202

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New Orleans region
You don't overcome sharp corners. You prevent them. If you take a look at most of the older
farm houses that were built back in the early 1900's, most of them had a lightning protection
system installed. It used a large braided cable about half an inch wide, lightning rods spaced
across the roof and one at each peak or tall part of the building. The people that installed
these systems had to have some sort of skill in knowing what they were doing.

Having grown up on a farm in central New Hampshire, I can remember many a storm. I
would sit in the room away from the window and watch the activity of the storm. Many
a time I have seen a bolt of lightning hit one of the rods on the top of the barn. The
following day we kids would climb up on the roof and take a look at where the bolt
had hit. The rods up there had many a melt spot in the copper where they had
sustained taking a strike.

Don't think I have ever seen a fire after a storm in one of the structures that had a
lightning protection system installed. Spent about 40 years on the fire departments
in a number of towns around the country over the years. Still stand on my words about
no building has had a fire in them that was protected. Seen a number of trees near
by that became splinters.

One more example of grounding and I will clam up. While working in the New Orleans
area for a cellular company, they had a 500 foot tower that kept having damage done
to some of the paging gear there. We dug up the grounding system to make sure it
was installed correctly. All the wires were where they should be, all the outside
connections were exothermically welded. The ground rods were spaced out at twice
their length. In general, couldn't find any reason for the damage that kept happening.
We did add a few more ground rods and added some more bonding. But in general,
the ground ring around the tower and the ring around the equipment shelter were
all by the book.

In desperation, we dug 2 trenches away from the tower in different directions. Added
new ground wire and more ground rods. After that, we never had another bit of
damage. The soil there was wet clay. You could almost get running water if you dug
more than 8 or 10 inches below the surface. The only thing that seems to have been
going on, was the soil just couldn't dissipate the lightning charge enough with only the
ground rings around the tower and the shelter. the added radials solved the problem.

As one of the instructors at General Electric always said when he talked about grounding
and lightning protection, "How do you know when you have installed enough of a
grounding system, when you can't afford any more". Guess he was right. You spend
your money repairing equipment, or you spend it on the copper that goes in the ground
system. Your pocket book will tell you when you have done it right.

Jim



Thanks Jack, I never heard of the roof ridge line conductor, but it seems reasonable, and is worth considering, I have a question however, how does one dissipate the potential for a "side-flash"? If you look an any roof and there are "air terminals" (masts and antennas) and the mast is mounted away from the edges and you add a ground rod at either end, there will be a sharp turn of conductor actually, at least two the one coming down from the mast then going horizontally along the ridge line then another sharp turn back down to the ground rod. From what I have read so far in my research it has been stated many times to avoid sharp turns in the lightning dissipating conductor, how do we over come any sharp corners?
 

KC0QNB

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Joined
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Messages
730
Location
Gothenburg, NE
You don't overcome sharp corners. You prevent them. If you take a look at most of the older
farm houses that were built back in the early 1900's, most of them had a lightning protection
system installed. It used a large braided cable about half an inch wide, lightning rods spaced
across the roof and one at each peak or tall part of the building. The people that installed
these systems had to have some sort of skill in knowing what they were doing.

Having grown up on a farm in central New Hampshire, I can remember many a storm. I
would sit in the room away from the window and watch the activity of the storm. Many
a time I have seen a bolt of lightning hit one of the rods on the top of the barn. The
following day we kids would climb up on the roof and take a look at where the bolt
had hit. The rods up there had many a melt spot in the copper where they had
sustained taking a strike.

Don't think I have ever seen a fire after a storm in one of the structures that had a
lightning protection system installed. Spent about 40 years on the fire departments
in a number of towns around the country over the years. Still stand on my words about
no building has had a fire in them that was protected. Seen a number of trees near
by that became splinters.

One more example of grounding and I will clam up. While working in the New Orleans
area for a cellular company, they had a 500 foot tower that kept having damage done
to some of the paging gear there. We dug up the grounding system to make sure it
was installed correctly. All the wires were where they should be, all the outside
connections were exothermically welded. The ground rods were spaced out at twice
their length. In general, couldn't find any reason for the damage that kept happening.
We did add a few more ground rods and added some more bonding. But in general,
the ground ring around the tower and the ring around the equipment shelter were
all by the book.

In desperation, we dug 2 trenches away from the tower in different directions. Added
new ground wire and more ground rods. After that, we never had another bit of
damage. The soil there was wet clay. You could almost get running water if you dug
more than 8 or 10 inches below the surface. The only thing that seems to have been
going on, was the soil just couldn't dissipate the lightning charge enough with only the
ground rings around the tower and the shelter. the added radials solved the problem.

