My THD has been outstanding since the CC install. I checked the signal strength on the digital channels last night, 68? Is this a problem? I have had no picture/audio trouble at all.
Signal strenght doesn't tell the whole story.
The quality of the signal is also important, as is the quality of the receiver.
I had a Sony DHG-HDD250 DVR and it's tuner was a PoS. With about 70% of signal I would barely receive a few channels. My Toshiba TV had no problem and even reported higher signal. The THD reports about 75%.
So three tuners all reported different signal levels.
I get an occasional pixel drop out for a second now and then, but the THD performs on par with the Toshiba TV.
Signal quality can be affected by reflections from nearby buildings etc.
A poor quality signal can have a high strength and still be unusable.
A good quality 68% is fine as long as you get a good picture.