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You need to learn the difference between an electrical signal vs time and its spectrum of frequencies.
If you look at a video signal with an oscilloscope, you can pick out the time sequence of frames, fields, lines, and the particular spot on the screen left to right.
The diagrams you posted are frequency spectra, and represent a long term average of the different frequencies in the signals. In general, a lower frequency (towards the left) represents a coarse repeating pattern of lines or dots in the picture, and higher frequencies represent finer patterns. When such a signal is modulated on a carrier, it generates new frequencies spaced up and down from the carrier frequency.
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Last edited by old_tv_nut; 09-20-2022 at 08:12 PM.
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