DCF77, synchronize the time of your clock without problems

Aplicación DCF77 Emulator

    What is dcf77?

    DCF77 is a radio station located in Mainflingen (Germany). It belongs to the German Meteorological Institute and is used to broadcast a time reference signal.

    DCF77 refers to the frequency on which the radio control signal is broadcast (77.5Khz).

    In Europe there is another antenna that transmits the radio-controlled signal, the MSF (60 kHz) emitted by the National Physical Laboratory of England from the Anthorn radio station.

    Our watch may only receive the signal from a single station. For example, Citizen watches usually receive the DCF77 signal only, while Casio Multiband watches can receive the signal from both stations, improving the chances of synchronizing the time.

    How does the dcf77 radio control system work?

    Internally, our watch has an antenna that allows it to receive radio signals from the Mainflingen station. This synchronization is executed automatically several times in the morning (because there is less interference than during the day).

    The automatic synchronization occurs until it is received correctly or the maximum number of daily synchronizations with error has been reached.

    It is also possible to manually force the synchronization with the radio controlled signal, in case it has failed during the early morning.

    It is also possible to manually force the synchronization with the radio controlled signal, in case it has failed during the early morning.

    If you are interested in knowing more about the DCF77 protocol, you can visit this article from javiergutierrezchamorro.com, where it is explained in detail in a very simple way.

    Mainflingen signal coverage

    DCF77 signal coverage is approximately 1500 kilometers. This coverage includes the northern half of Spain, but as we will see later, there are many more factors that influence signal reception and our clock may not be able to synchronize.

    Factors that make it difficult to synchronize your radio-controlled clock

    In addition to geographic location, there are more factors that can make our watch unable to synchronize every day.

    Supported stations

    Logically if we have a clock model that includes synchronization from the DCF77 and MSF station, there are more possibilities to synchronize correctly.

    By being able to receive two different signals, there is less chance that weather or interference can weaken them and thus receive correctly.


    Storms, and generally bad weather, weaken the radio control signal, which can result in it being too weak to be detected by the clock and synchronized.


    As indicated in the manuals of radio-controlled watches, it is important to face the watch towards a window. Normally orienting the 12 o'clock or 6 o'clock indexes towards the sale to facilitate synchronization.

    In our manual it will indicate the position, which corresponds to the place of the clock where it has the receiving antenna of the DCF77 signal.


    There is also electromagnetic interference, such as the wifi network or having a mobile phone nearby, which can distort the signal and make it difficult to receive it.

    It is advisable to keep the clock away from such interference to facilitate synchronization.

    Nearby obstacles

    Even if the geographic location where we live is within the DCF77 signal coverage area, it is possible that other types of obstacles, for example having a building nearby, may prevent us from receiving properly.

    Improve radio-controlled signal reception

    But it's not all bad news. If our clock has difficulty synchronizing the time, we can try the following methods to improve reception.

    Changing the position of the clock

    Sometimes, it is convenient to change the position of the clock at night to improve the reception of the signal.

    We can try in different places, at different heights to improve the signal, sometimes with such a simple solution, we can fix our synchronization problems.

    Amplifier antenna

    Citizen includes with some of its watches the RCW/SU-3 amplifying antenna for DCF-77 radio controlled signal.

    Antena amplificadora DCF77
    DCF77 Amplifier Antenna
    Antena DCF77
    DCF77 Amplifier Antenna

    This antenna does not need any kind of batteries, we just have to place the clock on it and it improves the synchronization of our clock.

    Although the antenna is of the brand Citizen, when amplifying the DCF77 signal it will be useful for any clock that receives from the Mainflingen transmitter, independently of its brand.

    Using an android application DCF77 Emulator

    If all the above options do not allow our clock to synchronize normally, we can opt for what I believe is the best solution.

    If you have an Android phone, you can download the DCF77 Emulator application.

    By not relying on the radio control signal generated from the Mainflingen station, it allows us to synchronize our clock if we are out of signal coverage. For example, if we live in Ceuta or the Canary Islands, we will be able to synchronize our watch without any problem.

    This application generates a DCF77 radio control signal through a headset connected to our mobile phone. The big advantage is that we can use another application like Clocksync to synchronize the clock of our mobile with ntp time servers, adjusting the precision to the maximum.

    The operation of the DCF77 Emulator is very simple. After installing the application in our mobile, we will follow the next steps:

    1. We turned up the volume on our mobile phone to the maximum
    2. We run the DCF77 Emulator app

      Sincronizando Casio PAW-1300
      Synchronizing Casio PAW-1300 with DCF77 Emulator
    3. We place the headset over the area where the watch's receiving antenna is located. If we don't know where it is, we will consult the watch's manual.

      Sincronizando Casio PAW-1300
      Synchronizing Casio PAW-1300 with DCF77 Emulator
    4. We force the manual synchronization of the clock and we just have to wait.

      Sincronizando Casio PAW-1300
      Synchronizing Casio PAW-1300 with DCF77 Emulator
    5. We already have the clock synchronized!

      Sincronizando Casio PAW-1300
      Synchronizing Casio PAW-1300 with DCF77 Emulator


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