Broadband Related > Telephony Wiring + Equipment

Modem-to-wallsocket cables recap (again, groan)

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Weaver:
I’m wondering about using RJ-11 to RJ-45 DSL cables for the modem to wallsocket link. We have talked about this before quite a few times.

I use Tandy RJ-11 to RJ-11 ones currently, but I'm wondering if RJ-45 plugs might be a better fit with the non-filtering faceplates / NTE5/A-fronts that I have. The filterless fronts came from the Andrews and Arnold Shop (https://aa.net.uk/broadband-accessories.html) It explicitly says they are RJ-45 sockets, not RJ-11, but does it even matter? Or is ‘good enough’ good enough?

The cables that I am using are Tandy (former ADSLNation) 0.5m and 1.0m ones (http://www.tandyonline.co.uk/high-speed-rj11-dsl-cable-0-5m.html) which have a real quality feel to them. They measured extremely well compared to the cables I was using before, a shocking difference, one which could be down to bad testing methodology, or shoddy construction of the other cables, or both. This has been discussed in earlier threads.

The alternative I was thinking about is https://www.run-it-direct.co.uk/rj11-to-rjJ45-patch-leads/RJ11toRJ45patchlead1M/ which is very expensive by comparison and the appearance fails to seduce: not gold-plated, unless they're keeping it a secret, twisted pair but no overall shield, no moulded plugs so less robust-looking and no metal around the plug bodies. I don't see any immediate reason why they might be an improvement, and at a far higher price

j0hn:
All of the OpenReach MK(1,2,3,4) filtered faceplates also have an RJ45 socket. Most people don't even realise it's RJ45 as the ISP supplied RJ11 cable fits as expected.

I use the same unfiltered faceplate as yourself, purchased directly from AAISP. With both the OpenReach filtered and the AAISP unfiltered faceplates I prefer using a cable with an RJ45 socket. It fits much more snug, as the smaller RJ11 has a bit of "wiggle" in the RJ45 socket.

I use a RJ45 to RJ11 cable made by Mr Telephone (My mate Vince), purchased from his EBay store. I recall you saying in the past you had a bad experience with 1 of his cables. I've tried expensive Belkin cables and the Tandy cables and neither performed as well as Vinces. His cable being RJ45 at 1 end is a nice bonus.

ejs:
Run IT Direct have changed their DSL patch cables since I bought one.

They have a CAT-5e one which is higher specification and cheaper than the one you linked to:
https://www.run-it-direct.co.uk/adsl-vdsl-patch-leads/adslvdslcat5patchlead1m/ (other lengths also available)

The one I bought used a standard 4-pair CAT-5e Ethernet cable, and only wired one pair to the centre two pins of the plugs. Now they are using 2-pair cable and wiring up both pairs to the RJ-11, not that wiring up a pair of wires which aren't going to be used for anything will make any difference.

The more expensive cable you linked to is not CAT-5, it's telephone grade CW1308.

I suppose nobody makes high specification cables with an RJ-11 plug on one end and a BT phone plug on the other, then you wouldn't need a special faceplate.

Weaver:
Ejs wrote:
> suppose nobody makes high specification cables with an RJ-11 plug on one end and a BT phone plug on the other, then you wouldn't need a special faceplate.

Good point. I had thought about that, it would just mean a posh dial-up modem cable, and they must still be around, from someone such as Belkin. However they will all be too long by far, and you can't beat shortness.

@j0hn - thanks for the tip about your good experience with Vince. The one that I had was simply falling apart, perhaps I would have done fine with a different individual unit. I should perhaps give Vince's ones another try. I have to say though that measuring these things is tricky because of DLM messing you about and if I were doing the comparison now I would be much more careful about it. (See http://forum.kitz.co.uk/index.php?topic=15905.0 )

Weaver:
I have decided for the sake of science to compare a short 0.5m Vince CAT6 RJ11-to-RJ45 cable with a Tandy one. I will do so carefully this time and report back. I think that he even does 0.3m ones, if memory serves.

What is the best thing to capture? Simply go on sync rates with repeated a-b comparison? Do we try and get some information about SNRM over time? Or some kind of error rates?

One way of looking at it is to think of science only and try to decide on which measure is the most revealing in some aspect or other than you have to argue about the relevance of that measure.

The other way is just to decide what you want to see optimised and your preference is what it is. In my case I am just trying to optimise sync rates, first downstream and then upstream. And I am trusting the systems to keep to a standard level of reliability so that we are comparing like with like in the sense that we don't by some strange miracle end up with modem plus cable A going faster than B but at the expense of differences in SNR.

My modem of one of these cables is that it has a certain transfer function and lets in a certain amount of noise. Is that fair enough? Do I need to mentally include impedance mismatch/ power transfer?

Someone who has ready access to full stats from their modem might be in a better position to make the comparison. Even if I were to isolate a modem and telnet into it I can't use the good continuous stats capture tools that most of us have because of the firmware in question. Any volunteers to try the two cables back to back?

I have the advantage of a very weak DSL signal so I tell myself that these small effects are more significant in my case than for someone with a short line and hence high voltage. However, I am not testing higher frequencies so that could mean that the reverse argument could be made, that a VDSL2 user might be able to contribute something that I cannot. Perhaps we need a slow long line user and a VDSL2 user both?

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