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[neil]

Hello can anyone help me guess whats causing this drop in SNR?
for upstream

[burakkucat]

It might be the result of a joint beginning to show high-resistance or semi-conductive tendencies.

If you look closely, between 21:44 and 22:04 hours, you can see that the DS is also affected.

[neil]

It might be the result of a joint beginning to show high-resistance or semi-conductive tendencies.

If you look closely, between 21:44 and 22:04 hours, you can see that the DS is also affected.

there is also some noise in the phone from the past week, looks like i need to contact my lineman

[burakkucat]

there is also some noise in the phone from the past week, looks like i need to contact my lineman

Ah, yes. Audible noise, noticed while using the telephone, is another strong pointer towards a HR or semi-conductive joint.

[neil]

today lineman refreshed my jumpers from msag and here are the snr for upstream.
There are still some dips when i pickup the phone and there is still noise in the line but he said he fixed it.
SNR for downstream are fine.

[burakkucat]

There is a definite improvement since around 1025 hours but, possibly, there is still another suspect joint.

It might be worthwhile just checking the circuit, one every 24 hours, and to see if it gets any worse. If the noise is not too intrusive and your Internet service is workable then do not worry too much about it.

[neil]

There is a definite improvement since around 1025 hours but, possibly, there is still another suspect joint.

It might be worthwhile just checking the circuit, one every 24 hours, and to see if it gets any worse. If the noise is not too intrusive and your Internet service is workable then do not worry too much about it.

i have one more question
vdsl/adsl connection uses single wire out of a pair? or it needs both wires of a pair to work? or communicate properly with the MSAG?

[burakkucat]

An xDSL circuit uses the pair as a radio frequency transmission line in differential mode and, for proper operation, it requires both wires of the pair to be connected.

Under fault conditions, where one wire of the pair is disconnected, it is possible for the service to operate in a severely degraded state.

[neil]

An xDSL circuit uses the pair as a radio frequency transmission line in differential mode and, for proper operation, it requires both wires of the pair to be connected.

Under fault conditions, where one wire of the pair is disconnected, it is possible for the service to operate in a severely degraded state.

yesterday night it again cause some issues when phone was in use, internet lost sync and SNR dropped. Internet synced again with full download speed but upstream was sync at only 500-600kbps instead of 10k kbps
i flipped the wires connection and it is much more stable for now
i will keep monitoring

[neil]

I have one more question if there is some joint issue and high resistance then why Hlog is not showing it?

[burakkucat]

Hlog, the logarithmic representation of the channel characteristics function, is a frequency dependent, complex, function of a number of different circuit parameters. The insertion of either some resistance or semi-conductive properties into a circuit does not have any strong frequency correlation. It is more of a "bulk effect" and so does not have any obvious "fingerprint" in a classic Hlog plot.

The best way to visualise a HR or semi-conductive joint in a telephony circuit is to establish a time domain reflectometry trace from the customer's end back into the telephony network. (I.e. Looking towards the serving telephone exchange's battery.) Adjust the scale and gain such that any impedance changes can be seen in the trace and then arrange for the exchange equipment to apply the ringing voltage to the circuit. Any HR or semi-conductive joint would then tend to show a cyclic change in the TDR trace, in synchronism with the ringing voltage cadences.

[neil]

Hlog, the logarithmic representation of the channel characteristics function, is a frequency dependent, complex, function of a number of different circuit parameters. The insertion of either some resistance or semi-conductive properties into a circuit does not have any strong frequency correlation. It is more of a "bulk effect" and so does not have any obvious "fingerprint" in a classic Hlog plot.

The best way to visualise a HR or semi-conductive joint in a telephony circuit is to establish a time domain reflectometry trace from the customer's end back into the telephony network. (I.e. Looking towards the serving telephone exchange's battery.) Adjust the scale and gain such that any impedance changes can be seen in the trace and then arrange for the exchange equipment to apply the ringing voltage to the circuit. Any HR or semi-conductive joint would then tend to show a cyclic change in the TDR trace, in synchronism with the ringing voltage cadences.

time domain reflectometer
wow it is very expensive
is their any other way to calculate it? the distance to fault location.
My line is using pair from old underground cable so, maybe it has fault somewhere.  new cable which is overhead on the poles, all the way from msag, should i switch to it?

[burakkucat]

is their any other way to calculate it? the distance to fault location.

Unfortunately I cannot think of any other method that you could use from your end of the circuit.

Of course, at the moment, there is only a suspicion of a fault. A suspicion which is based on your description of certain observations.

My line is using pair from old underground cable so, maybe it has fault somewhere.  new cable which is overhead on the poles, all the way from msag, should i switch to it?

I really cannot advise you with regards to your local infrastructure. That is a decision you will have to make, after discussing it with your service provider.