Re: [time-nuts] Looking for advice to get a submillisecond setup
On 2015-02-24 03:48, Matt wrote: Thanks for all the advice received on and off list. My main doubt was about the quality of cheap receivers but you cleared that doubt. To answer a few questions, the antenna would be put on top of the building on top right corner of http://referentiel.nouvelobs.com/file/2458497.jpg (the only square with some kind of roof) in Paris. So I am confident we can receive a good signal here. I don't think the tower could be a problem. The tower could create multipath reflections, and electrical equipment on a roof, such as elevator motors, could add noise. On top of the tower or further away south west would reduce reflections. -- Take care. Thanks, Brian Inglis ___ 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] Looking for advice to get a submillisecond setup
The tower could create multipath reflections, and electrical equipment on a roof, such as elevator motors, could add noise. On top of the tower or further away south west would reduce reflections. This might be a very small problem if the goal were nanosecond level timing. But the goal here is sub millisecond so the tower is a non-issue. All you need is a view of most of the sky. don't worry about noise either. NTP will NEVER notice effects smaller than a microsecond 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] Looking for advice to get a submillisecond setup
On 2/20/2015 4:25 PM, Jim Lux wrote: /For an inexpensive NTP for few hundred dollars to get better than a millisecond end of things, I think the integrated GPS antenna/receiver with a suitable computer right next to it is the way to go. Then you're just running a network cable and power. / Given that the subject of a GPS unit integrated with the antenna has been touched, maybe some kind soul could give me some information on this unit : https://dl.dropboxusercontent.com/u/15089947/NavSymm1.jpg https://dl.dropboxusercontent.com/u/15089947/NavSymm3.jpg https://dl.dropboxusercontent.com/u/15089947/NavSymm2.jpg Google is of no help... TIA Alberto --- This email has been checked for viruses by Avast antivirus software. http://www.avast.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] Looking for advice to get a submillisecond setup
Looks like you need the other half of this unit. It looks like it is designed to use fiber optic cable. You would need to other box to accept the fiber cables, decode the data and interface it to a normal computer port. A good, brand new timing receiver is less then $100. So I'd not want to spend that much making something else work. On Sat, Feb 21, 2015 at 1:54 AM, Alberto di Bene dib...@usa.net wrote: On 2/20/2015 4:25 PM, Jim Lux wrote: /For an inexpensive NTP for few hundred dollars to get better than a millisecond end of things, I think the integrated GPS antenna/receiver with a suitable computer right next to it is the way to go. Then you're just running a network cable and power. / Given that the subject of a GPS unit integrated with the antenna has been touched, maybe some kind soul could give me some information on this unit : https://dl.dropboxusercontent.com/u/15089947/NavSymm1.jpg https://dl.dropboxusercontent.com/u/15089947/NavSymm3.jpg https://dl.dropboxusercontent.com/u/15089947/NavSymm2.jpg Google is of no help... TIA Alberto --- This email has been checked for viruses by Avast antivirus software. http://www.avast.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. -- 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] Looking for advice to get a submillisecond setup
Symmetricon swallowed Navstar Systems Ltd. In 1993. So if there were any information available, they would likely have it, but I fear it may be long gone. I did find this reference in the time-nuts archive: http://www.navsync.com/docs/mushroom_data_sheet.pdf Which looks like the same animal ... HtH 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] Looking for advice to get a submillisecond setup
Hi, My university would like to have a 1ms precise source of time to do some networking experiments (measure one way propagation delays etc...). So I wandered on the internet to find the best choice with a budget of ~1000€ (~1100 American dollars). I've been overwhelmed by the number of possibilities (atomic clocks/GPS signal etc...) and as no price appear on the seller websites, it's difficult to rule out options. I hope it's within the scope of the mailing list but I would like some advice on good hardware with the previous constraint (budget ~ 1100 $, precision 1ms). [] I wonder if we should buy a specific box or if we could not plug the antenna to a linux box with gpsd/NTPd on it ? Any advice ? Best regards Matt ___ Matt, As others have said, adding a GPS/PPS device to an existing Linux box should be fine (if you can find one with a COM port these days!). Here are some performance measurements - you can see that even with the low-power and low-cost Raspberry Pi you can get sub ten microsecond results easily: http://www.satsignal.eu/mrtg/performance_ntp.php From those plots, you can see that even the Windows 8.1 boxes with a PPS source would meet your needs. There is a quick-start guide for the Raspberry Pi here: http://www.satsignal.eu/ntp/Raspberry-Pi-quickstart.html Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Looking for advice to get a submillisecond setup
