Dealing with Lightning

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

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.

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...

Recommended above is ESE (Early Streamer Emmission) technology that was rejected by the National Fire Protection Association (authors of the National Electrical Code).

PDF page 18+) 00-60 D#00-22 starting with mention of Heary Brothers Lightning Protection Company, Inc., Bryan Panel Report follows:

Also Dissipation Arrays and pipe cleaners, do they work?:

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

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.

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.

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

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.

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

snipped-for-privacy@panix.com (Al Dykes) wrote in news:e7f4h4$q8k$ snipped-for-privacy@panix5.panix.com:

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?

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?

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?

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?

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

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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.

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.

...

ISTR = "I seem to recall".

There is a tiny transformer behind each RJ45 jack that blocks Bad Shit up to several thousand volts from getting past the jack. Trust me, I have a degree in science. :-)

Can't have too much.

100 Meters is the Spec limit for Ethernet over CAT5/5e/6 cable between two ethernet devices. It will work if the connectors are put on right.

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...

snipped-for-privacy@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.

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.

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.

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:

snipped-for-privacy@sushi.com hath wroth:

The SMT components are probably varistors. My guess is: |

'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.

That's what Polyphaser uses in some of their products.

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.

No clue. Are those for lightning or are they just to eliminate static electricity buildup on the fence?

snipped-for-privacy@panix.com (Al Dykes) hath wroth:

The original source:

various protectors look a bit different than those in the Hyperlinktech photo. This one appears to have real spark gaps:

I'm not sure of the ratings, but the case style is correct.

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:

some repeater owner knows the name.

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.

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:

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.)

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.

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.