[time-nuts] Looking for ADEV plot(s) for the SRS model SG384 sig gen
I'm considering purchasing one of these units, but would like to know just how bad/good is bad/good before I leap. I'd get the most useful info for the case of all modulations OFF, "perfect" external reference, and for a reasonable assortment of RF frequencies (or one frequency plus a statement of the rule governing transfer to other frequencies). Thanks, Dana ___ 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] Project GREAT - Galloping Galileo version
If a little eccentricity makes for a good test of relativity, wouldn't a lot of eccentricity be even better? :-) Does anyone know what clock facilities are on the Parker solar probe? Atomic clock? And a drag-free mode would have been great too, but I doubt that was included. 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] Project GREAT - Galloping Galileo version
On 12/8/18 10:12 AM, Peter Monta wrote: If a little eccentricity makes for a good test of relativity, wouldn't a lot of eccentricity be even better? :-) Does anyone know what clock facilities are on the Parker solar probe? Atomic clock? And a drag-free mode would have been great too, but I doubt that was included. Extremely unlikely.. I know one of the PIs for Parker, I'll ask him. If anything, they would fly a USO (a really good crystal in a temperature stabilized enclosure). I'm flying an atomic clock (a CSAC), launching next week, but it will be in a circular orbit, and I'll bet the gravity variations are small enough that they are less than the uncertainty. The other problem is that you need to *measure* that atomic clock against something. The best I can do with my CSAC is compare its 1pps against a Novatel OEM-6 single frequency GPS 1pps, and an onboard 100 MHz oscillator - none of them are outstanding by timenuts standards. (CSAC is around 1E-12 at 1000-1 seconds - see http://www.leapsecond.com/pages/csac/ It's about an order of magnitude worse than a PRS-10 Rb) Tom, with his herd of clocks, can leave some at home and take some with him, and compare them upon return. I would imagine that someone looks at the behavior of the atomic clocks on the GPS satellites in excruciating detail. The signals from GPS are incredibly well studied, and have been recorded at carefully maintained ground sites for decades with high quality reference clocks. There are folks developing and flying a Deep Space Atomic Clock (DSAC), a trapped Hg-ion, which is substantially better. Launch is currently March 2019 (on the Falcon Heavy) It's a bit of a beast: 17.5kg, 17.4 liters (a bit bigger than their original goal of 1kg, 1 liter, ) and 44 watts. It's supposedly going to be in the 1E-14 range at 1000 seconds, and 1E-15 at 100,000 seconds. It will be in LEO, but maybe you can see the variation from the Moon and Sun? ___ 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] Project GREAT - Galloping Galileo version
In message <65c07521-6efc-f139-0722-a28b40330...@earthlink.net>, jimlux writes: >There are folks developing and flying a Deep Space Atomic Clock (DSAC), >[..] >It will be in LEO, but maybe you can see the variation from the Moon and Sun? In LEO for testing ? Otherwise the name seems a bit grandiose ? -- 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@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] Project GREAT - Galloping Galileo version
On 12/8/18 10:58 AM, Poul-Henning Kamp wrote: In message <65c07521-6efc-f139-0722-a28b40330...@earthlink.net>, jimlux writes: There are folks developing and flying a Deep Space Atomic Clock (DSAC), [..] It will be in LEO, but maybe you can see the variation from the Moon and Sun? In LEO for testing ? Otherwise the name seems a bit grandiose ? You take the ride you get, I suspect. I've not talked with the DSAC folks in a while. It might have been a SLS EM-1 originally (to the moon), but they decided to go with FH, just so they could get a ride. I seem to recall way back when that they were going to do a "hosted payload" on something like Iridium Next or a telecom. But that might also have changed. Rummaging on the web a bit, I find that DSAC is riding on Orbital Test Bed from General Atomic maybe it will be in a higher than usual LEO (I saw mention of 720km) or elliptical? ___ 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] Project GREAT - Galloping Galileo version
Hi You might be surprised by how well the CSAC does in orbit. There have been a lot of cases over the years where a device has done much better once it is away from “poking fingers” like pressure and other semi-random stuff …. Bob > On Dec 8, 2018, at 1:49 PM, jimlux wrote: > > On 12/8/18 10:12 AM, Peter Monta wrote: >> If a little eccentricity makes for a good test of relativity, wouldn't a >> lot of eccentricity be even better? :-) >> Does anyone know what clock facilities are on the Parker solar probe? >> Atomic clock? And a drag-free mode would have been great too, but I doubt >> that was included. > > Extremely unlikely.. I know one of the PIs for Parker, I'll ask him. > If anything, they would fly a USO (a really good crystal in a temperature > stabilized enclosure). > > I'm flying an atomic clock (a CSAC), launching next week, but it will be in a > circular orbit, and I'll bet the gravity variations are small enough that > they are less than the uncertainty. > > The other problem is that you need to *measure* that atomic clock against > something. The best I can do with my CSAC is compare its 1pps against a > Novatel