I think the process of setting up a QAM system involves installing a QAM transcoder for each transponder. It would be a piece of equipment that tunes in a single transponder (either QPSK or 8PSK) and then converts it into a QAM modulated signal. If there is no QAM transcoder installed for that particular transponder, then there won't be a QAM signal present for the channels carried on it, hence no CNN HD.