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Value Engineering: Don't Cut Corners

Part of my responsibility to the company where I work, and I guess to the AV industry in general through PRO AV, is to pass along what I've learned in my IT career and help close the knowledge gap between the two camps.

In my earlier discussion of UTP, I mentioned in passing the use of plastic zip ties for securing UTP bundles to each other and to cable management apparatus. This is commonplace on the AV side, but an absolute crime on the networking side. The use of hook-and-loop fasteners is the only sanctioned method.

While it may be argued that this doesn't allow for as tight a securing, that's actually the idea—the wires are not cinched tight against each other, thus not promoting cross-talk between them. Another handling issue is the maximum radius the cable can be bent—one inch. I've seen cable pulled through ceilings by untrained techs and a kink develops in the cable, which in turn is pulled tight. You've just caused a potentially disastrous condition that could render the cable useless.

Every precaution should be taken to carefully handle this cable. It is easily susceptible to damage when mishandled. It may cost just pennies per foot, but a bad run that needs to be re-pulled costs big money in labor.

Another common technique that I would love to squash once and for all is the practice of terminating solid UTP directly with RJ45 connectors. While this isn't an “illegal” practice, it's a bad habit to fall into.

First, most people are not aware that there are two different types of RJ45 connectors—those for solid-core cable and those for stranded-core cable. The difference is in the prongs that either straddle or pierce the core. Using piercing prongs on solid core cable causes the prongs to curl and can lead to intermittent signal passing.

Some might say, “OK then, I'll just buy solid-core RJ45 connectors and be fine.” But I've given both types to people and asked which is which and they were wrong. So if you can't tell, then it's no good guessing. The right way is to always terminate to a keystone jack or patch panel and use a patch cable to do the cross-connect. While this adds cost to any job (jacks, jack housing, etc.), it pays for itself in not having to rectify the situation when an intermittent connection is wreaking havoc.

IT and AV infrastructure have a lot in common, but where requirements differ even a little, doing things the wrong way can make a big difference between success and failure. Make sure the client understands that. And use the right equipment for the job.

Kris Vollrath is vice president of Advanced AV in West Chester, Pa., and an industry consultant. He can be reached at kris@digitaldesignage.com.



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