Re: [time-nuts] New ISO8601 ?
So this new revision enables essentially for the encoding of ``ca.''? Obviously the current revision allows for varying degrees of fixed chronological granularity levels. -Ruslan On Thu, Nov 23, 2017 at 9:01 AM, Dana Whitlow wrote: > I believe the phrase "circa 1967" fits the bill pretty well, although > it may fall a little bit short of "...but it’s all a bit of a blur”. > > Dana > > On Thu, Nov 23, 2017 at 7:18 AM, Poul-Henning Kamp > wrote: > >> >> In message <4bec82c4-583e-4632-8589-d898cc2bd...@n1k.org>, Bob kb8tq >> writes: >> >> >I had never realized there was a format for expressing “I think it was >> 1967 but it’s >> >all a bit of a blur”. >> >> I think that is one of the major reasons for the revision. >> >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> p...@freebsd.org | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by incompetence. >> ___ >> 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. -- Ruslan Nabioullin Wittgenstein Laboratories rnabioul...@gmail.com (508) 523-8535 50 Louise Dr. Hollis, NH 03049 ___ 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] 53230A weirdness
Hi, all I've done some experiments on my 53230A, and I've come across an issue I think could be worth knowing about. I have not tested this on other 53230A's - if anyone has a 53230A and some spare time, I'd be grateful if someone could try to replicate. In a nutshell, the first frequency measurement following an INIT is biased. The magnitude of the bias is dependant on measurement mode (CONT/RCON), and gate time. It is worth noting that every READ implicitly calls INIT - so any software collecting a time series using repeated calls to READ to fetch single readings will give biased results. Not for the first sample in the series, but all of them. As an example, the last time series I collected this way using RCON and 0.1s gatetime gave an average frequency error of -5.2e-10. A writeup is here: http://www.efos3.com/HPAK53230A-1.html Best regards, Ole ___ 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] Symmetricom X72 rubidium oscillator breakout board now avaiable
Well, I ordered one this morning and I am reading the doc I found online. Please save a set of your boards and if you want to send me some heatsinks, I’ll mill them for everyone. Regards, Jerry Jerry Hancock je...@hanler.com (415) 215-3779 > On Nov 20, 2017, at 12:29 AM, Mark Sims wrote: > > Maybe: > > https://www.ebay.com/itm/Symmetricom-X72-Rubidium-Oscillator-10-32V-DC-10MHz-USED/132116702248?epid=1023910441&hash=item1ec2c4e428:g:2p8AAOSwXYtYvKWc > > I don't know if RDR Electronics still have any X72's. > > There used to be a lot of X72's for sale that were pulled from something. > They came with an adapter board that only broke out 16 of the 26 pins. I > bought a couple... they had less than 1000 hours of run time on them. > > My signal board has support for the SA22.c rubidium, but I need to figure out > how to connect to that horrid connector that is in the middle of the > baseplate. I am also laying out an interface board for the Spectratime > SRO-100 rubidium. > > ___ > 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] Next upgrade
The Next upgrade has touched several subjects we deal with on a dayle basis. Allow mw to add my thoughts. First we are time nuts trying within our limits to advance time and frequency generation and measurement with affordable resources. We are at least a factor four orders of magnitude behind the big boys in performance and combined available resources. As a market we are to small potato's so products tailored to our needs are limited and are getting less. An example SRS FS740 a nice box but no help to get past E-12. New GPSDO's for Telecom do not have 5 or 10 MHz output. PRS-10 a nice Rb, originally intended for FRS replacement has ADC and DCA control limeting it to 2 E-12. I have one, have not said anything because I want to get rid of it. The question of why Rb. For our work there are only two reasons. Not living next to NIST the