Re: [time-nuts] Very challenging phase noise measurement, does anyone have an idea??
Hi, We have an FSUP8 which means it Works up to 8GHz. It's an impressive piece of equipment, but the control interface has some bugs, it regularly crashes so hard you have to turn it off so that is a bit of a bummer. However, it measures quite good. The spectrum analyzer functionality starts at 20Hz, but since it has a pll phase noise measurement system, it's limited at the lower end. I think RS specify 10Mhz but it will start working at 5MHz with the limitation that you cannot measure at large offsets. Best regards, Hans Rosenberg -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani Sent: woensdag 5 december 2012 22:25 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Very challenging phase noise measurement, does anyone have an idea?? Isn't the FSUP a 110K euros equipment 20Hz-50GHz capable? 125KHz shouldn't be a problem. I had an FSUP for 25 seconds to play with... really impressive but too limited test time to appreciate fully. On Wed, Dec 5, 2012 at 1:14 PM, Bob Camp li...@rtty.us wrote: Hi Just about any of the high speed CMOS parts should work. A 74AC86 is about the earliest part I would trust. Any of the fast logic families that came after that should do equally well. Bob On Dec 5, 2012, at 7:03 AM, Hans Rosenberg hrosenb...@catena.nl wrote: Hello Time-nuts, I have to do a phase noise measurement and I'm wondering if anyone here has any ideas on that. We have to measure the phase noise of a 125kHz carrier (5Vp-p signal level). The measurement system should have a noise floor that is -164dBc/Hz at a distance of 1kHz to 8kHz away from the carrier. Our current plan is to use 2 of these sources, have one in free running mode and lock the other one to the first one using an XOR gate and then use the output of the XOR gate as an output signal. However, we are wondering if any of you know a better idea. Maybe there is an off-the-shelf piece of equipment that can do that that we could rent. Or maybe we could increase the frequency to a few megahertz using a pll, which means the signal comes into the measurement range of our FSUP phase-noise analyzer. Problem is, the phase detector would then need to have an insanely low noise-floor (in our idea the XOR also has to have this insanely low noise floor as well off course) so does anyone have experience with anything like this? Does anyone know an XOR with these good specs? I don't have a clue what a standard 74lvc1g86 would do. Needless to say the supply of this XOR would have to be ridiculously clean, but I do have a solution for that problem. Any help is greatly appreciated! Best regards, Hans Rosenberg ___ time-nuts mailing 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] GPSDO Alternatives
Now you can see the problem with designs that require both a PCB and a programmed uP. Most people can't do either of these and those who can typically are good at only one. Then you find someone and after he looses interest the project is dead and un-suportable. So I was thinking of how to build a GPSDO that does not need a programmed uP and would be so simple that a PCB would not be needed. It shoud be simple enough that after getting the parts could be built quickly by anyone. The Arduino has a USB interface and both ADC and DAC and digital IO. I read about the concern about using USB power. The Arduino can also be powered by a 9V battery so it will continue to run if the USB power goes away. Or you can use a power cube (aka wall wort) Anyone can program an Arduino even if you know nothing about uP. It is VERY easy and the software runs on Mac OS X, Linux and even Windows. I would use a separate power supply for the OCXO as they take more power and this needs to be cleaner than I'd expect USB power to be. The question I have again is about a simple phase detector. On Wed, Dec 5, 2012 at 3:28 AM, ewkeh...@aol.com wrote: Chris There is a low cost solution and I have the input circuit perfect for GPS on a $1 gate array I have boards and am presently using Shera original version. Would like to buy his version 402NE but have not been able to get a response from him. Have repeatedly asked for help on this list for some one to step forward to write the uproc. program. No one. The total material cost would be less than $ 25 PCB included GPS receiver OCXO or RB would be extra. If the FE 5680A with RS232 would be used cost is less than $ 15. There are now PIC's out there that can also do the timing function reducing cost even more but that will take more smarts. Bert Kehren 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 Alternatives
Yes. The idea was the simplest GPSDO that can be build with no PCB around an Arduino. We already know how to build compllelx and expensive GPSDO. That is too easy. I think you can use the PWM DAC on the Aruino to drive the OCXO. The bandwidth of this signal is way low so you can filter the PWM output with a (say) 1Hz low pass filter. On Wed, Dec 5, 2012 at 4:57 AM, Jim Lux jim...@earthlink.net wrote: On 12/5/12 12:06 AM, Bruce Griffiths wrote: Hal Murray wrote: albertson.ch...@gmail.com said: What is the simplest phase detecter that could work? I think only that, and then a duouble oven crystal from eBay, a GPS and and Arduido. You also need a good D2A to drive the EFC on the osc. A synchronous filter of a suitably level translated (CMOS analog switch plus low noise reference) PWM output should work well. True.. but I think the OP was wanting something that doesn't require designing a circuit and building it. -- 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 Alternatives
Don't need anything so complex. A GPSDO depend on an OCXO that is VERY stable. It can be controlled with a very low bandwidth analog signal. The output from a OCXO is divided down and then the phase of the divided down 10MHz RF is compared to the PPS and you don't need to even know the how far apart they are. All you need to know is led or lag just a one bit answer. An XOR gate or a flip flop can tell you that. If you want to get more fancy you can connect a few temperature sensors to the Arduino's ADC lines and push those over the USB port along with other statistics. Youcan also do things like control the time constants the software uses via USB also. But you don't need this. It can be added later or not. On Wed, Dec 5, 2012 at 9:31 AM, Bob Camp li...@rtty.us wrote: Hi If the intent is to come up with something in the same league as the TBolt there are a few other things you will need: 1) Something to compare the two pps signals to within 0.1 ns. 2) A large amount of code on the control processor (there are a multitude of special cases ...) 3) A large amount of code on a PC to monitor it and control it (like Lady Heather) 4) A set of standards to compare it to while you train and debug it 5) The test gear to collect and analyze the comparison and debug data with (you will have many months of data) 6) Some sort of control over the feature list. The complexity of 2-5 will go up significantly each time a nice to have thing is added. Once you get past step one, the rest of that list dwarf's anything like which D/A to use. I'm not at all saying it can't be done. Only that the bulk of the effort starts after you have the hardware. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Wednesday, December 05, 2012 7:58 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives On 12/5/12 12:06 AM, Bruce Griffiths wrote: Hal Murray wrote: albertson.ch...@gmail.com said: What is the simplest phase detecter that could work? I think only that, and then a duouble oven crystal from eBay, a GPS and and Arduido. You also need a good D2A to drive the EFC on the osc. A synchronous filter of a suitably level translated (CMOS analog switch plus low noise reference) PWM output should work well. True.. but I think the OP was wanting something that doesn't require designing a circuit and building it. So what you really want is a high performance DAC on a Arduino shield, or, alternately, a high performance DAC on a cheap eval board that you can easily hook up to an Ardino type processor. This is a bit trickier.. Lots of ADC stuff out there, not so much DAC stuff. http://embeddednewbie.blogspot.com/2011/02/review-of-arduino-dac-solutions.h tml seems to have a number of approaches. Adafruit has a shield with a Microchip MCP4921 12 bit serial dac here's a 16 bit solution http://www.shaduzlabs.com/article-12.html but it's a build it yourself solution. If you're not size/mass/power constrained, you might be able to find an inexpensive used programmable power supply. I do this using a Prologix controller driving Agilent E3646 power supplies.. Big, Expensive, etc. but it does work. Yes the Aruino is expensive compared to a bare uP chip but using one, I thin you could build a GPSDO without a PCB and the Arduino's USB connection could be usful for power and logging/control. I wouldn't want to power a GPSDO from USB. It will get power cycled every time I need to work on the logging PC. Besides, you only get 2.5 watts. The oven will probably take more than that during warm-up. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] GPSDO Alternatives
Chris, If you want to understand how to approach the issue, you need to study the Shera controller system. It does exactly what you and others are discussing doing. It is relatively simple, straight forward and the HEX file is available to program the CPU with. The circuit board is all ready made and available. The only hard part is the D/A which may be a bit of a problem with respect to the original part. However, even that may be available from another vender. If not there are some similar replacements, but that may require making new boards to account for the parts being surface mount types. Do yourself a favor and look at the following URL and download the reprint of the QST article. http://www.rt66.com/~shera/index_fs.htm BillWB6BNQ Chris Albertson wrote: Now you can see the problem with designs that require both a PCB and a programmed uP. Most people can't do either of these and those who can typically are good at only one. Then you find someone and after he looses interest the project is dead and un-suportable. So I was thinking of how to build a GPSDO that does not need a programmed uP and would be so simple that a PCB would not be needed. It shoud be simple enough that after getting the parts could be built quickly by anyone. The Arduino has a USB interface and both ADC and DAC and digital IO. I read about the concern about using USB power. The Arduino can also be powered by a 9V battery so it will continue to run if the USB power goes away. Or you can use a power cube (aka wall wort) Anyone can program an Arduino even if you know nothing about uP. It is VERY easy and the software runs on Mac OS X, Linux and even Windows. I would use a separate power supply for the OCXO as they take more power and this needs to be cleaner than I'd expect USB power to be. The question I have again is about a simple phase detector. On Wed, Dec 5, 2012 at 3:28 AM, ewkeh...@aol.com wrote: Chris There is a low cost solution and I have the input circuit perfect for GPS on a $1 gate array I have boards and am presently using Shera original version. Would like to buy his version 402NE but have not been able to get a response from him. Have repeatedly asked for help on this list for some one to step forward to write the uproc. program. No one. The total material cost would be less than $ 25 PCB included GPS receiver OCXO or RB would be extra. If the FE 5680A with RS232 would be used cost is less than $ 15. There are now PIC's out there that can also do the timing function reducing cost even more but that will take more smarts. Bert Kehren 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 mailing 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] STM32 based thing (was GPSDO Alternatives)
Hello Michael! Michael Tharp g...@partiallystapled.com ha scritto: On 12/05/2012 08:03 AM, Fabio Eboli wrote: I'm seriously thinking to attempt a gpsdo. ... The platform I will try to use is the STM32F103 microcontroller Coincidentally, my previous time-nut project was built around the same chip. I built a simple GPSDO using a STM32F103C with a bit of ... Here are the design documents, if you're curious: http://hg.partiallystapled.com/circuits/serafine/raw-file/d75ab09ca163/out/production.PDF Thank you very much, I will study it with interest, it will be very helpul to see what you have done. Can I ask you more details? I didnt's understand how you are using the timers: are you timestamping each pps transistion using the internal clock? Are you using the pll to obtain 72MHz (x9) for the clock? same as many, if not all, other GPSDOs out there. I'm reasonably happy with the hardware as a GPSDO experimentation platform (but not looking to sell anything at this time). Good, to be clear my project will not be commercial in any way, only an amateur attempt, documented as far as my time permits. And my skills are not enough for anything that can be sold in this field :) The current project, as I've mentioned before, is a self-contained GPS-to-NTP server based on STM32F107, which has built-in ethernet but is otherwise very similar to the F103. The finished board won't be This is another advantage of the STM32 (or other manufacturers cortex arm micros), one can easily port the project up to higher specs devices; for example ST sells the stm32F4 discovery for around 20eu that is powered by an stm32F407 that is cortex M4F device full of ram and flash and communication ports, and that support FPU etc, it's a 168MHz device, but I'havent checked it's timers capability. I will stick with the 103 for now, my goals are the basic ones: building a counter and figuring out how to discipline a Rb, the communication/logging/pc support software is really a big work to do and i'm not planning to go there for some time :) Fabio. This message was sent using IMP, the Internet Messaging Program. ___ time-nuts mailing 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 Alternatives
On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. -- 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 Alternatives
Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] Very challenging phase noise measurement, does anyone have an idea??
Hi True, but you can do a fairly simple filter to separate the 250 KHz note you don't want from the 8 KHz highest frequency that you do want. There are a lot of ADC's that will do that for you with their built in filtering. Bob On Dec 5, 2012, at 9:23 PM, Rick Karlquist rich...@karlquist.com wrote: Bob Camp wrote: Hi You might be surprised by the noise floor of an XOR run at 125 KHz. They are quite good at that low a frequency. Bob An XOR, unlike a mixer, does not have a null when the phases are in quadrature. This is the fundamental problem with using it as a phase detector. 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] Very challenging phase noise measurement, does anyone have an idea??
Karen, I still have maybe another half an hour of work to do. If I can wake up to be on the call I will. I'd say there might be a 50% chance I'll make it... -- Harlan Stenn st...@ntp.org http://networktimefoundation.org - be a member! ___ time-nuts mailing 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 Alternatives
Hi Simple answer - no, not in a precision part. They are neither high enough resolution or deterministic enough to give you very high resolution. More complex answer - you can do just about anything if you are willing to limit the best possible outcome. With the normal integration times you probably will be in the 1x10^-9 to 1x10^-10 noise (ADEV) range. You would do better with an input capture port. They would be more deterministic, but they still have limited resolution. If they are driven by a clock multiplier, they likely will have a jitter component on their clock. Since low jitter is not a money spec in these low end parts, there can be some issues there. There are many cheap / simple ways to to the counter. Five dollars will easily solve the problem with change left over to pay for breakfast coffee. Next up on the expanded list is a way to align the pps signals. If you tune your OCXO by 0.1 ppm to align them, it will take you 100 days to get to the first stage of lock. If you use a CPLD to do that part, you can toss much of the counter in with it. You still have change from your five dollars. Bob On Dec 6, 2012, at 4:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] Very challenging phase noise measurement, does anyone have an idea??
