Re: [time-nuts] WWVB Disciplined Oscillator
Hi The gotcha with WWVB is correcting for the day / night ionosphere issues. Since they are not 100% predictable, it’s not a real easy problem to solve. Toss on top of the the ambiguous status of WWV or WWVB ( = will it be there next year …. if so in what format ….) there layers and layers. Best guess is that WWVB at a “one day” sort of range is a 10 ppt sort of thing. At the same observation time, GPS is a < 0.1 ppt sort of thing. If the objective is accuracy … WWVB come in a bit far back …. Bob > On Apr 6, 2019, at 7:27 PM, Wayne Holder wrote: > > Perhaps this has been mention before, but I found the following document > while researching some details on WWVB and thought it might interest the > group: > > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf > > I know that Spectracom once made a WWVB Disciplined Oscillator in the form > of the Model 8164, but I figured that this approach probably was obsolete > in the era of GPS and network-based time. However, the author seems to have > produced some interesting results. Has anyone else built, or tried to > build a WWVB Disciplined Oscillator? > > Wayne > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
Not personally, but in the UK a company called Quarztlock made both MSF (similar to WWVB) and 198kHz (a frequency-standard broadcast station) that were popular frequency standards in labs. They still exist but have replaced those products with Rubidium and GPS based standards. http://www.quartzlock.com/ On Sun, Apr 7, 2019 at 1:00 AM Wayne Holder wrote: > Perhaps this has been mention before, but I found the following document > while researching some details on WWVB and thought it might interest the > group: > > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf > > I know that Spectracom once made a WWVB Disciplined Oscillator in the form > of the Model 8164, but I figured that this approach probably was obsolete > in the era of GPS and network-based time. However, the author seems to have > produced some interesting results. Has anyone else built, or tried to > build a WWVB Disciplined Oscillator? > > Wayne > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
Wayne good read on the paper. All of the spectracoms and such were rendered useless by the new BPSK modulation. Though now that 5 years or so have passed not so new. Unless the modulation is accounted for they can't track the carrier. There are external modifications and other approaches that have been suggested. I have design and tested numbers of them with a final approach using the cheat'n d-psk-r. Won't go into that as its been shared here on time-nuts enough. A lot depends on your location and signal strength. Clearly taking advantage of the new modulation for carrier prediction has advantage. But the fact is even I am now spoiled by GPSDOs. I also built a far simplere approach called a remodulator for simply allowing the spectracoms to get time. They are nice displays. Not sure you can get even those piece parts any longer. Regards Paul WB8TSL On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder wrote: > Perhaps this has been mention before, but I found the following document > while researching some details on WWVB and thought it might interest the > group: > > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf > > I know that Spectracom once made a WWVB Disciplined Oscillator in the form > of the Model 8164, but I figured that this approach probably was obsolete > in the era of GPS and network-based time. However, the author seems to have > produced some interesting results. Has anyone else built, or tried to > build a WWVB Disciplined Oscillator? > > Wayne > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
Hi Wayne, Great to see you found my presentation! The paper is available here: https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018_paper.pdf I traveled to CO and met with NIST people there and gathered more data then. We're planning to put out another paper soon (I'm finishing up my bachelor's right now so I'm a bit preoccupied though). I think LF timing is still very relevant in this day and age, and WWVB still shows promise as a national timing source. Let me know if you have any questions. Best, Kevin On Sat, Apr 6, 2019 at 10:00 PM paul swed wrote: > Wayne good read on the paper. > All of the spectracoms and such were rendered useless by the new BPSK > modulation. Though now that 5 years or so have passed not so new. Unless > the modulation is accounted for they can't track the carrier. There are > external modifications and other approaches that have been suggested. I > have design and tested numbers of them with a final approach using the > cheat'n d-psk-r. Won't go into that as its been shared here on time-nuts > enough. A lot depends on your location and signal strength. Clearly taking > advantage of the