I just received the KC901V and ran it through a number of tests and it did really well. I have attached two pictures: First an S21 plot of a precision 20Db attenuator after user cal of S21. Second showing a precision 2:1 mismatch (25 ohms) using system Cal and S11.Both plots show excellent correlation from Khz to 7 Ghz. I am impressed so far. The only problem I have found is the keyboard LED back light is only partly working. The 1,4,7,. keys are not lit but the others are fine. I tried the back light intensity adjust but it did not affect these keys. I will open it up later to see if I can fix it. Overall, this is a great VNA for the money, and feels solid and reliable.