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 The basics of multi-room video To maximize performance of your DSS system we recommend connecting the audio and video outputs directly to your home theater system. The multi-room techniques we talk about here could also let you watch your VCR, videodisc player, or front door CCTV camera from every room in your house. |
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INTRODUCTION
If
you are like most new DSS owners, your system looks like this. You also probably have more
than one TV in the house. The natural question is “How come I just spent a bundle on
a satellite system, but can only use it in one room?!?”
In this document, we will explain the many options and tradeoffs of creating a whole house video system. Because this is a basic guide, we will avoid technical jargon as much as possible. And, although we sell many of the products we talk about, we will try to keep our opinions under control and minimize the hype.
First, let’s look inside your DSS receiver. The signals from
the dish are sent to the satellite tuner. The satellite tuner selects the program of your
choice and creates audio and video signals. 
The video modulator takes the audio/video
signals and creates a television type signal that will appear on TV channel 3 or 4. We
refer to this type of TV signal as RF (for radio frequency). There is a switch in the DSS
receiver. When you press the ‘Antenna’ button on the front of the DSS receiver,
this switch disconnects the TV from the ch3 modulator and connects the TV to the antenna.
The audio/video signals are available on jacks at the back of your DSS receiver. Your DSS
manual tells you how to use these signals for the highest performance on your home
theater. Finally, if you want to watch 2 DSS programs at the same time, you must have 2
receivers. (Just like a VCR. To watch two tapes at the same time you need 2 VCRs.)
A
‘channel 3 combiner’ inserts the channel 3 RF output of the DSS receiver onto
the coax that has the local programming. To watch the DSS program, tune either TV to
channel 3. No switch to throw, the ultimate in simple operation.
But watch out! If you have local programming on channels 2, 3, 4, or 5, we do not recommend the use of a ‘channel 3 combiner’. (Note that this eliminates anyone using Cable for their local programming.)
EXPLANATION of the PROBLEMS:
1) If you already have a channel 3 on the antenna coax, the ‘channel 3 combiner’
will not completely eliminate it. This broadcast signal will interfere with the DSS
receiver channel 3 signal. Even a very weak broadcast signal will cause some interference.
(In the commercial world, there are such things as channel deletion filters, but they are
extremely expensive.)
2) The channel 3 modulator inside your DSS receiver lacks the expensive filtering of
broadcast modulators. The DSS channel 3 signal is ‘wider’ than it should be and
the channel 3 signal will spill into nearby channels. Adding this signal to the coax will
cause interference on channels 2, 4, and 5.
COST: $20 for the combiner
ADVANTAGES: Each television can watch the DSS program or any of the local programming, independent of the other TV. (Yes, there are channel 4 combiners also.).
DISADVANTAGES: Works well in only a small percentage of installations. If you live in a rural area with no VHF channels, give this a try. Otherwise, stay away.
WE BET YOU DIDN’T KNOW: The channel 3 output of your DSS receiver is monaural (as are all VCRs, videodisc players, etc that are sold in the US.). The stereo television standard used in the US (referred to as MTS) makes stereo encoding difficult and expensive. To maximize performance of your DSS system we recommend connecting the audio and video outputs directly to your home theater system. The multi-room techniques we talk about here could also let you watch your VCR, videodisc player, or front door CCTV camera from every room in your house.
Typical Satellite DistributionSystem
All broadcast channels appear normally on all Tvs. Satellite receiver appears on an unused UHF channel number on all Tvs. IR control signals can be relayed from remote TV locations to the satellite receiver, using IR targets and emitters. Model 3025 has video/audio inputs for two devices. (Put satellite on channel 26, DVD on channel 28.) Model 3025 has outputs for 5 Tvs.
USING TWO DSS RECEIVERS If you want to watch 2 DSS programs at the same time, you must have 2 receivers and you must have a dual LNB. Here is the classic dual LNB, dual receiver connection. Each receiver is totally independent of the other. Unfortunately, things get messy when you add local channels. |
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More on USING TWO DSS RECEIVERS Splitting the local programming allows each TV to select what to view with complete independence. DISADVANTAGE: You must run two coax cables to the remote TV. |
DIPLEXERS Because the DSS dish signals and TV RF signals use different frequencies, they may be combined. A diplexer combines the dish signals and the antenna signals on a single coax and then breaks them apart again at the DSS receiver. This way you need only one coax to the remote TV. COST: Diplexers cost $30. |
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Wireless systems are the easiest to install. One unit at each end will transmit the signal from the DSS receiver to a remote TV. These are available from several manufacturers and can be purchased from major electronics dealers and some home centers.
WHAT YOU CAN DO: Either TV can watch any local programming without affecting the other TV. One or both TVs can watch DSS, but they must watch the same DSS program.
COST: $100-$250
ADVANTAGES: No coax cable to run
DISADVANTAGES: Only the DSS receiver signals get transmitted to the remote TV. To watch local programming you will need rabbit ears on the remote TV, or a separate coax. Wireless systems are subject to interference from outside sources. Wireless systems are subject to transmission difficulties. (Think how putting your hand near a rabbit ear antenna affects the picture. There will be some amount of that.) ! ! !
