TV Antenna booster
The device which amplifies the weak signal received by antenna to the extent so that it can be viewable on TV set is called booster.
Precaution should be taken to mount such antenna booster in strong signal areas as it will overdrive and cause problem to TV set. It is recommended to use such TV antenna boosters in weak signal areas.
Often it is used by cable service provider as they will be providing the service using digital splitters. The signal output of multiple splitters result into weak signal. This requires booster to boost the signal before it goes to the TV set.
Antenna related links
Antenna tutorial covering antenna functions, antenna terminologies, antenna types, antenna radiation pattern (near field, far field) and antenna testing, Refer Antenna Tutorial.