Re: [time-nuts] New +/- 1 sec in 100 days mech clock
On 4/20/15 12:59 AM, Attila Kinali wrote: Moin, On Mon, 20 Apr 2015 00:40:06 -0700 Tom Van Baak t...@leapsecond.com wrote: Mechanical, yes. Home brew, no. It is an absolutely stunning clock, both in beauty and performance. Given the fact that a CNC milling machine can be bought quite cheaply today, i would say that homebrew is easily possible. All you need is a good understanding on different materials and how to machine them. (This can be aquired using various machining books out there) I don't know about that.. I suspect that more than a CNC mill is required: there's often a lot of craft and art in precision machinery (like optical systems). There's a lot of craft in high performance quartz oscillators: selecting the crystal, mounting it in a holder so that it doesn't see untoward stresses, doing the seals, etc. Certainly, a CNC makes a lot of the fabrication easier, and the fact that you can mail order CNC parts is even cooler. Front Panel Express, for instance, is a great way to make breadboard plates for connectorized modular RF components. It's what I use after I decide that double stick foam tape isn't appropriate any more. But for things like threads and helices, your standard CNC isn't going to do it. And I suspect the machining of the gears might have been done in a special way (other than a dividing table). For these kinds of high precision applications, there's a lot of tricks in getting all the periodic errors to cancel out:essentially to make the system precision higher than some of the manufacturing steps. Look at the ruling engines used to make diffraction gratings for instance. ___ 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] Tuning a Trimble Thunderbolt
On Mon, Apr 20, 2015 at 8:48 PM, Charles Steinmetz csteinm...@yandex.com wrote: Pete wrote: when using the default parameters it doesn't meet the holdover specifications of +/- 1 us over 2 hours with a maximum of +/- 15C temperature change: it will drift at least 20 us over 2 hours in holdover. Executive summary -- you are expecting way too much, way too soon. Fair enough. It's new to me, so I wanted to tinker shortly after I got it. 2. Is it typical for an oscillator in holdover to drift in a non-linear way? Yes Can this non-linearity be corrected through the judicious choice of tuning parameters or some other means? Probably not, but it should calm down significantly after the unit has been on continuously for several months. Ok. I'll save the data from this measurement and see how things compare in a few months. That document says the units under test were standard Thunderbolts (not Thunderbolt E's) and were on for three days and had a training period of two hours prior to the test. I don't even know what been on for three days and had a two hour training period means. Tbolts are training whenever they are locked and operating normally. I parsed the statement to mean the Thunderbolts had been powered on for three days, so everything is warmed up and in thermal equilibrium, but we did a factory reset to clear the training data two hours before the test. I could be mistaken in my interpretation. On a related note, is it possible to extract any data regarding the training from the unit? It'd be interesting to see how the filter coefficients change over time. Also, are there any published details about how the training works? The user guide is somewhat lacking when it comes to the nitty-gritty. My Thunderbolt has been on for a week and had been locked to the GPS signal for at least 12 hours prior to the test. Quartz crystals are creatures of habit. They need to be on continuously for months before they settle down to their best behavior. And the Kalman filter needs to train long enough to see significant temperature changes and long periods of steady (that is, settled-down) drift. Thinking in terms of days and hours is orders of magnitude shorter than any realistic expectation of good behavior. If a Tbolt has been running locked and normally for months, and is turned off for a day and then turned back on, it may settle down in a day or three. But if you bought it surplus, it may have been off for years, and banged around considerably (or much worse) between the last use and you receiving it. In that case, you may well need to leave it alone for months before the crystal settles down and the Kalman filter is well-trained. Will do. Good advice. Are the training parameters saved periodically to non-volatile memory, or are they purely stored in RAM and so will be lost if powered down? If the latter, does the RAM have any provisions for backup power (e.g. a coin-cell battery or supercapacitor), even if it'd require some soldering to wire in such