Re: [time-nuts] GPSDO Alternatives
Hi To make things play nice, you would like to have the timer counters reset at a specified point. That way the math all works out nicely. Bob On Dec 7, 2012, at 12:18 AM, Hal Murray hmur...@megapathdsl.net wrote: 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. ___ time-nuts mailing 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 You are driving an integrator (the OCXO). You want a very stable voltage on the EFC to get the loop to close. A PWM is as simple a model for a 1 bit D/A as any. One bit A/D's are a feedback on a 1 bit D/A. You do some stuff to move the noise around and to get it all to work. Bob On Dec 7, 2012, at 2:12 AM, Hal Murray hmur...@megapathdsl.net wrote: 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. ___ time-nuts mailing 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 In this case it's very much a you get what you pay for sort of thing. You are indeed comparing an hourglass to a cesium standard. Bob On Dec 7, 2012, at 2:20 AM, Don Latham d...@montana.com wrote: 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 mailing 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 an impressive hourglass. In the context of the thought experiment swap offer - no, mine is not a work of art. It's only value is as a time keeper. Bob On Dec 6, 2012, at 10:37 PM, DaveH i...@blackmountainforge.com wrote: 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. ___ time-nuts mailing 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 1:56 PM, Bob Camp wrote: 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 Of course, the process of experimenting and trying to duplicate the Tbolt is fairly educational. It touches a lot of interesting areas in RF design and metrology, as well as software algorithms. One might do it for the same reason that someone builds a fusor in their garage. There are easier ways to get neutrons, but building a fusor is a nice combination of learning about high vacuum, high voltage, nuclear physics and metrology, etc. Both are a heck of a lot cheaper than building and flying a CubeSat, for instance. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Alternatives
On 12/6/12 11:12 PM, Hal Murray wrote: 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? ... yes.. what you've described is essentially a first order control loop. You can add higher order terms (e.g. integral or derivative) so that you don't get overshoot. 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. Yes.. that's another approach.. you figure out what the model is, and solve backwards. But that all sounds too complicated. What would hardware-only guys do with a 1 bit A/D? ___ time-nuts mailing 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 (GLUE)
On 12/6/12 5:01 PM, Bob Camp wrote: 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. I think that's the interesting aspect of this discussion (because it mirrors many similar such discussions I've had over the years).. The challenge is not in building a GPSDO.. there's tons of ways to do that at minimal hardware cost.. The challenge is how do you do it without using any additional glue logic or hardware That is, given things you can buy off the shelf, and no hardware work other than fabricating cables or soldering a wire or two, what can you do inexpensively. ___ time-nuts mailing 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 11:20 PM, Don Latham wrote: Good thought, Bob. AD9548 $27, eval board a whopping $250, get a thunderbolt :-). The eval board has a lot of SMA's on it... This is a general problem with eval boards these days.. They provide a lot of functionality on the board to make it easy to evaluate the chip (USB interfaces, buffer memories, etc.) but that makes it hard to use the eval board as a sort of glorified chip carrier. For instance, all those nice serial interface ADC and DAC parts.. it would be nice to have a little board with the converter, power supply filtering and maybe an opamp buffer, and bring the serial interface pins to the edge where you could just wire it to something like a PIC eval board or Arduino or parallel printer port. But no.. they have a weird connector that goes to a mother board with a fancy preprogrammed micro and dual port memory and stuff.. all so you can just hook up a signal generator and capture samples to run FFTs to duplicate the databook graphs. ___ time-nuts mailing 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 (GLUE)
Jim right on target for my 2 cents, Simple is often hard. Regards Paul WB8TSL On Fri, Dec 7, 2012 at 10:12 AM, Jim Lux jim...@earthlink.net wrote: On 12/6/12 5:01 PM, Bob Camp wrote: 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. I think that's the interesting aspect of this discussion (because it mirrors many similar such discussions I've had over the years).. The challenge is not in building a GPSDO.. there's tons of ways to do that at minimal hardware cost.. The challenge is how do you do it without using any additional glue logic or hardware That is, given things you can buy off the shelf, and no hardware work other than fabricating cables or soldering a wire or two, what can you do inexpensively. __**_ 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. ___ time-nuts mailing 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 Without some qualifier on how good, we all will be talking about hourglasses and cesium standards at the same time. That makes sorting things out a bit difficult. It may get you into building a controlled hourglass that's less accurate than a free running $10 wrist watch. So far the only suggestion of a how good has been TBolt performance. At least that's how this started out. Building a cpu only GPSDO can be done with a big enough chip. If you are limited to clip leads to wire it up, the cost advantage over a TBolt may not be there. That makes the issue of significant performance loss a very real issue. -- Just as surplus deals on TBolts come and go, so do deals on OCXO's and GPS's. Do I price the OCXO at the $13 that I once saw it for, or the $70 that they sell for today? Is the GPS in the junk box (that I paid $200 for) free because it's sitting there? Let's not even wonder if any of the stuff works... For the sake of moving this forward, I'll suggest that half the fair cost of a (working) TBolt is the OCXO and the GPS. Put another way, your $200 (or what ever) is split $100 for the OCXO plus GPS and $100 for: 1) The nice shielded case it's all in 2) The connectors 3) The onboard power regulation and filtering 4) The communications in and out of it 5) The 10 MHz and PPS buffering and generation 6) The PC board it's all built on 7) Putting it all together 8) Programming all the parts in there 9) Testing it and troubleshooting it 10) The smarts to get it to do what it does I'm sure we could spend at least a year splitting hairs on that division of costs :) To win the hourglass vs cesium fair trade proposition you need to come up with a gizmo that: 1) Does 1-10 above 2) Works with just a GPS and OCXO added. 