Re: [time-nuts] : L1 GPS timing signal(s) into local time on computer(s)
On 8/21/12 9:53 AM, Sarah White wrote: Wow. Okay. The user manual actual considers this cable delay to be worth mention? I can see why the trimble thunderbolt is a favorite among time nuts 3 I'm sold. Cable time offset is in basically all GPSes. An awful lot of GPS receivers (for timing) are installed where there's a long run of coax to the antenna. 100 ft wouldn't be unusual, and that's 120-150 ns in typical coax. Since even the lamest GPS receivers put out a 1 pps that's good to tens of ns, you might as well offer the correction. If all you're interested in is frequency, then you may not care about the correction. If all you're interested is time to, say, microseconds, likewise (until you get up into the 1000 ft of cable range). But, since it's a basic parameter in the GPS engine's calculations, and some applications need it, you might as well always have it. I always thought it was weird to have that feature available in a handheld GPS with a fixed antenna, but I was at a tradeshow asking a Trimble guy about it some 20 years ago.. Here is a paraphrase of the reasons: 1) Our competitor has a removable antenna and they need the cable correction, so we need the cable correction so that in a comparison chart we both have a check mark in that Cable Length Correction. 2) We use the same chip set and software in multiple receivers, and it's easier to just keep it the same. 3) We have a reradiator thing that lets you use an external antenna a cable, and a coupler to the handheld, and for that, the length correction is useful. ___ 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] : L1 GPS timing signal(s) into local time on computer(s)
On Mon, Aug 20, 2012 at 3:10 PM, Sarah White kuze...@gmail.com wrote: I really like that the thunderbolt can (assuming the initial location has been uploaded, or the default site survey has been completed) still keep accurate time / discipline based on a single satellite lock (before falling back on the ovenized crystal in pure holdover mode) All timing mode GPSes can keep time with one GPS sat in view. It works becaus ethe GPS knows it is not moving. and it has the exact location f the one satellite. Holding over when there are zero satellites is not standard and required a good local oscillator. You can built one froma cheap $20 timing GPS and a OCXO and some logic chips. The t-bolt is a GPS with a built-in GPSDO. 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] : L1 GPS timing signal(s) into local time on computer(s)
Thanks Chris. I always appreciate clear explanations. I'm assuming that the fixed location requirement is important to note for purposes of compensating for any dopler shift, as well as the distance the signal must first travel before being decoded. ... I would presume that the fixed location used for above calculations would be relative to the position of the antenna? I read somewhere that even compensating for the length of the antenna cabling is important? This is all so exciting. Thanks everyone. On 8/21/2012 2:01 AM, Chris Albertson wrote: On Mon, Aug 20, 2012 at 3:10 PM, Sarah White kuze...@gmail.com wrote: I really like that the thunderbolt can (assuming the initial location has been uploaded, or the default site survey has been completed) still keep accurate time / discipline based on a single satellite lock (before falling back on the ovenized crystal in pure holdover mode) All timing mode GPSes can keep time with one GPS sat in view. It works becaus ethe GPS knows it is not moving. and it has the exact location f the one satellite. Holding over when there are zero satellites is not standard and required a good local oscillator. You can built one froma cheap $20 timing GPS and a OCXO and some logic chips. The t-bolt is a GPS with a built-in GPSDO. 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] : L1 GPS timing signal(s) into local time on computer(s)
On 08/21/2012 12:35 PM, Sarah White wrote: Thanks Chris. I always appreciate clear explanations. I'm assuming that the fixed location requirement is important to note for purposes of compensating for any dopler shift, as well as the distance the signal must first travel before being decoded. ... I would presume that the fixed location used for above calculations would be relative to the position of the antenna? I read somewhere that even compensating for the length of the antenna cabling is important? Yes, the antenna location is what's being measured. You will want to compensate for cable delay but this is simply a matter of subtracting however many nanoseconds it takes the signal to flow through the cable. It does not directly affect the process of doing fixes (whether for position or for time) because the pulses from all of the satellites flow in parallel once they're inside the cable. ___ 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] : L1 GPS timing signal(s) into local time on computer(s)
