Broadband Related > Broadband Technology

Variation between copper lines (again)

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Weaver:
This table shows the downstream and upstream sync rates for my lines currently, and with the values of the fractional deviations from the geometric mean are given for both directions.

Line  Downstream    Upstream   kbpsdev  kbpsdev130374.27%  5155.77%22803-3.76%  55513.99%32891-0.74%  435-10.66%429240.39%  452-7.17%Geo mean:2913  487
* I am sure I have asked this question before, but - why the differences?

The lines are supposed to be identical apart from line 2 which probably has a different story E-side now. (I think now we have established I actually have a D-side and an E-side now, but I take it that I had no such thing before - Is that correct? Because the PCP cab now shown in photos of the main road at Harapul is not there in Google StreetView earlier.)

Could it be down to different joints, of better or worse quality?

Pairs 1+3 are in the older drop cable into my house and 4+2 are in a second drop cable. They are in that order chronologically, ie. 1 being the oldest, then 3, then 4 and 2 the most recently made live.

I can’t see how invoking crosstalk really helps us explain the precise results. Otherwise I am stumped.

andyfitter:
How can they *ever* be identical? Nothing in the world is. They might be nearly identical lengths, but that’s about it. Different places in the cable bundle, different levels of interference from different crosstalkers, minute differences in attenuation from a whole load of factors. If everything were identical we’d all get the same sync rate every time we did a resync.

On lines as long as yours all of these factors probably play a far bigger part, as you’re at the extremes of the technology.

I’d be more surprised if they were exactly the same.

jelv:
I'd agree with you in respect of the downstream, the variation Weaver is seeing is about what I'd expect.

But around a 25% difference between the best and worst on the upstream?

dee.jay:
Whilst I agree, the upload figures are very low anyway, so a small variance will be a bigger percentage, I think?

burakkucat:

--- Quote from: Weaver on September 14, 2018, 11:40:10 AM ---The lines are supposed to be identical apart from line 2 which probably has a different story E-side now. (I think now we have established I actually have a D-side and an E-side now, but I take it that I had no such thing before - Is that correct? Because the PCP cab now shown in photos of the main road at Harapul is not there in Google StreetView earlier.)

--- End quote ---

Correct. Certainly for line number two. What is still not certain is whether lines one, three and four now have what can be considered as E- & D-sides.

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