what are ideal power levels and snr

[jfish]

Just upgraded to 30M and got a fancy new Super Hub

are these adequate power levels/snr

Downstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power SNR Docsis/EuroDocsis locked
Locked QAM256 58 55616000 Kbits/sec 307000000 Hz 8.5 dBmV 39.8 dB Hybrid
Locked QAM256 56 55616000 Kbits/sec 291000000 Hz 9.1 dBmV 39.9 dB Hybrid
Locked QAM256 57 55616000 Kbits/sec 299000000 Hz 8.7 dBmV 40.2 dB Hybrid
Locked QAM256 59 55616000 Kbits/sec 315000000 Hz 8.4 dBmV 39.9 dB Hybrid
Locked QAM256 60 55616000 Kbits/sec 323000000 Hz 9.3 dBmV 40.5 dB Hybrid
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown


Upstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power
Locked ATDMA 50 20480 Kbits/sec 35800000 Hz 37.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

[Jumping]

There is a sticky post in here...but here is the info from there.

Downstream

* Knowsley networks using QAM64 are: -7 to +3 dBmV.

* Knowsley networks using QAM256 are: -3 to +7 dBmV.

* Langley & Bromley networks using QAM64 are: -10 to 0 dBmV.

* Langley & Bromley networks using QAM256 are: -4 to +6 dBmV.


Upstream

* Upstream signal levels (from the modem) should be between 34 and
55dBmV.

So you downstreams are a bit high.

[Nopanic]

It depends who you ask, people get number stuck in their head, if it works, don't mess with it.

[Sephiroth]

Is it all going well?

Strictly speaking your downstream power levels are a bit high. Most usually, these levels work perfectly well but the "fancy" SuperHub needs not to mind being higher than +7 dBmv. The VM Techs won'r raise an eyebrow unless it's over 10.

The one thing I did notice is that your street cabinet amplifier seems to be incorrectly sloped. The higher frequencies should show attenuated power and they don't. It might not matter in your case, but amplifiers should be correctly sloped as a matter of principle.

Your upstream levels are OK.

[jfish]

I have one of them forward path attenuator 10dB - will this help get the the readings down on the downstream.

[Sephiroth]

The FPA will get the downstream levels down to -1 or -2.

Are you having problems and if so what? Does the event log record errors or critical events other than at the time of reboting the modem?

Is the SuperHub resetting all the time? If so are you working wirelessly which is badly imlemented in the SH?

[jfish]

The FPA will get the downstream levels down to -1 or -2.

Are you having problems and if so what? Does the event log record errors or critical events other than at the time of reboting the modem?

Is the SuperHub resetting all the time? If so are you working wirelessly which is badly imlemented in the SH?

Only had it since yesterday, thus far no problems that I am aware of. I turned the SH into a modem only mode.

[General Maximus]

if it aint broken dont fix it

[Sephiroth]

As per Mon General's post. Stick it on if power rises to 11 dBmv or higher and let us know. That level is unhealthy because when you have 8 downstream channels, that would hit the DOCSIS 3 input maximum for a cable modem.

[SnoopZ]

As per Mon General's post. Stick it on if power rises to 11 dBmv or higher and let us know. That level is unhealthy because when you have 8 downstream channels, that would hit the DOCSIS 3 input maximum for a cable modem.

This is off topic Seph but my power levels are around -1 so when 8 channels arrive on my shub will this make my power level rise a bit as i am already on the highest tap and don't really want them to drop? Will it also have a negative affect on SNR levels too as mine is around 35?

[Sephiroth]

When 8 channels arrive, the lower frequency channels should have a higher power level than the higher frequency channels. Attenuation at higher frequencies riser faster with distance than lower frequencies. So you may see a c. 2 dBmv gap between the highest and lowest power levels. Nothing to worry about. The SNR isn't affected by the number of channels.

Have a read of the attached document. It explains how 11 dBmv on each channel can bust the modem; -1 dBmv won't bust it.

