BTOR Flat modem cable

Today I moved my BTOR modem from the living room to under the stairs where it would be tucked away nicely.

I did this by crimping some RJ11 plugs on around 10-15m of CAT5.

Upon checking the max attainable rate, I discovered it'd gone up by nearly 2000kbps - rising from the low 88,000s to the high 89,000s, despite going from a 1m cable to 10m! I've been logging the data from my ECI modem since I had it, and the max attainable has never moved from the low 88,000s.

It makes me wonder what gains are to be had from using a short, high quality twisted pair cable in lieu of the supplied item.

Edited by mikehiow (Thu 25-Apr-13 00:58:45)

It really depends on the environment. DSL is designed to work on twisted pair conductors that aids interference rejection. A length of flat cable in a noisy environment can cause degradation in the signal quality.

?
I'm confused.

You describe moved the router, not the modem, and changing the cable between the two.

But the Subject and the max attainable suggest you moved the modem?

I didn't even notice it said router in the first sentence, must have meant modem because of the RJ11
plugs.

In reply to a post by kasg:

I didn't even notice it said router in the first sentence, must have meant modem because of the RJ11
plugs.

Indeed - the router terminology was simply out of habit.

You can edit it for up to 12 hours after posting .

Way ahead of you

Uh uh . Three minutes 57 seconds behind me actually .

Your reply wasn't visible when I started editing, but fair one

Edited by mikehiow (Thu 25-Apr-13 01:10:21)

It's a very interesting result though! A big increase in potential speed for longer lines than your yours.

It was probably just that the noise margin is higher in the daylight hours so attainable rate is higher. I find my attainable varies quite a lot.

Interesting though!

You're not the only one. In practice I'm getting an extra 2Mbs down with a 5M Cat5e with RJ11 heads though I bought mine. Not sure I'd be very good at doing it myself!

I'm not convinced. Like I say, it's never ventured from the low end of 88k for me.

As for making your own RJ11 CAT5 cables, it's easy :-

Pick a pair to go in the center two, and a pair to go in the outer (although kind of irrelevant as the modem only uses the inner pair AFAIK).

Pull the sheathing back and cut the two unused pairs a few centimeters back, align your two remaining pairs, trim to length, put a RJ11 plug on and crimp.

It's a bit more faff than putting an RJ45 plug on, as they aren't really designed to go on CAT5, but easy enough!

Edited by mikehiow (Thu 25-Apr-13 09:38:52)

I gained about 5 Mbps on the attainable (up from 83Mbps - 88Mbps) by replacing the flat cable with the same length of Cat 5.

It does kind of assume you have access to a crimp tool though. For a one off it is probably cheaper to buy ready made.

In reply to a post by ian72:

It does kind of assume you have access to a crimp tool though.

Doesn't everyone have a crimp tool I do

Agreed, a 2M cable can be had off eBay for £1.99, free delivery.

In reply to a post by greenglide:

Doesn't everyone have a crimp tool I do

Likewise, but I'm lazy

I have crimped an RJ11 straight onto the end of the BT overhead dropwire where it enters my house (I don't use the telephone) for max sync.

Edited by deleted (Thu 25-Apr-13 10:16:18)

You can buy a crimp tool on eBay for less than £5 - every geek should have one.

I use mine for work, but I've had the same one since before I was of working age and it's been invaluable. Whether it's running a cable through holes you could not fit a connector, making funky length cables or hacking up cables to run my home phone/VDSL over structured cabling in my house - I'd have spent a fortune without it.

Very naughty. I hope you can put it back the way it should be if ever you need to get OR to investigate a fault.

Can anyone suggest a good supplier of suitable madeup cable for us non-crimpers?

The item below looks appropriate, even though it says ADSL2+ in the description. (I think I'm allowed to post vendor items on this forum? Apologies if I've misread the FAQ)

http://www.ebay.co.uk/itm/3m-ADSL2-High-Speed-Broadb...

That looks fine

IDIOT.

You are interfering with a part of te service the you should not touch. Crimping the connector on breaks the Ts & Cs you contractually agreed to. When you line finally fails - don't run off crying when BT turn round and ignore their part of the contract. Also, in doing so you introduced a short circuit across the line which can harm both the DSLAM and voice circuit. You also have no surge arrestor in the circuit which open you up to other faults and when 250v comes down the line and destroys your modem - hard luck.

Looks OK, but it use infrastructure cable rather than patch cable. However on te plus side the cable is probably only 2 pair rather than four pair cut back.

Infrastructure cable is solid conductor and is designed to stay in place and not be flexed too much or it will break and should go into the Krone type IDC terminals. Patch cable is multi stranded and will take plenty of movement and flexing and works well with the penetrating pins of an RJ plug.

