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Virgin upgrade works has messed up power levels

madmanx
On our wavelength

Hi had some work on my local network done today as it says it was doing upgrade work to improve the services, 

But after being down for half the day when the hub came back online I saw the power levels are way out if sync now. The downstream before was between 0 and 3dbmv and the upstream dbmv was about 38 dmbv, now the downstream is +10 dbmv and the upstream is now around 34dbmv, do I need an engineer to fix it? I have a 6db forward path attenuater fitted at back of hub which i could change to a 10db forward path attenuator to bring down the downstream power levels but its the upstream I'm concerned about as its only 34dbmv?

Have I a problem now?

 

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Router status

Downstream bonded channels

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID
11387500009.838256 qam1
21467500009.538256 qam2
31547500009.538256 qam3
41627500009.538256 qam4
51707500009.638256 qam5
61787500009.538256 qam6
71867500009.538256 qam7
81947500009.638256 qam8
92027500009.638256 qam9
102107500009.538256 qam10
112187500009.638256 qam11
122267500009.638256 qam12
132347500009.838256 qam13
142427500009.638256 qam14
152507500009.838256 qam15
162587500009.838256 qam16
172667500001038256 qam17
182747500009.838256 qam18
192827500009.838256 qam19
202907500009.838256 qam20
212987500001038256 qam21
223067500001038256 qam22
233147500001038256 qam23
2432275000010.138256 qam24


Downstream bonded channels

Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors
1Locked38.960
2Locked38.660
3Locked38.660
4Locked38.950
5Locked38.670
6Locked38.650
7Locked38.6180
8Locked38.9150
9Locked38.950
10Locked38.960
11Locked38.640
12Locked38.970
13Locked38.950
14Locked38.950
15Locked38.940
16Locked38.650
17Locked38.660
18Locked38.640
19Locked38.950
20Locked38.960
21Locked38.660
22Locked38.950
23Locked38.950
24Locked38.950
79 REPLIES 79

madmanx
On our wavelength
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Router status

Upstream bonded channels

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID
12359997534.5512064 qam5
23660000034.8512064 qam3
33010000034.5512064 qam4
44310001534.8512064 qam2
54960000035.3512064 qam1


Upstream bonded channels

Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts
1ATDMA0020
2ATDMA0010
3ATDMA0040
4ATDMA0020
5ATDMA0000

Hi I need to change appointment but won't let me do it, it doesn't work?

Perhaps you could look int the drop box outside your property to see if it's waterlogged.  If s, that's you upstream shot till it dries out and then electrolytic micro-reflections can occur.

Also I recommend checking with the neighbours.  If they have the same problem, then it could be water getting into the nearby cabinet.

 

Seph - ( DEFROCKED - My advice is at your risk)

legacy1
Alessandro Volta

15 dBmV can be fine on downstream mostly the your upstream is the problem the Modulation can change so fast that BQM might not show a drop or spike even when T# show 

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madmanx
On our wavelength

Hi thanks for reply seph, no water in omnibox that I can see, most of my neighbours aren't on vm but I will try and find one and ask them.

madmanx
On our wavelength

Hi legacy1, Oh I didn't know that the downstream power levels can go up to 15dbmv and still be OK, interesting..

Not the Omnibox, but the drop box in the street outside your property.  Btw, thx for your kind words earlier.

Seph - ( DEFROCKED - My advice is at your risk)

madmanx
On our wavelength

Hi seph are u talking about the little plastic square box cover on the ground?

IPFreely
Fibre optic

It looks as though whatever work they did has been left with the network not being properly lined up.

Your upstream transmit is too low. I suspect that's the case for more people in your area.

Wherever the planned work was done they either need to lower the return path gain or add attenuation to get your modems transmitting at a higher power and get them higher above the noise floor. 

This needs a network engineer. The planned works don't seem to have quite been done right, your upstream transmit seems 6 dBmV lower than it was and unless the cable plant is insanely clean 64QAM is challenging.

Your actual stats in terms of modulation and T3s fit with this. The lower frequencies are naturally more noisy so the idea that there's no real obnoxious source of noise just upstream transmit is too low to give a high enough noise margin over the regular noise floor fits. 

Yes I am.  The one in the ground.  Btw, 15dBmv is within DOCSIS spec but this power level is at the mercy of the components and in less robust hubs, the extra power also amplifies noise.

Seph - ( DEFROCKED - My advice is at your risk)