Surge protection for external LTE antenna?

[steelghost]

I've got an LTE modem / antenna hooked up to my router as a backup internet connection. The LTE antenna is currently inside my house but would work much better if installed outside to get direct LOS to the mast (which is only about 0.5km away).

Physically, the way this would work would be about 20m of ethernet through my loft, terminated in a keystone jack inside the wall where the LTE would go. Then I fix this bracket to the (external, brick) wall, and run an exterior rated patch cable through a hole in the wall to the device mounted on the bracket. LTE modem would be powered directly via PoE from the router. Point being, there is very little cabling outside the building envelope, in case that matters.

What probably matters more is that where we are (near Manchester in the UK), we do not often get lightning storms, and when it strikes there's plenty of other more "attractive" targets eg church with a spire, aforementioned LTE mast, electricity pylons. So a direct or even nearby strike seems pretty unlikely.

That said the router also powers a handful of IP cameras and WAPs, which would presumably all be at risk if there was a surge induced via the external LTE antenna. And the router is in a rack with a couple of grand worth of server / switching hardware. So the question I am trying to answer is what is the risk profile of this setup (my W.A.G.: low) and is it worth incorporating some sort of surge protection. I know such things are only worthwhile if properly earthed / grounded. Where the antenna is attached, I could run a cable down the wall and attach it to an earth rod (I'd have to drill a hole in the flagstones to be able to hammer it in but that side of the house is not somewhere people would be bothered by such a thing).

The actual connection to the LTE device is only 100Mbit, so any impact to the ethernet performance is probably not a factor.

Thoughts, observations and pointing out things I have missed all welcomed.

Edit: Added a missing "we"

 

[Kyuu]

I would advise against a "DIY" grounding rod. Not only is there the risk of you damaging something underground (water pipe, gas pipe, electrical conduit, seal on a portal to hell, etc.), but also there's no guarantee that simply pounding a rod into the dirt will result in a good ground. Also also, you generally don't want multiple grounds which will likely have different potentials resulting in current flowing in your equipment chassis/cable shields/etc.

My advice would be not to worry about it. I have a lot of equipment and antennas on towers, the side of buildings, and roofs, and, while we do typically use a surge protector as the vendor typically declares it mandatory in the documentation, a lot of ends up without the surge protection for one reason or another. How many incidents of equipment getting damaged by surges have we experienced in the 20-30 years that some of this equipment has been there? Zero. For your house, the risk is way too minimal for it to be worth the hassle IMO.

That said, if you want to do it anyway just for peace of mind, I would recommend just getting an indoor suppressor and installing it on your rack and then grounding your rack to the same earth ground that the rest of your electrical system uses.

 

[Tinlad]

I had a similar thought recently, regarding the 20 m ethernet I have run out to my garage/office. I'm also UK based, on the other side of the Pennines. Someone more experienced/qualified may come along, but until then I'll share my tuppence worth:

My understanding is that the risk isn't so much from direct strikes (you're likely to have bigger problems in that case), but from nearby strikes creating a gradient in potential that your cable will pick up like an antenna. The objective is therefore to keep both ends of the cable at the same potential.

The router is at one end, earthed by your house's wiring. Therefore the ideal is to also earth the surge protector to the house wiring, so they are at the some potential. Actually, I think the ideal is to install a surge protector at both ends of the cable. Either way, using your house's existing earth is fine - then it's all at the same potential, which you can't guarantee with a new DIY earth.

Regarding the risk though... is the 20 m run in a straight line, out in the open? A cable run mostly inside a house isn't a great antenna, and I don't think it's typical to use surge protectors in these cases. We don't get many thunderstorms in the UK, and they aren't typically very severe. You've noted that you aren't in a particularly exposed area. So it sounds like the likelihood of a surge is extremely low, roundable down to zero.

Edit: Ninja'd. Sounds like we're aligned on our advice!

