Re: [time-nuts] Holdover
Thanks Magnus! These look like good guidelines. I'll see what I can come up with. Bob - AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Magnus Danielson To: time-nuts@febo.com Cc: mag...@rubidium.se Sent: Tuesday, August 16, 2016 6:49 PM Subject: Re: [time-nuts] Holdover Bob, On 08/16/2016 11:31 PM, Bob Stewart wrote: > Hi Attila, > In my unit, which is a frequency standard, I chose to tell the receiver to > stop sending 1PPS pulses when it loses sync to the sats. And since the 1PPS > is no longer coming, the PLL does nothing and the DAC doesn't change. (Let's > avoid the question of aging correction for now.) So, I'm wondering where to > go and what to do if I want to get time from my unit. Clearly I could just > tell the receiver to continue to send 1PPS pulses and sync to those - marking > the time as unreliable. When the receiver synced back up, then it would warp > the time output, the 1PPS would warp in phase, and the PLL would correct the > phase error. > > So, that's one way, but probably not a desirable way. My interest was in the > option of using the OCXO to create the time, which clearly gives a better > option when the receiver syncs back up to the sats. Is there a published > standard for this, or is this something that everyone (except the newbie) > knows so well that it's not worth discussing? There is no standard, but a few basic ways to go about which seems reasonable and used by most is: 1) As you go into hold-over, keep producing PPS etc 2) As you leave hold-over, attempt to adjust the phase back. 3) If your system been in hold-over for a longer time, say that it reasonably deviates outside of +/- 10 us (or some other limit), alarm and turn output off I have selected a somewhat more intricate setup in which you can set a re-assignment limit, so when the phase error is outside of that limit, you turn the output off, jumps the phase difference, and then starts to track in from there. The reason being that at some time deviation, the time it takes to track in the phase error is too large to be practical so turning of and jump has less impact. Cheers, Magnus > Bob > - > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > > From: Attila Kinali > To: Bob Stewart ; Discussion of precise time and frequency >measurement > Sent: Tuesday, August 16, 2016 3:46 PM > Subject: Re: [time-nuts] Holdover > > On Tue, 16 Aug 2016 04:35:40 + (UTC) > Bob Stewart wrote: > >> It's been pointed out to me that I didn't understand the function of >> the 1PPS of a time standard. I confess that somehow I had confused the >> term to be timing standard; which would be an entirely different thing. >> But, this is time-nuts, so I should have realized... >> Anyway, is there a standard, or at least an accepted practice, for how >> holdover is handled in a time standard? > > There are many ways how to do that and which one you choose depends > on the application and its requirements. You can find everything between > "jump imediatly" and "just keep the frequency stable and don't care about > alignment". > > Attila Kinali > ___ 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] Holdover
What to do during and right after holdover depends on the reason you have a time standard. If it is for maintaining a lab standard, then just shut down as you can't perform your primary function. It you have this standard because you are required to time stamp financial transactions then you have to keep going until you estimate some error threshold then stop. If you are using it to aim a telescope then again, stop using it the estimated error is enough that you'd miss your targets.It depends on the use case. I remember aiming a telescope when our best source of time was NTP over a dial-up phone modem in the days before always-on Internet This was in the 1980's and it worked well enough. The normal case was "outage" as the modem connection was short and only a few times per day. But was good enough to re-calibrate a local clock 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] Holdover
The Trimble GPSDOs and most of the SCPI ones (like the Z3801A) have "jam sync" commands that force the receiver to do an immediate time sync (the Z3801A requires the device to be in holdover before it will accept a jam sync). Some also have commands where you an also specify thresholds where the receiver alarms and/or does an automatic jam sync and thresholds for loss-of-signal time before the device goes into holdover mode. --- I have selected a somewhat more intricate setup in which you can set a re-assignment limit, so when the phase error is outside of that limit, you turn the output off, jumps the phase difference, and then starts to track in from there. The reason being that at some time deviation, the time it takes to track in the phase error is too large to be practical so turning of and jump has less impact. ___ 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] HP 3010Axxxxx oscillator
