[QuadList] History - what is the REAL story

[C. Park Seward]

Don,

Thanks for your great email. Yes, stories sometimes take on a life of  
their own after 50 years.

Interesting that the color quad standard was not the RCA one but the  
one developed by Ampex. I guess it was the development of the Colortec  
that enabled color.

So it's possible Jim was not clear or my question was not correct.  
More research to be done.

 From Broadcast Engineering:

The November 2002 Freezeframe question, “Name the early TBCs from RCA  
and Ampex, define the acronym and tell the key difference between the  
two,” resulted in some great answers.


Exacting and correct answers were received from David Fibush, Don  
Eckis, Jim Borgioli, John Turner and Tim Stoffel. Shown below are  
answers from Turner and Stoffel. For you newbies out there, this  
represents real history!

Editor's note: This question generated a number of excellent  
responses. Shown below are two of the most complete answers to the  
question.

 From John Turner:

First of all, you cannot equate AMTEC and CAVEC to each other as they  
perform very different signal corrections.

AMTEC:

This is an electronically variable delay line based on varicap diodes  
invented by Charles Colson of WBBM-TV and originally called ColTEC.  
When Ampex hired Colson away from WBBM, the name was changed to the  
“Ampex Time Element Compensator”, i.e., AMTEC. When used with the  
Ampex “Intersync” servo, the machine would output FCC stable  
monochrome video.

The RCA equivalent to AMTEC was called MATC for “Monochrome Automatic  
Timing Corrector,” which worked with the RCA “Pixlock” servo.

For color stability, the manufacturers used COLORTEC and CATC  
circuitry, respectively.

CAVEC:

This was a module (at least pre TR-600) that performed two very  
different functions. The acronym stands for “Chroma Amplitude and  
Velocity Error Corrector.” The Ampex equivalent to the RCA “CA___” was  
the “AutoChroma” circuitry. This portion of the CAVEC acted to  
equalize on a line-by-line basis the amplitude variations of chroma  
using the fixed amplitude of demod burst as a reference. The  
correction was applied to the demod and had nothing to do with the  
downstream TBC systems.

The RCA “__VEC” section is analogous to the Ampex “Velcomp” accessory.  
Both of these devices measured the burst phase at the beginning and  
end of a single line. This data was used to create a line time linear  
ramp error signal, which was added back in to the TBC error signal to  
reduce the appearance of color hues that shift horizontally across a  
picture. This correction was needed due to the “step” nature of the  
MATC/CATC/AMTEC/COLORTEC error signal derivation.

Just my two cents.
John Turner
Proud owner of Camden and Redwood City Big Iron

 From Tim Stoffel:

AMTEC-AMPEX Ampex Time Element Compensator

CAVEC-RCA Chroma Amplitude and Velocity Error Corrector

The timing corrector used in earlier quad VTRs consisted of three  
blocks. These timing correctors used electronically variable delay  
lines to effect their correction. The first of these three was a  
coarse timing error corrector. This corrector would eliminate all but  
say, 30 nanoseconds, of timing jitter. (The input jitter had to be low  
to begin with. This is why video heads had air bearings and the female  
guide position was servo'ed.) This was good enough for black and white.

The Ampex device for this was the AMTEC (invented by Charlie Coleman,  
who lives out here somewhere in the deserts of Nevada), and the RCA  
device was the ATC (Automatic Timing Corrector). (RCA loved acronyms!  
A good future question would be to define some of them, like BALPS,  
BALLS and PLACH.)

The second of the three correction steps was a fine corrector. This  
corrector worked to get the residual jitter down to a point where  
color was possible. It used a shorter but faster variable delay line.  
The Ampex device for this was the COLORTEC. The RCA device was the CATC.

The third stage of timing correction, which was optional, removed  
residual errors caused by changes in video head velocity as the head  
scanned through each band of the picture. These errors were of a  
nature that required an analog memory circuit to keep track of the  
error from beginning to end of a video line, as well as the average  
error for each line in a band, for each of the four heads. These  
devices, which were bleeding-edge technology for their time, were  
generically referred to as velocity compensators. Their error  
correction signal was summed into the CATC or COLORTEC's error signal.  
The RCA velocity compensator was called the CAVEC, and the Ampex  
velocity compensator was simply called an “Automatic Velocity  
Compensator.”


Best,
Park

C. Park Seward
Visit us: http://www.videopark.com



On Apr 29, 2009, at 8:09 PM, Don Norwood wrote:

