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] Austron 1250A
Thanks all I decided to replace the batteries, expecting delivery any minute now. Surprisingly expensive to replace those NiCd's.. Anyway, after looking at the schematics a bit, I was able to stop the relay chatter by setting the unit to charge, and holding down the reset switch for a couple of minutes. That gave the batteries enough charge to power the base of the transistor that holds the relay. Ole ___ 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] XOR frequency doubler question 5/10 Mhz
Chuck Thanks and indeed I do need filters that I have not experimented with and in that respect this would be more like some of the circuits discussed here on time-nuts. I am using nice controlled delay lines and at $66 each thats pretty un-attractive. But hey when you get them for 50 cents at a hamfest you can get crazy. Kind of kicking my self as I think the guy had more. Wasn't sure what to do with them. So the next step would be a 5 Mhz notch. Regards Paul WB8TSL On Fri, Feb 20, 2015 at 11:28 AM, Chuck Harris cfhar...@erols.com wrote: Hi Paul, It isn't that it is bad, it is just that 5 and 15MHz products at 8 to 10dB down isn't very encouraging. To make decent use of this technique, I believe that you would have to install 20 to 30dB of 5MHz rejection, and a 10MHz low pass filter in the output circuitry And, that is in addition to making a simple very stable 90 degree phase shifter. The 5MHz rejection filter is necessary to prevent phase anomalies from appearing due to the beating of the doubled 5MHz fundamental with the XOR gate created 10MHz signal. Any time you add filters, you are adding temperature dependent phase shifters to your circuit. -Chuck Harris paul swed wrote: Experimenting with a 74ls86 XOR doubler for 5 to 10 Mhz. Typically this would use a 90 degree phase shift to the other gate. The gate acting as a mixer to produce 10 Mhz. The reason to experiment is that I have noticed most of the doubler discussions take a 5 Mhz square wave filter it to a sine wave, feed it to a multiplier scheme and then filter the output. The 7486 method eliminates one of those processes. I have accurate delay lines I can adjust in 2 ns increments (Allen Aviation lump LC). The output is a semi asymmetrical square wave due to some gate timing I need to deal with if possible. Setting the delay taps to 90 degrees produces a 10 MHz output with 5 and 15 Mhz 8-10 db down. Lots of other higher frequency outputs. At this point I have no filtering on the output of the 7486. Purposely mis-adjusting the taps sets either the 5 Mhz or 15 Mhz level higher. Other noise and such are many DB down 50 plus. Why is this a bad method as compared to our typical time-nuts discussions? Regards Paul WB8TSL ___ 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] XOR frequency doubler question 5/10 Mhz
Chuck wrote: To make decent use of this technique, I believe that you would have to install 20 to 30dB of 5MHz rejection, and a 10MHz low pass filter in the output circuitry * * * The 5MHz rejection filter is necessary to prevent phase anomalies from appearing due to the beating of the doubled 5MHz fundamental with the XOR gate created 10MHz signal. If you start with 5MHz down 10dB in the output, and apply 30dB of filtering, you end up with 5MHz down 40dB. That is nowhere near enough to avoid anomalies in stability plots. You need the 5MHz component in the output closer to -80dBc than to -40dBc to get the anomalies down toward the noise floor. That is a massive amount of filtering very close to the desired 10MHz output, and is why it is important to start with 5MHz below -40dBc straight from the doubler (no filtering). Best regards, Charles ___ 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.
