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I don't know that it is using the 5GHz signal (well for every device on the network). But if I wanted to know, on a Mac I would hold down the option key while clicking on the WiFi symbol in the menubar and it would tell me at what channel and frequency the Mac is connected.

yeah, I knew there was a way on mac...too bad there is no way that i know of on PC to do this.
 
Maybe I can fix that for you.

Code:
netsh wlan show networks mode=bssid

The channel setting listed under the SSID should give you a clue as to which band that particular SSID uses.

thanks but it says there are no wireless interfaces on my system :-/
 
there is an option on the extreme to turn on the 5ghz. there you can assign a name to it or use your 2.4ghz name but it will add a 5ghz at the end of that. i connect which ever device i have that is capable to the 5ghz channel and those who only uses wireless n, that goes to the 2.4ghz
 
I use two different network names to solve the precise problem that has been mentioned above, so I can quickly and easily determine whether I'm connected to 5Ghz or 2.4Ghz.
 
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