Hi The purpose here is to estimate the stability of a GPSDO. For that, you don't need "perfect". You simply need to get the Rb close enough that it's error is manageable.
Bob On Sep 18, 2013, at 8:18 PM, Azelio Boriani <[email protected]> wrote: > The GPS's PPS wanders but it can be used to have an idea whether your > Rb is fast or slow. How much the wander will be, depends on the type > of GPS receiver, the antenna position and the survey, the GPS clock > granularity (the sawtooth). Given a suitable amount of time (5 > minutes, for example) you can see if the Rb PPS is fast or slow. I > have measured up to 200nS of PPS peak-to-peak wander using a Z3815A as > a reference. > > On Thu, Sep 19, 2013 at 1:37 AM, Bob Stewart <[email protected]> wrote: >> Hi John and Azelio, >> >> The problem with the GPS 1PPS is the +/- 52ns sawtooth. Without some magic >> hardware, you're left with using a stable 1PPS and then calibrating that to >> the correct frequency. If my software does what my math says it does, then >> my OCXO is very close to correct. Testing is time consuming to say the >> least. >> >> Bob >> >> >> >> >> >>> ________________________________ >>> From: "John C. Westmoreland, P.E." <[email protected]> >>> To: Discussion of precise time and frequency measurement >>> <[email protected]> >>> Sent: Wednesday, September 18, 2013 6:13 PM >>> Subject: Re: [time-nuts] GPSDO vs Rb standard >>> >>> >>> Azelio and Fellow Time Nuts, >>> >>> Isn't the GPS 1PPS signal supposed to be 'precise' to within what error? I >>> imagine this is in the specs of the specific receiver - >>> but I was wondering if some of you have actually measured what that is - >>> and could report the numbers that you have found. >>> >>> Thanks! >>> John Westmoreland >>> >>> >>> >>> On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani >>> <[email protected]>wrote: >>> >>>> Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you >>>> will find out that the Rb is slow... you can also check the Rb's PPS >>>> against the GPS's PPS. >>>> >>>> On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart <[email protected]> wrote: >>>>> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz >>>>> GPSDO to Channel A, .05us trace, and turned the lights out so I could >>>>> see it. The 10MHz is marching right to left about 1 cycle every 20 >>>>> seconds. So, can I say that the Rb considers my GPSDO to be too fast by >>>> about 5ppb? >>>>> >>>>> >>>>> Bob >>>>> _______________________________________________ >>>>> 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. >>> >>> >>> >> _______________________________________________ >> 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.
