"Geoffrey S. Mendelson" wrote:

Martin Brown wrote:
The main difference seemed to be like with RIAA equalisation that the
Japanese engineers read the specification and implemented it fully where
as the US engineered version was "near enough" and cheaper.

PAL was more complex still but got around the inherent drift problems by
having phase alternate line so on average chroma drifts cancel out.

According to many postings here, NTSC originated the alternating line
phase shift.

It was not necessary in the US due to the difference in the way that
TV signals were disseminated off the air, e.g. between the studio and
the transmitter.

The problem with the odd color shifts, or lack of color stability in
the US was usually a problem between the camera and the transmitter
due to something not being properly adjusted.

Bear in mind that the US had NTSC on the street in the 1953,
the BBC did not broadcast in color at all until the end of 1967, and
regularly two years later.

So if there was any reason to adopt the phase alternating line color
sync (which there was in retrospect), the BBC had 14 years to figure it
out.


The phase shift in the chroma was mot obvious on coast to coast
network feeds, when it was carried on a mix of coaxial and microwave
networks. The addition of VITS eliminated the need to adjust the
equalization at every hop. This has been discussed repeatedly, but the
British trolls just can't grasp the concept. The earliest US TV network
feeds didn't cross the country. 16 mm film was sent to various regions,
and live national news didn't have the bandwidth for a flat response so
detail was lost. Even worse was Kinescope film for Monochrome time
shifting, or for places with no network feed. Hell, the TV stations in
Alaska were still getting their network feed on 2" video tape into the
mid '70s because Sat TV wasn't available, and the White Alice network
just didn't have the spare bandwidth for video. It barely handled the
AFN radio network and military TTY. Of course, it was built in the '40s
for military communications, then opened to civilian traffic at a later
date.

Color in house, and over the STL to the transmitter was no problem,
once all vacuum tube equipment was phased out. The station's sync
generator & vectorscopes took care of that. hell, I had a two studio
feed set up for a telethon in the '80s with each studio 30 miles from
the transmitter and could fade from one studio to the other with no
phase shift. A pair of TBCs, but no VITS. We had the phase error well
under .1% which was the limit of the TBCs calibration.