Re: [time-nuts] GPS Usage
In message 55371.12.6.201.2.1299648580.squir...@popaccts.quikus.com, J. Fors ter writes: in reality more than 90 percent of the users of GPS worldwide use it primarily for a timing reference. That makes the LORAN shutdown look even more idiotiuc! Well, how can you argue with closing a system that was aiding terrorists ? The reason LORAN-C got killed was that DoD/DHS couldn't jam it if a terrorist with a suitcase-nuke was trying to find his way to Congress. Your government money at work... -- 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] GPS Usage
p...@phk.freebsd.dk said: The reason LORAN-C got killed was that DoD/DHS couldn't jam it if a terrorist with a suitcase-nuke was trying to find his way to Congress. Why can't they jam it? It's just a matter of signal strength. If want to jam a small region, they can use a local transmitter. If they want to disable a large region, they can turn off the transmitters or have them transmit garbage. -- These are my opinions, not necessarily my employer's. 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] GPS Usage
In message 20110309082926.d5f9f800...@ip-64-139-1-69.sjc.megapath.net, Hal Mu rray writes: p...@phk.freebsd.dk said: The reason LORAN-C got killed was that DoD/DHS couldn't jam it if a terrorist with a suitcase-nuke was trying to find his way to Congress. Why can't they jam it? They can, All the need is 3 truck mounted generators, a truck with the electronics and then drape a superconducting loopantenna over a couple of skyskrapers... DHS was concerned this would not be immediately available in an emergency, whereas pretty much any army or air-force base can deliver GPS jamming on minuted notice. -- 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] GPS Usage
El 09/03/2011 06:29, J. Forster escribió: This is a surprise: in reality more than 90 percent of the users of GPS worldwide use it primarily for a timing reference. This is a phallacy, except if we are taking into account indirect GPS users, i.e. admitting that a credit card user is a GPS user because the timestamping of the translation relies on a GPS :) But I suspect that, except in our time-nuts laboratories, the percentage of GPS receivers dedicated to timing compared to those dedicated to positioning is really low. Also, sometimes GPS timing is used because it is unexpensive, but provides an accuracy orders of magnitude better than the real needs (a traffic control radar camera tags the pictures with a one second precision... but uses a GPS, could be tagged with microsecond precission ;) ). And anyway, in a no-GPS world with real mass high-precission timing needs, other methods could be used... that would suppose a higher demand of Cs clocks and H-masers (so we could buy a good user H-maser for USD100 at the place you all know? mmm... not so bad ;) ) -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ 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] GPS Usage
In message 4d7740b8.2040...@hvsistemas.es, Javier Herrero writes: El 09/03/2011 06:29, J. Forster escribi=F3: This is a surprise: in reality more than 90 percent of the users of GPS worldwide use it primarily for a timing reference. This is a phallacy, except if we are taking into account indirect GPS users, By far the biggest one is cell-phone base stations, and since these don't work without good timesync (See recent story about the Koreas) I think it is fair to include the indirect users in the collateral damage. -- 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] Low noise power supply
H I wasn't impressed. The 'scope screen shot of noise levels on the outputs used 20mV/division, and the thickness of the regulated traces told us precisely nothing. Now if the author had measured 20uV noise over a BW of 10Hz to 100kHz (about 63nV/rtHz), or 3uV over the same BW (about 10nV/rtHz), I'd have started to get interested. However as no claims were made, I took the title of Ultra-Low Noise with a large shovel of salt. Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of ewkeh...@aol.com Sent: 08 March 2011 21:41 To: time-nuts@febo.com Subject: [time-nuts] Low noise power supply There is an interesting article in the March 2011 Electronic Products magazine design an ultra low noise supply for analog circuits. It is a combination of switcher and LDO's and written by P Hunter TI so it may also be available on their site. Bert Kehren ___ 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] Low noise power supply
If one can say that the actual noise-floor signal is approx. white noise than the peak to average is a factor of 6 to 7 on a analog scope. I once read this somewhere and found it not a so bad decision. - Henry -- ehydra.dyndns.info David C. Partridge schrieb: H I wasn't impressed. The 'scope screen shot of noise levels on the outputs used 20mV/division, and the thickness of the regulated traces told us precisely nothing. Now if the author had measured 20uV noise over a BW of 10Hz to 100kHz (about 63nV/rtHz), or 3uV over the same BW (about 10nV/rtHz), I'd have started to get interested. However as no claims were made, I took the title of Ultra-Low Noise with a large shovel of salt. Regards, David Partridge ___ 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] Spacecraft Timekeeping
On 3/8/11 9:57 AM, Kevin Watson wrote: Hi Jim, As part of my research into keeping time on rockets and spacecraft, I joined this list to see what I could learn from the masters. Of course I'm a knuckle-head for not assuming that you'd be one of the resident masters grin. Anyway, as my accuracy needs are modest (~10uS across many onboard computers), have access to GPS most of the time and don't really need to worry about relativistic effects (yet, anyway grin) or radiation effects (due to redundancy), I thought I'd use a GPSDO that can handle a decent amount of holdover and then use PTP to distribute time across the vehicle. Do you, or anyone else, have a recomendation for the GPSDO? Jackson Labs' (http://jackson-labs.com/) DROR seems like it might work, but I wonder if there might be better alternatives. I don't know that GPS is your big problem, more the holdover when you can't get a GPS signal because your antenna isn't pointed in the right direction or the high dynamics of the rocket cause it to loose lock. So, you want sync to 10 microseconds over how long a time span? 1ppm would be 10 seconds, or are you looking at minutes or days? And, do you need to sync to the outside world or just within your rocket/spacecraft? That is, as long as local time stays synced, so that simultaneous events on different boxes are simultaneous, even if the local clock drifts, relative to UTC, that's ok. I assume you're looking for small and relatively inexpensive, as opposed to just buying, say, a space qualified Rubidium reference from one of the various suppliers. You also mentioned PTP... so you're interested in distributing time (or at least synchronization), and not adding extra wires for, e.g. IRIG timecode or a 1 pps. PTP can certainly do the microsecond scale sync across Ethernet. If you're using SpaceWire, the timecodes can get microsecond scale sync, as well. ___ 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] Spacecraft Timekeeping
