1. Get an HD OTA antenna to connect to the 'cable' input on your TV, or
2. Use a splitter on your cable line: 1 feed to your cable card tuner, and 1 feed to your TV. You can get all your SD channels and your TV probably has a QAM tuner which should tune your local channels in HD; which I think the cable companies have to send 'Clear QAM'. These are usually the same channels you would receive OTA using an antenna.
Living Room: Denon X4000, XPA-5, Polk RTiA9, CSiA6, RTiA3-wides, FXiA4, OWM3, SVS PC12+, 4 Shakers, Epson 5030, VApex 92”, Sony XBR9 52”, PS3, Xbox 360, Darbee, Harmony 1.
Bedroom: Denon X2000, Polk: RTiA3, CSiA4, RTiA1, SVS SB12-NSD, Sony XBR-55X850B, Sony BPD-S590, Xbox 360, RPi2-RasPlex, Darbee, Harmony 510.
Home Office: Onkyo 707, Polk: LSiM 703, LSiM 704, Monitor 70, Yamaha SW315 x 2, Turntable, Triple Monitors, Harmony 610.