The DVB default mux definition files provided with TVHeadEnd have the center frequencies slightly off. For example the mux for channel 17 has as its center frequency 491.028 Mhz. However the real center frequency is 491.000 Mhz. This is typical for all pre-defined muxes for the USA. This small offset results in poor reception and signal degradation.
I manually changed all of the center frequencies, and reception is equal to or better than my Channel Master DVR. I have also started a bug report on the TVHeadend website.