On 3/8/11 11:41 AM, Chris Albertson wrote: On Tue, Mar 8, 2011 at 9:57 AM, Kevin Watsontime-n...@enuuf.com wrote: Hi Jim, As part of my research into keeping time on rockets and spacecraft, I joined this list to see what I could learn from the masters. Of course I'm a knuckle-head for not assuming that you'd be one of the resident masters grin. Anyway, as my accuracy needs are modest (~10uS across many onboard computers), have access to GPS most of the time and don't really need to worry about relativistic effects (yet, anywaygrin) or radiation effects (due to redundancy), I thought I'd use a GPSDO that can handle a decent amount of holdover and then use PTP to distribute time across the vehicle. Do you, or anyone else, have a recomendation for the GPSDO? Jackson Labs' (http://jackson-labs.com/) DROR seems like it might work, but I wonder if there might be better alternatives. Off hand I'd worry a little about vibration. How do crystals work when being shaken with huge amount of mechanical and acoustic energy during launch? Oh, I'm sure that's just a matter of ordering the right oscillator, or packaging. People launch optical payloads that can only tolerate a few Gs, so that's doable. Unless you're doing something like mounting the oscillator on the engine grin... The oscillator in your wristwatch or in a manpack radio probably sees a tougher environment, vibration wise, than most spacecraft gear. There's already crystal controlled radios on rockets for things like range safety and telemetry, and I don't think they do anything particularly exotic. On the other hand, they also probably don't try to do timing to nanoseconds, either. Cooling. Almost all commercial off the shelf gear depends on air and has a maximum altitude at which it will operate. Off gassing might be a problem too if there is flux left on the PCB or even fingerprint oil leftover from assembly. yes and no. Cooling of most leaded components is through the leads to the PC board. Cleaning takes care of outgassing, etc. The Mars Pathfinder rovers used essentially off the shelf commercial radio modems that were cleaned by hand. PTP is a new and not so mature technology so you will need to characterize it on your own and likey port it so the specialized processors you use your self Well.. it's new compared to IRIG and NTP, but it has been around a while. However, given that the 1588 spec has had a couple significant revs, I suspect that interoperability might be dicey. But the basic concept is pretty straightforward, and if you're implementing the ethernet PHY so you can get the hooks to the timing info, then you're in good shape. ___ 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] Spacecraft Timekeeping
On 3/8/11 1:45 PM, Magnus Danielson wrote: Kevin, On 03/08/2011 06:57 PM, Kevin Watson wrote: Hi Jim, snip Do you, or anyone else, have a recomendation for the GPSDO? Jackson Labs' (http://jackson-labs.com/) DROR seems like it might work, but I wonder if there might be better alternatives. First thing to consider is that standard GPSes will not meet your needs, since they have to obey the height and speed limits for export rules. OTOH, if you're building a rocket that's big enough to need something like this, you can likely get the needed export licenses, or at least, comply with the export control laws. But yes, the vanilla off the shelf GPS probably has the don't report over 60,000 ft or 1000 km/hr lockouts. The side-effect is that doppler frequencies may be much higher and both tracking and acquisition needs to include these more extremer doppler frequencies. That would be my concern with GPS... the so called high dynamic environment. LEO orbit is 7km/sec, so you'd think the Doppler would be huge, but actually, that's not a big problem, since you already have to deal with an even higher Doppler from the GPS SVs already. Whether your receivers nav solution can work with a fast moving platform is another story. It may assume that nothing can go that fast, and so it doesn't track. OTOH, if you're buying a GPS module from someone like Trimble or Motorola or whoever, you can probably ask them. Use of PTP within a rocket or spacecraft may or may not be a good thing. NMEA + PPS may suffice and be less power-hungry. IRIG may also be an option. I would agree.. unless you're trying to minimize wire count and you already have Ethernet. Spacecraft designs are very mass and pin count sensitive (every pin in the connector needs to be tested, which costs money, etc.) ___ 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] GPS Usage
OK really getting off topic S without GPS timing Celphones would not work. How is this a bad thing? That means the people talking and texting while driving, might actually stay in their lanes. Sounding pretty good to me. We did not shut down Loran for some crazy plot. We did it to save the budget and the world. That $36M was just killing the Obama administration. With LORAN off we are greening the world, saving birds, improving the economy and creating 1000s of new jobs. (I don't know about the last comment but all of our politicians finish off every sentence with that comment). Regard Paul On Wed, Mar 9, 2011 at 4:37 AM, Javier Herrero jherr...@hvsistemas.eswrote: By far the biggest one is cell-phone base stations, and since these don't work without good timesync (See recent story about the Koreas) I think it is fair to include the indirect users in the collateral damage. Yes... most collateral damages are ever inflinged to indirect users :) Regards, Javier -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ 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] Spacecraft Timekeeping
On 3/8/11 11:05 PM, Magnus Danielson wrote: On 03/09/2011 06:08 AM, Kevin Watson wrote: Hi All. Thanks for responding. There are quite a few GPS receivers that will work outside of the usual commercial-grade GPS limitations, but I'm not too sure I need such a receiver. As my application is to just accuratly time-tag messages for a data recorder, my thinking is to allow a ruggedized GPSDO to stabilize on the pad before launch, and then just before launch force the GPSDO into holdover mode and act as the PTP grandmaster for the onboard computers until we reach orbit. Once on orbit I have other means to synchronize the PTP grandmaster. Why carry the dead weight of something unusable in orbit. Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... I'm going to guess that you want a GPS receiver on orbit for other reasons (like to know where you are, if your IMU or star tracker dies) ___ 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] Low noise power supply