On Tue, Aug 21, 2012 at 9:35 AM, Sarah White kuze...@gmail.com wrote: Thanks Chris. I always appreciate clear explanations. I'm assuming that the fixed location requirement is important to note for purposes of compensating for any dopler shift, as well as the distance the signal must first travel before being decoded. ... I would presume that the fixed location used for above calculations would be relative to the position of the antenna? I read somewhere that even compensating for the length of the antenna cabling is important? Yes, the GPS' site survey measure the antenna location. And it will not be exactly right unless you measure the cable length. Yes. the cable length delay is close to the speed of light or aboutone nanosecond per foot. Actually there is a correction called velocity factor that a given cable will have. All this is in the Trimble user manual and I'm sure the UMs for other GPSes. There is delay in the serial cable and in any glue logic chps and in the PPS distibution amp.To push the state of the art you have to carefully model all of this. For normal use you may not have to except if you have really long cables. 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] : L1 GPS timing signal(s) into local time on computer(s)
Wow. Okay. The user manual actual considers this cable delay to be worth mention? I can see why the trimble thunderbolt is a favorite among time nuts 3 I'm sold. On 8/21/2012 12:48 PM, Chris Albertson wrote: On Tue, Aug 21, 2012 at 9:35 AM, Sarah White kuze...@gmail.com wrote: Thanks Chris. I always appreciate clear explanations. I'm assuming that the fixed location requirement is important to note for purposes of compensating for any dopler shift, as well as the distance the signal must first travel before being decoded. ... I would presume that the fixed location used for above calculations would be relative to the position of the antenna? I read somewhere that even compensating for the length of the antenna cabling is important? Yes, the GPS' site survey measure the antenna location. And it will not be exactly right unless you measure the cable length. Yes. the cable length delay is close to the speed of light or aboutone nanosecond per foot. Actually there is a correction called velocity factor that a given cable will have. All this is in the Trimble user manual and I'm sure the UMs for other GPSes. There is delay in the serial cable and in any glue logic chps and in the PPS distibution amp.To push the state of the art you have to carefully model all of this. For normal use you may not have to except if you have really long cables. 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] : L1 GPS timing signal(s) into local time on computer(s)
kuze...@gmail.com said: ... I would presume that the fixed location used for above calculations would be relative to the position of the antenna? A side effect of figuring out where you are is figuring out when you are there. There are 4 unknowns: X, Y, Z, T, so you need 4 equations. You get one equation from each satellite so you need 4 satellites. If you assume you are on the surface of the earth, you can get away with only 3 satellites. Yes, that tells you where the antenna is located. If you know where you are, you only need 1 satellite to get the time. I read somewhere that even compensating for the length of the antenna cabling is important? Wow. Okay. The user manual actual considers this cable delay to be worth mention? Sure. The speed of light in air/vacuum is 1 ft/ns. Coax (and fiber) is slower. Junk coax is roughly half as fast. Good coax (foam) is roughly 2/3rds as fast. So it's easy to get 100 ns but unlikely to get more than a microsecond on an amateur budget. Whether that is important for you depends upon your application and the length of the antenna cable. With a modern not super-expensive scope, it's easy to see 1 ns offsets, so cable lengths could be important on something as simple as comparing the PPS outputs from 2 GPS systems. Don't forget to consider the lengths of other cables in your setup. I remember getting an interesting lesson in this area many years ago. We had a couple of scope probes with long cables. I was using one long one and one normal one and looking at high speed digital signals. The offset was enough to confuse me. -- 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] : L1 GPS timing signal(s) into local time on computer(s)
On Sun, 19 Aug 2012 15:29:22 -0400, Sarah White wrote: oh wow, thanks. I'll try that. Also, I figured out that typing in trimble thunderbolt instead of thunderbolt gps gives me zero hits for phone... but fewer hits for the GPSDO too :( Try to search on : 10mhz gps You should see most thunderbolts,and especially this one (eB#) 170886463609 US located , and the only decent priced Tbolts left on eB CFO - Denmark ___ 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] : L1 GPS timing signal(s) into local time on computer(s)
CFO: oooh, really. So 10mhz reference is pretty standard for a GPS disciplined frequency standard. Thanks. I really like that the thunderbolt can (assuming the initial location has been uploaded, or the default site survey has been completed) still keep accurate time / discipline based on a single satellite lock (before falling back on the ovenized crystal in pure holdover mode) ... Is that a common feature? Know of any good ones other than the trible thunderbolt? On 8/20/2012 5:07 PM, cfo wrote: On Sun, 19 Aug 2012 15:29:22 -0400, Sarah White wrote: oh wow, thanks. I'll try that. Also, I figured out that typing in trimble thunderbolt instead of thunderbolt gps gives me zero hits for phone... but fewer hits for the GPSDO too :( Try to search on : 10mhz gps You should see most thunderbolts,and especially this one (eB#) 170886463609 US located , and the only decent priced Tbolts left on eB CFO - Denmark ___ 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] : L1 GPS timing signal(s) into local time on computer(s)
