One more comment regarding maximum cable length. If you have option 010 (time domain), there is a limit to the time interval you can display, but I think that's tied to the math for the transform. Just to make sure that there is no such problem in the frequency domain, compare your measurement with a small number of points with a measurement with the maximum number of points. If you pick some low number of points (e.g. 11) and the analyzer no longer gives good results, it's because it couldn't make sense of "N".
Vladan
