50M : What can low upstream levels affect ?

[Saint man]

Trying to research with Googling, I have a Shub 2 with downstream approx 2.1dBmV but upstream approx 30.5dBmV.
My downstream seems fine from what I can read, yet my upstream seems low.
However I have read that if you are close to the large green box then this shouldn't be an issue. Green box is just accross the road from me.
I don't have any issues apart from over utilisation, but what could having a low upstream cause in the future, if at all. A strange request I know seeing as I haven't a problem yet, but could this be an issue later?

[jb66]

30 used to be way too low but with the recent upgrades its more and more common. As long as your upstream snr is good (only vm can tell) ive never seen an issue with a low upstream.

Normally you get a low upstream when your far away from the box, do you have an attenuator on your hub

[Sephiroth]

Originally Posted by jb66

30 used to be way too low but with the recent upgrades its more and more common. As long as your upstream snr is good (only vm can tell) ive never seen an issue with a low upstream.

Normally you get a low upstream when your far away from the box, do you have an attenuator on your hub

I'm sure JB has made a slip of the finger here. When you are far away from the street box, attenuation back to the box is higher and more power is require to overcome this attenuation.

When you are close to the box, then if everything else in the circuit is the same, the upstream power will be lower.

Thing to note though is that upstream power is commanded from the VM end (the CMTS). If the CMTS can't understand what it receives, it commands your modem to increase power until it can understand what the CMTS receives.

That being so, only 30 dBmv of power is required in your case. Quite OK.

[jb66]

Its not a slip up.

When your close to the box you should be connected to a 29db attenuated tap port. When your far away you could be connected to the 15db tap. The further away house should in theory have 14db lower upstream than the house closest to the cabinet.

Remember upstream uses a very low frequency. If I test the upstream at the pit using a sunrise meter it may be 30db. Add 50m cable and retest it sits at 32db. The length of the cable doesn't affect upstream that much at all.

A few areas I've been in have a 4 db tap port which now is impossible to get in spec. Either you leave the upstream in the high 20s or the downstream at -6

[Sephiroth]

Originally Posted by jb66

Its not a slip up.

When your close to the box you should be connected to a 29db attenuated tap port. When your far away you could be connected to the 15db tap. The further away house should in theory have 14db lower upstream than the house closest to the cabinet.
Remember upstream uses a very low frequency. If I test the upstream at the pit using a sunrise meter it may be 30db. Add 50m cable and retest it sits at 32db. The length of the cable doesn't affect upstream that much at all.

A few areas I've been in have a 4 db tap port which now is impossible to get in spec. Either you leave the upstream in the high 20s or the downstream at -6

Well, I did say "everything else being equal". You didn't mention the tap point choice as part of your earlier answer.

Not all street boxes have the 4 attenuation levels of tap points. The photo below is typical of most in my area. The block is 15 dBmv attenuation. In this case, what I have said will be exactly true.

[Ignitionnet]

Your houses must be nicely spread out or a pretty fair size if a line extender is only serving 16 properties, Seph.

[Saint man]

this is current readings and the green box is about 5 car widths away from my house, and was advised by Virgin CS on forum that an engineer would be required. Thing is trying to find the time at the momment to be in when an engineer is available is not too good. Would I have problems if I didn't have engineer visit?



Downstream Channels Lock Status Channel ID Frequency Modulation Rx Power RxMER Pre RS Errors Post RS Errors Locked 100 298750000 Hz 256 QAM 3.3 dBmV 37.9 dB 5316 300 Locked 98 282750000 Hz 256 QAM 3.0 dBmV 37.4 dB 9259 296 Locked 99 290750000 Hz 256 QAM 3.1 dBmV 37.9 dB 4318 1044 Locked 101 306750000 Hz 256 QAM 3.4 dBmV 37.9 dB 5089 301 Locked 102 314750000 Hz 256 QAM 2.9 dBmV 38.3 dB 8264 285 Locked 103 322750000 Hz 256 QAM 2.6 dBmV 37.9 dB 13577 895 NotLocked Unknown NotLocked Unknown To reset the Pre and Post RS error counts please use the Downstream screen under the router status screen available from the login page.


