"Dave" wrote in message
...
One manufacturer of a similar "wind-up" antenna adds a capacitor to the
wire
in order to lower the resonance frequency of the wire. If I were going to
try something similar (adding a capacitor, in series) in an attempt to
bring
the resonance of the wire down into the 30 MHz range, what size (roughly)
capacitor should I use? Should I just try a few with different ranges, or
does anyone here have any suggestions?

This isn't likely to help your basic problem, which appears
to be a lack of selectivity in the radio (in other words, it
is accepting signals over too wide a bandwidth, so you hear
not only the station you're interested in, but those "to either
side" as well. Having the passband too wide also makes
for more noise in general. There are filters that can be
added (within the receiver) to improve this, but your best
bet may be to simply look for a better receiver.

Bob M.