Umatic variants

[ARC Tech-109]

US spec BVU was geared more towards integration to the broadcast infrastructure than the VO series, transformer balanced XLR's for the audio external hard genlock, framing servo and the external TBC rear panel connector for the optional Sony BVT time base corrector. There were some improvements with the chroma/luma separation and bandpass filters but the biggest thing was the BVU is far more mechanically robust than the VO series. Dynamic tracking and tape tension, the switching power supply and additional shielding really set the BVU apart. The decks were far more service man friendly despite the addl weight.

Regardless of the baseband the 3/4 U-Matic is still a heterodyne composite format and is limited by the chroma/luma bandpass filters. With the chroma down to 688 khz it's only about 100 khz wide giving it a resolution of about 30 horizontal lines. The luma passband is cut off around 3.08 MHz giving it an academic resolution of about 250 horizontal lines that is similar to VHS Betamax and Video -8. In reality the U-Matic format looks far better than the aforementioned formats due to the higher head writing velocity, linear tape speed and overall stability of that flywheel head drum.
I can't speak to the difference between NTSC and PAL beyond my own experience of watching the BBC in its native format and my eyes feeling like two piss holes in the sand from the slower vertical refresh of 25hz. There seems to be a debate regarding the move to highband in the PAL format, this is something you have to research on your own.
To conclude the BVU is far away from the VO series in the design and overall stability, this is also reflected by the position of the decimal point of the price tag. When a few points of a stations ratings are influenced by the big picture quality and millions are at stake the BVU is a wise investment.

[DVtyro]

Originally Posted by ARC Tech-109

US spec BVU was geared more towards integration to the broadcast infrastructure than the VO series

Right, thanks, I got this.

Originally Posted by ARC Tech-109

Regardless of the baseband the 3/4 U-Matic is still a heterodyne composite format and is limited by the chroma/luma bandpass filters. With the chroma down to 688 khz it's only about 100 khz wide giving it a resolution of about 30 horizontal lines. The luma passband is cut off around 3.08 MHz giving it an academic resolution of about 250 horizontal lines that is similar to VHS Betamax and Video -8. In reality the U-Matic format looks far better than the aforementioned formats due to the higher head writing velocity, linear tape speed and overall stability of that flywheel head drum.

Um, this is what I wanted to talk about. I understand that Umatic was preferred to, say, VHS or Beta because of the pro connectors and overall integration of the pro workflow, but if we take the first generation video, it did not look better than consumer formats, and the videos that I linked support this claim.

As for stability, again, the first generation VHS looks good enough, and for further generations a TBC can be used just like for Umatic. I can see that linear Umatic sound is much better than VHS/Beta because of faster tape speed. I suppose that SVideo connector and EDIT mode on consumer SVHS/Hi8 machines could achieve similar quality as Umatic over DUB connector even for a second or third generation, am I wrong?

Anyway, I have another question that I posted in this thread, but I can repeat it here, since I am getting great answers in this thread.

The other day I was reading Umatic SP specs in a late 1980s magazine, and it said: 330 lines in monochrome mode, 240 lines in color mode. Well, I know that Umatic only has about 30-40 lines of chroma resolution, it is as pitiful as any other color-under format. So, what did they mean?

This low-band VO-5800 model shows different values for monochrome and color:



The SP VO-9800 shows the same resolution both for monochrome and color:

• Did they mean that without color, the signal is cleaner, there is no interference in the lower part of the luma band, so it actually does provide higher resolution?
• Or did they mean that colorful picture LOOKS less sharp to a human eye?
• Or something else?
• Why the numbers are the same for SP models even in the "conventional" mode (says 250 lines color/monochrome)?

Other manufacturers who made Umatic machines, did they only make low-band ones, never high-band/SP compatible?

Finally, when they talk about VHS/Beta resolution of, say, 250 lines, do they mean in monochrome mode or in color mode? I suppose they mean color mode, as base VHS is similar to base Umatic.

[old_tv_nut]

It means the luminance resolution in the different modes. Chroma resolution was not speced.

Apparently the high end machines could have more luma bandwidth in monochrome mode. Since color subcarrier was not present they didn't have to TBC to accurate color phase.

[DVtyro]

Originally Posted by old_tv_nut

It means the luminance resolution in the different modes. Chroma resolution was not speced.

Apparently the high end machines could have more luma bandwidth in monochrome mode. Since color subcarrier was not present they didn't have to TBC to accurate color phase.

Did you mean to say, "Apparently the low end machines could have more luma bandwidth in monochrome mode"? I would agree with it. So, chroma interferes with luma? And because high-band machines have wider luma bandwidth, chroma interference does not affect luma resolution that much? I am not sure how TBC is related, considering that old machines did not have built-in TBC.

[ppppenguin]

As others have said, all these machines use "colour under". The chroma is separated from the luma, heterodyned on to a much lower frequency carrier, and recorded as an AM signal. The luma is FM, as it always was.

There will always be compromises separating Y and C, especially before comb filters were common. It's also much harder in PAL than NTSC. There will also be overlap between the lower sidebands of the FM Y signal and the AM C signal. The effects of this are minimised by various means.

I'm just amazed the whole thing worked as well as it did.

625 line PAL has a wider luma bandwidth than NTSC so there was more urgency to move to high band in PAL.

[DVtyro]

Originally Posted by ppppenguin

As others have said, all these machines use "colour under". The chroma is separated from the luma, heterodyned on to a much lower frequency carrier, and recorded as an AM signal. The luma is FM, as it always was.

Sure. So why is the difference in resolution in monochrome and color mode for low-band machines, but no difference for high-band machines?

