Re: Phase or frequency modulation?

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
 
 

... The crystal mode is a mass-spring
oscillation, so an instantaneous change in the spring constant causes an
instantaneous change of frequency.
 
There’s no need for the resonant energy to die out, unlike the case of
external forcing, where a change in the forcing frequency takes on the
order of Q cycles to change the response.

 
Could I ask you to explain this a bit more please.  Where is the
'spring' that is variable?
 
 

 
The spring is the mechanical stiffness of the quartz, plus the
piezoelectric force caused by the interaction with the external circuit.
The mass is the mass. ;)
 
Dorking the load capacitance slows down or speeds up the piezo restoring
force.

Interesting, I hadn't come across that before.  Presumably the effect
would be the same if the controlling reactance were an inductor or a
tuned circuit?  In my case, the 'variable reactance' is an
amplitude-modulated 90-degree phase-shifted current injected into the
controlling inductor.


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~ Liz Tuddenham ~
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