only precise frequency reference is GPS. To overcome its limits you need long time averaging. Aging compared to a OCXO is orders of magnitude less. Second because of aging and tuning range a 16 bit DAC will do the job. There was recently discussion of the use of the LTC1655 which is still my # 1 choice. What was not mentioned on the 1650 is that in needs a external reference discontinued and double ling the cost. 18 bits would be nicer but we have not found one affordable. Using a modified Shera with 1 E-14 steps yields a range up to 6.4 E-10. We are presently running three Tbolts, standard, OSA 8600 and the Efratom M100 with 40 000 seconds and 6 E-17 per uV direct C field drive through a 10 K resistor. Temperature, pressure and some start up issues make it a less desirable option.For temperature and pressure we have an interface board, but automatic recovery after power or GPS loss is not there after two weeks. That is why we keep going back to 1655/Shera. Going to 6 E-17 keeps the jumps we all see below ! E-13. Attila recently caught up with me on my Europe trip at Juerg's home in Switzerland and can tell you about all our projects. Using the standard Tbolt we also showed him the consistent jumps with a Tracor 527E and a Cesium reference. Yes doing a Cesium GPSDO again with 1655/Shera is doable but the question has to be: is it necessary. I worked with Richard McCorkle on it 4 years ago. The question is does it make sense. My HP5061B with the new smaller tube shows no aging but my GPS measuring capabilities are limited to 1 E-12. We have decided to monitor 1 pps from a Tbolt against a 1pps derived from our respective Cs and if necessary manually adjust.. To do it with le least amount of equipment we decided to take a PICTIC II a divider chain and a custom V drive using USB stick and blue tooth monitoring low cost, no fan and low power. I never built a PICTIC but did combine Richard's and my boards for cost reason. Bill Riley did an extensive evaluation and recommended to consider 4 layers. This was the first time I looked at the board. Richard used schematic capture resulting in no ground plane and long ground runs not what you want when you chase nsec. I took a look and decided 4 layers is not necessary but was able to add a nice ground plane. I have boards of PICTIC, divider and V drive. Right now we still have work to do on M100/FRK GPSDO and the high resolution Austron counter. If some one wants to build a unit, please contact me off list, if I am convinced you will do it, I will send you the boards free of charge. Richard did a PICTIC III and was working on a 4 and I was working on a 5. Sadly contact with him has stopped, the last correspondence was two years ago, he had fallen and broken some ribs and had prostate cancer. His last words where, he would get back with me after health was back under control. I have tried what I did with Brooks, send a letter with USPS which resulted in Brooks Wife responding, you know the details, no response from Fairbanks. Has any one heard from Richard? He did a lot of work for us, brilliant, I would ask a question, because of the time zone the typical next day response was working PIC code. Bert Kehren In a message dated 11/22/2017 7:26:57 P.M. Eastern Standard Time, k8yumdoo...@gmail.com writes: For the most part the SRS-10 is a nice choice, although I'd always be wary of buying a used one. My only real beefs are that the tuning granularity is rather coarse, about 2E-12, and the disciplining loop seems to be a bit aggressive so that the poor oscillator gets jerked around quite a bit by the GPS. This makes for rather ugly-looking plots of time error over time. The above comments are derived from about 3 years of operating one as a hot emergency spare at the Arecibo Observatory against the day when the H-maser crashed abruptly. In this case the SRS-10 was embedded in an FS725 which we bought new. Dana On Wed, Nov 22, 2017 at 4:16 PM, Jerry Hancock wrote: > Three questions: > > 1) Now that I’ve split my
Re: [time-nuts] New ISO8601 ?
