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Home Toys Article - February 2005 - [Home Page] |
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Balanced Signal Delivery for a
Unbalanced World 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. |
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What are baluns, what do they do? A balun is a device that joins a balanced line (one that has two conductors, with equal currents in opposite directions, such as a twisted pair cable) to an unbalanced line (one that has just one conductor and a ground, such as a coaxial cable).
The concept and process of sending various electrical signals over twisted pair dates back some 25 years, in the late 1970's Unshielded Twisted Pair (UTP) cabling was originally developed by the computer industry for transmitting low data rate signals over computer networks. Digital data signals are relatively forgiving and can tolerate substantial interference and degradation before affecting the integrity of the signal. Unfortunately, most of these early devices provided poor performance and inadequate noise immunity and no ground loop isolation, which prohibited them from being used for other applications. Other early adopters of this technology included the security CCTV field for video surveillance camera's and equipment. But today's balun technology is going Hi-Tech, using 100 Ohm (UTP) solid conductor cables to send Data, Video, Audio & Control signals long distances over off the shelf Category 5 (Cat5), Category 5 enhanced (Cat5e) or Category 6 (Cat6) cables. Balanced networking cables are changing the distribution schemes of signal delivery in residential and commercial applications. Using this technology for mid to long runs can both cut cost and reduce installation time.
Today's balun transmission system's carry HDTV signals and are
available as active or passive devices and require two pieces one at
each end. Active systems are unidirectional, (Transmitter and Receiver)
and use semiconductors that require power to achieve a balanced line
driver circuit which usually has the ability to drive the signal further
then a passive design which is Bidirectional, requires no power and
makes use of special transformers, inductors and passive components to
convert audio & video signals from unbalanced to balanced and vice
versa. By doing so, baluns make the necessary impedance adjustments for
A/V signal transmission between different wiring systems. There are many
custom audio-video cabling problems that can be solved using baluns. One
of several problems that come up is how to distribute audio-video
signals from one area to another without drilling large holes in walls
and pulling several cables. For example, if a homeowner wants to connect
his DVD from their Home theater system to an audio-video monitor located
at the other end of the house, he would normally have to route three
bulky coaxial cables, one for video and two for stereo audio or a
sizeable molded single combination A\V cable.
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 640 x 480 or if a signal is component video or composite video. Why Use Baluns? Baluns extend transmission distances. 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 support's 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. S-Video, whose bandwidth requirement is on the order of 5 to 8 MHz will perform well at distances up to 1000 feet. Baluns can passively transmit audio and low bandwidth video signals up to 2,500 ft., high bandwidth signals such as component video up to 500 feet and actively transmit component video and VGA signals up to more than 500 feet. Baluns can utilize existing wiring, and many buildings already contain structured cabling systems. If so, the hard work is already done, simply connect a balun at each end of the cable run to transmit your signal. Baluns reduce installation cost and increase installation efficiency. Traditionally, a single cable could not transmit both audio and video. By using baluns, many types of low voltage signals can be transmitted via one inexpensive run of Cat 5 cable. Some baluns can reduce interference because they contain special circuitry, isolation transformers and utilize twisted cabling that can help eliminate the ground loops that cause EMI and RFI interference. Baluns lower installation cost. In many installations, the cost of baluns plus Cat 5 cable is less than traditional wire, such as coaxial and twisted pair audio.
Not all industry professionals subscribe to the uses of baluns as a permanent fixture or standard method of long cable integration, but rather to conventional shielded cables and other existing or emerging technologies such as (DVI) Digital Visual Interface, (HDMI) High Definition Multimedia Interface, the all in one cable solution that carries digital video, audio and the CEC, AV.link remote control protocols. But DVI and HDMI is plagued with signal delivery length issues, HDMI has a poor non-locking interconnect design and the inability to separate the video and audio into usable signal components for current analog components or multi-room audio systems. HDMI at present has limited product integration between many electronic products and that not all manufactures abide by the DDWG standard specifications. There are many technical issues involved using baluns that go beyond the scope of this article. Most consumers are not aware of the advances in cabling and balun technology using inexpensive Cat 5 wiring solutions. Each day the internet and other technical news sources are providing more relevant information and additional product awareness. Balun technology is available to the industry from many reliable sources, its use can provide the addition options and problem solving solutions when necessary, placing this technology within the reach of both installers and the average homeowner. More information about video balun solutions can be found at :
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Installation
of a single (UTP) Ethernet cable and a set of baluns will achieve the
same result, in some cases it is possible to use spare or existing (UTP)
cable that may be available in the wall, eliminating the need to run
additional cables at all. 
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 as a balanced signal. Baluns provide many uses,
audio-video environments such as composite video, S-Video, VGA, RGB,
component video, stereo audio, low current DC power, infrared signals
and even CATV for broadband, TV RF. Video baluns come in all types of
sizes and configurations, new products are being introduced regularly,
balun distribution amplifiers, switchers, hubs. 
