Technical > Cable & Satellite TV > [Cable] help with splitter configuration

[Cable] help with splitter configuration

Current setup

planned setup

Your "current" diagram show (3) lines going to TVs, one listed as digital. You said there's no digital boxes though...

In your proposed setup, you're still keeping the cable modem on it's own, unsplit leg, which is good. As for stacking splitters, I don't know, but there's plenty of techs here who do. I know you can do it this way, but then you get into amplifying certain legs different amounts.

I meant that the addition did not have any digital boxes. There is still one digital box on one of the existing lines. The added lines will be used for analog only.

reply to ilikeme
I have a setup very similar to your described planned setup, only 2 legs are to digital cable and 3 to analog. I needed an amplifer for that third split even though I have been told buy a cable tech that I have a very strong signal to the house. So I am guessing that you are marginal.

reply to ilikeme
I'd add an amplifier to the setup to keep the analog signals clean. If you have the cable company do it, they'd probably want to install an amp as well.

It's simple to do. Using a 1GHz 2-way splitter, one leads to the cable modem, the other to an 8-way amplifier. The amplifier MUST be bi-directional, otherwise the digital box will cease to function.

Electroline makes an excellent line of "Digital Bi-Directional" amps. Most cable companies I've seen use them, so you can't go wrong using one. They're easily found on eBay, just run a search for "Electroline 8 amplifier" and you'll find a bunch of them. Just make sure you see either "Drop Amp" or "Active Return" or "5-40 54-1000 MHz" somewhere in the description.
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reply to ilikeme

Nicely done!

Thanks

reply to ilikeme
sweet, thats exactly how mine is, except the main split is done OUTSIDE my house in the cable company access box located on the side of my house, then 2 wires are entering the basement electrical panel, one to the TV line which is split up afterwards, the other to the internet line.
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reply to ilikeme
Why don't you start with finding out what kind of signal you have going to that modem to begin with. Many modems have a user accessible diagnostics screen (»192.168.100.1 is the most common) where you can check the readings the modem is reporting. That way you can see if you can afford to split the signal more or if you'd need to leave it alone.

The contention that many make about having a cable modem on direct "un-split" leg is a farce. Sending HALF of all the signal to your modem can be overkill in so many cases.

The cable signal on the way to your modem is split and tapped off along the network on it's way to your home in the same way that the splitters and directional couplers on the side of your house do the same. Houses being fed in a cable system are nothing more than big outlets. The signal is spliced and diced, split and amped on the way to each home.

The transmitting power for your modem (the power level at which your modem needs to communicate to make it to the first reverse amp in the system to get upstream through the network) is an important factor in your modems performance.

You'll often hear about transmit levels being too high (I don't like mine above 49) but too LOW of a transmit level can also cause problems as well. I've seen it many times . Especially if you're off of a low value tap at the end of a cascade. In which you might actually want to put your modem behind more splits to the bring those levels closer to where they should be.

Forgive the rant, of sorts. But sure, if you've no idea as to what sort of levels up and down are coming in to your house, then err on the side of caution.

With the digital box you can also gleen a fair amount of information about the rest of the sigal levels on the other frequencies. It's been a couple years, but if you have a Scientific Atlanta digital box then I think I recall those boxes reporting dowstream power level on the digital frequencies. Therefore, with some basic knowledge of attenuation you'll know if you need an amp at all.

I've worked with two different networks. One where we'd be lucky to run more than 4 outlets without a house amp(i'd install an amp every few days , and another system where it wasn't uncommon to have 20dBmV which is enough to power an 8 way splitter and have plenty of juice to spare in an average sized house (i'd go MONTHS sometimes in between amps .

malvado I don't know if you're in Mediacom area but that is not correct. Yes a lot of areas have too high signal right now and sometimes running the modem off of a two way will cause problems but that's why the line techs are there to fix the signal.

3 years ago or so modem was just fine after a lot of splitters, but that has changed. With phone service most likely you will have borderline upstream power level or even worse.

You can see my setup in this thread and take a look at these values (note that upstream goes up to 49 sometimes)

Downstream
Freq/Power: 111.000 MHz 1 dBmV
Signal to Noise Ratio: 36 dB
Modulation: QAM256
Upstream
Freq/Power: 25.008 MHz 47 dBmV
Channel Type: DOCSIS 1.x (TDMA)
Symbol Rate: 2560 kSym/sec
Modulation: QPSK

reply to ilikeme
i'm not sure what i'm supposed to deduce from your levels. my point in my post is that there is a litany of factors that affect the transmit levels for a modem. including tap values, position in the cascade, splits and dc's after the amp, etc etc.

My upstream is at 47. That's just with a two way splitter. My point is

Modems should be fed from the first split.

reply to ilikeme
YOUR modem is at 47 after one split because you may be off of a high value tap, or have something impeding your return path, or something unique to YOUR situation.

My Tx is at 43 and I'm behind a 4way splitter and the directional coupler that is inside my digital phone equipment.

It is a high value tap. But it's still better to have it fed from the first split because fewer people will have problems.

reply to ilikeme
Re-read my original post. There is such a thing as having too low of a transmit level. I've seen it with CBR telephony modems, voip modems, and regular modems.

As I alluded to originally, if you have absolutely no idea as to what sort of levels you are dealing with, err on the side of caution and send half of all the signal coming to your home to the modem.

But the contention that doing this is necessary in all situations, is ridiculous. Especially when responders are telling posters to send half the signal to a modem and then AMP the other outlets. These are the same people that think 15dBmV is better that 0dBmV.

I don't know if that applies to me but when it gets warmer, people with 5 outlets or more will most likely need an amp. It's been like that for a while now.

Actually for cable just "basic" 2-99 analog can be fine with up to 10 splits, since it can generally go to -25db without any notice of picture quality. This also varies with the size of a tv with bigger tv's i would say 32" or bigger no less than -9db but lets say you have 1 split for a modem right at a 2 way splitter, then a 8 way splitter you should be good since most 8 ways are -8db each leg. Now this all varies with length from tap to tv, signal from Ground Block to Tv and also if you have Digital ( Which I have seen Scientific Atlantic converters go to -14db and still not pixelate/tile and still go 2way

reply to ilikeme
IMO, your service standards must not be very high if analog picture quality at -25dBmV is acceptable. And I have seen digital qam's push -20 and be fine with a good enough SNR.

BTW, the loss off of an 8-way is about -11dB.