[TowerTalk] Grounding

[john at kk9a.com]

W2FU did a great job designing these controllers!

John KK9A
Sent via the Samsung Galaxy 7 edge, an AT&T 4G LTE smartphone.


On Thu, Sep 5, 2019 at 2:12 PM <wc1m73 at gmail.com> wrote:

> Not thyristors. They use Transient Voltage Suppressor (TVS) diodes in
> series with the motor control and pot lines. Now that you mention it, I may
> have had to replace the TVS diodes, too, but I can't remember. I know I
> have some on hand, as well as some replacement FETs in case it happens
> again. As I recall, the TVS diodes and FET are mounted on the terminal
> strip in the back, so easy to replace without removing any circuit boards.
>
> I do remember telling Jeff about the strike and the symptoms, and he
> pointed me right at those components. Cheap and easy to fix.
>
> Evidently, the transient was too fast and/or below the TVS threshold
> (82V), and got to the FET. As with MOVs, there's a tradeoff between the
> activation threshold of the protection device, the operating voltage of the
> semiconductor and how much back voltage it can withstand.
>
> It's not clear to me why the GH RS-232 interface and CPU weren't damaged.
> As I recall, they were the only devices connected to the computer where
> that was the case. The schematic doesn't show enough detail to tell.
>
> 73, Dick WC1M
>
> -----Original Message-----
> From: john at kk9a.com <john at kk9a.com>
> Sent: Wednesday, September 4, 2019 8:53 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Grounding
>
> I thought that Green Heron has built in thyristors to protect the
> controller's components.
>
> John KK9a
>
>
>
> Quoting wc1m73 at 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 at kk9a.com <john at kk9a.com>
> > Sent: Wednesday, September 4, 2019 11:45 AM
> > To: towertalk at 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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