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Ricksterm
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Power Levels + Packet Loss

Hi All,

I have noticed recently that we have a sputtering of packet loss on our TBB graph, spikes around 1 - 2% throughout the entire day, though not as bad as earlier on in the year.

We have a 10dB Forward Path Attenuator which was fitted after serious issues in 2019 resulting in total loss of broadband for over a month and my mum not knowing how to deal with it while I was away.

I noticed last week that our power levels were down to -7dBmV so I removed the FPA taking us back up to around 7 to 8dBmV on the highest frequencies but when I checked the other day this was now up to 9.3dBmV on the lowest frequency.

I put the FPA back in place and this brought the power levels back down to -5.3dBmV on the lowest frequency (currently 5dBmV).

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID

1402750000-4.538256 qam30
2202750000040256 qam9
3210750000-0.238256 qam10
4218750000-0.540256 qam11
5226750000-0.538256 qam12
6234750000-0.740256 qam13
7242750000-0.938256 qam14
8250750000-140256 qam15
9258750000-1.240256 qam16
10266750000-1.540256 qam17
11274750000-238256 qam18
12282750000-1.740256 qam19
13290750000-1.738256 qam20
14298750000-1.738256 qam21
15306750000-240256 qam22
16314750000-238256 qam23
17322750000-2.238256 qam24
18330750000-2.238256 qam25
19370750000-3.238256 qam26
20378750000-3.538256 qam27
21386750000-3.938256 qam28
22394750000-438256 qam29
23410750000-4.738256 qam31
24418750000-538256 qam32

 

What does stand out to me is that there is a wide slope and over 5dBmV between the lowest and highest frequencies, generally what I have seen with other peoples is that this is no more than 3dBmV and usually less, they used to be much closer together for me too.

Also on the upstream side of things we are seeing that one of the channels is flapping rapidly between 32QAM and 64QAM (almost every time that page is refreshed). and sometimes it is resulting in some T3's on that channel.

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID

13940000034512064 qam10
22580000037512032 qam12
33259997135512064 qam11
44619998335512064 qam9

 

Thoughts?

Thank you.

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MikeRobbo
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Alessandro Volta
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Re: Power Levels + Packet Loss

Your Downstream Power Levels individually are all within spec but, the differential between the lowest at -5.0dBmV and the highest at +0dBmV is too great.

This will need an engineer to put right.

You can either call in (08:00 is the best time) or wait on here for a few days (6 to 10 days average) until one of the VM Forum Staff comes along.

If you wait on here Do Not bump the thread it will put it further down the VM 'to do list'.

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID

1402750000-4.538256 qam30
2202750000040256 qam9
3210750000-0.238256 qam10
4218750000-0.540256 qam11
5226750000-0.538256 qam12
6234750000-0.740256 qam13
7242750000-0.938256 qam14
8250750000-140256 qam15
9258750000-1.240256 qam16
10266750000-1.540256 qam17
11274750000-238256 qam18
12282750000-1.740256 qam19
13290750000-1.738256 qam20
14298750000-1.738256 qam21
15306750000-240256 qam22
16314750000-238256 qam23
17322750000-2.238256 qam24
18330750000-2.238256 qam25
19370750000-3.238256 qam26
20378750000-3.538256 qam27
21386750000-3.938256 qam28
22394750000-438256 qam29
23410750000-4.738256 qam31
24418750000-538256 qam32

*********************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
BT Smart Hub 2 with 70Mbs Download,18Mbs Upload, 9.17ms Latency & 0.35ms Jitter.
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gitty
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Re: Power Levels + Packet Loss

The modem is designed to work with a large range of power levels, because they can move a lot out in real world cable plants. The table that shows the codewords is the most important one, at least in this case. Those numbers tell you how well the modem is reading the signal.
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