Thanks for the detailed response
My iwconfig output:
wlan00 IEEE 802.11ac ESSID:""
Mode:Master Frequency:5.18 GHz Access Point:
Bit Rate=1.3 Gb/s Tx-Power=19 dBm
RTS thr:off Fragment thr:off
Encryption key: [3] Security mode:open
Power Management:off
Link Quality=94/94 Signal level=-96 dBm Noise level=-95 dBm
Rx invalid nwid:2354 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
wlan10 IEEE 802.11ng ESSID:""
Mode:Master Frequency:2.462 GHz Access Point:
Bit Rate:216.7 Mb/s Tx-Power=20 dBm
RTS thr:off Fragment thr:off
Encryption key: [3] Security mode:open
Power Management:off
Link Quality=94/94 Signal level=-96 dBm Noise level=-95 dBm
Rx invalid nwid:2752 Rx invalid crypt:8201 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
It's currently on channel 36 (there are only 4 channels available, and IIRC 80MHz will cover them all), country is UK and there are zero other 5GHz networks where I am... Max permissable power is 200mw, which is around 23dBm IIRC.
I'll try changing it to 20MHz and see if that's any different.
J