Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
Hi fellow time-nuts, sorry for keeping quiet after having dropped my question. I was busy travelling an since yesterday our booth at the IMS2016/MTT keeps me busy too. I will answer to the various comments as soon as I got some more quiet minutes. I look forward to see many time-nuts this afternoon at 5:00 pm at the Dynamic Engineers booth #714 Bernd ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
From: Wes A cleaver design, but the OP wanted 1pps. I have the Leo Bodnar GPSDO. It too is a nice frequency standard, but it doesn't know what time it is. = This box can do either 10 MHz or 1 PPS. http://leontp.com/ "Coming soon" Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
However the value of the second time constant in the active PI filter required to achieve reasonable damping will be around 1600 seconds. This corresponds to an active PI filter proportional gain of 16. Bruce On Wednesday, 25 May 2016 3:20 PM, Bruce Griffiths wrote: When comparing a 10MHz OCXO divided down to 1Hz with a GPS PPS signal, the effective VCO gain (Ko/N) is likely to be around 6E-7 rad/s/V (eg HP10811A) and the phase detector gain around 1V/rad. Consequently a PLL loop bandwidth of 100uHz only requires an Integrator time constant of around 100 sec or so for a second order PLL with an active PI filter. The required integrator time constant can be reduced further by using an attenuator between the filter output and the OCXO EFC input. Bruce On Wednesday, 25 May 2016 9:00 AM, Wes wrote: A cleaver design, but the OP wanted 1pps. I have the Leo Bodnar GPSDO. It too is a nice frequency standard, but it doesn't know what time it is. On 5/24/2016 9:53 AM, Graham / KE9H wrote: > If you want an "existence proof" for a simple, mostly analog, a few digital > counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO.. > He designed it for his own use, then put it into production because of > demand for a simple, cheap GPSDO. It has been characterized, and works > well for the simple circuit. > > The schematics are published, since it started as a hobby project. > > http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm > > http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm > > You can buy his, or build your own with his design as a starting point. > > He does use a GPS with 10 kHz output to simplify some of the timing and > integration issues Bob referred to. > > --- Graham > > == > ___ time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
When comparing a 10MHz OCXO divided down to 1Hz with a GPS PPS signal, the effective VCO gain (Ko/N) is likely to be around 6E-7 rad/s/V (eg HP10811A) and the phase detector gain around 1V/rad. Consequently a PLL loop bandwidth of 100uHz only requires an Integrator time constant of around 100 sec or so for a second order PLL with an active PI filter. The required integrator time constant can be reduced further by using an attenuator between the filter output and the OCXO EFC input. Bruce On Wednesday, 25 May 2016 9:00 AM, Wes wrote: A cleaver design, but the OP wanted 1pps. I have the Leo Bodnar GPSDO. It too is a nice frequency standard, but it doesn't know what time it is. On 5/24/2016 9:53 AM, Graham / KE9H wrote: > If you want an "existence proof" for a simple, mostly analog, a few digital > counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO.. > He designed it for his own use, then put it into production because of > demand for a simple, cheap GPSDO. It has been characterized, and works > well for the simple circuit. > > The schematics are published, since it started as a hobby project. > > http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm > > http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm > > You can buy his, or build your own with his design as a starting point. > > He does use a GPS with 10 kHz output to simplify some of the timing and > integration issues Bob referred to. > > --- Graham > > == > ___ time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
A cleaver design, but the OP wanted 1pps. I have the Leo Bodnar GPSDO. It too is a nice frequency standard, but it doesn't know what time it is. On 5/24/2016 9:53 AM, Graham / KE9H wrote: If you want an "existence proof" for a simple, mostly analog, a few digital counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO. He designed it for his own use, then put it into production because of demand for a simple, cheap GPSDO. It has been characterized, and works well for the simple circuit. The schematics are published, since it started as a hobby project. http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm You can buy his, or build your own with his design as a starting point. He does use a GPS with 10 kHz output to simplify some of the timing and integration issues Bob referred to. --- Graham == ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
