Why can't I see a drop in amplitude on a scope when I induce RF on one side of a toroid compared to the other?
If there is no load, then there will be no series attenuation.
Beads come in all sizes and ratings. for Z(f) and DCR . In order to be effective the circuit closed loop impedance must be at least 1 or 2 decades below the bead at lower frequencies.  &quot;Any wire&quot; cannot achieve that.
It is intended to be a low loss at DC or low frequencies and lossy at some RF, thus the DCR resistance must be shunted by an impedance at the Rf which you require to attenuate.



simulate this circuit &ndash; Schematic created using CircuitLab
This would be my Model to demonstrate how to measure a ferrite bead.