kuze...@gmail.com said: ... Is that a common feature? Know of any good ones other than the trible thunderbolt? It's standard in GPSDOs. It requires special firmware in the GPS unit. -- 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] : L1 GPS timing signal(s) into local time on computer(s)
Just order one from RJB1998 (http://www.ebay.com/itm/120969870669?ssPageName=STRK:MEWNX:IT_trksid=p3984.m1497.l2649) Friday and it's here today. $169 with free shipping. He included a power cable (6 pin to leads) and a TNC-F cable. Mike Blazer On 8/20/2012 4:07 PM, cfo wrote: On Sun, 19 Aug 2012 15:29:22 -0400, Sarah White wrote: oh wow, thanks. I'll try that. Also, I figured out that typing in trimble thunderbolt instead of thunderbolt gps gives me zero hits for phone... but fewer hits for the GPSDO too :( Try to search on : 10mhz gps You should see most thunderbolts,and especially this one (eB#) 170886463609 US located , and the only decent priced Tbolts left on eB CFO - Denmark ___ 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] L1 GPS timing signal(s) into local time on computer(s)
kuze...@gmail.com said: this is a no-name cheapo SIRF module 1) I need a computer with a serial port. The curent GPS module I'm using is INTERNALLY RS232 -- USB converter, and recognized by my windows 7 computer as: Prolific USB-to-Serial Comm Port (COM3) ... the latency and jitter is horrible, and both are seemingly random. The serial data stream basically doesn't work very well for timekeeping. The problem is a software bug. The info has a wander of roughly 100 ms. I say wander rather than jitter because it is very low frequency. You can't reasonably filter it out. The time constant is hours. http://www.megapathdsl.net/~hmurray/ntp/GPSSiRF-off.gif It is easy to correct for a constant offset. You also need a GPS unit that puts out a PPS signal. I don't know of any low cost ready-to-go units. A low cost unit is a demo board from Sure. http://www.sureelectronics.net/goods.php?id=99 http://www.satsignal.eu/ntp/Sure-GPS.htm You need to add a wire or two. You can also use the Garmin 18X LVC. Google will find directions. The other alternative is something like a Thunderbolt. It will keep good time if the GPS signals fades out - holdover. 3) I'm clueless about mounting an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. Modern GPS receivers are much more sensitive than older gear. They may work well enough without an external antenna. On the other hand, a TBolt only needs 1 satellite after the survey. I'd suggest trying the Sure unit. It's only $35 plus shipping, and that includes antenna and power supply. You do have to add a wire or two. If it works well enough, you are done. If not, you will have learned a lot and can upgrade to a TBolt and/or try an external antenna. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support They contain a lot of noise from ages ago when the PPS stuff wasn't included in the Linux kernel. On a modern Linux system, the kernel is ready to go. You may want to install the pps-tools package. I think you need pps-tools-devel if you want to recompile ntpd and have it support PPS. You will have to do something like this before starting ntpd: if [ ! -e /dev/gps10 ]; then # GPS 18 LVC ln -s /dev/ttyS0 /dev/gps10 setserial /dev/ttyS0 low_latency ldattach PPS /dev/gps10 # makes /dev/pps0 ln -s /dev/pps0 /dev/gpspps10 fi You will also have to learn enough about general system administration to put that chunk of code in a reasonable place. The details probably depend upon which distribution you are using. On Fedora, I used to put it in /etc/sysconfig/ntpd but that broke when they switched to systemd. (I haven't worked out a clean solution yet. I just hacked it in to rc.local) For FreeBSD, I think you have to recompile the kernel to include PPS support. -- 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] L1 GPS timing signal(s) into local time on computer(s)
I will jump in a bit. I, and many have been right where you are. You are correct...USB is a no go for accurate time. Same on windows. So you need a Linux box with serial port. Anything from a Beaglebone, pandabox...or pc will work. You certainly need a gps with a pulse per second output (most have) and you can wire that up to the appropriate line on the serial cable or send to the target computer via gpio pin. The pps thing is fairly simple really. If you are receiving gps data via serial connection it takes a variable amount of time to get each status report from the gps...list time etc etc in text format and sends it repeatedly. This gets ntp to within a second or some fraction thereof...the pps part refines that..no text or anything... Just a one pulse per second separate from the gps info that acts as a exclamation point to tell ntp right here is the actual start of the second! alone the pps wouldn't be useful for time but with the time info ntp already has from the nmea sentences it is priceless for really precise time. That's about it. Once you have gps and pps configured on Linux you should be in the sub 5 microsecond range. It gets tricky getting better than that and you have to Ntpns and really worry about hardware issues that affect precision (system clock stability etc) but it can be done. Doc KX0O Sent from my iPad On Aug 18, 2012, at 11:25 PM, Sarah White kuze...