[TowerTalk] Grounding

[john at kk9a.com]

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