A lot depends on the winding dimensions of your coil. Inductors are passive devices used in electronic circuits to store energy in the form of a magnetic field. This will affect the measured inductance up at high VHF due to capacitance effects. I'm not sure how far up into the VHF band you are working at but the 120nH coil might begin to be creeping towards self resonance in the lower part of UHF. So if you also want to measure the Q of the inductor you would have to use the nanoVNA in a different way. With a basic S11 measurement the little nanoVNA will struggle to indicate the Q of your inductor across this range because it looks like you are trying for inductors wound with thick wire and a good form factor. You just need to do a basic S11 measurement across maybe 10MHz to 150MHz and you should then be able to measure the inductance across this frequency range.
If you do buy one it should be able to measure inductances of 33nH to 120nH (across a few MHz to 150MHz) about as well as a megabucks lab VNA as long as you learn how to calibrate it properly for the (simple) test fixture. The nanovna is the best choice for this if you can buy one locally and quickly. I'll try again with a fresh brain tomorrow and hopefully a better capacitor, and a better quality homebrewed etched PCB. Using this method above, the calculated inductance of one such wirewound came to be 1.5nH, which is very far from the ballpark of where it should be. For eg, one test inductor measures 3.5mm length by 4mm outer dia, and wire thickness of 1mm. Is the diameter the inner or outer diameter (or midpoint)? Asking because the thickness of the wire is nontrivial. I'll try again tomorrow with (hopefully) better components- if I can find them, and share photos.Īlso, the calculators for air core inductors All interconnects are short, so there should not be big stray capacitances or inductances at play, but when I tried normalizing the capacitance value against two inductances, the capacitance came out to be 21nF (instead of 10nF). And as test inductances, I tried again SMD 0805 inductances. I'm using 0805 caps, (which may be highly inaccurate) - perhaps I need to shift to silver mica caps as you say. Also in the range of inductances where I want to test, perhaps I need to go with a capacitor smaller than 10nF, but here's a hitch. Perhaps a parallel resonant circuit is better as you say. Rf-Out is coming from a hackRF, and I put the probe between 45ohm-C
The circuit is simple RF-Out-45ohm-C-L-GND. Will send photos tomorrow (late night here, too tired ).
I created a R, L, C series circuit with R=47ohms, C=10nF, and playing around with L. Air Core Inductor Coil Inductance Calculator Capacitor-Energy-Time-Constant-Calculator. Unfortunately I don't have a nanoVNA, but fortunately I do have a 100MHz oscilloscope capable of 1GSPS. The following is a collection of passive electronic design calculators from Daycounter, Inc., a rapid product development services company.