Re: [time-nuts] GPSDO vs Rb standard
Understood. If I do anything, it will probably be to cut pins 8 and 9 at the board side of the connector and route the serial connections there. I dislike opening this thing up any more often than I have to. Thanks for all the info. Bob > > From: Bob Camp >To: Discussion of precise time and frequency measurement >Sent: Friday, September 20, 2013 5:34 PM >Subject: Re: [time-nuts] GPSDO vs Rb standard > > >Hi > >All of my FE Rb's have serial out of a 9 pin D connector. They bring power >(+15 and +5) in on that connector, and put 1 pps and 10 MHz out on the same 9 >pin D. > >There are (apparently) dozens of variations of the FE 5680. There is no single >standard for what is hooked up where. I'd be *very* careful about playing with >wires I had not either traced out or had data from the seller on. It's *very* >easy to blow one of these beasts up. > >On mine serial is normal RS-232 levels on pins 8(rx) and 9(tx). 15 V power is >on pin 1, ground on pins 2 and 5, +5 power is on pin 4. > >Outputs are on 6 (pps), 7 (10 Mhz), 3 (lock). > >Again - I'd be *very* careful with information that may or may not apply to >your specific Rb. > >Bob > > >On Sep 20, 2013, at 5:25 PM, Bob Stewart wrote: > >> Bob, >> >> >> Does your Rb send the serial out on the DB-9, or did you solder in a >> connection? I'm looking at mine and it looks like pin 8 is connected to >> something and pin 9 seems to come in to an empty SMT slot for a cap or >> resistor. I was thinking of bringing a ribbon cable out between the covers >> above the DB-9, but maybe I should just take over 2 pins on the DB-9? Any >> ideas what the pins 8 and 9 would have been hooked up to if they don't go to >> the serial input? >> >> >> Bob >> >> >> >> >>> >>> From: Bob Camp >>> To: Discussion of precise time and frequency measurement >>> >>> Sent: Wednesday, September 18, 2013 7:25 PM >>> Subject: Re: [time-nuts] GPSDO vs Rb standard >>> >>> >>> 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 >>> >>> >> ___ >> 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.
Re: [time-nuts] GPSDO vs Rb standard
Hi All of my FE Rb's have serial out of a 9 pin D connector. They bring power (+15 and +5) in on that connector, and put 1 pps and 10 MHz out on the same 9 pin D. There are (apparently) dozens of variations of the FE 5680. There is no single standard for what is hooked up where. I'd be *very* careful about playing with wires I had not either traced out or had data from the seller on. It's *very* easy to blow one of these beasts up. On mine serial is normal RS-232 levels on pins 8(rx) and 9(tx). 15 V power is on pin 1, ground on pins 2 and 5, +5 power is on pin 4. Outputs are on 6 (pps), 7 (10 Mhz), 3 (lock). Again - I'd be *very* careful with information that may or may not apply to your specific Rb. Bob On Sep 20, 2013, at 5:25 PM, Bob Stewart wrote: > Bob, > > > Does your Rb send the serial out on the DB-9, or did you solder in a > connection? I'm looking at mine and it looks like pin 8 is connected to > something and pin 9 seems to come in to an empty SMT slot for a cap or > resistor. I was thinking of bringing a ribbon cable out between the covers > above the DB-9, but maybe I should just take over 2 pins on the DB-9? Any > ideas what the pins 8 and 9 would have been hooked up to if they don't go to > the serial input? > > > Bob > > > > >> >> From: Bob Camp >> To: Discussion of precise time and frequency measurement >> >> Sent: Wednesday, September 18, 2013 7:25 PM >> Subject: Re: [time-nuts] GPSDO vs Rb standard >> >> >> 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 >> >> > ___ > 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.
Re: [time-nuts] GPSDO vs Rb standard
Bob, Does your Rb send the serial out on the DB-9, or did you solder in a connection? I'm looking at mine and it looks like pin 8 is connected to something and pin 9 seems to come in to an empty SMT slot for a cap or resistor. I was thinking of bringing a ribbon cable out between the covers above the DB-9, but maybe I should just take over 2 pins on the DB-9? Any ideas what the pins 8 and 9 would have been hooked up to if they don't go to the serial input? Bob > > From: Bob Camp >To: Discussion of precise time and frequency measurement >Sent: Wednesday, September 18, 2013 7:25 PM >Subject: Re: [time-nuts] GPSDO vs Rb standard > > >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 > > ___ 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.
