Superhub : Power levels - should I be concerned?

[kwikbreaks]

Upstream looks to be outside VM specs. It was ~ 40dBmV with my VMNG300

As this SH is on the R36 trial I won't be complaining immediately unless I see issues which I haven't so far.

No T3's etc. but only up an hour on R36...


Downstream Channels Lock Status Channel ID Frequency Modulation Rx Power SNR Pre RS Errors Post RS Errors
Locked 77 443000000 Hz QAM256 4.9 dBmV 43.2 dB 476 0
Locked 76 435000000 Hz QAM256 5.1 dBmV 43.9 dB 322 0
Locked 78 451000000 Hz QAM256 5.1 dBmV 43.7 dB 450 0
Locked 79 459000000 Hz QAM256 4.4 dBmV 43.2 dB 569 0
Locked 80 467000000 Hz QAM256 3.7 dBmV 43.0 dB 1320 0
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Upstream Channels Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate
Locked 57 45800000 Hz ATDMA 29.8 dBmV 16QAM 6400000 20480 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec

[qasdfdsaq]

I wouldn't be too concerned. Too low is not nearly as much of a problem as too high.

You could try the ancient tried and trusted method. Unplug it and wait a minute before restarting, PC and SuperSlug. Sometimes it does the trick.

[adzzzbatch]

My upstream is 52 dBmV, which is a bit too high isn't it? Sometimes get T3 errors but I don't notice it effecting anything.

[kwikbreaks]

Originally Posted by jempalmer

You could try the ancient tried and trusted method. Unplug it and wait a minute before restarting, PC and SuperSlug. Sometimes it does the trick.

I'll probably give that a go but it's certainly rebooted itself enough times during the process of reserving IPs when I set it up to make me think that may not sort it out.

The only reason I am concerned at all is Seph's writeup on the VM community board - http://community.virginmedia.com/t5/...ER/td-p/148068

THE EFFECTS OF LOW UPSTREAM POWER

This can be a tricky one. A house that is close to the street cabinet needs less power than one that is further away, subject to the tap point used at the street cabinet. This is why upstream values like 29 dBmv can work OK (though there can then be SNR issues) - but it could mean that the house is connected to a low attenuation tap point and thus the downstream power might be too high.

If you are only 20m from the street cabinet instead of 100, you immediately gain 3 dB and if you are on the 10 dB tap, you only need 32.5 dBmv to make 15 dBmv at the optical node.

So, if you are some distance from the street cabinet AND your upstream power is low (with possible attendant SNR issues) AND you're having problems, then you could have a faulty modem.

I'm at least 100m from the cab and actually had high upstream power a couple of times. A couple of network changes brought it to ~ 40 until I just got this SH. When I first had one the installers went through three before they got one to work at all so I'm not impressed with the QC and suspect this one could be dicey.

[General Maximus]

all I am going to say is if i ain't broken, don't fix it

[kwikbreaks]

I'm not going to do anything until R36 is general release as a change in SH means I'll probably lose that but I'll probably ask the techs on the VM community board to check the upstream SNR at the CMTS which I assume they should be able to do. With no errors obvious it's probably fine.

[kwikbreaks]

Rebooting it 3 days back made no difference.

I've just rechecked it and...

Upstream Channels Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate
Locked 57 45800000 Hz ATDMA 37.8 dBmV 16QAM 6400000 20480 Kbits/sec

Close to what it was with the VMNG300. Nothing in modem log to suggest a resync.

[Sephiroth]

Kwikkie,

When you had that 29 dBmv, was that a repeatable stat - you said rebooting made no difference but stat refresh?? You might have caught that level whilst it was cycling through up to 37.8 dBmv or beyond if something had glitched.

[kwikbreaks]

No it was stable at ~ 30 for quite some time it wasn't just after the initial connection or a re-boot. I'm not at all sure what it was. Still sitting at 38.5dBmV so I'll put it down to either a glitch in the connection or the reporting and assume all is well now.

[jb66]

Originally Posted by kwikbreaks

I'll probably give that a go but it's certainly rebooted itself enough times during the process of reserving IPs when I set it up to make me think that may not sort it out.

The only reason I am concerned at all is Seph's writeup on the VM community board - http://community.virginmedia.com/t5/...ER/td-p/148068


I'm at least 100m from the cab and actually had high upstream power a couple of times. A couple of network changes brought it to ~ 40 until I just got this SH. When I first had one the installers went through three before they got one to work at all so I'm not impressed with the QC and suspect this one could be dicey.

Upstream uses a low frequency carrier, even on a long cable it still appears only a few db higher than at the tap. My area the upstream has dropped by 5db almost everywhere. Part of the upgrades it seems

[kwikbreaks]

Originally Posted by jb66

Upstream uses a low frequency carrier, even on a long cable it still appears only a few db higher than at the tap. My area the upstream has dropped by 5db almost everywhere. Part of the upgrades it seems

Well I would say that makes sense apart from the fact that it was ~ 40 on the VMNG300 and changed to ~ 30 as soon as I swapped that out for a Superhub. Now it's showing as back to ~ 40. It's been the same channel at all times - I'm pretty much certain that there is only the one in this area.