Re: [time-nuts] New to list and GPSDO questions
I like that explanation. I think I get it. I don't think it is likely to cause me any worry. My actual measurement of ADEV on my VE2ZAZ device gave me a 100,000s sigma of just under 1E-10 and that works for me (best is at 1000s, 4E-11). Maybe the strength and the danger of the VE2ZAZ design is the wide range of integration settings. If I were to pick some very unfortunate settings, maybe it would degrade overall performance in the way you describe. Thanks for taking the time to explain it to me. Chris On 6/13/2013 10:15 PM, Richard H McCorkle wrote: Chis, Over time without phase correction the analogy would be more like zig to the right, correct to go straight, zig to the right, correct again, and keep repeating this sequence ad infinium as the source ages in predominantly one direction. Each time the phase shifts in the same direction and before long you are on a different road a full clock cycle to the right and continuing to shift in the same direction. The total number of clocks over the period has changed from the ideal even though the average frequency has been correct. So over the short-term the right number of cycles occur, but over the long term there is an increasing error from the ideal number of clock cycles as the period increases. If all you need is a frequency that is stable over short periods then the phase is of no concern. But when using a scope or TIC to compare a device under test (DUT) to the reference to determine its Adev over longer periods then you need the phase of the reference to be constant over the maximum measurement period (typically 4-5 days for a 1-day Adev value) to determine the DUT long-term drift. By keeping track of the total accumulated count from an arbitrary starting point (i.e. when the reference sample is taken) and adding 6800 HEX each update the reference count would represent the ideal count after X updates if no drift had occurred. Comparing the current count to this ideal gives the total change since the arbitrary reference was first stored. By adding steering to keep the actual sample count at the ideal value then over the long-term there would be no drift as it would be corrected out. The actual phase to GPS isn't the important factor - the change in the phase over long periods (like a day or week) is as it represents an error in the total number of counts over that period and a reduction in the long-term stability. Richard I'm with Bob in that I don't really understand this description. And what are we trying to be in phase with? the 1PPS? Is it possible to reproduce the actual phase of the clock in the GPS birds once it has been through my GPS and come out as 1PPS? I picture the EFC steering the car straight down the road. And you want to adjust not just the drift to the right but steer back to the center of the lane. I think I get that part. I don't get who is setting the lane and why I should care. Do the statistics (ADEV, etc.) show that this is an improvement? If I'm doing my slow zigzag down the center line or the right shoulder, again, do I care? Chris w0ep ___ time-nuts mailing 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] New to list and GPSDO questions
As far as I can see from the pictures, the LED must be connected directly to the PPS output so, yes, can be used. Removing the LED can help in getting a full LVTTL swing. On Thu, Jun 13, 2013 at 5:29 AM, Bob Stewart b...@evoria.net wrote: Hello to the list. I saw on K3PGP's site a mention that the UT-41 GPS receiver had a 10KHz signal on-board so I decided, why not build a GPSDO for my new HP 5334B? Unfortunately the one I bought doesn't have a 10KHz point, and the board doesn't even pull out the 1PPS signal from the chip. So I've had to switch gears and will go with VE2ZAZ's board. I've got a Motorola UT+ on order, but I was wondering about using the board's LED output as a sort of low-rent source of 1PPS. Would the short term accuracy be too bad to even bother with? Has anyone done any tests to see if the LED and 1PPS signals are essentially the same signal on one of these cheapo boards, or at least to find out how often the LED output is corrected? The one I got has a Prolific PL-6313 chip. Bob - AE6RV ___ time-nuts mailing 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] New to list and GPSDO questions
On Wed, 12 Jun 2013 20:29:26 -0700, Bob Stewart wrote: I saw on K3PGP's site a mention that the UT-41 GPS receiver had a 10KHz signal on-board so I decided, why not build a GPSDO for my new HP 5334B? Unfortunately the one I bought doesn't have a 10KHz point, and the board doesn't even pull out the 1PPS signal from the chip. As a backup plan have a look at this one *Bay 290860812674 It has 10Khz, afaik it's the one mentioned for the Miller GPSDO. Make sure also to get the Antenna cable that belongs to it. CFO Denmark ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New to list and GPSDO questions
