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Author Topic: FTTC - Distance from the Cabinet - Realistic speed estimate  (Read 254029 times)

burakkucat

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #570 on: April 16, 2012, 08:38:31 PM »

The perils of attempting to interpret another persons experimental evidence, remotely, is fraught with difficulty.  ;D

All we can definitely say is that there appears to be some form of abnormality present in the D-side, which has shown up in that Exfo's TDR trace.

 :drink:
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Blackeagle

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #571 on: April 16, 2012, 08:58:13 PM »




If you were allowed contact with the various wizards within your employer's Grimbledon Down (a.k.a. Martlesham Heath), I'm sure they could give you practical evidence of such an occurrence. Somewhere in the back of my mind I have a recollection that a reverse-biased diode can be used as a form of a white-noise source. Perhaps an electronic engineer could comment, please?


Yes, you can reverse bias a Zener diode to get it operating in "junction-breakdown" mode and then amplify the white noise produced on the anode.  This would give you several hundred MHZ of white noise.
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burakkucat

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #572 on: April 16, 2012, 10:01:49 PM »

If you were allowed contact with the various wizards within your employer's Grimbledon Down (a.k.a. Martlesham Heath), I'm sure they could give you practical evidence of such an occurrence. Somewhere in the back of my mind I have a recollection that a reverse-biased diode can be used as a form of a white-noise source. Perhaps an electronic engineer could comment, please?

Yes, you can reverse bias a Zener diode to get it operating in "junction-breakdown" mode and then amplify the white noise produced on the anode.  This would give you several hundred MHZ of white noise.

Excellent! Thanks for the confirmation. :thumbs:
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Black Sheep

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #573 on: April 16, 2012, 10:19:55 PM »

Thanks for the info guys, how could a corroded joint be akin to a reverse-biased zener diode ?? Genuine question.
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burakkucat

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #574 on: April 16, 2012, 11:46:35 PM »

I do know that some of the earliest rectifiers were based on sandwiches of copper and copper oxide.

One only needs to have two different metals / metalloids in contact to create a semi-conducting materiel (or a voltaic cell).

The physics / chemistry / materials science / what-not is way outside my area of expertise . . .

All I can say is that, in theory, all manky-joints should be remade, as a matter of course, to eliminate any potential for "mischief".   
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #575 on: April 20, 2012, 07:51:03 AM »

Update 20/04/12:


I am still awaiting Plusnet to contact me since reporting 5 re-syncs in a row, simply from using the phone on Monday 16th (4 from dialling out & 1 from receiving a call).

Therefore no engineer visit has been arranged & I am not aware of any work being carried out on my connection that did not require a home visit.


Would you believe it? Just look at a couple of graphs showing the latest 3 days connection:-






You can see on the R/H side that I was so confident with the stability that I rebooted the modem this morning to achieve a higher sync speed (now 31244 k).


The connection appears to have stabilised IMMEDIATELY after receiving the incoming call.
Hence my earlier query about ringing voltages creating temporary fixes.

I am also back on a 40Mb/10Mb max profile (by request) following the 80/20 trials.

I think the switch back is purely coincidental as the phone calls causing the re-syncs occured AFTER the switch back.


Compare the 3 day graphs shown above with these - from the latest 8 days.
The immediate difference since that incoming call can be clearly seen:-






Due to the scale/resolution of the graphs, the 5 re-syncs cannot be seen clearly, but I could separate the period around 07:00 to show them as evidence & my modem log has also recorded them.



The phone issue & general stability appear to have gradually improved since Monday.
I can now use the phone with hardly any drop in SNRM being seen.

Is it pure coincidence that the weather has been wetter & colder since Monday?


In a way I am slightly disappointed with this stability as I am sure it has only prolonged the inevitable return to instability & lower speeds.

If an engineer turned up right now, no doubt all his tests would return LTOK results.

I wonder if any return to instability will coincide with weather changes i.e. (hopefully) improving as we head toward summer?

« Last Edit: April 20, 2012, 07:56:53 AM by Bald_Eagle1 »
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Blackeagle

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #576 on: April 20, 2012, 10:08:39 PM »

Hi BE,

I'm glad your line is looking stable at the moment, but I'm slightly confused by
Quote
The phone issue & general stability appear to have gradually improved since Monday.
I can now use the phone with hardly any drop in SNRM being seen.

Is it pure coincidence that the weather has been wetter & colder since Monday?

In my (limited) experience, water is generally a bad thing, although having said that, it is an excellent conductor, but this is usually why its a bad thing !!  Heat I can see.  An expanding joint somewhere could be making a bad contact, causing large fluctuations and introducing noise.  When cold the joint could contract and make a better connection.  Could be tough to track down Paul  :(
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #577 on: April 20, 2012, 10:50:52 PM »

Cheers BE,

I didn't really pay that much attention to the weather previously.

Like you, I had it in my mind that water in cables & joints was an especially bad thing, but looking back over a few months worth of various graphs, the connection has looked a little "better" during the colder & wetter winter period.

