Just heard back from the smart guy and this was his response "I did not find an OID which simply says radio 'ON' or 'OFF'. But If I disable all wlan services for a radio, and try to get the current channel for that radio, the OID returns “0”. That’s an indication that the radio is off." I "think" this is the OID he is referring to. He wasn't testing on the model of AP you are so I'm not sure if this will work exactly, but hopefully, this helps.