Hi Note to self - coffee first , morning emails second…. Bob On Dec 6, 2012, at 6:39 AM, Harlan Stenn st...@ntp.org wrote: Karen, I still have maybe another half an hour of work to do. If I can wake up to be on the call I will. I'd say there might be a 50% chance I'll make it... -- Harlan Stenn st...@ntp.org http://networktimefoundation.org - be a member! ___ time-nuts mailing 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 Alternatives
Hi There are many marvelous things you can do in software. In some cases you are fundamentally limited by the hardware. Regardless of the hardware chosen, the effort is 99.99% in other areas. Starting with a hardware platform that lets you evolve (even if it's a few dollars more) is generally a good decision. Bob On Dec 6, 2012, at 4:28 AM, Chris Albertson albertson.ch...@gmail.com wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. -- 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 mailing 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] EIP545A 18GHz counter query
Chris wrote: I have the 10MHz output from David's divider feeding the counter. When fed from this the Band 2 seems unreliable starting at 10MHz. If I feed it 10Mhz at 50mV from my sig gen it starts reliably. Is it a mismatch from the divider, or has it perhaps not got enough drive level? First, what does the counter manufacturer's specification say with respect to acceptable signals at the external reference input? Second, what happens if you feed the TB output directly to the counter's reference input? IIRC, the outputs of the Partridge divider are 5V TTL from a ~50 ohm source, so low peak-to-peak signal amplitude should not be an issue. If anything, the divider could be overdriving the counter's reference input. Note that the TTL signal ranges from 0V to ~+5V and does not cross ground -- if the counter is expecting the reference to be bipolar (i.e., if it switches on a zero-cross), it may not respond reliably to TTL levels. Beyond that, depending on how the counter terminates the external reference line, you may have steps or ringing at the reference input (see the thread on terminations). Look at the counter's reference input with a high-impedance (divide by 10) scope probe to see what the feed looks like there. Best regards, Charles 06/12/2012 12:28 Here's a resume of where I am at, I hope this is sufficiently on topic for this forum, please say if it's not. The dedicated forum for EIP devices seems very very quiet. Manual is at http://www.gatesgarth.com/EIP_545A_Service_Manual.pdf Saga starts with counter as received, showing just dashes, not able to do anything more than a display test, and won't perform basic 200 MHz test function: I have had a good look at board A108 the U6 chip is missing from, and apart from a mysterious pair of multi turn pots the schematic parts list seems to say are not used I can see no anomalies save for U6 being missing altogether I'll post the results of fitting this device. The replacement for the missing U6 chip arrived this morning and it now completes the 200 MHz self test. It will read up to the limit of my frequency generator on Band 3 which is only 1040 MHz, but looks promising. Band 1 also works fine. Band 2 sort of works, but seemingly has a serious anomaly. I cannot get Band 2 to read below 185.000 MHz. To even get over 185 MHz needs a lot of drive power, too. 2 volts or so. Even then this somnetimes doesn't start a display of other than zeros. If I input 184.900 it won't read it and displays zeros. 185 and up is OK... Weird. IF frequency? It should read from 10 MHz up to 1 GHz. It'll go to 1 GHz plus AOK. I believe I may have isolated the issue to the A109 board. Until the unit warms up Band 2 is deaf and needs plenty of millivolts input to trigger, sometimes it won't trigger at all. Once warm it sometimes settles down to near the makers spec on how much input at what frequencies it should need to trigger. (NOTE -- EDIT Seems not to trigger at all of late, save with warming Q12) I used freeze spray to isolate a small area, and the fine tip of a de soldering iron connected backwards to the pump, so it blows a fine jet of hot air. The problem is in the area marked on the schematic of board A109, device Q12. As I have no riser board access is terribly limited. It's a 2N4126 component number Q12 If I just touch it with a piece of stiff, heavy copper wire wound round the tip of a small 15W iron, it changes state almost immediately and the Band 2 is very sensitive again, and immediately displays a frequency, down to 10 MHz, just fine. As soon as it cools it reverts to the insensitive state. But bear in mind above 185 MHz it works in a fashion hot or cold, with a lot of drive... If the counter is left to warm up naturally and I cool this device with some spray, it reads zeros again. I am not 100% sure what it's switching function is, but I have removed it, and isolated on my Peak semiconductor tester it varies gain form 170 cold to 190 warm, and it will suddenly go to a gain of just 4 if it gets a bit warmer still. R10 is also playing up. It should be a 43K 2% but measures 32K cold and warmed a touch changes to 4.8K ! It should have a 1 PPM/C temperature coefficient, too, so something has happened to that as well. I am not sure if any previous abuse would have damaged diode CR1, shown as a ND4991 ? New Q12 and new R10 fitted, problem just the same. Warming the new Q12 brings the display back. Voltage tests done, results below all with a 30mV emf input to the Band 2 socket: TP2 No input signal 3.4 / 3.5V Displays zeros TP2 10 MHz 3.4 / 3.5V Displays zeros TP2 50 MHz 3.4 / 3.5 V Displays zeros TP2 100 MHz 3.4 / 3.5V Displays zeros TP2 400 MHz 3.4 / 3.5V Displays zeros TP2 500 MHz 0.06V Displays frequency TP2 900 MHz 4.9 / 5.0V Displays frequency For TP2 the change over seems circa 450MHz *** BUT *** Input 650 MHZ and TP2 shows 4.2 / 4.3V and displays
Re: [time-nuts] Power Grid Time and Frequency
On 12/05/2012 02:32 PM, M. Simon wrote: Do you have a link for the nifty site? This one is not just for the west coast, but has good reporting of grid conditions: http://fnetpublic.utk.edu/index.html They have several real time graphic and table displays of grid frequency. The Sample Events tab has links to movies of the grid frequency during major storms and an east coast earthquake. -- Bob Smither, Ph.D. smit...@c-c-i.com attachment: smither.vcf___ time-nuts mailing 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] GPSDO Alternatives
On Mon, Dec 4, paul swed wrote: Yes sir $139. But boy I have not seen cheap tbolts in bit. As I recall $260 these days? On Mon, Dec 3, 2012 at 9:12 PM, Bob Camp lists at rtty.us wrote: Hi The gotcha is that you go from paying surplus prices to paying new prices. New price to new price, they certainly are cheaper. Not so easy to beat a $100 TBolt on price (if you can find one). Bob Comments like these make me smile because they're kind of like the ads you used to see for buying $50 jeeps from DOD. Yes, someone at some time in the distant past had probably bought one jeep for $50 but these ads continued for decades like urban legends and a lot of people believed them. As to Tbolt prices, over the past year or so I had sold close to 200 Tbolts on the popular auction site at $170 each so I have a pretty good idea what the market was like during that time. All the Tbolts I had were removed from the original equipment and tested by me so all the units I sold were clean and worked exactly as they were intended to work. If you watched the price of all the Chinese dealers over this same period last year they all went up in unison, first to $189, then to $260 as Paul mentioned above. What you would have noticed if you checked the actual units sold is that they were not selling any at those prices but buyers were getting their Tbolts from me instead. I suspect that all the Chinese dealers are basically store front resellers for some distributor who set the price. As others on this list had commented, the condition of some of the electronic parts from China indicate that these parts like Tbolts and OXCOs were removed at some scrapyard by someone who didn't know or care what they were but was only interested in throughput and the parts were thrown into bins for later distribution and sale. Check the photos of bent and/or rusted OXCOs for listings 170950828042, 170558942064, and 300579197899 to see what I mean. -Arthur ___ time-nuts mailing 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 Alternatives
On 12/6/12 1:06 AM, Chris Albertson wrote: Yes. The idea was the simplest GPSDO that can be build with no PCB around an Arduino. We already know how to build compllelx and expensive GPSDO. That is too easy. I think you can use the PWM DAC on the Aruino to drive the OCXO. The bandwidth of this signal is way low so you can filter the PWM output with a (say) 1Hz low pass filter. I would worry about how you'd build that filter to be low noise AND suitably filter the PWM output so that there's no leakage of the PWM modulation. Seems it would be easier to hook up a serial interface DAC with lots of bits than fool with filters.. ___ time-nuts mailing 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] Power Grid Time and Frequency
On 12/6/12 4:42 AM, Bob Smither wrote: On 12/05/2012 02:32 PM, M. Simon wrote: Do you have a link for the nifty site? This one is not just for the west coast, but has good reporting of grid conditions: http://fnetpublic.utk.edu/index.html They have several real time graphic and table displays of grid frequency. The Sample Events tab has links to movies of the grid frequency during major storms and an east coast earthquake. I think there's another one that is similar somewhere on the west coast (Washington state?) .. I'm hunting for the URL (it was on this list, 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] Very challenging phase noise measurement, does anyone have an idea??
If you want a low noise mixer use a varicap mixer. A varicap has no ohmic characteristics thus no Johnson noise. Secondly, You can create low noise harmonics using a vaicap multiplier or a nonlinear transmission line using inductors and nonlinear capacitors (varicaps). NIST has been doing this for some time and even has used nonlinear fiber optics to phase lock oscillators to lasers as atomic references. Guys got Nobel Prize for that one. Measuring the phase noise at a high order harmonic has the advantage that the phase is multiplied by the harmonic number thus bring the sidebands up further from the noise floor. Here is a reference, that could be scaled down for your frequency, on phase noise measurements using harmonics produced by a nonlinear transmission line. This example just a few sections in its nonlinear transmission line 73 Bill wa4lav http://ecee.colorado.edu/microwave/docs/publications/2008/Milos-Jason-TMTT-July08.pdf ___ time-nuts mailing 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] EIP545A 18GHz counter query
Very interested as I have one of these and its troubled but differently. Can't really dig in right now. Paul WB8TSL On Thu, Dec 6, 2012 at 7:33 AM, Chris Wilson ch...@chriswilson.tv wrote: Chris wrote: I have the 10MHz output from David's divider feeding the counter. When fed from this the Band 2 seems unreliable starting at 10MHz. If I feed it 10Mhz at 50mV from my sig gen it starts reliably. Is it a mismatch from the divider, or has it perhaps not got enough drive level? First, what does the counter manufacturer's specification say with respect to acceptable signals at the external reference input? Second, what happens if you feed the TB output directly to the counter's reference input? IIRC, the outputs of the Partridge divider are 5V TTL from a ~50 ohm source, so low peak-to-peak signal amplitude should not be an issue. If anything, the divider could be overdriving the counter's reference input. Note that the TTL signal ranges from 0V to ~+5V and does not cross ground -- if the counter is expecting the reference to be bipolar (i.e., if it switches on a zero-cross), it may not respond reliably to TTL levels. Beyond that, depending on how the counter terminates the external reference line, you may have steps or ringing at the reference input (see the thread on terminations). Look at the counter's reference input with a high-impedance (divide by 10) scope probe to see what the feed looks like there. Best regards, Charles 06/12/2012 12:28 Here's a resume of where I am at, I hope this is sufficiently on topic for this forum, please say if it's not. The dedicated forum for EIP devices seems very very quiet. Manual is at http://www.gatesgarth.com/EIP_545A_Service_Manual.pdf Saga starts with counter as received, showing just dashes, not able to do anything more than a display test, and won't perform basic 200 MHz test function: I have had a good look at board A108 the U6 chip is missing from, and apart from a mysterious pair of multi turn pots the schematic parts list seems to say are not used I can see no anomalies save for U6 being missing altogether I'll post the results of fitting this device. The replacement for the missing U6 chip arrived this morning and it now completes the 200 MHz self test. It will read up to the limit of my frequency generator on Band 3 which is only 1040 MHz, but looks promising. Band 1 also works fine. Band 2 sort of works, but seemingly has a serious anomaly. I cannot get Band 2 to read below 185.000 MHz. To even get over 185 MHz needs a lot of drive power, too. 2 volts or so. Even then this somnetimes doesn't start a display of other than zeros. If I input 184.900 it won't read it and displays zeros. 185 and up is OK... Weird. IF frequency? It should read from 10 MHz up to 1 GHz. It'll go to 1 GHz plus AOK. I believe I may have isolated the issue to the A109 board. Until the unit warms up Band 2 is deaf and needs plenty of millivolts input to trigger, sometimes it won't trigger at all. Once warm it sometimes settles down to near the makers spec on how much input at what frequencies it should need to trigger. (NOTE -- EDIT Seems not to trigger at all of late, save with warming Q12) I used freeze spray to isolate a small area, and the fine tip of a de soldering iron connected backwards to the pump, so it blows a fine jet of hot air. The problem is in the area marked on the schematic of board A109, device Q12. As I have no riser board access is terribly limited. It's a 2N4126 component number Q12 If I just touch it with a piece of stiff, heavy copper wire wound round the tip of a small 15W iron, it changes state almost immediately and the Band 2 is very sensitive again, and immediately displays a frequency, down to 10 MHz, just fine. As soon as it cools it reverts to the insensitive state. But bear in mind above 185 MHz it works in a fashion hot or cold, with a lot of drive... If the counter is left to warm up naturally and I cool this device with some spray, it reads zeros again. I am not 100% sure what it's switching function is, but I have removed it, and isolated on my Peak semiconductor tester it varies gain form 170 cold to 190 warm, and it will suddenly go to a gain of just 4 if it gets a bit warmer still. R10 is also playing up. It should be a 43K 2% but measures 32K cold and warmed a touch changes to 4.8K ! It should have a 1 PPM/C temperature coefficient, too, so something has happened to that as well. I am not sure if any previous abuse would have damaged diode CR1, shown as a ND4991 ? New Q12 and new R10 fitted, problem just the same. Warming the new Q12 brings the display back. Voltage tests done, results below all with a 30mV emf input to the Band 2 socket: TP2 No input signal 3.4 / 3.5V Displays zeros TP2 10 MHz 3.4 / 3.5V Displays zeros TP2 50 MHz 3.4 / 3.5 V Displays zeros TP2 100 MHz 3.4 / 3.5V Displays zeros TP2 400
Re: [time-nuts] PTTI 2012, part 3/3