Corby wrote: The 3010A prefix identifies that date it was made. Specifically, it identifies the "series" of the product -- the date the last revision to the product was adopted. The "3010" part is the encoded date for that particular series (10th week of the 30th year past HP "year one"), and the "A" indicates that it was manufactured in the US. [I've forgotten what "year one" was for the Instrument Division. It was 1960 for the calculators -- I/D may also have used 1960.] 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] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd
On Tue, Aug 16, 2016 at 3:36 PM, Attila Kinali wrote: > I disagree here. With the APU and its IRQ system you get already to > sub-us PPS time stamping (probably in the 10ns-100ns range). > An APU1 post said they had 50ms of jitter (as measured by Chrony) so they assumed the PPS driver was broken on the hardware. Pascal suggested elsewhere that the combined LPC plus system IRQ jitter would be too much for NTP. While I don't believe this I'm disinclined to test it . So I was -- clearly too briefly -- implying that there are solutions that should be less expensive* and known to achieve micro-second jitter. I had no reason to suspect Pascal would overestimate the issues however another APU1 owner** used an mPCIe serial card and an mPCIe GPS card and got expected microsecond jitter (as measured by NTP) results. Again this is not quite what the OP is proposing but it's encouraging. These are time sync. protocol results and don't speak to sub-microsecond time-stamping in the hardware. * which is not to say pcengine hardware is expensive. It's not. ** https://wiki.polaire.nl/doku.php?id=versalogic_vl-mpeu-g2_ntp ___ 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] Holdover
Bob, On 08/16/2016 11:31 PM, Bob Stewart wrote: Hi Attila, In my unit, which is a frequency standard, I chose to tell the receiver to stop sending 1PPS pulses when it loses sync to the sats. And since the 1PPS is no longer coming, the PLL does nothing and the DAC doesn't change. (Let's avoid the question of aging correction for now.) So, I'm wondering where to go and what to do if I want to get time from my unit. Clearly I could just tell the receiver to continue to send 1PPS pulses and sync to those - marking the time as unreliable. When the receiver synced back up, then it would warp the time output, the 1PPS would warp in phase, and the PLL would correct the phase error. So, that's one way, but probably not a desirable way. My interest was in the option of using the OCXO to create the time, which clearly gives a better option when the receiver syncs back up to the sats. Is there a published standard for this, or is this something that everyone (except the newbie) knows so well that it's not worth discussing? There is no standard, but a few basic ways to go about which seems reasonable and used by most is: 1) As you go into hold-over, keep producing PPS etc 2) As you leave hold-over, attempt to adjust the phase back. 3) If your system been in hold-over for a longer time, say that it reasonably deviates outside of +/- 10 us (or some other limit), alarm and turn output off I have selected a somewhat more intricate setup in which you can set a re-assignment limit, so when the phase error is outside of that limit, you turn the output off, jumps the phase difference, and then starts to track in from there. The reason being that at some time deviation, the time it takes to track in the phase error is too large to be practical so turning of and jump has less impact. Cheers, Magnus Bob - AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Attila Kinali To: Bob Stewart ; Discussion of precise time and frequency measurement Sent: Tuesday, August 16, 2016 3:46 PM Subject: Re: [time-nuts] Holdover On Tue, 16 Aug 2016 04:35:40 + (UTC) Bob Stewart wrote: It's been pointed out to me that I didn't understand the function of the 1PPS of a time standard. I confess that somehow I had confused the term to be timing standard; which would be an entirely different thing. But, this is time-nuts, so I should have realized... Anyway, is there a standard, or at least an accepted practice, for how holdover is handled in a time standard? There are many ways how to do that and which one you choose depends on the application and its requirements. You can find everything between "jump imediatly" and "just keep the frequency stable and don't care about alignment". Attila Kinali ___ 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] Lady Heather
