It also looks like the two radios count their memories differently, one
being from zero and the other from one. In that case, you might just add
a method like this for the uv5:

  def _get_mem(self, number):
      return self._memobj.memory[number]

and then override it in the UV6 class like this:

  def _get_mem(self, number):
      return self._memobj.memory[number - 1]

then in get_memory(), you can do this:

  mem = self._get_mem(number)

and it will do the right thing in each class.