@Yucca,

Your waveforms are very close to what I got, as is your amperage.  Get rid of that iron powder core!

Yep the core was from a PC PSU, it was the mains filter. I have a big roll (5kg of 25mm width) of metglass tape on the way from canada woohoo primarily for working on Thane's bitoroid. But I will make a little toroid up for blocking oscillator research too.

I have not been able to replicate EM's results yet though I have wound numerious toroids with the cores I have available. Today I purchased 2n4401 transistors, as EM used, and was still not able to get results so I can assume that the core material is the component I am missing. I have order more cores from Amidon so hopefully they will be here early next week.

I have had some rather interesting wave forms develope that I thought I would share. I got these today after installing the 2n4401 in the circuit. The other transistors that I tried with the same circuit did not produce these results.

Here's a list of the transistors I tried that did not work

mps8099 hfe=267
2n2222a hfe=195 (cross match for 2n4401)
bc547   hfe=363
2n3904, hfe=272
2n3440, hfe=53
2n3439  hfe=207




The octagonal ring came from an old 20" Gateway monitor that someone threw away and I tried it as a last resort being that I gotten no results with my other toriods.

The ring has all kinds of possiblilities for managing rotation

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

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.

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

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

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