ATSC tuners - internal TV vs. external

Being internal will not hamper a tuner's abilities as it gets what it needs from the antenna. I suspect that most built-in tuners do as well or better than the CECB units.

With a built tuner you can watch the programs in HD and not downgraded to SD which is a requiement of the Coupon boxes.
The TV manufacturers pick good quality tuners since they have to make sure that the competition does not have better quality tuners.

In general the newer the equipment the newer the generation of tuner - that's what counts, not what it's install in. Most of these $60 CECB have better tuners than a $3000 flat screen from a couple of years ago simply because of generational gains.

If you're asking about a "new HDTV" having as good as a tuner as that available in the CECBs - yes the tuners should be equal for all intents and purposes.

My Accurian ATSC receiver is a bit better than the tuner in my brand new Panasonic TH-42PX80U, but the difference is not large. Both are rather better than an old Zoom box.

I can give you my example. I have a new Panasonic TH-50PZ85U (50" 1080p plasma) and right next to it I have a Zenith DTT900 feeding a DVD recorder. Both the plasma and the Zenith are fed from the same antenna, split with a distribution amp. The signal strength meters run about the same for both tuners. They both lock on tight to all my digital channels except NBC and FOX who are broadcasting the minimum digital they have to. All my other digitals measure >85% signal strength on both tuners. Fox is intermittantly flakey and usually runs around 70% on both tuners. NBC is a great test channel to compare the tuners because it is practically dead and swings from 0-60%. It is usually unwatchable on either tuner. The plasma's tuner seems to have a threshold of about 45-50% where if it is below the picture freezes and macro blocks. The Zenith in side-by-side testing does a little better and will deliver a watchable picture at about 40% with a few skips. On the other side of the coin is CBS. The Zenith pulls in CBS at a steady 90-95%; the Panasonic plasma has locked onto CBS and pegged at 100% signal strength since the day I hooked it up.

So overall, comparing the Panasonic tuner and the Zenith CECB, I would give them equal marks for tuner sensitivity. Of course, performance-wise there is no comparison. The Panasonic tuner outputs HD.