[time-nuts] Alternate frequency sources : DVB-T and ISDN & OT comment

[Kit Scally]

Guys,


Don't get confused with (a) recovering the transmitter's carrier
frequency and (b) recovering the colour burst and/or data stream in a
DVB-T signal for use as a "house frequency standard".  They're not one
of the same !

Most TV carrier frequencies here in Sydney, Aust (analogue & digital -
we've got both running at the present time) are bog-standard xtals
(possibly ovened).    As noted by others, this crude approach isn't good
enough for SFN's

Attempting to recover any part of a RAW MPEG data stream from a "$49
digital STB" may be doomed to failure. Most STB of this ilk use a single
jungle-chip with RF in and various flavours of video out.  The data
streams you need to access for any clock recovery strategy is
unfortunately buried in silicon....


OT - Happy Thanksgiving holiday to all those in the USA & Canada.


Kit

VK2LL
Sydney

Christian Vogel wrote:
> Hi Alan,
> 
> 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/

>>snip