Re: [time-nuts] Why not TAI?
Le 10/08/2011 07:41, Attila Kinali a écrit : On Fri, 15 Jul 2011 05:57:45 + Poul-Henning Kampp...@phk.freebsd.dk wrote: Everybody but the time-lords have always been told to stay away from TAI in the strongest possible terms by said time-lords, who again and told the world to use UTC. May i ask what the reason was to stay away from TAI? I mean, it is obvious (for me) that for any application that needs a steady, continious and monotone clock that TAI is one of the best alternatives among all those time standards. Attila Kinali There are all manner of time scales , and each has its use so there is no need to keep away from any. Just pick that which suits your application. I think that Poul-Henning was just indicating in a humorous manner his dislike of the unilateral imposition of a non uniform scale, UTC, as the transmitted time standard. So if you want a uniform scale, take TAI. You can get TAI from GPS time by adding 19secs. A number of GPS receivers can be configured to report GPS time rather than UTC. ___ 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] Why not TAI?
Le 10/08/2011 12:55, Attila Kinali a écrit : If TAI is a paper clock, what else should be used if a strictly monotone time scale is needed? Do you have any specific application in mind? If you need an SI seconds rated scale, then you need something based on TAI. GPS time has a TAI second rate and is monotonic. But of course you would need a GPS receiver to access it. And what makes UTC different from TAI to be a real clock, as UTC is derived from TAI by adding leap seconds? I don't think TAI is any less real than UTC. UTC just happens to be the international transmitted time scale. TAI is not generally available, though both GPS time, and UTC have the same rate. Would a reverse definition of TAI (or rather TAI' ) by using UTC without the leap seconds be a good enough approximation? Well, UTC doesn't exist without leap seconds by definition, but if you only have UTC available to be able to track TAI , then you can recover the TAI scale by deducting leap seconds. I'm quite sure i'm not the first one asking this question, but i couldn't find an answer, neither with google nor in the time-nuts archives. 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] UTR timescale draft spec
Le 06/08/2011 04:32, WB6BNQ a écrit : Michael Sokolov, I do not mean to be disrespectful, but this list is not about creating time scales No, indeed, but as the subject is time I see no reason that he should not advertise the project here. I am going to ask that you respect this position and take your problems back to the list that is centered on that subject matter. Or from another perspective, you could create your very own list server and call it “Time-Scales” which would seem to be much more appropriate. Michael does in fact address that. I quote from his draft review: An open membership Internet mailing list will need to be set up to which any person or entity with an interest in UTR can subscribe and participate in free unmoderated discussion. ___ 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] Weird TEC data
Le 03/08/2011 17:32, Francis Grosz a écrit : Hi, Scott, Here in New Orleans a friend in the power company who was interested in its history told me a story. In the very early days, frequency control was pretty poor and it was hard to keep up with the changing load. So by 5 PM every day, every electric clock in the city was 10 or 15 minutes slow. So overnight they'd speed up the system and so by 8 AM the next morning every electric clock would be 10 or 15 minutes fast because the total slip during the day was 20 or 30 minutes. Good story. Hmmm, If I was the power company boss I'd have given all my employees a nice shiny mains clock when they joined ... ___ 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] GPSDO for my rubber duckie
Le 02/08/2011 04:35, Michael Sokolov a écrit : snip Henry Hallamhe...@pericynthion.org wrote: The parameters you'll want for conversion between MCAT and mean solar time are given daily in the IERS bulletins: http://hpiers.obspm.fr/eop-pc/products/bulletins/bulletins.html Yes, I know. By making use of these you should be able to do much better than the slightly inelegant leap second rubberization-over-10-seconds method you had proposed. Your rubber seconds should be smooth and continuous, to the limit of the IERS measurement accuracy. But that would be quite a bit harder. :-) I'll leave that as an exercise for Version 2.0; but I'll start with building 1.0 that does my simple rubberization. I am also looking to create a duck, quacking to MST. I have a T'bolt for a tick which configures easily for GPS time rather than UTC, though other GPS receivers could do as well as I wasn't thinking of using the 10MHz source. There are also receivers which provide GPS/UTC locked 10KHz signals as well as 1PPS, ex.Jupiter T that could be another option for you. . My original idea was to use the IERS data to steer the system clock frequency to tick to MST. However, I did not want to have to script a weekly data transfer from the IERS bullitins to get dUT1, and was hoping that I could get it from the GPS data. Unfortunately, it seems not to be avialable there, or at least I can't find it. Various radio time transmissions do carry it, ex. MSF in my neck of the woods, and as I have lashed up an MSF receiver I may start testing with that, or more likely a hybrid, just using the dUT1 data from MSF, as MSF spews legal time rather than TAI. However, even that would only be good if leap secs do not disappear as the current data format only allows for a dUT1 of +/-1 sec with a resolution of 0,1 sec. As an aside, there does not appear to be anything in the American proposal to abandon leap seconds to get a larger dUT1 corrections into the radio transmissions. ___ 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] GPSDO for my rubber duckie
