I'm interested in optimizing my current coaxial splitter setup that was primarily done by Comcast on one of their service calls.

enter image description here

During the first stage the coaxial cable from the cable provider is split (1000mhz, -3.5db on both outputs) (black splitter on left of image). 1/2 goes to an return amplifier (white box center of image) and then an 8 port splitter (far right of image; unknown specs) which provides all the TV's in the house with a signal, and the other 1/2 goes directly to a cable modem.

I am curious as to how I can possibly optimize this setup for better all around performance. The signal on the TV's is fine and not grainy, but I sometimes experience Internet outages for a minute or so in the afternoon.

Would it be beneficial for me to replace the splitter in the first stage? Or to boost the signal for the modem with a separate amplifier? Do you see any issues in my current setup?

Modem Power Levels

  • My guess is the first splitter splits of your high speed internet modem line, the second larger white box is an amplifier feeding the larger splitter ... My advice is don't change it. Digital TV will never be "grainy" in the same way analog once was.
    – Tyson
    Dec 20, 2016 at 3:31
  • You don't have to guess that's exactly what I said haha. But yea I'm more concerned about the first splitter.
    – Alex
    Dec 20, 2016 at 3:32
  • Moving the internet to the other side of the amplifier will likely break your internet. With Comcast you're actually best to complain about intermittent outages on twitter-- when @ComcastCares sends a tech it's an entirely different level of service than you get calling ... [hint]
    – Tyson
    Dec 20, 2016 at 3:37
  • I don't disagree with that. I was just wondering if I should add a dedicated amplifier between the first splitter and the modem.
    – Alex
    Dec 20, 2016 at 3:39
  • It depends on what your signal and noise levels are. Most Comcast modems sit on your network at if you can get there and post a screenshot of the signal and noise levels you can get better advice. There will either be 8 or 16 downstream channels and 1-4 upstream channels to capture in the screenshot
    – Tyson
    Dec 20, 2016 at 3:43

3 Answers 3


I doubt your symptoms have much to do with inside the house, though following up the comments to look at what the modem shows (ideally capturing what it shows when you are having an outage) is a good idea. I had lots of dropouts on "Time Warner Business Class" that various service calls (with replacements of various cables - no splitters on that one, but replacing them is also "cable-guy Standard Operating Procedure") didn't fix. One day it became evident that they had changed their central office equipment and things got a WHOLE lot better. But not perfect.

Any 2-way splitter is going to be down by at least 3 dB - that's just half power, and if it's a splitter, that's all you can get from a perfect one. The extra 0.5 dB is reality .vs. a perfect world.

Likewise, an 8-way splitter is 1-2-4-8 so it will be down by at least 9 dB from its input, which is why the amplifier is in front of it. Presumably the amplifier is not kind to your DOCSIS signals (or won't pass them upstream) which is why the modem is split off before that.


This sounds like a standard setup, agree that modem should be split on the first stage. Possible that the outages are due to an older/out dated modem? Consider purchasing a newer model perhaps (if you are renting it will pay for itself). Also be on the lookout as many companies are throttling people as more and more turn to internet streaming. Is your bandwidth package sufficient for your usage?

  • Indeed it is. Also the modem is a modern one. Comcast is the worst...
    – Alex
    Dec 20, 2016 at 3:33

This particular amplifier is bidirectional and is supposed to improve cable modem performance when you have a weak signal. So, if a weak signal is the problem (and I bet it is), putting the amplifier in front of the modem should help.

I suggest you move the small splitter from the left side to the right side of the amplifier. The coax from the cable company will go directly into the amplifier. The lower right port on the amp will go to the input of the small splitter. One output from the small splitter will go to the cable modem. And the other output from the small splitter will go to the big splitter.

Give it a try. If it doesn't help, you can always put things back the way they were and ask the cable company to fix it.

  • I just realized that I answered a very old question. @Alex, were you able to find a solution?
    – mrog
    Mar 12, 2018 at 21:14
  • 1
    Yes. Called comcast, they replaced the splitter with a whole house powered one (like an upgraded version of this one) that has a faster port for the internet coax (and presumably less "split"). So either that was it, or Comcast got their *&*# together after my incessant calling.
    – Alex
    Mar 12, 2018 at 21:59

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