For me, this looks like a advertisement campaign only. Not very sophisticated or ingenious. Read that you don't need LC-filters at the output because of the LDOs. *lol* If the designer ever heard of corner frequency?? And the ISL9000A is the same. - Henry -- ehydra.dyndns.info David C. Partridge schrieb: H I wasn't impressed. The 'scope screen shot of noise levels on the outputs used 20mV/division, and the thickness of the regulated traces told us precisely nothing. Now if the author had measured 20uV noise over a BW of 10Hz to 100kHz (about 63nV/rtHz), or 3uV over the same BW (about 10nV/rtHz), I'd have started to get interested. However as no claims were made, I took the title of Ultra-Low Noise with a large shovel of salt. Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of ewkeh...@aol.com Sent: 08 March 2011 21:41 To: time-nuts@febo.com Subject: [time-nuts] Low noise power supply There is an interesting article in the March 2011 Electronic Products magazine design an ultra low noise supply for analog circuits. It is a combination of switcher and LDO's and written by P Hunter TI so it may also be available on their site. Bert Kehren ___ 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] Low noise power supply
Electronic Products is not a real engineering publication. It is a forum purely for new product releases. Always has been. Articles there are almost always written by applications engineers for the product being touted. I got it free for decades, and threw the magazine away at once, unread. Why, you ask? Simple, the EEM... Electronic Engineers' Master, the giant, multi-volume industry directory with company names and phone numbers, about the size of a cinder block... came free, with a subscription. Best, -John = For me, this looks like a advertisement campaign only. Not very sophisticated or ingenious. Read that you don't need LC-filters at the output because of the LDOs. *lol* If the designer ever heard of corner frequency?? And the ISL9000A is the same. - Henry -- ehydra.dyndns.info David C. Partridge schrieb: H I wasn't impressed. The 'scope screen shot of noise levels on the outputs used 20mV/division, and the thickness of the regulated traces told us precisely nothing. Now if the author had measured 20uV noise over a BW of 10Hz to 100kHz (about 63nV/rtHz), or 3uV over the same BW (about 10nV/rtHz), I'd have started to get interested. However as no claims were made, I took the title of Ultra-Low Noise with a large shovel of salt. Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of ewkeh...@aol.com Sent: 08 March 2011 21:41 To: time-nuts@febo.com Subject: [time-nuts] Low noise power supply There is an interesting article in the March 2011 Electronic Products magazine design an ultra low noise supply for analog circuits. It is a combination of switcher and LDO's and written by P Hunter TI so it may also be available on their site. Bert Kehren ___ 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] Low noise power supply
Hi John and group - For us germans, american magazines always look overloaded with advertisments. The marketenders don't like to hear that the generations under 40-50 are mostly advertisment blind just by natural adaption. The times where I read paper electronics are long gone. The Internet completely took over. Sometimes I go for wooden pdfs in the local university library. But back to the interesting subject - that I personally not fully resolved so there is a need of discussion! Here is a first insight: http://waltjung.org/PDFs/Sources_101_P2.pdf In general: LDO is bad. low Iq is bad too. cheers - Henry -- ehydra.dyndns.info J. Forster schrieb: Electronic Products is not a real engineering publication. It is a forum purely for new product releases. Always has been. Articles there are almost always written by applications engineers for the product being touted. I got it free for decades, and threw the magazine away at once, unread. Why, you ask? Simple, the EEM... Electronic Engineers' Master, the giant, multi-volume industry directory with company names and phone numbers, about the size of a cinder block... came free, with a subscription. Best, -John ___ 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] GPS Usage
Lots of people use GPS for timing because it's cheaper or more convenient in a budgetary sens than alternate approaches. Here at JPL, it's easier, in general, for me to put a GPS timing receiver and GPSDO in a lab than it is to try and run cables from the house sources. The latter requires involvement of more facilities folks and touching more organizations (e.g. the people who send the signal, the people who maintain the wires or fiber, etc.), many of whom will have some sort of continuing charge (which is reasonable.. they ARE providing a service), for which you need a valid charge number. Putting a GPSDO in a lab requires a one-time purchase and a one time facility request to put the antenna in. We did a bit of an informal trade a few years back to look at 4 alternatives for a half dozen labs in our building. 1) Distribute frequency standard and derived time code from JPL Frequency/Timing Lab (the maser) 2) Install a single GPSDO, and distribute the frequency reference and timecode 3) Install a single antenna, splitter, and install a separate GPSDO in each lab 4) Install multiple antennas and GPSDOs, one set for each lab. the latter is the most flexible, and has the smallest individual increment cost (i.e. there's no capital improvement going on) Given the plethora of GPS antennas sprouting from the tops of buildings around here, I suspect others have made similar analyses. ___ 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] Spacecraft Timekeeping
Magnus, Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... I need to keep computers time synchronized from launch through at least arrival on orbit so that time-tagged network messages can be played back with some degree of fidelity. For this, I need the time source on the rocket. Using a GPSDO in holdover mode seems like a good solution. -Kevin - Original Message - From: Magnus Danielson mag...@rubidium.dyndns.org To: time-nuts@febo.com Sent: Tuesday, March 08, 2011 11:05 PM Subject: Re: [time-nuts] Spacecraft Timekeeping On 03/09/2011 06:08 AM, Kevin Watson wrote: Hi All. Thanks for responding. There are quite a few GPS receivers that will work outside of the usual commercial-grade GPS limitations, but I'm not too sure I need such a receiver. As my application is to just accuratly time-tag messages for a data recorder, my thinking is to allow a ruggedized GPSDO to stabilize on the pad before launch, and then just before launch force the GPSDO into holdover mode and act as the PTP grandmaster for the onboard computers until we reach orbit. Once on orbit I have other means to synchronize the PTP grandmaster. Why carry the dead weight of something unusable in orbit. Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... Cheers, Magnus ___ 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] Spacecraft Timekeeping
