Frequent disconnections and very low SNR margin

Forums › 2degrees (including Slingshot, Orcon, Flip, Stuff Fibre, MyRepublic, 2talk and Vocus) › Frequent disconnections and very low SNR margin

corksta

2397 posts

Uber Geek

Trusted

Subscriber

#39663 17-Aug-2009 16:50

I've been on Orcon's Purple+ plan since the beginning of the year and overall have been very impressed with the service, connected to the Takapuna exchange.

Normally I'd get maybe 3 - 5 reconnections per month which is fine, but from 3rd to 13th August I experienced a total of 44 reconnections as per the usage stats through their website - it was getting to the point where it would last a few minutes to a couple hours before disconnecting and the only way to get it back again was to reset the modem.

I called support and they changed my profile, then after that the modem stopped working and wouldn't reconnect. I confirmed it at two addresses that it was stuffed, so I replaced it with the same one (D-Link 502T) but remained on an ADSL1 profile and didn't have a single disconnect for almost two days.

They were going to send a tech out but of course if they found nothing I have to pay the ~$200 fee so I asked then to switch me back to ADSL2 and I'd monitor it, thinking that after all these months with no problems that it must have been the modem.

I was switched back to ADSL2 yesterday (16th Aug) but have already had 25 disconnections so far!

On ADSL1 I had a SNR margin of 12dB down and 13dB up.

Right now on ADSL2 I have a SNR margin of 2dB down and 9dB up, but it's normally 6dB down and up.

Line attenuation is 34dB down and 23dB up.

How come the disconnections are only occurring on ADSL2 and why is the SNR margin so poor, and why all of a sudden after so many months without a problem?

Will it be worth getting a tech out to take a look or is there anything I can do myself to improve things?

Our internet is on a second line to the house - nothing else is connected through any other jacks on this line.

cyril7

9058 posts

Uber Geek

ID Verified

Trusted

Subscriber

#247852 17-Aug-2009 19:24

Hi, ADSL2+ is capable (due to enhanced error correction) to operate quite happily down to 6-7dB S/N compared to ADSL1. That said Telecom, bless their cotten little socks have imposed sync target profiles on their ISAMs on ADSL2+ that continue to aim for 12dB S/N, the end result is more stable connection with little or no disconnections, but rarely connect over 18Mb/s. Personally I think this is a good plan, I would rather have a slightly reduced speed and more reliable connection.

Both Voda and Orcon seem to prefer the max it out speed.

Seems to me however that your modem is struggling to track noise movement on the line and as a result of living close to the margin is dropping out.

Personally I would run a mile from a Dlink modem on ADSL2+, there are better solutions out there based on broadcom solutions that seem to target more conservative sync speeds in exchange for more consistant connections. Also be aware that the Texas chip used in the 502 is well known for dropping out on lower S/N connections due to a firmware glitch in the DSP assembly, once again run a mile, try another non Texas based modem.

Cyril

corksta

2397 posts

Uber Geek

Trusted

Subscriber

#247855 17-Aug-2009 19:29

Thanks Cyril, what I can't understand though is why after months of happy browsing this has suddenly happened? Has my wiring deteriorted or is it a coincidence that two separate modems are faulty?

Do you have any suggestions for non-Texas based modems?

z2k

320 posts

Ultimate Geek

Trusted

#247860 17-Aug-2009 19:34

Try testing your connection with the modem isolated.

cyril7

9058 posts

Uber Geek

ID Verified

Trusted

Subscriber

#247861 17-Aug-2009 19:34

Hi, when its good, what type of attenuation do you have and sync rates. Tell me about your house wiring, is there a central filter or lots of inline units. How far do you think you are form the exchange, and are you sure you have not been cabnitised as this will stuff things big time.

DSE XH9949, TP-Link TD-8840, both the same unit, ones a DSE badge of the other, very good units. The Dynalinks use the same chipset, however have a reputation of over heating, something I have not seen in the above units.

Cyril

corksta

2397 posts

Uber Geek

Trusted

Subscriber

#247863 17-Aug-2009 19:40

My attenuation stays at about the rates I've mentioned above (34/23) and sync rates right now are 12056 and 320. Also right now my SNR margin is 0dB down! We're about 2km from the exchange.

There's no central filter. We had a second line installed at the start of the year (fiance and I live upstairs at her parents' place) so the line comes straight in from outside to our jack on the wall - modem plugs into this, which is then connected to a D-Link DGL-4100 router.

cyril7

9058 posts

Uber Geek

ID Verified

Trusted

Subscriber

#247872 17-Aug-2009 19:47

hmmm, 320 up indicates a potential issue with you wiring for sure. So the line terminates on the one jack nothing is connected to that and nothing is connected to the line elsewhere, no alarm systems, no tap off to the inlaws downstairs?

Cyril

corksta

2397 posts

Uber Geek

Trusted

Subscriber

#247878 17-Aug-2009 19:55

Nope nothing at all. They've got their own line downstairs, just the single jack upstairs for us which only has the modem connected to it. They used to have broadband downstairs but cancelled it so can't check the stats for their line.

There used to be a monitored alarm (about 10 years ago) downstairs but again that was connected to their line.

AliExpress

Shop now on AliExpress (affiliate link).

corksta

2397 posts

Uber Geek

Trusted

Subscriber

#247993 18-Aug-2009 07:55

So yesterday I set a personal record of 38 reconnections, so I took Cyril's advice and was able to buy a brand new Dynalink RTA1320 on Trade Me for $30, which I went and picked up straight away.

Line stats are 13401/315, SNR 6dB/9.4dB, and attenuation 27dB/20.4dB.

Set it up in bridge mode with my router, and what do you know, not a single reconnection since I set it up, which is going on about 9 hours now and is something that hasn't happened in a long time, so thanks for your help Cyril!

cyril7

9058 posts

Uber Geek

ID Verified

Trusted

Subscriber

#248005 18-Aug-2009 08:38

Hi, glad you got it somewhat sorted although unless Orcon have impossed a upload speed cap I am still suspicious of the 320 upload, this could indicated a noisy or bad connection, maybe one leg out of bed. Does this service have pots on it aswell, if so what does it sound like.

Cyril

corksta

2397 posts

Uber Geek

Trusted

Subscriber

#248027 18-Aug-2009 09:43

Nope no POTS just a Naked DSL connection.