BCD436HP - Scanning Question

Hey There,



So I figured out how to lock channels when you find something you want to hear, but after a little while (20 seconds ish) it will go blank. Surely their conversation is not over. It does not seem to be following?? Is there some feature I need to activate to get the trunking p25 features to work properly. I am new to this radio and have only had it for a few hours. I programed it by zip.



Also, about the zip, I set it for one mile but it still scans way beyond that. Why is that?



Thanks