@gmail.com wrote: Hi, this is my first post. First off. Windows 7 USB connection to the GPS (no serial ports / modern computer) and I'm pretty sure that is my main problem. Past few months, I've been trying to figure out my timing issues. Lots of reading trying to figure out how to best configure everything. I'm typically still off (randomly) by 20-100 miliseconds. I'd like to at least get to within 50 microseconds (nanoseconds would be wonderful) 1) I need a computer with a serial port. The curent GPS module I'm using is INTERNALLY RS232 -- USB converter, and recognized by my windows 7 computer as: Prolific USB-to-Serial Comm Port (COM3) ... the latency and jitter is horrible, and both are seemingly random. 2) I need to run my stratum 1 clock (connected to the stratum 0 time source via old-school RS232 serial) on linux or a form of BSD with support for kernel timestamps, and a version of NTP with a driver to supports my reference clock... points 1 and 2 seem fine. 3) I'm clueless about mounting an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. For software, I've used 4.2.6 (stable / production) as well as 4.2.7 (dev version) NTP and haven't been able to tell any difference. Just using the generic NMEA driver / this is a no-name cheapo SIRF module. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support And here is where I give up. As the subject line suggests: HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on computer(s) ___ 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] L1 GPS timing signal(s) into local time on computer(s)
Just one further question. When the pps input triggers, so my linux box knows a second has just ticked; is the time of that second the one the NMEA sentence has just sent, or will send next? Or to put it another way, when I receive an NMEA sentence is this the current time (as was when the sentence was constructed) or the time at the next PPS 'tick'? Thanks in advance. KenD On 19/08/12 11:23, Bill Dailey wrote: I will jump in a bit. I, and many have been right where you are. You are correct...USB is a no go for accurate time. Same on windows. So you need a Linux box with serial port. Anything from a Beaglebone, pandabox...or pc will work. You certainly need a gps with a pulse per second output (most have) and you can wire that up to the appropriate line on the serial cable or send to the target computer via gpio pin. The pps thing is fairly simple really. If you are receiving gps data via serial connection it takes a variable amount of time to get each status report from the gps...list time etc etc in text format and sends it repeatedly. This gets ntp to within a second or some fraction thereof...the pps part refines that..no text or anything... Just a one pulse per second separate from the gps info that acts as a exclamation point to tell ntp right here is the actual start of the second! alone the pps wouldn't be useful for time but with the time info ntp already has from the nmea sentences it is priceless for really precise time. That's about it. Once you have gps and pps configured on Linux you should be in the sub 5 microsecond range. It gets tricky getting better than that and you have to Ntpns and really worry about hardware issues that affect precision (system clock stability etc) but it can be done. Doc KX0O Sent from my iPad On Aug 18, 2012, at 11:25 PM, Sarah White kuze...@gmail.com wrote: Hi, this is my first post. First off. Windows 7 USB connection to the GPS (no serial ports / modern computer) and I'm pretty sure that is my main problem. Past few months, I've been trying to figure out my timing issues. Lots of reading trying to figure out how to best configure everything. I'm typically still off (randomly) by 20-100 miliseconds. I'd like to at least get to within 50 microseconds (nanoseconds would be wonderful) 1) I need a computer with a serial port. The curent GPS module I'm using is INTERNALLY RS232 -- USB converter, and recognized by my windows 7 computer as: Prolific USB-to-Serial Comm Port (COM3) ... the latency and jitter is horrible, and both are seemingly random. 2) I need to run my stratum 1 clock (connected to the stratum 0 time source via old-school RS232 serial) on linux or a form of BSD with support for kernel timestamps, and a version of NTP with a driver to supports my reference clock... points 1 and 2 seem fine. 3) I'm clueless about mounting an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. For software, I've used 4.2.6 (stable / production) as well as 4.2.7 (dev version) NTP and haven't been able to tell any difference. Just using the generic NMEA driver / this is a no-name cheapo SIRF module. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support And here is where I give up. As the subject line suggests: HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on computer(s) ___ 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] L1 GPS timing signal(s) into local time on computer(s)