Jim, I guess I should also have mentioned that I want to synchronize events across the rockets with those happening in our mission operations, and thus need a common time source. Furthermore, this is currently just an experiment, and is not safety or mission critical. We have other GPS units on board that can track all the way to orbit, but they're used for navigation, not time keeping. BTW, you can get oscillators that can withstand 30, 000 gs of shock. The Q-Tech QT88 is one example. -Kevin - Original Message - From: jimlux jim...@earthlink.net To: time-nuts@febo.com Sent: Wednesday, March 09, 2011 6:15 AM Subject: Re: [time-nuts] Spacecraft Timekeeping On 3/8/11 11:05 PM, Magnus Danielson wrote: On 03/09/2011 06:08 AM, Kevin Watson wrote: Hi All. Thanks for responding. There are quite a few GPS receivers that will work outside of the usual commercial-grade GPS limitations, but I'm not too sure I need such a receiver. As my application is to just accuratly time-tag messages for a data recorder, my thinking is to allow a ruggedized GPSDO to stabilize on the pad before launch, and then just before launch force the GPSDO into holdover mode and act as the PTP grandmaster for the onboard computers until we reach orbit. Once on orbit I have other means to synchronize the PTP grandmaster. Why carry the dead weight of something unusable in orbit. Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... I'm going to guess that you want a GPS receiver on orbit for other reasons (like to know where you are, if your IMU or star tracker dies) ___ 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] Spacecraft Timekeeping
On 03/09/2011 03:09 PM, jimlux wrote: On 3/8/11 1:45 PM, Magnus Danielson wrote: Kevin, On 03/08/2011 06:57 PM, Kevin Watson wrote: Hi Jim, snip Do you, or anyone else, have a recomendation for the GPSDO? Jackson Labs' (http://jackson-labs.com/) DROR seems like it might work, but I wonder if there might be better alternatives. First thing to consider is that standard GPSes will not meet your needs, since they have to obey the height and speed limits for export rules. OTOH, if you're building a rocket that's big enough to need something like this, you can likely get the needed export licenses, or at least, comply with the export control laws. But yes, the vanilla off the shelf GPS probably has the don't report over 60,000 ft or 1000 km/hr lockouts. Considering the linked GPS, I just wanted to make the point that a standard off the shelf civilian GPS won't cut it, unless it's for launch pad use only. The side-effect is that doppler frequencies may be much higher and both tracking and acquisition needs to include these more extremer doppler frequencies. That would be my concern with GPS... the so called high dynamic environment. LEO orbit is 7km/sec, so you'd think the Doppler would be huge, but actually, that's not a big problem, since you already have to deal with an even higher Doppler from the GPS SVs already. Whether your receivers nav solution can work with a fast moving platform is another story. It may assume that nothing can go that fast, and so it doesn't track. OTOH, if you're buying a GPS module from someone like Trimble or Motorola or whoever, you can probably ask them. I was trying to point out issues beyond that of export limitations where a normal civilian GPS would not quite cut it. There is many such issues. Use of PTP within a rocket or spacecraft may or may not be a good thing. NMEA + PPS may suffice and be less power-hungry. IRIG may also be an option. I would agree.. unless you're trying to minimize wire count and you already have Ethernet. Spacecraft designs are very mass and pin count sensitive (every pin in the connector needs to be tested, which costs money, etc.) If you only run fast ethernet, you can use spare pins for whatever signal you like. Cheers, Magnus ___ 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] Spacecraft Timekeeping
On 03/09/2011 03:15 PM, jimlux wrote: On 3/8/11 11:05 PM, Magnus Danielson wrote: On 03/09/2011 06:08 AM, Kevin Watson wrote: Hi All. Thanks for responding. There are quite a few GPS receivers that will work outside of the usual commercial-grade GPS limitations, but I'm not too sure I need such a receiver. As my application is to just accuratly time-tag messages for a data recorder, my thinking is to allow a ruggedized GPSDO to stabilize on the pad before launch, and then just before launch force the GPSDO into holdover mode and act as the PTP grandmaster for the onboard computers until we reach orbit. Once on orbit I have other means to synchronize the PTP grandmaster. Why carry the dead weight of something unusable in orbit. Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... I'm going to guess that you want a GPS receiver on orbit for other reasons (like to know where you are, if your IMU or star tracker dies) Notice his last sentence... I agree that there are many uses for a GPS onboard a sat... and if one wants one it needs to handle the altitude, speed, different amount of atmospheric shift, etc. etc. etc. But if he only wants a GPS for launch pad synchronisation and then reverts to other methods, it seems like dead weight to bring it all the way up. Cheers, Magnus ___ 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] Spacecraft Timekeeping
Kevin, On 03/09/2011 06:39 PM, Kevin Watson wrote: Magnus, Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... I need to keep computers time synchronized from launch through at least arrival on orbit so that time-tagged network messages can be played back with some degree of fidelity. For this, I need the time source on the rocket. Using a GPSDO in holdover mode seems like a good solution. If you only need to synchronise on launch pad, then you can separate off the OCXO and training logic (TIC, CPU and DAC) from the GPS receiver and antenna. Then you run in hold-over mode using the pieces you need. You then use the same core for whatever other method you use. If you use a space-capable GPS receiver, then just hook in. Cheers, Magnus ___ 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] Spacecraft Timekeeping
