5 GHz Wi-Fi Network Is Occasionally Disabled (radar Signal)

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To the knowledge base Knowledge document #1349 FRITZ!Box 7490 This support document is available for the following products:

FRITZ!Box 7690
FRITZ!Box 7682
FRITZ!Box 7590 AX
FRITZ!Box 7590
FRITZ!Box 7583 VDSL
FRITZ!Box 7583
FRITZ!Box 7582
FRITZ!Box 7581

FRITZ!Box 7560
FRITZ!Box 7530 AX
FRITZ!Box 7530
FRITZ!Box 7520
FRITZ!Box 6890 LTE
FRITZ!Box 6850 5G
FRITZ!Box 6850 LTE
FRITZ!Box 6690 Cable

FRITZ!Box 6670 Cable
FRITZ!Box 6660 Cable
FRITZ!Box 6591 Cable
FRITZ!Box 6590 Cable
FRITZ!Box 6490 Cable
FRITZ!Box 5690 Pro
FRITZ!Box 5590 Fiber

FRITZ!Box 5530 Fiber
FRITZ!Box 5491
FRITZ!Box 5490
FRITZ!Box 4060
FRITZ!Box 4050
FRITZ!Box 4040
FRITZ!Box 3490

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 on the selected channel [...] for [...] min. because of check for higher-priority users (e.g. RADAR)"
"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.

If you are using the FRITZ!Box at a location where a radar is detected continuously or every hour, you can manually configure a Wi-Fi channel from 36 to 48 under "Wi-Fi > Wi-Fi Channel" ("Wireless > Radio Channel") to prevent the 5 GHz Wi-Fi network from being disabled. Wi-Fi channels 36 to 48 are not used by radar systems, so they do not have to comply with the wait time. However, since the range and data throughput of Wi-Fi channels over 48 is significantly better, it only makes sense to manually set a Wi-Fi channel from 36 to 48 in exceptional cases.

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