sudden drop in downstream snr

[alancamuk]

Hi there
been fine for days, was in the middle of a skype call to son in law in USA. connection dropped and started dropping regularly...... noticed teh downstream snr has fallen from 6.4 to 2.8 - 2.9.

nothing has been switched on etc.

ADSL Link Downstream Upstream
Connection Speed 18904 Kbps 1003 Kbps
Line Attenuation 15.6 dB 4.6 dB
Noise Margin 2.9 dB 6.5 dB


any ideas?

[Steve]

We know adsl2+ will survive with a margin of 3db obviously that's no good if it's dropping all the time. One would hope the MSAN would regulate you to a higher margin and lower sync ( it's probably interference one or other side of the master socket).

[alancamuk]

i suspected it may be our phones, both bt graphite wireless, as it dropped when we got a call. but why all of a sudden, it's been stable for 2 weeks at 6.4 ish.

[Steve]

The mysteries of BT line management.

[alancamuk]

getting wierder. still falling now down to 2.3, although the connection has remained up for 4 hours, and we've had 2-3 phone calls inbetween, so I think the phones are rules out. may go for a pull power cycle on the router

[Steve]

Surely if it keeps dropping the line management will up your margin eventually with the associated inevitable reduction in sync.

[alancamuk]

still up at 18mb, but downstream snr still 2.7 - 2.9db.
wondering if...... our phone is still with virgin, and doesnt go to idnet until 22nd, could this cause the drops when answering the phone.

not sure if it would affect snr tho

[armadillo]

Does the connection drop when you answer the phone or when the phone rings?

If it drops when the phone rings, regardless of whether you answer it, does the drop still occur even if no phone is connected to the system? To test that, you would need to disconnect all your phones and then call your home number from a mobile or another line and see if your broadband connection drops.

If the drop occurs regardless of the phone connection, that rules out faulty phones as the cause.

People with technical knowledge (not me) would be able to explain but I wonder if a line fault that could cause dropping with no phone connected might also be responsible for a drop in SNR.

Just so you know where I am coming from, my SNR drops to zero when I get an incoming phone call, even if there is no phone connected, i.e. when the only thing in the system is the broadband router. However, my router holds onto the connection even with zero SNR and does not lose sync so I am not bothered. Also, unlike your case, my downstream SNR is usually high (11dB to 13dB at a sync of 8064 on adsl max).

[alancamuk]

now changed both filters.
and still as below
drops every 5 hours or so

Connection Speed 18601 Kbps 1228 Kbps
Line Attenuation 15.7 dB 4.5 dB
Noise Margin 2.5 dB 5.8 dB

[Glenn]

Do you have access to another router that you could try?

[Ardua]

I had this problem when I first moved to ADSL2+ a year or so ago. I tried various types of router and, whilst things got better with the Fritz!Box, I couldn't stop the box from re-synching when the phone rang. I disconnected bell ring wires and fitted a NTE5 filtered faceplate. I still got the occasional disconnect. I then followed the advice on an Aussie forum which was to double filter the phone line. I also 'tweaked' the target SNR to 4/5 (the Fritz!Box has this facility) and my connection has been pretty well rock solid for weeks. I am 1.3Kms from the exchange and I have a 17Mbps connection.

[alancamuk]

unfortunately I have no other routers (and really cant afford to purchase any).

just ran BT speedtester and I'm down to a 2mb connection despite a 16md ipprofile

1. Best Effort Test:  -provides background information.

Download  Speed
2.55 Mbps
   
0 Kbps 21 Mbps
Max Achievable Speed

Download speedachieved during the test was - 2.55 Mbps
For your connection, the acceptable range of speeds is 4 Mbps-21 Mbps.
IP Profile for your line is - 16.41 Mbps

2. Upstream Test:  -provides background information.

Upload Speed
1.17 Mbps
   
0 Kbps 832 Kbps
Max Achievable Speed

[Rik]

Contact support, the throughput is lower than the acceptable range.

[alancamuk]

Thanks Rik. I'm thinking it's a line fault now.

have mailled all to support

[alancamuk]

Bt claim their investigation showed no line fault..... but suddenly the downstream snr has risen to 4.6 and thruput to 13mb. I think they may have done an snr reset sneakily 

[Rik]

It wouldn't be the first time.