Bridge Tap + Interference on my U-Verse line?? [ Edited ]

[RipRidah2]

Hey Guys,

So I just got u-verse today hoping that my constant disconnecting problems from AT&T DSL would go away (I had originally thought it was a problem with the modem). Unfortunately, the problem persisted so I did some web searches that lead me to take a look at bit loading graphs. Being completely new to it, can someone correct me if I'm wrong with my interpting the bit loading graph.

It looks like there might be a bridge tap somewhere in the line in the dips at 0.5, 1.25, and 2.8 MHz. There also looks like there's interference somewhere due to the big black spot between 1.0 and 1.333 MHz.

Looking at the error table, there seems to be a lot of errors that according to the manual should not exist in a properly configured line such as the Link Retrains, loss of framing, singal, and margin failtures.

Do you guys think these are grounds to contact technical support to have them take a look at the line?

Thanks everyone!

[texasguy37 ACE - Champion]

Yes, there could be bridge tap on your line.  Also, the Error Table indicate some issues with your system.

Call Technical Support at the number shown in my signature.  They will run some tests on your system.

[oufanindallas]

Those stats are terrible.  As TG stated you probably do have a bridge tap on your line.  There is no way your recommended profile should be that low for the distance from the VRAD that you are.

[RipRidah2]

I just got off the phone with Technical Support. They confirmed that there is a tap somewhere in the line and will be sending someone out tomorrow to take a look at it. Hopefully the tap is over on AT&T's side and not mine.

Thanks for your help, will update you guys soon with new screen shots tomorrow.

[oufanindallas]

If there is a bridge tap, then the lineman will find it and remove it. It's not a my side/their side problem.

[JefferMC ACE - Wizard]

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oufanindallas wrote:
If there is a bridge tap, then the lineman will find it and remove it. It's not a my side/their side problem.

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It is possible to have an unterminated pair running inside your house that shares all the characteristics of a bridge tap out in the AT&T maintained lines.  I believe that is what the poster meant.

[ScottMac]

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JefferMC wrote:

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oufanindallas wrote:
If there is a bridge tap, then the lineman will find it and remove it. It's not a my side/their side problem.

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It is possible to have an unterminated pair running inside your house that shares all the characteristics of a bridge tap out in the AT&T maintained lines.  I believe that is what the poster meant.

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Yep, it's true; every unoccupied phone jack on the line acts as a stub attenuator (like a bridge tap). With all other things being equal, the length of the unoccupied pair, internal or external, compared to the length of the primary run determines the frequencies affected (and the harmonics of those frequencies).

Shorter stubs affect higher frequencies.

Stubs terminated with a matching impedance absorb all of the energy that would otherwise reflect back as destructive interference. i

Most unshielded twisted pair has a characteristic impedance of about 100 ohms; putting a nominal 100 ohm resistance at or near the end of a bridge tap (farthest from the junction with the main run) would appear to eliminate the bridge tap, but would still divide the power with the primary line (two or more resistances in parallel split the power/current  proportionally).