OEM-6 single frequency GPS 1pps, and an onboard 100 MHz oscillator - > none of them are outstanding by timenuts standards. > > (CSAC is around 1E-12 at 1000-1 seconds - see > http://www.leapsecond.com/pages/csac/ > > It's about an order of magnitude worse than a PRS-10 Rb) > > Tom, with his herd of clocks, can leave some at home and take some with him, > and compare them upon return. > > I would imagine that someone looks at the behavior of the atomic clocks on > the GPS satellites in excruciating detail. The signals from GPS are > incredibly well studied, and have been recorded at carefully maintained > ground sites for decades with high quality reference clocks. > > > There are folks developing and flying a Deep Space Atomic Clock (DSAC), a > trapped Hg-ion, which is substantially better. Launch is currently March > 2019 (on the Falcon Heavy) It's a bit of a beast: 17.5kg, 17.4 liters (a bit > bigger than their original goal of 1kg, 1 liter, ) and 44 watts. > > It's supposedly going to be in the 1E-14 range at 1000 seconds, and 1E-15 at > 100,000 seconds. > > It will be in LEO, but maybe you can see the variation from the Moon and Sun? > > > > ___ > 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] Project GREAT - Galloping Galileo version
On 12/8/18 11:30 AM, Bob kb8tq wrote: Hi You might be surprised by how well the CSAC does in orbit. There have been a lot of cases over the years where a device has done much better once it is away from “poking fingers” like pressure and other semi-random stuff …. Bob Oh, I'm pretty sure it will do well in a very benign environment - I joked with the reps that if we could figure out how to vent the enclosure after on orbit, the whole "getter filling up" issue would go away. I don't know that I'll be able to measure the performance. We sort of added it at the last minute, to be able to demonstrate the ability measure & calibrate an OCXO without a GPS 1pps, and didn't give a huge amount of thought to how to do real performance measurement. ___ 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] Project GREAT - Galloping Galileo version
Hi What, no 0.046 +/- -.002” vent hole? That used to be a requirement on this sort of thing. Bob > On Dec 8, 2018, at 6:35 PM, jimlux wrote: > > On 12/8/18 11:30 AM, Bob kb8tq wrote: >> Hi >> You might be surprised by how well the CSAC does in orbit. There have been a >> lot of cases >> over the years where a device has done much better once it is away from >> “poking fingers” >> like pressure and other semi-random stuff …. >> Bob > > Oh, I'm pretty sure it will do well in a very benign environment - I joked > with the reps that if we could figure out how to vent the enclosure after on > orbit, the whole "getter filling up" issue would go away. > > I don't know that I'll be able to measure the performance. We sort of added > it at the last minute, to be able to demonstrate the ability measure & > calibrate an OCXO without a GPS 1pps, and didn't give a huge amount of > thought to how to do real performance measurement. > > > > ___ > 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] Project GREAT - Galloping Galileo version
On 12/8/18 4:52 PM, Bob kb8tq wrote: Hi What, no 0.046 +/- -.002” vent hole? Not on the physics package of the CSAC. As I understand it, the vacuum around the physics package is more for thermal isolation than anything else. You can tell that the vacuum is fading because the heater current starts to rise Long digression, near rant, on venting requirements follows We use a Volume/Area ratio <2000 inches (oddly, in US customary units, not metric, unless you want to spend time analyzing the launch pressure profile and your orifice flow rates). I have no idea where the specific value came from, other than it's the lowest tick mark on figure 1 in this paper. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980236692.pdf In particular that paper cites a reference from 1970. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710018690.pdf which alludes to failures, and also talks a lot about how you can do venting wrong (put your vent hole where there's a shock wave, let hot gases in, etc.), but doesn't really address the venting of a box within a box scenario. I find that there is often little actual detailed rationale for such requirements, other than "it worked before, it's easy to meet, so why bother arguing". I'll bet that paper (from 1998?) is basically an attempt to provide an analytical rationale for the "rule of thumb" that probably dates back to the turn of the 19th century in some way. Maybe Lord Rayleigh wrote about it? . That used to be a requirement on this sort of thing. Bob On Dec 8, 2018, at 6:35 PM, jimlux wrote: On 12/8/18 11:30 AM, Bob kb8tq wrote: Hi You might be surprised by how well the CSAC does in orbit. There have been a lot of cases over the years where a device has done much better once it is away from “poking fingers” like pressure and other semi-random stuff …. Bob Oh, I'm pretty sure it will do well in a very benign environment - I joked with the reps that if we could figure out how to vent the enclosure after on orbit, the whole "getter filling up" issue would go away. I don't know that I'll be able to measure the performance. We sort of added it at the last minute, to be able to demonstrate the ability measure & calibrate an OCXO without a GPS 1pps, and didn't give a huge amount of thought to how to do real performance measurement. ___ 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.
