Weakened Airport Extreme Signal

Good afternoon.

I recently have run into problems with receiving a signal from my airport extreme base station on my Mac G4 laptop. My unit is about 3 years old and has worked perfectly until several months ago. I route it through an older G3 Mac desktop which is located on the first floor (just about directly below where I most often use my laptop). If I move my laptop directly next to my base station, I receive full power. If I move into the other room downstairs or back upstairs, I either recieve a very weak signal (one or two bars) or none at all. I have a cable modem (Roadrunner) which seldom (if ever) drops a connection. I recently loaded Leopard onto my laptop hoping that might solve the issue, but it had no effect. When I search for other networks in the area, none are found. Could it be that my base unit is wearing out and it is time to buy a new one? I would appreciate any and all advice.

Thanks.

Forestfowl