Connect to the main deco through web browser and under ADVANCED->system I can see the wireless channels and bands.

The 2.4Ghz band is enabled and on channel 9

The 5GHz-1 band is enabled and on channel 48

and the 5GHz-2 band is disabled. 

When I scan the wireless network with an analyzer app ther is an active wireless channel with "unknown SSID name"

My 4 decos are connected with Ethernet backhaul and configured as AP (not router)

at first I thought that this (5GHz-2) network is reserved for a wireless backhaul so I disconnected the Ethernet cable, the unit then connected to wireless backhaul but still the Advantech -> system section shows that the 5Ghz-2 is disabled. 

What is that inactive/disabled 5Ghz-2 network? Can I enable it to accumulate additional more network band/traffic??