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Grounding Outdoor TV Antenna

07/27/2008 5:08 PM

Hi,

Does anyone know if it is possible to ground an outdoor TV Antenna inside the attic instead of installing a grounding rod outside of the house? I don't have a water pipe or an electric meter nearby so, grounding onto those objects would require at least 75 feet of ground wire across the roof to reach the water pipe or electric meter. I am trying to avoid doing that.

Problem:

Currently I have an antenna mount on an antenna mast on the roof-top and a RG6 Coax cable runs from the antenna through the attic and down the wall into the living room TV. At the moment, I have no grounding from the antenna or the antenna mast.

Question:

Can I ground the Antenna and the Antenna Mast by installing a grounding block inside the attic and run a #10 AWG ground wire from the grounding block to a near-by metal electrical box in the attic? Will I get the same ground protection as an outside grounding rod? Thanks!

Ken

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#1

Re: Grounding Outdoor TV Antenna

07/27/2008 5:25 PM

Are you talking about signal grounding, or fretting about lightning?

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#2

Re: Grounding Outdoor TV Antenna

07/27/2008 8:40 PM

I thought grounding the antenna will prevent static buildup, signal and reduce damages from lighting. I am not aware there are different ways to ground a TV antenna for static, signal and lighting.

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#3
In reply to #2

Re: Grounding Outdoor TV Antenna

07/27/2008 11:27 PM

You only have 205 days to worry about analog TV broadcasts--At least in the USA, but I would imagine that includes the UTC. If you are serious beyond this then check the ARRL website and check for ground plane info on antennas/frequencies here www.arrl.org/

Rabbit ears will be getting bobbed.

OOOPS- I just read the entire original post and it looks like a lightning protection question. Advise: Don't get hit by lightning for 205 more days and then take your antenna down.

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#7
In reply to #3

Re: Grounding Outdoor TV Antenna

07/28/2008 10:48 PM

I used to have the impression that the antenna was going to become useless next year too...

NOT true! You simply have to have a TV capable of receiving HDTV, or a converter box to convert digital to analog before it gets to your old TV. I just got a new flat screen TV a couple of months ago, and my current (30 or so year old) antenna receives digital signals just fine. This, of course is assuming that you live close enough to one or more local stations to receive their signals in the first place.

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#4

Re: Grounding Outdoor TV Antenna

07/28/2008 10:09 AM

In terms of signal, the coax outer will be grouded by the euipment it plugs into, so you don't need aditional grounding.
In terms of lightening strike... a little bit of earth strap is going to make no difference whatsoever to whether you get struck or not...and if you do get stuck it will make no difference to the pathe it takes to ground.

So...to sumarise...open a beer and just chill out.

(I'm willing to incur the wrath of 'expert' on this...but I stand by my opinion..well I curl up and sleep by it really)

Del

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#8
In reply to #4

Re: Grounding Outdoor TV Antenna

07/29/2008 12:00 AM

(I'm willing to incur the wrath of 'expert' on this...but I stand by my opinion..well I curl up and sleep by it really)

Having repaired tens of thousands of TV's over the past 45 years I believe I would qualify as an 'expert' on this. You certainly won't incur my wrath, I will also stand by your opinion. But since I'm old and tired maybe I'll just curl up and sleep by it also.

Actually you're dead right. An analogy would be using a half-inch pipe to contain the flow of water when a dam breaks.

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#9
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Re: Grounding Outdoor TV Antenna

07/29/2008 2:05 AM

Nice analogy...I shall remember it for future use unless you expect royalties on it.

Del

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#5

Re: Grounding Outdoor TV Antenna

07/28/2008 2:38 PM

http://www.polyphaser.com/ has good info on grounding, and lightning arrestor products.

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#6

Re: Grounding Outdoor TV Antenna

07/28/2008 10:18 PM

No you won't get the type ground protection as an outside ground rod without using a ground rod but as Del wrote you don't need it. Or you could discharge any static by dangling a medium size nail from a string tied to the mast, don't ask me why it just works.

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#34
In reply to #6

Re: Grounding Outdoor TV Antenna

08/06/2008 5:50 AM

Hello Guest,

what you say is true with ref' to TV's and any other product which has an aerial to it.