Still, there are always a number of talks of more general interest to us time nuts. In the next few postings I'll give more details on a couple of topics: And here's the third part of my PTTI report... - Vendor presentations/Symmetricom/Miles Besides 3 days of presentations, PTTI also hosts a vendor/exhibit area. This includes the usual TF suspects like FEI, Symmetricom, TRAK, Spectracom, SpectraDynamics, TimeTech, etc. Most of this gear is outside the budget of a regular time-nut but it's always nice to see and touch what's on display, knowing in ten years it will show up on eBay. Yes, that was John Miles in the Symmetricom booth showing off his, I mean, their new TimePod and wearing a Symmetricom shirt. We've had a number of time nut graduates over the years: Rick Hambly went on to start CNS Systems, Said Jackson started Jackson Labs, John Miles became Miles LLC and both have ties with Symmetricom. You'll see press releases like this one: http://www.gpsworld.com/symmetricom-expands-test-set-portfolio-with-high-performance-test-probe If you have more questions, I'm sure John will be happy to answer then on- or off- the list. - M12/uBlox GPS board It was very nice to see Tom Clark (grandfather of time-nuts) at PTTI; it was from his work at NASA with VLBI, masers, and Motorola Oncore GPS receivers that a number of us caught the precise time bug in the early 90's. Many of you know him as the author of the often recommended paper Critical Evaluation of the Motorola M12+ GPS Timing Receiver vs. the Master Clock at the United States Naval Observatory, Washington DC which is available here: http://www.gpstime.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf http://www.gpstime.com/files/PTTI/PTTI_2002_CNS_Testbed_VG.ppt Anyway, this year Tom Clark presented performance results of a new GPS board. It is h/w and s/w compatible with the Motorola M12 receiver used in many existing TF products, but it's based on a uBlox-6T chip instead of the Motorola or iLotus M12 chip. The trick is that Rick Hambly added a PIC on the board to make it talk exactly like an M12. The reason for this is to allow drop-in replacement of the original Motorola M12 or still-current iLotus M12+ with this new one. It's called the Synergy SSR-6T. That means that any instrument (e.g., GPSDO) that uses an M12 can be upgraded to the uBlox-6T. Tom's presentation contains charts showing the performance improvement: http://www.cnssys.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf http://www.cnssys.com/publications.php I have one to play with and hope to duplicate his results. I didn't get pricing/availability info but it is supposed to be really cheap. (Tom Clark -- can you provide this info when you get it?) - Quartz in space With all the focus on fiber and optical and atomic clocks, it's refreshing to hear now and then about good old quartz. This was a fascinating talk about real-world (or real out-of-this-world) performance of quartz oscillators in space. What they did was mine recorded telemetry from many space missions looking to directly/indirectly measure the frequency of the quartz oscillator over years in space. Just like we use LH to monitor the EFC of a GPSDO, they monitor the EFC of the quartz LO in the GPS sats. In addition to normal drift there are effects of radiation dose and solar flares. I'll post the URL of the paper when it's out. Meanwhile I saw a bunch of fine papers/presentations at the FEI site: http://www.freqelec.com/tech_lit.html - ION/PTTI 2013 in Bellevue, WA (!) After 44 years, PTTI is changing management. Instead of being organized by the US government (USNO, NASA, JPL, and DoD) it will now be run by ION (Institute of Navigation). This keeps the government out of the hospitality and conference business. The next ION/PTTI will be held in Bellevue, WA. If you haven't considered attending an ION or PTTI conference before, this might be a good one to try. Also, since that's my hometown, I plan to have an open house during the conference. That means I have a year to clean up the lab so more than one person can walk in it... A number of people continued to comment on the relativity experiment I did a few years ago. I have now posted the original (190 page) power-point presentation I gave at PTTI that year: http://www.leapsecond.com/ptti2006/ - The state of Time-Nuts Lastly, I wanted to make a note about time-nuts. I was pleasantly surprised how many professionals already know about the time-nuts list or lurk here. This group has really done well. Perhaps propelled by advances in the telecom/optical world or neutrino experiments, there's a whole new crop of scientists in the precise time field. Formal technical journal articles by PhD's tend not to deal with the mundane details of precise time measurement and lab equipment so people turn to google, and find us here. As the list grows we face some issues about posting bandwidth,
Re: [time-nuts] Power Grid Time and Frequency
On 12/06/2012 08:04 AM, Jim Lux wrote: On 12/6/12 4:42 AM, Bob Smither wrote: On 12/05/2012 02:32 PM, M. Simon wrote: Do you have a link for the nifty site? This one is not just for the west coast, but has good reporting of grid conditions: http://fnetpublic.utk.edu/index.html They have several real time graphic and table displays of grid frequency. The Sample Events tab has links to movies of the grid frequency during major storms and an east coast earthquake. I think there's another one that is similar somewhere on the west coast (Washington state?) .. I'm hunting for the URL (it was on this list, I think).. I found this: http://gridstat.net/trac/ which links to an interesting demo page: http://www.gridstat.net/javaDemo/graph.html Project of Washington State University. attachment: smither.vcf___ time-nuts mailing 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 Alternatives
As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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 Alternatives
Interesting Arthur. I don't think I had a clue you were selling them and would have paid the difference of what I actually picked one up for. Though mine was clean and I have not a complaint in the world. Like you I watched things go up and they were very controlled day by day. At the time it seemed that all of the units were out of China and I really felt like it was quite the gamble. It paid off but I was worried about it. Regards Paul On Thu, Dec 6, 2012 at 8:27 AM, Arthur Dent golgarfrinc...@yahoo.comwrote: On Mon, Dec 4, paul swed wrote: Yes sir $139. But boy I have not seen cheap tbolts in bit. As I recall $260 these days? On Mon, Dec 3, 2012 at 9:12 PM, Bob Camp lists at rtty.us wrote: Hi The gotcha is that you go from paying surplus prices to paying new prices. New price to new price, they certainly are cheaper. Not so easy to beat a $100 TBolt on price (if you can find one). Bob Comments like these make me smile because they're kind of like the ads you used to see for buying $50 jeeps from DOD. Yes, someone at some time in the distant past had probably bought one jeep for $50 but these ads continued for decades like urban legends and a lot of people believed them. As to Tbolt prices, over the past year or so I had sold close to 200 Tbolts on the popular auction site at $170 each so I have a pretty good idea what the market was like during that time. All the Tbolts I had were removed from the original equipment and tested by me so all the units I sold were clean and worked exactly as they were intended to work. If you watched the price of all the Chinese dealers over this same period last year they all went up in unison, first to $189, then to $260 as Paul mentioned above. What you would have noticed if you checked the actual units sold is that they were not selling any at those prices but buyers were getting their Tbolts from me instead. I suspect that all the Chinese dealers are basically store front resellers for some distributor who set the price. As others on this list had commented, the condition of some of the electronic parts from China indicate that these parts like Tbolts and OXCOs were removed at some scrapyard by someone who didn't know or care what they were but was only interested in throughput and the parts were thrown into bins for later distribution and sale. Check the photos of bent and/or rusted OXCOs for listings 170950828042, 170558942064, and 300579197899 to see what I mean. -Arthur ___ time-nuts mailing 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] PTTI 2012, part 3/3
Great comments and a good read. OK so what does the drop in replacement cost??? Thanks lots to read here. Later Paul WB8TSL On Thu, Dec 6, 2012 at 10:24 AM, Tom Van Baak t...@leapsecond.com wrote: Still, there are always a number of talks of more general interest to us time nuts. In the next few postings I'll give more details on a couple of topics: And here's the third part of my PTTI report... - Vendor presentations/Symmetricom/Miles Besides 3 days of presentations, PTTI also hosts a vendor/exhibit area. This includes the usual TF suspects like FEI, Symmetricom, TRAK, Spectracom, SpectraDynamics, TimeTech, etc. Most of this gear is outside the budget of a regular time-nut but it's always nice to see and touch what's on display, knowing in ten years it will show up on eBay. Yes, that was John Miles in the Symmetricom booth showing off his, I mean, their new TimePod and wearing a Symmetricom shirt. We've had a number of time nut graduates over the years: Rick Hambly went on to start CNS Systems, Said Jackson started Jackson Labs, John Miles became Miles LLC and both have ties with Symmetricom. You'll see press releases like this one: http://www.gpsworld.com/symmetricom-expands-test-set-portfolio-with-high-performance-test-probe If you have more questions, I'm sure John will be happy to answer then on- or off- the list. - M12/uBlox GPS board It was very nice to see Tom Clark (grandfather of time-nuts) at PTTI; it was from his work at NASA with VLBI, masers, and Motorola Oncore GPS receivers that a number of us caught the precise time bug in the early 90's. Many of you know him as the author of the often recommended paper Critical Evaluation of the Motorola M12+ GPS Timing Receiver vs. the Master Clock at the United States Naval Observatory, Washington DC which is available here: http://www.gpstime.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf http://www.gpstime.com/files/PTTI/PTTI_2002_CNS_Testbed_VG.ppt Anyway, this year Tom Clark presented performance results of a new GPS board. It is h/w and s/w compatible with the Motorola M12 receiver used in many existing TF products, but it's based on a uBlox-6T chip instead of the Motorola or iLotus M12 chip. The trick is that Rick Hambly added a PIC on the board to make it talk exactly like an M12. The reason for this is to allow drop-in replacement of the original Motorola M12 or still-current iLotus M12+ with this new one. It's called the Synergy SSR-6T. That means that any instrument (e.g., GPSDO) that uses an M12 can be upgraded to the uBlox-6T. Tom's presentation contains charts showing the performance improvement: http://www.cnssys.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf http://www.cnssys.com/publications.php I have one to play with and hope to duplicate his results. I didn't get pricing/availability info but it is supposed to be really cheap. (Tom Clark -- can you provide this info when you get it?) - Quartz in space With all the focus on fiber and optical and atomic clocks, it's refreshing to hear now and then about good old quartz. This was a fascinating talk about real-world (or real out-of-this-world) performance of quartz oscillators in space. What they did was mine recorded telemetry from many space missions looking to directly/indirectly measure the frequency of the quartz oscillator over years in space. Just like we use LH to monitor the EFC of a GPSDO, they monitor the EFC of the quartz LO in the GPS sats. In addition to normal drift there are effects of radiation dose and solar flares. I'll post the URL of the paper when it's out. Meanwhile I saw a bunch of fine papers/presentations at the FEI site: http://www.freqelec.com/tech_lit.html - ION/PTTI 2013 in Bellevue, WA (!) After 44 years, PTTI is changing management. Instead of being organized by the US government (USNO, NASA, JPL, and DoD) it will now be run by ION (Institute of Navigation). This keeps the government out of the hospitality and conference business. The next ION/PTTI will be held in Bellevue, WA. If you haven't considered attending an ION or PTTI conference before, this might be a good one to try. Also, since that's my hometown, I plan to have an open house during the conference. That means I have a year to clean up the lab so more than one person can walk in it... A number of people continued to comment on the relativity experiment I did a few years ago. I have now posted the original (190 page) power-point presentation I gave at PTTI that year: http://www.leapsecond.com/ptti2006/ - The state of Time-Nuts Lastly, I wanted to make a note about time-nuts. I was pleasantly surprised how many professionals already know about the time-nuts list or lurk here. This group has really done well. Perhaps propelled by advances in the telecom/optical world or neutrino experiments, there's a whole new crop of scientists in the precise time field. Formal
Re: [time-nuts] GPSDO Alternatives
Hi There are at least 500 different processors out there that could / might work in a GPSDO. I can think of 40 or more families of parts one could look at from more than a dozen companies. That's just counting the majors, and not getting into any of the smaller outfits. It's also not including any of the stuff that's likely overkill for the job. If you head off into ARM land, there are a number of hobby oriented projects out there. Raspberry PI is one, there are *many* others in the sub $50 price range. One of many is the http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=FRDM-KL25Z The board is somewhere from free (sit in a room for 2 hours) to $13 (buy it from distribution). It's got a full blown debugger and it will interface with Adruino shields. It also has free software and a free RTOS to go with it. For those who like data logging, it's set up for a SD card. Price wise - at least as cheap as any Arduino I've seen. (... and it's a dual CPU card, if you re-use the debugger CPU). No I don't know if that's the right card or not to use. I'm only tossing it up as another example of what might be used. It is representative of many boards one might consider. The obvious gotcha here is that there are *way* too many choices rather than too few. I don't know of any boards or CPU's that will do the job without some glue externally. CPU's have a following, just as brands of cars do. This has turned into a Ford / Chevy debate in the past. That doesn't move anything forward. There really is no right or wrong, just a lot of personal preferences with a lot of emotion involved. Until a group of people decide they want to do this, I'd leave the CPU choice wide open. Once you have a willing group, let them work with what ever they are comfortable with. The bigger decisions and issues are elsewhere. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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 Alternatives
Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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 Alternatives
Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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] time-nuts Digest, Vol 101, Issue 40
Hello All - Just a quick comment from an olde RF engineer. Bob Camp wrote: Hi You might be surprised by the noise floor of an XOR run at 125 KHz. They are quite good at that low a frequency. Bob An XOR, unlike a mixer, does not have a null when the phases are in quadrature. This is the fundamental problem with using it as a phase detector. Rick A XOR does have a null of sorts - at quadrature the average DC level of the output is a 1/2 the supply voltage. For a DBM it is zero. The DBM in inherently quieter with noise figures of about 7 dB which is not the case of any XOR. Finally to avoid DC loading of the output of either type the DC level should be blocked by a capacitor of suitable value to pass the lowest frequency of interest. A 1 K or similar resistor on the IF port of the DBM will assure a known load and consistent output voltage. Finally a low pass LC filter should follow the capacitor to suppress the high level 2F output of the mixer and keep it out of the following circuitry. This is old hat to most I know. -73 john k6iql -Original Message- From: time-nuts-request time-nuts-requ...@febo.com To: time-nuts time-nuts@febo.com Sent: Wed, Dec 5, 2012 8:24 pm Subject: time-nuts Digest, Vol 101, Issue 40 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: Very challenging phase noise measurement, does anyone have an idea?? (John Miles) 2. Re: Very challenging phase noise measurement, does anyone have an idea?? (Bob Camp) 3. Re: Very challenging phase noise measurement, does anyone have an idea?? (Jim Lux) 4. Re: Very challenging phase noise measurement, does anyone have an idea?? (Bob Camp) 5. Re: Very challenging phase noise measurement, does anyone have an idea?? (Rick Karlquist) -- Message: 1 Date: Wed, 5 Dec 2012 17:24:00 -0800 From: John Miles jmi...@pop.net To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: Re: [time-nuts] Very challenging phase noise measurement, does anyone have an idea?? Message-ID: 012801cdd350$5f8a5c80$1e9f1580$@pop.net Content-Type: text/plain; charset=us-ascii That would be a good way to do it. I wouldn't use an XOR gate or other digital phase detector for this, due to the low slew rate among other things. Instead, you could phase lock two of your sources with a double-balanced mixer, then run the IF through a lowpass filter and a quiet opamp or other LNA. The baseband noise can then be viewed on a spectrum analyzer that goes down to whatever the minimum offset of interest is. The analyzer's noise floor doesn't matter, it just needs to be something that can tune down to the 100 Hz-1 kHz area. An old-school HP 8566 or 8568 is ideal. For calibration details, see the references in the last FAQ entry at http://www.ke5fx.com/gpib/faq.htm , especially HP 11729B-1. Alternatively, I'm not sure where the noise floor of the FSUP is, but if it is otherwise low enough, you could mix the 125 kHz with an ultra-low-noise OCXO and measure one of the resulting sidebands. It might or might not be necessary to filter the other sideband depending on how the FSUP works. You could also build a low-noise 8x active multiplier to get to 1 MHz where the FSUP can see it, as well. This would have the advantage of not requiring a ULN OCXO for mixing, and would also boost the PN by 18 dB for easier measurement on the FSUP. However, you'd need to be careful with the multiplier's residual noise, especially in the first couple of stages. If you need to make these measurements over and over, go with the multiplier or mixer, otherwise I'd use an analog quadrature PLL. -- john Miles Design LLC -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Adrian Sent: Wednesday, December 05, 2012 4:40 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Very challenging phase noise measurement, does anyone have an idea?? You can always use an external mixer / phase detector and the baseband input of a HP 3048A or FSUP. Just to name a few: For low power (+7dBm) you can use a SRA-3 which goes from 25kHz to 200MHz SRA-3MH +13dBm from 25kHz to 200MHz SRA-3H +17dBm from 50kHz to 200MHz For high power signals use a RAY-3. It goes from 70kHz to 200MHz. The IF must be specified from DC, which for the above is the case. Between
