In article , Avery Fineman
writes
In article , Paul Burridge
writes:

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?
Len Anderson
retired (from regular hours) electronic engineer person

Earned a good living designing (fairly) reliable crystal oscillators for
many years.
The enemy is excess gain or not enough gain.
For non series res designs like Coulpitts/Pierce I always establish a
negative resistance across the crystal that is 3X the max specified
crystal ESR.
See Telequarz app note now Corning)
Or read my orig? Wireless World paper (1968)

For overtones use the resistor substitute method (one or two transistor
Butler) and ensure again that the osc will go with 3X the ESR.
Note the phase shift osc can be converted to series by adding sufficient
L in series with the crystal to establish zero phase.

Higher overtone may need the crystal C0 tuning out.






--
ddwyer