a power source? Similarly, is there any provision for applying power to the oscillator oven even if the rest of the Thunderbolt is powered down? Considering that it's meant to operate in telecom structures with reliable power and a fixed location, I assume not. 3. Is it normal for there to be spikes in the phase and frequency error when the number of satellites being tracked changes? Yes. The better your survey is, the smaller they will be. But even with the best possible survey, you will see 10nS plus or minus when the constellation changes. And the poorer your antenna location is, the more often the constellation will change. Good to know. Thanks for the details. I observe changes of ~100ns and 100-200ppt whenever there's a change in the number of satellites. Can this be smoothed out? That's quite a lot. I suspect you do not have an accurate survey, or you have a marginal antenna location (poor carrier to noise ratio and/or multipath problems), or both (the latter pretty much guarantees the former). If you have multipath problems, a good choke-ring antenna can help substantially. Alas, the location for the antenna is suboptimal: in the best location available to me (an outdoor balcony) I have a clear view of the southern sky from 150-300 degrees (az) and from horizon to zenith with only a few low-elevation obstructions. However, this is only accessible in warm months as it's in my living room and the antenna cable needs to go out a window. My 10 month old daughter may soon make the current location a bad idea as she gets more mobile and tries to eat the Thunderbolt. The only other option is a window on the north side of the building with a much more limited view of the sky -- although that location works reasonably well for my Garmin 18x receiver (which is much more sensitive[1]) the less-sensitive Thunderbolt would need to go into holdover several times per day. The surveyed position
Re: [time-nuts] New +/- 1 sec in 100 days mech clock
Hi I suspect you could buy quite a few nice new high end cars for the price of that clock. Bob On Apr 20, 2015, at 3:59 AM, Attila Kinali att...@kinali.ch wrote: Moin, On Mon, 20 Apr 2015 00:40:06 -0700 Tom Van Baak t...@leapsecond.com wrote: Mechanical, yes. Home brew, no. It is an absolutely stunning clock, both in beauty and performance. Given the fact that a CNC milling machine can be bought quite cheaply today, i would say that homebrew is easily possible. All you need is a good understanding on different materials and how to machine them. (This can be aquired using various machining books out there) There's more information about the clock, additional press links, and a copy of my talk about Clock B at the Harrison conference: I would be very much interested in detail photographs and the construction plans of the clock. Oh.. and if they happen to have a spare clock, i'd like ot have that one too :-) 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. ___ 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] Tuning a Trimble Thunderbolt
Hi Expecting that unit to meet holdover after only being locked for 12 hours is not a reasonable thing. Let it run for a week. Let it lock up for at least 4 or 5 days and get a good survey on the location. It should run +/- 5ns one sigma with a good survey. Bob On Apr 20, 2015, at 5:39 AM, Pete Stephenson p...@heypete.com wrote: Hi all, I recently acquired a 2004-era Trimble Thunderbolt with firmware 3.00 from eBay. It looks essentially identical to the one sold in the TAPR/Time Nuts 2009 group buy[1]. A sticker says it's the Rev E (it's not a Thunderbolt E, just revision E of the original Thunderbolt). I don't use it for anything critical, just local timekeeping and hobby stuff (I'm beginning to get into ham radio, so a good frequency reference will be handy). I've been really impressed with it, but I'm interested in tuning it for even better performance. The list archives here have been useful, as have other outside resources[2], but I have a few questions for the gurus here if that's not too much trouble. I don't have a time-interval counter or local reference clock; all my data is from Lady Heather. The Thunderbolt is resting in the shade on a foam block on a table in my living room, which is not actively temperature-controlled but is well-insulated and typically within a few degrees of 20C. It's been running for about a week with uninterrupted GPS signal, though I typically enable manual holdover for a few hours a day for testing. The default tuning parameters keep the phase and frequency error within the published specifications[3] of +/- 20 ns (1 sigma) and ~10^-12 over the course of a day, respectively, so long as the receiver is locked to the GPS signal. However, when using the default parameters it doesn't meet the holdover specifications of +/- 1 us over 2 hours with a maximum of +/- 15C temperature change: it will drift at least 20 us over 2 hours in holdover. 