Additionally, this is a link to elsewhere here that illustrates the NSP system. https://www.radioreference.com/apps/db/?sid=6699
The Homepatrol has all this in it. You just need to update every week or two so you get the changes made to the system. Referencing what I said just above Look at the grid labeled "System Frequencies." On the left side, you see the "Site, that is the tower I was referring to above. Then comes the name of the tower which is probably the closest town to the tower, and finally the county that the tower is located in. I am sure there is a map somewhere online that shows the locations of the sites. You can guess as to those within range and those that are not
Again someone else who has the HP1 should be able to clarify but I believe you have to tell the radio what you want to listen to this is done as a menu to allow in what you want to hear. Make sure you have those setting in the menu set for what you want to allow the radio to listen to.
Going back to the grid again, you see other information about the various patrols and other units within the NSP. The codes and such are automatically translated to your display by the HP1 but you might find it interesting to look at it to see all the work the radio is doing for you. Once you get more proficient with the radio, you can create your own special listening files on top of what you just import from the database weekly. I hope this helps you out