Noisy Line?

After a couple of days living at the parents over Christmas i couldn't put up with their terrible internet any longer.

They are currently on a Zen 8Mb service but were getting at worst 20kb/s download.

Original equipment was Netgear DG834GT, this connected at 5.4Mb ish with a SNR of 6.5, during the day this would hover from 5 - 6.5 on the netgear and jump up to +13 during the evening.

Updated the router to latest DGTeam with no change.

Replaced the router with a old Draytek 2800VG, sync has dropped to 4.8Mb with a SNR of 8.5 hovering around 7-8.5 and jumping to 16 last night.

I have traced and removed all cables, all phones and used the master socket all with little difference.

Line stats

Running Mode : G.DMT State : SHOWTIME
DS Actual Rate : 4864000 bps US Actual Rate : 448000 bps
DS maximum Rate : 4864000 bps US maximum Rate : 448000 bps
DS Path Mode : Interleave US Path Mode : Interleave
NE Current Attenuation : 19.0 dB Cur SNR Margin : 8.5 dB

As you can see 19dB attenuation whilst syncing at 4.8Mb at 8.5 SNR

Other line stats

ADSL Information (ADSL Firmware Version: E.67.36.1 )
ATM Statistics TX Blocks RX Blocks Corrected Blocks Uncorrected Blocks
187232 2874103 58463 2

That is for a connection of 1 hour as you can see the corrected blocks is very high considering the length of time it has been connected.

I'm at a loss of what to suggest / try, to me this is noise on the line or a dodge line card maybe? I usually expect the SNR to drop during the evening not increase..

Any suggestions?

Thanks

Andy

In reply to a post by PJ02:

After a couple of days living at the parents over Christmas i couldn't put up with their terrible internet any longer.

They are currently on a Zen 8Mb service but were getting at worst 20kb/s download.

Original equipment was Netgear DG834GT, this connected at 5.4Mb ish with a SNR of 6.5, during the day this would hover from 5 - 6.5 on the netgear and jump up to +13 during the evening.

Updated the router to latest DGTeam with no change.

Replaced the router with a old Draytek 2800VG, sync has dropped to 4.8Mb with a SNR of 8.5 hovering around 7-8.5 and jumping to 16 last night.

I have traced and removed all cables, all phones and used the master socket all with little difference.

Line stats

Running Mode : G.DMT State : SHOWTIME
DS Actual Rate : 4864000 bps US Actual Rate : 448000 bps
DS maximum Rate : 4864000 bps US maximum Rate : 448000 bps
DS Path Mode : Interleave US Path Mode : Interleave
NE Current Attenuation : 19.0 dB Cur SNR Margin : 8.5 dB

As you can see 19dB attenuation whilst syncing at 4.8Mb at 8.5 SNR

Other line stats

ADSL Information (ADSL Firmware Version: E.67.36.1 )
ATM Statistics TX Blocks RX Blocks Corrected Blocks Uncorrected Blocks
187232 2874103 58463 2

That is for a connection of 1 hour as you can see the corrected blocks is very high considering the length of time it has been connected.

I'm at a loss of what to suggest / try, to me this is noise on the line or a dodge line card maybe? I usually expect the SNR to drop during the evening not increase..

Any suggestions?

Thanks

Andy

The first question ... are there any flashing Christmas lights near the router, filter or phone lines?

The jump of SNR in the evening - is it a single step or gradual rise?


19dB attenuation with 6dB SNR would normally give better speeds. Possibly a noise source is disappearing and the SNR then rises.


Can you get RouterStatsLite and run it - sampling every minute for 24 hours to give 3000 point graphs for up and down sync and up and down SNR. Than willl show exactly when teh noise level is changing and how it changes.

I've set Router Stats Lite up and shall run it for the rest of the day, i can't be sure when the SNR jumps up atm though.

The only thing next to the master socket is an electric garage switch which we isolated and switched off, no Christmas lights this year i'm afraid as they were busy doing building work in the house.

I've tried switching other old appliances fridges / freezers in the garage. The master was moved into the garage quite awhile ago when an extension was done to the property. There is then a cat6 distribution panel next to the master socket with a clarityIT filtered faceplate providing filtered phone connections to the rest of the house.

The faceplate has been removed and tested with a brand new standard filter with an actual decrease in SNR so the filter should be good.

