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  #46  
Old 02-26-2018, 01:42 AM
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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.

As for PAL N, I worked for MIchael Cox Electronics in the early 1980s when Argentina went to PAL N. We designed and supplied PAL B to PAL N transcoders as all production was done with standard PAL B kit. ISTR the pictures, as viewed side by side in the lab, weren't bad. On critical material you could tell the difference. Of course VHS and Betamax recorders reduced picture quality to below PAL N.
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  #47  
Old 02-26-2018, 08:26 AM
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Do you think Argentina, Brazil, being what they are, might have been open to a discreet bribe or two... thus leading to those bastardized systems?

How did the UK deal with US videotapes 1967 - 1980? Did they get 16mm kinephoto copies? How good were analogue NTSC -> PAL tape conversions (using glass delay-lines to repeat/insert extra lines?) Did Cox make a box for this?
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  #48  
Old 02-26-2018, 04:24 PM
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I remember watching the Andy Williams show on BBC1 (405 lines black & white) in the mid/late 1960's & the picture quality was dire = it looked blurred & any movement was jerky. Into the 70's the conversion quality improved but there was still the jerkiness & when in colour the colours were often wrong. The first live moon landing was converted twice = from 240 lines 10 frames per second to 525/60 FPS then to 405/50 FPS. The later landings looked very clear in comparison
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  #49  
Old 02-27-2018, 01:07 AM
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Cox never made field rate converters.

The world's first electronic (as against optical) 525/60 <> 625/50 converter was the BBC's analogue machine using glass delays. From 1968. I believe it worked well but was a beast to keep working nicely. The IBA "DICE" was the first digital converter and worked very well. 1971 I think. Followed by the BBC's ACE with 4 field, 4 line interpolation. This set a pretty high bar for quality until motion compensation was feasible.

Most 2" quadruplex machines were multistandard so could reply NTSC tapes in Europe. A lot of US programmes back then were produced on film which was just run 4% fast in 50Hz countries. A rather happier solution than 3:2 pulldown.

Argentina were stuck between a rock and a hard place. US channel spacing and 625/50 meant wahever they used would be unique unless they opted for a wholesale change to 525/60 and NTSC. In retrospect this might have been feasible as just about any 625/50 monochrome set will display 525/60 with minimal adjustment.
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Old 03-23-2018, 08:29 AM
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We had a 19" GE set with VIR that we got shortly after it was introduced. Ours was a 1977 model. It never worked right. Saturation and hue would just randomly jump all over the place. I have never seen faces such a brilliant shade of bright blue as on that set. It seemed to vary from one station to another, and I was convinced that our local ABC affiliate wasn't actually transmitting the signal but had some kind of noise present that tricked the TV into switching into VIR mode. Anyway we turned it off after a while.

About the same time the shop I worked in was selling Quasar TVs and in around 1979 or 1980 they came out with Super Dynacolor that also had VIR. I believe those and the GEs were the first on the market.
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  #51  
Old 03-27-2018, 09:57 PM
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The second set of controls for VIR only meant that there were two ways for the consumer to monkey with the color setting and make everything terrible with or without VIR. The awful truth of VIR to the consumer is that only GE sets seemed to support it, and GE had a reputation for lousy quality and iffy reliability.

There were three GE color 19" sets in the extended family (one a JCPenney rebadge) and each one had a CRT that went bad quickly with weak green and smeared reds. The one my mother had came with a hair-trigger color-killer that no number of shop trips could correct. I think they gave up after the 8th repair visit. The tube went south and lost correct color along with focus within 5 years from new even with minimal hours (due to that color-killer annoyance).
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  #52  
Old 03-28-2018, 07:35 AM
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A friend owns the only GE VIR set I've seen in person. That set has a gassy CRT.... it arcs between CRT elements then goes into shutdown.
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  #53  
Old 03-28-2018, 10:45 AM
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Quote:
Originally Posted by ppppenguin View Post
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.
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  #54  
Old 03-28-2018, 11:02 AM
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Originally Posted by NewVista View Post
Do you think Argentina, Brazil, being what they are, might have been open to a discreet bribe or two... thus leading to those bastardized systems?
Well, there are other reasons to consider before one comes to the conclusion that a few billion Cruzandos changed under the table.