Le 03/08/2011 00:49, Chris Stake a écrit : I don't get it. Does that mean that leap days are OK but leap seconds are unacceptable? Chris For the moment yes, as they are animals from two different species. Leap seconds form part of the current definition of UTC which is a time scale, even though not uniform due to the leap seconds. Leap days form part of a calendar and there are lots of different flavours to chose from. They are needed as the year isn't exactly 365 mean solar days days but about 365,2424. However if leap seconds are abandoned and nothing is done in between times there may need to be a real leap day in around 86400 years as MST is slow by about 1s/year. ___ 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] The future of UTC
Le 23/07/2011 01:39, Horst Schmidt a écrit : Ha, you may well ask. The reason to hate DST is given to us in the southern parts of Australia, by our Queensland cousins: The problems with DST is : 1. The Cows get very confused and the farmers have problems milking them. 2. The chickens don't know anymore when to lay the eggs. it is rumoured, that the shape of the eggs may suffer. However, this has not been proven, since Queensland never had DST. and 3. most importantly, The extra daylight fades the curtains more, and as every housewife will tell you: That will never do Not having DST looks dangerous to mental health. Luckily, my brother, who lives on the west coast has regular doses of DST and should not be affected. ___ 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] The future of UTC
Le 15/07/2011 07:57, Poul-Henning Kamp a écrit : snip Everybody but the time-lords have always been told to stay away from TAI in the strongest possible terms by said time-lords, who again and told the world to use UTC. The time lords are not completely deaf. For more than 10 years there has been debate about whether or not to revert to a TAI scale, but consensus has never been obtained. There are three requirements for time transmission that the current system supports in recommendation ITU-R TF.460-6 which the americans are trying to vote out. 1. SI second ticks 2. corrections to UTC for earth rotation , DUT1, so that UT1 can be calculated. 3. A civil time scale, UTC which is a descendant of GMT and roughly measures the mean solar day. One or other , if not both, figure in all the legal codes of the planet. The definition of 3 ensures that there are 86400 +/-1 ticks per mean solar day . This is quite useful as my watch and just about everyone else's measures days in 86400 units . The proposed change to ITU-R TF.460-6 provides 1 but removes 2 and 3. Sheer folly to my mind. The current recommendation is good for another 2-300 years . So in my humble opinion, the proposition for change should be rejected until consensus be achieved and that ALL three above requirements are met. ___ 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] The future of UTC
Le 15/07/2011 10:33, Poul-Henning Kamp a écrit : In message4e1ffa88.9050...@sfr.fr, cook michael writes: Michael, there are a few details you overlook, and rather than repeat myself, I'll point you at an article I wrote for Queue and Communications of The ACM, trying to lay out the bits: http://queue.acm.org/detail.cfm?id=1967009 Thanks for your ref. I am aware of the shortcomings of the present scheme and am not particularly pro leap second. It seems to me that the right questions are not being addressed and certainly the proposition for change as expressed and to be voted on in 2012 is premature. The US are just wanting leap seconds abolished without proposing alternative schemes covering all the requirements of time signal users.Once they have been defined , recommendations can be considered. Till then , fix the bugs. ___ 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] 58503A, GPS vs UTC?
Le 07/06/2011 21:15, r...@lcs.mit.edu a écrit : I have an HP 58503A. It has an Option H14,H19 sticker on the back. The circuit board has 58503-60001 Rev C stamped on it. It has been running continuously and locked to GPS for a few days, and it knows the correct number of seconds between GPS and UTC. The unit displays GPS time, without the leap seconds correction. The front-panel display says GPS xx:yy:zz, and :system:status? says GPS 1PPS Synchronized to GPS Time, not to UTC as the manual shows. I'd be much obliged if anyone could tell me how to get the unit to display UTC instead of GPS time. I think these use a similar command set to the Z3801A try :diag:gps:utc?should show 0 if the unit is in GPS, 1 if UTC if that gives coherent results, try :diag:gps:utc 1 to force the mode Thank you, Robert ___ 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] IEEE Spectrum Magazine interviews one of our own...
Le 25/05/2011 04:00, Tom Holmes a écrit : snip Steven Cherry is exaggerating when he says most systems go down for planned maintenance instead of trying to deal with leap seconds in real time. As someone who has been supporting major industrial, banking, airline systems for the last 30 years, I remember NO down time, or outage due to leap second insertion. In fact, I don't know of any commercial applications, that care about it. Most systems administrators that I had contact with didn't know that th leap seconds existed, and did not configure, check or update their ntp servers to enable them to be taken into account. There were of course outages and errors due to clock updates, but they were all attributable to operators trying to change the clocks by large increments manualy or bad ntp configurations, such as allowing large step changes instead of slewing . We have up till now been faced only with positive leap second insertion, but negative updates are also possible. Testing I have done on unix based operating systems show no adverse effects to negative leap second insertion either. ___ 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] What are these towers?
