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Lightening Arrestors

Posted: Tue May 17, 2016 5:05 pm
by Sjones1
I have a Mimosa link that is having what I believe a grounding issue. We use shielded ends with a drain wire but do any of you use lightening arrestors? Which ones work with these units if you do?


Re: Lightening Arrestors

Posted: Tue May 17, 2016 5:09 pm
by sirhc
More importantly is good grounding:

Re: Lightening Arrestors

Posted: Sun May 29, 2016 12:18 pm
by rebelwireless
I don't care for lightning arrestors myself, good grounding essentially removes any benefit of them and they add another failure point.

The 'ground' wire isn't for lightning production (because it can't do anything, too small), it's an ESD (electrostatic discharge) dump. Basically, radios will build up a static charge from having a magnetic field + charged wind + nature, ESD keeps that in check. This does help during electrical storms, but not because it can dump a lightning hit.

Re: Lightening Arrestors

Posted: Sun May 29, 2016 12:31 pm
by sirhc
Correct, few things can protect you from a direct hit. But most damage as you said is from ESD, Static, and ground potential differences.

People just hear the loud BOOM, the FLASH of light and say they went down from a lightening strike which 99.9% of the time is a false assumption.

Humidity variations along with high winds that accompanies the storm finds the right balance to create large amounts of static at the antennas/radios, or ESD discharge from a near by strike, or sudden ground potential shifts from rain sheeting across the ground finding and enveloping ground rods in poor condition is normally the cause.

But people are distracted from the shock an aw of the light and sound show and miss the real cause.

If your damage to your routers, switches and such came in through the AC chances are those AC power supplies would be toast but the damage is coming in through the Ethernet cables and the power supplies are fine.

Re: Lightening Arrestors

Posted: Wed Nov 22, 2017 12:55 pm
by beambarossa
Hi all looking for some advice - during a lightening storm last night we suffered some equipment damage. We have grounded everything at ground level to R56 standards and havent had an issue for years however tonight we lost 2x prism gen 2's and a netonix DC switch. It was not a large hit, the mains had tripped but after resetting everything came back up ok power supply wise.

The netonix had a power light on and the sfp was saying it was up to the remote device but no connectivity was present. No poe was working, or the switch was not discover able - its dead.

Whats your thoughts on how this has occurred roughly going by the damage and here we can improve grounding? The two broken aps appear to have shorts in them by the looks, e.g if plugged into the new switch it seems to upset communication to other aps breifly - they are now unplugged.


Re: Lightening Arrestors

Posted: Wed Nov 22, 2017 9:59 pm
by beambarossa
Just a follow up after some more reading - fairly sure this would be ESD potential difference that has caused this. From reading here the best way to solve would be run a 2 awg up the tower as discussed and attach to radios - i cant find info on this in motorola R56 from a quick look - can someone help with these queries?

We have antennas at various heights up the tower will it be best to mount multiple insulated bus bars up the tower in a series fashion, all bars below lowest radio at the point?

On a guyed tower terminate this at ground system on base of tower (which is connected to internal bus bar about 3m away, or go straight to internal bus bar?

On Ubiquiti sectors with prisms is is best to lug on the leg clamp or lug to lug to bolts in back of sector

Do shielded cable earth straps help on cat6 (like LDF / LMR type) or does radio float free?

On rocket dishes with af5x ground af5x and dish or just dish?

Thanks for any advice.

Re: Lightening Arrestors

Posted: Thu Nov 23, 2017 3:39 pm
by sirhc
#2 to insulated ground bus near antenna clusters. You can go from one ground bus to another up the tower just make sure good lug connectors with anti corrosion paste.

#6 with lug to antenna bolts.

Ground wires should be run direct route as possible (shortest) and never loop.

I would also add 1 ro 2 NEW ground rods to electrical service and make sure bond wire from electrical service ground rods to tower ground rods is direct/short and corrosion free.