3) Costs less than $100 4) Works as well as a TBolt 5) Has a Lady Heather like monitor program to go with it For the sake of eliminating crazy GPS cards. Let's say you also need a source where we can buy both the OCXO and GPS used for less than $100. If you want to factor in lower performance, I'll grant a waver for the fact that you can average multiple gizmos and the result will get better by the square root of the number of gizmos. If it's half as good as a $200 TBolt it needs to be 1/4 the price. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Friday, December 07, 2012 10:13 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives (GLUE) On 12/6/12 5:01 PM, Bob Camp wrote: 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. I think that's the interesting aspect of this discussion (because it mirrors many similar such discussions I've had over the years).. The challenge is not in building a GPSDO.. there's tons of ways to do that at minimal hardware cost.. The challenge is how do you do it without using any additional glue logic or hardware That is, given things you can buy off the shelf, and no hardware work other than fabricating cables or soldering a wire or two, what can you do inexpensively. ___ time-nuts mailing 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
And then it becomes popular and guess what happens to the price? Tom - Original Message - From: Bob Camp li...@rtty.us To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Friday, December 07, 2012 12:15 PM Subject: Re: [time-nuts] GPSDO Alternatives To win the hourglass vs cesium fair trade proposition you need to come up with a gizmo that: 1) Does 1-10 above 2) Works with just a GPS and OCXO added. 3) Costs less than $100 4) Works as well as a TBolt 5) Has a Lady Heather like monitor program to go with it For the sake of eliminating crazy GPS cards. Let's say you also need a source where we can buy both the OCXO and GPS used for less than $100. If you want to factor in lower performance, I'll grant a waver for the fact that you can average multiple gizmos and the result will get better by the square root of the number of gizmos. If it's half as good as a $200 TBolt it needs to be 1/4 the price. Bob ___ time-nuts mailing 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
but we could use a less expensive one. a simple light interruptor senses the end of flow, a robust servo turns over the hourglass for the next cycle. our favorite arduino counts seconds from the gps, and adjusts the turnover appropriately. If magnetite sand is used, an external magnetic field can provide rate correction for phase control rather than frequency control? A smaller version would generate the perfect 3 minute egg. o gosh maybe this thread is petering out in my head don L Bob Camp Hi That is an impressive hourglass. In the context of the thought experiment swap offer - no, mine is not a work of art. It's only value is as a time keeper. Bob On Dec 6, 2012, at 10:37 PM, DaveH i...@blackmountainforge.com wrote: 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. ___ time-nuts mailing 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
Bob Yes would agree these are the attributes of a solution thats interesting. Numbers of folks have created solutions over the years. But the reference architecture should be as good as or better then the tried and true tool we have like the HP 38XX or Tbolt. Otherwise is just another GPSDO. Regards Paul WB8TSL On Fri, Dec 7, 2012 at 12:15 PM, Bob Camp li...@rtty.us wrote: Hi Without some qualifier on how good, we all will be talking about hourglasses and cesium standards at the same time. That makes sorting things out a bit difficult. It may get you into building a controlled hourglass that's less accurate than a free running $10 wrist watch. So far the only suggestion of a how good has been TBolt performance. At least that's how this started out. Building a cpu only GPSDO can be done with a big enough chip. If you are limited to clip leads to wire it up, the cost advantage over a TBolt may not be there. That makes the issue of significant performance loss a very real issue. -- Just as surplus deals on TBolts come and go, so do deals on OCXO's and GPS's. Do I price the OCXO at the $13 that I once saw it for, or the $70 that they sell for today? Is the GPS in the junk box (that I paid $200 for) free because it's sitting there? Let's not even wonder if any of the stuff works... For the sake of moving this forward, I'll suggest that half the fair cost of a (working) TBolt is the OCXO and the GPS. Put another way, your $200 (or what ever) is split $100 for the OCXO plus GPS and $100 for: 1) The nice shielded case it's all in 2) The connectors 3) The onboard power regulation and filtering 4) The communications in and out of it 5) The 10 MHz and PPS buffering and generation 6) The PC board it's all built on 7) Putting it all together 8) Programming all the parts in there 9) Testing it and troubleshooting it 10) The smarts to get it to do what it does I'm sure we could spend at least a year splitting hairs on that division of costs :) To win the hourglass vs cesium fair trade proposition you need to come up with a gizmo that: 1) Does 1-10 above 2) Works with just a GPS and OCXO added. 3) Costs less than $100 4) Works as well as a TBolt 5) Has a Lady Heather like monitor program to go with it For the sake of eliminating crazy GPS cards. Let's say you also need a source where we can buy both the OCXO and GPS used for less than $100. If you want to factor in lower performance, I'll grant a waver for the fact that you can average multiple gizmos and the result will get better by the square root of the number of gizmos. If it's half as good as a $200 TBolt it needs to be 1/4 the price. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Friday, December 07, 2012 10:13 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives (GLUE) On 12/6/12 5:01 PM, Bob Camp wrote: 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. I think that's the interesting aspect of this discussion (because it mirrors many similar such discussions I've had over the years).. The challenge is not in building a GPSDO.. there's tons of ways to do that at minimal hardware cost.. The challenge is how do you do it without using any additional glue logic or hardware That is, given things you can buy off the shelf, and no hardware work other than fabricating cables or soldering a wire or two, what can you do inexpensively. ___ time-nuts mailing 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 At least one should compare similar to better than approaches. This is a multi year design. Pick a goal first, then try to fit a specific approach to the goal. If the approach makes sense, move on with the design. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Friday, December 07, 2012 1:38 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Bob Yes would agree these are the attributes of a solution thats interesting. Numbers of folks have created solutions over the years. But the reference architecture should be as good as or better then the tried and true tool we have like the HP 38XX or Tbolt. Otherwise is just another GPSDO. Regards Paul WB8TSL On Fri, Dec 7, 2012 at 12:15 PM, Bob Camp li...