Re: [time-nuts] Considerations When Using The SR620
On Tuesday, 4 December 2012, Tom Van Baak wrote: We are using the SR620 to measure the interval between 1PPS signals from two clocks. One is the Septentrio PolaRx4 GPS receiver and the other is a Rubidium clock. Many Thanks, Paul 1) If you are making frequency measurements, the warm-up of the internal oscillator is the major factor limiting accuracy. ... Plotting digits of precision as a function of warm-up time would make a very educational graph you could tape to the top of your SR620. 2) If you are making time interval measurements and using an external standard, the warm-up time will also affect the accuracy of your TI measurements, but to a far lesser degree. Here are informal results for TI (time interval) mode after a 5 minute power-down (see also attached plots): - if you need 1 ns accuracy, you can use the SR620 immediately after power-up - if you need 100 ps accuracy, wait 2+ minutes - if you need 10 ps accuracy, wait 15+ minutes - if you need 1 ps accuracy, you need a seriously stable lab environment or a different counter. Given that you plan to use the SR620 with high-end GPS gear I would suggest you try this quick experiment for yourself to see what *your* SR620 does, with *your* inputs, in *your* environment. Your numbers will come out different than mine; but the methodology is the same. Your procedures can then be based on measurement and confidence instead of guesswork and folklore. Tom Co., Thank you! These plots are excellent and will be very helpful. You are quite right; we should do the test ourselves. We will definitely do that. Obviously, there is not need to worry, as we can characterize the instrument behavior ourselves, which is probably necessary anyway if we're going to publish these measurements with error values. Many Thanks, Paul -- Paul DeStefano ___ time-nuts mailing 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 Alternatives
Boy do I have to agree. uProcs by the dozens and with all kinds of counters onboard. I think it was Bob who said none of thats the challenge. It is the phase comparison method and a stable D/A converter and reference. From what I have seen and I could be dead wrong here the on board uprocs have D/As but the quality is simply OK. The other comment is that whoever writes the software gets to choose the software and everything else. Its actually not really democratic at all. Cause we will all use it if its reasonably good. ;-) If I do it it will be basic! Though it will run at very high speeds. Now someone should be jumping in with Forth real soon now. Last tidbit the Rasberry is a pretty interesting widget and there had been a thread about a time server. Was looking forward to the results. Nothing ever happened. Regards Paul WB8TSL On Thu, Dec 6, 2012 at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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] Considerations When Using The SR620
Volker, That's a great question and I'm afraid I don't have a good answer for you. If pressed, I would estimate less than 100ps. The error of this measurement contributes to the error in our final measurement which has many components. I haven't worked out an error budget for each contributor. Our goal is a final error of less than 10ns. But a few contributors are already expected to be around 1ns, so this error really needs to be less than 1ns, preferably less than 100ps. Cheers, Paul On Tuesday, 4 December 2012, Volker Esper wrote: I agree. Since Paul want's to use an SR620 I presume he needs precision. Otherwise almost any TIC with a fairly stable osc would do, for example one with a battery backup. So I further presume that he needs nearly the full accuracy / stability. But that's just speculation, surely Paul can answere this question? -- Paul DeStefano ___ time-nuts mailing 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] Open source GPSDO
Keenan, You can see my GPSDO source code for a mere $50. It comes with manual and executables. The executables alone are $20. See http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm While this design does not use a Kalmann filter, it has pretty good holdover, and you can see how the phase detector, error integrator, filters, PID controller and D-A converter etc are done. The hardware is pretty simple. There is a PC monitoring and control program. 73, Murray ZL1BPU - Original Message - As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. [snip] ___ time-nuts mailing 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 Alternatives
Hi This is a project that is a multi year endeavor in a commercial setting. That's where you have multiple people on the payroll who can put 40+ hours a week into it. You are set up with groups of people who do this or that. They all aren't on this job full time, but there's a lot of resources available. As a hobby project, it's going to take longer. Signing up for years of work, and sticking to it is not at all easy. Getting to make the fun decisions is about the only compensation for doing an awful lot of work. Unless you just won the lottery, there's also a non-trivial cost to making up several revisions of boards. Not at all simple. Not un-doable either. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Thursday, December 06, 2012 1:17 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Boy do I have to agree. uProcs by the dozens and with all kinds of counters onboard. I think it was Bob who said none of thats the challenge. It is the phase comparison method and a stable D/A converter and reference. From what I have seen and I could be dead wrong here the on board uprocs have D/As but the quality is simply OK. The other comment is that whoever writes the software gets to choose the software and everything else. Its actually not really democratic at all. Cause we will all use it if its reasonably good. ;-) If I do it it will be basic! Though it will run at very high speeds. Now someone should be jumping in with Forth real soon now. Last tidbit the Rasberry is a pretty interesting widget and there had been a thread about a time server. Was looking forward to the results. Nothing ever happened. Regards Paul WB8TSL On Thu, Dec 6, 2012 at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify.
Re: [time-nuts] GPSDO Alternatives
On 12/6/12 9:45 AM, Dale J. Robertson wrote: Arduino is Dirt Cheap! And available over the counter retail at hundreds of Radio Shacks.. You get an idea during the day, and you can run out and buy one right then.. (yes, you can mail order, but the fastest turnaround is a few days, unless you pay an enormous next day shipping premium) This is one reason why Arduino is by far and away the most common uProc in, e.g., high school science projects. ___ time-nuts mailing 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] GPSDO on the cheap
I would use a digital pot for coarse setting. Or a manual trimpot. That way your control signal holds even if your comparison goes away or if for some reason your loop comes out of lock. Something like that also reduces the noise contribution of the DAC. Simon = Date: Thu, 6 Dec 2012 01:17:52 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Message-ID: cabbxvhs_xibax15h27c38l4gevmmgnzwo+9fw2j-bqg9k5z...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Don't need anything so complex. A GPSDO depend on an OCXO that is VERY stable. It can be controlled with a very low bandwidth analog signal. The output from a OCXO is divided down and then the phase of the divided down 10MHz RF is compared to the PPS and you don't need to even know the how far apart they are. All you need to know is led or lag just a one bit answer. An XOR gate or a flip flop can tell you that. If you want to get more fancy you can connect a few temperature sensors to the Arduino's ADC lines and push those over the USB port along with other statistics. Youcan also do things like control the time constants the software uses via USB also. But you don't need this. It can be added later or not. Engineering is the art of making what you want from what you can get at a profit. ___ time-nuts mailing 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 Alternatives
Most of the free tool chains are not truly free I.e. open source including all libraries and coupled with an open source compiler and debugger. In addition few of them are currently offered in hobbyist friendly DIP packages. Once you resign yourself to having to build hardware glue for some of the special functions required, CPU performance becomes mostly a non issue. For quick and dirty lash ups on perf board (as I believe the OP is looking for), It's hard to beat a pic or Avr and for code re-use from a large online community it's hard to beat the arduino eek-o-system Dale Sent from my iPhone On Dec 6, 2012, at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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] GPSDO Alternatives
Hi That is where most of these tools were many years ago. Competition has forced them to open things up quite a bit. You can code a very nice GPSDO and not use anything but freely available tools. You can do it on several processors, none of which come from AVR (and thus use the Arduino chain). Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 1:47 PM To: Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Most of the free tool chains are not truly free I.e. open source including all libraries and coupled with an open source compiler and debugger. In addition few of them are currently offered in hobbyist friendly DIP packages. Once you resign yourself to having to build hardware glue for some of the special functions required, CPU performance becomes mostly a non issue. For quick and dirty lash ups on perf board (as I believe the OP is looking for), It's hard to beat a pic or Avr and for code re-use from a large online community it's hard to beat the arduino eek-o-system Dale Sent from my iPhone On Dec 6, 2012, at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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
Re: [time-nuts] GPSDO on the cheap
In past designs I just included an EEPROM so in the event of a cold start, the last settings would be known. On Thu, 6 Dec 2012 10:45:48 -0800 (PST), M. Simon msimon6...@yahoo.com wrote: I would use a digital pot for coarse setting. Or a manual trimpot. That way your control signal holds even if your comparison goes away or if for some reason your loop comes out of lock. Something like that also reduces the noise contribution of the DAC. Simon = Date: Thu, 6 Dec 2012 01:17:52 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Message-ID: cabbxvhs_xibax15h27c38l4gevmmgnzwo+9fw2j-bqg9k5z...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Don't need anything so complex. A GPSDO depend on an OCXO that is VERY stable. It can be controlled with a very low bandwidth analog signal. The output from a OCXO is divided down and then the phase of the divided down 10MHz RF is compared to the PPS and you don't need to even know the how far apart they are. All you need to know is led or lag just a one bit answer. An XOR gate or a flip flop can tell you that. If you want to get more fancy you can connect a few temperature sensors to the Arduino's ADC lines and push those over the USB port along with other statistics. Youcan also do things like control the time constants the software uses via USB also. But you don't need this. It can be added later or not. ___ time-nuts mailing 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 Alternatives
Bob, Did Atmel (AVR) kill your dog or something? They have some pretty powerful MCU's. Are you flatly stating that none of them could be used for a very nice GPSDO? Dale Just fooling around, no offence intended. -Original Message- From: Bob Camp Sent: Thursday, December 06, 2012 1:57 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] GPSDO Alternatives Hi That is where most of these tools were many years ago. Competition has forced them to open things up quite a bit. You can code a very nice GPSDO and not use anything but freely available tools. You can do it on several processors, none of which come from AVR (and thus use the Arduino chain). Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 1:47 PM To: Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Most of the free tool chains are not truly free I.e. open source including all libraries and coupled with an open source compiler and debugger. In addition few of them are currently offered in hobbyist friendly DIP packages. Once you resign yourself to having to build hardware glue for some of the special functions required, CPU performance becomes mostly a non issue. For quick and dirty lash ups on perf board (as I believe the OP is looking for), It's hard to beat a pic or Avr and for code re-use from a large online community it's hard to beat the arduino eek-o-system Dale Sent from my iPhone On Dec 6, 2012, at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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 Alternatives
Hi By no means am I saying that they *can't* be used. My point is that there are a multitude of alternatives that are at least equally as cheap and attractive. There is no clear you must use this one to pick. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 2:09 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] GPSDO Alternatives Bob, Did Atmel (AVR) kill your dog or something? They have some pretty powerful MCU's. Are you flatly stating that none of them could be used for a very nice GPSDO? Dale Just fooling around, no offence intended. -Original Message- From: Bob Camp Sent: Thursday, December 06, 2012 1:57 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] GPSDO Alternatives Hi That is where most of these tools were many years ago. Competition has forced them to open things up quite a bit. You can code a very nice GPSDO and not use anything but freely available tools. You can do it on several processors, none of which come from AVR (and thus use the Arduino chain). Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 1:47 PM To: Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Most of the free tool chains are not truly free I.e. open source including all libraries and coupled with an open source compiler and debugger. In addition few of them are currently offered in hobbyist friendly DIP packages. Once you resign yourself to having to build hardware glue for some of the special functions required, CPU performance becomes mostly a non issue. For quick and dirty lash ups on perf board (as I believe the OP is looking for), It's hard to beat a pic or Avr and for code re-use from a large online community it's hard to beat the arduino eek-o-system Dale Sent from my iPhone On Dec 6, 2012, at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a
Re: [time-nuts] GPSDO Alternatives
How about quit talking and build something and show us some results! Bert Kehren In a message dated 12/6/2012 2:09:38 P.M. Eastern Standard Time, d...@nap-us.com writes: Bob, Did Atmel (AVR) kill your dog or something? They have some pretty powerful MCU's. Are you flatly stating that none of them could be used for a very nice GPSDO? Dale Just fooling around, no offence intended. -Original Message- From: Bob Camp Sent: Thursday, December 06, 2012 1:57 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] GPSDO Alternatives Hi That is where most of these tools were many years ago. Competition has forced them to open things up quite a bit. You can code a very nice GPSDO and not use anything but freely available tools. You can do it on several processors, none of which come from AVR (and thus use the Arduino chain). Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 1:47 PM To: Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Most of the free tool chains are not truly free I.e. open source including all libraries and coupled with an open source compiler and debugger. In addition few of them are currently offered in hobbyist friendly DIP packages. Once you resign yourself to having to build hardware glue for some of the special functions required, CPU performance becomes mostly a non issue. For quick and dirty lash ups on perf board (as I believe the OP is looking for), It's hard to beat a pic or Avr and for code re-use from a large online community it's hard to beat the arduino eek-o-system Dale Sent from my iPhone On Dec 6, 2012, at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and
Re: [time-nuts] GPSDO Alternatives
