UTP cable used as horizontal cable (permanent cable or cable in the walls) has a solid conductor, as opposed to patch cable and cable that is run over short distances, which usually have stranded conductors. Stranded-conductor wire consists of many smaller wires interwoven together to form a single conductor.
Connector types (such as patch panels and modular jacks) for solid-conductor cable are different than those for stranded-conductor cable. Stranded-conductor cables will not work with insulated displacement connector (IDC)-style connectors found on patch panels and 66-style punch-down blocks.
Though stranded-conductor wire is more flexible, solid-conductor cable has much better electrical properties. Stranded-conductor wire is subject to as much as 20 percent more attenuation (loss of signal) due to a phenomenon called skin effect. At higher frequencies (the frequencies used in LAN cables), the signal current concentrates on the outer circumference of the overall conductor. Since stranded-conductor wire has a less-defined overall circumference (due to the multiple strands involved), attenuation is increased.
|KEY TERM: core|
The core of the cable is anything found inside the sheath. The core is usually just the insulated twisted pairs, but it may also include a slitting cord and the shielding over individual twisted pairs in an STP cable. People incorrectly refer to the core of the cable when they mean the conductor (the element that conducts the electrical signal).
Most cabling standards recommend using solid-conductor wire in the horizontal or permanent portion of the link, but the standards allow for stranded-conductor wire in patch cables where flexibility is more important. We know of several UTP installations that have used stranded-conductor wires for their horizontal links. Although we consider this a poor practice, here are some important points to keep in mind if you choose to use a mixture of these cables:
- Stranded-conductor wire requires different connectors.
- Stranded-conductor wires don't work as well in punch-down blocks designed for solid-conductor cables.
- You must account for reduced horizontal-link distances.