LuCI allows to set a channel for an ssid. So, I was trying two different ssids on two different channels on a single radio. Soon I found that change in channel on first ssid propogates to the other one. It seems the channel number is associated with a radio.
I have OpenWrt 19.07.4 r11208-ce6496d796 running on my BTHH5A. Maybe some other router have a facility to run multiple ssids with their own channels...?
In the end, I would like to know if there is any reason behind providing channel number for an ssid rather than its parent radio. I would also like to know if there is any way to activate multiple channels on a single radio.
Edit : Spelling