Following on from Common mode choke measurement – length matters #2 which demonstrated that the following test fixture gave invalid results due to the 20mm length of resistor pigtails, the connection length in general terms
Above is a pic of my experimental setup. The resistor on Port 1 is a 10k 1% metal film resistor. The NanoVNA has been SOL calibrated at the Port 1 jack.
These plots should be horizontal lines at R=10k and X=0. They can be improved by shortening the connections, try the experiment yourself, you will learn more than if I show you the results.
If you do the experiment, you will be better placed to critically appraise the test configurations that abound online, especially on Youtube, and form a view as to whether the results are credible.
A thought exercise: do you think the fixture for this choke is good?
