Re: [time-nuts] Cheap jitter measurements

I would say my implementation is simpler than Nick’s: https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/?all . It is just an Arduino+ two HCMOS and a few passive components. >From the beginning Nick copied my interpolator. Later he added a FET that >might

Re: [time-nuts] Furuno GT-87

So the orange is the second to second timestamp difference minus 1s, or the period time measured every second minus 1s. As the period is very close to 1s the frequency difference just will be the negative value so what the graph shows is the same as eg Stable 32’s frequency data for 1s but

Re: [time-nuts] Furuno GT-87

Thanks Marks, Just a question about what reference you used for the TICC? Another question is about the orange and gray scale with respective 8 and 22ns span. The orange says TIEb and the gray PHchB. What are they? You talk about +-4ns over 24hours but what are the 22ns span when? Best

Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

Hi all, If I look on the NIST database for the last days it seems to be a daily variation of about 8-10ns. Could this be for the same reason as Ole’s variation? Is the daily variations due to not perfect ionosphere correction? Can you get much better than the data in the NIST database for an

Re: [time-nuts] Weird GPSDO behavior - update

Hello, If I look on the one hour plot it look like it goes in hold mode due to zero used satellites. If my assumption that the light blue graph in the bottom is satellites it sees no satellites during about a minute and after that it selects a fast time constant. From the TIC offset and DAC

Re: [time-nuts] Weird GPSDO behavior

If I look on the TIC graph it looks like something happen at about + or - 500ns. Could it be that the software change algoritm? Like a ”Jam Sync”. Seems like it tries to get the TIC to zero quick by changing the DAC. Maybe it thinks it gets enough close in frequency and stops and goes back to

Re: [time-nuts] Weird GPSDO behavior

If I look on the TIC graph it looks like something happen at about + or - 500ns. Could it be that the software change algoritm? Like a ”Jam Sync”. Seems like it tries to get the TIC to zero quick by changing the DAC. Maybe it thinks it gets enough close in frequency and stops and goes back to

Re: [time-nuts] Excel logarithmic function (was Thermal impact on OCXO)

ars_1Year.png". If you are willing to share the next month, we can add that to the fit. Cheers, On Fri, Nov 18, 2016 at 1:26 PM, Lars Walenius <lars.walen...@hotmail.com> wrote: > > Hopefully someone can find the correct a and b for a*ln(bt+1) with stable32 or matlab for this data s

Re: [time-nuts] Excel logarithmic function (was Thermal impact on OCXO)

are going > through some behavior that isn't representative of long-term aging, like > warm-up, retrace (I'm sure bob could name half a dozen more examples). So > the next two plots are fits of the 4 data points after day10, and seem to > fit well, "Lars_FitAfterDay10.png", "

Re: [time-nuts] Thermal impact on OCXO

Thanks Azelio, I have also thought that the EFC range probably says something. The datasheet for the OFC4834 says EFC range +-0.4ppm and that that should be enough for 15 years. The OFC MC834, I have seems very similar, but without EFC. So my 68ppm drift is well within the +-400ppb Lars

Re: [time-nuts] Thermal impact on OCXO

23 Hi > On Nov 18, 2016, at 1:31 PM, Lars Walenius <lars.walen...@hotmail.com> wrote: > > Hi Bob (and all others), > > I agree to all your points but am curious to your comment: ”that OCXO is > aging a lot for one that has been on that long”. > As I have only done this test

Re: [time-nuts] Thermal impact on OCXO

OCXO is aging a >lot for one that has been on that long). >Bob >> On Nov 16, 2016, at 2:41 PM, Lars Walenius <lars.walen...@hotmail.com> wrote: >> >> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch >> type without EFC marked OFC MC834X4-

Re: [time-nuts] Excel logarithmic function (was Thermal impact on OCXO)

Bob wrote: >As mentioned earlier in this thread. The function that has been used in >several posts >isn’t the right log function. The proper fit is to ln(bt+1) You are absolutely right. It was my mistake to use the ln(t) in the graph. As that was what I know in Excel and I don´t have Stable32

Re: [time-nuts] Thermal impact on OCXO

Many thanks to Dan! A question: About what temperature span has it been during these runs? Or do you have the temperature coefficient? Seems that the yellow line has about 50ppt due to temperature. For the orange it seems to me to have about 6E-12/day aging, is that high? Compared to the

Re: [time-nuts] Thermal impact on OCXO

FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch type without EFC marked OFC MC834X4-009W with date code 97. Probably it was from some base station testing and it had been sitting in my shelf since 98. The OCXO were battery backed but at two occasions (2004 and 2007) we