 

[redleader]

In terms of protecting your house wiring the antenna correctly may be important, but it is unlikely that any amount of grounding or surge protection is going to protect ethernet devices during a direct lightning strike. If that is a concern, isolate the modem using wifi or fiber.

 

[steelghost]

In terms of protecting your house wiring the antenna correctly may be important

Can you expand a bit on what you mean?

By default the antenna (which is actually an integrated LTE antenna, modem and router) is just going to be powered via PoE, so the only electrical connection it has to anything is via that cabling. My understanding (partially derived from this thread) is that if you install a surge protector the only time the ground it's attached to becomes important is if there is sufficient current/voltage to trigger the protection, which tries to direct it to that earth / ground connection.

it is unlikely that any amount of grounding or surge protection is going to protect ethernet devices during a direct lightning strike

I appreciate that even with proper, well designed lighting protection (which being a normal house we definitely don't have) there are no guarantees, but a direct strike is pretty unlikely. I would be mildly more concerned about the potential induced by a vaguely nearby strike. But even that feels fairly improbable based on experience (I've lived in this part of the world for most of my life, on and off).

Overall it feels like it's probably not a thing worth doing.

 

[meisanerd]

My old company ran a security camera on our roof to monitor the nearby rail crossing, we installed a surge protection device on our ethernet cable (PoE camera) after the first one got hit by a leader. We had ordered the SPD but it hadn't arrived yet, saw the storm coming, and disconnected the ethernet cable inside. Camera took a hit and was completely melted inside, the strike followed the ethernet cable down, jumped from the end (disintegrated the RJ45 jack) and arced to the side of one of our NASs, where it followed that to ground. The camera was on a 5ish ft pole on the roof. There were other towers nearby that we thought would have been a better target for lightning, but our equipment still got hit.

 

[w00key]

the strike followed the ethernet cable down, jumped from the end (disintegrated the RJ45 jack) and arced to the side of one of our NASs, where it followed that to ground.

^ this is exactly why you use Shielded Twisted Pair for outside and ground it with a surge protector.

Bottom of the Unifi one looks like this

S(F)TP is always only grounded on 1 side, and this is the side. The uplink to the switch/patch panel should be ungrounded, either a UTP patch panel / keystone or even just a UTP cable. The outdoor part is STP and acts as ground for the end device.

This acts as a CHONKER path to ground, you should attach a thick like 2.5mm2 grounding wire to the screw and let it take the hit. Once voltage exceeds set level the TVS or gas discharge tubes open and shunt it to the ground, possibly sacrificing itself to protect the indoor side.


Ethernet ports have isolation transformers with ~1.5 kV rating but those are for static zaps, not stray lightning or induced current in long outdoor wires acting as antenna. This guy makes sure voltage doesn't exceed that level so it doesn't fry the isolation transformers and any trace and IC the power jumps through.

 

[SandyTech]

I've got an LTE modem / antenna hooked up to my router as a backup internet connection. The LTE antenna is currently inside my house but would work much better if installed outside to get direct LOS to the mast (which is only about 0.5km away).

Physically, the way this would work would be about 20m of ethernet through my loft, terminated in a keystone jack inside the wall where the LTE would go. Then I fix this bracket to the (external, brick) wall, and run an exterior rated patch cable through a hole in the wall to the device mounted on the bracket. LTE modem would be powered directly via PoE from the router. Point being, there is very little cabling outside the building envelope, in case that matters.

What probably matters more is that where we are (near Manchester in the UK), we do not often get lightning storms, and when it strikes there's plenty of other more "attractive" targets eg church with a spire, aforementioned LTE mast, electricity pylons. So a direct or even nearby strike seems pretty unlikely.

