Discussion:
GPS Antenna Grounding/Lightning protection.
(too old to reply)
Dan Kemppainen
2018-06-18 18:29:38 UTC
Permalink
Raw Message
Hi,

I have (or had, I guess) a GPS antenna on a tower that took a lightning
hit yesterday.

You can tell it's going to be a bad day when you walk into your shop,
and smell burnt electronics. Still have to troubleshoot exactly what got
hit, but the GPSDO was flashing no GPS signal, the 5V supply for the
antenna to the GPS splitter was dead, the data logging computer had
rebooted and the data logging computer monitor was dead. Other network
hardware was dead also.

This is a bit surprising since the tower itself is grounded with 4
ground rods and bonded to a 150 foot deep well casing near by. The
antenna is on the end of 250 ft run of RG6. The GPS antenna cable shield
has a grounding block bonded to two ground rods driven down below the
basement foundation where it enters the house. I'm guessing the surge
ran the coax into the splitter, then through everything connected to it,
despite the grounding block.

So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let
DC power through. If so, can you recommend some starting points? Other
suggestions also welcome.


Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said
earlier, it's a bad day when you smell burnt electronics in the shop.

Thanks,
Dan

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Chris Smith
2018-06-18 18:38:29 UTC
Permalink
Raw Message
I have purchased and deployed Huber+Suhner lightning protectors
<https://www.hubersuhner.com/en/products/radio-frequency/lightning-emp-protectors/gas-discharge-tube-gdt-protectors>
in the past but have thankfully never suffered an actual strike, so I can't
say how well they work under duress.

I've heard it said that basically nothing can protect you from a direct
hit, but again, I haven't had the opportunity to test that theory that you
so recently suffered.
Post by Dan Kemppainen
Hi,
I have (or had, I guess) a GPS antenna on a tower that took a lightning
hit yesterday.
You can tell it's going to be a bad day when you walk into your shop, and
smell burnt electronics. Still have to troubleshoot exactly what got hit,
but the GPSDO was flashing no GPS signal, the 5V supply for the antenna to
the GPS splitter was dead, the data logging computer had rebooted and the
data logging computer monitor was dead. Other network hardware was dead
also.
This is a bit surprising since the tower itself is grounded with 4 ground
rods and bonded to a 150 foot deep well casing near by. The antenna is on
the end of 250 ft run of RG6. The GPS antenna cable shield has a grounding
block bonded to two ground rods driven down below the basement foundation
where it enters the house. I'm guessing the surge ran the coax into the
splitter, then through everything connected to it, despite the grounding
block.
So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let DC
power through. If so, can you recommend some starting points? Other
suggestions also welcome.
Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said earlier,
it's a bad day when you smell burnt electronics in the shop.
Thanks,
Dan
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Graham / KE9H
2018-06-18 19:05:11 UTC
Permalink
Raw Message
If you want to protect your installation from lightening, then there is a
body of information that has been developed within the cellular industry
that allows a properly installed cellular base site to take a direct hit
and continue operating.

An example of what they do is documented in "Motorola R56 2005 manual.pdf"

Google that term to download the document.

It is likely more than most individuals are willing to take on, but you can
see the approach.

In addition to good grounding and common Voltage points, it also involves
making sure that there is not a Voltage differential across the equipment
that you want to protect, during the event.

There is an old folk saying that "Lightning never strikes twice."
Why?
Because it doesn't have to.


--- Graham

==
Post by Chris Smith
I have purchased and deployed Huber+Suhner lightning protectors
<
https://www.hubersuhner.com/en/products/radio-frequency/lightning-emp-protectors/gas-discharge-tube-gdt-protectors
in the past but have thankfully never suffered an actual strike, so I can't
say how well they work under duress.
I've heard it said that basically nothing can protect you from a direct
hit, but again, I haven't had the opportunity to test that theory that you
so recently suffered.
Post by Dan Kemppainen
Hi,
I have (or had, I guess) a GPS antenna on a tower that took a lightning
hit yesterday.
You can tell it's going to be a bad day when you walk into your shop, and
smell burnt electronics. Still have to troubleshoot exactly what got hit,
but the GPSDO was flashing no GPS signal, the 5V supply for the antenna
to
Post by Dan Kemppainen
the GPS splitter was dead, the data logging computer had rebooted and the
data logging computer monitor was dead. Other network hardware was dead
also.
This is a bit surprising since the tower itself is grounded with 4 ground
rods and bonded to a 150 foot deep well casing near by. The antenna is on
the end of 250 ft run of RG6. The GPS antenna cable shield has a
grounding
Post by Dan Kemppainen
block bonded to two ground rods driven down below the basement foundation
where it enters the house. I'm guessing the surge ran the coax into the
splitter, then through everything connected to it, despite the grounding
block.
So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let DC
power through. If so, can you recommend some starting points? Other
suggestions also welcome.
Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said
earlier,
Post by Dan Kemppainen
it's a bad day when you smell burnt electronics in the shop.
Thanks,
Dan
_______________________________________________
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/mailman/listinfo/time-nuts
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Charles Steinmetz
2018-06-18 21:51:23 UTC
Permalink
Raw Message
Post by Graham / KE9H
If you want to protect your installation from lightening, then there is a
body of information that has been developed within the cellular industry
that allows a properly installed cellular base site to take a direct hit
and continue operating.
An example of what they do is documented in "Motorola R56 2005 manual.pdf"
Google that term to download the document.
Oz and Bill also provided good information.

PolyPhaser is the generally-accepted gold standard for lightning
protection, and has many technical notes available.

Tisha Hayes has a big fat folder full of good stuff relating to
"Grounding Surge and Filtering" at her dropbox site, and another one
full of "Transient Protection Documents." See:

<https://www.dropbox.com/sh/qjnu6cp03ahajpc/AAABcWVmOZdyPWquiz3az58Ha?dl=0>

Best regards,

Charles



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Scott McGrath
2018-06-19 02:27:28 UTC
Permalink
Raw Message
Also see this

https://www.bicsi.org/uploadedfiles/bicsi_conferences/fall/2012/presentations/CONCSES_4C.pdf

Content by Scott
Typos by Siri
Post by Graham / KE9H
If you want to protect your installation from lightening, then there is a
body of information that has been developed within the cellular industry
that allows a properly installed cellular base site to take a direct hit
and continue operating.
An example of what they do is documented in "Motorola R56 2005 manual.pdf"
Google that term to download the document.
Oz and Bill also provided good information.

PolyPhaser is the generally-accepted gold standard for lightning protection, and has many technical notes available.

