I came across the RCA Petition to the FCC on behalf of the NTSC for the color standard. On January 27,1953, over the air tests of what was to become the final NTSC color standard began to test consumer reactions to the compatibility of the system to viewers home receivers and reception in the field to prototype color receivers.
In 1952, after almost a year of testing CPA (Color Phase Alternation), the NTSC, by December 1952 had arrived at the assymmetrical chroma bandwidth solution (I, Q). The concern was a tradeoff between chroma resolution vs quadrature crosstalk. The CPA plan for PAF (Phase Alternate Field) and PAL (Phase Alternate Line) to compensated for the planned vestigial sideband chroma channel could not be made to work without flicker artifacts. We have to appreciate that the 64us glass delay line later used for PAL decoders was not to become available for many years and without it, PAL had to be ruled out. So RCA and the NTSC reached the compromise whereby the I chroma channel would be 1.5MHz wide and the Q 500kHz wide.
According to the petition document, January 1953 was spent by by RCA modifying the broadcast and receiving equipment leading up to the first public over the air testing on January 27, 1953 over RCA-NBC's WNBT-TV channel 4. Interestingly, the live 15minute color broadcasts orginated from Studio 3H from the RCA Building at Rockefeller Center, the first equipted color studio in the world. Studio 3H was also historic as it was from there the first public fully electronic over the air test broadcast occurred on July 7, 1936 (a month before the BBC's first demonstration at Radio Olympia in August 1936). Incidentally Studio 3H is currently the home of the daily live broadcast of MSNBC' "All In with Chris Hayes".
Test broadcasts of what was to become the standard commenced on January 27 with the NTSC voting to accept the standard on February 2, 1953. The RCA-NTSC petition leading to the FCC acceptance on December 17,1953 is attached here.
The petition includes details the two receivers that the RCA used: Prototypes number 3 and 4. Prototype 4 bear a resemblance to Prototype 5 and the CT100. Unfortunately the schematic diagrams published in the on linepetition pdf cannot be clearly discerned.
Here is the link to the 700 page petition document.
https://worldradiohistory.com/BOOKSH...n-FCC-1953.pdf