Line sync increased to 5115kbps but SNR is dropping

[IchigoK]

For a few months I've had an intermittent problem with my DGN2200 Router (getting a new modem/router end of Nov). It would drop connection randomly and reboot itself, this led to ASSIA flagging my line as unstable and dropping my line sync speed every now and then.

Recently, my router has had a stable connection and my 4Mbps line downstream sync has increased from 3700kbps to 5115kbps, however I have noticed that my SNR has dropped from around 25dB to around 13dB.

About two weeks ago, there was major noise on my line and Telkom had their technicians fix the problem but since then my Noise Margin has decreased steadily.

Should I be concerned about this?
I am planning on getting an 8Mbps line in Dec.

 

[ɹǝuuᴉM]

How far are you from the exchange? What is your line attenuation? Given the 13dB SNR @ 5115kbit, you should be at around 1.5Km from the exhange and your line attenuation should be around 28dB (down link). If you are much closer you should have the line checked out! If you are 13dB on a 4mbit line (5115kbit link) you should be fine at 10mbit line (12479kbit link). Your SNR would go down to 10bB, wich is OK.
But if your SNR margin was indeed 25dB @3700kbit than you are much closer to the exchange and there is a issue with the line (or the modem)

 

[IchigoK]

How far are you from the exchange? What is your line attenuation? If you are 13dB on a 4mbit line (5115mbit link) you should be fine at 10mbit line (12479mbit link). Your SNR would go down to 10bB, wich is OK.

Attenuation 30dB (so according to my calculations, approx 2.2km)

 

[ɹǝuuᴉM]

30dB on ADSL2+ is the absolute limit for a 10mbit line! Get yourself a good modem! 8mbit should be just about nice and stable. Get the 10mbit line and play around with the settings. If is not working 100% you always can bring it down to 8mbit without having to phone telkom. Use the online tool

 

[IchigoK]

Update: I disconnected my router from the lightning protection ports on the power supply transformer and connected it directly to the Telkom wall socket and instantly my SNR increased to 18dB.

 

[ɹǝuuᴉM]

Are you not using the power supply transformer/lightning protection at all? If so, you realize that any static from any form of electrical discharge, will affect your line? Not only lightning which happens a few km away but any other EM noise will get directly into your modem. Keep in mind, the telkom wires are not only bringing internet into the house. Because they are not shielded and veeery long, they are also very good antennas. Your line will be faster but on occasion you'll get disconnected and even risk damaging your modem!
On the other hand, if your SNR dB has improved so much, perhaps you should replace the power supply transformer/lightning protection. It should not make such a big difference.

 

[IchigoK]

Are you not using the power supply transformer/lightning protection at all? If so, you realize that any static from any form of electrical discharge, will affect your line? Not only lightning which happens a few km away but any other EM noise will get directly into your modem. Keep in mind, the telkom wires are not only bringing internet into the house. Because they are not shielded and veeery long, they are also very good antennas. Your line will be faster but on occasion you'll get disconnected and even risk damaging your modem!
On the other hand, if your SNR dB has improved so much, perhaps you should replace the power supply transformer/lightning protection. It should not make such a big difference.

A few months ago, my line went down and they had to replace my Telkom wall socket but the Telkom technician that did the repair left my RJ11 leads for my modem unplugged from the lightning protection on the modem transformer as well as my POTS filter. I noticed this and plugged them back in. We had a massive thunderstorms a few weeks later and that's when I started having problems again. That's what really prompted me to try unplugging my RJ11 leads from the lightning protection a few days ago.

I am going to get a new router in about two weeks though, so hopefully a new router and new power supply will sort everything out and I'll be able to use the lightning protection again.