[MLB-WIRELESS] Lightning protection?

[Adrian Close]

On Fri, 8 Feb 2002, lkhoo at csc.com.au wrote:

> After an eventful night with the weather last night (I live in Lilydale and
> got pretty much flooded!) I started thinking about what would happen if an
> antenna used for wireless was hit by lightning?  I'm not very knowledgeable
> in this area so I suppose this would apply to the average TV antenna also.

I knew we chose the house on the hillside for a reason...

Bad things happen when lightning strikes antennae.  But I suspect the more
likely source of problems for you would be the power and phone lines into
your house, unless you have quite a high mast.

The company I work for supplies surge protection gear for all sorts of
stuff.  We also do a lot of lightning protection work (mostly on tall
buildings).  This is not so much as shameless plug as a statement of fact.

Any form of protection on your antenna feed is going to result in loss
(probably a couple of dB by the time you add up all the extra connectors
and the protection device itself).  You might want to consider providing a
more attractive target for a lightning strike that is a better path to
ground than your antenna mast/rig/whatever.  At the high end of the scale
you can spend $3000 on an "early streamer emission terminal", which is
designed to actually send out a charge to actively attract the lightning.
Or you can do the passive lightning rod thing.  Just make sure that
whatever you do is higher than the thing you're protecting.

Bottom line:  don't worry so much about direct lightning strikes if you're
in a house.  Definitely consider surge protection on all your indirect
inputs.

Adrian Close			email:	adrian at close.wattle.id.au
1 Old Gippsland Rd.		web:	http://www.close.wattle.id.au/~adrian
Lilydale, VIC, 3140, Australia	mobile:	+61 412 385 201


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