So long as you are not driving the toroid to the point of
nonlinearity, a model with two standard inductors in series should
work fine for a tapped toroid winding. If the mu of the core material
is high, the coefficient of coupling between the coils will be quite
high; it will be somewhat less if the core mu is low (like one of the
high-frequency powdered iron mixes). The one time when I got really
serious about using a toroid-core transformer model in Spice, a linear
one worked just fine, but I did take the time to characterize the
physical transformer's parasitic capacitance, leakage inductance and
effective resistance. In fact, I was amazed at how accurately the
Spice output matched the overall circuit performance in that case.
(3.5MHz switching power supply, using a LAN transformer -- the ringing
and damping of that ringing of the parasitics up near 100MHz matched
what I measured in the circuit almost exactly.)

Cheers,
Tom

(Greg Nelson) wrote in message . com...
#1.) I recently built a basic Hartley VCO and made measurments on it
with a scope.

#2.) I thought that I would make a model of it with Micro-Cap and see
how well the simulation matched the real thing.

#3.) I used 2 inductors to model the torroid(probably a mistake).
When I simulated the VCO it worked. However voltage measurments of
the top part of the inductor and the lower part(tap) were in phase.
This did not match my scope measurements of the real thing.

#4.) Is there a model available in Micro-Cap for a toroid?

#5.) I also have access to Micro-Sim Pspice. Is this a better
package? Is there a model for this package?



Thanks!

Greg