The bifilar pancake coil at its resonant frequency

[MileHigh]

Gyula,

You obviously know your stuff.  I am really not proficient in these matters, more of a Joe Blow that just knows some basics.  For example, the attached two images of Smith charts make me queasy just looking at them, and I never really got into the advanced EM stuff.

MileHigh

[TinselKoala]

Once you have found the self-resonant frequency of your coil by looking for maximum voltage amplitude on your scope, the above suggests a second test to confirm your findings:

[signal generator] -> [coil] -> [non-inductive resistor] -> [ground]

Suppose your coil is two ohms and self-resonates at 200 kHz and you use a 10-ohm non-inductive resistor.

If your signal generator is set to output 12 volts peak-to-peak at 200 kHz then you should observe a 10-volt peak-to-peak signal across the resistor that is in phase with the signal generator if the coil is acting like a series LC circuit.  Then, as you increase the frequency you should see the voltage across the resistor start to drop as the impedance of the inductor starts to predominate.  Likewise, as you decrease the frequency you should see the voltage across the resistor start to drop as the capacitance starts to predominate.  However, will that really happen considering that we are dealing with a distributed capacitance and not a true series capacitance?

There may be a surprise, and at the self-resonant frequency of 200 kHz, there is no voltage across the resistor.  That would be explained by the coil acting as a parallel LC circuit at the self-resonant frequency.

An astute experimenter would measure the self-resonant frequency of his coil by looking for the maximum voltage swing, and then move on to this second test and do a full frequency sweep looking at the voltage and phase across the non-inductive resistor.  There may be some "surprises" to be found where there may be one or more "poles" and "zeroes" in the observed voltage and phase across the non-inductive resistor.

Behold:

This is a one-minute sweep of frequency between 10 kHz to 500 kHz of one of my TBF pancakes. (661 uH, F_R = 273.2 kHz, distributed capacitance calculated as approx. 513 pF)

The Yellow trace is the voltage across a 9.4 ohm, 1 percent, noninductive precision resistor pair (2 x 4.7 ohm in "opposite series"), connected as you describe. It behaves just as you predict for the parallel LC circuit, with the minimum voltage across the resistor occurring at the resonant frequency of 273.2 kHz.

[TinselKoala]

A bit more dramatic:  30 second sweeps from 10 kHz to 1 MHz, same setup as above.

[synchro1]

Note the beautiful high q, high amplitude ringing from "shock charging" my single wire MONOFILAR flat coil with a depleted 9v battery. No magnets in sight, just the coil, the battery, some wire, and an oscilloscope. Oh... yes.... and the skill and knowledge to use them.


Anyone with the skill, knowledge and test equipment can reproduce EVERYTHING I have ever demonstrated.

So that lets you out three ways, incompetent ignorant ill-equipped Synchro.

@Tinselkoala,


Another "Krell 7th level" Scope Shot? That's the same scope you can't read "Negative Current" off of!  It would help  to understand Australian to translate this: A watt hour is a negative Henry.


Neither you nor Milehigh has ever had a Physics course nor can either of you read or understand the Algebraic expressions we use in the "Henry Formula". This is where you both turn into Hydro-encpheletic Pinheads.

[synchro1]

@Milehigh and Tinselkoala,


I first mentioned "Negative-micro henries" to you both on Gotolucs Than Heinz regenerative gain video, and I insisted you include a "Negative Henry" value as a gain of power factor to add onto the COP. Neither of you had a clue and that raised an eyebrow on you frauds back then. A higher inductance coil field would factor into an electric power equivalent to deduct from the input. You two sneaked 'Rim Lead" onto the tote wheel in favor of loss.