Paul I agree. That is my main frustration, lot of talk no results. The good part of time nuts is that I have made some very good contacts that share my interest of actually building some things and results are great. Remember the Loran simulator? Bert Kehren In a message dated 12/6/2012 1:17:14 P.M. Eastern Standard Time, paulsw...@gmail.com writes: Boy do I have to agree. uProcs by the dozens and with all kinds of counters onboard. I think it was Bob who said none of thats the challenge. It is the phase comparison method and a stable D/A converter and reference. From what I have seen and I could be dead wrong here the on board uprocs have D/As but the quality is simply OK. The other comment is that whoever writes the software gets to choose the software and everything else. Its actually not really democratic at all. Cause we will all use it if its reasonably good. ;-) If I do it it will be basic! Though it will run at very high speeds. Now someone should be jumping in with Forth real soon now. Last tidbit the Rasberry is a pretty interesting widget and there had been a thread about a time server. Was looking forward to the results. Nothing ever happened. Regards Paul WB8TSL On Thu, Dec 6, 2012 at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent and easy to understand and modify. ___ time-nuts mailing 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,
Re: [time-nuts] Open source GPSDO
On 6 December 2012 18:28, Murray Greenman denw...@orcon.net.nz wrote: Keenan, You can see my GPSDO source code for a mere $50. It comes with manual and executables. The executables alone are $20. See http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm Murray , There's a huge difference between open-source and paying $50 to view the code for ones own use. Even if the code was cost just $0.01, but the code was not open to public scrutiny, it detracts from its value. I've no objection to you, or anyone else writing code for proffit - I have done it myself many times. But your code is not open-source, and does not have the advantages that open-source code has - open to public scrutiny, ability to share improvements with the community etc. I can't quite work out why the title is Open source GPSDO when the code is not open-source. BTW, I suspect you reduce potential sales by not accepting Personal checks, bank checks, internet pay services or money orders. Having banknotes wrapped inside a letter posted to you does not appeal to many people now. http://www.qsl.net/zl1bpu/MICRO/Index.htm#NOTES Before the days of Paypal, I found posting banknotes was the cheapest way to send small amount of money overseas. I'd generally buy USD from a travel agent in the UK and post them off in an envelope, as the bank costs to get a small amount of money transfered were too high. But it is not to everyones liking. Dave. ___ time-nuts mailing 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 Alternatives
I'm excited, for sure. I've got a whole box of goodies over here I bought full of the Arduino uP and a ton of its 'shields'. Been collecting, so-to-speak. I just new I could use it for a, down-and-dirty GPSDO. The Trimble Lassen looks good down to 20ns UTC (I got two for $10); then add a cheap datum ocxo; coupled that with the Arduino. Voilà. I can't wait, ..and you guys are reinforcing that just because its' cheap won't mean it won't work. -Don -- From: ewkeh...@aol.com Sent: Thursday, December 06, 2012 1:38 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Paul I agree. That is my main frustration, lot of talk no results. The good part of time nuts is that I have made some very good contacts that share my interest of actually building some things and results are great. Remember the Loran simulator? Bert Kehren In a message dated 12/6/2012 1:17:14 P.M. Eastern Standard Time, paulsw...@gmail.com writes: Boy do I have to agree. uProcs by the dozens and with all kinds of counters onboard. I think it was Bob who said none of thats the challenge. It is the phase comparison method and a stable D/A converter and reference. From what I have seen and I could be dead wrong here the on board uprocs have D/As but the quality is simply OK. The other comment is that whoever writes the software gets to choose the software and everything else. Its actually not really democratic at all. Cause we will all use it if its reasonably good. ;-) If I do it it will be basic! Though it will run at very high speeds. Now someone should be jumping in with Forth real soon now. Last tidbit the Rasberry is a pretty interesting widget and there had been a thread about a time server. Was looking forward to the results. Nothing ever happened. Regards Paul WB8TSL On Thu, Dec 6, 2012 at 1:00 PM, Bob Camp li...@rtty.us wrote: Hi It's a rare microcontroller these days that does *not* come with a free tool chain. Same goes for the debugger. Most MCU lines have family members with similarly low (or lower) prices and good availability. They pretty much all either work with a crystal two caps and a resistor. Most will run fine with none of the above on the internal clock. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: Thursday, December 06, 2012 12:45 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Arduino is Dirt Cheap! At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor with the arduino bootloader programmed into it. Easily obtainable from several sources for 5 bucks or so. All the code, toolchain etc. (the ecosystem as it were) is free. it's real easy to put one together on a piece of perfboard. If you're gonna put the phase detector, dividers etc. together anyway there's really no need to clutter things up with some ginormous commercial arduino board. Dale -Original Message- From: Keenan Tims Sent: Thursday, December 06, 2012 10:38 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. There are quite a few open hardware designs out there, but as Bob suggests, all the interesting bits are tied up in the closed-source software they run. And most of them are no longer maintained, meaning it's getting hard to find parts. I've thought on designing a hardware platform to support a GPSDO as well, but don't have the time-nut or control theory skills (or equipment) necessary to make the software any good. My hope at the time was that a build it and they will come approach would solve those problems, but I haven't had time to make that gamble. As far as uP choice, Arduino's only saving grace is the pool of existing 'developers' in the amateur community for it - but that's perhaps a big deal here. It's expensive, doesn't include debug hardware, and is slow with not many peripherals. I'd second the STM32 ARM Cortex platform, or suggest MSP430 if you want to stay cheap and slow. Keenan VE7XEN On 2012-12-06 1:28 AM, Chris Albertson wrote: On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote: If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. This is the reason I suggested using the Arduino. It is so easy to program that MANY people will be able to contribute. That is my goal, a GPSDO that can be a living project that is not dependent on one or a few experts. I'd like to see a budget of well under $100, again so that more people can contribute and experiment. A design that can evolve will have just about any performance people want. So don't worry about if it is 1E-12 or 1E-15. Just make it transparent
Re: [time-nuts] Open source GPSDO
If by OpenSource he means that he used the OpenSource tool chain, and libraries, and then is keeping his source and executables closed, he may be in violation of the GNU licenses. -Chuck Harris David Kirkby wrote: On 6 December 2012 18:28, Murray Greenman denw...@orcon.net.nz wrote: Keenan, You can see my GPSDO source code for a mere $50. It comes with manual and executables. The executables alone are $20. See http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm Murray , There's a huge difference between open-source and paying $50 to view the code for ones own use. Even if the code was cost just $0.01, but the code was not open to public scrutiny, it detracts from its value. I've no objection to you, or anyone else writing code for proffit - I have done it myself many times. But your code is not open-source, and does not have the advantages that open-source code has - open to public scrutiny, ability to share improvements with the community etc. I can't quite work out why the title is Open source GPSDO when the code is not open-source. ___ time-nuts mailing 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] Open source GPSDO
On 6 December 2012 20:33, Chuck Harris cfhar...@erols.com wrote: If by OpenSource he means that he used the OpenSource tool chain, and libraries, and then is keeping his source and executables closed, he may be in violation of the GNU licenses. -Chuck Harris According to the web page http://www.qsl.net/zl1bpu/MICRO/Index.htm#NOTES the code is written in Microsoft Quick Basic 3.2 compiler syntax. So it is not an open-source tool chain. I'm not sure what you mean by OpenSource tool chain, but if you are thinking of gcc, then there is a special GCC RUNTIME LIBRARY EXCEPTION. http://www.gnu.org/licenses/gcc-exception-3.1.html so you can use gcc to create closed-source software, despite the fact gcc is a GPL program. As a reader of the gcc mailing lists, it is a fairly common question on there, from people who want to use gcc for closed-source software, but are not sure if it legal to do so. The answer is yes, you can use gcc for commerical closed-source software. Dave David Kirkby wrote: On 6 December 2012 18:28, Murray Greenman denw...@orcon.net.nz wrote: Keenan, You can see my GPSDO source code for a mere $50. It comes with manual and executables. The executables alone are $20. See http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm Murray , There's a huge difference between open-source and paying $50 to view the code for ones own use. Even if the code was cost just $0.01, but the code was not open to public scrutiny, it detracts from its value. I've no objection to you, or anyone else writing code for proffit - I have done it myself many times. But your code is not open-source, and does not have the advantages that open-source code has - open to public scrutiny, ability to share improvements with the community etc. I can't quite work out why the title is Open source GPSDO when the code is not open-source. ___ time-nuts mailing 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] Open source GPSDO
GPL violations are a good thing. That is how the FSF makes money. ;-) http://www.linuxfordevices.com/c/a/News/Cisco-settles-with-FSF-on-GPL-violations/ ___ time-nuts mailing 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 Alternatives
Don wrote: you guys are reinforcing that just because its' cheap won't mean it won't work. Of course it doesn't. But keep in mind that working spans several orders of magnitude in this area, and what one needs to design and build depends on what degree of working one needs to support the uses to which the finished standard will be put. First, there is performance during normal operation (good, continuous satellite tracking) -- ADEV at all taus of interest, PN at all offsets of interest, distortion and spurs, residual AM, stability over temperature, PPS jitter, etc. Then, there is performance with poor satellite visibility, and finally performance in holdover (no satellite visibility) for however long one needs it (if one needs it at all, which many amateurs may not). For some, there will be power consumption issues. There may also be issues of interfacing to monitoring devices, both simple (e.g., LCD status displays) and sophisticated (e.g., computer running Lady Heather or Z38xx). Does it need to work with existing programs, or is writing a new monitoring program part of the project? Then there are the construction issues. Does it need to be assembled entirely from connectorized modules, no soldering required? Or capable of being thrown together on a scrap of perfboard? Or will a PC card be designed? If so, can it use SMT parts? How adaptable must it be, particularly in accommodating different oscillators? Does it need to support rubidium oscillators as well as quartz? Etc., etc., etc. Thunderbolt and Z38xx commercial GPSDOs are plentiful and relatively affordable, so they are natural benchmarks for any DIY project. From my perspective, the most interesting development would be an offer by someone with a very well equipped lab to test any DIY GPSDO with a consistent protocol and publish the results. That way, we could all see how the various approaches compare with respect to the characteristics that are most important to each of us. 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] GPSDO Alternatives
Hi The single best thing about a TBolt is Lady Heather. Consider how many years it's taken to get it to where it is today. Consider how many people have worked extensively on it. It's a wonderful thing to have available. Could you make a homebrew gizmo look just like a TBolt? Sure you could. It might well take you forever to do all the reverse engineering, validation, and testing, but it can be done. I'd guess it would take less time to re-write a version of LH from scratch -- Another thing to consider: Z3801's got scrapped out, flooded the market, and the price went to real good. The supply dried up and prices climbed. This took years. TBolts went through the same cycle. Again over a time period of many years. In both cases you had a long time to look at them and make a decision about weather you wanted one or not. It was never a buy it this week or they are gone thing. These aren't the only things that will ever get scrapped. There's something somewhere in the world that's going to get junked. Some sort of GPSDO will flood the market in the future. It will be around for many years at low prices. What ever you do as a project needs to be pretty good to survive the competition. Otherwise it'll die before anybody ever sees one. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Charles P. Steinmetz Sent: Thursday, December 06, 2012 4:36 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Don wrote: you guys are reinforcing that just because its' cheap won't mean it won't work. Of course it doesn't. But keep in mind that working spans several orders of magnitude in this area, and what one needs to design and build depends on what degree of working one needs to support the uses to which the finished standard will be put. First, there is performance during normal operation (good, continuous satellite tracking) -- ADEV at all taus of interest, PN at all offsets of interest, distortion and spurs, residual AM, stability over temperature, PPS jitter, etc. Then, there is performance with poor satellite visibility, and finally performance in holdover (no satellite visibility) for however long one needs it (if one needs it at all, which many amateurs may not). For some, there will be power consumption issues. There may also be issues of interfacing to monitoring devices, both simple (e.g., LCD status displays) and sophisticated (e.g., computer running Lady Heather or Z38xx). Does it need to work with existing programs, or is writing a new monitoring program part of the project? Then there are the construction issues. Does it need to be assembled entirely from connectorized modules, no soldering required? Or capable of being thrown together on a scrap of perfboard? Or will a PC card be designed? If so, can it use SMT parts? How adaptable must it be, particularly in accommodating different oscillators? Does it need to support rubidium oscillators as well as quartz? Etc., etc., etc. Thunderbolt and Z38xx commercial GPSDOs are plentiful and relatively affordable, so they are natural benchmarks for any DIY project. From my perspective, the most interesting development would be an offer by someone with a very well equipped lab to test any DIY GPSDO with a consistent protocol and publish the results. That way, we could all see how the various approaches compare with respect to the characteristics that are most important to each of us. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] Open source GPSDO
Hi Many of the vendor tool chains are now (or soon will be) gcc and Eclipse based. It's very common to do closed source code on open source based platforms. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Kirkby Sent: Thursday, December 06, 2012 3:56 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Open source GPSDO On 6 December 2012 20:33, Chuck Harris cfhar...@erols.com wrote: If by OpenSource he means that he used the OpenSource tool chain, and libraries, and then is keeping his source and executables closed, he may be in violation of the GNU licenses. -Chuck Harris According to the web page http://www.qsl.net/zl1bpu/MICRO/Index.htm#NOTES the code is written in Microsoft Quick Basic 3.2 compiler syntax. So it is not an open-source tool chain. I'm not sure what you mean by OpenSource tool chain, but if you are thinking of gcc, then there is a special GCC RUNTIME LIBRARY EXCEPTION. http://www.gnu.org/licenses/gcc-exception-3.1.html so you can use gcc to create closed-source software, despite the fact gcc is a GPL program. As a reader of the gcc mailing lists, it is a fairly common question on there, from people who want to use gcc for closed-source software, but are not sure if it legal to do so. The answer is yes, you can use gcc for commerical closed-source software. Dave David Kirkby wrote: On 6 December 2012 18:28, Murray Greenman denw...@orcon.net.nz wrote: Keenan, You can see my GPSDO source code for a mere $50. It comes with manual and executables. The executables alone are $20. See http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm Murray , There's a huge difference between open-source and paying $50 to view the code for ones own use. Even if the code was cost just $0.01, but the code was not open to public scrutiny, it detracts from its value. I've no objection to you, or anyone else writing code for proffit - I have done it myself many times. But your code is not open-source, and does not have the advantages that open-source code has - open to public scrutiny, ability to share improvements with the community etc. I can't quite work out why the title is Open source GPSDO when the code is not open-source. ___ time-nuts mailing 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] Open source GPSDO
