Quote from: Magluvin on January 12, 2014, 07:54:18 PM
Your right. Just applying dc, especially low voltage, if your not looking for it, you wont see it.

45pf, you better be looking for very high freq initial spike at the time of applying the dc, not just looking at the DC magnetic field after the spike.

Oh well. Cheap tests. Cheap results. Testing pancakes such as shown, the motor better be running somewhere below FM radio freq of rotation. Doing low freq or dc tests on a coil that is designed for radio freq doesnt make any sense to me.  And then to say the results are conclusive when it comes to the difference between bifi and normal coils is only half baked.

Just made a second bobbin to match a coil I have(normal 1 strand, 42awg, 5kohm, 1.6h 2 1/4 dia, 1/8 in thick) to make an equal bifi for comparison.  The normal coil lights an led with a slow pass of a mag.

Will be using a primary pulse coil of 2 turns on the outer diameter for testing.


Mags

gain 4 to 1:
http://alexfrolov.narod.ru/frolov_transformator.html

Quote from: tim123 on January 13, 2014, 11:12:21 AM
I think Tesla found that the 'magic' of the bifilar pancake coil was it's ability as an antenna...

Do you mean, the bifilar coil is a better antenna than the monofilar coil?

When doing the "self resonance measurements" with an exciter coil ( see http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg382408/#msg382408 ) I saw that the exciter coil can be very far away from the pan cake coil (100 mm tp 150 mm). Is this an indication that a pan cake coil is a good antenna? What kind of experiment could one do in respect of "being a better antenna"? (Again comparing the monofilar and bifilar coil. Magic should be in the one and not in the other?)

Is this the claim: a bifilar pan cake coil is a better antenna than an equivalent monofilar coil?

Quote from: tim123 on January 13, 2014, 11:12:21 AM
The fact that the coil is both the inductor and capacitor in the tank means that the electrostatic component isn't hidden inside a capacitor shell - so the antenna is both electromagnetic and electrostatic. (Not sure if you're aware, but there are such things as capacitive/es antennas...)

When I do the "self resonance measurements" the bifilar coil is "inductor and capacitor" (no separate capacitor). The self capacitance which defines the self resonance frequency is the "hidden capacitor". But this is true for all coils? A coil is always an inductor and a capacitor (I mean its self capacitance).

Yes, the bifilar pan cake coil has a bigger "self capacitance" than an equivalent monofilar pan cake coil, but that is not magic, it might even be a flaw if you want higher frequencies. (A monofilar pan cake coil can be used at higher frequencies than an equivalent bifilar pan cake coil because it is not burdened with such a high "hidden capacitor".)

Yes, my bifilar pan cake coil can swing at 4 MHz without an external capacitor because it has a "hidden 45 pF internal capacitor". But my monofilar pan cake coil can swing at 9 MHz without an external capacitor because because it has a "hidden 9 pF internal capacitor". Where is the magic, only the "hidden capacitor" has a different value which causes the known consequences (like a certain self resonance frequency).

I am not criticising or ridiculing, I am asking "what is the magic"? The higher self capacitance is there, yes, but I see no consequences than the known ones. Every coil has a self capacitance, does the amount of self capacitance matter? Self capacitance matters in a known way (defines self resonance frequency), but does higher self capacitance bring in a principally new feature or effect?

Greetings, Conrad

Quote from: conradelektro on January 13, 2014, 06:06:22 AM
@Farmhand:

I showed that my bifilar pan cake coil has a lower self resonance frequency than my monofilar pan cake coil (bifilar ~ 4 MHz, monofilar ~ 9 MHz).

From this follows that the bifilar pan cake coil has a higher self capacitance than the monofilar pan cake coil (bifilar ~45 pF, monofilar ~ 9 pF).

The inductance of both my pan cake coils is ~34 µH.


What do you mean by "negating the self inductance of the coil by exciting it at or around it's self resonant frequency"? What is "self inductance"?

I excited both coils around their self resonance frequency and they behave like all coils. (The reactance increases which can be seen as a rise of the Voltage over the coil.)

What should happen in a bifilar pan cake coil when it is excited at its resonance frequency?

