[SGVLUG] WiFi detected RADAR

[Claude Felizardo via SGVLUG]

Got an interesting email from my WiFi controller this morning:

UniFi Alarm: AP Radar Detected
Message: AP[xx:xx:xx:xx:xx:xx] detected radar on channel 100 (5500 MHz)

Followed by a link to what looked like my WiFi controller but not 
trusting it I opened up a web browser and entered the internal IP 
manually and looked at the dashboard and saw a nice display showing what 
channels my AP's are using with nothing in use around channel 100. 
Pretty slick.  I also got a reminder that there is a firmware update 
which I had skipped initially because I usually try to wait a few weeks 
or more in case they pull it.

As for the RADAR alert I found a couple of links that talk about RADAR 
Detection in Dynamic Frequency Selection (DFS) Channels which is 
standardized in 2003 as part of IEEE 802.11h.

Short answer is when WiFi Access Points use certain channels in the 5 
MHz band they are suppose to switch to another channel if RADAR is 
detected.  I live in the San Gabriel Valley not to far from El Monte 
airport but it looks like it could have been Weather or military RADAR. 
 From the event log is looks like it was detected at 9:08 am.  Digging 
around some more I see that one of my APs was using channel 100 and has 
automatically moved to another channel. The other AP has been on another 
channel and did not have to move.

www.cisco.com/c/en/us/support/docs/wireless-mobility/80211/213882-radar-detection-in-dynamic-frequency-sel.html
wifi-insider.com/wlan/dfs.htm
en.wikipedia.org/wiki/Dynamic_frequency_selection
en.wikipedia.org/wiki/IEEE_802.11h-2003