Using multi-strand in an IDC will often result in failure and the inner conductors move and the blades do not cut the insulation or if they do contact can be iffy. Using solid conductor in an RJ plug will result in te blade sitting to one side of teh conductor and little pressure on the side and again an iffy connection can occur - or at worst no connection at all.

I know you're not *supposed* to use infrastructure cable in RJ plugs, but I've never had any real problems doing so. I have had issues using stranded cable in IDC terminals, though.

What I've just done was done using infrastructure stuff as I had no stranded cable left.

Of course, I wouldn't do it for a customer, but in real world conditions I don't really see an issue with it.

Good advice as ever. There is a type of RJ11/RJ45 plug for solid core cable. Instead of using blades that press into the multistrands, it has 'cup' style connectors that wrap around the solid cores.

cheers, a

Thanks for the comments. I ordered the cable when I got an earlier reply (indeed, it is already marked as dispatched) so I'll see how it goes.
I'll report back on any speed changes that result.

It will be fine provided you install it and leave it there. If you unplug it or it gets nudged by your feet or teh vacuum cleaner every week then that is what can cause failure.

I actually have used infrastructure cable for one of mine but it is plugged in and fixed in place - does not get nudged or moved.

If anyone has their modem close to the master socket and would like to try a short twisted pair cable, I have an 18inch one made from a pair removed from an old cat6 patch cable, RJ45 (for the faceplate) to RJ11

Free to the first one to pm their address.

I already use a short cable - 50cm long. The difference I see is minimal between the twisted pair and flat - measurable in kbps or 10s kbps However, mine is a special situation: all my comms equipment is situated in a small purpose built roof space. The roof above is copper, the ceiling below is foiled backed plasterboard, some of my floors are steel plates and the only equipment in there is comms related - modem, router, switch &c with the PSUs blocks located as far as possible away from the modem. so everything is fairly well shielded or remote from external or house generated interference.

I have at times tried long (10m or more) flat and twisted pair cables and certainly the improvement with twisted pairs can be significant.

In reply to a post by MHC:

I already use a short cable - 50cm long. The difference I see is minimal between the twisted pair and flat - measurable in kbps or 10s kbps However, mine is a special situation: all my comms equipment is situated in a small purpose built roof space. The roof above is copper, the ceiling below is foiled backed plasterboard, some of my floors are steel plates and the only equipment in there is comms related - modem, router, switch &c with the PSUs blocks located as far as possible away from the modem. so everything is fairly well shielded or remote from external or house generated interference.

I have at times tried long (10m or more) flat and twisted pair cables and certainly the improvement with twisted pairs can be significant.

Oh I say!! You are not one of those people I see on Discovery preparing for the end of the world are you? Lots of tinned food laid in. (between you and me i'm a bit like that I found my Tilley lamp repair kit the other day, left over from the three day week and power cuts)

Edited by deleted (Thu 25-Apr-13 15:06:34)

In reply to a post by systemx:

Oh I say!! You are not one of those people I see on Discovery preparing for the end of the world are you? Lots of tinned food laid in.

No, just planned it that way when I built a large extension. Put 600m of Cat5e in the extension - all terminating in this attic which is above an upstairs hallway. Then had lines moved to there - PSTN, ADSL and ISDN. Plenty of sockets, and it is on a separate RCBO so that if something else trips the power this room will stay up. So it houses all the comms, networking and alarms easy to work on and te BT Techs have all commented how nice it us to have space and easy access.

I also put in a wine store - fairly stable temperature wise.

On a serious note yes it does sound just the job.

Sounds the opposite of mine. Mains box with several fuse boxes and a meter, ancient old bell with mains transformer, wireless phone base station, master socket, modem fairly all huddled together. Maybe I should neaten/separate that a bit as well as trying the new cable?

In reply to a post by StephenTodd:

Sounds the opposite of mine. Mains box with several fuse boxes and a meter, ancient old bell with mains transformer, wireless phone base station, master socket, modem fairly all huddled together. Maybe I should neaten/separate that a bit as well as trying the new cable?

As it was when I had ADSL

And now with VDSL

The patch leads are normally tidier than that, and I now have 2 VDSL modems installed, ECI & Huawei, one above the other.

The red and black wire disappearing off the top goes to a small extractor fan powered from a clean 12v supply - on really hot days it keeps the temperature down.

Your loft looks like one of the training set up boards you get to practice on before you can wreak havoc in the real world.

So when you have to report a fault with the VDSL, they run a line test, it comes back as dis in network, and you get some hairy ar**d jointer with no knowledge of VDSL to fix it.

Oh, and you'll get a hefty bill.

Buffoon.

