Issue link: https://www.e-digitaleditions.com/i/1156106
12 I ICT TODAY easily pulled through conduits and raceways and field terminated. HDBaseT can carry AV and related signals up to 328 feet (100 meters) over twisted pair. For longer runs or where security or radio frequency interference (RFI) are concerns, there are transmitter-receiver pairs that work with optical fiber cable to carry the same signals, minus power, over many miles. Here, the focus is on HDBaseT over twisted pair. Twisted-Pair Cable Construction When running digital AV content over Category twisted- pair cable, outside interference or alien crosstalk is a major concern. The interference can come from nearby electrical equipment, adjacent signal or power cables or from near- by radio transmitters. Interference can cause bit errors in the audio and video data streams, and it can corrupt EDID, HDCP and control signal data transfers and hand- shakes. The results range from image dropouts and flash- ing to audio dropouts and no image or sound at all. Cat 6A SF/UTP cable (Figure 3) offers optimum interference pro- tection and ease of termination. The combination of over- all aluminum foil and copper braided shields effectively repels interference encountered in all but the most hostile environments, while keeping the cable diameter small enough to terminate into an RJ45 connector. Termination and Patches There should be no more than two patch points between transmitter and receiver (Figure 4). All RJ45 plugs and jacks, patch cables, and punch-downs should carry the same rating as the Category cable (e.g., Cat 6A). Use shielded plugs, jacks, and punch-downs. Maintain the twists of the pairs as close as possible to the point of termination and no more than 0.5 inches (12.7 mm) untwisted wire. Shielded cables must be grounded from end to end for safety and immunity against interference; this means carrying shield connections through patch points and grounding all system components. Pair Conductor Insulation Outer Jacket Foil Shield Braided Shield FIGURE 3: Cat 6A SF/UTP cable construction has two overall shields for 100 percent coverage. FIGURE 4: Cable infrastructure; no more than two patch points are recommended between transmitter and receiver. 2 1 2 Punch Block Receiver Receiver Patch Cable Patch Cable Patch Cable 1 Wallplate Wallplate Wallplate Transmitter Transmitter