That said the router also powers a handful of IP cameras and WAPs, which would presumably all be at risk if there was a surge induced via the external LTE antenna. And the router is in a rack with a couple of grand worth of server / switching hardware. So the question I am trying to answer is what is the risk profile of this setup (my W.A.G.: low) and is it worth incorporating some sort of surge protection. I know such things are only worthwhile if properly earthed / grounded. Where the antenna is attached, I could run a cable down the wall and attach it to an earth rod (I'd have to drill a hole in the flagstones to be able to hammer it in but that side of the house is not somewhere people would be bothered by such a thing).

The actual connection to the LTE device is only 100Mbit, so any impact to the ethernet performance is probably not a factor.

Thoughts, observations and pointing out things I have missed all welcomed.

Edit: Added a missing "we"

We run a similar setup for our WISP customers, and we protect them with Ditek's DTK-MRJPOE. We'll basically run a standard UTP drop to a spot near the CPE radio, hang one of those (or its outdoor capable cousin) up, ground it to the building and then run an outdoor rated STP patch cable between the surge protector and the CPE radio. I'd estimate we replace 5 or 6 a year, and sometimes the CPE radios even survive! but it's a damn sight cheaper than replacing whatever the customer has attached to the other end. Usually.

 

[Randomizer]

^ this is exactly why you use Shielded Twisted Pair for outside and ground it with a surge protector.

Bottom of the Unifi one looks like this

View attachment 134390

S(F)TP is always only grounded on 1 side, and this is the side. The uplink to the switch/patch panel should be ungrounded, either a UTP patch panel / keystone or even just a UTP cable. The outdoor part is STP and acts as ground for the end device.

This acts as a CHONKER path to ground, you should attach a thick like 2.5mm2 grounding wire to the screw and let it take the hit. Once voltage exceeds set level the TVS or gas discharge tubes open and shunt it to the ground, possibly sacrificing itself to protect the indoor side.


Ethernet ports have isolation transformers with ~1.5 kV rating but those are for static zaps, not stray lightning or induced current in long outdoor wires acting as antenna. This guy makes sure voltage doesn't exceed that level so it doesn't fry the isolation transformers and any trace and IC the power jumps through.

Shielded cabling is NOT intended for lightning surge protection!! This is terrible advice.
Shielded cabling is only intended for EMI protection in electrically noisy environments (manufacturing, for example). They may have a thin drain wire along the very thin foil inside (and many cables only have that foil and no drain wire) to block EMI, but it is nowhere near enough for any kind of reasonable lightning protection. These Ethernet surge protectors do very little - they can help a bit with some minor induced surges, but not enough protection worth bothering with and they introduce a bunch of extra points of failure.

In commercial environments, outdoor cabling is not STP. If lightning is a concern (and stapling it to the ouside wall of a building is not a lighting concern) then is protected by running it within properly grounded or bonded metal conduit. To isolate equipment that is prone to strikes (such as rooftop radio equipment), you would typically use a sacrificial switch or media converter that is bonded to ground, running off of a separate (and usually dedicated) power circuit and located near the radio equipment, and then you would connect your network to that media converter or switch via fiber (even a short, 1-foot fiber patch cable is excellent isolation). Just mount that sacrifical equipment on, for example, a piece of plywood and not on a metal shelf in your network rack.

I have been managing ~20 or so sites out of ~1k total that have had WISP dishes on roofs for about 10 years. I have had 4 lightning strikes on sites so far (2 at one site), all in the southeast (Florida and Georgia) killing the WISP dish every time but only ever lost 1 router that way and that was because of a strike on a coax line that had copper connectivity though the cable modem all the way through to the router, not a strike on or near the dish. That strike thoroughly burnt the cable modem, the router, and the switchport that router was connected to - I seriously doubt an ethernet surge protector would have done much there. I have some sites with Starlink now as well, and I isolate the Starlink router from my router the same way - via fiber (media converter on the Starlink side via fiber to an SFP port on the router) because the Starlink dish is usually up on a roof.

