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Author Topic: Does crosstalk attenuate other noise?  (Read 866 times)

konrado5

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Re: Does crosstalk attenuate other noise?
« Reply #15 on: July 26, 2018, 04:32:37 PM »

As long as the other user(s) are connected, then cross-talk is a constant.  EMI/RFI noise is variable.
I know.
Quote from: kitz
You wouldn't normally spot crosstalk on QLN.  Your line is an exception because you are in a truly unique situation whereby you are the only user on your MSAN who is able to use those notched tones
I know.
Quote from: kitz
As others have already said, one type of noise (crosstalk) does not decrease or mask noise from another source (RFI).
I suspected it is possible because of my observation.

Quote from: kitz
If you were not in the unique situation of being the only user who doesn't have the notching applied, then in theory I would anticipate that the QLN would show a peak at those tones during the time of RFI from the buzzing on the radio.
Why peak at these tones? As I know higher frequency the worse longitudinal balance (sensitivity to noise). I would suspect the peak at end tones (483-511) and not 415-483. 
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kitz

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Re: Does crosstalk attenuate other noise?
« Reply #16 on: July 26, 2018, 07:45:13 PM »

If
Graph [1] is no Crosstalk and no RFI
Graph [2] is no Crosstalk but with RFI
Then
Graph [3] with Crosstalk and RFI  in theory should look something like the blue line.


Please note the graph is NOT to scale, nor have I analysed individual tones, but just based on tones 432+ are affected more than tone 414.  Its a very quick and crude projection.
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konrado5

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Re: Does crosstalk attenuate other noise?
« Reply #17 on: July 26, 2018, 07:52:23 PM »

I don't understand why these tones (432-483) are most affected by impulse noise. This is not HAM band noise. This is wideband noise (heared on AM radio on differerent frequiences).
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kitz

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Re: Does crosstalk attenuate other noise?
« Reply #18 on: July 26, 2018, 08:13:31 PM »

The MSAN manufacturers are aware those particular tones can be problematic.  That's why they decided to mask them in the first place by applying a notch.
What the cause is I've no idea, the MSAN manufacturer will know more.   
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konrado5

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Re: Does crosstalk attenuate other noise?
« Reply #19 on: July 26, 2018, 09:35:40 PM »

A I know only reason why this tones are masked is that they are used by amateur radio (HAM band). But impulse noise heared on AM radio is not amateur radio.

It is evident on my graphs that QLN caused by impulse noise is not larger than about -120 dBm/Hz. It is not visible on tones with crosstalk significantly larger than -120 dBm/Hz. Perhaps buzzing on AM radio causes intermittent noise (not whole second) and crosstalk causes stable noise and thereby these noises are not summed. It is evident that crosstalk mitigates impulse noise effect on ADSL.
« Last Edit: July 26, 2018, 09:54:50 PM by konrado5 »
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