? on grounding TV antenna

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Was talking with someone the other day and mentioned that I had just grounded the TV antenna (the mast, actually) to protect against lightning strikes, and they said that was not such a good idea because lightning is more likely to strike a path that goes straight to ground. Now I am not sure what to do. Anyone have any input on this topic? Ideas are gratefully received...
Thanks,
Dave
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Nah. Don't bother the lightning; if it strikes the antenna will go to ground through the TV set etc. (probably blowing the sh*t out of it!). And then find a way to the home's water supply pipe through Grandma's vintage silverware.
More seriously: Some may remember church towers that had heavy copper strips from ground to a spike on top of the steeple etc. The idea being to try and discharge the high voltage of an incipient lightning strike before an arc occurred. Metal boat masts should be 'grounded' to the water for similar reason.
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wrote:

Nah. Don't bother the lightning; if it strikes the antenna will go to ground through the TV set etc. (probably blowing the sh*t out of it!). And then find a way to the home's water supply pipe through Grandma's vintage silverware.
More seriously: Some may remember church towers that had heavy copper strips from ground to a spike on top of the steeple etc. The idea being to try and discharge the high voltage of an incipient lightning strike before an arc occurred. Metal boat masts should be 'grounded' to the water for similar reason.
--
So, I should leave it grounded and not worry about it being more likely to
get struck by lightning?
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wrote:

Church behind my house in VT took such a hit a couple of years ago when I was there.
Pics of big bang result and rebuilding on pg 72. http://www.town.williston.vt.us/website/images/documents/annual_report/annrept.pdf
http://www.usatoday.com/weather/news/2007-06-04-tower_N.htm?csp4
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Red Green wrote:

http://www.town.williston.vt.us/website/images/documents/annual_report/annrept.pdf
So what are you supposed to do if antenna is on opposite side of house from electric service and ground stake, and no plausible way to run a cable between them? Yes, this is an actual question.
-- aem sends...
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aemeijers wrote:

You can use a ground rod at the base of antenna tower. Good way of testing quality of ground rod is try to light up a light bulb between ground rod and hot wire from house power wiring. If the bulb lights up bright it is good. As a ham operator my grond is 3 rods tied together in triangular pattern. Also the holes have charcoal pieces in them. Also it is OK to install ~2 Meg. Ohm resistor across coax leads or twin leads to bypass static build up.
If you got struck by direct hit even good grounding is not a safe bet. Once I had a direct hit on my super large scale IT system located in the basement of 7 story building. It knocked off main power breaker situated in the next room with back up M-G set, wiped out most of data from mass storage sub-system randomly. 3 day and nights to restore the system from back up. So my idea on lightning strike is there is no 100% protection. In my 50 odd years of HAM operation I never suffered a lightning damage to my equipment. I have been lucky.
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wrote:

If you don't find a way to bond them together the lightning will find it for you.
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Antennas should be grounded in two ways. First the mast should be grounded and second, the cable feeding from the antenna should be grounded to a grounding block that is wired to a ground source before entering the home.
Grounding is not only for lightning strikes. Wind blowing over the tines creates static electrical charge that will be discharged through the ground wire.
Larry
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Hadn't even thought of this. My heartfelt thanks,
Dave
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Dave wrote:

If you've ever listened to any sort of shortwave broadcasts on a whip antenna, you may have heard static discharges that make a zip, zip, zip sound through the speaker at regular intervals.
TDD
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GoHabsGo wrote:

The NEC (if you are in the US) requires the earthing Larry describes. It must be to the same earthing system as the power and telephone.
A separate ground rod that is not tied to the power earthing system is a code violation and bad idea. I wouldn't even use a rod if it is bonded to the power earthing system. With a close strike, like to a tree, the rod can be thousands of volts from the earthing system used for power. That voltage shows up at TVs and anything else connected to the antenna and power.
The earthing is not for a direct lightning strike - it is totally inadequate. If you expect the antenna (and house systems) to survive a direct strike you would have to use the much more elaborate protection used by hams.
--
bud--

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The problem is that you never want to bring the coax into the house unless it and the mast were grounded in some way shape or form. Grounding them inside the house is not good. So if you dont have easy access to the service ground (maybe service meter is way over on the other side of house). Then in that case the ground rod is your only choice. You would not want to run a ground wire through the house to the other side, just to get a service ground. With that you would be bringing the lightining into the house.
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RickH wrote:

You guys really can't figure out this is gargbage from the retarded google newsreader that is of no interest to anyone?

