Re: [time-nuts] Another atomic clock question
On 3/2/14 12:21 PM, Bob Camp wrote: Hi As long as your resistor keeps the temperature to within a micro degree it will do pretty well. Oh, you were looking for 1E-12.. I was thinking 1E-9 would be good enough. The other issue is that the phase noise might be pretty bad with a cheap crystal, if it's not particularly high Q. Probably not what you want to use if you're multiplying it up for the carrier on your 240GHz narrowband transmitter. ___ 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] Another atomic clock question
On 3/2/14 1:00 PM, Magnus Danielson wrote: On 02/03/14 21:45, Bob Camp wrote: Hi The gotcha is that there are second order temperature effects. If you are going to run the crystal very far off turn, you need to keep it more stable than you might think. hysteresis, memory effect, restart of frequency drift Yeah, it puts a limit on how good a TCXO can track-and-compensate. I was also considering the use of XOs for temperature sensing, it has the benefit that it is relatively easy to sense with resolution, but after that frequency/phase measures is in, getting a good temperature reading isn't as easy. Is there a good temperature-sensing set of modes in AT-cut crystals, as I know being used in SC-cut crystals? There's the scheme which measures the temperature by comparing fundamental and third overtone modes of a crystal. But if you want to measure temperature, a SAW might be one way. You mix the output of a SAW oscillator with a more stable bulk oscillator, and count the difference frequency. Back in the 80s, I worked at a place that made tons of sensors for all sorts of things which either measured a SAW resonator, or measured the difference between two SAW resonators that were back to back (so their temperatures were the same). The sensor depended on what you did to the SAW: bend it, deposit mass on it, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Another atomic clock question
As Jim mentions in another post, you can run on the fundamental and the third (or 5th or 7th) and get a thermometer out of the delta between the two modes. The gotcha is that a change in load impedance will shift the frequencies unequally. That will give you an apparent temperature change. I already know about the fundamental and third trick, my question was if it could be done to AT-cut as well. I interpret your statement as yes, it does. I don't trust it to be perfect, but reasonable. Ideas for means to handle shift would be welcome. It was originally proposed by a very nice guy from Ft. Monmouth for use with AT cut resonators. I believe the paper is in the FCS proceedings from the mid 1980’s. The DOD kept rights to the technique and licensed it to a couple of oscillator companies. Hmm. SC cut, perhaps? (see the third reference down.. R. L. Filler and J. R. Vig, “Resonators for the microcomputer compensated crystal oscillator,” 43rd Ann. Symp. Freq. Contr., pp. 8- 15, 1989. there's also The microcomputer compensated crystal oscillator (MCXO) Bloch, M. ; Frequency Electron. Inc., Mitchel Field, NY, USA ; Meirs, M. ; Ho, J. The MCXO uses a novel technique to achieve temperature compensation without the use of ovens or conventional temperature-compensating components. The crystal oscillator in the MCXO, which is free to vary with temperature, operates on two modes simultaneously-the fundamental and the third overtone. Several advantages accrue because this method of temperature compensation does not resort to frequency pulling. The authors presents the details of how the MCXO operates and the details of the performance of the delivered systems Published in: Frequency Control, 1989., Proceedings of the 43rd Annual Symposium on Date of Conference: 31 May-2 Jun 1989 Page(s): 16 - 19 Meeting Date : 31 May 1989-02 Jun 1989 INSPEC Accession Number: 3685419 Conference Location : Denver, CO Digital Object Identifier : 10.1109/FREQ.1989.68853 But then, Yoonkee Kim (from Ft Monmouth) has a paper (DTIC ADA484423) Aging of Dual Mode Resonator for Microcomputer Compensated Crystal Oscillator Abstract— A Microcomputer Compensated Crystal Oscillator (MCXO) utilizes the dual c-mode excitation (fundamental mode and 3rd overtone (OT)) of an SC-cut resonator for self- temperature sensing and compensation. The long-term stability of the MCXO depends primarily on the aging of the dual mode resonator. When two modes age differently in time, the aging MCXO’s output frequency curve would shift with a tilt over its operating temperature range ___ 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] 5370 processor boards available
On 2/27/14 6:40 AM, Didier Juges wrote: The BBB has 2GB of flash on board (non removable) and has a micro SD socket. Would not be too hard to keep a backup copy of the OS and apps on the SD card so that it would be easy to boot from SD and reload the built-in flash if the BBB fails to boot from the built-in image. Alternately, running the flash read only, copy OS, apps and everything else to a RAM disk and run from the RAM disk would probably be the safest. Not sure you can do that with 512MB of RAM without some serious pruning of the Linux kernel. Back in 2004, I was running a stripped down linux off a small compact flash (256MB or 512MB, I think) on a VIA Eden 700 MHz motherboard with very limited RAM. It included busybox to provide the usual command line utilities. As I dimly recall, it booted from a compressed filesystem (on CF) to ramdisk only. I also had a version of Debian that net-booted, and also ran entirely in ram. I could probably dig it up if someone's interested. We run RTEMS (www.rtems.org) at work, which provides a Posix compliant interface, but is designed for embedded systems, and has a bunch of targets (ours is SPARC, but there's x86 versions, for sure). You can definitely fit that in well under 128 MB. We've found that most everything that compiles and runs under Linux will compile/run under RTEMS, unless you're using something peculiar to Linux, or you need dynamic loading/linking (RTEMS is statically linked). That is, we have very few #ifdef LINUX kind of things in our code. ___ 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] A small piece on HP's hydrogen maser in 1968
On 2/26/14 12:44 AM, Hal Murray wrote: rich...@karlquist.com said: Solid dielectric cable and connectors of 3.5 mm size are mode limited to 18 GHz. That is why there is so much stuff rated at 18 GHz as opposed to 16 or 20 GHz. Thanks. That's what I was looking for. Wiki says that SMA works to 18 GHz and the 3.5 mm is good for 34 GHz. http://en.wikipedia.org/wiki/SMA_connector#Variations And, as pointed out earlier, the market is smaller, so volumes are smaller, and driving the price down from being able to change to truly mass production is harder. There's also a manufacturing tolerance issue. The higher you go, the tighter the mechanical tolerances get. I suspect there is a huge amount of tooling out there for SMA connectors and other things of that size where the machining tolerances are good enough for SMA and 18GHz, but not good enough for higher. That drives all sorts of things. THere's also semiconductor parts. Lots and lots of stuff in the under 12-13 GHz range that are inexpensive. A fair amount up to 18-ish, and then it sort of falls off. There, it's driven by market, which in turn is driven by international allocations. DBS satellites at 12-13 GHz is a high volume market, so there's lots of things like MMIC low noise amplifiers. Likewise anything around 2.45 or 5.1-5.8 GHz. You see a big break in RF equipment model capability at 3GHz and 6GHz, and I suspect that's driven by the desire to test cellphones and wifi and BT (3 GHz) and 802.11a/802.11n, WiMax, etc at 6GHz. Parts that are cheap and easy to use lead to interesting products like the SignalHound spectrum analyzer, but I don't expect to see a 50GHz SignalHound any time soon. ($900 for 4.4 GHz, $2k for 12.4GHz). You could probably *build* a front end converter for a signal hound fairly inexpensively, but the parts for, say, 32 GHz would cost as much as the Signal Hound backend. ___ 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] A small piece on HP's hydrogen maser in 1968
On 2/25/14 1:40 PM, Tom Van Baak wrote: So what's all this about a Thallium Beam Tube??? For info about the pro/con of Thallium beam frequency standards, see: http://tf.boulder.nist.gov/general/pdf/9.pdf http://tf.boulder.nist.gov/general/pdf/211.pdf http://leapsecond.com/history/1965-Metrologia-v1-n3-Cesium.pdf Imagine 21310.833946 MHz instead of 9192.631770 MHz... Excellent, connectors that cost $50 each instead of $5. Test equipment that costs 5x as much. I work a lot with 32/34 GHz (deep space Ka-band) at work, and I hate having to explain to people who haven't had to buy equipment since back when they worked with X band (7.15/8.45 GHz) that there's a BIG jump in cost when you cross that 18GHz boundary line. ___ 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] Different breed of time nuttery
On 2/23/14 8:11 PM, Daniel Mendes wrote: This is a different breed of time nuttery than usual in this list but i think that at least some of you will enjoy it: http://www.behance.net/gallery/FLUX-1440/2420150 Found it at hack a day An enormous amount of work went into painting the pattern on that rope too. A cleverer approach would have been if there were multiple shorter rope loops... Or geared ropes. ___ 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] Different breed of time nuttery
On 2/24/14 6:08 AM, Chuck Harris wrote: Really impressive would be to have it create the patterns that make the numeric display out of only several feet of slowly moving rope connected as a loop... but that would require some thinking, rather than just a brute force approach. It's art, after all.. Maybe the huge pile of rope is part of the art? Like the threads of life that the 3 fates decide to cut. Or if the rope/thread gets tangled and jammed. And the fact that the machine cannot go backwards. There is a mention in the write up of the whole order out of chaos thing, too. The artist has some other interesting things.. the dot matrix graffiti printer, 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] A small piece on HP's hydrogen maser in 1968
On 2/24/14 8:17 AM, Poul-Henning Kamp wrote: In message caa-f0u_jbz5dyb+hacmwfpkz6vhfo7arz+jpsmhrt9uss2n...@mail.gmail.com , Pete Lancashire writes: http://www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/pdf/1968_09.pdf pages 8 9 As far as I know, those satellites never made it to orbit ? Wasn't that Gravity Probe B.. which finally launched in 2004, and had equivocal results. Also: You can just see the writer twist his brain in order to get to that final punch-line :-) ___ 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] connor winfield GPSDO module phase noise
I ran across these units http://www.conwin.com/time-frequency_references-gps_disciplined-gps_references.html and I found some references from a few years ago in the time-nuts archives, but I can't find any data on phase noise, etc. for the disciplined output. The data sheet/user manual/etc just say NCO, but there's no specs on the performance. Has anyone measured one of these? ___ 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] comparing two clocks
On 2/22/14 5:17 AM, Jimmy Burrell wrote: I need some help with a 'noob' question regarding some practical examples in some of the NIST literature. When attempting to compare two clocks, I'm a bit confused on the subject of exactly how to use my counter to compare a delayed clock relative to another. Or perhaps I should just say 'comparing two clocks'. Let's take some concrete examples. Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the counter's input 'A'. Obviously, I can feed in a second, external reference clock at 10MHz into input 'B'. Suppose, however, I didn't have an external reference clock. Can I compare against the counter's internal time base by hooking a line from the rear jack time base output to channel 'B' input? Or am I making it too complicated? Do I simply plug into input 'A' and go? Just plug it into A and go.. Fire up TIMELAB and see the curves revealed.. Just remember that what you're seeing is sqrt( ADEV(unknown)^2 + ADEV(counter osc)^2) If your counter is worse than your Unit Under Test, then you're really measuring the counter's performance (which is actually quite fun..if you have something you know is high quality) In a somewhat related question, in this article (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf) where two clocks, both divided to 1PPS, were compared, W.Riley makes the following statement, The two 1 PPS outputs were connected to a Racal Dana 1992 time internal counter having 1 nanosecond resolution, and the start and stop signals were separated sufficiently in time for the counter to function properly. I wonder what exactly is meant by separated sufficiently in time for the counter to function properly and how one would go about doing this? For example, is inverting one of the signals sufficient separation? If not, how is this typically done? Delay line? Inverting would work.. Generally, in this sort of thing, you want to make sure that A always occurs before B, so you're counting the right thing, and that you're getting small changes in, say, 0.25 seconds, as opposed to getting 0.01 seconds on one measurement, and then 0.99 seconds on the next. A lot of 1pps systems (e.g. those not synchronized to an outside source) have a starting phase that is arbitrary. You have a 10 MHz crystal running to a divide by 1E7. Turn it on, and you start getting 1pps pulses out. ___ 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] connor winfield GPSDO module phase noise
On 2/22/14 10:01 AM, Said Jackson wrote: Jim, Check the archives, I am pretty sure I reported on one of them, I think it was on the FTS-250.. Or FTS-125. Found it.. thanks.. the key was to put your name in the search My recollection: Not that bad for the price, but phase noise and spurs on my sample unit were significantly worse than what they show in their plots no matter what I tried, and quite large phase/frequency jumps when disconnecting/re-aquiring GPS. Drawbacks of NCOs versus GPSDOs I guess. Bye, Said Sent From iPhone On Feb 22, 2014, at 5:33, Jim Lux jim...@earthlink.net wrote: I ran across these units http://www.conwin.com/time-frequency_references-gps_disciplined-gps_references.html and I found some references from a few years ago in the time-nuts archives, but I can't find any data on phase noise, etc. for the disciplined output. The data sheet/user manual/etc just say NCO, but there's no specs on the performance. Has anyone measured one of these? ___ 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] connor winfield GPSDO module phase noise
On 2/22/14 6:06 PM, saidj...@aol.com wrote: Jim, not sure if I had sent these before, or if you found them in the archives, here are my ADEV, phase noise, and frequency stability measurements results of the FTS-250. All I did was remove the GPS antenna for about 10 seconds during the test to show the effect of the missing antenna. As you can see the phase noise is full of spurs, the unit jumped a whooping 120ppb off-frequency, and the phase took some minutes to stabilize again. I am sending two email attachments so they don't get stuck in the Febo server due to file-size. b the archives had them.. (you had zipped them.. 4 files all told) ___ 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] ID this filter
On 2/21/14 5:37 PM, Scott McGrath wrote: It may be a downconverter rather than a filter some GPS time systems notably ones by true time used an active down converter to transform signal to baseband for long cable runs. Voltage to converter was rather high as I recall Sent from my iPhone On Feb 21, 2014, at 6:21 PM, Pete Lancashire p...@petelancashire.com wrote: https://plus.google.com/u/0/photos/111617808980322733757/albums/5982995737892775185 Any have the specs ? I read the part number as X6L114-X400-N/N It's obviously a special since KL usually uses letters like B for bandpass filters and L for low pass, but the X means something. Assuming this is a low pass.. The N/N is the connectors the 6 is the number of sections L is the low pass the 114 is the size, but 114 is not a standard tubular filter size (110 is, and is comparable to what you've got.. more than an inch in diameter, and 200W power handling) the 400 is the cutoff (400 MHz) But I'd send them an email.. they'll look it up and tell you ___ 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 WWVB modulation format receivers (NOT)
On 2/20/14 4:40 PM, Brian Lloyd wrote: On Thursday, February 20, 2014, J. Forster j...@quikus.com wrote: The large amplitude swings happen on a very short time scale too. Certainly 1 second at times. 8-bits is 48 dB. 16-bit parts at 60kHz should be cheap now. Why bother with AGC? Just make sure the ADC doesn't clip. I sample at 100 kHz with 16 bits on a teensy3.. ___ 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] Valentines Day Love Numbers
On 2/19/14 10:24 AM, Brooke Clarke wrote: Hi: This means that the concrete piers where many Cesium clocks and GPS reference stations are located are bobbing up and down as if they were on a ocean, although only tens of inches. My GPS friends comment when you start getting to sub-meter precision for non-differential measurements, there's a whole lot of effects that start getting in the way. ionosphere, multipath, solid earth tides, etc. They're all in the centimeters but not meters bucket. I think there was an earlier post saying this puts a limit (E-16?) on the ultimate quality of a clock because of it's movement. I wonder if NIST has one of the GWR gravitymeters on a pier and uses that to discipline their fountain clocks for the elevation change of the pier or if that's done for the GPS reference antennas? ___ 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 accuracy specs
On 2/16/14 11:55 AM, Jimmy D. Burrell wrote: I've looked at several different manufacturer GPS datasheets now regarding the 1 PPS output in an attempt to compare apples to apples. Some of them rate their 1 PPS output as something on the order of PPS signals have an accuracy ranging 10ns which seems ambiguous. Does that mean the leading edge of their 1PPS is within 10ns of the GPS clock? Or simply that the stability of their 1 PPS is within 10ns? Or both? Perhaps there's an industry standard for these specs of which I'm unaware? Hah.. It's read the specs carefully and ask questions. The datasheet for my (presumably much older) Globalsat ER-102 seems, to me at least, to be much more clear stating time reference at the pulse leading edge aligned to GPS sec., +/- 1 us. Which I interpret as the leading edge of my receiver's 1PPS is aligned with the GPS's clock to within +/- 1 us. And is that always within 1 us? or 90% or 2 sigma or ?? ANd is that spec assuming some accuracy of the underlying GPS. At 1 us, it probably doesn't matter, but at 10ns, you start worrying about position uncertainty. ___ 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] Fwd: Atmega?
