Inline Lightening Arrestors
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| May 21st 2013, 18:27 | |
KK1NGJTotal Topics: 0 Total Posts: 0 |
I was looking at some pictures of lightening arrestors, and thinking about the coax that feeds both sides. Then I thought about how much potential voltage they might be called on to handle. Then I wondered how such voltage would ever get to such a device. Thru the coax shielding, right? Upwards of a million volts in some cases, right? Would the shielding handle that for even an inch? Let alone fifty feet to a lightening arrestor. Are these devices one of a group of 'Great, but useless' products? BTW it was difficult to pick a category for this question, feel free to move it where you think it might better fit in. |
| May 29th 2013, 01:50 | |
WA0CBWTotal Topics: 0 Total Posts: 0 |
The purpose of the surge arrestor (they are not lightning arrestors) is to shunt any surge voltage on the center conductor to ground. Surge arrestors need to be connected to the stations single point ground. In commercial installations the surge arrestor must be mounted no more than 24 inches from where the coax enters the building. Also remember that the NEC (National Electrical code) requires the coax shield to be grounded to the single point ground before it enters the building. For more grounding information look at section 810 of the National Electrical code. Motorolas R-56 manual also provides additional information for correctly grounding your station. The ARRL also has much useful information for grounding your station. Bill |
| May 30th 2013, 16:22 | |
KB0HAETotal Topics: 0 Total Posts: 0 |
Hi. Bill is right. Nothing can reliably protect your station from a direct lightning strike. I can't quote the exact numbers, but if all of the energy of an average lightning strike could be captured, it could power everything in Los Angeles for a year or more! |
| Oct 8th 2013, 08:49 | |
M0ELSTotal Topics: 0 Total Posts: 0 |
what about rather trying to bleed off a static charge before it can build up to a level where a strike occurs. We know there are normally streamers from the clouds coming down and from the ground up to the clouds. If we can disrupt the streamer going up by bleeding off the static charge, the downward streamer would possibly find another route to ground, away from one's antenna. |
| Oct 9th 2013, 14:34 | |
WA0CBWTotal Topics: 0 Total Posts: 0 |
Actually "bleeding off" is really equalizing the charge. This is why you ground the coax braid just before it enters your shack. This is also why you should use DC grounded antennas. DC grounded antennas will show a short between the center conductor and the outer shield. You should also ground the metal mast or tower supporting the antenna. And last be sure that ALL grounds are connected together at some common point (usually the house electrical system ground). Bill |
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