> I am just starting out using Lady Heather. > > I am trying to create a .cfg file to set the program to COM 3 at startup. > > I created the file and saw the instructions to put it in my “Documents” > folder. > The only documents folder in Windows is “My Documents.” > > I created a text file and called it “Heather.cfg” and put it in the My > Documents > folder, but it does not work. I just put “/3” to change the COM port to COM > 3. > > I also tried putting in the “Heather” program folder. It works OK at this end. But having just checked, I've noticed that things can get complicated if you want to use a config filename other than HEATHER.CFG, or if you want to put it in a directory other than the one Heather suggests in the '?' help dialog. Heather allows you to specify a .cfg filename other than the default HEATHER.CFG with the /h= option, but if I run a command like: "c:\program files (x86)\heather\heather" /h="my config file.cfg" ... it doesn't treat the quoted string as a valid pathname, even though it ought to. So, there are at least two things to check if you're still having problems: 1) If you use a filename other than HEATHER.CFG, make sure your /h= argument doesn't contain any spaces. Just use the filename itself, with no directory prefix. 2) Make sure the .cfg file goes in the directory that Heather suggests in the '?' help screen. Again, it doesn't have to be called HEATHER.CFG (if you use the /h= option) but it does need to go into the directory where the program expects to find it, because there's currently no robust way to force it to read the file from another directory. > Also, I have read and re-read the list of commands and don’t see any to change > the display to show the “sky” view of the satellites, as is shown on the Lady > Heather web page. I see the line that turns it on "plot_signals = 4", but I'll be darned if I can see how the code gets there. Mark? -- john, KE5FX Miles Design LLC ___ 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] Holdover
Hi Attila, said "Ie you need to figure out what you want to do with those PPS, then figure out what the desired behaviour during hold-over and recovery is and from that you can design the frequency standard." What is the most usual method for *time standards*? I'm satisfied with how my unit works as a frequency standard. Bob - AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Attila Kinali To: Bob Stewart Cc: Discussion of Precise Time and Frequency Measurement Sent: Tuesday, August 16, 2016 4:37 PM Subject: Re: [time-nuts] Holdover On Tue, 16 Aug 2016 21:31:17 + (UTC) Bob Stewart wrote: > So, that's one way, but probably not a desirable way. My interest was in > the option of using the OCXO to create the time, which clearly gives a > better option when the receiver syncs back up to the sats. Is there a > published standard for this, or is this something that everyone (except the > newbie) knows so well that it's not worth discussing? No, there is no standard[1]. A system like this is always tailored to the consumer of the PPS pulses and its requirements. Ie you need to figure out what you want to do with those PPS, then figure out what the desired behaviour during hold-over and recovery is and from that you can design the frequency standard. Attila Kinali [1] https://m.xkcd.com/927/ -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] Holdover
Hi Attila, In my unit, which is a frequency standard, I chose to tell the receiver to stop sending 1PPS pulses when it loses sync to the sats. And since the 1PPS is no longer coming, the PLL does nothing and the DAC doesn't change. (Let's avoid the question of aging correction for now.) So, I'm wondering where to go and what to do if I want to get time from my unit. Clearly I could just tell the receiver to continue to send 1PPS pulses and sync to those - marking the time as unreliable. When the receiver synced back up, then it would warp the time output, the 1PPS would warp in phase, and the PLL would correct the phase error. So, that's one way, but probably not a desirable way. My interest was in the option of using the OCXO to create the time, which clearly gives a better option when the receiver syncs back up to the sats. Is there a published standard for this, or is this something that everyone (except the newbie) knows so well that it's not worth discussing? Bob - AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Attila Kinali To: Bob Stewart ; Discussion of precise time and frequency measurement Sent: Tuesday, August 16, 2016 3:46 PM Subject: Re: [time-nuts] Holdover On Tue, 16 Aug 2016 04:35:40 + (UTC) Bob Stewart wrote: > It's been pointed out to me that I didn't understand the function of > the 1PPS of a time standard. I confess that somehow I had confused the > term to be timing standard; which would be an entirely different thing. > But, this is time-nuts, so I should have realized... > Anyway, is there a standard, or at least an accepted practice, for how > holdover is handled in a time standard? There are many ways how to do that and which one you choose depends on the application and its requirements. You can find everything between "jump imediatly" and "just keep the frequency stable and don't care about alignment". Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] Holdover
