[HBR] HBR with switched coils

[john_wilkinson3 at sky.com]

Thank you for the help.I did think of using toroids for the RF stage, but I was worried how to vary the coupling from the transformer primaries.As I understand, in the original design the coupling was varied to just below the point of re-gen, to give the maximum selectivity. How would I do this using toroids? does anyone have experience of trying to do this?
Also How would I vary the inductance of toroids when aligning them?
regards,John