Media converter with PoE (on LTE side):
https://www.amazon.com/a/dp/B0BJ24FD1T

If your switch doesn't have an SFP port, then another media converter on the other side - you can use a cheaper one with no PoE-out:
https://www.amazon.com/a/dp/B0834LP56W
(or just get a switch with an SFP port - you can find hundreds on Amazon for <$50 if you don't need a managed switch)

Pair of SFPs:
https://www.amazon.com/a/dp/B08BP3JDBV

Fiber patch cable (3ft - $6.99, 66ft - $20.99):
https://www.amazon.com/FLYPROFiber-Fiber-Patch-Length-Options/dp/B093GV4N5K
Put the media converter in a conditioned space near the LTE equipment and run fiber, not copper, and you will be safe from any strikes.

 

[w00key]

Shielded cabling is NOT intended for lightning surge protection!! This is terrible advice.
Shielded cabling is only intended for EMI protection in electrically noisy environments (manufacturing, for example). They may have a thin drain wire along the very thin foil inside (and many cables only have that foil and no drain wire) to block EMI, but it is nowhere near enough for any kind of reasonable lightning protection. These Ethernet surge protectors do very little - they can help a bit with some minor induced surges, but not enough protection worth bothering with and they introduce a bunch of extra points of failure.

You're not hanging it up on the highest point on the roof but anything external WILL get a jolt when it storms whether you like it or not. The pole gets the main hit, but anything on and near also gets shocked. Electricity takes ALL paths concurrently and at that voltage, plastic insulation and air means nothing.

These protectors have a 10 or 20 kA rating. That's not for static, that is high voltage but micro amps worth of current.


You are right that lightning prone dishes on huge poles need even better protection but that doesn't negate what a "simple" surge protector does. A sacrificial media converter, sure, but I would always run it with a surge protector in front. Most hits aren't direct and 20 kA should be plenty for a near miss and induced current.


SFTP is there mostly to act as a faraday cage - nothing gets through it to induce current on data wires. The coax-style mesh plus individual wraps keeps EMI/EMP away from the pairs.

The shield on the connector will drain directly to ground, no need to have a gas discharge tube and avalange diodes between it and grounding nut. Only if that fails, the protection with a max rating of 10/20 kA gets to work on the data wires, over 100VDC => short to ground.


I have nothing against media converter, I have a bunch of them too, but let's not start with the overkill solution when something simple works lol. @meisanerd only got crispy electronics because of two strikes in a row, first one, the protector worked just fine. Then a second hit took out the site before a replacement was installed.


It's not high tech. Simple diodes that open when reverse voltage spikes and drains to ground making it the preferred path, it's old and proven tech. Gas discharge tubes is like your fluorescent lights, "start" it and it's again, a path to the ground that lightning or surges prefers, much over 1.5 kV+ isolating transformers on devices.

Absent this protector, duh it follows any and all paths.

 

[meisanerd]

No, we only had a single strike. It was before our isolator arrived, we had ordered it but it hadnt come in yet, and we were gambling on good weather before it arrived. Im not sure the stuff on the roof would have survived a strike either way

 

[w00key]

Ah, okay, I misread that. Anyway, STP is recommended by pretty much any manual I pick up, like the Unifi Protect G6 Turret, which links to https://store.ui.com/us/en/category...outdoor?variant=uacc-cable-patch-outdoor-1m-w

Or Nanobeam AC

Shielded Category 5 (or above) cabling should be used for all wired Ethernet connections and should be grounded
through the AC ground of the PoE.
We recommend that you protect your networks from harmful outdoor environments and destructive ESD events
with industrial-grade, shielded Ethernet cable from Ubiquiti Networks. For more details, visit www.ubnt.com/toughcable

Or the Rocket Prism, literally a WISP base station for pole mount. This one suggests two surge protectors to protect both ends, it's not a throwaway CPE.

 

[KD5MDK]

Quick note - There are ethernet surge protectors which trigger at 5V and then there are PoE Ethernet surge protectors which trigger at 60V. So be sure you're picking the right one.