Ethernet lightning protection on antenna tower?

[DylanMadigan]

I have an antenna tower with a couple things on it, in addition to an Ethernet CCTV camera about half way up (on a 48ft tower). Would I need some sort of surge protection on the Ethernet line? I'd imagine yes, but would a cheap one suffice or would I need A nice one to actually protect it? Can't imagine the actual lightning would hit anywhere near that low on the tower but the energy would of coarse be carried through it.

I also heard something about having a loop or two in the Ethernet and LMR-400 cables can help reduce any surges before the protection device, or whatever gets through after the device? Looking around online I've seen mixed answers, but I don't think most of them were professionals.

This is not commercial so I can't really just dump money into the best of everything, but I would like to get what is necessary to protect the equipment adequately.

 

[a417]

Lightning protection for WLAN links – Engineering Radio

www.engineeringradio.us

Paul's blog can be VERY informative. He builds & maintains things designed to be struck by lightning.

tl:dr, shielded uv resistant cat5/6 w/ appropriate termination (watch the video) and then surge protection (as much as you can afford) and appropriate grounding. You can save money now, or spend money later.

you half ass it, and your tower gets hit, hopefully you can rebuy everything that was toasted.

 

[mmckenna]

https://www.polyphaser.com/surge-protector-1-pair-100base-t-ethernet-ix-1h

Yes, you need protection on it.
I'd not go cheap on anything to do with grounding/safety. You are essentially giving that energy a path directly into your home.

Doesn't matter if it's a direct strike or not, the induced energy from a nearby strike can do damage. If the tower gets hit, some of that energy will make it on to the Ethernet cable. Remember, that lightning bolt traveled thousands of feet through the air. A little bit of 300 volt rated insulation isn't going to stop it.

I've heard of the "loop" thing before as a way to create a choke for the high frequency pulse. Can't say I've ever seen it at a commercial site, though. What you will find is that the antenna/radio/camera, etc. will be grounded to the tower. The coaxial cable/twisted pair outer shield is grounded near the top, and every so many feet on the way down. It's grounded at the base of the tower, then again where it enters the enclosure as well as at the suppressor.

Polyphaser brand is expensive, but it's good stuff. You can probably find something cheaper, but buyer beware.

 

[DylanMadigan]

The coaxial cable/twisted pair outer shield is grounded near the top, and every so many feet on the way down. It's grounded at the base of the tower

Is it better to ground it to the tower directly, or to a ground wire wire leading directly to the block at the bottom of the tower with all the ground wires attached? Not sure if it would make a difference.

 

[mmckenna]

Is it better to ground it to the tower directly, or to a ground wire wire leading directly to the block at the bottom of the tower with all the ground wires attached? Not sure if it would make a difference.

The tower legs should be well grounded and will work just fine near the top.
At the base of the tower where your cable transitions from vertical run coming down the tower to a horizontal run to your home, you'd ground to the ground buss at the bottom of the tower.

 

[mmckenna]

Motorola R56 should be downloaded and consumed at your leisure.

 

[mmckenna]

There is also some good stuff here:

https://www.polyphaser.com/resources/white-papers

and here:

Resource Library | Harger Lightning and Grounding

Welcome to Harger's Resource Library. We have assembled a filterable collection of brochures, line cards, literature, and news articles for your informational needs. Please contact us if you have any questions.. widget

www.harger.com

 

[jim202]

Well, I would start by doing some reading in Motorola's R56 standard. There is some very good information there to learn.

Let me say this. A tower needs to be well grounded to start your protection. Next the coax cables need to be grounded on the tower where they start, where they leave the tower and where they enter a shelter or home. Inside the equipment shelter or home, you need a good ground that is common to the tower and equipment.

Your ground SYSTEM is the heart of your surge protection. It generally takes multiple ground rods to obtain a low resistance ground SYSTEM.

Let me explain that just a little. Around each ground rod is a "Cone of Influence". This has a diameter that is equal to their length. The ground rod length required will depend on the soil resistance and your location. But in simple terms, you need to space the ground rods apart that is double their length. So if an 8 foot ground rod is good enough for your soil conditions, then the rods need to be spaced every 16 feet. This makes the maximum use of the cone and not having the cone of influence overlap each other and not produce the minimum resistance and the lowest cost.