Le 21/05/2011 08:30, Robert Darlington a écrit : Guys, I gotta ask, what does this have to do with time keeping? Am I missing something? -Bob I know what you mean. I was desperately fighting down the urge to reply to Lamar's post to query the significance of cows and horses. On Fri, May 20, 2011 at 9:59 PM,w...@aol.com wrote: So here are some URL's to explain the pattern for KNTH... If you will note, there are two Texas stations that KNTH is protecting, since they are SENIOR on the frequency... Also, WAPI in Birmingham 50KW daytime non-directional is being protected in the ENE null. We could go on and on!! The first stations that must be protected are those ND (non-directionals) that are within several hundred miles of the Houston transmitter site. Also any directionals (DA) that do not have nulls towards Houston must be protected. Oh, 1060 and 1080 also have to be protected to a lesser extent!! ;-) _http://www.amlogbook.com/freq/freq.htm#1070_ (http://www.amlogbook.com/freq/freq.htm#1070) Here is the page to look at the day and night patterns of KNTH... Note that the patterns are essentially the same: _http://www.radio-locator.com/cgi-bin/finder?call=knthsr=Ys=Cx=16y=6_ (http://www.radio-locator.com/cgi-bin/finder?call=knthsr=Ys=Cx=16y=6) and the stations being protected... KOPY WSW of the KNTH transmitter site _http://www.radio-locator.com/info/KOPY-AM_ (http://www.radio-locator.com/info/KOPY-AM) Note that KOPY DOES NOT have a NULL towards KNTH either day or night... and note that non-directional KWEL is in the null off the back of the KNTH array. Bottom line here... someone wanted an AM station in Houston... After a lot of midnight oil, and a lot of station day and night pattern searches, it was calculated that a pattern could be created for 1070 in Houston using 9 or 11 towers!! AM antenna array black magic at work!! Oh... the AM rig is most likely GPS locked!! ;-) 73, Don, W4WJ In a message dated 5/20/2011 6:47:39 P.M. Central Daylight Time, lo...@pari.edu writes: On May 20, 2011, at 7:42 PM, Jim Lux wrote: 1070 kHz is also KNX, a 50kW clear channel station in Los Angeles. That might be why the pattern's so small in any direction but southeast at night. So what is generally south east from Houston. Galveston, I know, but that's not very far away. Are they trying to broadcast to Cuba as well? Or the Yucatan peninsula or oil rig and boat crews out in the gulf? Nah; KNTH is north-north-west of the population center, and thus 'throws' its pattern toward the population center. FCC rules require a certain field strength for the station's 'city of license' and to do that the pattern is pointed towards the population center. I remember hearing some SBE (Society of Broadcast Engineers) friends talking about this 'crazy 11 tower array in Texas' years ago; nice to actually see it from the air :-) ___ 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. ___ 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] Sidereal timekeeping
Le 16/05/2011 00:29, iov...@inwind.it a écrit : You are right, the right value for the crystal would be about 32859.27, but I thought that such a difference could be compensated in the circuitry, that's why I omitted the decimals. before you get into grinding I have a question on your chosen frequency. It doesn't square for me. 1,002737909350795 solar/sidereal time ratio x 32768 crystal frequency 32857,72 required frequency for sidereal clock with 2^15 divider chain Regarding the 2^15 division, forget for a moment the second as we know it, and consider a shorter (sidereal) second. Our crystal which makes 32859.27 oscillations in our ordinary second, will make 32768 oscillations in the shorter second. The ratio is saved and we will have the shorter second I'm looking for. Hope I've been clear. Antonio I8IOV Messaggio originale Da: michael.c...@sfr.fr Data: 16/05/2011 0.14 A: iov...@inwind.itiov...@inwind.it Ogg: Re: [time-nuts] Sidereal timekeeping Le 15/05/2011 23:39, iov...@inwind.it a écrit : I don't think this will work as the divider chain will give wrong length seconds. Michael, I'm just looking for shorter seconds, in order to keep sidereal time with ordinary clocks. Antonio, Yes I figured that, but I thought the frequency wrong for the 2^15 division. The ration for siderial/solar time according to wiki is 1⁄1.002737909350795, using your value I got 1/1,002777099609375 , which makes your day 86160,723089564, rather than 86,164.090530833. Quite a bit short. My maths may be wrong though. Antonio I8IOV ___ 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] Sidereal timekeeping
Le 15/05/2011 23:22, iov...@inwind.it a écrit : Hi all, does anybody out there have any ideas as where to find a 32859Hz crystal (1/2 that value would be better) to be used to replace 32768 crystals in ordinary clocks? I don't think this will work as the divider chain will give wrong length seconds. I think that 32768 crystals cannot be dragged that much. I've already read the JimLux article somewhere on the web, but I would be pleased finding a simpler solution. Also, I already have computer programs that show sidereal time. Thanks, Antonio I8IOV ___ 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] Z3816A Serial Port Parameters
Le 25/04/2011 18:35, Iain Young a écrit : Hi Guys, Having finally got the time to get my Z3816A connected up to both a power supply and antenna, I find myself with a minor issue. It powers up just fine (minus the silly Antenna alarm, really must add that resistor sometime...) gets GPS Lock, and I can *tell* it's squirting stuff down the RS-232 line [correct led blinks now I have a Null MODEM cable] But can I figure out the baud rate ? Can I heck...Think I've tried most of them, at 8N1. Anyone know what it should be set as ? Maybe even just by default ? The Z3816A is sending time by default and will not communicate till put in SCPI mode. You will need to try all baud rates to see where you can send the appropriate command . Check out http://www.realhamradio.com/gps-satstat-software.htm. There is a DOS utility that does the magic, though I have not tried it as I am not lucky enough to have the box. Iain ___ 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] Mitac MGE100 ?