On Tue, 16 Aug 2016 21:31:17 + (UTC) Bob Stewart wrote: > So, that's one way, but probably not a desirable way. My interest was in > the option of using the OCXO to create the time, which clearly gives a > better option when the receiver syncs back up to the sats. Is there a > published standard for this, or is this something that everyone (except the > newbie) knows so well that it's not worth discussing? No, there is no standard[1]. A system like this is always tailored to the consumer of the PPS pulses and its requirements. Ie you need to figure out what you want to do with those PPS, then figure out what the desired behaviour during hold-over and recovery is and from that you can design the frequency standard. Attila Kinali [1] https://m.xkcd.com/927/ -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] Holdover
On Tue, 16 Aug 2016 04:35:40 + (UTC) Bob Stewart wrote: > It's been pointed out to me that I didn't understand the function of > the 1PPS of a time standard. I confess that somehow I had confused the > term to be timing standard; which would be an entirely different thing. > But, this is time-nuts, so I should have realized... > Anyway, is there a standard, or at least an accepted practice, for how > holdover is handled in a time standard? There are many ways how to do that and which one you choose depends on the application and its requirements. You can find everything between "jump imediatly" and "just keep the frequency stable and don't care about alignment". Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] HP 3010Axxxxx oscillator
Perry, The 3010A prefix identifies that date it was made. It should also have a 10811A marking. The resistor value is for applications needing precise EFC. Usually found in HP 5065A, 5061A, and 5061B. If it also has a 60109 marking it has slightly better short term stability at one Tau. Specs are otherwise the same as any 10811A. There is no outer oven! Since the design is a complete departure from the original 105 oscillator it makes sense they issued a new part ID. The 10811A started to go into the 105A and the 5061A and 5065A after the 105 style oscillator was discontinued. Cheers, Corby ___ 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] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd
On Mon, 15 Aug 2016 16:57:27 -0400 Paul wrote: > Finally, these boxes are intended to be routers (hence the three network > interfaces) not time-servers and unless you're irrevocably wedded to the > miniPCIe in APU2 route there are probably better choices for time servers. I disagree here. With the APU and its IRQ system you get already to sub-us PPS time stamping (probably in the 10ns-100ns range). This is way than good enough for a NTP server. It should be even good enough for an PTP system, if normal network switches are used. The advantage of the APU is that you have a standard PC, which simplifies the use of software considerably. Of course, with an embedded system you can get the PPS timestamping down to <10ns precision. But at an several times larger software complexity, which you also have to build yourself to a large extend. Unless time-nuts levels of precision/accuracy are required, an APU is good enough and an easy solution. If you go for time-nuts levels, then I would question the use of ethernet long before I question the hardware platform. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] Mini ovens packaging
Hoi Guillermo, On Mon, 15 Aug 2016 11:07:41 + Guillermo Sobreviela Falces wrote: > -Temperature stability of 0.1ºC, what means temperature control > included. As Bob already wrote, this value has little meaning without the temperature range at which you want to operate the oven. From what you wrote, i guess it will be some office environment or a place with relatively low temperature swing? Then it should be easy to get to that level. > -Inner cavity of 2cm x 2 cm x 1 cm. That is nice and small. How much space do you have on the outside? Does it need to fit into something else? > -In addition to the connectors needed for the oven I need 3 pins > reserved for the system. That's easy to acheive. Mechanically, the easiest construction would be to use a PCB with cut-outs and put some CNC'ed aluminium case through these cut-outs. The PCB then acts as mounting system and electrical connection. The thermal conductance of a PCB (without copper) is moderately low. Maximum temperature for standard PCB's is 80°C, for higher temperatures you need special base material with higher Tg (at least 20°C higher than the maximum expected temperature). > -The system must be included into the oven via a chip socket, or > pasted inside with silver paint and wire bonded to the oven connections. I do not get what you mean with this. > -PCB compatible oven > > I have been looking for a Peltier junction in order to reduce the oven > temperature to 50ºC (Reducing the temperature is good for my system). > But the temperature stability is a must and I am not sure of the precision > level I can reach with a Peltier junction. For