Lee, if I can make a couple of comments, first, you can have large voltage differences among your 23 "ground" rods, depending on the ground terminus of the lightning strokes. Second, antennae and feed lines that do not attract lightning due to being "hidden" can still be subject to large induced voltages. I'd suggest all the ground rods and antenna bases be connected directly with large cable so they are all truly at the same ground potential... Don
Lee Mushel > Lightning is certainly one of Old Mother Nature's principal weapons as > well > as being extremely unpredictable. My House/Shack is on the side of a > hill > with the Antenna Farm on top of the hill about 120 yds away with an > additional 30 ft. of elevation. There is a metal "lightning rod" > extending > high enough to provide a "cone of protection" for the house and is > grounded > directly. And there are five other metal antennas on that roof, two to > a > separate ground and three to still another which is close to the shack > "ground field" which is three additional ground rods. All ground rods > I > mention are the standard 8 ft. copper plated steel items. Each of five > antennas in the antenna field also have individual ground rods and I > guess > if you follow the cable shields you could say that they are all > connected > together. A couple of years ago I counted all ground rods and came up > with 23. Before all of the metal was added and the "lightning rod" was > the > only metal extending about 20 ft. above the roof and we had an > electrical > storm my wife would complain that she could feel her hair trying to rise > in > response to the field coming from the cable which ran across the roof > and at > it's closest point was only 6-7 ft. from her head as the crow flies. > But > after all the additional metal was added in the form of antennas with > grounds she no longer complained. > > I do not claim to understand what goes on around here at an elevation of > about 102 ft. above the valley floor but I believe that we have been > "fortunate" (or lucky if you prefer that word) and we have so much > metal in > the air that most "discharges" are not of the type that is accompanied > by > thunder! Two years ago we had a tree die that was no more than 30 ft. > from > the house. Since I have not always been able to accurately predict > where > trees will fall that I cut myself I hired a professional to take it down > and > he took one look at it, reached up and stripped off a piece of bark and > commented, "See those lines? This tree was struck by lightning. > That's > what killed it!" But no lightning related damage to structure or > equipment > here for nearly 15 years! > > My only thought on the subject was that only a fool would fail to > disconnect > an antenna that rises above the house roof during an electrical storm. > I > freely admit that I have several ham radio VHF antennas (and a GPS > antenna > supplying the disciplined system for frequency reference) well below > roof > peak level (clear view to south for GPS, of course) that I do not > disconnect from inexpensive radios maintained for the purpose. > > This is risk I accept. And I certainly have seen paths followed by > lightning that are truly amazing! ....and horrendously damaging. Never > forget that you only live once and you do have a perfect right to enjoy > your > hobby without fear. > > Regards, > > Lee A. Mushel K9WRU > > > ----- Original Message ----- > From: "quartz55" <quart...@hughes.net> > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Sent: Sunday, September 15, 2013 12:13 PM > Subject: Re: [time-nuts] New NTBW50AA > > > . I'm not thrilled having it above the beams, it's the highest metal > thing > in the area and most likely more prone to lightning than anything else > excpet the trees and it will blow around a bit up there as well as > rotating > once in a while. I did have a strike here once, but it was down by the > barn > and was looking for the underground telephone cables, it blew apart a > post > and knocked off the boards, it was maybe 100 yards from the shack. It > wouldn't be much of a problem to dig a tiny trench to the fence and I > may > try that after this precise survey is done, then do another and see if > anything changes. I could hide it i >> n a bird box at the fence too. After all at this point I'm just >> playing. >> I'll eventually make up my mind. Also, I don't have an attic, so >> that's >> not an option. >> >> Dave >> N3DT >> _______________________________________________ >> 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. > -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.com _______________________________________________ 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.
