Hi Roger,
Thanks for this, your results look very similar to mine, there is a slight difference in the frequency of the dips but I assume this is due to differences in the mix of the core material, winding pattern (causing a difference of capacitance between turns) and also stray capacitance and inductance on connecting wires.
The images below show my results of two back to back 1T to 8T impedance transformers using BN73-202 binocular cores with plastic insulated wires compared to yours (mine look just like the ones in the photo you attached, they are wound in exactly the same way). I have added your images next to my results for comparison, mine are the left ones and yours are the right ones.
I am pleased my results match so closely to yours - it is always helpful to be able to compare results.
Thanks for taking the time do do this.
