Ti PowerBook Antenna Mystery
In a Developer Note on the PowerBook G4 available as a PDF download, on page 41 under the heading Airport Hardware, it states: "Two AirPort antennas are built into the computer's cover, on either side of the flat panel display."
This note is dated November 2002. I have a Ti PowerBook manufactured after this date and have had good/very good reception on wireless.
I believe that Apple changed the specks on this machine at some point, given the poor results with the antennas in the base.
When Steve Jobs announced the Al PowerBooks he stated that the antennnas were in the lid where they always should have been, (if I recall the exact words). This doesn't preclude the antennas being moved on later model Ti PBs.