I believe the phrase "circa 1967" fits the bill pretty well, although it may fall a little bit short of "...but it’s all a bit of a blur”. Dana On Thu, Nov 23, 2017 at 7:18 AM, Poul-Henning Kamp wrote: > > In message <4bec82c4-583e-4632-8589-d898cc2bd...@n1k.org>, Bob kb8tq > writes: > > >I had never realized there was a format for expressing “I think it was > 1967 but it’s > >all a bit of a blur”. > > I think that is one of the major reasons for the revision. > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > ___ > 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] Allan variance by sine-wave fitting
The harmonics limit the perfomance if you want to find the frequency of a given, sampled sinewave with linear methods. Thats at least my finding when I built a device to measure grid frequency fast and with high accuracy. I had to use high-Q digital filters for the fundamental. Their slow transient response limited the speed of new frequency measurements. Cheers Detlef DD4WV "time-nuts" schrieb am 23.11.2017 16:34:39: > Von: Tim Shoppa > An: Discussion of precise time and frequency measurement > Datum: 23.11.2017 16:35 > Betreff: Re: [time-nuts] Allan variance by sine-wave fitting > Gesendet von: "time-nuts" > > I wonder how much a fitting approach is affected by distortion (especially > harmonic content) in the waveform. > > Of course we can always filter the waveform to make it more sinusoidal but > then we are adding L's and C's and their tempcos to the measurement for > sure destroying any femtosecond claims. > > Tim N3QE > > On Wed, Nov 22, 2017 at 5:57 PM, Ralph Devoe wrote: > > > Hi, > >The fitting routine only takes up 40 uS of the 1 sec interval > > between measurements, as shown in Fig. 1 of the paper. This is less than > > 10(-4) of the measurement interval. It just determines the phase difference > > at the start of every second. I don't think the filtering effect is very > > large in this case. > > The interesting thing is that good results are achievable with such > > a short fitting interval. One way to think of it is to treat the fitting > > routine as a statistically optimized averaging process. Fitting 40 uS, that > > is 4096 points at 10 ns/point, should reduce the noise by a factor of 64 > > (roughly). The single shot timing resolution of the ADC is about 10 pS (see > > Fig. 4), so dividing this by 64 brings you down into the 100's of fs range, > > which is what you see. > > > > Ralph > > ___ > > 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] Allan variance by sine-wave fitting
I wonder how much a fitting approach is affected by distortion (especially harmonic content) in the waveform. Of course we can always filter the waveform to make it more sinusoidal but then we are adding L's and C's and their tempcos to the measurement for sure destroying any femtosecond claims. Tim N3QE On Wed, Nov 22, 2017 at 5:57 PM, Ralph Devoe wrote: > Hi, >The fitting routine only takes up 40 uS of the 1 sec interval > between measurements, as shown in Fig. 1 of the paper. This is less than > 10(-4) of the measurement interval. It just determines the phase difference > at the start of every second. I don't think the filtering effect is very > large in this case. > The interesting thing is that good results are achievable with such > a short fitting interval. One way to think of it is to treat the fitting > routine as a statistically optimized averaging process. Fitting 40 uS, that > is 4096 points at 10 ns/point, should reduce the noise by a factor of 64 > (roughly). The single shot timing resolution of the ADC is about 10 pS (see > Fig. 4), so dividing this by 64 brings you down into the 100's of fs range, > which is what you see. > > Ralph > ___ > 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] Allan variance by sine-wave fitting
Hi, There is trivial ways to estimate phase and amplitude of a sine using linear methods. I saw however none of these properly referenced or described. It would have been good to see those approaches attempted in parallel on the same data and compare their performance with the proposed approach. It seemed "fuzzy" how it worked, and that is never a good sign in a scientific article, especially as it is n the heart of the method described in the paper. The actual method should be named, referenced and then also referenced with "as implemented by..." and we only got the last part. Cheers, Magnus On 11/23/2017 01:34 PM, d.schuec...@avm.de wrote: Hi, just my two cents on sine wave fitting. A undamped sine wave is the solution of the difference equation sig(n+1)=2*cos(w)*sig(n)-sig(n-1) This is a linear system of equations mapping the sum of the samples n+1 and n-1 to the sample n. The factor 2*cos(w) is the unknown. The least-squares solution of the overdetermined system is pure linear algebra, no nonlinear fitting involved. The trick also works for a damped sine wave. Care must be taken for high 'oversampling' rates, it works best for 4samples/sinewave, ie near Nyquist/2. Cheers Detlef DD4WV ___ 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] New ISO8601 ?
