chuck wrote:

Hi Tom,

Don't know toward whom your post was directed, but I'll comment anyway
--if that's OK. ;-)

I'm quite comfortable with your statements on electrostatics. Regarding
theories and testing, however, there is perhaps more to be said. A lot
of anecdotal evidence of p-static has been described, more or less
roughly, in the group. That's really great. But before meaningful tests
can be designed, I think an attempt at understanding the mechanisms
behind the various p-static reports should be explored. A big part of
the problem is that we probably can't cause the p-static to appear on
command in our testing laboratories! Moreover, we are pulling stuff out
of the air if we believe all reported cases of p-static arise from
similar conditions. In more blunt language, I most humbly suggest we
seem to be having difficulty understanding what is going on and I hope
that the more it is discussed the more likely we can achieve closure.

We have, if I am following correctly, at least two suggested causes for
the observed phenomena. Charge impingement and electrostatic induction.
Yeah, they're both electrostatic actions, but very different. They can
even occur simultaneously, which adds additional complication. Moreover,
we're concerned with an electrodynamic consequence (a current in the
receiver input circuit) of some electrostatic event(s).

It is beginning to appear that in some minds, these two explanations are
merging: both can cause coronal discharges. I am somewhat skeptical
about the induction mechanism, at least in the case of an insulated
wire. Here is why: if the field is strong enough to cause coronal
discharge of an insulated conductor, it will also cause coronal
discharge of almost everything in the vicinity. I think a very strong
field would be required for that to occur, surely much more than 10
KV/meter. Didn't W8JI describe something like that with discharges from
trees?

Electrostatic induction will not generally transfer a charge to an
ungrounded conductor. It will simply redistribute the free charges
thereon so as to render the net field within the conductor zero. In
other words, only charged object(s) brought into direct contact with the
conductor will impart a charge. An electroscope comes to mind: bringing
a charged comb near the electroscope will cause the leaves to fly
outward, but no charge is transferred; the comb (i.e., its field) merely
redistributes the charges preexisting on the electroscope.

For a grounded wire antenna (even one grounded through the 50 ohm input
impedance of the receiver), there is a vast supply of charges that can
be "induced" by charged clouds into the conductor from the earth itself.
All the free charges in the wire (rather than 50%(?) of them in the
insulated case?) may make coronal discharges possible at lesser field
strengths.

I hope we can continue to kick this around.

73,
Chuck NT3G




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Hi Chuck,
Read "Meteorological Aspects of Precipitation Static" By
Lieutenant Robert C, Edwards, U.S.N.R., and Captain George W. Brock,
U.S.A.A.F. from the Journal of Meteorology, Vol. 1, Number 4,
December, 1945. If you Google "Precipitation Static" you can
find a pdf file of it. They actually went up in three different
airplanes, an RB-37, a B-25D, and a B-17G and did some measurements.
You might be interested in their methods and conclusions.
73,
Tom Donaly, KA6RUH