Enhance Wifi range on a TimeCapsule
Solution 1:
Run iStumbler from your Mac. (Get it here). Look at the other wireless networks in your vicinity - and check what channel(s) they're running on. You want your device to be as far away from those channels as possible. There is a 3-channel overlap. That means, a device on channel 1 will interfere (albeit only slightly,) with a device on channel 3 (or 4? I forget.) So if lots of devices are on channel 6 (most come out of the box on this channel,) you want to be on 9/10/11 or 3/2/1. I almost always just use 1 or 11.
There is also a "use network robustness" option which I think increases range but decreases bandwidth. See this Apple Article.