Logo PTB
View of the Mainflingen long-wave radio station for transmission of the DCF77 signal: transmitter building (in the back), antenna building (yellow bricks) and antenna masts.

Dissemination of Time

Working Group 4.42


The Working Group 4.42 is providing accurate time to Germany. Hereby the realization of the national reference time scale UTC(PTB) is the basis of all activities and is done jointly with Working Group 4.41 Time Standards.

Alike to about 70 timing institutes scattered world- wide, PTB contributes with its atomic clocks to the realization of International Atomic Time TAI by BIPM (Bureau international des poids et mesures). This requires that UTC(PTB) is regularly compared via international time- and frequency comparisons with practically all other timing institutes world-wide. Therefore we have numerous international contacts and are frequently invited to cooperate in leading roles in the various working groups of the Consultative Committee for Time and Frequency (CCTF).

UTC(PTB) is the basis for legal time in Germany. An important task with large impact in the public is the dissemination of legal time using different methods.

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In cooperation with various institutes our working group is striving for an improvement of the performance of satellite-based time comparisons.

Starting 2010 the time scale UTC(PTB) has been realized using an active hydrogen maser as physical source, steered with respect to the very accurate and long-term stable caesium fountains. In the meantime, other institutes have followed our example as one can see here.

Not far from now, a communication terminal reaching to the International Space Station will be put in operation in PTB. This will allow time comparisons between PTB and the Atomic Clock Ensemble (ACES) in Space with unprecendented accuracy. In early 2016 one can see structures of the ground terminal  on a roof of a high building of PTB, waiting for completion with the electronics inside. 

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The dissemination of legal time is prerequisite for the availability of accurate time in our country (and beyond).

Radio-controlled clocks are very popular in Germany and in common usage. Signals of the long-wave transmitter are received by estimated 100 million receivers in Germany and almost all over Europe.

Of similar significance ist he time dissemination vie the Internet that is pursued by our colleagues from PTB’s IT-sector (Q.42). Our group provides the timing information that is then distributed using the Network Time Protocoll (NTP).

A few staff members of our group are active as technical consultants for the Deutsche Akkreditierungsstelle DAkkS. In total 60 accreditated calibration laboratories with time and frequency activities are supervised thereby in Germany.



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WG 4.42 provides a large set of measurement data that can be used for obtaining traceability of local measurements to the national standard and to legal time. Access is via ftp.ptb.de/pub/time.

The folder "bulletins" contains the weekly Time Service Bulletin (filename  ptb_WWJJ.tsb, WW: week number of the year, JJ year number, 16 for 2016). It contains the difference between GPS time and time disseminated via DCF77 with respect to UTC(PTB) and to UTC.

Another type of bulletin is ptb_mmjjjj.dcf and log_jjjj.dcf which inform about the properties and service interruptions of the DCF77 transmitter

The folder "GNSS" contains up-to-date GNSS observation data. The sub-folders contain data in format CGGTTS and RINEX. A Readme-file in the main folder explains the use of the data.

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+6DCF77 off air for short periods

The operator Media Broadcast GmbH of the transmitting facility in Mainflingen, hosting also the transmitter DCF77, announced interruption of service in advance for short periods:

08.11.2016, 09:00 – 11:00 CET

14.11.2016, 14:00 – 16:00 CET.

They are caused by major refurbishing of the antenna structures that require shut-down of all transmissions on site. To our observation this is the first planned shut-down since a decade. Usually, the DCF77 transmission is continued via its back-up antenna in case that service needs to be made on the primary system. Occasional off-air periods of DCF77 were always caused by unpredictable impact of weather, such as strong strom and ice rain.

The mentioned dates will be updated if necessary, reported status is of 12.10.2016.