On 19 mayo, 20:25, 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

Cecil,

Lumped circuit approach gives a good solution for your brainteaser
(maybe against your expectations or hope). It is just distributed
capacitance to ground that can be concentrated into 1 or more
capacitors if you are well below the first resonance frequency.

In a real application when using a lumped 72uH inductor for
calculations, one will find out that the capacitors for a certain
application (for example pi-filter section) have to be somewhat
smaller then based on the lumped circuit calculation.

Regarding transmission line behavior
It is the reason to mention "without using transmission line
sections". Because my PSPICE package also allows use of transmission
lines, if convenient I use them. Do you know how I made my first guess
for the capacitors? Just by using transmission line theory. BTW,
what is the wire length of the inductor in your HF rig (for 4 MHz
band)? It is very likely well below the length for the bugcatcher
example.

Did you know that many delay lines were/are made by using multiple CLC
sections (for example used in oscilloscopes)?

Again, look to the circuits of your rig, do you really think that the
design is carried out by modelling each component as a transmission
line. The answer is no (for sure).

We have various religions around the globe; I think we don't need
another one based on transmission lines! Maybe for you it was
wonderful to explore transmission line theory, but for RF Engineers/
Designers (antenna designers included), it is just one of their means
to get the job done.

Wim
PA3DJS
www.tetech.nl