I've tried that and could watch them - at least what the cpu allowed, e.g. QVC HD worked flawlessly with ~60% CPU but Das Erste HD had ~100%, but I knew that this could be so. That means it works ... at times because sometimes I don't get a signal in TBS viewer too.Did you try to actually view the channels in TBS viewer?
If no, you should try it. If your signal strength/quality isn't good enough, the channels will be unwatchable (pixelation, black screen etc.).
I'll try to increase the signal (although I bought this antenna some month ago to be ready for DVB-T2 ...) and keep you informed.
EDIT: Does the CrazyScan-graph tell anything about the signal strength? Or is there another tool you can recommend to get quick infos on that?