Quote:
Originally Posted by earlyfilm
You posted at 12:35 and I copied it at 1:55, but when I went to view it on my better monitor at home at 5:30PM it was gone. I assumed that you had canceled it to correct the upside down drawings.
If I've done this reply correctly, it is attached.
Jas.
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That's the one, thanks. Yes, I did correct the upsidedown drawing and posted it. But later it was gone. Very odd.
I suspect their were many variations to the CPA demodulator. Note from the time this article was written, it appeared that CPA support was dying. I believe it was just too difficult to implement effectively in 1952.
Note the upside of IQ and a lower subcarrier frequency was elimination of the crosstalk and the bothersome flicker. The downside was reduced Q resolution and the lower subcarrier frequency reduced the luma bandwidth hence luma resolution.
Engineering is all about trade offs.
A sidenote: the BBC was planning to adopt a modified NTSC as late as 1966. The UK 625 line channel is 8MHz wide with the sound carrier 6.0MHz away from the video carrier. This means that the bandwidth was available for full double sideband chroma (4.43MHz +/- 1.4MHz). Hence IQ working in the UK would not have been necessary. The UK could have had wide matching bandwidth for B-Y and R-Y. The dropping of NTSC in favor of PAL in the UK was very late. Proof of this were the rubidium frequency standards used at Television Centre and Lime Grove in London: the standards were cut for NTSC and augmented equipment was required to provide the PAL subcarrier frequency (1/4 line offset plus 25Hz).
I think NTSC for the wide channel UK 625 would have looked terrific and better than PAL.
Some may refer to NTSC as "Never Twice the Same Color"
But in a similar vein, PAL may be referred to as "Problems are Lurking"