Upstream Channels Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate Locked 44 25800000 Hz ATDMA 30.0 dBmV 16QAM 6400000 Hz 5120 Ksym/sec NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec Locked 43 32600000 Hz ATDMA 31.3 dBmV 16QAM 6400000 Hz













5120 Ksym/sec

[Sephiroth]

Originally Posted by Ignitionnet

Your houses must be nicely spread out or a pretty fair size if a line extender is only serving 16 properties, Seph.

That's right, Igni. This part of Winnersh comprises houses/bungalows on the standard ¼ acre plot. The cabinets are c. 250m spaced.

---------- Post added at 00:12 ---------- Previous post was at 00:03 ----------

Originally Posted by Saint man

this is current readings and the green box is about 5 car widths away from my house, and was advised by Virgin CS on forum that an engineer would be required. Thing is trying to find the time at the momment to be in when an engineer is available is not too good. Would I have problems if I didn't have engineer visit?



Downstream Channels Lock Status Channel ID Frequency Modulation Rx Power RxMER Pre RS Errors Post RS Errors Locked 100 298750000 Hz 256 QAM 3.3 dBmV 37.9 dB 5316 300 Locked 98 282750000 Hz 256 QAM 3.0 dBmV 37.4 dB 9259 296 Locked 99 290750000 Hz 256 QAM 3.1 dBmV 37.9 dB 4318 1044 Locked 101 306750000 Hz 256 QAM 3.4 dBmV 37.9 dB 5089 301 Locked 102 314750000 Hz 256 QAM 2.9 dBmV 38.3 dB 8264 285 Locked 103 322750000 Hz 256 QAM 2.6 dBmV 37.9 dB 13577 895 NotLocked Unknown NotLocked Unknown To reset the Pre and Post RS error counts please use the Downstream screen under the router status screen available from the login page.


Upstream Channels Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate Locked 44 25800000 Hz ATDMA 30.0 dBmV 16QAM 6400000 Hz 5120 Ksym/sec NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec Locked 43 32600000 Hz ATDMA 31.3 dBmV 16QAM 6400000 Hz

5120 Ksym/sec

There is nothing wrong with those stats. As I mentioned in another reply in this thread, the VM end commands the upstream power level and if all it needs is 30 dBmv, all the better.

You don't need a technician if everything's OK with your internet experience.

[Saint man]

Thank you Sephiroth, thing is I would have been non the wiser if I hadn't been looking too deeply into things I have no knowledge of. Thanks.

[Sephiroth]

You're welcome.

[horseman]

Originally Posted by Ignitionnet

Your houses must be nicely spread out or a pretty fair size if a line extender is only serving 16 properties, Seph.

There's some bedtime reading on VM CU/SA boards if you like any DOCSIS capacity fiction? Haven't quite worked out whether Daves in the 6 bed detached house with dual driveway and swimming pool though?

[Sephiroth]

Ah - "quite worked out", Horse? I'm surprised you haven't found out with the information to hand (to you).

[horseman]

Originally Posted by Sephiroth

Ah - "quite worked out", Horse? I'm surprised you haven't found out with the information to hand (to you).

You kindly provided 250m cab spacing and 0.25acre plot's to Igni's query which only leaves me with the final question which is whether the 716 Homes Passed actually represents only those homes with a visible "street drop"/"omnibox" ?
(as per my thread elsewhere! )

[Sephiroth]

Originally Posted by horseman

You kindly provided 250m cab spacing and 0.25acre plot's to Igni's query which only leaves me with the final question which is whether the 716 Homes Passed actually represents only those homes with a visible "street drop"/"omnibox" ?
(as per my thread elsewhere! )

The attachment should answer your question about reconciliation.

[horseman]

Originally Posted by Sephiroth

The attachment should answer your question about reconciliation.

598HPPN Nice one! - which is back to my original 600HPPN metric which I thought was too little as an average? Perhaps 900HPPN for high density housing is nearer? Gives a 750HPPN median.