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what are ideal power levels and snr
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Old 22-04-2012, 16:57   #1
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what are ideal power levels and snr

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
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Old 22-04-2012, 17:03   #2
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Re: what are ideal power levels and snr

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.
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Old 22-04-2012, 17:07   #3
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Re: what are ideal power levels and snr

It depends who you ask, people get number stuck in their head, if it works, don't mess with it.
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Old 22-04-2012, 17:14   #4
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Re: what are ideal power levels and snr

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.
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Old 22-04-2012, 17:27   #5
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Re: what are ideal power levels and snr

I have one of them forward path attenuator 10dB - will this help get the the readings down on the downstream.
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Old 22-04-2012, 17:34   #6
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Re: what are ideal power levels and snr

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?
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Old 22-04-2012, 17:43   #7
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Re: what are ideal power levels and snr

Quote:
Originally Posted by Sephiroth View Post
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.
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Old 22-04-2012, 17:55   #8
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Re: what are ideal power levels and snr

if it aint broken dont fix it
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Old 22-04-2012, 20:26   #9
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Re: what are ideal power levels and snr

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.
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Old 22-04-2012, 21:32   #10
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Re: what are ideal power levels and snr

Quote:
Originally Posted by Sephiroth View Post
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?
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Old 22-04-2012, 22:04   #11
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Re: what are ideal power levels and snr

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.
Attached Files
File Type: pdf Of dB & dBmv.pdf (173.4 KB, 27 views)
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Old 22-04-2012, 22:10   #12
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Re: what are ideal power levels and snr

Thanks Seph.
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Old 24-04-2012, 07:37   #13
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Re: what are ideal power levels and snr

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
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Old 24-04-2012, 08:24   #14
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Re: what are ideal power levels and snr

Better, keep it on
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Old 24-04-2012, 08:27   #15
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Re: what are ideal power levels and snr

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