How to find out what’s wrong with the phone (DSL) line


I'm trying to wire up a phone line on my land. I don't care about voice, just about internet (DSL). It's 1.5Mbps, the only speed available.

The TELCO NID is on the same post as the power meter and main panel.

There are several runs of conduit to another post with a subpanel on it. I pulled 250' of UTP Cat5e. I attached one end at the NID, and the other end got a a Leviton Quick Port Voice jack. I plugged in the DSL modem and it failed to connect to the DSL.

Some things I have tried:

  • The box of Cat5e was 500', so the leftovers are the same length as what's underground. I connected it between the NID and the DSL modem, without pulling it all out of the pull box. The DSL modem was able to connect. This eliminates:

    • 250' is too long for DSL

    • I wasn't punching down correctly at the jack

    • I was punching down on the wrong slots on the jack

    • I wasn't correctly attaching at the TELCO NID.

  • I stripped the ends of the blue pair and twisted them together. At the other end I verified continuity in that pair with a multimeter. The wire is not broken.

I have not tried plugging in a regular handset to check for a dial tone, since I don't own such a device. I will borrow one and add the results to this post.

My best guess right now is electromagnetic interference in the trench caused by the subpanel's feeders. The conduits may not be 1' apart. I wasn't here when the trench was filled, so I'm not sure. If this is the problem, would STP work?

EDIT I tried an experiment to eliminate underground interference from the feeder wires. I would turn off the subpanel's main breaker and see if the DSL could connect.

For power I used the inverter in my truck. I plugged the DSL modem in to the inverter and it was able to connect to DSL. The subpanel was still on at this point. I am surprised this worked. I immediately plugged the DSL modem back in to the subpanel's receptacle and it failed to connect to DSL. Weird.

I tried switching the breaker for that circuit to the other leg of the electric service, and that worked, too! It seems to work about 50% of the time this way. Weird.

What should I try next?

Best Answer

STP should help. Just make sure to ground it properly, or the interference can be worse - like a long antenna.