However, it is not true for most other routes the lightening could take.

A friend had her TV explode (because it was plugged in) and all her lights and, light and power sockets blown clear out of the wall after a strike. I think if she had a lightening rod to earth it may have taken that route instead. Who knows? But an aerial on top of the house will be more likely to receive a strike than if it was not there. And I can't think of anything on the house, other than an iron soil pipe on the outside which could get hit and damage the house? Metal window may not be advisable?

stay safe

babybear

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#10

Re: Grounding Outdoor TV Antenna

07/29/2008 4:22 AM

You should read your home-owner's insurance policy carefully.

If you live in the US, the NEC requires that an outdoor antenna be grounded, and its lead-in be protected with a listed antenna discharge unit. Even a grounding system installed according to code (Chapter 810, section 20 of the NEC) might not prevent all damage to your house or your equipment in the event of a direct strike, but it could considerably reduce damage from voltages induced by nearby lightning.

Some thirty years ago I had a similar problem, so I bought a broadband amplifier and moved the outdoor antenna, a commercially produced log-periodic, into the attic. I lost Channel 13, which I seldom watched, but kept all the other local VHF and UHF channels. If I had wanted to go to the extra trouble and expense, I could have installed a rotator and kept them all.

This arrangement worked without intervention for over twenty years, until I moved out of the house. Living a sheltered life in the attic greatly prolonged the useful life of the antenna, and there were no more anxious jitters when the thunder rolled.

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#11

Re: Grounding Outdoor TV Antenna

07/29/2008 6:34 AM

Hello, Meterman,

Welcome to CR4. I've been a little busy trying to do the impossible with neolithic tools. 75 feet of properly installed ground cable is better than the 1 in 1000 chance of a lightning strike.

If you do get hit with lightning and you don't have a a lightning arrestor . . . I'm not 100% sure, but it can't be a good thing.

When in doubt, I always check with Del the Cat. Good luck.

/Ari (Orpheuse)

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#36
In reply to #11

Re: Grounding Outdoor TV Antenna

08/06/2008 5:59 AM

Hello Orpheuse:

hope you are fine............

Yes...........I agree, just ask the cat man! Know what I mean dude?........

stay safe

babybear

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#39
In reply to #11

Re: Grounding Outdoor TV Antenna

08/06/2008 9:30 AM

Hello Orpheuse:............king of Poets eh?

I am really interested in neolithic tools. What have you been doing then?...........Or, is what you said to be derogatory?

You kind of look Greek if I squint a little!

stay safe

babybear

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#12

Re: Grounding Outdoor TV Antenna

07/29/2008 8:46 AM

Tis True and I also agree with Del. Everyone says to use surge protectors and lightning arresters etc.etc.etc. But if you've ever watched shows on atmospheric anomolies, lightning doesn't care where it goes and basically follows no rule of thumb. From what I understood of lightning rods was they were suppose to give a guidance to the discharge in the HOPES it would not ignite the barn.

I've seen several arrays of antenae, CCTV for security and all sorts of posts, rods and other forests of metal get bypassed by lightning and screw up the one tiny thigamajig that you don't have a replacement for, and GSA won't have one for at least 3 weeks.

The only thing I would worry about would be that if you grounded your antenna to your electric box or water pipe wouldn't you just be inviting the lightning to take out your whole houses system and possibly fry all your contacts, electronics and otherwise rather than just setting your roof on fire?

Chances of a direct hit are slim, but I would rather go with an exterior ground pounded into the ground.

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#40
In reply to #12

Re: Grounding Outdoor TV Antenna

08/06/2008 9:52 AM

Hello charsley99:

Hey, can you cut down on the big words like, anomalies, atmospheric, and protectors, I have a head ache!

I pretty much agree with you really. I use my surge protector to level out surges from the mains, not to stop me getting hit with lightening. It is a powerful thing and after seeing my friends switches and lights and TV blown to bits after a hit, you have to wonder firstly, why it went that route. And, secondly, if a lightening arrestor would have redirected the strike? I mean, I know they work on churches but, a churches lightening arrestor can be a hundred feet or more away from anything that may have gotten damaged anyway? An arrestor on a normal house or single story dwelling has very little choice at to where it strikes. It can be just inches difference between a short lightening rod and an aerial or chimney?

