SNR margin no longer drops in the evenings

As I have a long line (54 dB attenuation), I found that leaving my SNR margin at BT's default 6 dB causes my SNR margin to drop too low in the evenings going down to only around 2 or 3 dB (on a 4 Mb sync which is slightly higher than I have now)

I have therefore tweaked my SNR margin to a 'target' 9 dB by using the DMT tool.

What used to happen was this used to stay at 9 dB through the day and drop to around 6-7 dB in the evenings because there's more AM radio interference, etc.

However, I've just noticed that my SNR margin doesn't drop from 9 dB even in the evenings anymore (I took the screenshot below just a few minutes ago (23:13)) :

http://i11.tinypic.com/89irqy8.jpg

Does anyone know why this happens?

The only difference I can see now (after 40 days uptime) is the bit loading on frequencies from (aprox) 518 to 636 kHz have lost some bandwidth as this range of bit loading used to be slightly higher in fact comparable with the overall bitloading of aprox 8 - 11 bits i.e. the overall left to right line.

Could this have anything to do with it?

p.s. for all those people who say that the SpeedTouch router exaggerates the FEC errors, then how come my FEC error count is low at just over 3 million FEC errors on an uptime of over 40 days ?!

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What used to happen was this used to stay at 9 dB through the day and drop to around 6-7 dB in the evenings because there's more AM radio interference, etc.

However, I've just noticed that my SNR margin doesn't drop from 9 dB even in the evenings anymore (I took the screenshot below just a few minutes ago (23:13)) :

Does anyone know why this happens?

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Chances are you will never know why, could be a million and one reasons.

My db reading some evenings drops by 1-2db other evenings it doesnt (and no ive not got SNR switched on when ive observed this).

It could indeed be down to a drop in the frequencies you mention.

Or it could be down to something as simple as the change in weather and the evenings being cooler (interference from any radio frequency in my expereience is less if the outside temp is low). Could even be something as simple even as someone in your road not listening to a radio in the evening. COuld be a faulty street light that the council have fixed... basically it could be almost anything.

Edited by deleted (Sat 29-Dec-07 01:31:55)

Thanks.

It could be like you said a 'one-off' so I will be checking it tonight to see if it's the same.

My current SNR margin is 9.5 dB (through the day) and so the SNR margin only varies by 0.5 dB which does seem low and is usually indicative of a short line not a long line like mine is.

Oops forgot to post the screenshot:

http://i1.tinypic.com/6wzagcg.jpg

This was taken around 5 minutes ago.

Could it be that DLM (rambo) has adjusted your lines target SNR, and as a result you now see 9db-ish 24/7 ?

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Could it be that DLM (rambo) has adjusted your lines target SNR, and as a result you now see 9db-ish 24/7 ?

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It could be but I won't know until I re-check tonight.

One thing that I have noticed is that on an uptime of nearly 41 days what did used to happen was that my target margin used to automatically downgrade after around 14 days i.e. go back to the default 6 dB margin and I had to manually tweak it back up to 9 dB again using the DMT tool (this is the reason why I have the 1 'loss of signal' in the stats)

This hasn't happened this time so you could be right.

Totally agree - months ago my snr margin would go from 15db right down to -db after 1800 hrs every evening apart from weekends. Margin doesn't go below 8db at all now and currently the most stable its ever been.
Have a speedtouch st585v6, atten 55, sync 4192, snr margin now stuck at 9db although connection now rock solid for 5 weeks.
Tweeked margin with dmt tool at default 15db, got 14 day 3db drop twice,l then swapped to newest firmware at 9db and there it has stayed.
As for FEC errors, had over 2000000 in two days before but after last resync only 180000 in two days - go figure!

Took so long to type this missed the other posts - sorry!

Edited by deleted (Sat 29-Dec-07 09:25:07)

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Totally agree - months ago my snr margin would go from 15db right down to -db after 1800 hrs every evening apart from weekends. Margin doesn't go below 8db at all now and currently the most stable its ever been.

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It's also the stablest my connection has ever been with relatively low FEC, HEC and CRC error rates considering I have a long line and my uptime is over 40 days.

I only ditched the 6 dB target as I found that my line was re-syncing in the evenings although this was sporadic and wasn't happening every evening.

If I knew that my line would hold on a 6 dB target margin then I would try it for the extra 512 Kb speed but I prefer to have a stable line.

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Took so long to type this missed the other posts - sorry!

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Don't worry about it

The more opinions, the better

most likely explanation is bitswapping has turned of the tones that drop every evening and as the uptime gets higher the snrm stabilises. It is also possible with it been the christmas period you have much less crosstalk so have a higher snrm then you will have next week.