Due to the electrical properties of copper wiring, data signals
will undergo some corruption during their travels. Signal
corruption within certain limits is acceptable, but if the electrical
properties of the cable will cause serious distortion of the signal, that
cable must be replaced or repaired.
As a signal propagates down a length of cable, it loses some of its
energy. So, a signal that starts out with a certain input voltage,
will arrive at the load with a reduced voltage level. The amount of signal
loss is known as attenuation, which is measured in decibels, or dB. If the
voltage drops too much, the signal may no longer be useful.
Attenuation has a direct relationship with frequency and cable
length. The high frequency used by the network, the greater the
attenuation. Also, the longer the cable, the more energy a signal loses by
the time it reaches the load.
A signal losses energy during its travel because of electrical
properties at work in the cable. For example, every conductor
offers some dc resistance to a current (sometimes called copper losses).
The longer the cable, the more resistance it offers.
Resistance reduces the amount of signal passing through the wires –
it does not alter the signal. Reactance, inductive or capacitive,
distorts the signal.
The two concerns of signal transmission are:
- That enough signal gets through. (Quantity)
- That the signal is not distorted. (Quality)