What if I enter a zip code into my 436 Uniden- can it be a zip 40 miles from my location? And if I do that also set Range at 50 miles? Have been doing this and at that time my scanner does not only receives sites in that zone but another 60 or 70 miles farther , usually all I see is the Department,System , and sometimes the channel , usually never any audio!! What gives ?
I think you are not understanding how the Range setting actually works.
You set your location via zip code, or the actual latitude & longitude values.
Then, enter a range.
But the way the scanner actually handles a range is that it, in effect, creates a circle around your location, at the radius (range) you specified. However, individual departments and sites also have ranges set in the database, which creates a virtual circle around their location.
If the "range circle" of your scanner intersects/overlaps the range circle of the site or department, that enables the system to be scanned. That's one reason why, when you set a large range, you are seeing systems that are way too far out to hear. A fifty mile range on the scanner would enable a system 70 miles away from you if the system's range is 20 miles or more.
For a lengthier illustration of how range works, with explanatory graphics, see this page:
How it Works: Location, Location, Location