@rtty.us wrote: Hi Without some qualifier on how good, we all will be talking about hourglasses and cesium standards at the same time. That makes sorting things out a bit difficult. It may get you into building a controlled hourglass that's less accurate than a free running $10 wrist watch. So far the only suggestion of a how good has been TBolt performance. At least that's how this started out. Building a cpu only GPSDO can be done with a big enough chip. If you are limited to clip leads to wire it up, the cost advantage over a TBolt may not be there. That makes the issue of significant performance loss a very real issue. -- Just as surplus deals on TBolts come and go, so do deals on OCXO's and GPS's. Do I price the OCXO at the $13 that I once saw it for, or the $70 that they sell for today? Is the GPS in the junk box (that I paid $200 for) free because it's sitting there? Let's not even wonder if any of the stuff works... For the sake of moving this forward, I'll suggest that half the fair cost of a (working) TBolt is the OCXO and the GPS. Put another way, your $200 (or what ever) is split $100 for the OCXO plus GPS and $100 for: 1) The nice shielded case it's all in 2) The connectors 3) The onboard power regulation and filtering 4) The communications in and out of it 5) The 10 MHz and PPS buffering and generation 6) The PC board it's all built on 7) Putting it all together 8) Programming all the parts in there 9) Testing it and troubleshooting it 10) The smarts to get it to do what it does I'm sure we could spend at least a year splitting hairs on that division of costs :) To win the hourglass vs cesium fair trade proposition you need to come up with a gizmo that: 1) Does 1-10 above 2) Works with just a GPS and OCXO added. 3) Costs less than $100 4) Works as well as a TBolt 5) Has a Lady Heather like monitor program to go with it For the sake of eliminating crazy GPS cards. Let's say you also need a source where we can buy both the OCXO and GPS used for less than $100. If you want to factor in lower performance, I'll grant a waver for the fact that you can average multiple gizmos and the result will get better by the square root of the number of gizmos. If it's half as good as a $200 TBolt it needs to be 1/4 the price. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Friday, December 07, 2012 10:13 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives (GLUE) On 12/6/12 5:01 PM, Bob Camp wrote: 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. I think that's the interesting aspect of this discussion (because it mirrors many similar such discussions I've had over the years).. The challenge is not in building a GPSDO.. there's tons of ways to do that at minimal hardware cost.. The challenge is how do you do it without using any additional glue logic or hardware That is, given things you can buy off the shelf, and no hardware work other than fabricating cables or soldering a wire or two, what can you do inexpensively. ___ time-nuts mailing 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
Re: [time-nuts] GPSDO Alternatives
John wrote: 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. I agree, but I didn't dare to dream so large when I 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. At bottom, any such testing requires (i) a comparison standard at least as good (and hopefully at least somewhat better) than the DUT at all taus and offsets (which may, in reality, be several standards, each doing part of that job), (ii) a reliable TIC (and, potentially usefully, frequency counter) that can exploit the stability of the comparison standard, and (iii) the capability to process the raw data to produce meaningful information. [Additionally, to characterize poor-signal behavior one would presumably use attenuators and a well-situated antenna. Some may not have good antenna sites to begin with, and in any case, it would be hard to standardize the signal strength between locations.] My thoughts were (1) for many (most?) of the people who would want to build a DIY GPSDO, it would likely be their first really good standard, and therefore their best; and (2) the range of TICs/frequency counters owned by the target base is so wide, and covers such a large range of capabilities (to say nothing of whether any given counter is in good repair and being used to best advantage), that obtaining comparable results from one amateur lab to another would be just as much if not more dependent on the individual counters involved than on the GPSDOs under test. However, that is no reason not to push forward with standardized measurement protocols, which would focus all of us on what the relevant desiderata are and how to measure them. 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 - Bert's boards
Hello Bert, The boards look nice but tell me nothing of the circuitry. How about sending the schematics ?? That way I can appreciate what it is that you have. BillWB6BNQ p.s. By the way, what ever happen with that DMTD you were going to produce about three years ago ? ewkeh...@aol.com wrote: Attached is my latest ExpresPCB layout of a GPSDO. A clear understanding of the GPS limitations, a goal as to what I want to control ,focus on attainability, reproducibility KISS, cost and tests of partials on development boards and what you see if you download the ExpessPCB software is on the right the saw tooth correction, in the middle the analog board with opto isolation to prevent ground loop and on the right the actual GPSDO. This particular unit also allows you to link a 20 Hz offset FRS-C (part of my dual mixer) to my house reference. Total material cost depending how many boards one buys is below $ 40. I will include this particular board along with other designs on my next order and subsequently cut with a sheer. The board on the right could be used by itself with minor modifications to directly drive a FE 5680 if some one would step up to the task. Total cost below $ 15. I use the analog board, which by the way is the most expensive since it has a LTC 1655 and REF 02. No dither 16 bits, dither 18 bits and depending on loop time, clock frequency range starting at 3 E-9 and resolution up to 6 E-16. Again I am only interested in to controlling a Rb which gives me way more flexibility, the Rb's are either modified with a 10811 or in one case with the M1000 and in the case of the FE 5680 a MV89 with a separate analog loop. And in all cases the RB is temperature controlled. All this based on over 10 years of work with the Shera controller, exclusively controlling Rb's. Bert Kehren One more thought you may want to look at a 1 $ gate array for all your timing issues. Simplifies the work dramatically. With the long loop times associated with Rb and high sample rate, 100 psec. are no problem. Name: Shera 3 board.pcb Shera 3 board.pcbType: PCB Wizard Document (application/x-unknown-content-type-PCBWizard.Document) Encoding: base64 ___ time-nuts mailing 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
