I forgot to mention: using a voltage balun on an antenna can have
RF-in-the-shack implications. A 20M folded dipole I once built with a
4:1 trifilar wound voltage balun was terrible even though it was
center-fed. Tuning was extremely touchy and removing my hand from the
tuner knob would detune the antenna. I did not try a current balun on
that antenna and it is history now. Maybe some one else has had
simialr experience.

Glenn