Ground Or Not To Ground Receiving Antenna In Storm ?
 

Hello:

Have been reading up on lightning a bit, and it certainly
is a confusing subject.

Let's say I have an Inverted-L or a Sloper in the yard (receiving only).

If a lightning storm is in the vicinity, obviously the best protection
possible is to just disconnect the radio from the antenna. No differences
of opinion here, I would imagine.

But, as a more or less theoretical question, to minimize the possibility of
lightning hitting the antenna at all, or inducing large voltages in it, is
it better to just leave the now "floating" antenna alone, or is it better to
ground one end of it ?

Why ?

Thanks,
B.

Ground Or Not To Ground Receiving Antenna In Storm ?
 

On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11"
wrote:

But, as a more or less theoretical question, to minimize the possibility of
lightning hitting the antenna at all, or inducing large voltages in it, is
it better to just leave the now "floating" antenna alone, or is it better to
ground one end of it ?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I doubt it matters. A lightning bolt, having traveled thousands of
feet to the vicinity of your antenna, will not be deterred by a few
more inches.

73, Bill W6WRT

Ground Or Not To Ground Receiving Antenna In Storm ?
 

In article , Bill Turner
wrote:

On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11"
wrote:

But, as a more or less theoretical question, to minimize the possibility of
lightning hitting the antenna at all, or inducing large voltages in it, is
it better to just leave the now "floating" antenna alone, or is it better to
ground one end of it ?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I doubt it matters. A lightning bolt, having traveled thousands of
feet to the vicinity of your antenna, will not be deterred by a few
more inches.

Bill-

That's what I was going to say!

I recall a field day activity where the club was using the press box of a
high school football field, with antennas strung between light poles. As
a storm approached, there were sparks several inches long jumping between
disconnected antenna connectors and nearby grounded equipment. These
sparks were induced by lightning strikes that were some distance away.

Grounding would have eliminated the sparks by providing a metalic path for
the discharge. I doubt it would have had any influence on whether an
antenna would be directly hit, or would have provided any substantial
protection in the event of a direct strike.

Traditional wisdom is that having tall trees nearby, as well as tall
objects such as light poles, will shield you from lightning. But there
are no guarantees. And lightning doesn't always strike the top of tower!

73, Fred, K4DII

Ground Or Not To Ground Receiving Antenna In Storm ?
 

On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11"
wrote:

Hello:

Have been reading up on lightning a bit, and it certainly
is a confusing subject.

Let's say I have an Inverted-L or a Sloper in the yard (receiving only).

If a lightning storm is in the vicinity, obviously the best protection
possible is to just disconnect the radio from the antenna. No differences
of opinion here, I would imagine.

But, as a more or less theoretical question, to minimize the possibility of
lightning hitting the antenna at all, or inducing large voltages in it, is
it better to just leave the now "floating" antenna alone, or is it better to
ground one end of it ?

Why ?

You have to think carefully about what you are trying to protect.

It seems to me that in the event of a lightning stroke in the near
vicinity of your antenna, large voltages will be induced in the
antenna wrt "ground", whether or not your antenna or its support
structure features as a streamer, or takes the current from a leader.

That voltage may be sufficient for insulation breakdown, and charge
will flow to ground via some path, not necessarily of your choosing.
Substantial physical damage may occur where insulation breaks down,
the path of the side-flash current may result in further damage to
persons or equipment.

If you make a substantial connection from the feedline to some thing,
you have some degree of control over the path that the discharge
current flows. Properly chosen and implemented, that might be better
than doing nothing, but if poorly designed or implemented, it could be
worse than doing nothing. Side-flash can still occur where you have
provided a path to ground.

Very often, the target of effective lighting protection of radio
installations is minimisation of voltage drops or potential
differences internal to an installation as a result of lightning
discharge current rather than trying to minimise the voltage to
"ground" resulting from the current.

Owen
--

Ground Or Not To Ground Receiving Antenna In Storm ?
 

I always tell new Hams to ground everything they can.... but if they get a
direct hit then they will be too busy fighting fire to worry about the
antenna...

-Dave-
K5DRC Since 1969
BULL SHOALES LAKE
http://www.bullshoals.org/lake.htm
AR/MO STATE LINE

Some day someone will give a WAR and nobody will go

"Owen Duffy" wrote in message
...
On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11"
wrote:

Hello:

Have been reading up on lightning a bit, and it certainly
is a confusing subject.

Let's say I have an Inverted-L or a Sloper in the yard (receiving only).

If a lightning storm is in the vicinity, obviously the best protection
possible is to just disconnect the radio from the antenna. No differences
of opinion here, I would imagine.

But, as a more or less theoretical question, to minimize the possibility
of
lightning hitting the antenna at all, or inducing large voltages in it, is
it better to just leave the now "floating" antenna alone, or is it better
to
ground one end of it ?

Why ?

You have to think carefully about what you are trying to protect.

It seems to me that in the event of a lightning stroke in the near
vicinity of your antenna, large voltages will be induced in the
antenna wrt "ground", whether or not your antenna or its support
structure features as a streamer, or takes the current from a leader.

