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Author Topic: HLog & QLN  (Read 439 times)

tiffy

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HLog & QLN
« on: July 16, 2017, 09:08:55 PM »

While I appreciate that the HLog & QLM parameters are only produced when the modem/router is actually synch'ing with the DSLAM and do not update until the next re-synch., I have very little appreciation the significance of the graphs produced in DSLStats or any similar stat's. monitoring program.

I would greatly appreciate if any of the very knowledgable forum members could perhaps explain the significance of the HLog & QLN graphs, ie., what does good & bad look like ?
I am on PN 38/2 fibre and have attached by latest DSLStats HLog & QLN graphs for reference.
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Chrysalis

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Re: HLog & QLN
« Reply #1 on: July 16, 2017, 10:01:51 PM »

no comment on the hlog, but to me the QLN looks quite good for a vdsl line. Low levels of crosstalk on the DS, moderate levels on the US.
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tiffy

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Re: HLog & QLN
« Reply #2 on: July 16, 2017, 10:40:32 PM »

Chrysalis, many thanks for your comments, much appreciated.

Please excuse my ignorance on this matter but what would higher levels of crosstalk look like on the graph, perhaps bigger spikes on the graph lines ?
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Chrysalis

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Re: HLog & QLN
« Reply #3 on: July 17, 2017, 12:30:39 AM »

yeah the lines would be higher, -140 is usually around the base level of no crosstalk.
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kitz

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Re: HLog & QLN
« Reply #4 on: July 17, 2017, 12:35:53 PM »

hlog - Looks ok for a long line - Nice smooth drop off and no indication of any problems with the physical line.

QLN - Line looks relatively quiet.  Shows a few line spikes at around tone 150 - 200.   Those particular tones can often be affected by RFI (radio transmission) so its not unusual to see spikes in that area, particularly if you live near a radio transmitter.

Tones 320 to 500 shows possible crosstalk typical from an adsl2 connection in the same binder.   Its sometimes difficult to diagnose in D1 due to PSD masking, which is why you see how the graph goes up after tone 550ish.
Tones 1450 to 1700 shows a bump typical of crosstalk centred around tone 1600 which tends to 'spread' over a band of frequencies.

Spikes = RFI/EMI noise.   Smooth bumps over a wider range of tones = crosstalk.



*Please note I have been approximate with the tone numbers - you would need to zoom in on the graph for more exact figures
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tiffy

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Re: HLog & QLN
« Reply #5 on: July 17, 2017, 02:32:58 PM »

kitz, thank you so much for your detailed explanations, much appreciated.
I have diligently read all of your excellent site guides but could not find any detailed, definitive guide to analysis of Hlog & QLN, this explanation certainly helps a lot.

Zooming of the graphs is now so easy on the MDWS site, can certainly home in on the tone ranges in question for more detailed analysis.

Am I correct in thinking that the Hlog & QLN graphs represent a snapshot of a very small area in time as they are taken just prior to the modem synch'ing with the DSLAM so would really only represent that instant in time ?
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roseway

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Re: HLog & QLN
« Reply #6 on: July 17, 2017, 03:45:12 PM »

Quote
Am I correct in thinking that the Hlog & QLN graphs represent a snapshot of a very small area in time as they are taken just prior to the modem synch'ing with the DSLAM so would really only represent that instant in time ?

Yes, that's correct.
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