On Fri, 15 Feb 2008 11:40:50 -0800 (PST), Swoozie Pellegrino
wrote:

What might the impedance of this look like, say, if I
took the last 10 meters of a 100' 50-ohm coax piece
and slice it to split out into a 20-meter sleeve dipole
and hung the dipole part vertically from the balcony?
Can I just screw the other end onto the back of
my transceiver and go? Or....

Sure, if you can live with the mismatch. Better if you can tune it
for one band. Or simply stick with my suggestion and run it into a
tuner which you will probably need anyway. The difference between any
of these will be undetectable at the far end of the QSO.

To reduce the chance of a hot chassis due to common mode currents, you
should use a 1:1 W2DU style BalUn (aka choke).

73's
Richard Clark, KB7QHC