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Author Topic: Lightning and Grounds - Looking for suggestions  (Read 1008 times)
KC8PIH
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« on: October 31, 2000, 02:20:41 PM »

My house is a ranch style. Ham shack is in the north end of the basement. Power utility comes in on the south end with an existing ground rod. Telco enters on the east side, no ground rod yet, this service was just relocated to the south side. Tower is on the north end. My question is how best to ground the antenna and shack systems? How should I tie in to the existing gounds (utility and telco) to not open myself up to ground loops? Is a ground array of rods, located on the north end, by the tower best? and the use of a ground panel/bulkhead with isolators (polyphaser) also a good idea?  thanks in advance

73's
KC8PIH
john....  
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N9EYL
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« Reply #1 on: November 03, 2000, 10:50:58 PM »

John,

I also have a similar situtation.  Here is my experience.  First after really looking at what was grounded my Telco ground was the only thing I saw at my house that looked like it was competently grounded.  My AC ground had the standard 10 foot copper coated steel ground round but the AC connection was just a wire loosely twisted around a cable.  My gas pipe had a insulated wire wraped around it and my cable modem cable only had a wire pushed through the multistranded cable going to my ground electrical ground rod.  Anyway, did I mention my house was built in two weeks??  The point here is first you have to see what you have got first.  Which in my case wasn't much.

In my opinion you have to ground for two or three main reasons.  You need lightning protection, TVI prevention and an RF conterpoise.  

True for lighting protection you want a tall lightning rod with a big fat cable going to a big ole ground rod via the most direct path.  A rule of thumb here is that a lightning rod to a good ground will provide a 45 degree cone of protection underneath it.  Lightning is DC by nature and plain and simple OHM's law aplies here.  At my vertically challenged ranch I have an inverted 3' RS Shack Copper ground rod on a pole up about 25' going thru 6 gauge solid copper to two 5 foot 3/4 inch copper pipes.  The electrical joints are both mechanical grounding hardware and also soldered with a blow torch.  Solder and propane are good for continuity but in case of a lightning hit you want mechanical joints in case the solder melts under the high amperage.

RF is much different.  It is more likely to see inductive reactance in a long wire.  You want the wire from your shack to your earth ground to be as short as possible.  Less than three foot IF possible.  I had a ten foot copper plated steel rod for that.  

Next you mentioned ground loops.  Ground loop currents are the product of the voltage divider network which is all of the wires tying everything together.  Multipoint grounds are by far better for eliminating ground loops because more points of the complex voltage divider network are tied to ground potential.  Also multipoint grounds are very good ground planes for RF.

So what I have here is a continous unbroken twelve gauge bare copper wire circling the outside of my house soldered to my AC ground.  Then hooked with a feed through F-type connector to my cable and then to my telco ground and then to a 10 foot 3/4 copper pipe then mechanically connected before my dielectric to my gas pipe and then ran around my house to my back faucet which has another ground rod under it.  That seems to be a good place for a ground rod because it always stays wet.  Then I go through another F-type bullet for my cable and tie into the TV's AC ground at the wall socket.  All of my wifes audio video equipment is tied together electrically and then ran to ground.  I use one of those RS HAM/TVI filters here too.

Then that wire comes around to my shack to its ground rod and then to two 1/2 inch copper pipes sitting under the gutter spout.  It always seems to stay wet there too.  Then this wire continues on to the other side of the house to the other outside water faucet and to two more buried pieces of copper pipe and the Lightning ground.

So basically I have everything tied together in multiple places with multiple paths to ground.

Whether that works for you is another question.  But the more grounds you have the better off you will be as far as ground loops are concerned.  Big loops of wire to one ground will work as an inductive voltage divider and everywhere that you tap it you might just be picking RF voltage off of the divider network.

Sounds like a lot of money but it more about time.  Copper pipe is cheaper than most ground rods and tweleve guage wire don't cost much.  I sunk most of the pipe with some sweated plumbing hardware and a waterhose.  If I couldn't go any deeper than three feet than so be it.  I just cut the pipe attached the wire and kept moving.  After all I didn't have all of my eggs in one basket.  Best of all for me I had no ground loops and my wife could watch TV while I played radio.  Hey that's worth a hundred bucks worth of copper isn't it?


Jeff
N9EYL
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K3AN
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« Reply #2 on: December 08, 2000, 01:28:56 PM »

Check out this page from the Polyphaser Web site. It is a downloadable PDF document titled "Ham Radio Station Protection."

http://www.polyphaser.com/download/PTD1016.pdf

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G4AON
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« Reply #3 on: February 17, 2001, 03:04:32 PM »

While I won't pretend to understand USA style electrics, I have one or two suggestions from how we earth here in the UK.

In the UK almost everything is earthed to mains neutral at the point where the electricity supply comes into the house. The supply line neutral itself is earthed at several points in the area. This is known as protective multiple earthing. The unfortunate side effect for amateur radio is that you can't just connect an earthed tower, earth rod, earthed radials, etc. to a transceiver and then connect that to the mains earth via the third pin of the mains plug (although I suspect many people do). The problem with this is if the mains neutral feed to the house breaks, the entire house is drawing mains current through your extra earth via the thin cable in the transceiver's mains lead...

There are two ways around this.

