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[TowerTalk] my long lightning story (was RE: lightning strike)

To: "'Roger \(K8RI\)'" <>, "'Skip K3CC'" <>
Subject: [TowerTalk] my long lightning story (was RE: lightning strike)
From: "Dick Green WC1M" <>
Date: Fri, 30 May 2008 03:32:58 -0400
List-post: <">>
For 10 years I thought I could protect my station from anything but a
superstrike, but that was before I put up a 110' tower, and before the
summer thunderstorms around here became more violent (Climate change? Who

Previously, all I had was my 72' tubular crankup, almost always retracted to
22', a 75' AB-577, two 48' AB-577s, and several wires antennas strung in
trees at the 65'-75' level. All the "towers" are either below the level of
nearby trees or close to it, and all are at least 30' below the tops of
trees on the high points of our land. The crankup has an extensive ground
system, 12 ground rods spaced 12' apart, Cadwelded to four radials of 1/0
wire attached to the base mounting bolts. There's a utility cabinet next to
the tower with Polyphaser coaxial suppressors for every antenna and
Polyphaser rotor suppressors for all control cables. All wires run to the
shack through 265' conduits buried 4' deep, and there's a length of 1/0 in
the bottom of the trench for the entire length. At the shack end, there's an
identical utility cabinet with an identical set of suppressors. The panel in
the cabinet is attached to a single point ground. The long buried piece of
1/0 is also attached to the SPG. There's a copper bus bar running along the
wall behind the operating desk to which all equipment is grounded, with
individual leads, and the bar is bonded to the SPG. The SPG is also bonded
to the AC and telco grounds (through the house, unfortunately, but that was
the only practical way to do it.)

The only problem I had with this system was a pair of CMOS NAND gates in a
homebrew antenna switching system blowing almost every time we had a
significant lightning storm. I suspected a bad MOV in one of the Polyphaser
rotor control suppressors. I replaced it, but decommissioned that switching
system before I had a chance to prove it was in fact a bad MOV. More on this

Almost a year ago, I completed 110' of Rohn 55 with a 40-2CD at the top and
a 3-stack of 4-el SteppIRs. The ground and lightning suppression system is
similar. The pier contains a Ufer ground, which was required by our local
electrical inspector. The rebar is wired together and 50' lengths of 1/0
wire are clamped to the rebar and run out through the sides of the block
about 2' below the surface in a radial pattern. Each radial leg is Cadwelded
to an 8' ground rod every 16' (four rods per leg.) The tower end of each
radial runs up through the concrete block and out the top, where they're
clamped to the tower legs (it's a pier-pin foundation, not a buried
section.) There's a utility cabinet at the bottom of the tower with a
Polyphaser coaxial suppressor for each coax or heliax run, plus K5FD
lightning suppressor boards for all control leads (96 at present, requiring
eight 12-position boards -- the SteppIRs, TIC rings, stack match and SO2R
switch require a lot of wires!) The cables run down into the ground through
a short piece of conduit, where they run direct-buried about 2' down 225'
back to the shack (no conduit this time.) RF is carried by two 1-5/8" runs
of heliax. I didn't lay a long 1/0 wire in the trench this time to connect
the tower ground with the SPG because I figured the massive outer conductors
of the two heliax runs would provide a much lower impedance path to ground.
Besides, Polyphaser says the ground systems won't "see" each other if
separated by more than 75' because of the inductance of the wire (some
disagree with this.)

There are a few pictures of the 110' tower system on my website at They're not complete, but do show the cable connections and
ground system.

All shack and entertainment system devices are connected to surge
suppressors. These aren't the high-end ones recommended by (I think) by
K9AY. The computer is on a UPS with surge suppressor, but it's not one of
the super high-dollar units either.

