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CM500 cable modem -- losing connections & grounding

ToastSensei
Tutor

CM500 cable modem -- losing connections & grounding

Heya folks...would like to get insight on grounding, in-house wiring, and cable modems here. Currently with Comcast and a CM500, was fine for a few years, now currently dealing with several losses of connectivity a day. I've done the whole capture log cycle and had a Comcast tech at the house already -- I'll post a link to the details on the Comcast forum site below -- but I'd really like to direct attention to the interaction between house electric grounding and the NetGear CM500 on this discussion post. I've seen lots of support posts saying there may be issue with the lines in the house, and I want to start the discussion there. 

 

Conclusion from the Comcast tech: although my house is a relatively new construction @ 6yrs old, fluctuation from the electric panel is causing the modem to hiccup, with the likely possible cause being a 'patina' if you will on the grounding behind the breaker panel. Suggestion was to get an electrician in to clean and reset the grounding. Can someone explain the impact of this on the cable modem to me?

 

Let me share a few thoughts...

  • Just to get rid of the obvious...there are no splitters on the Comcast line from the street to the coax panel to the modem. We also set up the modem in the garage, where the modem actually saw worse (!?) noise. He confirmed internet signal from the street was fine, and we both looked at the street connection, also fine.
  • If this is indeed a real thing, why are cable modems so sensitive to this? Rest of the house is fine...TV runs without interruption, lights don't flicker, FM receiver can maintain a radio signal...don't (or shouldn't) modems have some built-in regulator to handle this kind of thing?
  • Maybe I just have the wrong modem? CM500 is fairly basic standard issue, is there another model that takes care of this?
  • The tech said that modems use the cable coax for grounding...notice the two prong electric cord vs not having a third prong...which doesn't help maintain it's own grounding, hence greater sensitivity.

If I step back and pause for a moment, I appreciate the amount of black magic where the internet passes through a bunch of wires and in the air for us to watch a movie or buy things from a store...lot of moving parts to help make all happen. And I would just like to maintain a reliable internet connection that doesn't drop a video phone call at bad moments. 

 

Thanks for your thoughts!

 

Comcast forum link for scenario, modem logs, etc.

Repeated loss of connectivity | Xfinity Community Forum 

Model: CM500|16x4 DOCSIS 3.0 Cable Modem
Message 1 of 7
FURRYe38
Guru

Re: CM500 cable modem -- losing connections & grounding

What is the brand and model of the host wifi router connected to the modem?
Please post a copy and paste of the modems connection status page.
Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly. If a tech is needed on site, ask for one. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html

Message 2 of 7
ToastSensei
Tutor

Re: CM500 cable modem -- losing connections & grounding

Hey Furry...thanks for taking a look at the message. The troubleshooting details you're asking about are in the link to Comcast forum post at the bottom of my message, and has all the relevant background. Router is a Netgear Nighthawk, it's irrelevant to this post, as I've taken it out of the equation. Realize you're just catching up on details I've already been through, so thank you again for taking a look!

 

I am specifically jumping past all those details to ask specifically about cable modem sensitivities to variations in house electricity groundings, and would love to know more about that.

 

Or maybe the modem is just flakey and I need to get a new one...?

Message 3 of 7
FURRYe38
Guru

Re: CM500 cable modem -- losing connections & grounding

You'll need to get with the ISP and have them check the items mentioned here. Most modem issues found are betweent the ISP service and modem. 

 

Good Luck. 

Message 4 of 7
ToastSensei
Tutor

Re: CM500 cable modem -- losing connections & grounding

Hi Furry...realize you're on the front lines of all kinds of networking issues and see repeat incidents over and over. In this case, I've already had a tech to the house and am trying to understand the impact of house electric grounding to a Netgear CM500 cable modem. Can't imagine I'm the only one who's run into this.

 

Have seen lots of support incidents trace connectivity issues back to line issues from the street or a bad splitter somewhere, or maybe the ISP monkeying with something the customer doesn't know about...in this case the ISP is SUGGESTING that my variable house current is causing the cable modem to hiccup, resulting in packet loss. Do you have any experience with that angle?

 

Thanks again for listening!

Message 5 of 7
FURRYe38
Guru

Re: CM500 cable modem -- losing connections & grounding

You'd need to get a power meter and check your house hold power to see if there is any fluxuations in power and if you have any grounding problems. Find any power devices that maybe introducing power fluxuations. If you feel there is a house hold problem, then you might get a Qualified Electrician out to the home and have him run some tests on the power in the home. You might power everything in the home off while testing is happening. Large items. Try them all off and then bring them online 1 at a time and have the electrician test. Have them check grounding points as well. 


Try a different power adapter for the cable modem as well. 

 

 

Message 6 of 7
ToastSensei
Tutor

Re: CM500 cable modem -- losing connections & grounding


@FURRYe38 wrote:

You'd need to get a power meter and check your house hold power to see if there is any fluxuations in power and if you have any grounding problems.

 


Right...have done this already, which is where I'm trying to have the conversation -- why is a cable modem sensitive to power fluxuations when other electrical units in the house are not? i.e., TV stays on during viewing, lights don't flicker, can still listen to FM radio, etc. Shouldn't cable modems have some built-in electronics to manage this?

Message 7 of 7
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