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David Looser · 26th Jul 2006, 3:59 pm

I wouldn't get to bothered about the niceties of the spec for the Baird 240-line system. I remember reading an open letter from Cossor to the BBC (but not where I read it - dammit!) that asked when the Baird transmissions were going to start conforming to the published spec. In particular they complained that the sync-vision ratio, nominally 40:60, varied and could be as high as 60:40 and that there was considerable uncertainty about the position of the frame sync pulse relative to the frame blanking. Sometimes they complained that the sync pulse overlapped the end of the blanking period giving the line timebase no time to recover from it's long period of free-running. Also the frame pulse jittered relative to the line syncs (a bit like the jitter of the head-switch point of a VCR I guess) causing the picture to move up or down one line as the phase relationship of the line and frame syncs changed.

26th Jul 2006, 3:59 pm	#12
David Looser Retired Dormant Member Join Date: Jul 2006 Location: Ipswich Posts: 5	Re: Baird 240 line standard details wanted I wouldn't get to bothered about the niceties of the spec for the Baird 240-line system. I remember reading an open letter from Cossor to the BBC (but not where I read it - dammit!) that asked when the Baird transmissions were going to start conforming to the published spec. In particular they complained that the sync-vision ratio, nominally 40:60, varied and could be as high as 60:40 and that there was considerable uncertainty about the position of the frame sync pulse relative to the frame blanking. Sometimes they complained that the sync pulse overlapped the end of the blanking period giving the line timebase no time to recover from it's long period of free-running. Also the frame pulse jittered relative to the line syncs (a bit like the jitter of the head-switch point of a VCR I guess) causing the picture to move up or down one line as the phase relationship of the line and frame syncs changed.