[time-nuts] Alternate frequency sources : DVB-T and ISDN?

[Magnus Danielson]

Christian Vogel wrote:
> Hi Alan,
> 
>> I cant remember the detail now but my converstaion with a BBC engineer at
>> the NPL meeting a few years back suggested along the lines of "yes there
>> would be a stable frequency available on a digital TV signal but no it 
>> would
>> not be related (tracable) to any given standard because it didnt need to
>> be."
> 
> at least here in Germany the digital TV transmissions (DVB-T) are using
> (in some areas) Single Frequency Networks[1]. I live near one of the 
> transmitters
> and when I visited the facility, they had Meinberg GPS receivers in the
> racks housing the TV signal generators.

SFN requires synchronisation of frequency (10 MHz) and phase (PPS).
DVB-T transmitters using SFN will broadcast pilot-tones. See ETSI EN 300 
744, accessable through:

http://www.dvb.org/technology/standards/

> Speaking of alternate sources: Has any time-nut considered using the ISDN
> telephone network [2]?

I think ISDN is finally dead here in Sweden. I can check if my ISDN 
connection is out for good. However, I wonder if the modern replacement 
to ISDN, such as ADSL is actually synchronised. It too uses OFDM/COFDM 
transmission and provides pilot-tones.

>        Chris
> 
> [1] http://en.wikipedia.org/wiki/Single-frequency_network
> [2] http://openbsc.gnumonks.org/trac/wiki/isdnsync

Cheers,
Magnus