On Fri, 07 Dec 2012 17:50:55 -0500, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: John wrote: 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. I agree, but I didn't dare to dream so large when I 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. At bottom, any such testing requires (i) a comparison standard at least as good (and hopefully at least somewhat better) than the DUT at all taus and offsets (which may, in reality, be several standards, each doing part of that job), (ii) a reliable TIC (and, potentially usefully, frequency counter) that can exploit the stability of the comparison standard, and (iii) the capability to process the raw data to produce meaningful information. [Additionally, to characterize poor-signal behavior one would presumably use attenuators and a well-situated antenna. Some may not have good antenna sites to begin with, and in any case, it would be hard to standardize the signal strength between locations.] My thoughts were (1) for many (most?) of the people who would want to build a DIY GPSDO, it would likely be their first really good standard, and therefore their best; and (2) the range of TICs/frequency counters owned by the target base is so wide, and covers such a large range of capabilities (to say nothing of whether any given counter is in good repair and being used to best advantage), that obtaining comparable results from one amateur lab to another would be just as much if not more dependent on the individual counters involved than on the GPSDOs under test. However, that is no reason not to push forward with standardized measurement protocols, which would focus all of us on what the relevant desiderata are and how to measure them. For myself: 1. My current lack a comparison standard is the reason I would design and build a GPSDO. At best I might buy a used rubidium oscillator at some point. People talk about good deals on Thunderbolts but I have yet to see one. It seems peak Thunderbolt passed before I was seriously looking. 2. So far my best universal counter is a rebuilt Racal Dana 1992 with a TCXO but it lacks GPIB. It might be easier and cheaper for me to duplicate my GPSDO phase detector and add a counter chain and trigger so it can make and report its own time interval measurements against a secondary asynchronous source but that would hardly be reproducible by a third party. 3. I am less interested in this since I will be at the mercy of whatever timing GPS I use and my current antenna environment. ___ time-nuts mailing 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] 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] 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] 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] 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] 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] 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] 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] 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.
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 https://www.febo.com/cgi-bin/mailman/listinfo/time
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
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
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
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] 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] 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] 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.
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.
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] 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.
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.
Re: [time-nuts] GPSDO Alternatives
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. 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.
Re: [time-nuts] GPSDO Alternatives
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 In a message dated 12/4/2012 9:06:26 P.M. Eastern Standard Time, albertson.ch...@gmail.com writes: With the price of T-Bolts now higher, does it make sense to build your own GPSDO? 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. 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. If ther phase detector where simple enough it could be build on a prototype board the fits on top of the Arduino. There are some other designs but because programming a uP and making a PCB seem to be rare skills that job tends to fall on one person. Anyone can program an Arduino and with out need of a PCB the entire design could be puted on a web page and the replicated with common parts. On Tue, Dec 4, 2012 at 4:01 PM, Bob Camp li...@rtty.us wrote: Hi I would guess that HP/Agilent/Symmetricom and Trimble made 100X more GPSDO's than the next five people in the business combined over the 1995 to 2005 period. Bob On Dec 4, 2012, at 10:26 AM, paul swed paulsw...@gmail.com wrote: Al I like the truetime products. In general easy to understand and last a long time. But there never seemed to be that many. Sure they were used in broadcasting and maybe power. But the others like the 3801 and tbolt were used in telco and mobile apps so there were 10,000s turned out and thats why we get them for cheap. I simply never see the truetime dc60 or gps units around. Though I have my stock of dc468 sat clocks. :-) Working. I hacked a goes sat replacement 3-4 years ago. That said some of the older gps technology is a bit slippery on exactly how good they are. So for perhaps amateur purposes they are totally fine but when you start comparing to a Tbolt or 3801 various behaviors apear. Odetics GPStars as an example slip cycles on purpose. Its a mode you can set and by default is how they are set. For what they were intended for they are perfect. But at least 1 X10 poorer then other devices. Its not at all broken. It was a general time piece for radio networks. Give or take 500 ms. Regards Paul WB8TSL On Tue, Dec 4, 2012 at 9:58 AM, Al Wolfe alw.k...@gmail.com wrote: Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc, but I have never seen anyone mention the TrueTime XL-AK. It advertises 40 nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work well but have no way to test it against anything else yet. It has four each 10 MHz sine output that I have been using for house sync for HP3586, HP8924c, PTS160, etc. So how does the TrueTime compare to other GPSDO's? Al, K9SI __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nuts 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. ___ time-nuts mailing 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 Does the synchronous filter on the PWM still have a sample and hold in it, or has somebody come up with a different approach? Bob On Dec 5, 2012, at 3:06 AM, Bruce Griffiths bruce.griffi...@xtra.co.nz 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. 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.
