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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 2nd Nov 2014, 5:20 pm   #1
PaulM
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Default Broadcast spec black and burst

Recently I've been preparing for a new workshop which should be a lot better for working on ex-broadcast kit 'on the bench' as my existing facilities have been over-run with storage and 'jumble'. I'm planning on having a full range of test patterns and waveforms delivered from the main equipment bays via a patch panel but I've been pondering about the ultimate 'reference' for all the 625 line PAL sources. I have full broadcast spec SPGs available as part of the OB trucks and the workshop area, but I can no longer do what I used to do which was lock all the SPGs to a broadcast source which 'should' be deadly precise (buried s/c references and all that). In this all-digital world there appears to be no way of accessing this resource of deadly correct black and burst (digiboxes generate their own internally referenced low-grade PAL, of course). In principle this doesn't matter providing the broadcast class SPGs are maintained and checked, but that's another chore when a simple genlock to off-air used to do the trick for all the sources. Question: does anybody know of a broadcast source (PAL satellite from a major broadcaster perhaps) that is still on-air with a high-grade PAL reference? Just one of those annoying things that used to be easy! Cheers, Paul M
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Old 2nd Nov 2014, 11:49 pm   #2
winston_1
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Default Re: Broadcast spec black and burst

Sadly there are no analogue satellite broadcasts anywhere in the world now.
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Old 3rd Nov 2014, 10:57 am   #3
John Caswell
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Default Re: Broadcast spec black and burst

Hi Paul
I think that there still some PAL signals on satellite, Germany springs to mind, but failing that, the only way I can think of, is to see if any of your genlock SPGs will accept a 5/10Mhz ref and get yourself a rubidium standard. I am sure I have seen some at sensible prices

John

Last edited by John Caswell; 3rd Nov 2014 at 10:57 am. Reason: Typo
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Old 3rd Nov 2014, 11:28 am   #4
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Default Re: Broadcast spec black and burst

If memory serves me right, the colorburst of ZDF was locked to an atomic source. Or the timing of the sync itself (which is locked to the color subcarrier anyway). However, a quick check at Lyngsat revealed that all analog channels have disappeared from Astra 19E. So you will have to lock to an external source (like GPS Disciplined Oscillator).

Tjerk, 9ZZ
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Old 3rd Nov 2014, 1:31 pm   #5
PaulM
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Default Re: Broadcast spec black and burst

Many thanks to all for the replies. It's as I suspected, there's nothing left to pull from the ether in terms of CVBS. Sadly, I don't currently have an SPG capable of locking to a 5/10 MHz reference which is what triggered my query. I think that in the short-term I will check over the best of the SPGs and then lock all the others to it. In the longer term I will try to source a more modern and capable unit which can lock to an external 'round number' reference. It used to be so easy! Best regards, Paul M
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Old 3rd Nov 2014, 5:47 pm   #6
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Default Re: Broadcast spec black and burst

Surely you can lock the timebase of an existing TPG to an external source? If not via a kludge? I'm sure the excellent SAA1043/1044 chipset can also do this.

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Old 4th Nov 2014, 12:14 am   #7
PaulM
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Default Re: Broadcast spec black and burst

Locking the myriad of vintage TPGs, cameras, telecines VTRs etc. together is not the problem - that system already exists. What I need to do is make sure that the system syncs and s/c are to a tight specification as existed 'over the air' before the great analogue switch-off. I may be on to a solution for this with a Courtyard SPG which can lock to a 10 MHz 'deadly accurate' reference or a GPS based system. It will become the 'master' and everything else will then lock to that. I don't want to burn up a lot of time on this designing custom circuits as it's not that important on the scale of things, but it would be good to know that the fundamental timings are spot on across the system.

Best regards, Paul M
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Old 4th Nov 2014, 10:48 am   #8
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Default Re: Broadcast spec black and burst

Quote:
What I need to do is make sure that the system syncs and s/c are to a tight specification
Do you really need it? I would have thought a crystal would be more than good enough for a local system.
 
Old 4th Nov 2014, 6:48 pm   #9
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Default Re: Broadcast spec black and burst

It doesn't matter if the TS really needs it. I have a GPS DO hooked up to most of my stuff. Do I need it? Not really, but it's absolutely awesome to have a rock solid reference. And to have it display as 9 999 999.998 Hz on my free-running OCXO referenced HP89440 spectrum analyzer.

@Paul: If you already have the solution by all means go for it. Don't kludge together something that might work fine but wastes your time...

Tjerk, 9ZZ
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Old 4th Nov 2014, 7:51 pm   #10
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Default Re: Broadcast spec black and burst

Nothing suitable in the TVC auction Paul?
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Old 4th Nov 2014, 8:17 pm   #11
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Default Re: Broadcast spec black and burst

Some reference-lockable broadcast kit may have a very narrow range of acceptance if it itself is crystal-locked, they'll have been designed with a tightly specced master in mind- otherwise, it's arguable that it doesn't deserve the term "master"... A situation might arise where everything is fine and dandy at the start, or at the end, of a day but, in between, random things are teetering on the edge of colour-lock if an only average crystal master is used. Agree with Paul, the reference needs to be above reproach to avoid a frustrating tail-chase of what-do-I-tweak-to-what this time?
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Old 6th Nov 2014, 8:59 pm   #12
PaulM
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Default Re: Broadcast spec black and burst

For what it's worth, it looks like my problem is on the way to being solved with the purchase today of a Courtyard SPG capable of locking to an external 10 MHz reference (it was a good price). Using a suitable GPS disciplined reference unit to feed it I should be in good shape - at least whilst GPS stays on air! I had just hoped that there might still have been a good old-fashioned PAL source on-air to avoid all this.

Thanks to all.

Best regards, Paul M
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