Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
   Glossary   Glossary
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Author Topic: 2-pairs connected in same cable , cause crosstalk?  (Read 876 times)

ste91

  • Just arrived
  • *
  • Posts: 11
2-pairs connected in same cable , cause crosstalk?
« on: February 28, 2020, 08:40:38 PM »

We have two BT lines connected through the same main dropwire outside and we have cancelled the service on one of the lines (still has dial tone though), would disconnecting the unused pair now in the cable help reduce cross talk and increase stability of VDSL on the remaining connected active line?
« Last Edit: February 28, 2020, 08:46:02 PM by ste91 »
Logged

mofa2020

  • Reg Member
  • ***
  • Posts: 108
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #1 on: February 28, 2020, 09:01:40 PM »

If one pair just has the dial tone and no internet service then there will be no cross-talk between the two pairs..
Logged

Black Sheep

  • Helpful
  • Addicted Kitizen
  • *
  • Posts: 5061
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #2 on: February 28, 2020, 09:05:26 PM »

As well as what mofa has written .................... try and put into context the distance involved in just the drop-wire, compared to the total distance your working pair travels back to the DSLAM (Fibre Cab), with in the D-side bundle.

The laws of physics dictate it will make 'a' difference, but as to the extent of that difference, it could be negligible ??
Logged

Alex Atkin UK

  • Reg Member
  • ***
  • Posts: 915
    • My Broadband History
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #3 on: February 29, 2020, 01:41:32 AM »

I find its VERY negligible.

I tried syncing my lines one at a time and couldn't see any difference whatsoever.  I think its when there are several lines all using the same frequencies that the EFI starts to add up, basically the cable bundle back to the cabinet.
« Last Edit: February 29, 2020, 01:46:47 AM by Alex Atkin UK »
Logged
WiFi: Ubiquiti nanoHD Router: pfSense (i5-7200U) Modems: 2x BT Home Hub 5A running OpenWrt Exchange: INTAKE, ECI Cabinet ISPs: Zen + Plusnet.

Weaver

  • Addicted Kitizen
  • *****
  • Posts: 8443
  • Retd sw dev; A&A; 4 7km ADSL2; IPv6; Firebrick
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #4 on: February 29, 2020, 02:11:15 AM »

I have two drop cables each with two copper pairs with ADSL2 in them making four pairs in all. The activation of the second pair in a cable has made no measurable difference to the DSL performance in the other pair; things did not get noticeably worse.
Logged

Alex Atkin UK

  • Reg Member
  • ***
  • Posts: 915
    • My Broadband History
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #5 on: February 29, 2020, 05:05:49 AM »

I'd imagine different frequencies and power levels could make a difference though.  Not sure of ADSL compares to VDSL, the power limiting to allow both to play nice with each other probably offsets it.
Logged
WiFi: Ubiquiti nanoHD Router: pfSense (i5-7200U) Modems: 2x BT Home Hub 5A running OpenWrt Exchange: INTAKE, ECI Cabinet ISPs: Zen + Plusnet.

j0hn

  • Kitizen
  • ****
  • Posts: 2766
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #6 on: February 29, 2020, 11:00:16 AM »

I find its VERY negligible.

I tried syncing my lines one at a time and couldn't see any difference whatsoever.  I think its when there are several lines all using the same frequencies that the EFI starts to add up, basically the cable bundle back to the cabinet.

Every bundle is different, everyone's experience will vary.

I've seen a number of users over the years order a 2nd line from the 2nd pair in their drop cable and see zero impact from crosstalk.

I've seen cases where a 2nd line instantly knocks 15-20Mb off the sync speeds of the 1st line, and vice-versa.

There's a few members on this forum who have 2 lines that cause considerable crosstalk to each other.
Logged
Plusnet FTTC 80/20 -  ECI now Huawei cab
retx low @ 3dB target SNRM
Zyxel VMG1312-B10A bridged with 1508 MTU + Asus RT-AC68U running Asuswrt-Merlin

Black Sheep

  • Helpful
  • Addicted Kitizen
  • *
  • Posts: 5061
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #7 on: February 29, 2020, 11:20:29 AM »

Every bundle is different, everyone's experience will vary.

