On May 19, 11:25*am, Cecil Moore wrote:
On May 19, 9:03*am, Wimpie wrote:

From simulation, but now a pi filter C=6pF, L=72u, C=6pF, load = 2570
Ohms

You just proved one of my points. Inventing impedors that do not exist
in reality in order to rationalize the real-world delay through a real-
world loading coil is exactly what I have been complaining about. Are
the imaginary lumped-circuit capacitors, to which you are forced to
resort, part of the actual impedance in reality or a figment of your
imagination?

http://hamwaves.com/antennas/inductance/corum.pdf
"The concept of coil 'self-capacitance' is an attempt to circumvent
transmission line effects on small coils when the current distribution
begins to depart from its DC behavior." About the capacitors you added
above it says: "Of course, this is merely a statistical determination
appropriate for computations ... and *not at all a physical
quantity*."

The reason that the source voltage and source current are in phase in
the example is because the load resistor equals the Z0 of the coil
which is functioning in transmission line mode with a VF = 0.019, i.e.
like a transmission line, it is indeed 0.1167 wavelengths long
electrically. I have verified such (within a certain degree of
accuracy) through bench experiments.
--
73, Cecil, w5dxp.com

First I'll point out that the model Wim used doesn't match "the
concept of coil self-capacitance," so it's not clear that the rest of
what you wrote is relevant.

Now, what do you do about your coils when you discover that they do
NOT behave like a TEM transmission line? Indeed they do not; it's
pretty easy to verify from measurements on real coils and real
circuits. It seems like now you are stuck, because you (seem to) have
a lot of trouble looking at a circuit and understanding what's really
important and what isn't, with regard to performance in a particular
application. Sometimes it's appropriate to use a model that goes well
beyond a simple transmission line model of a coil; sometimes the
simple transmission line model is far more complex than you need. See
Wim's previous posting about the value of understanding that.

FWIW, I understand perfectly well where the capacitances Wim put into
his model come from. I know exactly how I would estimate them from a
particular physical configuration, and I suppose Wim does something
very similar to what I would. They come very much from the real
physical world, not from our imaginations.

Cheers,
Tom