HI > On Nov 23, 2017, at 8:18 AM, Poul-Henning Kamp wrote: > > > In message <4bec82c4-583e-4632-8589-d898cc2bd...@n1k.org>, Bob kb8tq writes: > >> I had never realized there was a format for expressing “I think it was 1967 >> but it’s >> all a bit of a blur”. > > I think that is one of the major reasons for the revision. That’s the way I read it. It’s all a bit of a blur so I could be wrong … :) Bob > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. ___ 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] New ISO8601 ?
In message <4bec82c4-583e-4632-8589-d898cc2bd...@n1k.org>, Bob kb8tq writes: >I had never realized there was a format for expressing “I think it was 1967 >but it’s >all a bit of a blur”. I think that is one of the major reasons for the revision. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Allan variance by sine-wave fitting
Hi One other side to this: There are a number of papers out there on this basic technique (ADC frequency measurement). There are a number of commercial products that do ADEV and other measurements this way. It might be a good idea to at least mention them. It would be even better to look at the sort of accuracy they achieve. Bob > On Nov 22, 2017, at 6:38 PM, Ralph Devoe wrote: > > Hi Time-nuts and Attila, > Thanks for the very interesting and informative criticisms. That > is what I was looking for. I don't agree with most of them, but I need > some time to work out some detailed answers. > To focus on the forest instead of the trees: The method uses a > $300 student scope (Digilent Analog discovery- a very fine product), which > any skilled amateur can modify in a weekend, and produce a device which is > 10-100 times better than the expensive counters we are used to using. The > software contains only 125 lines of Python and pretty much anyone can > write their own. In practice this device is much easier to use than my > 53132a. > > Ralph > ___ > 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] Next upgrade
Hi Yes, the “has no GPS” box becomes the active device in a REF0 / REF1 pair. If a survey is involved, it can take a *long* time for things to sort out. Bob > On Nov 23, 2017, at 7:22 AM, Adrian Godwin wrote: > > Turns out is does work - Initially, when I linked them, both boxes had the > standby light go out and the unmodified ref-0 (with no GPS receiver) showed > Fault and No GPS. > > So I assumed there was some problem that might be causing them to conflict > over the interface, and unplugged it. > > I've tried it again with more patience and after 10 minutes or so, the > modified ref0 goes into standby and the one without a receiver has only the > green ON light. I guess that's working correctly :) > > > > On Thu, Nov 23, 2017 at 12:23 AM, Jerry Hancock wrote: > >> Adrian, when you stated it didn’t work, what were the results? >> >> I had mine running in HA mode, if you can call it that, because only one >> has a GPS. Actually now that I think about it, the separate but modified >> REF0 and modified REF1, assuming separate power and antennas, is probably >> closer to HA than the original application. I have both mine running now >> with Lady Heather tracking each and I’ve been playing around with >> comparisons. Now in my case, if either goes down for any reason the other >> can take over. I guess in order to make them truly HA, we would need a >> diode or relay switched transfer to the active unit. >> >> Jerry >> >>> On Nov 22, 2017, at 4:10 PM, Adrian Godwin wrote: >>> >>> Yes, I cross-connected the pins, but I didn't cut any short. >>> >>> >>> >>> On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq wrote: >>> Hi I have run a number of the REF0 / REF1 combos. They all seem to work >> fine. The standard cable has some odd short pins on it. If you are not hot plugging the cable I don’t think they matter at all. If anything, the system is more reliable with a normal length pin on the connector. Bob > On Nov 22, 2017, at 6:08 PM, Adrian Godwin >> wrote: > > I've got several of the Ref 0 boxes but none of the Ref 1. I've added >> an > Oncore GPS receiver to one of them as per Peter Garde's notes and it works > well. > > But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1 > configuration. Not that I need an HA reference but just for interest. I've > only had a quick look so far and found that connecting the two together > with a 15-pin cable didn't work. > > Has anyone