[ARC Tech-109]

Actually it has to do with the switching of the bandpass filters between color and monochrome. If no 3.58 MHz signal is present the filters are left out and the full recording bandwidth is used thus giving the 300+ lines of resolution. When the 3.58 MHz colorburst is detected the bandpass filters are switched in and everything above about 3.08 MHz is diverted to the chroma down conversion thus cutting the resolution down to the upper limits of the filters limiting the resolution to 240-250 horizontal lines, if the luma was to creep into the chroma downshift side it makes some really wierd distortions. The 250 lines for SP monochrome I suspect has to do with the chroma filters and how the signals are processed, I would have to look at the schematic to give a better explanation. It appears that the SP circuits are completely separate from the highband side. It's possible that engineering decided not to switch the filters around during highband color/monochrome being redundant and adding expense. The VO-5800 is a highband with 250 lines color, I've seen both specs published in various places. There was a medical spec VO that was monochrome only with a 330 line resolution. The 250 line limitation is the bandpass filter slope at about 3.08 MHz, the chroma side comes up at this point and is about 1 MHz wide (500 khz either side of 3.58 MHz) or 4.08 MHz. (MHz X 0.8=lines) to simplify. VHS, Betamax and Video-8 are bandwidth limited to about 240-250 lines in color recording, Betamax-1 was on the higher end of this with a faster tape speed, most of the decks would switch the filters around during monochrome to use the full recording bandwidth.


One big advantage of 3/4 over say VHS & SVHS is the video dynamic range, home grade and some of the "prosumer" VHS isn't as linear on the higher end of the luma and tends to knee and compress on the highlights. I don't know if that is design feature or flaw but it's definitely noticable. U-Matic was less about the cost compromise and focused on the professional who wasn't going to compromise on quality. Panasonic had some "pro" decks like the AG-7500 that have the higher end connectors (BNC video) but the lack of format stability made VHS unsuitable for prime broadcast. You can TBC to a certain extent but the mechanical variations once recorded are going to remain. I'm not going to trust a magazine for accuracy regardless of the source, they're not technical people and mistakes are common in advertising. RTFM (read the factory manual)

[old_tv_nut]

Let's clarify the color under process. All tape mechanisms produce timing jitter that is too great for a receiver or monitor to follow the chroma frquency and phase changes. Full bandwidth systems like quad 2 inch correct the whole baseband signal including luma and chroma.
Color under systems separate the hgh frequency part of the composite signal including chroma and luma but the only correction is the phase of the chroma and burst. The jitter of the luma between 0 and 3 MHz is acceptable uncorrected. But no chroma can be allowed to go through the luma channel because it would give a total mess of corrected and uncorrected chroma.

When the signal is known to be monochrome, the color circuits can be turned off and wider bandwidth luma can be passed through the FM luminance channel. Still jittery compared to a machine with TBC, but acceptable.

[Electronic M]

I think part of the reason early U-Matics didn't have the engineering to provide as good a picture is that the VO series was originally intended to become a consumer format at launch in 1971 and pivoted to be broadcast/prosumer orientated after it failed to get consumer traction.

I have the first U-Matic model VO-1600 as well as the second or third Betamax Sony made (rebadged as a Zenith, but besides cosmetic styling it's no different from it's Sony badged version)....Both machines are basically identical ignoring styling, tape format and the extra EIAJ-8 consumer VTR to TV interface jack on the U-Matic. Both machines have internal RF modulators, TV tuners, and had optional matching external timers for time shifting TV shows. Sony clearly meant the U-Matic to have the same consumer application as it did with the Betamax...It just didn't attract the market Sony wanted so they pivoted it's design to match the customers that were attracted to it and started working on making the Betamax in hopes it would do what U-Matic couldn't in the consumer market.

[ppppenguin]

Originally Posted by old_tv_nut

Let's clarify the color under process. All tape mechanisms produce timing jitter that is too great for a receiver or monitor to follow the chroma frquency and phase changes. Full bandwidth systems like quad 2 inch correct the whole baseband signal including luma and chroma.
Color under systems separate the hgh frequency part of the composite signal including chroma and luma but the only correction is the phase of the chroma and burst. The jitter of the luma between 0 and 3 MHz is acceptable uncorrected. But no chroma can be allowed to go through the luma channel because it would give a total mess of corrected and uncorrected chroma.

When the signal is known to be monochrome, the color circuits can be turned off and wider bandwidth luma can be passed through the FM luminance channel. Still jittery compared to a machine with TBC, but acceptable.

Thanks for the explanation. The colour under signsal from the tape is heterodyned back up to a stable subcarrier otherwise the receiver or monitor wouldn't be able to lock to the burst.

Quite apart from the jitter, a PAL, NTSC or SECAM colour signal has lots of energy at high video frequencies. Even if the FM recording system has enough bandwidth to record high frequency Y, it can struggle with signals that are both high frequency and high amplitude. Hence the use of high band on 2" quadruplex machines, especially in PAL with its higher frequency subcarrier.

I once worked with an A format (predecessor of C format) VTR that had a set of high band boards as an option (Ampex VR7003H). The pictures looked pretty good on high band and you got occasional colour lock. Only a few TBCs could correct a signal like this (Quantel 2001?) and I never had access to one. C format VTRS always had built-in TBCs designed to cope with this sort of signal.

Now we can look back, it's obvious that composite colour systems were a compromise. Quite a serious compromise. But at the time it was the best we could do and they were brilliant achievements.

[old_tv_nut]

The comment about high frequency with high amplitude being a problem is correct. RCA's ads for high band quad emphasized they could handle yellow better than the old machines.