On 2/13/14 10:09 AM, Chris Albertson wrote: -- Forwarded message -- From: Chris Albertson albertson.ch...@gmail.com Date: Thu, Feb 13, 2014 at 8:58 AM Subject: Re: Atmega? I posted this off list, but I'm reposting on the list with mnor edits. I think there might be people looking to buy stuff. If so here are some links The real Arduinos are made in Italy, not China. Nothing wrong with the lower priced clones BUT you need to understand what you are getting and the differences. If you just want to load and go and not have to make changes for pin-numbers, different resistor values and other little things then by the real product. If you don't have the cash, buy a clone that claims to be an Uno (Italian for one) and you need the ATmega328P chip. I am a huge fan of the teensy3 from PJRC.com. $19 for a faster, lower power version of the Arduino on what looks like a wide DIP28 kind of carrier. Works with the Arduino IDE or with separate tools. Has better ADCs, better timers, etc. and 50 MHz instead of 16 or whatever the Arduino is. A lot of the Arduino libraries are from Paul Stoffregen, who's the teensy designer/seller. ___ 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] Atmega?
On 2/13/14 4:27 PM, Bob Camp wrote: Hi The number of bits and the performance of the ADC’s on the Arduino’s is pretty underwhelming compared to the stuff on other similarly priced MCU’s. If you are doing a design where the ADC matters, a PIC or just about anything from TI or Freescale will do a better job. That's what actually drove me to the teensy3.. 16 bit ADC (no, you probably can't get that kind of accuracy, but 13-14 bits, yes) with differential inputs. It's based on a Freescale Kinetix ARM MCU A lot more memory than the Arduinos, too. My only complaint with the micro-b USB is that it's awfully easy to rip that connector right off the board, and then it's buy a new board time, because soldering wires on is almost impossible: the pads and traces most likely went with the connector. If I do a board layout for these things, I'd use a standard 0.1 center header and a USB to header adapter or something, like they do on PC mobos. ___ 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] Nortel GPSDO osc age alarm
On 1/24/14 11:57 AM, Volker Esper wrote: Nice! I didn't know that. But what a number, 300... Why such a digital-hostile factor? Why not 256 or 512? Volker Am 24.01.2014 20:51, schrieb tmil...@skylinenet.net: 9.8304 MHz divided by 300 is 32,768 Hz. Feed that to an electronic clock and you will have an atomic clock of sorts. Regards 9.8304 is 300 baud * 32768. So you can generate all the conventional digital data rates (1200,2400,.., 38.4k with powers of two). Typically, a UART wants to see a clock that is 16x or 8x bit time, so you need something a bit higher. ___ 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] Arduinos in time and near space
On 1/19/14 10:31 PM, Chris Albertson wrote: On Sun, Jan 19, 2014 at 6:41 PM, Lizeth Norman normanliz...@gmail.comwrote: Is it possible to write (assuming the poor little creature would do it) a piece of code, that given your lat/long, the time and a two line element set for an orbiting object, such as the ISS, that would give you the acquisition of signal time/loss of signal time and so forth? The term Arduino now covers a very wis range of computers at are all programmed using the same easy to learn system. You can use the uno whig is the standard 16Mhz AVR CPU or now you can swap in a due with is a much faster processor. But I doubt you would need a lot of CPU power as you are not re-computing this at a fast rate. The Slow AVR chip executes 16 million instructions per second. More than enough for what you want. But I think yout would be more concerned with power. There are far better chips that are just as easy to use. This is why I am a fan of the Teensy3... It's a Freescale micro based on ARM cortex, and fast, low power, etc. However, I happened to have an Arduino sitting in front of me on the table on Saturday when this started. The computer you've got is better than the one you have to order and wait for. ___ 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] latest version of arduino solar clock
here's the latest version..
I'm not sure the sign is right on the rate adjustment.
It will allow a time set in two different ways:
Unix time as Uunixtime
or
conventional time as Tmmddhhmmss
I haven't tested it with the mechanical clock yet, but the basic code to
control the clock is in tick() and tock(). It puts out the right pulses
(you can see them with a LED and resistor). I'll head out to the store
to get a clock a bit later to try the real thing.
One aspect that needs work is the actual timing. The Timer1 library
uses a 16 bit counter, so the resolution is poor. (16 usec/tick) There
have been multiple messages suggesting ways to do the accurate timing at
a low level.
What I would like to do is figure out a way to use vanilla Arduino
libraries to do this.
Either one could calculate the error after setting, and let it
accumulate, and then adjust the rate to compensate..
Or, provide a finer resolution for the timer libraries.
I suspect someone has already done this, so I'll do some googling.
#include TimerOne.h
#include Time.h
// Solar clock to drive mechanical mechanism
// Jim Lux, 19 Jan 2014
// assumes a mechanical clock is connected (with appropriate current limiting
resistors)
// to pins 6 and 7 (see clkpin1, clkpin2, below)
// puts out a short pulse to those pins, with alternating sign, each second
// the interval between pulses is adjusted according to the current date and
equation
// of time.
// the pulse interval is set using the Timer1.setPeriod( period in
microseconds) call
// Since the underlying timer might be 16 bits and the clock is 16 MHz, it is
likely
// that the period is some integer multiple of some multilple of microseconds
// depending on the prescaler value. On the Arduino Uno, the prescaler will
// be 256, because that's what works for 16 MHz and 1 second, so the ticks are
// actually 16 microseconds.
// this will probably nee dto be fixed in the future to keep the accuracy
sufficient
// for solar time. Or a fancier timer scheme.. maybe counting interrupts at a
higher rate
// (e.g. 20 Hz, 50 ms, underlying clock rate of 2 MHz)
//
#include math.h
#define UNIX_MSG_LEN 11 // time sync to PC is HEADER followed by Unix time_t
as ten ASCII digits
#define UNIX_HEADER 'U' // Header tag for serial time sync message
#define TIME_REQUEST 7// ASCII bell character requests a time sync message
// U1262347200 - sample sync message using unix time
#define TIME_MSG_LEN 15
#define TIME_HEADER 'T'
// Tmmddhhmmss - alternate form
// T20140120080500
const double refclk=31376.6; //16 MHz/510?
const int clkpin1=6; // pins going to external clock
const int clkpin2= 7;
int dd, hh; //current day and hour
boolean UpdateClockFlag; // tells loop() that an interrupt has occurred
boolean pulsepol;
void setup(){
pinMode(clkpin1,INPUT); // set pins as inputs High Z for now.
pinMode(clkpin2,INPUT);
Timer1.initialize(100); // one second
Timer1.attachInterrupt(Tick);
Serial.begin(9600);
delay(1000);
UpdateClockFlag = false;
pulsepol = false;
}
void loop(){
int DOY;
double e1,e2;
double secsperday,ratedelta;
time_t t;
t = now(); // get the time
if(Serial.available() )
{
processSyncMessage();
}
// delay(1000);// hack, til we get ISR timer running
// UpdateClockFlag = true;// hack
if (UpdateClockFlag) {
if(timeStatus() == timeNotSet)
Serial.println(waiting for sync message);
else {
DOY = DayWeekNumber(year(),month(),day(),weekday());
hh = hour();
e1 = eot(DOY,hh);// EOT in minutes
e2 = eot(DOY,hh+1);
secsperday = (e2-e1)*1440;
ratedelta = secsperday*1.E6/86400; //ppm for now,
// but we'll change to divisor later
Serial.print(ratedelta); Serial.print( );
digitalClockDisplay();
Tock();
// code in here to update interrupt divisor, etc.
long newper = 100+ratedelta;
Timer1.setPeriod(newper);
};
UpdateClockFlag = false;
}
}
// tick tock, drive clock
// tick is an ISR gets called on the interrupt and enables the outputs (with
alternating
// polarity). tick sets a flag so that the loop() code can finish the job.
// tock finishes the pulse.
