This topic

SNR like a roller-coaster ? - help

xlr8r — Tue, 15 Jun 2021 10:16:17 GMT

hi guys.

I wanted to know if anyone can advise on a solution for a problem i have with BT FTTC (Infinity 2 it was known as).

I use a Zyxel VMG8324-B10A router (in bridged mode) as a modem. and an Asus GT-AX11000 router. Im on FTTC and Cabinet is a Huawei i believe, having looked it up.

Every day my line speed will rise and fall for no apparent reason on the Zyxel (also happens with BT Openreach modem). Also, Each day my (DOWN ONLY) SNR will sits stable (at around 5.5) until around 7:30 am - 8:00 am when it jumps up to 9.2 ?? it does this every day, and reduces again around 9pm to normal. it can drop as low as 2.2 (but briefly ? i.e. an hour or so) - (see screenshot)

What could cause such a sudden SNR increase and decrease ? And, what could be causing my dropouts ? (let me know if you need any additional data for diagnosis)

thanks

Occasionally i monitor line stats from my Zyxel modem, here is a days worth of SNR behaving badly!

Modem Stats

================================================================================
VDSL Training Status: Showtime
Mode: VDSL2 Annex B
VDSL Profile: Profile 17a
G.Vector: Enable
Traffic Type: PTM Mode
Link Uptime: 1 day: 12 hours: 40 minutes
===============================================================================
VDSL Port Details Upstream Downstream
Line Rate: 11.368 Mbps 59.806 Mbps
Actual Net Data Rate: 11.338 Mbps 59.807 Mbps
Trellis Coding: ON ON
SNR Margin: 6.1 dB 9.4 dB
Actual Delay: 0 ms 0 ms
Transmit Power: 6.6 dBm 13.9 dBm
Receive Power: 0.0 dBm -6.3 dBm
Actual INP: 0.0 symbols 55.0 symbols
Total Attenuation: 0.0 dB 20.7 dB
Attainable Net Data Rate: 11.338 Mbps 70.835 Mbps
===============================================================================
VDSL Band Status U0 U1 U2 U3 U4 D1 D2 D3
Line Attenuation(dB): N/A 29.9 48.6 N/A N/A 15.3 38.4 62.2
Signal Attenuation(dB): N/A 29.0 47.2 N/A N/A 18.0 38.0 62.4
SNR Margin(dB): N/A 6.1 6.1 N/A N/A 9.4 9.3 9.3
TX Power(dBm): N/A -13.0 6.6 N/A N/A 11.6 7.9 5.3
===============================================================================

VDSL Counters

Downstream Upstream
Since Link time = 40 min 15 sec
FEC: 158746699 198
CRC: 87 12
ES: 7 10
SES: 7 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 6 min 15 sec
FEC: 124777 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 183598 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 14 hours 21 min 15 sec
FEC: 101489128 85
CRC: 0 4
ES: 0 2
SES: 6 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 62710436 124
CRC: 3148 12
ES: 54 12
SES: 48 0
UAS: 1740 1693
LOS: 1 0
LOF: 3 0
LOM: 34 0
Total time = 1 days 14 hours 21 min 15 sec
FEC: 164199564 209
CRC: 3148 16
ES: 54 14
SES: 54 0
UAS: 1740 1693
LOS: 1 0
LOF: 3 0
LOM: 34 0
===============================================================================

Re: SNR like a roller-coaster ? - help

imjolly — Tue, 15 Jun 2021 10:32:10 GMT

have you checked your landline for noise - dial 17070 option 2 should be silent and best with corded phone from test socket

Re: SNR like a roller-coaster ? - help

xlr8r — Tue, 15 Jun 2021 10:53:26 GMT

Hi, i remember doing this test a year or so ago when it was just the same, there was no noise. i havent done the test recently , but i will later this evening when i get home. Remind me , is the noise test done with or without the Openreach Mk4 faceplate (ie or tested using the socket behind it) ?

thanks

Re: SNR like a roller-coaster ? - help

pippincp — Tue, 15 Jun 2021 10:57:03 GMT

If done without the faceplate it doesn't rule out any internal wiring fault. Personally I'd do both.

Re: SNR like a roller-coaster ? - help

imjolly — Tue, 15 Jun 2021 10:56:40 GMT

it is best to use the test socket behind the faceplate as this eliminates any problem with faceplate and internal wiring

Re: SNR like a roller-coaster ? - help

xlr8r — Tue, 15 Jun 2021 11:25:35 GMT

ok, i rang home and asked the missus to do the noise test (with faceplate attached) using an old wired phone.

she says the line is crystal clear , no noise at all. (this was tested while the SNR value is at it peak, 9.3 SNR)

Oddly, when i looked at the stats after the noise test was done, the was a slight SNR increase (i.e. went up to 10 SNR) while it was being noise-tested ?

what's my next move ?

thanks

Re: SNR like a roller-coaster ? - help

xlr8r — Tue, 15 Jun 2021 14:38:56 GMT

ok, no noise on line as per earlier post and graph (one little spike occurred on eth SNR while the noise test was being done).

what else can i do ?

