Wow, a G4 with 1Mhz..
I have the same router and my signal is 100% when I am close to it (802.11b or DWL650 802.11gx2). There is an option for your router to spare more power for the antenna and get a higher range. Check out the web-interface. There is a new firmware for the dl-624 rev C as well..
However, there are also some tricks how you can increase the signal reception of the powerbooks. I know the trick for my tibook, but not for the alubooks since their antenna is on the screen. Search in the forum. I remember a thread on this problem.
iBook 600; 12''; 640mb; 8mb Rage; DVD-CDRW-Combo, 20GB
P4 1.6; 2x80GB Raid1 (file-server)
tiBook 1Ghz, Superdrive, 768MB, 64mb 9000, 60GB