I thought so...
Thank you anyway.
The automatic feature of the router to change the band is a nice thing all in all. But not in this case :D. I'm running a TVHeadend server on my pi. When I start streaming to the Client and the router realizes the traffic, it does change to 5 GHz after a few minutes.
I did allow the channels 12 and 13 and this helped.
But until it changes, performance is just not that great.
I realized that the 5 GHz module on my router has a different MAC-Address.
Does iw have a command to specify the Mac address rather than the ssid?