Try again... may be of interest ... Ulrich wenzel crystal oscillator schematic - Google Search In a message dated 4/15/2018 3:00:46 PM Eastern Standard Time, firstname.lastname@example.org writes:
Good work, yes, we did not include the fundamental frequency suppressor in the circuit diagram, we needed the oscillator for the evaluation of the test equipment at the time.. happy Sunday evening ... Dj2LR In a message dated 4/15/2018 2:02:01 PM Eastern Standard Time, dk...@arcor.de writes: Am 17.03.2018 um 00:57 schrieb Ulrich Rohde via time-nuts: > > https://synergymwave.com/articles/2013/04/full_article.pdf > > This may be still of interest... happy weekend, 73 de Ulrich, N1UL > > Since the weather did not look so nice this weekend, I canceled a 2-day motorcycle tour and tried the much applauded Colpitts instead. I think it is not possible to make it closer to the published circuit. OK, I dismissed the 0.5fF C0 modifier which is probably only a placeholder for simulation experiments. I had no 200nH parts, so I took 220nH, 150 nH did not make a difference other than less output voltage. I did not test the buffer stage because the BFG540 is obsolete and I could not find anything that fits its weird pinout. From the Altium Designer to .pdf, to Laser printout on foil as a photo mask and the contact copy to the unpopulated pcb can be done in a good hour, so it's a nice weekender. Circuit: < https://www.flickr.com/photos/137684711@N07/41468657011/in/album-72157662535945536/ > Layout: < https://www.flickr.com/photos/137684711@N07/40754928234/in/album-72157662535945536/ > Hardware: < https://www.flickr.com/photos/137684711@N07/41427204622/in/album-72157662535945536/ > It turned out that the circuit, as it is, leaves the choice of the overtone to the crystal. From a collection of 100...120MHz crystals not one worked at the intended overtone. There were results from 20 to 70 MHz. The test point is where the BFG540 emitter would be. < https://www.flickr.com/photos/137684711@N07/40754932194/in/album-72157662535945536/ > < https://www.flickr.com/photos/137684711@N07/41468662151/in/album-72157662535945536/ > < https://www.flickr.com/photos/137684711@N07/40754931924/in/album-72157662535945536/ > I forwent measuring the phase noise. Call me amateurish again, but I'll stay with the Driscoll. It has the tank circuit to enforce the correct overtone and I can adjust the delay so that 0 degrees around the loop coincides with maximum dp/df. Maximum Q helps nothing when it does not happen on the oscillation frequency. When I'm asked in a design review how I have made sure that the frequency of a single point of failure VCXO is not off by 30 to 80 percent, then I like to have an answer. And WRT vastly changing transistor parameters: They don't need to. If one looks into the emitter of a BJT at 10 or 20 mA bias, one sees 1 or 2 Ohms. That depends only on Ic, K, T, q and some minor parasitics such as RE. The emitter is fed by the crystal in Driscoll's case with 50 to 70 Ohms on resonance, which takes nice care of the transistor's shot noise. Off frequency it gets even better, esp. with C0 compensation. The base is fed with a huge step down ratio, so the base voltage is stiff. The cascode isolates from the effects of the tank circuit and it can easily be bootstrapped. If one dislikes Schottky limiting, one can duplicate the cascode transistor and divert some of the RF current to nirvana and not to the transformer, whenever the AGC voltage wants that. So the environment of the crystal and the sustaining amplifier can be very, very time-invariant. The whole thing is just a current conveyor belt with the crystal enforcing the current trough the whole cascode to the tank/load. The output IS the resonator current. That is the very same structure as the proposals to extract to output "directly from the resonator, where it has the best SNR". Given the little bit of power that we can steal from the resonator: must we really split it between extraction amplifier and sustaining amplifier right at the location where the signal is weakest? When we can build an extraction amplifier that adds less noise than the sustaining amplifier, why don't we take the feedback also from there and cut out the sust.amp. and the signal power it requires? The Driscoll does that. regards, Gerhard, DK4XP (the loyal heretic :-) _______________________________________________ time-nuts mailing list -- email@example.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- firstname.lastname@example.org To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- email@example.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.