Using Cisco access points with CleanAir function you might come across this alarm. It means that the CleanAir chip have detected an access point using a frequency that is more than 500KHz off the specified frequency for the channel.

When this happens a normal AP or client will not be able to detect the signal. Two things is relevant in this case. First this enable a possible hacker to implement an invisible network. I.E placing a rogue AP on the network and connect to it from outside the building. It can also be caused be cheap or defect wireless equipment. Not necessary  Wi-Fi. Could also be a sound or video system. The effect is that this equipment will interfere with legal “on channel” equipment like your Wi-Fi network.

BUT! Be aware that many of these alarms from CleanAir can be caused be general high Wi-Fi congestion resulting in CleanAir “getting it wrong”.

My recommended action.

• Start by eliminating possible false alarms caused by checking general wifi performance. Channel overlap, data rates and the likes.
• Search for the interfering device using a laptop with a spectum-expect adaptor or a battery powered AP with CleanAir.
• If the source of the interferer is impossible to trace. Like it’s just no special place an searching around make no logical difference it likely to be a false alarm.