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I & Q Demodulation
To this day, the NTSC signal is still broadcast using the wideband I and narrowband Q subcarrier quadrature modulation.
It was realized early that narrowband demodulation could save a tube or two, ($$$), and that the loss of color detail was not very noticeable. Westinghouse was demonstrating narrowband R-Y/B-Y (red and blue color difference signals) demodulation in prototype sets in 1952. This became the method most manufactures choose to use, and still use to this day.
It is also true that wideband demodulation has some additional undesirable visual artifacts which the narrow band schemes do
not.
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John Folsom
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