Less than a month after completion, we had the most violent lightning storm
I have seen in 37 years of living in West Central NH. The storm began with
no warning -- absolutely clear skies. The lights in our house got *very*
bright, then we lost power (it was out for 13 hours.) Evidently, this was
caused by a strike at a distant power substation. The first wave of the
storm came up suddenly after that, but the lightning wasn't particularly
violent or close. It was pretty typical for what we see in this area. We're
far from any large body of water and the mountains tend to break up storm
systems as they travel over the region. It's relatively rare for us to see
large cloud-to-ground strokes. This first wave passed (the power was still
out), and I went into town to get some take-out. Most of the town and
surrounding region was without power (except the part with the take-out
restaurant.) At the time, I noticed bright flashes and rumbling thunder far
to the south and northeast, suggesting that the storm had already passed
over us. I didn't see anything to the west, which is where most of our
weather comes from. I got home with the take-out, and as we were eating
dinner, a *huge* lightning storm hit very suddenly. There were very bright
flashes and booming, cracking thunder, and the strikes moved to within a
mile or so of the house. I was just getting my head around what was going on
when there was a tremendous flash and crack of thunder very near the house.
We heard loud cracking noises, like gunshots, from behind the entertainment
center. I wasn't in the shack, so I don't know what sounds or flashes may
have occurred there. I wasn't looking out the window, so I don't know if the
new 110' tower got hit. I'm pretty sure another lightning strike hit
something in the woods behind the house, maybe a tree.

When the power came back on in the morning, I heard a loud buzz coming from
the entertainment center. It sounded like an alarm clock. It was coming from
inside a high-end CD player that's designed to be on all the time. I killed
the power switch and the buzzing stopped. For the next few hours, I took
stock of the damage. In all, I lost over a dozen pieced of electronic
equipment, mostly ham gear. The damage included: my computer (dead
motherboard and I/O cards), an Orion transceiver (deemed unrepairable by Ten
Tec), an Acom 2000A amp (dead serial line drivers, dead CPU), an Alpha 87A
amp (dead line drive, bad CPU), an FT-1000D (no serial communications -- the
RS-232 line driver in the W1GEE interface cable sacrificed its life for the
radio), three 4-element SteppIR controllers (dead driver boards), two Green
Herron rotor controllers (burned out FET drivers), a microHam Stack Max
(dead RS-232 line drive and dead CPU), microHam Info Panel (dead ROM),
microHam Stack Switch (on the tower -- four blown relay protection diodes
and a vaporized PCB trace), a Writelog W5XD keyer (dead RS-232 line driver
and dead CPU), a feedline connector to the 40-2CD at the top of the tower, a
high-end CD player (bad D/A converter and other damage), a C/Ku-band
satellite system (dead C-band LNB and servo motor), a garage door opener
(bad encoder), a digital postage scale (connected to computer via RS-232),
an HD media processor, a telephone surge suppressor (part of a wall-mount AC
suppressor) and a phone line (blown apart on the pole.)

In all, this equipment cost over $30K new, and the bill for damage came to
about $10K. That was cheap: I diagnosed and fixed most of the gear myself
and was able to get either free or inexpensive repairs done to the amps
without shipping, by hand-carrying them in for repair.

Remarkably, most of the equipment in the entertainment center survived,
including a brand-new plasma TV, a Dish HD receiver, a tube pre-amp, a phono
amplifier, a turntable,  two solid-state audio amplifiers, an FM tuner, a
DVR, and several other pieces of gear. Only the CD player and HD media
processor were damaged. 

Except for the dead semiconductors, there was no trace of physical damage
inside the house, such as melted metal, scorch marks, vaporized PCB traces,
exploded semiconductors, etc. No power supplies were damaged. I still don't
know what caused the cracking noises behind the entertainment center. It was
probably exploding components inside the CD player. I thought it might have
been the surge suppressors on 
the AC outlets but their "protected" LEDs are still on.

The K5FD boards have fuses inline with each conductor to protect against
accidental shorts, and they were blown on all of the SteppIR leads, all of
the TIC ring leads, most of the stack switch leads, and some of the SO2R
switch leads. The SteppIR leads had 5A fuses, the TIC rings had a 5A on the
motor leads and .5A on the pot leads and the switches had .5A fuses on all
leads. More fuses were blown on the tower suppressors, but some were blown
at the shack end, too.

