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5 GHz Wi-Fi network is occasionally disabled (radar signal)

Every now and then, the 5 GHz Wi-Fi network is disabled and the FRITZ!Box shows a message with "RADAR"? ✔ Here you can find out what that means.

The 5 GHz Wi-Fi network of the FRITZ!Box or a Mesh Repeater (for example FRITZ!Repeater) is occasionally disabled. The message "Radar detection enabled. At the moment no Wi-Fi connection (5 GHz) is possible; please wait" may be displayed under "Wi-Fi > Wi-Fi Channel" ("Wireless > Radio Channel") in the FRITZ!Box user interface. One of the following messages is also displayed in the event log of the FRITZ!Box:

  • "5-GHz band cannot be used for [...] min. because of check for higher-priority users (e.g. RADAR) on the selected channel (frequency [GHz])"
  • "RADAR was detected on channel [...]; channel switched automatically because of higher-priority user"
  • "RADAR was detected on channel [...] (frequency [...] GHz), repeater on the 5-GHz-band deregistered from the access point for [...] min. (+ 1-10 min. additional RADAR waiting time, depending on the channel assignment)"

1 5 GHz Wi-Fi network is disabled for the search for higher-priority users

The FRITZ!Box makes the Wi-Fi network available in both the 2.4 GHz and 5 GHz frequency bands. However, the 5 GHz frequency band is not only used by wireless devices, it is also used by radar systems (for example air traffic control, the military, and weather service), so-called higher-priority users. In order not to disturb these higher-priority users, at first the FRITZ!Box only enables the 2.4 GHz Wi-Fi network after a restart or changes to the Wi-Fi settings. The FRITZ!Box does not enable the 5 GHz Wi-Fi network until after completing the check (DFS wait time) that can take up to 10 minutes.

Even during operation, the FRITZ!Box continuously checks whether the Wi-Fi channels it uses are still unused by higher-priority users. If the FRITZ!Box detects one of these users, it disables the 5 GHz Wi-Fi network, searches again for higher-priority users for up to 10 minutes, and then re-enables the 5 GHz Wi-Fi network on a different Wi-Fi channel not used by them.

Mesh Repeaters connected to the FRITZ!Box notify the FRITZ!Box immediately if they detect a higher-priority user. Then the FRITZ!Box notifies all of the Mesh Repeaters connected to it that there is a higher-priority user so that the FRITZ!Box and Mesh Repeaters can all disable the 5 GHz Wi-Fi network together and then re-enable it together after it has completed the search for higher-priority users.

This behavior is also called Dynamic Frequency Selection (DFS) and is mandatory in all countries of the European Union.

2 Effect on the wireless devices

To ensure that the Wi-Fi network can still be used even while the 5 GHz Wi-Fi network is disabled (DFS wait time), the FRITZ!Box steers the wireless devices to the 2.4 GHz Wi-Fi network or to a different wireless access point if necessary:

  • The FRITZ!Box can seamlessly steer wireless devices that support the wireless standards 802.11k and 802.11v from the 5 GHz to the 2.4 GHz Wi-Fi network or to a different wireless access point.
  • The FRITZ!Box can only steer older wireless devices that do not support the wireless standards 802.11k and 802.11v from the 5 GHz to the 2.4 Wi-Fi network by briefly clearing the Wi-Fi connection. The FRITZ!Box cannot steer these devices to a different wireless access point.

As soon as the 5 GHz Wi-Fi network is available again, the FRITZ!Box steers the wireless devices back to the 5 GHz network or a different wireless access point if necessary.

Note:The FRITZ!Box displays wireless devices that support the standards 802.11k and 802.11v under "Wi-Fi > Wi-Fi Network > Known Wireless Devices" ("Wireless > Radio Network > Known Wireless LAN Devices") with the properties "11k" und "11v".

3 Optimizing the FRITZ!Box's Wi-Fi settings

In the factory settings, the FRITZ!Box is configured so that it can steer wireless devices to the other Wi-Fi network or a different wireless access point. This is not possible if different names were given to the 2.4 GHz and 5 GHz Wi-Fi networks in the FRITZ!Box or the other wireless access points were not correctly integrated into the Mesh. In this case you must optimize the Wi-Fi network of the FRITZ!Box.