An "average" lightning strike is 20,000 amps. If you have a ground rod with a resistance of 10 ohms to earth it is a near miracle. The lightning strike will then lift the isolated ground rod 200,000 volts above "absolute" earth potential. (There can be arcing across the ground surface away from the rod.) The rest of the house electrical will be many thousands of volts from that. The coax will "be bringing lightning into the house".
If you have lightning rods (now called air terminals), the down conductor will be far larger than you would use on the TV antenna. An there will probably be at least 2 of them. The earthing system of a lightning rod system *must* be connected to the earthing system for the building electrical. The NEC has a note referencing NFPA780, the standard on lightning rod installations. The standard may require metal 6 feet from lightning rod conductors be bonded to the rod conductors (for instance a rooftop A/C unit on a flat roof). There may be enough voltage from the rod conductors to the metal to cause a side flash across 6 feet, even with the rod and building earthing systems connected.
The provisions of the NEC for TV antennas, which are more than what is used on some installations, are not intended to protect from a direct lightning strike to the antenna. If you want to protect from a direct strike find out what hams use for protection.
In gfretwell's post, a large conductor goes to the house grounding electrode system. The house grounding system will be raised above "absolute" earth potential, but all the wiring rises together. (That also requires service panel suppressors (which are required by NFPA780) and good connection to phone and cable entry protectors.)
--
bud--

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That someone is wrong.
You need to ground the mast directly to a ground rod or electrical service ground (outdoors), AND also ground the down-lead coax with a grounding block BEFORE the drip looop and before the coax enters the house. Use minimum of #8 wire for grounding.
The only exception to not grounding your mast is if the mast itself is buried 4 feet or more to hold it up (ground mounted mast), so a house mounted mast you have to ground. You always have to ground the coax outdoors.
http://winegard.com/kbase/upload/1450089.pdf
http://winegard.com/kbase/kb_tip_results.php?tip_num=471
http://winegard.com/kbase/kb_tip_results.php?tip_num=398
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wrote:

That someone is wrong.
You need to ground the mast directly to a ground rod or electrical service ground (outdoors), AND also ground the down-lead coax with a grounding block BEFORE the drip looop and before the coax enters the house. Use minimum of #8 wire for grounding.
The only exception to not grounding your mast is if the mast itself is buried 4 feet or more to hold it up (ground mounted mast), so a house mounted mast you have to ground. You always have to ground the coax outdoors.
http://winegard.com/kbase/upload/1450089.pdf
http://winegard.com/kbase/kb_tip_results.php?tip_numG1
http://winegard.com/kbase/kb_tip_results.php?tip_num98
Wow. THANK YOU for these links. And the good, specific advice. I have the mast grounded to an 8' copper clad ground rod driven into the earth outside the house, but do not have the coax grounded. Will take care of that post-haste. Many, many heartfelt thanks.
Dave
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Y'know, that is interesting.
The logic seems to be that a conductive path disperses the buildup of static, that would increase likelihood of a strike.
But also, it would seem that a tall conductive path would increase the likelihood of a strike to a large-area charge buildup that causes lightning.
So, do ground systems have a high resistance, to attempt to achieve the one and not the other?
J.

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From what I have read, for cloud-to-ground lightning, the sequence generally goes like this. A "stepped leader" comes down from the cloud base in a series of steps or jumps. When it gets within a couple hundred feet of the ground, now there is kind of a target area on the ground, maybe one or two hundred feet in diameter. Within that area, positive charges from the ground move up and make "streamers" from tall objects. One of the streamers eventually connects with the stepped leader, creating a cloud-to-ground conductive path, and then the main stroke happens. All this takes place very fast, in milliseconds. But from this description, it seems like what you do will not much change the chance of lightning striking the house - if you're in the target area then you may very well get struck, but otherwise not. -- H
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On Thu, 15 Oct 2009 09:26:29 -0700 (PDT), Heathcliff

I believe that charge builds up on the ground over a fairly large area in advance of even the beginning of a strike, so the question is what kind of tall objects conduct it effectively up to where the charges in the cloud can "see" it. Does it matter if you run a copper rod from ground to steeple, or give it an air gap or insulator gap of an inch or three? I wonder. My guess is, it doesn't matter much, that the fields and charges are actually fuzzy and distributed.
Too bad someone can't figure out a way to actively attract - and capture! - all that energy.
J.
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This link seems to have a reasonable analysis:
http://www.weatherimagery.com/blog/lightning-rods-attract-lightning /
Since strikes are so rare (unless you live atop a skyscraper), it makes it hard to do a cost-risk analysis even without the lightning attraction issues.
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AIUI, it's the other way around. During a lightning storm, a negative** charge can build up on (or near?) the tops of buildings, attracted by the positive** charge repeatedly building up in the sky.
**I might have these two backwards, at least for some/most of the time.
The lightning is attacted to places with the opposite charge. The grounding allows the antenna to reach equilibrium with the earth, basically neutrality, so the charge and thus the attraction isn't present, and it's LESS likely to get struck when it's grounded.
Same with lightning rods. The notion that the relatively small wires grounding your antenna or a lightning rod are there to carry the lightning to ground is false. They would melt in an instant if lightning actually struck.
I"m still confused about the needles. Typical rods, last I looked, have balls with iiuc store a charge, and needles maybe a foot long pointing upwards. I heard a story about some farmers who would break off the needles because they thought things were prettier that way, but that ruins the rod.

The American Radio Relay League, www.arrl.com might have stuff on this. In the 50's and 60's the ham radio license exam included antenna construction, but had a lot to do with how oscillators work and other electronic internals. Based on the exam I took last year, they are no concentrating on antenna construction, avoiding interference with other radios, and safety. I guess because radios are too complicated now for anyone to build one at home, unless he just assembles a kit. So the exam used to be very hard, at least for me as a 14 year old. This time I passed without even studying, 10% because I remembered things I learned for the first exam, 10% because of things I'd learned along the way, and 80% becaue it's easier.

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