I'm reasonably certain that either lightning struck the tower, or it picked
up a large EMP surge from a nearby hit, perhaps the one that blew the phone
line off the pole (same direction as the hit I thought was in the woods
behind the house.) It seems clear the bad connector at the junction of the
40-2CD rotor loop and feedline was caused by a hit or surge at the tower,
perhaps on the antenna itself (found a black carbon path between the center
pin and shell when I sawed it in half.) Unfortunately, I had not grounded
the feedline shield to the tower (it is now, top and bottom.) It also seems
clear that the surge traveled through most of the control lines, which is
why the fuses blew.

My theory is that before the fuses blew, the surge hit the SteppIR
controllers, shorting all of the driver chips, and found its way to the
RS-232 ports connected to the driver boards. From there, it propagated back
to the multi-port RS-232 card, destroyed the computer motherboard and all
the I/O cards, and propagated back out the multi-port RS-232 card to every
device connected to the computer via RS-232, which included the Orion, the
W1GEE cable, the 87A, the 2000A, the W5XD box, the microHam Stack Max,
digital scale, etc. The failure mode in all these devices was almost
identical: the RS-232 line driver was blown, and in most cases the CPU was
blown, too. In almost all these designs, the CPU is directly connected to
the RS-232 line driver. The 87A was unusual in that its CPU was damaged, but
only the I/O port connected to the line driver. Apparently, the I/O ports
are individually fused in that chip. All the other CPUs were killed stone
dead. The Green Heron controller FET drivers were damaged in a similar way,
by a surge coming in via the motor control lines, but since they were not
connected to the computer's RS-232 card, the damage stopped there.

This is where the theory gets a little hazy. The C-band LNB was connected to
three different satellite receivers, one of which was in the computer. It's
conceivable lightning struck the 10' satellite dish, killed the C-band LNB,
travelled back to the computer, killing the satellite tuner card, and
propagated through the multi-port RS-232 card to all those RS-232 devices,
then back out to the tower via the control lines. But I doubt it. The other
two satellite receivers were not damaged at all. My guess is that the surge
went the other way. When it got to the computer from the SteppIR
controllers, it went through the satellite tuner card back out to the C-band
LNB on the dish. It didn't kill the other satellite receivers because
they're connected through DC-blocking splitters. Something similar happened
to the HD media processor. Its Ethernet port was fried, which was connected
to a LAN card in the computer.

The biggest mystery is the CD player. It had to have taken a hit either on
the AC line (perhaps when the lights got bright, then again when the big
surge hit), the audio connectors going to the preamp, or the coaxial digital
input from one of the satellite receivers. But none of the boxes at the
other ends of those cables was damaged. Plus, the CD player was on a surge
suppressor. Note that this CD player was replaced under warranty about 6
years ago with symptoms suspiciously suggesting it had been damaged during a
storm (they kept trying to repair it, then it would fail, so they finally
gave up and replaced it.) I suspect the design is susceptible to lightning
damage, but I don't know the entry mode.

I'm pretty sure the AC surge killed the garage door opener encoder, but it
might have been the flash that vaporized the phone line connection.

Although a phone surge suppressor blew, none of the connected phone
equipment was damaged, including a DSL modem.

So, why didn't the K5FD surge suppressors protect my system? Well, I think
they actually did. The SO2R switch lines terminate at open relays in the
shack, so there was no path to ground. Since some of the fuses on those
lines blew, I think the MOVs actually did conduct the surge on those lines
to ground, causing the fuses to blow. The same thing must have happened with
the microHam Stack Max controller, where the control lines are also
terminated in relays that were open at the time (I believe the box was
killed by the surge that propagated back out the computer RS-232 ports.) I
suspect the MOVs may have conducted on most if not all of the control lines,
which may be why there was no evidence of melting scorching etc. The fuses
probably provided protection from that, too. 

Unfortunately, the SteppIR and Green Heron controllers had delicate
semiconductors directly attached to the control lines, and I suspect the
MOVs didn't start conducting until the max voltage level of those
semiconductors was exceeded. Remember those CMOS NAND gates in my old
antenna switching system? They were the only semiconductors directly
attached to the control lines, and they were the only parts that
consistently failed during storms, despite being on surge suppressors. 

