[time-nuts] Finding a spare part for HP5370B
Hello! I have been given an HP5370B; I have checked it and it seems to work fine, but unfortunately its missing the red plastic in the display window. If anyone has one of these equipments for spare parts, I would be very grateful if I can buy this part. Please contact me off list if you can help at p.arb...@securimar.com Many thanks P. Arbona ___ time-nuts mailing 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] Another "atomic" clock question
David, Thanks - got it. Best Regards, John W. On Fri, Mar 7, 2014 at 10:53 PM, David J Taylor < david-tay...@blueyonder.co.uk> wrote: > Hello David, > > Not sure what is wrong here - I still can't reach it. > > If it isn't too much trouble - can you send me a screen shot off-list - I > can look up the patents as long as the numbers are listed. > > Thanks! > John W. > > > Screen-shot and page HTML sent as requested. > > Cheers, > > David > -- > SatSignal Software - Quality software written to your requirements > Web: http://www.satsignal.eu > Email: david-tay...@blueyonder.co.uk > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing 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] Another "atomic" clock question
Hello David, Not sure what is wrong here - I still can't reach it. If it isn't too much trouble - can you send me a screen shot off-list - I can look up the patents as long as the numbers are listed. Thanks! John W. Screen-shot and page HTML sent as requested. Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Another "atomic" clock question
j...@jtmiller.com said: > I may switch the GPS module at a later date to one which provides sawtooth > info if I really feel the need and add a delay line. Frankly I think I'll > never get around to it. One nasty problem with hanging bridges is that if you don't believe in them, then you won't setup your monitoring system to notice them. -- 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] Another "atomic" clock question
On 08/03/14 00:52, Bob Camp wrote: Hi With a “real” 12 to 13 bit ADC and a 200 ns TDC pulse you would ideally get < 200 / 4096 as your LSB. Nothing like this is ever perfect, so you probably aren’t going to get <50 ps. You probably will be below 100 ps. That’s plenty good enough to make sawtooth correction useful. When you have sawtooth corrections, the actual time of the PPS is not so important, but it will be that reference pulse which gives the high time-resolution info about the oscillators phase. The sawtooth correction will reduce the GPS modules TCXO into a common view oscillator which (almost) cancels out. If you do not have sawtooth corrections, indirect tracking might be possible to consider. 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] Another "atomic" clock question
On 07/03/14 19:28, Lars Walenius wrote: Chris, about using one Arduino for two GPSDO controllers: Even if a microcontroller has lots of capacity I would recommend to use separate controllers for each oscillator. One of the reasons is what Tom van Baak said about using only one interrupt to avoid jitter and even if you trigger both channels from the same PPS and have just one interrupt you will have a problem that you can´t read two ADC´s at the same time. Even the HC390 I wouldn´t use for two different oscillators to prevent crosstalk. Both the processor and HC390 is so cheap it isn´t worth the risk IMO. Cross-talk typically happens though ground-bounce. Just using separate chips reduces the effect. May not be much of an issue at ns level, but below. Actually I would also recommend to put them in separate boxes even if it is more work (and I´m lazy ) to get best performance. Having two GPSDO´s that you can compare is very nice as long as you understand how they correlate , if that is not what you want to test. Of course you can also set one or both in hold mode to test them freerunning. Some telecom rubidiums have fairly noisy output. Steering an OCXO for clean-up might actually provide the best of both worlds. Holdover of the rubidiums and phase-noise of the OCXO. In that case, keeping them in the same box makes sense. The arduino could contribute long-term integrator memory and possibly do temperature compensation of the OCXO as a feed-forward approach. I have thought of connecting the M12 to the Arduino and if someone can help with code to get the sawtooth correction value into the Arduino and decoded I would be glad to have it. I've proposed to some of my local friends here, and we will probably do something with LPROs. We need to look at what GPS modules there is. I think sawtooth correction should be added. It's not that hard. One really wants two serial ports, one for the GPS and one for monitoring. 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] Another "atomic" clock question