Re: SNR like a roller-coaster ? - help

imjolly — Tue, 15 Jun 2021 14:50:41 GMT

your connection speed will only change as and when there is a reset by modem dropping the internet connection. your attainable speed will change with line conditions as your noise margin fluctuates so will your attainable speed but actual connection speed remains constant

Re: SNR like a roller-coaster ? - help

xlr8r — Tue, 15 Jun 2021 16:22:39 GMT

OK GUYS , I have just had a bit of a eureka!! moment.... hopefully this will help others....

The one thing i never tested was our cordless house phone (duh!).

...and so what I did was , just for fun, to double micro-filter the phone-line socket (but leaving the VDSL socket untouched).

and guess what, immediately the SNR dropped quite dramatically!!

SNR went from 9.3 down to 6.0 !!

For double-micro-filtering, I tried 4 different micro-filters, each having mixed results. The best one turned out to be an 'unbranded' type with marked with only, ADSL SPLITTER - PBS-58043-C

This was the one that worked in reducing SNR the most. And yes, the phone still works fine...

just need to see if i can tweak it a little more to find that 2.8 SNR sweetspot that I got for 2 hours....

SNR Graph after double-filtering with 4 different microfilters....

The phone base causing the problem!! (now heading for the recycle bin)...

Double microfiltered phone socket

Hope info helps.

Re: SNR like a roller-coaster ? - help

pippincp — Tue, 15 Jun 2021 16:31:19 GMT

I suspect it was more the faceplate not being seated correctly and changing filters has resolved it. Those faceplates are notorious for that.

Re: SNR like a roller-coaster ? - help

xlr8r — Tue, 15 Jun 2021 17:52:22 GMT

What would be a better faceplate to use ? thanks

Re: SNR like a roller-coaster ? - help

imjolly — Tue, 15 Jun 2021 18:09:43 GMT

I use that faceplate without any problems. You just need to make sure that you clip in place correctly and avoid any further contact and it will be fine

Re: SNR like a roller-coaster ? - help

xlr8r — Thu, 24 Jun 2021 17:22:03 GMT

....oh dear... i seem to have been too quick to assume I had discovered the problem.

seems its not my cordless house phone at all.... it was just a coincidence that the SNR dropped at the same time i disconnected it to test.

I even bought new phones, same problem. I bought a new complete nte5c mk2 and MK4 faceplate, same problem! Tested the silence test, clear as a bell. And im still getting occasional line drops , 1 a day usually...

SNR is still up and down. It can go as low as 2 and high as 12! (highest yet today?) That cant be within normal expectations surely ?

Anything else I can try ??

Re: SNR like a roller-coaster ? - help

imjolly — Thu, 24 Jun 2021 17:39:23 GMT

Normally your noise margin should be static with maybe fluctuating by +/- 0.1db

Do you have any extension sockets. Did you check there was no dial tone when you connected to the test socket?

Re: SNR like a roller-coaster ? - help

xlr8r — Fri, 25 Jun 2021 09:46:39 GMT

Hi, no extensions.

my line comes in at the front of my house and into the openreach socket/mk4 faceplate. (uses two wires only)

double socket (BB and landline)

the dsl line is cat6'd to the modem , the landline goes to a cordless Dect phone.

do i not need a dial tone to do the quiet test ?

thanks

Re: SNR like a roller-coaster ? - help

licquorice — Fri, 25 Jun 2021 09:50:56 GMT

@xlr8r wrote:

do i not need a dial tone to do the quiet test ?

thanks

What @imjolly meant was make sure there is no dial tone at an extension socket when faceplate removed at master to reveal test socket. I.e make sure extension socket is wired correctly from faceplate rather than star wired. Irrelevant in your case as you have no extensions.

Re: SNR like a roller-coaster ? - help

licquorice — Fri, 25 Jun 2021 09:58:20 GMT

It certainly looks as though there is some sort of interference coming and going at those times. Its weird that the noise margin increases rather than decreases though as though the interference is there most of the time and then goes off for a while.

Re: SNR like a roller-coaster ? - help

xlr8r — Fri, 25 Jun 2021 11:31:53 GMT

thanks

i am at a loss as to the cause of the interference. in a last ditch effort , i even bought some RFI & EMI material to shield everything that could potentially cause interference... no difference at all.

Tried switching everything off in the house, bar the router and modem, no difference...

willing to trade my soul with the Devil now for FTTP !

Re: SNR like a roller-coaster ? - help

licquorice — Fri, 25 Jun 2021 11:54:02 GMT

To be honest, I'm not sure why you are so concerned as your speed is not being affected by the fluctuations.

Bear in mind the source of any interference may not be in your house.

Re: SNR like a roller-coaster ? - help

xlr8r — Fri, 25 Jun 2021 16:18:38 GMT

thanks, but it does affect it,

1. it drops the line almost daily

2. my line speed rises and falls by roughly 10Mbps in parallel to SNRM

also, does it make any difference whatsoever if you make the modem handle the PPPoE , or the Router ? I ask because i seem to automatically lose another 10Mbps from modem to Router when letting the Router handle it...

* there must have been an epic Solar Flare this am just before 12 noon ? Quite a spike on both Up and Down...followed by a weird drop (flatlined also?) maybe line died for a while, not sure...I was at work.

Current stats , just now 17:15 25-6-2021