Basically… no. Every so often, we get a question from someone who has both cable and satellite. Some folks do, in order to get all the channels they want. These folks want to know if there’s a way to record both the DIRECTV and cable signal on a single DVR.
Cable DVRs don’t have any inputs but cable, but you can put an AM21 antenna module on your DIRECTV DVR. Since a regular TV can accept antenna signals on the same port that it accepts signals from cable TV, these enterprising individuals want to know if they can just plug the cable TV line right into the AM21.
Sorry, it doesn’t work that way. The AM21 can only pick up ATSC broadcast signals, while cable TV uses the QAM system. A cable-ready TV can read both kinds of signals but the AM21 can’t.
So, then the next question is… can you somehow convert from QAM to ATSC? Well… not really. You could buy a very expensive piece of equipment to do it but that’s not very realistic. It’s “kinda” possible to use the composite outputs of your cable box and an RF modulator to put the signal on NTSC channel 3, but since DIRECTV’s AM21 doesn’t scan for channels, there really isn’t a way to get the AM21 to see that channel, and it would only be SD anyway.
So, for now, there really isn’t a device that will let you record DIRECTV HD and cable HD at the same time, not for any sane price.