Next comes the selection of the wire size that you use to connect everything together. You will find in your reading, that solid #2 plated wire is what is recommended in the R56 standard. Your next issue is how to connect the ground rods to your ground wire. I like to use the Exothermic welding to secure the wire to the ground rods and ground bars. But there is compression clips that can be used. Your trying to make a low resistance joint that won't start corroding with time. The compression clips will require a special crimping tool. The Exothermic welding will require some graphite molds for the type of connection your trying to make.

Having been in the cellular field and Public safety radio Systems field for many years, I have seen a number of slight variations from the R56 Standard. But the differences are minor.

Now with all this stated, there will be others that may contradict me or say that a tower can't stand a DIRECT STRIKE from lightning. This is an old wife's tale. With the proper grounding SYSTEM, you can survive. Some will say this good ground SYSTEM is way outside your pocketbook. This may or may not be the case.

There should be a ring around the tower, with a run of wire attached to each tower leg. Then a run to the equipment shelter or house. There should also be a ring around the equipment shelter. Just remember to space the ground rods double their length apart. This will space the ring away from the tower the correct length. Use some stakes when trying to figure out just where the ground rods need to be placed. Make sure you stay at least 3 feet away from any foundation.

While talking about grounding tower legs, you don't want to connect the ground wire directly to the tower legs. The copper will eventually cause an electrolysis action that will leach the zinc out of the galvanization and cause rust with time. You will want to use a bronze clamp to go between the tower steel and the copper wire. Same thing goes for grounding any guy wires the tower may have. Again use a minimum of 2 ground rods at each guy wire anchor point.

No sharp bends in the ground wire. Use a radius bend of at least 6 inches.

You might also check with your insurance company to see if they have any specific steps that they may require you to take.

I know this is a long post. But for the new comer, there are many things that it takes to make a good GROUND SYSTEM.

I haven't mentioned that you should tie your ground to the electrical meter ground, so that you don't end up with a difference of potential between the 2 grounds. Hopefully your radio room is near the electrical meter feeding the structure.

There are some well talented people on here. But keep in mind that if you ask 5 people about how to ground your equipment, your going to end up with around 8 answers. So be flexible and ask them why they are saying it should be done their way.

Jim

 

[WA4HHG]

https://www.polyphaser.com/surge-protector-1-pair-100base-t-ethernet-ix-1h

Yes, you need protection on it.
I'd not go cheap on anything to do with grounding/safety. You are essentially giving that energy a path directly into your home.

Doesn't matter if it's a direct strike or not, the induced energy from a nearby strike can do damage. If the tower gets hit, some of that energy will make it on to the Ethernet cable. Remember, that lightning bolt traveled thousands of feet through the air. A little bit of 300 volt rated insulation isn't going to stop it.

I've heard of the "loop" thing before as a way to create a choke for the high frequency pulse. Can't say I've ever seen it at a commercial site, though. What you will find is that the antenna/radio/camera, etc. will be grounded to the tower. The coaxial cable/twisted pair outer shield is grounded near the top, and every so many feet on the way down. It's grounded at the base of the tower, then again where it enters the enclosure as well as at the suppressor.

Polyphaser brand is expensive, but it's good stuff. You can probably find something cheaper, but buyer beware.

I'll second another coastie (mmckenna) recommendation. PolyPhaser equipment is not cheap but their lightning/EMP mitigation equipment work very, very well. Still, a direct hit to your tower will not end well. My 110' has an 8 leg star ground made of 2" copper strap buried 12" below ground to dissipate a strike, feed and control lines that are underground, disconnected and pulled away from the tower about 30' as well as multiple static drains. The tower took a hit about 10 years ago which besides destroying things like phone lines, magantized my then CRT computer monitor causing shadows to be displayed. Had to bring the purity back with a bulk tape eraser.

 

[prcguy]

+1. Semper Paratus from an AUX member.

I'll second another coastie (mmckenna) recommendation. PolyPhaser equipment is not cheap but their lightning/EMP mitigation equipment work very, very well.

 

[speedway_navigator]

I got my copper strap from Georgia Copper

GEORGIA COPPER - Copper ground strap

.0225" Copper Ground Strap

gacopper.com

 

[DylanMadigan]

I'll definitely read up on R56

I figured towers can be hit and be fine, I think mmckenna was the one to tell me a while ago that generally systems that are quite robust are generally out of the budget of hobby operators. I figured I'd start by minimizing damage and over time work my way up to a system that is as close as we can get to lightening safe. I do already have a decent ground system, I was told I should use two rods and I have 4 for now.

