A cable with nothing attached to the end acts as an aerial and picks up noise that affects the VDSL2 signals

Consider this example, you have a SW or FM radio how do they pick up the signal - often a short piece of wire dangling out of them, this extension is doing the same.

In reply to a post by cypher007:

...ive ordered a BT MK3 plate from ebay, so will rewire and report back.

Regarding the router extension: be sure to connect one pair of wires in the CAT5e cable to the unfiltered A&B terminals on the Mk3 plate. If you are not fitting a RJ11 socket for the router (CAT5e + rj11 socket = "data extension") then the standard phone extension socket will be OK used in conjunction with a good quality dangle filter splitter.

Good luck.

In reply to a post by MrSaffron:

A cable with nothing attached to the end acts as an aerial and picks up noise that affects the VDSL2 signals

Consider this example, you have a SW or FM radio how do they pick up the signal - often a short piece of wire dangling out of them, this extension is doing the same.

Yep, still a bridge tap and still going to affect speed. NTE5 and SSFP sneed to be where the incoming feed from outside and the router needs to be connected to the SSFP, or on a data extension connected in the correct fashion to the SSFP. Anything else will not be optimum.

In reply to a post by MrSaffron:

A cable with nothing attached to the end acts as an aerial and picks up noise that affects the VDSL2 signals

Consider this example, you have a SW or FM radio how do they pick up the signal - often a short piece of wire dangling out of them, this extension is doing the same.

Not only that, but the unused end of the cable acts like a mirror. With nowhere to go, the signal reflects back down the cable, and merges with the original back at the joint. Some of the reflection heads towards the DSLAM, but some heads to the modem where it works as noise.

Stopping reflections is as important as stopping RF.

And that is where things can get funky as the length of cable makes a difference...

Using the Hlog diagnostic graph of such a line, you can calculate exactly how long the extra cable is.