? on grounding TV antenna

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

Reply to
Dave
Loading thread data ...

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.

Reply to
terry

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.

Reply to
Dave

"Dave" wrote in news:-vudnakOvMPvukrXnZ2dnUVZ snipped-for-privacy@posted.internetamerica:

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

Reply to
GoHabsGo

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.

formatting link
formatting link
formatting link

Reply to
RickH

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.

formatting link
formatting link
formatting link

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

Reply to
Dave

Hadn't even thought of this. My heartfelt thanks,

Dave

Reply to
Dave

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.

Reply to
zzznot

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

Reply to
Heathcliff

This link seems to have a reasonable analysis:

formatting link
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.

Reply to
mike

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,

formatting link
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.

Reply to
mm

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.

Reply to
bud--

Ground it.

In addition to the other responses. A nearby lightning strike that we all have seen will induce current that may damage the electronic equipment hooked to the antenna.

Reply to
tnom

Just a little Gee Whiz info I put up a weather station on a 10' pole above my garage with an air terminal on top, grounded via a 2ga copper into my grounding electrode system. It has been hit at least twice that I am sure of. Both times it took out the serial port on the PC the weather station is on. nothing else. Once I was actually in the driveway when it was hit ... that was exciting ;-) The other time we were out in the pool bar.

I put in surge protection on the lead in to the indoor part of the weather station and I haven't had any more problems. I am not sure if it was actually hit since tho.

Reply to
gfretwell

People used to spend lots on "lightning rods". And then, through observation, they saw that lightning just as often hit things that didn't have the rods on them, or never hit the rods and did hot other things. And then think of it this way: If you put a better conductor higher up there, aren't you putting out a sign that says "Lightning - HERE I AM!"

People have many misconceptions about lightning. One is that once it strikes an object, it conducts through that object to the ground. That is not true, and I have first hand experience with that. I was standing about

40' from a drilling tower. Lightning hit the tower, and ran down the side of it to ground. How do I know? Well, for about five minutes, there was this image burned onto my brain and eyes and whenever I closed my eyes, I could see it plain as day. And the lightning was swirling, just like a twisted piece of rope.

I had a lightning bolt hit a pecan tree outside my house one time. It branched. It then hit my truck, blowing diagonal hubcaps off, then jumped to a cow, which it killed. It also killed my dryer and tv in separate rooms.

"Protect against lightning strikes"? You're putting up something that will attract them. Even if you put it up on a wooden pole, the pole and wiring will be a path of a lightning bolt. I'd take the ground wire iff'n it was me. Isn't it already grounded where it touches the ground, or close enough that a big bolt of lightning couldn't arc that short of a distance? If it's on the side of the house, and the bottom is up from the ground, it can jump that far. Remember, this bolt I had struck a green leafy pecan tree. Doesn't sound like anything that lightning would be attracted to to me.

Steve

Reply to
SteveB

There are "lightning arrestors" made to be used between the antennae and ground, but not sure about the mast (most are already grounded). I suggest talking with your local firefighters for the safest configuration.

Reply to
Phisherman

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.

Reply to
RickH

terry wrote in news: snipped-for-privacy@p36g2000vbn.googlegroups.com:

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.

formatting link
formatting link

Reply to
Red Green

formatting link

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...

Reply to
aemeijers

formatting link

Hi, 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.

Reply to
Tony Hwang

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.