Re: [time-nuts] Trimble Resolution SMT GG weirdness
dginsb...@gmail.com said: > First, the frequency offset of the microcontroller. I use a built-in > counting timer in the uC which runs at 84MHz to measure the duration between > 2 PPS. What I get is ~84008000 timer ticks between two pulses, which > corresponds to about 95ppm offset. While the crystal on the board is of the > cheapest variety, I think 95ppm is just too much. Is that correct, and 95ppm > offset even for a the most crappy oscillator is not a reasonable value? It isn't totally unreasonable. Yes, 95 PPM is the high end of even cheap crystals, but it could easily be a design error. The capacitive loading of the circuit might not match the specs on the crystal. There is also the possibility of a software bug. OSes have a long history of not getting that quite right. They are usually close enough so that nobody cares unless some geek starts monitoring the details. -- These are my opinions. I hate spam. ___ 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] Trimble Resolution SMT GG weirdness
I agree with Hal and if you have a reference you can tell how much the crystal is off. My timing GPS receiver after 1 hour has a total uncorrected wander of 112ns. Never seen 400ns on a timing receiver (maybe I haven't waited long enough). On Tue, Apr 23, 2013 at 12:49 AM, Azelio Boriani wrote: > Have you any reference? A TBolt, Z3801 or similar? > > > On Mon, Apr 22, 2013 at 9:53 PM, Daniel Ginsburg wrote: > >> Hi all, >> >> I have bought a Resolution SMT GG for me to play with, and build a very >> simple breakout board. >> >> The receiver appears to be working (in a sense). That is, it powers up, >> it emits valid TSIP, it was able to survey it's position - a sane one. >> Trimble GPS Studio is able to recognize it, and extract validly looking >> data from it. In other words, I don't believe I have botched the module >> while hand-soldering it. >> >> Now I have hooked it up to a stm32f4discovery board to sync with PPS. >> That's were the weirdness begins. >> >> First, the frequency offset of the microcontroller. I use a built-in >> counting timer in the uC which runs at 84MHz to measure the duration >> between 2 PPS. What I get is ~84008000 timer ticks between two pulses, >> which corresponds to about 95ppm offset. While the crystal on the board is >> of the cheapest variety, I think 95ppm is just too much. Is that correct, >> and 95ppm offset even for a the most crappy oscillator is not a reasonable >> value? >> >> Second, the GPS sawtooth. The PPS does exhibit sawtooth, which is >> expected. But the sawtooth is HUGE. While the spec claims +-15ns, I see >> more that +-400ns with period about 30 seconds. This is not sane. I must >> have done something totally wrong. >> >> Something has to be terribly wrong with my measurements. I'd really >> appreciate any hints on how to find out the cause of the described >> weirdness. >> ___ >> 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] Trimble Resolution SMT GG weirdness
On 4/22/13 3:15 PM, Hal Murray wrote: dginsb...@gmail.com said: First, the frequency offset of the microcontroller. I use a built-in counting timer in the uC which runs at 84MHz to measure the duration between 2 PPS. What I get is ~84008000 timer ticks between two pulses, which corresponds to about 95ppm offset. While the crystal on the board is of the cheapest variety, I think 95ppm is just too much. Is that correct, and 95ppm offset even for a the most crappy oscillator is not a reasonable value? It isn't totally unreasonable. Yes, 95 PPM is the high end of even cheap crystals, but it could easily be a design error. The capacitive loading of the circuit might not match the specs on the crystal. There is also the possibility of a software bug. OSes have a long history of not getting that quite right. They are usually close enough so that nobody cares unless some geek starts monitoring the details. Assuming the software is reading some hardware counter when it gets the pulse, there could be variable latency in the routine. 8000 ticks is a lot of instructions though.. If you read, say, 100 intervals, what does the distribution look like? is it always the same number (crystal is too high in frequency), or does it vary (software might be an issue) ___ 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] Trimble Resolution SMT GG weirdness
