The Airport function is built in to my iMac, as it is in the Brother printer. From the Network preferences panel it shows that "AirPort has the self-assigned IP address 169.254.205.150". (and goes on to say that it will not connect to the Internet).
The printer is approximately 15 feet away from the iMac, pretty much in the line of sight. (Occasionally, my head might get in the way -- perhaps that's the problem with my airport connection).
The firmware is shown as " AirPort Utility: 5.5.3 (553.20) "
Infact all of my Software Versions are:
Software Versions:
Menu Extra: 6.2.2 (622.2)
configd plug-in: 6.2.5 (625.6)
System Profiler: 6.0.1 (601.1)
Network Preference: 6.2.2 (622.2)
AirPort Utility: 5.5.3 (553.20)
IO80211 Family: 3.2 (320.1)
Regarding manual settings and playing with channels, I'm somewhat at a loss at where to find them.
In Network preferences for Airport it has Airport ID as 00:17:f2:54:81:b2.
Adam/