Protecting 1Gb Ethernet From Lightning Strikes

Thu Aug 15 01:29:13 UTC 2019

On 8/13/19 2:32 PM, Warren Kumari wrote:
> This probably won't fully solve your problem, but I run a bunch of
> Ubiquiti access points and similar -- I suffered a number of lightning
> related outages, and then started using their TOUGHcable -
> https://www.ui.com/accessories/toughcable/

While ToughCable isn't bad (especially for the price), if you want 
something REALLY durable both physically and against electrical 
transients, I've been very happy with Primus C6CMXFS-1864BK.  It costs 
quite a bit more than the ToughCable but has real water blocking (which 
means you had better be prepared to deal with "Icky Pic"), heavy 
shielding with drain, meets or exceeds CAT6 (which means you can push 
gigE a bit beyond 100m pretty reliably if you've got a tall tower or a 
hut far away from a tower base), and has 23AWG wire so PoE, especially 
Ubnt's crummy 24V passive POE, can go farther, too.

Be warned it's a bear to terminate.  In addition to the waterblock, the 
cable diameter is too large for typical crimp-on RJ45 ends.  You have to 
either use special ends (which Primus sells, among others) or terminate 
it to a punch block which, while not usually a problem in a hut, is 
often problematic up on a tower.

Ubnt also makes an outdoor fiber media converter I've found useful for 
"small cell" style wISP deployments where I can drag my own fiber to the 
tower/pole and don't want/need a hut or enclosure at the base.  Part 
number is F-POE-G2.  That'll let you get your power and signal 
separated.  I do wish they'd just put SFP slots in their radios, but at 
the price they sell them for, I guess I can't complain too much.  I'd 
put real 802.3af/at PoE higher on the list of wants, honestly.

As to actual surge protectors, I see there have been some other 
suggestions in the list, and I'll defer to them.  I've personally had 
decent luck with just making sure the Ubnt passive POE injectors (which 
I need since I don't usually use their switches) are well grounded to be 
mostly sufficient (along with the tower and hut having proper grounding 
infrastructure).  I've not lost any radios, though I've had some lockups 
requiring power cycle after nearby lightning strikes on some of the 
lower end WA based platforms.  The XC based platforms seem hardier.  My 
sample size isn't huge, though.

I'm usually of the impression that, unless you've got carrier (cellular 
or committed-rate microwave) class wireless gear on the tower or 
aggressive SLAs you have to meet from a wireless PoP, it's probably 
cheaper overall to just take reasonable precautions against lightning 
than it is to try to make things handle a "direct" strike.  Figure in 
the wISP world, tech moves so fast that you're having to put new things 
on the tower at least every 3-5 years anyway, so as long as an 
unscheduled trip up to the tower doesn't cost you $ARM+$LEG, it's 
probably easier to just take a lightning strike that fries everything 
due to extreme proximity as an unscheduled upgrade than the try to 
handle it electrically.

"Nearby" strikes, static, electrical transients on your utility line, 
etc. are a different matter.  Those you can economically protect against 
i.e. the protection will not cost as much or more than the gear and 
service you're protecting.
-- 
Brandon Martin