On Wed, 07 Sep 2011 10:48:55 -0700, Jim Lux
wrote:

but just the clear sky current could provide some charging.

There is a earth-sky current in the femtoamperes per cm² that has a
constant potential gradient on the order of 600V/m (or something like
that). This current is the return path for all lightning strike
charge transfers, world-wide.

Few dipoles are co-planar, parallel wrt ground.

Actually, humidity doesn't affect the charging all that much. What
humidity affects is the leakage current across dirty insulators.

Which could easily overwhelm this femtoampere charge where a gigaOhm
leakage is trivial (zealous Hams using teflon technology?).

Actually measuring this current (ca 1970s) required using two
polonium-210 coated probes (what are still available as static brushes
for vinyl records) feeding FETs.

The following link:
http://www.angelfire.com/electronic/...rad/brush.html
illustrates what the brush is like, and its electrical attributes.
Another source, the manufacturer (which deeply hides the polonium
reference):
http://www.nrdstaticcontrol.com/doc/microbalance.pdf

73's
Richard Clark, KB7QHC