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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