void Tick(){
UpdateClockFlag = true;// tell the outside world
if (pulsepol) { // set up the polarity appropriately
digitalWrite(clkpin1,HIGH);
digitalWrite(clkpin2,LOW);
} else {
digitalWrite(clkpin1,LOW);
digitalWrite(clkpin2,HIGH);
}
pinMode(clkpin1, OUTPUT); // enable the outputs
pinMode(clkpin2, OUTPUT);
digitalWrite(13,digitalRead(13) ^ 1); // toggle LED
}
void Tock() {
pinMode(clkpin1, INPUT);//disable the outputs
pinMode(clkpin2, INPUT);
pulsepol = !pulsepol;// do the next one with reverse pol
}
// equation of time code from Tom Van Baak
//http
Re: [time-nuts] latest version of arduino solar clock
On 1/20/14 8:48 AM, Bob Camp wrote: Hi If 1) Your table of errors at noon is always good to 0.1 second and it has no cumulative error (you did it on a PC with a fancy math pack). 2) Your timer has a resolution of 0.1 second. 3) Your basic time source is accurate. (it’s not the issue here). You will always be right at noon to within 0.1 second. The only issue is how far out you are over the 24 hours. What ever error you make during the day is wiped out at noon the next day. If you have 16us adjustments, that’s plenty good enough to hold 0.1 seconds on the display. As long as you drop / add pulses in a fairly uniform fashion you will never see the granularity of the counter. But the current code doesn't try to accumulate errors and adjustments.. it just looks up the rate from the equation (floating point) and jams it into the tick generator. It's not a add/drop ticks sort of scheme. (which could be done). Interestingly, it occurred to me that one could just add a sufficiently large deviation random number to the period each time to dither it. The rate changes once per hour (per tvb's EOT routine), so there's 3600 ticks at a given rate. If I were to vary the rate (as set to the routine) by, say, +/- 50 microseconds, the truncation to 16 microsecond chunks will average out over the 3600 ticks in an hour. A quick simulation shows sd of 1/2 microsecond for the result. You need to add an 8 microsecond offset, because the SetPeriod routine truncates, rather than rounds. I'd like to keep it all in high level Arduino land, rather than delving into counting cycles and ticks at a low level: makes it easier to move to a new platform. For example with 30 seconds delta over the day, you want to drop (or add) 30 pulses out of every 86400. If it’s 27.6831 pulses, then the math takes a hit. The drop / add process is still the same. You simply need to hang on to the remainder (as pointed out elsewhere) in the calculation. The number is never big enough to need to drop multiple pulses. It really does not matter if the noon seconds offset from UTC time data source is a table or a calculation. You still have a net offset at noon. What ever it is, you correct to it. The smoothing in-between noon points still can work as above. If you need to correct the CPU clock to the incoming time source, the drop / add process is pretty much the same for it as well. The math gets a bit more complicated, but the drop / add result nets out to the same thing. Yes, that's something I need to add: a overall rate adjust to calibrate the crystal. Bob On Jan 20, 2014, at 11:19 AM, Jim Lux jim...@earthlink.net wrote: here's the latest version.. I'm not sure the sign is right on the rate adjustment. It will allow a time set in two different ways: Unix time as Uunixtime or conventional time as Tmmddhhmmss I haven't tested it with the mechanical clock yet, but the basic code to control the clock is in tick() and tock(). It puts out the right pulses (you can see them with a LED and resistor). I'll head out to the store to get a clock a bit later to try the real thing. One aspect that needs work is the actual timing. The Timer1 library uses a 16 bit counter, so the resolution is poor. (16 usec/tick) There have been multiple messages suggesting ways to do the accurate timing at a low level. What I would like to do is figure out a way to use vanilla Arduino libraries to do this. Either one could calculate the error after setting, and let it accumulate, and then adjust the rate to compensate.. Or, provide a finer resolution for the timer libraries. I suspect someone has already done this, so I'll do some googling. solarclock4.cpp___ 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] latest version of arduino solar clock
On 1/20/14 9:20 AM, Jim Lux wrote: Interestingly, it occurred to me that one could just add a sufficiently large deviation random number to the period each time to dither it. The rate changes once per hour (per tvb's EOT routine), so there's 3600 ticks at a given rate. If I were to vary the rate (as set to the routine) by, say, +/- 50 microseconds, the truncation to 16 microsecond chunks will average out over the 3600 ticks in an hour. A quick simulation shows sd of 1/2 microsecond for the result. You need to add an 8 microsecond offset, because the SetPeriod routine truncates, rather than rounds. I'd like to keep it all in high level Arduino land, rather than delving into counting cycles and ticks at a low level: makes it easier to move to a new platform. new dither code: long newper = 100+ratedelta + 8 + random(-DITHERWIDTH, DITHERWIDTH); Serial.println(newper); Timer1.setPeriod(newper); Seems to work ok.. (ran for a few minutes, checked the average period, etc.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] latest version of arduino solar clock
On 1/20/14 9:48 AM, Bob Camp wrote: Hi There are *lots* of ways to do any sort of code. I can’t think of any practical problem that has a single unique “best” way to do it. All I’m trying to say is that there is a way to get the job done (to much better accuracy than you need) with what you have. If there’s one way, there must be other ways as well. Bob Yep.. what I was trying to avoid was trying to count cycles and implement an add/drop scheme (which is sort of a feedback loop scheme), and have a more forward only. The way the Arduino Timer1 library works is that the onchip timer generates an interrupt (and resets) when it is equal to a comparison register. This is convenient, because it means that you can set the comparison register while the timer is counting, without starting a new counting cycle (as opposed to a scheme where you reload a countdown timer on each interrupt). I think the real errors are going to be things like whether tvb's algorithm for EOT is good enough for leap years, for instance. Right now, if you integrate the rates over a whole year of hours (hmm, have to try that) you should come back to zero, but if you stick in an extra day, you'll wind up 30 seconds off (because it's changing fast at that time of year). Now I'm going to start working on what the rate equation needs to be for sunrise/sunset at 6'o clock, given latitude. I have the EOT for Mars, as well, and some of the previous posts have given references from which I can generate an EOT for other heavenly bodies if needed. (of course, if someone had a cheap source for clock displays that have absolute positioning (e.g. something like a synchro), that would make life easier. All of this generating pulse streams for a relative positioning device (basically a stepper motor) has enormous potential for cumulative errors, not to mention the power fail issue. There's a reason why those centrally controlled clocks have the sync pulse mechanism at the top of the hour, and why my old floppy drives have a track zero sensor. However, if one stays with stepper motor clocks, there's an enormous selection at places like Ikea, which are nice looking and cheap. ___ 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] 24 hr clock movements...
On 1/19/14 1:51 PM, Tom Van Baak wrote: Use 24h clocks for best results. They can be had from www.clockkit.com, an excellent source of DIY quartz clock parts. I couldn't find 24hr movements on the clockkit.com site.. where are they? ___ 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] 24 hr clock movements...
On 1/20/14 10:06 AM, Jim Lux wrote: On 1/19/14 1:51 PM, Tom Van Baak wrote: Use 24h clocks for best results. They can be had from www.clockkit.com, an excellent source of DIY quartz clock parts. I couldn't find 24hr movements on the clockkit.com site.. where are they? http://www.klockit.com/depts/SpecialtyClockMovements/dept-379.html ___ 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] more solar clock stuff
So here's my next idea.. Set up a 24 hour movement (no minute hand) so that you have the sun moving around the dial: at the top at solar noon, with the rate being reasonably constant around the dial(e.g. using the solar clock algorithms developed) Then, have two other pointers or sectored disks on the face to indicate sunrise and sunset time. I haven't figured out the mechanical aspects, but maybe a small motor driving the edge of a clear plastic disk. (or if there were a good cheapish source for multi axis pointer systems). One could also add a moon pointer (and all the rest of the planets too). Sort of a geocentric Orrery. The planets would need to be able run in both directions to accommodate retrograde apparent motion. It would be easy with laser pointers or light beams and stepper motors driving a tilted mirror to project moving dots on the wall, but a more mechanical display would look nicer, I think. Once the mechanical aspect is figured out, the software should be fairly straightforward to drive whatever motors there are. (After noticing Saturn this morning when I went to go get the paper before dawn) ___ 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] more solar clock stuff
On 1/20/14 11:00 AM, Bob Camp wrote: Hi I realize this is *exactly* what the OP didn’t want to do, but …. A PI or any of the little dedicated ARM + GPU gizmos driving a cheap junk HDMI monitor or TV would make for a very nice display of all that data… The total cost could still be under $100. With Linux running on the “gizmo” locking it up to NTP should be a snap. No messy issues with code size …. Power consumption of even the most efficient display is large. And, they're not readable in all illuminations. A big advantage of a mechanical wall clock (aside from the art aspect) is that you can read it in a variety of lighting conditions. Of course, for a *real* challenge.. make a display that reflects beams of sunlight onto the display (at least during the day time). Sort of an inverse sundial. ___ 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] 24 hr clock movements...
On 1/20/14 3:32 PM, Rex wrote: That listing is a bit vague about if it has a second hand. For the kind of pulse drive that has been discussed here, it seems you would want a definite second capability and step vs. smooth second hand drive. I know nothing except a little web searching, but this one seems to have the right features... http://www.clockparts.com/clock-part/24-hour-high-torque-movement/ but, although they mention a 24-hour dial available, the page for it on the site has no content. it is very much a matter of buying a few and trying them. If you don't install a second hand, then that solves the inertia of the secondhand problem. The challenge is that because the motor for these things is basically a step at a time, if the hand has too much inertia, then the hand will either not move enough to get to the next tep (dying battery syndrome we've all seen), or, it will move past (because the braking torque isn't high enough. It's sort of the torsional resonance effect that afflicts stepper motors in another form. The magnetic impulse is basically driving a spring (the magnetic field) with a mass on it. These things are always highly idiosyncratic. I would imagine that fiddling with the duration and magnitude of the step pulses (or, for that matter the shape of the pulse) could have a huge effect if one wanted to optimize it. A couple decades ago we built a large (5-6 foot diameter) stopwatch prop with a stepper motor, and we had to play with the drive voltage, the capacitance and resistance in the step channels to make it work right. Today, you'd do microstepping, or use a clever algorithm to customize the step waveform. Generally you want a voltage profile that's sort of a spike (to get the current flowing in the winding) with a back porch, and then a reverse polarity at the end (to stop the motion). (I note that this problem is not unique to AA powered clocks. The hands of the clock on the UC Berkeley Campanile are wood for a similar reason.) ___ 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] 24 hr clock movements...
On 1/20/14 5:57 PM, Robert LaJeunesse wrote: Since most of those cheapo movements are a simple single-coil motor, energized with alternating polarity short pulses, it would seem that there is no need for a 24 hour movement. You can just have your micro pulse it twice the normal period, but with the same as normal pulse width(s). Check out the movement teardown in lunchtime clock at Instructables.com - http://www.instructables.com/id/Lunchtime-Clock/ The difference is that a 24 hr clock has a 24:1 gear ratio between minute and hour hands, and a 12 hr clock has 12:1. If you're doing hour hand only, yep, any movement will do. ___ 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] Arduinos in time and near space
On 1/20/14 6:15 PM, Chris Albertson wrote: On Mon, Jan 20, 2014 at 6:54 AM, Jim Lux jim...@earthlink.net wrote: On 1/19/14 10:31 PM, Chris Albertson wrote: On Sun, Jan 19, 2014 at 6:41 PM, Lizeth Norman normanliz...@gmail.com wrote: This is why I am a fan of the Teensy3... It's a Freescale micro based on ARM cortex, and fast, low power, etc. However, I happened to have an Arduino sitting in front of me on the table on Saturday when this started. The computer you've got is better than the one you have to order and wait for. Thanks for the pointer to teensy3 I did not know they were using ARM. they are very cool.. I'm going to look into this because I'm adding a Kalman filter in a project that is now Arduino based It's working out to be a 12x12 matrix. I'm not at all sure the little AVR chip and do floating point math fastest enough to run a Kalman filter that large inside a even a slow 1Hz control loop. I suspect it would. I'm running a 50 MHz teensy3 and a pair of 19 tap FIR filters at 200 Hz (actually after decimating from 50kHz, but the two stage decimator is an integer CIC type). I was thinking I Wanted Beagle Board Black. But if the navigation Kalman filter and motor control PID loop fit on a Teensy I've by better off. Eventually I need something that can run a real-time version of Linux. Back on topic: Arduino contributed code includes a Time library that can input time using NTP over Ethernet and from the German version of WWVB as well as a few other methods of time transfer. So there appears no need to re-invent time transfer into an Arduino. yes.. and that runs on a teensy, as well. ___ 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] Local Solar Time Clock
On 1/19/14 2:00 AM, P Nielsen wrote: To Jim Lux. After you get it working, would you consider putting the details online, or selling as a kit? Half coded. I'll publish all the details.. It's pretty easy.. a Arduino, a clock, a wall wart to power it. I haven't tried it yet (no clock to test with until the stores open), but I'm assuming that it's just a wire from the digital output port to the clock. Might need a resistor in series. The other burning question is how accurate does it have to be. The scheme I have now basically has a table of rate vs day of year (which I still need to calculate). Right now, the EOT is changing almost 30 seconds/day, which implies that the clock could be some seconds off during part of the day (although true at noon). Given the tens of ppm accuracy of the crystal = some seconds/day it seems that I want a bit better algorithm. Rather than drive from a table, maybe actually calculating it. the Arduino is no ball of fire for floating point computation, but still, it doesn't have that much to do. It could be that I can just calculate the rate every second. But then I have to differentiate the equation of time... and I haven't had enough coffee yet to differentiate the chain of sinusoids analytically. P Nielsen ___ 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] Local Solar Time Clock
On 1/19/14 1:49 AM, Chris Albertson wrote: On Sat, Jan 18, 2014 at 11:14 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Are you perhaps thinking of sidereal time, Chris? Either way, the difference is within the limits of the basic tin wind-up alarm clock. A quality wrist watch would not work because it is to good and harder to adjust. Something like this: Westclox-15396-Ardmore-Twin-Bellhttp://www.amazon.com/Westclox-15396-Ardmore-Twin-Bell/dp/BV0DEW/ref=pd_sim_hg_1 Now if the OP wants to track apparent solar time to better then a few seconds per month, then it gets real hard if you have to do it with springs, pendulums and gears because the clock needs to track the date. I think you might need some kind of of non-round cam that revolves once per year. That's what the 'equation clocks' in the Wikipedia article do. ___ 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] Local Solar Time Clock
On 1/19/14 9:17 AM, Chuck Harris wrote: The usual quartz clock that runs off of a AA cell is a little trickier to drive than you might think. You need to feed its stepper motor coil with an alternating +1.5V and -1.5V pulse. The pulse follows the rising or trailing edge of a 1/2 Hz square wave. I have driven them using a series capacitor and resistor to ground...arranged as a differentiator, but I don't recall the part values anymore. You arduino could certainly be made to generate such a pulse using a couple of resistors and a couple of digital outputs in a simple DAC sort of circuit. Yeah.. that *is* the challenge. Use two outputs and make a sort of H bridge ___ 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] Local Solar Time Clock
On 1/19/14 9:40 AM, David J Taylor wrote: From: Jim Lux Right now, the EOT is changing almost 30 seconds/day, which implies that the clock could be some seconds off during part of the day (although true at noon). [] 30 seconds/day? http://www.sundials.co.uk/pix/c/eot3.gif from: http://www.sundials.co.uk/equation.htm http://www.wsanford.com/~wsanford/exo/sundials/equation_of_time.html 5 Jan 5.2 minutes 6 Jan 5.7 minutes 30 seconds in a day.. The total variation over the year is +/- 15 minutes, but the derivative is a lot bigger at some times of the year (now) ___ 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] Local Solar Time Clock
On 1/19/14 10:11 AM, Chuck Harris wrote:
Given the relatively low currents needed by the clock
motor, and the relatively high currents that can be
sourced/sinked by the arduino, and the fact that the
motor winding is floating relative to the arduino,
one could probably connect the motor like this:
D0---SomeResistor--MOTOR-D1
Then, how to describe the way to drive it?
Well, starting out with D0=D1=0,
Set D1=1, then in 0.1 sec set D0=1.
Wait 0.9 sec then:
Set D0=0, then in 0.1 sec set D1=0...
Wait 0.9 sec then:
wash rinse repeat...
That's what I'm going to try.
Actually, on an arduino, you can set the output pin to Hi Z..
