When a signal is introduced into a channel of bandwidth B , the signal emerging from the end of a channel has its bandwidth reduced to the bandwidth B of the channel. Signals lying outside the bandwidth of the channel are removed. The channel places a maximum value of the bandwidth of the system, irrespective of the signal bandwidth. The longer the channel, the higher the absorption. It is usually specified in .
Absorption is usually frequency dependent.
It reduces the available bandwidth. The effects of channel absorption Attenuation is the decrease of signal strength as it propagates along a channel. Repeaters are amplifiers placed along the channel that restore the signal power. Some attenuation affects are due to absorption. The amount of attentuation is measured in .