View Full Version : RCA vs CBS


ceebee23
01-06-2017, 06:08 PM
An article from 1953 explaining the difference between CBS and RCA color camera setups.... with CBS' field sequential output being transcoded using their Chromacoder system into NTSC standards

Image courtesy of XRayDelta at Flickr

Full size version here: https://www.flickr.com/photos/x-ray_delta_one/31249802184/sizes/o/

old_tv_nut
01-06-2017, 06:32 PM
Other descriptions of the Chromacoder have shown three CRTs to feed the three "transfer" tubes.

http://www.earlytelevision.org/pdf/r-e-engineering-12-54.pdf

WA3WLJ
01-06-2017, 08:17 PM
What's with all the BEER sitting on the table ?!?

ohohyodafarted
01-06-2017, 08:17 PM
And so you end up with a second generation picture of a B&W picture tube. Whoopty Doo!

Penthode
01-06-2017, 10:41 PM
I had no idea CBS would have attempted to use a B&W TK11 for NTSC color!

It is does appear feasible however. And the CBS method would eliminate convergence problems. My guess how it worked was like this:

The only modification would to speed up the disc to 6 x 29.97Hz (NTSC picture rate). This means the CBS camera color field rate would be raised from 144 f/s (6 x 24) to 179.82 f/s (6 x 29.97). The transfer tubes are simply primitive rescaling converters.

I suspect the picture resolution was not as good as a TK40, but the solution would at least have likely made Bill Paley less angry with Peter Goldmark. :thmbsp:

Funny I saw Wayne's excellent descriptive posting only after I guessed the process. The article said 180 color frames per second nominal but the actual NTSC rate would be 179.82 color frames per second.

old_tv_nut
01-06-2017, 10:53 PM
... And the CBS method would eliminate convergence problems...

Actually, the scheme with one monochrome CRT and three storage tubes would have the same registration problems as a 3-tube camera, and the later scheme with 3 CRTs could be twice as bad. In my opinion, the Chromacoder was a "tour de farce" as bad as RCA's experiments with high-speed linear video tape.

David Roper
01-08-2017, 09:24 AM
I know the wheel turned considerably faster for Chromacoder than for the CBS fs standard. I also know that the interim step scanned the line top-to-bottom rather than side-to-side, that is, the image that the fs camera delivered to the three NTSC cameras was, although right side up, being scanned at a 90 degree rotation.

Sorry, I know I'm not explaining it well and I can't seem to locate the detailed article I read (a long time ago) that explains the technical aspects in depth.

old_tv_nut
01-08-2017, 12:13 PM
Fink's 1957 Television Engineering Handbook notes the rotated scanning raster in the Chromacoder cameras, but does not have a drawing illustrating it. It also has a list of technical cautions about getting good pictures through it.

Penthode
01-12-2017, 12:23 AM
Actually, the scheme with one monochrome CRT and three storage tubes would have the same registration problems as a 3-tube camera, and the later scheme with 3 CRTs could be twice as bad. In my opinion.

Yes my mistake. I confused the "transfer tubes" with simple photoelectric pickup devices. Of course the transfer tubes are creating the final 525 rasters which have to be registered. :thumbsdn:

ceebee23
01-12-2017, 12:35 AM
How did NASA color system worked..since they essentially used a CBS style spinning disk rgb sequential camera to generate NTSC signals on the later moon missions?

old_tv_nut
01-12-2017, 03:14 PM
How did NASA color system worked..since they essentially used a CBS style spinning disk rgb sequential camera to generate NTSC signals on the later moon missions?

They used an analog magnetic disc to record each field and play it back three times.

See p.12:
https://www.hq.nasa.gov/alsj/ApolloTV-Acrobat5.pdf