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What does a good DSL waveform (signal) look like?

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TheChas

If you have a lot of static on your phones, then you either have a bad device on the phone line, or your premise wiring is bad.

I would start by taking a close look at your POTS / DSL splitter.
Next, check with the DSL off, plug a phone straight into the main line with no other device connected and see if you still have static.
If no static on a direct connection, the problem is a device or your wiring.
If you have static on the incoming line, the problem is between your building and the central switch.

My guess is that you will find either a phone cord that has been rolled over by a chair or pinched in a door. Or, a line in a wall that has been rubbing on a staple for years.

Taking a quick review of DSL technical data, a low frequency spectrum analyzer is going to be a better tool than a scope to look at the DSL signal. The signal can vary between 26 KHz and over 1 MHz.

While this article is for designing DSL receiver circuits, it does provide decent technical data.

http://www.eetimes.com/electronics-news/4163500/Signal-and-noise-levels-underline-ADSL-line-driver-receiver-design

One other point, the phone signal is balanced and most scope inputs are unbalanced. To see a signal of any value you either need an isolated scope with a differential input, or a 2 channel scope that allows you to view the sum or difference of the 2 channels.

Chas