Re: [time-nuts] Adafruit (MT3339) problems today
[] WAAS only works in North America. I don't know details elsewhere, but the PMTK313 message says it turns searching for SBAS satellites on and off. --Jim Harman == Thanks for the information on the messages, Jim. For your information, in Europe we have EGNOS, which works in the same was as WAASfrom a different set of geostationary satellites. http://www.esa.int/Our_Activities/Navigation/The_present_-_EGNOS/What_is_EGNOS I have not WAAS/EGNOS tested on the MT3339 chipset, but it does work on my Garmin GPS 60 CSx. I don't know whether the iPad uses WAAS/EGNOS, or my Moto-G phone, but the latter can see GLONASS as well as GPS, which I didn't know until I checked it after the recent GLONASS outage. Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] First success with very simple, very low cost GPSDO
csteinm...@yandex.com said: (Note that a 256 cycles per second error is 51 PPM at 5 MHz.) You need a bit for the sign. That leaves only 25.6 PPM error from nominal, 51.2 peak-peak. Half that at 10 MHz. In the real world, you should be able to trust that any oscillator that is chosen for a GPSDO will free-run within 1 PPM when it is warmed up, and that your PPS will always be within 1 PPM, as well. Why? The original goal was low cost. I could easily believe that an inexpensive oscillator would be off by more than 1 PPM. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Crystal Aging
Hi Brooke, HP had some way around SA that improved the timekeeping. HP called it the Smartclock Algorithm and you can find some very basic information about it here: http://www.hpl.hp.com/hpjournal/96dec/dec96a9.pdf I have been trying months to find a reference on how it REALLY works but it seems that this is one of the better kept secrets of HP. Best regards Ulrich -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Brooke Clarke Gesendet: Donnerstag, 10. April 2014 22:56 An: Tom Van Baak; Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] GPSDO Crystal Aging Hi Tom: That makes sense because the GPS was just coming on line and not anywhere near a full compliment of satellites and SA was on. HP had some way around SA that improved the timekeeping. Has that ever been disclosed? Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Tom Van Baak wrote: Hi Brooke, True, except that in most cases the long-term frequency drift rate is so tiny compared to all the short- and mid-term instability that it is not worth worrying about. In other words, I agree it is modeled as a linear ramp, but the ramp, even at huge timescales, is so close to flat, what's the point? Look at the output of a typical OCXO. Short-term the frequency varies by tens or hundreds of ps/s; that's parts in 10^11 or 10^10. By contrast, you have wait an entire day or week before you get that level of frequency error due to drift. When you're in a rowboat outside SF bay, it's the 3 m waves every 5 to 10 seconds that you need to steer against, not the 3 m tides that occur gradually over 12 hours. Can someone show me a counter-example? Why is it better to include aging rate into the PID. What quantitative improvement in performance does this actually represent? I don't disbelieve it, I just have never seen the numbers. One case where knowing the aging rate is important is during multi-hour or multi-day holdover. Perhaps that's why HP included the 128-hour circular record of frequency/aging into their firmware. /tvb Hi: AFAICR the HP GPSDOs included the idea of measuring the aging rate of the crystal and applying that correction during holdover. This was also mentioned by Brooks Shera in relation to his GSPDO (there was a plot), but I don't think it was part of the firmware? So rather than just locking the control voltage to the last used value it would be much better to add a linear ramp. http://www.rt66.com/%7Eshera/ ___ 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] ARM boards for low-cost GPSDOs
Hi All, I've used the STM32F4 for a few projects, and was considering it for a time tagger for a DMTD system. I have a question about the clocking though that someone may be able to help me with. The 32F4 (like lots of similar ARMs) uses a PLL to generate the internal clocks from much lower frequency clock or crystal. Has anyone quantified the stability of the synthesised clock? Thanks, david On 11/04/2014 8:02 AM, Alberto di Bene wrote: On 4/10/2014 11:38 PM, Hal Murray wrote: Does anybody have a favorite low-cost ARM board? I'm looking for a simple Arduino like setup rather than something that runs Linux. The idea is to get 32 bit counters so a bunch of the recent discussion can be ingnored. == I can't recommend warmly enough the Discovery board from STM. It sports a Cortex ARM M4F that can run at 180 MHz, has a native IEEE compliant floating point core, 2MB flash and 256 kB RAM, and a wealth of interesting peripherals on chip, TFT display touch enabled included. And at 23.52 USD is cheaper than a much less powerful Arduino... I implemented on it a fully featured SDR, without using any opsys, talking directly to the bare metal using the Keil IDE/compiler. A joy to use. Look here : http://www.st.com/web/catalog/tools/FM116/SC959/SS1532/LN1848/PF259090 73 Alberto I2PHD --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ 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] Cesium 133 on kickstarter
I wonder if a CSAC used as a wristwatch would need constant C-field adjustment? On Thu, Apr 10, 2014 at 12:41 PM, Attila Kinali att...@kinali.ch wrote: On Thu, 10 Apr 2014 10:43:13 -0400 Ronald Held ronaldh...@gmail.com wrote: I am curious what people think of this watch at least from the time-nut POV. Considering that they are not the first, but at least the third with that idea (see archives for other CSAC wrist watches). But seriously, a modern, temperature compensated quartz watch goes better than +/-10s in half a year (about 1ppm), which is already about as good as you need for a wrist watch. Any better is just unnecessary overengineering. Of course, it's a different matter if you like to show of to your peers. Other than that, i probably would buy a CSAC and put it into some equipment instead. :-) Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Crystal Aging
