http://www.leapsecond.com/pages/vp/sawtooth.htm

http://www.leapsecond.com/pages/vp/heater.htm

http://www.leapsecond.com/pages/m12/sawtooth.htm

Thanks for the info and the links! Bob ----- Original Message ----- From: <bg@lysator.liu.se> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Thursday, June 24, 2010 12:02 PM Subject: Re: [time-nuts] Substitute GPS in a Z3801A Hi Bob, Old GPS receivers had bad resolution with regard to when they could flipp the 1PPS signal. Think along these lines... you have a digital system, clock running at say 10MHz. You can only invoke the 1PPS at a clock edge, this gives you 100ns resolution. The receiver then needs to calculate GPS/UTC time and use the clock edge closest to its solution. With the current non SA GPS system the accuracy of the calculation is in the 10-30ns-ish region. This means the receiver internally have much better clock information than it have means to export via the 1PPS signal. It can however send its estimate on how wrong the 1PPS signal is via the serial port. Newer receivers have hardware with better 1PPS resolution - and better tracking/position etc. Tom probably has a much better explaination... http://www.leapsecond.com/pages/vp/sawtooth.htm http://www.leapsecond.com/pages/vp/heater.htm http://www.leapsecond.com/pages/m12/sawtooth.htm -- Björn > So there is no point in substituting another GPS RX? What is the > sawtooth > compensation is see mentioned? What about the antenna cable length > compensation? How much does that affect the AVAR? > > Bob > > > ----- Original Message ----- > From: "Steve Rooke" <sar10538@gmail.com> > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Sent: Thursday, June 24, 2010 11:11 AM > Subject: Re: [time-nuts] Substitute GPS in a Z3801A > > > Sorry to butt in on this thread but, although you need a number of > birds to get an accurate position, you really only need one to get > timing. If you have a six sat tracking receiver there should be enough > to give accurate time. You can always set the elevation to limit what > sats you can see so to screen out multipath reflections and it can > still track six birds. OK, my Z3805A is currently tracking 9 birds but > 3 of those are quite low horizon, although I really don't have > anything to cause multipath from where I'm situated. The minimum > number of sats I track is 4 and the max is 12 on a day, night cycle > and the average is about 6. > > Steve > > On 25 June 2010 02:01, Robert Benward <rbenward@verizon.net> wrote: >> Mike, >> Thanks for the info!. Does anyone know for sure if the timimg improves >> with more satellites tracked? I don't know how they derive the 1PPS, is >> it >> a blend or one satellite at a time? Maybe I will leave well enough >> alone. >> >> Bob >> >> >> >> ----- Original Message ----- From: "Mike S" <mikes@flatsurface.com> >> To: "Discussion of precise time and frequency measurement" >> <time-nuts@febo.com> >> Sent: Thursday, June 24, 2010 9:01 AM >> Subject: Re: [time-nuts] Substitute GPS in a Z3801A >> >> >>> At 10:48 PM 6/23/2010, Robert Benward wrote... >>>> >>>> Has anyone ever put another GPS in a Z3801A? Will the software >>>> accommodate >>>> another GPS that tracks say, 12 channels? >>> >>> Possibly 8 channels. You must use a Motorola Oncore VP. A 6 channel one >>> was what HP used. There are mixed reports on using an 8 channel VP - >>> some say it works fine, others say you must configure it in 6 channel >>> mode (but you do pick up improved reception). Whether the different >>> reports are due to changes in configuration or firmware of the z3801a, >>> the Oncore, or both - I have no idea. >>> >>> The commands/responses used by the z3801a prevent it from working >>> directly with newer GPS modules, like the GTs, UTs or M12s (even if you >>> adapted them physically). >>> >>> If you want to try and get better performance with a newer GPS >>> receiver, you should be able to leave the existing board in place, and >>> bypass the 1PPS input with the signal from the newer receiver. You'd >>> only get in trouble in exceptional conditions (new receiver loses sync, >>> but existing one is reporting good satellite lock, etc.). Of course, >>> the z3801a satellite reporting wouldn't be worth much. >>> >>> >>> _______________________________________________ >>> 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. >> >> >> -------------------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.829 / Virus Database: 271.1.1/2958 - Release Date: 06/23/10 >> 07:11:00 >> >> >> _______________________________________________ >> 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. >> > > > > -- > Steve Rooke - ZL3TUV & G8KVD > The only reason for time is so that everything doesn't happen at once. > - Einstein > > _______________________________________________ > 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. > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.829 / Virus Database: 271.1.1/2960 - Release Date: 06/24/10 > 02:35:00 > > > _______________________________________________ > 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. -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.829 / Virus Database: 271.1.1/2960 - Release Date: 06/24/10 02:35:00

