Quote from: TinselKoala on April 16, 2017, 08:08:07 PM
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.

Very nice TK,

To compare, here is my 10 second sweep of frequency between 10 kHz to 500 kHz of my TBF pancake. (528uH, FR = 307kHz, distributed capacitance calculated as approx. 509 pF)

Using the same method, so measuring across a 10 Ohm resistor (yellow)


Itsu

@Tinselkoala

Any reference to beat off cream by me would translate into German as"Schlag".

Quote from: synchro1 on April 17, 2017, 11:07:50 AM
@Tinselkoala

Any reference to beat off cream by me would translate into German as"Schlag".

Hmm. You are still stuck in crap mode.  Sorry. I give 3 strikes, then you are out. As soon as I figure out how to do it cuz you will be the first I have booted.
Apparently you wanted this, so it will be done today.

mags

Using a hall sensor i tried to chart the magnetic field of my TBP coil using 4V DC (1.5A).
The compass shows the field to mainly come from the center, the hall sensor more clearly shows this.

Video here:  https://www.youtube.com/watch?v=F9-vtR6KGZ0


The rough sketch shown below shows what i think the magnetic field looks like according to my measurements.


Itsu

Itsu:

Nice to see that you did the frequency sweep and got similar results to TK.  It makes you ponder the Tesla patent where the statement is that the bifilar pancake coil is modeled as a series LC circuit.  Perhaps with larger "industrial scale" coils they start to look like series LC circuits and not parallel LC circuits at the main self-resonant frequency.

With respect to your magnetic field diagram, the more your shape deviates away from something regular like a conventional bar magnet, the less useful the concepts of "North" and "South" are.  The real essence of the magnetic field is to determine its direction and "follow the loop" so you know where it's going.  Knowing the magnitude is nice also but perhaps of secondary importance.

Please see the attached diagram showing the magnetic field around a pancake coil.  As you can see, you had your Hall sensor in the wrong orientation or plane, in order to track where it was going and follow the loop of the magnetic field.  Sure you can nominally say that over the top of the center axis of the coil is "North" and under the bottom of the center axis of the coil is "South" also.

If you look down on a flat pancake coil along the axis of the coil, as you can imagine the magnetic field on the top half of the coil will look like radial spokes of a wheel going from say the center towards the outer edge, and the magnetic field below the coil will look like radial spokes of a wheel going from the outer edge towards the center.

MileHigh