Part of the problem is that all my K5FD suppressors had 82V MOVs in them
(Polyphaser uses a similar value in their suppressors.) I'm sure this was
too high for the driver chips in the SteppIR controllers. SteppIR later told
me a value around 45V is best for MOV protection for the controller. The FET
drivers in the Green Heron controllers can use the same value because the
TIC rings run at less than 40V. K5FD has been great about helping me to
replace or retrofit MOVs into the boards that more closely match the max
voltage levels of the connected devices.

However, after this experience, I'm not convinced this is enough. It's one
thing to rely on MOVs to protect switches, relays and the old analog rotor
controllers. But it's not clear to me that the semiconductors in more modern
equipment can stand any reasonable level of voltage above their operating
voltage. It may not be possible to find a MOV that will conduct at a voltage
less than what it takes to kill the semiconductor without getting tripped by
operating voltage spikes. If the device happens to be connected to other
devices through a communications link, a lot of damage can occur if one of
the semiconductors breaks down.

For this reason, I finally decided to throw in the towel and construct a
master patch panel for my station. With two separate SO2R switch banks,
seven rotors, three SteppIRs, a stack switch and numerous coax runs, the
cabling inside the shack is very complicated and its tough to get to all the
cables to disconnect them, let alone getting to all the outlets behind the
desk to unplug the equipment. I had previously moved my autotune amps to the
basement under the shack, where the cables enter the house, and we had built
a closet around it. I moved the rest of the switching control gear
(PC-controlled, Ethernet-based) to the basement, and built a patch panel
containing plugs for every single line that comes into the house from the
tower, including coax, switches, relays, stack switch, SteppIRs, rotors,
etc. I also installed a disconnect for three phone lines coming into the
shack and a Dish satellite TV antenna. I relocated the 220V outlet so I
could quickly disconnect the amps from AC, and also installed AC disconnect
panels for two AC lines running into the shack. So, except for SPG and AC
ground, the equipment in the shack can be disconnected from everything else
(there are about 35 cables to pull.)

I plan to install a similar set of panels in the basement underneath our
entertainment center, to cut off the rooftop antenna, C-band antenna and AC

I'm not taking out the suppressors, of course. I think they still provide
valuable protection for all the cable runs, and will provide some level of
protection if a storm comes up suddenly when I'm operating or if I forget to
disconnect everything at the patch panel.

[The only question in my mind is leaving the equipment connected to the AC
and SPG grounds. I worry about the ground system not being able to absorb a
direct hit or superstrike. Then again, I think the equipment would have to
be connected to some lower potential for the surge to find a path through
it, and I think I've eliminated that possibility. Anyway, if I had my
druthers, I'd disconnect the grounds, too, to have the equivalent of putting
each piece of equipment back in its shipping carton. But the available AC
disconnects don't provide for ground to be disconnected, and it would be
pretty hard to devise a quick disconnect for my SPG.]

So, that's my story, and I'm sorry it was so long and detailed. It's been a
real watershed event for me to have converted from "B/C stations stay on the
air during operation, so I can too" to "Disconnect everything." All it takes
is one bad experience.