So it's more like
#define PulseLength1 100// milliseconds
#define PulseLength2 100
void ClockTick(){
digitalWrite(D0,LOW); //preload the bits
digitalWrite(D1,HIGH);
pinMode(D0,OUTPUT); // now make them an output
pinMode(D1,OUTPUT);
delay(PulseLength1);// wait til pulse first part
digitalWrite(D0,HIGH); // flip direction
digitalWrite(D1,LOW);
delay(PulseLength2);// wait til second part
pinMode(D0,INPUT); // turn off pulse
pinMode(D1,INPUT);
}
That way you're not drawing power most of the time..
-Chuck Harris
Jim Lux wrote:
On 1/19/14 9:17 AM, Chuck Harris wrote:
The usual quartz clock that runs off of a AA cell is a little
trickier to drive than you might think. You need to feed
its stepper motor coil with an alternating +1.5V and -1.5V pulse.
The pulse follows the rising or trailing edge of a 1/2 Hz square
wave. I have driven them using a series capacitor and resistor
to ground...arranged as a differentiator, but I don't recall the
part values anymore.
You arduino could certainly be made to generate such a pulse using
a couple of resistors and a couple of digital outputs in a simple
DAC sort of circuit.
Yeah.. that *is* the challenge.
Use two outputs and make a sort of H bridge
___
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Re: [time-nuts] Local Solar Time Clock
On 1/19/14 10:47 AM, Don Latham wrote: Jim: I used a simple f/f, q and ~q and 180 ohm resistors. Could easily be done with two ard outputs. needs 1/2 sec cycle. i just disconnected the coils from the epoxied blob with the clock electronics. You can also drive it backwards if it amuses. . . Don Does it need any biphase pulse, or does it really need to be 500 ms pos and 500 ms neg? If it's 500/500, then I'll change my code to count half seconds instead of seconds... it's cleaner. ___ 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] Local Solar Time Clock
On 1/19/14 11:21 AM, Tom Van Baak wrote: Yeah.. that *is* the challenge. Use two outputs and make a sort of H bridge Jim, No problem. 1) equation of time: See www.leapsecond.com/tools/eot1.c, source code that generates the equation of time and its derivative. Sample output attached. You can see the time varies from about -14 minutes to +16 minutes. The clock rate varies from -28 seconds to +22 seconds per day, which is about -324 ppm to +262 ppm. This is easy to do with leap cycles on a microcontroller. See my sidereal PIC code for an example: http://leapsecond.com/pic/src/pd28.asm When driving a quartz clock stepper motor from a microcontroller, the trick I use is to configure two pins as *input* (tristate), and set output latches to 0 and 1. Then once a second all you do is change the mode to *output* for 50 ms. During the 950 ms idle time, XOR the two output latches with 11. Exactly what I was going to do.. That way you get the identical waveform as seen in the oscilloscope trace above. Pick current limiting resistors such that the clock ticks confidently but not violently. So it's one pulse per second, with the polarity alternating on each pulse... Easy enough.. ___ 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] arduino solar clock
So, Tom's EOT routine takes less than a millisecond to execute (in double precision) on the Arduino.. So what I can probably do is call it every minute or hour to update the rate for the next minute/hour. Now I just have to figure out how to conveniently set the current date/time (for now, I just edit the sketch and reupload). Actually, that's probably ok.. hook up USB pod, set time/date, start program, let it run, disconnect USB. Hey, what about leap years, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Local Solar Time Clock
On 1/19/14 11:24 AM, Bob Camp wrote: Hi I’d put the table(s) in flash. You aren’t going to change it often enough to matter in terms of re-flash cycles. They would all be pre-calculated for that clock at that location, starting from today. In my approach this would be a very application specific shoot of the code. The 18F24J10 is $1.66 in the cheapest package. No combination of package and temp range is over $2 in quantity one. It’s got 16K flash and way more of everything else you probably would need. There are other parts from other vendors that are also under $2 that might make more sense. For me time is money.. so I'm willing to invest $30 in an arduino at the local radio shack and call it done. If it were a product one were selling, then, yes.. program a PIC, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Local Solar Time Clock
On 1/19/14 12:20 PM, David J Taylor wrote: From: Jim Lux http://www.wsanford.com/~wsanford/exo/sundials/equation_of_time.html 5 Jan 5.2 minutes 6 Jan 5.7 minutes 30 seconds in a day.. The total variation over the year is +/- 15 minutes, but the derivative is a lot bigger at some times of the year (now) ___ Higher than I expected from a quick look at the graph. I had 17 minutes total variation in 6 months in my mind! So did I until I started coding it up... ___ 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] keeping Arduino timekeeping and clock synced up
It turns out there's a handy Arduino library for time. And it will ingest GPS or NTP, etc., as well as run off the internal clock. One strategy, then, is: Set the clock in the Arduino then, periodically (once a minute or hour) look up the date and time calculate rate set tick rate for external clock driver Then you have a thing which generates 1pps ticks at the desired rate. Right now, I have a little interrupt loop that runs once a second(adjusted by rate) do it. One could also calculate solar time (as UTC + EOT offset) repeatedly (after all, there's nothing else for the Arduino to do) and whenever the seconds changes, send a tick to the clock. This technique doesn't try to keep the integral of ticks aligned with UTC + EOT offset, though. If the tick rate were slightly off (roundoff errors in the math, most likely), then there will be some relative drift. So, periodically, one would need to reset both the analog clock AND the Arduino clock to bring them back to proper alignment. I suppose that periodically, one could compare number of ticks sent with UTC + EOT offset and try to compensate (by dropping ticks or adding them). ___ 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] keeping Arduino timekeeping and clock synced up
On 1/19/14 1:51 PM, Tom Van Baak wrote: So, periodically, one would need to reset both the analog clock AND the Arduino clock to bring them back to proper alignment. I suppose that periodically, one could compare number of ticks sent with UTC + EOT offset and try to compensate (by dropping ticks or adding them). And then you'd have a GPSDST (GPS disciplined solar time) clock... While you're at it, add a rotary switch and allow the (JPL) user to select which planet's solar time they want to display. Since there are now only 8 planets you can also do it with a 3-bit configuration switch (now you know the real reason Pluto was demoted). If your project works ok for the earth clock, the next step is a jaw-dropping array of 8 (9) clocks in a JPL lobby showing the differently ticking solar time for each planet. Use 24h clocks for best results. They can be had from www.clockkit.com, an excellent source of DIY quartz clock parts. You have divined my ultimate goal..Display local solar time for every lander, for instance. Except at work, I'd get a bunch of 3325Bs (since we have pallet loads of them around), driven from the maser based reference, and have a PC sending GPIB commands to them to adjust the rates. Handy to have a source for 24hr clock movements. Last time, I bought a couple MFJ 24 hour clocks at the local Ham Radio Outlet.. To be honest, one of the interesting challenges is dealing with power failures in these kinds of systems. The Arduino is not a low power device..(at least not in the AA battery for 2 years sense). So, do you run the whole thing off 12V (which is what I'm going to do) and a float charged battery OR do you do something clever like detect when power is failing and save it in NV storage, then when you come back up, you send a bunch of clock ticks real fast to catch up. Our lobby isn't that big at JPL.. I'll probably hang them down the hall outside my office or something. I had the Mars clock outside my office (with a 50 ft coax to the signal generator under my desk) for about a year before I had to take it down in the annual clean everything up festival. ___ 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] arduino solar clock
On 1/19/14 3:58 PM, Chris Albertson wrote: It is. Both double and float are 32-bits. Arduino uses the GCC AVR compiler. If you care a lot about precision you use integer math and do all your calculations in integer units of milli or microseconds. If you try to keep time in floats you are working with about four decimal digit approximations which might not be good enough. however, calculating the rate offset for the equation of time might not need double precision. That is, if you're calculating, say, a ppm offset, rather than the actual rate, you may not need that level of precision. For instance, to gain 30 seconds in a day (the rate right now), the clock needs to be running 347.22 ppm faster than nominal. if I calculate as 347, then I gain 29.98 seconds, if I calculate as 348, then I gain 30.0672 seconds over the day. So 0.02 seconds/day isn't a huge error, just from approximation of the EOT. Really, what it is is calculating the new 1pps divisor for the timer driving ISR, which divides down from the clock rate of the Arduino. ___ 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] keeping Arduino timekeeping and clock synced up
On 1/19/14 4:10 PM, Tom Van Baak wrote:
So, do you run the whole thing off 12V (which is what I'm going to do)
and a float charged battery OR do you do something clever like detect
when power is failing and save it in NV storage, then when you come back
up, you send a bunch of clock ticks real fast to catch up.
Use a high-res Arduino web cam facing the wall of clocks and write OHR (Optical
clock-Hand Recognition) code. That way its a single robust solution for setting
it the first time, restarting it on power failure, resyncing after replacing a
failed clock, or self-correcting after any mechanical glitch. You can also use
the same video feed to show off the project live on the JPL web site.
No, a low res cam with a robotic arm that moves it in front of each
clock in turn..
That is what is called scope creep..
I'll be happy if I get ONE clock running reasonably..
I've got the Arduino code running that does the EOT, once a second (but
using delay(1000) not the ISR), calculates the rate estimate, and
accepts a sync command over the (emulated) serial port to set the time
and date.
Curse the folks who develop processing because the current version
supports Mac OSX 10.7 and later, but not 10.6, which I am using, so I
don't have the nifty click here to sync the Arduino routine that's
provided as an example with the Arduino Time library.
Next I have to integrate the code I've got now with the other sketch
that does the ISR off the hardware timer.
---
#include Time.h
// Solar clock to drive mechanical mechanism
// Jim Lux, 19 Jan 2014
#include math.h
#define TIME_MSG_LEN 11 // time sync to PC is HEADER followed by Unix
time_t as ten ASCII digits
#define TIME_HEADER 'T' // Header tag for serial time sync message
#define TIME_REQUEST 7// ASCII bell character requests a time sync
message
// T1262347200 - sample sync message
const double refclk=31376.6; //16 MHz/510?
const int clkpin1=6; // pins going to external clock
const int clkpin2= 7;
int dd, hh; //current day and hour
boolean UpdateClockFlag; // tells loop() that an interrupt has occurred
void setup(){
pinMode(clkpin1,INPUT); // set pins as inputs High Z for now.
pinMode(clkpin2,INPUT);
Serial.begin(9600);
delay(1000);
UpdateClockFlag = false;
}
void loop(){
int DOY;
double e1,e2;
double secsperday,ratedelta;
time_t t;
t = now(); // get the time
if(Serial.available() )
{
processSyncMessage();
}
delay(1000);// hack, til we get ISR timer running
UpdateClockFlag = true;// hack
if (UpdateClockFlag) {
if(timeStatus() == timeNotSet)
Serial.println(waiting for sync message);
else {
DOY = DayWeekNumber(year(),month(),day(),weekday());
hh = hour();
e1 = eot(DOY,hh);// EOT in minutes
e2 = eot(DOY,hh+1);
secsperday = (e2-e1)*1440;
ratedelta = secsperday*1.E6/86400; //ppm for now,
// but we'll change to
divisor later
Serial.print(ratedelta); Serial.print( );
digitalClockDisplay();
// code in here to update interrupt divisor, etc.