Didn't mean to cause a firestorm. Just used the term simple to describe a Lead/Lag D FF phase comparator. I view it as simple compared to a high speed counter. My GPSDO will have just such a FF whose state will be read by the micro which will implement a PI filter in software and drive a 20bit TI sigma delta DAC to apply corrections to the OCXO. Micro and all other clocks on the design are driven from the OCXO. I may switch the GPS module at a later date to one which provides sawtooth info if I really feel the need and add a delay line. Frankly I think I'll never get around to it. I'll publish a schematic, code and test results once I have something working. Thanks Jim ab3cv Date: Fri, 7 Mar 2014 09:23:54 -0800 From: Chris Albertson To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Another "atomic" clock question Message-ID: Content-Type: text/plain; charset=ISO-8859-1 On Fri, Mar 7, 2014 at 5:25 AM, Jim Miller wrote: > I think the hardware delay line approach is the only solution for a simple > D FF lead/lag phase comparator. It would be placed ahead of the FF. Simple? You are going to need a micro controller and software to (1) tall the GPS to output the sawtooth function, they don't typically output it untell you tell it to. then (2) recover the sawtooth function from the serial data. Then(3) convert it to the "counts" that units used in the delay line. Finally (4) you need to interface the delay line to the processor and send the current sawtooth function value over that interface once per second. Also when I do stuff like this I always want some kind of LCD display or at least blink LEDS so I know what's going on inside and then it is at least running. Your simple analog devices no longer a simple analog device. Do a full up parts count for both designes. I think the digital correction comes in lower. Both solutions need the same micro controller and it's support circuitry. As to which GPSes send sawtooth. It's a common feature but typically you need to enable it, the same way you'd enable a self-survey or set a minimum elevation angle or whatever. 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] Another "atomic" clock question
On Fri, Mar 7, 2014 at 9:32 PM, Bob Camp wrote: > On the 4's and 5's you only got a pulse + correction with the T model. I have a 6T so I can only read the data sheets for the others but the OP said uBlox-6. Perhaps there are various firmware releases but the LEA-5 family is described as being operationally the same as the LEA-6 family with respect to PG reports. ___ time-nuts mailing 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] Another "atomic" clock question
Hi On the 4’s and 5’s you only got a pulse + correction with the T model. Bob On Mar 7, 2014, at 8:06 PM, Paul wrote: > On Fri, Mar 7, 2014 at 5:45 PM, Bob Camp wrote: > >> You must have the T version of the modules to get the sawtooth out of them. > > > Per the documents (and M Tharp) you don't need a T model to get > quantization correction (I only have a T so I don't have first-hand > information). I understand this is also the case with the NEO models as > well. In the LEA-6 generation only T models provide RTK data, dual > Timepulse and support "Time Mode" which is what they call a stationary > antenna with high quality position information. > ___ > time-nuts mailing 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] Another "atomic" clock question
On Fri, Mar 7, 2014 at 5:45 PM, Bob Camp wrote: > You must have the T version of the modules to get the sawtooth out of them. Per the documents (and M Tharp) you don't need a T model to get quantization correction (I only have a T so I don't have first-hand information). I understand this is also the case with the NEO models as well. In the LEA-6 generation only T models provide RTK data, dual Timepulse and support "Time Mode" which is what they call a stationary antenna with high quality position information. ___ time-nuts mailing 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] TRACOR_600_Rubidium_reference ops/svc manual uploaded
Hello to the group. I had the opportunity to remotely help Chris troubleshoot his Tracor model 600 RB. A nice old unit. Its now operational again. He was kind enough to send me the ops/svc manual and I have scanned it into a pdf. The manual has been uploaded to Diddiers site and it will take a few days to find its correct home. http://www.ko4bb.com/manuals/ So now there are at least two Tracor RB references manuals on the net. The 304 in Italy and the 600 on Diddiers site. Regards Paul WB8TSL ___ time-nuts mailing 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] Another "atomic" clock question