Hi Magnus, As I said in an earlier message, this is an experiment that I want to run and would rather not touch mission and safety-critical GNC components, like our navigation GPS receivers. Mass is not an issue. -Kevin - Original Message - From: Magnus Danielson mag...@rubidium.dyndns.org To: time-nuts@febo.com Sent: Wednesday, March 09, 2011 10:25 AM Subject: Re: [time-nuts] Spacecraft Timekeeping Kevin, On 03/09/2011 06:39 PM, Kevin Watson wrote: Magnus, Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... I need to keep computers time synchronized from launch through at least arrival on orbit so that time-tagged network messages can be played back with some degree of fidelity. For this, I need the time source on the rocket. Using a GPSDO in holdover mode seems like a good solution. If you only need to synchronise on launch pad, then you can separate off the OCXO and training logic (TIC, CPU and DAC) from the GPS receiver and antenna. Then you run in hold-over mode using the pieces you need. You then use the same core for whatever other method you use. If you use a space-capable GPS receiver, then just hook in. Cheers, Magnus ___ 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] difference between Oncore M12 and M12+T (useful when buying online)
Every now and then I see e-mails like these. I would like to remind everyone that Synergy Systems, the USA distributor for the M12 series receivers, offers Ham Radio and Educational (time nuts) users a new M12M with the precision time firmware and an on board battery for only $59.18 with the 10% Ham/Edu discount (sown from $65.75). This unit also includes both Motorola binary and NMEA message formats. Synergy can be found at www.synergy-gps.com or at (858) 566-0666. They have been very good to the Ham and educational communities for many years. Rick W2GPS -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Saturday, March 05, 2011 3:06 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] difference between Oncore M12 and M12+T (useful when buying online) Indeed its not easy to tell whats, what either until you paid for it. I purchased from Fluke.I and my modules is a M12 +. But who knows maybe I was just lucky. Regards Paul WB8TSL On Sat, Mar 5, 2011 at 5:15 PM, John Beale be...@bealecorner.com wrote: In case anyone else is shopping online for a used Motorola Oncore M12+T timing GPS, it's probably useful to know what I just learned: Some online sellers offering M12+T 100 pps GPS may instead send you a M12 Navigation (non-timing) GPS. The differences: Motorola Oncore M12 Navigation GPS: --- * Supports Motorola Binary and NMEA output * does not have 100 Hz output * does not have TRAIM (Timing Receiver Autonomous Integrity Monitor) * does not have sawtooth correction output * 1 PPS 500 ns timing crystal nearest MMCX antenna connector is two-lead can style with bent leads for surface mounting example p/n label: P183T12N12 (final N = Navigation?) photos: http://www.wa5rrn.com/GPS%20Other/Motorola%20M12/m12.pdf https://picasaweb.google.com/bealevideo/GPS#5580118907079326290 Motorola Oncore M12+T Timing GPS: --- * Supports Motorola Binary output only * 1 Hz or 100 Hz output selectable * TRAIM (Timing Receiver Autonomous Integrity Monitor) * sawtooth correction (clock granularity) message available * 1 pps 2nS 1 Sigma, 6nS 6 Sigma (using sawtooth correction message) * 1 pps 10nS 1 Sigma, 20nS 6 Sigma (without correction) smaller leadless surface-mount crystals example p/n label: P283T12T17(final T = Timing?) photos: http://www.wa5rrn.com/GPS%20Other/Motorola%20M12/m12plusbrochure.pdf http://cgi.ebay.co.uk/ws/eBayISAPI.dll?VISuperSizeitem=290308535362 ___ 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] Spacecraft Timekeeping
On 03/09/2011 07:58 PM, Kevin Watson wrote: Hi Magnus, As I said in an earlier message, this is an experiment that I want to run and would rather not touch mission and safety-critical GNC components, like our navigation GPS receivers. Mass is not an issue. In that case, take a Thunderbolt, replace the OCXO with a more vibration tolerant variant, slap an antenna on the top, force it to hold-over mode just before launch and you are all done. For best performance you want to tune up the Thunderbolt parameters to the new OCXO, which is a nice static exercise. For a test it would suffice. Cheers, Magnus ___ 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] Spacecraft Timekeeping
On 3/9/11 10:58 AM, Kevin Watson wrote: Hi Magnus, As I said in an earlier message, this is an experiment that I want to run and would rather not touch mission and safety-critical GNC components, like our navigation GPS receivers. Mass is not an issue. -Kevin So this makes it pretty simple.. You have a GPS receiver that operates on the pad to get initial sync (and perhaps to calibrate your onboard oscillator... you don't actually need to discipline it, just have knowledge) Then, you launch, and do your timestamping with the oscillator... When you get on orbit, and your GPS reacquires, you can recalibrate or resync. For that matter, what you could do is very simple.. run your oscillator and run a counter. Snapshot the value of the counter every time you get a 1pps tick from the GPS. Log the time/position/status messages from the GPS as well. You can then fairly easily post process to back-out the variations in your oscillator (which will be small) and recalibrate your timestamps to UTC. Now.. if you need to have different *spacecraft* be synchronized, the post processing scheme won't work. A separate issue is the onboard distribution of time to 10 microseconds. PTP over Ethernet, SpaceWire Timecodes, or IRIG on a wire would meet that easily. ___ 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] difference between Oncore M12 and M12+T (useful when buying online)
This is an alternative: http://shop-emea.u-blox.com/abashop?s=274p=productdetailsku=553 Nice, as you can program it for PPS at 10KHz or some other frequency. - Henry -- ehydra.dyndns.info Rick Hambly (W2GPS) schrieb: Every now and then I see e-mails like these. I would like to remind everyone that Synergy Systems, the USA distributor for the M12 series receivers, offers Ham Radio and Educational (time nuts) users a new M12M with the precision time firmware and an on board battery for only $59.18 with the 10% Ham/Edu discount (sown from $65.75). This unit also includes both Motorola binary and NMEA message formats. Synergy can be found at www.synergy-gps.com or at (858) 566-0666. They have been very good to the Ham and educational communities for many years. Rick W2GPS ___ 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] NTP IRIG config help
