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Advise on Router stats - SNR

RobRS
Grafter
Posts: 53
Registered: 29-10-2015

Advise on Router stats - SNR

I am just trying to get my head around router stats, have worked out the basics but not sure how to interpret the below graph, to the untrained eye it suggests that I am only using 150 of 500+ available tones?
16 REPLIES
ian007jen
Rising Star
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Registered: 06-09-2007

Re: Advise on Router stats - SNR

If your on ADSL1 or 2  then 256 tones  ......if on ADSL2+ then 512 tones used
The modems train at synch time....what are your router stats?
Community Veteran
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Registered: 31-08-2007

Re: Advise on Router stats - SNR

Well, looking at a couple of your previous posts I see it's a 21CN connection, but if the attenuation from the stats is correct, you unlikely to ver be using any of the higher tones, so you can set the graphing to 255 tones.
Looking at that graph, it suggests something is not right. There is a rather sharp cut-off at tone~152 and there's a lot of interference there from R4 Long Wave, this suggests a line fault or internal wiring problem.
Do you have a Master Socket similar to the one on the left?
Do you have any extension phone sockets - hard wired or plug in, and what is normally plugged in where? Do you use any extension leads between the phone socket and filter or filter and modem/router?
Do all your Microfilters look similar to this? And is everything that is connected plugged in via a microfilter?
RobRS
Grafter
Posts: 53
Registered: 29-10-2015

Re: Advise on Router stats - SNR

OK, I now, after a lot of reading, get the idea with the tones. and appreciate that the higher frequencies are attenuated more than lower ones, so long line = more attenuation = less available channels = less bandwidth  Smiley
Also noticed I had forced ADSL2+ on the router, so have now gone back to ADSL2 because I get nothing above 875khz
So thinking on a bit it would be good to get the most out of the tones/channels available. I have tried a few things with the internal wiring, but get the same sort of graph when connected into the test point on the master socket.
Definitely looks like R4 is an issue at 198khz and a few dips in other areas? I have attached today's graph I am now getting a bit more frequency spread but lower SNR overall.
Two graphs, one where the SNR went up to 4.4db not sure why, i didn't change anything at the time. Also attached SNR Margin graphs, the disconnects are me rearranging the wiring, I always do graceful disconnect so hopefully this won't mess anything up.

Community Veteran
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Registered: 31-08-2007

Re: Advise on Router stats - SNR

So what did you try with the internal wiring? Although you haven't mentioned anything in relation to my previous questions, I assume you have at least one extension socket. Are only terminals 2 & 5 connected throughout, and what colour are the wires on those terminals?
Have you done a Quiet Line Test 17070 option 2?
Those step changes in the SNRM suggest some significant cross-talk or interference. If it's cross-talk it could be due to a fault on your line, or the line from which it's coming. Unless you are quite close to the R4 LW transmitter, the 2 things suggest maybe your line.
If it's just interference then something obviously switched off around 13 minutes past one pm. and switched on again at around 20 past 2 pm.
Are you aware of anything electrical/electronic being switched off & on at around those times.
It could be anything from discharge lighting (fluorescents, CFLs etc) to anything with a switch mode PSU including items like Sky boxes etc.
RobRS
Grafter
Posts: 53
Registered: 29-10-2015

Re: Advise on Router stats - SNR

Internal wiring was old 4 core non twisted so I have replaced that with cat5 style twisted pair, it also took a long route to the one extension socket so I have made this more direct.
System consists of 1 cordless phone, plugged into the only extension, via micro filter, only uses terminals 2 & 5 wired in twisted pair back to the NTE5 master socket. router is plugged into master socket face plate via micro filter.
On the last attached graphs the disconnection at 12:23 ish was me removing the router from the NTE5 test socket and then plugging in face plate and extensions, so I don't think there are any internal faults.
I am not aware of anything that switches here at those times, but will do some checks, SNR went back up to 4.3 at almost exactly 18:00 so may suggest something on a timer (or just coincidence).
I am in the North of Scotland near Elgin so, as far as I know not close to R4 transmitter.
Have tried quiet line test but cordless phone is noisy so hard to tell, will try and find a corded to test with.
Community Veteran
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Registered: 31-08-2007

Re: Advise on Router stats - SNR

The graph at circa 1223, as you say, suggests the internal wiring is fine.
Quote from: RobRS
I am not aware of anything that switches here at those times, but will do some checks, SNR went back up to 4.3 at almost exactly 18:00 so may suggest something on a timer 

Excellent thinking, keep going down the same thought process.
The bad news is you have 50kW of R4 NW of you on the coast at Burghead Sad  so any issues with the line will not help.
Quote from: RobRS
Have tried quiet line test but cordless phone is noisy so hard to tell, will try and find a corded to test with.

