First Question - are these dips at this particular frequency 'normal' / what might be causing them?
The first obvious dip, where all bits/SNR values gradually decrease to some minimum point at tone 512 or earlier, is a deliberate power reduction by the cabinet. They do this to ensure that VDSL from the cabinet doesn't swamp the lower power of the ADSL from the exchange. The actual tone of the dip, and the height, depend on the distance of the cabinet from the exchange.
The smaller dips, around tone 1024 and 2048, seem strange. Perhaps the ECI cabinet has been told not to use them for some reason.
Second Question - Despite the similarity, Ronski is using tones much higher than mine - mine cut dead at 2143. Is this indicative of a particular issue or mode of interference, or just a characteristic of my perhaps slightly longer line?
Basically, the modem doesn't use any tones where it thinks the signal level is too low relative to the noise. If you compare the Bits/tone graph with the SNR/tone graph, you see that bits stop being allocated when the SNR is less than around 9-10dB, and the SNR graph stops getting any value at all below 8dB.
The signal level you receive is a function of the length, diameter, and quality of your line. The Hlog graph gives you an idea of this part of the environment.
The noise level interfering with you comes from your environment, and from the VDSL2 signals from all neighbouring within the cable bundle: more subscribers = more interference. The QLN graph shows you the noise environment that you are working within.
So, in comparing your line with Ronski's, I can see:
- The Hlog graph shows your line is a little worse than Ronski's - perhaps being longer, thinner or both. You will get less signal at the extreme distances, about 5dBm/Hz less than Ronski at the end of D2 & start of D3, which results in you getting less bits/tone at the upper end of D2 and no tones in D3.
- The QLN graph shows a similar shape, but your line is slightly noisier around the U2 band. The extra noise here means you get fewer bits/tone within U2.
- The SNR/tone graph shows the combination of the two above (signal - noise): you run out of usable tones earlier.
There isn't anything that appears *obviously* abnormal there. Just a longer line, with
(This myDSLWebststats thing is great for comparisons, isn't it?)