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Author Topic: High QLN & Other Issues.  (Read 20382 times)

roseway

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Re: High QLN & Other Issues.
« Reply #15 on: July 19, 2014, 07:27:39 PM »

I'm curious what type of fault causes such Hlog, SNR margin fluctuations, attenuation fluctuations.

An intermittent HR (high resistance) line fault most probably.
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  Eric

burakkucat

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Re: High QLN & Other Issues.
« Reply #16 on: July 19, 2014, 07:43:11 PM »

I'm curious what type of fault causes such Hlog, SNR margin fluctuations, attenuation fluctuations.

An intermittent HR (high resistance) line fault most probably.

From the evidence presented, it certainly seems to indicate a defective joint.

As for the "missing" DSLAM/MSAN information, that is a puzzle. However from what notaclue recalls, I'm sure it is a Infineon chipset.

Checking the service received in The Cattery, I see --

Code: [Select]
# xdslcmd info --vendor
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 8000
Max: Upstream rate = 1044 Kbps, Downstream rate = 6424 Kbps
Channel: INTR, Upstream rate = 1016 Kbps, Downstream rate = 5583 Kbps

ChipSet Vendor Id: IFTN:0x71c6
ChipSet VersionNumber: 0x71c6
ChipSet SerialNumber:
#

IFTN is the abbreviation for Infineon.
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konrado5

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Re: High QLN & Other Issues.
« Reply #17 on: July 19, 2014, 07:51:26 PM »

Quote from: burakkucat
From the evidence presented, it certainly seems to indicate a defective joint.
What way does defective joint cause notaclue Hlog undulations? It seems he has intermittent signal reflections. You have said earlier that HR faults are not noticable at Hlog.
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notaclue

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Re: High QLN & Other Issues.
« Reply #18 on: July 19, 2014, 08:09:53 PM »

Would anyone like anymore information? Is there supposed to be 0 power on the downstream?
(I also used the address checker and it had no mention of a cabinet, thanks for that!)
« Last Edit: July 19, 2014, 08:12:15 PM by notaclue »
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kitz

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Re: High QLN & Other Issues.
« Reply #19 on: July 19, 2014, 08:50:06 PM »

I agree with Eric and b*cat, looks like a physical line fault.  HR possibly caused by an oxydised/corroded joint.

Corroded joints can cause capacitive faults which particulary affect the lower frequencies - hence why it normally affects the upstream tones the most. All the symptoms are there. You may also find the line loses sync when the phone rings or is in use.

In its current state the line is not able to support Annex_M.  Upstream Power showing as 0 is a known bug for certain routers but Ive not seen it occur on the downstream.   Its most likely to be a reporting issue because there must be power there.

Ive no idea why its not showing the chipset types when it did previously.  The only possible thing I can think of is that when in Annex_M mode the DSLAM responds differently?  :hmm:
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boost

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Re: High QLN & Other Issues.
« Reply #20 on: July 19, 2014, 08:56:30 PM »

Quote from: burakkucat
From the evidence presented, it certainly seems to indicate a defective joint.
What way does defective joint cause notaclue Hlog undulations? It seems he has intermittent signal reflections. You have said earlier that HR faults are not noticable at Hlog.

HLOG = Copper issues

QLN = RFI/Interference


HLOG doesn't care about RFI and the QLN doesn't care how many tie pairs were accidentally tagged onto yours from the PCP, etc.
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notaclue

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Re: High QLN & Other Issues.
« Reply #21 on: July 19, 2014, 09:03:46 PM »

I agree with Eric and b*cat, looks like a physical line fault.  HR possibly caused by an oxydised/corroded joint.

Corroded joints can cause capacitive faults which particulary affect the lower frequencies - hence why it normally affects the upstream tones the most. All the symptoms are there. You may also find the line loses sync when the phone rings or is in use.

In its current state the line is not able to support Annex_M.  Upstream Power showing as 0 is a known bug for certain routers but Ive not seen it occur on the downstream.   Its most likely to be a reporting issue because there must be power there.

Ive no idea why its not showing the chipset types when it did previously.  The only possible thing I can think of is that when in Annex_M mode the DSLAM responds differently?  :hmm:

A few things, the phone line works (with noise) and doesn't interrupt the broadband, at least I haven't noticed a correlation with how little it is used.

I have turned on Annex_M from within my router and the stats are roughly the same, with it fluctuating between the same sorts of figures as posted earlier. From what DSLstats says it's a not reported by the router rather than the dslam, so it leads me to believe my router could very well be the culprit?

