Cable distance

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Derived from Cisco Systems:

UTP cable is composed of pairs of wires. Each of the eight individual copper wires in UTP cable is covered by an insulating material. The wires in each pair are twisted around each other.

To reduce crosstalk between the pairs in UTP cable, the number of twists in the wire pairs varies.

UTP cable often is installed using a Registered Jack 45 (RJ-45), an eight-wire connector used to connect computers in a local-area network (LAN) Ethernet.

When used as a networking medium, UTP cable has four pairs of either 22- or 24-gauge copper wire with an impedance of 100 ohms.

UTP's small size can be advantageous during installation. Because it has such a small external diameter, UTP does not fill up wiring ducts as rapidly as other types of cable. This is an extremely important factor to consider, as when installing a network in an older building. UTP cable is easy to install and is less expensive than other types of networking media. UTP costs less per meter than any other type of LAN cabling, because UTP can be used with most of the major networking architectures, it continues to grow in popularity.

Disadvantages include UTP cable more prone to electrical noise and interference than other types of networking media, and the distance between signal boosts is shorter for UTP than it is for coaxial and fiber-optic cables.

UTP is considered the fastest copper-based medium today.

•Speed and throughput—10 to 1000 Mbps

•Average cost per node—Least expensive

•Media and connector size—Small

•Maximum cable length—100 m or 328 feet.

•Category 3—In 10BASE-T networks, can transmit data at speeds up to 10 Mbps.

•Category 5—Can transmit data at speeds up to 100 Mbps.

•Category 5e —Used in networks running at speeds up to 1000 Mbps.

•Category 6—Typically, Category 6 cable consists of four pairs of 24 American Wire Gauge copper wires. Category 6 cable is currently the fastest standard for UTP.

Shielded Twisted-Pair Cable
Shielded twisted-pair (STP) cable combines the techniques of shielding, cancellation, and wire twisting. Each pair of wires is wrapped in a metallic foil. The four pairs of wires then are wrapped in an overall metallic braid or foil, usually 150-ohm cable. As specified for use in Ethernet network installations, STP reduces electrical noise both within the cable (pair-to-pair coupling, or crosstalk) and from outside the cable (EMI and RFI). STP usually is installed with STP data connector, which is created especially for the STP cable. However, STP cabling also can use the same RJ connectors that UTP uses.

Although STP prevents interference better than UTP, it is more expensive and difficult to install. In addition, the metallic shielding must be grounded at both ends. If it is improperly grounded, the shield acts like an antenna and picks up unwanted signals. Because of its cost and difficulty with termination, STP is rarely used in Ethernet networks.

The following summarizes the features of STP cable:

•Speed —10 to 100 Mbps

•Average cost per node—Moderately expensive

•Media and connector size—Medium to large

•Maximum cable length—100 m (short)



•The speed of both types of cable is satisfactory for local-area distances.

•These are the least-expensive media for data communication. UTP is less expensive than STP.

•Most buildings are already wired with UTP, many transmission standards are adapted to use it, to avoid costly rewiring.

The solution is to place a hub or router between two 60m lengths of utp or stp to regenerate the signal, giving an effective length of 120m.