[time-nuts] Broken Ovenaire OSC 85-50

[Bruce Griffiths]

Pascal Nguyen wrote:
> Hi Joe
>
> Please open the link below
>
> http://www.airlab.com.au/nuts/joe_1.htm
>
> for an update of a simulated fault from an out of tune of the narrow band
> pass filter
>
> Kind regards
>
> Pascal Nguyen
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>   
Pascal

On a closer look your simulation has very little value at all.
If one is using an AC analysis its far more informative to open the
feedback loop an inject a signal to measure the loop gain and phase.
One then has sufficient information to determine if the oscillator has
sufficient gain and an aprpriate phase shift for oscillation to occur at
a given frequency.
Your analysis injects an external signal whilst leaving the oscillator
feedback loop closed - not helpful or particularly useful at all.

If one wishes to simulate the actual output amplitude, then no extra
source is required with a good simulator the oscillator will oscillate
and limit.
With the relatively low Q for the the crystal you have assumed the
oscillator will start and limit within a reasonable time without
problems as long as you dont use to short a minimum time step.

You have also assumed a fundamental crystal, an overtone crystal with a
somewaht higher ESR than 7 ohms is far more likely to have been used,
but without measuring the actual crystal one cannot be certain.

Bruce