VDSL Performance & Tuning

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#747109 18-Jan-2013 20:18

SamF: Hmm, 17db downstream attenuation is a bit high. Questions:

Distance from cabinet?
Naked or Clothed line?
Internal wiring setup?
Splitter installed?

a. less than 350M
b. Naked with VOIP line
c. Internal wiring is good. House is only 7 years old. Was getting 14000kbps downstream and 1100kbps upstream on ADSL2+
d. no splitter installed. Modem is plugged straight into the telephone jack. no other telephone jack around the house being used.

Do whatever you want to do man.

sidefx

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#747160 18-Jan-2013 21:48

billgates:
d. no splitter installed. Modem is plugged straight into the telephone jack. no other telephone jack around the house being used.

How many unused jacks? Even if nothing is plugged into them they will still degrade performance is my understanding - much more so for VDSL than ADSL. Either get a master filter or disconnect the unused jackpoints.

Though your attentuation still looks way to high for 350M, and I don't think that can be caused by unterminated stubs...? I'm around 600-700 metres and mine is 12db.

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Dairusire

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#747227 19-Jan-2013 02:35

sidefx:
billgates:
d. no splitter installed. Modem is plugged straight into the telephone jack. no other telephone jack around the house being used.

How many unused jacks? Even if nothing is plugged into them they will still degrade performance is my understanding - much more so for VDSL than ADSL. Either get a master filter or disconnect the unused jackpoints.

Though your attentuation still looks way to high for 350M, and I don't think that can be caused by unterminated stubs...? I'm around 600-700 metres and mine is 12db.

Correct me if I'm wrong, but just because he's a physical 350M (give or take), doesn't necessarily mean the cable is on a direct route from the cabinet to the house.

This may account for the higher line attenuation. and low speeds.

stevehodge

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#747228 19-Jan-2013 02:54

Dairusire: Correct me if I'm wrong, but just because he's a physical 350M (give or take), doesn't necessarily mean the cable is on a direct route from the cabinet to the house.

This may account for the higher line attenuation. and low speeds.

You're correct but 17db corresponds to something like 1.2km of cable (assuming typical cable loses - we've had at least one report of smaller guage cable being used which would have higher attenuation). It'd be a pretty extreme case if the cable was really that long for a cabinet only 350m away.

The speeds do look about right for the attenuation though.

billgates

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#747268 19-Jan-2013 10:01

sidefx:

How many unused jacks? Even if nothing is plugged into them they will still degrade performance is my understanding - much more so for VDSL than ADSL. Either get a master filter or disconnect the unused jackpoints.

Though your attentuation still looks way to high for 350M, and I don't think that can be caused by unterminated stubs...? I'm around 600-700 metres and mine is 12db.

3 telephone jacks in total. 2 have no devices connected to them and the 3rd has the fritzbox plugged directly into it.

Do whatever you want to do man.

SamF

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#750476 24-Jan-2013 23:08

billgates:
sidefx:

How many unused jacks? Even if nothing is plugged into them they will still degrade performance is my understanding - much more so for VDSL than ADSL. Either get a master filter or disconnect the unused jackpoints.

Though your attentuation still looks way to high for 350M, and I don't think that can be caused by unterminated stubs...? I'm around 600-700 metres and mine is 12db.

3 telephone jacks in total. 2 have no devices connected to them and the 3rd has the fritzbox plugged directly into it.

Yup, as sidefx pointed out, even unused jacks can cause significant issues with VDSL, but yeah, this probably won't account for the large attenuation you're getting... It might be worth disconnecting them (at the source end) so that you can put your hand on your heart and say that there are no internal wiring issues, then, if there is still an issue, get the ISP involved.

I'm about 350m from the cabinet and getting 10db attenuation and 50+mbit downstream(with tweaking).

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SamF

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#750930 25-Jan-2013 20:00

Hmm, I had to re-sync last night and despite the errors initially being about half what they were prior to the resync, some mysterious force has caused an issue on my connection since 8am today:

Maybe it's just general crosstalk as it seems to correlate with what I'd expect typical usage patterns to be. I'm going to leave it tonight and see what happens. One other possibility is that since I've synced 0.4mbit higher than I had previously, it's just a corresponding increase in errors. Very odd that fluctuating so much tho...

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#750933 25-Jan-2013 20:17

billgates:
sidefx:

How many unused jacks? Even if nothing is plugged into them they will still degrade performance is my understanding - much more so for VDSL than ADSL. Either get a master filter or disconnect the unused jackpoints.

Though your attentuation still looks way to high for 350M, and I don't think that can be caused by unterminated stubs...? I'm around 600-700 metres and mine is 12db.

3 telephone jacks in total. 2 have no devices connected to them and the 3rd has the fritzbox plugged directly into it.

You definately need to disconnect these. They have the potential to cause a massive impact. I've seen VDSL2 installs where two unused jackpoints add 10dB to the connection. Reflections have a massive impact on VDSL2 signals.

billgates

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#751139 26-Jan-2013 12:49

sbiddle:

You definately need to disconnect these. They have the potential to cause a massive impact. I've seen VDSL2 installs where two unused jackpoints add 10dB to the connection. Reflections have a massive impact on VDSL2 signals.

Never done this before or actually know how to do it but have couple of work mate's that can prob help me with this. Do I need to disconnect the cables where the telephone jacks actually are or somewhere at the demarc point level where all the cabling terminates?

Do whatever you want to do man.

SamF

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#751140 26-Jan-2013 12:51

You need to disconnect at the demark point, or wherever the jacks connect to initially.

billgates

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#751146 26-Jan-2013 12:59

Great. Thanks. Will the sync rate change change automatically after a quick modem reboot when 2 jacks have been terminated or will I have to wait for the DLM to kick in after few days for better sync rates?

Do whatever you want to do man.

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SamF

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#751171 26-Jan-2013 14:16

Apparently sync rates aren't directly controlled by DLM, but I have noticed that they tend to improve with time. The main thing to watch for now is your attenuation.

sbiddle

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#751176 26-Jan-2013 14:35

Attenuation and sync should change immediately.

SamF

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#751247 26-Jan-2013 17:31

Well, my CRC error rate didn't settle last night so I did a 5 min power off reset. Things have been a lot better since then with errors about half of what they were yesterday, although still higher than they were previously and my SNRM is still down 2db from normal, but this is likely to be due to the higher sync rate I've got this time around (up to 55mbit).

stevehodge

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#751383 27-Jan-2013 04:18

My Fritz spontaneously rebooted about 30 minutes ago. Here's the new connection:

The previous connection was about 45000 down and 0.4-0.5 CRC/min. Not sure why it connected at such a high speed this time. If the errors don't come down I'll reset it tomorrow.

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