Dunno, someone else in my class had a samsung d600 on tmobile and he had full coverage, while i meanwhile was on 1-2 notches on windows mobile, which according to voice command is approx 40 - 60 % coverage
but moving around the room, can cause me to lose coverage completely
Another has some old nokia 3310 or something on orange, and he too only gets 1 bar but his phone is really old so he thinks it might be that.