System:
Raspberry Pi3
OSMC 2016.06-2
TP-Link Archer T4U AC1200 (added yesterday)
Router with 2,4GHz and 5GHz wifi (separate)
First i used the Pi with onboard wifi in 2,4Ghz network.
Yesterday i added the TP-Link AC1200 cause of slow speed and problems with 1080p / 3d movies.
Installing the dongle works fine… just plug in.
Now i connected with putty…
connmanctl
technologies → wifi is enabled
scan wifi
agent on
services → found my 5Ghz network
connect wifixxxxxxxxxxxxx → 5Ghz network connected
Speed was fine. No Problems with 1080p / 3d movies.
BUT… after reboot the Pi sometimes connects to 2,4Ghz and sometimes to 5Ghz (most times 2,4Ghz)
How can i solve this problem?
Is there a way to disable onboard wifi permanent or delete the 2,4Ghz network?
ifconfig shows
wlan0
Link encap:Ethernet HWaddr ec:08:6b:08:a3:27
UP BROADCAST MULTICAST DYNAMIC MTU:1500 Metric:1
RX packets:0 errors:0 dropped:1 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
wlan1
Link encap:Ethernet HWaddr b8:27:eb:47:f8:9f
inet addr:192.168.178.30 Bcast:192.168.178.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST DYNAMIC MTU:1500 Metric:1
RX packets:33870 errors:0 dropped:604 overruns:0 frame:0
TX packets:20654 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:34191039 (32.6 MiB) TX bytes:2425482 (2.3 MiB)
wlan0 / wlan1 changes between onboard and dongle
Thank you in advance! 
