Broadband Related > FTTC and FTTP Issues
Curate's Egg in Lancaster (http://www.yourdictionary.com/curate-s-egg)
waltergmw:
Gentlefolk,
We have been grinding on with a long-lasting difficulty for an EU who should have a near-perfect VDSL service as estimated by both BT Wholesale and Openreach (See below on the estimator data).
The last Openreach engineer spent a long time swapping pairs from PCP 76 all the way to the house which did improve matters as shown on the bit loading graph; but in so doing has left a very nasty bridge tap on the Hlog graph.
Out next problem is convincing the (uninformed) case handler that there is a bridge tap and then get it fixed.
He still insists that the Wholesale estimator tells him there is no bridge tap !
Kind regards,
Walter
WWWombat:
That certainly looks like a bridged tap.
With the first dip at around tone 100-110, one formula tells you the extra wire is about 340ft in length.
Another method, when looking at the dips at tone 100 and 1,000 (with 3 sub-dips inbetween), suggests a length of roughly 100m.
Could that relate to something in the house or premises? or the length of the drop wire?
Persuading BT, though, isn't so easy.
The usual way would be through the consequences the bridged tap causes - ongoing SNR variation and disconnection problems, or significantly low speed.
Unfortunately, the downstream doesn't seem to help you there. While you get troughs in the Hlog (and signal), you also get troughs in the QLN ... so the bitloading stays relatively even ... so the sync speed isn't particularly affected.
Upstream is different, perhaps affected by the way UPBO works to adjust upstream power. There are dips in Hlog, but no difference in QLN, so there are significant dips in the bitloading. Upstream is slower than it would otherwise be ... but I don't think Openreach have fault threshold in this direction. And, as it reaches 10Mbps anyway, it might be hard to persuade anyone of a fault worth pursuing.
waltergmw:
Thanks very much indeed WWWombat for that useful information.
The EU is, not unreasonably, peeved that he is paying for a premium rate VDSL service but not getting it - particularly on the upstream.
We had noticed a degree of reluctance, prevarication and unfamiliarity - not helped by the BT Wholesale estimator clearly showing that there is NO bridged tap!
That is compounded by statements that the line test does not show a fault.
All of which, despite many hours of chats, leaves the EU nearly incandescent!
I've never understood why the estimator shows the "Left in jumper" against ADSL offerings either - when it's clearly a VDSL function.
Kind regards,
Walter
[Moderator edited to fix a typo.]
waltergmw:
We are now told that BT Retail are unable to communicate with Openreach but we have been rewarded with this link to raise a complaint direct to Openreach !
https://www.formwize.com/run/survey3.cfm?idx=505d0401000108
burakkucat:
--- Quote from: waltergmw on June 26, 2017, 03:04:36 PM ---I've never understood why the estimator shows the "Left in jumper" against ADSL offerings either - when it's clearly a VDSL function.
--- End quote ---
Sorry Walter but there are also jumpers, for G.992.X (a.k.a. ADSL) exchange based services, which can be "left in".
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