The time when the names sentence was sent is the time in the sentence.. The pps signals every second..they are independent. Tat is the very nature of the problem with the nmea sentence..latency associated with the message itself. Sent from my iPad On Aug 19, 2012, at 6:11 AM, Ken Duffill k.duff...@ntlworld.com wrote: Just one further question. When the pps input triggers, so my linux box knows a second has just ticked; is the time of that second the one the NMEA sentence has just sent, or will send next? Or to put it another way, when I receive an NMEA sentence is this the current time (as was when the sentence was constructed) or the time at the next PPS 'tick'? Thanks in advance. KenD On 19/08/12 11:23, Bill Dailey wrote: I will jump in a bit. I, and many have been right where you are. You are correct...USB is a no go for accurate time. Same on windows. So you need a Linux box with serial port. Anything from a Beaglebone, pandabox...or pc will work. You certainly need a gps with a pulse per second output (most have) and you can wire that up to the appropriate line on the serial cable or send to the target computer via gpio pin. The pps thing is fairly simple really. If you are receiving gps data via serial connection it takes a variable amount of time to get each status report from the gps...list time etc etc in text format and sends it repeatedly. This gets ntp to within a second or some fraction thereof...the pps part refines that..no text or anything... Just a one pulse per second separate from the gps info that acts as a exclamation point to tell ntp right here is the actual start of the second! alone the pps wouldn't be useful for time but with the time info ntp already has from the nmea sentences it is priceless for really precise time. That's about it. Once you have gps and pps configured on Linux you should be in the sub 5 microsecond range. It gets tricky getting better than that and you have to Ntpns and really worry about hardware issues that affect precision (system clock stability etc) but it can be done. Doc KX0O Sent from my iPad On Aug 18, 2012, at 11:25 PM, Sarah White kuze...@gmail.com wrote: Hi, this is my first post. First off. Windows 7 USB connection to the GPS (no serial ports / modern computer) and I'm pretty sure that is my main problem. Past few months, I've been trying to figure out my timing issues. Lots of reading trying to figure out how to best configure everything. I'm typically still off (randomly) by 20-100 miliseconds. I'd like to at least get to within 50 microseconds (nanoseconds would be wonderful) 1) I need a computer with a serial port. The curent GPS module I'm using is INTERNALLY RS232 -- USB converter, and recognized by my windows 7 computer as: Prolific USB-to-Serial Comm Port (COM3) ... the latency and jitter is horrible, and both are seemingly random. 2) I need to run my stratum 1 clock (connected to the stratum 0 time source via old-school RS232 serial) on linux or a form of BSD with support for kernel timestamps, and a version of NTP with a driver to supports my reference clock... points 1 and 2 seem fine. 3) I'm clueless about mounting an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. For software, I've used 4.2.6 (stable / production) as well as 4.2.7 (dev version) NTP and haven't been able to tell any difference. Just using the generic NMEA driver / this is a no-name cheapo SIRF module. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support And here is where I give up. As the subject line suggests: HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on computer(s) ___ 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] L1 GPS timing signal(s) into local time on computer(s)
an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. For software, I've used 4.2.6 (stable / production) as well as 4.2.7 (dev version) NTP and haven't been able to tell any difference. Just using the generic NMEA driver / this is a no-name cheapo SIRF module. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support And here is where I give up. As the subject line suggests: HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on computer(s) ___ 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] L1 GPS timing signal(s) into local time on computer(s)
ntp already has from the nmea sentences it is priceless for really precise time. That's about it. Once you have gps and pps configured on Linux you should be in the sub 5 microsecond range. It gets tricky getting better than that and you have to Ntpns and really worry about hardware issues that affect precision (system clock stability etc) but it can be done. Doc KX0O Sent from my iPad On Aug 18, 2012, at 11:25 PM, Sarah White kuze...@gmail.com wrote: Hi, this is my first post. First off. Windows 7 USB connection to the GPS (no serial ports / modern computer) and I'm pretty sure that is my main problem. Past few months, I've been trying to figure out my timing issues. Lots of reading trying to figure out how to best configure everything. I'm typically still off (randomly) by 20-100 miliseconds. I'd like to at least get to within 50 microseconds (nanoseconds would be wonderful) 1) I need a computer with a serial port. The curent GPS module I'm using is INTERNALLY RS232 -- USB converter, and recognized by my windows 7 computer as: Prolific USB-to-Serial Comm Port (COM3) ... the latency and jitter is horrible, and both are seemingly random. 2) I need to run my stratum 1 clock (connected to the stratum 0 time source via old-school RS232 serial) on linux or a form of BSD with support for kernel timestamps, and a version of NTP with a driver to supports my reference clock... points 1 and 2 seem fine. 3) I'm clueless about mounting an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. For software, I've used 4.2.6 (stable / production) as well as 4.2.7 (dev version) NTP and haven't been able to tell any difference. Just using the generic NMEA driver / this is a no-name cheapo SIRF module. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support And here is where I give up. As the subject line suggests: HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on computer(s) ___ 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. ___ 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] L1 GPS timing signal(s) into local time on computer(s)