new modulation for carrier prediction has advantage. But > the fact is even I am now spoiled by GPSDOs. > I also built a far simplere approach called a remodulator for simply > allowing the spectracoms to get time. They are nice displays. Not sure you > can get even those piece parts any longer. > Regards > Paul > WB8TSL > > On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder > wrote: > > > Perhaps this has been mention before, but I found the following document > > while researching some details on WWVB and thought it might interest the > > group: > > > > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf > > > > I know that Spectracom once made a WWVB Disciplined Oscillator in the > form > > of the Model 8164, but I figured that this approach probably was obsolete > > in the era of GPS and network-based time. However, the author seems to > have > > produced some interesting results. Has anyone else built, or tried to > > build a WWVB Disciplined Oscillator? > > > > Wayne > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > -- Kevin Croissant ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
Hi After the passing of Clive Green HCD Research has taken over the Quartzlock business mid 2016 Regards Bernd DK1AG > Not personally, but in the UK a company called Quarztlock made both MSF (similar to WWVB) and 198kHz (a frequency-standard broadcast station) that were popular frequency standards in labs. > They still exist but have replaced those products with Rubidium and GPS based standards. > http://www.quartzlock.com/ On Sun, Apr 7, 2019 at 1:00 AM Wayne Holder wrote: > Perhaps this has been mention before, but I found the following > document while researching some details on WWVB and thought it might > interest the > group: > > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf > > I know that Spectracom once made a WWVB Disciplined Oscillator in the > form of the Model 8164, but I figured that this approach probably was > obsolete in the era of GPS and network-based time. However, the author > seems to have produced some interesting results. Has anyone else > built, or tried to build a WWVB Disciplined Oscillator? > > Wayne > ___ > time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go > to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
Wayne, there was a superb 2015 QEX article by KD2BD on his WWVB disciplined frequency standard. Full article is online here: http://www.arrl.org/files/file/QEX_Next_Issue/2015/Nov-Dec_2015/Magliacane.pdf As a frequency standard I have no major disagreement with the PTTI article. But the 100 microsecond number they give for absolute time transfer seems to be based entirely on propagation characteristics and ignores the difficulty I've always had in resolving the mushy edge of the timecode pulses. 100 microseconds implies a system bandwidth of 10kHz, which is pointless because the transmitter antenna bandwidth has to be quite narrow - hundreds of Hz if not less. Tim N3QE On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder wrote: > Perhaps this has been mention before, but I found the following document > while researching some details on WWVB and thought it might interest the > group: > > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf > > I know that Spectracom once made a WWVB Disciplined Oscillator in the form > of the Model 8164, but I figured that this approach probably was obsolete > in the era of GPS and network-based time. However, the author seems to have > produced some interesting results. Has anyone else built, or tried to > build a WWVB Disciplined Oscillator? > > Wayne > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
> Hi Wayne, > Great to see you found my presentation! > The paper is available here: > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018_paper.pdf Kevin, thanks for the link to the paper. I'd like to know more about how correlation works and how you were able to use to to sync with the WWVB bitstream. From what I read in your paper, I'm guessing that the "local" code you use for correlation is generated by prediction once the receiver has locked on the broadcast code and these two bit streams are then "compared" in some way via multiplication... But, I don't really understand how this is done at a practical level as it would seem that his would require multiple passes over the code with some type of sliding time offset that advances with each pass? Or, are there simpler techniques? Can you suggest a reference where I can learn more? BTW, for everyone else following the WWW/WWVB/WWVH defunding saga, a post on this web page: http://cqnewsroom.blogspot.com claims that "*Congress has restored full funding for WWV, WWVB and WWVH, despite a budget proposal from the National Institute of Standards and Technology to shut down the three standard time and frequency radio stations. The Consolidated Appropriations Act of 2019 included some $725 million for NIST's Scientific and Technical Research and Services (STRS), the budget category that includes the stations' funding, according to NIST Public Affairs Director Gail Porter. The conference report accompanying the budget bill notes that "(t)he agreement rejects the proposed terminations and reductions for all STRS programs" and includes "not less than fiscal year 2018 funding" for several services, including "Time and Fundamental Measurement Dissemination."