Airport Express.
Click on the item in airport utility
Click Manual setup
Click Wireless Tab
Select Wireless Options
ummmm
I think from memory it's the logging / snmp tab (sorry not at computer)
gives signal strength, interference etc.....
3rd row it the speed items are connected at.
that is....
54 < wireless G
181
255
281 < mine 5ghz and nice fast speed copying files 😛