If you have a newer TV (most all HD TVs) with a QAM tuner and Comcast is not encrypting your Basic tier channels (they are in some areas) you can plug the cable directly into your TV and "scan". If they are encrypting your Basic tier, you could try asking them for a uDTA box?
Comcast is currently in a large field trial with HD digital transport adapters (DTAs), with plans to have them more broadly deployed in customers’ homes later this year.
“We started field trials of the HD DTA in the first quarter of this year,” said Comcast’s Steve Reynolds, senior vice president of CPE and home networking. “We’re just wrapping up those field trials at this point and time. We haven’t actually announced the date when paying subscribers will start getting HD DTAs.
“We have been in field trials for a number of months, and the technology is working well, and all of the devices are stable, so all systems look good.”
Similar to its SD DTA effort, Comcast is working with Pace, Motorola and Technicolor on the HD DTAs.