It has Demodulated IRIG as its main IRIG output, but it does have one Modulated IRIG. Others have told me I want the Modulated IRIG; I honestly don't know what the differences are, and I haven't gotten out a scope to see. --Jim On Tue, Mar 8, 2011 at 4:25 AM, Rob Kimberley r...@timing-consultants.com wrote: I looked at the data sheet of the sel-2407 and interestingly it states demodulated IRIG-B, which seems a bit odd. Either it's a modulated code i.e. a sinusoidal wave with amplitude modulation (usually about 3:1), or it's what we call a DC code i.e pulse width data stream not superimposed on the 1 KHz carrier. Rob Kimberley ___ 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] Spacecraft Timekeeping
Hello, El 09/03/2011 19:58, Kevin Watson escribió: As I said in an earlier message, this is an experiment that I want to run and would rather not touch mission and safety-critical GNC components, like our navigation GPS receivers. Mass is not an issue. So I understand that timing is not distributed (or at least not available to you) in the spacecraft, that's a pity... I've seen in some spacecrafts that time is distributed using a PPS signal and a broadcasted message through MIL-1553 bus - would be a lot easier if you could hang to it (in the cases I know, it was a MIL bus only for the science payload TCs HKs - independent from the GNC MIL bus). At least you're lucky since mass is not an issue (I've met people that would have killed for and aditional kg) Regards, Javier -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ 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] NTP IRIG config help
Thanks for the info! I was adjusting the levels with alsamixer, which I suspect is a digital mixer. I hadn't thought of the potential issues there. I was using the onboard sound, but I also have a higher quality Soundblaster sound card. Do some of these vary in quality so much as to be unable to decode IRIG at all? I think I will deploy PPS; I'd also like to deploy something to set my time myself (IRIG sounds good), but I realize its not required. I haven't taken time to find all the connector-pieces to make the required custom cable yet to do PPS; I had the parts on my shelf to dump IRIG into my Line In on the sound card. A related question: for my IRIG out, should I directly dump that into the sound card, use one BNC-T with a terminator, or two BNC-T's with terminators, and pull the connection there? Does it matter? Thanks! --Jim On Mon, Mar 7, 2011 at 11:36 AM, Chris Albertson albertson.ch...@gmail.com wrote: There is an NTP email list. questi...@lists.ntp.org But really, all you need is the 1PPS output and some pool servers. If you have PPS working then all you need is a way to number the seconds and anything can do that. Yes the PPS driver works with other non-NMEA ref clocks It would be good to get IRIG working. One thing you don't say is how you are adjusting the levels. Is it a digital control or an analog? In general you want to keep any digital control at maximum. Reducing it even a little causes loss of dymanic range and reduces the effective with (number of bits) of the sample. In the extream case your nice 24 bit WAV file is turned into 4-bit wide samples. Such is the nature of integer math. Also if you are using the bui8lt-in sound on some PC, quality varies a lot. I'd start with a quality external audio interface. But eiother way. I think the first step is to look at the audio. capture some to a file then look at the waveform using an audio editor. Check for a reasonable amplitude with no clipping. You will need to adjust the analog gain to get a good signa -- = 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. ___ 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] NTP IRIG config help
My clock generates a couple variants of IRIG-B. I wasn't able to find docs on what variant of IRIG-B that NTP expects. I know one variant (which I tested, but am not using, nor do I expect to work) is high precision, and is supposed to include the same accuracy as standard IRIG-B + 1kPPS. --Jim On Mon, Mar 7, 2011 at 12:42 PM, Russell Rezaian rreza...@motorola.com wrote: This may sound a bit basic, so apologies if you have already passed this particular hurdle, but there are several different types of IRIG time code. A number of the clocks I have which generate IRIG can generate different versions of IRIG (e.g. IRIG B, IRIG H) If memory serves, the NTP code expects IRIG B. Have you confirmed that's what your clock is currently configured to generate? -- Russell ___ 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] NTP IRIG config help
IRIG is sometimes provided as a digital code at something useful for directly driving logic (I've seen this intended to drive TTL), and as the same digital code amplitude modulating an audio frequency carrier. The modulated audio is the kind of IRIG that is usually decoded by the sound card input decoders. It's also pretty easy to put on a track on mag tape, which was a very common use in days gone past when you could still get mag tape and people still used it for instrument data recording. The demodulated IRIG sounds like the simple digital signal, and I'd guess you clock generates something that might be intended to drive some sort of digital logic, probably TTL. I strongly suspect you'll get better results with the modulated IRIG using the NTP code and a sound card decoder. -- Russell At 11:35 AM -0800 2011/03/09, Jim Kusznir wrote: It has Demodulated IRIG as its main IRIG output, but it does have one Modulated IRIG. Others have told me I want the Modulated IRIG; I honestly don't know what the differences are, and I haven't gotten out a scope to see. --Jim On Tue, Mar 8, 2011 at 4:25 AM, Rob Kimberley r...@timing-consultants.com wrote: I looked at the data sheet of the sel-2407 and interestingly it states demodulated IRIG-B, which seems a bit odd. Either it's a modulated code i.e. a sinusoidal wave with amplitude modulation (usually about 3:1), or it's what we call a DC code i.e pulse width data stream not superimposed on the 1 KHz carrier. Rob Kimberley ___ 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] NTP IRIG config help
Hi Jim, From what you've described, I think you need to use the modulated IRIG output. I sent a previous email to that effect. The audio card IRIG drivers expect IRIG B data used to modulate an audio carrier (AM). -- Russell At 11:42 AM -0800 2011/03/09, Jim Kusznir wrote: My clock generates a couple variants of IRIG-B. I wasn't able to find docs on what variant of IRIG-B that NTP expects. I know one variant (which I tested, but am not using, nor do I expect to work) is high precision, and is supposed to include the same accuracy as standard IRIG-B + 1kPPS. --Jim On Mon, Mar 7, 2011 at 12:42 PM, Russell Rezaian rreza...@motorola.com wrote: This may sound a bit basic, so apologies if you have already passed this particular hurdle, but there are several different types of IRIG time code. A number of the clocks I have which generate IRIG can generate different versions of IRIG (e.g. IRIG B, IRIG H) If memory serves, the NTP code expects IRIG B. Have you confirmed that's what your clock is currently configured to generate? -- Russell ___ 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] Spacecraft Timekeeping
