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Does running multiple coaxial splitters on a single coaxial cable line effect quality of service for cable internet connections? Suppose there are 2-4 splitters between the cable line coming into a building before the connection to a cable modem, does this negatively effect the latency, throughput, etc of a cable internet connection by any measurable amount?

Is there a maximum number of times that a coaxial cable can be split into multiple internet and TV connections before QoS suffers?

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5 Answers 5

up vote 11 down vote accepted

It could... possibly.

You're not likely to have any problems. Many people do it themselves. If you are already receiving a marginal signal, a splitter might add enough signal loss to cause problems. If you have problems, I would suggest having your cable company install it for you. Most will do it for free (or possibly a small fee). They will have the right parts and be able to check the signal. If the signal strength is too low, they can often boost the incoming signal from the outside or provide the correct type of amplified splitter.

There are different types of splitters. Passive and active splitters, amplified splitters, different numbers of ports, and even splitters for different types of applications (TV only, high def, etc).

If you are going to do it yourself, here are a few hints that come to mind:

  • Test the speed of your un-split connection before you start. This is a good place to test your Internet speed: SpeedTest.net. Then test again after you split the signal.
  • Check your speed again the next day. I have heard splitters working for a short time after being disconnected and reconnected before problems reappear.
  • Check the lowest number cable channels. On many cable systems, those are the channels that are most likely to show interference.
  • Use a splitter with as few connections as possible (two way splitters will typically have the least signal loss).
  • Try not to daisy chain splitters (splitter attached to a splitter). If you need more ports, a four-way splitter is better than 3 two-way splitters. I've seen splitters with as many as 16 ports.
  • Use a new splitter with high-quality components. Splitters are being improved all the time. Don't dig something out of the bottom of your drawer and expect it to work as well as a new one.
  • Use a splitter specifically labeled for digital cable use (or, even better, digital Internet use).
  • Longer runs of coaxial cable have larger signal loss. If you have problems, try a shorter run.
  • If you have a loss of signal, try an amplified splitter. That may or may not boost the signal into the range required by your components.
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Note: Amplified splitters can cause problems, because they are only intended to amplify the cable signal coming from the cable provider. As a result, they can block or significantly degrade cable modem connections, as they send signals the opposite way. –  Fake Name Mar 13 '10 at 10:08
    
Don't use splitters on cable internet connections. You want a tap. Looks like a splitter, but one leg is low loss. The input hooks to the ground block, the low loss leg goes to your cable modem, the lossy side goes to your TV distribution. –  Fiasco Labs Mar 4 '12 at 18:52
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Yes, this definately degrade performance. On my Y splitter, on each split it says -3.5 dB. Which is the loss. So this means.

-3.5 = -10 * log(P1 / P2)

so

10^.35 = P1 / P2 = 2.23872114

P2 is the output, so you get P1/ 2.23872114 output power. The next question is, will you notice? For analog signals, like TV, I notice just a little extra noise. That might be my imagination though. For digital signals, like you internet, this means your bit error rate will go up slightly. (Since the signal to noise ratio will be lower). So, you get more packets with flipped bits. When this happens sometimes the packet can correct itself, sometimes you to resend the packet. This basically, means your internet connections will be a little slower.

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ouch! now my head hurts. too early for math! –  BillN Aug 6 '09 at 15:46
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one too many splits and you will lose modem connectivity frequently

[just went through this with Comcast; they ran a separate line for my cable modem split off the main, problem went away]

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I'd give you +100 if I could just for not typing "loose". –  bmb Aug 2 '09 at 6:21
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@[bmb]: people using "loose" when they mean "lose" is also one of my pet peeves, as I am an ASCII Conservationist ;-) –  Steven A. Lowe Aug 2 '09 at 16:58
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You will not notice any errors or speed differences with your internet as long as you are within the specified operating range that it is supposed to run in. For a 256 qam carrier you want a 32 snr, you want better than a 1 e - 8 Bit error rate. And you want better than a -10 dbmv signal level. You also want no worse than a 55 dbmv upstream level. If you can stay within those ranges you will not notice any difference. As an fyi, as long as their is not any issues such as ingress, cable damage, passive damage, or other issues such as to low MER ETC. You will not see bit error rates. You will see bit errors, when bits of information start to fall outside of the decision boundaries for a qam signal. Their are many factors that can cause that but as long as you follow the afforementioned guidelines you will not cause these at the house.

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Yes, splitters can have significant effects on the signal quality. The topic is fairly well covered here.

However, another thing to be aware of is that having unterminated cables can also affect your signal quality (By unterminated, I mean not connected to a device. Any device with a cable input will have a 75 ohm terminating resistor on the input [ref]).

Basically, you should only have as many cable splitter ports as you are actively using, or are at least hooked up to devices.

If you have cable drops in each room, disconnect the cable runs that are not in use. Otherwise, you can get signal reflections off the unterminated cable ends, that interfere with your signal quality and television.

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