FRITZ!Box 3390 Service - Knowledge Base

FRITZ!Box 3390 Service

FRITZ!Box reports "A microwave was detected"

The speed of the wireless connection (WiFi) to the FRITZ!Box displayed by wireless devices such as computers, smartphones, or tablets, is significantly lower than the data rate possible with the wireless standard 802.11n. The following 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, for example a microwave in the frequency range around 2.45 GHz. To ensure stable wireless connections, the FRITZ!Box automatically reduces the channel bandwidth from 40 MHz to 20 MHz. Although wireless devices then display a lower data rate, the user data rate is increased because there is less interference and the wireless connection is no longer affected by constant retransmissions.

Note:The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS for your FRITZ!Box.

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

1 Identifying sources of interference

  1. Turn off all devices that could interfere with the wireless network.

    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. Check whether the wireless connection is still impaired.
    • If the wireless connection is no longer impaired:
      1. Turn the devices back on, one after the other.
      2. Each time you turn on a device, check whether the wireless connection is impaired again.
        • If you identify a device or devices causing interference, you have the following options:
          • Leave the devices that cause interference turned off,
            • or:
          • Enable or refresh the auto channel (see the section "Enabling or refreshing the auto channel"),
            • or:
          • Find the ideal location for the FRITZ!Box (see the section "Finding the ideal location for wireless devices").

2 Enabling or refreshing the auto channel

When the auto channel is enabled, the FRITZ!Box checks the wireless environment and automatically selects the most suitable wireless channel settings. The allocation of the frequency bands can change significantly over the course of the day, though. The FRITZ!Box does not refresh the auto channel as long as wireless devices are still connected with it. However, you can manually update the auto channel at any time:

  1. Click "Wireless" ("WLAN") in the FRITZ!Box user interface.
  2. Click "Radio Channel" in the "Wireless" ("WLAN") menu.
  3. Enable the option "Set radio channel settings automatically (recommended)".
  4. Click "Apply" to save the settings.

    Note:All wireless connections to the FRITZ!Box are cleared and then automatically re-established when you enable or refresh the auto channel.

  5. Click the "Refresh Auto Channel" button.

3 Finding the ideal location for the FRITZ!Box

  1. If possible, position the FRITZ!Box in a room that is centrally located.
  2. Do not position the FRITZ!Box directly in the corner of a room.
  3. 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.
  4. Position the FRITZ!Box as high in the room as possible, for example on a shelf.
  5. Position the FRITZ!Box so that there are as few obstacles as possible between it and other wireless devices. In particular, metallic objects or objects containing water, for example radiators, refrigerators, or even houseplants, significantly reduce the quality of the wireless signal.
  6. Position the FRITZ!Box so that it is away from other transmitters, for example microwaves, wireless speakers, or Bluetooth devices.

4 Establishing a wireless connection to the 5 GHz frequency band

The FRITZ!Box makes a wireless network available in the 2.4 GHz as well as the 5 GHz frequency band. The 5 GHz frequency band is not affected by interference as often. 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. If only one field is displayed, enable the Advanced View first.

    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 the 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.