Kitz Forum
Broadband Related => Telephony Wiring + Equipment => Topic started by: ste91 on February 28, 2020, 08:40:38 PM
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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?
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If one pair just has the dial tone and no internet service then there will be no cross-talk between the two pairs..
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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 ??
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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.
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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.
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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.
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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.
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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 ?? ;) :) :)
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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.
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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.
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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?
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If there is no active dsl on it, then I wouldnt expect it to cause any crosstalk at all.
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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:
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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.