[Cu-wireless] lightning protection?

David Young dyoung at ojctech.com
Fri Oct 4 22:31:55 CDT 2002

I was going to send this to my landlord, who is an electrician and
who was once an electrical inspector, but I want to give the list the
opportunity to answer these questions, first.



I am involved with a volunteer project to build a broadband computer
network using radio technology. It involves installing a lot of antennas
on high spots, so protection from lightning is a concern.

For the project, we are putting a small computer on the chimney of a
downtown building.  The computer attaches to an antenna with a short
cable.  It also attaches to computer equipment inside the building with a
lengthy Category 5 phone cable.  We want to protect the building and its
contents from lightning strikes as best we can. We also want a modicum
of lightning protection for the computer on the chimney.

I have done a little research on lightning protection. It seems like it
is typical to bond the computer enclosure and the outer braid of the
antenna cable to a #6 copper wire which is bonded to a good ground in
the building, because that shunts a lightning strike from our equipment
to the earth.  For added protection, (expensive) lightning arrestors
can be installed on the data cable and on the antenna cable.

We may have to run our ground wire to the back of the building and down
two stories before we can bond it to ground. That is probably more than
100 feet of wire, or more. Is that a prudent strategy for grounding
our equipment?  Is it legal? Someone tells me that in Urbana, only 20
feet of ground wire are allowed in one stretch.

If there are any suggestions you can make concerning lightning protection,
I would appreciate it.


David Young             OJC Technologies
dyoung at ojctech.com      Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933

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