Issue link: https://www.e-digitaleditions.com/i/1327492
January/February/March 2021 I 51 IF HDBaseT IS USED TO EXTEND SIGNALS, WHAT CATEGORY RATING SHOULD BE USED FOR CABLE? HDBaseT allows AV systems to be installed using the same materials and skills currently used for a LAN infrastructure. It enables the trans- mission of AV signals at speeds up to 10 Gb/s and a frequency of 500 MHz (HDBaseT 2.0). Telecommu- nication Industry Association (TIA) specifications for unshielded twisted- pair (UTP) cable define the frequency capability for Cat 5e at 100 MHz, Cat 6 at 250 MHz, and Cat 6A at 500 MHz. Most top-tier cables are sweep tested to an additional 100 MHz or more past their TIA limits. By comparison, uncompressed video has a bandwidth of 550 MHz. This means that Cat 5e has the potential to fail, as its bandwidth (100 MHz) is well below the video frequency requirements. While Cat 5e channels are capable of carrying HDBaseT signals in a point-to-point link, they do not support HDBaseT very well in many real-world installations with adjacent data or HDBaseT channels or HDBaseT over longer distances. Using Cat 5e UTP cable in these applications can lead to signal dropouts and total link loss because the channels are not designed to resist alien crosstalk (AXT). Category 6 signals may also struggle for the same reason. A series of tests were conducted to verify the capability of different category channels, cable, and con- nector types. 1 Testing concentrated on the effectiveness of the extenders at their maximum distance capability (shorter distances may have better performance) and was conducted using 1080p/60 frames per second (fps) video sources. The results found that Cat 5e channels can carry HDBaseT signals in single point-to-point isolated channels, but they did not support HDBaseT signals in installations bundled with adjacent HDBaseT channels. When a Cat 5e UTP channel was tested with even one adjacent HDBaseT "disturber," the HDBaseT extender attempted to connect but never succeeded. Category 6 channels demon- strated marginal success during testing, but actual video signal failures did occur. Category 6 UTP cables have their limitations in carrying signals when adjacent to other cables carrying HDBaseT signals. It is not designed to support frequencies above 250 MHz nor is it capable of effectively resisting AXT. The Cat 6A cable was the only category rating to consistently support HDBaseT signals in the presence of multiple disturbers, both from data as well as other HDBaseT signals. No discernable video drop- out occurred, as it did with Cat 5e and Cat 6 cable, although some errors were detectable with an HDMI test device. Across the board, Cat 6A cable consistently delivered the signal quality required for higher resolution over long distances. Alien crosstalk may not be an issue with single isolated links within individual classrooms, confer- ence rooms, lecture halls, or other spaces that can benefit from longer distance IT/AV signals. However, applications and pathways where multiple cables are bundled together generate enough AXT to cause significant signal interference. Specifying Cat 6A cable for HDBaseT applications can help avoid unfore- seen factors that can come into play as applications, equipment choices, and structured cabling environ- ments evolve and converge during or after construction and impact the ongoing use of the functional space. UPDATED! BICSI'S FLAGSHIP RCDD ® PROGRAM FOR ICT DESIGNERS Begin your journey to elite BICSI RCDD certification. Visit bicsi.org/rcdd for details.