Le 24/04/2011 20:04, Pete Lancashire a écrit : Mitac MGE100 Yes; looks like a dev kit. I find it's a 12-Channel GPS Receiver Module Based on SiRF Technology Chipset. What version of SIRF I cant see. Google for SIRF NMEA Reference manual , hook it to a Serial port and away you go. There are some monitors which read SIRF. gpsd IIRC , you could Google one to try. ___ 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] 60hz disciplined watch
Le 20/04/2011 16:17, John Ackermann N8UR a écrit : I wonder if it's smart enough to have a sanity check to determine whether the line frequency is 50 vs. 60 Hz? BTW -- I have an Ecodrive watch, but it's radio controlled (as well as solar charging), so haven't seen any reference to this setting method before. John On 4/20/2011 10:13 AM, paul swed wrote: My bet would be flicker and divide by 120. Doesn't really matter. But since these watches use the light to charge the battery, sensing the frequency is a byproduct. Nice and simple. I don't buy it. Makes a nice urban myth though. Incandescent sources don't flicker like fluorescent sources and the Skyhawk user manual does not recommend charging in front of flouresecent tubes to maintain accuracy. ___ 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] PIC processor CTMU module used for sub-ns TIC applications?
Le 17/04/2011 00:20, beale a écrit : The application note merely asserts the possibility, but neglects to present a specific design. Has anyone here attempted to use a PIC CTMU in that way? The app note doesn't give a complete design, but the principle of precision time measurement is explained with a corresponding block design under Precision Time Measurement. It relies on A/D sample and hold capacitor charging between 2 edge detections. Worth looking into though. I expect the data sheets will show how to implement it and define its limitations. ___ 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] FE-5680A word of caution
Le 07/04/2011 16:20, Jerry a écrit : The 10 MHz output is not close to the expected frequency tolerance. The first of the units that I received puts out a signal at 9,999,945 Hz. The vendor then sent a second unit which puts out a signal at 10,000,025 Hz. Could it be the transport conditions that cause the problems? i have noticed that all I get that comes by DHL/UPS/TMS is very cold on arrival. Another possibility might be security screening. I stopped getting film from the US because some got fogged, maybe by x-ray security. ___ 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] SI Unit Problems
Le 05/04/2011 17:51, Jim Lux a écrit : On 4/5/11 8:25 AM, Brooke Clarke wrote: Hi: Just reading at: http://futureboy.us/frinkdata/units.txt First about the candela and all it's problems, then what's a Time Nut issue Hz . // This means that, if you follow the rules of the SI, // 1 Hz = 1/s = 1 radian/s which is simply inconsistent and violates basic // ideas of sinusoidal motion, and is simply a stupid definition. Isn't his premiss wrong? I see no required relation between s^-1 or 1/s and angular measure. If I am dropping rocks into a pool at 1 second intervals I get splashes at 1Hz . Not many radians in that. Maybe that is why cps was dropped. actually 1/s (= Hz) = 2*pi rad/sec BTW, if anyone is confused, I have a handy direct reading graph published by HP a few decades ago to assist engineers in converting from cycles per second to Hertz. I'll see if I can scan it and attach it later. I know I really should have mentioned this last Friday. ___ 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] Result of Earth Quake speeds up earth?
