this may seem crazy, but bare with me... 😎
cover your ibook in aluminium foil all-around apart from a opening the size of your fist where the glowing apple logo is.
then pick up the ibook and slowly aim the hole at areas of the room and watch signal increase or descrease.
my thinking is that laptop antenneas are usually across the backs of monitors, a fist size hole should diffract the wave less, the foil blocks the signal 😛
thinking about it now, you wouldnt be able to see the signal detector so, either use an external monitor connected or put the foil hole over the from of the screen where the signal can be seen.
(I'm sorry if this comes out as gobbeldigouk, its early in the morning here, i should be asleep. It should give you lot a chuckle anywho 🙂 )