a classical oven, the inner temperature is defined by the maximum ambient temperature and the minimum required temperature delta. A minimal temperature difference is needed to keep the loop stable. Peltier elements have the nice advantage that you can cool directly and thus are not bound by the temperature difference to ambient. But you need to be aware that Peltier elements are not symmetric: They are much better heating elements than cooling elements. This means that you need to design your loop carefully to prevent oscillation. > > Also, I have been designing a temperature detector based in a power divider > using a resistor and a RTD that will trigger an OPAMP (comparator). This > OPAMP will activate/deactivate a high power BJT or FET transistor that will > warm the oven. In order to reduce the thermal inertia I thought to make an > escalated temperature detector as the shown in the attached picture. The > main idea is have a fast heating and reduce the warming current when the > temperature is approaching the final equilibrium temperature (120ºC). Instead of using a bang-bang controller as you have shown, it is better to use a linear controller, that controls how much current is flowing through the FET. This eliminates temperature cycling and current spikes that may disturb your oscillator. > > Another problem is related to the shell of the oven. It should be metallic > in order to equilibrate the temperature, but, would it be interesting to use > an external shell made of an isolator material in order to reduce thermal > loses or will it difficult the thermal stability? Depends. In theory, it's good to have the oven well isolated. But you need some way to get the heat out of the oven. And this thermal resistance must be low enough to keep the loop stable. You need to calculate the thermal parameters for this. If you are not 100% confident with this, start with an unisolated oven, see how it performs on a step response, add isolation (can be something as simple as some pieces of cardboard), tweak the loop parameters a bit and check the step response again. > > After this discussion, would it be possible to buy a system that meet > the characteristics described above? I am not sure about I would be able > to design and test this system on time, but I need this kind of oven with > this temperature stability as soon as possible (This is why I am looking for > a commercial solution). It is very unlikely that you will find an off the shelf system that does what you need. But you can find a company to design you one. Most people with a decent electrical engineering knowledge should be able to do so. It is also relatively easy to do it yourself, if you are not out for optimal performance over an wide range of temperature and are ready to measure and tweak the system parameters a bit after production. The simplest is probably to start with a PI controller, which are fairly easy to keep stable and only have two knobs to turn. Use that as a basis with some simple mechanical setup. That should get you already to the 0.1°C in an office environment. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ time-nuts mailing
Re: [time-nuts] Lady Heather
If you start Lady Heather from a command line prompt, the cfg file should be in the directory you are in. If you start it clicking on an icon or the start menu, it should be in your My Documents folder (which depends upon the OS version you are running). You can find out for sure by typing ? on the keyboard. Scroll down the bottom of the help screen and Lady Heather will tell you where to stick it [😉] For screen data, generally, RED means something is wrong/not normal/not usable/not available/unexpected/could affect normal receiver operation etc, YELLOW means something is not quite right or optimum, GREEN means it is normal. White is used for data from the receiver or program configuration values. Not all program configuration options are available from the command line. You can create a keyboard .SCRipt file which, when read, will simulate keyboard typing. You can specify a script file on the command line with the /r=xxx.scr command. Script files must have a ".scr" file name extension. Also, not all configuration options are available directly from the keyboard menus. You can set most command line only options with the "/" keyboard command. From: Richard Mogford Sent: Tuesday, August 16, 2016 3:00 PM To: hol...@hotmail.com Subject: Lady Heather Mark I am a new user on Lady Heather (LH). Thanks for creating it! Is there a user manual that shows what the various types of data and color coding on the screen mean? I am trying to switch LH to COM3. I figured out how to do this using the shortcut, but wanted to try a .cfg file. I put “/3” in a heather.cfg text file and tried it in the Heather directory and in My Documents. So far, it does not seem to get read. What am I doing wrong? Richard ___ 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.