They are legally private, non-broadcast, signals.
A talk station will never get fined for running pre-delayed audio over an SCA.
A translator can not translate an SCA on its main program channel or an unscrambled HD sub-channel.
FMX was nixed because it placed digital broadcast signal on the SCA sub-channel.
Raising the baseband subcarrier frequency to 67 or 92 khz is just as much scrambling as moving video sync signals to another frequency to make the picture more stable or going from negative video modulation to positive to improve the s/n ratio. Both scenarios might be true, but both are considered scrambling.
A talk station will never get fined for running pre-delayed audio over an SCA.
A translator can not translate an SCA on its main program channel or an unscrambled HD sub-channel.
FMX was nixed because it placed digital broadcast signal on the SCA sub-channel.
Raising the baseband subcarrier frequency to 67 or 92 khz is just as much scrambling as moving video sync signals to another frequency to make the picture more stable or going from negative video modulation to positive to improve the s/n ratio. Both scenarios might be true, but both are considered scrambling.