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From: "Talbot Andrew" <ACTALBOT@dera.gov.uk>
To: rsgb_lf_group@blacksheep.org
Subject: LF: RE: Freq stability
Date: Thu, 4 Jan 2001 12:19:55 -0000
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Yes, there is a published design for a TV frequency standard, need to
search for it at home before saying where !.   There was a German
article published several years ago for a 10MHz frequency standard
locked to TV line sync and this reappeared a few months later, slightly
updated, in the UK Microwave Newsletter.  It requires a TV receiver of
some sort but only generating a low level video signal; the frequency
standard incorporates its own sync separator.   I butchered an old
portable TV destined for the rubbish tip for its receiver board.

Beware of local opt-outs (or whatever they are called) where local or
regional TV stations transmit local information rather than that
nationally.   In that case, they usually go to a locally generated
reference rather than the central high stability one.   In the UK,  BBC
Television is Caesium or Rubidium locked nationally, but for local news
etc experience shows phase / frequency shifts at certain times.
However, I've always seen a few parts in 10^-9 short and long term
stability.

Another source of high accuracy transmissions is Longwave braodcasts -
in the UK and France at least, the carriers are all generated locked to
national standards.  At Droitwich a Rubidium source is actually used as
it has a lower phase noise than using a Caesium source directly, but it
is compared in phase and corrected with a Cs source on a daily basis (to
quote a BBC employee).   The only problem is locking to the 'unusual'
frequencies actually in use eg. 198kHz

Andy  G4JNT


> ---> 
> Vernall wrote:
> 
> >
> > The TVNZ nationwide network, with two Tv channels, has a 
> Rubidium source for
> > timing.
> >
> I'm wondering if some simple circuit diagram is to be found 
> somewhere, to receive and
> recover the synch timings, without using a real TV, bulky and noisy.
> 


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