* The article then adds: *"With the shutdown threat ended, preparations continue for marking WWV's centennial this fall. According to the ARRL Letter, the Northern Colorado Amateur Radio Club will be operating a special event station from the WWV transmitter site from September 28 through October 2, using the callsign WW0WWV."* Wayne Wayne Wayne On Sat, Apr 6, 2019 at 9:00 PM Kevin Croissant wrote: > Hi Wayne, > > Great to see you found my presentation! > The paper is available here: > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018_paper.pdf > I traveled to CO and met with NIST people there and gathered more data > then. We're planning to put out another paper soon (I'm finishing up my > bachelor's right now so I'm a bit preoccupied though). > I think LF timing is still very relevant in this day and age, and WWVB > still shows promise as a national timing source. > > Let me know if you have any questions. > Best, > Kevin > > On Sat, Apr 6, 2019 at 10:00 PM paul swed wrote: > > > Wayne good read on the paper. > > All of the spectracoms and such were rendered useless by the new BPSK > > modulation. Though now that 5 years or so have passed not so new. Unless > > the modulation is accounted for they can't track the carrier. There are > > external modifications and other approaches that have been suggested. I > > have design and tested numbers of them with a final approach using the > > cheat'n d-psk-r. Won't go into that as its been shared here on time-nuts > > enough. A lot depends on your location and signal strength. Clearly > taking > > advantage of the new modulation for carrier prediction has advantage. But > > the fact is even I am now spoiled by GPSDOs. > > I also built a far simplere approach called a remodulator for simply > > allowing the spectracoms to get time. They are nice displays. Not sure > you > > can get even those piece parts any longer. > > Regards > > Paul > > WB8TSL > > > > On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder > > wrote: > > > > > Perhaps this has been mention before, but I found the following > document > > > while researching some details on WWVB and thought it might interest > the > > > group: > > > > > > https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf > > > > > > I know that Spectracom once made a WWVB Disciplined Oscillator in the > > form > > > of the Model 8164, but I figured that this approach probably was > obsolete > > > in the era of GPS and network-based time. However, the author seems to > > have > > > produced some interesting results. Has anyone else built, or tried to > > > build a WWVB Disciplined Oscillator? > > > > > > Wayne > > > ___ > > > time-nuts mailing list -- time-nuts@lists.febo.com > > > To unsubscribe, go to > > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > > and follow the instructions there. > > > > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > > > -- > Kevin Croissant > ___ > time-nuts mailing list -- time-nuts@li
Re: [time-nuts] WWVB Disciplined Oscillator
On 4/7/19 4:30 AM, Wayne Holder wrote: Hi Wayne, Great to see you found my presentation! The paper is available here: https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018_paper.pdf Kevin, thanks for the link to the paper. I'd like to know more about how correlation works and how you were able to use to to sync with the WWVB bitstream. From what I read in your paper, I'm guessing that the "local" code you use for correlation is generated by prediction once the receiver has locked on the broadcast code and these two bit streams are then "compared" in some way via multiplication... But, I don't really understand how this is done at a practical level as it would seem that his would require multiple passes over the code with some type of sliding time offset that advances with each pass? Or, are there simpler techniques? Can you suggest a reference where I can learn more? One thing that helps is that you know the structure and content of the bitstream after the fact - that is, the SNR needed to decode the bits is lower than that to recover precision timing. So you take the "known" bitstream and do a cross correlation against the received signal. pseudocode for the cross correlation is something like this: for lag=0:N sum=0 for i=0:M-1 sum = sum + input[i]*reference[i+lag] end for crosscorrel[lag] = sum/M end for this is a O(N*M) number of operations, so most folks use a technique using FFTs: FFT each of them, multiply term by term, then inverse FFT back. That's O(3*M*log2(M) +M operations) You'll get something that has a peak in the middle, which corresponds to the point of "maximum alignment" between the two data streams. There's all sorts of things one can do to get "sub sample" resolution - essentially by interpolating. Zero padding the data set before FFTing is one way. The other thing that might save computational burden is that you don't need to try ALL possible time lags - you have an estimate, and so you can slide around just that ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