What should happen in a monofilar pan cake coil when it is excited at its resonance frequency?


Again, I am not criticising, just trying to understand so that I can measure an alleged effect.

Greetings, Conrad

P.S.: I am not off topic, I just measure systematically to separate the known from the unknown.

Same thing will happen with both except with the bifilar it will happen at a lower frequency. As you've shown.

Negating the self inductance means that the current will flow with nothing more than the DC resistance of the wire.

It's all explained in the patent. And it's pretty much all the patent is about.

I think a distinction needs to made between exciting a coil at or about it's resonant frequency, and exciting a coil to resonance.

Self inductance as seen by the supply. When we power factor correct an inductance we add a capacitance to stop the false currents or reactive power. Basically we tune the inductance/capacitance so its resonance under load is at about the applied frequency.

No magic, just a use. If you want a higher frequency you would not do it, same as you would not use a capacitor if it caused the frequency to be too low, that is also in the patent.

Saying it isn't so is calling Tesla a liar. And saying the patent examiner was wrong to grant the patent.

QuoteIn electric apparatus or systems in which alternating currents are employed the self induction of the coils or conductors may, and, in fact, in many cases does operate disadvantageously by giving rise to false currents which often reduce what is known as the commercial efficiency of the apparatus' composing the system or operate detrimentally in other respects. The effects of self-induction, above referred to, are known to be neutralized by proportioning to a proper degree the capacity of the circuit with relation to the self induction and frequency of the currents. This has been accomplished heretofore by the use of condensers constructed and applied as separate instruments.

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

I would here state that by the term coils I desire to include generally helices, solenoids, or, in fact, any conductor the different parts of which by the requirements of its application or use are brought into such relations with each other as to materially increase the self-induction.

l have found that in every coil there exists a certain relation between its self-induction and capacity that permits a current of 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. This is due to the mutual relations existing between the special character of the current and the self-induction and capacity of the coil, the latter quantity being just capable of neutralizing the self-induction for that frequency. It is wellknown that the higher the frequency or potential diierence of the current the smaller the capacity required to counteract the selfinduction; hence, in any coil, however small the capacity', it may be sufficient for the purpose stated if the proper conditions in other respects be secured. In the ordinary coils the difference of potential between adjacent turns ror spires is ,very small, so that while they are in a sense condensers, they possess but very small capacity and the relations between the two quantities, self-induction and capacity, are not such as under any ordinary conditions satisfy the requirements herein contemplated, because the capacity relatively to the self-induction is very small.

Cheers

@Farmhand: thank you for taking the time to explain. I think you read the patent correctly, it says just that. But one has to read attentively and with some background knowledge to get it.

Just to check that I understood correctly I make up a hypothetical example.

Let's take my two pan cake coils (the monofilar has a self capacitance of 9 pF and the bifilar has a self capacitance of 45 pF):

- the supplied or applied frequency is 4 MHz (I just make that up to have an example)

- in order to "power factor" correctly we have two possibilities:

A) we take the monofilar pan cake coil and add a 36 pF capacitor (9 + 36 = 45 pF) so that it resonates at 4 MHz

B) we take the bifilar pan cake coil which is in resonance with 4 Megahertz without adding any capacitor because its self capacitance happens to be 45 pF

- Alternative B) is cheaper because we do not need to buy a capacitor.

- if the supplied or applied frequency were 2 MHz we would need a capacitor for both of my pan cake coils in order to "power factor" correctly (from my many experiments with my pan cake coils I happen to know that we need a 100 pF cap for the monofilar and a 74 pF cap for the bifilar pan cake coil to make them resonate at 2 MHz)

Greetings, Conrad

Quote from: conradelektro on January 13, 2014, 01:34:28 PM
Is this the claim: a bifilar pan cake coil is a better antenna than an equivalent monofilar coil?

No claim as such, just a thought... If it's acting as a capacitive antenna - then the increased capacitance would probably help by making a bigger electrostatic field.

I think it's interesting that he did use this coil config for power transmitting & communications experiments too. He obviously developed it for the application described, and then found it useful for other things...