Solutions
  Analog carrier.
    Amplify signal. 

    However any distortion or static also amplified.

    Different frequencies may have to be amplified differently.
      Dolby noise reduction.

  Digital carrier. 
    Repeater - something like an amplifier.

    Signal sampled while in range of tolerance,
      Since values binary, 
        New exact copy of digital value regenerated.

    Sample possibly not "real" value measured.

    Equipment/conversion more complex/expensive.