jimlux, thanks for the info cross correlation. That's sort of how i imagined it should work, but I wasn't sure. I guess it really helps that we live in the age of fast computation. Wayne On Sun, Apr 7, 2019 at 10:00 AM jimlux wrote: > On 4/7/19 4:30 AM, Wayne Holder wrote: > >> Hi Wayne, > >> Great to see you found my presentation! > >> The paper is available here: > >> https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018_paper.pdf > > > > Kevin, thanks for the link to the paper. I'd like to know more about how > > correlation works and how you were able to use to to sync with the WWVB > > bitstream. From what I read in your paper, I'm guessing that the "local" > > code you use for correlation is generated by prediction once the receiver > > has locked on the broadcast code and these two bit streams are then > > "compared" in some way via multiplication... But, I don't really > > understand how this is done at a practical level as it would seem that > his > > would require multiple passes over the code with some type of sliding > time > > offset that advances with each pass? Or, are there simpler techniques? > Can > > you suggest a reference where I can learn more? > > > > > One thing that helps is that you know the structure and content of the > bitstream after the fact - that is, the SNR needed to decode the bits is > lower than that to recover precision timing. So you take the "known" > bitstream and do a cross correlation against the received signal. > > pseudocode for the cross correlation is something like this: > > for lag=0:N > sum=0 > for i=0:M-1 > sum = sum + input[i]*reference[i+lag] > end for > crosscorrel[lag] = sum/M > end for > > this is a O(N*M) number of operations, so most folks use a technique > using FFTs: FFT each of them, multiply term by term, then inverse FFT > back. That's O(3*M*log2(M) +M operations) > > > You'll get something that has a peak in the middle, which corresponds to > the point of "maximum alignment" between the two data streams. > > There's all sorts of things one can do to get "sub sample" resolution - > essentially by interpolating. Zero padding the data set before FFTing > is one way. > > The other thing that might save computational burden is that you don't > need to try ALL possible time lags - you have an estimate, and so you > can slide around just that > > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
tsho...@gmail.com said: > As a frequency standard I have no major disagreement with the PTTI article. > But the 100 microsecond number they give for absolute time transfer seems to > be based entirely on propagation characteristics and ignores the difficulty > I've always had in resolving the mushy edge of the timecode pulses. 100 > microseconds implies a system bandwidth of 10kHz, which is pointless because > the transmitter antenna bandwidth has to be quite narrow - hundreds of Hz if > not less. Does NIST publish the transmitter bandwidth? I've never seen it, but I haven't done a serious search. Maybe somebody near enough to get a clean signal could measure it. What does a spectrogram look like? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
> > Does NIST publish the transmitter bandwidth? I've never seen it, but I > haven't done a serious search. > > Maybe somebody near enough to get a clean signal could measure it. What > does a spectrogram look like? > Some of the KiwiSDR receivers are close enough to get an excellent signal. Coincidentally I gave this very experiment a try some weeks back; give me a few days to find the recordings and analysis scripts. But the bottom line is that 100 microseconds seems possible. The antenna bandwidth is some hundreds of Hz, if I remember right, but the high resolution would come from tracking a specific point on the amplitude trailing edge (say, the 90% point). Another interesting aspect of the WWVB recordings is that the constellation diagram shows some brief, large phase excursions during amplitude changes. Phase accuracy is pretty good steady-state, but near the edges it goes kind of wild. Transmitter nonlinearity no doubt. It could be predistorted out (even adaptively if desired), but it's probably not worth the trouble. Cheers, Peter ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
