[plug] lightning, Re: modem

[Mark J Gaynor]

*********** REPLY SEPARATOR  ***********

On 14/06/2006 at 3:23 PM Michael Holland wrote:

>Thanks for the answers.
>
>On Wed, 14 Jun 2006, Bernd Felsche wrote:
>> That still leaves the infernal modem as a direct connection to one
>> of your domestic lightning conductors.
>
>which leaves me wondering about the big lightning rod 5m above my roof,
>and the coaxial cable connecting it to the DVB card in my mail and
>file-server.  I put a lightning arrestor(?) in the cable in the roof, a
>small cylindar maybe 3x8cm. Any use?

The problem with an arrestor is it's installation. You MUST remember that
lightning takes the shortest route to ground. The antenna , arrestor and
earth MUST form a straight line to ground. The first kink is where the
million volt bolt will leave the system and you may as well not installed
it
at all. I have seen this first hand on more than one occasion. The rule
is simple, straight line to ground. You cannot use the in house earth,
which is often the case. I have to smile with the configurations of power
boards that say they have lightning suppression, it is more like spike
suppression and then I would question its efficiency.

>Would I be right in guessing that the telephone system is good at
>collecting surges from lightning strikes over a large area, while the TV
>antenna will only collect very near strikes, so is less likely to do
>damage? (But when it does...)

Mark
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