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  #16  
Old 09-28-2016, 10:05 AM
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Speaking of UHF, I got in an auction, one of the RF modulators used at one of the UHF stations in the area. Among a weird coaxial baseband video input, it also has the emergency broadcast inputs too. And when I got it, it was still set on the frequency that the station aired, it was never messed with.
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  #17  
Old 09-28-2016, 10:26 AM
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Quote:
Originally Posted by Electronic M View Post
I know someone with a VIR set that has a gassy CRT.
My parents bought a GE 25" console with VIR new in '77. Lasted until '83. Been looking for a VIR equipped set for many years and never found one.
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  #18  
Old 09-28-2016, 11:03 AM
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Quote:
Originally Posted by Kamakiri View Post
My parents bought a GE 25" console with VIR new in '77. Lasted until '83. Been looking for a VIR equipped set for many years and never found one.
His is a 19" GE...I don't know if he would sell it, but I could check.
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  #19  
Old 09-28-2016, 11:05 AM
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So I'm guessing VIR has nothing to do with the auto color button on my TV?
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  #20  
Old 09-28-2016, 12:15 PM
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Quote:
Originally Posted by kf4rca View Post
VIR was required till the end of analog transmission. The ONLY set I ever remember that utilized it was a 19 inch GE that was installed at a station I worked at in '77 in SC.
And I remember seeing a Sylvania that used the GCR in the 90's.
That's what I thought, only really seen it on the GE 19" with that red VIR light on controls panel. What a pity as VIR was a brilliant innovation
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  #21  
Old 09-29-2016, 12:55 AM
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=old_tv_nut;3170654
The local burst must be reinserted to standard amplitude and clean waveform per FCC rules. Therefore, it at least loses its relation to the chroma amplitude, which may have changed due to analog transmission distortion over the network. In practice, the reinserted phase is also adjustable and therefore can be misadjusted. If there is significant phase distortion of the chroma over the network, the phase of the incoming burst may also vary over its width, making it difficult to know where to set the phase of the re-inserted burst. The VIR reference had a much wider burst of chroma during the active line, which was supposed to fix this by ignoring edge distortions. ..
The whole idea of VIR was to insert it at the originating studio and not replace it anywhere along the chain, not even at network central control; but not every program had it inserted...
Some great info there!
Brilliant of General Electric to have a wider burst in active line - and at a luminance level of a typical flesh tone!

So, to me, the "problems" would have been easily avoidable with good broadcasting practice:
For example source material with VIR needed to be first reclaibrated thru a professional VIR processor
that also regenerated burst & VIR (with exact phase similitude) to the gated line 19 sample).
Was there such an instrument?

Last edited by NewVista; 09-29-2016 at 12:59 AM.
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  #22  
Old 09-29-2016, 08:51 AM
kf4rca kf4rca is offline
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I remember quad videotapes (2 inch) coming in that had a sticker saying "Protected by VIRS- adjust proc amp to pass."
In reality burst and sync got "regenerated" 2 times. After leaving the switcher it went to a proc amp where it would get black and white clip and agc. (I thought the best AGC amp was the RCA TA19. You could always tell a station that had one of these on the air.) Sync and burst would also be regenerated. Then it went to the virs inserter where it sync and burst would be regenerated again.
NOW, all of this is ahead of a pre-corrector that was required to compensate for non-linearities in the modulation process of the transmitter. It had to look flat on the air.
AND don't forget the low pass filter. Video was band limited to 4.2 MHZ to avoid components bleeding over into the sound at 4.5 MHz.
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  #23  
Old 09-29-2016, 10:51 PM
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Quote:
Originally Posted by old_tv_nut View Post
.. If there is significant phase distortion of the chroma over the network, the phase of the incoming burst may also vary over its width, making it difficult to know where to set the phase of the re-inserted burst. The VIR reference had a much wider burst of chroma during the active line, which was supposed to fix this by ignoring edge distortions. .
Didn't know of this problem of burst phase distortion , nevertheless the burst must be the reference for regeneration I would think and not the higher level VIR chroma which may have phase shift wrt the burst?

To eliminate any guesswork, just have color bars on another vert interval line!
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  #24  
Old 09-30-2016, 09:43 AM
kf4rca kf4rca is offline
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They DO run a line of color bars. But one of the biggest problems of NTSC is that it was compromised from the beginning. It had to fit in the same space as the existing B&W system.
As a result the bandwidth of the chrominance was limited. The I components were limited to 1.5 MHz and Q is limited to .5 Mhz. Not much detail in the color. AND its not even symmetrical. How screwey is that???
NOW, in Japan they had an analog HD system called the MUSE which I've heard took a 12 MHz channel. So when color (and HD) came along ,they should have allowed MORE bandwidth than what the old B&W system started out with.
SO, even today we are stuck with the constraints of an old system.
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  #25  
Old 09-30-2016, 08:58 PM
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Quote:
Originally Posted by kf4rca View Post
They DO run a line of color bars. .
I've seen them sometimes at top of underscanned picture.
So alternatively, this is as good as VIR insomuch as there should be no guesswork for the tech before adding new VIR before transmission, as all he has to do is line up the color bars in the vectorscope avoiding subjectivity.

And since, by 1975, NTSC still had 40 more years (counting cable), LSI chips could have been produced for consumer TVs to either derive reference from V.I. colorbars or VIR and making this the default mode of the receivers - keeping consumers' fingers away from contrast and tint - if not also saturation - knobs!
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  #26  
Old 09-30-2016, 11:51 PM
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Cool early 80's GE projection with vir on ebay.

http://www.ebay.com/itm/Vintage-Anti...sAAOSwHoFXu0Kd
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  #27  
Old 10-01-2016, 12:49 AM
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Originally Posted by dishdude View Post
Cool early 80's GE projection with vir on ebay.
That set has 'VIR II' - wonder what improvements were made by then (1982)?

Magazine article on VIR

Last edited by NewVista; 10-01-2016 at 10:46 AM. Reason: fixed link
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  #28  
Old 10-01-2016, 07:18 PM
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Had a Mot WARDS 19" with the VIR back in late 70s we paid $444 for brand new.. Great set till the fly shorted. Neighbor had a similar WARD set they tossed with a dead Vertical circuit. Swapped they Flys and it was up and runnin till i sold it years later and the vertical died 2 yrs after and it was tossed..

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  #29  
Old 10-02-2016, 02:25 PM
kf4rca kf4rca is offline
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Not sure what VIR2 is. Never heard of that.
Even before the HD switchover, stations were going digital in NTSC days.
I remember spots and syndicated programs coming in as a file from a digital satellite.
The files were fed directly to the playout server (a raid 5 computer). And then to air.
Sometimes the programs had low video or high chroma. Since it never went to analog at the station there was no way to adjust it.
This was eventually corrected as stations raised hell with the syndicators. Turns out the spots and programs had been uplinked by a secretary who had no knowledge of video parameters.
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  #30  
Old 10-05-2016, 09:42 AM
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Quote:
Originally Posted by Boobtubeman View Post
Had a Mot WARDS 19" with the VIR back in late 70s .. Great set...

SR
Did it make much difference when you ran it with VIR switched 'on'?
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