Assuming it's the same as the 2002, the antennas are the things on the rear
side windows that look like defroster lines.  There is an on-board amplifier
for those antennas, then the factory radio uses a diversity system to pick
whichever antenna has the best reception at any given time.  I learned a bit
about that when I replaced the radio in our 02.

If you replace the radio, you'll need to make sure the line going to the
antenna amp is powered off of the line out of the radio for the "power
antenna" (or something switched) or you won't get very good reception.  You
also only end up using one of the 2 (the only one that fits into the back of
a non-factory radio) antennas.  I don't recall now which wire it is, but the
harness didn't have it, so I had to splice into the factory wiring on that
one wire.  I got it from a local Crutchfield store (also online at
www.crutchfield.com) and their tech support was able to tell me exactly
which one.

Hope that helps...

Wesley