Tisha Hayes has a big fat folder full of good stuff relating to "Grounding Surge and Filtering" at her dropbox site, and another one full of "Transient Protection Documents." See:

<https://www.dropbox.com/sh/qjnu6cp03ahajpc/AAABcWVmOZdyPWquiz3az58Ha?dl=0>

Best regards,

Charles



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Scott McGrath
2018-06-19 02:21:13 UTC
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Raw Message
You might want to look at your grounding system. Your tower ground is probably not connected to your building ground. So when a nearby strike occurred there was a potential difference between your grounds and a current flowed as a result.

My house/shack/tower is within a ‘halo’ ground with rods every 20’ or so this means in the event of a nearby strike all grounds are at SAME potential. And yes during intense storms i do see ‘St Elmo’s Fire’ up on the tower which tells me system is working as intended by preventing potential buildup.

Content by Scott
Typos by Siri

On Jun 18, 2018, at 2:38 PM, Chris Smith <***@alum.mit.edu> wrote:

I have purchased and deployed Huber+Suhner lightning protectors
<https://www.hubersuhner.com/en/products/radio-frequency/lightning-emp-protectors/gas-discharge-tube-gdt-protectors>
in the past but have thankfully never suffered an actual strike, so I can't
say how well they work under duress.

I've heard it said that basically nothing can protect you from a direct
hit, but again, I haven't had the opportunity to test that theory that you
so recently suffered.
Post by Dan Kemppainen
Hi,
I have (or had, I guess) a GPS antenna on a tower that took a lightning
hit yesterday.
You can tell it's going to be a bad day when you walk into your shop, and
smell burnt electronics. Still have to troubleshoot exactly what got hit,
but the GPSDO was flashing no GPS signal, the 5V supply for the antenna to
the GPS splitter was dead, the data logging computer had rebooted and the
data logging computer monitor was dead. Other network hardware was dead
also.
This is a bit surprising since the tower itself is grounded with 4 ground
rods and bonded to a 150 foot deep well casing near by. The antenna is on
the end of 250 ft run of RG6. The GPS antenna cable shield has a grounding
block bonded to two ground rods driven down below the basement foundation
where it enters the house. I'm guessing the surge ran the coax into the
splitter, then through everything connected to it, despite the grounding
block.
So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let DC
power through. If so, can you recommend some starting points? Other
suggestions also welcome.
Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said earlier,
it's a bad day when you smell burnt electronics in the shop.
Thanks,
Dan
_______________________________________________
To unsubscribe, go to https://lists.febo.com/cgi-bin
/mailman/listinfo/time-nuts
and follow the instructions there.
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Oz-in-DFW
2018-06-18 19:24:40 UTC
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Raw Message
Not sure I have much to specific offer, other than some observations.

1. A path to ground is only a small part of the story.  What's really
important is the ground reference of all equipment to all other
equipment. The huge currents and substantial risetimes can cause
large voltage spikes across even large conductors (>8 AWG.) You want
everything to stay at the same voltage reference, and you'd really
like to keep that close enough to ground to prevent arcs from that
equipment to ground and other equipment.
2. Long wire runs of even large gauge wire are inductors and can be of
little value during an event.
3. No matter what you do, it's unlikely you can do anything within
economical reason to survive a direct strike and the 10's to 100's
of kiloamps involved. The real question is how close of a near miss
can you survive.
4. Most of the non-telecom smoking fails I've seen have been power line
transients. If you took a direct tower hit it's more likely than not
that your RG-6 would now be plating on a tower leg. An old tower can
be a pretty poor ground for the microseconds (or sometimes
milliseconds when you consider return strokes) it takes the
corrosion in the leg joints to flashover and fuse, or resistance
heat and weld.
5. The large currents of a direct strike have predictable but less than
obvious physical effects like conductor shortening (if they don't
fuse,) and other significant forces caused by magnetic attraction of
conductors. One failure case I saw years ago collapsed the conduit
around a ground conductor. Made no sense until we discovered that
the conduit was the actual ground path. I'll see if I can find the
pictures.
6. Even near misses can induce huge currents (kiloamps) on their own,
particularly in long vertical cable runs.  I've seen solder joints
in small empty copper water pipes melt and reflow from a strike a
100 feet away.
7. The best coax lightning suppression units I have seen are
essentially 1/4 wave grounded stubs. These are common is cell site
installations (and the top /AND/ bottom of the lines.) These are
always at DC ground and the coax is a the weak point (and ultimately
the fuse.)  I've seen them surplus and at hamfests and some cover
GPS freqs.
8. A near strike will induce some really impressive voltages on
Ethernet cable runs. Most residential buildings are
electromagnetically transparent and the protection on most Ethernet
interfaces is oriented toward ESD.

Oz (in DFW)
Post by Dan Kemppainen
Hi,
I have (or had, I guess) a GPS antenna on a tower that took a
lightning hit yesterday.
You can tell it's going to be a bad day when you walk into your shop,
and smell burnt electronics. Still have to troubleshoot exactly what
got hit, but the GPSDO was flashing no GPS signal, the 5V supply for
the antenna to the GPS splitter was dead, the data logging computer
had rebooted and the data logging computer monitor was dead. Other
network hardware was dead also.
This is a bit surprising since the tower itself is grounded with 4
ground rods and bonded to a 150 foot deep well casing near by. The
antenna is on the end of 250 ft run of RG6. The GPS antenna cable
shield has a grounding block bonded to two ground rods driven down
below the basement foundation where it enters the house. I'm guessing
the surge ran the coax into the splitter, then through everything
connected to it, despite the grounding block.
So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let
DC power through. If so, can you recommend some starting points? Other
suggestions also welcome.
Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said
earlier, it's a bad day when you smell burnt electronics in the shop.
Thanks,
Dan
_______________________________________________
To unsubscribe, go to
https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
mailto:***@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)



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Bill Hawkins
2018-06-18 21:15:30 UTC
Permalink
Raw Message
Oz has some useful observations.

I've worked on a 50 foot ocean-going fishing party boat that had a 10
foot aluminum mast on top of the wheel house. That will be the shortest
path to ground on the open sea. The best you can do is to connect a 4"
wide copper strap from the mast to the keel, with as few bends as
possible and none greater than 45 degrees. This seems to work.

I've also worked at a blasting cap plant where 50 foot masts were
erected at both ends of an earth-covered powder magazine. They provide a
"cone of protection" that prevents a direct hit on the magazine. The
mast grounds were measured quarterly with a hand-cranked device
specifically made for ground resistance. It had to be less than 100
milliohms.

But if you really want protection from a direct hit, you must disconnect
the tower device(s) before the storm hits. The coaxial cable must have
only one ground point. The other end should be far from a metallic
ground. You'll probably lose any electronics in the antenna, but there
are far more expensive things in your lab.

