#16
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Last edited by andy; 12-07-2021 at 01:55 PM. |
#17
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Although PAL does correct for phase errors, it comes at a substantial cost. The phase errors are replaced with saturation errors, which if bad enough become Hanover Bars, and the PAL system cuts the vertical color resolution in half. With the stability of modern equipment, NTSC can actually provide a better color picture.
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#18
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This is for Jeff: The VIR signal you're talking about was usually generated at the station or mastering house using a Tektronix 1441 VIR signal Deleter/Inserter. The signal could be inserted on line 19 or 20 to give an absolute reference for amplitude and phase characteristics of a color TV program or recording. The signal placed a sample subcarrier burst of 40 IRE at 70% video level followed by a sample unmodulated 50% video pulse on the selected line. The receiver could use these two samples to lock the color reception of the set without worry about transmission distortions which might occur at or near "0" IRE where line burst reference is placed in NTSC. In essence the VIR signal was placed well above sync/subcarrier and the potential distortions which can occur in analog broadcasting.
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#19
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The original thought with VIR was that it could be inserted early in the signal path and allow correction for all that happened along the way. But then people started to reinsert it along the way, and I believe, even just before the transmitter so that it could be used to adjust the transmitter. Of course, it had no relation to all the preceding distortions then, and became useless in a consumer set. I remember doing competitive analysis of a GE set some time after VIR had been around for a while, and much of the time you would prefer to turn it off.
[EDIT - I mean turn off the VIR - but maybe you would prefer to turn off the set too! ] |
#20
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Quote:
Most if not all color televisions worked better with these systems turned off and disregarded, anyway. I shut off the auto-color control on my RCA CTC185 some time ago as it isn't needed, given today's rock-stable chroma circuits in the sets themselves (all televisions manufactured in the last decade or so, not just RCAs) and the vastly improved stability of the signals from TV stations, especially if you are on cable.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. |
Audiokarma |
#21
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Did anyone even insert the VIR signal? Does anyone even do it anymore?
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#22
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Not to incite the debate between PAL and NTSC, just remember, People Are Lavender.
With digital processing and transport in the signal path to the average consumer receiver, NTSC is vastly better than in the past. I can't however stand artifacts of digital compression. Don't even get me started on message crawls and dogs/bugs on the bottom of the screen. |
#23
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The first set I saw with VIR was a mid to late '70's GE console. I think it used the "YM" chassis. I also saw a Curtis-Mathes with the feature. On both sets, the picture looked better with VIR turned off. It was sometime in the mid '90's when I had these sets. Most of the "auto color" systems I saw were a switch that would disable the front panel adjustments and enable preset controls that were hidden inside the set. In some sets, the user controls would have limited effect with the auto color switch on. Our old '77 RCA ColorTrak 19" had a photocell that would adjust the picture according to room light. I think RCA continued to use the photocell in their better sets up until the early '90's. I've ran into plenty of Thomson era RCA's that have an auto color setting in the user menu. I really couldn't tell any difference in the picture no matter if it was on or off. Like has already been said, most TV broadcast signals are much more stable with less error than they used to be.
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#24
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We had a GE VIR set in the 80s; I never saw a great difference either way. (I was never crazy about that set; I preferred its tube predecessor) I have also seen ads for "VIR II" but I don't know the scoop on that.
Did you know that the General won an actual Emmy award for VIR?
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Bryan Last edited by bgadow; 05-10-2008 at 11:04 PM. Reason: clarify |
#25
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Quote:
GE's VIR system was a novel experiment, but it just didn't catch on with the viewing public. In fact, I'm downright surprised the system won an Emmy, since it was nowhere near the greatest thing to happen to television since color. For that matter, IMO, neither was RCA's ColorTrak system, which did not rely on signals transmitted in the vertical blanking interval but used a photocell under the CRT to adjust color and black level according to room light conditions. Magnavox, in its high-end color consoles of the '70s, had a similar system it called "Total Automatic Color" which also used a photocell to adjust the same parameters of the picture, again according to room lighting conditions. These systems, however, were not infallible; the ColorTrak system, for example, could well be "fooled" into raising the black level abnormally high (taking the color saturation with it) if, again for example, the set were being viewed in a dark or dimly-lit room. I hate to imagine what some of these ColorTrak sets' pictures may have looked like under such lighting conditions. There are people who enjoy watching television in the dark, much to the horror of eye doctors, who have been warning people for generations against watching TV in a totally-darkened room because of the very real risk of eyestrain. I guess, however, that most people who insisted on watching their TV sets in darkness or dimly-lit rooms would just turn off the ColorTrak or TAC functions of their sets, or, if they left them on, tolerated the horribly overbright, oversaturated color picture that likely resulted when the circuits were bamboozled into lowering the CRT bias to near zero and raising the color level to maximum.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. |
Audiokarma |
#26
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I am glad most or all of those "automatic"/dynamic circuits and buttons are long gone. A display device should be properly adjusted, once, for correct levels, and then left alone until it might need recalibration. The room lighting should be adjusted to allow for good display viewing, not the reverse.
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
#27
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Last edited by andy; 12-07-2021 at 01:55 PM. |
#28
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Degauser?
I remember using a little round plastic degauser that I plugged in to the wall outlet on my folks first color tv (RCA), about 1966. It was always fun to watch the weird color patterns it caused, but I'm not sure it really did anything?
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A vintage fellow Rega w/AT; Sony SACDs; McIntosh; Marantz; Adcom; DENON; DVD players; RJ Colletti; AR4x; AR2ax; AR3a; mostly Monster wire. |
#29
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But on the other hand, the color subcarrier of PAL is 4.43 MHz, the color subcarrier of NTSC is only 3.58 MHz. PAL does provide a much larger video bandwidth, and together with 25 frames per second, while NTSC has nearly 30 frames per second, the horizontal resolution is much better than with NTSC. If you watch the same video content with a PAL and with a NTSC receiver, you will find the PAL display much sharper and detailed than the NTSC display. On the other hand, with larger displays, you can notice more flicker with PAL. The color reproduction of NTSC with a proper adjusted NTSC color tv set might be much better than with a PAL set due to the higher color resolution. - Eckhard |
#30
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I discovered that the crt monitor on my work computer has a manual deguassing feature in the on-screen menu. So when I get really bored I will go on and do it, just to see the special effects!
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Bryan |
Audiokarma |
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