Low Downsteam Noise Margin- is this ok?

[Mit321]

Correct me if i'm wrong but if I remember right it is good to have low attenuation and high noise margin?

I live very close to my exchange (about 100 yards) and about 2 years ago they but in a brand new line.
Looking at my router stats attenuation looks very very good yet I don't think downstream noise margin is good (because it is so low, esepcially compared to upstream)? I'm on Orange and have just go interleaving removed (before Noise margin was about 12) but I play games so really want lower pings.
Does this low noise margin say there is a fault somewhere or is it acceptable?

ADSL Link Downstream Upstream
Connection Speed 8128 kbps 448 kbps
Line Attenuation 8.0 db 2.5 db
Noise Margin 6.7 db 21.0 db

These stats got from an ageing DG834GT Router

[abaxas]

Yep.

Your modem will lower output power as the line is so short. I'm about 100m as the crow flies from our exchange, here re my stats.

Noise Margin: 8.5 dB 15.0 dB
Output Power: 7.0 dBm 12.5 dBm
Attenuation: 5.0 dB 0.5 dB

Worst thing is, no LLU here :<

[daniel_owen_uk]

Perfectly acceptable.

[arthurleung]

Item Downstream Upstream Unit
SNR Margin 6 6 dB
Line Attenuation 18 7 dB
Data Rate 17844 1283 kbps

AFAIK the exchange adjust the power output to reach a SNR margin set by the ISP (For Be ADSL2+ I think its 4db for fast, 6db for normal and 8db for reliability setting). If you're seeing a value much higher than 6 then I would guess its your line have some intermittent fault so that the exchange increase the power level so that you get a minimum noise margin of 6. If more users connected to the exchange or there is some interference down the line could see the noise margin fluctuate over time (say between 6~12).

If the power output is already at the maximum, the data rate is adjusted to get to the margin. On the other hand if the data rate is already at maximum the power output drops.

There is a limit on the maximum power because higher power will drown out other ADSL lines' signal margin.

[daniel_owen_uk]

The SNR is set when you sync, so if it syncs and your line improves over time then you can see a higher SNR margin.

This normally happens if you sync during a period of high contention.

SRA should stop this happening, but I have never seen it working properly.

[Mit321]

Yep.

Your modem will lower output power as the line is so short. I'm about 100m as the crow flies from our exchange, here re my stats.



Worst thing is, no LLU here :<

We have no LLU here either. Though am on Orange and am getting horrible ping spikes in the evening and bad consistent pings to some UK servers, so will be switching to Plusnet soon hopefully.

Why is my upstream so good/high comapred to my downstream?

Also is there any way of checking my output power?

Also on a slightly different note, the master phone line sockets in your house. People say you can test to see if your connections any better by unscrewing the faceplate and plugging it into the socket inside. What excactly then is the point of the front face plate. I was reading on Kitz ADSL advice that if you unplug some of the wires in the back of the front faceplat it can get you better stats?

[arthurleung]

We have no LLU here either. Though am on Orange and am getting horrible ping spikes in the evening and bad consistent pings to some UK servers, so will be switching to Plusnet soon hopefully.

Why is my upstream so good/high comapred to my downstream?

Also is there any way of checking my output power?

Also on a slightly different note, the master phone line sockets in your house. People say you can test to see if your connections any better by unscrewing the faceplate and plugging it into the socket inside. What excactly then is the point of the front face plate. I was reading on Kitz ADSL advice that if you unplug some of the wires in the back of the front faceplat it can get you better stats?

The upstream and downstream are on different frequency ranges, and even people with extremely long line usually have problem with downstream only, upstream is never a problem so the modem will give maximum power regardless of line condition, which translates to higher noise margin.

The face plate have wires that split your phone signal to other phone sockets in your house. And that bit of wire can pick up noise like an antenna (or was that because the signal reflects off the end). So unplug it gives less noise.

[Steve]

And that bit of wire can pick up noise like an antenna (or was that because the signal reflects off the end). So unplug it gives less noise.