I am a HAM Radio man so it is relatively easy to ground a radio aerial. My straight wire aerial is connected both ends to ceramic links which stop any lightening reaching the radio............(I think). Fingers crosses now I have said that!

If you put it on a metal pole outside, do you think the areal has to be a couple of fee lower than the top of the pole, so if any strike happens it with hit the pole and note the areal?

What do you think?

stay safe

babybear

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#41
In reply to #40

Re: Grounding Outdoor TV Antenna

08/06/2008 10:30 AM

BB,

if you're a 'ham' you should know this stuff...standard tricks of the trade...

"My straight wire aerial is connected both ends to ceramic links which stop any lightening reaching the radio..."

?! unless the ceramic links look like those on 400-600kV overhead high-tension lines , if the lowest-resistance path is on the other side of the link, it will flash over that ceramic like it's wet copper...after all, BB, the flash already descended through a kilometer or so of air to get to the antenna...so a few cm's of ceramic ain't nothin'.

I'll paraphrase my earlier reply, - the lightning strike current will find the lowest-impedance path to ground...so the idea (in lightning-protection systems) is to provide (a path whose) surge impedance 'seen' by the incoming current is low enough that the current follows that path, and doesn't jump somewhere else (with the attendant consequences of warming things up in a hurry..).

Again: ARRL has lots of good info, for a more general approach to lightning physics, any of the fine books by Martin A, Uman.

RF_G

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#42
In reply to #40

Re: Grounding Outdoor TV Antenna

08/06/2008 10:31 AM

It is my understanding that a lightning rod 'protects' a roughly 45° cone under its tip, so the rod should extend at least as far as half the antenna width above the antenna.

I haven't seen anyone mention here that a properly grounded, sharp pointed conducting rod will spray charge into the atmosphere, partially neutralizing the clouds directly above, and thereby preventing at least some lightning strikes.

I once observed this on a pointy mountain top, with my finger being the pointed rod. St. Elmo's fire was visible for about 2 inches from my fingertip. Of course I didn't linger long, but lightning did strike the mountain top about 5 minutes after I left.

Of course I don't know whether my presence delayed or prevented a strike while I was there...

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#43
In reply to #42

Re: Grounding Outdoor TV Antenna

08/06/2008 10:57 AM

Correct - all such lightning protection systems rely on the concept of 'shadowing' - the ground wire running across the tops of high-tension towers is the classic example, along with lightning rods.

You want the corona/streamers to form on a conductor which is firmly bonded to ground, so the strike, if it occurs, hits there, and the energy is conducted harmlessly away.

Dude you are *real* lucky to be hear after the mountain peak stunt. People get killed in the Alps here and very often in much lower hills like the White Mtns of New Hampshire under such conditions!

RF_G

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#44
In reply to #42

Re: Grounding Outdoor TV Antenna

08/06/2008 10:58 AM

I don't know whether my presence delayed or prevented a strike while I was there...

Offering presents to the Gods is a novel technique...

Your point about charge from the rod locally neutralizing the cloud is in agreement with what I had believed (but was too unsure of to propose)..the lightening rod is there to prevent not conduct it...
Conductor is a misnomer... or is it?
Don't hit me I'm just a cat..

Del

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#45
In reply to #44

Re: Grounding Outdoor TV Antenna

08/06/2008 11:15 AM

I've always been led to believe that the 'lightning rod' thingies somehow defused the situation. If this wasn't the case (i.e. they actually attracted strikes), I'd've thought there'd be a lot of buildings with blobs of melted copper streaking the outsides.

Don't know if any of you guys have done the I2t sums, but I reckon it must come to quite a big number.

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#46
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Re: Grounding Outdoor TV Antenna

08/06/2008 1:14 PM

Just some random observations; In 1959 working at a TV Transmitter on top of a mountain, The Transmitting Antenna was atop a 200 foot tower. The tower had heavy guy cables from several heights to concrete blocks buried deep in the earth. At regular intervals the cables were interrupted by long ceramic insulators. During Lighning storms it was really awesome to watch the static discharge jump across each insulator like a giant Jacob's ladder. Flowing downward from top to bottom. (It was also a bit frightening). As far as I know there never was a full lightning strike on that mountain top. The regular discharge of static buildup seemed to prevent a full build-up of power.

