Mysterious Resonant Circuit

[Peterae]

Duff
EM used 15 turns and 8 for the base drive, also i used a 47k res and a 47k pot in series to allow the base resistor to be adjusted.

Peter
Also your Inductance is way off mine 302uH and 98uH for base drive.

[gyulasun]

Hi Duff,

EMDevices wrote about his coils number of turns in the 1st page of this thread for you:

duff,  the toroid has 3 sets of windings, each 15 turns.  My added coil for driving the transistor base has 8 turns. Not sure what core type it is.

So eventually you have used the same because Peter also used EMDevices's turns numbers as he wrote.

What I find interesting about the waveforms is the pulsing action along with the resonance in the envelopes OR is this modulation? I don't think I've ever seen the rectangular waveforms before coming from a oscillator....

Regarding your waveforms shown in the previous page I think you have two oscillations of different frequencies in the same oscillator circuit.  This is not unusual in HF oscillators where there are at least two frequency selective networks or pair of components. 
The first is I think the R2C1, this gives the lower frequency oscillations (this is about the 20us time (4 * 5us)). (Notice the value of C1 is modified by the base-emitter input capacitance which from the 2N4401 data sheet can be max 30pF, for a Philips made such transistor, http://www.nxp.com/acrobat_download/datasheets/2N4401_4.pdf ).

The second is your 8.2uH base feeding coil L1 together with C1 + also the base-emitter input cap value, I think this constitutes the higher frequency operation of around 16 MHz as your digital meter in the oscilloscope shows.

Because the waveforms from EMDevices or Peter do not show a two frequency operation I think the lower frequency operation cannot occur in their circuits due to smaller loopgain or feedback for that lower frequency but in your circuit it can.
Mannix reports he has not used ferrite cores (if I understood it right) so this explains why his wire lengths affect so much the frequency (without ferrite core the coils has much less inductances).  He has not reported on the double frequency oscillations but he can see this with a scope only.

Regards,
Gyula

[aleks]

Sorry to be a naysayer... But what should be checked for sure is resistance of resistor at that high frequency (it may rise or may fall in comparison to DC I believe). Another serious obstacle is low-watt rating of resistor. I probably know too little about electricity to tell anything for sure, but the volt/amp reading across some component does not necessarily mean energy DRAW is as high. E.g. in a superconductor you can have voltage and amperage as high as necessary, and for as long time as necessary - all measurable, but they won't be doing WORK. Hence, until you attach MOTOR instead of transistor, the motor that rises a piece of weight up and down, you can't be sure your schematic produces more work than it takes energy from the battery. Better to show layman's proof than EE's "magical" formulas.

[eldarion]

Sorry to be a naysayer... But what should be checked for sure is resistance of resistor at that high frequency (it may rise or may fall in comparison to DC I believe).

I, and many other engineers, have used these carbon film resistors in VHF radio equipment--they do not change value by any significant amount, even at 144Mhz.  If the measurements of resistor voltage were taken with the scope probe and scope ground attached close to the resistor body, then the results are definitely valid.

Eldarion

[BEP]

Sorry to be a naysayer...- all measurable, but they won't be doing WORK. Hence, until you attach MOTOR instead of transistor, the motor that rises a piece of weight up and down, you can't be sure your schematic produces more work than it takes energy from the battery. Better to show layman's proof than EE's "magical" formulas.

@aleks

I'm sure you understand that actual work being done is not limited to things as tangible as a weight being lifted. Conversion of an energy to heat or another energy is a valid form of work. Similar to what Eldarion stated... in a carbon resistor little will change until heat extremes are met or the frequency applied is so high that the inductance of that resistor and the leads must be considered.
I dislike having to deal with the complexities of pulsing and alternating signals but it is a simple fact of life with electronics. Accuracy with these signals causes problems for more than the layman.