Jerry wrote:
I don't understand why when there is already a clean crystal current in the circuit, someone wouldn't want to take advantage of that signal and use that rather than add filters and poor biasing to the mix to claim that something can be done when we are talking about ideal situations where the lowest phase noise is desired.
It was I who originally described the "high harmonic" oscillator, so I'll respond. I didn't suggest that you'd *want* to do that. You said you couldn't even imagine how one would build an oscillator with high harmonics, and I detailed one way. And while it's not the most promising way to design a low-PN oscillator, it *is* a design that has been used in many commercially produced oscillators over the years.
And there are reasons for using at least some features of the design -- it is very robust over changes in component values and characteristics, so the designer can be confident that thousands can be made and they will all oscillate and have a predictable output amplitude. This is not always the case with low-distortion designs that have very little excess gain. Remember, while time-nuts and hams can select components and tweak every oscillator they make individually, manufacturers who are turning them out in quantity for sale at a reasonable price have more limited options. Finally, it is not always convenient to tap the resonator current directly, and where it is possible the need to avoid loading the resonator may compromise noise performance.
So -- I was not suggesting that the architecture I described is the best way (or even a good way) to make a low-PN oscillator, but there are reasons why it has, nevertheless, been used by the designers of many commercial products.
Best regards, Charles _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