[SnoopZ]

Thanks Seph. :)

[jfish]

I have just added a forward path attenuator - these are my readings now

Downstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power SNR Docsis/EuroDocsis locked
Locked QAM256 58 55616000 Kbits/sec 307000000 Hz -0.4 dBmV 37.0 dB Hybrid
Locked QAM256 56 55616000 Kbits/sec 291000000 Hz 0.0 dBmV 37.2 dB Hybrid
Locked QAM256 57 55616000 Kbits/sec 299000000 Hz -0.1 dBmV 37.1 dB Hybrid
Locked QAM256 59 55616000 Kbits/sec 315000000 Hz -0.5 dBmV 37.0 dB Hybrid
Locked QAM256 60 55616000 Kbits/sec 323000000 Hz 43.7 dBmV 39.5 dB Hybrid
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Upstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power
Locked ATDMA 50 20480 Kbits/sec 35800000 Hz 36.5 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

[jb66]

Better, keep it on

[General Maximus]

you need a reboot to fix the power on that 5th channel

[jfish]

you need a reboot to fix the power on that 5th channel

will do when I get home, that did suprise me one of the channels being very high, any reason for that.

[jb66]

It's a firmware fault, it's not really that high

[jfish]

you need a reboot to fix the power on that 5th channel

just rebooted it now and all looks good

Downstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power SNR Docsis/EuroDocsis locked
Locked QAM256 58 55616000 Kbits/sec 307000000 Hz -1.6 dBmV 38.6 dB Hybrid
Locked QAM256 56 55616000 Kbits/sec 291000000 Hz -1.0 dBmV 39.4 dB Hybrid
Locked QAM256 57 55616000 Kbits/sec 299000000 Hz -1.5 dBmV 39.5 dB Hybrid
Locked QAM256 59 55616000 Kbits/sec 315000000 Hz -2.0 dBmV 39.4 dB Hybrid
Locked QAM256 60 55616000 Kbits/sec 323000000 Hz -0.9 dBmV 39.9 dB Hybrid

[General Maximus]

cool

[Helix]

My power levels are all around 20dBmV and my connection worked fine when it was 4 channels. Now it is 8 channels it keeps cutting out and I'm not sure if it is because of maintenance work for double speed, or if the signal being that high has caused problems now the channels have increased.

Looks like I am going to have to give faults a call.

[Sephiroth]

If you now have 20 dBmv downstream and you have 8 channels, under the 3 dBmv doubling rule (you'll have to Google that), the aggregate power hitting the modem is 29 dBmv which is close to the 33 dBmv DOCSIS 3 limit. Domestic cable modems are cheap items and in any case the DOCSIS 3 spec says that no single channel should exceed +17 dBmv. So tuner crosstalk, overdriven amplifiers and so on are failure conditions that you are experiencing.

My advice is that you either et a VM engineer to attenuate your modem input by 20 dB, or you go on eBay and buy two 10 dB forward path attenuators (85 - 860 MHz sensitivity); fit them in series on the end of your coax cable and all that will be sorted.

[Ignitionnet]

As per Mon General's post. Stick it on if power rises to 11 dBmv or higher and let us know. That level is unhealthy because when you have 8 downstream channels, that would hit the DOCSIS 3 input maximum for a cable modem.

Nah, 8 channels = 2^3, so total power = 11 + 3 + 3 + 3 = 20dBmV, very short of the maximum 33dBmV.

Each doubling of channels increases total power by 3dBmV on the logarithmic scale, so even if the power were perfectly balanced to break 33dBmV with an average power of 11dBmV you'd be looking at bonding 256 channels, 256 channels at 11dBmV average giving 11 + (3 x 8) = 35dBmV, the 3 x 8 is due to 256 being 2^8.

Across 8 channels you actually need an average power of 24dBmV per channel, a tad outside the specifications.

EDIT: Which is what you said in the post before this one, I'm guessing you had an off moment on the post I quoted there :)

[Sephiroth]

Yeah - I realised that when answering the other post you referred to.

Thanks.

[Helix]

My advice is that you either et a VM engineer to attenuate your modem input by 20 dB, or you go on eBay and buy two 10 dB forward path attenuators (85 - 860 MHz sensitivity); fit them in series on the end of your coax cable and all that will be sorted.

Thanks, I will try calling faults. Hopefully they will see the problem straight away and send someone out, rather than make me jump through several hoops first. Otherwise I will try ordering some attenuators.