You will also have to deal with the electromagnetic pulse, so all of
your equipment, including the computers, must have a common ground
point. This provides a ground plane that can change potential relative
to the Earth without inducing potentials between devices. Every
connection to/from the ground plane must have a surge arrestor. If the
risk of nearby direct hits is high enough, isolate the ground plane from
all external connections before the storm. You'll need battery backup on
the ground plane for all temperature controlled ovens and crystal
oscillators. Maybe the Cs and Rb packages also need to keep running.

It would help to move away from Florida, or high hilltops.

Bill Hawkins


-----Original Message-----
From: time-nuts [mailto:time-nuts-***@lists.febo.com] On Behalf Of
Oz-in-DFW
Sent: Monday, June 18, 2018 2:25 PM
To: time-***@lists.febo.com
Subject: Re: [time-nuts] GPS Antenna Grounding/Lightning protection.

Not sure I have much to specific offer, other than some observations.

1. A path to ground is only a small part of the story.  What's really
important is the ground reference of all equipment to all other
equipment. The huge currents and substantial risetimes can cause
large voltage spikes across even large conductors (>8 AWG.) You want
everything to stay at the same voltage reference, and you'd really
like to keep that close enough to ground to prevent arcs from that
equipment to ground and other equipment.
2. Long wire runs of even large gauge wire are inductors and can be of
little value during an event.
3. No matter what you do, it's unlikely you can do anything within
economical reason to survive a direct strike and the 10's to 100's
of kiloamps involved. The real question is how close of a near miss
can you survive.
4. Most of the non-telecom smoking fails I've seen have been power line
transients. If you took a direct tower hit it's more likely than not
that your RG-6 would now be plating on a tower leg. An old tower can
be a pretty poor ground for the microseconds (or sometimes
milliseconds when you consider return strokes) it takes the
corrosion in the leg joints to flashover and fuse, or resistance
heat and weld.
5. The large currents of a direct strike have predictable but less than
obvious physical effects like conductor shortening (if they don't
fuse,) and other significant forces caused by magnetic attraction of
conductors. One failure case I saw years ago collapsed the conduit
around a ground conductor. Made no sense until we discovered that
the conduit was the actual ground path. I'll see if I can find the
pictures.
6. Even near misses can induce huge currents (kiloamps) on their own,
particularly in long vertical cable runs.  I've seen solder joints
in small empty copper water pipes melt and reflow from a strike a
100 feet away.
7. The best coax lightning suppression units I have seen are
essentially 1/4 wave grounded stubs. These are common is cell site
installations (and the top /AND/ bottom of the lines.) These are
always at DC ground and the coax is a the weak point (and ultimately
the fuse.)  I've seen them surplus and at hamfests and some cover
GPS freqs.
8. A near strike will induce some really impressive voltages on
Ethernet cable runs. Most residential buildings are
electromagnetically transparent and the protection on most Ethernet
interfaces is oriented toward ESD.

Oz (in DFW)
Post by Dan Kemppainen
Hi,
I have (or had, I guess) a GPS antenna on a tower that took a
lightning hit yesterday.
You can tell it's going to be a bad day when you walk into your shop,
and smell burnt electronics. Still have to troubleshoot exactly what
got hit, but the GPSDO was flashing no GPS signal, the 5V supply for
the antenna to the GPS splitter was dead, the data logging computer
had rebooted and the data logging computer monitor was dead. Other
network hardware was dead also.
This is a bit surprising since the tower itself is grounded with 4
ground rods and bonded to a 150 foot deep well casing near by. The
antenna is on the end of 250 ft run of RG6. The GPS antenna cable
shield has a grounding block bonded to two ground rods driven down
below the basement foundation where it enters the house. I'm guessing
the surge ran the coax into the splitter, then through everything
connected to it, despite the grounding block.
So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let
DC power through. If so, can you recommend some starting points? Other
suggestions also welcome.
Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said
earlier, it's a bad day when you smell burnt electronics in the shop.
Thanks,
Dan
_______________________________________________
to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
mailto:***@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)



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Van Horn, David
2018-06-19 16:22:20 UTC
Permalink
Raw Message
About that "cone of protection"
http://lightningsafety.com/nlsi_pls/cone-of-protection-myth.html



-----Original Message-----
From: time-nuts <time-nuts-***@lists.febo.com> On Behalf Of Bill Hawkins
Sent: Monday, June 18, 2018 3:16 PM
To: ***@ozindfw.net; 'Discussion of precise time and frequency measurement' <time-***@lists.febo.com>
Subject: Re: [time-nuts] GPS Antenna Grounding/Lightning protection.

Oz has some useful observations.

I've worked on a 50 foot ocean-going fishing party boat that had a 10 foot aluminum mast on top of the wheel house. That will be the shortest path to ground on the open sea. The best you can do is to connect a 4"
wide copper strap from the mast to the keel, with as few bends as possible and none greater than 45 degrees. This seems to work.

I've also worked at a blasting cap plant where 50 foot masts were erected at both ends of an earth-covered powder magazine. They provide a "cone of protection" that prevents a direct hit on the magazine. The mast grounds were measured quarterly with a hand-cranked device specifically made for ground resistance. It had to be less than 100 milliohms.

But if you really want protection from a direct hit, you must disconnect the tower device(s) before the storm hits. The coaxial cable must have only one ground point. The other end should be far from a metallic ground. You'll probably lose any electronics in the antenna, but there are far more expensive things in your lab.

You will also have to deal with the electromagnetic pulse, so all of your equipment, including the computers, must have a common ground point. This provides a ground plane that can change potential relative to the Earth without inducing potentials between devices. Every connection to/from the ground plane must have a surge arrestor. If the risk of nearby direct hits is high enough, isolate the ground plane from all external connections before the storm. You'll need battery backup on the ground plane for all temperature controlled ovens and crystal oscillators. Maybe the Cs and Rb packages also need to keep running.

It would help to move away from Florida, or high hilltops.

Bill Hawkins


-----Original Message-----
From: time-nuts [mailto:time-nuts-***@lists.febo.com] On Behalf Of Oz-in-DFW
Sent: Monday, June 18, 2018 2:25 PM
To: time-***@lists.febo.com
Subject: Re: [time-nuts] GPS Antenna Grounding/Lightning protection.

Not sure I have much to specific offer, other than some observations.