Le 20/03/2011 05:59, Bruce Griffiths a écrit : jimlux wrote: A 10-12m diameter dish is probably close to the minimum feasible aperture. A 4m dish can be made to work in conjunction with a mauch larger dish (eg 30m). The original speculation was for measuring the small change in earth rotation rate, for which some sort of interferometric measurement of a stellar source could be used. I sincerely doubt that it will be possible to get undisputed verification of this speed up as the magnitude is swamped by the irregular diurnal and sub-diurnal rotation rates induced by tidal effects that are at lease a magnitude greater and for which the error bars are of the same order or grater than the predicted shift. There was a similarly predicted rotation shift predicted for the Chile quake of 28 February 2010 (1,26us). There was IIRC no verification of that AFAIK. Check the tidal effects at http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html for the tidal effect and http://hpiers.obspm.fr/ for rotational measured speed changes http://hpiers.obspm.fr/eop-pc/index.php?index=newsfor the statement of detectability. The source has to be bright (so you can detect it with a practical antenna.. not everyone has a 30m dish in their back yard) The source has to be small angle (or at least something that you could accurately determine the centroid of) The source has to be not moving (which I think leaves out using something like jupiter) The frequency of measurement has to be somewhere that the atmosphere won't dominate the uncertainty (leaving out optical, I think) SO what's the brightest small angular radio source out there? 3C273 RA 12:29.1 DEC 02:03.1 As someone else has pointed out, measuring the earth surface position relative to spacecraft orbits, e.g. GPS, would be another technique. In fact, a high resolution measurement of the position of a geosync sat might do.. If the earth's rotation rate changes you'd have to adjust the height of the satellites in Clarke orbit to keep them stationary. Unfortunately, for earth orbiters, there's enough other perturbations that you probably can't see it. They already have to move satellites around to compensate for things like solar wind, air drag (for LEO), etc. But maybe for a spacecraft in deep space, between planets, which is on a well understood trajectory? Bruce ___ 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] Result of Earth Quake speeds up earth?
Le 17/03/2011 22:14, Jim Palfreyman a écrit : Just for fun I plotted the UT1-UTC data from the IERS Bulletin A. Here's the raw data: I add the deltas UT1-UTC s delta -0.18115 -0.182320,00161 -0.183530,00121 -0.1847 0,00117 -0.185760,00116 -0.186740,00098 -0.187630,00109 -0.188420,00079=== 11/3 day of the quake -0.189120,00090 -0.1897 0,00059 -0.1903 0,00060 -0.191030,00073 -0.192 0,00079 -0.193240,00124 If you check that against the excess day length graph I don't think that is change is significantly different, and any change would be expected to be permanent as the mass redistribution is. This is from March 4 to Match 17 inclusive. I don't know if it's a fluke, but the line takes a definite step to the right before continuing on its merry way. At a glance x an y graphs seem to show nothing. Jim Palfreyman ___ 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] Result of Earth Quake speeds up earth?
Le 20/03/2011 11:02, cook michael a écrit : Le 17/03/2011 22:14, Jim Palfreyman a écrit : Just for fun I plotted the UT1-UTC data from the IERS Bulletin A. Here's the raw data: Ooops - I correct the deltas ... UT1-UTC s delta -0.18115 -0.182320,00117 -0.183530,00121 -0.1847 0,00117 -0.185760,00106 -0.186740,00098 -0.187630,00089 -0.188420,00079 === 11/3 day of the quake -0.189120,00070 -0.1897 0,00058 -0.1903 0,00060 -0.191030,00073 -0.192 0,00097 -0.193240,00124 If you check that against the excess day length graph I don't think that is change is significantly different, and any change would be expected to be permanent as the mass redistribution is. ___ 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] Coalition to Save GPS
Le 13/03/2011 10:28, Charles P. Steinmetz a écrit : Mahlon wrote: The Lightsquared terrestrial network will be LTE, same as most carriers are migrating to. They will almost certainly use GPS timing receivers at the cell sites for network timing. and their timing receivers antenna will probably be at the antenna mast head and so out of the radiation pattern. Paradoxically, they will be the only ones not affected. ___ 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] Physics !
