Frequently Asked Question
UniFi reports radar detected and my 5 GHz WiFi briefly disconnects. How do I check DFS events?
QUICK ANSWER
An access point using a DFS channel must react to radar detection. Correlate the radio event with the disconnect before changing roaming or resetting the access point.
Applies to: Supported UniFi APs using 5 GHz DFS channels. Permitted channels, power and availability checks depend on the deployment country.
Match the time and affected radio
Record the AP, 5 GHz channel and event time, then compare them with the affected client's disconnect. An Ethernet uplink problem or whole-console outage requires a different diagnosis.
Check channel history
Review the radio and system events around the incident. A radar event can cause the AP to leave its channel; an ordinary scheduled optimisation change is a different trigger.
Understand the waiting period
DFS operation can include a channel-availability check and temporary avoidance after radar detection. Ubiquiti documents that an affected channel is prohibited for at least 30 minutes. Repeated manual selection does not override this requirement.
Use a controlled non-DFS comparison
During an agreed window, select a permitted non-DFS channel and suitable channel width for one test AP. Record the previous configuration, verify client support and observe whether the matching disconnect recurs.
Review the wider channel plan
Consider neighbouring APs, channel overlap and airtime usage before applying a fleet-wide change. Channel AI can recommend a plan, but regulatory DFS reactions can still occur.
Compare a useful observation window
Keep the test conditions stable and compare events and client experience. A short successful test is not proof that interference or all future disconnects have been eliminated.
Confirm the result
The event timeline distinguishes a DFS channel change from roaming, cable or power faults. The controlled test provides evidence for the next channel-plan decision.
Before going further: Keep the correct country setting and regulatory limits. Do not change the country or use unsupported firmware to evade radar requirements.
If you need help
Include these details in your ticket: AP/Network versions, deployment country, radio/channel/width, event timestamps and the controlled-test result.
Related guidance: Why does my phone or laptop disconnect when I walk between UniFi access points? · Why does my UniFi access point show FE or a 100 Mbps uplink, with Wi-Fi stuck around 90 Mbps?
Updated 261110