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For about one year now, I've had an Arris SB8200 cablemodem and Cox 300Mbps Internet tier, and this has worked esssentially flawlessly in that time. I've had Cox Internet even longer with very few issues - until about two days ago.
I noticed decreased download speeds, and when I logged into my account, I was notified that an "issue" in my area was detected, and I assumed my speed issue would be resolved when the issue was solved. About two hours later, the issue was clear, but my Internet speeds were still decidedly abnormal. I then noticed that the middle-two lights on the front panel of the cablemodem indicated the *downstream* connection was DOCSIS 3.1 (bonded downstream), colored blue, but the *upstream* light was now *green*, indicating only DOCSIS 3.0. This is a change from the previous behavior in which both up and down lights were bonded (blue).
That was two days ago. The problem has persisted, across multiple reboots of my cablemodem, and reboots of the firewall appliance that receives the Ethernet out from the cablemodem. I contacted Cox and they said the signal looked clear, but they agreed that my struggle to reach 200Mbps (usually topping out around 170-190) is not consistent with the 300Mbps service tier. They went so far as to re-provision the modem, all to no avail.
I took a look at my cablemodem serivce page, and it shows that the upstream channels hover between 39.0 and 42 dBmV. I found that Arris states the required upstream signal must be between 45-55 dBmV.
A bit of Googling has revealed a bit of warfare normally has to be undertaken to get Cox to increase power to the upstream channels, which is precisely what the Arris tech support rep told me when I reached out to them for assistance (cablemodem is only one year old and under warranty). He flatly stated the ISP must increase channel strength. Excerpt of my upstream channel status listed below:
I traced the line all the way back to the Cox input, eliminating an intermediate cable in the attic, and directly attached the Cox coax to the cablemodem and powered it up - no difference - bonded down, unbonded up. This means the signal to the modem from Cox is too low. But if I know from research Arris says Cox has to increase power, but Cox will refuse, what on earth do I do? Go out and drop another $200 on a new/different cablemodem?
Any suggestions appreciated.
SoonerDave said: This is a change from the previous behavior in which both up and down lights were bonded (blue).
Cox doesn't use DOCSIS 3.1 for upstream. There is no OFDM channel on the upstream, only the downstream. Must have been a glitch with the modem.
SoonerDave said: I found that Arris states the required upstream signal must be between 45-55 dBmV.
Says a Arris Tier 1 rep. not official. IMO the sweet spot for upstream is 42, which you are near. If anything, it should be a tad lower.
Can you show your downstream power levels too?
I like to see downstream power levels + or - 10dB so a 3dB pad would bring you below that. So your call if you want to add a pad.
Would you add one? Appreciate the help.
I would buy one and try it, just in case I am wrong about it bringing back the upstream channel. However long term, it's just another possible point of failure, so I wouldn't use it. Instead, try to see what is lowering the signal so much. Off the tap should be +3-4dB, and if so, something else is lowering it down. Do you have a really long drop from street to house? Anything in the house box where the coaxial grounds?
The Cox cable runs from the pedestal in our neighbor's yard (underground) diagonally to the opposite side of the house at the demarc, which I would estimate to be about 125 feet. The feed from the demarc runs up the wall cavity into the space above the garage and rides the rafters to the original junction box put in when the house was built, but later bypassed by Cox. That's probably another 40 or so feet, and the connector Cox put in goes from there across the ceiling to the wall drop, which is about another 30 or so feet.
I think I mentioned this before, but I took the cable modem to the attic and connected it to the cable from the demarc and no change. I looked at the connection at the demarc and it seemed sealed up with no sign of corrosion or damage.
Ideally, if they did it from scratch, they'd run the cable from the pedestal to the nearest corner of the house and then directly to my drop and probably shorten it to maybe 80 feet total. It was placed where it is back when Cox took over phone service across their coax and had to route the phone wires through their interface box.
Wish it were as simple as a power supply LOL.
its current location is probably near the Earth Ground of your house.