1. Is there some preferred, step-by-step method for manual tuning? I'm familiar with the Ziegler–Nichols method for tuning PID controllers and that method works reasonably well for adjusting PID controllers used for temperature control in the lab at my workplace. Is there some method that's comparable? As a general example, would Adjust time constant until the phase error starts to oscillate but frequency error is stable and low. Reduce damping value until phase error stabilizes. be sensible? I ask because although Lady Heather's autotune function works well at setting the gain and DAC values, the time constant (500 seconds) and damping constant (1.00) is hard-coded into the source and want to know how to adjust those parameters for my particular Thunderbolt. 2. Is it typical for an oscillator in holdover to drift in a non-linear way? For example, with a bit of tuning my Thunderbolt drifted to a PPS offset of 1 us after 126 minutes. However, at 160 minutes the offset was 2 us, at 190 minutes it was 3 us, and so on. After about five and a half hours (330 minutes) the offset was 11 us. Can this non-linearity be corrected through the judicious choice of tuning parameters or some other means? 3. Although my attempts at tuning have improved the holdover performance over the default parameters, I'm nowhere near the performance reported by [4]. That document says the units under test were standard Thunderbolts (not Thunderbolt E's) and were on for three days and had a training period of two hours prior to the test. My Thunderbolt has been on for a week and had been locked to the GPS signal for at least 12 hours prior to the test. Lady Heather shows N/A for the Kalman filter (the PV, static, and altitude filters are on). This appears to be normal, as screenshots from others [2] show the same thing. Is this expected? Is there still some internal Kalman filter? 3. Is it normal for there to be spikes in the phase and frequency error when the number of satellites being tracked changes? I observe changes of ~100ns and 100-200ppt whenever there's a change in the number of satellites. Can this be smoothed out? Many thanks. I apologize if I'm duplicating an earlier discussion, but my search-fu didn't turn up answers to these questions in the list archives. If this has been discussed before, pointers to the earlier discussion would be most appreciated. Cheers! -Pete Bern, Switzerland [1] http://www.leapsecond.com/pages/tapr-tbolt/ [2] http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:thunderbolt_damping [3] http://trl.trimble.com/docushare/dsweb/Get/Document-10015/ [4] http://www.w8bapdstar.info/library/PrecisionClocking/Trimble%20Thunderbolt/Thunderbolt%20Holdover%20Document-8428.pdf -- Pete 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] New +/- 1 sec in 100 days mech clock
On Mon, 20 Apr 2015 09:59:06 +0200 Attila Kinali att...@kinali.ch wrote: Mechanical, yes. Home brew, no. It is an absolutely stunning clock, both in beauty and performance. Given the fact that a CNC milling machine can be bought quite cheaply today, i would say that homebrew is easily possible. All you need is a good understanding on different materials and how to machine them. (This can be aquired using various machining books out there) Just to make sure there is no misunderstanding. What I ment here was, that once you have the plans, machining the parts and building the watch is easy. Comming up with a good plan is still hard. Attila Kinali -- _av500_ phd is easy _av500_ getting dsl is hard ___ 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] New +/- 1 sec in 100 days mech clock
Perhaps it is not a good analogy, but I think of the cesium beam tube in the 5071A. The plans alone are very non-trivial. Then there are a bunch of proprietary machining details that I can't disclose, that are way beyond the merely having access to a CNC tool. The systematic error due to the CBT is below something like 1 part in 10^14, which is 1 second in 3 million years. Perhaps that is in some sense equivalent to Harrison's 1 second in 0.3 years. 7 orders of magnitude difference. As many time-nuts are probably aware of, most if not all cesium clocks that are better than the 5071A have reversible beams to cancel out CBT assymmetry. Rick Karlquist N6RK ___ 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] Tuning a Trimble Thunderbolt
