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Did the BBC 2 Test Card ever have the 1986 "TWO" ident?

SP
Steve in Pudsey Yorkshire Look North (Yorkshire)
I thought Natlock merely automated the adjustments required to the SPG at the remote source (eg the regional studio) to get it in sync with the destination?
Write that down in your copybook now.
BL
bluecortina
I thought Natlock merely automated the adjustments required to the SPG at the remote source (eg the regional studio) to get it in sync with the destination?


Others will know for sure about Natlock.

My understanding is that in very, very general terms with Natlock the destination SPG sent a series of audio tones to the remote SPG to use as feedback to ‘steer’ the remote pulses such that the pulses on that remote SPG (and the remote studio output for example ) become time co-incident at the local end which might typically be a studio mixer.

With Genlock, an SPG takes incoming pulses from a source and synchronises the pulse outputs of Itself to that source. So the Local SPG output is synchronous with the Remote source of pulses but not timed - you have to fine tune that by hand. If the incoming pulses move, so does the output of the genlocked SPG.

So, if you’ve genlocked yourself to an incoming video feed and that video feed cuts to you - you are genlocking to yourself with spectacular results! Natlock works differently and eliminates that possibility.

I hope that makes sense.

Edited to add. Thinking about it a bit further. If the BBC had an immutable rule that the output of the two networks would always be sourced from the local SPG’s in telly centre then I suppose local source genlocking would work for the BBC. But, I recall watching something like Nationwide, and in it’s early days you would occasionally get frame rolls as they cut between the various regions during the programme which would seem to indicate the Nationwide studio output pulses were those of the various regions and not fixed locally generated ones? In which case remote genlocking would not be the way to go. Interesting conundrum.
Last edited by bluecortina on 15 August 2020 1:36pm - 3 times in total
SP
Steve in Pudsey Yorkshire Look North (Yorkshire)
That's my understanding too. So let's say BBC Manchester is contributing to Nationwide. Natlock adjusts Manchester's SPG so that the studio output is synchronous when it arrives at the Lime Grove mixer. Manchester isn't genlocked to net1 at this point so the howl situation you are suggesting wouldn't happen.

After the contribution, the SPG relocks to the incoming network feed ready to opt out for North West Tonight.

The occasional frame rolls you saw would presumably coming from regions that weren't equipped with Natlock yet or where it failed to work properly? I think there were further complications based on which regions were contributing on a given day, Leeds was routed to London via Manchester, sometimes directly but on other occasions, when Manchester was also doing a bit on Nationwide, Leeds would be an OS into the Manchester studio. On those occasions Leeds would presumably need to adjust its SPG to be synchronous with the Manchester studio rather than with London.
Write that down in your copybook now.
TE
Technologist London London
Genlock is the destination locking to the source I,e destination moves
As described Natlock is a slave lock where the source is adjusting itself so that at the designation it is in sync I,e source moves .
Thus if you have got enough detectors at the destination ...all remote sources can be synchronous .

Of course a slave lock can be done manually with the destination talking in the source but doing it automatically is a lot easier....
as synchroniser were coming into service arround 40plus years ago I never got into the delights if natlock but I think you had to be roughly within range before letting the automatics steer you in and there were not that many comparators..

But most TC studio with BBC mixers had the caption scanner gen/slave locked so that you could caption a non sync source ....

With slave locking all remote sources were synchronous at the destination mixer
Genlock meant only one remote source was synchronous,

I'm not certain if all regions could be natlocked hence frame rolls on Nationwide .. but it is over 40 years ago.
SPGS were very expensive.....
but as the price came down it was easier to justify using them ..
And if you knew what you were doing it made many things easier to do both in system design /install and operationally.
A genlocked SPG meant that you had total flexibility on the timing of something ....

But using too many synchronisers was a sin many did .....
and in those day equivalent audio delays were rare !
Last edited by Technologist on 15 August 2020 2:13pm - 2 times in total
BL
bluecortina
That's my understanding too. So let's say BBC Manchester is contributing to Nationwide. Natlock adjusts Manchester's SPG so that the studio output is synchronous when it arrives at the Lime Grove mixer. Manchester isn't genlocked to net1 at this point so the howl situation you are suggesting wouldn't happen.

After the contribution, the SPG relocks to the incoming network feed ready to opt out for North West Tonight.

