What if the UK had adapted NTSC 525
MGBCTV
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Just curious about what would have looked like compared to the rest of Europe at the time
Apologies if this has already been discussed
Apologies if this has already been discussed
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But, if you mean 'adopted' then the UK running 525/60 NTSC would have been covered in hum bars.
Even with the 50Hz locked system, Channel Island viewers at one time used to get hum bars because the TV was locked to the power on the UK mainland but their power system was not.
Edit: Just realised your comment referred to the OP's title.
Very good article here:
http://www.sptv.demon.co.uk/405colour/
I was going to say wasnt it 405(50Hz)NTSC that was mooted for adoption?
I have thought about the idea that if 405 colour was adopted it the UK then we wouldve had the ability for 10 analogue channels in the UK (using a mix of the old VHF TV bands and the full UHF TV bands that we had availible for analogue with 625).
It would have been fun when digital was introduced, as the MUXs on DTT would have had to be 5MHz wide instead of 8MHz!
It may have also meant that 720p was introduced at the very beginning of digital and no 405 on digital!
That would have meant that all digital kit would have had to be dual standard outputs for both newer 720p TVs and older 405 TVs!
Just think also when we made the switch from VHS to DVDs I think the DVDs wouldve all been formatted for 720p! DVD players wouldve had to be dual standard outputs too!
Principles of PAL Colour Television by H. V. Sims - Head of Engineering Maintenance, Engineering Training Department, British Broadcasting Corporation
{I may have been taught by him at Wood Norton, I can't be sure.}
In section 2.3.5 - Sub-carrier stability requirements he quotes NTSC sub-carrier frequency being transmitted with an accuracy of +/- 0.00003 %
Discussing the PAL system, in Fig 4.10 - Simplified block diagram showing a method of deriving the PAL sub-carrier from NTSC 625-line sub carrier
the fundamental source from which MS MB LT & FT and 4.43361875 MHz was derived is shown as a crystal oscillator running at 4.4296875 MHz NTSC 625 sub-carrier.
This is what I have always believed to be the case - it was cheaper to use the already purchased highly stable NTSC crystals and convert their output than buy new PAL crystals with the same precision.
I don't think there were more than two of them, initially anyway, hot and spare.
Natlock tones didn't require anything like that level of stability; I think it ran using four audio frequencies -
We often used to listen to the incoming tones in Lime Grove control as the local SPG was driven into synchronism with the network mixer prior to telecine sourced transmissions.
I always credited Marconi, do you know different?
I doubt I ever asked how, but I would guess that genlock was a general BBC Engineering concept - generator locking - developed as outside and regional sources grew and TV Presentation demanded 'smoother junctions' (and Grandstand, as well). Probably a joint development between BBC Designs and Marconi as that half of the Marconi-EMI consortium moved to diversify away from just transmitter sets to cameras, scanners and ancillary equipment.
I would guess this was well established by 22nd September 1955.
Strange, though, Marconi never moved into the flying spot technology, that was left to EMI and, of course the Baird Development Company's off-spring Cinema Television; perhaps they had an understanding with EMI!
Don't understand monosync and monopulse; are they American?
All I know is genlock, slavelock and natlock - the latter being short for national slavelock.
Monosync/monopulse. As you know certain kit requires all 7 analogue signals/pulses. Monopulse was a Marconi design whereby all the 7 signals were encoded onto a single wire by a monopulse encoder. At the other end of your single wire was the receiving decoder that decoded this complex signal back into the 7 individual signals. I can't remember the details after all this time, but if you looked at it on a scope it was a pretty complicated and complex signal. It saved on wiring effort and of course eliminated any signal path differential timings between signals. Odd to think that at the time no-one appeared to think: Why don't we just distribute colour black around instead of making this complicated signal (!). Oh well.
Where I first worked there was a bay containing the station SPGs, next to that a bay of monopulse encoders and next to that a bay of monopulse decoders and thence all the 7 wires running from each decoder out to each individual item of kit that required the 7 pulses - negating the entire principle of monopulse distribution! When I enquired as to why this totally illogical situation had come about, the reply I received was that this was installed at the start of UK colour television and no one really understood what it was all about!
