[NTLUG:Discuss] lightning - was "lightening"

[Fred]

Lightning - el Zappo - something I know something about 
lightening - shedding weight - something that escapes me

Direct hits on homes are rare, but they do happen. One in the Dallas area last
week... big fire, total loss....  but the biggest worry is the zaps to power,
telephone and cable lines that run overhead. These blasts can, and often do,
damage any electronic equipment connected to them. A friend would shut down his
system and pull the plug from the wall anytime that lightning was in the area,
but he forgot about the phone line. ZAP! Destroyed the modem, of course, AND
fried the MB.

High voltage, fast rise time pulses can see "grounds" as high impedance
inductors and take an alternate route to the real ground. Grounding is good, it
just may not perform during a lightning hit like you want it to. - note - to
fully understand it, you gotta really know analog - like what happens when a
current of God-awful proportion causes an inducted current to flow in a
seemingly totally isolated conductor. It doesn't have to be but a tiny fraction
of the original crack of doom to destroy equipment. 

Good, low impedance ground paths, pulse suppression devices, an adequate UPS
and an understanding of UHF signal propagation in wiring will go a long way
toward keeping you and your equipment safe during stormy weather.

Fred

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