If you have signal fade at the antenna an amplifier can only amplify what it is given. The amplifier can not pull in signal that does not exist at the antenna. The only way an amplifier can help you is if the signal level drops after the antenna but is still good at that the antenna. If your signal is weak at the FM tuner, but good at the antenna, you can build it up using an amplifier so that you can overcome your downlead (cable) loss and any splitter loss that is between the antenna and your FM tuner.
