Origins of PAL: 1956 radio engeenering airticle from UK mag -- phase alternations (and effects) considered...

Origins of PAL: 1956 radio engineering article from UK mag -- phase
alternations (and effects) considered...

I can't remember the exact magazine name, however.

HDTV's origins are easier to trace, but wavlet DTV seems to be nearly absent
from all technical literature.

"http://HireMe.geek.nz/" wrote in message
...
Origins of PAL: 1956 radio engineering article from UK mag -- phase
alternations (and effects) considered...

Actually, phase alternation was considered by the NTSC team, but declined
because of several technological problems at that time.

John

"John Dyson" wrote in message
...

"http://HireMe.geek.nz/" wrote in message
...
Origins of PAL: 1956 radio engineering article from UK mag -- phase
alternations (and effects) considered...

Actually, phase alternation was considered by the NTSC team, but declined
because of several technological problems at that time.

John

I believe it was the delay-line technology that lagged behind everything.
Size perhaps ? Remenbering how big the original Philips delay lines were in
early sets. I believe there was a picture of a delay line developed for the
SECAM system that was about 2 feet long in 'Wireless World' in the early
sixties.
Mike Davison

On Sun, 10 Oct 2004 11:20:23 +0100, "J.Michael Davison"
wrote:


"John Dyson" wrote in message
...

Actually, phase alternation was considered by the NTSC team, but declined
because of several technological problems at that time.

I believe it was the delay-line technology that lagged behind everything.

You do not necessary need a delay line to receive PAL. In "Simple PAL"
used previously by some small portable receivers, the averaging was
done visually on the screen between adjacent lines.

When the Japanese TVs appeared on the European market in 1970s, they
"converted the PAL signal to NTSC" before decoding, to avoid some PAL
patent issues, apparently just inserted the PAL switch in front but
did not use the delay line.

So if the delay line was too costly for consumer electronics when NTSC
formalised the standard, the standard could have used phase
alteration, but only expensive second generation receivers would have
included this phase error cancelling a few years later.

Paul

Paul Keinanen wrote:


So if the delay line was too costly for consumer electronics when NTSC
formalised the standard, the standard could have used phase
alteration, but only expensive second generation receivers would have
included this phase error cancelling a few years later.



That's true, but a better way was used: intrinsically fix the
"problem" that PAL was designed to cover up with a kludge
solution.

The color problem for NTSC was fixed long before color sets
became big sellers. I bought a color TV set for our dorm
when I was in college in 1962, not my money of course.
This was a mid-level Heathkit set. It worked fine. The color
was quite accurate both for local originated material and
network material. You did have to adjust the "tint" control
as parts aged, but once a month or so was quite sufficient.

And, of course, semiconductors solved the problem
permanently and completely by allowing feedback circuits.

Doug McDonald

"Paul Keinanen" wrote in message
...
On Sun, 10 Oct 2004 11:20:23 +0100, "J.Michael Davison"
wrote:


"John Dyson" wrote in message
...

Actually, phase alternation was considered by the NTSC team, but
declined
because of several technological problems at that time.

I believe it was the delay-line technology that lagged behind everything.

You do not necessary need a delay line to receive PAL. In "Simple PAL"
used previously by some small portable receivers, the averaging was
done visually on the screen between adjacent lines.

True but no simple-PAL TV was ever manufactured in Europe for mass sale. If
I remember a Mullard lecture about the PAL system, the eye can
tolerate/average out a 20degree phase error. DeLuxePAL with a delay line can
correct for a 70degree phase error this being converted to an amplitude
error by the delay line so probably there would be noise apparent in the
chroma signals which is less disturbing visually than purple faces. A
5degree phase error was said to be noticeable in the NTSC system

So if the delay line was too costly for consumer electronics when NTSC
formalised the standard, the standard could have used phase
alteration, but only expensive second generation receivers would have
included this phase error cancelling a few years later.

