Troubleshooting erratic broadband connection

[lcotton]

Hi

I have been seeing some very up and down behaviour in my broadband connection (Measuring speed over a period of time shows both US and DS rates are quite erratic and every now and then one, the other or both will drop dramatically - often causing what I'm working on to freeze) and am trying to troubleshoot the reason for it.

Virgin Media is my ISP and I have a Virgin Media Hub 3.0:
Hub 3.0 device information
The information below shows current status of this Hub 3.0.

Standard specification compliant : DOCSIS 3.0
Hardware version : 10
Software version : 9.1.1811.401
System up time : 1 days 21h:10m:46s
Network access : Allowed

I have put the Hub in modem mode and am using my own router. As an initial step I upgraded my router (to a Netgear Nighthawk R7800) which has indeed made a difference to the overall average rates (especially US), but has not solved the problem.

Having done some searching and looking at the modem diagnostics page it looks like US power levels are very low (can't seem to add a table to the post, so just had to type the info)

Upstream bonded channels
Channel: 1
Frequency (Hz): 25799976
Power (dBmV): 4.425
Symbol Rate (ksps): 5120
Modulation: 64 qam
Channel ID: 4

Channel 2: 46200000
Frequency (Hz): 5120
Power (dBmV): 4.5
Symbol Rate (ksps):
Modulation: 64 qam
Channel ID: 1

Channel 3:
Frequency (Hz): 39399991
Power (dBmV): 4.475
Symbol Rate (ksps): 5120
Modulation: 64 qam
Channel ID: 2

Channel 4:
Frequency (Hz): 32600000
Power (dBmV): 4.45
Symbol Rate (ksps): 5120
Modulation: 64 qam
Channel ID: 3

From what I have read on several sites the US power for 64qam should be between roughly 40 and 50dBm - so these values are very low, is that correct ?

Does anyone know what this may indicate ? I was thinking there may be something up with my coax cable, or one of the connections to it. Is it possible to do some measurement/tests to check this ?

I'd be interested to see what the US SNR valus are - does anyone know if it is possible to get hold of that ? (presumably the measurements need to be taken at the other end - wherever that is)

Any suggestions on how else I might go about troubleshooting this ?

[heero_yuy]

There is a software bug in the SH3 that shows the US power levels with the DP in the wrong position so the power looks 10x too small.

AFAIK the end user cannot see the US SNR. VM would need to check this is satisfactory.

[lcotton]

> There is a software bug in the SH3 that shows the US power levels with the DP in the wrong position so the power looks 10x too small.

Ah Ok. US power levels look OK then.

Thank you for that information.

Getting hold of VM at the moment is nearly impossible, but I'll try and get the SNR info anyway.

Anyone got any suggestions as to how I might troubleshoot the sudden nosedives in connection speeds ? Bit stuck on where to go next to try and determine cause of the problem.