On Sat, Aug 18, 2012 at 10:23 PM, li...@lazygranch.com wrote: If you are using a desktop, I'd suggest putting in a serial card. The Netmos chip based cards work on windows and linux, though your should do an internet search on the particular card before you buy. I have the prolific based converter. It didn't work with my Starloc. (The netmos worked fine with Lady Heather.) I just got a Gearmo branded FTDI based usb to serial. I haven't tried it on the Starloc, but it works well on other I just worked out the cost of power. If you, like me are paying $0.21/KHW a new Atom based PC will pay for itself in less then 6 months . It is astonishing when you actually compute the cost to run a PC 24x7 for one year. A normal desktop or notebook PC is not so expensive to run because it spends most time either powered off or in sleep mode. But an NTP server needs to stay active 24x7.A standard desktop PC can burn $400 or more in electric cost per year. A notebook PC is almost as bad (Notice the 100+ watt rating on the notebook's power brick) The new Atom boards are about 6W and costs only $100 at Amazon.com But, yes, I agree stuffing a PCI serial card in a desktop PC can get you the serial port you need. They work well. Just remember that the desktop will have to stay powered up 24x7 for years. 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] : L1 GPS timing signal(s) into local time on computer(s)
Sarah, If you want to filter in ebay, you can use a- for a subject that you don't want to see. It is the same syntax as you can use in a browser. Regards, Willy -Oorspronkelijk bericht- Van: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Namens time-nuts-requ...@febo.com Verzonden: zondag 19 augustus 2012 19:07 Aan: time-nuts@febo.com Onderwerp: time-nuts Digest, Vol 97, Issue 48 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: L1 GPS timing signal(s) into local time oncomputer(s) (Sarah White) 2. Modern motherboard with RS232 port (Stan, W1LE) 3. Re: L1 GPS timing signal(s) into local time oncomputer(s) (KD0GLS) 4. Embedded NTP servers? (Michael Tharp) 5. Re: Modern motherboard with RS232 port (Chris Albertson) -- Message: 1 Date: Sun, 19 Aug 2012 10:41:39 -0400 From: Sarah White kuze...@gmail.com To: time-nuts@febo.com Subject: Re: [time-nuts] L1 GPS timing signal(s) into local time on computer(s) Message-ID: 5030fb23.7040...@gmail.com Content-Type: text/plain; charset=ISO-8859-1 Ken: From what I've read, most GPS modules which output PPS, the NMEA sentence has the timestamp of the next, upcoming pulse. Regardless of how the NMEA or other time data is, the PPS itself is only a guarantee this is the boundary for a second and NTP documentation typically recommends a second reference clock to number the seconds anyway. Everyone: Thanks everyone. I got many responses which confirm my initial conclusions. I had trouble locating a GPS thunderbolt on ebay because there is an HTC phone with thunderbolt in the name. (I got a few hits for the GPS module, but there is no way to filter out phones or I might just be bad at operating ebay) uhm... yeah. As someone pointed out. It is a total nightmare to figure out which direction my GPS time is wandering, and finding the correct offset. I'm just gonna give up on this USB module, and get a real one with PPS Also, I really hate google's new shopping experience. They started listing less content, and now push content from stores which charge 2-3 times as much. As far as existing hardware goes, I don't have any slots free in my desktop for a serial board... Despite the new google shopping headache, I was able to determine that many older computers from the windows XP era which still have serial ports, and are available refurbished from walmart of all the crazy places. (most of the time, better price than the ones being pushed by google shopping, and even have XP installed and a 1 year warranty) So no problem. I can source a suitable machine to run NTP, and for less than $200, guaranteed. Will probably be using gentoo linux, as the default configuration does NOT expect you to run any specific kernel. I can easily recompile anything I need without breaking unusual, unforeseen dependencies. (doesn't hurt that I've been using gentoo since the stage1 install was preferred, all the way back to the GCC 2.x era) I'm really aiming to run a server which ONLY runs NTP, and at most 1 or two other daemons (light duty on those) Thanks so much everyone. On 8/19/2012 7:11 AM, Ken Duffill wrote: Just one further question. When the pps input triggers, so my linux box knows a second has just ticked; is the time of that second the one the NMEA sentence has just sent, or will send next? Or to put it another way, when I receive an NMEA sentence is this the current time (as was when the sentence was constructed) or the time at the next PPS 'tick'? Thanks in advance. KenD On 19/08/12 11:23, Bill Dailey wrote: I will jump in a bit. I, and many have been right where you are. You are correct...USB is a no go for accurate time. Same on windows. So you need a Linux box with serial port. Anything from a Beaglebone, pandabox...or pc will work. You certainly need a gps with a pulse per second output (most have) and you can wire that up to the appropriate line on the serial cable or send to the target computer via gpio pin. The pps thing is fairly simple really. If you are receiving gps data via serial connection it takes a variable amount of time to get each status report from the gps...list time etc etc in text format and sends it repeatedly. This gets ntp to within a second or some fraction thereof...the pps part refines that..no text or anything... Just a one pulse per second separate from the gps info that acts as a exclamation point to tell ntp right here
