Thanks all for responding. I reinstalled the SensarPro today. It's a neat little device and it seems to be doing everything it is supposed to do except for not seeing the two weak VHF channels.
All the other channels I get here are UHF and according to TV Fool the two VHF channels are the weakest of the bunch. Most all of the UHF channels still come in on the TV even when I set the gain on the SensarPro to 1. That drops the signal level for these stations considerably but they still come in even with signal readings in the 30's.
Another issue that may be pertinent is that one of the VHF channels broadcasts on Real RF 12 and the other on Real RF 13. Perhaps there's some adjacent channel interference going on that the SensarPro can't deal with?
And if there are strong FM stations etc in the area I suppose that could further affect things.
The weak VHF signals just don't seem to get past the SensarPro so the TV itself is not part of the situation.
At this point I'm thinking that my SensarPro probably isn't defective per se and that the device just may have some issues with weak VHF stations in general or in resolving the specific channel situation at my location or a combination of both.
I bought the SensarPro hoping to solve a specific problem at this location regarding the reception of NBC and CBS. With my original power supply I can receive NBC anytime and receive CBS most evenings. With the SensarPro I cannot watch either channel at any time. Now to see if the RV dealer will accept a return.