};
UpdateClockFlag = false;
}
}
// equation of time code from Tom Van Baak
//http://www.leapsecond.com/tools/eot1.c
double eot(int day,int hour){
double Pi = 4 * atan(1);
double y = (2 * Pi / 365.0) * (day - 1 + (hour - 12) / 24.0);
double eqtime = 229.18 *
( 0.75
+ 0.001868 * cos(y)
- 0.032077 * sin(y)
- 0.014615 * cos(2*y)
- 0.040849 * sin(2*y)
);
return(eqtime);
}
void processSyncMessage() {
// if time sync available from serial port, update time and return true
while(Serial.available() = TIME_MSG_LEN ){ // time message
consists of header 10 ASCII digits
char c = Serial.read() ;
Serial.print(c);
if( c == TIME_HEADER ) {
time_t pctime = 0;
for(int i=0; i TIME_MSG_LEN -1; i++){
c = Serial.read();
if( c = '0' c = '9'){
pctime = (10 * pctime) + (c - '0') ; // convert digits to a
number
}
}
setTime(pctime); // Sync Arduino clock to the time received on
the serial port
}
}
}
void digitalClockDisplay(){
// digital clock display of the time
Serial.print(hour());
printDigits(minute());
printDigits(second());
Serial.print( );
Serial.print(day());
Serial.print( );
Serial.print(month());
Serial.print( );
Serial.print(year());
Serial.println();
}
void printDigits(int digits){
// utility function for digital clock display: prints preceding colon
and leading 0
Serial.print(:);
if(digits 10)
Serial.print('0');
Serial.print(digits);
}
int DayWeekNumber(unsigned int y, unsigned int m, unsigned int d,
unsigned int w){
int days[]={0,31,59,90,120,151,181,212,243,273,304,334};// Number
of days at the beginning of the month
Re: [time-nuts] Arduinos in time and near space
On 1/19/14 6:41 PM, Lizeth Norman wrote: Hi all, Funny how this topic of the arduino time library comes around. Have been following your conversations regarding the precise nature of arduino time (gps time aware) Is it possible to write (assuming the poor little creature would do it) a piece of code, that given your lat/long, the time and a two line element set for an orbiting object, such as the ISS, that would give you the acquisition of signal time/loss of signal time and so forth? Of course, and it could easily generate real time look angle (az and el). You might want to go with something like a teensy3 rather than an Arduino: faster, lower power, a LOT more memory space, and cheaper. I don't know that anyone has ported a decent orbit propagator (like SGP4 from celestrak.com, which is sort of the standard) to the Arduino environment. I don't think it would be all that hard. Having done this kind of thing quite a few times now, I would recommend you work in XYZ (either Earth Centered Fixed or Earth Centered Inertial) kind of coordinates and do things with matrix computations, rather than trying to do the trig solid geometry approach. (e.g. don't use what's in the ARRL books). ISS is at one XYZ coordinate, you're at another XYZ, so the vector from you to ISS is (ISS-You). The Doppler can be computed from the difference in the two velocity vectors. Look angles are computed by looking at your local vertical vector. If you need better than 1 degree pointing, you DO need to take into account that the earth is not spherical. Am interested in this as part of a balloon project. My part of the payload would be a small 5w radio with a modem, driven by an arduino. Was thinking APRS on the high frequency bands, as well as the digipeater on the ISS. BTW: Had a look at the scheduler in the Arduino Time (official site) download. Looks like it'd be pretty easy to set up. Norm n3ykf ___ 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] Local Solar Time Clock
On 1/19/14 8:00 PM, P Nielsen wrote: It's not clear if the OP wants true local time or the time at the center of his time zone. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html My original idea was to have 12 noon equate to the sun's highest position in the sky at my locality, and remain so reliably throughout the year. There is obviously some very specialized talent in this group, and I would have trouble following all the suggestions so far. I hope one of the outcomes of this thread will be a timepiece that a moderately skilled electronics hobbyist can replicate. For example, I can program PIC's and build circuits, but not write code. Anything electromechanical is fine. A one-off solution created in a well-equipped lab as a curiosity piece would probably not be within my resources. I had originally imagined something like a PIC coded to deliver modified pulses to a wall clock module. Is it possible to arrive at anything close to that level of simplicity? For my use, this was not intended to be a research grade instrument. Most certainly... Having got most of the way through it, it turns out that some of the trickier areas are user interface... A regular old wall clock has a knob on the back to set the time. BUT, for the solar clock you need to tell it: 1) your longitude 2) What time and date it is (in either local solar time, or in standard time) In a mechanical clock, you'd probably set the month and day somehow on a dial, and deal with the longitude offset by just applying a fixed offset from local standard time (e.g. I'm at 119W, so I'd set the clock 4 minutes fast, because my time zone's meridian is at 120W, so noon happens 4 minutes earlier for me) My going in solution is that you do that with a serial connection (via USB) and some simple commands. The vanilla Arduino Uno has a USB connector on it, so it's pretty easy to use. ___ 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] Local Solar Time Clock
On 1/18/14 2:25 PM, P Nielsen wrote: I am looking for a physical clock (not software) that will indicate local solar time. IOW when the sun is at its highest point, the clock would reliably read 12:00 throughout the year. So it needs to take into account the equation of time? there's probably some exotic all mechanical geared scheme for this in some $20k pocket watch.. Is there a commercial product or kit available for this? I know you're not interested in a software solution, but my approach would be to drive a conventional electric clock (1pps ticks) with some logic that implements the equation of time. It would be pretty easy to have a table that sets the divisor from the clock to the 1pps and slowly changes it above and below the nominal rate so that the clock reads noon at solar noon. I did it back in 2004 using a HP 3325 replacing the 32 kHz crystal in a 24 Hr clock to build a Mars clock. It kind of depends on what instantaneous accuracy you need, too. the deviation is on the order of 15 minutes, but do you want the error of your clock to be a maximum of 1 second or 10 seconds or what... ___ 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] Local Solar Time Clock
On 1/18/14 2:25 PM, P Nielsen wrote: I am looking for a physical clock (not software) that will indicate local solar time. IOW when the sun is at its highest point, the clock would reliably read 12:00 throughout the year. Is there a commercial product or kit available for this? http://en.wikipedia.org/wiki/Equation_clock so what you're looking for is an Equation Clock.. There's examples referenced in the wikipedia article in the British Museum. The article also describes some of the ways of doing it. ___ 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] Local Solar Time Clock
On 1/18/14 4:22 PM, Tom Van Baak (lab) wrote: Add GPS if you want the clock to self-adjust when moved east or west (noon moves a couple of milliseconds per meter). This feature would be especially cool if the clock were used in a vehicle. Ooohh... an automatic self adjusting sundial for boats, planes, automobiles... It will become a must have for every megayacht. ___ 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] Local Solar Time Clock
On 1/18/14 2:25 PM, P Nielsen wrote: I am looking for a physical clock (not software) that will indicate local solar time. IOW when the sun is at its highest point, the clock would reliably read 12:00 throughout the year. Once you buy into a microprocessor, it's pretty easy to make all sorts of clocks.. When I built the Mars clock, I also thought about how cool it would be to building a clock that reads 6 at sunset and sunrise, 12 at noon/midnight, or, for that matter, using conventional analog clocks as the display device for relative positions of astronomical bodies (e.g. moon, planets) Sort of a locally centered orrery. I've also contemplated building a satellite pass clock (as opposed to displaying it on the usual screen display). Over the years I've had opportunity to care about when a particular satellite was above the horizon and where it was in the sky, and some sort of at a glance display would have been useful. For example, last year I was doing some experiments with measuring radio propagation from the ground to a radio on ISS, so there was a whole get ready for the measurement, ok, it should be over the horizon now, etc. And you're doing this outdoors in bright sunlight, and it would have been handy to have a big analog dial to look at (like the start clock in some races) ___ 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] Arduino Frequency Accuracy
Just in case you want to build a clock with an Arduino.. http://jorisvr.nl/arduino_frequency.html ADEV measurements, etc. take home message.. absolute accuracy is a few kHz out of 16 MHz... probably a 100 ppm crystal. On some Arduinos (or Teensy3's which is what I use) there's a provision for a 32kHz clock crystal.. that might be a bit better as a time base. ___ 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] Local Solar Time Clock
On 1/18/14 5:11 PM, Bill Dailey wrote: http://www.precisionsundials.com The sawyer looks like it fits the bill. $8,000 Actually, only $2,100.. that fancy helical thing Renaissance was the 8 kilobuck one.. The Sawyer thing has a lot of nice design features. Very clever how they do the equation of time compensation, and I like the wedge. ___ 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] Local Solar Time Clock
On 1/18/14 5:23 PM, Mark Sims wrote: Lady Heather can display time in LMST/LAST/GMST/GAST I made a version that has an option to just show the date/time in full screen mode for Jim Lux/JPL but never heard back from him. I have passed it on to the person who was asking about it..I'll have to go over and see what happened. ___ 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] Local Solar Time Clock
I'm working on it now. Got the arduino UNO, need to go get a cheap cook tomorrow On Jan 18, 2014, at 18:01, P Nielsen pniel...@tpg.com.au wrote: Thank you for the suggestions so far. When I said no software, I meant not something like this: http://www.jgiesen.de/sunmoonclock/index.html I was hoping someone here might have come up with a cheap quartz clock driven by a microprocessor, and the necessary code. That would seem to be the most practical solution. Anyone? P Nielsen ___ 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] L1/L2 GPS Receiver
On 1/17/14 8:43 AM, Michael Perrett wrote: Magnus, I believe that he is referencing the the new L2 C/A code, which is not protected. Reference http://www.gps.gov/systems/gps/modernization/civilsignals/ Is the L2c officially on yet? and how many S/V are radiating it? I know there was some testing last summer for L2c but I don't recall the details. ___ 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] L1/L2 GPS Receiver
On 1/17/14 11:35 AM, Magnus Danielson wrote: On 2014-01-16 20:29, Hal Murray wrote: anders.e.e.wal...@gmail.com said: The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! Has anybody considered doing it in software? If I wanted to play with that sort of stuff, is there any particular SDR hardware package/project that would good to start with? Well, considering that you will need to get the P(Y) signal at 10,23 Mchip/s on both L1 and L2, requiring say 40 Msamples/s for both frequencies, and that you will need to do it for say 12 channeles and a bit of interesting processing beyond doing the same amount of channels for the C/A code, it will be an interesting challenge to do that in CPU code, rather than doing the baseband-processing in some form of hardware/FPGA. ALmost certainly in an FPGA. But unless you want fast acquisition, implementing the tracking loop and despreading in FPGA isn't mindbendingly difficult. I'll bet there's open source out there. You could also record raw bits and decode off line in software in non-real time, as long as your clock that you timestamp with isn't too bad. ___ 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] NTP as vector for DDOS attacks?
http://arstechnica.com/security/2014/01/dos-attacks-that-took-down-big-game-sites-abused-webs-time-synch-protocol/ Interesting.. throw requests at an NTP server that look as if they come from the target, prompting large responses to the victim, presumably to overload it. The article talks about how the victim site can easily filter out the messages from the NTP server, but does not seem to discuss the societal impact of potentially screwing up a public service (the NTP server) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] NTP as vector for DDOS attacks?
On 1/10/14 1:06 PM, Paul wrote: On Fri, Jan 10, 2014 at 2:52 PM, Chris Albertson albertson.ch...@gmail.comwrote: It's not a big deal. Even if one pool NTP server is down On Fri, Jan 10, 2014 at 4:32 AM, Jim Lux jim...@earthlink.net wrote: The article talks about how the victim site can easily filter out the messages from the NTP server, but does not seem to discuss the societal impact of potentially screwing up a public service (the NTP server) It's an amplification attack. It's about taking down citi.com or whitehouse.gov -- not taking down pool.ntp.org (or any part of it). Yes.. but how long before someone thinks of putting the amplifier after a botnet, rather than driving it directly. ___ 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] WAAS.....
On 1/8/14 9:06 PM, David I. Emery wrote: On Wed, Jan 08, 2014 at 08:09:04PM -0500, Charles Steinmetz wrote: Nathaniel wrote: Following from that, suppose a jammer parks nearby and doesn't leave in a timely fashion. How long does it take for the FCC to swoop in (do they swoop? in my mind they do) and find the source? One of my clients had exactly that problem with radar detectors in parked cars interfering with its satellite earth stations. In that case, the answer was about three years. Did the FCC actually DO anything about these things ? I imagine there are some type acceptance issues that could be invoked here... It depends on what's being interfered with. Park your jammer on the approach to a big airport on a foggy night and jam the glide slope and localizer, and the DF van will be out there in minutes. Run a bootleg FM station that doesn't interfere with any one, and you'll get a NOUO in the mail eventually. In general, jamming or interfering with public safety gets the attention and more rapid enforcement actions. ___ 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] WWV/WWVH audio simulator?
On 1/6/14 9:44 PM, Magnus Danielson wrote: Jim, On 07/01/14 05:43, Jim Lux wrote: On 1/6/14 8:36 PM, Magnus Danielson wrote: Bob, It works the other way around. The standard Bell handset (103A I believe the designation was) has the 300-3400 Hz response, and with not so fancy analogue filtering, you can handle 4 kHz and thus 8 kHz sampling rate. The ITU-T G.711 A-law (where naturally the americans wanted their own, so u-law appeared) does non-linear pseudo-dynamic compression into 8 bits. T1s cram 24 channels into one frame, and adding 1 bit for framing, giving 24*8+1=193 bits per frame, giving the 1544 kb/s rate. 193 being a prime have caused a bit of headache over the years. In Europe, cramming 30 channels into a bundle was preferred, and allowing 2 bytes for framing and signalling. In T1, you do signalling by bit-stealing every 6th LSB on a channel. Caused some grey hairs for modem designers back in the day, and followed along over into the ISDN, as the primary rates was over E1 and T1. T1 also had three different line-encodings, of which only one was really transparent to all binary combinations. Oh the joy of early digital telephony. Many lessons where hard to learn. Synchronization was only one of them. Don't forget the length of ATM cells.. 53 bytes.. because of how big France is. No, that's not it. It's a design-by-committee thing. As I recall it, the Europeans wanted a 32 byte payload, as then you throw in a 32-byte E1 into it, but this was judged to small for datacom which the North American side wanted, that wanted a 64 byte payload. Since no agreement could be done, they went half-way and made it 48 bytes payload, so both would be equally annoyed. Toss a 5 byte header that people where agreeing on and we have the lovely 53 byte (prime number again!) ATM cell size. And why did Europe want 32 byte payloads? Because they were small enough that they wouldn't need echo suppressors for within country links, while 64 was too long. In the US, they were already stuck with 5000 km paths and needed echo suppressors even at the long length. I believe that at the time, France was the country with the longest point to point (via wire) distance, so they were the rate limiter. ___ 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] sand9 TCMO
On 1/6/14 6:05 AM, Magnus Danielson wrote: MEMS might be good for certain tasks, but for closer in noise I've only seen some progress recently, but not measured it myself. Close-in noise seems to have been pretty bad for all MEMS so far. I think that's probably related to the physically small size. It's hard to get a high Q in something that's smaller than a gnat's eyelash. I wonder if someone has done some sort of fundamental analysis, like there is for antennas that establishes a laws of physics limit on how good it can possibly be for a given size or mass. For antennas, there's the Chu or Chu-Harrington limit that says there's a tradeoff between directivity, stored energy and physical size. A high directivity, small antenna will have a lot of stored energy, which in practice means low efficiency. For instance, at some point, the resonator is so small that the amount of energy in it is comparable to the thermal noise, so if it's uncooled, that sets a floor on best performance. It's a quick way to stop those entrepreneurs who know just enough to be dangerous when they say that they're going to make 1 degree wide beams with something the size of a cellphone. You know, the companies that have one or two folks in engineering and 35 in investor relations. They often combine their not realizable in real world antenna with a new form of modulation and coding that provides 10x performance over best methods today. ___ 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] WWV/WWVH audio simulator?
