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 <[email protected]> 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 -- [email protected] > 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 -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