Have you any reference? A TBolt, Z3801 or similar? On Mon, Apr 22, 2013 at 9:53 PM, Daniel Ginsburg wrote: > Hi all, > > I have bought a Resolution SMT GG for me to play with, and build a very > simple breakout board. > > The receiver appears to be working (in a sense). That is, it powers up, it > emits valid TSIP, it was able to survey it's position - a sane one. Trimble > GPS Studio is able to recognize it, and extract validly looking data from > it. In other words, I don't believe I have botched the module while > hand-soldering it. > > Now I have hooked it up to a stm32f4discovery board to sync with PPS. > That's were the weirdness begins. > > First, the frequency offset of the microcontroller. I use a built-in > counting timer in the uC which runs at 84MHz to measure the duration > between 2 PPS. What I get is ~84008000 timer ticks between two pulses, > which corresponds to about 95ppm offset. While the crystal on the board is > of the cheapest variety, I think 95ppm is just too much. Is that correct, > and 95ppm offset even for a the most crappy oscillator is not a reasonable > value? > > Second, the GPS sawtooth. The PPS does exhibit sawtooth, which is > expected. But the sawtooth is HUGE. While the spec claims +-15ns, I see > more that +-400ns with period about 30 seconds. This is not sane. I must > have done something totally wrong. > > Something has to be terribly wrong with my measurements. I'd really > appreciate any hints on how to find out the cause of the described > weirdness. > ___ > 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] Trimble Resolution SMT GG weirdness
On 23.04.2013, at 3:02, Jim Lux wrote: > > Assuming the software is reading some hardware counter when it gets the > pulse, there could be variable latency in the routine. 8000 ticks is a lot > of instructions though.. The hw timer latches the counter value to a separate register when the leading edge of PPS arrives, and raises an interrupt. The ISR simply reads the latched value and subtracts the previous value to get the duration. So interrupt latency shouldn't be an issue. > > If you read, say, 100 intervals, what does the distribution look like? > is it always the same number (crystal is too high in frequency), or does it > vary (software might be an issue) These are 100 intervals, you can see them going steadily up and then down, and up again. A sawtooth of gigantic proportions. 84007993 84008000 84008001 84008004 84008005 84008007 84008010 84008012 84008014 84008017 84008018 84008021 84008025 84008026 84008030 84008031 84008036 84008037 84008038 84008042 84008045 84008046 84008049 84008051 84008053 84008054 84008058 84008059 84008061 84008064 84008067 84008069 84008071 84008038 84007998 84008001 84008005 84008005 84008009 84008010 84008013 84008015 84008018 84008018 84008023 84008024 84008025 84008029 84008032 84008034 84008036 84008037 84008043 84008044 84008046 84008048 84008051 84008054 84008056 84008058 84008059 84008061 84008064 84008068 84008069 84008067 84007993 84008000 84008001 84008004 84008008 84008009 84008012 84008014 84008016 84008019 84008021 84008022 84008025 84008026 84008030 84008030 84008035 84008036 84008039 84008041 84008045 84008046 84008048 84008051 84008054 84008055 84008058 84008060 84008062 84008062 84008067 84008068 84008068 84007993 ___ 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] Trimble Resolution SMT GG weirdness
On 23.04.2013, at 2:57, Azelio Boriani wrote: > I agree with Hal and if you have a reference you can tell how much the > crystal is off. My timing GPS receiver after 1 hour has a total uncorrected > wander of 112ns. Never seen 400ns on a timing receiver (maybe I haven't > waited long enough). > No other reference except the PPS from the module I'm playing with, unfortunately. I wonder, what kind of timing GPS gives 112ns wander? Is it when locked to the signal? If yes, what are the other conditions? If you know what happens to your receiver it might give a clue to what goes on in mine. > > On Tue, Apr 23, 2013 at 12:49 AM, Azelio Boriani > wrote: > >> Have you any reference? A TBolt, Z3801 or similar? >> >> >> On Mon, Apr 22, 2013 at 9:53 PM, Daniel Ginsburg wrote: >> >>> Hi all, >>> >>> I have bought a Resolution SMT GG for me to play with, and build a very >>> simple breakout board. >>> >>> The receiver appears to be working (in a sense). That is, it powers up, >>> it emits valid TSIP, it was able to survey it's position - a sane one. >>> Trimble GPS Studio is able to recognize it, and