I have seen first-hand several Direct lighting strikes on TV Antenna systems. One blew a 9 foot hole in the roof of the house. One hit an antenna connected to several TV's through an amplifier/splitter. A young man in his 20's was lying on his bed listening to an FM station on a radio connected to the system. (Paws over ears Del).

His cat was lying by his legs and was thrown across the room when the FM receiver blew apart. (All 9 lives in one fell swoop).

Mom was standing on the front porch and was thrown across the yard landing about 50 feet away (According to eye-witness accounts). She survived the ordeal.

Antenna lead-in wire crossing water lines melted solder in water lines causing water leaks in basement ceilings.

I could go on and on with details of TV antenna and Lightning strikes, but I am convinced that you guys are right when you say that absolutely nothing will protect from a full lightning strike. Static discharge protection is wise and often pays. And it is possible in some cases that good static discharge may actually prevent a full blown strike.

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#50
In reply to #45

Re: Grounding Outdoor TV Antenna

08/07/2008 2:00 AM

Some more reading..

http://www.lightningsafety.com/nlsi_lhm/lpts.html

nice day

RF_G

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#13

Re: Grounding Outdoor TV Antenna

07/29/2008 9:04 AM

Your safest bet would be to mount your antenna on a steel pipe at the side of the house and ground this with an earth spike at the end of the pipe, a lightening strike will tend to take this path rather than to your TV equipment. Also spark gap flash overs tied into your coax down feed and directed to the metal pipe would help to redirect the strike.

Your equipment would not necessarily be saved but it could save you major fire and other damage.

I still cannot log onto CR4 or should I say I can log on but am only recognised as a guest.I will come back to this question as it will be the only way I can read any suggestions from other members as to what my problem is.

Thanks Garth.

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#21
In reply to #13

Re: Grounding Outdoor TV Antenna

07/30/2008 8:33 AM

While reading from the top, yours was the first correct post.

Many thanks, you saved me the bother!!

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#23
In reply to #13

Re: Grounding Outdoor TV Antenna

07/30/2008 8:43 AM

Actually I agree with Andy (hi Andy), I hadn't seen your post when I wrote mine, which I did assuming the poor guy didn't want to re-engineer the whole dang installation...but yeah, a metal mast into the ground...that's a pretty robust path.

Pretty much any metal that penetrates the roof and worms its way around within the house ain't good, because once all the other requirements are fullfilled for the strike to get that far, that's when it gets unpredictable, where the strike energy will end up being disappated.


Added a vote for your answer

RF_Guy

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#25
In reply to #23

Re: Grounding Outdoor TV Antenna

07/30/2008 8:59 AM

Thanks for your votes but wont do me much good as a guest, as I said my CR$ name is Garth but it wont let me reply as anything but a guest??

If I re register presumably my previous name will not be available to me as I all ready have it, if the powers that be can suggest what might be wrong with my link to the sight I would appreciate it.

Thanks Garth.

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#26
In reply to #25

Re: Grounding Outdoor TV Antenna

07/30/2008 9:22 AM

Hey Garth/Guest,

check here

http://cr4.globalspec.com/browse/members?mode=all&sort=joindate&order=desc

maybe send him an email to sort your registration

http://cr4.globalspec.com/member?u=2


cheers

RF_G

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#27
In reply to #25

Re: Grounding Outdoor TV Antenna

07/30/2008 9:42 AM

Hi, Garth,

Presumably this is you?...

If so, I'm sure a quite word with Chris (or one of the other guys) could sort things out.

Don't know whether Guests can send PMs - if you can't, let us know here & we'll pass the message on.

Regards, John

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#28
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Re: Grounding Outdoor TV Antenna

07/30/2008 10:17 AM

...them big dudes is always up there, circlin' around, ready to fix a problem when one pops up..


