Two radios appearing in single-band router


I am seeing two radios in inSSIDer in my single-band wifi router / Modem which is operating in 2.4GHz frequency and two channels (9, 11) in the channel column. The MAC address 10:10:81:83:E0:40 is unknown to me. Can someone explain me where second radio comes from and how can i delete it? It looks suspicious to me as MAC address 10:10:81:83:E0:40 does not belong to any known connected device neither channel 9 and 40 MHZ bandwidth is configured from my end. I have attached picture for consideration.