The problem is you dont have a gigantic antenna. Look at the antenna on the GSP units, unless you have an antenna tuned to their freq. you arent going to hear much unless you close to a unit or the GSP post.
They are using one of the oldest statewide radio systems in the nation, there is no repeater at all, unless your in Atlanta.
Its not uncommon for a trooper having to get dispatch to relay what another unit is saying.