The highest-quality HDTV signals are available from satellite or HD digital cable-boxes. With either of these, the satellite receiver or set-top digital cable boxes will receive and decode HD signals as well as analog TV stations carried by the cable system, so you won't need a separate HD tuner built into the HD set you purchase. However, you may be within range (30 or 40 miles) of terrestrial digital HDTV over-the-air broadcasts, which of course are free but you must have an HDTV tuner to receive them. All HDTV sets manufactured since March 2005 must have built-in HDTV tuners. If you have an earlier HD display, you may need to buy a separate HD tuner for over-the-air HD broadcasts.