Hi If you have a less than optimum antenna location, that will impact how fast you can do a good survey. The worse your survey location, the poorer your time accuracy. The worse the time accuracy, the longer it will take to converge on a frequency. A “normal” test environment for this sort of thing provides at least 6 stat’s at all times and typically has 8 to 12 in range of view. A 48 hour survey with 6 sats at all times is a typical way to set up a TBolt for best performance. None of the people making GPSDO’s talk much about what’s inside, Trimble is at least as quiet as anybody else. The best place to start tuning is with the auto tune *if* you have 6 sats in view at the time. From there the two basic coefficients can be modified by LH commands. The conventional wisdom on the list appears to be that the TBolt does no tuning or adaptation of the filter / control loop parameters on it’s own. Bob On Apr 20, 2015, at 5:24 PM, Pete Stephenson p...@heypete.com wrote: On Mon, Apr 20, 2015 at 8:48 PM, Charles Steinmetz csteinm...@yandex.com wrote: Pete wrote: when using the default parameters it doesn't meet the holdover specifications of +/- 1 us over 2 hours with a maximum of +/- 15C temperature change: it will drift at least 20 us over 2 hours in holdover. Executive summary -- you are expecting way too much, way too soon. Fair enough. It's new to me, so I wanted to tinker shortly after I got it. 2. Is it typical for an oscillator in holdover to drift in a non-linear way? Yes Can this non-linearity be corrected through the judicious choice of tuning parameters or some other means? Probably not, but it should calm down significantly after the unit has been on continuously for several months. Ok. I'll save the data from this measurement and see how things compare in a few months. That document says the units under test were standard Thunderbolts (not Thunderbolt E's) and were on for three days and had a training period of two hours prior to the test. I don't even know what been on for three days and had a two hour training period means. Tbolts are training whenever they are locked and operating normally. I parsed the statement to mean the Thunderbolts had been powered on for three days, so everything is warmed up and in thermal equilibrium, but we did a factory reset to clear the training data two hours before the test. I could be mistaken in my interpretation. On a related note, is it possible to extract any data regarding the training from the unit? It'd be interesting to see how the filter coefficients change over time. Also, are there any published details about how the training works? The user guide is somewhat lacking when it comes to the nitty-gritty. My Thunderbolt has been on for a week and had been locked to the GPS signal for at least 12 hours prior to the test. Quartz crystals are creatures of habit. They need to be on continuously for months before they settle down to their best behavior. And the Kalman filter needs to train long enough to see significant temperature changes and long periods of steady (that is, settled-down) drift. Thinking in terms of days and hours is orders of magnitude shorter than any realistic expectation of good behavior. If a Tbolt has been running locked and normally for months, and is turned off for a day and then turned back on, it may settle down in a day or three. But if you bought it surplus, it may have been off for years, and banged around considerably (or much worse) between the last use and you receiving it. In that case, you may well need to leave it alone for months before the crystal settles down and the Kalman filter is well-trained. Will do. Good advice. Are the training parameters saved periodically to non-volatile memory, or are they purely stored in RAM and so will be lost if powered down? If the latter, does the RAM have any provisions for backup power (e.g. a coin-cell battery or supercapacitor), even if it'd require some soldering to wire in such a power source? Similarly, is there any provision for applying power to the oscillator oven even if the rest of the Thunderbolt is powered down? Considering that it's meant to operate in telecom structures with reliable power and a fixed location, I assume not. 3. Is it normal for there to be spikes in the phase and frequency error when the number of satellites being tracked changes? Yes. The better your survey is, the smaller they will be. But even with the best possible survey, you will see 10nS plus or minus when the constellation changes. And the poorer your antenna location is, the more often the constellation will change. Good to know. Thanks for the details. I observe changes of ~100ns and 100-200ppt whenever there's a change in the number of satellites. Can this be smoothed out? That's quite a lot. I suspect you do not have an accurate survey, or
Re: [time-nuts] Tuning a Trimble Thunderbolt
