Software Updates Explain Dual-Band Networking – TheAppleBlog
Hold down the option key when clicking on your airport icon in the menu bar. That’ll give you your network specs, like what band, signal strength, etc.

Hold down the option key when clicking on your airport icon in the menu bar. That’ll give you your network specs, like what band, signal strength, etc.

pjdavis
March 7th, 2009
Maybe my Airport Extreme and Unibody MacBook only work on G, but I never see a band indication on my Option-Airport pulldown, only a channel indication.
rich
March 8th, 2009
@pjdavis good point. We only use 2.4 at home because it propagates better and still get 5MBps peak cmoaedd with 8MBps I see for 5ghz wide channel. I assume channels 13 and below mean 2.4 and others are 5ghz