> Hi Park:
>
> Much of this very same discussion about RCA and Ampex took place on  
> the Ampex mail list at various times between 1999 and 2005.  During  
> that time, a number of former Ampex employees contributed to the  
> discussion including Ross Snyder who was video products manager at  
> the time of the events in question, David Sarser, Stan Busby and  
> others.
>
> Unfortunately, after almost 50 years, there are some differences in  
> first-hand accounts. Consequently, written material from the actual  
> time period tends to be more accurate.  Still, there was total  
> agreement in these exchanges that what Ampex wanted and got from RCA  
> was rights to their color technology, and that is borne out in the  
> written documents on the subject as well.  I'm fairly certain based  
> on verifiable information that it was indeed color technology, and  
> not transistor technology, that Ampex received in exchange for their  
> knowledge of the FM recording system.
>
> That being said, the sort of conversation that you had with Jim  
> offers fascinating insight into what it was like "back in the day".   
> The stories from all the folks that were actually present comprise a  
> fascinating look into the history of this technology.    
> Unfortunately, Ross Snyder passed away last year and there is an all  
> too quickly vanishing opportunity to capture the memories of others  
> in the esteemed group.  However, while I cherish the stories I've  
> heard, I'm always mindful of the need to consider the effects of  
> time on the accuracy of the details.
>
> Below is an excerpt from what I posted on the Ampex list in early  
> 2005.  It sumarizes the outcome of my research at that time and the  
> conversations with the folks who worked at Ampex at the time of the  
> color developments:
>
> Thanks to everyone for all your input regarding the development of  
> color
> capability for the quad machines!  As Larry pointed out, there's  
> lots of
> sometimes conflicting information, and often from good sources that  
> may have
> been involved in different aspects of the project.  Since I wasn't old
> enough in the late 50's to be aware of videotape, all of my  
> knowledge has to
> be built on what I can learn from experts such as yourselves and  
> from what
> printed material I can find.  My collection of machines consists  
> only of
> Ampex but the first VTR's I ever saw were RCA and they were probably
> responsible for my lifelong fascination with these beasts.
>
> There's lots of documented info on the VR-1000 development, both from
> Ginsburg and Dolby.  After that, I have been able to find less info  
> about
> the ongoing developments through the years.  RCA published  
> 'Broadcast News'
> which did a fairly good job of documenting their product development  
> but I
> do not have similar info from Ampex.  Having gone through a lot of the
> printed material I have, here are my findings, some of which support  
> what
> has been said here and some of which may need more discussion or
> clarification.
>
> 1)  Ampex was experimenting with color in 1957.  At that time, they  
> had
> given a development contract to Stanford Research Institute, and  
> they were
> attempting to achieve color by perfecting the servo system of the  
> machine to
> a point where timebase errors would be almost non-existent.   
> Mechanical
> limitations proved this to be impossible.  According to Dolby's  
> notes as
> presented to SMPTE in 1986, on Aug 28, 1957 he demonstrated a pilot  
> tone
> system to achieve color and noted that "color stability appears to  
> be good".
> Beyond that point, I can find no further reference to this method  
> being
> considered for use on the quads and as far as I know, it was not  
> used until
> the helical machines applied a similar approach in the 60's.
>
> 2)  At about this same time, RCA demonstrated a color tape system to  
> the
> trade press in October of '57.  The February 1958 edition of  
> "Broadcast
> News" previews the new "Color Processing in RCA Video Tape  
> Recorder".  A
> small number of prototypes were delivered to NBC in 1958 as the  
> model VTRX
> quads.  These used the heterodyne system that would later be the  
> basis for
> their first production color machines.  In 1959 (month unknown but  
> see #3
> below), they began delivery of the color rack for updating the RCA  
> TRT-1A
> quads.  A later updated version of the color system was made  
> available the
> following year in 1960 (month unknown) with the delivery of the TRT-1B
> machines.  References for this info include "Engineering Color Video  
> Tape
> Recording" by A.H. Lind.
> Finally, to wrap up an already too long post, there are a couple of  
> books that are good sources of information about both RCA and Ampex  
> machines.
>
>     "Video Tape Recording" by Julian Bernstein, copyright 1960 by  
> John F. Rider, 268 pages, covers the VR-1000 and the TRT-1 and their  
> respective color systems.
>     "Television Broadcasting Tape and Disc Recording Systems" by  
> Harold E. Ennes, copyright 1973 by Howard W. Sams, ISBN  
> 0-672-20933-0, 576 pages, covers everything from the first models up  
> through the ACR-25 and the TCR-100.  There is also a second edition  
> published in 1979 (ISBN 0-672-21567-5) that is updated accordingly  
> but actually contains less info on the early models.
>
> Both books are available on Amazon and the Ennes books are cheap!   
> Good additions to your ancient technology libraries.
>
> Don
>
> ----- Original Message -----
> From: "C. Park Seward" <park at videopark.com>
> To: "Quad List" <quadlist at quadvideotapegroup.com>
> Sent: Wednesday, April 29, 2009 4:39 PM
> Subject: Re: [QuadList] History - what is the REAL story
>
> > Jim Wheeler joined Ampex five years after the first Quad was
> > introduced. I had the pleasure of speaking with him today and asked
> > him about our question.
> >
> > Jim was familiar with the Ampex/RCA exchange and said Ampex got
> > transistor technology plus $100,000 and RCA got the FM patent. As we
> > know, analog video needs FM recording to make the VTR possible.
> > Without that patent, RCA would have never made compatible quad VTRs.
> >
> > He said RCA was first with experimental color recording. They used a
> > direct recording with heterodyning playback. This was the method  
> used
> > in the famous Astaire recording. Ampex invented high band direct  
> color
> > record and direct color playback in 1964.
> >
> > Jim was the inventor sol-mo replays, of the air bearing effect of  
> the
> > Ampex scanners, the VR-660, the AST slo-mo heads and the product
> > manager for the VPR-1 and 2.
> >
> > Best,
> > Park
> >
> > C. Park Seward
> > Visit us: http://www.videopark.com
> >
> _______________________________________________
> Please trim posts to relevant info when replying!
> Send QuadList list posts to QuadList at quadvideotapegroup.com
> Your subscribe, unsubscribe and digest options are here:
> http://mail.quadvideotapegroup.com/mailman/listinfo/quadlist_quadvideotapegroup.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://quadvideotapegroup.com/pipermail/quadlist_quadvideotapegroup.com/attachments/20090430/f6a1e756/attachment-0004.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 207be04_01.jpg
Type: image/jpeg
Size: 35175 bytes
Desc: not available
URL: <http://quadvideotapegroup.com/pipermail/quadlist_quadvideotapegroup.com/attachments/20090430/f6a1e756/attachment-0002.jpg>