extract validly looking >>> data from it. In other words, I don't believe I have botched the module >>> while hand-soldering it. >>> >>> Now I have hooked it up to a stm32f4discovery board to sync with PPS. >>> That's were the weirdness begins. >>> >>> First, the frequency offset of the microcontroller. I use a built-in >>> counting timer in the uC which runs at 84MHz to measure the duration >>> between 2 PPS. What I get is ~84008000 timer ticks between two pulses, >>> which corresponds to about 95ppm offset. While the crystal on the board is >>> of the cheapest variety, I think 95ppm is just too much. Is that correct, >>> and 95ppm offset even for a the most crappy oscillator is not a reasonable >>> value? >>> >>> Second, the GPS sawtooth. The PPS does exhibit sawtooth, which is >>> expected. But the sawtooth is HUGE. While the spec claims +-15ns, I see >>> more that +-400ns with period about 30 seconds. This is not sane. I must >>> have done something totally wrong. >>> >>> Something has to be terribly wrong with my measurements. I'd really >>> appreciate any hints on how to find out the cause of the described >>> weirdness. >>> ___ >>> 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] Trimble Resolution SMT GG weirdness
> I wonder, what kind of timing GPS gives 112ns wander? How good is your antenna? 112 ns is roughly 112 feet. That's not at all surprising if your antenna is inside or under trees. You might watch the number of satellites and/or watch the position while it does a survey. -- These are my opinions. I hate spam. ___ 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] Trimble Resolution SMT GG weirdness
I'd bet you could determine a lot about the cause by looking at the spectra of the error.I'm guessing that if the cause is an inaccurate survey location then the wondering will be periodic because at one point in the satilite's orbit it will be "too close" and then the distance will be to far. It might be hard to see this with multiple sats in view but still I'd not expect white noise. Another guess is that when yo do see white noise then you have things set up about as good as you can. I supose some one has looked at this. Is randomness in the timing error a good test? If so then I am more motivated to compares my GPSDO and Rb oscillators. On Mon, Apr 22, 2013 at 7:15 PM, Hal Murray wrote: > > > I wonder, what kind of timing GPS gives 112ns wander? > > How good is your antenna? 112 ns is roughly 112 feet. That's not at all > surprising if your antenna is inside or under trees. > > You might watch the number of satellites and/or watch the position while it > does a survey. > > > -- > These are my opinions. I hate spam. > > > > ___ > 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. > -- Chris Albertson Redondo Beach, California ___ 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] Trimble Resolution SMT GG weirdness
On 23.04.2013, at 6:15, Hal Murray wrote: > >> I wonder, what kind of timing GPS gives 112ns wander? > > How good is your antenna? 112 ns is roughly 112 feet. That's not at all > surprising if your antenna is inside or under trees. > Not perfect, but should be reasonably good. It's an external magnetic antenna on my windowsill. Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed location is better than this. > You might watch the number of satellites and/or watch the position while it > does a survey. > 6-10 SVs, with PDOP in range 1.6 - 3.9 (about 2.0 most of the time). > > -- > These are my opinions. I hate spam. > > > > ___ > 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] Trimble Resolution SMT GG weirdness
Daniel, a timing GPS receiver is not a GPSDO so its PPS is wandering about the nominal position. Using a digital oscilloscope, I can see how much the total wander is by activating the infinte persistence mode of the display. After 10 minutes, 1 hour, 1 day or whatever you have an idea of the total "coverage" of the wander. The trigger comes from a Z3815A reference. To see the "dance" of the PPS coming from a GPS receiver, a simple crystal oscillator as a reference is enough: use your microprocessor to generate a PPS from its clock and visually compare this generated PPS with the GPS PPS by a 'scope. On Tue, Apr 23, 2013 at 7:49 AM, Daniel Ginsburg wrote: > > On 23.04.2013, at 6:15, Hal Murray wrote: > > > > >> I wonder, what kind of timing GPS gives 112ns wander? > > > > How good is your antenna? 112 ns is roughly 112 feet. That's not at all > > surprising if your antenna is inside or under trees. > > > > > Not perfect, but should be reasonably good. It's an external magnetic > antenna on my windowsill. > Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed > location is better than this. > > > You might watch the number of satellites and/or watch the position while > it > > does a survey. > > > > 6-10 SVs, with PDOP in range 1.6 - 3.9 (about 2.0 most of the time). > > > > > -- > > These are my opinions. I hate spam. > > > > > > > > ___ > > 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] Trimble Resolution SMT GG weirdness