Did I say anything about cost ? It probably did enter into it but glass
delay line technology didn't show its face until that 2feet long glass delay
line was produced for SECAM on which work began in 1956(ref Wikipedia) which
is 3 years after the NTSC system was set in stone.
Mike D.

On Sun, 10 Oct 2004 20:47:48 +0100, J.Michael Davison
wrote:

You do not necessary need a delay line to receive PAL. In "Simple PAL"
used previously by some small portable receivers, the averaging was
done visually on the screen between adjacent lines.

True but no simple-PAL TV was ever manufactured in Europe for mass sale. If
I remember a Mullard lecture about the PAL system, the eye can
tolerate/average out a 20degree phase error.

You can see phase errors much less than that, which is why all broadcast
grade 1 monitors used to use simple PAL (we struggle to buy them with the
facility these days) - you want to see the phase errors so you can do
something to correct them.

DeLuxePAL with a delay line can
correct for a 70degree phase error this being converted to an amplitude
error by the delay line

This is rather misleading. Delay line PAL can cope with any error in
principle. The thing is, the bigger the error, the more SATURATION you
lose, not amplitude. It is a function of the cosine of the phase error,
so at 90 degrees you get black and white. At 70 degrees, you have lost
2/3 of your colour, which is rather noticeable.

so probably there would be noise apparent in the chroma signals

No there wouldn't. Visually there is probably less noise on the picture
because there is less noisy chroma signal.

which is less disturbing visually than purple faces. A
5degree phase error was said to be noticeable in the NTSC system

Indeed, and it is uncorrectable if it's a differential phase errro, which
is why NTSC is so crap.

"Paul Ratcliffe" wrote in message
...



Indeed, and it is uncorrectable if it's a differential phase errro, which
is why NTSC is so crap.

"The pioneers take all the arrows."

"Sal M. Onella" wrote in message
news:[email protected]

"Paul Ratcliffe" wrote in message
...



Indeed, and it is uncorrectable if it's a differential phase errro, which
is why NTSC is so crap.

"The pioneers take all the arrows."

On worked on early RCA Color sets in 56 through 59, and some live broadcasts
out of NYC on NBC such as the Bell Telephone Hour were perfection. Even
early CBS live color broadcasts direct from film of the Wizard of Oz were
absolute perfection. No color shift or phase shift and beautiful color that
would make your mouth water. Early color video tape inserted into live shows
were noisy and lacking in resolution. Sure, my first 17 inch Sony solid
state color set was the first "perfected" NTSC color set I saw, but it
simply could not reproduce color with the beauty and accuracy of those tube
based RCA sets. Changes in color saturation was an issue until some time in
the early 60's, from what I remember. Today NTSC simply does not suffer from
any of the issues PAL was designed to address.

Richard.

Richard wrote:





Indeed, and it is uncorrectable if it's a differential phase errro, which
is why NTSC is so crap.



On worked on early RCA Color sets in 56 through 59, and some live broadcasts
out of NYC on NBC such as the Bell Telephone Hour were perfection.

I did not own a color set until 1962, but two neighbors did, one of
thm dating from the day (actually, two days BEFORE) our NBC station went
all-color locally in 1954. That one was the station's weatherman,
and his son was in some of my school classes. I personally was there
and "on camera" when the station went color.

Even in 1954 the local programming in color was quite reliable.
The color was, as others have said, gorgeous.

Most live network programming as also OK, most of the time, though
admittedly there was the occasional offset of say 10 degrees.
Early color tape could be awful. Early local color telecines were ALWAYS
awful.

The NTSC system of that day DID require that the equipment with its
myriads of overheated vacuum bottles (and no feedback!) be kept
in tune ACTIVELY ... meaning that somebody had to check it. That was
the only actual problem ... PAL would have allowed sloppiness
to be covered up.

But, of course, PAL was simply infeasible as a consumer
technology in 1950-1953 when color TV was developed ...
and we note, NOT developed by Europeans, who simply
adapted the ideas of the Americans (even, of course, SECAM,
which used a subcarrier and split luma-chroma rather than
actual RGB).

Doug McDonald