1. A path to ground is only a small part of the story.  What's really
important is the ground reference of all equipment to all other
equipment. The huge currents and substantial risetimes can cause
large voltage spikes across even large conductors (>8 AWG.) You want
everything to stay at the same voltage reference, and you'd really
like to keep that close enough to ground to prevent arcs from that
equipment to ground and other equipment.
2. Long wire runs of even large gauge wire are inductors and can be of
little value during an event.
3. No matter what you do, it's unlikely you can do anything within
economical reason to survive a direct strike and the 10's to 100's
of kiloamps involved. The real question is how close of a near miss
can you survive.
4. Most of the non-telecom smoking fails I've seen have been power line
transients. If you took a direct tower hit it's more likely than not
that your RG-6 would now be plating on a tower leg. An old tower can
be a pretty poor ground for the microseconds (or sometimes
milliseconds when you consider return strokes) it takes the
corrosion in the leg joints to flashover and fuse, or resistance
heat and weld.
5. The large currents of a direct strike have predictable but less than
obvious physical effects like conductor shortening (if they don't
fuse,) and other significant forces caused by magnetic attraction of
conductors. One failure case I saw years ago collapsed the conduit
around a ground conductor. Made no sense until we discovered that
the conduit was the actual ground path. I'll see if I can find the
pictures.
6. Even near misses can induce huge currents (kiloamps) on their own,
particularly in long vertical cable runs.  I've seen solder joints
in small empty copper water pipes melt and reflow from a strike a
100 feet away.
7. The best coax lightning suppression units I have seen are
essentially 1/4 wave grounded stubs. These are common is cell site
installations (and the top /AND/ bottom of the lines.) These are
always at DC ground and the coax is a the weak point (and ultimately
the fuse.)  I've seen them surplus and at hamfests and some cover
GPS freqs.
8. A near strike will induce some really impressive voltages on
Ethernet cable runs. Most residential buildings are
electromagnetically transparent and the protection on most Ethernet
interfaces is oriented toward ESD.

Oz (in DFW)
Post by Dan Kemppainen
Hi,
I have (or had, I guess) a GPS antenna on a tower that took a
lightning hit yesterday.
You can tell it's going to be a bad day when you walk into your shop,
and smell burnt electronics. Still have to troubleshoot exactly what
got hit, but the GPSDO was flashing no GPS signal, the 5V supply for
the antenna to the GPS splitter was dead, the data logging computer
had rebooted and the data logging computer monitor was dead. Other
network hardware was dead also.
This is a bit surprising since the tower itself is grounded with 4
ground rods and bonded to a 150 foot deep well casing near by. The
antenna is on the end of 250 ft run of RG6. The GPS antenna cable
shield has a grounding block bonded to two ground rods driven down
below the basement foundation where it enters the house. I'm guessing
the surge ran the coax into the splitter, then through everything
connected to it, despite the grounding block.
So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let
DC power through. If so, can you recommend some starting points? Other
suggestions also welcome.
Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said
earlier, it's a bad day when you smell burnt electronics in the shop.
Thanks,
Dan
_______________________________________________
to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
mailto:***@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)



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Bill Hawkins
2018-06-20 03:56:34 UTC
Permalink
Raw Message
Seems to me that lightning protection for timenuts who put things on
masts keeps this from being completely off topic.

People who store explosives in earthen bunkers have learned from many
years of experience how far away bunkers have to be spaced so than an
explosion in one bunker won't affect others. That same body of
experience came up with the cone of protection.

It is not a myth.

Note that lightningsafety.com sells lightning protection. The scrolling
set of pictures on the home page shows a picture of four masts
protecting a rocket launch site.

Bill Hawkins

P.S. Lightning can enter a home in other ways. A neighbor had a direct
hit to a tree 15 feet from the house. After generating enough steam in a
2 foot diameter tree to split the length of it, a side strike hit an
outdoor light and did considerable damage in the house. The tree was not
the highest thing around. That same strike produced an EMP that took out
one of my two GPS antennas, about 100 feet away. The time from flash to
BANG was about 100 milliseconds. No, I didn't measure it - I experienced
it.


-----Original Message-----
From: time-nuts [mailto:time-nuts-***@lists.febo.com] On Behalf Of
Van Horn, David
Sent: Tuesday, June 19, 2018 11:22 AM

About that "cone of protection"
http://lightningsafety.com/nlsi_pls/cone-of-protection-myth.html



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Oz-in-DFW
2018-06-20 22:45:02 UTC
Permalink
Raw Message
The "Cone of Protection" is a thumbrule.  It's not a myth, but it's also
not an absolute law of nature. It's a self-fulfilling prophecy to some
degree because it drives component design guidelines. 

Bunker spacing is also a thumbrule, based on a lot of horrible
experience. It's also a function of many variables and differing
requirements, largely the explosive involved.  It's also self-fulfilling
prophecy because it enters into design guidelines for explosives
packaging. There's a multitude of reasons those bricks are in a foil
bag. This is one of them.

I'm not a lightning protection expert, but I do a bit of work where I
have to be concerned about it. I look at that thumbrule, but I'm also a
belt and suspenders guy and apply many others. And I build shipping gear
as if it's going to South Africa (much worse that Florida.)

Back to my original statement early in this thread (rope?) "No matter
what you do, it's unlikely you can do anything within economical reason
to survive a direct strike and the 10's to 100's of kiloamps involved.
The real question is how close of a near miss can you survive." for a
small business/residential install, as a minimum I would:

1. Make sure your tower is grounded.
2. Make sure your tower is electrically sound (a good electrical
conductor - all sections are well connected electrically. this is
*/NOT /*a given with used or old tower.) If you are going to clamp
copper straps to the tower or antennas, use some stainless shim
stock as a barrier.
3. Mount your antenna(s) with grounding as specified by the manufacturer.
4. Use a lightning/drip loop at the top of the tower as a absolute
minimum.  Better to use a real suppressor, preferably of the 1/4
wave stub type.
5. Ground the coax shield to the tower at the top and the bottom.
6. If you have control lines (power, rotator controls, etc.) use
shielded cable, ground, and suppress as with coax.
7. Use a master ground bar entry into your building, and make sure you
have effective lightning suppression on */everything/* that enters
the building: Coax, AC power, phone lines, ethernets, hopes, wishes,
etc.
8. Make sure the master ground bar is well grounded to the tower.  See
https://www.solacity.com/docs/Polyphaser/Coaxial%20cable%20entry%20panels%20and%20coax%20grounding.PDF 
Commercial installs are copper bus bar.  I use it where I can, but I
also have ham installs that use unistrut and copper strap.  In an
ideal world this is next to the electrical service panel and ground
there with suppressors on the AC lines into the building. The world
is rarely ideal. 
9. I /try/ to bury at least 8 AWG ground wire around the building, but
I'm usually lucky to get it between the AC panel,  coax entry, and
tower.  One time I used scrap 1/2" copper water pipe. 
10. Get a good suppressor on the input feed to the AC panel. The /vast/
majority of failures I've seen come in the AC line. Or phone line if
you still have copper.
11. Make sure your grounds really are.  A six foot 14 AWG wire is not a
ground, even for a cable TV entry block. Use wide braid, strap, or
welding cable size wire. And be careful how you route it.  There is
a lot of literature on this alone. don't run it across the attic  ;-)
12. If you want the buried stuff to last, look at some form of cathodic
protection.

