I heard a story from a guy who worked maintenance for Comcast in the Seattle area about a bizarre fix for this kind of thing. They had a neighborhood that was doing offline everyday at the same time, like from 8-10 pm, everyday like clockwork and they couldn’t get a fix on the cause. So they finally got a couple nightshift guys in bucket trucks to sit in the neighborhood and, using online tools to monitor the node, watch for the noise to kick in. One guy was sitting in front of a house and right about 8, he notices a person in the house sit down in front of a window and turn on a light. Instantly he starts seeing noise in the node. On a hunch he went and knocked on the door, explained what was happening and asked the customer if they could indulge him and just go turn that light off ta few minutes. They do, and the nose goes away. The customer let him in to investigate and it turned out it was an antique lamp with a fraying old fabric wrapped power cord, plugged in to the same outlet that the modem was plugged into. So somehow this lamp was feeding voltage or low frequency noise into the outlet and the modem was picking it up through its power cord and feeding it back into the system. The customer said it was his nightly before bed routine to sit in that chair under that lamp and read a book. They had to ask the customer to please not use that lamp, or get it repaired, or move the plug for the modem to another outlet He said it was one of the more bizarre coincidences that they were able to just witness the cause. If they hadn’t seen it, it might have taken a few days of nightly monitoring to chase the nose down to that one particular house in the 2 hours it was happening everynight.

Yes. This is true for coax. Due to how coax is wired, every signal goes to every house, just like tv goes to all the houses on the circuit. It’s up to the coax equipment to filter out the signals that aren’t for that connection (just like a cable box is programmed to only allow the channels you pay for).

But the issue is, if a cable isn’t terminated correctly, it looks exactly like an antenna. This will cause noise on the whole coax system and affect everyone on the same circuit.

Man, coax goes berserk when the shield breaks down. A good example is CCTV, some buffoon at my old work thought it would be smart to order copper shielded coax, and use steel crimp ends in a tropical area. It was a few years but the moisture caused electrolysis between the dissimilar metals, and the copper shield disintegrated. In the space of around 6 months the CCTV feeds started to fail. It was fun replacing all of the coax with fibre.

This is 90% of my job every day. Something in your house is acting like an antenna and interfering with the return path. Most of the time it’s a loose connector behind the modem but any bad connection can cause it. I usually track the noise to a house and use a filter at the tap that blocks the noise and leaves the sub online, then create a job to get an tech in the house

You are lucky they contacted you. I had comcast just come out and disconnect me at the pole and when I got home and noticed i had no internet had to call for support and have them come by in a few days to reconnect me and also figure out why the other line team disconnected me.

Do you have an antenna on your system or a distribution box?

Would amplifiers like the Motorola Cable amplifier cause something like this? Also, what about not using termination caps on non used connections? Answer me!!!

Same thing happened to me, they said my “Internet was leaking”. Replaced two splitters and an old coax cable.

Totally normal. They detected egress and needed to correct it.

This is very common with spectrum because they’re about to do their high split in which will be expanding uploads to 1gig so they’re going to be utilizing up to 1.2ghz so they’re cleaning up all the ingress in the system

Uncapped outlets can cause backfeeding, as can damaged cables; when I worked in the field a factory had a damaged coax feed and when one of their machines started up it would knock out the leg. Coax is basically a wireless signal that is stuck on the antenna (wire) rather than a digital signal like Ethernet, and it is a shared medium unlike DSL.

maybe powerline adapters

Had this happen and it was a loose connection to my modem. Was also during a solar flare.

I work at an ISP and we have guys doing this constantly. It’s not always at a customers house but yeah. A fault on the cable going to your house causes your modem to increase the power it uses to talk to the node in your neighborhood that connects back to the ISP. If your modem uses too much power and drowns out the signals from your neighbors going to the same node, then everyone else’s service can suffer and yours is just fine. It’s weird but that’s how it is.

A connector might have gotten rusted or a landscaper might have nicked a cable with a weed Wacker or something.

I had cable internet for about 9 years, no issues at all, one day the isp truck came by and disconnected my connection at the street pole end without any warning. ISP said my connection the cause of the signal interference to my neighborhood cable internet issue. The tech tested the cable from the street pole to my house demarc. The connector at the street pole end is rusted and there were sign of water get into the cable and turned the cable into an antenna. They ran a new cable replaced that segment. Everything was okay since. I switched over to fiber now.