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Sudden drop in SNR

N/A

Sudden drop in SNR

Hi

I have just had a sudden drop in snr, i would normally connect at
3600 with a SNR of 12

Now since this afternoon, I am now connecting at
1900 with a SNR of 12, before I noticed my SNR went down to 4.4, to which then I lost the LCP, rebooted the router then thats when I connected @ 1900 with 12
so I seem to have lost 7 dB;s

Any ideas?Huh
9 REPLIES
vic_newey
Grafter
Posts: 802
Thanks: 2
Registered: 30-07-2007

Sudden drop in SNR

The same has happened to me suddenly, I am on 1.5 meg & have been syncing at 1880 & for weeks & get just about the best speed possible for my 1.5meg with snr of 9.
now I suddenly sync at around 1550 with snr of 12 but speeds are way down to what I was getting before. this is the pits if its BT auto adjust equipment as I was quite happy with my 1.5 before Evil
daveyb
Grafter
Posts: 128
Registered: 04-08-2007

Sudden drop in SNR

Hmmmm........ I posted this in the Community Support forum last night http://portal.plus.net/central/forums/viewtopic.php?t=43905

David.
N/A

Sudden drop in SNR

Well the failure only seemed to last about an hour as my SNR jumped back to 18,
So I rebooted the router and it now syncs at 3400ish again. With a SNR of 12.

So I am a little confused to what had happed.

As up until now, I have had a Rock steady connection, with the exception of the change over back in early April. I was one of the 1st to get the migration.

The bRAS system seem to think my max stable rate is 12dB. Which is fine for me.

but why the drop then increase?Huh
N/A

Sudden drop in SNR

Well the samething has happened again tonight @ 19:15..

very interesting?

Any ideas?
N/A

Sudden drop in SNR

These drops seem to coincide with the re-instatement of MaxDSL bulk upgrade tool. I read somewhere that the bulk upgrades tend to be done overnight - if so is it possible that upgrades taking place within your exchanges could be causing the drops?

We all know how sensitive our lines are to outside interference - could something like the upgrade process on other lines cause such a phenomenon?

Sounds daft I know, but I guess there aren't many fairy lights around at the minute to blame it on, and the street lights don't come on till pretty late this time of year....
Community Veteran
Posts: 38,215
Thanks: 913
Fixes: 54
Registered: 15-06-2007

Sudden drop in SNR

just trying - without sucess - to solve a similar problem.
router very happy at 9db SNR and synch at 2976kbs since this morning (power cut caused resynch) but suddenly (30 sec monitoring step at 16.10 this afternoon) it dropped to 6.5 SNR, crc error rate jumped to 2,000 per minute and resynched to 2336 kb/s at 12db SNR - no obvious cause
daveyb
Grafter
Posts: 128
Registered: 04-08-2007

Sudden drop in SNR

That's interesting Jim - I managed to telnet into my router when it dropped tonight and had 7,378 CRC errors and 711,111 FEC errors in 5 minutes despite a reported SNR of 7 dB throughput dropped to a mere 79kbps.

Yet, the lines been fine all day long sync'd at 2336kbps (which is normal for my line) and without any problems.

I can't say about the whole distance to the exchange (some 3-4km) but for most, if not all, of it there aren't any street lights at all (we're a rural exchange and there's no street lights in, or between, the villages).

Similarly, before Monday I hadn't had s single problem and been on MaxADSL for over a month.

David
Community Veteran
Posts: 38,215
Thanks: 913
Fixes: 54
Registered: 15-06-2007

Sudden drop in SNR

snr just dropped progressively to 9db then resynched at 2080 after an enormous number of errors - I'm going to try a different router tomorrow - my old Netgear which doesn't give any snr figures but I want to see how it handles the variations
N/A

Sudden drop in SNR

I am glad its not just me in a way....

Seems like a comming issue this, it happened again last night about 18:30 again.

I seem to keep sync, but loose the LCP, but once I reboot my router and sync at the lower speed its fine. Then 30 mins later snr back to normal. so a re sync again.