A very good reference for EMP protection is MIL-HDBK-419.
This is downloadable for a number of web sources.
It is about 600 pages and is in two volumes.
This discusses a number of different sources of EMP such as nuclear and
lightning.
A lot is for protection of military industrial complexes, but, there is
a lot that pertains to us.
I worked for a military complex that assembled nuclear missiles.
The site was built to this handbook specs.
We had no EMP related damage at the site.
Number one rule, bond all grounds together. If something on your
property takes a hit, you want everything on your property to elevate to
the same level and the same rate.
If you have multiple, non bonded grounds, there is a different reference
for each ground. This is a major source for disaster.
I spent seven years in lightning mitigation. I was told by professionals
that I was wrong. The third time that their tower was struck, destroying
all of the lights and attached equipment, they followed my
recommendations. That was ten years ago. The three hits were within four
months of each other. The site has been free of destructive hits since then.
73
Glenn
WB4UIV
On 8/5/2016 10:37 AM, Eric Scace wrote:
Unfortunately, an antenna, cable, or piece of electronics located indoors is
just as susceptible to lightning surges as one that is outdoors.
Lightning-induced surges couple into these systems electromagnetically across a
wide range (VLF to SHF) of frequencies. When you think about your home from an
electromagnetic viewpoint, just imagine your structure with all non-conductive
materials absent. For a typical wood or brick/stone house in North America,
what you are left with is:
metal plumbing pipes and fixtures, with their geometry suspended in space
house wiring, CATV, Ethernet, and telephone cabling, and their service drops,
all suspended in space
electrical & electronic circuits of every kind (WiFi note, computer,
appliances), their power supplies and AC power cords, also suspended in space
metal furniture? That’s hanging out there, suspended in space, too.
any I-beam or other steel structural elements, some random aluminum flashing,
door knobs, and other similar metal construction materials used in the home.
That is what an electromagnetic pulse sees as it approaches and sweeps over
your home… all hovering over a lossy ground plane (earth) its varying
dielectric constant.. Each one of those pieces of metal, hanging in space, is
an unintentional antenna that experiences voltage differentials and current
flows.
A GPS antenna and its coax line that is installed next to a window is no
different from the same antenna/coax installed one meter outside the window… or
10 meters away outside the window. All three installations are effectively
“outdoors” from an electromagnetic viewpoint, and all three need effective
surge protection from lightning-, cloud-, and precipitation-induced voltage
surges.
(N.B.: Snow can be particularly bad for voltage surges. I’ve seen thousands of
volts per meter potential differences in moderate-to-heavy snowfall that
produced very significant current flows on cables.)
Surge protection for your antenna, its attachment to your receiver(s), AC/DC
power supply lines, and any other signal lines of significant length is cheap
insurance.
My continuously-operating electronics lives in an enclosed rack cabinet — not
too much worse than a proper Faraday cage. Every cable entering the cabinet has
surge protection at the point of entry. The cabinet is bonded to earth ground
by 2” copper flashing. In the past this system lived 22 years on a mountaintop
home, 1200 ft above surrounding terrain. Lots of thunderstorms — zero
damage/disruptions during that time… a sample size of one, admittedly, but
during the first 18 months at that site I had two lightning-surge damaging
events before I got serious about protection.
I have equipment at a coastal site with multiple 130-ft towers. That site had
damage events every 2 years or so — even when cables to the “outside” were
disconnected, and AC mains power was shut off at the main circuit breaker box.
After implementing comprehensive surge protection, we have had zero damage over
the last 12 years.
— Eric
On 2016 Aug 04, at 19:46 , Bob Camp <kb...@n1k.org> wrote:
Grounding the antenna is always a good idea.
A surge suppressor in the line could save you some
real cost if there is a lightning strike.
I did a quick search for SMA/BNC/TNC based surge
protectors and not much did come up, any suggestions
what to use there?
There are a *lot* of them on eBay. Many of them have N connectors on them.
I don’t know about Austria, but here in the US,
both are required.
Outside definitely, "inside" I'm not sure, but it
won't hurt to have additional protection for the
receiver(s).
It is a good bet that the antenna will be outside. I’d plan it that way.
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Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4...@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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