150- W STP-A: Comparison with UTP

W STP A Comparison with UTP

It is presumed by many engineers that STP cabling, because of its shield, should be less susceptible to external noise and interference. This is not necessarily true.

In 1992 Robert Pritchard and Doug Smith compared the susceptibility of 150- W STP-A and UTP cables using the IEC 801-4 Electrical Fast Transient test method, a severe form of susceptibility testing [80] . These researchers concluded that "both UTP and STP can provide adequate immunity to interference." The susceptibility depends, in the case of UTP, on the symmetry and rate of twist of the wires. In the case of STP the susceptibility depends on the integrity of the shield.

Of these two dependencies, I would rather the integrity of my system depend on the twisting of the wires, because

Customers will not maintain the shields on an STP system .

The integrity of any STP system hinges on a continuous connection of the shield from end to end along the entire cable path . This requires good connections at multiple points along the way, with all the connectors firmly seated and no dirt or corrosion at any critical connection point. In my opinion such connections will not be properly maintained , and the shield will fail, leaving the system open to outside interference. STP may make sense for short interconnections, but not, in this author's opinion, for general-purpose building wiring.

POINT TO REMEMBER

• Customers will not maintain the shields on an STP system.