The occasional frame rolls you saw would presumably coming from regions that weren't equipped with Natlock yet or where it failed to work properly? I think there were further complications based on which regions were contributing on a given day, Leeds was routed to London via Manchester, sometimes directly but on other occasions, when Manchester was also doing a bit on Nationwide, Leeds would be an OS into the Manchester studio. On those occasions Leeds would presumably need to adjust its SPG to be synchronous with the Manchester studio rather than with London.


Technologist has given a good description. But I am somewhat confused by your post. Natlock is not the same as Genlock - they are two very different processes looking to achieve the same end result.

Natlock is a local SPG providing audio tones (feedback if you wish) to a remote SPG to steer it slowly into timed synchronism with the local SPG. Genlock is a process of a local SPG literally dropping lines and phasing line and subcarrier signals to bring itself into synchronism with a remote signal. ‘Fast Genlock’, as it was known, could sync an SPG to a source of video in a couple of seconds. Natlock, I believe, would take very much longer.

For my clarity in your post above, is Manchester Natlocking or Genlocking?
SP
Steve in Pudsey Yorkshire Look North (Yorkshire)
Both.

In the case of contributing to Nationwide, Manchester is Natlocking, such that its contribution is correctly timed when it arrives in London.

In the case of opting out in the North West, Manchester is Genlocking such that it is in sync with Net1 so it can go into circuit cleanly.
Write that down in your copybook now.
BL
bluecortina
Both.

In the case of contributing to Nationwide, Manchester is Natlocking, such that its contribution is correctly timed when it arrives in London.

In the case of opting out in the North West, Manchester is Genlocking such that it is in sync with Net1 so it can go into circuit cleanly.


I’ve read that a couple of times and get it now - two different requirements needing two separate operational solutions. Thanks for the further explanation. Thumbs up
BL
bluecortina
I’ve found my old Poly notes on how the BBC managed to use their NTSC crystals to generate PAL subcarrier.

The lecturers told me the BBC ‘jumped the gun’ in the early 60’s thinking a variation of NTSC was going to be adopted in the UK and bought some NTSC kit in anticipation, when PAL was subsequently chosen they didn’t want to chuck the NTSC crystals (SPGs?) away. I believe they were purchased at great cost originally. That’s what I was told anyway.

If Markymark would like to host it?
MA
Markymark Meridian (Thames Valley) South Today
I’ve found my old Poly notes on how the BBC managed to use their NTSC crystals to generate PAL subcarrier.

The lecturers told me the BBC ‘jumped the gun’ in the early 60’s thinking a variation of NTSC was going to be adopted in the UK and bought some NTSC kit in anticipation, when PAL was subsequently chosen they didn’t want to chuck the NTSC crystals (SPGs?) away. I believe they were purchased at great cost originally. That’s what I was told anyway.

If Markymark would like to host it?


I'll do that, send me the files.....
--
Avatar credit: © BBC, ITA, BREMA 1967
BL
bluecortina
I’ve found my old Poly notes on how the BBC managed to use their NTSC crystals to generate PAL subcarrier.

The lecturers told me the BBC ‘jumped the gun’ in the early 60’s thinking a variation of NTSC was going to be adopted in the UK and bought some NTSC kit in anticipation, when PAL was subsequently chosen they didn’t want to chuck the NTSC crystals (SPGs?) away. I believe they were purchased at great cost originally. That’s what I was told anyway.

If Markymark would like to host it?



I'll do that, send me the files.....


Could you send me your email address via a pm please.
MA
Markymark Meridian (Thames Valley) South Today
I’ve found my old Poly notes on how the BBC managed to use their NTSC crystals to generate PAL subcarrier.

The lecturers told me the BBC ‘jumped the gun’ in the early 60’s thinking a variation of NTSC was going to be adopted in the UK and bought some NTSC kit in anticipation, when PAL was subsequently chosen they didn’t want to chuck the NTSC crystals (SPGs?) away. I believe they were purchased at great cost originally. That’s what I was told anyway.

If Markymark would like to host it?


Here we go, (warning, contains lots of maths)

https://www.dropbox.com/s/t7257h497obljvc/Establishing%20the%20Correct%20relationship%20between%20Colour%20subcarrier%20and%20Line%20frequency.pdf?dl=0

Some of it is still relevant today, all modern digital coding methods are derived from the values you see in that paper
--
Avatar credit: © BBC, ITA, BREMA 1967

61 days later

GE
thegeek Founding member London London
I occasionally see W on circuits originating in Salford (though probably won't again until the Premier League season starts again), but will have to have a closer look to see if theirs flashes.

An update, for anyone who still cares: they do not.

(Though strictly speaking it's not W, it's an unidentified HD variant)
Avatar credit: SMPTE RP198

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