No matter. I think you will probably need to reconnect the Homehub soon as it looks like you need to report a fault to BT and get an engineer visit as your actual speeds are so far below your estimates.

In reply to a post by WilliamGrimsley:

In reply to a post by MrSaffron:

How much cross talk does the line have on it then?

You can't measure crosstalk to a specific amount, it's either there or not.

Not true. The amount of crosstalk is fully variable, can be measured (at least in the labs) and depends on how close your copper pair is to other VDSL2 subscribers in the access cable. It also depends how well your line has been twisted.

Take a look at this 100x100 image that documents the amount of crosstalk (aka FEXT) on each pair in a 100-pair cable, alongside an indication of which of the other 99-pairs that crosstalk is coming from.

https://postimg.org/image/77xt3e8o1/

Notice how the worst crosstalk (the red blocks) tends to come from a subgroup of just 25 other lines? That's because a 100-pair cable is internally constructed in bundles of 25-pairs known as "binders"; your biggest disturbers are the 24 other pairs in the same binder.

The equivalent "bluest" blocks will be from binders running on the opposite side of the cable, with their pairs having the most minimal physical contact, leading to the least opportunity to interfere.

Sorry, WWWombat, I didn't mean you couldn't measure it at all, but trying to measure crosstalk in terms of a decrease in line rate is quite tricky.

Long answer. Sorry

Your actual line speed isn't a nice round number (or a few bytes under), and your downstream SNR isn't significantly higher than 6dB. Both of these are indicators of banding ... so you are not banded.

Instead, you seem to have plain G.INP active on the line. There seems to be nothing strange about the settings.

It is, however, unusual to come across an ECI line with G.INP active. Are you a TV subscriber? I believe the ECI turn-off last year left TV subscribers with active G.INP.

You are getting a few FECs, small amounts of retransmission, and no failures of retransmission (so no CRC or ESs). Everything looks to be running fine.

The only oddity is that your speed is very low for your attenuation. Compare (on MDWS) with William's line - same speed, but an attenuation of 26.

Understanding Hlog and QLN graphs: Think of these as the input parameters to the SNR/tone graph, which will define the bits/tone graph. Hlog really defines how well the signal will get through. The QLN defines how much noise there is on your line when there isn't any signal. Once you have a signal running, that noise is going to compete with it.

Your Hlog looks OK, though the tail drops off quickly. It isn't the cause of your problems, though.

For comparison with a similar line with a good Hlog, take a look at alexatkin. For other similar lines with reasonable Hlog, look at tom34 or ashlez.

For comparison with similar lines that appear to have faults (bridged taps), look at jelv or Plutox.

Your QLN looks really, really noisy (and by noise, I mean signals picked up from other lines - crosstalk). A very quiet line would be around -140. A plain, simple line would be maybe -110 to -130 with occasional drops to -140. There is usually some variation across the frequencies - with peaks and troughs especially evident in the ADSL2+ spectrum.

In comparison to the other lines I mentioned, I've ranked them from noisiest down to quietest...
- wj66
- ashlez
- Plutox (affected by bad Hlog)
- jelv (affected by bad Hlog)
- tom34
- alexatkin

One line has a fairly "pretty" look: Wharfedale.

What impact does the noise on the QLN graph have? Essentially, each 3dB of extra noise means 3dB less usable signal on the SNR/tone graph, which in turn means 1 bit less on the bits/tone graph.

For example, compare your line with @alexatkin in the region of tones 600-700.
- On Hlog, your lines are both around -12 to -14.
- On QLN, your line is around -96dB, @alexatkin is around -113. About 17dB difference.
- On SNR/tone, @alexatkin is around 48dB, while your line is around 31dB. About 17dB difference.
- On bits/tone, your line is 7 bits.@alexatkin gets 12 bits.

Can you see how the extra 17dB in noise on your QLN graph translates to 17dB less on the SNR graph, and translates to 5 less bits per tone?

Looking across the whole spectrum, you are getting a pretty consistent number of bits. No massive peaks and troughs. That suggests the problem is crosstalk from other lines, rather than some specific RF source externally.

