Range depends almost totally on two things: How high your antenna is above the ground, and how high the transmitting antenna is above the ground.
Of course, things in between the two are the real problem, but whether they ARE 'in between' or not depends on the antenna heights.
Your antenna height, on a handheld, is maybe 4-6 feet. Range to Horizon, on flat ground: 2-3 miles
The transmitting antenna usually becomes the main determiner of 'range'.
If it's 100 feet up on a building, it's good for 10 miles. Add your end's antenna, you get 12-13 miles.
Oh, at times, the possible range may be up to double that, but that's the range you normally figure as 'reliable' range.
Some radio systems use repeaters on mountaintops, that might be 2000 feet up, or higher. 44 miles, for 2000 feet.
Trunking systems in cities, however, are often designed for 'minimum necessary coverage', and use low level transmitter sites, scattered around the city, which do not get much range, and are monitorable only near the city. This allows the frequencies to be reused much closer by others.
To determine why you aren't hearing something, we need to know what you're trying to listen to, and where YOU are, exactly. It's possible to look up the transmitting sites at the FCC records, to see how high the antennas are, and get a guesstimate of range from that.
If you are trying to listen to the Palmetto 800 system, the antenna heights I find for the Columbia area are from 100-200 feet above average terrain. While this in theory says 10-15 mile range, even relatively low hills can block antennas at these low heights quite easily.
It's possible your home is just plain in a 'dead area' for the system, and a spot a half mile away might be much better, or worse.
It looks like you should be programming in Site 30 of the Palmetto 800 system for that area. Are you?
030 1E Richland Simulcast (RICHCO)
855.78750 856.23750 857.23750 858.23750 858.73750 859.33750 859.73750 860.23750
860.33750 866.03750 866.53750 867.03750 867.53750 868.03750 868.53750