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Video Distribution Tutorial Your video distribution need may be as simple as getting a decent quality cable TV hookup to each TV. Or you may be planning to have several video cameras that you want to view from any TV, and want to "share" VCRs, satellite receivers, DVDs, etc. among all the TVs in the house.
In either case, if you're going to be wiring the video distribution system in your new or remodeled home, you need to come up to speed on what it's all about and how its done. It isn't terribly difficult or complicated. In fact, I think its actually quite fun! Its pretty much a science until you get to the "tuning" part at the end. So don't be scared. Dive in and enjoy! You can do a much better job than your electrician or local TCI "cable guy."
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A Little HistoryResidential video distribution has come a long way since the days of a roof-mounted antenna connected to a TV by a length of 300 ohm twin-lead flat-cable snaking through a window screen. Back in those days just about anybody could hook up a TV. And when a home had more than one TV (which was rare) the other sets made do with rabbit ears!Then came cable. At first the cable companies were more than happy to hook up your TVs for free, just to get your long-term business. If you had more than one TV, they just put a splitter on the side of your home. They controlled the signal level coming down the cable so if they needed more signal strength, they handled it "up at the pole." After a while, the cable companies became the de-facto masters of video distribution and, thus, were able to charge for installations. Over the last few years, there has been a trend for the homeowner to take charge of the low-voltage wiring within the home. This trend was driven, for the most part, by the phone and cable TV companies' attempt to make installations a "profit center." When phone and cable installations got expensive enough (and sloppily done, at that) the homeowners started doing it themselves. Today, it seems, neither the phone or cable companies care who does the installation. Which suits us just fine, because we know that we can help you do awholelot better job than they would. All the cable company cares about (besides you paying your bill) is that you don't mess up the signal going to neighboring "drops" (in other words--don't send any signals back up the cable) and that you don't get them in trouble with the FCC by "leaking" their signals into the air. |
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Introduction To Video DistributionVideo distribution is all about getting a strong clear signal, of all channels (regardless of the source), to all video destinations within the home. This involves three general functions: Gathering, and in some cases creating, the signals in one area; Combining, conditioning, and amplifying the signals; And distributing the signals to their destinations.The first thing your need to know about video distribution is that what you are really distributing is Radio Frequency (RF) signals. These signals, given the opportunity, would happily fly through the air to your TVs. But this method of video distribution is frowned upon by the FCC because they would rather let the "licensed broadcasters" handle that method of distribution. Instead, we force the RF signal to go down shielded coaxial cables. Apart from the distribution task itself, the two most important parts of creating a video distribution system are to keep your signals inside the cables, and to keepothersignals out of the cables! A single coaxial cable can carry 130, or more, standard channel frequencies. Each channel includes video and audio components. With MTS encoding, each channel can even have stereo audio. Contrary to an RF channel, which can coexist on a coaxial cable with many other channels, "baseband" video takes the whole cable, and doesn't even include sound! Baseband video and audio is what comes out of the RCA (a.k.a. "phono") jacks on the back of your VCR. Since it takes two coaxial cables to transport a single baseband video and audio source, you generally want to convert baseband into RF as "early" as possible. Which means as close to the source as possible. You convert baseband to RF with a device called a modulator. Most modulators today are simple little digital boxes that are similar to,but the reverse of, a cable box. They have inputs for video and audio, and an output for RF. (RF is almost always an "F" type connector.) You can use one or more modulators to create your own "in-house" channels. In effect, you create your own cable TV company. A cable coming in from your antenna or the cable company contains many RF channels and needs no modulation. From a "block diagram" standpoint, there are four key pieces to any video distribution system: The coaxial cables themselves, which serve as a conduit for the RF signals and allow interconnecting the other key pieces; RF Amplifiers that "boost" the RF signals to make up for the signal losses the other pieces impose; Combiners which "add" two or more cables together to create a single output that contains all channels frombothinput cables; And splitters that take a single input cable and distribute the same signal to two or more output cables. Planning a video distribution system is not difficult. You need to understand what the key pieces do, have a blueprint of your home, and be able to do a littleverysimple math. That's it! Ready to Go On?This application note covers video distribution in four sections:
Please note that this application noteis notabouthome theatersystems, although it obviously describes how to get RF signals to and from the home theater system, and how to share home theater video sources with the rest of the home. It does not, however, describe how to interconnect baseband video/audio between the home theater components, or how to carry baseband or s-video signals throughout your home. (A practice we do not recommend.) Nor does this application note cover whole-house audio distribution. See our Whole-House Audio Tutorial. Although video source components may supply audio to the whole-house audio system, we will treat whole-house audio distribution as a separate system. This document also does not cover DSS/Satellite signal distribution. See How Do I...Connect Multiple DSS Receivers. To integrate DSS distribution with your video distribution system, design the video distribution system first, then "piggyback" the DSS signals to the appropriate locations on the video distribution cable as described in the DSS document. Throughout this document you will see highlighted part numbers. These are hyperlinks to more information elsewhere on our website about specific products. Unlike other "sterile" documents that claim to educate you about whole-house audio without actually naming any products or even brands, this document lets you click your way all the way through to actual product specifications, pictures, and prices!
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Glossary
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