Why do long cables measured with a VNA show a "drop" in their attenuation curve?
I found this white paper on the internet:

Insertion Phase Errors in long lengths of coaxial cable assemblies by Ronnie Rice of RF Industries (https://www.rfindustries.com/pdfs/white-papers/Insertion-Phase-Errors-in-Long-Cable-Assemblies.pdf)

According to the paper, the "step" appears due to phase errors that can be corrected using a slower Sweep Time.

I changed the default sweep time (I don't remember the exact value, but it was in the order of some milliseconds) to a 2-second sweep time and the "steps" disappeared (see the figure below).



Thank you all for your help!

Best regards.