Edit. As you know Marconi did have telecine machines, but not flying spot. I'm thinking of that b****y great contraption I saw at their training college. They used to refer to it internally as the 'fish and chip shop deep fat fryer'. Looking at it they weren't far wrong!
mixed syncs
mixed blanking
line triggers
field triggers
colour sub-carrier
no.6 is Pal Ident and
no.7 is burst gate.
Was Bruch Blanking a part of 7? I think it was not a part of the original specification -
which was NTSC is essence with added 'swinging burst' to minimise phase errors
and a 25Hz offset on the sub-carrier to reduce the noticeability of chroma dots on B&W receivers.
Bet others are thoroughly enjoying this!
... For those who need an explanation .
Colour burst which was put in back porch was blanked for some lines in the vertical blanking interval .
In some way it is mixed burst gate .. Like MS and M B containing field and line information.
I think the classic answer to the board question was along the lines of ... Bruch blanking is a technique whereby burst blanking is advanced by half a line per field over four fields .. have I sort of remembered that correctly after all those years?
Yes, Well I am at least!
About that....
Or maybe it was just the all-around wonderfulness of the BBC programming that dazzled us. We were always very envious of it ;-)
ABC / Thames in the 1960's / 70's used a system called 'Unipulse' which I believe had been developed in the engineering lab at Teddington.
The encoder took the required pulses from the master Marconi PG and used them to generate fast narrow positive and negative spikes corresponding to the leading edges. These were then fed down a single coax, and decoders using monostables reconstructed the pulses locally for each piece of equipment, ie camera channels , telecine's and VTRs.
From memory the pulses were :- line drive, field drive, mixed syncs, burst gate, and PAL ID. 4.43MHz subcarrier was sent down a seperate coax.
The Ampex VTR's of the day, VR2000, and VR1200 only locked to a 4 field sequence, and so to simulate matching the 8 field PAL sequence during editing we had the option of delaying the ref subcarrier to the 'play in' VT by half a cycle. Crude, but it worked very well.
Thank goodness for colour black !
A BBC booklet called "BBC TV a British engineering achievement" printed in 1961 refers to experimental transmissions of 405 line NTSC using a studio at Alexandra palace in 1955 and states that experimental 625 line colour transmissions using an adaption of NTSC would start on UHF in 1962.
Dr Bruch encountered problems with colour flicker at the top of frame which he cured by removing the colour burst from 9 lines during field blanking. This is known as Bruch blanking, (Ref same H.V.Sims book as Dans Dad has quoted, supplied to all BBC engineers then).
I think that monopulse was a pulse distribution system similar to the sandcastle pulse system used in TV's. From what I have heard it was somewhat unreliable, needing constant realignment of its various slicer circuits which were possibly valve back then.
Although ITV used fast genlock for synchronisation the BBC used Natlock ( a system too complex to go into here) until broadcast quality frame synchronisers became available. The final Natlock system using icicle lock with rubidium clock was a nightmare on OBs.
line drive = line triggers
field drive = field triggers
colour black = black and burst
and roll telecine = run telecine
two sides of the same coin!
we used to send 16mm news reports over Early Bird (I think, could have been another satellite) when it rose over the horizon around 11 pm.
Absolute technical standards in the UK where not regulated by an external body,
basically it was down the the professionalism of those writing here and our colleagues!
You'd never put a **** paper between either side of the divide, but 'they' had to answer to the ITA / IBA
I'm applying for a management position so I don't have to answer that.
But as we all know Fsub = (283.75 x 15625)+25hz, without the 25hz offset the relationship between fields and s/c would repeat on a 4 field basis, the addition of the 25hz offset causes it to repeat over 8 fields, causing no ending of sweating in VTR departments in the UK.
Can we move on to the perks of the job please?
The US receiving networks of our sales dubs were always very tight on what they would accept or reject. Mind you, a lot of the 'newer' VT operators didn't understand the difference between UK mV and US IRE units and would continually try to set the NTSC burst amplitude to 300mVpp on a PAL wfm. Eek.