/RF_G

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#29
In reply to #27

Re: Grounding Outdoor TV Antenna

07/30/2008 11:26 AM

Hi John,

I must check my spelling a bit more often.

Yes you are correct that is me. Problem is if I log in it accepts me OK but when I come back to the post it says I am not logged on. Normally I did not have to log on my browser { Fire fox] did it automatically, so I presume there is an automatic link in the browser which has stuffed up. My browser threw a tizzy a week or so ago and decided to ask for a lot of start up info again and as far as I am aware is working 99% except for this CR4.

I cant seem to find an email for Chris so as you surmise I have to be logged in properly. It is late now and am tired must go to bed, will follow up on this later thanks for the offer to help I might need it.

Regards Garth

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#30
In reply to #29

Re: Grounding Outdoor TV Antenna

07/30/2008 12:24 PM

Have you tried just logging on again? Sometimes you get forgotten I find (server should "remember you" again!!), so just use the logon at the top of the page somewhere. If your ISP keeps changing things around, that could cause the same problem.

I also notice that I have to log on again agter using my laptop or PC and going to the other one......same ISP but it still forgets me.....you are also missing getting updates without your logon working properly....

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#31
In reply to #30

Re: Grounding Outdoor TV Antenna

07/31/2008 7:11 AM

Hi Andy ,

Have tried log on every which way it recognises me OK but when I move from that window I am asked to log on again??

The new posts are still coming through to my email OK but as you say no updates.

Have sent a query to fire fox maybe they can offer some solution.

Cheers Garth

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#52
In reply to #27

Re: Grounding Outdoor TV Antenna

08/09/2008 6:46 AM

Hi John,

Am still frustrated as cannot get CR4 to recognise my posts. I am receiving notifications of earlier posts which is strange. No reply from Fire fox yet don't know why they ask for notification of bugs if they are not going to reply to the bu gee.

If you think Chris could help would you contact him for me, other wise I will have to start a new registration.

Thanks Garth.

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#53
In reply to #52

Re: Grounding Outdoor TV Antenna

08/09/2008 1:18 PM

Hello Guest,

I am nothing to do with Admin but, have been in touch a few days ago with Chris Leonard and he in away for a couple of weeks. He may well be able to answer from where he is I don't know.............Just thought I would let you know OK?

You can still write to Admin though and perhaps another person can answer your question?

Not sure if it would make any difference but. have you entered the correct GMT time or whatever applies? Is it a case of your notification being several hours off or days?

stay safe

babybear

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#54
In reply to #53

Re: Grounding Outdoor TV Antenna

08/09/2008 11:00 PM

Thanks babybear;

The time does not seem to be a problem, I am now thinking that the specific file for this program is corrupted.

Have sent a note to admin so will see what they can come up with.

Cheers garth

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#55
In reply to #54

Re: Grounding Outdoor TV Antenna

08/10/2008 2:57 AM

Hello Guest,

How long have you been using the site? And did you download the CR4 Menu Bar?

If you have no GA's or have not used the site that much, try canceling and restarting with a new name (that's if you are a member)?

If you wrote to Chris directly, he said to me when I was talking about some stuff of my own, he would be away for a couple of weeks.

Try writing the same letter with a slightly different header addressed to 'ADMIN'.

babybear

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#56
In reply to #55

Re: Grounding Outdoor TV Antenna

08/10/2008 10:11 AM

Thanks babybear,

Have been posting since May/2006

garth CR4

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#57
In reply to #56

Re: Grounding Outdoor TV Antenna

08/10/2008 1:54 PM

Hello Guest,

OK...................!

Keep in touch telling us how you get on OK?

stay safe

babybear

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#58
In reply to #57

Re: Grounding Outdoor TV Antenna

08/11/2008 6:23 AM

Garth is not really a Guest, he's a longterm user of CR4, but has had some problems getting logged in under his correct name and cannot get these problems fixed easily it would appear......

I hope that the CR4 admin can do something for him fairly soon......