Brooke, Ulrich, Keep in mind the hp SmartClock product line dated from the early-90's and it was one of the first GPSDO on the market. So even simple things like using timing receivers, partial ionospheric correction, sawtooth correction, sub-ns TIC, 1PPS filtering, high-quality OCXO, PIID, DAC dithering, aging history and compensation would qualify as smart. That's not to say there weren't other tricks going on. One can learn a lot by playing with SCPI and pForth commands, as has been discussed here over the years. But the point is what was called smart 20 years ago may no longer be that magic. Page 6+ of the Kusters paper is interesting but nothing we don't already talk about weekly here. Still, this is guessing. How about we find out for sure? Two ideas: As a block box, a 58503A/Z3801A has only two inputs and two outputs. One input is the 1PPS from the Oncore VP (along with Motorola binary messages). The other input is the 10811. One output is 10 MHz, the other output is 1PPS, which is usually just locked to the phase of the LO. Or you could argue that there is really only one input (GPS 1PPS) and one output (DAC setting). I propose someone on the list take a working 58503A and replace the Oncore VP with a pseudo GPS timing receiver and maybe also replace the 10811 with a DDS. In a very controlled manner, we can then mimic SA and post-SA jitter from the synthetic 1PPS. We can also mimic various oscillator phase and frequency behavior, including offsets, drift, and jumps using the DDS. The digital input to the DAC/EFC can be monitored to continuously track steering attempts. Or one could do man-in-the-middle games on the data to the DAC and avoid the need for the DDS. By precisely watching how the SmartClock reacts to precise stimulus over seconds to days we can infer how the algorithms work with high confidence. Any number of people on the list can suggest clever stimulus scenarios to try. Unlike the GPSDO simulator (gpsim1), which can simulate a day in a seconds, the SmartClock experiment would have to run in real-time. That is, to infer how it handles aging prediction and holdover you'd actually have to let it run for a week. The other idea, which I keep hoping Magnus will do, is to run the firmware under 68k emulation. It would be a large project, but I know he's already spent time on firmware disassembly. /tvb - Original Message - From: Ulrich Bangert df...@ulrich-bangert.de To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Friday, April 11, 2014 3:06 AM Subject: Re: [time-nuts] GPSDO Crystal Aging Hi Brooke, HP had some way around SA that improved the timekeeping. HP called it the Smartclock Algorithm and you can find some very basic information about it here: http://www.hpl.hp.com/hpjournal/96dec/dec96a9.pdf I have been trying months to find a reference on how it REALLY works but it seems that this is one of the better kept secrets of HP. Best regards Ulrich -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Brooke Clarke Gesendet: Donnerstag, 10. April 2014 22:56 An: Tom Van Baak; Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] GPSDO Crystal Aging Hi Tom: That makes sense because the GPS was just coming on line and not anywhere near a full compliment of satellites and SA was on. HP had some way around SA that improved the timekeeping. Has that ever been disclosed? Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Tom Van Baak wrote: Hi Brooke, True, except that in most cases the long-term frequency drift rate is so tiny compared to all the short- and mid-term instability that it is not worth worrying about. In other words, I agree it is modeled as a linear ramp, but the ramp, even at huge timescales, is so close to flat, what's the point? Look at the output of a typical OCXO. Short-term the frequency varies by tens or hundreds of ps/s; that's parts in 10^11 or 10^10. By contrast, you have wait an entire day or week before you get that level of frequency error due to drift. When you're in a rowboat outside SF bay, it's the 3 m waves every 5 to 10 seconds that you need to steer against, not the 3 m tides that occur gradually over 12 hours. Can someone show me a counter-example? Why is it better to include aging rate into the PID. What quantitative improvement in performance does this actually represent? I don't disbelieve it, I just have never seen the numbers. One case where knowing the aging rate is important is during multi-hour or multi-day holdover. Perhaps that's why HP included the 128-hour circular record of frequency/aging into their firmware. /tvb Hi: AFAICR the HP GPSDOs included the idea of measuring the aging rate
Re: [time-nuts] ARM boards for low-cost GPSDOs
David we may be drifting from Hals thread. So don't want to do that. I looked at the system and its governed by the xtal they use. Granted its cheap and totally in an uncontrolled environment. Mine typically is +.79 ppm at 1 Mhz. Semi consistent. Its really easy to bypass that xtal and to inject some higher quality source and reap those benefits. They have little pads and such to allow it. Regards Paul WB8TSL On Fri, Apr 11, 2014 at 7:49 AM, davidh dho...@gmail.com wrote: Hi All, I've used the STM32F4 for a few projects, and was considering it for a time tagger for a DMTD system. I have a question about the clocking though that someone may be able to help me with. The 32F4 (like lots of similar ARMs) uses a PLL to generate the internal clocks from much lower frequency clock or crystal. Has anyone quantified the stability of the synthesised clock? Thanks, david On 11/04/2014 8:02 AM, Alberto di Bene wrote: On 4/10/2014 11:38 PM, Hal Murray wrote: Does anybody have a favorite low-cost ARM board? I'm looking for a simple Arduino like setup rather than something that runs Linux. The idea is to get 32 bit counters so a bunch of the recent discussion can be ingnored. == I can't recommend warmly enough the Discovery board from STM. It sports a Cortex ARM M4F that can run at 180 MHz, has a native IEEE compliant floating point core, 2MB flash and 256 kB RAM, and a wealth of interesting peripherals on chip, TFT display touch enabled included. And at 23.52 USD is cheaper than a much less powerful Arduino... I implemented on it a fully featured SDR, without using any opsys, talking directly to the bare metal using the Keil IDE/compiler. A joy to use. Look here : http://www.st.com/web/catalog/tools/FM116/SC959/SS1532/LN1848/PF259090 73 Alberto I2PHD --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ 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] NIST Radio Station WWV now on 25 MHz
