ATI AIW8500 DV: Is TV tuner input supposed to be better than composite input?

[author]

I have ATI AIW8500 DV. The TV tuner is connected directly
to a cable extended from the wall. No cable box is used. I
see horizontal lines on some channels. I can also use
composite cables to connect to the cable box at my living
room. With this connection, all channels look sharp. The
difference in quality is even more obvious when I capture
from both inputs and then compare.

So in my case, the composite input provides better video
quality than the TV tuner. I'd like to know if that's the
way or I'm doing things wrong.

 

[JAD]

It can be with any input device, It would depend on the source, A VHS can drop the signal power through the Composite output. Cheap
composite cables (not shielded very well) Too long of composite cables. etc... on the other hand your cable may have many splitters
on the line..or your internet connection shares your TV connection and your picking up interference...

 

[Vance McNeil]

I've been told that the PC's components cause interference with the tuner.
That's why the composite/rca connector gives a clearer picture.

I have notied the same thing you have. Had I know this would be the case, I
would simply have chosen a card with Video-In as I now use my VCR to provide
the cable tuning.