[time-nuts] Vibration isolation of quartz oscillators

[Bob kb8tq]

Hi

Accelerometer compensation of OCXO’s is indeed possible. There are parts out there
that will do the job. Phase shift is your enemy in this case. You are trying to get two AC
signals to sum to zero. Fairly small phase shifts will limit the “floor” of a process like this. 
Mounting the accelerometer *very* close to the blank is the key. In a large package part
like the 8700 series / working from the outside …. yikes ….. Your “max frequency” is going
to be mighty low. Forget about taking care of fan blade noise ….

Bob

> On Jun 27, 2020, at 10:29 AM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
> 
> If compactness is needed and you're operating in anything like a 1 g field,
> I think that
> it will be impossible to do a spring suspension that is both compact and
> effective
> down to the milli-Hz level (or less).
> 
> It might be worthwhile doing a compensation scheme based on a 3-axis
> accelerometer
> (one should suffice for multiple oscillators) whose outputs are scaled and
> combined
> to form a single signal (per oscillator) to be summed into the EFC input.
> 
> But some strong caveats immediately come to mind:
> 1. Noise in the accelerometers' outputs.
> 2. Dealing with the inevitable tuning nonlinearity of the oscillators.
> 3. Calibrating the compensation system well enough to satisfy.
> 
> Good luck.
> 
> Dana
> 
> 
> On Sat, Jun 27, 2020 at 7:38 AM Michael Wouters <michaeljwouters at gmail.com>
> wrote:
> 
>> I have three Oscilloquartz 8607-Bs that I'm rehousing.
>> 
>> In their former life they were part of the frequency synthesis chains
>> for H-masers and they hung vertically from a rubber suspension that was
>> presumably intended to provide vibration isolation. Unfortunately, the
>> person responsible for this has long since retired so is no longer
>> around to ask questions of.
>> 
>> In the experiment I will be averaging over  100 s, which suggests to
>> me that very low frequencies are what I need to filter out (if at
>> all), and I am skeptical that the rubber will do this. Space is tight
>> so I am wondering
>> whether I should simply ditch the isolation.
>> 
>> What do other people do with their quartzes ? I thought I should ask
>> for some advice before attempting measurements.
>> 
>> Cheers
>> Michael
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.