Category 6 Cable

What is Category 6 cable and what are the specifications and uses of it? Category 6 cable will provide approximately double the performance of Category 5 or Category 5E cable. Cable is divided into categories according to the specification standards. The higher the number of the category, the more stringent the standards are for the cable.

Category 6 cable is a high performance cable, usually used for data transmission, made up of four twisted copper wire pair conductors. The wire specifications are for 22 to 24 gauge wire, but 23 gauge wire is commonly used. Because of the twisting of the conductor pairs, the cable is given some defense against unwanted interference infiltration. Category 6 cable is now included in the 568A standard officially.

There are set specifications for Category 6 cable. The first specification is the specified frequency range. For Category 6 cable the specified frequency range is 1 Mhz to 250 Mhz.

The second important specification is Attenuation. This is a signal loss in a segment of cable because of the wire resistance and any other electrical factors that contribute to additional resistance, such as Capacitance and Impedance. The total level of Attenuation will depend on several factors including the length of the cable, any poor or bad connections, ambient noise, high levels of crosstalk, or any bad insulation. Ambient noise is similar to crosstalk because an unwanted signal gets in the cable. The difference between ambient noise and crosstalk is that ambient noise comes from outside the cable and is induced into the cable, and crosstalk comes from the pairs in the cable itself. The Attenuation specification for Category 6 cable is 21.7 dB with a specification of 36 dB for performance that is at 250 MHz.

The next set of specifications for Category 6 cable concern crosstalk. Crosstalk is when the signals that are carried by one pair of conductors bleeds onto another pair by the induction process. The pairs do not have to touch for this to happen as the signals can be transferred magnetically. Crosstalk is an undesired effect that can inhibit or slow the data signal transfer over the segment of cable. Reducing crosstalk and the effects of it is the reason for the twisting of the conductors in cable that is Category 5E and higher. Two relevant types of crosstalk are Near End (NEXT) crosstalk and Far End (FEXT) crosstalk. The only way to have 100% immunity to crosstalk is to use fiber optic cable as this is the only cable type that is immune to crosstalk of both types.

Category 6 cable has a Near End (NEXT) specification of 39.9 dB with the specification at 33.1 dB when performance is at 250 MHz. The Power-Sum Next specification is 37.1 dB, with a 30.2 specification at 250 MHz performance.

ACR specifications for Category 6 cable are 18.2 dB with a -2.9 dB specification with performance at 250 MHz. Specifications for Power-Sum ACR are 18.2 dB, and at 250 MHz performance these specifications change to -5.8 dB.

The next specifications for Category 6 cable are the ELFEXT and Power-Sum ELFEXT requirements. The ELFEXT specification is 23.2 dB, and 15.3 dB when performance is at 250 MHz. For Power-sum ELFEXT the normal requirement is 20.2 dB, and 12.3 dB at 250 MHz performance.

Return Loss in cable is signal attenuation that is caused by impedance variations that are in the structure of the cable and any affiliated connection hardware. These variations will cause the signal to return to the source instead of traveling through, and result in signal loss. The specification for Category 6 cable is 12 dB, and for performance at 250 MHZ the specification changes to 8 dB.

Propagation delay is another specification for Category 6 cable. Propagation delay is the amount of time it takes for the signal to propagate from one end to the other end. This time is stated in nanoseconds. The specification for Category 6 cable in regards to Propagation delay is 548 nsec., and at 250 MHz performance the specification drops 2 nsec. to 546 nsec.

Propagation Delay Skew is the last specification to be discussed. The Propagation Delay Skew is a comprehensive calculation of the difference between the signaling delay from the slowest pair of conductors and the signaling delay from the fastest pair of conductors. This specification is expressed in nanoseconds. For Category 6 cable the Propagation Delay Skew specification is 50 nsec no matter what the MHz performance is.