http://www.leapsecond.com/pages/vp/sawtooth.htm

http://www.leapsecond.com/pages/vp/heater.htm

http://www.leapsecond.com/pages/m12/sawtooth.htm

Excellent explanation. Is it possible the phase shift is caused by the doppler of the satellite? And the instantaneous change of the ramp slope (on boundries) caused by the receiver changing the PPS tracking from one satellite to another? As the satellite passes overhead the spacing of the timing pulses will change, closely space on the horizon, far apart overhead. As the satellite drops below the horizon, the RX changes PPS tracking to a bird higher in the sky, accounting for the apparent change in phase slope. Approaching birds will slant the sawtooth one way, and departing birds will slant the other way. Does any of this sound plausible? Bob ----- Original Message ----- From: <bg@lysator.liu.se> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Thursday, June 24, 2010 12:02 PM Subject: Re: [time-nuts] Substitute GPS in a Z3801A Hi Bob, Old GPS receivers had bad resolution with regard to when they could flipp the 1PPS signal. Think along these lines... you have a digital system, clock running at say 10MHz. You can only invoke the 1PPS at a clock edge, this gives you 100ns resolution. The receiver then needs to calculate GPS/UTC time and use the clock edge closest to its solution. With the current non SA GPS system the accuracy of the calculation is in the 10-30ns-ish region. This means the receiver internally have much better clock information than it have means to export via the 1PPS signal. It can however send its estimate on how wrong the 1PPS signal is via the serial port. Newer receivers have hardware with better 1PPS resolution - and better tracking/position etc. Tom probably has a much better explaination... http://www.leapsecond.com/pages/vp/sawtooth.htm http://www.leapsecond.com/pages/vp/heater.htm http://www.leapsecond.com/pages/m12/sawtooth.htm -- Björn > So there is no point in substituting another GPS RX? What is the > sawtooth > compensation is see mentioned? What about the antenna cable length > compensation? How much does that affect the AVAR? > > Bob > > > ----- Original Message ----- > From: "Steve Rooke" <sar10538@gmail.com> > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Sent: Thursday, June 24, 2010 11:11 AM > Subject: Re: [time-nuts] Substitute GPS in a Z3801A > > > Sorry to butt in on this thread but, although you need a number of > birds to get an accurate position, you really only need one to get > timing. If you have a six sat tracking receiver there should be enough > to give accurate time. You can always set the elevation to limit what > sats you can see so to screen out multipath reflections and it can > still track six birds. OK, my Z3805A is currently tracking 9 birds but > 3 of those are quite low horizon, although I really don't have > anything to cause multipath from where I'm situated. The minimum > number of sats I track is 4 and the max is 12 on a day, night cycle > and the average is about 6. > > Steve > > On 25 June 2010 02:01, Robert Benward <rbenward@verizon.net> wrote: >> Mike, >> Thanks for the info!. Does anyone know for sure if the timimg improves >> with more satellites tracked? I don't know how they derive the 1PPS, is >> it >> a blend or one satellite at a time? Maybe I will leave well enough >> alone. >> >> Bob >> >> >> >> ----- Original Message ----- From: "Mike S" <mikes@flatsurface.com> >> To: "Discussion of precise time and frequency measurement" >> <time-nuts@febo.com> >> Sent: Thursday, June 24, 2010 9:01 AM >> Subject: Re: [time-nuts] Substitute GPS in a Z3801A >> >> >>> At 10:48 PM 6/23/2010, Robert Benward wrote... >>>> >>>> Has anyone ever put another GPS in a Z3801A? Will the software >>>> accommodate >>>> another GPS that tracks say, 12 channels? >>> >>> Possibly 8 channels. You must use a Motorola Oncore VP. A 6 channel one >>> was what HP used. There are mixed reports on using an 8 channel VP - >>> some say it works fine, others say you must configure it in 6 channel >>> mode (but you do pick up improved reception). Whether the different >>> reports are due to changes in configuration or firmware of the z3801a, >>> the Oncore, or both - I have no idea. >>> >>> The commands/responses used by the z3801a prevent it from working >>> directly with newer GPS modules, like the GTs, UTs or M12s (even if you >>> adapted them physically). >>> >>> If you want to try and get better performance with a newer GPS >>> receiver, you should be able to leave the existing board in place, and >>> bypass the 1PPS input with the signal from the newer receiver. You'd >>> only get in trouble in exceptional conditions (new receiver loses sync, >>> but existing one is reporting good satellite lock, etc.). Of course, >>> the z3801a satellite reporting wouldn't be worth much. >>> >>> >>> _______________________________________________ >>> 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. >> >> >> -------------------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.829 / Virus Database: 271.1.1/2958 - Release Date: 06/23/10 >> 07:11:00 >> >> >> _______________________________________________ >> 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. >> > > > > -- > Steve Rooke - ZL3TUV & G8KVD > The only reason for time is so that everything doesn't happen at once. > - Einstein > > _______________________________________________ > 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. > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.829 / Virus Database: 271.1.1/2960 - Release Date: 06/24/10 > 02:35:00 > > > _______________________________________________ > 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. -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.829 / Virus Database: 271.1.1/2960 - Release Date: 06/24/10 02:35:00

