bj,
You have presumably discovered that Mode S and Mode C are filtered within PAW from the configure screen, both for relative altitude and 'Range'. Be aware that Mode C/S is 'off' by default, so you need to switch it on if you want to use it. If you also run a transponder, you MUST select the Mode CS + Filter (Beta) option to filter out your own transponder. If not, you might like to start with Mode S, then add Mode C later.
Any probs, we're here to help!
Regards
Peter