hittade lite ang STP/UTP
Some twisted-pair cables contain a metal shield to reduce the potential for electromagnetic interference (EMI). EMI is caused by signals from other sources such as electric motors, power lines, high-power radio and radar signals in the vicinity that may cause disruptions or interference, called noise. Shielded twisted-pair (STP) cable encases the signal-carrying wires in a conducting shield. At first glance, it may appear that because STP cable is physically encased in a shield, all outside interference is automatically blocked; however, this is not true.
Just like a wire, the shield acts as an antenna, converting received noise into current flowing in the shield when it has been properly grounded. This current, in turn, induces an equal and opposite current flowing in the twisted pairs. As long as the two currents are symmetrical, they cancel each other out and deliver no net noise to the receiver. However, any discontinuity in the shield or other asymmetry between the current in the shield and the current in the twisted pairs is interpreted as noise. STP cable is only effective at preventing radiation or blocking interference as long as the entire end-to-end link is shielded and properly grounded. To work properly, every component of a shielded cabling system must be just that fully shielded.
man måste jorda STP kabeln annars kommer den bli som en antenn :D, men tyvärr så jag har i detta fallet ingen aning. UTP borde funka så länge det inte är några starka elkällor som ligger ivägen.
link: http://www.steinkuehler.de/belllabs_UTP_STP.htm
