As far as I know the amplifier is in the base of the aerial that is on the roof. However, when I looked at my aerial in preparation for a safari park visit (damn monkeys!!), mine wouldn't come off. It would unscrew and fold down, but really wouldn't come off.
I'm wondering whether you've damaged the connection that the aerial needs in order to receive the signal? If you put the original one back on do you get your old version of the signal back?