Hello David, Not sure what is wrong here - I still can't reach it. If it isn't too much trouble - can you send me a screen shot off-list - I can look up the patents as long as the numbers are listed. Thanks! John W. j...@westmorelandengineering.com On Thu, Mar 6, 2014 at 11:09 PM, David J Taylor < david-tay...@blueyonder.co.uk> wrote: > To the Mike that posted: > > http://www.pst.netii.net/patents.htm - I tried going to your site - can't > reach it. Is the site operational? I wanted to take a look at your > patents. > > Thanks, > John Westmoreland > == > > Jon, > > It's working OK from Edinburgh at 07:08 UTC. > > David > -- > SatSignal Software - Quality software written to your requirements > Web: http://www.satsignal.eu > Email: david-tay...@blueyonder.co.uk > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing 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] Another "atomic" clock question
Hi With a “real” 12 to 13 bit ADC and a 200 ns TDC pulse you would ideally get < 200 / 4096 as your LSB. Nothing like this is ever perfect, so you probably aren’t going to get <50 ps. You probably will be below 100 ps. That’s plenty good enough to make sawtooth correction useful. Bob On Mar 7, 2014, at 6:38 PM, Jim Lux wrote: > On 3/7/14 3:33 PM, Chris Albertson wrote: >> Let's see what is needed. >> >> The ADC is 10-bits so it can read to one part in 1024. It's a 5 volt >> full scale so we are only able to measure 5 millivolt increments >> > > if you use the teensy3 it has a 16 bit ADC with realistically, about 13 bits > performance. The teensy3.1 has a 12 bit DAC, but since I haven't got one in > my hot little hands yet, I don't know the performance. > > ___ > time-nuts mailing 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] Another "atomic" clock question
On 3/7/14 3:33 PM, Chris Albertson wrote: Let's see what is needed. The ADC is 10-bits so it can read to one part in 1024. It's a 5 volt full scale so we are only able to measure 5 millivolt increments if you use the teensy3 it has a 16 bit ADC with realistically, about 13 bits performance. The teensy3.1 has a 12 bit DAC, but since I haven't got one in my hot little hands yet, I don't know the performance. ___ time-nuts mailing 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] Another "atomic" clock question
Let's see what is needed. The ADC is 10-bits so it can read to one part in 1024. It's a 5 volt full scale so we are only able to measure 5 millivolt increments The uP runs about 16 million instructions per second. What if we wait 1000 instructions to read the ADC what will the error be? The "1000" number is conservative by at least a factor of 10. The discharge resister has (assume) a one second time constant. The read delay would be 1000/16,000,000 or 63 uSec. in that time the voltage would have changed about 300 microvolts. The change is about 15 times less then the DAC is able to measure.But because of the conservative estimate it might 150 times to small to measure. So randomly delayed reads of the ADC will not matter. That said I'm sure we can do 100X better then the 63 uS estimate. On the other side, charging the cap. Let's say I mis-measured a wire and it is 1cm longer then I though. The added delay adds a tiny delay but this is not going to show up in a 10-bit ADC. Same if the propagation delay changes through the 74HC390 based variable loading of other output pins or noise from the 78ls05 voltage regulator. The DAC is set up for 5 mV steps. I just don't need to worry about errors that are well under 0.5 mV. If I were building this using a 24-bit ADC and wanted to take full advantage of its resolution then tiny things matter. On Fri, Mar 7, 2014 at 12:47 PM, Jim Lux wrote: > On 3/7/14 12:31 PM, Chris Albertson wrote: >> >> On Fri, Mar 7, 2014 at 10:28 AM, Lars Walenius >> wrote: >>> >>> Chris, about using one Arduino for two GPSDO controllers: >>> >>> Even if a microcontroller has lots of capacity I would recommend to use >>> separate controllers for each oscillator. One of the reasons is what Tom van >>> Baak said about using only one interrupt to avoid jitter and even if you >>> trigger both channels from the same PPS and have just one interrupt you will >>> have a problem that you can´t read two ADC´s at the same time. >> >> >> You don't have to read both at the same time. All you need is to have >> a constant time between the interrupt and when you read the ADC. That >> constant can be any reasonable number so long as it remains constant >> >>> > > > there are plenty of Arduino-like boards out there that have ADCs triggered > by the timer, which also fires the interrupt, but you don't have to worry > about reading the ADC late. > > The teensy3.1 (new version of the teensy3 from PJRC) has a dual ADC, which > can simulataneously sample. I've run the teensy3 at 300ksps+ (48 MHz > processor clock). Right now, I've got software that is interrupt driven at > 50 kHz that does two adc reads in a row and then feeds a 2 stage CIC > decimator chain. It consumes about 60% of the processor, the bulk of which > is the actual ADC read and the first integrators. > > > for <$20, it's hard to beat.. the only downside is that you can't go down to > radio shack and buy one on the spur of the moment. > > They'll also do a not very optimized fixed point 128 point FFT in about 0.9 > milliseconds: > N pts μs > 128 897 > 64 402 > 32 175 > 16 82 > > > ___ > time-nuts mailing 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] OT - indicator question
