@ those attempting to tune the STAAAR Yoke device.

If my hunch is correct than the goal of the tuning procedure is to

**create a rotating magnetic field** inside of the ferrite. See the animation of it here:

two perpendicular coils create magnetic rotation...

See the animation of two orthogonal coil pairs below (click on it to see it rotate):

The animation above uses 2 pairs of windings (4 windings), but it is possible to create the same rotating magnetic field only with 2 perpendicular windings (see the attached picture).

Anyway, to accomplish the above objective, at least two perpendicular windings are needed. If two of them are used then:

**1**) The two windings need to be perpendicular to each other, in order to create orthogonal magnetic fields (H-fields)

**2**) The currents flowing in these two windings need to be:

**a**) bipolar symmetrical AC waveforms (preferably sine waves).

**b**) of the same frequency (preferred ratio) or an integer multiple of the frequency (harmonic / subharmonic).

**c**) 90deg. out of phase. This phase difference can be accomplished by one of these methods:

**i**) Driving the windings by two separate low-impedance AC voltage sources (signal generators + amplifiers)

outputting two separate waveforms of the appropriate phase difference.

**ii**) Driving both windings in parallel by one AC voltage source.

** iii**) Driving one winding by one AC voltage source and relying on the stray mutual inductance to drive the other winding.

Depending on configuration, the STAAAR Yoke device uses methods

**2c_ii** or

**2c_iii**, so let's analyze what is needed to maintain the 90deg. phase difference between the current in the windings.

From basic electronic engineering we know that:

**1**) in an RL circuit the current leads the voltage from 0deg. to +90deg.

**2**) in an RC circuit the current lags behind the voltage from 0deg. to -90deg.

**3**) in an RLC circuit the current leads or lags behind the voltage from -90deg. to +90deg.

Again, from basic electronic engineering we know that in an RLC circuit:

**A**) if the reactance of the inductor is greater than the reactance of the capacitor then the current lags behind the voltage of the AC source

**B**) if the reactance of the inductor is less than the reactance of the capacitor then the current leads the voltage of the AC source

**C**) if the reactance of the inductor is equal to the reactance of the capacitor then the current is in-phase (0deg.) with the voltage of the AC source.

Point C describes the resonance in an RLC circuit.

Note for Newbes: The reactance of a capacitor or an inductor (e.g. coil, winding) changes with frequency and is similar to resistance. Namely, it increases linearly with frequency for inductors and decreases linearly with the reciprocal of the frequency for capacitors.

For DC, an ideal inductor behaves as a 0ohm resistor and an ideal capacitor behaves as an infinite resistance resistor (open circuit). For very high frequencies it's the opposite...

The impedance (Z) is the combination of real resistance (R) and reactance (X). Its magnitude can be calculated according to the formula Z=(R

^{2}+X

^{2})^

^{0.5} Those wishing to study this further, look up the "ELI the ICE man" rule and see the attached graph of X

_{L} and X

_{C}.

Each winding in the STAAAR device can be modeled as an RLC circuit according to the attached schematic, where:

**Rx** is the internal resistance of the AC signal generator

**R** is the resistance of the winding

**L** is the inductance of the winding

**C** is the stray inter-winding capacitance of the winding plus any added external capacitors.

The AC impedance and current phase formulas for this circuit are quite complex, but whatâ€™s important, is that in order to achieve the 90deg. current phase difference between these windings:

**1**) the current in one winding has to

**lag behind** the voltage of the AC source (be more inductive than capacitive, see pt.

**A** above)

**2**) the current in the other winding has to

**lead** the voltage of the AC source (be more capacitive than inductive, see pt.

**B** above)

For example if current in one winding lags 30deg. and in the other leads 60deg. then the phase difference between them is 90 degrees, because 30+60=90.

Now, in the STAAAR Yoke device, the 50t winding has much higher inductance than the 1t winding which is confirmed by Itsu's measurements.

Thus the current in the 50t winding should be

**lagging** behind the voltage of the signal generator. Conversely, the capacitance should dominate in the 1t winding causing the current in it to

**lead** the voltage of the signal generator.

...and indeed the STAAAR team reports that the device does not work with narrow surface areas of the copper strips (narrow strips have smaller capacitance than wider strips).

Here, it should be emphasized that in the

**2c_iii** method of driving the 1t winding, the signal generator does not drive it directly but through a stray mutual inductance between the 1t and the 50t winding.

In summary the whole tuning process of the STAAAR Yoke device might amount to setting the capacitance of the 1t winding and the frequency of the signal generator to such values that the currents in the 50t and in the 1t winding are 90deg out of phase. According to pt.C, this precludes operation exactly at resonance (in method 2C_ii), because in such case the current is exactly in phase with the voltage of the AC source (signal generator).

The easiest way to measure whether these currents are 90deg. out of phase is to set the scope in XY mode to measure both currents and look for the roundest Lissajous figures. See:

http://www.allaboutcircuits.com/vol_2/chpt_12/2.html