Magnetic Resonance Amplifier 6: Effect of External Magnetic Field
Please watch the earlier videos in this series first.
Here I have the system tuned so that the applied magnetic field from the external magnets moves it closer to being in resonance at the driven frequency.
This allows me to regulate the brightness of the LEDs (meaning the power throughput, and the resonant voltage rise) by varying the external field. The current from the FG in the bifilar transformer’s primary isn’t enough to saturate the ferrite core fully, so there is room for its permeability to be moved around by the external field. This affects the coil’s inductance which in turn affects its resonant frequency. If the drive frequency doesn’t change, then the system is modulated by the applied external field. The modulating field could be provided by a third winding on the ferrite, for example.
The transformer is 98 + 98 turns, wound together “bifilar” but not connected together for this application. Since the turns ratio is 1:1, any output voltage amplification is due to resonant rise, I think … and the unfiltered FWB on the output side.