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Technical BULLETIN Patch Cable Stability and Network Performance TB-61 (Revised)
Based upon the results of aging, temperature and humidity tests, Belden® DataTwist® 350 Patch Cable is the only cable to pass the TIA/EIA 568-A Category 5 attenuation requirement. Choosing Belden® DataTwist® 350 Patch Cable addresses both environmental and installation concerns, giving the end-user comfort in knowing its network performance is secure. For More Information: Belden P.O. Box 1980 Richmond, IN 47375 765/983-5200 http://www.belden.com © Copyright 1997, Belden Inc.
The performance of Category 5 patch cables can be compromised both during and after installation. In fact, recent tests on a variety of patch cables showed significant attenuation variances (caused by temperature/humidity fluctuations) and impedance variations (caused by the separation of the insulated conductors during cable flexing). Belden's DataTwist 350 Patch Cable, part no. 1752A, eliminates these problems with a patented bonded-pair construction. This innovative bonded-pair design ensures electrical stability both before and after installation. Patch Cable Integration Patch cable is integral to the performance of a network based on Category 5 cabling. The cable is used in several areas: from the facility's wall outlets to its desktop workstations, within its telecommunication closets (TCs), and from the back of the termination blocks in the TC to the equipment itself. As part of the TIA/EIA channel, patch cable can have a major impact on system performance. Environmental Effects In a typical office environment or telecommunications closet, both temperature and humidity fluctuate. While testing several industry-selected Category 5 patch cables, Belden found these environmental fluctuations caused attenuation failures, thus jeopardizing the overall network performance. To document the phenomenon, Belden tested 10 reels each of three industryselected patch cables, and compared the results to our new DataTwist 350 Patch Cable. The samples were initially tested at ambient conditions and the results documented. Next, the samples were exposed to various elevated humidity conditions over an extended period of time. Once the exposure was completed, the samples were allowed to return to ambient conditions. Test Results In all cases, with the exception of the Belden DataTwist 350 Patch Cable, attenuation was seriously impacted as a result of the exposure to humidity. The lower the attenuation (dB/100m), the better the performance. Typically, the end-user might not realize this problem until the cable has been installed and is in place as part of the network. By choosing Belden's DataTwist 350 Patch Cable, environmental concerns are overcome, giving the end-user comfort in knowing its network performance is secure.
Impedance Stability Another serious problem with many Category 5 patch cables is impedance stability. It has been long known that Category 5 specifications use what is known as an "impedance smoothing function." This allows for a ±35 ohm cable to appear to be a ±15 ohm cable. Unfortunately, the problem becomes worse in patch cable environments where Category 5 patch cables with unbonded, insulated conductors, can experience flexing or torsional twisting -causing the conductors to separate. This separation will cause high fluctuations in impedance performance. Hence, a ±35 ohm cable can easily have ±50 ohms of true variance. And such a high degree of change can impact overall system performance. Unfortunately, many hand-held testers are unable to capture this effect, thereby causing the end-user to be unaware of this potential time bomb. DataTwist 350 Patch Cable, on the other hand, utilizes bonded pair technology, and ensures stable, "unsmoothed" impedance. Wavering conductor-to-conductor spacing and air gaps between conductors will cause high fluctuations in impedance performance for a typical Category 5 pair. The uniformity of a Belden DataTwist 350 Patch Cable pair results in extremely stable impedance by providing both stable conductor-to-conductor spacing and no air gaps. Conclusion Patch cable can easily be viewed as the "weak link" in network performance since environmental and installation effects can be of great concern to the network's reliability. Choosing cables such as Belden's DataTwist 350 Patch Cable addresses both of these concerns, giving the end-user comfort in knowing its network performance is secure-both before and after cable installation.
