3 ms·

You'd have to use fiber. Copper between buildings is susceptible to ground loops and one lightning strike frying the entire network.

sitkack 13y ago
http://en.wikipedia.org/wiki/RONJA http://en.wikipedia.org/wiki/RONJA RONJA (Reasonable Optical Near Joint Access) is a free-space optical communication system originating in the Czech Republic. It transmits data wirelessly using beams of light. Ronja can be used to create a 10 Mbit/s full duplex Ethernet point-to-point link.
- gboudrias 13y ago
  Mmm full duplex... But yeah I helped on the Montreal meshnet and I think we either have or really want to have a RONJA link, because it's cool as hell as well as very useful in general.
  - sitkack 13y ago
    I know, I drool over the http://www.canon.com/bctv/canobeam/ http://www.canon.com/bctv/canobeam/
    - sOuqq 13y ago
      From what I've heard, optical wireless links are super sensitive to environmental conditions (precipitation, pollution, etc), and don't work too well in real-world deployments. I would love to hear about more people's experiences with it, though.
pedrocr 13y ago
Interesting, I have a bunch of Cat6 running on conduits in the ground between two buildings (about 80m apart) and they work fine. How would ground loops/lightning affect the install?
mey 13y ago
How much coverage do you get for ground buried, twisted pair shielding and integrated magnetics in the RJ45 jacks? (Just from EM, direct strikes I would assume to be handled via lightning rods) This is not my area of expertise by far, so I'd love to know what I'm missing.
pedrocr 13y ago
I just did a bit of googling and these don't seem to be major issues: http://ask.metafilter.com/57840/What-kind-of-network-cable-to-run-underground http://ask.metafilter.com/57840/What-kind-of-network-cable-t... Ground loops shouldn't be a problem as the APs have transformers that don't use ground at all so there's no ground connection to mess things up. If lightning is a big issue you might need surge protectors on the lines. Is a Cat6 cable inside a plastic conduit that susceptible to getting hit by lightning though?
- rosser 13y ago
  Is a Cat6 cable inside a plastic conduit that susceptible to getting hit by lightning though? IANAE (electrician), but per my understanding, putting copper cable inside a PVC (or other plastic) conduit is among the worst things you can do; it gives the strike only one place to go: down the copper. EDIT: I found a comment on a CCTV forum site that corroborates this: http://www.cctvforum.com/viewtopic.php?p=79496&sid=0e26864640365e658a8b0a6d54a50da3#p79496 http://www.cctvforum.com/viewtopic.php?p=79496&sid=0e2686464...
  - pedrocr 13y ago
    That's because you're protecting against the end-point getting hit (in your example a camera) and then using the cable to conduct. But if the APs are inside the buildings that's not what we're protecting against. Instead we're trying to not get the cable itself hit.
- jauer 13y ago
  On the radio side the cable doesn't have to be susceptible to getting hit by lighting since the radio itself is a big metal thing sticking up in the air. In many cases the cable from the AP down to the PoE injector is the most attractive path for lightning to reach the ground. You can make it less attractive but that often costs money or takes work (See the Motorola R56 Guidelines). This also goes for ethernet between buildings. Surprisingly enough if the building is poorly grounded the best path can be over your ethernet to a different building. The ethernet transformers don't really help. They are just another part to get melted off the circuit board if there's a close lightning strike. Surge protectors pretty much exist as a sacrifice to protect your more expensive electronics (switches and routers).

sitkack 13y ago

http://en.wikipedia.org/wiki/RONJA http://en.wikipedia.org/wiki/RONJA RONJA (Reasonable Optical Near Joint Access) is a free-space optical communication system originating in the Czech Republic. It transmits data wirelessly using beams of light. Ronja can be used to create a 10 Mbit/s full duplex Ethernet point-to-point link.

gboudrias 13y ago
Mmm full duplex... But yeah I helped on the Montreal meshnet and I think we either have or really want to have a RONJA link, because it's cool as hell as well as very useful in general.
- sitkack 13y ago
  I know, I drool over the http://www.canon.com/bctv/canobeam/ http://www.canon.com/bctv/canobeam/
  - sOuqq 13y ago
    From what I've heard, optical wireless links are super sensitive to environmental conditions (precipitation, pollution, etc), and don't work too well in real-world deployments. I would love to hear about more people's experiences with it, though.

pedrocr 13y ago

Interesting, I have a bunch of Cat6 running on conduits in the ground between two buildings (about 80m apart) and they work fine. How would ground loops/lightning affect the install?

mey 13y ago

How much coverage do you get for ground buried, twisted pair shielding and integrated magnetics in the RJ45 jacks? (Just from EM, direct strikes I would assume to be handled via lightning rods) This is not my area of expertise by far, so I'd love to know what I'm missing.

pedrocr 13y ago

I just did a bit of googling and these don't seem to be major issues: http://ask.metafilter.com/57840/What-kind-of-network-cable-to-run-underground http://ask.metafilter.com/57840/What-kind-of-network-cable-t... Ground loops shouldn't be a problem as the APs have transformers that don't use ground at all so there's no ground connection to mess things up. If lightning is a big issue you might need surge protectors on the lines. Is a Cat6 cable inside a plastic conduit that susceptible to getting hit by lightning though?

rosser 13y ago
Is a Cat6 cable inside a plastic conduit that susceptible to getting hit by lightning though? IANAE (electrician), but per my understanding, putting copper cable inside a PVC (or other plastic) conduit is among the worst things you can do; it gives the strike only one place to go: down the copper. EDIT: I found a comment on a CCTV forum site that corroborates this: http://www.cctvforum.com/viewtopic.php?p=79496&sid=0e26864640365e658a8b0a6d54a50da3#p79496 http://www.cctvforum.com/viewtopic.php?p=79496&sid=0e2686464...
- pedrocr 13y ago
  That's because you're protecting against the end-point getting hit (in your example a camera) and then using the cable to conduct. But if the APs are inside the buildings that's not what we're protecting against. Instead we're trying to not get the cable itself hit.
jauer 13y ago
On the radio side the cable doesn't have to be susceptible to getting hit by lighting since the radio itself is a big metal thing sticking up in the air. In many cases the cable from the AP down to the PoE injector is the most attractive path for lightning to reach the ground. You can make it less attractive but that often costs money or takes work (See the Motorola R56 Guidelines). This also goes for ethernet between buildings. Surprisingly enough if the building is poorly grounded the best path can be over your ethernet to a different building. The ethernet transformers don't really help. They are just another part to get melted off the circuit board if there's a close lightning strike. Surge protectors pretty much exist as a sacrifice to protect your more expensive electronics (switches and routers).