Dealing with Lightning

Have a question or want to start a discussion? Post it! No Registration Necessary.  Now with pictures!

Threaded View


For a POE Bridge device on a 10 foot mast, anyone have good ideas for a
home-made lightning arrester-ones I've seen advertised seem awfully
expensive for what should be a simple device. Mostly, I am concerned
about damage to my computer and to the  house. The ones I have seen
advertised are way too expensive, imo. Will a straight wire from top of
mast to good ground be a step in the right direction? How do I ground
the POE? I am not THAT about the radio being killed as I am about my
computer, house. What's a positive ground?
_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 140,000 groups
Unlimited download
http://www.usenetzone.com to open account

Re: Dealing with Lightning


wrote:

Quoted text here. Click to load it
For isolated buildings (farm barns, etc.) the best approach is to
place an array of static discharge points high on the building,
or nearby. These sharp static discharge points are connected to a
deep earth ground, such as a 6 foot copper rod like those used
for electrical power system grounds.

The array of static discharge points will "bleed off" the local
static charge that would otherwise entice a lightning strike. The
result is the building or whatever doesn't take a protected hit.
It just never gets hit at all.

Gordon

Re: Dealing with Lightning


Gordon wrote:
Quoted text here. Click to load it

  Recommended above is ESE (Early Streamer Emmission) technology that
was rejected by the National Fire Protection Association (authors of
the National Electrical Code).
http://www.nfpa.org/assets/files/PDF/700Minutes.pdf
(see PDF page 18+)  00-60 D#00-22  starting with mention of
Heary Brothers Lightning Protection Company, Inc.,   Bryan
Panel Report follows:
Quoted text here. Click to load it

  Also Dissipation Arrays and pipe cleaners, do they work?:
  http://www.polyphaser.com/ppc_TD1020.aspx


Re: Dealing with Lightning



Quoted text here. Click to load it
That is indeed an interesting paper, w_tom, but the issue seems
to be arguable. The text at the bottom of page 19 and top of 20
presents that the NFPA technology is no better validated than the
ESE technology.

I was speaking as an observer, not as an expert on the matter. I
grew up in a rural area of northwestern Oklahoma, where
thunderstorms are frequent and sometimes very severe. The use of
conventional lightning rods on rural buildings was a common
practice, but it was an observed fact that lightning did strike
these protective rods quite often. This usually did not produce
any severe damage to the building, but the acoustic explosion
would sometimes rip shingles off the roof.

Those buildings with the needle arrays were never struck, it
seems. I have seen these needle arrays glow, on a dark night,
when a severe thunder storm was settling in over the area, but
this was thought to have been caused by the slow, controlled
dissipation of the local earth charge. The local earth charge
would normally have brought about a lightning strike in the
immediate area, had the local earth charge not been dissipated in
a controlled way.

Gordon

Re: Dealing with Lightning


LittleJohn wrote:
Quoted text here. Click to load it

I think you'll find that for every POE device owner, there'll be a
different opinion on this. Some devices claim to have lightning
protection built in (whatever that means) and some have a Phasar
lightning suppressor between the device and the antenna. I've had very
good luck with an access point at a location that seems to be rich in
lightning strikes. With a Phasar lightning suppressor installed and
grounded to a copper rod driven into the ground, I've only had to
replace it once in about three years. At another location that's even
higher up and more open (on a steel tower), I've got the same history.
Had to replace everything once in the last three years.

Re: Dealing with Lightning



Quoted text here. Click to load it

No lightning protection will protect against a direct strike, or a nearby strike
that's carried over the antenna or power lines. The most you can do is try to
minimize the differences in voltage due to surges or distant strikes (ie the
grounding of the chassis or antenna), and to put up lightning protection (ie
rods) to minimize the air/earth potential in the immediate vicinity...

Re: Dealing with Lightning


Quoted text here. Click to load it


What he said.

IMO, you should ground the mast to earth, get a UTP lightning
protector and place it as close to the WiFi box as possible and ground
it to the mast.  

Bring the UTP cable into the house and right at the entry point use a
cheap Linksys router between the WiFi gear and your real computers.

Each CAT5 UTP jack is isolated to (ISTR) 4,000 volts so between the
lightning protector at the top of the mast and the linksys box you are
protected pretty well and if you get a really direct hit the Linksys
box will take the hit. They're really cheap.

The ARRL Ham Radio Handbook or several other ARRL publications will
discuss antenna grounding.  Your library should have a copy.

   http://www.rfparts.com/arrl_hb_2005.html


In addition, I'd get a max-length UTP cable (100 meters) , on the
spool, and use it to connect the entrypoint Linksys to the rest of
your network. The resistance, inductance, and capacitance will soak
up a surge that  makes it past the Linksys.  

The only thing that will protect you from a direct hit is full backups
stored offsite.



