Could NTSC VIR = PAL

[Robert Grant]

Originally Posted by ppppenguin

The concept of colour phase alternation, the basis of PAL, was considered by (I think) Hazeltine labs in the very early 1950s. While NTSC was being developed. Until there was a practical 1 line delay available at low cost the advantages of CPA were minimal. Both SECAM and PAL depended on having a 1 line delay in the receiver. Less critical for SECAM than PAL. Simple PAL receivers (without a delay line) were feasible but were hardly, if at all, marketed. The results were not good.

"Less critical for SECAM than PAL" caught my attention here.

I had always thought that the delay line was strongly encouraged in PAL for the color correction benefit, with some manufacturers leaving it out to save a few Marks (resulting in "Hanover bars", and called "Simple PAL") and others using a delay line to store alternate R-Y lines and escape patent royalties payment, wheras in SECAM a delay line would be absolutely essential as SECAM only transmitted one axis of chromience with each line.

[old_tv_nut]

Originally Posted by Robert Grant

"Less critical for SECAM than PAL" caught my attention here.

I had always thought that the delay line was strongly encouraged in PAL for the color correction benefit, with some manufacturers leaving it out to save a few Marks (resulting in "Hanover bars", and called "Simple PAL") and others using a delay line to store alternate R-Y lines and escape patent royalties payment, wheras in SECAM a delay line would be absolutely essential as SECAM only transmitted one axis of chromience with each line.

My understanding: In PAL, the length of the delay determines if the chroma is exactly phased right from line to line. In an NTSC comb filter, the exact length of the delay determines if the chroma and luma sidebands are precisely separated. In SECAM, the delay is only providing low-resolution FM chroma, so doesn't need to be so precise.

[ppppenguin]

What was the Japanese experience with their mix of 50Hz and 60Hz power?

In PAL the delay line length is very critical, to within a few degrees of subcarrier. A good NTSC comb filter is likewise critical to get good subcarrier cancellation. A SECAM delay line is relatively uncritical.