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.html 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.
Re: [time-nuts] GPSDO Alternatives
A low noise sample and hold is still required. Bruce Bob Camp wrote: Hi Does the synchronous filter on the PWM still have a sample and hold in it, or has somebody come up with a different approach? Bob On Dec 5, 2012, at 3:06 AM, Bruce Griffithsbruce.griffi...@xtra.co.nz 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. 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.
Re: [time-nuts] GPSDO Alternatives
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.
Re: [time-nuts] GPSDO Alternatives
Hi I was hoping somebody had worked out a way around that. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: Wednesday, December 05, 2012 12:27 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives A low noise sample and hold is still required. Bruce Bob Camp wrote: Hi Does the synchronous filter on the PWM still have a sample and hold in it, or has somebody come up with a different approach? Bob On Dec 5, 2012, at 3:06 AM, Bruce Griffithsbruce.griffi...@xtra.co.nz 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. 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. ___ time-nuts mailing 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 wonder if two hardware interrupts on the Arduino itself could not be used for phase locking? There's also an ARM 80 MHz version of the Arduino package that might be applied, admittedly at higher cost... Don Jim Lux 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.html 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. -- 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
Am 05.12.2012 18:31, schrieb Bob Camp: 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 Following Ulrich Bangerts suggestions, that a loop time constant should be at about 3 hours (GPS disciplining an OCXO), do I really need that resolution? Ok, the more accurate, the better. But the question is: can I reduce this requirement when using long time constants (1s)? The ratio then is 10E14... Volker ___ time-nuts mailing 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 forget that an OCXO needs faster than 10K seconds EFC updates, that's why you need resolution first. On Wed, Dec 5, 2012 at 10:24 PM, Volker Esper ail...@t-online.de wrote: Am 05.12.2012 18:31, schrieb Bob Camp: 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 Following Ulrich Bangerts suggestions, that a loop time constant should be at about 3 hours (GPS disciplining an OCXO), do I really need that resolution? Ok, the more accurate, the better. But the question is: can I reduce this requirement when using long time constants (1s)? The ratio then is 10E14... Volker ___ time-nuts mailing 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 TBolt does a resolution somewhere better than 0.1 ns. It (in some cases) has been shown to hold better than 1 ns stability. That would be hard to do with a low resolution timing setup. Some seem to like 100 seconds as an averaging time, others seem to want something longer. If you have an Rb, you would certainly want something much longer (days). Most modern setups step through a number of different time constants and stop when things get out of hand. The one on the bench in front of me is sitting at 8,000 seconds. A 1.0x10^-12 goal is often tossed around for this sort of stuff. A 1 ns timing accuracy (resolution would need to be better than the accuracy) would get you to that goal in 1,000 seconds. That's in a perfect world. In a noisy world you likely would have to wait a bit longer. TBolt to TBolt comparisons do hit that sort of goal well short of 10,000 seconds (but rarely short of 2,000). This all comes down to a what is your objective? sort of thing. You can not simultaneously decide you want to do 10X better than a TBolt, but that an approach that's 10X worse is ok. (Thus my reference to managing the feature list). If you are going to price the design against a $130 (or $200) item, then you should also spec it against the same item. To spec compare it one way and price compare it another way simply isn't being honest. Design is so much fun Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper Sent: Wednesday, December 05, 2012 4:25 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO Alternatives Am 05.12.2012 18:31, schrieb Bob Camp: 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 Following Ulrich Bangerts suggestions, that a loop time constant should be at about 3 hours (GPS disciplining an OCXO), do I really need that resolution? Ok, the more accurate, the better. But the question is: can I reduce this requirement when using long time constants (1s)? The ratio then is 10E14... Volker ___ time-nuts mailing 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