Le 11/03/2011 01:24, J. Forster a écrit : One Watt per square meter: http://www.ecd.bnl.gov/steve/watt.html === The ‘scandal’ of the kilogram First, it’s vital for us as consumers to be confident about what we buy – we don’t want to be ripped off at the checkout with an underweight bag of carrots or, more seriously, be given the wrong dose during radiotherapy for cancer treatment. Hmm. At the moment I do know that the mass of my carrots can be compared in a very legal way to a lump of platinum held at the BIPM. I suspect that I will be long dead before lawyers are comparing carrots with planks? -John === ___ 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] latest on the lightsquared 'saga'
The problem will probably resolve itself when the first idiot to lose his GPS at a T junction drives into the deli across the street as he/she was not told to take a turn. The driver will sue for denial of service and 50 million other Americans will jump on board the class action. Le 03/03/2011 21:22, Jim Cotton a écrit : The other scenerio is buy stock in the leading GPS makers and assume that they and Lightsquared will lobby effectively and everyone will be forced to buy new GPS units... There is precedent in that, the DTV converter box vouchers... Jim Cotton n8qoh On 3/3/11 3:09 PM, jimlux wrote: On 3/3/11 9:34 AM, Bob Camp wrote: Hi There's obviously major fuel behind this thing. I'm willing to pass up GPS underground. It's GPS out in the open that is my main concern. IF they are going to use this for last mile connect to homes it will indeed be everywhere and anywhere. IF that's the case, you loose all sorts of GPS stuff. I'd hate to see my GPSDO collection wind up sitting next to the Loran C stuff out in the shed. My theory is that the reason that this can't work is complex enough (yes, trivial for us time-nuts and GPS afficionados, but complex for most others) so it looks like could work to a lot of people, and is attractive, so the stock price would get bid up. So, a wise person would do the following: --- Wait for them to IPO --- Watch the runup in stock price because it's the greatest thing since sliced bread and will bring broadband to the unwashed masses, resulting in world peace, etc. --- short the stock or buy a default swap on them going under Lightsquared discovers that there is an insurmountable regulatory hurdle L2 says, bummer, I guess we have to close up shop or redirect our efforts Stock price crashes -- Cash in on the default swap or stock puts or, a more benign one... you could keep quite a crew of folks busy looking at all the ramifications and implications and doing studies for half a dozen years, and then move onto something else after having burned other people's money that was invested. ___ 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] Newby with questions
Le 28/02/2011 17:37, David VanHorn a écrit : I have a thunderbolt up and running since last week Friday. I'm doing this for a calibration source at work, eventually we will have two antennas, feedlines, and thunderbolts, so that we can have one fail and keep operating, but for the moment I just have the one receiver. Both antennas are mounted underneath a large skylight, as high as we can get them. I realize it's a compromise, but getting signals out to the roof will be a problem so I'm trying to work it without taking the feedlines through the roof if possible. I've done the 48 hour survey, but my signal plot shows a big circular shaped mouse bite on the north side. I'm showing no signal up through 70 degrees at north, 30 degrees from NE around to NW. How badly will this impact me? this is normal. The sats don't go over the poles. Temperature: My thunderbolt always reports -55C which can't possibly be right. :) Is this some configuration in Lady Heather, or is something broken? this has been reported before. you probably have a bad sensor ds1620. Otherwise, things are looking pretty good, I'm showing an average error of about 70ppt. I'm working my way through learning Lady Heather, there's a lot displayed there that I'm a bit fuzzy on, but in the end my main concern is that my 10 MHz output is as accurate as possible in the short term. Our calibration cycle will take about 4 seconds to run, and I need=1PPM error on the calibrated device. ___ 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] Z3815A Comm timeout
Le 22/02/2011 05:13, Hirokazu Makishima a écrit : Hi, I got my hands on a Z3815A(with hockey puck) and trying to communicate with it. It seems that Z38XX and gpscon work ok at first, then looses connection in about 30min.(error receiver timeout) If I reestablish connection, it works fine, but in another half an hour, it looses connection again. I tried switching off full duplex and TOD, no luck. can someone have any answers to this kind of problem? I unfortunately do not have a Z3815A, I only use Z38XX with a Z3801A. The guys on the list are very helpfull so I suspect that if you have not had a response it is due to the fact that the symptom is not recognised, Note that on the K8CU page , Z3815A is not in the list of supported receivers. Have you just tried using a terminal program to connect to the box to see if that also times out at 30mins. If so I suspect that the receiver RS232 may be at fault. thanks, Maxi ___ 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] Tool Needed to Access my Timer Battery
Le 16/02/2011 00:57, Chris Albertson a écrit : How can watches be OT on a time-nuts list? Yes the technology of today is electronic but mechanical time keeping was the center of this art for centuries. I agree , with the caveat that posts keep to technical topics. There are plenty of product centric lists covering the bling side. ___ 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] Tool Needed to Access my Timer Battery