The Open Source tool chain is generally GCC, its libraries, and debuggers. Closed source use of the GCC tool chain is done all the time, but there are numerous gotchas that catch the unwary. Some of the libraries are covered by the Lesser GPL license, and as such are available for that kind of use, others are not. This is why there is a seemingly never ending stream of legal challenges to GPL violators. Which is why I was very careful to say: May be in violation... But since he is using microsloth compilers, and is charging for access to the source and executable code, his project isn't OpenSource in any respect. -Chuck Harris David Kirkby wrote: As a reader of the gcc mailing lists, it is a fairly common question on there, from people who want to use gcc for closed-source software, but are not sure if it legal to do so. The answer is yes, you can use gcc for commerical closed-source software. Dave ___ time-nuts mailing 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 Alternatives
On 12/6/2012 4:35 PM, Charles P. Steinmetz wrote: From my perspective, the most interesting development would be an offer by someone with a very well equipped lab to test any DIY GPSDO with a consistent protocol and publish the results. That way, we could all see how the various approaches compare with respect to the characteristics that are most important to each of us. This is interesting, and I could bite -- for a limited definition of very well equipped. What's *really* interesting, though, is the idea that collectively we might develop some standard measurement protocols that would be reproducible in a number of (amateur) labs. John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Alternatives
You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design On Thu, Dec 6, 2012 at 1:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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. -- 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 Alternatives
Hi The math is pretty straightforward. Let's say the clock is 10 MHz, that's 100 ns. Say a handful is 5 +/- 3 (2 to 8) Your measure will bounce up and down by 6x100 ns = 600 ns. Over a 100 second period that's going to be 6.0 x10^-9 bounce in the data. If you run a 100 second loop as well, that's the noise in the loop (just from one source). Six times faster clock, you get 1.0x10^-9. Step up the handful for the faster clock's pipeline and you may be back at the same place. Take a bunch of readings (you only get one a second) and average - things get better by square root of the samples. That's IF you have enough jitter / dither in the system to smooth things out. If you have lumpy noise (as is often the case with interrupts) you may get very little gain from averaging. With a 100 second loop, a TBolt is doing sub 1x10^-11, so you are at least 100X worse. Bob On Dec 6, 2012, at 5:57 PM, Chris Albertson albertson.ch...@gmail.com wrote: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design On Thu, Dec 6, 2012 at 1:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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. -- 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 mailing 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 Alternatives
albertson.ch...@gmail.com said: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design Do some of the counter/timer modules have an option to run the counter off an internal clock and copy the value into another register on an external signal? That avoids any interrupt latency. -- 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 Alternatives
Hi That would be an input capture rather than an interrupt. Bob On Dec 6, 2012, at 6:16 PM, Hal Murray hmur...@megapathdsl.net wrote: albertson.ch...@gmail.com said: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design Do some of the counter/timer modules have an option to run the counter off an internal clock and copy the value into another register on an external signal? That avoids any interrupt latency. -- 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] GPSDO Alternatives
Bob et al: Have been following this thread with interest. Re the input capture versus interrupt, I do believe (at least the 2560 does this) that you can do both. It's been a while since I looked. a look at the hardware manual. Was interested in this feature to do hardware timing. Norm On Thu, Dec 6, 2012 at 6:25 PM, Bob Camp li...@rtty.us wrote: Hi That would be an input capture rather than an interrupt. Bob On Dec 6, 2012, at 6:16 PM, Hal Murray hmur...@megapathdsl.net wrote: albertson.ch...@gmail.com said: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design Do some of the counter/timer modules have an option to run the counter off an internal clock and copy the value into another register on an external signal? That avoids any interrupt latency. -- 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. ___ time-nuts mailing 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 Alternatives
Hi To be useful, you need an input capture that: 1) Runs at a fast enough clock (1 GHz would be nice) 2) Has enough bits to get to 1 pps (say 32 bits) 3) Has a built in period set, so the hardware works without a lot of silly stuff Often you find parts that will do some of the above, but not all. 16 bit captures running off of a few MHz clock are pretty common. Some (but not all) ARM's have 32 bit captures that run off of 10's of MHz clocks and have the ability to set the period. Bob On Dec 6, 2012, at 6:34 PM, Lizeth Norman normanliz...@gmail.com wrote: Bob et al: Have been following this thread with interest. Re the input capture versus interrupt, I do believe (at least the 2560 does this) that you can do both. It's been a while since I looked. a look at the hardware manual. Was interested in this feature to do hardware timing. Norm On Thu, Dec 6, 2012 at 6:25 PM, Bob Camp li...@rtty.us wrote: Hi That would be an input capture rather than an interrupt. Bob On Dec 6, 2012, at 6:16 PM, Hal Murray hmur...@megapathdsl.net wrote: albertson.ch...@gmail.com said: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design Do some of the counter/timer modules have an option to run the counter off an internal clock and copy the value into another register on an external signal? That avoids any interrupt latency. -- 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. ___ time-nuts mailing 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 Alternatives
You can use the ATmega328 16 bit timer/counter in input capture mode to count the number of 10 MHz OCXO cycles per pulse per second period to a resolution of 100ns but there are some problems: The ATmega328 16 bit timer/counter external clock is limited to 1/4 of the CPU frequency with an asynchronous source so the 10 MHz OCXO would need to be divided down which would further limit performance and require an external divider. Modifying the Aruino board to use the 10 MHz OCXO in place of the CPU clock solves that problem. Then operating the counter/timer in input capture mode with the GPS pulse per second signal connected to the input capture pin would allow almost Shera like performance. The timing resolution would be 2.4 times lower (and not asynchronous) limiting performance over short time spans. On Thu, 6 Dec 2012 14:57:19 -0800, Chris Albertson albertson.ch...@gmail.com wrote: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design On Thu, Dec 6, 2012 at 1:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don ___ time-nuts mailing 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 Alternatives
could you not add just a little 'glue' outside the uP to relieve it a tad. Let the GPS' 1pps gate some ttl counters and then read for overflow or underflow after xxx seconds. Have the uP determine dac correction setting back to the TXCO. -Don -- From: Bob Camp li...@rtty.us Sent: Thursday, December 06, 2012 5:55 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Hi To be useful, you need an input capture that: 1) Runs at a fast enough clock (1 GHz would be nice) 2) Has enough bits to get to 1 pps (say 32 bits) 3) Has a built in period set, so the hardware works without a lot of silly stuff Often you find parts that will do some of the above, but not all. 16 bit captures running off of a few MHz clock are pretty common. Some (but not all) ARM's have 32 bit captures that run off of 10's of MHz clocks and have the ability to set the period. Bob On Dec 6, 2012, at 6:34 PM, Lizeth Norman normanliz...@gmail.com wrote: Bob et al: Have been following this thread with interest. Re the input capture versus interrupt, I do believe (at least the 2560 does this) that you can do both. It's been a while since I looked. a look at the hardware manual. Was interested in this feature to do hardware timing. Norm On Thu, Dec 6, 2012 at 6:25 PM, Bob Camp li...@rtty.us wrote: Hi That would be an input capture rather than an interrupt. Bob On Dec 6, 2012, at 6:16 PM, Hal Murray hmur...@megapathdsl.net wrote: albertson.ch...@gmail.com said: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design Do some of the counter/timer modules have an option to run the counter off an internal clock and copy the value into another register on an external signal? That avoids any interrupt latency. -- 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. ___ time-nuts mailing 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] Open source
My mistake was inferring that my GPSDO software was open source. It's absolutely not. It is proprietary to me and written in AVR assembler. There is no reference anywhere in it to any libraries from any other source. So don't get too excited. You can still see what's inside it for $50, but you need to be able to understand AVR assembler source code. 73, Murray ZL1BPU ___ time-nuts mailing 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] Open source GPSDO
We need a real, Open Source GPSDO that uses an open source tool chain. Cost is not the issue it is the ability to modify and redistribute the modified copy that is what's needed. On Thu, Dec 6, 2012 at 10:28 AM, Murray Greenman denw...@orcon.net.nzwrote: Keenan, You can see my GPSDO source code for a mere $50. It comes with manual and executables. The executables alone are $20. See http://www.qsl.net/zl1bpu/**MICRO/SIMPLE/SimpleGPS.htmhttp://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm While this design does not use a Kalmann filter, it has pretty good holdover, and you can see how the phase detector, error integrator, filters, PID controller and D-A converter etc are done. The hardware is pretty simple. There is a PC monitoring and control program. 73, Murray ZL1BPU - Original Message - As a lurker, I just want to chime in and say that I for one would love to see an open-source GPSDO implementation. [snip] __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Time security musing - attacking the clock itself
The key here is to step the time a few milliseconds at a time as ntpd has various sanity checks. Sent from my iPhone On Dec 4, 2012, at 3:22 PM, Hal Murray hmur...@megapathdsl.net wrote: 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] GPSDO Alternatives
On Thu, Dec 6, 2012 at 4:09 PM, dlewis6767 dlewis6...@austin.rr.com wrote: could you not add just a little 'glue' outside the uP to relieve it a tad. Let the GPS' 1pps gate some ttl counters and then read for overflow or underflow after xxx seconds. Have the uP determine dac correction setting back to the TXCO. That is why my first post was to ask What is the simplest phase defector that can work? I think you only need a one-bit counter. A flip-flop will do that. The FF is a classic phase detector used in many PLL -- 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 Alternatives
Hi Again, the math is pretty simple. A 16 bit capture running at a 1/4 clock is not going to get you very near a Shera. It's even further from the more modern enhanced Shera designs. Bob On Dec 6, 2012, at 6:59 PM, David davidwh...@gmail.com wrote: You can use the ATmega328 16 bit timer/counter in input capture mode to count the number of 10 MHz OCXO cycles per pulse per second period to a resolution of 100ns but there are some problems: The ATmega328 16 bit timer/counter external clock is limited to 1/4 of the CPU frequency with an asynchronous source so the 10 MHz OCXO would need to be divided down which would further limit performance and require an external divider. Modifying the Aruino board to use the 10 MHz OCXO in place of the CPU clock solves that problem. Then operating the counter/timer in input capture mode with the GPS pulse per second signal connected to the input capture pin would allow almost Shera like performance. The timing resolution would be 2.4 times lower (and not asynchronous) limiting performance over short time spans. On Thu, 6 Dec 2012 14:57:19 -0800, Chris Albertson albertson.ch...@gmail.com wrote: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design On Thu, Dec 6, 2012 at 1:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don ___ time-nuts mailing 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 Alternatives
Hi The simplest phase detector does indeed work. It just does not work very well. Not correcting the oscillator at all works, you will have time and frequency to some level of accuracy. Not correcting it at all is a whole lot cheaper and simpler. Bob On Dec 6, 2012, at 7:30 PM, Chris Albertson albertson.ch...@gmail.com wrote: On Thu, Dec 6, 2012 at 4:09 PM, dlewis6767 dlewis6...@austin.rr.com wrote: could you not add just a little 'glue' outside the uP to relieve it a tad. Let the GPS' 1pps gate some ttl counters and then read for overflow or underflow after xxx seconds. Have the uP determine dac correction setting back to the TXCO. That is why my first post was to ask What is the simplest phase defector that can work? I think you only need a one-bit counter. A flip-flop will do that. The FF is a classic phase detector used in many PLL -- 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 mailing 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 Alternatives
What if the OCXO had a sine wave output and then you used the PPS leading edge to gate the sine wave to a sample and hold. then the sample is measured by the Arduino's ADC? I think(?) you get a 10-bit ADC or is it 8-bits. The problem is the required speed of the sample and hold, maybe not easy to build -- 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 Alternatives
Hi The solution to the problem is well known in several forms. Cost is below $5 for pretty much all of them. No need to re-invent the wheel. The gotcha is that you can't do it 100% with internal CPU peripherals. You will need *some* glue. Bob On Dec 6, 2012, at 7:43 PM, Chris Albertson albertson.ch...@gmail.com wrote: What if the OCXO had a sine wave output and then you used the PPS leading edge to gate the sine wave to a sample and hold. then the sample is measured by the Arduino's ADC? I think(?) you get a 10-bit ADC or is it 8-bits. The problem is the required speed of the sample and hold, maybe not easy to build -- 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 mailing 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 Alternatives
