Re: [ntp:questions] Can NTP sync within 1ms
On 27/04/14 19:20, j...@specsol.spam.sux.com wrote: The goal is not to have 12us difference in arrival time, but to be within 12us for transmission time. But it is the difference in arrival time that will affect the quality of the audio that is heard, so it is that which you would need to control. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
William Unruh un...@invalid.ca wrote: On 2014-04-27, Rob nom...@example.com wrote: j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote: The listeners should enjoy a smooth reception while driving around. So of course there should be no time lag between the modulation signals of the different transmitters. Experts in the field tell us we should be within 12us. Unless I fat fingered the calculator, that means the difference in distance between transmitters relative to the receiver can be no more than 3.6 km. 300 meters per microsecond; it is the law... The goal is not to have 12us difference in arrival time, but to be within 12us for transmission time. Why not within 12 psec? Ie, what is the reason for this requirement? And I thought this thread started with 1ms. I have hijacked this thread that was started by someone else who asked if Can NTP sync within 1ms. As usual on usenet, after some postings the topic drifted away. The 12us figure has been mentioned by two independent persons that are experts in the field of co-channel diversity networks and have implemented such networks in the past for professional purposes. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
David Woolley david@ex.djwhome.demon.invalid wrote: On 27/04/14 19:20, j...@specsol.spam.sux.com wrote: The goal is not to have 12us difference in arrival time, but to be within 12us for transmission time. But it is the difference in arrival time that will affect the quality of the audio that is heard, so it is that which you would need to control. But not necessarily within 12us. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
On 2014-04-28, Rob nom...@example.com wrote: Jochen Bern jochen.b...@linworks.de wrote: However, that *does* leave me wondering where the 12 us figure comes into play. With the typical distances between 2m and even 70cm repeaters, the mobile transceivers will see shifts *far* beyond that between different repeaters' signals. The figure comes from two different experts in the field. They have built such systems for the emergency services (police, fire brigade, ambulance) that have been operating in the country for a few decades and have been replaced by a digital (TETRA) system in the meantime. But their knowledge and experience remains valid. In those days we could not afford such an experiment, they used fixed analog leased lines to transfer audio with a fixed and known delay, but today we have internet and GPS and we can achieve the same thing much easier. FWIW, will you have the audio cards output AM (that will then get modulated onto an otherwise unsynchronized HF), or do you plan to have the card generate HF directly into the PA? The existing system mentioned above uses SDR techniques to synthesize the FM signal directly from the digital samples, but we like to use existing repeater hardware that already has FM modulation, so we want to use soundcards to produce analog audio that is fed into the repeaters. The HF is not unsynchronized, it is locked to a GPSDO. But I agree that it would be much more predictable to do it the digital way. Now we have extra variables like the exact deviation setting and the characteristics of the modulator. Fortunately all repeaters run the same hardware (Tait TB8100). I am still investigating how to output digital samples to a soundcard in Linux at exactly determined time (versus just writing sample blocks to the soundcard driver at a predermined moment. they will still be buffered after that) All in all it is funny to read all the that cannot be done-like comments by several persons on a ntp newsgroup while systems like this have been in use since the seventies, and in fact have already been build by amateurs and are in operation today. So I prefer to go by the experience of the people who built those networks, rather than the armchair experts. Not, it cannnot be done, but it is silly to try. I simply have a really really hard time figuring out why you want to do that. For voice, the max frequency is something like 4KHz (eg telephone quality) which is 250us (125us sampling) . It is really really hard for me to figure out what bad things would happen if that were the resolution you used instead of that 12us. It just seems wildly over-specified. And then you make statements like it is the transmission time that needs to be 12us not the reception time, which also do not make sense. And a phase jump even of 120usec I doubt would be audible, maybe 12 ms would be. (are you sure you did not misunderstand your experts?) If it really is 12us I would be really interested in knowing why. I might even learn something. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
On 28/04/14 16:19, William Unruh wrote: For voice, the max frequency is something like 4KHz (eg telephone quality) which is 250us (125us sampling) . Telephone quality is 3.1 kHz bandwidth from 300Hz to 3.4kHz, which allows for channel filters/realisable anti-aliasing filters. I believe that proper NBFM signals should have a 2.8kHz cut off. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
