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 . This introduces changes in shape of the signal. Propagation delay is the term used to describe the time taken for the signal to pass along the channel. Electromagnetic signals travel at velocities near that of light in vacuo of .