jim...@earthlink.net said: So really, it's a matter of finding a place to put your Garmin receiver and string a cable that's not too long to your *nix box running ntp. The place to put your Garmin receiver may not be as simple as it sounds. It needs a good view of the sky. Roof is best, but a window may be good enough. A machine room is unlikely to work, even if you have a good window. Too much EMI. An elevator control room may have similar problems. I've thought about building a pair of boxes that would use standard CAT-5 cables as an extender for this sort of thing. 4 pairs works nicely: power, TX, RX, PPS. People have done it with a Rpi, if you want to go that route. The RPi has its Ethernet chip connected by USB so that adds a bit of fuzz. I should try to measure that. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for advice to get a submillisecond setup
On Thu, 19 Feb 2015 18:11:08 +0100 Matt matta...@gmail.com wrote: My university would like to have a 1ms precise source of time to do some networking experiments (measure one way propagation delays etc...). So I wandered on the internet to find the best choice with a budget of ~1000€ (~1100 American dollars). I've been overwhelmed by the number of possibilities (atomic clocks/GPS signal etc...) and as no price appear on the seller websites, it's difficult to rule out options. Can you say a little bit more about your setup? There are many choices about how to get time accurately and precisely to a computer, but which one is the best depends highly on your setup and location (and what your requirements are, of course). Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] Looking for advice to get a submillisecond setup
I think the easiest cable to make really long, if one must be long is the antenna cable. Use 100 meters of the kind of cable they use for cable TV. It comes double shield and has those compression type F connectors. The cable can cary both the GPS signal and power for the amplifier that is built into the antenna. If the cable is very long, You would need another in-line amplifier, again powered by the cable itself. And yes, a gps antenna needs a good view of the sky, but the receiver itself can be 100+ meters away from the antenna On Thu, Feb 19, 2015 at 11:36 PM, Hal Murray hmur...@megapathdsl.net wrote: jim...@earthlink.net said: So really, it's a matter of finding a place to put your Garmin receiver and string a cable that's not too long to your *nix box running ntp. The place to put your Garmin receiver may not be as simple as it sounds. It needs a good view of the sky. Roof is best, but a window may be good enough. A machine room is unlikely to work, even if you have a good window. Too much EMI. An elevator control room may have similar problems. I've thought about building a pair of boxes that would use standard CAT-5 cables as an extender for this sort of thing. 4 pairs works nicely: power, TX, RX, PPS. People have done it with a Rpi, if you want to go that route. The RPi has its Ethernet chip connected by USB so that adds a bit of fuzz. I should try to measure that. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for advice to get a submillisecond setup
- Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Friday, February 20, 2015 10:25 AM Subject: Re: [time-nuts] Looking for advice to get a submillisecond setup On 2/20/15 6:30 AM, Chris Albertson wrote: I think the easiest cable to make really long, if one must be long is the antenna cable. Use 100 meters of the kind of cable they use for cable TV. It comes double shield and has those compression type F connectors. The cable can cary both the GPS signal and power for the amplifier that is built into the antenna. If the cable is very long, You would need another in-line amplifier, again powered by the cable itself. that's fine if you have a separate antenna(w/preamp) and receiver.. But something like the Garmin GPS-18x and other similar inexpensive receivers have integrated antennas. And yes, a gps antenna needs a good view of the sky, but the receiver itself can be 100+ meters away from the antenna I think you're getting into receivers that are well into the hundreds of dollars range, if bought new. For an inexpensive NTP for few hundred dollars to get better than a millisecond end of things, I think the integrated GPS antenna/receiver with a suitable computer right next to it is the way to go. Then you're just running a network cable and power. 4 pair Cat5 sometimes works ok with RS232, sometimes not. At the 4800 bps of the garmins, it would probably work ok. At least you're sending power from the same place as you're generating/consuming the signals, so you don't have the common mode voltage difference problem. I like that idea in general.. a pair for power, a pair for TxD, a pair for RxD and a pair for 1pps. I'm not sure you'd want to connect the ground at both ends of the signal pairs, though. What does the supply current to the GPS-18x look like? Maybe it really doesn't make any difference. Hopefully your computer's RS232 input isn't drawing 10s of mA. ___ One needs to be careful with extending the 18X RS232 signal. It really is not true RS232 but more like a 5 volt CMOS like signal. If you are using it in a wood frame house, it might work fine indoors. But in a steel/concrete multi-story commercial or industrial building, I would be more surprised if it worked than not. tm ___ 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] Looking for advice to get a submillisecond setup