Yea! I remember when they shut it down at the nadir of the sunspot cycle, saying no one was using it. Duh! David N1HAC On 4/11/14 12:07 AM, Max Robinson wrote: WWV used to be on 25 MHz but when the sunspot cycle hit a minimum they shut it down. That was years ago. I'm glad to know they are bringing it back. Regards. Max. K 4 O DS. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Woodworking site http://www.angelfire.com/electronic/funwithtubes/Woodworking/wwindex.html Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com To subscribe to the fun with wood group send a blank email to funwithwood-subscr...@yahoogroups.com - Original Message - From: Gordon Batey gpba...@wildblue.net To: Gordon Batey gpba...@wildblue.net Sent: Thursday, April 10, 2014 3:01 PM Subject: [time-nuts] NIST Radio Station WWV now on 25 MHz For what it is worth a friend sent me this link. WWV is now testing on 25 MHZ. http://www.nist.gov/pml/div688/grp40/wwv.cfm? 73 Gordon WA4FJC ___ 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] GPSDO Crystal Aging
I worked for the HP Santa Clara Division during the Smart Clock days and knew all the players. In terms of holdover, the report cited mentions temperature compensation and learning aging. The temperature compensation was simply a crutch for the 10811 to fix its tempco problems. The E1938A had much better tempco and eliminated the need for this crutch. As for the concept of learning aging is concerned, there was definitely no secret sauce I ever heard about in all the Smart Clock powerpoints I sat through. They simply measured linear aging and possibly its derivative and hoped that past performance would predict future results. It did to some extent, but how well it worked depended on the particular crystal. A misbehaving crystal could not be fixed by any cleverness in the algorithm. Attempts were made to screen crystals to get predictable ones, and this was someone successful by getting rid of bad actors. Still, there was no way to guarantee that a crystal in the future would never have a jump or sudden change in aging. What was really needed was an ensemble of oscillators, but that was not economically competitive with rubidium. Rick On 4/11/2014 3:06 AM, Ulrich Bangert wrote: Hi Brooke, HP had some way around SA that improved the timekeeping. HP called it the Smartclock Algorithm and you can find some very basic information about it here: http://www.hpl.hp.com/hpjournal/96dec/dec96a9.pdf I have been trying months to find a reference on how it REALLY works but it seems that this is one of the better kept secrets of HP. Best regards Ulrich -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Brooke Clarke Gesendet: Donnerstag, 10. April 2014 22:56 An: Tom Van Baak; Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] GPSDO Crystal Aging Hi Tom: That makes sense because the GPS was just coming on line and not anywhere near a full compliment of satellites and SA was on. HP had some way around SA that improved the timekeeping. Has that ever been disclosed? Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Tom Van Baak wrote: Hi Brooke, True, except that in most cases the long-term frequency drift rate is so tiny compared to all the short- and mid-term instability that it is not worth worrying about. In other words, I agree it is modeled as a linear ramp, but the ramp, even at huge timescales, is so close to flat, what's the point? Look at the output of a typical OCXO. Short-term the frequency varies by tens or hundreds of ps/s; that's parts in 10^11 or 10^10. By contrast, you have wait an entire day or week before you get that level of frequency error due to drift. When you're in a rowboat outside SF bay, it's the 3 m waves every 5 to 10 seconds that you need to steer against, not the 3 m tides that occur gradually over 12 hours. Can someone show me a counter-example? Why is it better to include aging rate into the PID. What quantitative improvement in performance does this actually represent? I don't disbelieve it, I just have never seen the numbers. One case where knowing the aging rate is important is during multi-hour or multi-day holdover. Perhaps that's why HP included the 128-hour circular record of frequency/aging into their firmware. /tvb Hi: AFAICR the HP GPSDOs included the idea of measuring the aging rate of the crystal and applying that correction during holdover. This was also mentioned by Brooks Shera in relation to his GSPDO (there was a plot), but I don't think it was part of the firmware? So rather than just locking the control voltage to the last used value it would be much better to add a linear ramp. http://www.rt66.com/%7Eshera/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] First success with very simple GPSDO
I wrote: (Note that a 256 cycles per second error is 51 PPM at 5 MHz.) In the real world, you should be able to trust that any oscillator that is chosen for a GPSDO will free-run within 1 PPM when it is warmed up, and that your PPS will always be within 1 PPM, as well. Hal wrote: Why? The original goal was low cost. I could easily believe that an inexpensive oscillator would be off by more than 1 PPM. Decent OCXOs are falling off the ebay tree for $20 every day (less, if you look and wait -- I've bought several for $5). I have bought dozens of them, and have yet to receive one that isn't within 2e-7. So I'm inclined to think any oscillator that is worth using for a GPSDO has a very good chance of being within 1ppm without any adjustment or selection. Further, there are good ways to get an oscillator within 1e-6 without a counter -- for example, beating with WWV. Indeed, if cost is the limiting factor, I submit that most people would be better served by spending their entire budget on the best OCXO they can buy and a box to put it in to reduce temperature fluctuations, then manually calibrating it periodically, than by buying a cheap oscillator and spending money on a GPS, uC, etc. in an attempt to make a silk purse out of it. GPS can only help at long tau (or said differently, it can only help at short tau if the oscillator is too unstable to be worth using in the first place). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Adafruit (MT3339) problems today
On Thu, Apr 10, 2014 at 2:48 PM, Bob Stewart b...@evoria.net wrote: The only particular anomaly I can see is that it uses satellites close to the horizon for position fixing.I'm getting a reported SNR of 39 at 5 degrees elevation and 37 at 3 degrees, though I notice the sat at 3 degrees is not being used to calculate position. I never got around to finishing the choke ring antenna with those pie pans. Maybe that needs to move higher on my priority list. Does the GPS' command set allow you to set a horizon mask? Some of them have a setting where you can specify a minimum elevation angle. 10 degrees is reasonable. So nothing within 10 deg. of the horizon is used. I don't think WAAS is going to help with 150ft jumps. It is more for fine tuning What you really need to do is spend $20 on a timing mode GPS, even an older Motorola Oncode has a self survey and fixed location mode. Pick a really good spot for the antenna -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Crystal Aging
