Some interesting reading from Mr. Gorchilinhttp://gorchilin.com/articles/radiant/second_magnetic_field_amplifier?lang=en
If you talking about this circuitRecommended frequency up to 300khzbut it will work on higher frequenciessee https://www.ti.com/lit/ds/symlink/tl494.pdf?ts=1646436249478&ref_url=https%253A%252F%252Fwww.google.com%252F-Vasik
Hi Vasik err no I was thinking more on this section
have you checked that it works?I see this as a clamping circuit only.
L2 + L3 tuned with C1 to 20khz resonance