[time-nuts] Digital TV signals
magnus at rubidium.dyndns.org
Wed Apr 16 04:02:21 EDT 2008
From: david brown <davidarbrown at bigpond.com>
Subject: [time-nuts] Digital TV signals
Date: Wed, 16 Apr 2008 09:25:21 -0700
Message-ID: <48062871.4060705 at bigpond.com>
> From a complete amateur, is there any useful timing info to be gained
> from the newer format of digital tv transmission(Australia) to replace
> that available from current analogue transmissions.? My recently
> repaired TV derived frequency standard looks to be becoming obsolete!
You are hanging of a DVB-T SFN system. SFN is a system variant where
transmitters use a common time source (often GPS, but not always) to transmitt
the signal at the same time. There is no real guarantee that any part of the
signal is traceable, unless local authoratives or broadcasters themself put any
such efforts in (which is possible).
There is a small part of the signal which can be assumed traceable, even if the
actual TV stream is not necessarilly traceable. Since you sit off an SFN
network, the TV transmitter is traceable to the 10 MHz clock being fed into it,
so the modulators pilot tones in the COFDM signal is indeed traceable back
through the GPS receiver.
If you download the ETSI documents for DVB-T I am sure you could engineer a
receiver design, but frankly you could spend your time better on just doing a
darn good GPS receiver instead, since you would be traceable back to GPS in
most cases anyway, and not through the best of channels.
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