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Re: [TowerTalk] Rotator Lightning Protection

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Rotator Lightning Protection
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
Date: Sun, 17 May 2015 11:55:45 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
If you are going to disconnect, disconnect everything. Remember that 1000 volts per meter of wire from a lightening strike a mile away and there are how many meters of wire in the house?

In my case I had the stations disconnected from the computers, but I failed to disconnect the computer network and it sure made an expensive and time consuming mess in the network and computers. The CAT-5 went through protection at each computer's UPS, but it welded the contacts together in one and melted the plastic RG-45 plug and socket together. It also took out 3 of 4 NICs. and one motherboard. The only things left were the 850 W PS, the video card and the hard drives. It also wiped out the 8 port smart switch and a 4 port router which also had dual channel wireless. Fortunately my wife's computer is wireless as is the printer.

The UPSs are under warranty, but weigh around 40# each. So there's the cost of shipping both ways, plus the down time. I'll probably just purchase the stock parts and DIY.

Had this computer and the one in the shop been hooked into the rigs using HRD it could have been much more expensive. I now have two servers in the den so I can leave the two computers in the shop, off line "most of the time" although I'm working toward remote control of both stations.

I have a 30 A 120 VAC line conditioner that I have to hurry and run a new circuit for. then the computers and rigs in the den will be on a regulate 120 VAC that is a clean sine wave. That does not include the amps that run on 240 VAC. In the early days computers ran on line conditioners, but the expense brought about simple UPSs. Like many things we become accustomed to, UPSs are now thought of as normal and line conditioners a gimmick, but in many areas with wide variations in line voltage, the line conditioners with a clean, regulated 120 VAC is good protection and a good investment even if a bit pricey compared to a UPS. If you can find one.

73

Roger (K8RI)

On 5/17/2015 9:03 AM, Bry Carling AF4K wrote:
I guess the moral of this story is don't connect your phone line to your 
amplifier?

On 16 May 2015 at 17:26, Chuck Dietz wrote:

I used to pull all plugs and disconnect all antennas but had a problem because 
I left the
equipment grounded and strike came over phone line through an amplifier to 
ground. Now I have
an equipment ground disconnect too.
Chuck W5PR

On Saturday, May 16, 2015, Bry Carling <bcarling@cfl.rr.com> wrote:
     My solution is to pull all AC plugs from the wall and disconnect all 
antennas whenever a
     storm is coming. That pretty much takes care of most problems.
My ground system is going to be improved from the current setup but I'm not going to the
     kinds of extremes that some people have, and assuming that will be a 
perfect system of
     protection.
Best regards - Brian Carling
     AF4K Crystals Co.
     117 Sterling Pine St.
     Sanford, FL 32773
Tel: +USA 321-262-5471 > On May 15, 2015, at 9:11 PM, Roger (K8RI) on TT <K8RI-on-TowerTalk@tm.net> wrote:
     >
     > Having worked with literally thousands of MOV,s from little ones up to 
50,000 Joul ratings,
     They will typically fail shorted, BUT I have seen many fail open.  It 
depends on the power
     contained in the "final spike" that causes them to fail.  From power line 
spikes and nearby
     lightening strikes the ODDS ARE it/they will fail shorted.  If enough 
power/energy is
     contained in that final spike at failure time, it becomes likely they will 
fail open and  that
     anything on that line will fail as well.
     >
     > Based on experience, you can expect the MOV to fail shorted and it will 
PROBABLY
     protect any electronic device connected to it. That being the case, the 
prop pitch motor will
     PROBABLY need some sort of "fail safe" to prevent over rotation.
     >
     > That's a lot of probables, but it's unfortunately a fact of life, 
leaving you playing the odds
     which favor the MOV failing shorted, but with no guarantee it will do so.  
 If the MOV works
     as we all hope, then you will need some sort of "fail safe"
     >
     > Since the big ground system was installed my tower has been hit at least 
7 times that can
     be verified with nothing disconnected and NO MOVs in the rotator lines.  
No damage was
     seen.
     >
     > I can not say the same for my computers and network.  A nearby strike 
did nothing to
     either station, but it sure cost me a lot in network and computer damage.  
The CAT-5 lines
     go through protection at the UPS for each computer.  The connectors were 
melted and the
     wire contacts welded together at one UPS.  The router, 8 port switch and 
most NICs were
     shot!
     >
     > So, lightening and MOVs are a crap shoot.  They will protect you from 
the smaller stuff,
     but cause other problems. They are unlikely to protect you from the larger 
stuff.
     >
     > In the end, I'd use them, plan on the MOVs failed as a short, and hope 
for the best  There
     is no guarantee, but you have tilted the odds in your favor..
     >
     > 73
     >
     > Roger  (K8RI)
     >
     > .
     >> On 5/15/2015 10:38 AM, Paul Christensen wrote:
     >> N4CC and I have finally completed our remote Internet station in 
Hilliard, FL.  Probably
     half our time spent before and during construction was studying and 
implementing lightning
     abatement.  Ground rings were created around each tower, and the 
communications
     shelter.  All grounds, including the adjacent electrical service ground 
are brought together at
     an external ground bus (EGB).  In total, 55+ ground rods are used with 
four rods each 24 ft.
     Lines are bonded at the top and bottom of the towers.  We do not 
disconnect anything.
     Everything stays up and running 24/7 regardless of the WX.
     >>
     >> Poyphaser rotator MOV protection devices are installed at the base of 
each tower.  At
     the EGB, we're using an Array Solutions model. In looking at all the 
failure modes, I missed
     one:  If the MOV on the rotator return lead was to short to ground, it 
creates a disastrous
     situation where the prop pitch will turn freely beyond the electrical stop 
point.  The MOSFET
     is controlled by a PWM circuit and the duty-cycle is what varies motor 
speed.  A shorted
     MOV will cause the lines to break apart up the tower at the coax loop.  
The prop pitch would
     stop at nothing and keep turning.  Do the MOVs in these units generally 
fail open or closed?
     >>
     >> We're using a pair of M2 PCX2800 controllers.  To help protect the 
MOSFET device
     from a similar "short-to-ground failure" during a lightning event, I 
designed a circuit that
     engages a vacuum relay such that the MOSFET is only exposed to the outside 
world during
     rotation.   It's not a 100% guarantee against MOSFET failure, but should 
help to mitigate
     damage.  This is an add-on that's similar to what K7NV did with the Green 
Heron prop pitch
     controller model.
     >>
     >> Here's my thought for a potential fix:  While another vacuum relay 
could be added on the
     +48V supply side to the prop pitches, I could isolate circuit ground from 
chassis ground on
     the secondary side of the controller's power transformer.  The primary 
would still be safety
     protected and meet UL. Isolating circuit ground from chassis ground would 
inhibit rotator
     turning in the event of a MOV failure on the return line.
     >>
     >> Anyone been through this?  I welcome comments on any better ways to 
manage this.
     >>
     >> Paul, W9AC
     >> _______________________________________________
     >>
     >>
     >>
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     >
     >
     > --
     >
     > 73
     >
     > Roger (K8RI)
     >
     >
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73

Roger (K8RI)


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