[QuadList] Gene Kelley Show color recordingsystem--which wasused?

[Don Norwood]

Hi Dennis and Park:

I think there may be some confusion as to what types of quad recordings have 
been discussed.  There were some "experimental" color recordings that were 
made before the standards were adopted.  I don't know what methods may have 
been used to record and playback those tapes.

However, as far as the color versions of the RCA TRT-1 machines and the 
Ampex VR-1000, the recordings were direct but the recovery was not.  As Park 
indicated, this predates the development of Colortec and CATC.  RCA and 
Ampex used different methods to produce the color playback.  RCA used 
bandpass filters to separate the luma and chroma from the composite playback 
signal, then used a heterodyne process to remove the phase errors from the 
chroma and recombine it with the luma to form the corrected color composite 
output.  Ampex used a different approach and decoded the composite signal 
into Y, I & Q, and then re-encoded the signal using station reference 3.58. 
Since in both systems the recording process was direct, a first generation 
recording can be played back with fully phased color, but a second 
generation must be played back in the non-phased color mode.

In low-band color, the carrier deviation was restricted to 1 MHz (5.5 to 6.5 
MHz) in order to minimize the sidebands which occurred at that operating 
frequency.  While this did limit the S/N ratio, it didn't limit the 
bandwidth of the recorded signal which was still 4.1 MHz, allowing direct 
recording of the video signal.  All of this is very different from the 
color-under heterodyne approach used for the helical formats.

The above is simplified but is based on information from both Ampex and RCA 
documents that I have as well as a 1960 text from Julian Bernstein entitled 
"Video Tape Recording".  Bernstein's book is especially helpful in that it 
compares the RCA and Ampex machines.  Another good reference that provides 
similar info is the Harold Ennes "Tape and Disc Recording Systems", 
available in several different editions beginning in 1973.

The very first quad machines I ever operated were TRT-1Bs.  Those machines 
are now in the hands of another collector.  I didn't know much about how the 
machines worked then, and my later experience has been mostly with Ampex 
decks, but those monstrous TRT-1's were what started my addiction to 
videotape machines!

Interestingly, I received a tape today that came originally from Mark 
Amistead Productions in Hollywood.  The label says that the first segment is 
a master recorded in LBC on an RCA machine and that the second segment is a 
HBC master.  I don't know what the content is, so it will be interesting to 
see what's really on the tape.

Don


----- Original Message ----- 
From: "Dennis Degan" <DennyD1 at verizon.net>
To: "Quad List" <quadlist at quadvideotapegroup.com>
Sent: Monday, December 29, 2008 1:54 PM
Subject: Re: [QuadList] Gene Kelley Show color recordingsystem--which 
wasused?


>
> On Dec 29, 2008, at 11:05 AM, C. Park Seward wrote:
>
> > Would the reason for heterodyne playback be because the time base
> stability was not tight enough and Colortec hadn't been invented yet?
>
> I offer:
>
> I don't think that was the reason.  Heterodyne color was used for the same 
> reason it was later used in U-Matic, VHS, and Beta:  The machines simply 
> didn't have the bandwidth for direct color.  You'll recall that when 
> low-band color came along, it had a much narrower bandwidth than 
> monochrome, which made the LB color tapes that much more noisy.  It could 
> be argued that the Het color recordings actually could be made clearer 
> than later direct color low band recordings because of the LB color tapes' 
> narrower bandwidth.  To some, it must have looked like a step backwards. 
> Of course, when high-band came along, it was used for both color and B/W, 
> so they both looked very good (certainly better than either LB color OR 
> Het color!).
>
> Dennis Degan, Editor-Consultant-Knowledge Bank
>   NBC Today Show, New York
>
>
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