DFS (dynamic frequency selection)

Under 47 CFR 15.407¹, a 5 GHz access point in the 5.25 to 5.35 GHz and 5.47 to 5.725 GHz ranges must detect radar. It must listen for 60 seconds before it starts using a channel. If it detects radar later, all transmissions must cease on that channel within 10 seconds, and normal traffic during that window is limited to a maximum of 200 milliseconds after detection. The access point cannot return for a non-occupancy period of at least 30 minutes.

The rule is fixed. What you control is the plan around it. A real hit is covered in DFS radar events, and a hit that was not radar is covered in DFS false detections. The spectrum and channels clauses say how to specify channel use so a hit does not become a line stop. Europe has its counterpart in ETSI EN 301 893². DFS does not tell you when radar will arrive, and it does not tell you where the access point will land. The radar rules apply to the ranges named above, so channels outside them are not subject to DFS, at the cost of fewer channels.

Ben Rutter. "DFS (dynamic frequency selection)." OT Wireless, published October 6, 2026. https://otwireless.com/glossary/dfs/

Rutter, B. (2026, October 6). DFS (dynamic frequency selection). OT Wireless. https://otwireless.com/glossary/dfs/

@misc{rutter2026dfs,
  author = {Rutter, Ben},
  title = {{DFS (dynamic frequency selection)}},
  year = {2026},
  howpublished = {\url{https://otwireless.com/glossary/dfs/}},
  organization = {OT Wireless},
}