...but remember, you don't need 10kHz to get the control loop working. Since you need a time constant of some hours, the PPS output will do. Even more important is to use a good OCXO. By the way: welcome to the list :-) Volker Am 13.06.2013 12:20, schrieb cfo: On Wed, 12 Jun 2013 20:29:26 -0700, Bob Stewart wrote: I saw on K3PGP's site a mention that the UT-41 GPS receiver had a 10KHz signal on-board so I decided, why not build a GPSDO for my new HP 5334B? Unfortunately the one I bought doesn't have a 10KHz point, and the board doesn't even pull out the 1PPS signal from the chip. As a backup plan have a look at this one *Bay 290860812674 It has 10Khz, afaik it's the one mentioned for the Miller GPSDO. Make sure also to get the Antenna cable that belongs to it. CFO Denmark ___ time-nuts mailing 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] New to list and GPSDO questions
On Wed, 12 Jun 2013 20:29:26 -0700 (PDT) Bob Stewart b...@evoria.net wrote: Hello to the list. I saw on K3PGP's site a mention that the UT-41 GPS receiver had a 10KHz signal on-board so I decided, why not build a GPSDO for my new HP 5334B? Unfortunately the one I bought doesn't have a 10KHz point, and the board doesn't even pull out the 1PPS signal from the chip. So I've had to switch gears and will go with VE2ZAZ's board. Please be aware that VE2ZAZ's design uses a frequency locked loop and not a phase locked loop. Thus you end up with a slight frequency error (instead of a slight phase error). Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New to list and GPSDO questions
Absolutely agree with this comment. But understand thats a trade off for simplicity and for many radio operators its good enough as they say. Whats really not been mentioned in the thread is how accurate do you want to be or need. Be very careful with the answer. Time is the drug that keeps on giving. $ Regards Paul WB8TSL On Thu, Jun 13, 2013 at 2:41 PM, Attila Kinali att...@kinali.ch wrote: On Wed, 12 Jun 2013 20:29:26 -0700 (PDT) Bob Stewart b...@evoria.net wrote: Hello to the list. I saw on K3PGP's site a mention that the UT-41 GPS receiver had a 10KHz signal on-board so I decided, why not build a GPSDO for my new HP 5334B? Unfortunately the one I bought doesn't have a 10KHz point, and the board doesn't even pull out the 1PPS signal from the chip. So I've had to switch gears and will go with VE2ZAZ's board. Please be aware that VE2ZAZ's design uses a frequency locked loop and not a phase locked loop. Thus you end up with a slight frequency error (instead of a slight phase error). Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ time-nuts mailing 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] New to list and GPSDO questions
Hi Paul, and everyone. Yeah, that's a good question: how much accuracy do I want? I'm really just looking for a relatively easy project; one that will go to successful completion and give me a sense of accomplishment. At this moment, I have the problem of the man with two clocks. Better than 1 Hz @ 10MHz accuracy would be good. But, realistically, if the 5334B and 8640B both tell me the same thing, then I'll probably be happy. I could do that with the Trimble 34310-T, a pot and a flip-flop, but then I'd feel compelled to listen to WWV on occasion and tweak the pot! LOL I do have OCD, so I'm getting involved with timing with more than a little trepidation. I want this to be as low budget as is reasonably possible, barring wastage, so I think a 1PPS source and Bert's FLL are the right choice. Is there actually a PLL circuit that works with a 1PPS reference? I only found a very few GPSDO projects during my search, and Bert's was the only one using the 1PPS signal. And, I just like the way he did it, right down to giving the possibility of powering the output op-amp from the VREF output of the 34310-T. I'm assuming that won't overload it, of course, so any comments on that would be appreciated. Bob - AE6RV - Original Message - From: paul swed paulsw...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: Sent: Thursday, June 13, 2013 1:47 PM Subject: Re: [time-nuts] New to list and GPSDO questions Absolutely agree with this comment. But understand thats a trade off for simplicity and for many radio operators its good enough as they say. Whats really not been mentioned in the thread is how accurate do you want to be or need. Be very careful with the answer. Time is the drug that keeps on giving. $ Regards Paul WB8TSL On Thu, Jun 13, 2013 at 2:41 PM, Attila Kinali att...@kinali.ch wrote: On Wed, 12 Jun 2013 20:29:26 -0700 (PDT) Bob Stewart b...@evoria.net wrote: Hello to the list. I saw on K3PGP's site a mention that the UT-41 GPS receiver had a 10KHz signal on-board so I decided, why not build a GPSDO for my new HP 5334B? Unfortunately the one I bought doesn't have a 10KHz point, and the board doesn't even pull out the 1PPS signal from the chip. So I've had to switch gears and will go with VE2ZAZ's board. Please be aware that VE2ZAZ's design uses a frequency locked loop and not a phase locked loop. Thus you end up with a slight frequency error (instead of a slight phase error). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New to list and GPSDO questions
The OP says the GPSDO will be used to drive an HP5334B. Doesn't that imply that about one part in 10^10 (or 1E-10) is required. That is very easy to do with any GPSDO. OK maybe 1E-10 is not the right answer but fact that this is for the HP5334B should tell us what he needs. On Thu, Jun 13, 2013 at 11:47 AM, paul swed paulsw...@gmail.com wrote: .. Whats really not been mentioned in the thread is how accurate do you want to be or need. -- 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] New to list and GPSDO questions
