Re: [time-nuts] Question about SA.33 Rb clock
Hi, On 10/12/2017 06:06 PM, Tom Van Baak wrote: Your use of the phrase "real cesium" may be the source of your confusion. The SA.3x uses rubidium and the SA.4x uses cesium. They are all real atoms. These modern MAC / CSAC atomic standards compete with high-end DOCXO quartz oscillators with respect to factors like temperature, stability, and drift. They do not compete with traditional laboratory rubidium or cesium standards. You may be thinking that because some CPT clocks use cesium instead of rubidium that they are special or more accurate, but this is not the case. None of these compact low-power laser / VCSEL / CPT -based frequency standards are primary standards. To follow up on that, even "rubidium" and "cesium" is a bit of misnomers, since you should really say "rubidium optically pumped gas cell clock" and "cesium atomic beam clock", you can build gas cells with cesiums and you can build atomic beams with rubidium. Traditionally rubidium have been very easy to build optically pumped clocks with, but today you can also do that with cesium, which is what the VCSEL based CPT clocks really is. All gas-cells will have the issues of frequency pulling, regardless of rubidium, cesium or other atom being used. The different technologies have different benefits and for some implementation aspects have made different atoms being more preferred over others. As we moved to fountains, rubidium turned out to be a better choice. Cheers, Magnus ___ 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] NTP linked PC clock is slightly ahead of Lady Heather GPS time
Hi Martin, Thanks for this. Rob -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Martin Burnicki Sent: 11 October 2017 18:17 To: time-nuts@febo.com Subject: Re: [time-nuts] NTP linked PC clock is slightly ahead of Lady Heather GPS time Hi Rob, Rob Kimberley wrote:> I'm using the Meinberg NTP Distribution here with their NTP Monitor prog on Win10-64, and two GPS NTP servers.> > Config settings: -> >server 192.168.1.120 iburst minpoll 4 maxpoll 5> server 192.168.1.121 iburst minpoll 4 maxpoll 5> > Consistent sub millisecond results. I've also found that Win10 actually performs way better than Win7. This is because with Windows 8 and newer there is a new API call to read the system time with 100 ns resolution. The older API provides only 1 ms resolution. ntpd uses the new API, if available. Martin ___ 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] Question about SA.33 Rb clock
Hi Hui Zhang, > in the paper CSAC was described that it is based on CPT technology > My question is the SA.3x(or SA.2x) also used this method? Yes. Here's another good read; and it also includes photos of the inside of your SA.33: http://www-users.york.ac.uk/~jke1/Atomic_Clocks/Papers/Commercial%20CPT.pdf > In my impression the SA.3x series clock is called Rubidium clock, > and the SA.45 is a real Cesium CSAC? Your use of the phrase "real cesium" may be the source of your confusion. The SA.3x uses rubidium and the SA.4x uses cesium. They are all real atoms. These modern MAC / CSAC atomic standards compete with high-end DOCXO quartz oscillators with respect to factors like temperature, stability, and drift. They do not compete with traditional laboratory rubidium or cesium standards. You may be thinking that because some CPT clocks use cesium instead of rubidium that they are special or more accurate, but this is not the case. None of these compact low-power laser / VCSEL / CPT -based frequency standards are primary standards. /tvb - Original Message - From: "Jar Sun via time-nuts" To: Sent: Saturday, October 07, 2017 8:27 PM Subject: [time-nuts] Question about SA.33 Rb clock Dear group: I have got a SA.33 Rb module from a second hand GPS clock, at first it works well, but soon after it was damaged that beacuse I was trying to install a heat sink on it, unfortunately I used screws which its size too long, so maybe the screws drilled into inside Rb lamp or inside circuit something? I don't know. I am not expecting this Rb can be receoveyed, I am just hope there is no some martirial hamfully leaked out. TVB gave me some information about this Rb module and a papers on this website: http://tycho.usno.navy.mil/ptti/2002papers/paper52.pdf I have read the paper for two times, but I am confused now, the paper described a principle of CSAC clock in 2002, in the papger CSAC was described that it is based on CPT technology, and the CPT is based on a VCSEL and a very small Cesium Cell and other implement necessarily. My question is the SA.3x(or SA.2x) also used this method? In my impression the SA.3x series clock is called Rubidium clock, and the SA.45 is a real Cesium CSAC? So if SA.3x or SA.2x used the technique which mentioned in paper52, can we say there is some Cesium material in SA.3x? I am totally confused, do anyone can give me some advice? Any information will be appreciated, Thanks a lot. Regards. Hui Zhang ___ 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] NTP linked PC clock is slightly ahead of Lady Heather GPS time
>> These days the speaker is almost the last usable interface for this. > > ….. and the mic input is one of the few inputs left to feed “events” into. Yes, and by connecting the speaker to the mic and issuing a pulse through the speaker you can estimate the latency of the OS. It should act like an echo chamber and the number of echoes per second is your inverse latency. The other trick is to use a TIC to compare the output pulse(s) against your house GPS/1PPS. You then compare the timestamp that the OS thought it was with the real UTC+TIC timestamp. Similarly, put a GPS/1PPS into the mic and compare the time the OS thinks it saw the pulse. The results of these should give a nice pair of UTC offset and jitter plots. If at the same time you also measure the XO directly you can then subtract and pinpoint how much of the error is due to the XO and how much is due to OS design. For extra credit put NTP into the mix and see how badly NTP s/w performs compared to what a h/w solution could so. /tvb ___ 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] NTP linked PC clock is slightly ahead of Lady Heather GPS time
Hi > On Oct 12, 2017, at 5:11 AM, Poul-Henning Kamp wrote: > > > In message > , > Mark Sims > writes: > >> The next release of Heather has an audible tick clock mode where >> it ticks at hh:mm:ss.000 This can be used to set your watch more >> accurately, etc. > > Consider the potential for people to attach wires to the PC-speaker > as a means to get an electrical signal also. > > These days the speaker is almost the last usable interface for this. ….. and the mic input is one of the few inputs left to feed “events” into. Bob > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > ___ > 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] NTP linked PC clock is slightly ahead of Lady Heather GPS time
Hello time-nuts folk, Thanks for all the replies, I see now that it is nothing to concern myself with, and my curiosity is satisfied, much appreciated, you are true time experts! :) Good to see Lady Heather continues to be updated, thanks Mark. on 12/10/2017 12:36 you wrote: > Lady Heather's screen clock ticks when the time message comes in > (which can be offset from the actual time in the message). Heather > applies a receiver type dependent adjustment to the time in the > message and then displays the time. If you enable the digital > millisecond clock you will see that the clock does not necessarily tick at > hh:mm:ss.000 > The next release of Heather has an audible tick clock mode where it > ticks at hh:mm:ss.000 This can be used to set your watch more accurately, > etc. > > ___ > 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. -- Best Regards, Chris Wilson. ___ 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] NTP linked PC clock is slightly ahead of Lady Heather GPS time
In message , Mark Sims writes: >The next release of Heather has an audible tick clock mode where >it ticks at hh:mm:ss.000 This can be used to set your watch more >accurately, etc. Consider the potential for people to attach wires to the PC-speaker as a means to get an electrical signal also. These days the speaker is almost the last usable interface for this. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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.
