The one time my station was damaged by lightning, the lightning actually
hit the power lines, and the surge came in, destroyed my 12V power
supply then went down into my IC-22S and came out through a programming
cable I had plugged into it, jumping across a two-inch or so gap between
the end of that cable and the coax going to my well-grounded 2m
antenna. The IC-22 had its reverse-voltage protection diode destroyed,
but suffered no other damage.
For the uninitiated, the IC-22S is an early synthesized 2m FM radio that
you could program with this diode matrix to set up to 22 channels. Some
enterprising individual had modified it to have a 23rd channel, which
was brought out to a 9-pin connector on the back, and had purchased a
box with thumbwheel switches that you could use to set any frequency
that could be used by the radio. It assumed the old 30kHz channel
spacing, which could hit all the repeaters in the area, but you couldn't
go to arbitrary frequencies. Anyway, the magic thumbwheel box had died,
and I had no clue how to fix it, so I just built a cable with an
8-position dipswitch on the end and was using that to set arbitrary
frequencies. When the lightning destroyed the dipswitch, I got a big
burned spot in the middle of the operating table which had a smaller
gold spot, from the gold-plated contacts, in the middle of the burned spot.
Other than the cool gold-plated spot on the operating table, what I got
out of it was the knowledge that just because you've disconnected the
antenna, you can still get lightning damage.
On 5/27/2021 2:25 PM, Robert Polinski via BVARC wrote:
Most lightning damage done in a house is due to a poor grounding
system on the AC service. All service panels should have at least 1
8ft ground rod with a min of #6 ground wire going to the panel board.
The size of this conductor is dependent on the size of the service. In
many cases, this ground is missing, the clamp has rusted off, or is
just making a poor connection. In many areas, the copper thieves have
cut the pole grounds, making your rod the last defense before the
surge hits your home. Ground rods need to have an impedance of lest
than 25 ohms, sometimes more than 1 rod is needed to get this.
Warning, before you do any checking or service on your grounding
system, turn off your main breaker & test your ground wire with a
clamp on amp meter. If it indicates any current, it is a sign that the
power co. ground is bad & working on it could cause electrocution.
Call an electrician.
The second issue is the failure to bond all grounds together.
Newer electrical services are required by code to have a intersystem
bonding block. On this block it has terminals for bonding CATV phone &
any other systems to the service ground. You ham station grounding
system MUST be bonded (connected) to this system with a #6 ground
wire. This is a NEC code requirement and a must to prevent station
damage & possibly a fire. If you do not connect the 2 systems
together, and a strike hits the power line, the lightning will seek
the lowest impedance path to ground. If your station ground is lower
than the service ground, it will pass thru your equipment to find it.
Bonding the ground together eliminates this problem. Robert KD5YVQ
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________________________________________________
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Publicly available archives are available here:
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