@Appu guru do you live in an apartment?
It's likely that in apartments the internal wire provided for cable TV has several joints.In each floor they have a box where the cable wire from mutiple dish comes in.The cable wire source would be from the terrace through a common duct to the box as input.Again output from the box is taken to next lower floor and so on.So if your flat is in a particular floor, the wire would go from the output of that master box(that is in your floor) to your flat's cable points which can be typically your living room or your bedroom. As joints are present in each floor, I assume the signal is definitely going to reduce and so also noise will enter at those cut points.
The box only provides an interface to input and output the wires at one single point.No signal boosting whatsoever.