Both

[Mit321]

The upstream and downstream are on different frequency ranges, and even people with extremely long line usually have problem with downstream only, upstream is never a problem so the modem will give maximum power regardless of line condition, which translates to higher noise margin.

The face plate have wires that split your phone signal to other phone sockets in your house. And that bit of wire can pick up noise like an antenna (or was that because the signal reflects off the end). So unplug it gives less noise.

I've removed the bell wire and my line attenuation has dropped from 8db to 7bd. I checked it using the test socket and was only getting 5db, which somehow means i'm gaining 2db on this extra cm of wire without the bell wire attached? The wires left in have been very badly done by whoever did them with a massive bit sticking out after its gone into the terminal, can i chop these off? Also my SNR Downstream has gone up to 10db. Is this somehow dictated by Orange or the DSLAM in the exchange increasing/decreasing power? Remembering i'm only about 100m from my exchange and with Orange am getting about 6mb download and 0.35mb upload.

[Steve]

You don't change SNR directly, you* alter sync speed and output power to get to an SNR target, or you sacrifice SNR to get a higher sync speed.

Sounds like the wiring isn't particularly good, but without seeing it I wouldn't be able to give any recommendations with any confidence.

* By "you" I mean your modem, or the DSLAM. It's not often within direct control of the user

[Mit321]

You don't change SNR directly, you* alter sync speed and output power to get to an SNR target, or you sacrifice SNR to get a higher sync speed.

Sounds like the wiring isn't particularly good, but without seeing it I wouldn't be able to give any recommendations with any confidence.

* By "you" I mean your modem, or the DSLAM. It's not often within direct control of the user

Should I not be bothered about my downstream SNR? I mean its perfectly acceptable as other users say but for the length of my line and its attenuation surely it should be nearer 20db? Also I know with 8mb broadband you don't get 8mb but surely I should be getting closer than 6mb?

[merdat]

You would not even get 8 meg at the point leaving the exchange also although you are 100 yards from the building your line will not be directly connected to the exchange but will prob. go through a 'green cabinet ' or something akin so I would guess that you are doing not to bad at 6 meg.

[Steve]

You would not even get 8 meg at the point leaving the exchange also although you are 100 yards from the building your line will not be directly connected to the exchange but will prob. go through a 'green cabinet ' or something akin so I would guess that you are doing not to bad at 6 meg.

Not true. I've synced at 8192 kbps with a ~1km line that was stable for a year, save some thunderstorms.

But if you're not syncing at 8 even when plugged into the master socket and with the rest of the home's phone circuitry disconnected, there might be a further problem, or simply the ISP has things configured to provide you greater stability at the expense of sync speed, in light of observed line issues.

[abaxas]

Not true. I've synced at 8192 kbps with a ~1km line that was stable for a year, save some thunderstorms.

But if you're not syncing at 8 even when plugged into the master socket and with the rest of the home's phone circuitry disconnected, there might be a further problem, or simply the ISP has things configured to provide you greater stability at the expense of sync speed, in light of observed line issues.

He could be on a bit of Aluminium cabling. Which as we all know is 'gash' for broadband.

I've also had issues with such things as microwaves, drills, ex neighbours lathe.

It could be anything!

[Mit321]

Not true. I've synced at 8192 kbps with a ~1km line that was stable for a year, save some thunderstorms.

But if you're not syncing at 8 even when plugged into the master socket and with the rest of the home's phone circuitry disconnected, there might be a further problem, or simply the ISP has things configured to provide you greater stability at the expense of sync speed, in light of observed line issues.

I'm on Copper Wire to the exchange, and live in the country side so its overhead straight to the exchange (no green cabinets). The wire was put in only a year ago cause our old one was crap. Also my router says it is synching at
Downstream Upstream
8128 kbps 448 kbps

Does that mean I could still have a different "profile" ??

[abaxas]

I'm on Copper Wire to the exchange, and live in the country side so its overhead straight to the exchange (no green cabinets). The wire was put in only a year ago cause our old one was crap. Also my router says it is synching at
Downstream Upstream
8128 kbps 448 kbps

Does that mean I could still have a different "profile" ??

yes... go to

http://speedtester.bt.com/

to check (provding you aint LLU)