I only really started to consider weather conditions as a "potential" factor when we recently experienced unexpectedly warm, dry & sunny weather.

It was during those spells that my connection appeared to suffer the most.

It could be pure coincidence though as I have occasionally experienced a few continuous days of stability over the months, with no real explanation as to why it suddenly deteriorates from one day to the next.

The biggest problem in trying to rectify matters is probably that more often than not the connection has "fixed" itself before an engineer visit can be arranged.

The graphs are good at showing the results of an issue, but are not too easy to use in determining the root cause.
e.g. use of the phone. Why would it lower SNRM & then drop the connection for a few days on the trot, apparently fix itself & then start dropping the connection again after a fews of stability (That was prior to the latest engineer's visit).
These events can be clearly seen in the graphs.

The engineer rejumpered the cabinet connections & conducted a few tests & everything seemed more or less perfect.
That only lasted for a few days & then the phone issue started again.

Things now look quite stable again, but no other work has been carried out.
Plusnet contacted me earlier today & there was no mention of arranging an engineer visit.
While my connection is behaving, there probably would be no point though.

If/when this particular issue rears its head again, it would be really useful to conduct line tests (TDR etc.) at the time.
It may then be possible to pinpoint the cause & effect a permanent remedy once & for all.

It would also be incredibly useful to have records of before, during & after tests for comparison purposes.
I'll have to see what can be done about that.

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Maturecheese

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #578 on: May 13, 2012, 12:47:12 PM »

I haven't read through the thread but in answer to the title  I live around 800 meters cable length from the cabinet and I was syncing at 38 mb I P Profile for the last three months until a recent ongoing fault.
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #579 on: May 21, 2012, 09:17:29 PM »

Hi Maturecheese,

I haven't read through the thread but in answer to the title  I live around 800 meters cable length from the cabinet and I was syncing at 38 mb I P Profile for the last three months until a recent ongoing fault.


It seems like I had missed your message, sorry.

Has the fault been rectified & if so, what was the diagnosis of the fault?

Paul.
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #580 on: May 21, 2012, 09:40:41 PM »

Quick Update: 21/05/012

Now that the weather has improved, it appears that another engineer visit is being arranged for Friday 25th (subject to staying warm & dry through this week.

My connection has been reasonably stable for a few days (cold & wettish weather), with using the phone not having any effect other than to lower DS SNRM by 0.1dB or 0.2dB.

Coinciding with the weather's improvement & gaining pace since last night, my DS SNRM level has quite gradually lowered to currently only 2.4dB & use of the phone now causes DS SNRM to drop to as low as 0.8dB.

The above doesn't really make much sense, as it usually wet cables that cause problems.
However, I have noticed this phenomenon on the rare occasions that the weather has been unseasonably warm & dry over the last few months.

I may try to conduct a copuple of tests of my own before Friday's visit if this issue does indeed persist.

FWIW, recent graphs attached.
I also notice a massive & prolonged increase in RSCorr errors, again commencing last night.

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JoshShep

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #581 on: May 23, 2012, 03:54:32 PM »

Good luck mate,

I'm reverting back to the 40M profile shortly, the 80M profile has had a negative effect on my line so it's for the best.

Being on the 80M profile has also stopped OpenReach from doing a lift and shift so that's the thing that will be done next.

Hope it all goes well anyway, and do wish they finally find out the cause of your issues.

All the best,

Josh

Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #582 on: May 23, 2012, 04:06:30 PM »

Update to my message of 21st May:

Fingers crossed for Friday's engineer visit (now confirmed).

Recent stats since my last message are attached, showing the difference a bit of sunshine makes.
« Last Edit: May 23, 2012, 04:08:39 PM by Bald_Eagle1 »
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Bald_Eagle1

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #583 on: May 23, 2012, 04:13:44 PM »


I'm reverting back to the 40M profile shortly, the 80M profile has had a negative effect on my line so it's for the best.

Being on the 80M profile has also stopped OpenReach from doing a lift and shift so that's the thing that will be done next.



Cheers Josh, & good luck for your L & S.

40Mb & stability have to be better than "up to 80Mb", but achieving nowhere near it combined with instability.

Has your REIN issue ever been sorted?
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JoshShep

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Re: FTTC - Distance from the Cabinet - Realistic speed estimate
« Reply #584 on: May 23, 2012, 04:57:18 PM »


I'm reverting back to the 40M profile shortly, the 80M profile has had a negative effect on my line so it's for the best.

Being on the 80M profile has also stopped OpenReach from doing a lift and shift so that's the thing that will be done next.



Cheers Josh, & good luck for your L & S.

40Mb & stability have to be better than "up to 80Mb", but achieving nowhere near it combined with instability.

Has your REIN issue ever been sorted?

Since moving to 80Mb profile I have seen a little more errors on the line, I guess it's to do with the higher frequency's.

And I did have a REIN Engineer come out, he found nothing external but that was too early afternoon to track anything to be honest.

He found the power supply for the modem was giving off some interference so that got replaced.

If the connection is still poor after the L&S, I guess they'll be sending out another one out to try track something down.
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