On 4/7/19 10:37 PM, Peter Monta wrote: Does NIST publish the transmitter bandwidth? I've never seen it, but I haven't done a serious search. Maybe somebody near enough to get a clean signal could measure it. What does a spectrogram look like? Some of the KiwiSDR receivers are close enough to get an excellent signal. Coincidentally I gave this very experiment a try some weeks back; give me a few days to find the recordings and analysis scripts. But the bottom line is that 100 microseconds seems possible. The antenna bandwidth is some hundreds of Hz, if I remember right, but the high resolution would come from tracking a specific point on the amplitude trailing edge (say, the 90% point). The precision of measurement isn't so much related to only the bandwidth of the signal as to the combination of bandwidth, integration time, and SNR. THe trick is knowing what the "decorrelation time" of the channel is, because that sets an upper bound on integration time. And, of course, the phase noise of the transmitter and receiver. In any case, extracting microsecond timing from a 1 kHz BW signal is straightforward (assuming sufficient SNR, etc.) As an extreme example, we measure timing of the round trip radio signal to Jupiter and back with an accuracy of 1E-15 (5 picoseconds). The signal is very narrow band (<<1 Hz), but we do integrate for 1000 seconds. And we use other means to disambiguate things like "which cycle" are we on. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWVB Disciplined Oscillator
Hi > On Apr 8, 2019, at 12:54 PM, jimlux wrote: > > On 4/7/19 10:37 PM, Peter Monta wrote: >>> >>> Does NIST publish the transmitter bandwidth? I've never seen it, but I >>> haven't done a serious search. >>> >>> Maybe somebody near enough to get a clean signal could measure it. What >>> does a spectrogram look like? >>> >> Some of the KiwiSDR receivers are close enough to get an excellent signal. >> Coincidentally I gave this very experiment a try some weeks back; give me a >> few days to find the recordings and analysis scripts. But the bottom line >> is that 100 microseconds seems possible. The antenna bandwidth is some >> hundreds of Hz, if I remember right, but the high resolution would come >> from tracking a specific point on the amplitude trailing edge (say, the 90% >> point). > > > The precision of measurement isn't so much related to only the bandwidth of > the signal as to the combination of bandwidth, integration time, and SNR. > > THe trick is knowing what the "decorrelation time" of the channel is, because > that sets an upper bound on integration time. And, of course, the phase > noise of the transmitter and receiver. > > In any case, extracting microsecond timing from a 1 kHz BW signal is > straightforward (assuming sufficient SNR, etc.) > > As an extreme example, we measure timing of the round trip radio signal to > Jupiter and back with an accuracy of 1E-15 (5 picoseconds). The signal is > very narrow band (<<1 Hz), but we do integrate for 1000 seconds. And we use > other means to disambiguate things like "which cycle" are we on. One would *assume* that there is a fixed relation between the code and the carrier “as transmitted”. By the time it gets to you. it may not be something nice like zero degrees, but there will be a (over some period of time) stable relation. If you can get the code demodulation to the point that you can start looking at carrier phase, you then have a *lot* more edges to integrate against. Since the vast majority of the code bits can be determined ahead of time, you are not looking for a needle in a haystack. You are looking for at least a pallet full of needles. :) Can you get to the 10 us range off of the code? It’s certainly worth trying. My guess is that indeed you can with enough samples. Once you are looking at carrier phase all is not perfect. Around sunrise and sunset, you will have a tough time with WWVB. You also have the basic issue that propagation *does* swing your local signal by more than a cycle, even at fairly short distances. Without some sort of propagation “aiding” your GPSDO or time source will be wandering a bit over each and every day. The sunrise / sunset part is ….. errr …. predictable as long as you know where you are. The first order part of the propagation (day vs night) can be roughly estimated. Do you get two eight hour long “windows” of data each day or is it more? If your local standard goes into holdover for 8 hours, is that better or worse than tracking a couple cycles (at 60 KHz) of swing? If you have the sort of OCXO that is commonly used in a CDMA GPSDO, it should be capable of 10 us for 24 hours. That should put it in the “couple of us for 8 hours” range. Compared to (many) 10’s of microseconds due to propagation, that sounds like a good choice. Bob > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