[time-nuts] XOR frequency doubler question 5/10 Mhz
Experimenting with a 74ls86 XOR doubler for 5 to 10 Mhz. Typically this would use a 90 degree phase shift to the other gate. The gate acting as a mixer to produce 10 Mhz. The reason to experiment is that I have noticed most of the doubler discussions take a 5 Mhz square wave filter it to a sine wave, feed it to a multiplier scheme and then filter the output. The 7486 method eliminates one of those processes. I have accurate delay lines I can adjust in 2 ns increments (Allen Aviation lump LC). The output is a semi asymmetrical square wave due to some gate timing I need to deal with if possible. Setting the delay taps to 90 degrees produces a 10 MHz output with 5 and 15 Mhz 8-10 db down. Lots of other higher frequency outputs. At this point I have no filtering on the output of the 7486. Purposely mis-adjusting the taps sets either the 5 Mhz or 15 Mhz level higher. Other noise and such are many DB down 50 plus. Why is this a bad method as compared to our typical time-nuts discussions? Regards Paul WB8TSL ___ 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] XOR frequency doubler question 5/10 Mhz
Hi Paul, It isn't that it is bad, it is just that 5 and 15MHz products at 8 to 10dB down isn't very encouraging. To make decent use of this technique, I believe that you would have to install 20 to 30dB of 5MHz rejection, and a 10MHz low pass filter in the output circuitry And, that is in addition to making a simple very stable 90 degree phase shifter. The 5MHz rejection filter is necessary to prevent phase anomalies from appearing due to the beating of the doubled 5MHz fundamental with the XOR gate created 10MHz signal. Any time you add filters, you are adding temperature dependent phase shifters to your circuit. -Chuck Harris paul swed wrote: Experimenting with a 74ls86 XOR doubler for 5 to 10 Mhz. Typically this would use a 90 degree phase shift to the other gate. The gate acting as a mixer to produce 10 Mhz. The reason to experiment is that I have noticed most of the doubler discussions take a 5 Mhz square wave filter it to a sine wave, feed it to a multiplier scheme and then filter the output. The 7486 method eliminates one of those processes. I have accurate delay lines I can adjust in 2 ns increments (Allen Aviation lump LC). The output is a semi asymmetrical square wave due to some gate timing I need to deal with if possible. Setting the delay taps to 90 degrees produces a 10 MHz output with 5 and 15 Mhz 8-10 db down. Lots of other higher frequency outputs. At this point I have no filtering on the output of the 7486. Purposely mis-adjusting the taps sets either the 5 Mhz or 15 Mhz level higher. Other noise and such are many DB down 50 plus. Why is this a bad method as compared to our typical time-nuts discussions? Regards Paul WB8TSL ___ 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] ***SPAM*** SRS TSD11 Rubidium Oscillator
TSD11 or TSD12? I have a couple of the latter and they seem to be the same at a PRS10 that I have. I have done some measurements on frequency and stability and they are in spec or there about. Hooked up to RS232, they look and drive like a PRS10. I use the RbMon tool. The ID string is in fact that of a PRS10. That said, I have had more difficulty in getting a lock to a GPS 1PPS source than I have with the PRS10. I haven’t run the cause to ground yet. There are differences in the EEPROM default setup compared to that of my PRS10 and that may be related to the locking issue. a) The PRS10 comes with a Lock Mode of 1, indicated as the default in the PRS10 manual, whereas both TSD12s came with LM of 2. b) The PRS10 came with a Time Offset calibration, whereas the TO value in the TSD12s are zero (uncalibrated). This may not be significant as I got my PRS10 second hand, but it did have a current calibration certificate from SRS. So, as frequency references they are OK, as 1PPS sources unlocked to UTC, they are fine too, but I am not sure on the locking to UTC. They do lock, but not as simply as I think they should. Hope that helps. Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une petite et provisoire sécurité, ne méritent ni liberté ni sécurité. Benjimin Franklin Le 17 févr. 2015 à 23:06, Skip Withrow skip.with...@gmail.com a écrit : Hello Nuts, Anyone know what the differences between a SRS TSD11 and PRS10 are? From all outward appearances it looks like a PRS10, and at first glance it looks like a PRS10 from the inside. Has anyone seen a spec sheet (or manual) for the TSD11? Thanks in advance, Skip Withrow ___ 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] Austron 1250A Tuning tool
Hello My 1250A has drifted outside the range of the front panel control, so the coarse adjust needs some fiddling. The manual makes mention of a special tool to be used for this. I don't have the tool, the closest I can get is a 10 bamboo stick that I cunningly liberated from my wifes sushimaking mat! I wondered if anyone else on the list has this tool, and can send me a description/photo of the tip? I tried widdling the tip of my stick to various shapes, but not knowing what it is supposed to mate with, it is a bit frustrating.. Thank you all ___ 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.
