Can coax survive after a lightening hit?

[fourstringburn]

Of all the rotten luck, yesterday I was heading home and as I was cresting over a hill on the east end of Albuquerque before dropping down into the canyon, my semi-truck was struck by lightning. This caused the truck to shut off possibly by having the trucks ECM fried out among other things, and I was fortunate to get it off the roadway fast enough without the benefit of power steering. The truck had to be towed back into town since the whole ignition system was dead.

I don't believe I had a direct vertical hit but rather I got hit by the branches of current from the main discharge since I recall seeing more horizontal streaks going across my windshield. Either way, a brief terrifying experience.

After checking for any physical damage to my truck, my attention turned to my radio equipment. My HF radio and CB radio were on but I wasn't transmitting at the time. My Icom 7000 receives but has no power out on transmit and my CB radio blows fuses when trying to transmit. I verified this on my home station as well. My HF amplifier internal fuses blew so I will have to check later to see if at least my amp survived as well as some of my other HF accessories.

My HF screwdriver antenna appears to have no damage physically but on the CB antenna, the stainless steel whip was completely burned off and a corner cap on the a pl-259 elbow used at the CB antenna connection was blown out.

After this experience, from now on anytime I see lightening in the area, I will unplug the coax cables at the antennas. I now have to see if my insurance might cover this but I doubt it. Hopefully the Icom and the CB is repairable.

My question on the coax is since I believe the lightning current traveled down the coax, is this coax probably fried out to or should I replace it anyway? I was using RG213 for the HF and CB, and LMR 240 for the VHF/UHF which can withstand high current but from lightning strikes, I'm not sure.

 

[Beetle]

If you can still actually SEE the coax, none of the main branches of the lightning (no "e") passed down it. RG-213 is less than 1/2 inch in diameter, and the actual conductive parts of it are not able to carry the tens or hundreds of thousands of amperes of any sort of a direct strike. It'd be vaporized. What you and your truck experienced is the induced current from a nearby (maybe within 1000 yards) strike. That will induce a large voltage spike on anything conductive within a good radius. That spike wants to find ground -- EARTH ground. If it's separated from Earth by an insulator or a poor conductor - like tires - it very likely will force its way to Earth anyway if the initial spike was typically hefty.

 

[unit_399]

4string -
You can test the coax pretty easily. Get two 50 ohm dummy loads, and an SWR meter. First, put a 50 ohm dummy load on one end of the coax, and connect a radio and an SWR meter to the other end. The SWR reading should be practically 1:1. If it checks ok, connect the 2nd dummy load in series with the first.(100 ohms total) and hook it across the coax. Your SWR reading should be about 2:1. If these are the results you get, you're good to go. If the readings are significantly higher, scrap the coax.

Like Beetle said, it is probably ok, but the test will give you peace of mind if nothing else.

Sorry for your bad luck. Hopefully the insurance will cover the damage.
73s.

- J.J. (unit 399)

BTW: if the insurance will pick up the tab, get some new coax too.

 

[binrat]

If that happened to me, I would just replace it.

 

[fourstringburn]

If you can still actually SEE the coax, none of the main branches of the lightning (no "e") passed down it. RG-213 is less than 1/2 inch in diameter, and the actual conductive parts of it are not able to carry the tens or hundreds of thousands of amperes of any sort of a direct strike. It'd be vaporized. What you and your truck experienced is the induced current from a nearby (maybe within 1000 yards) strike. That will induce a large voltage spike on anything conductive within a good radius. That spike wants to find ground -- EARTH ground. If it's separated from Earth by an insulator or a poor conductor - like tires - it very likely will force its way to Earth anyway if the initial spike was typically hefty.

Thanks for the reply.

I get what you are saying, but I believe I did get hit from what I saw and due to the electronic damage on my truck's ignition system, but why would the CB antenna's whip be completely burned off and also the corner cap on the pl-259 elbow be blown off?

Do you know of other people who been hit by lightning either at home or mobile and has their coax vaporized?