On 2/20/15 6:30 AM, Chris Albertson wrote: I think the easiest cable to make really long, if one must be long is the antenna cable. Use 100 meters of the kind of cable they use for cable TV. It comes double shield and has those compression type F connectors. The cable can cary both the GPS signal and power for the amplifier that is built into the antenna. If the cable is very long, You would need another in-line amplifier, again powered by the cable itself. that's fine if you have a separate antenna(w/preamp) and receiver.. But something like the Garmin GPS-18x and other similar inexpensive receivers have integrated antennas. And yes, a gps antenna needs a good view of the sky, but the receiver itself can be 100+ meters away from the antenna I think you're getting into receivers that are well into the hundreds of dollars range, if bought new. For an inexpensive NTP for few hundred dollars to get better than a millisecond end of things, I think the integrated GPS antenna/receiver with a suitable computer right next to it is the way to go. Then you're just running a network cable and power. 4 pair Cat5 sometimes works ok with RS232, sometimes not. At the 4800 bps of the garmins, it would probably work ok. At least you're sending power from the same place as you're generating/consuming the signals, so you don't have the common mode voltage difference problem. I like that idea in general.. a pair for power, a pair for TxD, a pair for RxD and a pair for 1pps. I'm not sure you'd want to connect the ground at both ends of the signal pairs, though. What does the supply current to the GPS-18x look like? Maybe it really doesn't make any difference. Hopefully your computer's RS232 input isn't drawing 10s of mA. ___ 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] Looking for advice to get a submillisecond setup
I think you're getting into receivers that are well into the hundreds of dollars range, if bought new. For an inexpensive NTP for few hundred dollars to get better than a millisecond end of things, I think the integrated GPS antenna/receiver with a suitable computer right next to it is the way to go. Then you're just running a network cable and power. I paid $36 for two Motorola Oncore receivers. These are 55 nanosecond (1 sigma) timing receivers. I think today they cost about $25 each. I paid $27 for the timing antenna that is a helix the inside a pointed redone. The dome has screw holes that fit a common galvanized pipe flange. This is not an expensive setup and the parts are all there on eBay. You need to add a power supply. I use a plug-in power cube. But as I said. Use what you have all GPS receivers have more precision than NTP can make use of. You don't need high-end gear if the requirement is only sub millisecond. Mostly I'd say don't spend money on performance you don't need but in some cases you get great performance for less money. -- 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] Looking for advice to get a submillisecond setup
Not sure how small your University is, Matt. But most telco/networking departments will have an NTP infrastructure already, that may include local GPS clocks. If you look around at the ntp servers on the university LAN and find one or more stratum-1's with millisecond or less delay, you probably already have the source you want. Tim N3QE On Thu, Feb 19, 2015 at 12:11 PM, Matt matta...@gmail.com wrote: Hi, My university would like to have a 1ms precise source of time to do some networking experiments (measure one way propagation delays etc...). So I wandered on the internet to find the best choice with a budget of ~1000€ (~1100 American dollars). I've been overwhelmed by the number of possibilities (atomic clocks/GPS signal etc...) and as no price appear on the seller websites, it's difficult to rule out options. I hope it's within the scope of the mailing list but I would like some advice on good hardware with the previous constraint (budget ~ 1100 $, precision 1ms). We can install an antenna in clear horizon. From what I gather, the GPS option looks a good choice but then I am unsure what the underlying NTP server would look like. It would be in a computer room (some temperature variation is expected, even though there is cooling). Meinberg looks great but I believe they are too expansive for our budget. I've seen that one cheap http://www.gpsntp.com/gps-ntp-services.php but this feedback ( http://www.reddit.com/r/sysadmin/comments/23e72i/gps_ntpserver_rack_mount_device_minireview/ ) is not fantastic. I also read good comments on Garmin 18 hardware but it is so cheap I wonder if it precise enough. I wonder if we should buy a specific box or if we could not plug the antenna to a linux box with gpsd/NTPd on it ? Any advice ? Best regards Matt Nb: the FOSDEM talks did a good job advertising your mailing list :) ___ 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] Looking for advice to get a submillisecond setup
