All, with MANY thanks to DB Admin "brian" who helped me get up and running and to those who contributed info in this thread, I can share with you all a few things I learned that may help the OP who was having trouble hearing Dorchester County Emergency Services in the Summerville area, just as I was.
On the BCD436HP, create a new P25 Automatic system. Turn ID Search ON. Create a new site called Knightsville with a control frequency of 860.4625. Fire up Discovery if you like. In the Oakbrook area of Summerville, this works for me.
For those of you who may now feel compelled to slap me and say, "I told you that earlier!" I can only say this. For some reason, I can only get reception of this P25 system when I hold my scanner at just the right angle and in just the right place...even out on my third story balcony I have issues. This caused intermittent reception that I interpreted as NO reception because I assumed that being THIS CLOSE to the transmitter, I shouldn't have any problems. I have an 800 Mhz antenna in the mail on the way to me. Hoping that fixes this.
Thanks to all!