William Unruh un...@invalid.ca wrote: All in all it is funny to read all the that cannot be done-like comments by several persons on a ntp newsgroup while systems like this have been in use since the seventies, and in fact have already been build by amateurs and are in operation today. So I prefer to go by the experience of the people who built those networks, rather than the armchair experts. Not, it cannnot be done, but it is silly to try. I simply have a really really hard time figuring out why you want to do that. You apparently are not familiar with the radio amateur hobby. Most people have a hard time figuring out why you would want to construct a repeater to talk to someone else driving around in a car, when you could simply dial his number on the mobile phone. If it really is 12us I would be really interested in knowing why. I might even learn something. I already said that I was suprised about this as well, but I have heard it from two different persons who had not been working together and it was explicitly asked if if would not be 12ms instead of 12us. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
On 2014-04-28, David Woolley david@ex.djwhome.demon.invalid wrote: On 28/04/14 16:19, William Unruh wrote: For voice, the max frequency is something like 4KHz (eg telephone quality) which is 250us (125us sampling) . Telephone quality is 3.1 kHz bandwidth from 300Hz to 3.4kHz, which allows for channel filters/realisable anti-aliasing filters. Not sure why they would need a lower cutoff, except that it would allow the ancient telephone receivers to comply. Certainly one can make cheap receivers now that go a lot lower than 300Hz. I believe that proper NBFM signals should have a 2.8kHz cut off. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
On Mon, Apr 28, 2014 at 10:14 AM, William Unruh un...@invalid.ca wrote: Not sure why they would need a lower cutoff, except that it would allow the ancient telephone receivers to comply. Certainly one can make cheap receivers now that go a lot lower than 300Hz. Because 3.1 kHz of bandwidth is cheaper for the telcos to trunk than 3.4 kHz. Henry ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
On 04/28/2014 07:37 PM, Henry Hallam wrote: On Mon, Apr 28, 2014 at 10:14 AM, William Unruh un...@invalid.ca wrote: Not sure why they would need a lower cutoff, except that it would allow the ancient telephone receivers to comply. Certainly one can make cheap receivers now that go a lot lower than 300Hz. Because 3.1 kHz of bandwidth is cheaper for the telcos to trunk than 3.4 kHz. Not really. The reason is that DC is used for signalling (e.g. on/off-hook, hookflash, pulse dialing). Way OT tho. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
On 28/04/14 18:14, William Unruh wrote: Not sure why they would need a lower cutoff, except that it would allow the ancient telephone receivers to comply. To give good carrier suppression on analogue carrier systems! I believe that there is also a lot of energy below 300Hz that doesn't contribute to intelligibility. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
On 2014-04-28, Rob nom...@example.com wrote: William Unruh un...@invalid.ca wrote: All in all it is funny to read all the that cannot be done-like comments by several persons on a ntp newsgroup while systems like this have been in use since the seventies, and in fact have already been build by amateurs and are in operation today. So I prefer to go by the experience of the people who built those networks, rather than the armchair experts. Not, it cannnot be done, but it is silly to try. I simply have a really really hard time figuring out why you want to do that. You apparently are not familiar with the radio amateur hobby. Most people have a hard time figuring out why you would want to construct a repeater to talk to someone else driving around in a car, when you could simply dial his number on the mobile phone. That was not what I had trouble figuring out. If it really is 12us I would be really interested in knowing why. I might even learn something. I already said that I was suprised about this as well, but I have heard it from two different persons who had not been working together and it was explicitly asked if if would not be 12ms instead of 12us. And they did not explain themselves!? ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Issues installing ntpd on Win 7
Has anyone recently (within the last few months) tried installing the Meinberg compiled ntpd on Win 7 successfully? I just built a new machine, put a clean copy of Win 7 on it, tried to install ntpd and ended up with the unable to start error (number 1053). The ntpd user account was created, the service was installed, the directories were populated, the config file was generated but it wouldn't start. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Issues installing ntpd on Win 7
