Amplifiers are generally not well understood by those who sell them and recommend them. They are very helpful when used under the right conditions. Digital has reduced the amount of amplifiers that are needed significantly. Anyone travelling the east coast predominately would not need an amplifier 85% of the time.
A signal can be too strong and the result is a poor picture. Exactly the same as not enough signal. Water is useful for getting some mass on the concept. Say you are cleaning the car. The hose is on but the water is not enough to shift any of the grime on the car – job does not get done or say the water is coming out in a forceful stream causing the water to hit a spot on the car and spraying everywhere including all over you. Neither situation is what you want. Weak and too strong signal is not useable. The TV set cannot process it.
Amplifiers are sold on “this thing called gain” It is meant to impress you but the key thing about an amplifier is how much of its own noise does it generate and therefore degrade the raw signal that the antenna picks up. Ever heard the car radio hiss. That is noise in the environment and an amplifier on an antenna picks up the noise and the wanted signal at the same time. If the noise is more than the signal then the amplifier does nothing to improve your signal.
We had a customer recently ring us and he was using our amplified RV antenna. It soon became apparent that his signal was overloaded and he needed to disconnect the amplifier. Our kit comes with the parts to do this. In fact you can buy an explorer caravan antenna with or without the amplifier. You can add the amplifier as an extra if you find you need it.