[time-nuts] Designing and building an OCXO and GPSDO

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Aug 13 00:01:42 EDT 2008

SAIDJACK at aol.com wrote:
>    Hi Bruce,
>    do you have any phase noise/stability measurements for these circuits?
>    thanks,
>    Said
No, I have no way of measuring phase noise at present.
Nor can I yet measure ADEV with adequate sensitivity and stability.

However the phase noise floor can be estimated to within a few dB.
Its even possible with some effort to estimate the phase noise of the 
buffer amplifiers in the flicker region.
If low phase noise buffer designs are used the phase noise floor depends 
(for a CB input stage) on the buffer equivalent input current noise and 
the crystal current.
With sufficient crystal current the phase noise floor can be very low 

A phase noise measurement system would be useful for optimising the 
close in phase noise.

The circuits are intended to be somewhat better than a gate oscillator 
but without the complexity involved when AGC is used.
The original request design was intended for a fundamental mode oven 
crystal the drift of which is unlikely to be very low.
Nor will the Q of such a crystal be particularly high.

With an overtone crystal a means of suppressing oscillation at unwanted 
overtones is required.


More information about the time-nuts mailing list