Jim and fellow Tower Talk members:
That message is kind of weird because I don't even use
the WW5L@gte.net address to send e-mails and haven't
in many months since I switched from dialup to DSL.
I wonder why if you got it through the list and I
didn't where the problem could be? I use McAfee
internet suite protection and it checks all my files
every night about 3 a.m. CDT, plus its set to auto
update my AV files too.
The mysteries of the internet never cease.
73 de Tom, WW5L
--- Jim Lux <jimlux@earthlink.net> wrote:
> Tom Anderson wrote:
> > Jim and fellow tower talk members:
> >
> > I'm in the process of having a 220 line run into
> the shack for a new
> > Alpha 9500 amp my XYL and I picked up at the plant
> in Boulder a month
> > ago. Still waiting on the electrician showing up
> though.
> >
> > While I had him on the phone I asked him (and yes
> I've known him for
> > years (I was his son's Eagle Scout advisor) and
> he's done work for me
> > before and does a lot of commercial work near us)
> about a whole house
> > protector and in his opinion he felt a good
> individual unit for the
> > plugs and equipment you wanted to protect was
> better than a whole house
> > protector. He said many strikes, surges, etc. come
> into the house via
> > phone lines, TV cable, satellite dishes, etc. and
> often bypass the whole
> > house protector before getting into the home
> electrical system, which is
> > why he prefers good single unit protectors when
> needed.
>
> Not to be argumentative, but it would seem that the
> peer-reviewed
> transient protection literature doesn't agree with
> the single unit
> protection philosophy.
> (i.e. things that aren't sales material or field
> application guidelines
> from one company or another.. but stuff that has
> been independently
> produced, or at least reviewed by folks without a
> financial or other
> interest. Sure, the guys from Erico publish papers
> on transient
> suppression, and Erico sells products that do this,
> but the journal's
> pre-publication review process generally makes sure
> that 2 or 3 other
> folks take a look at it and make sure it's not all
> bushwa.)
>
>
> Your friend is right that lots of transients come in
> other ways, which
> is why you need protection on *all* of them, and why
> everyone is so
> obsessed with all those "bonding" rules. However,
> there's a whole raft
> of reasons why protection at the entrance is needed,
> and preferred, and
> which should be properly coordinated with the
> downstream protection.
>
> The guidelines for things like safety critical
> installations (e.g. the
> FAA guidelines and DoD guidelines) all talk about
> transient protection
> at the service entrance, but make little or no
> mention of "point of use"
> protection.
>
> Also, a lot of protection devices get a lot of their
> protection ability
> by absorbing the transient (and getting
> spectacularly destroyed in the
> process). I think I'd rather have the spectacular
> failure out by the
> meter, rather than on some plugstrip behind the
> desk.
>
>
> Really, the only hazard that point of use protection
> protects against is
> a transient being induced in your house wiring
> closer to the equipment
> than to the service entrance, because of the time
> delays involved.
> (transients from outside, which are MUCH more
> common, get suppressed at
> the service entrance) Or, if you have something in
> your house that puts
> big transients on the power wiring (like that 1kW
> tesla coil you fire up
> in the garage.. been there, done that, cooked my
> garage door opener and
> a UPS.)
>
>
> Of course, a decent series mode suppressor (i.e. a
> LC low pass filter)
> will solve that problem. Most modern electronic
> equipment already has
> fairly decent low pass input filters on the AC line
> connection (to
> prevent signals inside the box from coming out and
> creating EMI havoc),
> so the sub microsecond transient resulting from that
> spurious induced
> voltage, and reflecting back from the clamp will get
> smoothed out by the
> filter to a level that is lower than the damage
> threshold for your device.
>
>
>
> For folks wanting to spend some time and about $20,
> get the book by
> Standler on overvoltage protection. (google standler
> overvoltage and
> you'll probably find it) He's got all the data, the
> impulse waveforms,
> the theory of what works and what doesn't. His
> website also has some
> info. I can't recall which off hand, but in one
> place or the other, he
> talks about the UL1449 standards, and the problem
> with "joule ratings"
> and "clipping voltage".
>
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