On 4/20/15 7:25 PM, Charles Steinmetz wrote: Unfortunately, you are unlikely to do any better than this with the antenna location you described. Time to buy a house, with no tall trees nearby. (You may already have heard that time-nuttiness can be expensive ;-) Actually, what you want is an isolated mountain top of solid granite connected to a big pluton below, with a nice drilled anchor. Your laboratory/lair can be in a cave below the mountain top. Being on top of a tall mountain also reduces the effect of atmospheric effects, but will increase the solid earth tides (and, of course, you are closer to the moon and sun). I wonder if being on top of a dormant volcano (e.g. Mt. Waialeale on Kauai) would be stable. An active volcano (Mauna Kea/Mauna Loa) is going to be moving around a lot. Tahiti, perhaps? Nice pleasant weather. Mt. Roriama in Venezuela appears to be well above the surroundings, but is quite flat on top, so you'd need a structure to get your choke ring antenna up high enough. Close to the equator too. As the previous poster pointed out, serious time-nuttery can get expensive. ___ 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] Tuning a Trimble Thunderbolt
Pete wrote: On a related note, is it possible to extract any data regarding the training from the unit? Not as far as the time-nuts community knows, no (other than looking at the DAC voltage and temperature reporting during holdover and attempting to reverse engineer the prediction algorithm by correlating those with the long-term DAC voltage -- good luck). Also, are there any published details about how the training works? Not as far as the time-nuts community knows, no. Are the training parameters saved periodically to non-volatile memory, or are they purely stored in RAM and so will be lost if powered down? If the latter, does the RAM have any provisions for backup power I doubt it -- mine always act as if they are training from zero if they have been powered down. Because of the lack of precise retrace of quartz crystals, I don't think you'd want old (pre-power-down) data, anyway. Some crystals will even come up drifting in the opposite direction after being powered down, and they all take some time (days, at least) to settle down after any disturbance (including power interruptions, however brief). Alas, the location for the antenna is suboptimal: in the best location available to me (an outdoor balcony) I have a clear view of the southern sky from 150-300 degrees (az) and from horizon to zenith with only a few low-elevation obstructions. However, this is only accessible in warm months * * * The surveyed position is within about 10 meters of the actual location according to Google Maps and local building information. That's a problem. Every meter is approximately 3.3nS, so 10m introduces a +/- 33nS error in the raw data (as much as 33nS closer to some satellites and 33nS farther from others). Add in the uncertainty due to noise, and you get easily hundreds on nS of error in the computed solution. Unfortunately, you are unlikely to do any better than this with the antenna location you described. Time to buy a house, with no tall trees nearby. (You may already have heard that time-nuttiness can be expensive ;-) 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.
[time-nuts] New +/- 1 sec in 100 days mech clock
List, http://www.dailymail.co.uk/news/article-3045499/Longitude-clock-stuns-experts-keeping-accurate-second-100-days-300-years-designed.html Personally I’m blown away howsomeone can homer brew a mechanical clock like this. Regards, Perrier ___ 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] New +/- 1 sec in 100 days mech clock
Perrier, Mechanical, yes. Home brew, no. It is an absolutely stunning clock, both in beauty and performance. The designer, Martin Burgess, is a giant among clockmakers and this project reflects a life's work. http://en.wikipedia.org/wiki/Martin_Burgess There's more information about the clock, additional press links, and a copy of my talk about Clock B at the Harrison conference: http://leapsecond.com/pend/clockb/ If any of you have specific questions about the clock let me know off-list. I'm still in Greenwich. /tvb - Original Message - From: Perry Sandeen via time-nuts time-nuts@febo.com To: time-nuts@febo.com Sent: Sunday, April 19, 2015 10:55 PM Subject: [time-nuts] New +/- 1 sec in 100 days mech clock List, http://www.dailymail.co.uk/news/article-3045499/Longitude-clock-stuns-experts-keeping-accurate-second-100-days-300-years-designed.html Personally I’m blown away howsomeone can homer brew a mechanical clock like this. Regards, Perrier ___ 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] Thank you note
