Throughput dropped 10% after wire changed

I moved my master socket by about 3M - don't slap me down .

The service wire enters the front of the house, and goes under my hallway to a white BT junction box, then ~1M of internal phone wire goes to my master socket. The two wire are joined with the jelly crimp gel connectors. I broke those connections and ran a longer wire, also telephone wire and re-made the join with new jelly connectors.

It's all working. However, I have observed the download throughput dropped from >150Mbps to ~135Mbps using Speedtest.

Then I looked at the router stats, and they show quite a drop in noise margin:

Text
1 23 4	*Before*        Downstream      Upstream        *Now*           Downstream      Upstream Conn Speed      159828 kbps     29851 kbps      Connn Speed     157213 kbps     26156 kbpsLine Atten      D1(39.0 dB)     U0(0.0dB)       Line Atten      D1(42.6 dB)     U0(0.0 dB) Noise Margin    13.1 dB         5.6 dB          Noise Margin    4.9 dB          3.5 dB

The original 1M phone wire was not twisted pair, and neither is the new phone wire I used. Given the cabinet is a couple of hundred meters away, I didn't really expect another few meters to have such an impact.

My question is, is this drop a consequence of the extra distance to the master socket, or would twisted pair wires help restore the throughput, or any other suggestions I might try?

Twisted pairs are largely self cancelling for noise pickup, whereas non twisted pairs are wide open. Proper BT phone wire is sufficiently twisted to make a quite reasonable job of this for ADSL over several hundred metres. But 10m of burglar alarm cable will kill ADSL over 10m or so.

Now 'fess up, what sort of cable did you use? and if it was BT cable, were you sure about what cores are twisted?

Lots of non-Openreach provided telephone cable is copper cladded steel (CCS) or copper cladded aluminium (CCA) so you really need to check that as it will affect your speed even over short distances.

As others have already alluded to but this does not seem normal to me - I would double check the wiring and any additional things you have introduced (faceplates etc).

Before doing that though it can't hurt rebooting your modem etc and forcing a re-sync just to make sure it isn't a fluke (in the negative sense!)

Honestly, the label is a little ripped so I can't read it entirely, but I can still read cable 4-core 0.5mm white YY47. Colours are Bl/Wh Wh/Bl Or/Wh Wh/Or. I bought it [many] years ago when I needed to run extensions around the house probably from Wickes or somewhere like that.

I just sliced the middle of the original 1M cable, and yes I can now see there is a slight twist, that was not obvious when I sliced back the end of the cable! I did the same of the 'new' stuff I used, I don't see any twist. I think I know what the problem is now, [censored] 'telephone' cable, will order more.

I have rebooted router too, that did force a resync, and the new stats above about the best achieved.

Is the new cable multi stranded inside the coloured sheathing ? The cheap stuff you used often is. It is pants for DSL, and the crimps often don’t take properly either.

In reply to a post by Zarjaz:

Is the new cable multi stranded inside the coloured sheathing ? The cheap stuff you used often is. It is pants for DSL, and the crimps often don’t take properly either.

I think the Openreach cable is solid copper, is that correct?

In reply to a post by PCJM40:

In reply to a post by Zarjaz:

Is the new cable multi stranded inside the coloured sheathing ? The cheap stuff you used often is. It is pants for DSL, and the crimps often don’t take properly either.

I think the Openreach cable is solid copper, is that correct?

Yes indeed.

Not sure about YY47, but YY seems to be a range of control and instrumentation cables. It will be fine for voice, but dubious for anything more.

It is not necessary to use telephone cable, but you cannot substitute just anything. Cat5 and cat6 premises cable will work fine ]although purists may disagree]. Premises cable has solid conductor for fixed wiring and allows you to reduce inventory with the one type for both analogue phones and ethernet.

For the present application, choose just one pair - BlueWhite and WhiteBlue is a good default.

Edited by DFScale (Tue 12-Aug-25 11:32:05)

In reply to a post by DFScale:

although purists may disagree

It shouldn't be about purists disagreeing, it should be about stepping into the Openreach side of the network and doing the job as if it was being done by Openreach using like for like products.