In reply to a post by systemx:

If anyone has their modem close to the master socket and would like to try a short twisted pair cable, I have an 18inch one made from a pair removed from an old cat6 patch cable, RJ45 (for the faceplate) to RJ11

Free to the first one to pm their address.

Now gone to a good home

Takes 2 seconds to put the socket back on, unless you are retarded. Are you?

Considering he is a very helpful and experienced BT engineer / technician I doubt it very much.

Some pretty bad results from my replacement of the original with the ebay cable I mentioned above.
Small increase in Max downstream rate, small decrease in max upstream rate.
Significant decrease in actual downstream rate, probably because I changed cable when the snr was a little low.

The really bad bit is that my downstream RSCorr rate has gone from around 60 per second to over 200 per second.

~~~


Taken just before the switch

Text

1 23 45 67 89 1011 1213

C:\utils>modem Microsoft (R) Windows Script Host Version 5.8Copyright (C) Microsoft Corporation. All rights reserved.  Max:    Upstream rate = 23552 Kbps, Downstream rate = 83056 Kbps Path:   0, Upstream rate = 20000 Kbps, Downstream rate = 76179 Kbps                Down            Up SNR (dB):        4.4             12.7D:              1207            1               (interleave) delay:          8.00            0.00               (interleave)ping bbc ...   Sent = 25, Received = 25, Lost = 0 (0% loss),  Minimum = 29.21ms, Maxiumum = 32.44ms, Average = 30.45ms

Taken just after the switch

Text

1 23 45 67 89 1011 1213

C:\utils>modem Microsoft (R) Windows Script Host Version 5.8Copyright (C) Microsoft Corporation. All rights reserved.  Max:    Upstream rate = 22182 Kbps, Downstream rate = 83336 Kbps Path:   0, Upstream rate = 20000 Kbps, Downstream rate = 70273 Kbps                Down            Up SNR (dB):        6.4             7.0D:              1113            1               (interleave) delay:          8.00            0.00               (interleave)ping bbc ...   Sent = 25, Received = 25, Lost = 0 (0% loss),  Minimum = 25.67ms, Maxiumum = 38.07ms, Average = 26.64ms

The max upstream decrease as well as losing 5dB margin is a little odd.

Can you make out which wire is connected to which pin at each end?

It is worth pointing out that there are lots of cables around that are not wired correctly. They need to be wired so that the centre two pins are wired on a single pair, but many are wired so that they are two pairs side-by-side resulting in the signal going down 2 halves of a pair, making the results as bad if not worse than the flat cable.

It is wired 1-1, 2-2, 3-3, 4-4.

Centre pair with orange and orange/white.
Outer pair with green and green/white

That sounds as if it is correct from what you say?
Maybe it would be better for the outside not to be wired at all, or ...?

Sounds like it is wired correctly then, suppose it could be a poor quality CCA (Copper Coated Aluminium) cable that might explain the difference. At the price they are charging with free delivery it is unlikely to be just copper as the price of coper is expensive at about US$7000 per ton.

Edited by deleted (Fri 26-Apr-13 20:48:00)

Yes, thanks for the comment. I've just got to assume it is rubbish cable.

I reinstalled it again temporarily, being very careful it was well separated from any other cables etc; and errors shot up again.
I might take it apart and have a look ~ it's valueless to me and probably to anyone else in its current form.
I just hope the several modem disconnects don't give DLM silly ideas.

Edited by StephenTodd (Fri 26-Apr-13 21:24:48)

I've reinstalled my original Openreach supplied flat cable and been more careful to route it away from everything else. (The various cables look even more of a mess now.)
The downstream max rate hasn't changed significantly (hovering around 83000),
and the downstream path rate is still the lower value (70258 against 76179 before fiddling) (? DLM lowered rate after short bad periods with the other cable?).

However, my downstream RSCorr rate seems to have dropped very significantly.
Was around 60 per second before fiddling, went up to 200 per second with the bad cable, and now showing an average of 8.5 per second after 17 hours.
I don't know how much that is to do with the slower speed from a more conservative 6.5 snr against around 4.5 before

Too soon to be confident of anything but ....
It'll be interesting to see if DLM sees the lower error rate and takes off at least some of my 8ms interleaving (D: 1113).
Maybe cable routing, even for a 2m cable, is more significant than I thought.

Send me a SAE big enough and I'll happily make you a cable to try...

Thanks for that very kind offer. I'd like to take you up on it if you can PM me your address, please?

I'm away for a bit towards the end of the week so may not have a chance to try it for a week or two.
Also just ordered an HG622 (now all gone, from the other active thread http://forums.thinkbroadband.com/fibre/f/4233951-hua... ). I'll try to keep experiments with that apart from experiments with the cable.

Hey, Ill take you up on that too if you want haha ive been looking at replacing the flat with cat5, but dont have a crimper etc!