If there are already other GPS units onboard, also be careful of interference. On some of our balloon work we have had COTS GPS receivers that would jam each other if placed to closely together. It'd be a shame if your $50 cheapie jammed the space-rated unit and sank the whole mission. ___ 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] NTP IRIG config help
On 3/9/11 11:40 AM, Jim Kusznir wrote: Thanks for the info! I was adjusting the levels with alsamixer, which I suspect is a digital mixer. I hadn't thought of the potential issues there. I was using the onboard sound, but I also have a higher quality Soundblaster sound card. Do some of these vary in quality so much as to be unable to decode IRIG at all? I doubt sound card quality makes any difference for IRIG.. it's a low bandwidth low dynamic range signal that doesn't require extreme fidelity. ___ 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] Spacecraft Timekeeping
Magnus, Drop the receiver and antenna out of the equation and just provide a timing signal on launch pad... I need to keep computers time synchronized from launch through at least arrival on orbit so that time-tagged network messages can be played back with some degree of fidelity. For this, I need the time source on the rocket. Using a GPSDO in holdover mode seems like a good solution. -Kevin Some GPSDO learn their hold-over parameters over time, sometime days, in which case you may be in for a surprise. Is there any way you can simulate the temperature, vibration, and g-force (or lack of) trauma that the GPSDO is going to experience during this hour of launch-to-orbit? If not, I suggest a simple test: just throw your GPSDO and battery in a backpack and go jogging. Twirl the backpack in the air every now and then. After an hour I'd be very curious by how many microseconds it's off. /tvb ___ 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] Spacecraft Timekeeping
Hi Tom, Kevin, the JLT DROR GPSDO mentioned by Kevin in the original email may be overkill for this application, as it is designed to provide very low phase noise under extreme vibration conditions, and it is state-of-the-art technology and priced accordingly. It is designed to interface directly with a vehicle power supply, so that may help in simplifying the installation. Phase Noise doesn't seem to be a requirement here, and we do have a standard version that does not have the phase-noise-under-vibration cleanup loop installed to save substantial cost. It should work quite well in the application, as it has various extremely low-g-sensitivity oscillators on board that will keep drift to very small values even under very large acceleration and vibration, and temperature changes. It was designed to be essentially indestructible. If cost is an issue, we have ultra-low-g versions of our FireFly-IIA products available (our g-force product line) that are designed and tested to provide a guaranteed holdover under the conditions that Tom mentions below. They are designed to guarantee drift in backpack type applications without GPS, but with lot's of thermal changes and a very wide temp range, loads of acceleration (shock, vibration, and tilt), and fast warmup. To give an example, we can achieve better than 0.1ppb per g per axis acceleration sensitivity on the worst-case axis on our g-force products. So for example the FireFly-IIA g-force would have the following drift in a hypothetical high-g application: g-force on average over entire trip - 3g (this extreme acceleration would never happen in reality of course) average thermal change - 40 Degrees C allowed warmup time with GPS - 1 hour Drift over 5 hour mission: 3g x 0.1ppb/g + 40C * 0.005ppb/C + 0.1ppb initial error = 0.6ppb overall average error over 5 hours So in this extreme scenario we have 0.6ppb * 5 * 3600 = 10.8 microsecond drift over 5 hours. Aging and retrace is not taken into consideration here, but that should be more than compensated by the unrealistic constant 3g acceleration error we added to the calculation. The cost of our g-force products is only about 2x to 2.5x the price of our standard DOCXO products. bye, Said In a message dated 3/9/2011 12:11:49 Pacific Standard Time, t...@leapsecond.com writes: Some GPSDO learn their hold-over parameters over time, sometime days, in which case you may be in for a surprise. Is there any way you can simulate the temperature, vibration, and g-force (or lack of) trauma that the GPSDO is going to experience during this hour of launch-to-orbit? If not, I suggest a simple test: just throw your GPSDO and battery in a backpack and go jogging. Twirl the backpack in the air every now and then. After an hour I'd be very curious by how many microseconds it's off. /tvb ___ 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] difference between Oncore M12 and M12+T (useful when buying online)
Thanks Rick had no idea On Wed, Mar 9, 2011 at 2:04 PM, Rick Hambly (W2GPS) w2...@cnssys.comwrote: Every now and then I see e-mails like these. I would like to remind everyone that Synergy Systems, the USA distributor for the M12 series receivers, offers Ham Radio and Educational (time nuts) users a new M12M with the precision time firmware and an on board battery for only $59.18 with the 10% Ham/Edu discount (sown from $65.75). This unit also includes both Motorola binary and NMEA message formats. Synergy can be found at www.synergy-gps.com or at (858) 566-0666. They have been very good to the Ham and educational communities for many years. Rick W2GPS -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Saturday, March 05, 2011 3:06 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] difference between Oncore M12 and M12+T (useful when buying online) Indeed its not easy to tell whats, what either until you paid for it. I purchased from Fluke.I and my modules is a M12 +. But who knows maybe I was just lucky. Regards Paul WB8TSL On Sat, Mar 5, 2011 at 5:15 PM, John Beale be...@bealecorner.com wrote: In case anyone else is shopping online for a used Motorola Oncore M12+T timing GPS, it's probably useful to know what I just learned: Some online sellers offering M12+T 100 pps GPS may instead send you a M12 Navigation (non-timing) GPS. The differences: Motorola Oncore M12 Navigation GPS: --- * Supports Motorola Binary and NMEA output * does not have 100 Hz output * does not have TRAIM (Timing Receiver Autonomous Integrity Monitor) * does not have sawtooth correction output * 1 PPS 500 ns timing crystal nearest MMCX antenna connector is two-lead can style with bent leads for surface mounting example p/n label: P183T12N12 (final N = Navigation?) photos: http://www.wa5rrn.com/GPS%20Other/Motorola%20M12/m12.pdf https://picasaweb.google.com/bealevideo/GPS#5580118907079326290 Motorola Oncore M12+T Timing GPS: --- * Supports Motorola Binary output only * 1 Hz or 100 Hz output selectable * TRAIM (Timing Receiver Autonomous Integrity Monitor) * sawtooth correction (clock granularity) message available * 1 pps 2nS 1 Sigma, 6nS 6 Sigma (using sawtooth correction message) * 1 pps 10nS 1 Sigma, 20nS 6 Sigma (without correction) smaller leadless surface-mount crystals example p/n label: P283T12T17(final T = Timing?) photos: http://www.wa5rrn.com/GPS%20Other/Motorola%20M12/m12plusbrochure.pdf http://cgi.ebay.co.uk/ws/eBayISAPI.dll?VISuperSizeitem=290308535362 ___ 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] Spacecraft Timekeeping