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kitz

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Re: High QLN & Other Issues.
« Reply #22 on: July 19, 2014, 09:12:21 PM »

Quote
at least I haven't noticed a correlation with how little it is used.

Easily tested on a BT circuit.  Dial 17070 and select Ringback.  When you replace the receiver your phone should ring.

Observe the behaviour on DSLstats - it may be an idea to temporary increase the graph sample time to say 15secs to ensure that dslstats collects some stats during this period. Looking to see if the SNRmargin takes a hit.
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notaclue

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Re: High QLN & Other Issues.
« Reply #23 on: July 19, 2014, 09:26:11 PM »

I have just followed the advice as given (I think have set my snapshot up right.)
The line test was performed at 21:21

I have also attached the SNR Margin for the past few hours also if that's any help?
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konrado5

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Re: High QLN & Other Issues.
« Reply #24 on: July 19, 2014, 09:43:10 PM »

Corroded joints can cause capacitive faults which particulary affect the lower frequencies - hence why it normally affects the upstream tones the most.
But notaclue has significantly higher SNR margin fluctuations on downstream (red graph).
« Last Edit: July 19, 2014, 09:47:21 PM by konrado5 »
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kitz

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Re: High QLN & Other Issues.
« Reply #25 on: July 19, 2014, 09:50:10 PM »

hmmm  so your SNRm did take a hit...  but surprisingly I didnt see too much effect on the upstream as I would have expected.


Do you happen to recall what happened at circa 20:55.  To me that looks like one of the symptoms I saw on my own line when I had this corroded terminal.  ie the upstream SNR would improve after opening the line.


---
Im always loathe to point fingers at one particular item when it comes to hlog and QLN because you have to look at a much wider picture and consider all factors..  but it looks like from your hlog that tones over the region of 40 to 80 are being affected the most...  which is still the low end of the spectrum.
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Whatever the cause there is a problem and I think its time to call BT.   The fact that your speed has dropped so much on an Annex_M connection & noise on the line should be enough to get an engineer called out.   If you can repeat that test and your SNRm takes a hit each time you do a ring back..  this is very worthwhile mentioning to the engineer, as he should be able to replicate this easily and see the results himself on his JDSU (if he has one).  If not you can always show him your live dslstats graph.   

 
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kitz

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Re: High QLN & Other Issues.
« Reply #26 on: July 19, 2014, 09:52:01 PM »

Corroded joints can cause capacitive faults which particulary affect the lower frequencies - hence why it normally affects the upstream tones the most.
But notaclue has significantly higher SNR margin fluctuations on downstream (red graph).

Ermm  will you give me time to respond please.   I just covered that in my post above which I was making at the same time as you.  I dont fire off replies as quick as you do.  :-\
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burakkucat

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Re: High QLN & Other Issues.
« Reply #27 on: July 19, 2014, 09:59:14 PM »

Corroded joints can cause capacitive faults which particulary affect the lower frequencies - hence why it normally affects the upstream tones the most.
But notaclue has significantly higher SNR margin fluctuations on downstream (red graph).

I will grant you that fact. But please remember, it is not a "hard and fast" science -- it is more of a "black art". If we take another look at the recent SNRM graphs that notaclue has posted, both DS and US have "taken a big hit" when the ringing voltage was applied to the circuit. And that is fairly conclusive evidence of either a HR or semi-conducting joint. When it is considered with the audible noise that is also apparent when the telephone is used, a defective joint is almost a certainty.

[If that was my circuit I would connect a TDR (time domain reflectometer) to the pair and display the trace (either to the primary cross connection point or to the exchange). From a mobile phone I would then instigate a call to the circuit. With luck, the position of the defective joint would become obvious -- as the one region of the trace that fluctuates in synchronism with the cadences of the applied ringing voltage.]
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burakkucat

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Re: High QLN & Other Issues.
« Reply #28 on: July 19, 2014, 10:04:36 PM »

As to Annex M . . . doesn't it need to be configured at the DSLAM/MSAN? In other words, if the CO end of the xDSL circuit has not been configured for that mode, toggling the mode on and off at the CPE end is nothing more than a no-op?  :-\
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konrado5

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Re: High QLN & Other Issues.
« Reply #29 on: July 19, 2014, 10:07:42 PM »

And that is fairly conclusive evidence of either a HR or semi-conducting joint.
What about Hlog? notaclue fault is visible on Hlog. But you have said HR faults are not noticable on Hlog. Defected joint cause temporary signal reflections?

Best regards
konrado5
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