As one of the instructors at General Electric always said when he talked about grounding
and lightning protection, "How do you know when you have installed enough of a
grounding system, when you can't afford any more". Guess he was right. You spend
your money repairing equipment, or you spend it on the copper that goes in the ground
system. Your pocket book will tell you when you have done it right.

Jim
Ok Jim I have a house with vertical walls, and no eaves to speak of, 2-3" tops the roof ridge runs north-south, so in order to avoid sharp corners on my ground wire(s) would I loop the wire out say, a foot beyond the roof line, then gradually return to the side wall in kind of a question-mark sort of shape with a say 1 foot radius, then drop it straight so the ground rod? , oops can't do that, the ground rod is about 10 inches from the foundation, so then I would have to sweep it out and make the connection to the ground rod? Where this particular ground rod is there will not be a trip hazard, unless my wife is working in her flower bed, but I will make her aware that it is there.

If I run a ridge line conductor as Jack suggested, the one ground rod would be no problem (it would be in a flower bed), on the south side however there is a sidewalk that is up against the foundation, I guess then the thing to do would be knock a hole in the sidewalk, and drive the south GR there up against the foundation, thereby avoiding the trip hazard issue.
 
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Ok, so in reading I have a little bit of confusion that I need to have clarified.

I have a single 10' mast mounted to the side of my house, extends probably 5-7' above the edge of the roof. I have an inadequate 16ga ground wire runnning from the base of the mast to a single 8' ground rod 1' away from the location where the coax is attached to a ground block and then enters the house. (This ground rod is not electrically bonded to the service ground, which after reading this seems most assuredly bad.)

In order to make this proper, I obviously need to install a much more adequate ground wire. My question is, is it enough for me to sink a series of 8' ground rods into the ground and bond my ground wire to those - 6" or so below the surface, or do I need to sink the ground rods and the ground wire itself below the frost line?

Also, since this is roughly 10' from the service entrance, is it acceptable for me to use a series of 8' ground rods to bond the service ground to the ground for my antenna mast?

And finally, where the heck do I find lightning protection for coax with F-connectors on it? ;)
 

KC0QNB

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Messages
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Location
Gothenburg, NE
Again I am no expert, but the bonding cable/wire doesn't need to be underground, not required, unless it may be a trip hazard a series of 8 foot ground rods between the two, main ground rods antenna and service, isn't going to hurt but aren't necessary. From what I understand as long as the antenna ground rod and service ground are bonded, to keep potentials the same a basic system will suffice, if there is anything else that needs done I will have to yield to someone else.
 

OceanaRadio

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Messages
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Location
Virginia Beach, VA
Ok, so in reading I have a little bit of confusion that I need to have clarified.

I have a single 10' mast mounted to the side of my house, extends probably 5-7' above the edge of the roof. I have an inadequate 16ga ground wire runnning from the base of the mast to a single 8' ground rod 1' away from the location where the coax is attached to a ground block and then enters the house. (This ground rod is not electrically bonded to the service ground, which after reading this seems most assuredly bad.)

In order to make this proper, I obviously need to install a much more adequate ground wire. My question is, is it enough for me to sink a series of 8' ground rods into the ground and bond my ground wire to those - 6" or so below the surface, or do I need to sink the ground rods and the ground wire itself below the frost line?

Also, since this is roughly 10' from the service entrance, is it acceptable for me to use a series of 8' ground rods to bond the service ground to the ground for my antenna mast?

And finally, where the heck do I find lightning protection for coax with F-connectors on it? ;)
In your case with only 10' distance between the mast ground rod and the home's AC-entrance ground rod, they are already too close to have much added value (the sum of the depth of both rod's is the minimum recommended horizontal separation, closer doesn't hurt but won't help much either). In other words your mast bonding conductor could have terminated directly on the AC-entrance ground rod. Now that you have another ground rod anyway, just bond it (shallow-bury any copper wire at least 6ga thickness) to the AC-entrance ground rod. If you wanted to add another ground rod it should be 16' equidistant from either of your existing two ground rods. That would benefit both your mast and home-entrance protection.

I have never seen an outdoor surge arrestor with F-connectors unless they were made for cable tv or satellite, which use different frequencies than you are interested in. Just buy an arrestor with BNC connectors and then add your own adaptor, the later is easily obtained at any RS.

Examples of a good surge arrestor available with BNC connectors is:

http://www.iceradioproducts.com/impulse1.html#1

Choose the model(s) for frequencies you will be using. Note that the 50-500MHz model for instance does not mean you cannot monitor 800MHz, but it would not be efficient to transmit on 800MHz using a protector designed for only thru 500MHz.

Brgds,
Jack
 
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