Re: [time-nuts] GPSDO vs Rb standard
Hi Some numbers: Your Rb should hold <10 ppt per month. It's 1 second ADEV should be about 10 ppt as well. (makes it interesting to measure). Your Rb should hold < 1 ppt per degree C on average. It will have a nasty glitch (around 1 ppt as it steps over a temperature boundary). Best to keep it stable to < 0.5 C. For long(er) averaging times the Rb should have an ADEV that goes as the square root of tau. It'll be 10X better at 100 seconds than at 1 second. It *could* be 100X better at 10,000 seconds except for that glitch. It's not going to get beyond 0.2 ppt ADEV without some major help. All that said, with simple temperature stabilization, it should let you check out your GPSDO for drift. Within the ADEV imposed limits it'll tell you if things are holding together on a day to day / week to week basis. Bob On Sep 18, 2013, at 8:32 PM, Bob Stewart wrote: > Bob, I've been mulling over the question of a case, and I was thinking of > getting a 2M brick amp and putting it inside, bolted upside down to the heat > sink. Good idea? Anybody got a busted one? > > Bob > > > > > >> >> From: Bob Camp >> To: Discussion of precise time and frequency measurement >> >> Sent: Wednesday, September 18, 2013 7:22 PM >> Subject: Re: [time-nuts] GPSDO vs Rb standard >> >> >> 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." >> 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 >>> 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 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. ___ 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.
Re: [time-nuts] GPSDO vs Rb standard
Hi There are lots of case solutions. A busted piece of HP gear is a nice way to come up with a case. Heatsink material is available from several web sites cut to order quite cheap. A simple computer fan is way more air than you will ever need. The obvious missing link is the controller. I'd run something up with a micro talking to a 4 wire fan header. That way you have tach feedback on the fan and all the PWM stuff is driven on the fan end. More or less a weekend project on a piece of pert board. Maybe a bit more than that if you do a pc board. (yes I realize this heading horribly close to talking about building things …. alarm bells are ringing somewhere…..) Bob On Sep 18, 2013, at 8:32 PM, Bob Stewart wrote: > Bob, I've been mulling over the question of a case, and I was thinking of > getting a 2M brick amp and putting it inside, bolted upside down to the heat > sink. Good idea? Anybody got a busted one? > > Bob > > > > > >> >> From: Bob Camp >> To: Discussion of precise time and frequency measurement >> >> Sent: Wednesday, September 18, 2013 7:22 PM >> Subject: Re: [time-nuts] GPSDO vs Rb standard >> >> >> 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." >> 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 >>> 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 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. ___ 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.
Re: [time-nuts] GPSDO vs Rb standard
Bob, I've been mulling over the question of a case, and I was thinking of getting a 2M brick amp and putting it inside, bolted upside down to the heat sink. Good idea? Anybody got a busted one? Bob > > From: Bob Camp >To: Discussion of precise time and frequency measurement >Sent: Wednesday, September 18, 2013 7:22 PM >Subject: Re: [time-nuts] GPSDO vs Rb standard > > >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." > 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 >> 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 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.
Re: [time-nuts] GPSDO vs Rb standard
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 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 >> To: Discussion of precise time and frequency measurement >> >> 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 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.
Re: [time-nuts] GPSDO vs Rb standard
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 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 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." >>> To: Discussion of precise time and frequency measurement >>> >>> 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 >>> 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 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. ___ 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.
Re: [time-nuts] GPSDO vs Rb standard
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." 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 > 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 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.
Re: [time-nuts] GPSDO vs Rb standard
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 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." >>To: Discussion of precise time and frequency measurement >>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 >>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 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.
Re: [time-nuts] GPSDO vs Rb standard
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." >To: Discussion of precise time and frequency measurement >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 >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 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.
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 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 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.
Re: [time-nuts] GPSDO vs Rb standard
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 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.
Re: [time-nuts] GPSDO vs Rb standard
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 >To: Discussion of precise time and frequency measurement >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 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.
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 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.
