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Lightning arrestor

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#1
Hi everyone, have a couple lightning arrestors for two antennas I would like to install before the coax enters the equipment but would like to know if I could install them inside the house behind the equipment table (where the ground plate is) or if I have to leave them outside, the reason I ask is because I have about 8 feet of coax inside the house all the way to the equipment and if I put them outside I would have to leave all that wire outside the house (don't know if is ok) and make a roll or something I really don't want to cut the coax since I bought it like that. Any responses and ideas would be appreciated thanks, Ricky.
 
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#2
Ideally you want it outside, to try to prevent it getting into the house. However, having it inside is OK.

Not sure I'd mount one at your operating position, while it might help protect the radio, you still need to get the possible energy back outside to the ground. Making that ground path as straight and short as possible is key.
 
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#4
Thanks for the advice and ideas. I will cut the coax and install new PL-259 connectors to leave the Lightning arrestos outside bolted to a copper plate that is attached to the ground rod and properly seal them or maybe put them in a box on the wall about a foot from the ground rod.
 
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#5
Something to consider is you will probably not be protecting your equipment from a direct lightning hit because it takes a lot more engineering and equipment than a lightning arrestor and a ground rod to survive a direct hit. At best the setup you describe might shunt some induced high voltage on your antenna from a nearby strike to ground, but if lightning hits your antenna with the arrestor on it, you will probably destroy your radio, all your TVs, computers, basically anything plugged into an outlet and some stuff that's not even plugged in.

The reason I'm bringing this up is because many people get a false sense of security from a lightning arrestor and the only way to prevent damage is to have a very expensive engineered and guaranteed lightning system, or disconnect the coax and toss it out the window if a storm is brewing.
 
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#6
If you make a good ground for your antenna and coax it will attract lightning. If you do not ground, the lightning will select your neighbours grounded tv antenna as its victim.

Overvoltage protection between inner lead and coax shield are always a good idea and having the coax curled up with air between the turns makes it an inductive coil that will make the lightning take another route to ground instead of your equipment inside the house.

The current from a lightning are so high than any type of cable goes high impedance and doesn't protect from a hit. You'll need something like a huge waterpipe that goes deep into ground to have a chance agains a lighting strike. Better then to try and avoid it completly in the first place and have somebody else trying to ground that huge lightning strike energy.

If you power your house from hanging power lines it will be a source for high voltage spikes and you should concentrate your efforts into making that power box at you house really well grounded and over voltage secured.

/Ubbe
 
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#7
As prcguy said these devices are "surge" arrestors. The NEC requires the shield of the coax to be grounded near the entrance point into the building (or within 2-feet inside per R56). Placing the arrestors outside is more convenient for grounding the shield but more problematic for water proofing. Also the ground rod for the coax shield ground must be connected to the main electrical panel ground (along with all other ground rods).
BB
 
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#8
National Electrical Code Article 810 deals with grounding of antennas and you can find all the details with a Google search.

As prcguy said these devices are "surge" arrestors. The NEC requires the shield of the coax to be grounded near the entrance point into the building (or within 2-feet inside per R56). Placing the arrestors outside is more convenient for grounding the shield but more problematic for water proofing. Also the ground rod for the coax shield ground must be connected to the main electrical panel ground (along with all other ground rods).
BB
 
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#9
If you make a good ground for your antenna and coax it will attract lightning. If you do not ground, the lightning will select your neighbours grounded tv antenna as its victim.
Sorry, but I do not agree with this, and I think it's colossally bad advice.

In the United States, the National Electric Code requires proper grounding of antennas.

Not grounding equipment and thinking that will protect your system is a rather foolish approach. Lightning will find it's path, and a fraction of a millimeter of insulation on the cable, in the radio, or on the power wiring will not stop a high energy bolt of lightning. Remember, it travels thousands of feet through the air to get where it's going.

And direct strikes are not the only issue. Even a nearby strike and induce enough energy to damage equipment, start a fire, or injure someone. Relying on a strike hitting your neighbors house, a lamp post, power pole or something else will not guarantee your equipment will survive.

Overvoltage protection between inner lead and coax shield are always a good idea and having the coax curled up with air between the turns makes it an inductive coil that will make the lightning take another route to ground instead of your equipment inside the house.
No. While it may encourage the energy to find another path, the induced energy from even a nearby strike will do damage, coiled coax or not.

The current from a lightning are so high than any type of cable goes high impedance and doesn't protect from a hit. You'll need something like a huge waterpipe that goes deep into ground to have a chance agains a lighting strike. Better then to try and avoid it completly in the first place and have somebody else trying to ground that huge lightning strike energy.
Commercial radio sites handle this by having a network of ground rods. The design of the system depends on the conductivity of the soil.
Again, not grounding and thinking that it will protect your equipment is foolish. If it has worked for you, it is simply because you have been lucky. Designing a system based on luck only works for so long and certainly shouldn't be given out as advice to others. Even if it did work, it would require others to do a proper job of grounding, and I've found that in the majority of hobby and consumer installations, there is no grounding at all.

If you power your house from hanging power lines it will be a source for high voltage spikes and you should concentrate your efforts into making that power box at you house really well grounded and over voltage secured.
This part is correct.
 
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#10
To add, it is possible and common in the two way radio, satellite broadcast and cell phone industry to design a lightning system that will survive multiple direct hits and the only damage will be physical damage or destruction of the antenna with everything connected surviving just fine. Its just not practical to do this in an existing house.

Grounding or floating an antenna or tower has nothing to do with lightning attracting it and I've seen lightning bypass everything on a two story house, go through a window at ground level and hit stuff inside the house below ground level, including its owner. That one brought up some religious connotations, or lack of.
 
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