If you want an "existence proof" for a simple, mostly analog, a few digital counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO. He designed it for his own use, then put it into production because of demand for a simple, cheap GPSDO. It has been characterized, and works well for the simple circuit. The schematics are published, since it started as a hobby project. http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm You can buy his, or build your own with his design as a starting point. He does use a GPS with 10 kHz output to simplify some of the timing and integration issues Bob referred to. --- Graham == On Mon, May 23, 2016 at 8:21 PM, Bob Camp wrote: > Hi > > Ok, so how would you do a pure analog GPSDO? > > The GPS receiver and that side of it are what they are. I’ll assume that > you have a 1 pps out of a module. > > Your OCXO needs to get to 1 Hz via dividers. You can do that with digital > dividers or with a chain of regenerative > dividers. One is a bit more analog, the other may be “ok” under the “don’t > go to crazy” ground rule. > > You now have a PPS that is off somewhere relative to the GPS. A push > button will get them into rough alignment. > Your OCXO is quite likely a bit high or low. A multi turn pot on the EFC > will let you get it within 1x10^-9 without a > lot of crazy work. A reasonable counter tied to a reference will let you > do this. > > Net result: The pps signals are roughly aligned and drifting < 1 ns / s. > Considering the delta between them is > bopping around by 10 ns, that’s quite good. > > Run a very normal bipolar charge pump off of the delta between the two pps > signals. Fire a sample and hold when > the transition is over. You now have a (maybe) +/- 60V signal that > corresponds to the phase error. Since you are using > film capacitors, the 60V comes along for free. Taking it to the maximum is > just a way to save money on caps. > > Next up, do a fairly simple 20 second time constant R/C filter. That will > take out a lot of the hopping around and make > the rest of the system a bit easier to quiet down. You now have a somewhat > linear +/- 60V signal that tells you how > far off phase the setup is. After the RC you have a high input impedance / > low drift buffer amplifier. Yes that’s a little > tricky. > > Next you need a P and an I term. Both need to be variable as the system > calms down. A rotary switch will do fine for > this. Relays might also do the job. The P is a bank of resistors, each one > to scale the buffered R/C to your control amp. > The I goes off to a similar set of resistors driving an integrator. Net > time constant there will be in the 200 to 2,000 second range. > That’s were the ovenized caps come in. You also need a really good amp as > part of the integrator to buffer out the signal. > > The nice thing about doing it this way is that you can *see* it all > happening. There is a nice *clunk* noise as the filter > steps off. Each number in the filter has a (likely large value) resistor > that sets it up. To change the filter characteristics, > you swap out resistors or twiddle pots. > > If you do the math, even with 60 V on the system, you probably don’t want > anything over 1 meg ohm involved. At 2K seconds > that gets you to a pretty big film capacitor bank. Even the 20 second > lowpass isn’t exactly small by the standards of fancy > capacitors. > > There are a few interesting tidbits like wire wound / high value / low > temp co resistors that would help things a bit. Swapping > those in and out as you change filter settings experimentally could get a > bit crazy. > > The net result should be a good starting point for a GPSDO. You still > would need to spend all of the time working out values > and matching it up to your OCXO. The need for a good local reference and > good measurement gear while doing this still is > a limit, just like the pure digital approach. > > Bob > > > > > On May 23, 2016, at 12:46 PM, Nick Sayer via time-nuts < > time-nuts@febo.com> wrote: > > > > > >> > >>> If that sounds too weird, I am open to receive advises for a > microcontroller based solution. > >> > >> If you want to go that way, probably the simplest solution would be to > >> take one of Nick Sayers boards, pull out the GPS receiver and feed the > >> PPS input from your GPS receiver. > > > > It’d be kind of an awkward fit. For the OCXO/TCXO, you’d need to pull > the oscillator as well as the GPS (I believe you said you had an oscillator > already), and your EFC would be 1.65 volts wide centered on 1.65 volts. > That’s unlikely to be absolutely correct for your oscillator. You could > change around the Vref for the DAC, but at that point I’d consider > redesigning the board for your purposes instead. > > > > That said, I think it’d be easy to adapt the circuit and code for a more > arbitrary setup. And I believe my system is good down to the ADEV 10E-11 > leve
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
Hi Ok, so how would you do a pure analog GPSDO? The GPS receiver and that side of it are what they are. I’ll assume that you have a 1 pps out of a module. Your OCXO needs to get to 1 Hz via dividers. You can do that with digital dividers or with a chain of regenerative dividers. One is a bit more analog, the other may be “ok” under the “don’t go to crazy” ground rule. You now have a PPS that is off somewhere relative to the GPS. A push button will get them into rough alignment. Your OCXO is quite likely a bit high or low. A multi turn pot on the EFC will let you get it within 1x10^-9 without a lot of crazy work. A reasonable counter tied to a reference will let you do this. Net result: The pps signals are roughly aligned and drifting < 1 ns / s. Considering the delta between them is bopping around by 10 ns, that’s quite good. Run a very normal bipolar charge pump off of the delta between the two pps signals. Fire a sample and hold when the transition is over. You now have a (maybe) +/- 60V signal that corresponds to the phase error. Since you are using film capacitors, the 60V comes along for free. Taking it to the maximum is just a way to save money on caps. Next up, do a fairly simple 20 second time constant R/C filter. That will take out a lot of the hopping around and make the rest of the system a bit easier to quiet down. You now have a somewhat linear +/- 60V signal that tells you how far off phase the setup is. After the RC you have a high input impedance / low drift buffer amplifier. Yes that’s a little tricky. Next you need