I do have a brass ground clamp on the one leg of the tower that all the ground wires connect to. I'll get a couple more and spread out the ground rods (currently have 4 ground rods a few feet down in the most sand, looking to attach one more to the end of a 10ft copper pipe and drive that 8ft below the surface as well for good measure with spare parts, at that point I think it would reach below sea level).

The more information the better, I see a text wall and I get happy because I know I'm about to learn something =)

Thank you everyone for the help and knowledge.

 

[mmckenna]

Ideally each tower leg should be bonded to the grounding system.

As for surviving lightning strikes, it happens all the time. This guy can probably confirm that… LIGHTNING ALMOST STRIKES MAN: ‘It was crazy': Lightning bolt nearly strikes S Carolina man

 

[DylanMadigan]

Random question: I have probably 80ft of aluminum utility wire from a pole, stuff is pretty darn thick, thicker then LMR400 at least. Could that work for grounding wire? I know its melting point would be lower but at what size it is I'm not sure that would be an issue, when I see lines on poles get hit they don't seem to melt or break.

 

[mmckenna]

I believe you can, but you will need to protect against corrosion where it joins the rod. Copper would be a better choice.

 

[a417]

you can, but I wouldn't.

Here's a good breakdown from some pretty smart people (at least according to them)

 

[Project25_MASTR]

I'm just going to add my $0.10.

The basics are typically ground radio chassis to tower, LPU within 3 ft of the radio, LPU at the base of the tower/entry and then another LPU inside connected to your block. Of course, you can also do things such as isolate the tower mounted equipment by using fiber. Bear in mind, a 7 kV discharge will vaporize shielded CAT5e and CAT6.

Equipment selection also comes into play though. Try and choose equipment that has grounding studs or metal chassis (one of my personal irks about a lot of Ubiquiti gear the interwebs rave about). ABS plastic can and will build up a charge over time...especially if you live in the middle of the dust bowl...and equipment that doesn't have a common ground typically will blow out the Ethernet transformer in the device as there is nowhere else to shunt the discharge to ground except through the transformer.

 

[bharvey2]

I'm just going to add my $0.10.

The basics are typically ground radio chassis to tower, LPU within 3 ft of the radio, LPU at the base of the tower/entry and then another LPU inside connected to your block. Of course, you can also do things such as isolate the tower mounted equipment by using fiber. Bear in mind, a 7 kV discharge will vaporize shielded CAT5e and CAT6.

Equipment selection also comes into play though. Try and choose equipment that has grounding studs or metal chassis (one of my personal irks about a lot of Ubiquiti gear the interwebs rave about). ABS plastic can and will build up a charge over time...especially if you live in the middle of the dust bowl...and equipment that doesn't have a common ground typically will blow out the Ethernet transformer in the device as there is nowhere else to shunt the discharge to ground except through the transformer.

I've installed my share of Ubiquiti hardware. The equipment that I've used is what they spec more for backhaul/industrial applications and they do have grounding lugs/screws. They also specify the used of shielded ethernet cabling. While that can address static buildup, the designs won't withstand a lightning hit. Despite proper installation, I had one failure that I'm quite sure was a static issue despite the modest threat of same in my area.

 

[Project25_MASTR]

I've installed my share of Ubiquiti hardware. The equipment that I've used is what they spec more for backhaul/industrial applications and they do have grounding lugs/screws. They also specify the used of shielded ethernet cabling. While that can address static buildup, the designs won't withstand a lightning hit. Despite proper installation, I had one failure that I'm quite sure was a static issue despite the modest threat of same in my area.

AirFiber versus AirMax...
AirFiber was designed by former Motorola Canopy engineers. AirMax on the otherhand, was not and boy does it show. Unfortunately, today, AirFiber is priced extremely high in the market compared to competitive offerings from Mimosa and IgniteNet for a fraction of the cost. Nearly all of the competing products offer grounding as well.

 

[bharvey2]

AirFiber versus AirMax...
AirFiber was designed by former Motorola Canopy engineers. AirMax on the otherhand, was not and boy does it show. Unfortunately, today, AirFiber is priced extremely high in the market compared to competitive offerings from Mimosa and IgniteNet for a fraction of the cost. Nearly all of the competing products offer grounding as well.

You're quite right. It's been primarily Airfiber products. I have used some of the older Airmax products long ago and they were on par with what I would consider a consumer device. I haven't worked with either the Mimosa or IgniteNet products. I'll have to research them before another project comes up. Thanks for the heads up.