The bifilar pancake coil at its resonant frequency

[web000x]

top coil (of 3 stacked coils,  center pulsed,  top bottom series connected) :  70 turns, 1.78 nF  0.51mH
bottom coil 0.47mH   1,72nF (coil tuned to topcoil, by adding 2x 50pF in parallel, so both resonate at the same frequency)
center coil (tighterwound)  2,58 nF 0.57mH

capacitance was measured by disconnecting the 2 windings (what i call "bridge")
my lcr meter is a very cheap chinese CA-4070L.

Edit: I havent done your reading yet, with 2  coils stacked, but not connected, and then one lead of each coil to measure capacitance.
The wire gauge, I dont know. the diameter including enamal coating is around 0.8mm. they are hand wound on cd sleeves with 70 turns total (2x35)

edit2: done the measurement. around 47pF between the top and bottom coil (without the center coil) not series connected,
again, a poor reading from a cheap LCR meter.

Thanks,
 
Those numbers aren't too far from a couple of coils I've got at 100 turns 23 gauge bifilar.  One coil (standard bifilar will little concern to proximity of two wires during winding process) measured 2.9 nF.  The second coil (wires twisted together with a drill to increase bifilar winding proximity) measured 2.6 nF.  I'm not sure why the twisted pair of wires had less capacitance which was another reason for my curiosity into the capacitance of the pancake coil.  Maybe a learned person will shed light, lol..


Dave

[evostars]

When he says:  "in other words, as though it possessed no self-induction...", he is NOT suggesting that there are no external magnetic fields or effects associated with magnetic fields!   


Undivided attention, and careful consideration should be given to the bold text......

"mutual relations" existing between the special character of the current and the self-induction and capacity of the coil......

If and when you comprehend what he's suggesting, you discover the true  purpose of the flat spiral wound "bifilar" coil, it's got nothing to do with anything that is being debated.  It's about purpose....he gave you the purpose in the title.....  Try asking yourself...what in the hell is he referring to by this "special character of the current".

Quote:

"I have found that in every coil there exists a certain relation between its self-induction and capacity that permits a current of a given frequency and potential to pass through it with no other opposition  than that of ohmic resistance, or, in other words, as though it possessed no self -induction."


So that its clear....  we are informed of what was "observed", as it applies to "every coil", we are informed of this "AFTER" we are informed of the "PURPOSE", which was.....:


"My present invention has for its object to avoid the employment of condensers which are expensive and cumbersome and difficult to maintain in perfect condition, and to so construct the coils themselves as to accomplish the same ultimate object.

That which was "observed" in every coil is to be kept in mind while becoming informed/familiarized with the latest development and or improvement.


Tesla is leading us to something profound here.....fucking recognize it!

The special character of the current.

spiraling. compressing inwards.

the compass points at the center of the coil, while the dielectric field is equaly concentrated between the windings, over the whole coil. where the "bloch wall" of a magnet would be.

what about the phase between the dielectric and magnetic fields? And its influence on the impedance.

[evostars]

Thanks,
 
Those numbers aren't too far from a couple of coils I've got at 100 turns 23 gauge bifilar.  One coil (standard bifilar will little concern to proximity of two wires during winding process) measured 2.9 nF.  The second coil (wires twisted together with a drill to increase bifilar winding proximity) measured 2.6 nF.  I'm not sure why the twisted pair of wires had less capacitance which was another reason for my curiosity into the capacitance of the pancake coil.  Maybe a learned person will shed light, lol..


Dave

Maybe because the fields twist around the windings

[evostars]

Yes Evostars , the father of pancake coils  say exactly that "it possessed no self-induction"  only need find the right frequency to that happens , and seems is that that some really don't agree  , and that is the reason to the compass not show any deflection even when  drive a load , not by the high frequency like someone say .

Hmm I dont know. I will check this, with a compass next to the coil. I have noticed the magnetic field doing funny things below its resonant frequency.
As the wave shape is not sinodial anymore.

Still I do wonder what the differnce of a biffilar coil would be if the windings where on top of each other, instead of next to each other.

As is a bifilar coil made from speaker wire. one winding on top of the other winding, so you have 2 pancake coils on top of eachother. The dielectric field wil then be between the 2 windings. the inductance would also be differnt, as the 2 coils are not alligned anymore.

The dielectric field will now be at 90 degrees to the magnetic field.

I really have to build this and check it.

The resonant frequency video is thougher then I tought. Even wikipedia has no propaganda page on it. Impedance, and the phase relation between the fields is a bitch. With DC the impedance is equal to resistance, due to the phase differnce being 0. 

So, I guess, at the right frequency the phase difference between the magnetic and dielelectric must be 0.
Man I really could use some VR to visualise the fields.

[MileHigh]

Those numbers aren't too far from a couple of coils I've got at 100 turns 23 gauge bifilar.  One coil (standard bifilar will little concern to proximity of two wires during winding process) measured 2.9 nF.  The second coil (wires twisted together with a drill to increase bifilar winding proximity) measured 2.6 nF.  I'm not sure why the twisted pair of wires had less capacitance which was another reason for my curiosity into the capacitance of the pancake coil.  Maybe a learned person will shed light, lol..

I am not sure how you guys are measuring the capacitance of your pancake coils but what I can say is that if you hook the leads of an LCR meter to the two terminals of the coil and set it to capacitance you are almost certainly getting an incorrect reading.  The basic problem is a capacitor has a DC open-circuit between the two terminals and a coil has a near DC short-circuit between the two terminals.

I am under the impression that capacitance and inductance meters excite the device under test with a series of discrete frequencies and measure the impedance and crunch the numbers back from that.  Honestly I am not sure what they actually do and I suspect different models and different brands do different things.  But it is safe to say that a capacitance meter is not expecting to see a near short-circuit in the device under test.

My suggestion is that a frequency sweep is the only way to measure the capacitance and then you have to crunch the numbers backwards to get the value.  I also suspect that as you sweep the frequency up that the pancake coil will manifest both series LC and parallel LC properties depending on the frequency and there might be multiple poles and zeros in the impedance as you do the frequency sweep. At higher frequencies just the proximity of your hand to the coil may affect the response.  This is all speculation on my part.  TK and others would know much more than me.

MileHigh