On 23.04.2013, at 12:50, Azelio Boriani wrote: > Daniel, > a timing GPS receiver is not a GPSDO so its PPS is wandering about the > nominal position. Using a digital oscilloscope, I can see how much the > total wander is by activating the infinte persistence mode of the display. > After 10 minutes, 1 hour, 1 day or whatever you have an idea of the total > "coverage" of the wander. The trigger comes from a Z3815A reference. To see > the "dance" of the PPS coming from a GPS receiver, a simple crystal > oscillator as a reference is enough: use your microprocessor to generate a > PPS from its clock and visually compare this generated PPS with the GPS PPS > by a 'scope. > Ah, I see now. Preoccupied with issue at hand I wasn't attentive enough and I somehow thought that you were talking about 112ns wide sawtooth, while in fact you were talking about wander in sense of ... well ... wander. Sorry for the confusion. > > On Tue, Apr 23, 2013 at 7:49 AM, Daniel Ginsburg wrote: > >> >> On 23.04.2013, at 6:15, Hal Murray wrote: >> >>> I wonder, what kind of timing GPS gives 112ns wander? >>> >>> How good is your antenna? 112 ns is roughly 112 feet. That's not at all >>> surprising if your antenna is inside or under trees. >>> >> >> >> Not perfect, but should be reasonably good. It's an external magnetic >> antenna on my windowsill. >> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed >> location is better than this. >> >>> You might watch the number of satellites and/or watch the position while >> it >>> does a survey. >>> >> >> 6-10 SVs, with PDOP in range 1.6 - 3.9 (about 2.0 most of the time). >> >>> >>> -- >>> These are my opinions. I hate spam. >>> >>> >>> >>> ___ >>> 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] Trimble Resolution SMT GG weirdness
Yes, the sawtooth correction is limited to tens of ns and is rapid: 10 to 30 seconds usually, the wander is larger and very slow. If you want to build a simple GPSDO with a PPS output and disciplined by the GPS PPS, take a look at my design: http://www.c-c-i.com/exchange/ file: PiAutoTIC1.zip On Tue, Apr 23, 2013 at 12:39 PM, Daniel Ginsburg wrote: > > On 23.04.2013, at 12:50, Azelio Boriani wrote: > > > Daniel, > > a timing GPS receiver is not a GPSDO so its PPS is wandering about the > > nominal position. Using a digital oscilloscope, I can see how much the > > total wander is by activating the infinte persistence mode of the > display. > > After 10 minutes, 1 hour, 1 day or whatever you have an idea of the total > > "coverage" of the wander. The trigger comes from a Z3815A reference. To > see > > the "dance" of the PPS coming from a GPS receiver, a simple crystal > > oscillator as a reference is enough: use your microprocessor to generate > a > > PPS from its clock and visually compare this generated PPS with the GPS > PPS > > by a 'scope. > > > > Ah, I see now. Preoccupied with issue at hand I wasn't attentive enough > and I somehow thought that you were talking about 112ns wide sawtooth, > while in fact you were talking about wander in sense of ... well ... > wander. Sorry for the confusion. > > > > > On Tue, Apr 23, 2013 at 7:49 AM, Daniel Ginsburg >wrote: > > > >> > >> On 23.04.2013, at 6:15, Hal Murray wrote: > >> > >>> > I wonder, what kind of timing GPS gives 112ns wander? > >>> > >>> How good is your antenna? 112 ns is roughly 112 feet. That's not at > all > >>> surprising if your antenna is inside or under trees. > >>> > >> > >> > >> Not perfect, but should be reasonably good. It's an external magnetic > >> antenna on my windowsill. > >> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed > >> location is better than this. > >> > >>> You might watch the number of satellites and/or watch the position > while > >> it > >>> does a survey. > >>> > >> > >> 6-10 SVs, with PDOP in range 1.6 - 3.9 (about 2.0 most of the time). > >> > >>> > >>> -- > >>> These are my opinions. I hate spam. > >>> > >>> > >>> > >>> ___ > >>> 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] Trimble Resolution SMT GG weirdness