Brazil used and still uses 60Hz utility power, so they logically used the 525-line, 60-field USA system. Like all of the Americas*, channels had/have 6MHz total bandwidth each, hence SECAM or PAL B, D, G or K were off the table. Brazil went color far later than the USA did. Whether their decision was done to reject American dominance or simply to throw away that pesky hue knob may never be known.

Argentina and Uruguay were another matter. The had/have 50Hz power. They used System N, with 625 lines at 50 fields (25 frames) per second. Like Brazil, they only started using color when the PAL system was well established, and no country ever made a standard of NTSC and 50 fields, so PAL must have seemed a logical choice.

*Excluding some Caribbean Islands that used 50-field systems from their parent countries, all either low power or cable only.
Mexico experimented with System N monochrome. A TV DXer showed me a photo of an ID slide from XEFB-TV (then channel 3), Monterrey NL. Below the call sign, it said: "Nuestra siguiente programa se ve mejor en un Phillips". This DXer told me he lost vertical hold the instant the slide was replaced by the program.

System M and system N had very closely matched matched line rates (15750 versus 15625), thus horizontal sync was no problem. It is also true that one system's vertical rate may be compensated to the other with adjustment of the vertical hold, size and linearity controls. However, having the field rate match the power supply frequency is still desirable.
I own an ATSC converter box that offers PAL B/G video output (along with 480i, 480p, 720p and 1080i).
When I fed its PAL output to my 1958 Emerson TV, the picture was sharper but with more flicker, as I expected. However, the picture wobbled in a cycle- the picture looked like an image atop a shaking bowl of jelly. My suspicion is that a 60Hz magnetic field from within my home (possibly the autotransformer power supply of the television itself) was interacting with the 50Hz field of the vertical yoke.

Last edited by Robert Grant; 03-28-2018 at 02:29 PM.
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  #55  
Old 03-28-2018, 11:24 AM
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Quote:
Originally Posted by Robert Grant View Post
Well, there are other reasons to consider before one comes to the conclusion that a few billion Cruzanandos changed under the table.

Brazil used and still uses 60Hz utility power, so they logically used the 525-line, 60-field USA system. Like all of the Americas*, channels had/have 6MHz total bandwidth each, hence SECAM or PAL B, D, G or K were off the table. Brazil went color far later than the USA did. Whether their decision was done to reject American dominance or simply to throw away that pesky hue knob may never be known.

Argentina and Uruguay were another matter. The had/have 50
There is probably some elderly engineer there or some obscure tech publication where that info exists.
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  #56  
Old 03-28-2018, 12:58 PM
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Quote:
Originally Posted by Robert Grant View Post
"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.
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  #57  
Old 03-29-2018, 01:20 AM
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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.
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  #58  
Old 03-29-2018, 09:09 AM
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Many import Japanese tube era TVs I've seen seem to have on average more and bigger lytic caps than American sets so I'd imagine they had issues and dealt with it by liberal use of capacitive filtering.
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  #59  
Old 03-29-2018, 10:07 PM
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A-ha! I see why I was confused.

In PAL, the quality (more specifically, the precision) of the delay line is critical, but the delay line can be left out if one were tolerant of "Hanover bars".

In SECAM, the mere presence of the delay line is critical (no delay line, no SECAM).
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  #60  
Old 06-26-2018, 12:58 AM
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Discovered Good article on VIR in RADIO-TELEVISION. It states VIR was designed for pro application, and only later was it extended to consumers (much the same way as DTMF routing was used behind the scenes by telcos, and only later extended to consumers.)

The article describes the use of the Tektronix 1440, a very precision instrument with no tweaking controls on front panel (unlike the consumer VIR) and how the 1440 (in a closed loop) would correct a transmitter for instance.

By providing subjective fine tuning on the home TV version, they were either admitting that they had lost the control VIR promised, or that the built-to-a-price GE circuit board lacked the precision of the pro 1440.
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