"art" == art writes:

art David I reviewed your page to find out how the capacitor was
art made and how it was driven. Unfortunately I could not figure
art it out!

The capacitor is made in a coaxial fashion with 3/4" polyethylene
"PEX" tubing as the dielectric, and copper pipe as the plates. The
inner copper tube (1/2" copper repair coupling) is the stator, and the
outer tube (3/4" copper repair coupling) the rotor. The rotor slides
over the joint between the dielectric and the stator (3/4" copper
pipe) which have the same outer diameter.

The capacitance is adjusted manually, by sliding the rotor from side
to side. I am relying on the tight fit and the large amount of
overlapping copper area between the rotor and its contact to keep
losses low. Also, because the sliding contact is at the high voltage
end of the loop, I presume resistive losses aren't as bad as they
would be at the bottom where voltage is low and current is high.

art One thing I thought about as I read the page was the
art soldered joints and its added resistance. [...]

Gee, how resistive is the solder? I know it's not as good a conductor
as copper, but the joints fit pretty well. I'm guessing the amount of
solder width in the electrical path is probably on the order of one
millimeter for the entire antenna. Given that the copper loop's DC
resistance is (in theory) around 40 milliohms, it's hard for me to
imagine that a solder "fuse" (if you will), connected in series, would
add much. But I'm prepared to learn something new -- it happens all
the time!

When I was first experimenting with the design, I had been worried
about the union joints, but they have something like 1cm^2 of surface
contact and the copper squishes together as the joints are tightened.

In any case, your suggestion about applying a continuous conductor and
checking for its influence is well taken. At least, I don't have a
horrible problem or the bandwidth would be too large and/or something
would be getting hot.

David
N5IZU