On 2014-04-28 17:53, A C wrote: Has anyone recently (within the last few months) tried installing the Meinberg compiled ntpd on Win 7 successfully? I just built a new machine, put a clean copy of Win 7 on it, tried to install ntpd and ended up with the unable to start error (number 1053). The ntpd user account was created, the service was installed, the directories were populated, the config file was generated but it wouldn't start. Which release - current stable 4.2.6p5 - or previous? Did you check to see if the process was already running under TaskManager all users processes? Does the ntp userid have access rights to the config, log, and stats directories? Are you running on W7 32 or 64 bit? What is the output from the command: reg query HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTP /s It should look something like below but perhaps with more quotes and backslashes, different paths, and shorter ImagePath (service start command line): HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTP TypeREG_DWORD0x10 StartREG_DWORD0x3 ErrorControlREG_DWORD0x1 ImagePathREG_SZC:\Program Files (x86)\NTP\bin\ntpd.exe -g -M -s C:/ProgramData/NTP/etc/ -p C:/ProgramData/NTP/etc/ntp.pid -l C:/ProgramData/NTP/etc/ntp.log -f C:/ProgramData/NTP/etc/ntp.drift -c C:/ProgramData/NTP/etc/ntp.conf DisplayNameREG_SZNetwork Time Protocol Daemon DependOnServiceREG_MULTI_SZTcpip WOW64REG_DWORD0x1 ObjectNameREG_SZ.\ntp DescriptionREG_SZSynchronizes the local system clock to a reference time source and (eventually) provide this time to NTP and/or SNTP clients HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTP\Parameters ConfigurationFileREG_SZC:/ProgramData/NTP/etc/ntp.conf If all else fails, try a restart, then an uninstall, then another restart, then another install, then maybe another restart. -- Take care. Thanks, Brian Inglis ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 12us for NBFM
On 2014-04-28 13:20, William Unruh wrote: On 2014-04-28, Rob nom...@example.com wrote: William Unruh un...@invalid.ca wrote: All in all it is funny to read all the that cannot be done-like comments by several persons on a ntp newsgroup while systems like this have been in use since the seventies, and in fact have already been build by amateurs and are in operation today. So I prefer to go by the experience of the people who built those networks, rather than the armchair experts. Not, it cannnot be done, but it is silly to try. I simply have a really really hard time figuring out why you want to do that. You apparently are not familiar with the radio amateur hobby. Most people have a hard time figuring out why you would want to construct a repeater to talk to someone else driving around in a car, when you could simply dial his number on the mobile phone. That was not what I had trouble figuring out. If it really is 12us I would be really interested in knowing why. I might even learn something. I already said that I was suprised about this as well, but I have heard it from two different persons who had not been working together and it was explicitly asked if if would not be 12ms instead of 12us. And they did not explain themselves!? Speculatively and IANA RE (asking in the hope that an RE or Time Nuts mailing list member of this group may provide the correct answer) I understand that the NBFM transmitter starts with phase modulation then integrates, multiplies, and filters the result to the FM carrier frequency, could a phase error more than 12us/s (PPM) possibly generate either a significant signal distortion, and/or unwanted harmonics within the filter passband? -- Take care. Thanks, Brian Inglis ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Attn Linux distributors - pse include PPS
On 26/04/2014 05:05, Harlan Stenn wrote: William Unruh writes: [] More recent ntpd combine server and client in one program. Not sure when that was. It's been the case for at least 20 years' time. This is something that may be different in the upcoming rewrite. H I hope not, as it would make much of the documentation out of date, and destroy much of the simplicity of deployment from the user's point of view. I would find it annoying to have to tell someone Oh, but if you want to pass on the time you need to uninstall what you have now and replace it with the client/server version. Better to have the server incorporated but sitting silent until needed. -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Issues installing ntpd on Win 7
On 29/04/2014 00:53, A C wrote: Has anyone recently (within the last few months) tried installing the Meinberg compiled ntpd on Win 7 successfully? I just built a new machine, put a clean copy of Win 7 on it, tried to install ntpd and ended up with the unable to start error (number 1053). The ntpd user account was created, the service was installed, the directories were populated, the config file was generated but it wouldn't start. Yes, I installed the Meinberg London distribution a few days ago, according to the instructions here: http://www.satsignal.eu/ntp/setup.html No problems, and I could later update it to 4.2.7p440 - the current dev release. Note that I installed /outside/ the Program Files tree, so that NTP and users could have write access to the necessary files. -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Issues installing ntpd on Win 7
