The Draytek I used for intial testing records 'Electrical length' for attenuation.
The last time I checked it with an identical router on both it was 10.2dB for the good connection and 14.2db for the bad one - a significantly 'longer' line. I don't know which frequency that relates to, nor the attenuation rate at that frequency as a function of length.
Edited by caffn8me (Thu 11-Jan-18 13:20:51)