Tom Donaly wrote:


You can easily charge up an insulator with a static charge. A comb is
usually made out of an insulating material. Run one through some hair
and it will pick up small pieces of paper. (I use my wife's hair.)
Secondly, particles don't have to be charged to create a charge on
an antenna. They just have to touch it and be pulled off. Google
triboelectricity. (I think I spelled that right. If I didn't, ask
Cecil how it's spelled. He knows.) Yes, there is more than one way to
charge an object to the point of creating corona discharge. Make a
small Van de Graf generator and try that. You also might want to
charge up an insulator (your comb), touch it to your antenna, and
measure how much charge was actually transferred to the antenna.
Discharging insulators is sometimes difficult because they're, well,
insulators and charge doesn't move around on them readily. Sometimes
you have to use Polonium 210, or a torch, or a specially built
fan to accomplish this. (You can buy a Polonium brush. The manufacturer
warns against taking it apart to see how it works, though.)

Make a homemade field mill and measure the earth's electric field
during a time when there's corona discharge from your antenna. A large
natural electric field from a big, honking thundercloud could easily
cause coronal discharge on your antenna under those circumstances.
There are lots of things a dedicated amateur can do to measure static
electricity, and, if he doesn't get killed, the effort is worth it.
Just making up theories out of the clear blue, however, without any
attempt to test them, is just a waste of time.
73,
Tom Donaly, KA6RUH

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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