I thought that Green Heron has built in thyristors to protect the
controller's components.
John KK9a
Quoting wc1m73@gmail.com:
I agree that simply disconnecting the coax isn't enough, and that a
quality whole house surge protector is a good idea. It certainly
can't hurt. But I highly recommend designing the station so that
*all* wires between the tower(s)/antenna(s) and the building can be
easily disconnected, with the possible exception of the ground
cables (see discussion below.) Belt and suspenders are worth every
penny.
12 years ago I had a lightning surge that caused over $10K in damage
to $30K worth of equipment (had I not done all of the
troubleshooting and repair myself, the bill would have been much
higher.) Luckily, my home insurance covered it. I've posted
extensively on TT about that event, so I won't repeat all of the
gory details here, but wanted to point out that the strike did not
hit the tower. It hit a tree several hundred feet from the tower,
and the damage was caused by an induced surge. Damage on the tower
was pretty minimal -- just the destruction of four relay diodes in
the stack match and complete vaporization of a wide ground trace on
its PCB (the only place where I found any scorch marks or physical
evidence of the surge.) Other than that, none of the hardline,
coax, cables or antenna switch relays were damaged. FWIW, the
shields of all the hardline and coax were bonded to the tower at the
top and bottom, and the relays were configured to be open rather
than shorted when not selected. None of the 24 SteppIR motors and
none of the four rotors on the tower were damaged. The rest of the
damage was indoors, as described below.
The tower that took the surge has a Ufer ground with three 50'
radials of 1/0 buried stranded cable, each Cadwelded to four 8'
ground rods spaced 16' apart (12 rods total). As it's 225' from the
shack, there's no ground cable running between the tower and the SPG
at the shack entrance (Polyphaser says that past 75' the grounds
don't "see" each other.) That said, there are two runs of 1-5/8"
heliax between the tower ground and shack SPG, and the huge
corrugated copper shields probably have much lower inductance than a
1/0 ground wire. So if the grounds can see each other past 75', I
think they're pretty-well bonded together. I have bulkhead
Polyphaser coaxial surge suppressors for every RF cable mounted
through the bottoms of metal utility cabinets at both ends (tower
and SPG), as well as panel-mounted surge suppressors in the utility
boxes with two MOVs and a fuse on both ends of each control wire.
All shields and ground wires are grounded at both ends. The tower
and SPG ground systems are bonded to the metal cabinets via 1/0
stranded wire. The SPG is also bonded to all the other ground
systems that enter the house -- telco, cable, satellite, electric.
Unfortunately, they external drops for those grounds are on the
other side of the house, so I had to run the bonding cable from the
utility cabinets directly a cross the basement ceiling to the
utility entry panel. It wasn't clear to me that installing a couple
hundred feet of ground wire around the house with 15-20 ground rods
Cadwelded to it was a better way to bond the grounds. Open to
discussion on that.
My theory on how the destruction occurred is that the surge was
handled by the coax surge protectors, and most of the MOVs, but the
MOVs connected to my three SteppIR controllers were of too high a
value to protect the delicate ICs. They were more suitable for
protecting old-style rotor controllers, which didn't have any
delicate ICs. As it was, the motor control FETs in my three Green
Heron controllers were destroyed, but I believe the GH circuit
design is such that the FETs acted as fuses to protect the CPUs and
other electronics. Not so the SteppIR controllers. Their delicate
SMD driver chips were fried, and the surge made it past them to the
RS-232 transceiver interface. From there it got to the computer,
destroyed the motherboard, CPU and multiport RS-232 card, and then
propagated to every device connected to that card, including a
Ten-Tec Orion (totaled), an Alpha 87A (RS232 IC fried and CPU
partially damaged) an Acom 2000A (RS232 IC and CPU fried), a
MicroHam StackMaX controller (totaled), a W5XD keyer (RS232 IC and
CPU). The StackMax could have been damaged by the voltage threshold
of the MOVs in the suppressors being rated too high. I also lost the
RS-232 level converter between an FT-1000D and the computer, but
there was no damage to the radio. Evidently, the level converter
saved the radio.