List, I want to thank all the memberswho have answered my questions, many being you really don’t want to do this andhere’s why as well as the current group that generally posts to the list. I really don’t want to learn by trying thingsthat have failed for others proving again to myself that they won’t work, I’ve learned much from the listby reading what other people have tried with varying degrees of success or havefailed at so I don’t make the same mistake. Many subjects are way over myhead and for those I just delete as I’ll never be interested in it or it farexceeds my skill level. I want to especially acknowledgetwo members in particular. Jim Lux: for his fascinating longand highly readable posts for a layman like myself on the JPL workings. Secondly, Bob Camp for both hislist and off list emails patiently *schooling * me so I continue to grow in TNknowledge. This is a great group and I concedethat I have made some less than prudent comments on several occasions for whichI apologize for. An extreme differencein opinion still calls for polite response of disagreement. I was appropriatelytaken, privately, to the wood shed. That issue aside, I could neverhave gotten such a fascinating education in timekeeping and its almost infinitevariations without this group. Regards, Perrier ___ 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] Visual clock comparison
From: Chris Albertson I think the question really was How close must two visual clock displays be to be perceived as being exactly in sync?. Some people (but not me) can see a 1/10 second difference and to me a one second difference is obvious. The answer is likely between 1.0 and 0.1 seconds. But if you add a tick every second then the 1/10 second difference is very easy to hear but most people can't hear a 1/40th second difference. [] = In HDTV, the BBC report that an offset of 20 milliseconds between sound and vision can be identified by most users, and they have achieved 2 milliseconds in tests. https://tech.ebu.ch/docs/techreview/trev_2009-Q1_HD-Audio-Delays.pdf 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] Visual clock comparison
On Sun, 19 Apr 2015 23:25:10 -0400, Chuck Harris wrote: 1/5th second is simply the rate at which the balance wheel on a standard stopwatch ticks... 18000BPM. -Chuck Harris You must mean 18000BPH. There are many balance wheel rates in use from 4.5BPS to 10BPS and higher. My Elgin jitterbug stopwatch runs at 40BPS. Bill Beam NL7F ___ 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] New +/- 1 sec in 100 days mech clock
Moin, On Mon, 20 Apr 2015 00:40:06 -0700 Tom Van Baak t...@leapsecond.com wrote: Mechanical, yes. Home brew, no. It is an absolutely stunning clock, both in beauty and performance. Given the fact that a CNC milling machine can be bought quite cheaply today, i would say that homebrew is easily possible. All you need is a good understanding on different materials and how to machine them. (This can be aquired using various machining books out there) There's more information about the clock, additional press links, and a copy of my talk about Clock B at the Harrison conference: I would be very much interested in detail photographs and the construction plans of the clock. Oh.. and if they happen to have a spare clock, i'd like ot have that one too :-) 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] Visual clock comparison
Yes, I meant 18000 BPH. My fingers have a mind of their own and type things that I don't always want. I apologize for my many and varied imperfections. I never said that 18000BPH was the only rate used... only that standard stopwatch ticks are 18000BPH. An Elgin Jitterbug is anything but a standard stopwatch. A variant of the Elgin was used with the Norden Bomb sight... Probably the only mechanical stopwatch in history to be classified as top secret by the US Govt.. (If your Elgin was last serviced more than a year ago, I would venture that it no longer runs at 40BPS.) 18000BPH was the standard beat for pocket watches and wrist watches when stopwatches were invented. 18000BPH is where any reference to 5 beats per second comes from. 18000BPH is where the 0.2 second limit on conventional stop watches comes from. And, 18000BPH is what you will get if you buy a normal mechanical stopwatch... Which, oddly enough, you can still buy. -Chuck Harris Bill Beam wrote: On Sun, 19 Apr 2015 23:25:10 -0400, Chuck Harris wrote: 1/5th second is simply the rate at which the balance wheel on a standard stopwatch ticks... 18000BPM. -Chuck Harris You must mean 18000BPH. There are many balance wheel rates in use from 4.5BPS to 10BPS and higher. My Elgin jitterbug stopwatch runs at 40BPS. Bill Beam NL7F ___ 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] Tuning a Trimble Thunderbolt