On Wed, Mar 9, 2011 at 22:09, jimlux jim...@earthlink.net wrote: OTOH, if you're building a rocket that's big enough to need something like this, you can likely get the needed export licenses, or at least, comply with the export control laws. Wait, he _is_ exporting the whole rocket, anyway, isn't he? Can you claim a rocket launch as an Export Credit? Yes, Officer, we will report to the Customs Department if this equipment re-enters US Territory. We will keep track of it, thank you. And believe me, I will know _precisely_ when that happens. -- Sanjeev Gupta +65 98551208 http://www.linkedin.com/in/ghane ___ 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] Spacecraft Timekeeping
On Wed, Mar 9, 2011 at 5:43 PM, Sanjeev Gupta gha...@gmail.com wrote: Can you claim a rocket launch as an Export Credit? Yes, Officer, we will report to the Customs Department if this equipment re-enters US Territory. We will keep track of it, thank you. And believe me, I will know _precisely_ when that happens. There is precedent for this in the US. I know a case where we paid import duty on an expensive part and then applied for refund and were granted the refund of duty after launch because the part was re-exported. I forget the exact technicalities but the US customs people treated the item as being imported only for re-shipment outside the US. Here is another also from US Customs (My all time favorite bit of bureaucracy) http://i.space.com/images/i/4460/i02/Apollo-11-Immigration-02.jpg Another well known case was the optical window used on a Pioneer Venus spacecraft. It was cut from a rather large diamond imported from Europe. As above import duty was refunded. This made the news because of the huge cost of the 3/4 inch diameter diamond they sliced the window from. -- = 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] Spacecraft Timekeeping
On 3/9/11 5:43 PM, Sanjeev Gupta wrote: On Wed, Mar 9, 2011 at 22:09, jimluxjim...@earthlink.net wrote: OTOH, if you're building a rocket that's big enough to need something like this, you can likely get the needed export licenses, or at least, comply with the export control laws. Wait, he _is_ exporting the whole rocket, anyway, isn't he? Can you claim a rocket launch as an Export Credit? Yes, Officer, we will report to the Customs Department if this equipment re-enters US Territory. We will keep track of it, thank you. And believe me, I will know _precisely_ when that happens. You may laugh, but such questions *do* come up. And accountants ask where things are..I see you received a GPS receiver 2 years ago, and I don't see a shipper for it leaving. Can you tell me where it is? ___ 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] GPS Usage
On Wed, Mar 09, 2011 at 08:01:31AM +, Poul-Henning Kamp wrote: Well, how can you argue with closing a system that was aiding terrorists ? The reason LORAN-C got killed was that DoD/DHS couldn't jam it if a terrorist with a suitcase-nuke was trying to find his way to Congress. Is this tongue in cheek, or do you have any actual basis for stating that DHS was afraid Loran C WASN'T jammable ? If the later, this is a rather provocative concept... make an increasingly vital but easily jammed resource the only readily available means of precision position and time determination so the government (or some government, or for that matter many private malefactors) can be sure to be able to reliably deny accurate position and or time to the public (or at least many targeted groups within the public) at will ? I wonder what the threat analysis behind this one was... making an increasingly vital service more fragile because of what some have called movie thriller plots ? Have they really convinced themselves that bad guys CANNOT figure out a workaround ? It has always happened in the past... Your government money at work... -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ 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] GPS Usage
A good thing every air force base doesn't have a homing beacon. Oh wait, never mind. On 3/9/2011 10:54 PM, David I. Emery wrote: On Wed, Mar 09, 2011 at 08:01:31AM +, Poul-Henning Kamp wrote: Well, how can you argue with closing a system that was aiding terrorists ? ___ 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] GPS Usage
In message 20110310065452.ge6...@pig.dieconsulting.com, David I. Emery writ es: The reason LORAN-C got killed was that DoD/DHS couldn't jam it if a terrorist with a suitcase-nuke was trying to find his way to Congress. Is this tongue in cheek, or do you have any actual basis for stating that DHS was afraid Loran C WASN'T jammable ? I have this information from several independent sources. I wonder what the threat analysis behind this one was... making an increasingly vital service more fragile because of what some have called movie thriller plots ? We are talking about DHS, the same people who want to see your junk in airports, what makes you think there is an analysis and not just security-theater involved ? Poul-Henning -- 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] Spacecraft Timekeeping
El 10/03/2011 02:43, Sanjeev Gupta escribió: On Wed, Mar 9, 2011 at 22:09, jimluxjim...@earthlink.net wrote: OTOH, if you're building a rocket that's big enough to need something like this, you can likely get the needed export licenses, or at least, comply with the export control laws. Wait, he _is_ exporting the whole rocket, anyway, isn't he? Can you claim a rocket launch as an Export Credit? Yes, Officer, we will report to the Customs Department if this equipment re-enters US Territory. We will keep track of it, thank you. And believe me, I will know _precisely_ when that happens. It is more a matter about that the involved technology could be ITAR classified or with other export restrictions. Ask Hughes and Boeing about the fine for export control violations in Intelsat 708 :) http://en.wikipedia.org/wiki/Intelsat_708 Regards, Javier -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ 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.
