Thanks to Gyula his calculator, especially the flat-wire-calculator:

https://chemandy.com/calculators/flat-wire-inductor-calculator.htm i noticed that my measurements using my Agilent U1733C LCR meter were somewhat off for the Riedon flat wire csr's, the type also used by CaptainLoz.

They calculate to be 23.5nH each, so for 2 in series that would mean 47nH, while i measured 29nH for the both in series.

Not surprisingly as we are dealing with very low inductances and more important, the fact that there always are connection leads added which also have some inductance.

So i used my mini VNA (Vector Network Analyzer) the nanoVNA-F2 to characterize the used csr's.

The advantage is that the "plane of reference" (the point from where we do the actual measurement) can be pinpointed very precies, so ommiting any connection leads.

The result can be seen in the 4 screenshots below:

1st is the Dale 0.1 Ohm csr (still the best with 12nH)

2th is the Ohmite 0.1 Ohm csr (16nH)

3th are the 2 Riedon 0.05 Ohm in series (0.1 Ohm) csr (48nH)

4th is a single Riedon 0.05 Ohm csr (25nH very close to the calculated 23.5nH).

The 4 screenshots show 4 graphs each and some data taken at 3 markers.

I used a scan from 10KHz (minimum) to 10MHz.

Markers are at 809Hz (~CaptainLoz his device), 5Mhz and 10MHz.

Upper left graph is the Smith chart which is default and not very usefull here.

Upper right is Resistance (blue) and Reactance (green)

Lower left is Inductance

Lower right is Impedance (combination of resistance and reactance)

The Inductance and Resistance stays fairly flat across the 10MHz range.

The Reactance and thus the Impedance shows an increasing line with frequency as expected.

The Dale seems the best one, followed by the Ohmite and last is/are the Riedon(s).

So captainLoz would be able to calculate very accuratly the inductance of his metal bridge csr, and from that calculate the added reactance at a certain frequency using this calculator:

https://www.66pacific.com/calculators/inductive-reactance-calculator.aspxI don't think this will explain the COP=2, but it can interfere with the measurements taken.

Regards Itsu