I'm in Montgomery co, MD right across the line from DC. Don't need a tuning adapter. I doubt that you do either or Comcast DC would have informed you. From the TIVO site: "A Tuning Adapter is a small set top box that gives your CableCARD-equipped HD TiVo DVR the ability to request switched digital video (SDV) channels. Like CableCARDs, Tuning Adapters are part of the digital cable system, so they must be issued by your cable provider." There is more information in the SDV FAQ.