If you were Registered and logged in, you could reply and use other advanced thread options
|
Posted by bud-- on October 15, 2009, 1:59 pm
GoHabsGo wrote:
>
>> 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...
>
> 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
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--
|
|
Posted by RickH on October 15, 2009, 6:58 pm
> GoHabsGo wrote:
> >> 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. =A0Now I am not sure what to do. =A0Anyone have any input on t=
his
> >> topic? =A0Ideas are gratefully received...
> > Antennas should be grounded in two ways. =A0First the mast should be gr=
ounded =A0
> > 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 ho=
me.
> > Grounding is not only for lightning strikes. =A0Wind blowing over the t=
ines
> > creates static electrical charge that will be discharged through the gr=
ound
> > wire.
> > Larry
> 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--- Hide quoted text -
> - Show quoted text -
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.
|
|
Posted by bud-- on October 16, 2009, 1:00 pm
RickH wrote:
>> GoHabsGo wrote:
>>>> 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...
>>> 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
>> 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--
>- Hide quoted text -
>> - Show quoted text -
You guys really can't figure out this is gargbage from the retarded
google newsreader that is of no interest to anyone?
>
> 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.
>
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--
|
|
Posted by RickH on October 15, 2009, 10:10 am
> 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. =A0Now I am no=
t
> sure what to do. =A0Anyone have any input on this topic? =A0Ideas are gra=
tefully
> received...
> Thanks,
> Dave
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=3D471
http://winegard.com/kbase/kb_tip_results.php?tip_num=3D398
|
|
Posted by Dave on October 15, 2009, 10:18 am
> 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
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
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
|
Page 3 of 5 < 1 2 3 > last >>
| Similar Threads | Posted | | Grounding TV antenna tower | April 11, 2006, 8:18 pm |
| TV antenna grounding question | October 31, 2006, 10:55 am |
| Q on grounding for cell phone antenna | November 19, 2007, 11:27 am |
| Adding another antenna to my existing antenna set-up | January 20, 2009, 9:52 am |
| OT: What's This Antenna For? | January 31, 2008, 3:28 pm |
| Is there any reason to keep this antenna? | July 18, 2008, 8:51 pm |
| TV Antenna splitters | December 13, 2005, 8:49 pm |
| Which way to point a TV antenna? | December 30, 2005, 11:54 am |
| Another TV antenna question | October 31, 2006, 8:57 pm |
| Advise For FM Antenna? | July 22, 2007, 1:26 pm |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap