Dual Wire Wind? (Alternative to tapping/splitting)

[John_H]

Means that a higher C lowers the Q-factor.

But more important than Q is that a large C means a low resonant frequency and thus poor HF response.

Thanks Roland.

[Chuck H]

Already discussed and pointed out repeatedly is the additional capacitace caused by the unused portion of a coil. My question now is whether that still applies if BOTH ends of the usuaed portion of the coil are switched open. With no landing place for any semiconductivity I wouldn't think so. It seems to me that this common problem might be solved with a little more switching circuitry effort?

[Helmholtz]

Already discussed and pointed out repeatedly is the additional capacitace caused by the unused portion of a coil.

The windings on the same bobbin are magnetically coupled as with a transformer.
Each winding is loaded with its own self-capacitance (which means an impedance load).
By transformer action each self-capacitance reflects to all other windings.
So the effective capacitance of all windings is increased no matter if the windings are connected or not.

[Chuck H]

The windings on the same bobbin are magnetically coupled as with a transformer.
Each winding is loaded with its own self-capacitance (which means an impedance load).
By transformer action each self-capacitance reflects to all other windings.
So the effective capacitance of all windings is increased no matter if the windings are connected or not.

Thank you. I think I finally have it.

[J M Fahey]

Shortest answer is: bifilar winding is BAD, except on PT primaries where we deal only with 50/60Hz so it does not matter.