rich...@karlquist.com said: Still, there was no way to guarantee that a crystal in the future would never have a jump or sudden change in aging. What was really needed was an ensemble of oscillators, but that was not economically competitive with rubidium. How many would you need? Is 3 enough? How well could you do with several low(er) cost oscillators relative to one good but expensive one? It might be an interesting experiment in a nutty sort of way. -- These are my opinions. I hate spam. ___ 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] ARM boards for low-cost GPSDOs
dho...@gmail.com said: The 32F4 (like lots of similar ARMs) uses a PLL to generate the internal clocks from much lower frequency clock or crystal. Has anyone quantified the stability of the synthesised clock? I'm not familiar with the 32F4, but most of the SOC type ARM chips have ways to generate clocks by dividing the main clock and a way to feed those clocks out a pin. So collecting data would be a small amount of code to set things up and then your normal clock analysis setup. There would be additional noise depending upon the package (and board layout) and how much is going on in the chip, mostly how often other output pins are changing, especially the nearby ones. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Crystal Aging
On 4/11/2014 11:04 AM, Hal Murray wrote: How many would you need? Is 3 enough? How well could you do with several low(er) cost oscillators relative to one good but expensive one? It might be an interesting experiment in a nutty sort of way. My guess would be 3 would be a minimum, so you could have a majority vote. Len Cutler's group actually built an experimental ensemble of 9 or 10, but it didn't seem to come to fruition. For this to make any sense, you would need to be able to cherry pick 9 or 10 really good oscillators. However, there was no way to get the production line to sign on to this. David Allan had this interesting concept to the effect that if you had a sufficient number of wristwatches (maybe 1000) and you averaged them together you could somehow get a quality clock, or at least 31.6 times better. Kind of like the notion of 1000 monkeys with 1000 typewriters... Rick ___ 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] First success with very simple, very low cost GPSDO
On 10 Apr, 2014, at 22:06 , Chris Albertson albertson.ch...@gmail.com wrote: You originally described a system that counts to 5M every second. Tom and others pointed out that you do not need the complete 5M count, all you need is the remainder of a modulo count. The question then is, how much of a remainder do you need to be sure that it spans all anticipated errors in both the PPS and the oscillator? Yes this right. I'm sure that under limited conditions I can get by looking only at the remainder. It is harder than was said because the overflows per second rate is a non-interger but there are till only two flavors of seconds: Those with N overflows and those with N+1 overflows. I think you are seeing a complexity that isn't there. 5,000,000 is 19531 * 256 + 64, so if you get an 8-bit counter sample t0 in one second and t1 in the next then the difference t1 - t0 will be equal to 64 if the oscillator is on frequency, and t1 - t0 - 64 will be equal to 0, when computed with 8 bit arithmetic. If the result of the latter, interpreted as a signed value, is less than zero your oscillator is going too slow, if greater it is going too fast. This will be true whether there have been 19531 or 19532 counter overflows in the second; the (t1-t0) subtraction will set the borrow bit in the latter case if you want to know that but there is no reason to care about it. 8 bits is enough to measure a +/- 25 ppm error in this case, which seems sufficient for any oscillator you are likely to want to discipline with this. All keeping the full count seems to do is require you to subtract two much larger numbers to find the same small difference. Dennis Ferguson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Crystal Aging
Interesting idea. It might be an interesting experiment to couple a large number of inexpensive xtals to see how it impacts effects such as sudden changes in a single xtal. With sufficient monitoring of each one, you could even tune the coupling to amplify/attenuate the results of the 'good' and 'bad' ones over some interval. Of course, what effect this has on things like phase noise, drift, and so on is a whole different matter. Bob On Apr 11, 2014, at 14:14, Richard (Rick) Karlquist rich...@karlquist.com wrote: On 4/11/2014 11:04 AM, Hal Murray wrote: How many would you need? Is 3 enough? How well could you do with several low(er) cost oscillators relative to one good but expensive one? It might be an interesting experiment in a nutty sort of way. My guess would be 3 would be a minimum, so you could have a majority vote. Len Cutler's group actually built an experimental ensemble of 9 or 10, but it didn't seem to come to fruition. For this to make any sense, you would need to be able to cherry pick 9 or 10 really good oscillators. However, there was no way to get the production line to sign on to this. David Allan had this interesting concept to the effect that if you had a sufficient number of wristwatches (maybe 1000) and you averaged them together you could somehow get a quality clock, or at least 31.6 times better. Kind of like the notion of 1000 monkeys with 1000 typewriters... Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Crystal Aging
Ulrich Thanks for posting the reference. Very interesting and useful. The clues they give sounds like enough information to do the Smartclock loop control things that they talk about. ws *** Hi Brooke, HP had some way around SA that improved the timekeeping. HP called it the Smartclock Algorithm and you can find some very basic information about it here: http://www.hpl.hp.com/hpjournal/96dec/dec96a9.pdf I have been trying months to find a reference on how it REALLY works but it seems that this is one of the better kept secrets of HP. Best regards Ulrich ___ 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] First success with very simple, very low cost GPSDO
flavors of seconds: Those with N overflows and those with N+1 overflows. Just to beat this to death from a different angle... In a simple case of N = 0 and an 8-bit counter you can see that 200 - 190 (= 10) has no (N) overflows and 004 - 250 (= 10) has one (N+1) overflow. Yet they both represent 10 short ticks of a free-running 8-bit counter. The flavor doesn't matter, only the difference, mod-256. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Crystal Aging
