On Mon, Mar 17, 2025 at 03:22 PM, W0LEV wrote:
best "amateur" fixture is to solder cal. standards and test items to the
butt end of an SMA female connector - WITH ABSOLUTELY NO LEADS.
Indeed, the HP16092A is the butt end of an APC-7 connector, with just 3mm of the centre conductor protruding beyond the insulator. It has an advertised max freq of 500 MHz.
I agree with Dave that a DIY fixture can be made using a female SMA connector with its centre conductor sawn to the same level as the dielectric. Then, a plastic bulldog clip (similar to one in the photo of the S21 fixture) can be used to clamp the chip component down.
I have measured a 89 nH inductor (6.5 turn, ID2.9mm) using the 1st type of fixture (fixt s11.jpg). The fixture is calibrated using a 1206 size 50ohm chip, and a brass shorting bar. Using the nanoVna V2+, the S11 from 10 to 1000 MHz (s11.jpg). The self-resonance is above 1000 MHz. The trace stays inside the chart. The Q can be calculated from the impedance = R+jX at different freqs.
According to HP/KS, the VNA has poor accuracy when the S11 trace is near the perimeter. Hence, I also measured the same inductor using the S21 method in a microstrip fixture (fixt s21.jpg). A plastic bulldog clip is used to clamp the inductor to the PCB. The fixture is calibrated bridging the microstrip gap with a brass bar (thru). The measured and modeled S21 points a parasitic cap of 0.16 pF (s21_gra.jpg)