Hi all, I recently acquired a 2004-era Trimble Thunderbolt with firmware 3.00 from eBay. It looks essentially identical to the one sold in the TAPR/Time Nuts 2009 group buy[1]. A sticker says it's the Rev E (it's not a Thunderbolt E, just revision E of the original Thunderbolt). I don't use it for anything critical, just local timekeeping and hobby stuff (I'm beginning to get into ham radio, so a good frequency reference will be handy). I've been really impressed with it, but I'm interested in tuning it for even better performance. The list archives here have been useful, as have other outside resources[2], but I have a few questions for the gurus here if that's not too much trouble. I don't have a time-interval counter or local reference clock; all my data is from Lady Heather. The Thunderbolt is resting in the shade on a foam block on a table in my living room, which is not actively temperature-controlled but is well-insulated and typically within a few degrees of 20C. It's been running for about a week with uninterrupted GPS signal, though I typically enable manual holdover for a few hours a day for testing. The default tuning parameters keep the phase and frequency error within the published specifications[3] of +/- 20 ns (1 sigma) and ~10^-12 over the course of a day, respectively, so long as the receiver is locked to the GPS signal. However, when using the default parameters it doesn't meet the holdover specifications of +/- 1 us over 2 hours with a maximum of +/- 15C temperature change: it will drift at least 20 us over 2 hours in holdover. 1. Is there some preferred, step-by-step method for manual tuning? I'm familiar with the Ziegler–Nichols method for tuning PID controllers and that method works reasonably well for adjusting PID controllers used for temperature control in the lab at my workplace. Is there some method that's comparable? As a general example, would Adjust time constant until the phase error starts to oscillate but frequency error is stable and low. Reduce damping value until phase error stabilizes. be sensible? I ask because although Lady Heather's autotune function works well at setting the gain and DAC values, the time constant (500 seconds) and damping constant (1.00) is hard-coded into the source and want to know how to adjust those parameters for my particular Thunderbolt. 2. Is it typical for an oscillator in holdover to drift in a non-linear way? For example, with a bit of tuning my Thunderbolt drifted to a PPS offset of 1 us after 126 minutes. However, at 160 minutes the offset was 2 us, at 190 minutes it was 3 us, and so on. After about five and a half hours (330 minutes) the offset was 11 us. Can this non-linearity be corrected through the judicious choice of tuning parameters or some other means? 3. Although my attempts at tuning have improved the holdover performance over the default parameters, I'm nowhere near the performance reported by [4]. That document says the units under test were standard Thunderbolts (not Thunderbolt E's) and were on for three days and had a training period of two hours prior to the test. My Thunderbolt has been on for a week and had been locked to the GPS signal for at least 12 hours prior to the test. Lady Heather shows N/A for the Kalman filter (the PV, static, and altitude filters are on). This appears to be normal, as screenshots from others [2] show the same thing. Is this expected? Is there still some internal Kalman filter? 3. Is it normal for there to be spikes in the phase and frequency error when the number of satellites being tracked changes? I observe changes of ~100ns and 100-200ppt whenever there's a change in the number of satellites. Can this be smoothed out? Many thanks. I apologize if I'm duplicating an earlier discussion, but my search-fu didn't turn up answers to these questions in the list archives. If this has been discussed before, pointers to the earlier discussion would be most appreciated. Cheers! -Pete Bern, Switzerland [1] http://www.leapsecond.com/pages/tapr-tbolt/ [2] http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:thunderbolt_damping [3] http://trl.trimble.com/docushare/dsweb/Get/Document-10015/ [4] http://www.w8bapdstar.info/library/PrecisionClocking/Trimble%20Thunderbolt/Thunderbolt%20Holdover%20Document-8428.pdf -- Pete 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] [Bulk] Re: [Bulk] Re: [Bulk] Re: Ultra High Stability Time Base Options for 53132A