Look at what NTP does to select good clocks when it has many to choose from. It does not simply average them. It looks at the noise in each one and then sees which clocks have overlapping error bars. It assumes that all good clocks have the same time within limits of their precision. Then from the good clocks there is a second level weeding out process then finally it does a weighted average of the remainders where I think those with less jitter get more weight. It would not be impossible to do this with 10MHz oscillators. Certainly a simple average is not a good idea as a broken unit can pull the entire average way down. I think you'd have to check reasonableness first and eliminate outliers I think today you might simply digitize the signals and figure out which were best using software. In short the output is ensemble time (not average time) but there is a careful selection of who is allowed to be member of the ensemble. I used a joke last week to explain to a class why we don't use averages, with no other qualifications. The joke is Bill Gates walks into a bar What's the average net worth of everyone in the bar? Maybe $250 million. My point was that it is hard to describe a population that is not Gaussian distributed. Stuck and jumping crystals are not Gaussian. You'd have to detect the misbehaving devices. David Allan had this interesting concept to the effect that if you had a sufficient number of wristwatches (maybe 1000) and you averaged them together you could somehow get a quality clock, or at least 31.6 times better. Kind of like the notion of 1000 monkeys with 1000 typewriters... -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Adafruit (MT3339) problems today
On 10/04/14 23:48, Bob Stewart wrote: My Adafruit has gone walkabout again. This is a different unit than the one I spoke about some months ago. It's been about 150 ft from my actual location, which has, of course, made a mess of my GPSDO. Well, at least it verified my unlock code. I did a POR and it seemed to come home, but now it's off to the races again. Has anyone else seen this behavior with this device? The only particular anomaly I can see is that it uses satellites close to the horizon for position fixing.I'm getting a reported SNR of 39 at 5 degrees elevation and 37 at 3 degrees, though I notice the sat at 3 degrees is not being used to calculate position. I never got around to finishing the choke ring antenna with those pie pans. Maybe that needs to move higher on my priority list. Can you raise the elevation limit? Low elevation causes many problems, multi-path is certainly one but massive tropospherical delay errors. Maybe we should look at a bare minimum requirement for GPSDO-use? Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] NIST Radio Station WWV now on 25 MHz
Fired up the R1051 on 25 Mhz and its great to hear wwv back on the air in Boston. Pretty good signal. Regards Paul WB8TSL On Fri, Apr 11, 2014 at 10:12 AM, David McGaw n1...@dartmouth.edu wrote: Yea! I remember when they shut it down at the nadir of the sunspot cycle, saying no one was using it. Duh! David N1HAC On 4/11/14 12:07 AM, Max Robinson wrote: WWV used to be on 25 MHz but when the sunspot cycle hit a minimum they shut it down. That was years ago. I'm glad to know they are bringing it back. Regards. Max. K 4 O DS. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Woodworking site http://www.angelfire.com/electronic/funwithtubes/ Woodworking/wwindex.html Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com To subscribe to the fun with wood group send a blank email to funwithwood-subscr...@yahoogroups.com - Original Message - From: Gordon Batey gpba...@wildblue.net To: Gordon Batey gpba...@wildblue.net Sent: Thursday, April 10, 2014 3:01 PM Subject: [time-nuts] NIST Radio Station WWV now on 25 MHz For what it is worth a friend sent me this link. WWV is now testing on 25 MHZ. http://www.nist.gov/pml/div688/grp40/wwv.cfm? 73 Gordon WA4FJC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] First success with very simple GPSDO
I think the solution is easy. 1) count all the cycles using an overflow interrupt until you see the result is stable to about 1ppm. We all know that even a simple $8 controller can do this. 2) then switch to a mode where we look only at the last few bits of the counter. I think this will actually perform better than mode #1 above because there is zero chance of the two interrupts happening at the same time causing your PPS sample to be delayed because you had interrupts disabled while counting an overflow. The next step is to implement a quite time. This is common in some real time systems. If you KNOW a little in advance you are about to sample some sensitive signal then you turn off anything that is electrically noisy like motors or even updates to a serial device. In a GPSDO you can predict when the next interrupt will happen and insure there is not serial data or whatever happening near the tick time. A dual mode system means no one needs a counter or WWV or any other external reference. and you also, after syncing get very deterministic behavior. On Fri, Apr 11, 2014 at 8:23 AM, Charles Steinmetz csteinm...@yandex.comwrote: I wrote: (Note that a 256 cycles per second error is 51 PPM at 5 MHz.) In the real world, you should be able to trust that any oscillator that is chosen for a GPSDO will free-run within 1 PPM when it is warmed up, and that your PPS will always be within 1 PPM, as well. Hal wrote: Why? The original goal was low cost. I could easily believe that an inexpensive oscillator would be off by more than 1 PPM. Decent OCXOs are falling off the ebay tree for $20 every day (less, if you look and wait -- I've bought several for $5). I have bought dozens of them, and have yet to receive one that isn't within 2e-7. So I'm inclined to think any oscillator that is worth using for a GPSDO has a very good chance of being within 1ppm without any adjustment or selection. Further, there are good ways to get an oscillator within 1e-6 without a counter -- for example, beating with WWV. Indeed, if cost is the limiting factor, I submit that most people would be better served by spending their entire budget on the best OCXO they can buy and a box to put it in to reduce temperature fluctuations, then manually calibrating it periodically, than by buying a cheap oscillator and spending money on a GPS, uC, etc. in an attempt to make a silk purse out of it. GPS can only help at long tau (or said differently, it can only help at short tau if the oscillator is too unstable to be worth using in the first place). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Frequency of LC Tank.