 

[Captain Kilowatt]

I have had holes burned thru 7/8 inch coax cable phasing lines from lightning strikes to the tower at a commercial site. The holes were where the cable was against the tower. Also lost a few 7/16 DIN connectors in the process. If it were me I would just replace the coax. Why chance it down the road. It's going to be the cheapest thing to replace in all likelihood.

 

[222DBFL]

Replace all coax!! Like CK and also Beetle said are 110% true. Coax isn't made to handle the type of voltage that a lightning strike makes. It might look okay and may even test okay, but it may also have a weak spot. Best off to just replace it all and have the confidence of knowing it's all new. Sorry for the loss. That is wild and I'm sure your britches show the signs of a good scare!! Hope you are okay and that your Icom isn't toasted. Good luck man!!!

 

[fourstringburn]

Yeah, I think I might as well replace all the coax cables. It is very time consuming to do so since I ran them under the floorboards and out under the cab to 3 antennas in 3 different locations.

Thanks for the replies and advice!

 

[jessejamesdallas]

Lightning hits the truck....Possibly thousands of dollars worth of damage to electronics, and your main concern is 75¢ a foot coax?

 

[fourstringburn]

Lightning hits the truck....Possibly thousands of dollars worth of damage to electronics, and your main concern is 75¢ a foot coax?

Not my main concern at all. just another one possibly to contend with and as I said in post #8, it is a chore to replace it properly as I did previously plus my truck is being towed out of state and I can't get to it anytime soon. I only had a chance to take out what I could.

I counting on by the time I have my radio and other gear back up and running, my truck may be back up and running too and I can put my radio's back in and be good to go. I would like to think my coax is still good and shouldn't have to replace it but this may not be the case and that's why I was asking for people's opinions.

Does this make sense to you or do I have to quote your signature back at you?

I also wanted to share my experience with others that may read this to show what can happen and to take precautions so this might not happen to them.

 

[Captain Kilowatt]

The closest I came to being hit while in a vehicle was the time I was driving home from a call-out in the middle of the night during a thunderstorm. Just as I entered the steel overhead bridge across a river on a tidal marsh lightning struck the bridge. It blinded me and scared the bejesus out of me but all was well in the end. I would have had a VHF business band mobile in the car at the time but cannot remember if I had any other radio gear or not. All was good after anyway.

 

[jessejamesdallas]

Not my main concern at all. just another one possibly to contend with and as I said in post #8, it is a chore to replace it properly as I did previously plus my truck is being towed out of state and I can't get to it anytime soon. I only had a chance to take out what I could.

I counting on by the time I have my radio and other gear back up and running, my truck may be back up and running too and I can put my radio's back in and be good to go. I would like to think my coax is still good and shouldn't have to replace it but this may not be the case and that's why I was asking for people's opinions.

Does this make sense to you or do I have to quote your signature back at you?

I also wanted to share my experience with others that may read this to show what can happen and to take precautions so this might not happen to them.

Going by what you said happened to the CB Antenna (which I assume was connected to the coax in question) Even on the outside chance the coax looks to be good, there's no way I would trust re-using it, regardless of how difficult it maybe to replace, is what I was getting at...Coax is cheap enough to replace weekly if you have to, rather than talking a chance on damaging radio equipment using coax that has had 10,000 gigawatt's ran threw it!

 

[Beetle]

Not sure what you mean by "the corner cap" on a connector, but lightning is one of the strongest elemental forces there is. A "spark" carrying thousands of amperes of current and a potential to Earth, even across a mile or more of just air (which is a very good insulator) ... let's just say that lightning will go where it wants, by whatever route it happens to choose, through or around whatever it encounters, including rubber tires. It's unpredictable, just like a tornado.

I have seen radio antennas on Navy ships take direct strikes with no lasting effects - because the Navy knows how transmission lines must be installed. They inspect the antenna systems regularly and keep them ready to go.

You may have been struck, but I doubt it was the main part of the bolt. The antenna was the most vulnerable component of the moving vehicle and disappeared in a bit of plasma. It's possible that the ignition system damage got into the truck's electrical system via the coax' last hurrah.

 

[fourstringburn]

10,000 gigawatt's

Actually it's 1.21 gigawatts!

 

[jessejamesdallas]

Actually it's 1.21 gigawatts!

your right...I stand corrected!