Hello Jack I'm Richard.
If I understand your question, are you wishing to connect to an external router in either 2.4ghz or 5 ghz at your choosing?
You haven't charged anything I was asking a question in order to understand your question more properly.
I appologize for any confusion about how this site works. nobody has given you a final answer. Your question is not very clear.
the altheros you refer to is a wifi card not a router so it does not set up those bandwidths. It connects to either one. depending on which one is available and which you select. nor can it change the way it connects to a router. Instead a dual band router will show up on its list of routers as two seperate routers one with each bandwidth.
are you asking how to connect to either one ? you just select the proper one from the list of available routers. they should have been labeled that way when the router was set up.
or are you trying to turn the card into a wifi hotspot that other devices can connect to an want to set that up in dual band. i would have to look up if that is even possible with that card.