I've seen a number of users over the years order a 2nd line from the 2nd pair in their drop cable and see zero impact from crosstalk.

I've seen cases where a 2nd line instantly knocks 15-20Mb off the sync speeds of the 1st line, and vice-versa.

There's a few members on this forum who have 2 lines that cause considerable crosstalk to each other.


But, as mooted above, that example would take into account the entire D-side cable run, not just the drop-wire.

The only way to prove the effect would be for the EU to climb the pole and disconnect the pair at the DP .... I've a climbing harness they can borrow if needed ??  ;) :) :)
Logged

j0hn

  • Kitizen
  • ****
  • Posts: 2766
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #8 on: February 29, 2020, 12:34:56 PM »

I'm totally in agreement with that BS.

Where 2 pairs are close together in a 400m run to the PCP will cause considerably more crosstalk than just a short 20m drop cable.

Crosstalk is a lottery nobody wants to win.
Logged
Plusnet FTTC 80/20 -  ECI now Huawei cab
retx low @ 3dB target SNRM
Zyxel VMG1312-B10A bridged with 1508 MTU + Asus RT-AC68U running Asuswrt-Merlin

Chrysalis

  • Content Team
  • Addicted Kitizen
  • *
  • Posts: 6106
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #9 on: March 03, 2020, 02:15:09 AM »

Consider there is many pairs in a cable bundle, there is different bundle densities used, if you have 2 pairs at the opposite sides of the bundle carrying dsl, then crosstalk is likely to be low, but more likely to see if the cables are next to each other in the bundle.  So its no surprise that sometimes people dont notice anything, and other times it can be significant.  Its the crosstalk lottery.
Logged
AAISP - Billion 8800NL bridge & PFSense BOX running PFSense 2.4 - ECI Cab - LINE STATISTICS CLICK HERE

ste91

  • Just arrived
  • *
  • Posts: 11
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #10 on: March 03, 2020, 12:52:58 PM »

Thanks for the reply's guys. Basically it would not be worth me bothering to disconnect the cancelled line pair as it hasn't got an active broadband service therefore, wouldn't have any positive impact to the other active line with a service?
« Last Edit: March 03, 2020, 01:10:48 PM by ste91 »
Logged

Chrysalis

  • Content Team
  • Addicted Kitizen
  • *
  • Posts: 6106
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #11 on: March 03, 2020, 02:48:35 PM »

If there is no active dsl on it, then I wouldnt expect it to cause any crosstalk at all.
Logged
AAISP - Billion 8800NL bridge & PFSense BOX running PFSense 2.4 - ECI Cab - LINE STATISTICS CLICK HERE

Alex Atkin UK

  • Reg Member
  • ***
  • Posts: 915
    • My Broadband History
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #12 on: March 03, 2020, 03:44:21 PM »

But, as mooted above, that example would take into account the entire D-side cable run, not just the drop-wire.

The only way to prove the effect would be for the EU to climb the pole and disconnect the pair at the DP .... I've a climbing harness they can borrow if needed ??  ;) :) :)

It would be interesting to disconnect everyone elses line to see if my sync improves, I'm not sure Openreach would approve though.  :lol:
Logged
WiFi: Ubiquiti nanoHD Router: pfSense (i5-7200U) Modems: 2x BT Home Hub 5A running OpenWrt Exchange: INTAKE, ECI Cabinet ISPs: Zen + Plusnet.

Alex Atkin UK

  • Reg Member
  • ***
  • Posts: 915
    • My Broadband History
Re: 2-pairs connected in same cable , cause crosstalk?
« Reply #13 on: March 03, 2020, 03:48:04 PM »

If there is no active dsl on it, then I wouldnt expect it to cause any crosstalk at all.

Further to that, unless there is a shortage of pairs and someone orders a new line, Openreach wouldn't physically disconnect it anyway.

I believe the policy (at least used to be) to leave a dial tone on disconnected lines wherever possible, for emergency calls only.
Logged
WiFi: Ubiquiti nanoHD Router: pfSense (i5-7200U) Modems: 2x BT Home Hub 5A running OpenWrt Exchange: INTAKE, ECI Cabinet ISPs: Zen + Plusnet.
 

anything