ScratchFury said:
Is QAM what allows me to get HD cable channels even when the CableCARDs aren't in the box?
QAM is the method that most cable systems use to carry TV channels through their cables. 8SVB is the "Over the Air" equivalent. Both of them allow for encoding (also encrypting) multiple program streams onto one channel. That is why they use the channel numbering system of xx.yy, where the x is the old standard channels we are used to, and the y is the subchannel. If you know the QAM assignment of a program source you can "dial in" its channel and subchannel assignment and view that channel on any TV equipped with a QAM/8SVB (ATSC) tuner or TiVo S3/HD, and view it assuming it is not encrypted. Cable systems take this one step further however, and assign a virtual channel number to each QAM program source and they use that channel number in their program guide data, and in their cableboxes. They do NOT publish the QAM assignments, they publish the virtual channel numbers. TiVo on its own, at the moment, has no way of equating QAM and virtual channel numbers, so it can not use the guide data to tune in and record the shows you desire. The CableCard facilitiates the translation between QAM and virtual channel numbers from information passed on from the cablesystem and creates that link that allows TiVo to record your shows based on the published guide data. The CableCard also facilitates the all important decrypting of the encrypted channels, also based on information passed on from the cablesystem's headend.
So without cablecards, TiVo is, at this point, effectively useless, with regards to digital channels from your cablesystem. Search other posts about "manual channel mapping."
