Kitz Forum

Broadband Related => FTTC and FTTP Issues => Topic started by: digitalnemesis on October 08, 2020, 11:40:43 AM

Title: Why did i lose tones suddenly?
Post by: digitalnemesis on October 08, 2020, 11:40:43 AM

What is causing gaps in the higher frequencies all of a sudden? My sync dropped as a result. I didn't touch anything and the phone line has no noise when I listen to it.


(https://i.imgur.com/hQ1LMCU.png)


(https://i.imgur.com/GMEvulx.png)

Title: Re: Why did i lose tones suddenly?
Post by: niemand on October 08, 2020, 12:29:24 PM

Noise.

Those frequencies are miles beyond what the human ear can hear - way into ultrasonic and way beyond even a bat's hearing.

As far as what it is no idea. Could be direct interference or a higher frequency disturber rippling down.

Could even be a new customer connecting and their VDSL interfering with yours.

Take your pick. If you are still within the range of your service assume not a fault but the sad way of xDSL.

Title: Re: Why did i lose tones suddenly?
Post by: Chrysalis on October 08, 2020, 04:17:07 PM

As Carl said really, if it was sudden, and during working hours, then most likely cause is a new disturber.  Part and parcel of VDSL sadly.

Title: Re: Why did i lose tones suddenly?
Post by: digitalnemesis on October 11, 2020, 09:04:57 AM

Could an electric vehicle charging station on the same street as the FTTC box I'm connected to cause interference?

Title: Re: Why did i lose tones suddenly?
Post by: Alex Atkin UK on October 11, 2020, 01:13:26 PM

Anything electrical can.

Title: Re: Why did i lose tones suddenly?
Post by: PhilipD on October 12, 2020, 08:18:21 AM

Hi

Quote from: digitalnemesis on October 11, 2020, 09:04:57 AM

Could an electric vehicle charging station on the same street as the FTTC box I'm connected to cause interference?

Yes potentially but very unlikely given it's new kit to modern standards, probably just cross-talk from someone else coming on line, I had this happen several times on ADSL and VDSL at different properties, and you just have to accept that xDSL typically only ever degrades from your starting point.

Regards

Phil

Title: Re: Why did i lose tones suddenly?
Post by: digitalnemesis on October 12, 2020, 09:35:23 AM

Thanks for the replies.


Does crosstalk affect the higher frequencies more?


I recall I used to sync around 60 MBps around 9 years ago then over the years gradually decreased to around 40 Mbps. I even had a pair swap after much effort.

Title: Re: Why did i lose tones suddenly?
Post by: Weaver on October 12, 2020, 10:48:04 AM

Does crosstalk affect the higher frequencies more.

I don’t know. But I have never read anything to that effect.  ???

I would suspect that it is not the case. However because fewer bits per bin will be in use up in that part of the range, the modem will be less interested in a certain given voltage of noise, ie x V will be equivalent to fewer bits. I hope that my more experienced colleagues will comment on this.  :-\

Title: Re: Why did i lose tones suddenly?
Post by: PhilipD on October 12, 2020, 11:31:42 AM

Quote from: digitalnemesis on October 12, 2020, 09:35:23 AM

Thanks for the replies.


Does crosstalk affect the higher frequencies more?


I recall I used to sync around 60 MBps around 9 years ago then over the years gradually decreased to around 40 Mbps. I even had a pair swap after much effort.

Higher frequencies are always affected more by noise as they are harder to hear, and cross talk is just noise, also it isn't just about noise, often your modem might start using a lower power for various reasons, perhaps because it is disturbing someone else badly.  You need to know historically what power your modem was transmitting and receiving at over the years to get a better picture of what the changes are.

At the end of the day there is very little you can do about crosstalk or general noise and most people have seen their VDSL connects get slower unless they had tonnes of margin at the start being very close to the cab.  For example when I was on VDSL my margin was around 8db (reduced from 10 when I first went live), during a power-cut it shot up to 15db because everyone was knocked off apart from me on a UPS, so cross talk accounted for 7 or 8db of loss.

Regards

Phil

Title: Re: Why did i lose tones suddenly?
Post by: Alex Atkin UK on October 12, 2020, 12:37:36 PM

Quote from: PhilipD on October 12, 2020, 11:31:42 AM

Higher frequencies are always affected more by noise as they are harder to hear, and cross talk is just noise, also it isn't just about noise, often your modem might start using a lower power for various reasons, perhaps because it is disturbing someone else badly.  You need to know historically what power your modem was transmitting and receiving at over the years to get a better picture of what the changes are.

At the end of the day there is very little you can do about crosstalk or general noise and most people have seen their VDSL connects get slower unless they had tonnes of margin at the start being very close to the cab.  For example when I was on VDSL my margin was around 8db (reduced from 10 when I first went live), during a power-cut it shot up to 15db because everyone was knocked off apart from me on a UPS, so cross talk accounted for 7 or 8db of loss.

Regards

Phil

Even being close the cabinet doesn't necessarily save you.

2012 Digital Region

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Path: 0, Upstream rate = 10999 Kbps, Downstream rate = 43997 Kbps

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Pwr(dBm): 10.7 -9.22013 Digital Region

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Down Up
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Attn(dB): 13.2 0.0
Pwr(dBm): 13.8 5.22019

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Down Up
SNR (dB): 6.1 10.0
Attn(dB): 13.6 0.0
Pwr(dBm): 13.7 6.32020

Code: [Select]

Max:    Upstream rate = 24780 Kbps, Downstream rate = 62313 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 62249 Kbps

                Down            Up
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Attn(dB):        13.9            0.0
Pwr(dBm):        13.7            5.3
I'm having to load balance two lines to get the speed I had from one in 2014.