It is not a 16 bit capture and it does not run at 1/4 the clock rate. The Shera uses a 12 bit counter to capture the phase difference between the OCXO frequency divided by 16 and GPS pulse per second output to a resolution of about 42ns. What I suggested effectively captures the same phase difference but divides the OCXO by 65536 and only has a resolution of 100ns. The OCXO division is just conceptual though as it comes from the 16 bit timer/counter overflow internal to the microcontroller so in practice, the timer/counter is arbitrary length with an interrupt about every 6.5ms doing the housekeeping for the extra bits. It directly measures the pulse per second period to a resolution of 100ns using the OCXO as a clock. If a 20 MHz OCXO was used (limited by the maximum clock frequency of the microcontroller), then the resolution would be 50ns. That is not how I plan on designing my own GPSDO which has taken a significant turn from what I posted about here some time ago but I have stopped discussing that until I have some results to share. On Thu, 6 Dec 2012 19:34:08 -0500, Bob Camp li...@rtty.us wrote: Hi Again, the math is pretty simple. A 16 bit capture running at a 1/4 clock is not going to get you very near a Shera. It's even further from the more modern enhanced Shera designs. Bob On Dec 6, 2012, at 6:59 PM, David davidwh...@gmail.com wrote: You can use the ATmega328 16 bit timer/counter in input capture mode to count the number of 10 MHz OCXO cycles per pulse per second period to a resolution of 100ns but there are some problems: The ATmega328 16 bit timer/counter external clock is limited to 1/4 of the CPU frequency with an asynchronous source so the 10 MHz OCXO would need to be divided down which would further limit performance and require an external divider. Modifying the Aruino board to use the 10 MHz OCXO in place of the CPU clock solves that problem. Then operating the counter/timer in input capture mode with the GPS pulse per second signal connected to the input capture pin would allow almost Shera like performance. The timing resolution would be 2.4 times lower (and not asynchronous) limiting performance over short time spans. On Thu, 6 Dec 2012 14:57:19 -0800, Chris Albertson albertson.ch...@gmail.com wrote: You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design On Thu, Dec 6, 2012 at 1:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don ___ time-nuts mailing 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 Alternatives
David, The NXP LPC932 processor series are very cheap and small, and we got very excited to see timers running at up to 32MHz internally if I remember correctly. Then setting up a test system we noted that the timer can capture with 32MHz resolution which is good enough for a low-cost GPSDO implementation, but that they gated the input pin through a flip-flop running at CPU core speed, which was around 6MHz if I remember correctly. DAA. So all that fast timer resolution goes out the door by gating the input pin instead of using non-gated inputs for the timer functions. It does work however, in the end we made that processor do the chores in our quite old and discontinued FireFox GPSDO circuit. TVB has some plots on his website for that unit I think, and its quite surprising what type of stability we achieved with that little 8 bit bugger back then. bye, Said In a message dated 12/6/2012 16:00:27 Pacific Standard Time, davidwh...@gmail.com writes: You can use the ATmega328 16 bit timer/counter in input capture mode to count the number of 10 MHz OCXO cycles per pulse per second period to a resolution of 100ns but there are some problems: The ATmega328 16 bit timer/counter external clock is limited to 1/4 of the CPU frequency with an asynchronous source so the 10 MHz OCXO would need to be divided down which would further limit performance and require an external divider. Modifying the Aruino board to use the 10 MHz OCXO in place of the CPU clock solves that problem. Then operating the counter/timer in input capture mode with the GPS pulse per second signal connected to the input capture pin would allow almost Shera like performance. The timing resolution would be 2.4 times lower (and not asynchronous) limiting performance over short time spans. ___ time-nuts mailing 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 Alternatives
There are lots of sampling ADCs which will support that type of operation directly or you can easily design and build a sampling phase detector but that all involves significant extra circuitry outside of the microcontroller. Take a look at the Racal Dana 1992 reference frequency multiplier option (the schematic is on page 7-33 of the service manual) for an example of a sampling phase detector used in a similar application. On Thu, 6 Dec 2012 16:43:26 -0800, Chris Albertson albertson.ch...@gmail.com wrote: What if the OCXO had a sine wave output and then you used the PPS leading edge to gate the sine wave to a sample and hold. then the sample is measured by the Arduino's ADC? I think(?) you get a 10-bit ADC or is it 8-bits. The problem is the required speed of the sample and hold, maybe not easy to build ___ time-nuts mailing 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 Alternatives
The ATmega328 apparently has something similar going on since the datasheet says that the maximum external asynchronous clock frequency is 1/4 of the CPU frequency. That is why I suggested synchronously clocking the CPU directly from the OCXO. Atmel's datasheet is annoyingly vague about some matters and I assume the capture input works like it should. I have also heard about many low cost ARM microcontrollers suffering from problems similar to the one you describe. Apparently the ones that use an asynchronous interface between the CPU and peripherals either have slow interfaces or suffer from some odd problems. It is not *that* difficult to get to 10ns using a 100Mhz phase locked clock (or even faster) in timer/counter applications using discrete logic support but in the case of GPSDO design, I believe better results can be obtained without so much brute force. I am one of those weirdos who likes ECL whether integrated or discrete. On Thu, 6 Dec 2012 20:22:58 -0500 (EST), saidj...@aol.com wrote: David, The NXP LPC932 processor series are very cheap and small, and we got very excited to see timers running at up to 32MHz internally if I remember correctly. Then setting up a test system we noted that the timer can capture with 32MHz resolution which is good enough for a low-cost GPSDO implementation, but that they gated the input pin through a flip-flop running at CPU core speed, which was around 6MHz if I remember correctly. DAA. So all that fast timer resolution goes out the door by gating the input pin instead of using non-gated inputs for the timer functions. It does work however, in the end we made that processor do the chores in our quite old and discontinued FireFox GPSDO circuit. TVB has some plots on his website for that unit I think, and its quite surprising what type of stability we achieved with that little 8 bit bugger back then. bye, Said In a message dated 12/6/2012 16:00:27 Pacific Standard Time, davidwh...@gmail.com writes: You can use the ATmega328 16 bit timer/counter in input capture mode to count the number of 10 MHz OCXO cycles per pulse per second period to a resolution of 100ns but there are some problems: The ATmega328 16 bit timer/counter external clock is limited to 1/4 of the CPU frequency with an asynchronous source so the 10 MHz OCXO would need to be divided down which would further limit performance and require an external divider. Modifying the Aruino board to use the 10 MHz OCXO in place of the CPU clock solves that problem. Then operating the counter/timer in input capture mode with the GPS pulse per second signal connected to the input capture pin would allow almost Shera like performance. The timing resolution would be 2.4 times lower (and not asynchronous) limiting performance over short time spans. ___ time-nuts mailing 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 Alternatives
Sorry. The Shera counter is 16 bits and not 12 bits but that does not change what I posted. On Thu, 06 Dec 2012 19:17:48 -0600, David davidwh...@gmail.com wrote: It is not a 16 bit capture and it does not run at 1/4 the clock rate. The Shera uses a 12 bit counter to capture the phase difference between the OCXO frequency divided by 16 and GPS pulse per second output to a resolution of about 42ns. What I suggested effectively captures the same phase difference but divides the OCXO by 65536 and only has a resolution of 100ns. The OCXO division is just conceptual though as it comes from the 16 bit timer/counter overflow internal to the microcontroller so in practice, the timer/counter is arbitrary length with an interrupt about every 6.5ms doing the housekeeping for the extra bits. It directly measures the pulse per second period to a resolution of 100ns using the OCXO as a clock. If a 20 MHz OCXO was used (limited by the maximum clock frequency of the microcontroller), then the resolution would be 50ns. That is not how I plan on designing my own GPSDO which has taken a significant turn from what I posted about here some time ago but I have stopped discussing that until I have some results to share. ___ time-nuts mailing 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 Alternatives
Chris: yes, dividing would have to be done. Doesn't TVB have a simple divider block? You don't really have to close the difference, just maintain it? Don L Chris Albertson You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design On Thu, Dec 6, 2012 at 1:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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. -- 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] GPSDO Alternatives
Hi The Shera counter is not running in the same fashion you would be running an input capture pin. Bob On Dec 6, 2012, at 8:45 PM, David davidwh...@gmail.com wrote: Sorry. The Shera counter is 16 bits and not 12 bits but that does not change what I posted. On Thu, 06 Dec 2012 19:17:48 -0600, David davidwh...@gmail.com wrote: It is not a 16 bit capture and it does not run at 1/4 the clock rate. The Shera uses a 12 bit counter to capture the phase difference between the OCXO frequency divided by 16 and GPS pulse per second output to a resolution of about 42ns. What I suggested effectively captures the same phase difference but divides the OCXO by 65536 and only has a resolution of 100ns. The OCXO division is just conceptual though as it comes from the 16 bit timer/counter overflow internal to the microcontroller so in practice, the timer/counter is arbitrary length with an interrupt about every 6.5ms doing the housekeeping for the extra bits. It directly measures the pulse per second period to a resolution of 100ns using the OCXO as a clock. If a 20 MHz OCXO was used (limited by the maximum clock frequency of the microcontroller), then the resolution would be 50ns. That is not how I plan on designing my own GPSDO which has taken a significant turn from what I posted about here some time ago but I have stopped discussing that until I have some results to share. ___ time-nuts mailing 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 Alternatives
Hi Unless you really want to go crazy with measuring very long delays, you do indeed want to align the pps from your OCXO with the pps from your GPS. Bob On Dec 6, 2012, at 8:48 PM, Don Latham d...@montana.com wrote: Chris: yes, dividing would have to be done. Doesn't TVB have a simple divider block? You don't really have to close the difference, just maintain it? Don L Chris Albertson You'd have to seriously divide down the output from the 10MHz OCXO if you were going to use it as an interrupt. Maybe to divide by 10,000? and even at the higher clock rate you'd still have poor resolution. I image each interrupt handler would sample some internal counter and the background task would look at the delta between the two and adjust the DAC to drive the OCXO to close the difference. The resolution would be (maybe?) a handful of clock cycles. Given enough time, say a 1000 second period it might wrk well enough. I can't know without doing a more detailed design On Thu, Dec 6, 2012 at 1:59 AM, Don Latham d...@montana.com wrote: Chris: The question I have again is about a simple phase detector. I did ask if the arduino interrupt ports could be used as a phase detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor work? I'm simply too new at this to decide. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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. -- 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] GPSDO Alternatives
Hi PSoC's are another attractive possibility that suffers from the same basic re-clock everything flaw. Lots of time down the drain there…. Bob On Dec 6, 2012, at 8:22 PM, saidj...@aol.com wrote: David, The NXP LPC932 processor series are very cheap and small, and we got very excited to see timers running at up to 32MHz internally if I remember correctly. Then setting up a test system we noted that the timer can capture with 32MHz resolution which is good enough for a low-cost GPSDO implementation, but that they gated the input pin through a flip-flop running at CPU core speed, which was around 6MHz if I remember correctly. DAA. So all that fast timer resolution goes out the door by gating the input pin instead of using non-gated inputs for the timer functions. It does work however, in the end we made that processor do the chores in our quite old and discontinued FireFox GPSDO circuit. TVB has some plots on his website for that unit I think, and its quite surprising what type of stability we achieved with that little 8 bit bugger back then. bye, Said In a message dated 12/6/2012 16:00:27 Pacific Standard Time, davidwh...@gmail.com writes: You can use the ATmega328 16 bit timer/counter in input capture mode to count the number of 10 MHz OCXO cycles per pulse per second period to a resolution of 100ns but there are some problems: The ATmega328 16 bit timer/counter external clock is limited to 1/4 of the CPU frequency with an asynchronous source so the 10 MHz OCXO would need to be divided down which would further limit performance and require an external divider. Modifying the Aruino board to use the 10 MHz OCXO in place of the CPU clock solves that problem. Then operating the counter/timer in input capture mode with the GPS pulse per second signal connected to the input capture pin would allow almost Shera like performance. The timing resolution would be 2.4 times lower (and not asynchronous) limiting performance over short time spans. ___ time-nuts mailing 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] GPSDO Alternatives
I think only TIMER2 on the AVR has the clk/4 limitation. The other timers can count at full speed.I know that I have counted at 8-12 MHz before... ___ time-nuts mailing 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 Alternatives
Hi If all you want is a something locked to a GPS: Take the pps from the GPS and hook it to an AD9548. You probably will need a 50 cent CPU to set up the registers. No muss, no fuss, nothing to invent or design. Weather it does what you need to do is an entirely different question. Without a defined objective / need / performance goal this could go on for a couple hundred years….. Bob On Dec 6, 2012, at 7:43 PM, Chris Albertson albertson.ch...@gmail.com wrote: What if the OCXO had a sine wave output and then you used the PPS leading edge to gate the sine wave to a sample and hold. then the sample is measured by the Arduino's ADC? I think(?) you get a 10-bit ADC or is it 8-bits. The problem is the required speed of the sample and hold, maybe not easy to build -- 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 mailing 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 Alternatives
Hi Here's another way to look at this: An hourglass full of sand (with some attention) and a cesium standard are both ways to answer the question what time is it?. Let's say you need a new $40,000 tube replacement in your 5371 and management asks what else can we do?. An hour glass is indeed a something else we can do. They both deliver an answer to the time of day question. Without defining what you actually *need* to do, they are both valid approaches. The problem comes when you look at the $40,000 repair charge and decide that building an hour glass is a lot cheaper. While that's true, it's far from the whole story. One way to quickly work some of this out is a simple swap proposition. Would anybody on the list trade their (working) cesium for my (working) hourglass? I'll pay shipping…. Bob On Dec 6, 2012, at 9:03 PM, Mark Sims hol...@hotmail.com wrote: I think only TIMER2 on the AVR has the clk/4 limitation. The other timers can count at full speed.I know that I have counted at 8-12 MHz before... ___ time-nuts mailing 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 Alternatives
The other timer on the ATmega328 lacks an input capture pin and register. I did not check all of the different AVR microcontrollers used in Arduinos. On Fri, 7 Dec 2012 02:03:39 +, Mark Sims hol...@hotmail.com wrote: I think only TIMER2 on the AVR has the clk/4 limitation. The other timers can count at full speed.I know that I have counted at 8-12 MHz before... ___ time-nuts mailing 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 Alternatives
Perhaps this is all coming full circle. As more experience herein shows use of the 1-pps from the gps module is valid, that opens the door to many more cheap GPS modules available than just a few that have 10 KHz also. Some of the low-cost GPS modules have the 1-pps associated with UTC (accurate), ...many do not. It depends on what their original purpose was. Many were used for 'cheap' navigation devices, ...not intended for timing. Accuracy is on the order 10 to even 100 microseconds. It then seems to me a simpler state machine, driven by the gps 1pps could be designed. It could run at 2hz and have 6-to-10 states, as many as needed. Need to get out the old Karnaugh map book. a.. Reset, open counter gate, count two seconds, close counter gate, load dac with overflow/underflow, switch dac output to EVC cap, start over. Don -- From: Chris Albertson albertson.ch...@gmail.com Sent: Thursday, December 06, 2012 6:30 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives On Thu, Dec 6, 2012 at 4:09 PM, dlewis6767 dlewis6...@austin.rr.com wrote: could you not add just a little 'glue' outside the uP to relieve it a tad. Let the GPS' 1pps gate some ttl counters and then read for overflow or underflow after xxx seconds. Have the uP determine dac correction setting back to the TXCO. That is why my first post was to ask What is the simplest phase defector that can work? I think you only need a one-bit counter. A flip-flop will do that. The FF is a classic phase detector used in many PLL -- 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 mailing 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] STM32 based thing (was GPSDO Alternatives)
