DFS and Radar Simulator
Play through a radar event on a 5 GHz DFS channel under Thailand, Europe or US rules: the channel availability check, the Channel Switch Announcement, where the AP goes and the 30-minute block.
How to use this tool controls and what to look for
Choose the rules and the AP's channel, set when radar appears, and follow what happens on air and how long clients lose service.
Controls to change
- Rules: compare Thailand (NBTC), Europe (ETSI) and United States (FCC).
- Channel width: choose 20, 40, 80 or 160 MHz, then click a channel in the strip to put the AP there.
- Radar is on: pick which 20 MHz channel inside the AP's channel the radar hits.
- Radar appears after the AP has been serving clients for: set when the radar event happens.
- Beacons of warning (Channel Switch Count): change how many beacons carry the Channel Switch Announcement.
- Clients that miss the announcement: set how many clients don't hear the warning.
What to look for
- At start-up the AP must listen before using a DFS channel: 1 minute, or 10 minutes on the weather radar channels in Europe and Thailand.
- When radar appears, the AP warns clients with a Channel Switch Announcement and must leave quickly.
- Where the AP goes decides the outage: a non-DFS channel is immediate, a new DFS channel needs another check.
- The original channel is blocked for 30 minutes, and going back to it costs a second outage.
About this tool
Much of the 5 GHz band is shared with weather, military and airport radar, so an AP there must listen for radar before transmitting and leave the channel when radar appears. Pick the rules (Thailand, Europe or the United States), a channel and width, then play through a power-on and a radar event: the channel availability check, the Channel Switch Announcement, the move to another channel and the 30-minute non-occupancy period. A timeline and a clickable flowchart show what each choice, such as a non-DFS channel, a new DFS channel, zero-wait DFS or a narrower channel, costs your clients.
What you'll learn
- Which 5 GHz channels need DFS, and why the weather radar channels need a 10-minute check in Europe and Thailand
- What happens on air when radar is detected: the Channel Switch Announcement and the channel move time
- How long clients lose service with each recovery option, and why returning to the original channel costs a second outage
- How the rules of the FCC, ETSI and Thailand's NBTC compare
Common questions
How long is the DFS channel availability check?
60 seconds before using a DFS channel. In Europe, and in Thailand which follows the same ETSI standard, channels touching 5600–5650 MHz (weather radar) need 10 minutes.
What happens when an AP detects radar?
It must stop using the channel within 10 seconds, warns its clients with a Channel Switch Announcement in its beacons, moves to another channel and may not use the old one again for at least 30 minutes.
Should I avoid DFS channels?
Not necessarily: they give many more channels for a better channel plan. Avoid them near airports, weather radar or ports if radar events are frequent, and check whether your clients support them.
Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.