New drop wire, worsened linestats

Is it a bit odd that a new drop wire from the pole (changed because of an issue with a second line at the property on ADSL2+ - soon to switch to FTTC) would have worsened linestats?

It got changed today as a second line pair was damaged and the ADSL dropped out when it was windy, the previous drop it turns out was aluminium and the new drop is a 4 pair solid copper wire. (apparently BT don't do 2 pair drops anymore, only single pair and if somebody needs more they use a 4 pair...at least according to my engineer).

Anyways, on the new drop with my FTTC the attenuation has come down yet the SNR has worsened and the Pwr value has changed on the upstream.

This doesn't make much sense to me, a new drop which is solid copper and alumium anda shorter run (since the engineer didnt put a loop on at the house like the old wire was) has worse line stats?

Would that be due to an extra joint that is now in there to connect the old drop wire on the house to the new drop wire? Or is it bad termination?

I'm still getting max speed on the FTTC so it isn't too much to worry about at the moment, it's just curious as to why the stats would have dropped somewhat when I expected the opposite.

What were the exact stats before and after?

At the end you say you are still getting maximum speed, 79999kbps?, on the FTTC. An improvement on the line of the kind you describe, with a possible side-effect of removing noise on the ADSL2+ circuit, will have caused both your max attainable and noise margin to rise. In other words, what you see is good news not bad news.

If you go to my website linked in my sig there is a page about noise margin that explains it.

Previously Attn was 9.5 down
Pwr 12.8 down -8.1 up
SNR 13.6 down (down from the 14.6 i got a year ago which is much down from initially ) and 15.7 up

Current stats are...
Attn 9.0 down
Pwr 12.8 down, -9.6 up
SNR 12.8 down 14.9 up

Max attainable speed has also dropped somewhat although I don't have those figures to hand.

It is very confusing to me, changed out most of a run of aluminium for copper and slightly shorter shouldnt have a negative effect on it unless a) the engineers terminating is worse or b) the extra joint where he joined the old dropwire on the house with the new is affecting it?

On the contrary Roberto, the ADSL line (soon to be FTTC) will no longer have dropouts as its wires were sticking out and bent so that was damaged...the current FTTC line stats have actually worsened dropping the max attainable speed somewhat (although it does still get the max 80/40 sync currently).

See the other post I just made for attn/pwr/snr stats

Thanks

To be honest there is not much change at all and probably nothing to worry about.

Attenuation going from 9.5 to 9.0 - not really significant. Possibly due to the change from Al to Cu but that is all. SNR - 1dB change - again not significant, it will vary by the minute depending on what else is happening, what electronics are running locally, if there is a radio transmitter close by or a neighbour turning their modem on/off. Over time as more are connected the max atttainable and the above 6dB SNR will gradually degrade - very little you can do to alleviate that.

Provided the joint was made using the correct gel-crimps then than will not normally give any problems - they either work or totally fail and you would soon know if that happened.


In te time I have spent typing this my SNR as changed three or four times as has the max attainable

I tend to look at my SNR a lot to see the changes and it's been very stable at 13.6 for about a month now never really changing so the 1db drop did look very strange to me

On the flip side though there's been 0 FEC errors on the downstream in the 2 and a half hours it's been connected, that's not bad since i usually get at least a few an hour (although upstream has had 25 FEC's, 4 CRC's and 4 error seconds but no G.INP on the upstream).

I guess I'll monitor it, I'm expecting a drop again when the second line on this drop wire gets activated with FTTC too :|

In reply to a post by NBK:

and the Pwr value has changed on the upstream.

Remember that upstream has the "upstream power backoff" principle, which reduces your power so as to reduce the crosstalk you cause to other lines.

Upstream power can change at resyncs, as can the consequent SNRM and attainable values, sometimes in less than obvious ways.

Are you sure of te power levels on te upstream ... Are they actually -8.1 and -9.6 dBm ? I would not expect them to be negative.

Pwr(dBm): 12.8 -9.6

Copied straight from the modem running V100R001C01B030SP08

And from the dodgy web interface...

Line attenuation (dB) 12.8 -9.6
Output power (dBmV) 12.8 -9.6

It's always reported a negative upstream value as far as i can see
A paste I have from july 2015 shows...
Pwr(dBm): 12.8 -6.2