Date:    24 Dec 1997
From:    Mike Robson
To:      Mot-68HC11-Apps@freeware.mcu.motsps.com
Subject: thunder and lightning

Sitting quietly over a post-Xmas port, gazing out into a calm grey drizzly
sky of mid-rainy season in a drought year, when BLADABOOM!!! Without any
warning rumbles, and out of nowhere, the most tremendous lightning strike
somewhere near the front garden. Smell of ozone and fried tortoises, and
when I pull myself together I find that my US Robotics 14.4 internal modem
is dead. Well, not quite dead, it made noises like an opera singer in pain
when I tried to go online.

This happens all the time here. And a new modem costs about one-week's
salary for a University professor. Really, one should pull the phone plug
out of the computer when the modem is not actually in use. Yes, well I know
that NOW. But there must be a nice market for something which will pull the
plug for you when it smells the rain or detects a rise in the electrostatic
potentials, or whatever. 

I understand that this is a big problem too in parts of the USA, like in
Arizona? What do you guys do about it?

All the best

Mike
 
Mike Robson
Dept. of Computer Science
University of Zimbabwe
Box MP167, Mount Pleasant,
Harare, ZIMBABWE, Africa


Date:    29 Dec 1997
From:    Clyde Smith-Stubbs
To:      Mot-68HC11-Apps@freeware.mcu.motsps.com
Subject: Re: thunder and lightning

It got zapped by induced voltage on your phone line. Just like you can get
surge suppressors for the power line, you can get surge suppressors for the
phone line.

But you might also find that the modem is repairable. Some modems have
fuses on the input which can simply be replaced, or you might find a
resistor or capacitor got zapped. It's unlikely to have damaged anything
beyond the line interface components, which are fairly well isolated
from the rest of the modem.

Regards, Clyde


Date:    29 Dec 1997
From:    Chad Robinson
To:      Mot-68HC11-Apps@freeware.mcu.motsps.com
Subject: Re: thunder and lightning

I live in Connecticut, and we see a pretty high incident level of surges
too.  I'm not sure how effective they are but most surge strips sold in this
area have phone jacks for the modem.  Honestly, they're probably not more
than an MOV or two across the phone pair, but do you really need more?  :-)


Date:         29 Dec 97
From:         Tehmosp Khan
Organization: Slope Indicator Company
To:           Mot-68HC11-Apps@freeware.mcu.motsps.com
Subject:      Re: thunder and lightning

Your modem should have a FIVE year warranty.  I had mine sent for 
repair. Check if you have a local US Robotics repair center.

Good Luck

Tehmosp

Tehmosp Khan
Slope Indicator Company


Date:    29 Dec 1997
From:    Donald E. Haselwood
To:      Mot-68HC11-Apps@freeware.mcu.motsps.com
Subject: Re: thunder and lightning

Mike,

We split our time between Florida--Tampa/St. Pete area (which some rank is
#1 in the world for number of thunderstorm-days per year)--and the mountains
of North Carolina (which some have a ranked as #2 in the U.S. for lightning
caused deaths--ground conductivity is very poor in mountainous terrain).
Plenty of lightning.

My number one rule is ALWAYS unplug the phone line when it is not being
used, and unplug the computer when not being used.  In addition to cover
when things are plugged in, I use a _good_ surge protector (e.g. Isotel)
that has a phone line protection input as well.  I also have a good ground
system and have the equipment grounded (for the amateur radio equipment as
well as computers).

One neighbor (in NC) turned off his computer with the switch on a
convenience outlet strip, and left the phone line plugged in.  The "kick" on
the power line from a lightning hit about 1/2 mile away jumped the power
switch & went through to the phone line. It ruined his modem as well as
damaging the motherboard on his computer.  

Similar to your experience we had a hit (without warning rumbles) that hit
about 100 feet from the house (the computer was plugged in, but not on [I
cursed myself for ignoring the #1 rule!]) and suffered no damage (lightning
hit the same place [a tree] the next year too!--jumped from the tree to the
power line and into a neighbor's house where it tore some wallpaper off and
blew a light-dimmer to bits [looked someone had put a big firecracker in it] ).

More recently, the local power cooperative in NC offered a service where
they put a heavy-duty surge protector between the power meter and the house
power entrance (a service they offered as lightning damage is so common in
the area).  I got that too, and as there hasn't been any close strikes since
they installed it--maybe that has prevented lighting!

Polyphaser Corp has a book on lightning and protection (about $20 US).  It
is based on their research work (they make lightning protectors for coax
cable/ant feedlines).  It is practical (graphs and easy math).  My book is
in NC and we are in FL at the moment; I can send the address/fax number--Let
me know if you are interested.

Regards,

Donald E. Haselwood