Good idea. It can also be the case that the electronics even in a corded handset could suffer RF interference (I'm thinking R4 particularly), just be aware of that.
It might be worthwhile trying to lay your hands on a MK3 (vDSL) Service Specific Face Plate - they have an improved common-mode filter which might help with R4 signal rejection.
RobRS
Grafter
Posts: 53
Registered: 29-10-2015

Re: Advise on Router stats - SNR

Quote from: Anotherone
The bad news is you have 50kW of R4 NW of you on the coast at Burghead Sad  so any issues with the line will not help.

Embarrassed It never occurred to me that that was what is at Burghead, can see the two masts from my living room window, lit up like Christmas trees, direct line of sight 10 or so miles as the crow flies.
and my phone line is about 4000M long probably a good 1500M of it is also line of sight to Burghead, so this explains a few things Embarrassed
Will look into the faceplate option, did see some stuff on HAM radio sites about DIY common mode filters so may read up on this aswell.
Also I think my router to BT socket cord is flat so may try replacing with something better.
Wikipedia entry for burghead.
Quote
The Burghead transmitting station is a broadcasting facility near Burghead (grid reference NJ125685) in Scotland for long wave and medium wave radio transmission that started service on 12 October 1936.[1] The site is owned by Arqiva and houses a long wave radio transmitter on 198 kHz broadcasting BBC Radio 4 and two medium wave radio transmitters, broadcasting BBC Radio 5 Live on 693 kHz and BBC Radio Scotland on 810 kHz. The long wave transmitter is part of a network transmitting on the same frequency, the other transmitters being at the Droitwich and Westerglen.
198 kHz 50KW BBC Radio 4
693 kHz 50KW BBC Radio 5 Live
810 kHz 100KW BBC Radio Scotland
Community Veteran
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Re: Advise on Router stats - SNR

And sorry I should have mentioned that the two MW jobs will be what's knocking holes in your higher tones centred around tones 161 and 188 giving that apparent sharp cutoff. Any bad line balance is not going to be helpful.
RobRS
Grafter
Posts: 53
Registered: 29-10-2015

Re: Advise on Router stats - SNR

Obviously something is causing the SNR 1db jumps, still looking into that, also I will sort out better common mode filtering.
Other than this do you think anything can be done? is this likely just the result of old deteriorating line cabling, mindful that part of the line snapped recently so that bit couldn't have been very good.
or is it likely to be an actual fault that could be repaired? (answering my own question, guess the quiet line check might shed some light)
Thanks for all your help, I have learned so much recently from this site about ADSL etc. thanks to people like yourself who are prepared to share their knowledge.
Community Veteran
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Registered: 31-08-2007

Re: Advise on Router stats - SNR

No problem, ask away if you have any other queries.
If you have some noise on the line, then hopefully a Copper Line Test (CLT) will show a definitive fault. A decent OR engineer would do his best to make sure you were on the best pair that was available assuming it wasn't just a joint he could fix that was causing the problem.
RobRS
Grafter
Posts: 53
Registered: 29-10-2015

Re: Advise on Router stats - SNR

Well IMHO not bad now for 3+km from exchange and attenuation of 58.5db.  Smiley

Estimated line speed:
There's no speed estimate currently held on your account.
Current line speed:
4 Mb
Community Veteran
Posts: 19,100
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Registered: 31-08-2007

Re: Advise on Router stats - SNR

That attenuation (assuming that it's not decaying aluminum cable) suggests it's nearer 4km. Either way, with that attenuation or 4km, 4Mbps throughput speed is pretty fair.
RobRS
Grafter
Posts: 53
Registered: 29-10-2015

Re: Advise on Router stats - SNR

Probably is nearer 4km, not sure of the exact cable route.
To get to this I have changed the router to master socket cable with cat5, fitted a homemade common mode filter and filtered the phone extension at the master socket. This has made significant improvements to  the SNR / rejection of long wave signals.
To get 4Mbps I had to lower the target SNR, this was very stable at 1db for about 24 hours, but while I was out today the router has resynced at 3db, so now getting sync of 4106 Kbps I can live with this. Smiley
Community Veteran
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Re: Advise on Router stats - SNR

Well done with all the changes, sounds like you've tweaked things quite well  Wink
The only problem with "allowing" the SNRM to get too low though is that you can get a significant increase in errors, and if they are too high, there's two potential problems - reduced throughput speed due to the need for data retransmission, and DLM! - if it considers errors are too high then it may act to reduce them. So keep an eye on them, the ES as well as CRC.