I'll start by saying, this is basically a never ending quest for knowledge for me. I don't know everything about it but am still learning, not that man knows everything about it either. Also my quest is to find a better solution to a tower lightning strike shunt system for the everyman's wallet. Now I will begin to say I think the principle behind the multiple type protection system is a place to start. I was thinking the primary protection could be a large breaker like mechanical kick off arm. But that only would prevent the peak of the surge from getting through, you would need a shunt to divert the beginning of the surge (that is not powerful enough to open the breaker). But the shunt would also provide a low resistance path for the energy. It's commonly recommended to have 8ft of electrode in the ground of a Cu plated Zinc rod. But for a tower system I would recommend a 20-75ft stainless steel rod, depending on the towers height. These can be driven with a light electric jack hammer with the proper attachment if the rod is not too long, but a longer rod will need a commercial pile driver type or like machine. The depth will also be determined by the soils type and average annual moisture content. If I am correct acidic soils resistance is greater than base and alkaline type soils. So a soil test kit can be picked up, a good move may be to also test the soil when erecting a tower and testing the lowest dug out soil is a good move to determine depth of electrode. Basic electrode layout should include (at the least), each leg of the tower as close as possible to the tower, avoiding right angles in the bonding wire, gentle radii, and tight mechanical bonding, no brazing of soldering for major bonding points. It is recommended to use silicon-Bronze mechanical connectors and tinned copper conductors. The mechanical bonding can prevent loosening over time due to wind induced vibrations, especially through guy wires. All bonding points will greatly benefit from corrosion resistant paint. But not on any contact points.
Lightning bit through quite a bit of concrete to get to the rebar, knocked several 100lbs chunks out to do it.
It is very important to have all things in the system bonded well, antennas (different antennas may need different methods), towers and masts, buildings, radios and other equipment. Even the buildings earth wires. All needs to be properly connected to make a major grounding system effective. You may even benefit from a system like this.
I don't know that I would want to be anywhere near this in the event of a strike! But its a proven method.
Back to the breaker, before the breaker kick off, I would think (and it needs more research) a set of inductance coils to disallow RF from leaking through it but allowing lightning surge to pass into the grounding system. Now this would be dependent on where the strikes origin is. If it does hit the antenna and tries to travel through the coax or any rotator or beacon wires this breaker would be the savior of your equipment. Steps would also need to be taken to ensure some sort of insulator fills the gap between the contacts of the open breaker to insure the energy does not jump the gap and goes to shunt into the nearest electrode, which would need to be very close to the breaker unit. As for keeping the RF inside the transmission line through the breaker I was thinking some sort of hardline with machined contact points would mate and prevent RF from leaking. The breaker upon kick off would ground out to the shunt, shield and center conductor along with it. Maybe even having some sort of automatic reset like 30 seconds to a minute after the strike. But that involves electronics, the point is to keep it mechanical so less can go wrong.
Alright a lot said, I'm hungry and temporarily out of info, so after I do more research I will add more and maybe more photos. Sorry for the long winded read, I hope it was interesting.
-Bill
Lightning bit through quite a bit of concrete to get to the rebar, knocked several 100lbs chunks out to do it.
It is very important to have all things in the system bonded well, antennas (different antennas may need different methods), towers and masts, buildings, radios and other equipment. Even the buildings earth wires. All needs to be properly connected to make a major grounding system effective. You may even benefit from a system like this.
I don't know that I would want to be anywhere near this in the event of a strike! But its a proven method.
Back to the breaker, before the breaker kick off, I would think (and it needs more research) a set of inductance coils to disallow RF from leaking through it but allowing lightning surge to pass into the grounding system. Now this would be dependent on where the strikes origin is. If it does hit the antenna and tries to travel through the coax or any rotator or beacon wires this breaker would be the savior of your equipment. Steps would also need to be taken to ensure some sort of insulator fills the gap between the contacts of the open breaker to insure the energy does not jump the gap and goes to shunt into the nearest electrode, which would need to be very close to the breaker unit. As for keeping the RF inside the transmission line through the breaker I was thinking some sort of hardline with machined contact points would mate and prevent RF from leaking. The breaker upon kick off would ground out to the shunt, shield and center conductor along with it. Maybe even having some sort of automatic reset like 30 seconds to a minute after the strike. But that involves electronics, the point is to keep it mechanical so less can go wrong.
Alright a lot said, I'm hungry and temporarily out of info, so after I do more research I will add more and maybe more photos. Sorry for the long winded read, I hope it was interesting.
-Bill
