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Wireless

Lightning

Many wireless installations involve rooftops, which therefore exposes those systems to lightning. Members of the ISP-Wireless list discuss how to deal with lightning before it hits.

[August 1, 2000]

On the ISP-Wireless list in July, SV told the following story:

"We recently put wireless in a building which had four separate networks. We ran a single cable the length of the building with connections at each end to hook all four together. Very soon after we finished, they got struck by lightning twice in one week. In the middle of the run, our cable passes within about 20' of an 80' flagpole outside. The flagpole was picking up a field charge when the pole got struck and passing it to the hubs at either end, so we put a CAT5 surge protector at each end of the long cable. Now here's my question: Has anyone ever seen a CAT5 patch panel with lightning protection in it?"

[JS asked] "Why not replace the CAT5 run with a fiber run and transceivers, and eliminate the problem altogether?"

[SV explained] "Cost. This project was for a nearby city with no budget."

Then a couple of respondents offered alternate solutions:

[MKS offered] "I've heard of shielded CAT5. You might try some of that."

[EDH suggested] "Panduit's patch panels have surge suppression built into them, but I'm not sure about lightning protection."

Finally, PL offered a more thorough examination of the issue:

"JS is right: the best way to avoid this issue completely is to install fiber. It's certainly less expensive than replacing multiple pieces of hardware, or electrocuted humans. Regardless, whenever STP or UTP cable is used to connect structures that have power feeds coming from separate origins, punchdown blocks must be used, with replaceable modules designed to blow if excessive amps come down the cable. Be glad that professionals install the cable for your voice service. If they didn't use these safety systems, talking on the phone during a storm would as exciting as a game of Russian Roulette."

 —End