I recently switched plans (from 175Mbps to 600Mbps) and then a couple of weeks later switched modems from Motorola SB6121 (4x4) Motorola MB7621 (24x8). Since the modem switch, I've had all sorts of trouble, most pragmatically extremely fluctuating download speeds (between 1 and 90Mbps, which is slower than the 135Mbps that I used to get with the older modem), along with short disconnections throughout the day.
Looking into this more, the downstream channels aren't bonding, many of the channels are not locking, power levels are out of spec and some channels' SNR are too low. I also have hundreds of thousands/millions of uncorrected errors. There's also a wide range on the power and SNR levels.
Upstream looks fine, if a little on the higher end on the power levels. The upstream connectivity is quite steady and locked right around 17Mbps regularly, no matter what the downstream is like.
I've read through the long and very helpful Internet Troubleshooting Tips thread along with https://pickmymodem.com/how-to-fix-your-docsis-3-0-3-1-signal-issues and https://pickmymodem.com/signal-levels-docsis-3-03-1-cable-modem and https://www.motorolacable.com/documents/CableConnection.pdf
I also connected the modem directly to the cable outside my house (to the grounded connector) and that did not help much. I basically have a home run from there to the modem's usual place inside, with no splitters at all, just a couple of 1:1 connectors and the wallplate connector.
I've included numbers below of what it looked like when connected directly outside. Though the power levels are above -15dBmV, when inside they drop to between -15 and -17. This is after about 7 minutes of uptime, note the large number of uncorrected errors, some of which are more than the corrected ones. Usually channels 19-21 are not locked, but sometimes others are not locked too.
(You may need to scroll right to see all the columns)
|Channel||Lock Status||Modulation||Channel ID||Freq. (MHz)||Pwr (dBmV)||SNR (dB)||Corrected||Uncorrected||Uncorrected/Corrected|
|Channel||Lock Status||Channel Type||Channel ID||Symb. Rate (Ksym/sec)||Freq. (MHz)||Pwr (dBmV)|
I should mention that on the Comcast Status Centre, it says that it can't connect to my modem, although it's able to successfully do a remote restart, though this doesn't help.
We're having trouble finding a signal
I've power cycled the modem numerous times and have talked to Comcast support on chat several times, who were not able to make any progress.
I'm thinking that at this point, I need to schedule a technician to come and take a look at the external line - is that right, and if so, what's the best way to accomplish that?