I'm using my laptop for almost a month without any problem, always connected at 5ghz, yesterday I needed to connect to a 2.4ghz network and saw that the wifi channel is locked at 20mhz, even if I change the configuration on the router to 40mhz the laptop continues connected at 20mhz.
I use yosemite's IO80211family.kext
I don't use AirportBrcmFixUp.kext ...
would have any way to enable the 40mhz channel at 2.4ghz?