a P and an I term. Both need to be variable as the system calms down. A rotary switch will do fine for this. Relays might also do the job. The P is a bank of resistors, each one to scale the buffered R/C to your control amp. The I goes off to a similar set of resistors driving an integrator. Net time constant there will be in the 200 to 2,000 second range. That’s were the ovenized caps come in. You also need a really good amp as part of the integrator to buffer out the signal. The nice thing about doing it this way is that you can *see* it all happening. There is a nice *clunk* noise as the filter steps off. Each number in the filter has a (likely large value) resistor that sets it up. To change the filter characteristics, you swap out resistors or twiddle pots. If you do the math, even with 60 V on the system, you probably don’t want anything over 1 meg ohm involved. At 2K seconds that gets you to a pretty big film capacitor bank. Even the 20 second lowpass isn’t exactly small by the standards of fancy capacitors. There are a few interesting tidbits like wire wound / high value / low temp co resistors that would help things a bit. Swapping those in and out as you change filter settings experimentally could get a bit crazy. The net result should be a good starting point for a GPSDO. You still would need to spend all of the time working out values and matching it up to your OCXO. The need for a good local reference and good measurement gear while doing this still is a limit, just like the pure digital approach. Bob > On May 23, 2016, at 12:46 PM, Nick Sayer via time-nuts > wrote: > > >> >>> If that sounds too weird, I am open to receive advises for a >>> microcontroller based solution. >> >> If you want to go that way, probably the simplest solution would be to >> take one of Nick Sayers boards, pull out the GPS receiver and feed the >> PPS input from your GPS receiver. > > It’d be kind of an awkward fit. For the OCXO/TCXO, you’d need to pull the > oscillator as well as the GPS (I believe you said you had an oscillator > already), and your EFC would be 1.65 volts wide centered on 1.65 volts. > That’s unlikely to be absolutely correct for your oscillator. You could > change around the Vref for the DAC, but at that point I’d consider > redesigning the board for your purposes instead. > > That said, I think it’d be easy to adapt the circuit and code for a more > arbitrary setup. And I believe my system is good down to the ADEV 10E-11 > level at tau 1s or so. I don’t know how much better it can do, as I’ve simply > not tried to go below that (and I likely couldn’t properly measure the > results anyway). > > There’s also the FE-5680 board, but it has an RS-232 level shifter in place > of the DAC. On the other hand, it does have a very nice 2A @ 15V power > supply, which likely is very close to what you’d need for a really good OCXO. > A mash-up of that with the DAC put back in might be closer. But either way, > you’re designing a new board, I think. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cg
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
> >> If that sounds too weird, I am open to receive advises for a microcontroller >> based solution. > > If you want to go that way, probably the simplest solution would be to > take one of Nick Sayers boards, pull out the GPS receiver and feed the > PPS input from your GPS receiver. It’d be kind of an awkward fit. For the OCXO/TCXO, you’d need to pull the oscillator as well as the GPS (I believe you said you had an oscillator already), and your EFC would be 1.65 volts wide centered on 1.65 volts. That’s unlikely to be absolutely correct for your oscillator. You could change around the Vref for the DAC, but at that point I’d consider redesigning the board for your purposes instead. That said, I think it’d be easy to adapt the circuit and code for a more arbitrary setup. And I believe my system is good down to the ADEV 10E-11 level at tau 1s or so. I don’t know how much better it can do, as I’ve simply not tried to go below that (and I likely couldn’t properly measure the results anyway). There’s also the FE-5680 board, but it has an RS-232 level shifter in place of the DAC. On the other hand, it does have a very nice 2A @ 15V power supply, which likely is very close to what you’d need for a really good OCXO. A mash-up of that with the DAC put back in might be closer. But either way, you’re designing a new board, I think. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
Hi Is a DAC in our out? I can (with some effort) build the entire computing engine needed for a GPSDO out of 7400 series logic. It’s actually easier than you might think. Since that’s “small scale logic” is it in bounds? To me at least, analog is just that, no gates, no 1’s no 0’s, just a good old analog computer. They went out of style a while back, but they still work …Once upon a time in a land far away, control theory labs made students set up loops on them and do stuff like run motors :) Bob > On May 22, 2016, at 6:52 PM, Chris Albertson > wrote: > > If you can build with small scale TTL gates you can save the need for > a huge precision capacitor by storing the current EFC value in a > 16-bit register/counter. This 16-bit register drives a DAC. Then > you build a phase detector that can detect if the XO leads or lags the > GPS. If it leads you increment the counter, if it lags you decrement > the counter. Every second you either adjust the register or do > nothing. The DAC is nothing more than 16 precision resisters each > one twice the value of the next one, each connected to one bit of the > register by a transistor switch. > > I would only implement this as exercise to show how cool 1970's > technology was. It would be far more impressive if you limited > yourself to 1960's technology. I say this because one of my other > hobbies is building tube based audio gear. The last thing I built was > a spring reverb, using a steel spring as the delay.I already have > the software version but the physical spring is more fun to use. I > think a 60's or 70's vintage GPSDXO would be unique if strictly > limited to period correct technology > > On Sun, May 22, 2016 at 2:55 PM, Bob Camp wrote: >> Hi >> >> Of course it’s possible, you simply need enough high quality film capacitors >> to make up the control loop integrator. >> You probably also would use a pile of the same capacitors to slow down the >> PPS jitter a bit before it went into the loop. >> The setup process would probably involve a bunch of toggle switches or >> relays to walk the loop into the long time constant >> mode. You would be wise to put the caps all in some sort of oven >> arrangement. That way odd drafts hating the caps would >> not drive the GPSDO nuts. >> >> Bob >> >>> On May 22, 2016, at 1:41 PM, Bernd Neubig wrote: >>> >>> Hello Fellow time-nuts, >>> I am looking for a simple solution to discipline my 10 MHz reference OCXO >>> in my private lab with an 1 PPS signal from a separate GPS receiver. >>> I am curious if there is a solution possible without programming a >>> microcontroller, as I am an old-fashioned "analogue" guy ;) >>> I am well aware, that such a solution would have a lot of disadvantages, as >>> it cannot effectively compensate for short-term variations. However I would >>> be happy if such a KISS solution could achieve a stability (STS) of better >>> 1E-10 over an hour. I know this is a damned long integration time for an >>> analogue integrator... >>> If that sounds too weird, I am open to receive advises for a >>> microcontroller based solution. >>> >>> Thanks a lot for your comments to come. >>> BTW: you need not to teach me about basics of short-term stability. I just >>> want to evaluate the limits of a possible analogue solution. For sure, >>> that's not real disciplining, but more like a long-tau integration PLL >>> >>> Best regards >>> Bernd DK1AG >>> >>> ___ >>> time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
The grid current of most tubes (apart from electrometer tubes operated at low voltage) is much larger than most FETs (apart from very large area ones).. The other issue with tube grid currents is that zero current corresponds to a delicate balance between electon and ion currents so the grid current noise can be somewhat larger than one may at first expect. Bruce On Monday, 23 May 2016 8:04 PM, David wrote: On Sun, 22 May 2016 15:52:16 -0700, you wrote: >... > >The DAC is nothing more than 16 precision resisters each >one twice the value of the next one, each connected to one bit of the >register by a transistor switch. It will take beyond a heroic effort to get 16 bits of differential non-linearity out of a binary weighted DAC. It is difficult enough to do with an R-2R ladder. >I would only implement this as exercise to show how cool 1970's >technology was. It would be far more impressive if you limited >yourself to 1960's technology. I say this because one of my other >hobbies is building tube based audio gear. The last thing I built was >a spring reverb, using a steel spring as the delay. I already have >the software version but the physical spring is more fun to use. I >think a 60's or 70's vintage GPSDXO would be unique if strictly >limited to period correct technology I would not go back that far although with tube technology you do have the capability of better than FET input impedance for long time constants. Chopping would be needed if offset drift below 10s of microvolts is required. I would like to try a mixed signal design using charge pumping into an integrator. ___ time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
On Sun, 22 May 2016 15:52:16 -0700, you wrote: >... > >The DAC is nothing more than 16 precision resisters each >one twice the value of the next one, each connected to one bit of the >register by a transistor switch. It will take beyond a heroic effort to get 16 bits of differential non-linearity out of a binary weighted DAC. It is difficult enough to do with an R-2R ladder. >I would only implement this as exercise to show how cool 1970's >technology was. It would be far more impressive if you limited >yourself to 1960's technology. I say this because one of my other >hobbies is building tube based audio gear. The last thing I built was >a spring reverb, using a steel spring as the delay.I already have >the software version but the physical spring is more fun to use. I >think a 60's or 70's vintage GPSDXO would be unique if strictly >limited to period correct technology I would not go back that far although with tube technology you do have the capability of better than FET input impedance for long time constants. Chopping would be needed if offset drift below 10s of microvolts is required. I would like to try a mixed signal design using charge pumping into an integrator. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