Re: [time-nuts] : L1 GPS timing signal(s) into local time on computer(s)
oh wow, thanks. I'll try that. Also, I figured out that typing in trimble thunderbolt instead of thunderbolt gps gives me zero hits for phone... but fewer hits for the GPSDO too :( On 8/19/2012 3:21 PM, Willy Willemse wrote: Sarah, If you want to filter in ebay, you can use a- for a subject that you don't want to see. It is the same syntax as you can use in a browser. Regards, Willy -Oorspronkelijk bericht- Van: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Namens time-nuts-requ...@febo.com Verzonden: zondag 19 augustus 2012 19:07 Aan: time-nuts@febo.com Onderwerp: time-nuts Digest, Vol 97, Issue 48 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: L1 GPS timing signal(s) into local time on computer(s) (Sarah White) 2. Modern motherboard with RS232 port (Stan, W1LE) 3. Re: L1 GPS timing signal(s) into local time on computer(s) (KD0GLS) 4. Embedded NTP servers? (Michael Tharp) 5. Re: Modern motherboard with RS232 port (Chris Albertson) -- Message: 1 Date: Sun, 19 Aug 2012 10:41:39 -0400 From: Sarah White kuze...@gmail.com To: time-nuts@febo.com Subject: Re: [time-nuts] L1 GPS timing signal(s) into local time on computer(s) Message-ID: 5030fb23.7040...@gmail.com Content-Type: text/plain; charset=ISO-8859-1 Ken: From what I've read, most GPS modules which output PPS, the NMEA sentence has the timestamp of the next, upcoming pulse. Regardless of how the NMEA or other time data is, the PPS itself is only a guarantee this is the boundary for a second and NTP documentation typically recommends a second reference clock to number the seconds anyway. Everyone: Thanks everyone. I got many responses which confirm my initial conclusions. I had trouble locating a GPS thunderbolt on ebay because there is an HTC phone with thunderbolt in the name. (I got a few hits for the GPS module, but there is no way to filter out phones or I might just be bad at operating ebay) uhm... yeah. As someone pointed out. It is a total nightmare to figure out which direction my GPS time is wandering, and finding the correct offset. I'm just gonna give up on this USB module, and get a real one with PPS Also, I really hate google's new shopping experience. They started listing less content, and now push content from stores which charge 2-3 times as much. As far as existing hardware goes, I don't have any slots free in my desktop for a serial board... Despite the new google shopping headache, I was able to determine that many older computers from the windows XP era which still have serial ports, and are available refurbished from walmart of all the crazy places. (most of the time, better price than the ones being pushed by google shopping, and even have XP installed and a 1 year warranty) So no problem. I can source a suitable machine to run NTP, and for less than $200, guaranteed. Will probably be using gentoo linux, as the default configuration does NOT expect you to run any specific kernel. I can easily recompile anything I need without breaking unusual, unforeseen dependencies. (doesn't hurt that I've been using gentoo since the stage1 install was preferred, all the way back to the GCC 2.x era) I'm really aiming to run a server which ONLY runs NTP, and at most 1 or two other daemons (light duty on those) Thanks so much everyone. On 8/19/2012 7:11 AM, Ken Duffill wrote: Just one further question. When the pps input triggers, so my linux box knows a second has just ticked; is the time of that second the one the NMEA sentence has just sent, or will send next? Or to put it another way, when I receive an NMEA sentence is this the current time (as was when the sentence was constructed) or the time at the next PPS 'tick'? Thanks in advance. KenD On 19/08/12 11:23, Bill Dailey wrote: I will jump in a bit. I, and many have been right where you are. You are correct...USB is a no go for accurate time. Same on windows. So you need a Linux box with serial port. Anything from a Beaglebone, pandabox...or pc will work. You certainly need a gps with a pulse per second output (most have) and you can wire that up to the appropriate line on the serial cable or send to the target computer via gpio pin. The pps thing is fairly simple really. If you are receiving gps data via serial connection it takes a variable amount of time to get each
Re: [time-nuts] L1 GPS timing signal(s) into local time on computer(s)
