Coupled Toroidal Chokes

So, to save yourself having to wind wire through one toroid, you wound wire through two, and that's good. Uh, OK.

You have created two transformers, connected back to back. The more turns you wound, the higher the inductance of the coupling windings. Presumably you're working in voltage mode (sorry I'm not stating this well -- I haven't had breakfast yet) which is why more turns on the coupling windings are better up to a point, then the effect tapers off dramatically.

Figure out the inductance/turn on the coils, count turns in your coupling coils, and do the analysis accordingly.

Of course, those few turns on _one_ toroid, being driven directly at low impedance, will do.

Thanks, that's clarified things a bit. It's much easier to wind 25 turns through two toroids than about 200 through one! Also the isolation is better having more layers of insulation to get through.

Driving at a low impedance doesn't fit with the rest of the circuit, unless of course I used a transformer...

Cheers

It almost sounds like you want a telephone hybrid. Bi-directional voice (and faster for some applications) in the presence of DC and ringing voltages.

HTH

?-)