--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore. A Proud signature since 2001

Re: Dealing with Lightning


Quoted text here. Click to load it

Or a fiber converter.  Go UTP to 100FL and back for the link between the
devices.  Just make sure the AC adapters that drive the fiber converters are
also properly shielded and not on the same ground!  The added benefit is
that fiber can generally cover much longer distances that UTP.

-Bill Kearney


Re: Dealing with Lightning


Quoted text here. Click to load it


Good suggestion.  

What's the cheapest UTP-fibre converter?

It doesn't even have to be faster than 10MB for a long-haul WiFI or
cost-constrained application as they are unlikely to get the speed
advertised on the box.


--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore. A Proud signature since 2001

Re: Dealing with Lightning


adykes@panix.com (Al Dykes) hath wroth:

We don't get much lightning on the left coast, but it only takes one
hit to destroy some equipment.  I ran coax cable for the LAN at a
mountain top radio site.  Lightning hit the ground nearby and created
a substantial differential voltage across the ground as the charge
dispersed.  Because my stuff was seperately grounded at both ends of
the coax data link, I had what is commonly known as a ground loop.
Everything connected to the loop was fried.  I switched to fiber after
that and have had no furthur entertainment.

Quoted text here. Click to load it

10baseFX to 10baseT converters are fairly cheap.  Search eBay for
"fiber converter" or "fiber media converter".  Looks like about $40 to
$80 for "buy it now" depending on speed of the interface.  You'll also
need to look for "fiber cable".  Make sure the connectors and "mode"
of the fiber match the converter.

--
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Dealing with Lightning


Thanks to all for good answers to my post, more inline...


Quoted text here. Click to load it

<snip>

Quoted text here. Click to load it

I think I need a dummies guide to lightning arrestors. Do you mean an
arrestor device wired in series with the ethernet cable (UTP), and then
grounded to mast? If so, that's only to protect the indoor stuff and why
won't a simple mast to earth ground do all the bleeding off of the
surge, assuming it's a good ground attached to the top of the mast? Do
you have a source or url for example device? Should the mast ground be
connected as high on the mast as possible, with the radio a few feet
below it? Guess I don't understand why a second arrestor is needed if
the mast is grounded to earth at it's top?

Quoted text here. Click to load it


Please explain, how can they be isolated if they are connected directly,
don't know what ISTR is. Ethernet cable goes directly from radio to POE
injector,right? If the jacks are connected together, how can they be
isolated?

Quoted text here. Click to load it

I think I've got that solved? Good low (copper solid? gauge?) resistance
wire securely connected to top of mast straight line down to buried
copper rod, correct?

Quoted text here. Click to load it

Your talking again about the cat5 cable (is that universal twisted
pair). 100 meters sounds like a lot, is there no signal depreciation
in that?
 
Quoted text here. Click to load it

Well I will have that. Just don't want to replace my computer hardware
if I can avoid it.
_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 140,000 groups
Unlimited download
http://www.usenetzone.com to open account

Re: Dealing with Lightning


Quoted text here. Click to load it


Go to your public library and look for any edition of the American
Radio Relay League (ARRL) Ham Radio Handbook for an intro of antenna
grounding and grounding in general.

If you are going to put an antenna on a mast and hook it to a computer
you need all the protection layers you can get and if it's a direct
hit your only protection is off-site backup of your data.

If you get a direct hit, *some* of your computer gear is going to die
a horrible death. If you do the lightning protection and grounding
right it probably won't be your computer. The closest to sure-thing
protection is to disconnect the UTP cable when a storm starts.

Here's a CAT5/PoE Lightning protector that might be worth what it
costs.

  http://www.hyperlinktech.com/web/cat5e_lightning_surge_protector.php

It should be put outside the house on a grounding rod buried as
described in the ARRL handbook as close to the entry point as
possible. (note the copper clamp in the picture.

I'd have a "disposable" Linksys soho router on the inside
as another layer pf protection at the entry point.

This also serves as a convient place to disconnect the outdoor gear
when a storm gets close. Yank the RJ45 jack.

I'd also have *all* my computer power and all accessories running off
a decent UPS to isolate voltage differential in a close hit.  





--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore. A Proud signature since 2001

Re: Dealing with Lightning


adykes@panix.com (Al Dykes) wrote:
Quoted text here. Click to load it

Like many of the PoE lightning arresters I looked at recently, this
one only supports "midspan" PoE, and not "switch" PoE, so it's not
really 802.3af compliant.  Probably OK in the OP's circumstance, but
an important point, IMHO.

Besides, he wanted something home-made, and that (and the Polyphaser
device I settled on) cost $50-ish dollars...

