FTTC download speed halved - external cause?

Hi,

FTTC download speeds have halved in recent weeks.

Normal speed is 34Mbps (on 40/10) and cabinet is between 260-300m by cable run from the property.

This graph shows the spectrum in use and was captured when connected directly to the master socket, which is an LJ 2/1A type, without anything else connected.
Normal setup is an NT5E after the master and the same results are achieved.

Only differences between my modems is the attainable speed.

Reported to ISP and awaiting response.

Any ideas what would knock-out the upper part of the spectrum?

TIA.

G.

When you say download speed do you mean speed test or sync speed from modem?

What are teh max attainable speeds? Today and if you have/remember from before the problem. I would be expecting to see a download Max Achievable in the region of 90Mbps on a line that short - the attenuation figures should also be around 12dB. Upstream will should show a max in excess of 25Mbps

From VMG3925-B10C:

VDSL Port Details Upstream Downstream
Line Rate: 7.199 Mbps 16.493 Mbps
Actual Net Data Rate: 7.200 Mbps 16.494 Mbps
Trellis Coding: ON ON
SNR Margin: 17.2 dB 23.8 dB
Actual Delay: 0 ms 0 ms
Transmit Power: 6.8 dBm 11.2 dBm
Receive Power: -10.5 dBm -2.5 dBm
Actual INP: 54.0 symbols 55.0 symbols
Total Attenuation: 17.3 dB 13.7 dB
Attainable Net Data Rate: 23.341 Mbps 53.913 Mbps

From Vigor130 (bridge mode):

---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
Running Mode : 17A State : SHOWTIME
DS Actual Rate : 16494000 bps US Actual Rate : 7200000 bps
DS Attainable Rate : 87937712 bps US Attainable Rate : 19849000 bps
DS Path Mode : Fast US Path Mode : Fast
DS Interleave Depth : 1 US Interleave Depth : 1
NE Current Attenuation : 15 dB Cur SNR Margin : 23 dB
DS actual PSD : 6. 6 dB US actual PSD : 11. 4 dB
NE CRC Count : 0 FE CRC Count : 3815
NE ES Count : 0 FE ES Count : 1932
Xdsl Reset Times : 0 Xdsl Link Times : 3
ITU Version[0] : b5004946 ITU Version[1] : 544e0000
VDSL Firmware Version : 05-07-06-0D-01-07 [with Vectoring support]
Power Management Mode : DSL_G997_PMS_L0
Test Mode : DISABLE
-------------------------------- ATU-C Info ---------------------------------
Far Current Attenuation : 17 dB Far SNR Margin : 15 dB
CO ITU Version[0] : b5004244 CO ITU Version[1] : 434da48c
DSLAM CHIPSET VENDOR : < BDCM >

Original speed:

34Mbps was measured from ThinkBroadband speed test weeks before I registered.

Edit:

Fritz!Box summary:

Down Up
Attainable Kbps: 69881 22583
Current: 16494 7200
SNR (dB): 23 17
Line attenuation: 15 16

Edited by deleted (Mon 15-Jun-20 15:57:38)

In reply to a post by MHC:

Today and if you have/remember from before the problem.

No stats before the problem other than 34Mbps from ThinkBroadband speed test.

Do you have a clear dialling tone on the landline when tested at the master socket ?

In reply to a post by Zarjaz:

Do you have a clear dialling tone on the landline when tested at the master socket ?

Yes.

17070 only identifies line number - no option for silent test.

Downstream Attenuation 13.7 dB - not far from my guess but suggest top end or maybe a little more than your 300m. Max achievable of just under 88Mbps which ties in

The SNR at 23.8dB is the major cause of the slowdown and you are going to have to wait for that to recover - unless there is a major occasional noise source that comes and goes.

I would say, power off the modem/hub. Wait a minute and disconnect from line and all PCs. Wait for maybe an hour - power up modem and wait 5 minutes. Connect to the line and wait for another 5 minutes. Reconnect PC and access stats.

If there is not much change you can either push the ISP to get a reset on the line or wait for it to recover.

In reply to a post by MHC:

The SNR at 23.8dB is the major cause of the slowdown and you are going to have to wait for that to recover - unless there is a major occasional noise source that comes and goes.

It's persistent now for the past fortnight.

Using the SNR adjustment on the Vigor130 only gets the attainable rate to vary.

In reply to a post by MHC:

I would say, power off the modem/hub. Wait a minute and disconnect from line and all PCs. Wait for maybe an hour - power up modem and wait 5 minutes. Connect to the line and wait for another 5 minutes. Reconnect PC and access stats.

Ta.

In reply to a post by MHC:

Downstream Attenuation 13.7 dB - not far from my guess but suggest top end or maybe a little more than your 300m. Max achievable of just under 88Mbps which ties in

More than 400m see stats below (default at 6dB SNR)

500m long line (line attenuation 14.0dB on FTTC) 60/20
450m long line (line attenuation 13.3dB on FTTC) 65/20
400m long line (line attenuation 12.6dB on FTTC) 70/20
350m long line (line attenuation 11.9dB on FTTC) 75/20
300m long line (line attenuation 11.2dB on FTTC) 80/20
250m long line (line attenuation 10.5dB on FTTC) 80/20
200m long line (line attenuation 9.8dB on FTTC) 80/20

Edited by adslmax (Mon 15-Jun-20 16:39:37)