reply to Kurt's Toroid Measurement
It's quite easy to get a simple measurement on a toroid inductance and to see the inductor's behavior over a desired frequency band with a nanoVNA. So easy, I think it should be a matter of course for every build.
Getting the most accurate results requires using the proper set up for the expected impedance. Depending on the impedance, the measurement method will change. Using a simple one-port reflection measurement for impedances "somewhere" near 50 ohms is usually sufficient for a quick check. For higher and lower impedances, you'll have to change to a two-port series or shunt method.
To get a reasonable idea of the inductance and resistance of your toroid use a basic fixture and attach it to port 0. Set up the frequency start and stop values, switch to Smith Chart, and calibrate. Then attach your inductor. You will be able to see an estimate of the inductance at the desired frequency of operation. The inductor should create a trace in the upper half of the screen. The trace may be anything from a point to an arc along the entire outer edge of the display.
A good low-loss inductor should create a trace near the outside upper edge of the Smith Chart. If the trace moves inward from the edge, you have losses. If the trace crosses the horizontal axis, you have a self-resonance.
Don't be surprised if the readouts show unexpected results. The outcome really depends on where the toroid came from. Is it really the advertised material? Remember, that the AL values are usually for 10 kHz (the standard frequency) and your inductance might be quite a bit off what you expected if that is how you decided on the number of turns.
I like to check every component before I use it. I've been surprised by faulty parts. Often it's much harder to fix once you've assembled your circuit. A semiconductor tester, LCR meter, and nanoVNA generally get used on every part.
