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

Hi One cycle of 10 MHz would be 100 ns. 100 ns per second would be 100 ppb. 100ns per 20 seconds would indeed be 5 ppb. Since the Rb is *stable* but not *accurate*, the real question is - how much does the 5 ppb change by? The Rb can't tell you if the GPSDO is correct. The best it can do is tell you if it changed. If you can demonstrate that the GPSDO is locked up, and that it's stable for many days, you can reasonably conclude that the GPSDO is accurate. I'd say the first step is to get the Rb tuned closer to the GPSDO. You should be looking for < 0.01 ppb changes. That's going to be tough with a 5 ppb offset. Bob On Sep 18, 2013, at 5:47 PM, Bob Stewart <bob@evoria.net> 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 -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

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 <bob@evoria.net> 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 -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

Hi Bob, As always, thanks for your informed help.  I had been reaching the same conclusion, but needed unbiased confirmation.  I think the RUBY4 software does what I want?  I'll look into it. Bob >________________________________ > From: Bob Camp <lists@rtty.us> >To: Discussion of precise time and frequency measurement <time-nuts@febo.com> >Sent: Wednesday, September 18, 2013 5:01 PM >Subject: Re: [time-nuts] GPSDO vs Rb standard > > >Hi > >One cycle of 10 MHz would be 100 ns. 100 ns per second would be 100 ppb. 100ns per 20 seconds would indeed be 5 ppb. > >Since the Rb is *stable* but not *accurate*, the real question is - how much does the 5 ppb change by? The Rb can't tell you if the GPSDO is correct. The best it can do is tell you if it changed. If you can demonstrate that the GPSDO is locked up, and that it's stable for many days, you can reasonably conclude that the GPSDO is accurate. > >I'd say the first step is to get the Rb tuned closer to the GPSDO. You should be looking for < 0.01 ppb changes. That's going to be tough with a 5 ppb offset. > >Bob > >On Sep 18, 2013, at 5:47 PM, Bob Stewart <bob@evoria.net> 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 -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. > > >

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 <azelio.boriani@screen.it>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 <bob@evoria.net> 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 -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

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." <john@westmorelandengineering.com> >To: Discussion of precise time and frequency measurement <time-nuts@febo.com> >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 <azelio.boriani@screen.it>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 <bob@evoria.net> 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 -- time-nuts@febo.com >> > To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. > > >

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 <bob@evoria.net> 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." <john@westmorelandengineering.com> >>To: Discussion of precise time and frequency measurement <time-nuts@febo.com> >>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 <azelio.boriani@screen.it>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 <bob@evoria.net> 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 -- time-nuts@febo.com >>> > To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> > and follow the instructions there. >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>_______________________________________________ >>time-nuts mailing list -- time-nuts@febo.com >>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>and follow the instructions there. >> >> >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

Hi The Rb's have a couple of issues: 1) Its been years since they were set on frequency and they do have a yearly drift rate 2) They have a temperature coefficient of drift that may be fairly large (0.1 ppb over -30 to +70) 3) They self heat quite a bit, so they do move temperature / need a heatsink The solution to the temperature issue is a servo controlled fan. The solution to the first drift / accuracy issue is to calibrate them against something else. Bob On Sep 18, 2013, at 7:13 PM, "John C. Westmoreland, P.E." <john@westmorelandengineering.com> wrote: > 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 <azelio.boriani@screen.it>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 <bob@evoria.net> 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 -- time-nuts@febo.com >>> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

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 <azelio.boriani@screen.it> 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 <bob@evoria.net> 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." <john@westmorelandengineering.com> >>> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> >>> 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 <azelio.boriani@screen.it>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 <bob@evoria.net> 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 -- time-nuts@febo.com >>>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >>> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

Hi When I want to tune an Rb, I just hook up to it with a terminal program and hack away at it. There's not a lot to the protocol. Bob On Sep 18, 2013, at 6:49 PM, Bob Stewart <bob@evoria.net> wrote: > Hi Bob, > > As always, thanks for your informed help. I had been reaching the same conclusion, but needed unbiased confirmation. I think the RUBY4 software does what I want? I'll look into it. > > Bob > > > > > >> ________________________________ >> From: Bob Camp <lists@rtty.us> >> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> >> Sent: Wednesday, September 18, 2013 5:01 PM >> Subject: Re: [time-nuts] GPSDO vs Rb standard >> >> >> Hi >> >> One cycle of 10 MHz would be 100 ns. 100 ns per second would be 100 ppb. 100ns per 20 seconds would indeed be 5 ppb. >> >> Since the Rb is *stable* but not *accurate*, the real question is - how much does the 5 ppb change by? The Rb can't tell you if the GPSDO is correct. The best it can do is tell you if it changed. If you can demonstrate that the GPSDO is locked up, and that it's stable for many days, you can reasonably conclude that the GPSDO is accurate. >> >> I'd say the first step is to get the Rb tuned closer to the GPSDO. You should be looking for < 0.01 ppb changes. That's going to be tough with a 5 ppb offset. >> >> Bob >> >> On Sep 18, 2013, at 5:47 PM, Bob Stewart <bob@evoria.net> 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 -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.