Hi all, I have a question a bit OT but related to time nuttery. I like making unusual GPS controlled clocks including CRT displays like this: https://www.youtube.com/watch?v=Jjs7AWL8B1k A few years ago I picked up a 1970s vintage Japanese made Sperry Mk-8 Radar indicator unit with the intention of making a large screen radar clock. It's finally getting some bench time and before starting on a long and painful reverse engineering effort I was wondering whether anyone might have some data or schematics about it. It will be an interesting challenge - I've never done anything with a magnetically deflected CRT before. There are a few familiar bits such as the power supplies, video amp and IF strip but there's also some other boards which might be sweep generators or circle generators etc. Alas no deflection amplifiers - the yoke cable goes to a connector on the back panel. It's all discrete technology, no ICs. If this sounds familiar to any of the knowledgeable people here I'd love to hear from you . Thanks, Morris ___ time-nuts mailing 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] Another "atomic" clock question
Hi You can put the LEA-5T or the LEA-6T into a mode where they put out the sawtooth information on auto pilot. Once you get it set up (which you do each time you boot) it just keeps going. You must have the T version of the modules to get the sawtooth out of them. Bob On Mar 7, 2014, at 4:10 PM, Paul wrote: > On Fri, Mar 7, 2014 at 12:57 PM, Jim Miller wrote: > >> I'm new at this obviously. I was just looking at the uBlox-6 info and I >> don't see where in the NMEA sentences the sawtooth info is contained. >> > > u-blox calls it (Time)Pulse Granularity (PG). You're looking for the UBX > clock info sentence which is "proprietary" so it starts with a P ($PUBX,04 > in this case). It's a polled sentence > > It's in the GPS.G6-SW-10018-F document. > ___ > time-nuts mailing 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] Another "atomic" clock question
jim...@earthlink.net said: > for <$20, it's hard to beat.. the only downside is that you can't go down > to radio shack and buy one on the spur of the moment. At that price, you can keep a couple on the shelf. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Another "atomic" clock question
On Fri, Mar 7, 2014 at 12:57 PM, Jim Miller wrote: > I'm new at this obviously. I was just looking at the uBlox-6 info and I > don't see where in the NMEA sentences the sawtooth info is contained. > u-blox calls it (Time)Pulse Granularity (PG). You're looking for the UBX clock info sentence which is "proprietary" so it starts with a P ($PUBX,04 in this case). It's a polled sentence It's in the GPS.G6-SW-10018-F document. ___ time-nuts mailing 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] Another "atomic" clock question
On 3/7/14 12:31 PM, Chris Albertson wrote: On Fri, Mar 7, 2014 at 10:28 AM, Lars Walenius wrote: Chris, about using one Arduino for two GPSDO controllers: Even if a microcontroller has lots of capacity I would recommend to use separate controllers for each oscillator. One of the reasons is what Tom van Baak said about using only one interrupt to avoid jitter and even if you trigger both channels from the same PPS and have just one interrupt you will have a problem that you can´t read two ADC´s at the same time. You don't have to read both at the same time. All you need is to have a constant time between the interrupt and when you read the ADC. That constant can be any reasonable number so long as it remains constant there are plenty of Arduino-like boards out there that have ADCs triggered by the timer, which also fires the interrupt, but you don't have to worry about reading the ADC late. The teensy3.1 (new version of the teensy3 from PJRC) has a dual ADC, which can simulataneously sample. I've run the teensy3 at 300ksps+ (48 MHz processor clock). Right now, I've got software that is interrupt driven at 50 kHz that does two adc reads in a row and then feeds a 2 stage CIC decimator chain. It consumes about 60% of the processor, the bulk of which is the actual ADC read and the first integrators. for <$20, it's hard to beat.. the only downside is that you can't go down to radio shack and buy one on the spur of the moment. They'll also do a not very optimized fixed point 128 point FFT in about 0.9 milliseconds: N pts μs 128 897 64 402 32 175 16 82 ___ time-nuts mailing 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] Another "atomic" clock question
