Someone wrote previously "you could set just the couple channels on the north one (in channels list block the other overlaps) then put that tuner as a higher priority, so for the 1 or 3 channels that are better on it, cdvr will use that tuner first. the other channels will only be available on the 2nd tuner facing south".
But how and where precisely do you do that?
Under settings > sources, there is a drop-down next to “Add a Source” choose Adjust Priority inside that drop-down. Then drag the source to the top of the source list that you want. You can also heart the channels in the manage lineup settings to prefer a certain channel to record from. Sounds like you should adjust priority, heart the good channels in manage lineup, and hide the bad channels by clicking the circle with the line through it in manage lineup.