Le 16/02/2011 07:21, Heathkid a écrit : BLING? Really? Seriously? A watch is considered bling now? Can you build a mechanical watch in your workshop that is as accurate as those manufactured 100 years ago? That's technology! Otherwise, a precision watch mechanical or electronic is just as on-topic as a Cs standard and I'd like to hear more about mechanical watches. Btw, the tick sounds nice too! You appear to have misunderstood my comment. I entirely agree with you. When I mentioned bling I was talking about the fashion content. - Original Message - From: cook michael michael.c...@sfr.fr To: time-nuts@febo.com Sent: Wednesday, February 16, 2011 1:03 AM Subject: Re: [time-nuts] Tool Needed to Access my Timer Battery Le 16/02/2011 00:57, Chris Albertson a écrit : How can watches be OT on a time-nuts list? Yes the technology of today is electronic but mechanical time keeping was the center of this art for centuries. I agree , with the caveat that posts keep to technical topics. There are plenty of product centric lists covering the bling side. ___ 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] an interesting problem
I had a quick look at the IEEE-1355 HIC bus on which spacewire is based and it seems that although the clock is not on the wire, it can be reconstructed as an XOR of the strobe and data. So a passthrough connector sampling those lines (differential) with RS-644 receivers and a quad NAND may be all you need to recover it. Le 06/02/2011 07:14, Hal Murray a écrit : I've got a system at work with an internal clock oscillator that I want to get some statistics on, but there's no direct visibility for the oscillator, nor do I have a convenient test point that I can probe. ... Fun problem. Thanks for tossing it out. I see two approaches. Are there others? One is to generate something like a PPS pulse and capture timestamps. Then crunch the data and hope you see N buckets so you can ignore anything that isn't in bucket 0. (or correct them by shifting by N ticks) The other approach would be to measure the time between pairs of pulses. You can probably do that much faster than once per second. This should give you 2*N buckets. I can't quite figure out how far apart the pulses should be for best results. (It will probably be simple after I see it.) I expect it will depend on the ADEV of the measuring system and the ADEV of the clock you are trying to measure. I assume you can get a rough ADEV of the clock you want to measure by measuring a similar part on a typical lab setup. It's probably worth sanity checking the divide step to make sure it's dividing by M rather than M-1 or M+1. (Digital geeks are often off by one, especially if nobody has checked carefully.) I'm not sure how to do that. Probably something like divide by 2*M and see if it matches. Or divide by a small M and measure the frequency. --- Plan B would be to use an inconvenient test point. (or make one) Years ago, my boss gave a neat talk about how to prototype hardware. Step 0 was hire a good technician. :) ___ 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] counter
Not that the decks are cleared for this project yet. Heck, my picII's aren't built or programmed. Speaking of PICTIC II's. Great project, but I had originally decided not to go that route as list members were indicating that 5370Bs were to be picked up for 200 bucks. Not so in France I am afraid. I have not been able to find anything under 5 times that over here. Does anyone know if any boards are still available? I checked the mouser project and most parts seems available as I type. Only a serial driver unavailable, but I have plenty of those. Are any other parts needed that are not on that project list? thx. Mike ___ 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] GPS tests by the DoD
Le 21/01/2011 02:23, Stanley Reynolds a écrit : Looks like a upside down wedding cake a very familiar shape for pilots, ground receivers may not be effected if beyond the horizon of the testing device if it is at sea level. Yes this is just a guess on my part. One would assume that the DoD would not want to blind the emergency services. However, I would be interested to hear of any anomalies detected by list members GPS receivers that may be on in the area during the tests. ___ 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] LH v3.0 Beta and Z3816A Question
Le 18/01/2011 05:07, J. L. Trantham a écrit : An unrelated question. My Z3816A reports GPS time. I have looked but have not found a command to make it switch to UTC. Does such a command exist? If so, what is it? The command to do the same on the Z3801A might work with this box aswell. Using info from K8CU; http://www.realhamradio.com/GPS_Frequency_Standard.htm Issue the command: :diag:gps:utc? If it returns 0 you are in GPS mode; if 1 you are in UTC Use the command: :diag:gps:utc 1 followed by :syst:pon to set it to UTC mode. Some units have to be powered off to actually reset to UTC depending on software version. ___ 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] Symmetricom Launches CSAC Product for Precise Timing and Synchronization
Le 18/01/2011 20:59, Poul-Henning Kamp a écrit : In message4d35ef76.7020...@pacific.net, Brooke Clarke writes: The research that was announced some years ago was Cs atoms: http://physicsworld.com/cws/article/news/20177 There is a technology pdf available on their site. It gives more detail and perf data - you need a login to get it. It states that it is cesium. ___ 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] Not getting microsecond accurate time in Linux with GPS setup