On Fri, Mar 7, 2014 at 10:28 AM, Lars Walenius wrote: > Chris, about using one Arduino for two GPSDO controllers: > > Even if a microcontroller has lots of capacity I would recommend to use > separate controllers for each oscillator. One of the reasons is what Tom van > Baak said about using only one interrupt to avoid jitter and even if you > trigger both channels from the same PPS and have just one interrupt you will > have a problem that you can´t read two ADC´s at the same time. You don't have to read both at the same time. All you need is to have a constant time between the interrupt and when you read the ADC. That constant can be any reasonable number so long as it remains constant > > Even the HC390 I wouldn´t use for two different oscillators to prevent > crosstalk. Both the processor and HC390 is so cheap it isn´t worth the risk > IMO. Risk? It's easy to measure. Risk is when you don't know what is going to happen. But in this case we can test. > > Actually I would also recommend to put them in separate boxes even if it is > more work (and I´m lazy ) to get best performance. I think you might be addressing pico seconds on a system that works in the few nano seconds range.A serial commanded Rb oscillator moves in such large steps that I'm 100% sure the step quantization error will dominate everything. The step size is something like 5E-11. But the stability I expect will be very good. > > Having two GPSDO´s that you can compare is very nice as long as you > understand how they correlate , if that is not what you want to test. Of > course you can also set one or both in hold mode to test them freerunning. > > > I have thought of connecting the M12 to the Arduino and if someone can help > with code to get the sawtooth correction value into the Arduino and decoded I > would be glad to have it. I'm looking for an OCXO. Not much reason to start before I find one. People are over bidding on eBay for 30 year old salvage parts. eventually I'll win one at a reasonable price. Then I'll write up my results. In the mean time I've started a wholesale refactoring of the posted Arduino code. I need t make it a bit more modular and "testable." I have an Motorola Oncore UT+ type GPS. I think it might have the same sawtooth.I'm pretty sure there is code in the standard NTP distribution to read the Oncore type data and (maybe sawtooth???) I plan to read the NTP drivers and borrow whatever is usable. I did just build and finish testing a serial interfaced LCD display. Now I can display states using just two Arduino pins. (Without the serial interface an LCD takes 6 to 10 pins) I'm using I2C so I can add other devices to the same serial interface, like a DAC or whatever > > > > Lars > > > > > > From: Chris Albertson > > > > On Wed, Mar 5, 2014 at 5:43 PM, Didier Juges wrote: >> Tom and Bob, >> It is not obvious to me that it is "easier" to simply apply a correction in >> nS increments with a range as wide as 100nS. How is this done? Using >> switched delay lines or delay gates? > Here is my plan for processing saw tooth data. If it's not going to > work I'd rather hear about it now then a month from now after I've put > in some effort. > This is going into Lars' Arduino based GPSDO. Every second I read the > voltage on a TIC capacitor. This tells by the phase in nanoseconds > between the PPS and the OCXO. Then I add whatever the current GPS > sawtooth value is to whatever my TIC said. I compare this to a set > point. This is the phase error. The OCXO is adjusted based on a > filtered version of this error. > So in short, I don't correct even try to delay the pulse. I don't see > any need to do that. I measure the pulse and get a number in > nanoseconds. then I use sawtooth to correct the number. > It seems way-hard and with no purpose to correct the pulse and then > measure it. Better to correct the measurement. I think it is more > accurate too a delay could never be perfect. > The controller has LOT of spare capacity so I don't see way I can't > add one of more TIC channels and a few more DACs I should be able to > discipline an OCXO and my Rb oscillator from the same GPS PPS input. > The 74HC360 is only 1/2 used an Arduino has enough spare pins. Any > one more 74HC4046 and some passive parts would be required to build a > dual channel GPSDO. > It will be interesting to look at andompare the 10MHz outputs of two > oscillators that are being disciplined by the same controller and GPS > receiver. > > -- > > 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
Re: [time-nuts] Another "atomic" clock question
