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Broadcast analog signals had a stronger audio carrier relative to the video carrier [as high as -7 dB] than the channel 3/4 modulators used in VCRs, DVDs, or digital converter boxes. This is because these simple modulators first frequency modulated a 4.5 MHz audio intercarrier and added it to the baseband video before modulating on the channel 3 or 4 carrier. Lower level [typically -15 dB] prevents generation of chroma/sound beats, but makes the alignment of old sets more critical.
Professional agile modulators may have adjustable audio carrier level and be capable of the higher ratios.
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