USING A SPLITTER
A
splitter divides the power of the RF signals in half. Coax cable delivers the signals to
the remote TV.
WHAT YOU CAN DO: Either TV can watch any local programming without affecting the other. But, if either TV is watching a DSS program, both TVs must watch the DSS program (The Antenna/Satellite switch in the satellite receiver will control both TVs).
COST: $5 for the splitter, $0.25 per foot for RG-6 coax
ADVANTAGES: Cheap
DISADVANTAGES: Not versatile Every time you split the coax, you are reducing the signal strength. A long length of coax will also reduce the signal strength,. (Yes, you can add an RF amplifier to increase the signal strength, but this is a basic guide and things become much more complicated when you add amps and more splitters. Caveat emptor.) ! !
USING AN ALL-IN-ONE VIDEO DISTRIBUTION SYSTEM
A new class of product, the All-in-One Video Distribution System combines modulators, splitters, combiners, and amplifiers together in one package. These systems are ‘pre-engineered’ so you don’t have to design them. In this figure any of 4 TVs can watch any of the local channels, or tune to channel 60 to watch the satellite program.
COST: $250 at satellite specialty dealers and Radio Shack
ADVANTAGES: Each television can watch the DSS program or any of the local channels, independent of the other TVs. Some All-in-Ones have multiple modulators (watch the DSS on channel 60 and the front door camera on channel 62.) Some even allow you to use your remote controls to start the VCR or change the DSS program from any TV in the house. If what you want to do is use your one DSS receiver from any room in the house, this solution offers simplicity and convenience.
DISADVANTAGE: You still can watch only one DSS program at a time.
USING AN EXTERNAL MODULATORCOAX, SPLITTERS, AMPLIFIERS and CONNECTORS
COAX: RF distribution requires 75 ohm coax cable. Both RG-59 and RG-6 are 75 ohm coax cables. RG-59 coax has only slightly higher attenuation than RG-6 coax. But a lot of RG-59 is not made for this purpose and may be quite lossy at high frequencies. Virtually all RG-6 is a good choice. To be safe we recommend sticking with RG-6 coax. It costs only pennies more.
SPLITTERS: Do not use splitters that read ‘CATV’ or ‘50-450MHz’. They were designed for cable systems and will not work well for a whole house video system.
AMPLIFIERS: It sounds easy: Weak signals? Add an RF amp. More TVs? Add splitters and a higher gain amp. The more gain, the more powerful the signals. What could go wrong? Plenty! There is nothing harder in RF distribution than adding an amplifier. More gain in an RF amplifier increases the ability to overdrive the output stages of the amp. Expensive RF amplifiers have higher headroom, not more gain. Be cautious when adding an amp. The distortion you get from overdriving an amplifier is more objectionable than a weak signal.
CONNECTORS: Putting F connectors on coax cable is easy . Inexpensive coax strippers and crimpers are available for under $20 for both. This small investment will save you a lot of grief. More advice: The number one cause of video distribution problems is F connectors that were put on finger tight. Tighten them with a wrench! Good if you use the correct tools
Why not create an out-of-the-way channel instead of using channel 3? Stand-alone video modulators exist for just this purpose. These modulators are also referred to as ‘agile’ since you can select what number channel they create. The ‘combiner’ shown in the diagram is actually a splitter that is used backwards (do not use a ‘channel 3 combiner’).
COST: Cheap modulators are available for $40. (These will give you headaches by drifting off frequency.) Good modulators start at around $100 and go up to $800 for multiple modulator channels, MTS stereo and other features.
ADVANTAGES: Each TV can watch the DSS program or any of the local channels, independent of the other TV.
DISADVANTAGES: Hard to find. These devices are sold by satellite specialists and professional satellite installers. Combining modulator signals to an antenna has the potential to broadcast interference to your neighbors. Using an amplifier on the antenna feed will block the modulator signals from the antenna. ! ! Agile modulators are used by professional installers to distribute signals from DSS receivers , VCRs, videodisc players and closed circuit cameras to all TVs in a home. (Creating this type of elaborate system could be beyond the abilities of the home hobbyist. Professional installers have thousands of dollars of test equipment and years of experience designing and installing this type of system. Be aware, RF distribution can be tough!)
HOME RUN WIRING and PRE-WIRING A NEW HOME
In residential systems, the highest reliability and highest performance wiring scheme is to use ‘home runs’. Every TV coax should be run all of the way back to a central point, or ‘home’. This wiring style is also referred to as a ‘star’ topology because all coaxes radiate from this central point. Home run wiring allows you to have all of your splitters, combiners and amplifiers at one location. If you are building a new home, be sure to home run coaxes from all potential TV locations to the central distribution point. If the central point is not where the CATV enters your house, you will have to provide a coax from this central point to the cable entry location. In addition, run two extra coaxs from the central point to where you will locate your video equipment and two coaxs to the dish location. These cables will service the DSS dish and a video modulator . Even if you do not use the modulator coax or all of the TV feeds, you will enhance the value of your home and prepare for future expansion.
