"William Sommerwerck" wrote in message
...

1) NTSC I and Q color difference, PAL R-Y, B-Y
2) Different primaries, especially green. PAL had a smaller
color
gamut.
3) Different color bandwidth for different colors. NTSC had 1.3
MHz for I and 0.5 MHz for Q. PAL was equal for R-Y and B-Y.
4) Excellent interleaving of chroma-luminance frequency
components which was largely destroyed by the phase alteration.

That isn't immediately clear to me. How badly would pahse
alteration affect
the frequency components of the subcarrier?

You left out 3.5. The I and Q primaries' color and bandwidth are
based on
how the eye actually perceives color. NTSC not only transmits
more color
information, but uses the available bandwidth more effectively.


As a note, much of the advantage of points 2), 3) and 4) was
lost
on early sets which just used 0.5 MHz bandwidth for decoding
both
chroma components and bandwidth limiting the luminance signal
to
minimize chroma-luma crosstalk.

Actually, most early sets (at least RCA) had full-bandwidth
color. RCA
continued to offer such sets for two or three years. I suspect
many current
sets using digital processing are full-bandwidth, but there's no
easy way to
know which is which.


When integrated circuits became available, dual bandwidth
chroma
decoders started appearing...

Not that I'm aware of. Such sets require a second delay line,
which runs up
the cost.


as well as comb filters to separate the luminance and chroma
signals.

Correct.


More accurate phosphors were also gradually used in
sets. The result was a major improvement in picture quality
with
the original 1953 broadcast standards. No such receiver
improvement was possible with the PAL system.

Oh? Why?

1) They were stuck with the smaller color gamut because of the
color primary choices used in the encoding.
2) They could not use wide bandwidth decoders because the chroma
encoding was equal bandwidth.
3) Comb filtering in PAL is not nearly as effective since the
chroma components are 'smeared' out rather than tightly
interleaved between the main luminance components. The phase
alteration and the 25 Hz offset of the chroma carrier in PAL
(look up Hannover bars) kills the effective use of comb filters.

Your point 3.5 is well taken. Regarding the second delay line,
the extra delay needed in the I channel was just a simple lumped
component all pass filter that could be fabricated at very low
cost. I also remember the time when early VCRs actually included
the NTSC pre-distortion phase compensator that was part of the
broadcast standard to compensate for the nonlinear delay of the
IF stages in the receivers. The theory was that you pay only once
in the broadcast encoder rather than in every TV set. I actually
bought a few of these on the replacement part market to use in
other video projects for about $1.00 each. It was a passive
module with three leads containing a few inductors and
capacitors. I installed one in a RF modulator I had and they sure
eliminated the chroma smear and sharpened up the luminance. It is
interesting that even with SAW IF filters which could have been
made with uniform group delay, they are fabricated to reproduce
the delay characteristics of the older tuned inductor-transformer
IF amplifiers.

David