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Post by bobcat4109 on Apr 5, 2019 13:59:25 GMT -5
Just popped up in my head here during lunch.....
Has anyone ever a) seen or b) known of ... a lightning protector saving ANYTHING at ALL with a lightning hit?
As I understand them, they are supposedly a "spark gap" that the RF will not cross (so radio works fine) but current from a lightning hit will find attractive and jump across to ground.
Thinking about this.... there is a LOT of energy in a lightning hit. I don't doubt that the lightning will find it's way to ground through that gap... but I DOUBT VERY MUCH that it would be a perfect thing. In other words the coax from the antenna to the protector.... toast! The coax from the protector in to the radio gear..... still usable!!!!!
With this in mind, is it really enough to protect the equipment? Or should we still be throwing coax cables out the window when lightning approaches???
Thanks,Bob
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Sandbagger
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Post by Sandbagger on Apr 5, 2019 17:37:39 GMT -5
Just popped up in my head here during lunch..... Has anyone ever a) seen or b) known of ... a lightning protector saving ANYTHING at ALL with a lightning hit? As I understand them, they are supposedly a "spark gap" that the RF will not cross (so radio works fine) but current from a lightning hit will find attractive and jump across to ground. Thinking about this.... there is a LOT of energy in a lightning hit. I don't doubt that the lightning will find it's way to ground through that gap... but I DOUBT VERY MUCH that it would be a perfect thing. In other words the coax from the antenna to the protector.... toast! The coax from the protector in to the radio gear..... still usable!!!!! With this in mind, is it really enough to protect the equipment? Or should we still be throwing coax cables out the window when lightning approaches??? Thanks,Bob I used to have a lightning arrestor on our 220 Mhz repeater. I can't say whether it worked or not as we never took a direct strike. This thing had a replaceable gas discharge cartridge that "absorbed" or shunted the lightning charge to ground. One time we started having desense and SWR issues and it turned out that the gas discharge cartridge was starting to go "bad". Replacing it cure the problem. I don't know if near miss strikes eventually killed it, or if it just got tired of 80 watts of RF going through it all the time. A lot of what these things do revolves around reducing static build up which hopefully lessens the chance of a direct strike. But many years later, and long after I removed the protector (it seemed to add to the desense issues) we finally did take a direct lightning strike. Our antenna (which was a Hustler G7 colinear design), was a combination of aluminum broken up by coils on fiberglass. The lightning vaporized the coils and the only thing left of the antenna was the bottom 1/2 wave section, which surprisingly still had a 1.4:1 SWR after the hit. The majority of the strike went straight down the tower. We had a section of flexible flat copper braid that connected between the tower and our ground rod. The energy of the strike fused the braid into a solid copper bar. The only damage to the repeater was the receiver front end. Now if I had the lightning arrestor in line, would it have helped? Difficult to say. I don't think it could have saved the antenna from the meltdown that it received. It might have prevented the damage to the receiver. But who really knows. The bottom line, the best defense for your radio equipment against lighting strikes is to disconnect the feedline. Even if 95% of a direct strike goes directly to ground, that still leaves enough voltage to fry sensitive solid state components. Don't rely on a lightning arrestor. It's probably a false sense of security. |
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Post by bobcat4109 on Apr 6, 2019 18:03:21 GMT -5
A question I would have.......
If I put up an antenna should I do it in such a way that I go OUTSIDE to disconnect it..... so the the coax NEVER comes in to the house?
This story might explain why I ask:
Back in the mid-80's my sister's house went up in flames. She and the kids were fine but she lost just about everything she owned.
How did it happen? The final judgement was that lightning hit a pole behind her house, ran through the cable system, in to her TV set. This blew up the TV set which was very near curtains hanging on the back window. The curtains caught and that is all she wrote.
Since then, I've always wondered if a serious lightning storm came in the area ... is it best to go outside, disconnect the coax from the house, tape it up in a bag and lay it out there. With that, there would be no coax in to the house to follow....
Thoughts??
(of course it is all a game of statistics anyway..... but if you have a choice and a chance....)
