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Knowledge document #3336
FRITZ!Box 6850 LTE
This support document is available for the following products:

Mobile connection drops frequently

The mobile connection between your FRITZ!Box and your mobile network provider drops frequently (several times a day). During this time, the Power/Mobile LED on the FRITZ!Box flashes and then stays lit as soon as the internet connection is re-established. The following error message is displayed in the event log of the FRITZ!Box:

"LTE no longer responding"


  • The stability of the mobile connection depends on factors such as the distance from the mobile station and the shielding effect of the walls of your own house. It can also be affected if your mobile network provider is experiencing technical difficulties.

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

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

1 Checking the event log of the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Event Log" in the "System" menu.
  3. Check whether events also took place before the time when the error occurred, or whether only events are shown that took place after the error occurred.
  4. If events are also displayed that took place before the time the error occurred, proceed with the next section.

2 Installing the latest FRITZ!OS for the FRITZ!Box

Installing the latest FRITZ!OS makes your FRITZ!Box compatible with the latest mobile network technology used by mobile network providers in their radio cells:

  1. Install the latest FRITZ!OS on the FRITZ!Box.

3 Selecting the frequency band

If several frequency bands are available at your location, you may be able to increase the stability of the mobile connection by selecting a specific frequency band:

Note:In Germany, the frequency bands 2.6 GHz, 1.8 GHz, and 800 MHz are used. Not all frequency bands are available at all locations, and not all mobile network providers support all frequency bands.

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Account Information" in the "Internet" menu.
  3. In the section "LTE Frequency Band", enable the option "Manual" and disable all frequency bands except "2.6 GHz / band 7 (FDD)".
  4. Click "Apply" to save the settings.
  5. If the FRITZ!Box can establish a mobile connection using the frequency band you selected:
    1. Click "Internet" and then "LTE Information".
    2. Click on the "Mobile" tab.
    3. Check which speed is displayed in the "Throughput" line.
  6. Repeat steps 2 - 5 with the frequency bands "1.8 GHz / band 3 (FDD)" and "800 MHz / band 20 (FDD)", and use the frequency band the FRITZ!Box can achieve the highest throughput with.

4 Checking the mobile network antennas

Mistakes made when connecting the mobile network antennas can often be overlooked. Therefore, check whether the mobile network antennas were correctly connected to your FRITZ!Box:

  1. Check the pin in the connector of both mobile network antennas. If the pin is bent or has broken off, there can be no contact between the antenna and the FRITZ!Box.
  2. Make sure that both of the mobile network antennas included in the package are correctly screwed onto the sockets on the FRITZ!Box.
  3. Swap the mobile network antennas connected to the two antenna sockets on the FRITZ!Box. Check whether the FRITZ!Box can then establish a radio connection.
  4. If you are using an outdoor antenna, check whether you can establish a radio connection if you use a different outdoor antenna or a different antenna cable. If you can establish a connection then, either the outdoor antenna or antenna cable is not suitable or is defective.

    Note:If you are using the FRITZ!Box in the indoor coverage area of your mobile network provider, test whether you can establish a radio connection if you use the original antennas included in the package.

5 Finding the ideal location for the FRITZ!Box

You can use the alignment aid to find the ideal location for the FRITZ!Box and the best position for the mobile network antennas:

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "LTE Information" in the "Internet" menu.
  3. Click on the "Reception" tab.
  4. Click the "Start Alignment Aid" button.
    • Now the current signal strength of the antennas is displayed by the LEDs on the FRITZ!Box (in five levels) and in the user interface.
  5. Select a location for the FRITZ!Box where the signal strength is as high as possible. When doing so, note the following:
    1. Do not set up the FRITZ!Box in the corner of a room.
    2. Place the FRITZ!Box as close to an outside wall as possible. If you know where your provider's radio cell is located, place the FRITZ!Box by the wall facing the radio cell.
    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.

6 Connecting an outdoor antenna

If you are using the FRITZ!Box in the fringe area of the network coverage of your mobile network provider (outdoor coverage area), using mobile network antennas in your house may not be sufficient to establish a radio connection. In this case, increase the transmission and reception power of the FRITZ!Box by using an outdoor antenna on your roof or balcony, for example:

Note:Your mobile network provider can tell you whether you are using the FRITZ!Box in their indoor or outdoor coverage area.