Tesla's "COIL FOR ELECTRO-MAGNETS".

[MileHigh]

Synchro1:

Your motor works on "near-field" magnetic fields generated by your drive coil, I am assuming that you are using an SB coil.  You are not operating in the "far-field" realm of radio wave transmission.  Plus the radio frequencies are too high relative to your spinning rotor.  That article you linked to on "Mechanical Antennas" is wrong.  A basic oscilloscope has more than enough bandwidth to allow you to analyze your motor.

MileHigh

[MileHigh]

TK:

"As you sweep the frequency all that you see is a pure sine wave across the LC resonator. " That's not true (in my experience), even if you use a pure sine wave as stimulation. You don't see the pure sinusoidal output until you are close to the resonant frequency _or a harmonic_.

It's amazing how you can remember stuff from 30 years ago but you can't remember stuff from last year or last week.

I can't explain your observations because of the following:  If you start with a sine wave as stimulation, then you have no where else to go.  Your device under test has to respond with a sine wave at the same frequency (but not necessarily the same amplitude and phase.)  This presumes that the device under test consists of linear components.

The only way generate new frequencies, i.e.; "You don't see the pure sinusoidal output" is if your device under test has non-linear components in it, like a nasty diode.  I am assuming that the LC tank circuit is in general pretty damn linear.  So it's a mystery to me.

MileHigh

[TinselKoala]

But I think synchro is right about his motor: first it's working as a pulse motor, then it is working as a synchronous AC motor. Call it near-field EM or RF, whatever. The thing does not have to be "responding" to every cycle of the driving wave. The rotor magnet might be rotating at the tenth "subharmonic" of the applied EM or RF and still be getting a push from it.

At the higher speeds it's rotating for the same reason that the compass is rotating in this video. The line between "pulse motor" and "synchronous AC motor" is a fine, blurry line and you can define motors on either side of it.

http://www.youtube.com/watch?v=wd5w8KhYrQk

[MileHigh]

TK:

Farmhand has a clip where I think you also observe a similar phenomenon.  I used the term "metastability."  The rotor will stabilize at a base frequency and possibly at one or more higher or lower frequencies for reasons akin to what you outlined.

I used the term "electro-mechanical impedance" for how a pulse motor might respond.  In that sense it's yet another "filter."  Just like a fancy analog filter might have multiple poles (resonance points) and zeros in the filter response, an electro-mechanical filter can also have it's poles and zeros.

MileHigh

[Farmhand]

But I think synchro is right about his motor: first it's working as a pulse motor, then it is working as a synchronous AC motor. Call it near-field EM or RF, whatever. The thing does not have to be "responding" to every cycle of the driving wave. The rotor magnet might be rotating at the tenth "subharmonic" of the applied EM or RF and still be getting a push from it.

At the higher speeds it's rotating for the same reason that the compass is rotating in this video. The line between "pulse motor" and "synchronous AC motor" is a fine, blurry line and you can define motors on either side of it.

http://www.youtube.com/watch?v=wd5w8KhYrQk

Glad you brought that up, I just thought of a pulse motor rotor design to make use of harmonics in an attraction kind of way.
I'll whip a sketch and post it with an explanation a bit later.

Just an idea as an experiment. I have got an optical sensor circuit for a pulse motor (to replace reeds) but I haven't used it with an appropriate
motor setup yet, I tested it with the dodgy coils I made for the acceleration generator video's, but I have bought different magnets and have better shafts now
so I may construct a new pulse motor as a fast spinner. I don't know when but I will probably be out of action for some time soon, if I don't post for a while
it's because of a medical issue, just thought I should mention that. Nothing to worry about, much.

Cheers