Good list Bob, many people underestimate what it takes to make a working, commercial GPSDO, especially one that has to perform in volume and beyond a single well taken care of unit in a Ham shack. Once you have taken care of items 1) and 2), the real work begins. This is where our customers get confused some times, they think items 1) and 2) are easy to do, and all that needs to be done to make a working product, and they try themselves. We just had someone try connecting the CSAC to a GPS receiver themselves, and in their setup they spent two months trying to get it to work before they gave up. The GPS behaved such that the CSAC could not lock onto it reliably. This happens quite often because at first sight it looks simple to do, and folks like Shera have come up with solutions that are simple and work well, but don't have any bells or whistles. One item often overlooked for example is that every OCXO during a production run behaves very differently from the OCXO next to it. The retrace time is different. The tempco is different. The EFC sensitivity is specified in large ranges such as 1ppm to 10ppm, one crystal may jump, another may have EFC hysterisis etc, and the software/hardware has to be able to handle all of these variations without requiring every unit to be fine-tuned by hand during production. And then the OCXO will actually change it's behavior over time due to aging and deminishing retrace error as the unit is operated etc. It's surprising that we still find room to make major improvements to our software 5 years after we sold the first Fury, for example we recently added things like leapsecond prediction/compensation without having an almanac loaded yet, with the help of a time-nut we found a very obscure bug in the NXP ARM processor that was supposed to be fixed years ago but wasn't, and we continuously keep improving and fine-tuning our algorithms and adding more commands/features to it. 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. bye, Said In a message dated 12/5/2012 09:29:14 Pacific Standard Time, li...@rtty.us writes: 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 ___ time-nuts mailing 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
Over the last two years or so I've put some thought into various home brew alternatives to purchasing a surplus or new GPSDO. The goal for me would be to have a reference source that combined the short to medium term stability of one of my best OCXO's with the long term stability of a GPSDO. The application would be to serve as a house standard for my test gear and a time server. I've envisioned a scheme whereby I'd use an off the shelf time interval counter (probably a surplus HP5370) to continuously compare the OCXO output to the raw 1pps output from a suitable GPS receiver. (This project would likely give me the excuse I've been looking for to purchase a CNS II GPS receiver that I believe are one of the better choices for raw 1pps accuracy.) The counter would be connected to a PC via GPIB. I'd then need to write the necessary code to periodically steer the OCXO via a to be determined digital to analog converter which in turn would then drive the EFC input on the OCXO. Rather than implement a software PLL scheme I'd likely start by simply computing the average drift over each day and then simply adjust the OCXO every day or so but eventually I'd expect to implement a PLL scheme in software.I’m hopeful that at first I could implement this in EZGPIB or something similar. I expect eventually I’d end up coding this in C. The main missing piece in the puzzle for me is a suitable DAC that can commanded by a PC (either by RS 232 or GPIB.) I leave PC's and various pieces of test gear on all the time currently (they help heat my basement lab in the winter) so I'm not worried about dedicating a PC and TIC to this. I'd also need a low noise power supply for the DAC and I suspect the performance of the DAC and the pysical interface between the DAC and the OCXO would be the weakest link in this whole system. After contemplating the time, effort, and expense to complete a project such as this I've settled for now on simply manually adjusting my OCXO's from time to time and if I am concerned about the drift while using once of them as a reference I simply compare the OCXO in question to a GPSDO while carrying out my other measurement. The drift of the OCXO can then be accounted for. In reality I can’t imagine having the time to even properly plan let alone implement something like this until I retire and I suspect I’d be lucky if I matched the performance of my best existing GPSDO. The other alternative that occurs to me is simply connecting a high end OCXO to a Thunderbolt board. Sorry if I come across as overly cynical or pessimistic here (: Message: 3 Date: Wed, 05 Dec 2012 22:24:43 +0100 From: Volker Esper ail...@t-online.de To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Message-ID: 50bfbb9b.7010...@t-online.de Content-Type: text/plain; charset=ISO-8859-1; format=flowed Am 05.12.2012 18:31, schrieb Bob Camp: 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 Following Ulrich Bangerts suggestions, that a loop time constant should be at about 3 hours (GPS disciplining an OCXO), do I really need that resolution? Ok, the more accurate, the better. But the question is: can I reduce this requirement when using long time constants (1s)? The ratio then is 10E14... Volker -- ___ time-nuts mailing 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 you make the leap to - my control processor will be a PC, feature creep is a bit easier: 1) The email when in trouble feature 2) Wireless network interface 3) Ethernet network interface 4) HDMI video for that 1080P status display 5) Full keyboard and mouse for data entry 6) 16 TB raid array for log files 7) Parallel port for printed running status log 8) Auto update of firmware That's not saying you don't *also* have another computer as a monitor via client / server sort of stuff. You may grin at some of the above, but I can easily see all of that winding up on somebody's wish list. Bob On Dec 5, 2012, at 6:26 PM, Mark Spencer mspencer12...