Randy -
Right you are!! Years ago when I had a Cushcraft R-4 vertical, mounted on a
high-rise
roof, I followed the recommended grounding instructions. A year later it
got a direct hit, which blew the matching box and a couple of traps.
Needless to say, I replaced the antenna with an R-5 but left it ungrounded.
Once hit, made
aware (hi). It has been up at the same location for the past 10 years
without any lightning
problems. As a protection in the shack, the coax is disconnected when the
rig is not in use, and the AC power cord is pulled, just in case of a near
EMF hit.
73 - Don, VE1BN
----- Original Message -----
From: "Randy K4QO" <k4qo@earthlink.net>
To: <tentec@contesting.com>
Sent: Friday, May 05, 2006 11:19 AM
Subject: [TenTec] If you ground it - it will come!
With apologies to "Field of Dreams", what I mean is that just grounding
things sometimes means that you are inviting lightning to go to ground
there... through your equipment.
In my line of work with commercial radio towers, I have found that
sometimes it is a mistake to ground certain items. Improvements in
survivability were gained when certain protection points were removed.
For example, a serial communication line was protected with a device and
was always getting fried along with the device it was hooked to.
Removing the protection actually caused the devices to survive for more
than three years with no problems.
At my QTH, I look for ways to remove paths like was described by the
"RIP" post. Details like replacing switcher wall warts with
transformer based ones provide a slight measure of advantage. The
transformer ones have (admittedly small) isolation from ground and the
AC lines. This isolates the router and cable modem (which is attached
to the cable!) from the AC mains and doesn't "invite" the surge to use
this path to go to ground. I won't go into a full treatise about
grounding but if you take the time to personify lightning surges and see
what paths it can take to ground (via your AC power plugs), you might
see some opportunities for isolation. One more thought - I use a large
linear supply with better transformer isolation to power the cable modem
and router and my radio supplies are all linears for the same reason.
No switchers for me!
BTW, I have heavy surge arrestors at the cable entry point with ferrites
on the cable on the house side of things to encourage the surges (that
are basically an RF signal) to go to ground at the points I have
provided outside the house. Its my own brand of voodoo but it is based
on observations garnered at the commercial sites.
This is a topic fraught with lots of opinion and some science and I
don't mean that you shouldn't ground your station. The commercial sites
frequently have some of the best grounding known to man and still see
damage. Of course, at the end of the day, your best defense is to
totally isolate your prized possessions during the storms.
73,
Randy
K4QO
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