@gotoluc and all

Don't worry about threads. They are always here, ready to re-open anytime it is needed. No one signed a contract to release as per a set schedule so cut yourselves some slack guys. You have done some great work here and have prepared a base for others. Around here, we really can't ask for more. So thanks. Let's see what happens with @Groundloops circuit.

I myself am working on the FTPU right now, resonance and all. Just learning about the possibilities of how to drive it thanks to all the learning about resonance techniques is part and parcel. lol

But guys, here is an angle on pulsing your coils to resonance. Try to take the audio output of your computer sound card, put it through a small mixer or amp and connect it to your coils as left, right and common. I use a small mixer and take the headphones output via the available jack. Then use a frequency generator like the one I put here......

http://purco.qc.ca/ftp/Learning%20Electronics/software/
click on the following file to download it FrequencyGenerator.zip
It is only one file so you can just put it on your desktop, or anywhere else.
Lot's of fun. Crazy scope shots and you will understand about phasing and using two frequencies. You can open more then one windows and have more frequencies if you need it. .

Keep on keeping on.

Simple coils of wire are dispersive.
Dispersive in an electrical context, where a dispersion region is a frequency range over which permeability or permittivity is changing.

The term 'refractive index' is not much used in electrical engineering; but many will be familiar with 'velocity factor', which is its reciprocal.

This begs the question; "what has velocity got to do with inductance?" to which the answer is; "rather a lot". The traditional understanding of coils depends on the idea that they are effectively electromagnets, and that they have reactance because energy is stored in the surrounding magnetic field.

This picture is mostly wrong, even though it suffices at low frequencies. If we may take the liberty of using the word 'light' to mean electromagnetic radiation of any frequency; what a coil really does is to modify the refractive index of space in its vicinity in such a way as to bend light and force it to follow the electrical conductor.

All electrical circuits do that of course, but in inductors, the path is deliberately made long. Hence a coil is a waveguide or transmission line, which stores energy by trapping and detaining 'light' which would otherwise have made a much shorter journey.

The inclusion of self-capacitance into the lumped-component model gives rise to the prediction that a coil will still exhibit parallel resonance in the absence of an external circuit. This is indeed correct; except that, unless the coil is extremely long and thin, the actual self-resonance frequency (SRF) is considerably greater than predicted. This failure of the lumped component theory is mainly due to the onset of another dispersion-related effect; this time in which the apparent inductance declines (presuming that we adopt the view that the self-capacitance is constant) in such a manner that the SRF is pulled to the frequency at which the wire in the coil is very nearly one half-wavelength long.

     This time, there is no reprieve for the lumped element theory. The SRF occurs at the electrical half-wavelength point because that is the frequency at which a wave, trapped in the coil by reflection from the impedance discontinuities which occur at the terminals, arrives back at its starting point in phase with itself.

The pulling effect can be understood by considering the overall field pattern as the superposition (combination) of two waves, one traveling along the coil axis and the other following the helix.

At low frequencies, the axial wave dominates and the helical wave is forced to keep up. This causes the phase velocity (i.e., the apparent velocity) of the helical wave to be several times the speed of light.

As the frequency increases, the helical velocity falls steadily as propagation along the helix becomes increasingly important, but the change is smooth and corresponds to an impedance characteristic consistent with the lumped component model.

As the SRF is approached however, the scattering cross-section of the coil suddenly increases and the axial wave is overwhelmed. Hence the impedance characteristic deviates as the coil 'locks-on' to the half-wave resonance.

@gotoluc

On the bridge, the wind is probably coming from more then one direction and it is the coupled effect. If one is in resonance to the bridge structure and another is slightly off.

This is one reason why I suggested you try the audio scheme. You can see it on the scope by using only one frequency to reach resonance, then use the second frequency at the first frequency less 1 hz and put the phase off by at least 6.84 degrees, then watch your scope. This would also provide you a secondary method of pulsing to "learn even more" under the same coil conditions which you use the regular FG.

You can even use the two audio signals to run two mosfets and use the phasing and frequency to pulse dc in soooooo many ways. lol

The way I see it like with one frequency you take up space in mass and with the second frequency you create movement inside the mass depending on how they compliment each other..