Re: Dealing with Lightning



William P.N. Smith wrote:
Quoted text here. Click to load it

I wish they had a better photo, but this looks like  inductive PCB
traces and chip caps. That is not bad for simple ESD protection, though
I doubt it has any effect on a lightning hit.

http://www.okaya.com/HP3/image/GDT%20presentation.pdf
Some military gear I've bought uses a variant of these tubes.

The commercial installations I've seen use these things that look like
brushes that you put near the antenna. You can see one of these at the
left side of this photograph:
http://www.lazygranch.com/images/warmsprings/rad2.jpg


Re: Dealing with Lightning


miso@sushi.com hath wroth:

Quoted text here. Click to load it

The SMT components are probably varistors.  My guess is:
|
http://www.maida.com/content/products/varistors/smtseries/fullRecord.asp?iACVolts=115&iDCVolts=66&iDiskSize=3220&stylenum=8S17SM500
I'm not sure of the ratings, but the case style is correct.
500A for 20us isn't going to stop much, but it's better than nothing.

Quoted text here. Click to load it

That's what Polyphaser uses in some of their products.
  http://802.11junk.com/jeffl/pics/lightning/polyphaser-02.jpg
2000A for 20us is much better.  The only catch is that they destroy
themselves after each hit.  The photo above shows 4 spark gaps in
series.  That's good for 4 hits.

Quoted text here. Click to load it

No clue.  Are those for lightning or are they just to eliminate static
electricity buildup on the fence?
--
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Dealing with Lightning



Jeff Liebermann wrote:
Quoted text here. Click to load it

The manufacturer of those brush things is on the net, but I couldn't
find it. [Lost the bookmark between computer builds.] I think they are
used to dissipate static charge. [A brush has more surface area than
the tip of a lightning rod. ]

They are quite common in areas that get a lot of lightning.. Here is
another photo with 3 of the brushes:
http://www.lazygranch.com/images/bg/zigzagw.jpg
Maybe some repeater owner knows the name.


Re: Dealing with Lightning


On 27 Jun 2006 18:11:58 -0700, miso@sushi.com wrote:

Quoted text here. Click to load it



I go to plenty of mountaintop installation and have never noticed any
static dissipater brushes.  If they're really static eliminators, they
might have some radioactive Polonium-210 in them.  The alpha particles
are what makes the anti-static brushes for hi-fi records and such
work.

At one time, I worked for Granger Associates.  Their very first
commercial product was a static discharge system for aircraft.
  http://www.aaxico.com/aaxmfr/dayton.html
I guess they're called "lightning diverters".  I think the principle
of operation is different.  These are graphite brushes where the
bristles shrink as the electrical discharge burns off the ends.  I've
seen these on aircraft, but never on a fence surrounding a repeater
building.  That's about all I know about them.

I struck out looking for something relevant with Google.  Nothing in
the site managers magazines:
  http://www.agl-mag.com

I'd be interested (i.e. curious) if you find a reference to these
devices.

(1:15AM and still in the office.  This has not been a very productive
day.)

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558            jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com               AE6KS

Re: Dealing with Lightning



Jeff Liebermann wrote:
Quoted text here. Click to load it


I have static masters brushes, but this is different. I've only seen
these brushes in the dessert, so perhaps they are not effective in the
bay area.
Quoted text here. Click to load it

I made another google attempt to find the manufacturer for the brushes
with no luck. Next time I'm in the area, I'll see if there are markings
on the device.

There is a natural potential in the air when measured versus altitude.
That is, with an electrometer, you can measure the potential difference
between two points at different heights. I think these brushes are an
attempt to short out (if you will) the potential difference in the air,
making a lightning hit less likely.

I've witnessed two hits to the ground, both from my vehicle. You can
see a yellow glow on the ground as the sodium in the soil is being
ionized.


Re: Dealing with Lightning



miso@sushi.com writes:
Quoted text here. Click to load it

Neat!  How far were you from the impact point and did you feel any
effects?  I'm always wondered how well the shielding effect of a car
really is.  It has darn big windows and the doors aren't very well
connected to the frame electrically.

-wolfgang
--
Wolfgang S. Rupprecht                http://www.wsrcc.com/wolfgang /

Re: Dealing with Lightning



Wolfgang S. Rupprecht wrote:
Quoted text here. Click to load it

Many people have survived lightning hits (and many haven't), so a car
should be decent protection.

The hits were about a football field away. I was driving at the time,
though not very fast due to high winds. The rain itself was minimal. In
the high desert, the lightning is usually dry. Tumble weeds were flying
across the road and animals were doing the same (self powered, not wind
powered). This was on route 375 in Nevada, a very straight road where I
was driving, so I could take in the scenery.

Have fun checking this out:
http://www.sord.nv.doe.gov/Lightning/Lightning-sord.htm
Note the negative hits dominate.

http://www.lazygranch.com/images/bg/bgthing.jpg
http://www.lazygranch.com/images/bg/aldf.gif


Site Timeline