Configure old router as Wireless Access Point

[#1]

After several false starts and battles with the GUI I have managed to configure an old TG585 as a wireless access point with the following changes:
- set the SSID to be the same as the main router
- set the wireless key to be the same as the main router
- made sure the WAP  ip address was different to the main router and outside the DHCP range of the main router
- turned off DHCP in the WAP
- turned off firewall in the WAP
- set WAP and main router wireless channels to be different (actually 6 and 11)
However I noticed that on test I sometimes couldn't connect to the internet through the WAP even with a laptop right next to it (though I could connect using an ethernet cable).  Other times it seems to work OK.  I expected to get 'seamless roaming' with the laptop always connecting to the stronger signal.  What am I missing here?

[#2]

Try changing the SSID to Wireless Name_Ext
So add '_Ext' to end of SSID.  As there can be complications if there are the same SSID in a close range and broadcasting the same channel and password.
NE

[#3]

Thanks, NE, I will try that.  One thing which now occurs to me is that the old router uses just the 802.11b/g standards but the main router uses 802.11b/g/n.