I also had damage to a very expensive high-end CD player, a
C/Ku-band satellite dish LNB, a C/Ku-band 4DTV satellite receiver, a
C/Ku-band satellite TV DVB PCI card in the computer, a Dish
satellite receiver, a garage door opener, a phone line, a digital
scale (totaled via RS232 from the computer), and a ROKU media
processor. I believe the damage to those devices came via the
C/Ku-band satellite TV DVB PCI card in the aforementioned computer,
which was on the same PCI bus as the RS-232 card. It's possible the
surge was picked up by one or both satellite dishes, damaging the
entertainment system devices and propagating to the computer via the
DVB card, and to all the station devices, but given the damage and
the destruction of the SteppIR and GH motor drivers, I think it was
the other way around (or maybe both.) No power supplies were
damaged, and no devices outside the shack and entertainment center
were damaged, except the garage door opener and telco line. I've
lost several garage door openers after lightning storms, and have
read that they're quite susceptible to lightning (I suspect the long
wires to the manual switches acts like an antennas.) The damage to
the telco line was outside the house, so evidently it picked up the
surge there and the indoor suppressors did their job.
After repairing all the damage, I designed and installed a large
patch panel so I could quickly disconnect the many cables between
the tower and shack. It wasn't feasible to locate the panel outside,
which would have been preferable, so I installed it in a basement
closet. All the cables passing through the utility cabinets that are
connected to the SPG enter the house just above the sill, easily
routed down to the panel. The station side cables run from the patch
panel up through the basement ceiling into the shack. There are
about 20 or so cables on the patch panel, most of them multi-wire.
It takes about five minutes to disconnect all of them. I also
installed electrical disconnect panels so I can quickly cut off the
shack circuits from the house AC. My two amps and a couple of power
supplies, routers, etc. are also located in the closet, where I can
quickly unplug them from the AC as well.
I built a smaller panel on the other side of the wall behind our
entertainment center so I could disconnect it from the rooftop TV/FM
and satellite TV antennas, and there's also an AC disconnect box in
there.
Normally, I leave all the cables disconnected when the station isn't
in use. I only disconnect AC and TV cables when we go on vacation or
there's a really nasty storm in the area.
Note that I replaced the MOVs in the surge suppressors connected to
the SteppIR and (I think) GH controllers with MOVs that have as low
a value as I could get without going below the operating voltage of
the driver outputs.
This setup has worked well for 12 years, but I hasten to point out
that although we've had our share of lightning storms since then,
our area isn't prone to them and we haven't seen anything near as
nasty as the one that hit my station in 2007. So I'm not resting on
my laurels and am always on the lookout for anything I can do to
reduce the risk of lightning damage.
[BTW, if TT was on groups.IO, as I've pleaded for, I would be able
to attach photos of my patch panel, surge suppressors, tower, etc.
And likely the text of my post would have been shorter, one picture
being worth the proverbial 1,000 words!]
Hope this is helpful to someone.
73, Dick WC1M
-----Original Message-----
From: john@kk9a.com <john@kk9a.com>
Sent: Wednesday, September 4, 2019 11:45 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Grounding
GL rebuilding Keith.
A tower lightning strike will cause an induced voltage spike in a
home's electrical system, even if nothing is connected to the tower.
I have had this occur while building a new tower and the control
cables and coax were not yet connected or even touching the tower.
Simply disconnecting the coax which many hams do is ineffective
lightning protection. There is a lot of valuable protection
information on this list. Assuming that you have a bunch of ground
rods and a SPG, I would suggest a good whole house surge protector.
John KK9A
from [Keith Dutson] NM5G
My experience is that lightning can be managed, to a point. A
direct strike to your tower can be catastrophic. I suffered one on
May 9. My daughter lives about 600 feet away and witnessed the
strike. She said sparks flew in all directions. My losses are
huge. I am working with the insurance company, and expect the total
damage to be well in excess of $50K. There is evidence that high
voltage appeared on the tower, power lines, phone lines
(fiber) and even on my wi-fi connection from the house to the shack.
Every gigabit switch was toasted, and every PC connected was blown.
Another big loss was two large screen TVs, both connected to
internet via gigabit switches. Repairs were successful by replacing
the power supplies.
All this, plus my main two stations, both with Yaesu FTDX9000D and
Alpha 87A, are gone. Coax was not even connected because I had just
reconfigured the station and had not completed the coax switching
section. However, units were plugged into power, and the Yaesu
transceivers were connected to the PCs.
73, Keith NM5G
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