Of course you can do all of this and take losses from a hit, or none of
it and never see a problem.  This is, as the Polyphaser paper mentions,
insurance.

Oz

Shutting up now, sir.
Post by Bill Hawkins
Seems to me that lightning protection for timenuts who put things on
masts keeps this from being completely off topic.
People who store explosives in earthen bunkers have learned from many
years of experience how far away bunkers have to be spaced so than an
explosion in one bunker won't affect others. That same body of
experience came up with the cone of protection.
It is not a myth.
Note that lightningsafety.com sells lightning protection. The scrolling
set of pictures on the home page shows a picture of four masts
protecting a rocket launch site.
Bill Hawkins
P.S. Lightning can enter a home in other ways. A neighbor had a direct
hit to a tree 15 feet from the house. After generating enough steam in a
2 foot diameter tree to split the length of it, a side strike hit an
outdoor light and did considerable damage in the house. The tree was not
the highest thing around. That same strike produced an EMP that took out
one of my two GPS antennas, about 100 feet away. The time from flash to
BANG was about 100 milliseconds. No, I didn't measure it - I experienced
it.
-----Original Message-----
Van Horn, David
Sent: Tuesday, June 19, 2018 11:22 AM
About that "cone of protection"
http://lightningsafety.com/nlsi_pls/cone-of-protection-myth.html
--
mailto:***@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)



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Scott McGrath
2018-06-21 00:22:48 UTC
Permalink
Raw Message
Part of the problem is lightning protection is not sexy, its not like getting a 5071A or a H-maser, But it DOES provide a measure of insurance for those sexy items

Content by Scott
Typos by Siri

On Jun 20, 2018, at 6:45 PM, Oz-in-DFW <***@ozindfw.net> wrote:

The "Cone of Protection" is a thumbrule. It's not a myth, but it's also
not an absolute law of nature. It's a self-fulfilling prophecy to some
degree because it drives component design guidelines.

Bunker spacing is also a thumbrule, based on a lot of horrible
experience. It's also a function of many variables and differing
requirements, largely the explosive involved. It's also self-fulfilling
prophecy because it enters into design guidelines for explosives
packaging. There's a multitude of reasons those bricks are in a foil
bag. This is one of them.

I'm not a lightning protection expert, but I do a bit of work where I
have to be concerned about it. I look at that thumbrule, but I'm also a
belt and suspenders guy and apply many others. And I build shipping gear
as if it's going to South Africa (much worse that Florida.)

Back to my original statement early in this thread (rope?) "No matter
what you do, it's unlikely you can do anything within economical reason
to survive a direct strike and the 10's to 100's of kiloamps involved.
The real question is how close of a near miss can you survive." for a
small business/residential install, as a minimum I would:

1. Make sure your tower is grounded.
2. Make sure your tower is electrically sound (a good electrical
conductor - all sections are well connected electrically. this is
*/NOT /*a given with used or old tower.) If you are going to clamp
copper straps to the tower or antennas, use some stainless shim
stock as a barrier.
3. Mount your antenna(s) with grounding as specified by the manufacturer.
4. Use a lightning/drip loop at the top of the tower as a absolute
minimum. Better to use a real suppressor, preferably of the 1/4
wave stub type.
5. Ground the coax shield to the tower at the top and the bottom.
6. If you have control lines (power, rotator controls, etc.) use
shielded cable, ground, and suppress as with coax.
7. Use a master ground bar entry into your building, and make sure you
have effective lightning suppression on */everything/* that enters
the building: Coax, AC power, phone lines, ethernets, hopes, wishes,
etc.
8. Make sure the master ground bar is well grounded to the tower. See
https://www.solacity.com/docs/Polyphaser/Coaxial%20cable%20entry%20panels%20and%20coax%20grounding.PDF
Commercial installs are copper bus bar. I use it where I can, but I
also have ham installs that use unistrut and copper strap. In an
ideal world this is next to the electrical service panel and ground
there with suppressors on the AC lines into the building. The world
is rarely ideal.
9. I /try/ to bury at least 8 AWG ground wire around the building, but
I'm usually lucky to get it between the AC panel, coax entry, and
tower. One time I used scrap 1/2" copper water pipe.
10. Get a good suppressor on the input feed to the AC panel. The /vast/
majority of failures I've seen come in the AC line. Or phone line if
you still have copper.
11. Make sure your grounds really are. A six foot 14 AWG wire is not a
ground, even for a cable TV entry block. Use wide braid, strap, or
welding cable size wire. And be careful how you route it. There is
a lot of literature on this alone. don't run it across the attic ;-)
12. If you want the buried stuff to last, look at some form of cathodic
protection.

Of course you can do all of this and take losses from a hit, or none of
it and never see a problem. This is, as the Polyphaser paper mentions,
insurance.

Oz

Shutting up now, sir.
Post by Bill Hawkins
Seems to me that lightning protection for timenuts who put things on
masts keeps this from being completely off topic.
People who store explosives in earthen bunkers have learned from many
years of experience how far away bunkers have to be spaced so than an
explosion in one bunker won't affect others. That same body of
experience came up with the cone of protection.
It is not a myth.
Note that lightningsafety.com sells lightning protection. The scrolling
set of pictures on the home page shows a picture of four masts
protecting a rocket launch site.
Bill Hawkins
P.S. Lightning can enter a home in other ways. A neighbor had a direct
hit to a tree 15 feet from the house. After generating enough steam in a
2 foot diameter tree to split the length of it, a side strike hit an
outdoor light and did considerable damage in the house. The tree was not
the highest thing around. That same strike produced an EMP that took out
one of my two GPS antennas, about 100 feet away. The time from flash to
BANG was about 100 milliseconds. No, I didn't measure it - I experienced
it.
-----Original Message-----
Van Horn, David
Sent: Tuesday, June 19, 2018 11:22 AM
About that "cone of protection"
http://lightningsafety.com/nlsi_pls/cone-of-protection-myth.html
--
mailto:***@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)



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Dana Whitlow
2018-06-21 01:28:05 UTC
Permalink
Raw Message
Assuming that the coax down lead is well bonded to the tower at the
antenna, couldn't some additional
protection be obtained by running the coax down the inside of the tower?
And shouldn't the coax from
the tower base to the grounding panel at the house be run in close
proximity to the big fat ground lead
that connects the tower base ground to the house panel?