@yahoo.ca wrote: Over the last two years or so I've put some thought into various home brew alternatives to purchasing a surplus or new GPSDO. The goal for me would be to have a reference source that combined the short to medium term stability of one of my best OCXO's with the long term stability of a GPSDO. The application would be to serve as a house standard for my test gear and a time server. I've envisioned a scheme whereby I'd use an off the shelf time interval counter (probably a surplus HP5370) to continuously compare the OCXO output to the raw 1pps output from a suitable GPS receiver. (This project would likely give me the excuse I've been looking for to purchase a CNS II GPS receiver that I believe are one of the better choices for raw 1pps accuracy.) The counter would be connected to a PC via GPIB. I'd then need to write the necessary code to periodically steer the OCXO via a to be determined digital to analog converter which in turn would then drive the EFC input on the OCXO. Rather than implement a software PLL scheme I'd likely start by simply computing the average drift over each day and then simply adjust the OCXO every day or so but eventually I'd expect to implement a PLL scheme in software.I’m hopeful that at first I could implement this in EZGPIB or something similar. I expect eventually I’d end up coding this in C. The main missing piece in the puzzle for me is a suitable DAC that can commanded by a PC (either by RS 232 or GPIB.) I leave PC's and various pieces of test gear on all the time currently (they help heat my basement lab in the winter) so I'm not worried about dedicating a PC and TIC to this. I'd also need a low noise power supply for the DAC and I suspect the performance of the DAC and the pysical interface between the DAC and the OCXO would be the weakest link in this whole system. After contemplating the time, effort, and expense to complete a project such as this I've settled for now on simply manually adjusting my OCXO's from time to time and if I am concerned about the drift while using once of them as a reference I simply compare the OCXO in question to a GPSDO while carrying out my other measurement. The drift of the OCXO can then be accounted for. In reality I can’t imagine having the time to even properly plan let alone implement something like this until I retire and I suspect I’d be lucky if I matched the performance of my best existing GPSDO. The other alternative that occurs to me is simply connecting a high end OCXO to a Thunderbolt board. Sorry if I come across as overly cynical or pessimistic here (: Message: 3 Date: Wed, 05 Dec 2012 22:24:43 +0100 From: Volker Esper ail...@t-online.de To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives Message-ID: 50bfbb9b.7010...@t-online.de Content-Type: text/plain; charset=ISO-8859-1; format=flowed Am 05.12.2012 18:31, schrieb Bob Camp: 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 Following Ulrich Bangerts suggestions, that a loop time constant should be at about 3 hours (GPS disciplining an OCXO), do I really need that resolution? Ok, the more accurate, the better. But the question is: can I reduce this requirement when using long time constants (1s)? The ratio then is 10E14... Volker -- ___ time-nuts mailing 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 They certainly aren't flooding the market these days the way they were a few years ago. I suspect you still can get them cheap if you are willing to wait a while. Even the two hundred dollar price is pretty good compared to the price of a newly manufactured OCXO based GPSDO. Bob On Dec 3, 2012, at 9:56 PM, paul swed paulsw...@gmail.com 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 li...@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 On Dec 3, 2012, at 8:50 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 12/04/2012 02:44 AM, paul swed wrote: Hmmm new and better. That means better stability, noise, lower power, lower heat, for less and works with lady heather? :-) I can hope. Mostly cheaper actually. Better GPS to start with, probably. Lower power, most probably. We should discuss if we can't have Lady Heather take a larger client-base of GPSDOs. There are so many peaces in there that would be nice to be used with a larger set of tools, like G12, Z12s, Z3801/3815 etc. Cheers, Magnsu ___ time-nuts mailing 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
Indeed and it seems the 3801s have a premium above the Tbolts these days. I have both. I picked up the tbolt much later and I simply waited for a good deal to show up. It took a year. I wasn't in a hurry. But that said I am still interested in the newer versions if they are reasonable in cost. Regards Paul On Tue, Dec 4, 2012 at 7:32 AM, Bob Camp li...@rtty.us wrote: Hi They certainly aren't flooding the market these days the way they were a few years ago. I suspect you still can get them cheap if you are willing to wait a while. Even the two hundred dollar price is pretty good compared to the price of a newly manufactured OCXO based GPSDO. Bob On Dec 3, 2012, at 9:56 PM, paul swed paulsw...@gmail.com 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 li...@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 On Dec 3, 2012, at 8:50 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 12/04/2012 02:44 AM, paul swed wrote: Hmmm new and better. That means better stability, noise, lower power, lower heat, for less and works with lady heather? :-) I can hope. Mostly cheaper actually. Better GPS to start with, probably. Lower power, most probably. We should discuss if we can't have Lady Heather take a larger client-base of GPSDOs. There are so many peaces in there that would be nice to be used with a larger set of tools, like G12, Z12s, Z3801/3815 etc. Cheers, Magnsu ___ time-nuts mailing 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.
