The Smith Chart is the best display to view potential problems. Whenever
the locus crosses the center horizontal line on the chart, it is resonant
at that frequency. To the left of center is likely series resonance
(low-Z) and to the right of center is likely parallel resonance (high-Z).
The problem with testing with the choke directly across the S11 port is
that you now have embedded what should be a very high-Z in a 50-ohm
system. This is not how it operates, but will show resonances although
damped and therefore widened and slightly below their high-Z resonant
frequency(ies).
Dave - W?LEV
On Tue, Nov 19, 2024 at 7:07?PM Leif M via groups.io <leif.michaelsson=
[email protected]> wrote:
"A Choke is not more than an inductor. It should be measured as any other
one."
+1
Whatever inductance you want, you should measure it like inductors are
measured. On S11 port, one end to SMA center pin and the other to SMA
ground. If the reactance is much larger than 50 ohms, you should to use S11
and S22. Try calibrate your setup at the frequency you are going use, and
check the coil at that frequency too.
I think NanoVna is able to show the inductance. Your coil should have
correct inductance, and not negative or capasitance.
Quite often I measure components at 0-5MHZ, because connection wires do
not matter at lower frequencies. But if your coil is a capacitor at your
(higher) frequency, you'll get problems.
--
*Dave - W?LEV*
--
Dave - W?LEV