Dana
Post by Scott McGrath
The "Cone of Protection" is a thumbrule. It's not a myth, but it's also
not an absolute law of nature. It's a self-fulfilling prophecy to some
degree because it drives component design guidelines.
Bunker spacing is also a thumbrule, based on a lot of horrible
experience. It's also a function of many variables and differing
requirements, largely the explosive involved. It's also self-fulfilling
prophecy because it enters into design guidelines for explosives
packaging. There's a multitude of reasons those bricks are in a foil
bag. This is one of them.
I'm not a lightning protection expert, but I do a bit of work where I
have to be concerned about it. I look at that thumbrule, but I'm also a
belt and suspenders guy and apply many others. And I build shipping gear
as if it's going to South Africa (much worse that Florida.)
Back to my original statement early in this thread (rope?) "No matter
what you do, it's unlikely you can do anything within economical reason
to survive a direct strike and the 10's to 100's of kiloamps involved.
The real question is how close of a near miss can you survive." for a
1. Make sure your tower is grounded.
2. Make sure your tower is electrically sound (a good electrical
conductor - all sections are well connected electrically. this is
*/NOT /*a given with used or old tower.) If you are going to clamp
copper straps to the tower or antennas, use some stainless shim
stock as a barrier.
3. Mount your antenna(s) with grounding as specified by the manufacturer.
4. Use a lightning/drip loop at the top of the tower as a absolute
minimum. Better to use a real suppressor, preferably of the 1/4
wave stub type.
5. Ground the coax shield to the tower at the top and the bottom.
6. If you have control lines (power, rotator controls, etc.) use
shielded cable, ground, and suppress as with coax.
7. Use a master ground bar entry into your building, and make sure you
have effective lightning suppression on */everything/* that enters
the building: Coax, AC power, phone lines, ethernets, hopes, wishes,
etc.
8. Make sure the master ground bar is well grounded to the tower. See
https://www.solacity.com/docs/Polyphaser/Coaxial%20cable%
20entry%20panels%20and%20coax%20grounding.PDF
Commercial installs are copper bus bar. I use it where I can, but I
also have ham installs that use unistrut and copper strap. In an
ideal world this is next to the electrical service panel and ground
there with suppressors on the AC lines into the building. The world
is rarely ideal.
9. I /try/ to bury at least 8 AWG ground wire around the building, but
I'm usually lucky to get it between the AC panel, coax entry, and
tower. One time I used scrap 1/2" copper water pipe.
10. Get a good suppressor on the input feed to the AC panel. The /vast/
majority of failures I've seen come in the AC line. Or phone line if
you still have copper.
11. Make sure your grounds really are. A six foot 14 AWG wire is not a
ground, even for a cable TV entry block. Use wide braid, strap, or
welding cable size wire. And be careful how you route it. There is
a lot of literature on this alone. don't run it across the attic ;-)
12. If you want the buried stuff to last, look at some form of cathodic
protection.
Of course you can do all of this and take losses from a hit, or none of
it and never see a problem. This is, as the Polyphaser paper mentions,
insurance.
Oz
Shutting up now, sir.
Post by Bill Hawkins
Seems to me that lightning protection for timenuts who put things on
masts keeps this from being completely off topic.
People who store explosives in earthen bunkers have learned from many
years of experience how far away bunkers have to be spaced so than an
explosion in one bunker won't affect others. That same body of
experience came up with the cone of protection.
It is not a myth.
Note that lightningsafety.com sells lightning protection. The scrolling
set of pictures on the home page shows a picture of four masts
protecting a rocket launch site.
Bill Hawkins
P.S. Lightning can enter a home in other ways. A neighbor had a direct
hit to a tree 15 feet from the house. After generating enough steam in a
2 foot diameter tree to split the length of it, a side strike hit an
outdoor light and did considerable damage in the house. The tree was not
the highest thing around. That same strike produced an EMP that took out
one of my two GPS antennas, about 100 feet away. The time from flash to
BANG was about 100 milliseconds. No, I didn't measure it - I experienced
it.
-----Original Message-----
Van Horn, David
Sent: Tuesday, June 19, 2018 11:22 AM
About that "cone of protection"
http://lightningsafety.com/nlsi_pls/cone-of-protection-myth.html
--
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)
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Glenn Little WB4UIV
2018-06-19 01:39:27 UTC
Permalink
Raw Message
Unless all of your ground rods are bonded together, you are inviting
disaster.

If you have two ground systems, one at the tower and the other at the
house, you have a very dangerous situation.

If you have a unified (bonded) ground system and take a lightning strike
every thing elevates to to same level, be it 10 Volts or 100 KV.
There is no difference in potential between equipments and everything is
happy.
If there are two ground systems, they will not elevate to the same level
at the same rate.
In this case, you have differences in potential between equipments and
damage.


MIL-HDBL-419 is a very good grounding reference and is available for
free download.

To do the grounding correctly, all connections exterior to the building
are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is to
be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every 16
feet along the connecting cable and the cable welded to the rod.

I did lightning mitigation for seven years for a tower site monitoring
company.
When these steps were followed, lightning damage was very minimal or
non-existent.

You stated that the GPS antenna was on a tower.
To correctly install an antenna on a tower the feedline is to be bonded
to the tower near the base of the antenna.
The feedline is again bonded to the tower where to leaves the tower
heading for the building.
Prior to entering the building, the feedline is bonded to a copper plate
called a ground window.
This ground window is bonded to the ground system.
The feedline goes through a surge suppressor the is bonded to the ground
window prior to entering the building.

All equipment in the building should be bonded to a ground buss made of
number 6 copper and bonded to the ground window.

A lot of work, but, cheaper, in the long run, than continuing to
repair/replace equipment.