73, Dick WC1M

> -----Original Message-----
> From: Roger (K8RI) []
> Sent: Thursday, May 29, 2008 10:37 PM
> To: Skip K3CC
> Cc:
> Subject: Re: [TowerTalk] lightning strike
> Skip K3CC wrote:
> >     If everything is perfect in the world with your grounding
> systems  how
> > fast is fast enough to prevent damage from a direct lightning strike
> of over
> > 100,000 A at a freq near 10 Gigs.    The heat that can produced from
> a
> > strike is that greater then the temperature of the Sun.
> >
> > A little over 10 years I lived in Kempton, PA atop a ridge at 1000
> ft ASL.
> > My tower was grounded OO wire from each leg about 6 ft up from the
> base.
> >
> > We had an indirect strike of lightning come through our 400A
> underground
> > service, fuse the line and destroy all electrical and electronic
> devices
> > plugged into the outlets.  Cost over $30,000 w/o the electrical
> service.
> > The above ground transformer box was completely destroyed and the
> concrete
> > pad gone. that service was for about 6  homes
> >
> > I guess this is why I can't believe you can protect yourself from a
> direct
> > lightning hit.
> >
> You have to realize not all lightning is created equal. In fact what
> you
> witnessed is probably and exception called a "super strike". The
> average
> lightning bolt is probably an order of magnitude less than that at
> maybe
> 10,000A and of a very short duration.
> My tower has taken
> an
> average of  three *verified* direct strikes a year since it was put
> up.
> None last summer and 5 the previous summer.  I have no idea as to how
> many it's actually taken.  Since the present ground system was
> installed
> I've had no equipment damage including 5 computers of which 4 are on a
> CAT5e Gigabit network which has one run between the garage and shop
> about 10 feet to the right of the tower in the photo.  In addition
> there
> is one rotator control line, one remote antenna switch control line,
> two
> RG-6 coax  cables for the satellite  receiver and two RG-6 cables to
> a
> pair of UHF antennas (with antenna mounted preamps) near the top of
> the
> tower, and 5 runs of LMR-400 in the underground PVC conduit between
> the
> tower and when the cables enter the house through the grounded
> bulkhead
> connector.  I rarely disconnect any equipment or turn off computers
> when
> storms come through.  BTW the CAT5e runs with all those other cables
> for
> about 20 feet while in the basement. It then goes into the garage, up
> the wall, across the ceiling and down the North wall, through the wall
> and then underground to the shop.
> > In the 60's I worked for a radio station WAEB.  I remember what we
> went
> > through grounds and megging the system.  I was told the important
> thing was
> > to keep the strike outside the transmitter/studio building.
> >
> > I can't disagree with most of the steps that are taken,  It takes a
> lot of
> > copper in the ground, taking reading with a megger, and trying to
> stay away
> > from the RF  ground system.  However, I think they will only prevent
> > transients, not direct strikes
> >
> >
> I'd have to disagree as I've seen repeated direct strikes to my tower
> with no damage. However I hasten to add that any lighting is a crap
> shoot.  Although rare there is little one can do about one of the
> super
> strikes. Fortunately they are a tiny fraction of a percent so the work
> to protect a station is well worth the effort. IIRC Prior to
> installing
> the ground system (32 or 33 8' ground rods cad welded to over 600 feet
> of bare #2), adding the grounded bulkhead connector and grounding all
> coax shields on the tower at the top and bottom, I lost one repeater
> antenna (the repeater survived), one run of 7/8" Heliax,  one 2-meter
> rig, several runs of 9913 coax, and one computer (that was less than
> two
> weeks old). Since then I've lost one N connector and one Polyphaser,
> but
> I can't trace their failure back to any particular storm.  Let me
> restate that as "I think" I can trace the Polyphaser to one week end
> when we had numerous storms. OTOH I was standing out by the road,
> talking with a neighbor while listening to a storm way off in the
> distance. We could hear the thunder but nothing loud. Then a bolt of
> lightning struck the power pole that was no more than 12 feet to the
> North of where I was standing. We both made hasty exits heading for
> home.  Another bolt struck the next pole to the North and a pine tree
> about 200 yards to the East.  It literally blew the pine tree apart
> with
> pieces over three feet long embedded over a foot into the ground over
> 50
> feet from the base of the tree.  The neighbor to the North who's house
> was fed off that transformer lost a TV, sump pump, water heater,
> refrigerator and "a bunch of other stuff". I had no damage from the
> one
> that stuck the transformer that feeds my house and shop. Even though
> the
> tower is much taller and about 130' from the pole it didn't get hit.
> (that we saw)
> 73
> Roger (K8RI - ARRL Life Member)
> N833R (World's oldest Debonair)
> > de Skip K3CC
> >
> > _______________________________________________
> >
> >
> >
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> >
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> >
> >


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