an hdtv basically needs about 70db of gain from the cable operator to the hdtv.as the cable wire is connected to number of splitters before coming to ur house the quality of the picture or the strength of the signal counted in db gets reduced, so in order to make the signal above 70 db an cable tv amplifier is needed.
the cable operator uses many amplifiers places at regular interval so that the last tv connected to the cable gets all the picture quality.
