There's a small difference all across the SNR graph (yellow, upper one of the two). You'll notice it better if you overlay them (for example, by opening the two images in two seperate tabs on the web browser and then switching between them).

EDIT: BatBoy beat me to the reply lol.

Edited by Ixel (Wed 12-Sep-12 11:44:10)

In reply to a post by Ixel:

Just a follow up to say to everyone who's interested that you can bump the SNRM target up on the Line Settings tab with a BT Infinity connection. I've currently set my SNRM target on the downstream to 9dB successfully .

That seems very odd. Particularly as altering the noise margin by telnetting into the Openreach modem does not work we are accustumed to it doing on ADSLx connections. (I've had a few goes at it and the sync speeds did not respond in the way expected).

Additionally, the Openreach SIN defining the GEA system, and recently modified to specify CP-provided equipment for the coming wires-only installation, has also had the following added:-

Note : It is the DLM system that sets the line profile, and this should not be interfered with by CPs/users setting rates, SNR margins etc. at the Modem.

I imagine what you are seeing is just the HH3 setting getting through to the BT Wholesale DLM, which has no effect in this respect on the Openreach one.
_{Edit - typos.}

Edited by RobertoS (Wed 12-Sep-12 11:48:11)

In reply to a post by Ixel:

Good suggestion but I am already double filtering.

In that case, you could try yet another filter in addition, or purchase a new Y-cable...

Okay can see it now, no change in the bit loading, so what effect does this actually have on the connection?

In reply to a post by RobertoS:

Additionally, the Openreach SIN defining the GEA system, and recently modified to specify CP-provided equipment for the coming wires-only installation, has also had the following added:-

Note : It is the DLM system that sets the line profile, and this should not be interfered with by CPs/users setting rates, SNR margins etc. at the Modem.

I imagine what you are seeing is just the HH3 setting getting through to the BT Wholesale DLM, which has no effect in this respect on the Openreach one.

I'm a tad lost there. I thought FTTC uses the Openreach DLM, not Wholesale? Also I notice a difference in downstream sync when adjusting the downstream target SNRM on the Fritzbox. Over the next week or so I will post a series of screenshots confirming different syncs according to different targets, I don't want to do this 'hurridly' because it may throw DLM into a fit of its own.

In reply to a post by BatBoy:

In reply to a post by Ixel:

Good suggestion but I am already double filtering.

In that case, you could try yet another filter in addition, or purchase a new Y-cable...

Will do, triple filtering. Will post results shortly. As for a new Y-cable, I presume I'd need to contact AVM.

In reply to a post by MrSaffron:

Okay can see it now, no change in the bit loading, so what effect does this actually have on the connection?

The only noticeable effect so far is that my SNR decreases temporarily whilst using the phone.

Regarding my problem with the SNR dropping 3dB on using the phone, then increasing by 3dB when not using the phone, could it be that my Annex setting is wrong? I believe I should be using Annex B since the HG612 reported it as that before, where Fritz is currently on A.

Annex A and Annex Usually refer to DSL over POTS and DSL over ISDN.

So Annex A is usually the right one for UK. Not had a HG612 to play with or a VDSL2 line to ensure its not just a GUI bug

My HG612 reports Annex B

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

There are several Y-cables advertised : http://www.amazon.co.uk/Y-CABLE-FOR-FRITZBOX-VOIP-1-...

In reply to a post by Ixel:

I'm a tad lost there. I thought FTTC uses the Openreach DLM, not Wholesale?

You're right, but not entirely so.

The connection itself is managed by the OR DLM in the cabinet DSLAM. The BT Wholesale WBC DLM comes into play after the GEA handover at the exchange. (So doesn't affect Sky or TT FTTC connections).

Also I notice a difference in downstream sync when adjusting the downstream target SNRM on the Fritzbox.

I'm about to play ....

1) I had been away a few days with everything turned off. Connected at 22:08 last night. (The first two speeds are the actual, the second two the attainable).
10/09/2012 22:08 55918 13961 6.3 6.2 13.1 6.7 56764 13976 G.992.3_Annex_K_PTM)

2) Resync just now, no setting specified by me.
12/09/2012 13:36 56797 14253 6.3 6.2 13.2 6.7 57824 14241

3) xdslcmd configure --snr 50
12/09/2012 13:40 56789 14275 6.3 6.1 13.1 6.8 57816 14275

?
That's the sort of result I got before. Small movement of both up and down, in the wrong direction. Hence my statement earlier. But I accept it's odd, and there may be something being rejected by the DLM. What range of setting have you tried? Maybe 50% is outside some range.

I wonder .... In theory --snr 200 should give around 9dB.

4) xdslcmd configure --snr 200
12/09/2012 13:47 56618 14118 6.3 6.1 13.1 6.8 57644 14547

5) Back to safety, I hope ...
xdslcmd configure
12/09/2012 13:50 56634 14081 6.3 6.1 13.1 6.8 57492 14093

Drat!
My first default one there was nice.
_{Edit - typos.}

Edited by RobertoS (Wed 12-Sep-12 13:58:56)

DO NOT BUY THAT LEAD. It is not a UK spec lead, as does not have a telephone connector on the black phone part.

http://www.thinkbroadband.com/images/reviews/fritzbo... shows the UK lead, coiled up.

Update.

Triple filtering, no difference. I have increased my SNRM target by 1dB further and have dropped from 60184 downstream to 58568 downstream (respectively 9dB SNR to 10dB SNR). The SNR graph (yellow one) has slightly raised. I still believe that --snr <n> on the HG612 is for ADSLx type connections and wasn't modified in such a way to support the same adjustment on VDSLx type connections. On the default SNRM target (6dB) I originally got around 66000~ to 67000~ sync downstream. Either my speed tests and information from the Fritzbox are bugged or it's actually doing the SNRM target offsets.

Oh, interestingly when I pick the phone up my SNR drops to around 4-5dB, so perhaps the cabinet is trying to apply that but when the phone is not in use it's unable to? Or perhaps just coincidence that it's trying to reach 6dB~ when the phone is in use.

Annex A works, B doesn't.

Edited by Ixel (Wed 12-Sep-12 14:06:49)