On Fri, Mar 7, 2014 at 9:57 AM, Jim Miller wrote: > I'm new at this obviously. I was just looking at the uBlox-6 info and I > don't see where in the NMEA sentences the sawtooth info is contained. There is no NMEA sawthooth sentence. You typically have to put the serial data output into binary mode. NMEA is a "lowest common denominator" data format used by GPS, marine autopilots, compass, wind and log instruments. It was never designed for timing. It's for ship and boat instruments. -- 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] Another "atomic" clock question
Chris, about using one Arduino for two GPSDO controllers: Even if a microcontroller has lots of capacity I would recommend to use separate controllers for each oscillator. One of the reasons is what Tom van Baak said about using only one interrupt to avoid jitter and even if you trigger both channels from the same PPS and have just one interrupt you will have a problem that you can´t read two ADC´s at the same time. Even the HC390 I wouldn´t use for two different oscillators to prevent crosstalk. Both the processor and HC390 is so cheap it isn´t worth the risk IMO. Actually I would also recommend to put them in separate boxes even if it is more work (and I´m lazy ) to get best performance. Having two GPSDO´s that you can compare is very nice as long as you understand how they correlate , if that is not what you want to test. Of course you can also set one or both in hold mode to test them freerunning. I have thought of connecting the M12 to the Arduino and if someone can help with code to get the sawtooth correction value into the Arduino and decoded I would be glad to have it. Lars From: Chris Albertson On Wed, Mar 5, 2014 at 5:43 PM, Didier Juges wrote: > Tom and Bob, > It is not obvious to me that it is "easier" to simply apply a correction in > nS increments with a range as wide as 100nS. How is this done? Using > switched delay lines or delay gates? Here is my plan for processing saw tooth data. If it's not going to work I'd rather hear about it now then a month from now after I've put in some effort. This is going into Lars' Arduino based GPSDO. Every second I read the voltage on a TIC capacitor. This tells by the phase in nanoseconds between the PPS and the OCXO. Then I add whatever the current GPS sawtooth value is to whatever my TIC said. I compare this to a set point. This is the phase error. The OCXO is adjusted based on a filtered version of this error. So in short, I don't correct even try to delay the pulse. I don't see any need to do that. I measure the pulse and get a number in nanoseconds. then I use sawtooth to correct the number. It seems way-hard and with no purpose to correct the pulse and then measure it. Better to correct the measurement. I think it is more accurate too a delay could never be perfect. The controller has LOT of spare capacity so I don't see way I can't add one of more TIC channels and a few more DACs I should be able to discipline an OCXO and my Rb oscillator from the same GPS PPS input. The 74HC360 is only 1/2 used an Arduino has enough spare pins. Any one more 74HC4046 and some passive parts would be required to build a dual channel GPSDO. It will be interesting to look at andompare the 10MHz outputs of two oscillators that are being disciplined by the same controller and GPS receiver. -- 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] Another "atomic" clock question
j...@jtmiller.com said: > I'm new at this obviously. I was just looking at the uBlox-6 info and I > don't see where in the NMEA sentences the sawtooth info is contained. Is it > a manufacturer specific option that needs be turned on? Or is it contained > within a standard NMEA sentence somewhere. I also didn't see it mentioned in > the uBlox u-Center software users guide. NMEA doesn't cover sawtooth. You have to shift to the vendor's proprietary/binary protocol. Also, you have to get the timing version of the firmware. -- 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] Another "atomic" clock question
I'm new at this obviously. I was just looking at the uBlox-6 info and I don't see where in the NMEA sentences the sawtooth info is contained. Is it a manufacturer specific option that needs be turned on? Or is it contained within a standard NMEA sentence somewhere. I also didn't see it mentioned in the uBlox u-Center software users guide. Thanks Jim ab3cv Message: 3 Date: Fri, 7 Mar 2014 16:26:35 +0100 From: Azelio Boriani To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Another "atomic" clock question Message-ID: Content-Type: text/plain; charset=ISO-8859-1 Every timing GPS receiver has the sawtooth information: uBlox, iLotus, SkyTraq, Trimble just to name someone ___ time-nuts mailing 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] Another "atomic" clock question
