Hi Depending on construction of the resonator, an oscillator can have maximum sensitivities anywhere from 5x10^-8 / g to 5x10^-11 per G. Typical numbers for “good but not great” parts are in the 5x10^-10 to 2x10^-9 per G.
Since the sensitivity is *not* the same in every axis, a device with 2x10^-9 in (say) the X-Y axis might have a 1x10^-10 sensitivity in (say) the Z axis. In something like a rocket, your acceleration is likely to have a dominant axis. With characterization data on the individual oscillator, you might be able to reduce the impact by 10:1. So If the rocket continuously accelerates at 10,000 G’s, you will get a 20 ppm shift with typical sensitivity. If you do this for very long, you will also get into time dilation issues. (you hit 0.1C in < 2 minutes). If the oscillator has a 1 ppm / C temperature coefficient, a 20C change will give you the same (static) frequency shift. If you change temperature quickly (as you would in this case, you hit outer space in a few seconds) figure a 5 to 10X increase in that shift. Simply put - temperature will get you before acceleration does in terms of static shift. There are other things that will be a problem before either of these get in your way. Most tracking *assumes* good phase noise on the signal. Oddly enough rockets are not very quiet devices while accelerating. The same sensitivities that give you the issues from static acceleration give you phase noise under vibration. It is not at all unusual to see phase noise degradation of >60 db on physical small platforms doing high levels of acceleration. Bob > On Mar 28, 2015, at 8:25 AM, Peter Reilley <[email protected]> wrote: > > Some crystal oscillators specify their sensitivity to G forces. > Here is one: > http://www.abracon.com/Precisiontiming/AOCJYR-24.576MHz-M6069LF.pdf > > Available here: > http://www.digikey.com/product-detail/en/AOCJYR-24.576MHZ-M6069LF/535-12627- > 1-ND/4989033 > > Others specify shock and vibration limits but say nothing about > frequency stability. > > Pete. > > > -----Original Message----- > From: time-nuts [mailto:[email protected]] On Behalf Of Chris > Albertson > Sent: Friday, March 27, 2015 9:55 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Need advice for multilateration setup > > On Fri, Mar 27, 2015 at 10:29 AM, Chuck Harris <[email protected]> wrote: > >> The biggest problem I see is the crystal oscillator in the rocket is >> going to notice the G forces during acceleration in a pretty big way. > > > But all of the ground stations will see the same frequency shift on the > rocket's transmitter. I think this can be backed out in processing. > > Someone needs to write the equations and post them here. > -- > > Chris Albertson > Redondo Beach, California > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
