what's the different between using range or no range for distance for any Department ?
If you are using just the main database, with no Favorites lists, then you need to enter your location and a range, plus designate the Service types you want to monitor. More about how location works here:
How it Works: Location, Location, Location
If you are using one or more Favorites lists, you have a choice. You can specify whether or not any of your lists use Location Control. If the answer, for all of the lists you want to scan, is no (do not use Location Control), then you are not using location or a range. But if you are using location on any of the lists, that list may not be scanned unless you specify location & range details. For normal scanning, I do not use Location Control. I know which systems I can hear, and which I cannot, from my location.
However, if I were taking a trip to or through an area that I was not familiar with, then I would use location details to specify what the scanner should be focusing on. For a road trip, a GPS will keep your location updated/ However, you would need to specify a range.
For any System that you manually add, if you intend to use Location Control. then you need to specify location & range details for the system's Departments, as well as sites (if it is a trunked system). Otherwise, with those fields blank (no location entered for the department or sites), the scanner will treat them as out of range. (If no location is entered, the scanner treats that as zero degrees for botch latitude & longitude, which is a location in the Atlantic Ocean, off the coast of Africa, and will simply ignore that system if you are using Location Control.)