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Apr 6, 2019 21:36:22 GMT -5
A question I would have....... If I put up an antenna should I do it in such a way that I go OUTSIDE to disconnect it..... so the the coax NEVER comes in to the house? This story might explain why I ask: Back in the mid-80's my sister's house went up in flames. She and the kids were fine but she lost just about everything she owned. How did it happen? The final judgement was that lightning hit a pole behind her house, ran through the cable system, in to her TV set. This blew up the TV set which was very near curtains hanging on the back window. The curtains caught and that is all she wrote. Since then, I've always wondered if a serious lightning storm came in the area ... is it best to go outside, disconnect the coax from the house, tape it up in a bag and lay it out there. With that, there would be no coax in to the house to follow.... Thoughts?? (of course it is all a game of statistics anyway..... but if you have a choice and a chance....) Disconnecting the coax cable outside certainly makes sense. If the lightning can't get into the house, it really can't fry anything. This reminds me of another lightning story along those lines. A ham friend of mine took a direct hit. He had wisely (or so he thought) disconnected his coax cable from his radios but he left it hanging behind his operating table. The lightning traveled down his coax and shot out of the connector, and jumped across the room to a 110V wall outlet. Once the lightning hit that, it spiked the electrical system which fried his TV, stereo, computer power supply, and computer modem which were plugged into the AC line. Of course, his ham rigs, which were disconnected from the coax, managed to escape undamaged. But it just goes to show that lightning will seek the easiest path to ground, so your best bet is to provide it one, so that it doesn't find its own convoluted path through your house wiring or other appliances. When you disconnect the coaxial feedline, it's best to connect it to a ground point, so the lightning travels to it rather than striking out looking for its own path. It is a game of odds. I've been a radio operator with outdoor antennas for 45 years and I've never taken a strike at either one of my homes. Of course, now that I've said that, I'll probably take a hit this summer...... |
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Post by bobcat4109 on Apr 7, 2019 18:12:29 GMT -5
Man that is one heck of a story. Jumped across the room to an outlet!!!
Got to get my A99 back in the air!!
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Post by cbrown on Apr 10, 2019 12:59:16 GMT -5
I used to have a lightning arrestor on our 220 Mhz repeater. I can't say whether it worked or not as we never took a direct strike. This thing had a replaceable gas discharge cartridge that "absorbed" or shunted the lightning charge to ground. One time we started having desense and SWR issues and it turned out that the gas discharge cartridge was starting to go "bad". Replacing it cure the problem. I don't know if near miss strikes eventually killed it, or if it just got tired of 80 watts of RF going through it all the time. The bottom line, the best defense for your radio equipment against lighting strikes is to disconnect the feedline. Even if 95% of a direct strike goes directly to ground, that still leaves enough voltage to fry sensitive solid state components. Don't rely on a lightning arrestor. It's probably a false sense of security. Excellent points. I too use a gas tube discharge system nowadays. I installed lightning protectors after my Browning Mark III took what had to be an indirect strike while I was at school back in the 1970's. I just usually disconnect the coax if I know there will be lightning in the area, but then I also live on top of a hill higher than most everyone else with soil that has a fair amount of iron in it. In fact, during the revolutionary war they actually made cannonballs on the area due to the amount of iron available. |
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Post by crambone on Apr 10, 2019 18:42:55 GMT -5
Ok I actually got to attend the lightning institute in FL back in 2000 as I owned a tower construction company. The basics that I came away with is the coax needs to have a ground strap installed ever 100’ maximum. The structure or tower needs to be properly grounded and tested. Earth geo’s, liquid grounds, structural grounds..... the polyphaser must be installed just before building entry and all grounds must have zero bends and only flow downward. The grounding bar must also be properly grounded and tied into all other grounds. All grounds are for the reason of showing a ground plain of the antenna and tower to be equal. The exclusion was the polyphase as this is the last resort for safety. I have seen towers that took direct hits and the coax will suffer but the equipment can be saved as I’ve seen the results. Cad welding is also a big help when making all connections.
So this is what I took away from the class. The testing facilities actually demonstrated a home take a hit on an incoming power line. The amount of energy was incredible as it ripped anchors off the wall and destroyed almost everything in the demo home. The home grounded property suffered exterior damage but almost all interior equipment survived.
The instructor said if connections are good and all ground lines face downward with zero upwards curves you will be doing the customer a great service.
So im a firm believer in grounding and polyphasers
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Post by bobcat4109 on Apr 13, 2019 10:40:20 GMT -5
I can certainly research it....but i have never heard of a polyphaser. Is it something most home yokels can afford?
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Post by crambone on Apr 13, 2019 19:33:55 GMT -5
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Post by SIX-SHOOTER on Apr 16, 2019 22:19:05 GMT -5
Our local 2 meter & 440 repeaters both have Polyphasers on them & several times the antennas have been blown apart off of the tower & not a single issue with the gear on the ground connected to those destroyed antennas. Other gear in the same building from other antennas dead as a door nail each time but they still don't use them? We trust them because they have worked so well for us. Also our repeater owner works for Clear Channel communications & that is what they use & what made a believer out of him at sites that had been hit & the gear still 100% working fine with antennas destroyed. You get what you pay for in this case & our money is on Polyphasers every time for the best protection. SIX-SHOOTER |
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