Hal Murray wrote:
The problem is modulation of the reference signal via relative
movement of the transformer guts.  While I understand there are ways
to 'harden' magnetic devices, my application is far too sensitive to
even consider a magnetic approach given the availability of
alternatives.  Any spurious signals present on the 10 MHz reference
will be increased by 56 dB by the phase-locked loop.
Capacitors are piezoelectric too.

Does anybodyhave any handy numbers for this sort of stuff?


Most high K ceramic caps are ferroelectric below the Curie temperature and paraelectic above that. The resultant capacitance nonlinearity can allow low frequency noise to phase modulate a capacitor coupled RF signal if the phase shift due to the capacitor is sufficiently large. Yet another reason to avoid high K ceramic capacitors or at least ensure that the RF phase shift due to such capacitors is sufficiently small.

Low frequency magnetic fields can phase modulate transformer coupled RF signals by modulating the transformer phase shift.

Bruce


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