Understanding the Successful EMC Performance of Twisted Pair Cables.

This paper examines the commonly held misperception that shielded cable is unconditionally better at resisting radiated interference than unshielded cable. Both unshielded twisted pair (UTP) cables and shielded twisted pair (STP) cables resist interference, they just use different technique to do so. This paper explains the mechanisms used by both types of cables, and identifies the areas where these mechanisms work well and not so well. An experiment was performed to compare the noise immunity performance of three different cable types: EIA Category 3 (voice-grade) UTP, EIA Category 5 (data-grade) UTP, and Type 1 STP. The experiment shows that Category 5 UTP achieves comparable EMC performance to Type 1 STP, while Category 3 UTP is slightly worse.