Maximum PC

I'm running a Ubuntu 12.10 system which includes a first edition "Air2PC" ATSC TV tuner card. I'm positive I have the right firmware for the card, and that it's installed properly in the right directory. Myth TV does seem to recognize that the card is there, and that it's functioning. The problem is that when I tell MythTV to scan all available channels, it doesn't pick up anything! I can use the card perfectly well under Windows (using TechniSat's proprietary software, of course!), so I'm positive it's a software-related problem. (Oh, BTW, since I live in an apartment, I have no choice but to use an amplified indoor antenna.) What am I doing wrong?

Sadly, not all tuner cards work out of the box in Linux, let alone Myth...

As a thought, have you been able to get the card to work with something like TVTime?