Hi all, I'm thinking about an upcoming project, if this is off topic please disregard or contact me off list. :) I have a large LC tank, with a very lossy inductor. Being driven by a pulse width push pull driver, that is digitally controlled. The driver circuit will couple through a N:1 transformer. I need to be able to adjust the push/pull driver frequency to match the frequency of the tank circuit. (See frequency/time is involved :) ) The tank components can vary and are not adjustable, so the drive frequency needs to vary. I'm thinking some sort of a phase detector may be the way to go. I'm just not sure were to sample the V and I signals to look for phase differences, or where to get a good clean reference from. So the question is, when actively driving a tank circuit, how do you know you are driving it with the same frequency ad the same phase it naturally oscillates at. Any thoughts, suggestions, or readily available papers you guy could point me to? Thanks! Dan ___ 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] Frequency of LC Tank.
At resonance, an LC looks pure resistive. For a parallel LC, sample the voltage across the LC and the drive current, and tweek the frequency until they are in-phase. For a series LC, sample the voltage across the L or C and tweek as above. If you want to do it analog, dither the frequency a bit. With the quardature of the sweep signal as reference for a lock-in. The output of thye L-I is the tuning signal. (Roughly Pound Locking) YMMV, -John === Hi all, I'm thinking about an upcoming project, if this is off topic please disregard or contact me off list. :) I have a large LC tank, with a very lossy inductor. Being driven by a pulse width push pull driver, that is digitally controlled. The driver circuit will couple through a N:1 transformer. I need to be able to adjust the push/pull driver frequency to match the frequency of the tank circuit. (See frequency/time is involved :) ) The tank components can vary and are not adjustable, so the drive frequency needs to vary. I'm thinking some sort of a phase detector may be the way to go. I'm just not sure were to sample the V and I signals to look for phase differences, or where to get a good clean reference from. So the question is, when actively driving a tank circuit, how do you know you are driving it with the same frequency ad the same phase it naturally oscillates at. Any thoughts, suggestions, or readily available papers you guy could point me to? Thanks! Dan ___ 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] Adafruit (MT3339) problems today
Hi Magnus, Yeah, there's no getting over the fact that it's a cheap $30 (or whatever it was) nav receiver. But I think the walkabout issue has been resolved. I think this thing is going to be OK for me, but I certainly wouldn't even give it a glance for professional use. Now that I've got the basic PLL code working with the new TIC, I'm starting to expand what I'm monitoring. There seems to be such a close connection between when it wanders around and when there are blips on the phase that I'm going to add position change monitoring shortly. Who knows? Maybe I can tune it out with the poor man's sawtooth that I've asked about. Yeah, I know. Just wrinkle your nose or look away in disgust if it bothers you. =) My goal is to see what I can get out of this; not what I can get for a few hundred dollars more. The project is more important to me than the result. I don't really have a concrete use for an accurate timebase. But, I have to say that after I've learned what I can with this, I'll probably look for something better; like maybe an LEA-4T or whatever I can get for cheap. I don't like the UT+ I have. Comms is overly finicky to get started. In fact, I don't even have a reliable way to do it after a cold start. And I don't like the +/- 52ns sawtooth. Bob From: Magnus Danielson mag...@rubidium.dyndns.org To: time-nuts@febo.com Sent: Friday, April 11, 2014 2:49 PM Subject: Re: [time-nuts] Adafruit (MT3339) problems today On 10/04/14 23:48, Bob Stewart wrote: My Adafruit has gone walkabout again. This is a different unit than the one I spoke about some months ago. It's been about 150 ft from my actual location, which has, of course, made a mess of my GPSDO. Well, at least it verified my unlock code. I did a POR and it seemed to come home, but now it's off to the races again. Has anyone else seen this behavior with this device? The only particular anomaly I can see is that it uses satellites close to the horizon for position fixing.I'm getting a reported SNR of 39 at 5 degrees elevation and 37 at 3 degrees, though I notice the sat at 3 degrees is not being used to calculate position. I never got around to finishing the choke ring antenna with those pie pans. Maybe that needs to move higher on my priority list. Can you raise the elevation limit? Low elevation causes many problems, multi-path is certainly one but massive tropospherical delay errors. Maybe we should look at a bare minimum requirement for GPSDO-use? 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] Frequency of LC Tank.
First order approximation of course would be to sweep the frequency and look for a dip (peak for series resonant) in the DC current drawn by the driver. On Fri, Apr 11, 2014 at 4:15 PM, Dan Kemppainen d...@irtelemetrics.comwrote: when actively driving a tank circuit, how do you know you are driving it with the same frequency ad the same phase it naturally oscillates at -- --Jim Harman ___ 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] First success with very simple GPSDO
albertson.ch...@gmail.com said: 2) then switch to a mode where we look only at the last few bits of the counter. I think this will actually perform better than mode #1 above because there is zero chance of the two interrupts happening at the same time causing your PPS sample to be delayed because you had interrupts disabled while counting an overflow. If you use the capture register, you don't have to worry about timing quirks due to interrupts. Unless the CPU is doing something complicated (like serving web pages), you can do the whole thing without any interrupts. Just use a polling loop that checks the ready-now? status for all the things the CPU has to do. -- These are my opinions. I hate spam. ___ 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] Frequency of LC Tank.
I have a large LC tank, with a very lossy inductor. ... So the question is, when actively driving a tank circuit, how do you know you are driving it with the same frequency ad the same phase it naturally oscillates at. If it's lossy, the peak will be broad so tuning the driving frequency won't be critical. How about just measuring the amplitude and tune for a max? I'm thinking of something like a diode and R/C filter feeding an ADC. -- These are my opinions. I hate spam. ___ 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] Frequency of LC Tank.
