Margins are the same, but only one of them is reported as marginal - DTX CableAnalyzer

A question that often puzzles the experts is how two results with the same margin can be reported differently, as in the case below:

The asterisk indicates that the Worst Case NEXT Margin fell within the accuracy of the DTX CableAnalyzer. If that is true, then shouldn't both results above be marked with an asterisk? Not necessarily.

  • The accuracy of the DTX CableAnalyzer changes with frequency.
Let's look at the Worst Pair NEXT for Link 1:

NEXT for Link1 Showing Accuracy Band

And the compare it to the Worst NEXT Pair for Link 2:

NEXT for Link2 Showing Accuracy Band

Since Link 2's Worst Case Margin occurred at a lower frequency where the accuracy of the measurement is better, it is not reported as a marginal NEXT.

Need to find out more information on these accuracy bands?