Can i extend range of airport express n with an airport express g?
Can i extend an airport express N with an airport express G?
MacBook Air, Mac OS X (10.7)
No...
You need the "n" models to use the "Extend" feature....
You could set them up in "WDS" mode but that is not recommended as it slows everything down and cuts your speeds in half.
You could try the WDS if you are so inclined.
http://support.apple.com/kb/HT4262?viewlocale=en_US&locale=en_US
NOTE:
You do not need to use the relay in the above drawing...
Setting up a WDS is much more difficult that just clicking a button on the newer "n" versions to Extend the network and you are done.