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.

On Mon, Jun 18, 2018 at 2:29 PM, Dan Kemppainen dan@irtelemetrics.com
wrote:

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

==

On Mon, Jun 18, 2018 at 1:39 PM Chris Smith chris.smith@alum.mit.edu
wrote:

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)

On 6/18/2018 1:29 PM, Dan Kemppainen wrote:

--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)

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-bounces@lists.febo.com] On Behalf Of
Oz-in-DFW
Sent: Monday, June 18, 2018 2:25 PM
To: time-nuts@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)

On 6/18/2018 1:29 PM, Dan Kemppainen wrote:

--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Graham wrote:

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

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

On 6/18/2018 2:29 PM, Dan Kemppainen wrote:

--

Glenn Little                ARRL Technical Specialist  QCWA  LM 28417
Amateur Callsign:  WB4UIV            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"

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 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.

On Mon, Jun 18, 2018 at 2:29 PM, Dan Kemppainen dan@irtelemetrics.com
wrote:

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Also see this

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

Content by Scott
Typos by Siri

On Jun 18, 2018, at 5:51 PM, Charles Steinmetz csteinmetz@yandex.com wrote:

Graham wrote:

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

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

On 6/18/18 6:39 PM, Glenn Little WB4UIV wrote:

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.

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