Your 120 nm max range is too low for a good external aerial with 5m good coax, unless you are located inside a low lying valley.
(1) First check your maximum possible range by method given in first post of the thread What is the Maximum Range I can Get?
(2) Is your arial high enough to clearly see the horizon above surrounding trees and houses?
(3) Which aerial are you using?
(4) Which coax cable are you using?