Ultimately, there isn't a lot you can do about crosstalk, other than getting an engineer to try another pair. Which might get similarly afflicted in the future.

Edited by deleted (Tue 24-Jan-17 23:56:47)

In reply to a post by WilliamGrimsley:

Sorry, WWWombat, I didn't mean you couldn't measure it at all, but trying to measure crosstalk in terms of a decrease in line rate is quite tricky.

And, that rather than "being there or not there" it is much better thought of a "always there, but with a random amount of impact".

Because his service provider will require it done to rule out his, to them, non standard equipment.

That's because a 100-pair cable is internally constructed in bundles of 25-pairs known as "binders

Except that it's not, the unit's, bunches or 'whippings' are in units of 10 on UK PET cable....

1st five pairs with a white A leg, blue, orange, green, brown, slate, then the next 5 with a red A leg .... and that's the bundle.

In reply to a post by WWWombat:

And, that rather than "being there or not there" it is much better thought of a "always there, but with a random amount of impact".

Ok, thanks for confirming.

I agree, HomeHub in place and report a fault. Speeds are far below what should be provided at that line length.

Can you confirm, the landline works fine ie a dial tone and everything?

Thank you for the help and advice:

WilliamGrimsley
BatBoy
WWWombat
Zarjaz
Ukhardy07

House phone works OK no noise on the line, put the HH5 back inline but it must be faulty as It will not connect to internet, so have replaced with the V130 better rate than HG612 but still not in the BT range for my line. For my line Estimated download speed range 70Mb-80Mb with 64Mb Minimum speed guarantee*.
The Vigor 130 is running the latest BT firmware, as this is an approved BT modem would it be ok to report a fault to BT. Reading WWWombat I believe a pair swap would be worth trying but how do I get BT to agree? What would be the cost? I have a hearing problems and find it difficult using the phone and online chat all I get is the Indian support team (not helpful at all) below are the stats from the V130.

Thanks again, John



System Up Time 4:34:1
Vigor> vdsl status
  ---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
   Running Mode            :      17A       State                : SHOWTIME
   DS Actual Rate          : 50143000 bps   US Actual Rate       : 16460000 bps
   DS Attainable Rate      : 49584864 bps   US Attainable Rate   : 16223547 bps
   DS Path Mode            :        Fast    US Path Mode         :        Fast 
   DS Interleave Depth     :        1       US Interleave Depth  :        1 
   NE Current Attenuation  :       14 dB    Cur SNR Margin       :        5  dB
   DS actual PSD           :     5. 9 dB    US actual PSD        :     6. 0  dB
   NE CRC Count            :       18       FE CRC Count         :    59331
   NE ES Count             :        3       FE  ES Count         :    33100
   Xdsl Reset Times        :        0       Xdsl Link  Times     :        1
   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 :       13 dB    Far SNR Margin       :        6  dB
   CO ITU Version[0]       : b5004946       CO ITU Version[1]    : 544eb206
   DSLAM CHIPSET VENDOR    : < IFTN >
Vigor> vdsl status more
  ---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
                  Near End        Far End    Note
 Trellis      :      1               1
 Bitswap      :      1               1
 ReTxEnable   :      0               1
 VirtualNoise :      0               0
 20BitSupport :      0               0
 LatencyPath  :      0               0
 LOS          :      0               0
 LOF          :      0               0
 LPR          :      0               0
 LOM          :      0               0
 SosSuccess   :      0               0
 NCD          :      0               0
 LCD          :      0               0
 FECS         :      0            7317806 (seconds)
 ES           :      3            33100 (seconds)
 SES          :      1             126 (seconds)
 LOSS         :      0             129 (seconds)
 UAS          :     34            33302 (seconds)
 HECError     :      0               0
 CRC          :     18            59331
 RsCorrection :      0               0
 INP          :      0             225 (symbols)
 InterleaveDelay :      0              28 (1/100 ms)
 NFEC         :    255              32
 RFEC         :     16              16
 LSYMB        :   4414              16
 INTLVBLOCK   :    255              32
 AELEM        :      0            ----