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I’m not sure I agree with that explanation of the color subcarrier. The color subcarrier is modulated to a higher frequency, but on an old B&W TV, there are no

I’m not sure I agree with that explanation of the color subcarrier. The color subcarrier is modulated to a higher frequency, but on an old B&W TV, there are no pixels, only lines. The color subcarrier can appear as a pattern superimposed over the picture if it is not filtered out with a low-pass filter—and indeed, B&W TVs made after the advent of color television contain such a filter, which can be removed if you want to use the TV as a higher-resolution monitor for your home computer (ask how I know...) The two chroma channels are, however, “rotated”, similar to the way mid-side encoding is done. You take a YUV signal, you extract the chrominance UV channels, and then you rotate them to IQ channels. The I and Q channels are then quadrature modulated with different amounts of bandwidth assigned to the I and Q channels. The I channel gets, like, 3x as much bandwidth.

dweymouth 4y ago
Broadcast NTSC did actually modulate the color signal into a "comb-shaped" frequency spectrum that was overlaid onto the complimentary "comb-shaped" spectrum of the B+W signal, because they didn't want to have to re-allocate higher broadcast channel bandwidths to be able to support color (and therefore have fewer channels available). The comb-shaped nature of the spectrum is an artifact of the discrete lines the picture signal is made up of, and the pause between each line when the electron beam reset itself and prepared to draw the next line. The fact they were able to figure out how to do color in the same bandwidth in a backward-compatible way is actually kind of insane, and I've seen it mentioned somewhere as one of the, if not THE most impressive engineering achievements of the 20th century.