Tag: cat6 utp cable

Shielded vs. Unshielded Twisted-Pair Cable

As we all know, the advantages and disadvantages of shielded and unshielded twisted-pair cable are under debate for a long time. Advocates of STP cable, which includes screened twisted-pair and foil twisted-pair cables, claim that it is superior to UTP cable. Shielded versus unshielded twisted-pair cable, which is the winner? This post will give you the answer.

STP and UTP cable differ in design and manufacture. But their purpose should be the same–to provide reliable connectivity of electronic equipment. In theory, both types of cable should do this equally well. The true test comes when you look at how each of these cable types performs that task within its respective end-to-end system.

Shielded vs. Unshielded Twisted-Pair Cable

Shielded Twisted-Pair Cable

Shielded twisted-pair cable encases the signal-carrying wires in a conducting shield as a means of reducing the potential for electromagnetic interference. How effective the shielding is depends on the material used for the shield–its thickness and frequency, the type of electromagnetic noise field, the distance from the noise source to the shield, any shield discontinuity and the grounding practices. Also, crosstalk and signal noise can increase if the effects of the shield are not compensated for.

Some STP cables, for example, use a thick braided shield that makes a cable heavier, thicker and more difficult to install than its UTP counterpart. Other STP cables use only a thin outer foil shield. These cables, known as screened twisted-pair cables or foil twisted-pair cables, are thinner and less expensive than braided STP cable; however, they are not any easier to install. Unless the minimum bend radius and maximum pulling tension are rigidly observed when these cables are installed, the shield can be torn.

Unshielded Twisted-Pair Cable

Unshielded twisted-pair cable does not rely on physical shielding to block interference. It relies instead on balancing and filtering techniques using media filters, baluns or both. Noise is induced equally on two conductors and is canceled out at the receiver. With properly designed, manufactured and installed UTP cable (like CAT6 UTP cable), the network is easier to maintain than one in an STP cable plant, with its shielding continuity and grounding issues.

UTP cable has evolved during the years, and different types are available for different needs. Basic telephone cable, also known as direct-inside wire, is still available. Improvements over the years–variations in the twists or in individual wire sheaths or overall cable jackets–have led to the development of Cat3 cable that is compliant with the Electronic Industries Association/ Telecommunications Industry Association-568 standard for transmission rates up to 16 megahertz. Cat 4 UTP cable is specified for signal bandwidths to 20 MHz, and Cat5e UTP cable for specifications to 100 MHz–and possibly higher.

Shielded vs. Unshielded Twisted-Pair Cable

Since UTP cable is lightweight, thin and flexible, as well as versatile, reliable and inexpensive, millions of nodes have been, and continue to be, wired with this cabling medium. This is especially true for high-data-rate applications. For best performance, this UTP cable should be used as part of a well-engineered structured cabling system.

If STP cable is combined with improperly shielded connectors, connecting hardware or outlets, or if the foil shield itself is damaged, overall signal quality will be degraded. This, in turn, can result in degraded emission and immunity performance. Therefore, for a shielded cabling system to totally reduce interference, every component within that system must be fully and seamlessly shielded, as well as properly installed and maintained.

An STP cabling system also requires good grounding and earthing practices because of the presence of the shield. An improperly grounded system can be a primary source of emissions and interference. Whether this ground is at one end or both ends of the cable run depends on the frequency at which a given application is running. For high-frequency signals, an STP cabling system must be grounded, at minimum, at both ends of the cable run, and it must be continuous. A shield grounded at only one end is not effective against magnetic-field interference.

The length of the ground conductor itself can also cause problems. If it is too long, it no longer acts as a ground. Therefore, because specific grounding requirements depend on the application, a general grounding policy that ensures the best results for an STP cabling system is not possible.

UTP cabling doesn’t have this problem. While an STP cabling system is dependent on such factors as physical continuity of the cable shield or installation with adequately shielded and grounded components, a UTP cabling system inherently has fewer potential trouble spots and is much easier to install.

Copper Cabling Installation Guideline

As bandwidth demands continue to rise, both copper and fiber cable manufacturers are developing fast to provide greater capacity and flexibility. Copper cabling is still preferred by many network managers because copper cables especially UTP cables (eg. Cat6 UTP Cable), are as inexpensive as optical fibers and easy to install. And the components such as patch panels, wall-plate outlets, connecting blocks are economical. Here are the guidelines for copper cabling installation which would ensure a faster and safer copper network.

Standards

The first step when planing and deploying a telecommunication infrastructure is to make sure you are following the ANSI/TIA-568-C standard. This standard will ensure that your cabling system is interoperable with any networking or voice applications that have been designed to work with that standard.

Cable Distances

ANSI/TIA-568-C standard defines the maximum distance that a horizontal cable should traverse. The tips relating to distance and the installation of copper cabling are listed below.

  • Never exceed the 90-meter maximum distance for horizontal cables.
  • Horizontal cable rarely goes in a straight line from the patch panel to the wall plate. Remember to account for the fact that horizontal cable may be routed up through walls, around corners, and through conduit.
  • Calculate any additional cable distance that may be required as a result of trays, hooks, and cable management.
  • Leave some slack in the ceiling above the wiring rack in case re-termination is required or the patch panel must be moved. Some professional cable installers leave the extra cable loop in the ceiling bundled together or looped around a hook, shown as below.
extra cable loop
Wiring Patterns

The ANSI/TIA-568-C standard releases two wiring patterns for modular jacks and plugs: T568-A and T568-B. The only difference between them is that pin assignments for pairs 2 and 3 are reversed. As for the applications and working principles, these two wiring patterns make no difference. Remember to choose the same wiring configuration on both ends.

The cable pairs are assigned to specific pin numbers. The pins are numbered from left to right if you are looking into the modular jack outlet or down on the top of the modular plug. The following picture shows the pin numbers for the eight-position modular jack (RJ-45) and plug.

Installing Guide

Many factors need to be considered before you start installing copper cabling. Even if you have adequately planned your installation, situations can still arise that will cause problems either immediately or in the long term. Here are some tips to keep in mind for installing copper cabling.

  • Do not untwist the twisted pairs at the cable connector or anywhere along the cable length any more than necessary.
  • Bridged taps are not allowed.
  • Use connectors, patch panels, and wall plates that are compatible with the cable.
  • Never splice a data cable if it has a problem at some point through its length; run a new cable instead.
  • When terminating, remove as little of the cable’s jacket as possible, preferably less than three inches. When finally terminated, the jacket should be as close as possible to where the conductors are punched down.
  • Don’t lay data cables directly across ceiling tiles or grids. Use a cable tray, J hook, horizontal ladder, or other method to support the cables. Avoid any sort of cable-suspension device that appears as if it will crush the cables.
  • If you have a cable with damaged pairs, replace it. Don’t use another unused pair from the same cable because other pairs may be damaged to the point where they only cause intermittent problems, which are difficult to solve. Substituting pairs also prevents any future upgrades that require the use of all four pairs in the cable.

With the rapid development and upgrading of Ethernet technology and the surrounding standards, the applications of copper cables also develop like PoE technology, wireless access, digital camera, LED-based power system and sensor networks. Although fiber is very popular in the data center market, the advent of 25G and 40G copper cable standards demonstrate the continuous evolvement of copper cable technology, which still has a strong presence, particularly in the area of server end access.