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#60
In reply to #58

Re: Grounding Outdoor TV Antenna

08/11/2008 5:06 PM

Hello Andy Germany:

I have not been a member for long and did not realise Garth was a long standing member. OK. Thanks for the info Andy.

babybear

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#61
In reply to #60

Re: Grounding Outdoor TV Antenna

08/12/2008 10:00 AM

Its simply not a problem (except maybe for Garth!), you did not know, I mentioned it just to put you in the picture, alls well with the world!

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#62
In reply to #61

Re: Grounding Outdoor TV Antenna

08/12/2008 1:25 PM

Hello Andy,

I appreciate you telling me thanks .....................

babybear

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#59
In reply to #52

Re: Grounding Outdoor TV Antenna

08/11/2008 10:41 AM

Hi, Garth,

I've been away for a couple of days, but it looks like the other guys have stepped in.

A message to ADMIN in general should be seen by such high'n'mighties as Moose &/or mgaulin, who may be able to help.

Keep in touch here.

All the best, John.

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#14

Re: Grounding Outdoor TV Antenna

07/29/2008 9:05 AM

Sorry meterman but it's a little hard to understand what's inside and what's outside, but since you're asking the question and you write

"Currently I have an antenna mount on an antenna mast on the roof-top",

I'm assuming the antenna & mast is outdoors.

As far as 'signal ground' (and I guess, static charge - more about that later) is concerned, the connections to the TV set suffice (the outer conductor of the coaxial cable connects antenna to TV set..).

In the case that an active lightning cell passes over the house and charge build-up occurs, the electric field intensity between the 'cloud bottom' and ground will rapidly increase. Given the right conditions, this will lead to local corona breakdown of the air at sharp edges and protrustions of objects which are at or close to ground potential, including your TV antenna (BTW this corona activity can be detected by appropriate RF and optical devices, in the worst case by a 'fizzzzzing' noise heard in the area of an impending lightning strike )(yes, I've heard it)(and lived). This phenomena is constantly happening all over the world in areas beneath active lightning cells. As the electric field intensity builds, the corona breakdown increases and 'micro-streamers' followed by 'streamers' - basically, ionized channels of corona - form between the grounded objects and the clouds above. Eventually, given the right conditions, these link up and open a channel of lower resistance which forms a low-resistance path through which some of the built-up charge in the cloud flows, further ionizing and heating the channel, until things proceed to the point that a channel is established which short-circuits all of the available charge - a lightning strike.

If your antenna is 'chosen' then it is fairly likely that the strike will follow that signal cable to your TV set. The normal consequence is that the TV set explodes and often big holes get burned into walls etc. Whether a house fire starts depends on lots of other things, but where I grew up (upstate New York), blown-up TVs weren't unknown.

However, the strike currents absolutley adhere to the laws of physics (which get very subtle because of the energies, electric field intensities, and velocities involved with lightning activity), which means on the way down your cable the current surge may decide that jumping to the rain gutter or an interior water pipe or the telephone line etc. etc. provides it a lower-impedance (sic) path to ground. In other words it's hard to predict where it's going to go, without carrying out a lightning test (which outside of a suitably equipped H.V. lab most of us can't do).

All of the above distills down to 2 facts:

- the lightning strike current will find the lowest-impedance path to ground (and in some cases, it creates that path)

- a gentlemen named Benjamin Franklin figured all of this out in the 18th century and this is why lightning rods and lightning protection systems exist (and they work or else our entire high-tech society wouldn't - meaning cell-phone and broadcast antennas, ATC radars, high-voltage transmission systems, etc. etc. etc)

And shame on Del for implying grounding to mitigate the effects of lightning makes no sense. Do you know who Benjamin Franklin is, over there in merry olde England? Or perhaps they don't teach you about him because of his role in the other nasty business, that Revolution of ours?

oops, sorrrrrrrry

So...I would think twice - as poster #10 also points out, it may have consequences for your insurance - about leaving an ungrounded mast on the roof of your house. At the moment, barring some other low-impedance paths to ground nearby to the lead-in cable, your antenna looks like a lightning rod whose ground goes via your TV set and the wiring attached to it.

As pointed out by several posters, this is why there are (lots of) books about lightning grounding, esp appropriate are the ones from ARRL (because hams have to deal with this stuff on a routine basis), and companies that sell arrestors and so on.