No Sky boxes either, my guess was also a noise source hopefully the routerstatslite will pin point the timeframe which may give a clue to what.

Leave it running to find out when the change happens but if you are sure it will not happen in the next hour then try removing all of the filtered extensions from the network and connecting the modem/router direct to the socket and see what happens. I have a couple of thoughts but may be wrong - try it and see for a few minutes before returning the connections to normal.

5pm exactly it jumped from 8.5 to 15.5 SNR. Will be keeping an eye on it to try and see what time it drops again in the morning.

What were your thoughts?

A

Edited by deleted (Thu 29-Dec-11 19:39:23)

Did sync change?

That sounds as though a noise source is being turned off. One example, which was discussed here previously was a shop - plenty of fluorescent lights with old and cheap ballasts causing massive amounts of noise. In the morning - lights on, noise up, SNR drops to below zero, resync at lower speed with 6dB. Evening, lights off, SNR jumps up several dB but no rersync until forced. Could be a shop close to you, a factory, or something else.


Keep RSL running overnight and see when the SNR drops and then wait for tomorrow PM to see what happens at 17:00.

So we managed to get the huge SNR sweep they have been experiencing.

30th Decemeber Night

There was a resync at 21:58 from 4.8 @ 15.5 SNR to 6.4 @ 9 SNR which then increased to 14.5 SNR, back down to 9 this morning @ 8:33am and finally 2.5SNR at 9:10am which it is at atm.

This Morning

Edited by deleted (Fri 30-Dec-11 09:31:42)

Dial 17070 take the option for the quiet line test.

That looks so much like a noise source being switched on and off. Was the resync automatic or manual?

You need to run it for several days - it will auto save the graphs if set up correctly. Make sure you have set the sampling to 1 minute ...

Then compare day to day for times especially over the weekend and holiday.

I think it would be better using the DG834GT as you can use the full Routerstats package to monitor the line.

It does look like something is hitting the SNR during the day as others have mentioned, is the central heating or something else timed to come on during the day?

I've left it a few days so thought i'd check the connection

Comedy SNR

I need to go through the logfile but it's not a specific time, but generall in the 5pm->6:30pm SNR increases and 9am drops, neither of which tie into anything on a time in the premises.

I suspect this is either effecting the whole estate, or could just be something on this pair.

tbh it's time i probably involved Zen / BT to get them to investigate. But given they have no minimum's or sla's it's going to be a nightmare.

That is some REIN there! Never seen anything quite so drastic.

In my household I had some massive issues. Turned out a neighbour was building a plane in his garage. Whenever he started work on the plane, the broadband dropped and synod slower... Turned out the BT lines ran underground below where he was working & his equipment was interfering.

He didn't stop though, but now the planes finished the broad bands great again.

The steps are fairly well apart, so suggests its not constant, but maybe something switching off/on

I would monitor and when all the christmas lights are down in the area, talk to neighbours and see if they have similar issues. If so, then easier to get investigations going, with co-operative neighbours you might be able to identify the source of noise, e.g. new security light, treadmill, flourescent light, LV lighting.

An AM radio at around 600kHz tuned off a station can be a good tool for hunting down RF noise sources, and also a bin plot from the ADSL modem, to see at what frequencies the noise is most prevalent.

That is such a regular pattern it's got to be a timed source - my bet would be central heating or christmas lights.

Get out in the street and look for the set that come on at 5pm and stay on all night.

I thought i'd post a ADSL Spectrum from the Draytek.

ADSLSpectrum

for reference, 4.8Mb @ 8.5 SNR - daytime

Have some reading to do in relation to using an AM radio to find the source.

Don't forget though that the SNR is increasing during the evening not decreasing. The noise is therefore only during the day, typically when Central heating and lighting is off.

Edited by deleted (Thu 05-Jan-12 13:39:30)

There is not too much wrong with that ... There is just one notch at around 50 which is about 210 khz. The notch at 64 is the pilot frequency and not used for data.

Can you get a set for different SNR values.

Yeah, i'll check a little later this evening.

I've updated the OP as to the speed and snr value the sprectrum referenced so we can compare.

Sorry for the delay in getting back to you all,

ADSL Spectrum during the evening, doesn't look much different than during the day tbh.

22.5db SNR @ 4.8Mb