Although UTP cable was designed for use with phone and data networks, its popularity in the CCTV world is growing rapidly. UTP is often chosen over coax and fiber because of its ease of installation, cabling options, noise immunity, ground-loop isolation and surge protection.
UTP employs a robust, balanced mode of transmission, making it highly resistant to interference. Video signals can reside in the same wire bundle with signals for ringing telephones, Ethernet, 24 VAC, RS-422, RS-485 and other video signals. They can also reside in high-noise environments such as elevator traveling cables, or near fluorescent lights, radio transmitters or motors.
UTP wire is about one-tenth the diameter of RG-59, which makes it easier to pull and terminate. Both UTP and coax are available with plenum-rated jackets, but if you compare plenum coax and plenum UTP, the differences become quite apparent. As the number of cables needed increases, each added coax adds bulk in addition to its own plenum jacket. But since up to 100 UTP pairs can reside under a single plenum jacket, the UTP bulk is much less. One four-pair plenum Cat 5 UTP costs about one-fourth per channel what plenum coax does. However, for non-plenum wire runs under 250 feet, UTP transceivers may cost more than standard coax.
UTP transmission is also significantly less costly than fiber, from cable and installation to tooling and transceivers. A UTP passive-to-active system offers the same features as fiber. That's why many installers have switched from fiber to UTP cable for longer runs. Nonetheless, fiber is still the answer for extremely long runs (more than 8,000 feet, for instance). For safety, fiber is a good choice when video must run in the same conduit as high voltage.
What Is UTP Cable?
Sometimes called category cable, UTP cable is generally 22 or 24AWG copper wire that is twisted into pairs, with each pair color coded for easy tracing. Bundles can range from two to 2,400 pairs and are available in plenum, PVC, direct-burial, gopher-resistant, and aerial formats, among others. UTP is categorized into grades depending on cable characteristics. Category (Cat) 2 cable is what most buildings 20 years old and older have installed for their phone systems. Cat 3 cable has a tighter twist and better performance. Cat 2 or 3 cable is perfectly adequate for CCTV applications.
Cat 5 has been designed for optimum performance in data networks and phone systems, with a tight, controlled twist. Cat 5, 5e and new Cat 6 cables are also capable of sending CCTV signals but aren't necessary for distances under one mile.
Though Cat 5 data networks need to follow a specific set of rules to be certified, breaking some of these rules will not affect your video signal unless you are planning on sharing your cable with a high-speed data network. The most important UTP CCTV rules are simple:
1) Don't use shielded wire with individually shielded pairs (capacitance above 19pF/foot). A multi-pair cable with an overall shield surrounding six or more pairs is fine.
2) Don't use untwisted wireÃ¢â‚¬â€it will compromise noise rejection.
Types of UTP Systems
There are three types of UTP systems, defined by the transceivers used: passive transmitting to passive (un-amplified), passive transmitting to active (amplified), and active transmitting to active.
Totally passive systems are for short distances. They are low in cost and support up-the-coax pan/tilt/zoom (PTZ) control. The signal loss through the wire is similar to that of RG-59, so UTP can be used for normal-resolution cameras and analog recording and multiplexing up to 1,000 feet. For high-resolution and DVR applications, the maximum recommended distance is 750 feet. Passive-to-passive solutions have signal attenuation similar to that of RG-59 and do not provide ground-loop immunity.