Extending a wireless network with an Airport Express I have a wireless network based on a Time Capsule (802.11n, first generation). As wireless connectivity is rather bad in one part of the house I wanted to use an Airport Express (802.11g) to extend the network. The end result should look somehow like

Internet Router &lt;--LAN--&gt; Time Capsule &lt;--WiFi--&gt; Airport Express


with the Time Capsule and the Airport Express both running in the same WiFi network.

Based on the documentation I found (e.g. HT4262) I assume I should create a WDS network but this somehow doesn't seem to work (the Express disappears from Airport Utility as soon as I define it as a WDS relay/remote base station).

So how do I have to configure the network in both the Time Capsule and the Airport Express to get this to work?
Have you tried the automatic configuration for the Express?

Don't do anything on the Time Capsule. 

Do a cold reset of the express and bring it up on the Airport Utility.  You should have an option to join an existing Airport network. Choose the option to extend the range. That should do it.