40 miles, from a high level comm site to/from my house at a very RF- quiet elevated location. Interference is very unlikely. Matthew Kaufman (Sent from my iPhone) On Jun 24, 2010, at 9:08 AM, "Robert Benward" <rbenward@verizon.net> wrote: > When you say you changed location, are we speaking of moving the > antenna to the other side of the roof, or across town? Sounds > suspciously like interference. > > Bob > > > ----- Original Message ----- From: "Matthew Kaufman" <matthew@matthew.at > > > To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com > > > Sent: Thursday, June 24, 2010 11:41 AM > Subject: Re: [time-nuts] Substitute GPS in a Z3801A > > >> I now have *two* Z3801A units which misbehave in the following way >> (which this thread reminded me of): >> >> The GPS status says it acquires quite a few (5-6) satellites with >> high >> signal strength... then after a minute or two, for no apparent >> reason, >> it loses *all* of them simultaneously but immediately goes back into >> "acquiring" for the ones it was seeing, and a few seconds later, >> they're >> all back. During this time, survey (if in progress) is halted and >> then >> restarts and runs for a bit before halting again when it loses >> everything briefly again. Then, within days, the unit ends up out of >> lock... if I go check it, I see it doing the same thing, and when the >> satellites are being received it is in "fine frequency adjust" >> mode, but >> so far off the 1pps phase that it really has no hope of re-locking >> before the next time it drops and then reacquires all the satellites. >> >> This is independent of antenna, location, and 48v power source... one >> unit apparently has been this way since I got it, the other worked >> fine >> for months and then developed this problem. >> >> Without knowing more, I'm thinking it might simply be a bad GPS >> receiver >> board, thus the idea of trying to find a replacement, perhaps one >> that >> is better at staying acquired, has crossed my mind. >> >> Matthew Kaufman >> >> _______________________________________________ >> 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. > > > --- > --- > --- > --- > -------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.829 / Virus Database: 271.1.1/2960 - Release Date: > 06/24/10 02:35:00 >

I believe I've found a difference between the faulty units and the working units... The faulty ones come up as 1/1/1997 when you do :SYSTEM:PRESET, the good ones come up as 1/1/1998. Does this difference ring any bells for anyone? Matthew Kaufman On 6/24/2010 8:41 AM, Matthew Kaufman wrote: > I now have *two* Z3801A units which misbehave in the following way > (which this thread reminded me of): > > The GPS status says it acquires quite a few (5-6) satellites with high > signal strength... then after a minute or two, for no apparent reason, > it loses *all* of them simultaneously but immediately goes back into > "acquiring" for the ones it was seeing, and a few seconds later, > they're all back. During this time, survey (if in progress) is halted > and then restarts and runs for a bit before halting again when it > loses everything briefly again. Then, within days, the unit ends up > out of lock... if I go check it, I see it doing the same thing, and > when the satellites are being received it is in "fine frequency > adjust" mode, but so far off the 1pps phase that it really has no hope > of re-locking before the next time it drops and then reacquires all > the satellites. > > This is independent of antenna, location, and 48v power source... one > unit apparently has been this way since I got it, the other worked > fine for months and then developed this problem. > > Without knowing more, I'm thinking it might simply be a bad GPS > receiver board, thus the idea of trying to find a replacement, perhaps > one that is better at staying acquired, has crossed my mind. > > Matthew Kaufman > > _______________________________________________ > 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.

