Thanks for the info Jim. You have a good understanding of
testing procedures. Do you have the reference study/report
for the testing of the porcupine device as to whether it
reduces or does not reduce the incidence of lightning
strikes?
Doug
Subject: Re: [TowerTalk] Lightning
At 05:30 PM 1/5/2007, Doug Renwick wrote:
>So far nobody, NOBODY, has presented sound empirical data
>that proves the porcupine does or does not reduce the
>incidence of lightning strikes.
Aside from the problems inherent in "proving a negative",
there IS
published engineering testing that shows no statistically
significant
benefit AND there's a fair amount of theoretical physics
that says
they provide no benefit.
As the saying goes: "Extraordinary claims require
extraordinary proof"
> Without that data, you are
>nothing more than an opinion.
>At the bottom read the post from WD4K.
But nowhere does WD4K say anything about spending money on
something
that has no benefit. Sure, there's always a cost benefit
tradeoff on
all lightning protection. And, contrary to the guy from
Polyphaser's
statement, you CAN design and build a system that tolerates
ALL
strikes. For instance, the antennas on top of the Empire
state
building received so many direct hits that they provided a
lot of the
statistical lightning stroke data used for designining
protection
systems. The LLL study talks about how to design an
explosives
storage area to take worst case lightning or EMP (which is
actually a
tougher problem).
I've got an open mind. If a lightning eliminator/static
dissipator
manufacturer (or anyone else, for that matter) wants to do a
rigorously controlled study and publish the results, I'm
willing to
change my opinion. But, if they're going to rely on "we
installed it
in one place and we didn't get hit (as much) by lightning"
that's not
real convincing. And if the mfr is going to play the "as
sold to
NASA" game to imply an endorsement, that's really lame. The
problem
is that everybody who has actually gone out and done real
tests with
decent experimental processes has found no statistically
significant
effect. This is basic junior high scientific method stuff:
running a
control group, swapping devices between towers, etc.
And, of course, for lightning protection in general, it's
quite the
crap shoot, and, in the great middle ground between
absolutely
nothing and the nuclear trigger explosives vault bombproof
shelter, a
lot of what you do is "judgement calls". i doubt many hams
would go
to the trouble to actually do a cost/benefit analysis on all
parts of
the system, carefully trading off incremental protection
against
expected loss over time. You do what seems ok and go from
there. If
the porcupine makes you think it's safer and you can sleep
better at
night, it's worth it.
Jim, W6RMK
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