On 1/6/14 8:36 PM, Magnus Danielson wrote: Bob, It works the other way around. The standard Bell handset (103A I believe the designation was) has the 300-3400 Hz response, and with not so fancy analogue filtering, you can handle 4 kHz and thus 8 kHz sampling rate. The ITU-T G.711 A-law (where naturally the americans wanted their own, so u-law appeared) does non-linear pseudo-dynamic compression into 8 bits. T1s cram 24 channels into one frame, and adding 1 bit for framing, giving 24*8+1=193 bits per frame, giving the 1544 kb/s rate. 193 being a prime have caused a bit of headache over the years. In Europe, cramming 30 channels into a bundle was preferred, and allowing 2 bytes for framing and signalling. In T1, you do signalling by bit-stealing every 6th LSB on a channel. Caused some grey hairs for modem designers back in the day, and followed along over into the ISDN, as the primary rates was over E1 and T1. T1 also had three different line-encodings, of which only one was really transparent to all binary combinations. Oh the joy of early digital telephony. Many lessons where hard to learn. Synchronization was only one of them. Don't forget the length of ATM cells.. 53 bytes.. because of how big France 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] Measuring TV delays
On 1/1/14 10:28 PM, David J Taylor wrote: From: Hal Murray Are there any events similar to New Years where some specific countdown time is shown on TV? Rocket launches, although typically not on live TV any more. More likely streamed (at least that's how I watch them). In the post launch tracking part, there's usually a display showing TAI/UTC along with various parameters (perigee, apogee, etc). I always wait until perigee is 100km before really believing it's successful. But if you can get a feed from China or India, they're pretty big on publicizing their space program, so they might have live news feeds. ___ 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] Measuring TV delays
On 1/2/14 11:56 AM, Chris Albertson wrote: When they broadcast live TV like from a sports vent I wonder if the time code generated by the camera is preserved? But then even if it were the time might have been set manually to match the display on the camera operator's cell phone. Depends on how the live feed is derived. If it's an analog signal, there's no time setting involved. If it's B-roll from a GoPro, then yes, it's based on the camera person's watch. Same for scenes with clacks in the background. Do you trust them to be on-time? They might even have ben intentionally set wrong to hide the transmit delay. Unlikely that they'd fool with clocks in the background. Why would they care (except if they're faking the 1969 moon landing or something.. then they've got enough budget for someone to make sure the clocks in the fake mission control read correctly). They DO have people to set the clocks in filming for subsequent editing: it's just part of continuity like making sure cigarettes are the right length, the ice in the glasses has melted the right amount, etc. Not a job I would want. ___ 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] Measuring TV delays
On 1/2/14 11:33 AM, Bill Hawkins wrote: IIRC, the reason why NTSC has an almost 30 fps rate is that early vacuum tube TV sets could develop heater-cathode leakage that would put a black hum bar in the picture. Almost 30 allows the bar to move through the picture in a 60 Hz power distribution system. Seems like Europe would have had that problem. And, any ripple in the power supply wouldn't cause the sync to jump around. Noise that's power line related (brush noise from universal AC motors, as used in vacuum cleaners, for instance) would be in the same place on the frame, as well. But if the vertical retrace interval were, say, 59 Hz, and there were 60 or 120 Hz ripple on the power supply, you could see how there would be a periodic offset in the vertical sweep timing and the image would slowly drift up or down and jump every second. Which would be very annoying. When they went to color, they kept the 60 Hz field rate, but moved it a little bit to 59.94 so that it could be generated by a divider chain from a master oscillator at the burst frequency. And even with all this.. it's still Never The Same Color ___ 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] Measuring TV delays
On 1/2/14 2:33 PM, Chuck Forsberg WA7KGX wrote: Why didn't they make the color burst an exact multiple of 60 Hz? Round numbers and such http://en.wikipedia.org/wiki/Colorburst has a nice description.. The whole thing of backwards compatibility and squeezing the maximum amount of information into the bandwidth was really quite amazing.. For instance the whole thing of encoding the chroma as I/Q, but with different bandwidths for I/Q, and with a weird matrix of RGB to YUV, all to minimize the visible defects from non-ideal signal paths. And you had to be able to do it with off the shelf cheap equipment in the 1940s. ___ 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] sysclock source for AD9912 DDS?
On 12/31/13 8:07 AM, Anders Wallin wrote: Could the remaining -60 dBc spurs at +/- 50 kHz be due to my 10MHz clock source, an Agilent 33120A? Yes the spurs could be from your source. that's a function generator/ARB and spectral purity isn't one of the big design criteria for that kind of device. The spec sheet says spurious non-harmonic signals are supposed to be down -65dBc + 6dB/octave above 1 MHz. http://cp.literature.agilent.com/litweb/pdf/5968-0125EN.pdf I don't know all the gory details of how the 33120 works inside (though I've got 3 or 4 of them in my lab at work), but in general, it has a DDS running at 40MHz that clocks samples out of a waveform table to a 12 bit DAC. The output from the DAC is run through some analog circuitry for doing AM and setting offsets and levels. http://cp.literature.agilent.com/litweb/pdf/33120-90017.pdf 50 kHz is somewhat suspicious.. do you have any switching power supplies at that rate around? It doesn't take much noise added to a sine wave running into a comparator to create spurs. I've had that problem with leakage of a 66MHz processor clock into a 50 MHz sampling clock. ___ 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] sysclock source for AD9912 DDS?
On 12/30/13 7:56 AM, Anders Wallin wrote: I've tested the AD9912 evaluation board: http://www.anderswallin.net/wp-content/uploads/2013/12/dds_test_2013-12-30.png I want to use it with a 10MHz external input clock, but it looks like the on-board PLL that generates a 1200MHz sample clock from my input isn't that great, since I get strong side-bands on the output that are only 18-20 dB down from the fundamental. So it looks like I need to supply a clean 800-1000MHz clock to the DDS to get a clean output. Any ideas/suggestions for generating this from a 10 MHz sine? Driving the DDS system clock from an expensive RF generator (e.g. HP 8648A) would be possible but I'd prefer a PLL from 10MHz if it's doable simply/cheaply. Most of the time, they're expecting you to filter the output of the DDS to remove the spurs. Probably not a PLL, at least not one of the generic PLL chips, because you'll get spurs and sidebands from the comparison frequency in the loop, and they'll be fairly close in. You have two basic alternatives.. a PLL using a divider from your 1 GHz and using the 10 MHz as the comparison frequency, and then good filtering to get rid of the 10 MHz spurs. A bit challenging since that's a 1% bandwidth filter. (maybe you could do that with the onchip reference generator, and feed it back in) Or, You want a straight out multiplier chain with appropriate filtering in between stages. Maybe a x7, followed by 70MHz BPF (which should be readily available), then another x7 to 490 MHz, then a x2 or x3. Or end with a x5 (to 350 MHz) and a x3 to 1050. A sort of hybrid approach might also work.. take your 10 and make 100MHz(x5 x2) with it, then feed that into your DDS. That will put the spurs 100 MHz away, which is a lot easier to filter than spurs that are 10 MHz away. I'm pretty sure Wenzel has some application notes on this. When you say clean, how clean do you need it? What sort of tuning range are you going to run the DDS over? (maybe some of the spurs will wind up in places you don't care about and can filter out) ___ 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] fast edge, rise time.
On 12/26/13 8:07 AM, ct1dmk wrote: Hello, I'm willing to generate a pulse (of some few hundred volts) by discharging a capacitor into a pulse transformer I'm solely interested is the active edge (call it either rise or fall depending on the wiring of the output of the transformer). ns risetime pulses sounds like fairly straight forward radar stuff. the inductance of the transformer is going to be your challenge, depending on the energy level. What about a non-transformer alternative? Can you just charge your cap up to the few hundred volts and have a switch that can take the voltage? How much energy do you need? You said a few hundred volts, but is that microjoules, joules, or kilojoules? A small triggered spark gap would be one way. There's also the ever popular krytron, which has very good timing accuracy. YOu might look for circuits used for exploding bridge wires (EBW) The target is 4ns, while ideas seemed to be clear at some point, now I'm having doubts if better to use a MOSFET or a bipolar transistor as the switch element. Experiments with MOSFETs presented me some difficulties charging the gate capacitance having some trouble to achieve something in the 4ns region. Well 4ns seems hard whatever device anyway. You want some sort of RF transistor here. What about one of the new LDMOS FETs: some have fairly impressive voltage handling, and if they work at 1 GHz for radar applications, they will work for you. What about stacking a bunch of MMIC RF amplifiers (e.g. like the ERA or GAL from minicircuits) Other traditional approaches to fast pulse generation are avalanche transistors. There's also a variety of interesting pulse forming networks that can generate fast rise time high voltage pulses. Blumlein arrangements are one. Your 100ns pulse is fairly long for a transmission line scheme, though (20-30 m of coax) ___ 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] recommendations for master reference
On 12/12/13 6:31 AM, Brian Lloyd wrote: I am currently using both Trimble Thunderbolt and LPRO-101 Rb references. What I really would like to have is a rack-mountable unit that is a GPS-disciplined Rb reference and a built-in NTP server. (Yes, this is for my home. We are time-nuts, aren't we?) I could roll-my-own system for disciplining the Rb from the 1pps of the Thunderbolt, and produce NTP broadcasts on the LAN but, frankly, I am going to be happier if I find a unit where someone has already done the heavy lifting AND done a better job with the filtering to reduce GPS-induced error in the Rb output. So, if you wanted a rack-mountable reference with multiple 10MHz outputs that is a GPS disciplined Rb and an NTP server, what would you look for on the used market? TrueTime/Symmetricom made and still makes a whole line of just this sort of thing in a 1 U rack mount enclosure. Something like an XL-DC with the right plug in boards, for instance. The particular plug-in I've used in the past is the one with the quiet quartz oscillator with low phase noise (since I'm usually multiplying up to microwave frequencies), but they have plenty of other options. They also have NTP servers in the same box, IRIG, etc. Oh, I suppose I would go for a Cs reference if I could find one at the right price. I'm not picky. :-) ___ 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] Shortt Clock Recent Measurements
On 12/12/13 4:28 PM, Tom Harris wrote: The eccentric English physicist Boys made quartz fibres by attaching one end to a crossbow bolt, heating the middle and then firing the bolt, at what I have been unable to determine. He used this to measure the gravitational constant by suspending iron spheres from the resultant fibre, which of course was amazingly strong for it's diameter. Myself I'd use a pneumatic cannon, since I have one, rather than a crossbow. A crossbow is, shall we say, more English, although perhaps historically, a longbow might be more significant. Was that the same Boys who invented the Boys camera used to take lightning photographs? It's a sort of rotating drum streak camera. ___ 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] Shortt Clock Recent Measurements
On 12/10/13 5:57 PM, Don Latham wrote: I always thought invar was the magic metal. Quartz rod? You can get those at some reasonable cost? 12 mm dia fused qtz, about $10 per ft, so under $40 to get going, assuming 4 or 5 to learn how to do it right. It does break... 12.7 mm dia Invar 1 m long is $530 Amazing, and quartz is better (A single crystal would cost a pretty penny. I'm not sure a crystal that long can be drawn using a zone furnace). Pyrex is also available. These are quick 'net prices. John Strong's book tells how to make thin high-q fused silica fibers with an appropriate burner. Just the thing for your torsion balance, etc. back in the day when a self respecting experimental physicist built their own equipment. ___ 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] temperature
On 12/9/13 6:12 AM, Daniel Mendes wrote: It´s still used in the oil industry as the standard for temp and pressure monitoring... Probably because they're an inherently rugged sensor ___ 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] simulation of interconnected clocks
On 11/30/13 2:15 PM, Tom Van Baak wrote: Jim, Could you just replay real data instead of trying to generate simulated data? There's plenty of storage with Arduino or SD card shields. Attached is frequency and ADEV of my heart beat for 10 hours. You could do the same. In this case the flicker floor is just under 1e-1 from 10s to 10ks. One could do that. Or in a limited sense, have a shorter table which you play back repetitively. If you did some processing on your heartbeat data to remove the sinusoidal modulation from respiration, you might find the ADEV/phase noise is less. That's something I'm looking into. In my case, I need to be able to generate multiple different realistic targets. I could probably record a bunch of sequences and then play back different pieces of them. or use one person and have them breathe at different rates and depths. But an algorithmic approach is interesting. And even more interesting is being able to generate a particular pattern (using the model), and see if you can retrieve the model parameters using the device. Here's where I'm using it: http://www.jpl.nasa.gov/news/news.php?release=2013-281 http://www.jpl.nasa.gov/news/news.php?release=2013-290 http://www.jpl.nasa.gov/video/?id=1252 We use the model parameters to distinguish targets from one another (and targets from bystanders and the operator); and also to separate humans from other targets (oddly enough, that slowly rotating fan, or swinging grandfather clock pendulum have much lower 1/f noise than your heart). One finds as you delve into the physiology literature that they have exceedingly different ways to measure, describe, and model things than engineers do. In some cases it's because they're working from the biological structures that make it happen. In others, it's just because historically it's been described differently: often with reference to particular methods of recording the signal. It's kind of like how the Richter scale is in terms of the height of the trace in mm on a particular kind of seismograph. Someone goes out and records ECG data and they write the paper and say data was recorded using a Grass model X with the filter set at position 3, and since everyone in that field of research uses the same machines, they all know how it was recorded, and can duplicate it if needed. The signal processing details of the Grass Model X with filter set at Position 3 might be left as an exercise for the reader (or a letter to Al Grass at the Grass Instrument Company). The same thing happens in the nuclear instrumentation area, where everything is in terms of pulses and time domain processing, and you refer to a particular model of Ortec pre-amp, feeding some other model discriminator, finally feeding your multichannel analyzer (which name confused me, since it has only one input channel). The other thing is that a until recently, computers weren't used to analyze the data, so the analytical methods tend to favor those that are paper, pencil, and slide rule tractable. There's a lot of log/log plots with visually placed curve fits, with not a huge number of test subjects (20 subjects would be a lot in most of these papers). Finally, there might be a historical reason why decent math models aren't popular: The grand man of physiology was Carl Ludwig in Leipzig: he had hundreds of postgraduate students (Pavlov was one), but apparently he had little use for mathematical treatment of biological problems. Ludwig wrote the 1847 paper everyone cites as the beginning: Beitraege zur Kenntniss des Einflusses der Respirations bewegungen auf den Blutlauf im Aortensysteme. But hey, if your supervisor says math models aren't important, you're sure not going to argue with him, and someone of distinctly math modeling bent would likely find another place to study or field of study. So Ludwig casts a long shadow on published research, probably for 2 or 3 generations. Thanks to the miracle of the internet and big efforts to scan stuff this kind of thing is readily available. It's come a long ways since I had to hunt down a copy of Paschen's paper/thesis on high voltage breakdown as an actual printed copy and then photocopy it. http://archive.org/stream/beitrgezurkenn00hein#page/n55/mode/2up has some examples of data collected later in the 19th century from dogs and cats. ___ 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] simulation of interconnected clocks