73
Glenn
WB4UIV
Post by Dan Kemppainen
Hi,
I have (or had, I guess) a GPS antenna on a tower that took a
lightning hit yesterday.
You can tell it's going to be a bad day when you walk into your shop,
and smell burnt electronics. Still have to troubleshoot exactly what
got hit, but the GPSDO was flashing no GPS signal, the 5V supply for
the antenna to the GPS splitter was dead, the data logging computer
had rebooted and the data logging computer monitor was dead. Other
network hardware was dead also.
This is a bit surprising since the tower itself is grounded with 4
ground rods and bonded to a 150 foot deep well casing near by. The
antenna is on the end of 250 ft run of RG6. The GPS antenna cable
shield has a grounding block bonded to two ground rods driven down
below the basement foundation where it enters the house. I'm guessing
the surge ran the coax into the splitter, then through everything
connected to it, despite the grounding block.
So, I'm wondering if there are better surge protectors for lightning
protection? Maybe something that actually protect the center conductor
also? Hopefully something that will pass GPS signal reasonably and let
DC power through. If so, can you recommend some starting points? Other
suggestions also welcome.
Also, If you are considering upgrading your own lightning protection,
hopefully this will be some inspiration to get started. As I said
earlier, it's a bad day when you smell burnt electronics in the shop.
Thanks,
Dan
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--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV ***@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

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jimlux
2018-06-19 14:50:17 UTC
Permalink
Raw Message
Post by Glenn Little WB4UIV
To do the grounding correctly, all connections exterior to the building
are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is to
be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every 16
feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18"
burial requirement is to avoid accidentally digging it up or damaging
it. I can't think of an electrical reason for it.
Post by Glenn Little WB4UIV
A lot of work, but, cheaper, in the long run, than continuing to
repair/replace equipment.
It depends

Unless you're doing geodetic or precision timing work with a 2 or 3 band
GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna
itself might be sacrificial.

As always, there's a risk/budget tradeoff




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Scott McGrath
2018-06-19 14:56:03 UTC
Permalink
Raw Message
The 18” inch requirement is partially for damage resistance and partially to ensure adequate soil moisture for conductivity.

Content by Scott
Typos by Siri
To do the grounding correctly, all connections exterior to the building are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is to be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every 16 feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18" burial requirement is to avoid accidentally digging it up or damaging it. I can't think of an electrical reason for it.
A lot of work, but, cheaper, in the long run, than continuing to repair/replace equipment.
It depends

Unless you're doing geodetic or precision timing work with a 2 or 3 band GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna itself might be sacrificial.

As always, there's a risk/budget tradeoff




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Bob kb8tq
2018-06-19 15:19:41 UTC
Permalink
Raw Message
Hi

18” down in a swamp likely is plenty for conductivity. 18” down in a sandy desert (or on an ice sheet) may be way
short in terms of conductivity :) The real answer to any of this is “that depends”. (Yes, the ice sheet grounding
problem is from a real case that shows up in some class notes from way back ….).

Some locations get multiple hits on a weekly basis in the summer. Other locations get a close strike once every
few decades. What makes economic sense for one probably does not make sense for the other…. A “full up”
protection setup can easily run into hundreds of thousands of dollars. I’d much rather spend that kind of money
on a Maser … or two …. or three :) …. this is TimeNuts after all ….

Bob
Post by Scott McGrath
The 18” inch requirement is partially for damage resistance and partially to ensure adequate soil moisture for conductivity.
Content by Scott
Typos by Siri
To do the grounding correctly, all connections exterior to the building are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is to be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every 16 feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18" burial requirement is to avoid accidentally digging it up or damaging it. I can't think of an electrical reason for it.
A lot of work, but, cheaper, in the long run, than continuing to repair/replace equipment.
It depends
Unless you're doing geodetic or precision timing work with a 2 or 3 band GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna itself might be sacrificial.
As always, there's a risk/budget tradeoff
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Scott McGrath
2018-06-19 16:01:49 UTC
Permalink
Raw Message
Probably the easiest and most economical grounding system is the halo ground with antenna grounds bonded to the halo and the house ground bonded to the halo as well.

The halo conductor sizing is governed by local codes, But really what you are doing ensuring that the entire structure and earth around it is at the same potential so a nearby strike does not cause ground currents to flow.

A direct strike is probably going to fry anything it hits because of the gigajoules of energy concentrated within the discharge

But a proper ground system also ‘bleeds off’ the potential difference thereby preventing discharge

Content by Scott
Typos by Siri

On Jun 19, 2018, at 11:19 AM, Bob kb8tq <***@n1k.org> wrote:

Hi

18” down in a swamp likely is plenty for conductivity. 18” down in a sandy desert (or on an ice sheet) may be way
short in terms of conductivity :) The real answer to any of this is “that depends”. (Yes, the ice sheet grounding
problem is from a real case that shows up in some class notes from way back ….).

Some locations get multiple hits on a weekly basis in the summer. Other locations get a close strike once every
few decades. What makes economic sense for one probably does not make sense for the other…. A “full up”
protection setup can easily run into hundreds of thousands of dollars. I’d much rather spend that kind of money
on a Maser … or two …. or three :) …. this is TimeNuts after all ….

Bob
Post by Scott McGrath
The 18” inch requirement is partially for damage resistance and partially to ensure adequate soil moisture for conductivity.
Content by Scott
Typos by Siri
To do the grounding correctly, all connections exterior to the building are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is to be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every 16 feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18" burial requirement is to avoid accidentally digging it up or damaging it. I can't think of an electrical reason for it.
A lot of work, but, cheaper, in the long run, than continuing to repair/replace equipment.
It depends
Unless you're doing geodetic or precision timing work with a 2 or 3 band GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna itself might be sacrificial.
As always, there's a risk/budget tradeoff
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Bob kb8tq
2018-06-19 19:55:57 UTC
Permalink
Raw Message
Hi

If indeed a proper ground system *could* be depended on to “bleed off” and prevent discharge things
would be *much* simpler. Indeed I’ve been on towers and decided to exit that location as the bleed
process became audible. It very much does happen. It simply is not a 100% sort of thing.