Bob definition. Simple project works, costs little. Yes sir the VE2ZAZ does exactly that. By the way having several 8640bs you can lock the counter in it to your new reference and it will be quite good. far more accurate then it had been and stable. Doesn't help thesig gen unless you lock it. On Thu, Jun 13, 2013 at 3:27 PM, Chris Albertson albertson.ch...@gmail.comwrote: The OP says the GPSDO will be used to drive an HP5334B. Doesn't that imply that about one part in 10^10 (or 1E-10) is required. That is very easy to do with any GPSDO. OK maybe 1E-10 is not the right answer but fact that this is for the HP5334B should tell us what he needs. On Thu, Jun 13, 2013 at 11:47 AM, paul swed paulsw...@gmail.com wrote: .. Whats really not been mentioned in the thread is how accurate do you want to be or need. -- 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] New to list and GPSDO questions
On Thu, 13 Jun 2013 12:17:53 -0700 (PDT) Bob Stewart b...@evoria.net wrote: I want this to be as low budget as is reasonably possible, barring wastage, so I think a 1PPS source and Bert's FLL are the right choice. Is there actually a PLL circuit that works with a 1PPS reference? I only found a very few GPSDO projects during my search, and Bert's was the only one using the 1PPS signal. And, I just like the way he did it, right down to giving the possibility of powering the output op-amp from the VREF output of the 34310-T. I'm assuming that won't overload it, of course, so any comments on that would be appreciated. [1] is probably the most cited GPSDO design. It's simple, it works and you can build it quite cheaply [2] is similar to what Shera did, with slight modifications on how to measure the phase. [3] Describes how to use a clock synchronizer to build a GPSDO. Probably not the easiest and not the cheapest way, but definitly one with a very low parts count. I think the cheapest way how to do a GPSDO that is fairly well accurate is to use a uC with a high clock rate and a 32bit capture/compare unit (eg STM32F4 which can do 78MHz on their c/c unit, thus giving ~14ns resolution for ~15USD for the naked chip or an eval board). Feed the 10MHz from your OCXO to the uC's clock input. Use the internal PLL to upconvert it to what you need (i.e. as high a frequency as possible). Feed the 1PPS to one of the c/c pins and measure when it enters. If your OCXO is fairly stable, you can integrate over a minute or two (or even longer) and get down to uncertainties below 10^-9. If you tweak your control loop such, that the mean of your PPS pulse is exactly between two bins of your c/c, then you can get even better than the resolution of your c/c, if your GPS generates a symetrical distribution of the PPS pulse. HTH Attila Kinali [1] A GPS Based Frequency Standard, by Shera, 1998 http://www.rt66.com/~shera/QST_GPS.pdf [2] Building a GPSDO controller, by Pedersen, 2011 http://n1.taur.dk/gpsdo2a.pdf [3] The AD9548 as a GPS Disciplined Stratum 2 Clock, by Gentile, 2009 http://www.analog.com/static/imported-files/application_notes/AN-1002.pdf -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New to list and GPSDO questions
I like the LPC1114 chip (50 MHz). I am well along on the design of such a board using a 40MHz TCXO (good to about .1 PPM when calibrated and operated at room temperature) divided down to 10 MHz as the master clock. It has a 10 MHz real 50 ohm out with a +5V/0V nominal signal levels. You can put that in your counter to tweak it. It has a tweaking trimmer. The LPC1114 is available for about $3 in low quantities. Or free if you can get NXP to send you samples. There is probably another month or three of work to do to complete the project. The board will have a 32 bit fig-FORTH to go with it (how retro) making it easy to program. Of course if you insist on C you can do that too. The interfaces include - I2C (LCD display, extra control lines [slow], real time clock, etc). Real DB9 RS-232. TXD, RXD, installed. CTS, RTS, DSR, DTR, available. Output levels of +/- 10V nominal (about +/- 8V actual). Top expected speed of 115,300 Hz. Jumperable for DCE or DTE (header and jumper shorts). Male and Female DB9s. And of course the capture pins are on a nominal parallel port. I can post to the list when the project is completed if anyone is interested. Bare boards will be available. It is almost all Surface Mount (nothing smaller than 0603 case size), but designed for hand soldering. I'm an old man (68), my hands shake and my eyes are bad. If I can do it so can you. To help with that I have designed a low cost hot air iron. http://www.ecnmag.com/blogs/2013/06/diy-hot-air-iron I am open to modifying the MCU board design for TIME NUTS. Let me know what you want. Simon Date: Thu, 13 Jun 2013 22:39:01 +0200 From: Attila Kinali att...@kinali.ch To: Bob Stewart b...@evoria.net, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] New to list and GPSDO questions Message-ID: 20130613223901.26b487eed384b6cc8a860...@kinali.ch Content-Type: text/plain; charset=UTF-8 On Thu, 13 Jun 2013 12:17:53 -0700 (PDT) Bob Stewart b...