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Question

ADSL Line Stats

by Nov 24, 2018 7:53AM PST

I currently have 21 db downstream noise margin and 18 db line attenuation. I tried removing the splitter and directly putting the cable into my modem (which caused the landline to stop working obviously) and my noise margin increased to 28 db and line attenuation decreased to 12. Is this a result of a bad splitter or is this normal because I feel like the splitter I have is cheap.

Discussion is locked

7 Posts
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Answer
Time to talk to your ISP.
by Forum moderator Nov 24, 2018 8:27AM PST

Here, the DSL modem gets the line connection WITH NO FILTER. All other devices have the DSL filter.

I can't guess why your DSL modem worked when there was a filter, it usually won't lock onto the signal.

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Article about where to use and how to test filters.
by r. proffitt Forum moderator Nov 24, 2018 11:35AM PST
https://en.wikipedia.org/wiki/DSL_filter

The filters (again) go when you have an analog device such as the phone or alarm system. The DSL modem needs the unfiltered connection.

As to static on lines, be sure you have a filter on the phone when you do that test.
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Why?
by James Denison Nov 24, 2018 11:41AM PST

"As to static on lines, be sure you have a filter on the phone when you do that test."

Why? I'd go bare wire for the test, if ADSL has been disabled.

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Simple.
by r. proffitt Forum moderator Nov 24, 2018 11:46AM PST

The DSL frequencies can create noise in the phone and cause false sounds. Then you test with another phone and the line is fine. To avoid this, do the test with the DSL filter.

Here's the example ADSL2 frequencies.


We can't hear 144KHz but a phone's circuitry might convert that to sounds that can cause an unneeded service call. This is why that test is done with the DSL filter on the phone.

Post was last edited on November 24, 2018 11:47 AM PST

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the question then is...
by James Denison Nov 24, 2018 3:01PM PST

....does that run when the ADSL is not plugged to request the service? If not, then everyone else's phone would have the same problem, even if they didn't order ADSL, but still have landline phone.

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Have to write no.
by r. proffitt Forum moderator Nov 24, 2018 3:08PM PST

I've found one phone to convert the DSL frequencies down to audible clicks then another phone be just fine. In that test the DSL filter had both phones coming up clean.

So no, not all phones have that issue so to avoid a false service call where you get charged for the "no problem found" I go with the DSL filter for the noisy line test.

If they don't have DSL then there's no reason for the DSL filters anywhere. And without DSL service they have no reason to send the DSL signals or even connect to the DSLAM.

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Answer
check the phone line
by Nov 24, 2018 11:28AM PST

Unplug the ADSL, use a standard phone direct to the wall jack. Push a number, then listen. If you hear static, that will interfere and slow down the data transmission, so call the phone company and make them get you a clear copper line with NO static.

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