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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> >
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