What DFS is and why it exists
Part of the 5 GHz band is shared with radar systems. In the US, FCC rule 47 CFR 15.407 requires devices with any part of their emission bandwidth in 5.25 to 5.35 GHz or 5.47 to 5.725 GHz to use radar detection. Meraki's channel-planning guide groups these channels as UNII-2. In Europe, the harmonised standard ETSI EN 301 893 sets the same requirement for 5,250 to 5,350 MHz and 5,470 to 5,725 MHz. [1][2]
Cisco Meraki puts it simply: DFS is the process of detecting radar signals that must be protected against interference. A DFS-capable 5 GHz radio listens for radar and moves away from it. The lower 5 GHz channels (36 to 48) and, in the US, the upper ones (149 to 161) are not DFS channels. [3][4]
The rules in numbers
Both regulators set similar timings, with one big difference for European weather radar. The router (the master device) must check a channel before using it, keep listening while it does, and leave quickly if radar shows up. [1][2]
| Rule | US (FCC 15.407) | EU (ETSI EN 301 893 V2.1.1) |
|---|---|---|
| Channel availability check before use | 60 seconds, master devices [1] | 60 seconds; 10 minutes for channels within or partly within 5,600 to 5,650 MHz [2] |
| Channel move time after radar is detected | 10 seconds [1] | 10 seconds [2] |
| Normal traffic allowed after detection | Up to 200 ms, then only intermittent control signals [1] | Channel closing transmission time 1 second in total [2] |
| Non-occupancy period | At least 30 minutes [1] | 30 minutes [2] |
| Client devices | Must also vacate within 10 seconds [1] | Clients without radar detection need no CAC but must still shut down [2] |
US and EU channel table
Channel numbers below are 20 MHz channels. We mapped them to frequency ranges using the standard numbering, in which a channel's centre is 5,000 MHz plus 5 MHz times the channel number. The US channel list is the one in Meraki's channel-planning guide. A wider channel takes on DFS rules if any 20 MHz part of it falls in a DFS range. [4][1][2]
| Channels | Frequency range | US | EU |
|---|---|---|---|
| 36, 40, 44, 48 | 5,170 to 5,250 MHz | No DFS (U-NII-1) [4][1] | No DFS [2] |
| 52, 56, 60, 64 | 5,250 to 5,330 MHz | DFS, 60 s check [1][4] | DFS, 60 s check [2] |
| 100, 104, 108, 112, 116 | 5,490 to 5,590 MHz | DFS, 60 s check [1][4] | DFS, 60 s check [2] |
| 120, 124, 128 | 5,590 to 5,650 MHz | DFS, 60 s check [1][4] | DFS, 10 minute check (weather radar range) [2] |
| 132, 136, 140 | 5,650 to 5,710 MHz | DFS, 60 s check [1][4] | DFS, 60 s check [2] |
| 149, 153, 157, 161 | 5,735 to 5,815 MHz | No DFS (U-NII-3) [4][1] | Outside the bands covered by EN 301 893 [2] |
What you notice at home
Two symptoms point to DFS. The first is a delay: 5 GHz takes a minute or more to appear after a reboot or a settings change. GL.iNet's on-screen caution for DFS channels says the check runs every time Wi-Fi is enabled. During it, 5 GHz is unavailable for connection, and the process takes 60 seconds. [5]
The second is a sudden drop. Meraki describes what its access points do when radar is detected. They stop new transmissions, announce a channel switch, disconnect the remaining clients and pick another permitted channel. Only the 5 GHz radio is affected. GL.iNet's caution says its routers temporarily disconnect clients and switch to another channel, and that 5 GHz Wi-Fi is turned off while it scans. A video call on 5 GHz is likely to freeze or drop, then recover. Meraki also notes that newer, more sensitive radios such as Wi-Fi 6 models can see more DFS events. [3][5]
We did not find a vendor list of which clients skip DFS channels, so test rather than assume. If one device stops seeing 5 GHz after you move to a DFS channel, move back and treat that device as the limit.
Where routers let you include or exclude DFS
On GL.iNet firmware, the channel for each band is set under WIRELESS. GL.iNet's documentation says that with Channel on Auto, the router will not automatically switch to a DFS channel. Picking a DFS channel by hand brings up a caution about the 60-second check and radar moves. With 160 MHz bandwidth (available only on some models), Wi-Fi always uses a DFS channel even if you choose a non-DFS channel or Auto. So on a GL.iNet router, DFS is something you opt into, either by picking a channel or by choosing 160 MHz. [5]
On business systems the control is usually a channel list. Meraki recommends deselecting DFS channels in the RF profile's AutoChannel settings, or assigning non-DFS channels by hand, if radar events cause trouble. It notes that a radar event can still temporarily put an access point on a channel you excluded. Meraki Go's radar alert advice is the same: if alerts come with disconnections, choose 5 GHz channels that weather radar does not use. [3][6]
When to avoid DFS, and when it is worth it
For a home office, the deciding question is whether the non-DFS channels are crowded. If neighbours already fill 36 to 48 and 149 to 161, a DFS channel can be much quieter, and an occasional radar move may be a fair price. If they are not crowded, staying off DFS removes one cause of dropped calls.
- Avoid DFS if you take long video calls on 5 GHz and a forced disconnect and channel change after a radar event would be a problem. [1][5]
- Avoid 160 MHz on GL.iNet if you want to avoid DFS, because that width always lands on DFS. Apple suggests Auto or all widths for 5 GHz, so test whether 80 MHz is enough. [5][7]
- In Europe, avoid channels 120 to 128 if you reboot often, since each start means a 10-minute check. [2]
- Consider DFS if you live in a dense building and non-DFS channels are congested.
- Keep wired devices wired. Ethernet is not affected by radar.
Questions before you decide
Why does my 5 GHz Wi-Fi vanish for a minute after the router restarts?
If the router is on a DFS channel, it has to run a channel availability check first. GL.iNet's on-screen caution says 5 GHz Wi-Fi is unavailable during that check, and that it takes 60 seconds every time Wi-Fi is enabled. The FCC rule sets the same 60 seconds. ETSI sets 10 minutes for channels touching 5,600 to 5,650 MHz.
Why did every device drop off 5 GHz at once and then come back?
That is the pattern of a radar event. FCC rules require transmissions to stop within 10 seconds of detecting radar, and the channel then cannot be reused for at least 30 minutes. GL.iNet says the router temporarily disconnects clients and switches to another available channel. Meraki notes that only the 5 GHz radio is affected, not 2.4 GHz.
Will my GL.iNet router move onto a DFS channel by itself?
Not on Auto. GL.iNet's wireless documentation says that when Channel is set to Auto, the router will not automatically switch to a DFS channel. The exception is 160 MHz bandwidth, where GL.iNet says Wi-Fi will always use a DFS channel even if you pick a non-DFS channel or Auto.
Sources & verification
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- 47 CFR 15.407: General technical requirements (U-NII), via Cornell LII Accessed 30 Oct 2026
- ETSI EN 301 893 V2.1.1 (2017-05): 5 GHz RLAN harmonised standard Accessed 30 Oct 2026
- Cisco Meraki: Dynamic Frequency Selection (DFS) Accessed 30 Oct 2026
- Cisco Meraki: Channel Planning Best Practices Accessed 30 Oct 2026
- GL.iNet Router Docs 4: Wireless (firmware v4.8 and earlier), including DFS caution Accessed 30 Oct 2026
- Cisco Meraki Go: Radar Detected alert Accessed 30 Oct 2026
- Apple Support: Recommended settings for Wi-Fi routers and access points Accessed 30 Oct 2026
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