Color Line

Progress of the National Television System Committee (NTSC)

NTSC FLAG

The NTSC Pennant
Note: The NTSC Pennant illustrates the NTSC concept of transmitting full color in large areas, two-color information (orange-cyan I axis) in medium sized areas, and only luminance information in small details.

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As RCA-originated documentation is readily available, most historians incorrectly give all credit for the development of the U.S. color television system to RCA. It is not widely known that the first RCA Dot-Sequential Color System, as demonstrated during the 1949-1950 FCC hearing, was evaluated by the FCC as not acceptable. On September 1, 1950 the FCC reported that the poor performance of color fidelity, interfering dot and line crawl patterns, poor registration, and high studio and receiver cost associated with the RCA system precluded its adoption. They further stated that during no demonstration of record did the RCA system ever present acceptable color pictures.

It was within this framework that the entire television industry banded together to devise suitable compatible color television standards under the aegis of the National Television System Committee (NTSC). The chronological details of the creation and organization of the NTSC will be documented in future versions of this paper. The following is a summary of the NTSC efforts as excerpted from my IEEE paper.

Certainly RCA should be credited for developing the total set of integrated hardware elements , including studio, transmission, and receiver equipment, for a complete color television system - and it was RCA who almost single handily continued to fund the development and marketing of color television for more than ten years until its acceptance. However, it was the effort of the participants of the NTSC whose conceptual contributions made the U.S. color system acceptable and successful.

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Development of the NTSC Color Standards

Even before the demise of the CBS Color system, the industry began its cooperation to devise a suitable compatible color system. The early RCA system consisted of time-multiplexed sharp sampling of low band passed R,G, B components and the transmission of high frequency summed R,G, and B information. It took the efforts of the NTSC to recognize that this was a form of a subcarrier modulation process.

On April 6, 1950, the Hazeltine Corporation demonstrated its constant luminance concept. At that same time Hazeltine also introduced its "shunted monochrome" concept whereby the entire 4 MHz monochrome signal was transmitted (RCA had only transmitted "mixed highs"). On December 5, 1950, RCA demonstrated its improved system using the same "bypassed" concept (as they called it) which resulted in greatly reduced moire patterns on their early coarse shadow mask CRTs.

On July 28, 1950, General Electric announced a frequency interlaced color system and by February, 1950, Philco demonstrated a color signal with wide band luminance and two color difference signals encoded by a quadrature modulated subcarrier. Shortly after the first June 18, 1951 meeting of the reorganized NTSC, a demonstration was given the week of August 6, 1951 by G.E., Hazeltine, RCA, and Philco of a signal employing constant luminance and a Color Phase Alternation (CPA) field rate oscillating color sequence. Interestingly, alternation at the line rate - a pivotal concept of the European PAL standard - was also considered. The NTSC field test standard published on November 26, 1951 used quadrature modulation of 1 MHz. B-Y and R-Y color difference signal, CPA, a 3.898125 MHz. subcarrier, and reference burst on a pedestal on the back porch of horizontal blanking.

Extensive field testing using this standard began in February, 1952 by a number of manufacturers with continued RCA support of studio equipment development. On February 2, 1953 the second NTSC color standard was published: CPA was abandoned because of edge flicker effects, the color subcarrier was lowered to 3.579545 MHz, the pedestal on the reference burst was dropped, and the wideband orange-cyan I axis, and narrow-band Q axis modulation scheme suggested by RCA was adopted. The elegant I-Q modulation scheme provided full color reproduction in video frequencies of less than 0.5 MHz by a Q green-purple axis and the I axis, provided two-color reproduction between 0.5 and 1.5 MHz by the orange-cyan I axis, and presented detail between 1.5 MHz and 4.2 MHz in monochrome.

The NTSC forwarded this standard to the FCC in a petition on July 22, 1953. The high level of performance of the NTSC standard for more than 40 years is tribute to the individuals and corporations who developed its various concepts.


To be continued...... (with a detailed description of all NTSC deliberations, field tests, and demonstrations)

1/12/97
Color Line

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Color Line