Take a look at this nanoVNA TDR tutorial by W2AEW:
VF must be entered numerically in order to obtain correct physical length.
The X axis scale is defined by the stimulus start/stop freqs.
W2AEW presents a formula to determine stop freq based on expected cable length and VF.
Did my fist TDR measurement yesterday and got reasonable results (length, attenuation).
73, Markus HB9BRJ