looked into this ? > > > On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq wrote: > >> Hi >> >> >> >>> On Nov 22, 2017, at 5:16 PM, Jerry Hancock wrote: >>> >>> Three questions: >>> >>> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit >> with >> both supplying 10Mhz and 1PPS, is there a way to combine the outputs >> or >> some other technique to improve the short and/or long term >> performance? >> >> You can monitor one against the other. Ideally you would want three >> GPSDO’s and a >> monitoring setup. That way you can figure out which of the three has gone >> bad. >> >>> >>> 2) I’ve become interested in Rubidium Disciplined Oscillators >> recently >> and was now thinking of purchasing one of the PRS-10 that I see on Ebay. If >> I did that and replaced one of the DOCXOs from one of the Lucent >> boxes, >> what impact would this have on the overall performance both with and >> without (when in hold-over)? >> >> If you go into holdover, you are the exception. Most setups rarely go into >> holdover. When they >> do, it’s because a hurricane just went over the house. Generally >> that’s >> not when the focus is going >> to be on timing experiments. >> >>> Basically, is it worth the money to upgrade one of the boxes to a >> Rubidium disciplined oscillator assuming the GPS signal is rarely >> lost? >> >> Not worth the money if you are only looking at holdover and have a typical >> setup. >> >>> >>> 3) Figuring the PRS-10 will cost around $250 when all is said and >> done, >> is there a better option to improve my GPSDO system? >> >> >> Disciplining implies continuously correcting. Rb standards age much >> less >> than a typical >> OCXO. Oddly enough their temperature stability may not be as good as a >> high end >> DOCXO. It is fairly common to try to stabilize the environment your >> standards operate in. >> To the extent you are successful this reduces the need to deal with >> temperature. >> >> The net effect is that disciplining an Rb at a rate (filter / control loop >> / manual tweak) of less than >> a few days actually makes the Rb worse. Coming up with software to >> “back >> off” on the tuning is >
Re: [time-nuts] New ISO8601 ?
Hi I had never realized there was a format for expressing “I think it was 1967 but it’s all a bit of a blur”. Bob > On Nov 23, 2017, at 4:57 AM, Poul-Henning Kamp wrote: > > Seems there is an ISO8601 revision in progress ? > > https://www.loc.gov/standards/datetime/ > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > ___ > 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] Allan variance by sine-wave fitting
Hi, just my two cents on sine wave fitting. A undamped sine wave is the solution of the difference equation sig(n+1)=2*cos(w)*sig(n)-sig(n-1) This is a linear system of equations mapping the sum of the samples n+1 and n-1 to the sample n. The factor 2*cos(w) is the unknown. The least-squares solution of the overdetermined system is pure linear algebra, no nonlinear fitting involved. The trick also works for a damped sine wave. Care must be taken for high 'oversampling' rates, it works best for 4samples/sinewave, ie near Nyquist/2. Cheers Detlef DD4WV ___ 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] Next upgrade
Turns out is does work - Initially, when I linked them, both boxes had the standby light go out and the unmodified ref-0 (with no GPS receiver) showed Fault and No GPS. So I assumed there was some problem that might be causing them to conflict over the interface, and unplugged it. I've tried it again with more patience and after 10 minutes or so, the modified ref0 goes into standby and the one without a receiver has only the green ON light. I guess that's working correctly :) On Thu, Nov 23, 2017 at 12:23 AM, Jerry Hancock wrote: > Adrian, when you stated it didn’t work, what were the results? > > I had mine running in HA mode, if you can call it that, because only one > has a GPS. Actually now that I think about it, the separate but modified > REF0 and modified REF1, assuming separate power and antennas, is probably > closer to HA than the original application. I have both mine running now > with Lady Heather tracking each and I’ve been playing around with > comparisons. Now in my case, if either goes down for any reason the other > can take over. I guess in order to make them truly HA, we would need a > diode or relay switched transfer to the active unit. > > Jerry > > > On Nov 22, 2017, at 4:10 PM, Adrian Godwin wrote: > > > > Yes, I cross-connected the pins, but I didn't cut any short. > > > > > > > > On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq wrote: > > > >> Hi > >> > >> I have run a number of the REF0 / REF1 combos. They all seem to work > fine. > >> The standard cable has some odd short pins on it. If you are not hot > >> plugging > >> the cable I don’t think they matter at all. If anything, the system is > >> more reliable > >> with a normal length pin on the connector. > >> > >> Bob > >> > >>> On Nov 22, 2017, at 6:08 PM, Adrian Godwin > wrote: > >>> > >>> I've got several of the Ref 0 boxes but none of the Ref 1. I've added > an > >>> Oncore GPS receiver to one of them as per Peter Garde's notes and it > >> works > >>> well. > >>> > >>> But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1 > >>> configuration. Not that I need an HA reference but just for interest. > >> I've > >>> only had a quick look so far and found that connecting the two together > >>> with a 15-pin cable didn't work. > >>> > >>> Has anyone looked into this ? > >>> > >>> > >>> On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq wrote: > >>> > Hi > > > > > On Nov 22, 2017, at 5:16 PM, Jerry Hancock wrote: > > > > Three questions: > > > > 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit > with > both supplying 10Mhz and 1PPS, is there a way to combine the outputs > or > some other technique to improve the short and/or long term > performance? > > You can monitor one against the other. Ideally you would want three > GPSDO’s and a > monitoring setup. That way you can figure out which of the three has > >> gone > bad. > > > > > 2) I’ve become interested in Rubidium Disciplined Oscillators > recently > and was now thinking of purchasing one of the PRS-10 that I see on > >> Ebay. If > I did that and replaced one of the DOCXOs from one of the Lucent > boxes, > what impact would this have on the overall performance both with and > without (when in hold-over)? > > If you go into holdover, you are the exception. Most setups rarely go > >> into > holdover. When they > do, it’s because a hurricane just went over the house. Generally > that’s > not when the focus is going > to be on timing experiments. > > > Basically, is it worth the money to upgrade one of the boxes to a > Rubidium disciplined oscillator assuming the GPS signal is rarely > lost? > > Not worth the money if you are only looking at holdover and have a > >> typical > setup. > > > > > 3) Figuring the PRS-10 will cost around $250 when all is said and > done, > is there a better option to improve my GPSDO system? > > > Disciplining implies continuously correcting. Rb standards age much > less > than a typical > OCXO. Oddly enough their temperature stability may not be as good as a > high end > DOCXO. It is fairly common to try to stabilize the environment your > standards operate in. > To the extent you are successful this reduces the need to deal with > temperature. > > The net effect is that disciplining an Rb at a rate (filter / control > >> loop > / manual tweak) of less than > a few days actually makes the Rb worse. Coming up with software to > “back > off” on the tuning is > not as simple as it might seem. > > This comes back to the fact that the GPS signal (or any of the sat > signals) are quite noisy. You > need to average them over a *long* time to get good performance. Rb’s > >> are > enough better than > a GPSDO OCXO that the time rang
[time-nuts] New ISO8601 ?
Seems there is an ISO8601 revision in progress ? https://www.loc.gov/standards/datetime/ -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Next upgrade
I once did make a token attempt at tweaking the disciplining parameters in that SRS-10, but seemed to be getting nowhere and gave up on the effort. Dana On Wed, Nov 22, 2017 at 8:12 PM, Mark Sims wrote: > The PRS-10 does have disciplining parameters that you can tweak. But the > documentation is rather spotty on how to go about choosing good values. > > Also, I doubt that putting a Rb in an OCXO Lucent box would work well. > Rb loop parameters (like time constant) are rather different for the two > classes of oscillator. > > --- > > > the disciplining loop seems to be a bit aggressive so that the poor > oscillator > gets jerked around quite a bit by the GPS > ___ > 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.
