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Author Topic: Odd shaped SNR-vs-tone graph - line #4 fault again  (Read 8028 times)

burakkucat

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #105 on: September 26, 2020, 06:36:04 PM »

I only mentioned the line shunt components as they could, if damaged, cause peculiar circuit behaviour.

If all four lines are now well-behaved then it would be best to leave them alone. If, in the future, one becomes faulty then certainly ask A&A to request an NTE5 check as part of the fault-finding process.

To be absolutely correct, in terms of radio frequency transmission lines, you have no need for the shunt across the pair. The shunt is, er, detrimental. But it does provide a "signature" that can be "read" by a remote test set.
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #106 on: September 26, 2020, 08:27:03 PM »

Oh I see. And if the series DC blocking capacitor is dead, then youíd really know about it. Or is there a more subtle fault mode.
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burakkucat

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #107 on: September 26, 2020, 09:20:59 PM »

I would expect the capacitor to go open circuit, probably by exploding, and the resistor to, perhaps, be vaporised at one extreme. The other extreme would be a hard short-circuit.
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #108 on: September 27, 2020, 02:13:27 PM »

Thatís what I thought. Has any of our members had degraded performance or problems from a dodgy or blown NTE5 ?
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #109 on: September 28, 2020, 03:34:14 PM »

@Burakkucat : AA said that engineers will check NTE5s when they come into the house.

I still havenít seen the engineerís notes from that visit.
« Last Edit: September 28, 2020, 09:55:24 PM by Weaver »
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burakkucat

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #110 on: September 28, 2020, 04:47:08 PM »

AA said that engineers will check NTE5s whenís they come into the house.

Perhaps substitute a "should" for the "will" and an "if" for the "when's"?  :)

Quote
I still havenít seen the engineerís notes from that visit.

Maybe it was written in invisible ink.  :-\
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #111 on: September 28, 2020, 09:58:36 PM »

In the past, engineersí notes have always been posted onto AAís clueless.aa.net.uk server and appear in the log for the appropriate line. I donít know if this is automatic; I expect that it is; not sure exactly why I get that feeling.
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #112 on: October 24, 2020, 11:33:04 PM »

Here we go again; lightning strike 7 miles away and the four lines blipped and resynched at around 1620 UTC. I was asleep at the time they resynched and then we heard thunder and pulled the modem cables from the wall sockets. When I woke up later on, I noticed that downstream sync rates were really low on lines 2, 3 and 4. I performed a SNR reset on these lines using clueless.aa.net.uk and forced a resynch on each of the modems. The downstream speeds were still disappointingly low again.

And guess what, the culprit is evidently the hollow downstream SNR vs frequency phenomenon on lines 2, 3, 4. So Iíll have to contact AA.

Live sync rates, all at 3dB d/s 6dB u/s SNRM:
  #1: down 2876 kbps, up 529 kbps
  #2: down 2560 kbps, up 522 kbps
  #3: down 2080 kbps, up 386 kbps
  #4: down 2026 kbps, up 627 kbps

Notice the exceptionally high upstream speed of line #4 - weird. ???
« Last Edit: October 24, 2020, 11:45:59 PM by Weaver »
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #113 on: October 27, 2020, 06:15:13 AM »

Since then line 2 downstream rate has crashed to 178kbps :o

Lines 3 and 4 have both further deteriorated markedly.

Live sync rates:
  #1: down 2876 kbps, up 529 kbps
  #2: down 178 kbps, up 512 kbps
  #3: down 1867 kbps, up 389 kbps
  #4: down 1046 kbps, up 563 kbps
« Last Edit: October 27, 2020, 06:17:20 AM by Weaver »
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burakkucat

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #114 on: October 27, 2020, 04:22:24 PM »

If only you could have electrically non-conductive links . . .  :-X
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #115 on: October 27, 2020, 05:20:05 PM »

Indeed. I really would love to work out how to do the fibre media converter thing, but times 2 times 4 is a pain.

I pulled out the modems from the wall when I heard a thunder rumble; but I didnít hear a beep from the hardware lightning detector on the wall rack by my bed - its beeper is far too feeble - a big design failing, and thereís no volume control either  :(  I missed the alerts from the app on my ipad because I was asleep, but I did see the app alert notification later on sitting there saying strike at 6.9 miles (or some such) but I didnít carefully peruse the earlier alerts.

I ought to get rid of the OR Mk4 SSFP on line 2 (being the newest one) as thatís another thing to go wrong, can get cooked. Or failing that, have a spare on site.
« Last Edit: October 27, 2020, 05:23:45 PM by Weaver »
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burakkucat

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #116 on: October 27, 2020, 05:41:59 PM »

I really would love to work out how to do the fibre media converter thing, but times 2 times 4 is a pain.

I have been thinking about that . . . Ideally you would like the protection before the ZyXEL modems but the best I can come up with is between the modems and the Firebrick.

(I really need to document my current thoughts for you. It's the time that process will take . . . )
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #117 on: October 27, 2020, 05:49:39 PM »

And the latter scheme would be more convenient and would protect the expensive kit, the ZyXEL modems being relatively cheap.
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #118 on: October 31, 2020, 02:17:16 AM »

AA sent two Openreach engineers on Friday morning. Lines 3 and 4 are now perfect but line 2 is not fixed - still slow downstream. They are just having an awful time locating these faults. The engineersí notes arenít back yet.

Live sync rates, all at 3dB downstream / 6dB upstream SNRM :
  #1: down 3015 kbps, up 522 kbps
  #2: down 2343 kbps, up 519 kbps
  #3: down 2844 kbps, up 386 kbps
  #4: down 3012 kbps, up 557 kbps



Line 2 tonight, after engineersí visit:





« Last Edit: October 31, 2020, 02:29:27 AM by Weaver »
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Weaver

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Re: Odd shaped SNR-vs-tone graph - line #4 fault again
« Reply #119 on: November 02, 2020, 10:41:21 PM »

BT-speak: could anyone tell me what LLUMS stands for ?

I just got the engineersí notes back from AA; I canít make anything much out of them, they seem to be fairly detail-free. This is mentioned in some correspondence with [?]BTW.
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