On Tue, 23 Apr 2013 09:49:19 +0400 Daniel Ginsburg wrote: > Not perfect, but should be reasonably good. It's an external magnetic antenna > on my windowsill. > Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed > location is better than this. Windowsill? So you have only partial view of the sky? Then those 400ns sound about right. Said Jackson reported a couple of months back that a LEA-6T showed about 1us (IIRC) jitter until he avaraged the position for a couple of days (weeks?) to get the real position. After that, the jitter was much better. He also send some nice graphs of those measurements. You might want to look for them in the archives. Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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] Trimble Resolution SMT GG weirdness
On Tue, 23 Apr 2013 19:05:53 +0200, Attila Kinali wrote: >On Tue, 23 Apr 2013 09:49:19 +0400 >Daniel Ginsburg wrote: > >> Not perfect, but should be reasonably good. It's an external magnetic >> antenna on my windowsill. >> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed >> location is better than this. > >Windowsill? So you have only partial view of the sky? >Then those 400ns sound about right. Said Jackson reported a couple >of months back that a LEA-6T showed about 1us (IIRC) jitter until >he avaraged the position for a couple of days (weeks?) to get the >real position. After that, the jitter was much better. >He also send some nice graphs of those measurements. You might want >to look for them in the archives. > > Attila Kinali I always suspected something like this was at work. This would explain the ambiguous 1uS specification common in GPS receivers that are not intended for rigorous timing applications which I asked about a couple months ago. I did not ask the right question. :) With this in mind, I would assume that averaging over multiples of 12 hours would be necessary for maximum accuracy and days would be required to account for atmospheric transmission effects. Now I have a much better idea about how good the disciplined oscillator will need to be. A receiver intended for timing applications using position hold should allow accurate locking in a hundredth the time or less. ___ 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] Trimble Resolution SMT GG weirdness
On Tue, 23 Apr 2013 14:36:45 -0500 David wrote: > I always suspected something like this was at work. > > This would explain the ambiguous 1uS specification common in GPS > receivers that are not intended for rigorous timing applications which > I asked about a couple months ago. I did not ask the right question. > :) There is more to that than just sky view. Navigational and timing receivers differ slightly in the way they solve the equations. How and what exactly, i don't know, but guess it's optimizations for the common use case in timing receivers (fixed position, high precision time but low precision position required) > With this in mind, I would assume that averaging over multiples of 12 > hours would be necessary for maximum accuracy and days would be > required to account for atmospheric transmission effects. Now I have > a much better idea about how good the disciplined oscillator will need > to be. If you go for 12h integration time, you have to have a very good temperature compensation (ofcourse under the assumption you have a very stable oscillator in the first place). > A receiver intended for timing applications using position hold should > allow accurate locking in a hundredth the time or less. I think you overestimate what a timing receiver can do and what not. You cannot compensate for atmospheric effects with just a single frequency receiver unless you use WAAS/EGNOS/... and even that is not super accurate. For reference, u-blox specifies their timing models as being within +/-40ns and their navigational models being within +/-100ns. >From what i know about how these things work, that factor two is about what i would expect in imporvement in precision, probably even less. (those numbers are under "ideal" conditions, with good antenna position) Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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.
