Hi Bill, A lot of us are hams. The ARRL handbook has a section on grounds, including the need for bonding additional grounds to the power line ground. A loop of heavy gauge wire around the house that has periodic 8' ground rods is seen as a good thing as long as it's bonded to the power line ground. This is something entirely different from "multi-point ground". It is said to provide a circle of protection around the house, but yea, it's a lot more complicated than that. Check the handbook, or read whatever grounding documents you have access to and trust.
OK, I've had my say. Bob - AE6RV ----------------------------------------------------------------- AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Bill Hawkins <bill.i...@pobox.com> To: 'Discussion of precise time and frequency measurement' <time-nuts@febo.com> Sent: Sunday, August 7, 2016 10:06 PM Subject: Re: [time-nuts] GPS antenna selection - lightning This thread grows old, so here's one person's summary: There are two ways to be damaged by lightning: 1. A direct hit pumps 100 kiloamps of electrons into an ohm or so of your local wiring. There is no way to survive a direct hit except to implement stuff only the Military can afford. The probability is so low (outside of Florida and mountain tops) that your homeowners insurance may cover it. 2. A 100 KA strike goes to ground near you, with two effects: a. The ground resistance allows a large range of volts per meter to kill cows but not golfers with their feet together. b. A mighty electromagnetic pulse (EMP) induces voltages in anything inductive that is not shielded or twisted. Case 'a' argues for a single point earth ground. When the ground voltage goes up, you want all of your equipment to go up with it, as if it was on an isolated ground plane. It seems best to use the Electric Power Company's house ground for that reference point in your home. If you use a UPS for a set of equipment, everything on it should ground to that UPS (which should have a high capacity surge arrestor). You are left with telephone cords, TV cables, and antennas as peripheral connections to protect with surge arrestors. Marine supply stores sell rolls of 4 inch wide copper strap for connecting the mast on the wheelhouse cabin with the keel of fiberglass boats. This is also the ground for all electronic equipment. The strap is considerably less inductive than a wire. Case 'b' argues against long wires inside the area that contains the common ground and the surge arrestors at its periphery. Surge arrestors have energy ratings that refer to the energy of the EMP that caused the surge. I have no idea how that relates to lightning EMP energy so I buy the most capacity I can afford. I used these principles in a home that had a pair of HP GPS antennas four feet apart on a twenty foot mast of six inch plastic pipe, using N connectors and 50 feet of RG-8 to a pair of Z3801A receivers. The neighbor's tree took a direct hit (was split apart) less than 100 feet away. He had extensive electrical damage originating at the outdoor flood light six feet from the tree. I lost the GPS antenna closest to the tree but nothing else. FWIW, I had wireless G access points separating the area connected to the antenna from the rest of the house network. No attempt was made to beef up the grounds. Regards, Bill Hawkins _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.