That voltage may be sufficient for insulation breakdown, and charge
will flow to ground via some path, not necessarily of your choosing.
Substantial physical damage may occur where insulation breaks down,
the path of the side-flash current may result in further damage to
persons or equipment.

If you make a substantial connection from the feedline to some thing,
you have some degree of control over the path that the discharge
current flows. Properly chosen and implemented, that might be better
than doing nothing, but if poorly designed or implemented, it could be
worse than doing nothing. Side-flash can still occur where you have
provided a path to ground.

Very often, the target of effective lighting protection of radio
installations is minimisation of voltage drops or potential
differences internal to an installation as a result of lightning
discharge current rather than trying to minimise the voltage to
"ground" resulting from the current.

Owen
--

Ground Or Not To Ground Receiving Antenna In Storm ?
 

On Sat, 17 Dec 2005 01:48:24 -0600, " hillbilly3302"
wrote:

I always tell new Hams to ground everything they can.... but if they get a
direct hit then they will be too busy fighting fire to worry about the
antenna...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This summer my 80 foot tower took a direct hit, the first in my 48
years of hamming. The tower was grounded and there was no fire, but it
tripped a circuit breaker in my house and damaged a radio connected to
it. My point is that fire is not an automatic consequence.

Incidentally, the sound of thunder from a hit that close is remarkably
different from a hit some distance away. First, you hear the clap from
the nearest part of the bolt and then from parts successively farther
away, a long, rolling sound that continues much longer than one at a
distance. If I don't ever hear it again, that will be ok by me. :-)

73, Bill W6WRT

Ground Or Not To Ground Receiving Antenna In Storm ?
 

Bill Turner wrote:

On Sat, 17 Dec 2005 01:48:24 -0600, " hillbilly3302"
wrote:


I always tell new Hams to ground everything they can.... but if they get a
direct hit then they will be too busy fighting fire to worry about the
antenna...


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This summer my 80 foot tower took a direct hit, the first in my 48
years of hamming. The tower was grounded and there was no fire, but it
tripped a circuit breaker in my house and damaged a radio connected to
it. My point is that fire is not an automatic consequence.

Incidentally, the sound of thunder from a hit that close is remarkably
different from a hit some distance away. First, you hear the clap from
the nearest part of the bolt and then from parts successively farther
away, a long, rolling sound that continues much longer than one at a
distance. If I don't ever hear it again, that will be ok by me. :-)

73, Bill W6WRT


Bill;

Ain't been there, Ain't done that, Don't want no stinkin t-shirt. ;^)

Seriously though glad that nothing really serious happened. When I was
in retain sales I sold many electronic items to people that suffered
both direct and indirect hits. Lots of damage no injuries everyone was
lucky.

Dave WD9BDZ

Ground Or Not To Ground Receiving Antenna In Storm ?
 

"Bill Turner" wrote in message
...
On Sat, 17 Dec 2005 01:48:24 -0600, " hillbilly3302"
wrote:
This summer my 80 foot tower took a direct hit, the first in my 48
years of hamming. The tower was grounded and there was no fire, but it
tripped a circuit breaker in my house and damaged a radio connected to
it. My point is that fire is not an automatic consequence.

Incidentally, the sound of thunder from a hit that close is remarkably
different from a hit some distance away. First, you hear the clap from
the nearest part of the bolt and then from parts successively farther
away, a long, rolling sound that continues much longer than one at a
distance. If I don't ever hear it again, that will be ok by me. :-)

73, Bill W6WRT

Long years ago, 50 yearsor so before I reached Ham status, a thunderstorm
awakened me in the wee hours and proceeded to dance around in the shallow
hill pasture near the house. Stroke after stroke occurred and all so near I
could hear a loud click as the strike occurred and then the diminishing
rumble. I still haven't figured out the initial click sound, it came from
outside so wasn't a house internal electric phenomenon.

Harold
KD5SAK

Ground Or Not To Ground Receiving Antenna In Storm ?
 

Bill Turner wrote:
If I don't ever hear it again, that will be ok by me. :-)

Consider that there might be two ways that you would never
hear it again and one is NOT OK. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Ground Or Not To Ground Receiving Antenna In Storm ?
 

On Fri, 16 Dec 2005 22:55:09 GMT, Owen Duffy wrote:


Very often, the target of effective lighting protection of radio
installations is minimisation of voltage drops or potential
differences internal to an installation as a result of lightning
discharge current rather than trying to minimise the voltage to
"ground" resulting from the current.

I should have expanded that to say:

Minimisation of potential differences is often obtained by one or more
of:
- providing an alternate low impedance path to ground so that less
current flows through the equipment room;
- single point earthing to reduce the voltage drop in earthing
conductors internal to the equipment room;
- equipotential bonding to reduce the voltage drop between the
equipment room earth and other parts of the building, and other
services or structures (eg water, gas, telephone, power).

There may be standards or codes that apply to lighting protection in
your area, they are worth checking, and while they may not mandate
lighting protection, they may mandate the way in which it is done if
it is done. That may have implications for your insurance.

Effective lightning protection is a very expensive business, and if
you don't need "continuous operation" and have a simple configuration,
it is much cheaper and effective to ensure that feedlines and similar
conductors (like rotator cables) are totally disconnected from the
shack at times of high risk.

Owen
--