On 11/30/13 2:15 PM, Tom Van Baak wrote: Jim, Could you just replay real data instead of trying to generate simulated data? There's plenty of storage with Arduino or SD card shields. Attached is frequency and ADEV of my heart beat for 10 hours. You could do the same. In this case the flicker floor is just under 1e-1 from 10s to 10ks. The flat zero slope adev shows the basic 1/f characteristic reported in the literature. There's been quite a few people who have hooked up monitors to people for 24 hours or more and found that the power spectrum of heart rate follows 1/f from about 0.3 Hz down 4 decades at least. I'm not sure what the ADEV/Power spectrum of respiration rate would be, since it's mostly determined by what the person is doing. Power spectrum (averaged over a long time) would probably be more a histogram of level of physical activity. ___ 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] simulation of interconnected clocks
On 11/30/13 5:33 PM, Hal Murray wrote: t...@leapsecond.com said: Attached is frequency and ADEV of my heart beat for 10 hours. Neat. What did you use to collect the raw data? There's a few Arduino/Sparkfun/Adafruit widgets out there that receive the signals from off the shelf Polar heart rate monitors. I had a grad student last summer build a box to log heart beats using photoplethysmography (photocell sensing blood flow in fingertip). He used a widget from one of the dealers that has the analog circuitry to buffer the optical sensor. If I were collecting it on a long term (many hours) basis, I'd go with ECG based approaches (which is what the Polar sensors use), but with stick on electrodes. Motion artifacts are a big problem. Holter is the big name in commercial ECG loggers, but they're real pricey (being FDA approved medical devices and all). Microwave monitoring (radar) is a good standoff way to measure heartbeats, but only works in fixed locations (e.g. I can set it up in my office, in my car, or a room at home, and collect data, but it doesn't work well when you're out walking around). If you get one of those microwave Doppler door sensors at 10.5 or 24 GHz, you can get a good heartbeat signal from them. ___ 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] DIY QFH
On 11/27/13 11:21 PM, Attila Kinali wrote: On Wed, 27 Nov 2013 04:02:53 -0800 Jim Lux jim...@earthlink.net wrote: [Crossed dipole antennas] I don't know how they do the phase quadrature.. do they make one dipole a bit longer and the other a bit shorter? Yes. Same principle as with patch antennas. Yes, but on the picture, there's no dipole to speak of. It's more of a vertical monopole with a drooped hat. ___ 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] Simulation of oscillator noise
On 11/28/13 1:35 AM, Wolfgang Wallner wrote: Hello Time-Nuts community, I'm interested in the simulation of oscillator noise (especially in discrete event simulators). PS: When I use the word oscillator I mean the cheap quartz oscillators as found in typical consumer electronic stuff. PPS: I'm not sure if this mailing-list is the right place to ask my questions, as simulation is not listed in your mailing-list topics. Sorry if this mail is off-topic. I think it's the right place.. There's plenty of Allan deviation plots and data here for just about any kind of oscillator you care to name. One way to generate realistic spectra is to take white noise from a random number generator and run it through a filter which has the right shape (e.g. 1/f, etc.). Essentially this is implementing the Leeson model explicitly. A year or so ago, I was looking for a similar thing to simulate human heartbeats (which have a 1/f characteristic, just like other oscillators). http://www.febo.com/pipermail/time-nuts/2013-February/074505.html see also http://paulbourke.net/fractals/noise/ ___ 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] DIY QFH
On 11/28/13 6:27 AM, Chuck Harris wrote: As far as I know it is L1 only. It is a Bullet II HE, P/N 25045-10, the standard antenna specified in the Thunderbolt manual. If you look closely, you will notice that what appears to be a single soldered joint at the middle, is really two solder joints, one on each of the sides of the preamp's PCB. OK.. didn't see the double solder at the top, it looks like one in the photo. Each V has different length legs. The legs are drooped down to where they are capacitively loaded to the ground plane. So, what it is is two inverted V type dipoles in parallel, and oriented at 90 degrees crossed. And the classical approach of make one dipole a bit long and the other a bit short to get the 90 degree phase shift needed for CP. ___ 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] Simulation of oscillator noise
On 11/29/13 5:56 AM, Azelio Boriani wrote: Unfortunately that was a contribution from Magnus in 2010 (see www.febo.com/pipermail/time-nuts/2010-April/046932.html ) that I have simply reported without verifying the link and found that link unusable after sending the message. My best guess is this: http://www.crya.unam.mx/radiolab/recursos/Allan/Kasdin-Walter.pdf based on a search on FLFM (flicker of frequency). one limitation of the Kasdin-Walter method is that it is batch mode, and doesn't lend itself to an implementation which is continuous. The paper does have a nice discussion of why the white noise into a filter technique doesn't work very well if the slopes you need aren't integer powers of frequency. Integer powers in frequency correspond to rational functions in filter characteristics, which are straightforward, but how do you make a 1.5th order filter section or half a pole or zero? The fractal literature, though, may provide mechanisms that might be useful. ___ 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] Simulation of oscillator noise
On 11/29/13 8:50 AM, Magnus Danielson wrote: On 11/29/2013 04:11 PM, Jim Lux wrote: On 11/29/13 5:56 AM, Azelio Boriani wrote: Unfortunately that was a contribution from Magnus in 2010 (see www.febo.com/pipermail/time-nuts/2010-April/046932.html ) that I have simply reported without verifying the link and found that link unusable after sending the message. My best guess is this: http://www.crya.unam.mx/radiolab/recursos/Allan/Kasdin-Walter.pdf based on a search on FLFM (flicker of frequency). one limitation of the Kasdin-Walter method is that it is batch mode, and doesn't lend itself to an implementation which is continuous. The paper does have a nice discussion of why the white noise into a filter technique doesn't work very well if the slopes you need aren't integer powers of frequency. Integer powers in frequency correspond to rational functions in filter characteristics, which are straightforward, but how do you make a 1.5th order filter section or half a pole or zero? The fractal literature, though, may provide mechanisms that might be useful. Actually, NIST (or actually this was in it's NBS days) did a few good articles, comparing the Mandelbrot simulation method with their filter method. Turns out that you need to dimension the filter to the simulation length, as the number of lead-lag sections needs to cover the range where 1/f slope is needed and then the density of them (lead-lag pole/zeros per decade) will control how close it will approximate, that is, how little pass-band ripple there is from the ideal. Also, you need to apply the corrections to start the filter up in the correct state. That's essentially what the Kasdin-Walter paper talks about. The number of taps/sections is adjusted to approximate whatever curve you want well enough. Then, they sort of shunt all that with an FFT based method.. Generate white noise, filter it with a FFT convolution scheme where you've loaded the bins of the FFT with the desired power spectrum. It's non-trivial to do well. And, I suspect, non-trivial to do with low computational complexity. There are many many methods to do this. Everyone has a favorite. No doubt about it. ___ 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] DIY QFH
On 11/27/13 8:08 AM, Chuck Harris wrote: Here is some Electrical Engineer pr0n of the Trimble TBolt standard antenna. -Chuck Harris Apparently spelling out the P word gets your message rejected. Is that a L1 only antenna? What's interesting is that this is NOT a crossed dipole, at least from what I can see. It looks like all 4 arms are connected to the same point at the top. So it's some sort of funky folded monopole ___ 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] DIY QFH
On 11/26/13 8:51 AM, Attila Kinali wrote: On Tue, 26 Nov 2013 11:37:10 -0500 quartz55 quart...@hughes.net wrote: Does anyone know what is inside the commercial units, like the PCTEL GPS-TMG-HR-26N I have? Three types of GPS antennas are common: * ceramic carrier patch antennas * cross dipole antennas * helical designs The patch antennas are even found in expensive antennas with cones or choke rings. the challenge with a patch is getting a pattern that goes down to the horizon. The Trimble Bullet antenna is AFAIK a cross dipole type where the dipole ends are bend down for a more GPS like radiation pattern. Crossed dipoles are very common in survey grade antennas. Typically the dipole elements are more fan like, wide at the end skinny in the middle, and the whole thing is shaped like it is draped across a dome. The bowtie improves the bandwidth, which is important in a 3 band antenna. Drooping the ends helps improve the pattern, and also changes the input Z. I don't know how they do the phase quadrature.. do they make one dipole a bit longer and the other a bit shorter? I don't know that this works over the whole L5,L2, L1 band, though. Or some sort of quadrature hybrid. Helical designs vary greatly in their fabrication. I think most of the newer ones use some flex PCB that is bend into a pipe shape to form the helix (very cheap from a manufacturing point of view). High quality helix are either free space (like your QFH) or done on some ceramic pipe. I'm not aware of anyone using MID (molded interconnect device) for this kind of antenna. Although MID antennas have been the standard for cellphone antennas for quite some time already. The classic helibowl antenna uses wire or copper foil tape wound on a plastic cup. Helicals are pretty non critical in design, but don't necessarily have good patterns at the horizon. don't forget the spiral pinwheel antenna, e.g. from Novatel. ___ 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] Crude Survey Technique
On 11/24/13 4:23 AM, Didier Juges wrote: The Thunderbolt uses single precision floating point and digital filtering for temperature so yes, you are going to see values like this. This is not unusual (precision clearly out of step with accuracy), like the HP network analyzers returning gain in dB with 4 decimals at microwave frequencies. Not sure what your point is? Should Lady Heather pretend to know better and muck with what's sent by the receiver? I prefer not but it's a matter of opinion. Didier KO4BB David J Taylor david-tay...@blueyonder.co.uk wrote: I hope no-one believes all the decimal digits shown in that screen-shot! It seems to me that it would be better if more realistic values were presented! 37.808842 °C - really! Often it's useful to report all the digits used in the calculation, so you can reverse it back to the original, no doubt, limited precision fixed point number. ___ 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] Crude Survey Technique
On 11/21/13 11:32 PM, Robert Atkinson wrote: I'd also go for a compass if you want magnetic north, but then I have a good one, a medium landing compass. Mine dates from WWII but they are still made http://www.sirs.co.uk/ground/landing_compasses/patt2/landing_resource These are used to align the standbay and remote reading compasses on aircraft. Good to half a degree. If you need better ther is the Watts Datum Compass. Robert G8RPI. That compass is *precise* to 1/2 degree, but not *accurate* to 1/2 degree. It comes with a calibration card, and is presumably used in a place with a uniform field (e.g. for calibrating an aircraft compass, which is done in an open area with no known magnetic anomalies). If you're in a different environment, the card values may be incorrect. It is essentially as comparison standard. You put it next to the aircraft and move both in a systematic pattern and you use it to calibrate out the variations in the plane's internal compass. However you're going to be subject to the local magnetic field anomalies (and they're surprisingly large). http://minerals.usgs.gov/news/newsletter/v1n2/3aeromag.html On the 1km scale maps in the USGS reports, you can see magnetic anomalies of 500 nT. Earth's field is about 30-60 microTesla, so these anomalies are in the one part in 100 kind of range. It is true that the gradient is fairly small: It is unlikely you have an anomaly of 500 nT and your neighbor has -200 nT. But it's obvious that the magnetic variation (angle between true and indicated magnetic north) isn't the nice smooth surface implied by the map of variation you get with the compass. http://dspace.sunyconnect.suny.edu/bitstream/handle/1951/47859/Winslow_MS.pdf;jsessionid=7D7A116045A54816C9DCF963AF3D2580?sequence=1 is a short paper that talks about gradients in a small scale anomaly of 0.22 nT/meter (and I get the impression that that is big). There's also other locally produced magnetic fields you'd have to worry about. I gave an EM class a problem to figure out if you could tell whether you could use a hand compass to tell if the Pacific Intertie 1MV HVDC link (3000 A) was operating bipolar or unipolar. (at 50 meters, the field from one wire is about 6 microTesla, so yes, you can detect it) http://msi.nga.mil/MSISiteContent/StaticFiles/HoMCA.pdf is all about calibrating a ship's compass ___ 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] Crude Survey Technique
On 11/21/13 3:28 PM, Chris Albertson wrote: On Thu, Nov 21, 2013 at 11:11 AM, Don Latham d...@montana.com wrote: Lord no, John. No red wagon is needed. Use a pole and the equation of time, and a good watch or clock. At local noon, a shadow will be a n-s line. How accurate do you need to be? The above requires a very tall pole to case a 300 foot long shadow. Then you have to be quick to measure because the Earth turns at .25 degrees per minute. The original request was for accurate to a degree or two, so he has 4-8 minutes to make the measurement. The sun is 1/2 degree wide, which is actually the practical challenge in measuring using shadows, because the shadow is not sharp edged. I don't know why you need a 300 foot long shadow. Let's assume I have a 1 meter tall rod that is 1cm in diameter. The sun isn't that high in the sky at noon these days (in the Northern Hemisphere).. let's say it's about 45 degrees, so the 1 meter long stick casts a shadow that is 1 meter long. If the sun were a point source, the shadow would be 1 cm wide, or 1 part in 1/100 which is about half a degree. That's comparable to the width of the sun, so you might want to choose a bigger stick. maybe a 2 piece of pipe? estimate the center of the shadow, which could easily be done within 1/2. You now have your north direction. Solar noon is trivial to find out. The USNO Astronomical Applications page will give you a solar ephemeris for a specified lat/lon. or knowing your longitude and applying the equation of time, you can calculate when solar noon is. Or, whip out your current copy of the Nautical Almanac If you need a very tall pole that is 100% vertical then hang a weighted rope from a tall support. Then go to the other end and watch the seconds tick down. A GOOD magnetic compass can do this job too. Easier then finding s 1,000 food tall pole. The better compasses have some kind of optical aid for sighting a line. Getting 1 degree accuracy with a magnetic compass is challenging. Finding out the *current* magnetic variation is only part of the challenge, because it varies (about 1 degree in 10 years in Southern California, last I checked). ___ 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] Advice on getting a used Agilent E4432B RF-Generator
On 11/19/13 9:13 AM, Dr. David Kirkby wrote: If it is made up from PIN diodes, I wonder what the logic of Agilent letting you read the number of times they have switched? Common firmware between units? ___ 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 ALL of you Time Nuts really wants for Christmas!
