Paul Burridge wrote:
One thing bugs me about building oscillators and that's the
possibility that they may not start in the first place, or else start
fine then somewhere down the line just flip into an overtone or
sub-harmonic for no apparent reason. If only one could physically prod
the circuit around to induce instability but of course that's unlikely
to show up any potential problem. What's needed is some method of
instigating instability to try to show up any latent tendency for any
particular osc to go tits-up and I can only think of one practical way
of precipitating it: varying the power supply voltage.
If one can vary the supply over a fairly wide range and the oscillator
only responds by very small changes in output frequency and doesn't
jerk into another frequency/output mode altogether, is this a
sufficient test on its own of that oscillator's likely stability in
the field?
p.

I don't know, but if you know the frequency of the overtones, try
injecting that frequency. Use a really strong signal so that it
dominates, then switch it off and see if your oscillator snaps back
to the correct frequency.

--
local optimization seldom leads to global optimization

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