As the television signals passes through the cable lines the signal losses its strength. The impurity in the cable causes the signal to deteriorate and fade over distance. The signals therefore, have to be amplified at regular intervals. The number of amplifiers used and the spacing between them depends on the system bandwidth and the medium.
A cable system can have hundred of amplifiers and every couple of miles amplifier needs a power. So, we connect the power supply where ever needed.
The amplifier generally operates at 30v dc or less. The cable TV indooramplifier uses the house hold power (230v AC or 12v AC).
In order to minimize losses in coaxial cable that carry dish antenna signals to control room, the signals are first translated to a lower frequency range. This is done by using low noise block converter (LNB). The signal from the LNB is delivered to a Signal to a signal splitter which is actually a multi-coupler that divides the signal into independent paths. The signal splitter is commonly called a 'power divider' because it splits the signal into equal division of signals and one port is supplying 12v/8v to the LNB
Then the IRD receives input from one of the output ports of the power divider. Modulator receives the audio and video signals from the receiver and modulates these outputs to form the composite output signal. The output of each channel modulator feeds into a combiner unit. The multiplexed output from the combiner is then amplified by amplifier and transmitted to the trunk lines.