Early Television
Early Television
Early Television
Early Television
Early Television Early Television

Early Television

Home Page

The Set: Pete Deksnis's Site about the CT-100

Restoring a Vintage Color Television Set

Who Invented* Compatible Color Television?

1. (v.) To bring (a product or idea) into being:

Early Television THIS EXPERIMENTAL color television set was built for a December 1950 demonstration of the RCA compatible color television system. This set demonstrated for the first time RCA's use of a separate Y (luminance, or brightness, or black and white) signal and a chroma signal. Sometimes called bypassed monochrome, the technique was developed earlier in 1950 by the Hazeltine Laboratories of Long Island, New York. It became a major part of the NTSC system adopted three years later.

QUADRATURE MODULATION (QM) -- a technique that allows two chroma signals to be stuffed into an existing black and white television channel -- was not employed in this RCA set. QM was applied to color television by Philco, who demonstrated the application early in 1951, after this set was made. Quadrature modulation also became a major part of the NTSC system three years later.

Philco's application of QM to color TV:
  • In one Philco system, their color-minus-monochrome signals (Z - Y and X - Y) are restricted to 0.5 MHz and transmitted above the luminance signal, which is restricted to 3 MHz. (This completely eliminated the problem of fine dot strutcture interference caused by beats between luminance and chroma signals. But it limited the video resolution to that of a 3-MHz bandwith system.)
  • In a second 1951 Philco system, the luminance signal is transmitted to 4.2 MHz and the X - Y and Z - Y color signals are "interspersed" with the upper 3 to 4.2 MHz portion of the luminance signal using quadrature modulation. (Ironically, the standards adopted in 1953 forced manufacturers to limit video bandwidth to about 3 MHz until comb filters were implemented in the late 1970s.)
Early Television

THEN, BY MID-1951 the NTSC "proposed" some general standards based upon the work and demonstrations of RCA, Hazeltine, Philco, and others. It is these standards that became the basis of the refined and finalized compatible color television system adopted by the FCC in late 1953.

Early Television

General Standards -- NTSC 1951 (selected examples)
  • Standards for black and white shall be maintained for the transmission of compatible color television.
  • Chromatic information shall be transmitted by a subcarrier modulated in amplitude and phase and shall be transmitted simultaneously with and only during the video portion of the composite signal.
  • Color sync shall be maintained by placing a sample of the subcarrier frequency on horizontal blanking pedestals.
  • Color subcarrier frequency shall be an odd multiple of one-half the horizontal line frequency.
Early Television

* INVENT -- to produce or contrive (something previously
unknown) by the use of ingenuity or imagination.
Who Invented Compatible Color Television?
A combination of diverse elements
invented compatible
color tv...


[Pete's musing on Color Wars]