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Author Topic: Lightning/RF grounding??  (Read 622 times)
N4RS
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Posts: 1




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« on: October 23, 2000, 10:00:23 AM »

Will be building a home in the near future. Any thoughts/ideas on a state of the art ground system? Do I use rods or radials. I have an inexhaustable supply of copper so the materials are here. Just looking for the best system/layout...Tnx Tom N4RS
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NA4M
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Posts: 61




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« Reply #1 on: October 26, 2000, 04:21:09 PM »

Take a look at the Polyphaser site - www.polyphaser.com
They have technical articles and a very good book on
the subject. I think the book is called something
like "The Grounds for Lightning Protection" or something close.  The most protection for the money
seems to come from using the appropriate ground radial straps tied to the tower base and using a single-point ground panel bulkhead feed-thru panel for coax and control cable entry with appropriate protectors.
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WT8Y
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Posts: 65




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« Reply #2 on: October 31, 2000, 12:45:58 PM »

I laid over a thousand feet of 14 ga bare copper around the footer of my new house with a pig tail
(short) into the shack. Best ground I ever had.
Lighting, there is no protection for a direct lighting
hit. I say this with 8 years of job experiance in the
microwave tower and communication  biz. We did everything you could to protect the system's from lighting damage, it may have helped some, but when the towers took a direct hit it was all over. I disconnect
my radio's from AC main and use a coax switching system
that grounds all antenna's not used and when it's switched off grounds them all to a large combination of ground rod's and 80 or so radials connected at the tower base. 73
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WA4CNG
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Posts: 33




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« Reply #3 on: January 01, 2001, 07:44:07 PM »

The best defense against most intruders is the perimeter defense.  When we in the Commercial Land Radio Business build sites, it is very much like a perimeter defense system.  The shelter (Home) is surrounded by multiple ground rods (8ft) all tied together with minimum #2 tinned copper, cad welded (exothermic bonding) to tie each ground rod together.  Space the ground rods not more than 10 feet from one another.  Leave coiled 10 ft pigtails of tinned #2 copper at the locations where your AC Mains, Telco, Cable TV, and to tie to your tower base.  If installing a tower, you do the perimeter thing again with it, and tying that ring into the Home ring.  All connections are done in trenches about 12-18 inches deep, and backfilled after checking for ground resistance of less than 5 ohms.  This is done with commercial units made by Bittle and others.  When the AC Mains are installed, tie meter ground to pigtail, tie telco surges to pigtail, tie CATV surges to pigtail, and run one last #2 into the station area for your station ground.  Planning is of the upmost in this area as to where what is going to be located.  From a perimeter ground ring, it is relatively easy to make last minute changes on the fly.  Just remember to use Cad-Welding on all connections to the ground ring, anything else is less than priceless.  Be sure to add a whole house AC surge protector to your AC Distribution Panel.  Surge protection on antenna feeds occurs at the point they enter the Home.  Again all tied to the Ring Ground.  Good Luck.
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K9KJM
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Posts: 2415




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« Reply #4 on: November 18, 2002, 03:44:08 AM »

An Inexhaustable supply of copper?? I'll be right
over with an empty truck and some 807's.........
But seriously, If you follow the basic advice on
the Polyphaser "Tech notes" website, you should
have no trouble with lightning.  I have towers that
take direct lightning "hits" most every storm. And
do not suffer any damage. Most all modern communications towers are properly grounded and do NOT
have damage from direct strikes.
Proper grounding standards have changed a lot over the
years, In the 1950's a single solid number 6 copper
wire to a single 8' copperweld rod was considered
"good enough"   That is why lightning damaged
lots of equipment in the old days. Inadequate grounding.  Nowadays a commercial tower site starts
with over a dozen ground rods, 6" wide copper strap
to a "single Point" ground plate, and #2/0 copper wire
cadwelded to the tower and rods.......   Depending
on local soil conditions........   All of this stuff
costs big money if purchased new, But a resourceful
ham should be able to locate used wire, etc, and
install himself for lots less.....  Good Luck!
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KC7YRN
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Posts: 161




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« Reply #5 on: September 07, 2003, 11:30:07 PM »

If you're building a new house, you can really go to town. You could put a ground ring around the perimeter of the house, which is one of the options the National Electrical Code allows for an AC safety ground. You could build a Ufer ground, in which you tie together all the rebar in the foundation and get a big capacitance to ground. You could play with conductive concrete (example brand name "Conducrete"), which has conductivity as good as or better than a marsh.

Because of skin effect, the RF components of lightning won't want to follow a vertical ground rod deep into the earth(*). Radials are very good for handling this, not to mention being a ground plane for your antennas. You could lay down a mesh of wire from your unlimited supply of copper over the entire yard before the landscaping goes in.

An ideal system will use copper strap rather than wire for the grounding connections.

Ooh, and you can build a bulkhead into the walls! Then you could use it as a feedthrough for the TV cable, telephone, etc. as well as your antenna feedlines, and eliminate all sorts of chances for ground loops.

All this is much easier when the house is being built.  I'm kind of envious.

73 de Fred KC7YRN

(*) Sandia did some tests on this. Here's a picture of the flashover in between the vertical ground rods: http://www.saeinc.com/faqdetails.cfm?ID=2

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