Re: [time-nuts] GPSDO Alternatives
Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc, but I have never seen anyone mention the TrueTime XL-AK. It advertises 40 nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work well but have no way to test it against anything else yet. It has four each 10 MHz sine output that I have been using for house sync for HP3586, HP8924c, PTS160, etc. So how does the TrueTime compare to other GPSDO's? Al, K9SI ___ time-nuts mailing 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
Al I like the truetime products. In general easy to understand and last a long time. But there never seemed to be that many. Sure they were used in broadcasting and maybe power. But the others like the 3801 and tbolt were used in telco and mobile apps so there were 10,000s turned out and thats why we get them for cheap. I simply never see the truetime dc60 or gps units around. Though I have my stock of dc468 sat clocks. :-) Working. I hacked a goes sat replacement 3-4 years ago. That said some of the older gps technology is a bit slippery on exactly how good they are. So for perhaps amateur purposes they are totally fine but when you start comparing to a Tbolt or 3801 various behaviors apear. Odetics GPStars as an example slip cycles on purpose. Its a mode you can set and by default is how they are set. For what they were intended for they are perfect. But at least 1 X10 poorer then other devices. Its not at all broken. It was a general time piece for radio networks. Give or take 500 ms. Regards Paul WB8TSL On Tue, Dec 4, 2012 at 9:58 AM, Al Wolfe alw.k...@gmail.com wrote: Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc, but I have never seen anyone mention the TrueTime XL-AK. It advertises 40 nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work well but have no way to test it against anything else yet. It has four each 10 MHz sine output that I have been using for house sync for HP3586, HP8924c, PTS160, etc. So how does the TrueTime compare to other GPSDO's? Al, K9SI __**_ 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. ___ time-nuts mailing 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 I would guess that HP/Agilent/Symmetricom and Trimble made 100X more GPSDO's than the next five people in the business combined over the 1995 to 2005 period. Bob On Dec 4, 2012, at 10:26 AM, paul swed paulsw...@gmail.com wrote: Al I like the truetime products. In general easy to understand and last a long time. But there never seemed to be that many. Sure they were used in broadcasting and maybe power. But the others like the 3801 and tbolt were used in telco and mobile apps so there were 10,000s turned out and thats why we get them for cheap. I simply never see the truetime dc60 or gps units around. Though I have my stock of dc468 sat clocks. :-) Working. I hacked a goes sat replacement 3-4 years ago. That said some of the older gps technology is a bit slippery on exactly how good they are. So for perhaps amateur purposes they are totally fine but when you start comparing to a Tbolt or 3801 various behaviors apear. Odetics GPStars as an example slip cycles on purpose. Its a mode you can set and by default is how they are set. For what they were intended for they are perfect. But at least 1 X10 poorer then other devices. Its not at all broken. It was a general time piece for radio networks. Give or take 500 ms. Regards Paul WB8TSL On Tue, Dec 4, 2012 at 9:58 AM, Al Wolfe alw.k...@gmail.com wrote: Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc, but I have never seen anyone mention the TrueTime XL-AK. It advertises 40 nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work well but have no way to test it against anything else yet. It has four each 10 MHz sine output that I have been using for house sync for HP3586, HP8924c, PTS160, etc. So how does the TrueTime compare to other GPSDO's? Al, K9SI __**_ 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. ___ time-nuts mailing 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
With the price of T-Bolts now higher, does it make sense to build your own GPSDO? 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. 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. If ther phase detector where simple enough it could be build on a prototype board the fits on top of the Arduino. There are some other designs but because programming a uP and making a PCB seem to be rare skills that job tends to fall on one person. Anyone can program an Arduino and with out need of a PCB the entire design could be puted on a web page and the replicated with common parts. On Tue, Dec 4, 2012 at 4:01 PM, Bob Camp li...@rtty.us wrote: Hi I would guess that HP/Agilent/Symmetricom and Trimble made 100X more GPSDO's than the next five people in the business combined over the 1995 to 2005 period. Bob On Dec 4, 2012, at 10:26 AM, paul swed paulsw...@gmail.com wrote: Al I like the truetime products. In general easy to understand and last a long time. But there never seemed to be that many. Sure they were used in broadcasting and maybe power. But the others like the 3801 and tbolt were used in telco and mobile apps so there were 10,000s turned out and thats why we get them for cheap. I simply never see the truetime dc60 or gps units around. Though I have my stock of dc468 sat clocks. :-) Working. I hacked a goes sat replacement 3-4 years ago. That said some of the older gps technology is a bit slippery on exactly how good they are. So for perhaps amateur purposes they are totally fine but when you start comparing to a Tbolt or 3801 various behaviors apear. Odetics GPStars as an example slip cycles on purpose. Its a mode you can set and by default is how they are set. For what they were intended for they are perfect. But at least 1 X10 poorer then other devices. Its not at all broken. It was a general time piece for radio networks. Give or take 500 ms. Regards Paul WB8TSL On Tue, Dec 4, 2012 at 9:58 AM, Al Wolfe alw.k...@gmail.com wrote: Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc, but I have never seen anyone mention the TrueTime XL-AK. It advertises 40 nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work well but have no way to test it against anything else yet. It has four each 10 MHz sine output that I have been using for house sync for HP3586, HP8924c, PTS160, etc. So how does the TrueTime compare to other GPSDO's? Al, K9SI __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nuts 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
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. 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. -- 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 The TBolt is the newest of the used category. For newer, you skip up to brand new. Bob On Dec 3, 2012, at 7:42 PM, Tom Clifton kc0...@yahoo.com wrote: While the Trimble Tbolts are still out there and reasonably available, are there any newer alternatives in the same general price range? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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
Hmmm new and better. That means better stability, noise, lower power, lower heat, for less and works with lady heather? :-) I can hope. Regards Paul WB8TSL On Mon, Dec 3, 2012 at 7:52 PM, Bob Camp li...@rtty.us wrote: Hi The TBolt is the newest of the used category. For newer, you skip up to brand new. Bob On Dec 3, 2012, at 7:42 PM, Tom Clifton kc0...@yahoo.com wrote: While the Trimble Tbolts are still out there and reasonably available, are there any newer alternatives in the same general price range? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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
On 12/04/2012 02:44 AM, paul swed wrote: Hmmm new and better. That means better stability, noise, lower power, lower heat, for less and works with lady heather? :-) I can hope. Mostly cheaper actually. Better GPS to start with, probably. Lower power, most probably. We should discuss if we can't have Lady Heather take a larger client-base of GPSDOs. There are so many peaces in there that would be nice to be used with a larger set of tools, like G12, Z12s, Z3801/3815 etc. Cheers, Magnsu ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
