I recently purchased a Coby DTV-140 ATSC set top tuner. It works fine for receiving OTA signals from a large outdoor antenna. It is connected to an overhead projector with component video cables, and audio via SPDIF digital to a receiver. Excellent picture and audio for many OTA stations in Denver.
I also have Comcast basic digital cable and 2 standard HDTVs, neither with a "cable card" or set top box. Both off the shelf TVs will tune the digital channels from Comcast and display the current signal - some stations are in 720p and 1080i.
I tried to input the Comcast cable to the Coby (same service at to the TVs) and there was no way to scan for stations.
Now the dumb question: why not????
The obvious answer is, the DTV-140 isn't designed to do that. But on the chance I'm missing something, is there any way to configure the 140 to tune the cable channels the same way 2 inexpensive, off the shelf TVs will tune cable.
If there is no way to do this with the 140, what HD tuner (without DVR) will do that. I want to be able to switch between OTA input and cable input to the projector from a tuner that has component video and digital audio output.
Thanks, DenverDick

From the AVS Forums [Link: avsforum.com] , post # 36 states that unfortunaelly it does not have a clear QAM tuner , therefore it will not do what your TV's are capable to do with the digital cable unscarambled channels.

Ther are some other ATSC stand alone tuners that will also tune Clear QAM Digital cable signals. Google as usual your best friend probably.