Cable internet issue has me stumped

[geldankat]

Hi all,

I can't figure out what is causing this issue. I'll do my best to describe it in text even though a diagram would be much easier!

-Cable for TV/Internet comes in through basement wall and connects to 2-way splitter
-One port connects to inside-the-wall cable leading to wall jack in office. Wall jack connects patch cable to cable modem. Cable modem never comes online/no internet connectivity.
-Other port connects to a 4-way amplified splitter which connects to 4 inside-the-wall cables leading to wall jacks in 4 different rooms. 4 cable TV boxes are connected to each wall jack and cable TV works perfectly in each room

Here's what I know what the issue is NOT, after a lot of testing:
-It's not the cable signal because all the TVs work. Also when connecting the modem directly to the cable coming in through the outside wall, the modem comes online
-It's not patch cable or the 2-way splitter because when connecting the same patch cable I had been using in the office (before the Internet stopped working) from the splitter to the modem, it comes online
-It's not the section of cable inside the wall because when connecting a TV cable box and TV to the wall jack in the office, cable TV works fine
-What does not work, for no apparent reason, is connecting the modem to the wall jack in the office. It never comes online.

Clearly the signal is getting there if cable TV works from that wall jack. Why doesn't the cable modem? All the components of the system seem to function on their own, just not in this particular configuration. Any ideas? I'm stumped.

Thanks in advance,

Anne

 

[ex_bubblehead]

It IS that section of cable from the basement to the office. Just because the television signal gets through does NOT mean that the modem will work. Both use different sets of frequencies. I wouldn't be surprised if you found a staple embedded in the cable (possibly more than one). It might degrade but not block the television frequencies while blocking the typically much higher frequencies used by the modem.

 

[USAFRet]

Yup.
I've had specific instances where the TV signal works 100%, and the internet signal fails 100%.
On the same coax.

 

[geldankat]

Hmm, OK thanks for your answers. Please note the amplified splitter was just added today because we added a 4th TV. Previously, where the amplified splitter is now, we just had a basic 3-way splitter and all the in-the-wall cables seemed to work fine with that. So I would think if the cable in the wall was bad, the issue would have shown up before now.

This seems unlikely, but is it possible for the amplifier to damage the cables inside the walls? I'm now having an issue with one of the cable TVs in an upstairs bedroom which was working fine when we just had the 3-way splitter and seemed to be working OK earlier today through the amplifier.

Also please note the cable going to the wall jack in the office was incorrectly run through the amplifier temporarily while we were testing everything. None of the cables were labeled before we started all this so we had to do some trial and error.

Thanks again!

 

[ex_bubblehead]

Hmm, OK thanks for your answers. Please note the amplified splitter was just added today because we added a 4th TV. Previously, where the amplified splitter is now, we just had a basic 3-way splitter and all the in-the-wall cables seemed to work fine with that. So I would think if the cable in the wall was bad, the issue would have shown up before now.

Not necessarily. With the new splitter arrangement you may well have attenuated the signal being fed to the office enough to reveal the problem that existed from the beginning. Question, where did this 2-way splitter come from? Best to provide a picture clearly showing all markings. It's important to note that you can't throw just any splitter in the line, you need one with sufficient bandwidth (at least 1GHz) so as not to attenuate the high frequencies used by modems. Ideally you should use one known in the cable industry as a DC splitter (DC = "Direct Connect"). One side attenuates only 1dB while the other is 6dB. The 1dB side connects to the modem. This provides maximum signal strength to the modem, which requires a higher signal strength than do the TV tuners.

This seems unlikely, but is it possible for the amplifier to damage the cables inside the walls? I'm now having an issue with one of the cable TVs in an upstairs bedroom which was working fine when we just had the 3-way splitter and seemed to be working OK earlier today through the amplifier.

No, the amplifier cannot damage the cables. However, improper installation of the cables in the wall will cause a multitude of problems. Just one staple through the outer casing and shield, or pinching the cable so tight as to cut the outer insulation and crimp the inner shielding can cause complete loss of signal. This is very common.

Also please note the cable going to the wall jack in the office was incorrectly run through the amplifier temporarily while we were testing everything. None of the cables were labeled before we started all this so we had to do some trial and error.


Thanks again!

The only thing that would do is prevent the modem being able to talk back to the head end, unless the amp is bi-directional.

 

[geldankat]

Hi again,

Unfortunately I'm not certain where the 2-way splitter came from. I wanna say it was installed by the cable company when we moved in 13 years ago. Here's a (terrible) photo. Looks like it's not 1dB/6dB but 3.5dB/3.5dB.
http://imgur.com/Fk2BSS7

Here are pictures of the old 3-way that we replaced with the amplified splitter, and the amplified splitter itself if needed.
http://imgur.com/A5OcCBC
http://imgur.com/DbR6Gha

Thanks again for your expertise. Clearly this is not an area I know much about!

 

[ex_bubblehead]

Ok, the Antronix 2-way splitter is about as good as it gets. That's what a lot of cable companies use. It's got the bandwidth (1.002GHz). However, because it isn't a DC splitter you're losing about half the signal to the modem. I'm going to bite my tongue in my comments about that amp. It doesn't look anything like what a cable company would use. The kindest thing I can say about it is "junk". You might want to have the cable company have a look at that problem run of cable from the basement to the office. If the tech puts a reflectometer on it I'd wager that somewhere shy of the opposite end it will show either a short or pinch that results in loss of the higher frequencies. While the tech is there hit him/her up for a DC splitter (ask for a DC-6). They might even provide an amp if needed. Wouldn't hurt to ask.

 

[geldankat]

OK, thanks again ex_bubblehead. I was hoping to avoid getting the cable company involved because they're already screwing us enough just to rent the HD boxes every month. I didn't want to have to pay for a service call as well. But unfortunately it doesn't look like I have the equipment or the skills to resolve this myself.