I seem to remember a rollover about then that obsoleted older gps units. On Sun, Aug 29, 2010 at 5:40 PM, Matthew Kaufman <matthew@matthew.at> wrote: > I believe I've found a difference between the faulty units and the working > units... The faulty ones come up as 1/1/1997 when you do :SYSTEM:PRESET, the > good ones come up as 1/1/1998. Does this difference ring any bells for > anyone? > > Matthew Kaufman > > On 6/24/2010 8:41 AM, Matthew Kaufman wrote: > >> I now have *two* Z3801A units which misbehave in the following way (which >> this thread reminded me of): >> >> The GPS status says it acquires quite a few (5-6) satellites with high >> signal strength... then after a minute or two, for no apparent reason, it >> loses *all* of them simultaneously but immediately goes back into >> "acquiring" for the ones it was seeing, and a few seconds later, they're all >> back. During this time, survey (if in progress) is halted and then restarts >> and runs for a bit before halting again when it loses everything briefly >> again. Then, within days, the unit ends up out of lock... if I go check it, >> I see it doing the same thing, and when the satellites are being received it >> is in "fine frequency adjust" mode, but so far off the 1pps phase that it >> really has no hope of re-locking before the next time it drops and then >> reacquires all the satellites. >> >> This is independent of antenna, location, and 48v power source... one unit >> apparently has been this way since I got it, the other worked fine for >> months and then developed this problem. >> >> Without knowing more, I'm thinking it might simply be a bad GPS receiver >> board, thus the idea of trying to find a replacement, perhaps one that is >> better at staying acquired, has crossed my mind. >> >> Matthew Kaufman >> >> _______________________________________________ >> 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. >

would that have shown up in a firmware version id change? try *IDN? and see if there is any correlation Matthew. Le 30/08/2010 03:23, paul swed a écrit : > I seem to remember a rollover about then that obsoleted older gps units. > > On Sun, Aug 29, 2010 at 5:40 PM, Matthew Kaufman<matthew@matthew.at> wrote: > >> I believe I've found a difference between the faulty units and the working >> units... The faulty ones come up as 1/1/1997 when you do :SYSTEM:PRESET, the >> good ones come up as 1/1/1998. Does this difference ring any bells for >> anyone? >> >> Matthew Kaufman >> >> On 6/24/2010 8:41 AM, Matthew Kaufman wrote: >> >>> I now have *two* Z3801A units which misbehave in the following way (which >>> this thread reminded me of): >>> >>> The GPS status says it acquires quite a few (5-6) satellites with high >>> signal strength... then after a minute or two, for no apparent reason, it >>> loses *all* of them simultaneously but immediately goes back into >>> "acquiring" for the ones it was seeing, and a few seconds later, they're all >>> back. During this time, survey (if in progress) is halted and then restarts >>> and runs for a bit before halting again when it loses everything briefly >>> again. Then, within days, the unit ends up out of lock... if I go check it, >>> I see it doing the same thing, and when the satellites are being received it >>> is in "fine frequency adjust" mode, but so far off the 1pps phase that it >>> really has no hope of re-locking before the next time it drops and then >>> reacquires all the satellites. >>> >>> This is independent of antenna, location, and 48v power source... one unit >>> apparently has been this way since I got it, the other worked fine for >>> months and then developed this problem. >>> >>> Without knowing more, I'm thinking it might simply be a bad GPS receiver >>> board, thus the idea of trying to find a replacement, perhaps one that is >>> better at staying acquired, has crossed my mind. >>> >>> Matthew Kaufman >>> >>> _______________________________________________ >>> 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. > > >