I have a whole bunch of fair-rite very tiny balun cores, beads, etc. I have several materials.
I am assuming you want to try the effect of a small decoupling transformer vis-a-vis smoothing out the peakiness shown in the images?
Now I have an original nanona2 and a bunch of TH components, probably the ones you used (including the coil) as well as the toroids, probably. As well as the breadboards. I also have some gold plated DIP plugs with solderable pins ideal to carry the xformer. From experience this works great up to a few hundred MHz.
Can I attempt to replicate what you are trying to do which I am guessing likely involves either a 1:1 or fixed ratio transformer (1:4?) to match the nanoVNA to the "transmission line" on the breadboard?
I'd be happy to bang it together, scan the DUT at the proper range and then show you what the results are via screenshot here. I would be using the software that I have which is the QT software (which works fine for me)
I dont have a windows box so cant run windows apps. My wine install is broken now too.
This is not an inconvenience because I have been meaning to try exactly this, to check this out for a while.
I also have the nanovna test board and a bunch of stripboard (good for series and shunt testing fTH components but ...
And SMA connectors. and my x-acto knife and soldering iron. would be good for HF, too much capacitance to work well much above that. But okay for banging out filters for HF.
Sweeping 20KHz to 100M, still no transformer and unit is not calibrated. Plot A, starting with a tant for the bulk. B, adding a 0.1. C adding a 0.001uF.
Should be fine at 100 MHz.