When I use Ubuntu, my laptops can't see my WiFi network if it's on channels above 11. Both my laptops have the same issue despite the different hardware (one of the two was bought two months ago), but all the smart phones and Windows can detect the WiFi network, so it might be a problem with drivers, although I've tried using the open source driver and nothing changed at all. Therefore I turned to the solution of setting the channel myself.
But limiting my connection to a single channel means limiting much of it, and having it slow at times. Therefore I had to put it back to auto and restart the modem multiple times, till it got the channel that would let Ubuntu detect it.
After many tests I can say that the problem is any channel above 11. Therefore my question is: How can I remove those channels, in order to have the modem use only the first 11 channels?