With the proliferation of home audio-video equipment, the cabling can be fairly messy. Most equipment connections are still via bulky and expensive coaxial cable. In an effort to streamline home cabling and networking problems, a number of technologies such as Wi-Fi, USB, 1394 and Ethernet have evolved to manage the myriad interconnections. Despite the value these systems offer, they cannot solve all the cabling problems that crop up in a home audio-video/networking system.
There are many custom audio-video cabling problems that can be solved by relatively inexpensive cabling techniques. One of the frequent problems that come up is how to connect an audio-video signal from point A to point B without drilling holes in walls and pulling more coaxial cable. For example, if a homeowner wants to connect his DVD from the basement playroom to an audio-video monitor at the other end of the house, he would normally have to run three (3) coaxial cables; one for video and two for stereo audio.
Without going to considerable expense and assuming the home is pre-wired from a central wiring box with Cat 5 cable to each room, he could connect simple passive devices known as video baluns to the DVD and audio-video monitor and patch the connection through at the wiring box.
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Video baluns can save an enormous amount of time. Available in different flavors, they convert audio or video signals from unbalanced coax to balanced twisted pair. Contrary to popular belief, advances in twisted pair and balun technology have resulted in audio-video performance that is virtually as good as any coaxial cable and in some instances surpass coax in terms of distance. This is due mainly to twisted pair’s noise cancellation effect when the video is transmitted a balanced signal.
An example of this is S-Video. S-Video typically supports no more than 300 to 500 feet over S-Video cable. With the proper S-Video balun and Cat 5 UTP, distances of 1000 feet with excellent picture resolution are easily achieved in a point-to-point connection. Consequently at short distances, there is no perceptible difference in picture quality between using S-Video cable and twisted pair.
Today video baluns exist for many audio-video environments; composite video, S-Video, VGA, RGB, stereo audio and even CATV for broadband RF TV. Video baluns work in pairs and if the distance is within the vendor’s specifications, they can really get you out of a jam for a fraction of the price of active transceiver equipment.
Video baluns are used in pairs. In each case they convert one or more coax-based audio-video signals into one or more twisted pairs. Since each Cat 5 cable typically supports four twisted pairs, one can easily replace up to four coaxial cables by one Cat 5 cable. This translates into significant savings for the consumer and the installer. Their passive design eases installation by eliminating the need for an extra power supply.
The main issues in using video baluns are to determine whether the application is within the performance limits of the baluns and the cable. Video signals that have bandwidth requirements as the picture resolution increases will be more sensitive to cable length. VGA is one example. At 1200 x 1600, the maximum distance supported via Cat 5 will be shorter than if the picture resolution is set to 800 x 600.
S-Video, whose bandwidth requirement is on the order of 5 to 8 MHz will perform well at distances up to 1000 feet. Another issue is the ability to bundle multiple audio, video and other low voltage signals under the same Cat 5 cable. The excellent crosstalk performance of Cat 5 has allowed even further optimization of cable runs by allowing multiple audio-video signals to share the same multipair cable.
Ten years ago it might be possible to worry about the sound and picture quality at the end of a video balun connection. But today, these concerns are diminishing as the design quality of the video baluns and twisted pair cable keeps improving. In many instances, one would be hard-pressed to tell the difference between an audio-video signal transmitted via coax cable versus the same signal sent via twisted pair and video baluns.
In general, the consumer is probably unaware that advances in cabling and balun technology have put inexpensive Cat 5 cabling solutions within reach of the average homeowner. Video baluns are carving a niche for solving many point-to-point cabling problems. More information about video balun solutions can be found at www.muxlab.com.
NHC is a designer and manufacturer of connectivity and physical layer switching solutions for the structured cabling and networking industry. Jeffrey Herman is a Product Manager at NHC Communications Inc. He may be contacted at firstname.lastname@example.org or at 514-734-4320.