Lightning and Me

sahallie · Posted: Fri Mar 14, 2008 10:17 am Post subject: Lightning and Me

I own a Linksys WRT54G3G-ST. Actually, I now own two of them. The first one I bought from the 3G Store and the 2nd one I picked up at CompUSA during their going out of business sale ($75 new in the box). Anyway....

I have killed 4 of these things since September '07. The problem was that the ethernet ports kept going dead. My workaround was to move the network cable to the next open port and RMA the router back to Linksys. After the 2nd router died, I searched everywhere for a clue as to why this was happening. Then I discovered a pattern. The problem seemed to be happening during electrical storms. I bought an APC surge protector (network and AC) and waited for the next storm. It came and this time killed all 4 ports at once. That is when I discovered the CompUSA sale.

I was going crazy trying to figure this out. The mast is grounded to the same ground as the router. I was not taking a direct lightning hit. Not even close. I was totally baffled. Then, during my last storm while I was using the wireless with my laptop, the network died. I went to look at the router and it was lit up like a Christmas tree. I pulled my SA595 card out and that is when I saw it. When I sat the card down on the desk it sent a spark to a piece of metal on the desk. I touched the end of the card and got a really good jolt. I pulled the antenna lead and got an even bigger jolt. I am not talking about a little jolt. I am taking like ouch! Here's the wierd thing. The EVDO card worked perfectly, but of course, the router was toast. Again.

I spent a ton of time researching this. Apparently what was happening was that "static" electricity was building up in the air during the storms. This was driven by the wind and other physics stuff that I don't understand. But the point is, this static was collecting on the OUTSIDE of my antenna cable and charging the braided shield wire.

I had a big electrical storm yesterday and another is occurring as I write this so I am confident that I have fixed it. I simply grounded the OUTSIDE of the antenna cable. I did this by running a copper wire to the metal coupler on the antenna and attached it with a small hose clamp. I then ran the the other end of the wire to a standard household plug and attached it to the ground plug. I plugged it into my fancy APC surge protector and life is good. I just pulled a speed test and I am at 1220/400 so performance is not an issue.

Please forgive the dissertation. I hope that this helps someone.

Dave

JoeCHecht · EVDO Junkie Joined: 05 Jan 2008 Posts: 241

I'm no electrical engineer, and can only speak though experience and the research I have done.

Lightning and static buildup is an interesting issue. I own a sailboat (big time lightning issues), and live in (approx) the second highest house in the second most lightning struck place on earth. While you cannot keep the stuff out, you can minimize the damage.

Last year was the worst on record for lighting hits burning down houses in our area. We have better protection than anyone I know, and we lost about five thousand bucks in fried equipment last year alone. Here in Florida, the insurance companies are dropping policies by the millions, even if you have never had a claim, and its often impossible to get good insurance at any price. Needless to say, we do not make insurance claims (so far) for lighting damage. Since we foot the bill, we do a lot to minimize losses.

Some of the things we have learned:

1) Most of the "equipment coverage" provided by most power surge companies require that you register the surge unit, and the equipment plugged in to the unit to get any coverage, and play by the stated fine print rules. I know that Belkin is an exception (to both registrations), and I know that in general, you may you get pennies on the dollar by the time you go through all the hoops to make a claim, including spending a bunch of time and your own money to get repair estimates (shipping laptops, paying bench fees, bla bla).

2) If you do get hit, consider yourself lucky if 80% of consumer grade surge/ups units actually do the job. After a hit, you really need to replace all surge/ups units, regardless if the "protected" light is still on.

3) You need to be very careful to limit the number of lighting related entry points. For example, I am unsure of why, but I have read (and experienced) that doorbells seem to be popular with lightning. Twice, in two differing states, we have been hit on the roof, and we had an arc go over the roof, hit the doorbell, then arc five or six houses, hitting the doorbells on each house, and burning up electronics in every house. This year, we are going to wireless doorbells, and putting big honking grounding rods on anything that might might get arced. We are also building a Faraday cage over the exterior air conditioning unit, and putting up several lighting rods.

Exterior antennas are a special concern, and really require a lighting arrestor. This may even be a code requirement depending on where you live. Further, the grounding wire needs to go (as straight as possible) to a grounding rod, as opposed to the ground wire of an electrical plug in your house. A straight path is key.

I am unsure what the 3G experts would tell you about needing a lighting arrestor or proper grounding for an external antenna installation. I do not recall seeing anything on the website about it. I did see a wiring diagram showing an external antenna installation that looked suitable for harnessing the power of a lightning strike and blasting a person "back into the future", without the aid of a mad scientist, a Delorean or a flux capacitor.

The fact you are getting a static buildup on the coax shield (so often) concerns me. Are you sure this only happens just during lighting storms, and not (for example) on very dry days as well? I find it strange that you get this with every storm, as even here, its pretty rare to see electrical potential build up in the same place. If it happens more often (dry day), then something is very wrong with the wiring/equipment somewhere.

A static charge buildup is a very bad thing, and can ruin your equipment. The fact that you can feel it indicates to me that perhaps tens of thousands of volts are building up to create the charge. Not good. If it only happens during storms, consider yourself as lucky as Ben Franklin, and count your blessings that you are still here in good heath, with you, your house, and equipment still intact.

Its probably worth mentioning that a good ground may also massively improve your reception (or the lack of one may render massively degraded reception), depending on the antenna design, and its location. I was unable to find an expert reference about this at 3G.

Again, I am not an electrical engineer, and only speak from experience and the research I have done.

Should there be any experts out there that wish to chime in and correct any fault with what I have posted, please do so.

Joe

sahallie · Posted: Fri Mar 14, 2008 1:23 pm Post subject:

My antenna is the highest point on a ridge with nothing between me and the Pacific ocean 50 miles away. Lightning was a concern when I built the house and so I ran a wire between the roof and earth ground (big rod driven way down in the dirt). My weather station and Wilson antenna share a common mast and that mast is attached in a straight line to my earth ground. That is part of the reason I was so slow on the uptake about this router thing. I assumed that a good mast ground would take care of all but the worst events.

I searched in vain for a lighting arrestor for my antenna cable. It was an engineer at one of the lighting arrestor manufacturing companies that explained to me what was happening. He told me that even if I moved my antenna into into the attic, I would probably still get a static charge. He also told me that by allowing the static to 'bleed off" to ground, it would not have the opportunity to build up to a point of destroying my router. I did get a lighting arrestor but it doesn't fit my N type cable connectors. It is a gas discharge unit type. It is "supposed" to handle a direct hit. I hope I never find out.

Joe makes a good point. I too am no expert and everyone should do their own due diligence before playing with lightning.

JoeCHecht · EVDO Junkie Joined: 05 Jan 2008 Posts: 241

Sounds like you took this pretty seriously. Good job!

alhanson · Posted: Fri Mar 14, 2008 3:40 pm Post subject: bird on a wire

Sahallie.

Think of a bird on a high power line. Next think of your modem and how to make it like the bird on the high power line. If you put grounding block on the coaxial cable between the antenna and the modem, then ground the block into the ground of the electrical system of your home your modem will be like the bird. Of course then put the surge protectors on all the electrical outlets that power your LAN. Now all your computer routers and switches on your LAN are like the bird on the wire.

You have been grounding your antenna through your modem and the weakest point has been failing.

I am not an expert.

al
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alhanson

s2man · EVDO Newbie Joined: 10 Mar 2008 Posts: 6

I'll bet some of you guys slept at Holiday Inn Express.