On 2014-04-28 18:37, Brian Inglis wrote: On 2014-04-28 17:53, A C wrote: Has anyone recently (within the last few months) tried installing the Meinberg compiled ntpd on Win 7 successfully? I just built a new machine, put a clean copy of Win 7 on it, tried to install ntpd and ended up with the unable to start error (number 1053). The ntpd user account was created, the service was installed, the directories were populated, the config file was generated but it wouldn't start. Which release - current stable 4.2.6p5 - or previous? Did you check to see if the process was already running under TaskManager all users processes? Does the ntp userid have access rights to the config, log, and stats directories? Are you running on W7 32 or 64 bit? It's 64 bit Win 7. The version is the one available on Meinberg's site (4.2.6p5). The process was not running when it attempted to start after installation. All access controls were fine. The registry looked the same as below, too. It just refused to start. Restarts didn't help either. All the things one might expect to be incorrect were fine, it simply refused to start. What is the output from the command: reg query HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTP /s It should look something like below but perhaps with more quotes and backslashes, different paths, and shorter ImagePath (service start command line): HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTP TypeREG_DWORD0x10 StartREG_DWORD0x3 ErrorControlREG_DWORD0x1 ImagePathREG_SZC:\Program Files (x86)\NTP\bin\ntpd.exe -g -M -s C:/ProgramData/NTP/etc/ -p C:/ProgramData/NTP/etc/ntp.pid -l C:/ProgramData/NTP/etc/ntp.log -f C:/ProgramData/NTP/etc/ntp.drift -c C:/ProgramData/NTP/etc/ntp.conf DisplayNameREG_SZNetwork Time Protocol Daemon DependOnServiceREG_MULTI_SZTcpip WOW64REG_DWORD0x1 ObjectNameREG_SZ.\ntp DescriptionREG_SZSynchronizes the local system clock to a reference time source and (eventually) provide this time to NTP and/or SNTP clients HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTP\Parameters ConfigurationFileREG_SZC:/ProgramData/NTP/etc/ntp.conf If all else fails, try a restart, then an uninstall, then another restart, then another install, then maybe another restart. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Can NTP sync within 1ms
For Rob, I would suggest that each TX have a GPS/PPS reference with sky view, and that each PC was identical (e.g. all Raspberry Pi cards), and then getting them synced to with 12 microseconds should be easy. I achieve this even with indoor GPS puck antennas: http://www.satsignal.eu/mrtg/performance_ntp.php on six RPis, with only the occasional glitch caused by signal drop-out. A better located antenna would prevent that. -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Issues installing ntpd on Win 7
On 2014-04-28 21:24, David Taylor wrote: On 29/04/2014 00:53, A C wrote: Has anyone recently (within the last few months) tried installing the Meinberg compiled ntpd on Win 7 successfully? I just built a new machine, put a clean copy of Win 7 on it, tried to install ntpd and ended up with the unable to start error (number 1053). The ntpd user account was created, the service was installed, the directories were populated, the config file was generated but it wouldn't start. Yes, I installed the Meinberg London distribution a few days ago, according to the instructions here: http://www.satsignal.eu/ntp/setup.html No problems, and I could later update it to 4.2.7p440 - the current dev release. Note that I installed /outside/ the Program Files tree, so that NTP and users could have write access to the necessary files. Followed the same instructions, no dice. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Issues installing ntpd on Win 7
On 2014-04-28 21:51, A C wrote: On 2014-04-28 21:24, David Taylor wrote: On 29/04/2014 00:53, A C wrote: Has anyone recently (within the last few months) tried installing the Meinberg compiled ntpd on Win 7 successfully? I just built a new machine, put a clean copy of Win 7 on it, tried to install ntpd and ended up with the unable to start error (number 1053). The ntpd user account was created, the service was installed, the directories were populated, the config file was generated but it wouldn't start. Yes, I installed the Meinberg London distribution a few days ago, according to the instructions here: http://www.satsignal.eu/ntp/setup.html No problems, and I could later update it to 4.2.7p440 - the current dev release. Note that I installed /outside/ the Program Files tree, so that NTP and users could have write access to the necessary files. Followed the same instructions, no dice. Ok, so on a whim I purged it completely from the system. Installed from scratch and the same problem occurred, no starting up of the process. I let the installation complete without letting it try to start the service again. Then I simply performed a reinstall where it detected the existing installation and overwrote the files. It performed an update and suddenly the service starts up on its own. I have no idea why it did that but it took two back to back installations to fix it. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Issues installing ntpd on Win 7
On 29/04/2014 05:51, A C wrote: [] Followed the same instructions, no dice. .. and what are the messages in the Windows Event Log(s)? -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Issues installing ntpd on Win 7
On 2014-04-28 22:23, David Taylor wrote: On 29/04/2014 05:51, A C wrote: [] Followed the same instructions, no dice. .. and what are the messages in the Windows Event Log(s)? The original error messages were: A timeout was reached (3 milliseconds) while waiting for the Network Time Protocol Daemon service to connect. followed by The Network Time Protocol Daemon service failed to start due to the following error: The service did not respond to the start or control request in a timely fashion. No other errors or warnings. It's running now, the logs show synchronization and the only error is regarding the ability to generate the .rnd file. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