I am unsure which country you are in but the UK supplier http://www.galleon.eu.com/computer-time-clock.html has a range of reasonably priced units that may fit your requirements. Regards Peter Torry On 20/02/2015 16:40, Chris Albertson wrote: I think you're getting into receivers that are well into the hundreds of dollars range, if bought new. For an inexpensive NTP for few hundred dollars to get better than a millisecond end of things, I think the integrated GPS antenna/receiver with a suitable computer right next to it is the way to go. Then you're just running a network cable and power. I paid $36 for two Motorola Oncore receivers. These are 55 nanosecond (1 sigma) timing receivers. I think today they cost about $25 each. I paid $27 for the timing antenna that is a helix the inside a pointed redone. The dome has screw holes that fit a common galvanized pipe flange. This is not an expensive setup and the parts are all there on eBay. You need to add a power supply. I use a plug-in power cube. But as I said. Use what you have all GPS receivers have more precision than NTP can make use of. You don't need high-end gear if the requirement is only sub millisecond. Mostly I'd say don't spend money on performance you don't need but in some cases you get great performance for less money. ___ 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] Looking for advice to get a submillisecond setup
On Fri, Feb 20, 2015 at 1:10 PM, Tom Miller tmiller11...@verizon.net wrote: - Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Friday, February 20, 2015 10:25 AM Subject: Re: [time-nuts] Looking for advice to get a submillisecond setup On 2/20/15 6:30 AM, Chris Albertson wrote: I think the easiest cable to make really long, if one must be long is the antenna cable. Use 100 meters of the kind of cable they use for cable TV. It comes double shield and has those compression type F connectors. The cable can cary both the GPS signal and power for the amplifier that is built into the antenna. If the cable is very long, You would need another in-line amplifier, again powered by the cable itself. that's fine if you have a separate antenna(w/preamp) and receiver.. But something like the Garmin GPS-18x and other similar inexpensive receivers have integrated antennas. And yes, a gps antenna needs a good view of the sky, but the receiver itself can be 100+ meters away from the antenna I think you're getting into receivers that are well into the hundreds of dollars range, if bought new. For an inexpensive NTP for few hundred dollars to get better than a millisecond end of things, I think the integrated GPS antenna/receiver with a suitable computer right next to it is the way to go. Then you're just running a network cable and power. 4 pair Cat5 sometimes works ok with RS232, sometimes not. At the 4800 bps of the garmins, it would probably work ok. At least you're sending power from the same place as you're generating/consuming the signals, so you don't have the common mode voltage difference problem. I like that idea in general.. a pair for power, a pair for TxD, a pair for RxD and a pair for 1pps. I'm not sure you'd want to connect the ground at both ends of the signal pairs, though. What does the supply current to the GPS-18x look like? Maybe it really doesn't make any difference. Hopefully your computer's RS232 input isn't drawing 10s of mA. ___ One needs to be careful with extending the 18X RS232 signal. It really is not true RS232 but more like a 5 volt CMOS like signal. If you are using it in a wood frame house, it might work fine indoors. But in a steel/concrete multi-story commercial or industrial building, I would be more surprised if it worked than not. I've had poor luck extending fake RS232 using cat5 wire. It works well if you use differential signaling Convert the cos level serial to RS422 and you can go almost a mile using cheap cat-5 wire. And I've also have worse luck extending a 1PPS plus using cat-5. The solution is RS422 signaling for the plus.But I finally gave up as running a longer antenna cable has easier. tm ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for advice to get a submillisecond setup
Standalone receivers don't have to be expensive. Take a look at the GPS receiver modules at sparkfun.com. They are under $100 (some way under), and some either require or can take an external antenna, and they provide 1 PPS output. Garmin themselves sells receiver boards without integrated antennas. Now, they are navigation not timing receivers, so the 1 PPS accuracy is likely only a microsecond or so, not in the nanosecond range. But that's plenty for NTP. And because they are recent receiver designs, they have higher sensitivity and faster acquisition than older receivers. Some support WAAS corrections. -Dave On 20/02/2015 10:25, Jim Lux wrote: And yes, a gps antenna needs a good view of the sky, but the receiver itself can be 100+ meters away from the antenna I think you're getting into receivers that are well into the hundreds of dollars range, if bought new. ___ 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] Looking for advice to get a submillisecond setup
Hi, My university would like to have a 1ms precise source of time to do some networking experiments (measure one way propagation delays etc...). So I wandered on the internet to find the best choice with a budget of ~1000€ (~1100 American dollars). I've been overwhelmed by the number of possibilities (atomic clocks/GPS signal etc...) and as no price appear on the seller websites, it's difficult to rule out options. I hope it's within the scope of the mailing list but I would like some advice on good hardware with the previous constraint (budget ~ 1100 $, precision 1ms). We can install an antenna in clear horizon. From what I gather, the GPS option looks a good choice but then I am unsure what the underlying NTP server would look like. It would be in a computer room (some temperature variation is expected, even though there is cooling). Meinberg looks great but I believe they are too expansive for our budget. I've seen that one cheap http://www.gpsntp.com/gps-ntp-services.php but this feedback (http://www.reddit.com/r/sysadmin/comments/23e72i/gps_ntpserver_rack_mount_device_minireview/) is not fantastic. I also read good comments on Garmin 18 hardware but it is so cheap I wonder if it precise enough. I wonder if we should buy a specific box or if we could not plug the antenna to a linux box with gpsd/NTPd on it ? Any advice ? Best regards Matt Nb: the FOSDEM talks did a good job advertising your mailing list :) ___ 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] Looking for advice to get a submillisecond setup
