The limit of maximum range at any location is terrain based. Even the best possible equipment (antenna, receiver, amplifier, cable) cannot increase this limit.
The first step is to determin what maximum you can get
Second step is to compare it with what you are actually getting.
Third step is to improve your system if what you are getting is substantially less than what could you possibly get.
To determine what can you possibly get, please see this post:
What is the Maximum Range I can Get?
Since I dont know your exact latitude/longitude, I have done this exercise for city center of Pembroke, and result are in the map below (blue curve)