If you've got metal rain gutters, I'd at least clamp a good heavy chunk of wire to the mast with the other end clamped to the gutter. If you don't have rain gutters, well, then yeah, I'd run it down to the ground and drive a 1-1/2" water pipe down about 3 feet and clamp the wire to that. AWG#10 is the bare minimum, take a walk to a HV mast or cell tower or just find a building in the area with lightning rods, normally they're using something like AWG 4 (25mm2) or so. This is based on experience and calculation - the idea is to provide sufficient cross-sectional area so that the surge impedance 'seen' by the incoming current is low enough that the current follows that path, and doesn't jump somewhere else (like the aforementioned house wiring etc.)

As elsewhere posted, there is plenty of info out there, I'd suggest ARRL first, as it's straightforward and practical; there are lots of bright people looking at it all the time so the info is almost always very reliable.

cheers (sic)

RF_Guy

all the other mechanisms that are required to come together to create the condis

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#15
In reply to #14

Re: Grounding Outdoor TV Antenna

07/29/2008 9:35 AM

And shame on Del for implying grounding to mitigate the effects of lightning makes no sense.

That's not what I said...

There is a world of difference between a proper lightening conductor (probably 25x5mm solid copper running straight down to a solid grounding point) and '75 feet of ground WIRE'...
I stand by my assertion that the latter will do SFA, because, as you said yourself it won't be the lowest impedance path to ground.

Del

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#16
In reply to #15

Re: Grounding Outdoor TV Antenna

07/29/2008 10:11 AM

"That's not what I said..."

well...ok...

But it's (clearly - from 1000's of lightning-protection systems installed all over the planet) only necessary to get the (surge) impedance of the grounding cable lower than the other possible likely paths...so that lightning currents don't get onto other (semi) condutors (and thus warm them up..)

Sorry if I ruffled your fur


RF_G

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#18
In reply to #16

Re: Grounding Outdoor TV Antenna

07/29/2008 10:16 AM

S'allright...I like having my fur ruffled...
It's better than whistling into the void and watching the tumbleweed blow past...

I like mixing metaphors too
Del

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#22
In reply to #14

Re: Grounding Outdoor TV Antenna

07/30/2008 8:39 AM

Benjamin Franklin WAS British as all of you were in New England, that is of course before you became a "Revolting Colony" !!

Yes, we are also taught about him and his works in Schools in the UK.....

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#24
In reply to #22

Re: Grounding Outdoor TV Antenna

07/30/2008 8:45 AM

Exactly, he had to wait for the Revolution to succeed...

oops there I go again

RF_G

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#17

Re: Grounding Outdoor TV Antenna

07/29/2008 10:16 AM

Hi meterman, not an engineer here, but a property & casualty insurance broker

>>> If your locale requires adherence to any version of the NEC code and YOU FAIL to abide by the code, your homeowners insurance NOW has grounds to deny payment for any claim against your policy that involves a lightening strike on the covered property.

>>> In actuality it is highly unlikely they would deny your claim, HOWEVER you would have given them a way of saying, "Sorry, but your failure to follow the statute required building practices, in our evaluation, caused and precipitated the damage that would otherwise have been avoided. Your claim has been denied." legally.

>>>Evaluate the risk and proceed wisely.

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#19
In reply to #17

Re: Grounding Outdoor TV Antenna

07/29/2008 6:19 PM

RF--That is why I read this great stuff, nice rant and I will give you a vote.

What about the guy with the thin copper wire and a model rocket, seeding lighting strikes--Made a believer out of me. Anyone see it? I'll check youtube.

www.youtube.com/watch?v=buSaGIoNXu8

And there it is.

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#20
In reply to #19

Re: Grounding Outdoor TV Antenna

07/30/2008 1:47 AM

RF--That is why I read this great stuff, nice rant and I will give you a vote.

I'm forever greatful, Dr. Trout

What about the guy with the thin copper wire and a model rocket, seeding lighting strikes

As I wrote: the copper conductor - it's size...has a direct bearing on its surge impedance - its impedance only has to be less than other nearby convenient/accessible paths to ground. So even a thin copper wire, surrounded by normal air, will have a significantly lower resistance and impedance than air, and thus provide an 'easier' path for the current surge to follow (Mr. Franklin, of course, used a kite for the same purpose)(actually something I've been meaning to do for a long time, but I need some decent wire...Inconel would be sweet..)

the problem arises with other surrounding structure, as in house & building parts which may or may not present a more favourable path to ground than the intended lightning protection ground.