@evoria.net wrote: I want this to be as low budget as is reasonably possible, barring wastage, so I think a 1PPS source and Bert's FLL are the right choice.? Is there actually a PLL circuit that works with a 1PPS reference?? I only found a very few GPSDO projects during my search, and Bert's was the only one using the 1PPS signal.? And, I just like the way he did it, right down to giving the possibility of powering the output op-amp from the VREF output of the 34310-T.? I'm assuming that won't overload it, of course, so any comments on that would be appreciated. [1] is probably the most cited GPSDO design. It's simple, it works and you can build it quite cheaply [2] is similar to what Shera did, with slight modifications on how to measure the phase. [3] Describes how to use a clock synchronizer to build a GPSDO. Probably not the easiest and not the cheapest way, but definitly one with a very low parts count. I think the cheapest way how to do a GPSDO that is fairly well accurate is to use a uC with a high clock rate and a 32bit capture/compare unit (eg STM32F4 which can do 78MHz on their c/c unit, thus giving ~14ns resolution for ~15USD for the naked chip or an eval board). Feed the 10MHz from your OCXO to the uC's clock input. Use the internal PLL to upconvert it to what you need (i.e. as high a frequency as possible). Feed the 1PPS to one of the c/c pins and measure when it enters. If your OCXO is fairly stable, you can integrate over a minute or two (or even longer) and get down to uncertainties below 10^-9. If you tweak your control loop such, that the mean of your PPS pulse is exactly between two bins of your c/c, then you can get even better than the resolution of your c/c, if your GPS generates a symetrical distribution of the PPS pulse. HTH Attila Kinali [1] A GPS Based Frequency Standard, by Shera, 1998 http://www.rt66.com/~shera/QST_GPS.pdf [2] Building a GPSDO controller, by Pedersen, 2011 http://n1.taur.dk/gpsdo2a.pdf [3] The AD9548 as a GPS Disciplined Stratum 2 Clock, by Gentile, 2009 http://www.analog.com/static/imported-files/application_notes/AN-1002.pdf -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown Engineering is the art of making what you want from what you can get at a profit. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New to list and GPSDO questions
Chis, Over time without phase correction the analogy would be more like zig to the right, correct to go straight, zig to the right, correct again, and keep repeating this sequence ad infinium as the source ages in predominantly one direction. Each time the phase shifts in the same direction and before long you are on a different road a full clock cycle to the right and continuing to shift in the same direction. The total number of clocks over the period has changed from the ideal even though the average frequency has been correct. So over the short-term the right number of cycles occur, but over the long term there is an increasing error from the ideal number of clock cycles as the period increases. If all you need is a frequency that is stable over short periods then the phase is of no concern. But when using a scope or TIC to compare a device under test (DUT) to the reference to determine its Adev over longer periods then you need the phase of the reference to be constant over the maximum measurement period (typically 4-5 days for a 1-day Adev value) to determine the DUT long-term drift. By keeping track of the total accumulated count from an arbitrary starting point (i.e. when the reference sample is taken) and adding 6800 HEX each update the reference count would represent the ideal count after X updates if no drift had occurred. Comparing the current count to this ideal gives the total change since the arbitrary reference was first stored. By adding steering to keep the actual sample count at the ideal value then over the long-term there would be no drift as it would be corrected out. The actual phase to GPS isn't the important factor - the change in the phase over long periods (like a day or week) is as it represents an error in the total number of counts over that period and a reduction in the long-term stability. Richard I'm with Bob in that I don't really understand this description. And what are we trying to be in phase with? the 1PPS? Is it possible to reproduce the actual phase of the clock in the GPS birds once it has been through my GPS and come out as 1PPS? I picture the EFC steering the car straight down the road. And you want to adjust not just the drift to the right but steer back to the center of the lane. I think I get that part. I don't get who is setting the lane and why I should care. Do the statistics (ADEV, etc.) show that this is an improvement? If I'm doing my slow zigzag down the center line or the right shoulder, again, do I care? Chris w0ep ___ time-nuts mailing 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] New to list and GPSDO questions
Hello to the list. I saw on K3PGP's site a mention that the UT-41 GPS receiver had a 10KHz signal on-board so I decided, why not build a GPSDO for my new HP 5334B? Unfortunately the one I bought doesn't have a 10KHz point, and the board doesn't even pull out the 1PPS signal from the chip. So I've had to switch gears and will go with VE2ZAZ's board. I've got a Motorola UT+ on order, but I was wondering about using the board's LED output as a sort of low-rent source of 1PPS. Would the short term accuracy be too bad to even bother with? Has anyone done any tests to see if the LED and 1PPS signals are essentially the same signal on one of these cheapo boards, or at least to find out how often the LED output is corrected? The one I got has a Prolific PL-6313 chip. Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
