Mysterious Resonant Circuit

[xee]

@ duff
I think EM was using a 0.01 uF capacitor for C1 whereas you seem to be using a 20 pF capacitor. That might make a difference.

[duff]

@ duff
I think EM was using a 0.01 uF capacitor for C1 whereas you seem to be using a 20 pF capacitor. That might make a difference.

@xee,

I tried a 0.01uF in the circuit before swapping to a 20pF and it produced similar results.

Thanks for noticing

-Duff

[aleks]

@xee,

I tried a 0.01uF in the circuit before swapping to a 20pF and it produced similar results.

Thanks for noticing

-Duff

Your toroid looks different to say the least. Why are you not trying to have the same toroidal winding as EMdevices had? Inductances are also different as you wrote them - they should be equal, except the transistor's base inductor.

[Mannix]

I have made a few of these now but i do not have the right transistors.
My output is around 1 volt or so...and no heat any where
I have a few 2n types that run however.

I made it open, with no breadboard and a ferrrite core  and what is interesting is that component position and lead dress have more influence on the type of oscillation (pulse or continiuos) than the cap values...Im talking millimetres. so wire lengths are important.





Lindsay

[duff]

Your toroid looks different to say the least. Why are you not trying to have the same toroidal winding as EMdevices had? Inductances are also different as you wrote them - they should be equal, except the transistor's base inductor.

@aleks

Yes, it is different looking. I tried several different toroids before I tried the one in the pic. It was a last effort attempt before ordering more.

There are 14 turns on each of the collector, LC, & LR windings. The base had 8.

That's what Peterae used and EMdevices never explicitly stated the winding count on each of his.

The inductance varied - can only guess why. Maybe some of the turns pulled away for the toroid or it was the way I had to pull them off different sides for routing. The inductance was measured on an old marconi LCR bridge @10KHz (I have digital meters but don't trust them as much).

@all

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....

I need to look at this some more today and try to understand how this is happening.

Is this unusual or is it just me?

-Duff