[time-nuts] Comparing the performance of 17 different GPSDOs
I recently completed some comparison tests of the PPS and 10 MHz outputs of 17 different GPSDOs. The tests were done with a TAPR TICC time interval counter running in timestamp mode and the data was acquired and processed with Lady Heather. The TICC was clocked by a HP-5071A cesium beam oscillator with the high-performance tube. The TICC has a resolution of around 60 picoseconds. The PPS signal from the GPSDO was connected to channel A of the TICC (for those GPSDOs that have an easily accessible PPS signal). For receivers without a PPS signal available, Heather shows ADEV, HDEV, MDEV, and TDEV data for the 10 MHz signal. For receivers with a PPS, ADEV is shown for the 1PPS and 10 MHz signals. The GPSDO output frequency (10 MHZ) was connected to channel B of the TICC through a TAPR TADD-2 Mini divider to get a 1 Hz output. Note that PPS and 10 MHz plots have a display averaging filter applied. Without this filter the plots mostly show noisy "grass" and not any interesting details. A side effect of the display filter is to reduce the "span" (difference between the max and min values seen) of the plot data. Typically the unfiltered spans are around twice the value shown in the plot header, but for a couple of receivers it is up to a 10x reduction of the raw span. Each GPSDO was allowed to warm up for at least 24 hours, or longer... until the DAC output voltage slope leveled off. The GPSDO antenna was a L1/L2/GPS/GLONASS/BEIDOU antenna from China. With a L1/L2 survey receiver this antenna produces location error ellipse in the 5-10mm range. It is mounted on a 1 meter tripod and fed into an 8-way amplified L1/L2/Glonass/Beidou splitter. The antenna is in a rather horrible location for multi-path and sky view. Lots of tall trees and a 2 story stucco-over-wire mesh house. http://www.eevblog.com/forum/metrology/comparing-the-performance-of-17-different-gpsdos/msg2025295/#msg2025295 ___ 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] Comparing the performance of 17 different GPSDOs
Hi Mark, good job. Have you made an analysis of the results and made some considerations about the parameters you have measured? Luciano Da "time-nuts" time-nuts-boun...@lists.febo.com A "time-nuts@lists.febo.com" time-nuts@lists.febo.com Cc Data Sun, 9 Dec 2018 05:10:17 + Oggetto [time-nuts] Comparing the performance of 17 different GPSDOs I recently completed some comparison tests of the PPS and 10 MHz outputs of 17 different GPSDOs. The tests were done with a TAPR TICC time interval counter running in timestamp mode and the data was acquired and processed with Lady Heather. The TICC was clocked by a HP-5071A cesium beam oscillator with the high-performance tube. The TICC has a resolution of around 60 picoseconds. The PPS signal from the GPSDO was connected to channel A of the TICC (for those GPSDOs that have an easily accessible PPS signal). For receivers without a PPS signal available, Heather shows ADEV, HDEV, MDEV, and TDEV data for the 10 MHz signal. For receivers with a PPS, ADEV is shown for the 1PPS and 10 MHz signals. The GPSDO output frequency (10 MHZ) was connected to channel B of the TICC through a TAPR TADD-2 Mini divider to get a 1 Hz output. Note that PPS and 10 MHz plots have a display averaging filter applied. Without this filter the plots mostly show noisy "grass" and not any interesting details. A side effect of the display filter is to reduce the "span" (difference between the max and min values seen) of the plot data. Typically the unfiltered spans are around twice the value shown in the plot header, but for a couple of receivers it is up to a 10x reduction of the raw span. Each GPSDO was allowed to warm up for at least 24 hours, or longer... until the DAC output voltage slope leveled off. The GPSDO antenna was a L1/L2/GPS/GLONASS/BEIDOU antenna from China. With a L1/L2 survey receiver this antenna produces location error ellipse in the 5-10mm range. It is mounted on a 1 meter tripod and fed into an 8-way amplified L1/L2/Glonass/Beidou splitter. The antenna is in a rather horrible location for multi-path and sky view. Lots of tall trees and a 2 story stucco-over-wire mesh house. http://www.eevblog.com/forum/metrology/comparing-the-performance-of-17-different-gpsdos/msg2025295/#msg2025295 ___ 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.