Well, if you're open to something completely different, consider using a motor-driven potentiometer that provides a trim voltage to the OCXO. Adjust the motor at long intervals, leaving it off the rest of the time. It's called sampling control. You'll need to have an analog phase comparator for 1 PPS that has enough volts/degree to provide a useful error signal to the motor controller. Bill Hawkins -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bernd Neubig Sent: Sunday, May 22, 2016 12:41 PM To: 'Discussion of precise time and frequency measurement' Subject: [time-nuts] Simple solution for disciplining OCXO with 1 PPS Hello Fellow time-nuts, I am looking for a simple solution to discipline my 10 MHz reference OCXO in my private lab with an 1 PPS signal from a separate GPS receiver. I am curious if there is a solution possible without programming a microcontroller, as I am an old-fashioned "analogue" guy ;) I am well aware, that such a solution would have a lot of disadvantages, as it cannot effectively compensate for short-term variations. However I would be happy if such a KISS solution could achieve a stability (STS) of better 1E-10 over an hour. I know this is a damned long integration time for an analogue integrator... If that sounds too weird, I am open to receive advises for a microcontroller based solution. Thanks a lot for your comments to come. BTW: you need not to teach me about basics of short-term stability. I just want to evaluate the limits of a possible analogue solution. For sure, that's not real disciplining, but more like a long-tau integration PLL Best regards Bernd DK1AG ___ time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
I like the little boards at: http://navspark.mybigcommerce.com/development-boards/ It's a GPS with a fully programmable 32-bit Arduino-compatible processor. $22 Crowdsourced about 3 yr ago, matured now. Various versions; you can even have Beidou :-). Don On 2016-05-22 19:45, Tom Van Baak wrote: Can a pure analog design access the sawtooth correction? My GPS receivers send sawtooth as a digital message on a serial port. I don't know if saw tooth correction is required to meet his spec. Hi Chris, Many GPS/1PPS receivers don't output sawtooth information and yet they work really well. Sawtooth correction isn't necessary except for high-end GPSDO. The same is true for zero-D timing mode. Examples include: https://www.adafruit.com/products/746 https://www.parallax.com/product/28509 as well as any number of equivalent GPS/1PPS boards at half the price on eBay. See also: http://www.leapsecond.com/pages/MG1613S/ In fact many simple GPSDO rely on sawtooth dither to improve their performance; that is, it's a feature to be exploited, not a bug to be corrected for. A dirt cheap GPS receiver these days may have 1PPS error of 20 ns RMS. Over 1000 s integration that's 2e-11 in frequency stability; far better than the OP's modest target of 1e-10 at an hour. Here's another thought. OP wants STS of stability of 1e-10 at an hour. No mention of accuracy, or long-term performance. So if stability is all that's needed I would just use a old 10811-class OCXO, perhaps one that's been running faithfully for a few weeks or months. That will get you 1e-10 at an hour without any GPS any antenna any analog any digital any complexity any tuning. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
> Can a pure analog design access the sawtooth correction? My GPS > receivers send sawtooth as a digital message on a serial port. I > don't know if saw tooth correction is required to meet his spec. Hi Chris, Many GPS/1PPS receivers don't output sawtooth information and yet they work really well. Sawtooth correction isn't necessary except for high-end GPSDO. The same is true for zero-D timing mode. Examples include: https://www.adafruit.com/products/746 https://www.parallax.com/product/28509 as well as any number of equivalent GPS/1PPS boards at half the price on eBay. See also: http://www.leapsecond.com/pages/MG1613S/ In fact many simple GPSDO rely on sawtooth dither to improve their performance; that is, it's a feature to be exploited, not a bug to be corrected for. A dirt cheap GPS receiver these days may have 1PPS error of 20 ns RMS. Over 1000 s integration that's 2e-11 in frequency stability; far better than the OP's modest target of 1e-10 at an hour. Here's another thought. OP wants STS of stability of 1e-10 at an hour. No mention of accuracy, or long-term performance. So if stability is all that's needed I would just use a old 10811-class OCXO, perhaps one that's been running faithfully for a few weeks or months. That will get you 1e-10 at an hour without any GPS any antenna any analog any digital any complexity any tuning. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
Hi No, there is no purely analog way to access the sawtooth information. If you restrict yourself to “pure analog” then the PPS will be bopping around by +/- 10 to +/-20 ns each second. Put another way, you start out with 1 to 2x10^-8 at 1 second. The same thing is true at 10 KHz or at any other output frequency. To get down to the vicinity of 1x10^-10 with any sort of rational ADEV, you are going to need the equivalent of a very long time constant analog filter. It also needs to have *very* good DC characteristics and low noise. The simple answer is to use a *lot* of C and not much R in the beast. That gets you into a boatload of high quality film capacitors. There is no getting around having a narrow / long time constant filter if you want a useful signal out of the OCXO... Bob > On May 22, 2016, at 8:24 PM, Chris Albertson > wrote: > > On Sun, May 22, 2016 at 3:52 PM, Attila Kinali wrote: > >> Judging from the ADEV plots of the M12 receiver from TvB[1], which hit >> 10^-10 (w/ sawtooth) around 200s, I'd say that 10^-10 @1000s should be >> easy. > > Can a pure analog design access the sawtooth correction? My GPS > receivers send sawtooth as a digital message on a serial port. I > don't know if saw tooth correction is required to meet his spec. > > I think what he needs if he wants to go 100% analog is a GPS receiver > that outputs pulses at 10Hz not 1Hz. But to program the pulse rate > he'd need to send data to the serial control port. > > -- > > 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] Simple solution for disciplining OCXO with 1 PPS
