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Topic:
Properly distributed CATV system
This thread has 6 replies. Displaying all posts.
Post 1 made on Monday December 12, 2005 at 19:43
bennettavi
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Hey guys

I've got a residential job where we will be using 22-25 catv feeds through -out the house. There are 18 present now and only 5 hooked up. The old owners are selling the house and the new owners want all feeds hooked up and possibly 7 more. It doesn't matter why they want that many (i asked myself the same question) but I have a bit of a snag on proper signal distribution. There are also 2 headends. One in the old wing and one in the new wing of the house. 9 feeds at each end. One incoming line to old wing and an output from there to new wing headend. Its concrete between old and new areas so drilling holes are possible but not time effective.

Whats the best way to feed 2 headends where the main will have about 12 feeds and the other headend will have 10 -13? I'm concerned with serviceability for future calls and I am needing HDTV bandwidth to stay strong throughout. Thanks for your input.

Money is not a big object here.

Brian
Post 2 made on Tuesday December 13, 2005 at 00:06
Daniel Tonks
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Well, I'm not a CI so this is just coming from an end user that's currently servicing about 16 different CATV devices. I'm not familiar with commercial RF distribution equipment, so this is just with more readily available stuff that I use myself.

First, you're going to want RG6 throughout. Second, I would split the feed in the old wing, one line to the old headend and the other line to the new headend. Before the splitter and depending on incoming signal strength, I would probably install a quality amplifier.

At each headend I would put in something like the Channel Plus DA-8200BID, which is basically a lossless splitter (I tested and it only adds about 1db to each output) that also supports 2-way digital cable boxes. However it's only 8-way, so you could either add another splitter before each and have two 8200's or split some of the outputs 2-way (thus why you'll likely need an amp at the beginning of all of this). Channel Plus products are good quality and won't give RF interference issues like the cheaper stuff.

Of course, this all works better if you have a great cable signal to start off with. If it's crummy, then splitting this many times is not going to work well no matter what quality equipment you have.

Now, there are other solutions as well. What you pretty much need is a small apartment/condo distribution system. There are also all those fancy modular distribution panel systems out there, many designed to handle this many devices from the start.

Perhaps others more familiar can elaborate.
OP | Post 3 made on Tuesday December 13, 2005 at 18:06
bennettavi
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Daniel

Thanks for the input. I am planning on splitting the incoming signal and feeding both headends as if they were separate. Is it best to also amplify the MAIN incoming feed before the initial split and then reamplify later in the line?

Thanks
Post 4 made on Tuesday December 13, 2005 at 18:13
Daniel Tonks
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Mainly you have to make sure you don't amplify too strong before running through other amps. So, if your signal is +10db at the start, you don't want to add a +20db amp on top of that and THEN run it through an 8200 since that would overwhelm it. But it's unlikely to be +10.

I would try one good amp right at the beginning. If that doesn't work or goes too strong, try splitting and then running *two* amps, one on each leg, before getting to the distribution amps.
OP | Post 5 made on Wednesday December 14, 2005 at 20:06
bennettavi
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Ok. This is what I suspected, but just wanted to get some other ideas. I'll let you know how it goes. Thanks.

Brian
Post 6 made on Thursday December 15, 2005 at 02:11
Ernie Bornn-Gilman
Yes, That Ernie!
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Daniel is right on. The last distribution system I did that is worth mentioning here had 450 TVs and about 50 FM receivers.

With any long run, you will lose signal, and noise will stay constant. That means that signal to noise will get worse, which can show up as slight snow on an otherwise strong signal. This is not likely to happen in your case, but it illustrates a principle that Daniel suggested -- put an amp before splitting.

You want to amplify before a long run so you have plenty of signal to naturally attenuate along the line, not amplify downstream so you amplify a weaker signal and amplify its added noise too.

And you can easily overload the Channel Plus piece he suggests with a 20 dB amp. I would look for a 10 dB.

But let's back up -- google RG-6 signal loss and find out how much attenuation you will have in those long runs, then plan amplification to compensate for it. Don't worry about amplifying four to six dB too much, but ten dB over is way over.

You will need much more involved help if you have two-way communication on this cable system, for instance a cable modem or cable boxes.

Never use a VHF/FM/UHF amplifier. Cable starts at channel two and just marches up the spectrum, using all frequencies, although not in numerical order like you might expect. VHF and UHF have a huge gap of unused frequencies, corresponding to cable 23 - 64. (Cable 14 - 22 are between 6 and 7, as are a couple of channels in the 90s.) When they build amps for VHF and UHF, they parallel two amps, one for 2 - 13, and one for UHF 14 on up (cable channel 65 on up). If you use an antenna amp for cable, you will have unpredictable performance between 23 and 64, and probably horrible performance in the 40s. You can learn to see this by scanning through channels on cable; you just look at the relative snow as you go from 14 to 64.

If your cable signal looks lousy at any time, go right out to the drop, disconnect the distribution, connect a cable and run it directly to the nearest not-small TV. If the cable is lousy then, it is the cable company, and they will believe you if you show them that.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 7 made on Monday December 19, 2005 at 18:10
AVDesignPro
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If you are planning on using Channel Plus they will design the system based on your needs. That is assuming of course that you can provide them with specific information
such as signal type, signal strength, length of runs, etc.
Since as you said you are using existing wires I would hook up at the maun drop and see what I got then work my way forward adding if and when I need to.
As Daniel suggests though make sure to use good quality distribution, makes for a much easier time!
Good Luck!


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