Hi, A couple of things not mentioned in the previous responses: precision here is not how accurate your laptops clock is. precision is a measure of how much the time changes during successive reading of the system clock as viewed by ntpd. Its minimum value is 1us due to the timeval structure variable types. Your ntpq data is showing a high offset 24,5 ms but that it also has high jitter , adding the two gives you around 67 secs reported. Laptops often have variable speed oscillators to save power when not much is going on. This will cause unreliable timing and may be the source of your jitter. If your machine has that facility I suggest you turn it off (probably in the bios) and see if the stability improves. As mentioned , the time source is not optimal. I am pretty sure you only have the NMEA sentences to get time info and they are sent after the 1sec GPS mark. Check to see if the SHM driver has a fudge variable to take that into configuration. If you are seeing a constant offset of 25ms and the shm driver has a fudge to allow for it, then configure it. However I doubt that you will be able to get better than 10s of ms accuracy with the hardware you have. You should be configuring more time servers. Take them off the ntp pool for instance over the network. Le 18/01/2011 21:21, Mark Ngbapai a écrit : Hi all. I've grown interested in precise timekeeping so I decided to buy an inexpensive Transystem iBlue 737 GPSr clone with MTK 3301 + 3179 chipset (32-channel, -158dBm tracking sensitivity, Silicon Wave Bluetooth 1.2 chipset) for use with my Fedora 12 Linux Netbook (An Acer Aspire One D150). Having lock indoors of 5/9 satellites I've succeeded connecting the device via rfcomm to my netbook and using gpsd for parsing the data. I restart the nptd server in the machine and after a few minutes I get: [root@PHOENIX Streamer]# ntpq -p remote refid st t when poll reach delay offset jitter == *SHM(0) .GPS.0 l- 16 3770.000 24.511 42.977 If I execute ntpstat, it shows: [root@PHOENIX Streamer]# ntpstat synchronised to modem at stratum 1 time correct to within 67 ms polling server every 16 s In /var/log/mesages I see the lines: Jan 18 20:38:39 PHOENIX ntpd[6898]: ntpd 4.2.4p8@1.1612-o Wed Dec 9 11:49:22 UTC 2009 (1) Jan 18 20:38:39 PHOENIX ntpd[6899]: precision = 5.448 usec Jan 18 20:39:28 PHOENIX ntpd[6899]: synchronized to SHM(0), stratum 0 So why my system is telling me the time is correct within 67 ms and not 5.44 usec? My GPSr is located at 1-1.5 meters from my netbook (GPSr battery lasts around 40 hours, low power is not an issue). Does my Linux installation need special Kernel patching or I'm missing something? Thanks in advance, Mark ___ 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] Sure Electronics GPS
The SureElectronics unit is general within 10 feet with no observed off the wall excursions. With that in mind, I wonder how accurate is their 1pps output? Hi, There was some discussion on the MG1613S earlier. I ordered one off the bay and did a few test. I tried to post some pics of the PPS trace and my wiring mods and stats for those who might be interested but they didn't make it through the filters. Some details. The board is configured as an NMEA device and functions fine on all output interfaces available. You only get output at 9600 bps as standard and according to the manual it can only be configured otherwise through the serial interface. I didn't try changing it though. There is a nice GUI to monitor it. Works fine, but I haven't delved. Seems to allow sending NMEA commands so there may be some useful config changes possible. NMEA data output fixed at 9600bps, 8 bit, 1stop, no parity It is very sensitive, pulling in double the birds that I can regularly see from my unprivileged window sill , and also seems to be less sensitive to reflections than my motorola timing GPSs. That was good news as I have a big problem with the motorola receivers in that respect. The VP/UT+ are not able to filter out the birds that are detected out of line of site. I posted some time ago on that and still have no solution (WIP). When the unit is powered on but no satellites detected, output sentences in order of reception are GGA, GSA, GSV, RMC no PPS output When satellites are visible but no fix is available GGA, GSA, GSV, GSV, RMCnumber of GSV may vary due to those in view, but I always got 2 in this state no PPS output When a fix is available GGA, GSA, GSV, , GSV, RMC PPS is output Although the manual indicates that GLL and VTG are supported, I did not see either of these messages. I haven't tried manually configuring the chip. I do not know whether it goes to position hold, but suspect not. I scoped the PPS/NMEA stream output. PPS and. NMEA signal taken from test pads on the edge of the board. NMEA stream start is always at 300ms from the PPS . I guess that the end is variable depending on the number of birds in view, but for me, the stream ended at +720ms all through my test. So at least on this unit the data does not leak into the following second. That delay can be configured out in NTP. I selected just the GGA sentences for my test with the generic NMEA driver and it works ok. Though as I have better sources available I wouldn't use it to serve time. PPS measurement - the PPS is positive going and 100ms long . The doc I have been able to get at says that it is 200ms long. Anyway, what we get is exploitable without pulse stretching over the serial interface, once it is hooked up. The signal at the test pad is not a very good square wave with respect to the motorola receivers. It has a rise time of nearly 100ns and does not settle to 3v (not 3.3) until 500ns or more. There is no jitter that I can see (5ns ?), but would I see any?. Still for my purpose , NTP , it was a possible candidate. The PPS is not available on the DB9 connector. It is however a pretty simple operation to get it as there are unused pins on the SP232ECN driver chip. I connected the test pad to pin 11 and pin 14 out to the DB9 pin 1 leg for a DCD input to the PC rs232 port. The RS232 transition is +/- 5V in 750ns. However, although the PPS looks nice and steady on the scope , for some reason I did not get offsets from UTC measured by NTP using the ATOM driver that were as good as those from the motorola boards . I haven't investigated why, as the major issue for me is that the board is too big to fit in a Soekris case and can only be powered (standard hook up) by the USB interface, and although the Soekris has a USB interface, the size problem makes it a nono. I will probably hot glue it to a PC. I can then use both the NMEA and PPS together quite reasonably. ___ 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.