bneu...@t-online.de said: > Hello Fellow time-nuts, I am looking for a simple solution to discipline my > 10 MHz reference OCXO in my private lab with an 1 PPS signal from a separate > GPS receiver. I am curious if there is a solution possible without > programming a microcontroller, as I am an old-fashioned "analogue" guy ;) There are a couple of things you can try. Use a simple pot and adjust it by hand. You will have to run some tests to see if that is stable enough for your needs. The basic problem with the normal analog circuit for a PLL is that the time constant on the filter is way too long to build out of practical parts. The software in a micro doesn't need to be very complicated. (But since it's free once you have the micro most systems would probably add features beyond the bare minimum.) You can probably build something with no software but using a lot of digital logic. The key part is the DAC. There is a tradeoff between how many bits you need, the range it will cover and the step size. You can get a reasonable step size with non-fancy parts if you are willing to sacrifice range. The reduced range means you will have to readjust the centering occasionally as things drift. I'm not sure that's a practical approach, but if I wanted to play the no-micro game, that's the direction I would investigate. Suppose you have a 12 bit DAC connected to the top bits of a 20 bit up/down counter. The phase comparator says up or down every second. It takes 256 counts to bump the bottom bit of the DAC, so that's (handwave) a time constant of roughly 256 seconds. I'd probably try it in a micro before I built anything. :) -- 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] Simple solution for disciplining OCXO with 1 PPS
If you can build with small scale TTL gates you can save the need for a huge precision capacitor by storing the current EFC value in a 16-bit register/counter. This 16-bit register drives a DAC. Then you build a phase detector that can detect if the XO leads or lags the GPS. If it leads you increment the counter, if it lags you decrement the counter. Every second you either adjust the register or do nothing. The DAC is nothing more than 16 precision resisters each one twice the value of the next one, each connected to one bit of the register by a transistor switch. I would only implement this as exercise to show how cool 1970's technology was. It would be far more impressive if you limited yourself to 1960's technology. I say this because one of my other hobbies is building tube based audio gear. The last thing I built was a spring reverb, using a steel spring as the delay.I already have the software version but the physical spring is more fun to use. I think a 60's or 70's vintage GPSDXO would be unique if strictly limited to period correct technology On Sun, May 22, 2016 at 2:55 PM, Bob Camp wrote: > Hi > > Of course it’s possible, you simply need enough high quality film capacitors > to make up the control loop integrator. > You probably also would use a pile of the same capacitors to slow down the > PPS jitter a bit before it went into the loop. > The setup process would probably involve a bunch of toggle switches or relays > to walk the loop into the long time constant > mode. You would be wise to put the caps all in some sort of oven arrangement. > That way odd drafts hating the caps would > not drive the GPSDO nuts. > > Bob > >> On May 22, 2016, at 1:41 PM, Bernd Neubig wrote: >> >> Hello Fellow time-nuts, >> I am looking for a simple solution to discipline my 10 MHz reference OCXO in >> my private lab with an 1 PPS signal from a separate GPS receiver. >> I am curious if there is a solution possible without programming a >> microcontroller, as I am an old-fashioned "analogue" guy ;) >> I am well aware, that such a solution would have a lot of disadvantages, as >> it cannot effectively compensate for short-term variations. However I would >> be happy if such a KISS solution could achieve a stability (STS) of better >> 1E-10 over an hour. I know this is a damned long integration time for an >> analogue integrator... >> If that sounds too weird, I am open to receive advises for a microcontroller >> based solution. >> >> Thanks a lot for your comments to come. >> BTW: you need not to teach me about basics of short-term stability. I just >> want to evaluate the limits of a possible analogue solution. For sure, >> that's not real disciplining, but more like a long-tau integration PLL >> >> Best regards >> Bernd DK1AG >> >> ___ >> time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
On Sun, 22 May 2016 19:41:25 +0200, Bernd Neubig wrote: > Hello Fellow time-nuts, > I am looking for a simple solution to discipline my 10 MHz reference > OCXO in my private lab with an 1 PPS signal from a separate GPS > receiver. There seems to be some TU60 D102 on *bay search for #: 131819953988 CFO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
On Sun, May 22, 2016 at 3:52 PM, Attila Kinali wrote: > Judging from the ADEV plots of the M12 receiver from TvB[1], which hit > 10^-10 (w/ sawtooth) around 200s, I'd say that 10^-10 @1000s should be > easy. Can a pure analog design access the sawtooth correction? My GPS receivers send sawtooth as a digital message on a serial port. I don't know if saw tooth correction is required to meet his spec. I think what he needs if he wants to go 100% analog is a GPS receiver that outputs pulses at 10Hz not 1Hz. But to program the pulse rate he'd need to send data to the serial control port. -- 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] Simple solution for disciplining OCXO with 1 PPS
