Quote:
Originally Posted by miniman82
The signal is amplified, then sent to a bandpass transformer to ensure that only chroma signals are passed to the following stages....
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Problem is, high frequency luma signals also get thru. Causing the crawly rainbows on referee's shirts during football games. I spent years at the old Smirnoff Labs developing better methods to separate the luma from the chroma. Now, that analog NTSC TV is no longer broadcast, and our only sources are set top boxes, we could pre-process the luma and chroma before combining them to make the composite NTSC signal. Low pass the luma so anything above 3MHz is removed (vintage color TVs throw away anything above 3MHz on the luma abyway). This leaves empty spectrum for the chroma subcarrier. Now our vintage color TVs will produce better looking images without the crawly rainbows.
If I ran a TV station back in the late 50's to mid 70's, I would have done this in the station's color modulator. "Wow, your TV station has such good looking video". Around 1980 comb filters came out.