Nice day, watch out for lightning


/RF_Guy

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#32

Re: Grounding Outdoor TV Antenna

07/31/2008 11:18 PM

Hello meterman,

I have a surge protector which includes sockets for phone and antenna so you could get a small one and put it behind the TV and plug the antenna into it? Of course then it grounds through the earth wire of the mains supply. If you do not want that what is the hassle of fixing a 'lightening rod' down the house wall to the ground, (just in case)!

I know of someone who antenna was struck by lightening and it blew every light switch and electrical socket out of the wall. So don't hang about.

stay safe

babybear

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#33
In reply to #32

Re: Grounding Outdoor TV Antenna

08/01/2008 9:12 AM

Unfortunately protection at the back of your TV or computer is to close and to late and should only be considered as a secondary defence.

Surge protection needs to be placed at the incoming mains switch board and incoming telephone line where they hook on to the house and use separate grounding. Once a lightening strike gets its teeth into your distribution ground wiring you can kiss your gear goodbye.

Garth CR4.

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#35
In reply to #33

Re: Grounding Outdoor TV Antenna

08/06/2008 5:56 AM

Hello Guest,

I use my surge protection for just that.........>>>surges<<<

I do not expect it to stop any lightening strike. If anything is connected via the power supply including of course the surge protector, they will be good and dead after a strike!........So in that, I totally agree!

The incoming mains already has an earth strap on it.

stay safe

babybear

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#37

Re: Grounding Outdoor TV Antenna

08/06/2008 8:09 AM

Interestingly I had the people in to replace my lightning conductor as the house has just been fully insulated and the old stuff really does not look good against a brand new wall.

We are the second highest house in the village, so I do want to be fully protected!!

The Guy told me that the old method was not in use anymore (2M long Massive steel bar) and that he would be pounding a 9 meter rod into the ground!!!

I told him that I would be most surprised if he achieved that as my local knowledge tells me that bedrock is probably only 2 meters or less down, as several houses in the same road needed bedrock to be blown up/away(?) many years ago when built.....in fact one house had to be built one meter higher as a result as the amounts of bedrock that would have had to be removed would have upset the whole area for many days with the small (allowed) explosions!

I will let you all know what happens next week!!!

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#38
In reply to #37

Re: Grounding Outdoor TV Antenna

08/06/2008 8:21 AM

*YIKES!* NINE METERS?!

He's either built like Arnold Schwarzenegger in his young days and weilds a 10lb sledghammer like a roofing hammer, or he's going to need a pile-driver to get it all the way in...

I haven't heard of anything like that and in general, performance of an earthing rod (or any other earthing topology, for that matter) depends on soil resistivity, which at first approximation is determined by water content, and Germany is decidedly not considered an arrid region

Keep us posted! Maybe he'll drill into the bedrock and strike oil!

RF_G

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#48
In reply to #38

Re: Grounding Outdoor TV Antenna

08/06/2008 8:53 PM

He does have some sort of "Mini" Pile driver he said, so I may take photos and post them if it proves interesting enough!

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#47
In reply to #37

Re: Grounding Outdoor TV Antenna

08/06/2008 1:54 PM

Hi Andy!

Are you sure this guy wasn't an American, and meant 9 feet?

or perhaps he meant dig a trench and bury a horizontal bar 9m long...

Dick

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#49
In reply to #47

Re: Grounding Outdoor TV Antenna

08/06/2008 8:58 PM

No, he is German and that is the current DIN Standard he tells me!!!

An old joke:- "Should a Lightning Conductor get Thunderous Applause?"

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#51
In reply to #49

Re: Grounding Outdoor TV Antenna

08/07/2008 1:47 PM

Hello Andy Germany:

I like it, I like it!....................You mean as he is sizzling with 10,000,000 volts going through him?................. A little OTT there but what the hell.

stay safe

babybear

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