@user4879 you cannot control the noise margin that is set by the cabinet's DLM system. In simple terms the higher the margin the more stable the service but at the cost of speed. Lower margins give faster speed but are more likely to be affected by interference and therefore to drop or throw errors. Openreach give ISPs three sets of parameters a fast, medium and stable set to choose from on this but you cannot get them changed as Sky only buy one which is the middle one.
The normal starting level is 6dB and levels significantly higher are indications of a fault. If the line is in reasonably good condition the cabinet can operate with margins down 3.2dB. Longer lines are more liable to pick up interference so often have adouble whammy of lower speeds due to attenuation and due to higher than ideal noise margin. The figure your system settles at is down to luck.
We are seeing more reports that Openreach are not willing to rectify known faults on copper lines as the planned switch to fibre gets closer.
=========================================================
65inch Sky Glass, 3 Sky Streaming Pucks, Sky Ultrafast + and Sky SR213(white Wifi Max hub) main Wifi from 3 TP-Link Deco M4 units in access point mode