Bob
Post by Scott McGrath
Probably the easiest and most economical grounding system is the halo ground with antenna grounds bonded to the halo and the house ground bonded to the halo as well.
The halo conductor sizing is governed by local codes, But really what you are doing ensuring that the entire structure and earth around it is at the same potential so a nearby strike does not cause ground currents to flow.
A direct strike is probably going to fry anything it hits because of the gigajoules of energy concentrated within the discharge
But a proper ground system also ‘bleeds off’ the potential difference thereby preventing discharge
Content by Scott
Typos by Siri
Hi
18” down in a swamp likely is plenty for conductivity. 18” down in a sandy desert (or on an ice sheet) may be way
short in terms of conductivity :) The real answer to any of this is “that depends”. (Yes, the ice sheet grounding
problem is from a real case that shows up in some class notes from way back ….).
Some locations get multiple hits on a weekly basis in the summer. Other locations get a close strike once every
few decades. What makes economic sense for one probably does not make sense for the other…. A “full up”
protection setup can easily run into hundreds of thousands of dollars. I’d much rather spend that kind of money
on a Maser … or two …. or three :) …. this is TimeNuts after all ….
Bob
Post by Scott McGrath
The 18” inch requirement is partially for damage resistance and partially to ensure adequate soil moisture for conductivity.
Content by Scott
Typos by Siri
To do the grounding correctly, all connections exterior to the building are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is to be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every 16 feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18" burial requirement is to avoid accidentally digging it up or damaging it. I can't think of an electrical reason for it.
A lot of work, but, cheaper, in the long run, than continuing to repair/replace equipment.
It depends
Unless you're doing geodetic or precision timing work with a 2 or 3 band GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna itself might be sacrificial.
As always, there's a risk/budget tradeoff
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and follow the instructions there.
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djl
2018-06-19 21:12:39 UTC
Permalink
Raw Message
First, I recommend the following:
http://www.arrl.org/shop/Grounding-and-Bonding-for-the-Radio-Amateur/
well worth the price.
second, bleeding off does not prevent discharge. Many such systems are
garbage or worse. "bleeding off" is corona discharge from sharp points
submitted to a large electric field, such as under or near a
thunderstorm. It's gonna happen.
I think what's meant here by a halo system is a conductor dug in to a
shallow trench? If so, Scott is correct.
next, most of the time, damage is done by induced currents rather than
direct hit by the stroke terminus. These can be eased by proper power
treatment and good single point grounds. I personally do not trust MOV
ground protectors. They are only good for a certain, unknown, number of
hits, and are useless after that. There is no way to tell if the limit
has been reached. Surge protection on AC power needs doing only at the
main breaker box from each side of the 220 to ground.
and, if you are on a tower and hear the sizzling noise of corona, get
down pronto.
Hope this helps.
Don
Post by Bob kb8tq
Hi
If indeed a proper ground system *could* be depended on to “bleed off”
and prevent discharge things
would be *much* simpler. Indeed I’ve been on towers and decided to
exit that location as the bleed
process became audible. It very much does happen. It simply is not a 100% sort of thing.
Bob
Post by Scott McGrath
Probably the easiest and most economical grounding system is the halo
ground with antenna grounds bonded to the halo and the house ground
bonded to the halo as well.
The halo conductor sizing is governed by local codes, But really
what you are doing ensuring that the entire structure and earth around
it is at the same potential so a nearby strike does not cause ground
currents to flow.
A direct strike is probably going to fry anything it hits because of
the gigajoules of energy concentrated within the discharge
But a proper ground system also ‘bleeds off’ the potential difference
thereby preventing discharge
Content by Scott
Typos by Siri
Hi
18” down in a swamp likely is plenty for conductivity. 18” down in a
sandy desert (or on an ice sheet) may be way
short in terms of conductivity :) The real answer to any of this is
“that depends”. (Yes, the ice sheet grounding
problem is from a real case that shows up in some class notes from way back ….).
Some locations get multiple hits on a weekly basis in the summer.
Other locations get a close strike once every
few decades. What makes economic sense for one probably does not make
sense for the other…. A “full up”
protection setup can easily run into hundreds of thousands of dollars.
I’d much rather spend that kind of money
on a Maser … or two …. or three :) …. this is TimeNuts after all ….
Bob
Post by Scott McGrath
The 18” inch requirement is partially for damage resistance and
partially to ensure adequate soil moisture for conductivity.
Content by Scott
Typos by Siri
Post by Glenn Little WB4UIV
To do the grounding correctly, all connections exterior to the
building are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is
to be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every
16 feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18"
burial requirement is to avoid accidentally digging it up or damaging
it. I can't think of an electrical reason for it.
Post by Glenn Little WB4UIV
A lot of work, but, cheaper, in the long run, than continuing to
repair/replace equipment.
It depends
Unless you're doing geodetic or precision timing work with a 2 or 3
band GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna
itself might be sacrificial.
As always, there's a risk/budget tradeoff
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--
Dr. Don Latham
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

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Scott McGrath
2018-06-19 22:51:43 UTC
Permalink
Raw Message
If you see St Elmos fire ‘corona discharge bleed process is working as expected

Content by Scott
Typos by Siri

On Jun 19, 2018, at 3:55 PM, Bob kb8tq <***@n1k.org> wrote:

Hi

If indeed a proper ground system *could* be depended on to “bleed off” and prevent discharge things
would be *much* simpler. Indeed I’ve been on towers and decided to exit that location as the bleed
process became audible. It very much does happen. It simply is not a 100% sort of thing.

Bob
Post by Scott McGrath
Probably the easiest and most economical grounding system is the halo ground with antenna grounds bonded to the halo and the house ground bonded to the halo as well.
The halo conductor sizing is governed by local codes, But really what you are doing ensuring that the entire structure and earth around it is at the same potential so a nearby strike does not cause ground currents to flow.
A direct strike is probably going to fry anything it hits because of the gigajoules of energy concentrated within the discharge
But a proper ground system also ‘bleeds off’ the potential difference thereby preventing discharge
Content by Scott
Typos by Siri
Hi
18” down in a swamp likely is plenty for conductivity. 18” down in a sandy desert (or on an ice sheet) may be way
short in terms of conductivity :) The real answer to any of this is “that depends”. (Yes, the ice sheet grounding
problem is from a real case that shows up in some class notes from way back ….).
Some locations get multiple hits on a weekly basis in the summer. Other locations get a close strike once every
few decades. What makes economic sense for one probably does not make sense for the other…. A “full up”
protection setup can easily run into hundreds of thousands of dollars. I’d much rather spend that kind of money
on a Maser … or two …. or three :) …. this is TimeNuts after all ….
Bob
Post by Scott McGrath
The 18” inch requirement is partially for damage resistance and partially to ensure adequate soil moisture for conductivity.
Content by Scott
Typos by Siri
To do the grounding correctly, all connections exterior to the building are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is to be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every 16 feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18" burial requirement is to avoid accidentally digging it up or damaging it. I can't think of an electrical reason for it.
A lot of work, but, cheaper, in the long run, than continuing to repair/replace equipment.
It depends
Unless you're doing geodetic or precision timing work with a 2 or 3 band GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna itself might be sacrificial.
As always, there's a risk/budget tradeoff
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To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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Martin VE3OAT
2018-06-19 16:16:46 UTC
Permalink
Raw Message
I put my GPS antenna only as high as it needed to be to clear any
accumulation of snow in the winter, so it is about 3 feet above the
peak of the roof of the house and about 19 feet above ground level.
The 8-inch ground-plane under the puck antenna is grounded to my radio
ground. No other precautions have been taken except to disconnect the
antenna from the receiver whenever storms are expected or when I will
be absent. With this set up LH almost always reports 8 satellites
being tracked.

Having said that, the yard is "protected" by a 48-foot tower with a
4-element Yagi for 14 MHz atop it and lots of ground rods and radials.
The house is "protected" by a 28 foot TV-type tower at one end of
the house.

Still "waiting" for my first lightning strike -- hope I am long-gone
before it arrives.

... Martin VE3OAT





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