How do you measure "simple"? Do you count the chips and the passive components or do you count lines of code? Or maybe you draw a block diagram and count the blocks and the number of interconnections? If you count chips the design with the micro controller wins by a long shot But if you count lines of code, even a one foot square PCB loaded with op amps and precision passive parts wins. I think the design presented here by Lars Walenious is about as simple as it gets. I build a GPS disciplined XO using only part of Lars' design so it was even more simple but I don't know if I got to 1E-10. (my goal was to experiment to find the simplest design that could still work, so removed everything I could.) Lars used a regular Arduino for the micro controller. These are by far the easiest to program micro you will find. Ease of use was their primary design goal. I used a "mini" version of the Arduino, same thing but smaller and 8x cheaper. An advantage of using a micro controller is that it is easy to make changes but I find most important is that it can log internal data so you can collect performance statistics and make informed design changes until you like the logged statistics On Sun, May 22, 2016 at 10:41 AM, Bernd Neubig wrote: > Hello Fellow time-nuts, > I am looking for a simple solution to discipline my 10 MHz reference OCXO in > my private lab with an 1 PPS signal from a separate GPS receiver. > I am curious if there is a solution possible without programming a > microcontroller, as I am an old-fashioned "analogue" guy ;) > I am well aware, that such a solution would have a lot of disadvantages, as > it cannot effectively compensate for short-term variations. However I would > be happy if such a KISS solution could achieve a stability (STS) of better > 1E-10 over an hour. I know this is a damned long integration time for an > analogue integrator... > If that sounds too weird, I am open to receive advises for a microcontroller > based solution. > > Thanks a lot for your comments to come. > BTW: you need not to teach me about basics of short-term stability. I just > want to evaluate the limits of a possible analogue solution. For sure, that's > not real disciplining, but more like a long-tau integration PLL > > Best regards > Bernd DK1AG > > ___ > time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
On Sun, 22 May 2016 19:41:25 +0200, Bernd Neubig wrote: > Hello Fellow time-nuts, > I am looking for a simple solution to discipline my 10 MHz reference > OCXO in my private lab with an 1 PPS signal from a separate GPS > receiver. > I am curious if there is a solution possible without programming a > microcontroller, as I am an old-fashioned "analogue" guy ;) > I am well aware, that such a solution would have a lot of disadvantages, > as it cannot effectively compensate for short-term variations. However I > would be happy if such a KISS solution could achieve a stability (STS) > of better 1E-10 over an hour. I know this is a damned long integration > time for an analogue integrator... > If that sounds too weird, I am open to receive advises for a > microcontroller based solution. > Bernd - Get a gps with 10Khz or more out , i think the 10Khz jupiters are "gone" , but a LEA5-T or LEA6-T could output ie. 1Mhz , the divide the OCXO by 10 and phaselock the 2. Use "millers" XOR http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm Or this one using a 4046 http://gpsdo.i2phd.com/ Pure "Analog" 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] Simple solution for disciplining OCXO with 1 PPS
Hoi Bernd, Is there any special reason for this endavour or are you just courious what can be done? On Sun, 22 May 2016 19:41:25 +0200 "Bernd Neubig" wrote: > I am well aware, that such a solution would have a lot of disadvantages, > as it cannot effectively compensate for short-term variations. However I > would be happy if such a KISS solution could achieve a stability (STS) of > better 1E-10 over an hour. I know this is a damned long integration time for > an analogue integrator... With a pure analog solution, anything with a tau more than a couple of seconds will depend on the GPS receivers performance. Judging from the ADEV plots of the M12 receiver from TvB[1], which hit 10^-10 (w/ sawtooth) around 200s, I'd say that 10^-10 @1000s should be easy. > If that sounds too weird, I am open to receive advises for a microcontroller > based solution. If you want to go that way, probably the simplest solution would be to take one of Nick Sayers boards, pull out the GPS receiver and feed the PPS input from your GPS receiver. > Thanks a lot for your comments to come. > BTW: you need not to teach me about basics of short-term stability. > I just want to evaluate the limits of a possible analogue solution. For > sure, that's not real disciplining, but more like a long-tau integration PLL The simplest solution that comes to my mind would be some form of time to amplitude conversion, using the PPS from the GPS as start and some OCXO derived (aka divided down) signal. It can be a full fledged TAC like the ones used for TICs (see Bruce Griffith's design[2]) or something as simple as the 4046 based one in Nick Sayers circuit. Then, use a sample and hold circuit to replicate and stabilize this voltage and feed it to a discretely build PI controller. The big problem of this circuit will be the long time constant you will need in the PI controller and the droop of the capacitors in it. You will need a clean board and some guard rings at the critical points to keep the leakage currents low. Attila Kinali [1] http://www.leapsecond.com/pages/m12-adev/ [2] https://www.febo.com/pipermail/time-nuts/2012-December/073224.html (in case you have trouble viewing it, let me know, i have a pdf version) -- Reading can seriously damage your ignorance. -- 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] Simple solution for disciplining OCXO with 1 PPS
