Interesting from my HG612:

Software version V100R001C01B030SP08
Firmware version A2pv6C038m.d24j

and

SNR margin (dB) 16.6 0
Line attenuation (dB) 13.6 7
Output power (dBmV) 13.6 7

So exact same Software however my Line Atten and output power are positive and have NO decimal places. What Firmware does yours have?

As you already know, In the GUI the figures given as SNR margin are wrong - they are the Attenuation, The Attenuation figures given are the Output power. It is better to use DSLstats or Telnet in to get the correct figures:

Interesting that the older data you refer to has dBm whereas the newer is dBmV - they are distinctly different. Certainly accessing through Telnet brings it up in dB whereas the GUI (incorrectly?) refers to dBm. There is no easy direct conversion.

Never use the web interface for any stats other than the sync and max attainable rates. You can see by comparing with the telnet ones taken at the same time which are the dodgy ones on the web interface and which of the duplicated ones is valid.

Post deleted by RobertoS

I did not say they were right, although I believe they are, They are direct from the GUI ...

I'll PM a link.

My firmware is
Firmware version A2pv6C038m.d24j
Same as yours.

I've also dug up some linestats from Jan 2015 not long after I got FTTC and...

Max: Upstream rate = 43516 Kbps, Downstream rate = 134804 Kbps
Path: 0, Upstream rate = 19999 Kbps, Downstream rate = 79999 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 21.6 24.0
Attn(dB): 0.0 0.0
Pwr(dBm): 12.8 -6.9

Which quickly changed to this by Feb 2015...

Max: Upstream rate = 38966 Kbps, Downstream rate = 120440 Kbps
Bearer: 0, Upstream rate = 19999 Kbps, Downstream rate = 79987 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 17.5 23.4
Attn(dB): 9.1 0.0
Pwr(dBm): 12.8 -6.9

So yeah upstream Pwr has always been a negative value since day one

In reply to a post by MHC:

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.

My upstream power levels are negative (taken from a telnet session into a Billion 8800NL) - both the single aggregate value and the 3 individual bands too.

That's with an attenuation of under 9dB, and a line of around 100m (though probably 0.4mm copper).

Down            Up
SNR (dB):        11.3            14.8
Attn(dB):        8.7             0.0
Pwr(dBm):        13.1           -9.2

and

VDSL Port Details               Upstream                Downstream
Attainable Net Data Rate:           30489 kbps             102330 kbps
Actual Aggregate Tx Power:         -   9.2 dBm               13.1 dBm
====================================================================================
        VDSL Band Status                U0              U1              U2              U3              U4              D1              D2              D3
  Line Attenuation(dB):  1.9     8.5     11.2     N/A     N/A    4.7     10.8    17.0
Signal Attenuation(dB):  1.9     8.0     10.9     N/A     N/A    6.1     10.7    17.0
                SNR Margin(dB):  15.2    14.8    14.8     N/A     N/A    11.3    11.3    11.3
                 TX Power(dBm): -22.8   -34.1   -9.4      N/A     N/A    9.8     7.8     7.0

Edited by deleted (Mon 15-Aug-16 15:56:23)

I am just suspicious of such low power levels. In your case -22.8 and -34.1 dBm are down in the micro and 10s of nano watt region.

This is a common (but still irritating as it's repeated so often) misconception. Router/modems generally report the SNR noise margin (which is a "safety" buffer), not the actual SNR. If you have maintained line speed yet the noise margin has increased and your attenuation has decreased then your actual SNR has got better.

There are other reasons why the noise margine might get increased, typically because a line has become unstable, and that does decrease sync speed but that doesn't seem like the case here.

So please, please everybody repeat before posting. SNR/noise margi.n is not the same as SNR. They are related, but they are not the same thing.

In reply to a post by TheEulerID:

So please, please everybody repeat before posting. SNR/noise margi.n is not the same as SNR. They are related, but they are not the same thing.

I gave up trying to explain that about 10 years ago!

It appears however the OP's SNRM fell when the line was replaced. Contrary to my expectation (triggering my explanation to him early on), when he said it had got worse, which I assumed was the misconception you describe.

It had got worse - it fell. Though it now looks as though it wasn't by a significant amount.