A bit more on the baluns Roy mentioned...

If the feedpoint is a high impedance (an even number of half-waves back
from both ends of the antenna), it's difficult to get enough choke
impedance to do much good if you put a single balun right at the
feedpoint. It may end up being overkill, but if you don't have a good
way to measure your line for antenna currents, you'll do well to put
chokes about a quarter wave apart at the highest operating frequency.
You want to avoid having a length of line between two chokes being a
resonant half-wave long without anything in the middle to break up the
resonance. So for operation on multiple bands covering a wide range,
you should think about putting in three or more chokes.

Of course, if you put it up without any chokes and it does what you
want, that's fine...just don't expect it will match the model of an
isolated wire.

Cheers,
Tom