(a) arrange for the electrial supply company to include your external earth with theirs at the point the supply enters the house.
(b) the better alternative, run your radio shack from mains electricity without using the mains earth. Instead, run your own external earth into the shack. As a safety precaution, use a power feed with a residual current trip.

The latter suggestion was included in the RSGB handbook some time ago and was endorsed by the Institute of Electrical Engineers as being good practice. In any event, it keeps the radio earths away from mains earth and should reduce chances of TVI, etc.

Dave
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K7DFW
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« Reply #4 on: February 21, 2001, 01:23:35 AM »

The suggestion from K3AN is the best that you will get. The units are available at approx $50 each and the bottom line is, how much is your gear and residence worth? Read their information and see the saves that their units have made. Don't forget one for the rotor cable. 73 Rolynn K7DFW (1958).
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KA1MUY
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« Reply #5 on: May 31, 2001, 05:00:13 PM »

The web address for Polyphasers Technical Document on Ham Radio Station Protection is-
www.polyphaser.com/pdf/PTD1016.pdf
Eleven pages of very good info on protection from lightning strikes.
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KC7YRN
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« Reply #6 on: September 21, 2001, 12:39:05 PM »

Everything in the Polyphaser document made sense to someone with a physics degree.

Multipoint grounds need to be planned carefully so that your equipment is never in between two different grounds, if you want lightning protection.

You know how you're told to keep your feet close together if you're out in  a thunderstorm? If there's a lightning strike near you but not on you, the current trying to spread out from ground zero will create big E=IR voltage differences across the distance between your feet.

So, if one rig in your shack is grounded one place and a second rig is grounded someplace else, part of the lightning strike will flow between them. Bad.

Of course you'll have bonded your grounds together with something conductive, but two problems come up. One is sheer magnitude. Lightning strikes carry tens of thousands of amps. If the total resistance of your bonding wire and connections is 100 milliohms, the voltage drop will be in the kilovolts. The second problem is that while lightning has harmonics all the way into UHF. The gentleman above was correct in saying lightning is *basically* DC, but as it equalizes charges betweeen cloud and ground it generates a lot of RF (think of spark gap transmitters). Inductance counts. Straight wires are better than wires with bends in them, and flat straps are better than wires.

What Polyphaser recommends is, no matter how many ground rods and radials you've buried in your backyard, to tie all your requipment and all your incoming surge protectors to one macho sheet of copper with a very good ground connection.  That way, even if lightning raises the common grounding point to 2000 volts above earth, all your equipment will be at exactly the same potential and no current will flow between them.

73 de KC7YRN
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KC7YRN
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« Reply #7 on: October 01, 2001, 05:20:28 PM »

Here's something by a broadcast engineer who explains it well:

http://www.harvardrepeater.org/news/lightning.html
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K9KJM
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« Reply #8 on: June 26, 2002, 02:12:17 AM »

Good suggestions all. I would add that you should NOT solder grounding conductors with lead/tin solder! Use only true "silver solder" (Available from welding shops, used by the refrigeration trade, about $1 buck a stick, one stick does at least 10 connections) Use "MAPP" gas in a propane type torch to get the heat needed to flow the silver solder.
Bond ALL conductors together. This includes any copper plumbing, electrical mains, etc etc. I will echo the advise to check the Polyphaser "tech notes" website. Follow that information and you will have no problems. It does Not have to be expensive. Old used copper wire (stripped of any insulation) will work under ground as good as new wire, Copper sheet can be purchased from roofing companies. (Copper roof flashing) Sometimes used heavy duty (But bent slightly) ground rods can be obtained from electric utility line crews, etc etc.  
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KC7YRN
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« Reply #9 on: July 03, 2002, 06:10:25 PM »

Can I bring up something that K9KJM didn't mention because it's too obvious?

No matter what type of solder, lightning protection is the one application where you should *never* forget to make a good mechanical connection first.

The National Electrical Code forbids grounding connections that depend solely on solder. Lightning after all is noticeably hotter than your soldering iron.

Of course everybody knows this already -- I'm just emphasizing that if you cut corners anywhere, make it someplace other than your lightning ground.
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N0LLL
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« Reply #10 on: November 06, 2002, 09:28:52 PM »

Realizing that this is an old thread  - I nonetheless must chime in to point out that everything Jeff (N9EYL) mentions  seems fine except......
one should never ground anything to a gas pipe.
Major code violation and if you think about just not a good idea.

JM2C
Peter
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K9KJM
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« Reply #11 on: November 15, 2002, 01:17:07 AM »

The "real" Silver solder that I mention is an alloy
of real silver, nickel, copper and other metals that
actually has a Very high melting point. That is why
"mapp" gas is needed to get it to flow.
Do NOT use any lead/tin alloy type solder for
lightning protection, or any use underground.
(Soil acids eat up lead)  
Commercial tower installations no longer use any
type of mechanical connection on ground wires, only
the "Cadweld" process.  If you cannot do a "true
silver solder"  connection, By all means, use good
mechanical connectors.  Note: The silver solder I
am talking about is NOT the stuff sold for house
plumbing, which has a very low melting point!  
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N9ESH
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« Reply #12 on: September 24, 2003, 12:35:04 AM »

Visit your local library and request a copy of UL-96A,
Installation Requirements For Lightning Protection Systems. It's a good place to start.
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