AX88U to a repeater-mode AC66U. Not 5GHz

[Arve]

For best speed I need AX88U to use channel 52 at 5GHz.
But at the AC66U I do a repeater-mode. Use the setup Wizard. Scan for network. But it can't find any 5GHZ Band. But if the AX88U is at channel 40 or lover it scans and find my Aimesh_5G band. Se picture.

Is it possible to get 5GHZ band when AX66U is at channel 52?

 

[ColinTaylor]

Is it an RT-AC66U or an RT-AC66U_B1 ?

What firmware version?

 

[Arve]

This is the old one RT-AC66U. Firmware 3.0.0.4.382_51641-g46d2311

 

[ColinTaylor]

This is the old one RT-AC66U. Firmware 3.0.0.4.382_51641-g46d2311

IIRC that model didn't support DFS channels in the US. So that would mean that it can't use channels 52 to 144.