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Crosstalk?

sp1ke
Grafter
Posts: 70
Thanks: 2
Registered: ‎21-03-2013

Crosstalk?

Yes apologies another crosstalk thread... Crazy
I have been connected on the 80/20 package for 11 days now.
All has been very stable and still is as far as my sync goes but today my SNR dropped from 14db to 11db.
With it my attainable dropped from 108000 to 94600 kbit\s.
My errors remain fairly low.
My sync remains the same so I'm not too concerned yet, but I would just like to know if crosstalk can affect attainable and SNR in this way?
And at what SNR level would the DLM decide to kick in, 6db perhaps?
5 REPLIES
elfish
Grafter
Posts: 235
Registered: ‎22-02-2009

Re: Crosstalk?

You must have a quiet line and/or little uptake of VDSL2 at your cab, as your line attenuation suggests that you are not that close to the cab, but your attainable and SNRM are very good. But yes, crosstalk will affect SNR and thus attainable, obverse over time and possibly in a few months you may have different stats from now.
Are you running the 7390 or the 7490?
Could you take a capture of the spectrum page?
And are you running an SSFP or a dangly splitter?
sp1ke
Grafter
Posts: 70
Thanks: 2
Registered: ‎21-03-2013

Re: Crosstalk?

Hi elfish,
Thanks for the reply.
I'm using a 3390 with firmware 6.20.
I'm around 180m from my cabinet and it's an SSFP, Openreach Mk3.
I was just looking at the spectrum page but know little of what that means
elfish
Grafter
Posts: 235
Registered: ‎22-02-2009

Re: Crosstalk?

VDSL2 uptake must be quite low.Your spectrum graph looks pretty flat and doesn't feature any low drop offs, but I would of expected the SNR per tone to be higher overall at 180m. I wonder if your line goes further than 180m. I am probably the same distance away from the cab and I get 9dB down and 11dB up in terms of line attenuation, and the SNR per tone is higher, but my attainable rates are lower than yours as well as the SNRM, along with higher errors (G.INP is applied to the downstream now, so at the moment no errors on the DS), all most likely due to crosstalk.
I too am running a 7390 and SSFP mk3, but with a shielded cable between the two.
Is any part of the cable run to the cab overhead, or any idea if aluminium is used rather than copper along the run?
sp1ke
Grafter
Posts: 70
Thanks: 2
Registered: ‎21-03-2013

Re: Crosstalk?

Thanks for the informative reply elfish.
Well it may well be further than 180m. The BT checker indicated an impacted estimate of 61 Mbps.
The whole run is underground and no aluminium as far as I know. ADSL uptime was always months without a disconnect so it must just be good copper.
Oh and I have a poor man's 7390, the 3390  Smiley
elfish
Grafter
Posts: 235
Registered: ‎22-02-2009

Re: Crosstalk?

Ah sorry, I misread your post as being 7390.  Embarrassed The 3390 is nice piece though. 3x3 MIMO rather than 2x2. I don't use any of the phone features, so I should of got the 3390.
The main thing is that you are getting pretty much full sync (full sync would be 80,000 and 20,000, but as near as makes no difference), and that there is room to play with and also low error rates.
I would keep the FritzBox connected without any manual re-sync's, and only time will tell as to how your connection will fair.
Keep us posted!