Another option is a low end laptop. I use a Dell D400 laptop, with a 1.8GHz Pentium M and it draws about 20W from A/C with the display blanked, which is the way an NTP server will be most of the time. The power brick rating assumes running the laptop AND charging the battery at the same time. The D400 comes with a 60W power brick. Yet, it comes fully packaged with a hardware serial port and when you need to do anything with it, there is no need to hunt for a monitor or a keyboard, and they have built-in battery backup. Try to configure your Atom board similarly and see how much money and time you spend. I have 4 of those at home, they are workhorses. They can be found on Ebay for well under $100. Didier KO4BB Chris Albertson albertson.ch...@gmail.com wrote: On Sat, Aug 18, 2012 at 10:23 PM, li...@lazygranch.com wrote: If you are using a desktop, I'd suggest putting in a serial card. The Netmos chip based cards work on windows and linux, though your should do an internet search on the particular card before you buy. I have the prolific based converter. It didn't work with my Starloc. (The netmos worked fine with Lady Heather.) I just got a Gearmo branded FTDI based usb to serial. I haven't tried it on the Starloc, but it works well on other I just worked out the cost of power. If you, like me are paying $0.21/KHW a new Atom based PC will pay for itself in less then 6 months . It is astonishing when you actually compute the cost to run a PC 24x7 for one year. A normal desktop or notebook PC is not so expensive to run because it spends most time either powered off or in sleep mode. But an NTP server needs to stay active 24x7.A standard desktop PC can burn $400 or more in electric cost per year. A notebook PC is almost as bad (Notice the 100+ watt rating on the notebook's power brick) The new Atom boards are about 6W and costs only $100 at Amazon.com But, yes, I agree stuffing a PCI serial card in a desktop PC can get you the serial port you need. They work well. Just remember that the desktop will have to stay powered up 24x7 for years. 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. -- Sent from my Motorola Droid Razr 4G LTE wireless tracker while I do other things. ___ 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] L1 GPS timing signal(s) into local time on computer(s)
Hi, this is my first post. First off. Windows 7 USB connection to the GPS (no serial ports / modern computer) and I'm pretty sure that is my main problem. Past few months, I've been trying to figure out my timing issues. Lots of reading trying to figure out how to best configure everything. I'm typically still off (randomly) by 20-100 miliseconds. I'd like to at least get to within 50 microseconds (nanoseconds would be wonderful) 1) I need a computer with a serial port. The curent GPS module I'm using is INTERNALLY RS232 -- USB converter, and recognized by my windows 7 computer as: Prolific USB-to-Serial Comm Port (COM3) ... the latency and jitter is horrible, and both are seemingly random. 2) I need to run my stratum 1 clock (connected to the stratum 0 time source via old-school RS232 serial) on linux or a form of BSD with support for kernel timestamps, and a version of NTP with a driver to supports my reference clock... points 1 and 2 seem fine. 3) I'm clueless about mounting an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. For software, I've used 4.2.6 (stable / production) as well as 4.2.7 (dev version) NTP and haven't been able to tell any difference. Just using the generic NMEA driver / this is a no-name cheapo SIRF module. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support And here is where I give up. As the subject line suggests: HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on computer(s) ___ 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] L1 GPS timing signal(s) into local time on computer(s)
If you are using a desktop, I'd suggest putting in a serial card. The Netmos chip based cards work on windows and linux, though your should do an internet search on the particular card before you buy. I have the prolific based converter. It didn't work with my Starloc. (The netmos worked fine with Lady Heather.) I just got a Gearmo branded FTDI based usb to serial. I haven't tried it on the Starloc, but it works well on other devices. -Original Message- From: Sarah White kuze...@gmail.com Sender: time-nuts-boun...@febo.com Date: Sun, 19 Aug 2012 00:25:51 To: time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] L1 GPS timing signal(s) into local time on computer(s) Hi, this is my first post. First off. Windows 7 USB connection to the GPS (no serial ports / modern computer) and I'm pretty sure that is my main problem. Past few months, I've been trying to figure out my timing issues. Lots of reading trying to figure out how to best configure everything. I'm typically still off (randomly) by 20-100 miliseconds. I'd like to at least get to within 50 microseconds (nanoseconds would be wonderful) 1) I need a computer with a serial port. The curent GPS module I'm using is INTERNALLY RS232 -- USB converter, and recognized by my windows 7 computer as: Prolific USB-to-Serial Comm Port (COM3) ... the latency and jitter is horrible, and both are seemingly random. 2) I need to run my stratum 1 clock (connected to the stratum 0 time source via old-school RS232 serial) on linux or a form of BSD with support for kernel timestamps, and a version of NTP with a driver to supports my reference clock... points 1 and 2 seem fine. 3) I'm clueless about mounting an antenna, running cable, grounding / lightning protection, etc... Really want an easy to install one. For software, I've used 4.2.6 (stable / production) as well as 4.2.7 (dev version) NTP and haven't been able to tell any difference. Just using the generic NMEA driver / this is a no-name cheapo SIRF module. Also, trying to wrap my head around these: http://linuxpps.org/wiki/index.php/LinuxPPS_installation http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support And here is where I give up. As the subject line suggests: HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on computer(s) ___ 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.
