UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

flyback · 29th Jul 2004, 4:52 pm

Hello all

I feel that the 405-line standard should be preserved as it existed throughout its service life.

The 405-line sync waveform was maintaned in its original form even when both
BBC and ITA switched to using standards converters to supply the service to the public.

There are small deviations from the original specs, some changes seem to have happened because of
the division down from a master clock, making pulses timed to the nearest clock edge and with the clock
frequencies used then, that ment a few 100's of ns here and there, the field blanking period also increased.

I had the same problem with my mere 10 MHz sampling clock, the BBC (PYE) analogue converter was only a bit higher at 11MHz.

But the BBC and ITA never fiddled with the sync to " improve the interlace " , it's true that some sets
did not interlace as well as others, but that would have been down to cost and design issues.

Set designers sometimes went to great lengths to get good interlace, with the addition of various
clipper and trigger circuits, maybe even adding an extra valve to the sync circuits.

The later large screen ( >12 inch) sets late 50's to 60's dont seem to do to badly on the original
sync waveform.

And remember it was the programmes you watched not the Test Card or the lines!,
it's ok to nit-pick about the lack of interlace or frame (oops I mean Field!) scan jitters, but the
standard should be maintained as it was, with nothing added, its bad anough that they (BBC etc..)
take away some lines of the pictue for the letterboxing of most programmes today, making our 405-line
pictures have even less lines.

It may be best to have it (the corruption of the 405 sync) switchable so a few people can say
" oh look at the quality of the interlace! "

And while I'm at it (whinging that is..) whats the sudden interest in all these other line standards,
441, 362.5, etc.. it's supposed to be " 405 Alive " cant we keep at least one thing British!
I know there was the Baird electronic system but with only about 4.5 sets in the world and most
of those are in America.

In my small way I have kept a few people (and one American export) and their 405-line sets happy,
orders for my Domino (Blatent advertising!!) converter have slowed to a dry riverbed, so I dont know
how many UK 405-line television collectors will go for the Aurora converter but I wish you well in your endeavours.

all the best
Malcolm

(now on only one Prozac a day!)

(please do not PM me, email is best..)

29th Jul 2004, 4:52 pm	#7
flyback Retired Dormant Member Join Date: Apr 2003 Location: Swindon Wiltshire Posts: 26	Re: Specs and Feedback needed for converter Hello all I feel that the 405-line standard should be preserved as it existed throughout its service life. The 405-line sync waveform was maintaned in its original form even when both BBC and ITA switched to using standards converters to supply the service to the public. There are small deviations from the original specs, some changes seem to have happened because of the division down from a master clock, making pulses timed to the nearest clock edge and with the clock frequencies used then, that ment a few 100's of ns here and there, the field blanking period also increased. I had the same problem with my mere 10 MHz sampling clock, the BBC (PYE) analogue converter was only a bit higher at 11MHz. But the BBC and ITA never fiddled with the sync to " improve the interlace " , it's true that some sets did not interlace as well as others, but that would have been down to cost and design issues. Set designers sometimes went to great lengths to get good interlace, with the addition of various clipper and trigger circuits, maybe even adding an extra valve to the sync circuits. The later large screen ( >12 inch) sets late 50's to 60's dont seem to do to badly on the original sync waveform. And remember it was the programmes you watched not the Test Card or the lines!, it's ok to nit-pick about the lack of interlace or frame (oops I mean Field!) scan jitters, but the standard should be maintained as it was, with nothing added, its bad anough that they (BBC etc..) take away some lines of the pictue for the letterboxing of most programmes today, making our 405-line pictures have even less lines. It may be best to have it (the corruption of the 405 sync) switchable so a few people can say " oh look at the quality of the interlace! " And while I'm at it (whinging that is..) whats the sudden interest in all these other line standards, 441, 362.5, etc.. it's supposed to be " 405 Alive " cant we keep at least one thing British! I know there was the Baird electronic system but with only about 4.5 sets in the world and most of those are in America. In my small way I have kept a few people (and one American export) and their 405-line sets happy, orders for my Domino (Blatent advertising!!) converter have slowed to a dry riverbed, so I dont know how many UK 405-line television collectors will go for the Aurora converter but I wish you well in your endeavours. all the best Malcolm (now on only one Prozac a day!) (please do not PM me, email is best..)