On 12/6/2012 4:26 AM, Fabio Eboli wrote: Here are the design documents, if you're curious: http://hg.partiallystapled.com/circuits/serafine/raw-file/d75ab09ca163/out/production.PDF Thank you very much, I will study it with interest, it will be very helpul to see what you have done. Can I ask you more details? I didnt's understand how you are using the timers: are you timestamping each pps transistion using the internal clock? Are you using the pll to obtain 72MHz (x9) for the clock? Yes, the crystal oscillator is multiplied up to 72MHz which then drives the timer. Even though the particular timer peripheral I chose happens to be on the APB1 bus which is restricted to 36MHz, the timer itself is still fed with the 72MHz clock. Both PPS signals (generated from OCXO and received from GPS) are then independently timestamped. The timestamps are extended to 64 bits by adding the value captured from the IC to an epoch variable that is incremented every time the timer itself rolls over. This works fairly well but my implementation is slightly buggy, occasionally the timestamps will be off by an epoch (plus or minus 65536 ticks) but such a large deviation is easily detectable and is discarded. The timestamps are subtracted to get phase difference which is then fed into the proportional-integral controller which seeks to zero the phase difference, with two different speeds for early startup and later settling once the oscillations dampen. This last part is the bit that needs major work since the phase difference continues oscillating by up to 5 ticks (72MHz periods) and sometimes has excursions to 10 or 15 before it settles down again. NTPns seems to be self-tuning which could help a great deal. The coefficients I'm using are experimentally determined which is probably why the settling isn't very good. There's also the problem of not currently having a TIC or similar equipment for quantifying the performance of the system as a whole, I should buy or build one sooner rather than later. ___ time-nuts mailing 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 Alternatives
If you had an Ikepod, I might be interested. http://www.ablogtowatch.com/ikepod-hourglass-time-for-art/ http://www.hodinkee.com/blog/2011/3/29/the-ikepod-hourglass-by-marc-newson-q uite-possibly-the-coole.html http://www.ikepod.com/ Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Thursday, December 06, 2012 18:23 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Hi Here's another way to look at this: An hourglass full of sand (with some attention) and a cesium standard are both ways to answer the question what time is it?. Let's say you need a new $40,000 tube replacement in your 5371 and management asks what else can we do?. An hour glass is indeed a something else we can do. They both deliver an answer to the time of day question. Without defining what you actually *need* to do, they are both valid approaches. The problem comes when you look at the $40,000 repair charge and decide that building an hour glass is a lot cheaper. While that's true, it's far from the whole story. One way to quickly work some of this out is a simple swap proposition. Would anybody on the list trade their (working) cesium for my (working) hourglass? I'll pay shipping.. Bob On Dec 6, 2012, at 9:03 PM, Mark Sims hol...@hotmail.com wrote: I think only TIMER2 on the AVR has the clk/4 limitation. The other timers can count at full speed.I know that I have counted at 8-12 MHz before... ___ time-nuts mailing 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 Alternatives
saidj...@aol.com said: Then setting up a test system we noted that the timer can capture with 32MHz resolution which is good enough for a low-cost GPSDO implementation, but that they gated the input pin through a flip-flop running at CPU core speed, which was around 6MHz if I remember correctly. davidwh...@gmail.com said: The ATmega328 apparently has something similar going on since the datasheet says that the maximum external asynchronous clock frequency is 1/4 of the CPU frequency. That is why I suggested synchronously clocking the CPU directly from the OCXO. Atmel's datasheet is annoyingly vague about some matters and I assume the capture input works like it should. You have to do something appropriate when multiple clocks are involved or you get metastability issues. I think the 1/4 limit is to allow the external pin to be used to clock the counter. If you run the external signal through the standard pair of FFs to get a signal that is synchronous to your clock, 1/4 guarantees that you will see all transitions. At 1/2, with the duty cycle slightly off 50-50, you might end up with hanging-bridge type cases where the output of the synchronizer always sees the same level. Actually, metastability is hard to hit. Most metastability issues are really just setup/hold bugs. davidwh...@gmail.com said: I have also heard about many low cost ARM microcontrollers suffering from problems similar to the one you describe. Apparently the ones that use an asynchronous interface between the CPU and peripherals either have slow interfaces or suffer from some odd problems. Bingo. Many years ago, I found that sort of bug in an ARM chip. I forget which one. It needed 2 crystals, one at 32 KHz and one at xx MHz. The CPU could run at 32 KHz, or PLLed to the fast crystal, or sleep. While running at 32 KHz, it could turn on the fast osc and setup the PLL. Reading the 32 KHz counter while running off the fast crystal would occasionally get bogus results. -- 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] Discussion of precise time and frequency measurement
I'm doing some things of that order with the LPC1114. The board for the project will be back from fab in a few days. If it works out well I have a frequency/period counter designed around that chip. About $20 in parts. Not counting the TCVCXO. Add in a case, I/O and power supply plus a display and you are still well under $100. The counter is probably 3 months away due to software. What I lack is a front end design good to 200 MHz. You can buy counter chips guaranteed to 150 MHz for well under a buck. And there is a 74PYT74 (PYT = pick your technology - 74LVC1G74 is one) that guarantees 200 MHz (@5V - 280MHz typ @3.3V) . But I like having the enable part of the counter chip. It simplifies things. BTW the 150 MHz chip typicals at 200 MHz. I have done some things to speed it up - like lower the capacitive load with 10K resistors. Only Q3 of the input counter needs direct connection to the input of the next counter. So the capacitive load of Q0, Q1, and Q2 will be well under the 15 pF (or 50pF) where the testing is done. Q3 should be lower than 15 pF. All that will gain some MHz. Also running the chips a little hot: 3.4 V The LPC1114 has two 32 bit counters. I add 4 or 8 bits outboard to get from about a 20 MHz max count rate to 150MHz. I'm using the second '1114 counter as a 32 bit match counter to make up the time intervals. i.e. Match on 2 to start the count. Match on 50,000,0002 to stop the count. I use the 200MHz 74xxx74 as an RS F/F to control the counter enable. I'm running the '1114 chip at 50MHz from a clock that originates from a TCVCXO - 40MHz /4 . This also allows the use of external 10MHz sources. And of course there is capture for period. There is a one cycle delay (20ns) for edge recognition in the counter mode. This may or may not be a problem. The counter will have a board available for those of you into building. But that is down the road a ways. Where this could come in really handy is if you need a bunch of counters for a project. The counter will have a Serial interface that can be accessed with an RS-232 adapter or a USB adapter. Plus I2C. The poor man's IEEE488 bus. And a USB to I2C controller board for the PC side. All of the above is currently in development (boards on hand or on order) with some of the projects already on the 2nd turn so development is well along. This is not a pipe dream. But it is taking longer and costing more than I'd expected. (Doesn't It Always?) I also bring out PCLK to a test point so measurements of the chip's PLL could be done by those interested. Simon == Date: Thu, 6 Dec 2012 18:55:13 -0500 From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Message-ID: c851493c-c77b-41b9-a7df-3d3f89c91...@rtty.us Content-Type: text/plain; charset=us-ascii Hi To be useful, you need an input capture that: 1) Runs at a fast enough clock (1 GHz would be nice) 2) Has enough bits to get to 1 pps (say 32 bits) 3) Has a built in period set, so the hardware works without a lot of silly stuff Often you find parts that will do some of the above, but not all. 16 bit captures running off of a few MHz clock are pretty common. Some (but not all) ARM's have 32 bit captures that run off of 10's of MHz clocks and have the ability to set the period. Bob Engineering is the art of making what you want from what you can get at a profit. ___ time-nuts mailing 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 Alternatives
li...@rtty.us said: That would be an input capture rather than an interrupt. Thanks. Yes, that's the term I was trying to remember. li...@rtty.us said: To be useful, you need an input capture that: 1) Runs at a fast enough clock (1 GHz would be nice) 2) Has enough bits to get to 1 pps (say 32 bits) 3) Has a built in period set, so the hardware works without a lot of silly stuff What do you mean by period set? (I did a bit of googling, but didn't hit anything close to pay dirt.) My expectation is that the counter/timer just counts on the local/CPU clock or some sub-multiple of that. When the external signal makes a low-to-high transition, the value in the counter is copied into a holding register and sets a status bit that may generate an interrupt. The counter just keeps counting through overflows and such. -- The enough-bits from [2] above can be partially implemented in software. When the counter overflows, it sets a status bit and maybe generates an interrupt. The software keeps the high bits in memory. When it sees that status bit, it bumps that counter. Getting everything right is not simple. There is a standard recipe for reading a hardware counter that lives in two registers. You read high, low, high. If the two high readings match, the answer is (either) high and low. If not, try again. Some hardware supports a hack to latch the high when you read the low. -- 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 Alternatives
The output from a OCXO is divided down and then the phase of the divided down 10MHz RF is compared to the PPS and you don't need to even know the how far apart they are. All you need to know is led or lag just a one bit answer. An XOR gate or a flip flop can tell you that. Does a 1 bit A/D work? Is there a good web page discussing this aspect? Am I just confused?What question should I be asking? ... Can somebody give me a circuit or (pseudo) code so I can simulate things? I'm far from a PLL wizard. I think the catch in this case is that the EFC controls the frequency and what you are measuring is the phase, the integral of the frequency. Suppose you just implement a simple bang-bang control. Suppose the EFC is 1 volt and the frequency is correct but the GPSDO phase is a bit early relative to the GPS PPS. So the FF says early and the software says go-faster. That keeps happening for a while, the frequency keeps getting faster and faster. Finally, the GPSDO PPS catches up with the GPS PPS, but now it's frequency is way fast. The FF says go slower, so the control software starts dropping the EFC. But the frequency is still way too high so the error is still increasing. After a while the frequency gets low enough so the PPS/phase error starts catching up. Eventually the PPS error crosses over, but by then the frequency offset is way way low. ... Isn't that cyclic pattern stable? Is there a simple tweak to break that loop? Do you first have to recognize that you are in that mode? If so, how? ... I might be able to do fix that in software by looking at the times when things change state. Suppose it's 193 seconds between the first early and the last early and that the EFC went from X to Y. I think that's enough info to work out the crossover point and work back to the desired EFC. But that all sounds too complicated. What would hardware-only guys do with a 1 bit A/D? -- 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 Alternatives
Hello, metastability is not an issue in this type of application, nor can it be avoided since we have two different clock domains. It would only shift the capture point by one counter clock cycle back or forth if the edge happens right on the transition point. At that point we have 50% uncertainty where it should fall anyway's, so the best one could do is switch back and forth between the two counter values creating an average of half way between these two counter points! Also the GPS sawtooth will create enough jitter on the capture pin to avoid staying in metastability for more than one pulse. Metastability is an issue for applications that need to be bit-accurate, such as trying to capture a serial datastream etc. A 1PPS capture application in a GPSDO is not a bit-accurate affair, it is a heavily averaged (low pass filtered) system so statistics kick in. The real problem of the LPC932 capture system is that the resolution goes from 33ns on the counter to something around 200ns because of the pin clocking the input FF at 5MHz... its a waste of possible resolution on that chip. 200ns is quite a low resolution for a GPSDO, but there are ways to improve this resolution through dithering for example. bye, Said In a message dated 12/6/2012 20:35:35 Pacific Standard Time, hmur...@megapathdsl.net writes: saidj...@aol.com said: Then setting up a test system we noted that the timer can capture with 32MHz resolution which is good enough for a low-cost GPSDO implementation, but that they gated the input pin through a flip-flop running at CPU core speed, which was around 6MHz if I remember correctly. davidwh...@gmail.com said: The ATmega328 apparently has something similar going on since the datasheet says that the maximum external asynchronous clock frequency is 1/4 of the CPU frequency. That is why I suggested synchronously clocking the CPU directly from the OCXO. Atmel's datasheet is annoyingly vague about some matters and I assume the capture input works like it should. You have to do something appropriate when multiple clocks are involved or you get metastability issues. I think the 1/4 limit is to allow the external pin to be used to clock the counter. If you run the external signal through the standard pair of FFs to get a signal that is synchronous to your clock, 1/4 guarantees that you will see all transitions. At 1/2, with the duty cycle slightly off 50-50, you might end up with hanging-bridge type cases where the output of the synchronizer always sees the same level. Actually, metastability is hard to hit. Most metastability issues are really just setup/hold bugs. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Alternatives
Good thought, Bob. AD9548 $27, eval board a whopping $250, get a thunderbolt :-). The eval board has a lot of SMA's on it... Don L Bob Camp Hi If all you want is a something locked to a GPS: Take the pps from the GPS and hook it to an AD9548. You probably will need a 50 cent CPU to set up the registers. No muss, no fuss, nothing to invent or design. Weather it does what you need to do is an entirely different question. Without a defined objective / need / performance goal this could go on for a couple hundred years .. Bob On Dec 6, 2012, at 7:43 PM, Chris Albertson albertson.ch...@gmail.com wrote: What if the OCXO had a sine wave output and then you used the PPS leading edge to gate the sine wave to a sample and hold. then the sample is measured by the Arduino's ADC? I think(?) you get a 10-bit ADC or is it 8-bits. The problem is the required speed of the sample and hold, maybe not easy to build -- 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 mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] ANN: UK MSF 60 KHz shut-down on 13 December 2012 from 10:00 to 14:00 UTC
Folk, I have received the following announcement: + Notice of Interruption MSF 60 kHz Time and Frequency Signal The MSF 60 kHz time and frequency signal broadcast from Anthorn Radio Station will be shut down on Thursday 13 December 2012 from 10:00 to 14:00 UTC The interruption to the transmission is required to allow maintenance work to be carried out in safety. http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/msf-outages + 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.