I would have done exactly what Hal said. I do this all the time when trying to figure out the LC tanks operating frequency. An example keeping this time nuts friendly, the d-psk-r circuits at 60 Khz. I am lucky in that I can add or subtract C on the stuff I work on. Regards Paul WB8TSL On Fri, Apr 11, 2014 at 6:05 PM, Hal Murray hmur...@megapathdsl.net wrote: I have a large LC tank, with a very lossy inductor. ... So the question is, when actively driving a tank circuit, how do you know you are driving it with the same frequency ad the same phase it naturally oscillates at. If it's lossy, the peak will be broad so tuning the driving frequency won't be critical. How about just measuring the amplitude and tune for a max? I'm thinking of something like a diode and R/C filter feeding an ADC. -- These are my opinions. I hate spam. ___ 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] Frequency of LC Tank.
That's why you want to look for the phase of the tank impedance. The phase goes through zero at resonance. It is far more precise. The steepness of the phase v. frequency plot is steep w/ a high Q circuit... flatter w/ a low Q tank. Either way, it does go through zero at resonance. The phase v. freq looks kinda like this: Phase: /\ -/ \ /---Freq \/ ^ resonance The dither sweep, amplituse measurement, lock-in will tune the oscillator to maximize the amplituse. Either on should pretty much steer you to resonance. -John == I have a large LC tank, with a very lossy inductor. ... So the question is, when actively driving a tank circuit, how do you know you are driving it with the same frequency ad the same phase it naturally oscillates at. If it's lossy, the peak will be broad so tuning the driving frequency won't be critical. How about just measuring the amplitude and tune for a max? I'm thinking of something like a diode and R/C filter feeding an ADC. -- These are my opinions. I hate spam. ___ 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] NIST Radio Station WWV now on 25 MHz
Tried three times today to get WWV on 25, heard nothing under the power line noise. I did have a nice QSO on 12 meters with a station in Rochester, NY so the band is open. WWV is currently weak on 20, strong on 15 and 10 MHz. On 04/11/2014 12:09 PM, paul swed wrote: Fired up the R1051 on 25 Mhz and its great to hear wwv back on the air in Boston. Pretty good signal. Regards Paul WB8TSL On Fri, Apr 11, 2014 at 10:12 AM, David McGaw n1...@dartmouth.edu wrote: Yea! I remember when they shut it down at the nadir of the sunspot cycle, saying no one was using it. Duh! David N1HAC On 4/11/14 12:07 AM, Max Robinson wrote: WWV used to be on 25 MHz but when the sunspot cycle hit a minimum they shut it down. That was years ago. I'm glad to know they are bringing it back. Regards. Max. K 4 O DS. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Woodworking site http://www.angelfire.com/electronic/funwithtubes/ Woodworking/wwindex.html Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com To subscribe to the fun with wood group send a blank email to funwithwood-subscr...@yahoogroups.com - Original Message - From: Gordon Batey gpba...@wildblue.net To: Gordon Batey gpba...@wildblue.net Sent: Thursday, April 10, 2014 3:01 PM Subject: [time-nuts] NIST Radio Station WWV now on 25 MHz For what it is worth a friend sent me this link. WWV is now testing on 25 MHZ. http://www.nist.gov/pml/div688/grp40/wwv.cfm? 73 Gordon WA4FJC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chuck Forsberg WA7KGX c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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] First success with very simple GPSDO
On Fri, Apr 11, 2014 at 2:51 PM, Hal Murray hmur...@megapathdsl.net wrote: Unless the CPU is doing something complicated (like serving web pages), you can do the whole thing without any interrupts. Just use a polling loop that checks the ready-now? status for all the things the CPU has to do. I'm still looking for an example code that uses a capture register on an Arduino. I see how to access it from software but not the part about an external signal causing a timer capture. I think I read this was on page 125 of the documentation but there is LOTs of documentation and data sheets and version of each. I just got a couple small LCD graphic panels from China. Free shipping got them here is just a few days. Cost $2.60 each. They should make for a nice status display. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Yet another Arduino-based GPSDO
On Thu, Apr 10, 2014 at 6:42 AM, Jim Harman j99har...@gmail.com wrote: I have not tried the dual PWM-based DAC, but my concern is that depending on the ratio of the resistors it might not be monotonic as the output goes from say 0FF to 100 hex. You would see this problem in the output every 256 counts. Unless there is significant dither in the DAC values, this could cause the system to get stuck as it tries to track a slow change in the oscillator. The nominal resistor ratio is 255:1. I think it would be best to choose the resistors (including tolerance) so that the big one is sure to be more than 255x the smaller one. This would cause a jump rather than a kink in the output as the DAC varies. Lars uses 39k and 10 megs, which does not quite meet this criterion. My plan was to eventually fix this in software. Using ultra precision resisters is not a good fix. I'm using normal 5% 1/4W resisters. I don't think I will get stuck. if a step is to small it will simply move up the next DAC value. The I term in the PID controller will basically see that the current DAC setting is not enough can add more. I is (error * time) and given enough time it will push the DAC in the right direction even if the error is very small. I don't have a good way to test the DAC. My Fluke DMM can't see any problems. But eventually I want to add a self test or self calibration function. I figure that the OCXO should be a very good voltage meter. On the integrator, I am using Lars' circuit with a TDK C0G ceramic capacitor FK28C0G1H102J, which is supposed to be good to 30ppm/deg C, and no-name carbon resistors. I will fiddle with it and see if I can figure out where the sensitivity is coming from. On Wed, Apr 9, 2014 at 10:20 PM, Chris Albertson albertson.ch...@gmail.comwrote: But the cheap 16-bit Lars used is working very well. PWM works because we only need less then 1Hz bandwidth so we can filter the heck out of it.The steps are less than I can measure What TIC capacitor did you use. If it is that temperer sensitive you might want to replace it. -- --Jim Harman ___ 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. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] NIST Radio Station WWV now on 25 MHz