On 11/17/13 2:38 PM, Don Lewis wrote: I didn't think Stonehenge told 'time' ala a sundial. Its' purpose was to herald the seasons' change, etc, I thought. Ah, so you think this is more of a calendar-nut item than a time-nut.. What about a iPhone App? Orient the device using the built in magnetic sensor, use the front facing camera to detect the sun, display stonehenge in the proper orientation, etc. But should you compensate the trilithon positions for the GPS measured latitude? ___ 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] video of CSAC GPSDO
On 11/4/13 6:51 PM, saidj...@aol.com wrote: Hi John, well, I think he must have meant a new car back in 1971 :) That would be about right. It's not quite THAT expensive. Ford Pinto sold for $1999 in the early 70s. Not that I want to compare a CSAC to a Pinto, but... Symmetricom seized to exist as an independent company a couple of days ago, they were bought out by MicroSemi.. They do make great products, for sure. Please note that I do not think that the NIST CSAC effort had much to do with the commercialized Symmetricom product. Same funding, but competing groups I think. NIST never took it to commercial grade. We who work at National research labs and Federally Funded Research and Development Centers always face the thou shalt not compete with industry laws and regulations. Each and every job or project we do, we have to prepare an analysis to show why we are uniquely suited to doing whatever it is and why the government shouldn't buy it from industry. This, in general, is a good thing, but it also does mean that sometimes the technologists are a bit separated from the customer experience (because developing the customer experience is something you only get by, uh, working with customers of a product). So we get a lot of things to TRL 4 or 5, and it kind of languishes there, unless it's something unique (e.g. if you want to communicate to deep space probes, there aren't any industry sources with 70 meter antennas, cryogenic receivers, and 400kW transmitters). Ideally, you work with some industry partner(s) who can take it to commercial reality. And, hopefully, you stay in contact with industry, who can provide feedback on what is needed in the way of fundamental research. A lot of the development of error correcting codes works this way, for instance. Some government agency or FFRDC does the basic work, and comes up with a reference implementation, then the actual commercial implementations are done by someone else. Guys like Viterbi did their basic work at JPL. Turbo codes were invented at France Telecom. ___ 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 5MHz Sweet Spot
On 11/3/13 4:27 AM, Magnus Danielson wrote: Hi Jim, Ground-based GPS-like transmitters could be a nice option to consider. Well, that's basically what we do today. We transmit a very stable carrier with some tones or a PN sequence modulated onto it. The spacecraft recovers it, generates a return signal locked to it, which we get on earth and analyze to determine the range and range rate (or if we've got two stations, we can do some cross range with Delta DOR or VLBI). This is known as two way ranging. Having a onboard high quality source means we can do one way ranging, so we can range without an uplink, or conceivably, the spacecraft can figure where it is by looking only at the uplink. A high quality onboard source also can be used to provide navigation signals from an orbiter to a lander that's not visible from earth 12 hours a day, there's no direct to earth link to something on the surface of Mars. An even bigger deal to something like the far side of the moon, although various and sundry schemes have been proposed (a relay satellite at L2, for instance) Would also provide a frequency reference for steering/compensation of that oscillator. Either that avoids deep space ranging, or it is only needed for verification. Onboard, so far not many people need precise time and frequency. It's almost exclusively for navigation, and low rate communications (if you're receiving 8 bps at -160dBm, the phase noise of your LO has to be pretty good). One of the hopes of the DSAC (Deep Space Atomic Clock) is that with easy high performance, people will come up with science measurements that depend on it. Interferometry among a constellation of satellites is one. We do a lot of gravity science by measuring the orbits of spacecraft (it is, after all, how we know the earth is pear shaped). More recently, GRACE and GRAIL used two spacecraft in the same orbit with very accurate ranging between them to accurately map the gravitational field of the Earth and Moon, respectively. Once you know the gravity, you can infer the internal structure: is it layered, or uniform, or lumpy, etc. A small very quiet clock would make putting a constellation of little spacecraft around something like Europa possible. When the entire spacecraft is a liter or two, you can't burn another liter on a USO, and even 100cc is a big chunk of volume. I thought the important part of the mission was to keep stable phase and frequency? :D We in the space telecom business KNOW that the whole reason we launch satellites with science instruments is to provide data other than random PRBS for our telecom system, so that we have something interesting to look at. Solar panels exist to provide power for our telecom system. The attitude control is to properly orient our antennas. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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 5MHz Sweet Spot
On 11/2/13 7:40 PM, Magnus Danielson wrote: On 11/03/2013 02:45 AM, Bob Camp wrote: Hi I believe that you are talking to two very different groups, one who actually design the crystals and the other who use the products that are designed. One is talking about what they can buy, the other is talking about what could / could not be done and why. This is an important point. There is in fact a few different twists to this: 1) What is the best you could buy off the shelf 2) What is the best you can buy off the shelf 3) What is the best that could be built with the available tools 4) What is the best that could be built with sky-is-the-limit budget 5) What is the best that could be built, as physical size becomes smaller AS someone who gets involved in buying #4s, and also interested in #5s, this is very true. The appeal of the trapped mercury ion clock (aka DSAC) is that it gives orders of magnitude better performance than a state of the art USO with the rock in a dewar, with lower power and comparable 1 liter size. When it comes to shrinking, I think there would be substantial interest in a very small oscillator with USO kinds of phase noise/ADEV, in say, a 50 cc/50 gram package (size of the standard 2x2 OCXO). Not everyone will want to invest in DSAC Bear in mind that substantial interest in the scientific space probe biz is a few units per year, max, with enormous lead times. One reason we keep buying USOs that aren't a heck of a lot different than the ones of 20 years ago is that they're a known quantity. I find those MEMS silicon ring resonators in the 3x3mm package really interesting, just becase they're so darn tiny. Figure out a way to get really good ADEV performance in the 10-100 second sorts of tau, even if the frequency drifts and ages over days and months, and that's an interesting part for doing deep space navigation on very small satellites. There's a huge problem as folks want to send cube-sats past GEO with how do you know where it is (GPS doesn't work when you get to lunar distances), so you need to do traditional deep space ranging of one sort or another. When the entire spacecraft is a liter or two, you can't burn another liter on a USO, and even 100cc is a big chunk of volume. The last one is kind of relevant. Today packages shrink fast, and it's very handy and all... but what about the performance we get. We can hug our 5th overtone ovens all we want, but motivating their power and size doesn't always cut it. It's like comparing with 5 inch blanks in Bob's earlier post, it's more like 0,55 inch... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] Surface Mount OCXO Questions
On 10/31/13 4:02 AM, Bob Camp wrote: Hi The control voltage on the 12 V OCXO is likely 0-10V or 0-5V. The tune on the 3.3V part isn’t going to be above 3.3V and it may be 0-2.5V. The 3.3V part is going to be at least 8X more sensitive to grounding issues. I've got a BUNCH of VCOs that are 3.3V or 5V, and have 15V tuning ranges. It's a real pain when you're looking to swap VCOs in a PLL to change the tuning range in a breadboard. Minicircuits ROS-3710 is a fine example.. 5V operation, tuning range 0.5-13V ROS-3388-219 is the same. It's because the tune port goes right to the varactor, which is, not so oddly, DC blocked from the amplifier circuit running on 5V To put this in perspective, you can see a change on a normal 12V part grounding it on the top side of a PC board vs grounding it on the bottom side of the board. The 0.032” of solid ground lead has enough drop to be noticeable. ___ 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] Anyone Know What The Models Were In This NIST Paper?
On 10/30/13 3:46 PM, Magnus Danielson wrote: Hi, They have learned the hard way that they can't do that easily. They can, if they add the necessary mentioning of vendor X and their product Y does in no way means an endorsement. I've seen presentations starting with a non-endorsement statement so that they can then say Oh, this is the boxes we have chosen to use, which tends to just render spread of information and sharing of experience amongst the users. I expect them (NIST and other publicly funded institutions) to act like this. It is a bit annoying when you just want to know what they where using, but it's understandable. It is even more understandable as they start to list miss-features of device A, B and C, but not device D. It works both ways, when you have a device that you're particularly proud of, and it performs well in the tests, you want them to say Jim Lux's fabulous device performed orders of magnitude better than all other devices tested, particularly the unusually poor performance from the device from Magnus Danielson grin. But there are also other forces at work. There are cases where IEEE and authors were sued because of a paper that essentially said that a particular product not only didn't work, but that underlying physics guaranteed that it couldn't work. (early streamer emission devices, and a paper by Mousa, in particular) It would be an amusing story, if all the litigation hadn't happened. For instance, Mousa reports on one installation where the lightning eliminator was completely destroyed by a lightning stroke. The traffic controllers at Tampa saw a flash of light during a storm, heard thunder and observed a shower of sparks drop past the tower window. A later visit to the rooftop revealed that a part of the charge dissipater array of Manufacturer “A” had disappeared. that would tend to drive authors to such circumlocutions as Brand X, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Anyone Know What The Models Were In This NIST Paper?
On 10/29/13 6:31 PM, Bob Camp wrote: Hi That’s always one of those “we can only tell you if you work for the US government” sort of things. If anybody knows it’s one of those “you better not tell” things. or more likely.. If you put actual mfr and model in, then you have to go through a lot more paperwork to justify why you're doing that, and to verify that you aren't endorsing a particular manufacturer. If you want to get the paper through the internal review process, it's just easier to use A,B,C,D than ratty old POS I bought off eBay, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Anyone Know What The Models Were In This NIST Paper?
On 10/29/13 7:06 PM, John C. Westmoreland, P.E. wrote: Bob, Yes - well, it is a little dated - so I would think the chance for a competitive edge would have expired. Maybe not for models C and D but I would certainly think so for Models A B. There must be some sort of technical statute of limitations, correct? ;) Anyone can file a complaint or sue for anything, anytime. Sure, the suit is dismissed, but it's still a hassle to deal with. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 4193A 4815A probe compatibility?
On 10/17/13 4:46 PM, Steve Byan wrote: On Oct 17, 2013, at 3:38 PM, Richard Karlquist rich...@karlquist.com wrote: If you are below 80 MHz, Linear Technologies makes a thermal power meter on a chip. Alas, the LT1088 is no longer made. http://www.linear.com/product/LT1088 Rochester Electronics.. The leaders in the trailing edge of electronics... You'll probably pay for it, but they have a lot of older parts (they even go so far as to run a 3 and 4 fab, I think) ___ 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] Coax cable for volute antenna
On 10/16/13 8:26 PM, quartz55 wrote: I've been searching for the small copper hardline I can use for the feed on the gps volute (egg beater) antenna. Can anyone steer me where to get a foot or so of the small 50 ohm line so I can make a few antennas? I've been searching mouser to no avail. what size (0.141, 0.085, 0.047 OD)? You probably won't find it at Mouser type places. RF Coax, Pasternak, etc. are better bets. Uniform Tubes might send you a sample. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How hard is it to detect a GPS Jammer?
On 10/8/13 4:17 AM, Bob Camp wrote: Hi But there's obviously something wrong with the 400 KM number. 1) If +10 dbm is good enough to burry a useful signal at that distance, it should be good enough to communicate at that distance. That's pretty impressive QRP without high gain / directional antennas involved. 2) The radios (at least the modern ones) do have CW signal immunity. Weather that's 60 db or something else probably varies with the make / model of the GPS. How well that works with a VCO jammer - again, a that depends sort of thing. 3) There's a (maybe) 40 db variation in GPS signals. To deny service you need to take out the strong ones, not just the weak ones. 4) Even without specific anti-jam in the GPS, the code it's self does have some immunity to a jammer. Of course you don't have to look very far into the archives to find wonderful examples of slipped decimal points in my posts…. You're right, I forgot the process gain of the despreading. Assuming you're going from 1 Mchip/sec for the C/A code to 50 bps for the nav message, that's 43 dB That alone gets you to 2km jamming range from 400km, but that also assumes that the jamming signal doesn't inhibit acquiring the code and despreading. As Dixon's book on Spread Spectrum says, acquisition is the hard part; because you don't have the process gain yet. I suppose with a parallel acquisition strategy, you're basically trying all codes, and that might be able to work. But even so, those sorts of process gain arguments don't necessarily work if the receiver has a hard limiter or quantizer in it. I don't know that modern consumer GPSes have CW immunity. If they're using a 1 or 2 bit quantizer, a strong CW signal pretty much captures the front end. Easy to try. Let me just fire up my kilowatt 1.5 GHz transmitter heregrin ___ 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.