I have quite often seen the simple D FF lead/lag phase comparator mentioned but not found any practical implementation in a GPSDO. Has anyone a schematic and hopefully real data? What is the performance? Is it better than a conventional GPSDO with a TIC+uP+DAC or is it only simpler? Lars On Fri, Mar 7, 2014 at 2:25 PM, Jim Miller wrote: > I think the hardware delay line approach is the only solution for a simple > D FF lead/lag phase comparator. It would be placed ahead of the FF. ___ time-nuts mailing 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] Another "atomic" clock question
On Fri, Mar 7, 2014 at 5:25 AM, Jim Miller wrote: > I think the hardware delay line approach is the only solution for a simple > D FF lead/lag phase comparator. It would be placed ahead of the FF. Simple? You are going to need a micro controller and software to (1) tall the GPS to output the sawtooth function, they don't typically output it untell you tell it to. then (2) recover the sawtooth function from the serial data. Then(3) convert it to the "counts" that units used in the delay line. Finally (4) you need to interface the delay line to the processor and send the current sawtooth function value over that interface once per second. Also when I do stuff like this I always want some kind of LCD display or at least blink LEDS so I know what's going on inside and then it is at least running. Your simple analog devices no longer a simple analog device. Do a full up parts count for both designes. I think the digital correction comes in lower. Both solutions need the same micro controller and it's support circuitry. As to which GPSes send sawtooth. It's a common feature but typically you need to enable it, the same way you'd enable a self-survey or set a minimum elevation angle or whatever. 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] Another "atomic" clock question
As I am a poor programmer and also lazy (includes hardware and software), I would like to ask the following question: How much better would a GPSDO like the Arduino GPSDO be with added sawtooth correction? Let’s say we assume the 1ns resolution TIC is perfect, no jitter from the uP and the DAC have a perfect frequency setting resolution of 1E-13. The receiver in my case is a M12 set in position hold mode after a survey and my measured ADEV starts at 2E-8 for 1sec and is 2E-11 at 1000secs. The MDEV is 2E-8 at 1sec and 2E-12 at 1000sec (very similar to what found on the leapsecond.com M12 page). The oscillator is my “8663”-type OCXO that I have measured to have an ADEV just above 1E-12 over the range 1-1secs. Let’s say the oscillator is perfect at 2E-12 over 1-1secs. The Arduino GPSDO control loop works as follows, as far as I understand, if set to a time constant =1000secs and damping =2 : TIC value is pre-filtered similar to an RC filter with 250seconds time constant (I like to refer to analog RC-filters being an RF and analog engineer) The filtered TIC value is divided by the time constant 1000 and adjusts the DAC proportional to this. The filtered TIC value integrates the DAC value after dividing it by (time constant * time constant * damping) = (/1000/1000/2). My explicit question is how much better the ADEV of the GPSDO oscillator output will be with sawtooth correction added in the software? Another question is how much better the ADEV will be if the TIC had a resolution of 0.1nsec instead? Maybe a third question could be if the DAC only had 1E-12 resolution? Is some more important factors needed to be known to calculate this to a reasonable accuracy? e.g. room temperature variations of the M12. In my own measurements, with about the same conditions as above with a time constant of 1000s, I got an output ADEV of about 3E-12 at Tau 1000s measured with an HP5370 against an LPRO Rb (plot was attached to Arduino GPSDO thread Feb 12 2014). This value looks very similar to the combination of the 1PPS MDEV and OCXO ADEV. Is that just a coincidence? Lars ___ time-nuts mailing 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] Another "atomic" clock question
Every timing GPS receiver has the sawtooth information: uBlox, iLotus, SkyTraq, Trimble just to name someone. On Fri, Mar 7, 2014 at 2:25 PM, Jim Miller wrote: > I think the hardware delay line approach is the only solution for a simple > D FF lead/lag phase comparator. It would be placed ahead of the FF. > > Which GPS being built now provide sawtooth info? > > 73 > > jim ab3cv > ___ > time-nuts mailing 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] Another "atomic" clock question
I think the hardware delay line approach is the only solution for a simple D FF lead/lag phase comparator. It would be placed ahead of the FF. Which GPS being built now provide sawtooth info? 73 jim ab3cv ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