Bernd, On 05/22/2016 07:41 PM, Bernd Neubig wrote: Hello Fellow time-nuts, I am looking for a simple solution to discipline my 10 MHz reference OCXO in my private lab with an 1 PPS signal from a separate GPS receiver. I am curious if there is a solution possible without programming a microcontroller, as I am an old-fashioned "analogue" guy ;) I am well aware, that such a solution would have a lot of disadvantages, as it cannot effectively compensate for short-term variations. However I would be happy if such a KISS solution could achieve a stability (STS) of better 1E-10 over an hour. I know this is a damned long integration time for an analogue integrator... If that sounds too weird, I am open to receive advises for a microcontroller based solution. OK, I assume you can tolerate to work with digital gates. Square your sine up, if needed. Divide down in steps of 10 to 1 Hz. Resynchronize with original 10 MHz using a DFF. Use a SR-flip-flop to compare the two PPSes. Do a PI-filter with an op-amp, two resistors and a capacitor (one resistor and cap in the negative feedback part, one resistor from the source. That in principle is all what you need. You can use a standard RC lowpass filter to improve the noise filtering, but keep the bandwidth of it high enough not to interfere with the damping of the loop. Far from optimal, but you shuold be able to get it to lock. Dividers might be not be needed, and removing those will help to make divider state less of a track-in issue, thus maintaining lock quicker. However, there is a benefit in avoiding at least some of the cycle ambiguity, so at least the first divide by 10 should be maintained. I'm sure this can be optimized. Thanks a lot for your comments to come. BTW: you need not to teach me about basics of short-term stability. I just want to evaluate the limits of a possible analogue solution. For sure, that's not real disciplining, but more like a long-tau integration PLL Well, since the loop bandwidth will be larger than optimum, more of the GPS noise will creep into the output and not really give your measurement a good chance. Long-term will work, but short-term not so much. Longer tau/lower bandwidth will filter away more of the GPS noise. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS
Hi Of course it’s possible, you simply need enough high quality film capacitors to make up the control loop integrator. You probably also would use a pile of the same capacitors to slow down the PPS jitter a bit before it went into the loop. The setup process would probably involve a bunch of toggle switches or relays to walk the loop into the long time constant mode. You would be wise to put the caps all in some sort of oven arrangement. That way odd drafts hating the caps would not drive the GPSDO nuts. Bob > On May 22, 2016, at 1:41 PM, Bernd Neubig wrote: > > Hello Fellow time-nuts, > I am looking for a simple solution to discipline my 10 MHz reference OCXO in > my private lab with an 1 PPS signal from a separate GPS receiver. > I am curious if there is a solution possible without programming a > microcontroller, as I am an old-fashioned "analogue" guy ;) > I am well aware, that such a solution would have a lot of disadvantages, as > it cannot effectively compensate for short-term variations. However I would > be happy if such a KISS solution could achieve a stability (STS) of better > 1E-10 over an hour. I know this is a damned long integration time for an > analogue integrator... > If that sounds too weird, I am open to receive advises for a microcontroller > based solution. > > Thanks a lot for your comments to come. > BTW: you need not to teach me about basics of short-term stability. I just > want to evaluate the limits of a possible analogue solution. For sure, that's > not real disciplining, but more like a long-tau integration PLL > > Best regards > Bernd DK1AG > > ___ > time-nuts mailing 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] Simple solution for disciplining OCXO with 1 PPS
Among Simple , analog, 1PPS you'll have to pick two of the three. The miller GPSDO needs 10KHz it's simple and analog. http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm The IK0OTG is simple, uses 1PPS and is digital http://www.ik0otg.net/index.php?option=com_content&view=article&id=53%3Aoscillatore-10mhz-sinc-gps&catid=34%3Ahome-made&Itemid=59&lang=en At 10:41 AM 5/22/2016, Bernd Neubig wrote: Hello Fellow time-nuts, I am looking for a simple solution to discipline my 10 MHz reference OCXO in my private lab with an 1 PPS signal from a separate GPS receiver. I am curious if there is a solution possible without programming a microcontroller, as I am an old-fashioned "analogue" guy ;) I am well aware, that such a solution would have a lot of disadvantages, as it cannot effectively compensate for short-term variations. However I would be happy if such a KISS solution could achieve a stability (STS) of better 1E-10 over an hour. I know this is a damned long integration time for an analogue integrator... If that sounds too weird, I am open to receive advises for a microcontroller based solution. Thanks a lot for your comments to come. BTW: you need not to teach me about basics of short-term stability. I just want to evaluate the limits of a possible analogue solution. For sure, that's not real disciplining, but more like a long-tau integration PLL Best regards Bernd DK1AG ___ time-nuts mailing 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.
