another great stuff is that the feed back indicator clearly indicates resonant conditions and some harmonics too...
The only problem s that it is not locking in phase... maybe some problem with the lock in chip.. get to see
i'm using cooperatively my protoboard and the box plls to solve this problems...
i guess reflected impedance is what damped my resonance here... as the coils were air core, the single fact that this line gets into the current transformer it sees the reflected impedance of the secondary load-- basicaly as the current changes and induce a voltage in the secondary, the secondary current flowing induces a counter emf in the primary that reduces the applied emf directly... so damping resonance...