Originally Posted by freeeeeman
i have a fanless 7600GT. and i use a HDMI w/ the res of 720p. (tv is technically 720p). and the problem only sometimes happens. it seems to be more tuner related than anything else. some channels stutter sometimes, and then not. sometimes everything works great, and then for no reason, a channel will stutter...
What you are describing is most likely multipath distortion. This is caused by the reception of multiple overlapping signals in the RF front end of the tuner. There are three ways to address this:
1) Swap your antenna for one that has a higher gain. The antenna gain (measured in db) is simply a ratio of the signal strength of a station the antenna points at as compared to other signals (other stations AND reflections of the station you are tuned to). Thus a higher gain antenna has the ability to better reject the signals not on the exact compass bearing it is pointed at.
This is THE key factor in multipath - you cannot simply assume that because you have plenty of signal strength, you are golden. It is purely the ratio of the main signal to the reflected signals that matters. If the signal strength starts to overload the front end of the tuner it will reduce amplification using the AGC (Automatic Gain Control).
There is a limitation in gain which is that the higher the gain, the fewer stations will be within the narrower "beam width" of the antenna. The higher gain antennas which are the very best at multipath rejection will require that you point precisely at the station using an antenna rotor.
2) Swap your tuner with one that has better multipath rejection. In fact another of the exact model you own may work as well as another brand of tuner - there is considerable variation in inexpensive PC tuners. Few stores balk at "even exchange".
3) All else being equal, the higher you get your antenna, the better the multipath situation. The best antennas are high above the rooftops, and performance degrades the lower you go right down to an indoor antenna, the worst type for rejecting multipath signals that might be due to reflections off a neighbor's metal roof or aluminum siding.