FRITZ!Box 3390 – Service - Knowledge Base

FRITZ!Box 3390 – Service

Error message "Wireless LAN: a microwave was detected [...]"

The throughput of wireless connections (WiFi) is lower than the data rate supported by the wireless standard.

The following error message is displayed in the event log of the FRITZ!Box:

  • "Wireless LAN: a microwave was detected; radio channels optimized for 450 Mbit/s temporarily deactivated (2.4 GHz)."

Cause

  • The FRITZ!Box detects sources of interference in the frequency range around 2.45 GHz, for example a microwave. In order to still guarantee stable wireless connections, the FRITZ!Box automatically reduces the channel bandwidth to 20 MHz. Although the wireless devices display a lower throughput as a result, the user throughput is higher because it is not affected by retransmissions. The channel bandwidth is automatically increased again if no sources of interference are detected in the wireless vicinity when a scan is performed. These scans are performed every hour or 2 minutes after the connection to the last wireless device has been terminated.

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface. The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS

Simply proceed as described below. After each measure, check whether the issue persists.

1 Finding the ideal location for wireless devices

  • If possible, position the FRITZ!Box in a room that is centrally located.
  • Do not position the FRITZ!Box directly in the corner of a room.
  • Position the FRITZ!Box so that it is as unobstructed as possible, i.e. not directly in back of or under an obstacle such as pieces of furniture or a heater.
  • Position the FRITZ!Box as high in the room as possible, for example on a shelf.
  • Position the FRITZ!Box so that there are as few obstacles as possible between it and the other wireless devices. In particular, metallic objects or objects containing water (for example a refrigerator, houseplants) significantly reduce the quality of the wireless signal.
  • Position the FRITZ!Box so that it is away from other transmitters (for example microwaves, baby monitors, wireless speakers, Bluetooth devices).
  • For testing purposes, position the FRITZ!Box and the wireless device as close as possible.

    Note:Once you have ruled out all other sources of error, you can increase the distance between the two devices again.

2 Identifying sources of interference

  1. Turn off all devices that could interfere with the wireless network, one after the other.

    Note:All devices that emit radio waves are possible sources of interference. These include other wireless devices, wireless speakers, Bluetooth devices, baby monitors or microwaves, for example.

  2. After you have turned off a device, check whether the wireless connection is still impaired.

Once you have identified a device that causes interference, you can either leave it turned off or try to avoid the interference by setting the channel manually or changing the frequency band.

3 Selecting the best wireless channel

  1. Click "Wireless" ("WLAN") in the FRITZ!Box user interface.
  2. Click "Radio Channel" in the "Wireless" ("WLAN") menu.
  3. In the "Wireless Environment" section, click on the tab for the wireless frequency band being used.
  4. Use the graph "Use of the Wireless LAN Channels" to determine which channel in the lower frequency range is least affected by other wireless networks and sources of interference.
  5. Enable the option "Adjust radio channel settings" in the "Radio Channel Settings" section.
  6. From the drop-down list "Radio channel", select the channel that was affected the least in the wireless frequency band being used.
  7. Click "Apply" to save your settings.
  8. Check whether the issue with your wireless connection still occurs.
    • If the issue with the wireless connection still occurs:
      • Repeat steps 3 - 8 with a wireless channel in the middle and then with one in the higher frequency range. Once you have finished testing, use the wireless channel that was least affected by disturbances.

        Important:The diagram of the wireless environment only reflects the current situation! The allocation of the frequency bands can change significantly over the course of the day because many wireless networks are turned on when in use. Therefore, check several times to see which wireless channels are least affected by interference.

4 Establishing a wireless connection to the 5 GHz frequency band

The FRITZ!Box provides a wireless network in the 2.4 GHz as well as the 5 GHz frequency band. The 5 GHz frequency band is subject to interference less frequently. Therefore, switch to this frequency band if your wireless devices support the 5 GHz frequency band:

Note:Not all wireless devices support the 5 GHz frequency band.
FRITZ!WLAN Stick AC 430, FRITZ!WLAN Stick AC 860 and FRITZ!WLAN Stick N (v2) support the 5 GHz frequency band.

  1. Click "Wireless" ("WLAN") in the FRITZ!Box user interface.
  2. Click "Radio Network" in the "Wireless" ("WLAN") menu.
  3. Enable the option "Wireless radio network enabled" in the "5-GHz Frequency Band" section.
  4. Enter a different name in the field "Name of the wireless radio network (SSID)" so that you can distinguish the 5 GHz wireless network from the 2.4 GHz wireless network in the future.

    Important:Not all wireless devices support all special characters. Therefore, only use standard Latin letters (not letters such as ä, ë, ö, ü, á, é, í) and numbers in the wireless network name.

  5. Click "Apply" to save your settings.
  6. Establish a wireless connection to the FRITZ!Box wireless network with the name (SSID) that you assigned to the 5 GHz frequency band.