Data loss on RJ11 using DSL modems 4

[audiopimp]

Hi, Long time since Ive been here, nice to be back!! I got a question that been buuging me.

when using dsl modems whay would the rj11 jack from the wall to the modem have issues if it is long. Obviously there is a data loss somewhere. The DSL signal uses high frequency tones other then the analog for regular telephony devices might this be the reason mixed with the loss? Probably, but I just wanted to confkirm.
also, not sure if I have choosen the corect forum so let me know peeps! thx and bye

 

[greg5149]

Your cable is not a low loss cable. There is a spec. for the length. I would say anything over 12-15 ft. is out of spec. Try 2 different lengths, 1 short and 1 long. If the loss is different, you have your fix!
Greg5149

 

[Pyg]

One reason why it would have issues is because the longer the distance from the CO to your house, the slower the DSL speed is goig to be. EVERY foot of phone cord has an affect on DSL speeds. Even the amount of phone wiring in your house and the number of wall jacks in your house.

If you filter your voice lines on the outside of your house instead of at the wall jack you might see an increase in speeds. I was able to add a couple of hundred K to my DSL speeds doing this.

Here is a diagram of what I did

http://www.phenomfx.com/lbsc/dslfilterhack/dslfilterhack.htm

 

[pansophic]

More likely the problem is due to Electro Motive Force (EMF) and Electo Magnetic Interference (EMI) more than anything else. Telephone wire uses twisted pairs because it improves EMF while helping to reject EMI. In multipair cables, each pair in the cable is twisted at a different rate so that there is less common-mode noise between pairs.

The satin line cord that is used from the wall jack to your device is not twisted, but flat. While the pairs remain the same distance apart (which maintains the balance of the pair), they are no longer twisted, reducing the EMF and increasing their susceptibility to EMI.

One method that works reasonably well when you are using two wires from different pairs is to ground the unused wires in each of the pairs. You will gain back some of the EMF and improve the EMI rejection, but not as well as if the pairs were still twisted.

What will almost certainly work is to replace the flat cord with an actual twisted pair cable. Since most twisted pair cable is solid conductor cable, it is preferrable to permanently install this cable in the wall/ceiling, and use a short line cord from the jack to the DSL modem. Installing a solid conductor cable where it can be moved reptitively will cause it to break eventually, which is always a troubleshooting nightmare.


pansophic

 

[stevieblunder]

Depending how the building is wired, the problem is probably signal distortion due to reflections. High speed signals do not like a bus architecture, nor tree wiring. I wired my phone line directly to the DSL modem only, through a filter, then to all the phones in the house. This puts all the wiring taps and branches behind the filter. Read up on transmission line stubs and reflections. For audio, 10 or 20 feet of wire is a very small part of the wavelength, but not so for DSL carrier frequencies. Jacks and different cable also create transmission line impedance variations, and therefore reflections. The physical length of these objects determines at what frequencies they become a problem. If it is small/short enough, it only affect high frequencies; above those in use.

 

[audiopimp]

Thx Stevieblunder! You have any good links - references that I can read up on regarding transmission line stubs and reflections? If anyone else does.. please reply here! thx all!

 

[allteltec]

I work for a Telco that is a ISP, we sell dsl, the most common problems are phones without filters. People forget about alarm systems and satellite TV also people put the filters on backwards witch will kill the dsl.
Bridge taps, where the telco line is not cut off at your house but goes on down the street. Missed Cable Pair loads. A dsl should not work though a load but I had a trouble lost packets, downloads was 1.1 meg but uploads was 350kb the line was caped, downloads was ok but uploads should have been app. 630kb. I tested and fould one load at 10kf. not even the right load point for a normal loaded cable pair.
When I test most DSL lines with a ADSL Test meter thay will show a bandwith of 4 to 5 megs down and 1 meg to 800kb upload. the killer will be the noise margins you would need a dsl test meter you can test at the outside and then test inside an determine if the problem is in the house wireing of a telco problem if you are haveing problems you telco should be able to do there test for you.

Alltel Network tec.
Paul