Tom, Will do. Joe -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Miller Sent: Sunday, April 19, 2015 4:30 PM To: Discussion of precise time and frequency measurement Subject: [Bulk] Re: [time-nuts] [Bulk] Re: [Bulk] Re: Ultra High Stability Time Base Options for 53132A Hi Joe, You might upload them to KO4BB.com with a short note on what they are. There is a 53132 directory there. Regards, Tom - Original Message - From: J. L. Trantham jlt...@att.net To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Sunday, April 19, 2015 4:38 PM Subject: Re: [time-nuts] [Bulk] Re: [Bulk] Re: Ultra High Stability Time Base Options for 53132A If anyone is interested in adding a clearer version of the 53132-60011 board on page 13 of the CLIP for the 53132A, I have redrawn the schematic. I have the values of all components except 4 capacitors that appear to all be the same. I can measure them, if needed, but I will have to remove the unit from my counter. I plan to do that in a few weeks when the MV89 version of the time base arrives. Please let me know if you would like a .PDF of the 'redrawn' schematic. About 2.2 MB file. I also have pictures of the board if anyone needs that as well. Joe -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of J. L. Trantham Sent: Monday, April 13, 2015 7:04 AM To: 'Discussion of precise time and frequency measurement' Subject: [Bulk] Re: [time-nuts] [Bulk] Re: Ultra High Stability Time Base Options for 53132A Fuzzy page 13 is the 53132-60011, with the extra components not found on the 53132-60016, which is on page 45 and much clearer. It is an LM361M and is on both boards. Now that I have the 53132-60011 board, I plan to start with page 45 and 're-draw' a clear page 13. Joe ___ 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] Tuning a Trimble Thunderbolt
Pete wrote: when using the default parameters it doesn't meet the holdover specifications of +/- 1 us over 2 hours with a maximum of +/- 15C temperature change: it will drift at least 20 us over 2 hours in holdover. Executive summary -- you are expecting way too much, way too soon. 2. Is it typical for an oscillator in holdover to drift in a non-linear way? Yes Can this non-linearity be corrected through the judicious choice of tuning parameters or some other means? Probably not, but it should calm down significantly after the unit has been on continuously for several months. That document says the units under test were standard Thunderbolts (not Thunderbolt E's) and were on for three days and had a training period of two hours prior to the test. I don't even know what been on for three days and had a two hour training period means. Tbolts are training whenever they are locked and operating normally. My Thunderbolt has been on for a week and had been locked to the GPS signal for at least 12 hours prior to the test. Quartz crystals are creatures of habit. They need to be on continuously for months before they settle down to their best behavior. And the Kalman filter needs to train long enough to see significant temperature changes and long periods of steady (that is, settled-down) drift. Thinking in terms of days and hours is orders of magnitude shorter than any realistic expectation of good behavior. If a Tbolt has been running locked and normally for months, and is turned off for a day and then turned back on, it may settle down in a day or three. But if you bought it surplus, it may have been off for years, and banged around considerably (or much worse) between the last use and you receiving it. In that case, you may well need to leave it alone for months before the crystal settles down and the Kalman filter is well-trained. 3. Is it normal for there to be spikes in the phase and frequency error when the number of satellites being tracked changes? Yes. The better your survey is, the smaller they will be. But even with the best possible survey, you will see 10nS plus or minus when the constellation changes. And the poorer your antenna location is, the more often the constellation will change. I observe changes of ~100ns and 100-200ppt whenever there's a change in the number of satellites. Can this be smoothed out? That's quite a lot. I suspect you do not have an accurate survey, or you have a marginal antenna location (poor carrier to noise ratio and/or multipath problems), or both (the latter pretty much guarantees the former). If you have multipath problems, a good choke-ring antenna can help substantially. Find a good location for the antenna, find a good, out-of-the-way location for the Tbolt, and shield it from drafts (a simple cardboard box is a huge improvement). [Check the archives for other solutions. I have posted about my experiences with cast aluminum boxes, thermal mass, and thermal capacitance, and many others have posted lots and lots of other ideas.] Then, let it run for 3 or 4 months without playing with it. Don't change any parameters, don't go into manual holdover, don't do ANYthing. THEN see how it works. Until then, you're just chasing your tail tracking the crystal as it settles down. 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.