I'll second that. sub-millisend timing using NTP is very easy and not expensive. An old Motorola timing GPS receiver can be bought for about $20 and then all you need in some kind of computer. NTP can run on any existing computer while it does it's normal functions. Getting below a microsecond is MUCH harder but getting 100X better than your millisecond level goal is cheap and easy. I like the old Motorola Oncore series because of their price and performance. They are very inexpensive an 50 nanosecond 1 sigma error is typical. But the Garmin will work too. Use what you have. NTP really can't make use a nanosecond level clocks. NTP works in microseconds. On Thu, Feb 19, 2015 at 2:34 PM, Jim Lux jim...@earthlink.net wrote: On 2/19/15 9:11 AM, Matt wrote: Hi, My university would like to have a 1ms precise source of time to do some networking experiments (measure one way propagation delays etc...). So I wandered on the internet to find the best choice with a budget of ~1000€ (~1100 American dollars). I've been overwhelmed by the number of possibilities (atomic clocks/GPS signal etc...) and as no price appear on the seller websites, it's difficult to rule out options. An inexpensive GPS receiver with a 1pps output will easily get you to much better than 1 millisecond. The Garmin 18 is but one choice. It has the advantage that it's already packaged, as opposed to, say, one of the little modules designed to be attached to a Arduino. Configuring ntp to use it is just a matter of setting up the file properly. NTP will use the 1pps coming in on one of the modem control signals (DTR, DCD, RI, etc.) (I use a USB cable to get 5V to run my GPS-18x-LVC, and wire 1pps to DCD, pin 1 on the 9 pin connector) So really, it's a matter of finding a place to put your Garmin receiver and string a cable that's not too long to your *nix box running ntp. People have done it with a Rpi, if you want to go that route. I also read good comments on Garmin 18 hardware but it is so cheap I wonder if it precise enough. I wonder if we should buy a specific box or if we could not plug the antenna to a linux box with gpsd/NTPd on it ? That's exactly what you want to do. http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm http://www.rjsystems.nl/en/2100-ntpd-garmin-gps-18-lvc-gpsd.php (everything there should work fine with the current GPS-18x-LVC, but I'm sure someone on the list has actually done it and can confirm.) http://www.catb.org/gpsd/gpsd-time-service-howto.html Yeah, the Garmin is cheap ($85 US), so you're not going to get nanosecond timing, just microsecond level. Since you need milliseconds, it's plenty good enough. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for advice to get a submillisecond setup
On 2/19/15 9:11 AM, Matt wrote: Hi, My university would like to have a 1ms precise source of time to do some networking experiments (measure one way propagation delays etc...). So I wandered on the internet to find the best choice with a budget of ~1000€ (~1100 American dollars). I've been overwhelmed by the number of possibilities (atomic clocks/GPS signal etc...) and as no price appear on the seller websites, it's difficult to rule out options. An inexpensive GPS receiver with a 1pps output will easily get you to much better than 1 millisecond. The Garmin 18 is but one choice. It has the advantage that it's already packaged, as opposed to, say, one of the little modules designed to be attached to a Arduino. Configuring ntp to use it is just a matter of setting up the file properly. NTP will use the 1pps coming in on one of the modem control signals (DTR, DCD, RI, etc.) (I use a USB cable to get 5V to run my GPS-18x-LVC, and wire 1pps to DCD, pin 1 on the 9 pin connector) So really, it's a matter of finding a place to put your Garmin receiver and string a cable that's not too long to your *nix box running ntp. People have done it with a Rpi, if you want to go that route. I also read good comments on Garmin 18 hardware but it is so cheap I wonder if it precise enough. I wonder if we should buy a specific box or if we could not plug the antenna to a linux box with gpsd/NTPd on it ? That's exactly what you want to do. http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm http://www.rjsystems.nl/en/2100-ntpd-garmin-gps-18-lvc-gpsd.php (everything there should work fine with the current GPS-18x-LVC, but I'm sure someone on the list has actually done it and can confirm.) http://www.catb.org/gpsd/gpsd-time-service-howto.html Yeah, the Garmin is cheap ($85 US), so you're not going to get nanosecond timing, just microsecond level. Since you need milliseconds, it's plenty good enough. ___ 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.