Easily heard on a 12 ft wire in NH this afternoon. Chuck - You may be too close and it is skipping over. David N1HAC On 4/11/14 8:37 PM, paul swed wrote: Chuck The an/urr R1051 does not have a signal meter. It has level meters for audio. Those navy radios. I guess they figured the radio guys could not figure out signal strength. Come to think of it as I recall they could not figure out ships antennas either. That said I would give WWV a solid S5-S9 little QSB right now. Very comfortable. I am using a multi-band beam at 90' on top of a very tall hill. Regards Paul WB8TSL Near Boston On Fri, Apr 11, 2014 at 7:16 PM, Chuck Forsberg WA7KGX c...@omen.com wrote: Tried three times today to get WWV on 25, heard nothing under the power line noise. I did have a nice QSO on 12 meters with a station in Rochester, NY so the band is open. WWV is currently weak on 20, strong on 15 and 10 MHz. On 04/11/2014 12:09 PM, paul swed wrote: Fired up the R1051 on 25 Mhz and its great to hear wwv back on the air in Boston. Pretty good signal. Regards Paul WB8TSL On Fri, Apr 11, 2014 at 10:12 AM, David McGaw n1...@dartmouth.edu wrote: Yea! I remember when they shut it down at the nadir of the sunspot cycle, saying no one was using it. Duh! David N1HAC On 4/11/14 12:07 AM, Max Robinson wrote: WWV used to be on 25 MHz but when the sunspot cycle hit a minimum they shut it down. That was years ago. I'm glad to know they are bringing it back. Regards. Max. K 4 O DS. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Woodworking site http://www.angelfire.com/electronic/funwithtubes/ Woodworking/wwindex.html Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com To subscribe to the fun with wood group send a blank email to funwithwood-subscr...@yahoogroups.com - Original Message - From: Gordon Batey gpba...@wildblue.net To: Gordon Batey gpba...@wildblue.net Sent: Thursday, April 10, 2014 3:01 PM Subject: [time-nuts] NIST Radio Station WWV now on 25 MHz For what it is worth a friend sent me this link. WWV is now testing on 25 MHZ. http://www.nist.gov/pml/div688/grp40/wwv.cfm? 73 Gordon WA4FJC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. -- Chuck Forsberg WA7KGX c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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] Yet another Arduino-based GPSDO
albertson.ch...@gmail.com said: My plan was to eventually fix this in software. Using ultra precision resisters is not a good fix. I'm using normal 5% 1/4W resisters. I don't think I will get stuck. if a step is to small it will simply move up the next DAC value. The I term in the PID controller will basically see that the current DAC setting is not enough can add more. I is (error * time) and given enough time it will push the DAC in the right direction even if the error is very small. The way to get in trouble is to have the step size of the big DAC be bigger than 256 x the step size on the small DAC. That would leave a gap between, say, 3FF and 400 that you can't get to. [I see lots of opportunities to get the words wrong here.] If I was doing it, I'd try making the step size on the big DAC be 1/2 of the range of the small DAC. The idea is that you don't plan to change the big DAC. If you need to go up from 3FF, you will end up at, say, 440. That will leave you room to go back down without having to change the big DAC. Of course, that only works if the active/working range is a fraction of the total range of the small DAC. I don't have a good way to test the DAC. My Fluke DMM can't see any problems. But eventually I want to add a self test or self calibration function. I figure that the OCXO should be a very good voltage meter. Using the osc was the first thing that came to my mind. You might be able to see it on a scope if you took out the big caps and set up the software to toggle between two values and flap a pin to trigger on. -- These are my opinions. I hate spam. ___ 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] Yet another Arduino-based GPSDO
Yes I agree. My long term plan with the software is to write a C++ class called DAC where you send it a voltage. The class hides the way the DAC works. I was also thinking like you to treat this as two DACs where you use one for fine tuning and the other to make a course adjustment to place the desired voltage in the center of the fine adjustment DAC's range. And not treat this like a 16-bit DAC. This moves the discontinuity out to some place where it will never be used. But this is low on my list because by luck I not operating near the transition. But as I wrote before I first need a good way to test this and get the test data into a computer. On Fri, Apr 11, 2014 at 9:20 PM, Hal Murray hmur...@megapathdsl.net wrote: albertson.ch...@gmail.com said: My plan was to eventually fix this in software. Using ultra precision resisters is not a good fix. I'm using normal 5% 1/4W resisters. I don't think I will get stuck. if a step is to small it will simply move up the next DAC value. The I term in the PID controller will basically see that the current DAC setting is not enough can add more. I is (error * time) and given enough time it will push the DAC in the right direction even if the error is very small. The way to get in trouble is to have the step size of the big DAC be bigger than 256 x the step size on the small DAC. That would leave a gap between, say, 3FF and 400 that you can't get to. [I see lots of opportunities to get the words wrong here.] If I was doing it, I'd try making the step size on the big DAC be 1/2 of the range of the small DAC. The idea is that you don't plan to change the big DAC. If you need to go up from 3FF, you will end up at, say, 440. That will leave you room to go back down without having to change the big DAC. Of course, that only works if the active/working range is a fraction of the total range of the small DAC. I don't have a good way to test the DAC. My Fluke DMM can't see any problems. But eventually I want to add a self test or self calibration function. I figure that the OCXO should be a very good voltage meter. Using the osc was the first thing that came to my mind. You might be able to see it on a scope if you took out the big caps and set up the software to toggle between two values and flap a pin to trigger on. -- These are my opinions. I hate spam. ___ 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. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
