[ntp:questions] DRM: useless for NTP like services...

shoppa at trailing-edge.com shoppa at trailing-edge.com
Mon Jan 1 00:42:57 UTC 2007

Max Power wrote:
> http://www.cl.cam.ac.uk/~mgk25/time/lf-clocks/
> The Digital Radio Mondiale standard for long/medium/short-wave digital audio
> broadcasts (freely available for downloading as ETSI TS 101980) includes
> time data, but like with RDS and DVB, the data format specification is not
> really optimized towards high-precision clock synchronization and the DRM
> COFDM demodulator needed is significantly more complex than the AM receivers
> that decode the time signals listed above.
> It is a shame that the NTP.org has not set up a working group to define
> packet formats for RDS / DVB / DRM / AMSS.

Digital broadcasting and studio->transmitter links, in general, present
problems for time synchronization.

All of the digital links have some amount of delay in the
encoding/decoding process, the delay depending on details of error
correction and the amount buffered up.

There is a delay between studio and transmitter (now almost always a
digital link esp in urban areas) and the HDTV and digital radio
standards also introduce a delay.

The studio->transmitter delay is somewhat under control of the station
engineering, but even then they usually do not account for the delay in
their broadcasts.

The digital transmitter->home/car receiver has other issues because
different brands and models of receivers have different delays.

We have WWV and CHU decoders already in NTP and they're really very


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