lightning arrestor / fiber segment

Unanswered Question

Does anyone know?

I'm mounting patch antennas on an outside wall, drilling a small hole in wall, and connecting the antennas to a 1200AP on the inside wall. I plan on setuping up a fiber segment on the cable run to the switch. My questions, 1) Should I install lightning arrestors between the antenna cable and RP-TNC connectors? 2) How long distance should the fiber segment be? Thank you.

I have this problem too.
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scottmac Mon, 04/09/2007 - 08:01

1) Yes, you should install "entrance protection" for any copper/conductors entering the premises.

Aside from being a good idea, it's frequently required by electrical codes for the US, states, and localities.

2.) I believe the recommended minimum is one meter ... anything beyond that would just be iceing on the cake.

Good Luck


scottmac Mon, 04/09/2007 - 18:51

Nope, I missed that point. The (so-called)lightning arrestors should preferably be kept outside on the antenna-side of the fiber link, with the grounding system also outside, if at all possible.

The idea is to bleed static and surface charges to ground before they can call their biggest bestest friend, lightning, to come over to visit.

Especially in dryer climates with wind, static charges build up to a point where they can whack the equipment, lightning or not.

The fiber link will isolate the charges and the most significant power zaps from lightning, but a near strike can still pulse any nearby equipment into containers of useless components.

SO ... typical layout:

LAN--SWITCH--[fiber xceiver]===Fiber Link===[fiber xceiver]---AP:::::"Lightning Arrestor":::Antenna

If your switch has a fiber port, you can just get a single compatible fiber xceiver and take the fiber link directly to the switch.

The non-coax connection on the lightning arrestor shold go directly to a grounding system (buried rod, cold water pipe ...)on large guage copper wire (I believe 6ga copper is typical for a direct system)

It is critical that the connections be well-bonded, clean, and as direct as possible with no sharp bends.

If you are interested in reading up on lightning protection (a nice thing to know if you're installing stuff outdoors & on rooftops)), PolyPhaser (.com) has a very good book on the subject that explains the details of a good lightning protection system.

Post up any additional questions. This is one of those things that just has to be right or the whole system is at risk.

Good Luck


rob.huffman Wed, 04/11/2007 - 05:47

Hi Scott,

Excellent answer here (as usual)! Haven't seen much of you lately, you must be busy. 5 points for this one :)

Take care,


scottmac Wed, 04/11/2007 - 07:57

Thanks Rob!

Yes, things have been pretty busy (and likely to continue for a while ...)

I still try to get through for a quick read now & then though.

Take care.


srosenthal Sun, 04/15/2007 - 14:21

It is also critical to keep the fiber transcievers plugged into seperate AC breakers. If lighting does travel thru the AP, ethernet cable to the fiber transciever, you do not want it then traveling thru the AC line to the other transcieve and continuing down the ethernet line to the switch.


scottmac Mon, 04/16/2007 - 16:43

Excellent point! (5 Points!) Thanks for putting it up.



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