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

What is the specification for the Spectrum analyzer? They don´t tend to be useful for OCXO measurments so is this especially good? Or is it only the Analyzer phase noise we see? Lars Från: David C. Partridge Skickat: den 18 september 2016 14:43 Till:

Re: [time-nuts] A new take on the all-hardware GPSDO concept

Hi Nick, Jim Millers design is very clever and as I see can give results as good as a digital approach but it has the same limitations: The GPS jitter and the oscillator jitter in combination with the loop bandwidth. The only ADEV I have seen for the Miller GPSDO is this one

Re: [time-nuts] Jim Miller simple GPSDO

.epsondevice.com/en/products/vcxo_standard/vg4231ca.html I don't know exactly what Epson does inside that particular unit, but a trick to get wide pull range with discrete circuits is to put two or more crystals in parallel. Tim N3QE >>On Wed, Sep 14, 2016 at 4:40 AM, Lars Walenius <lars

Re: [time-nuts] Jim Miller simple GPSDO

The VCXO sensitivity given is strange as it indicates a far to wide span so I guessed 30ppm and if it is higher it still needs the damping from R2-C2. For the OCXO I used the figures given. With 2Hz per volt and 8 Volt span you have 16Hz of span. 16Hz divided with 10MHz is 1.6ppm (parts per

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Can anybody say more about the integrator term in the Tbolt? In the Arduino GPSDO I have, I use 1/TC/TC/damping and use damping = 2. I see Nick Sayer do the same but use damping 1.75. Simulations I have done in Excel seems to indicate that a damping in my sense of about 3 could be better to

Re: [time-nuts] Jim Miller simple GPSDO

As I have understood it the change of VCXO gain is the reason that R2-C2 can be omitted. With the VCXO with a large span the damping is needed otherwise it will oscillate. The XOR phase detector has a range of 50us with 10kHz in. The VCXO has maybe a span of 30ppm (us/s) and with R1-C1 time

Re: [time-nuts] Tbolt issues

l loop's response >to them. In some designs the response may be multi level. The temp transient >hits the voltage reference, DAC, and crystal in the OCXO at different times... >Bob >> On Sep 2, 2016, at 3:08 PM, Lars Walenius <lars.walen...@hotmail.com> wrote: > > I might b

Re: [time-nuts] Tbolt issues

or bump like that in the ADEV plot. >Thus the quick rule of thumb stuff falls apart. The correct way to do it will >always be to work out what the noise process is and calculate based on it. >That is not a popular thing to do .... >Bob > On Sep 2, 2016, at 6:38 AM, Lars Walen

Re: [time-nuts] Tbolt issues

Hello Tom, What are the conditions for your charts? Are the Tbolts in locked condition or holdover? If locked what settings do you have for time constant and damping? Is it any other setting that is important? For the frequency chart I see excursions up to +-3E-11 so not so far from the

Re: [time-nuts] Tbolt issues

Hello Bert, For me your findings look very much the same as this: http://www.leapsecond.com/pages/tbolt-8d/ At least for me I should say the (absolute) frequency accuracy for this Tbolt is not better than +-1E10 with 1 or 10 seconds gate times on a counter. Maybe I am totally wrong as both Tom

Re: [time-nuts] GPSDO and PPS measurement precision

By the way: Have anyone compared the 30sec average from the Shera with a TI counter to see the real result? Lars Från: Lars Walenius<mailto:lars.walen...@hotmail.com> Skickat: den 3 juni 2016 18:23 Till: Discussion of precise time and frequency measurement<mailto:time-nuts@febo.com&

Re: [time-nuts] GPSDO and PPS measurement precision

Hej, Using Tom van Baak´s GPSDO simulator is very informative as it can limit the TIC resolution. Shera´s design is much more complicated than the 42ns resolution as it depends on the noise in the 24MHz oscillator. With an oscillator with enough noise during a 30 sec period it might be below

Re: [time-nuts] More graphs: OCXO step, holdover recovery

Lars wrote: >> What puzzles me is the large hump upwards in DACvalue. Anyone knows what is >> the reason? Hal wrote: >My guess is poor filtering on the initial data when coming out of holdover, >probably complicated by inadequate testing and/or that case not being >important. > >I'm pretty sure

Re: [time-nuts] Advise on building a DIY GPSDO?

Thanks Magnus and Charles, Could you please explain a little more about this: Charles wrote: >> Loop filters in commercial GPSDOs use algorithms that suppress >> systematic ripple on the VCO control related to the comparison frequency. Magnus wrote: >It will be there, so you need to manage it

Re: [time-nuts] Advise on building a DIY GPSDO?

Hello Charles and others I have wondered what is meant by a proper digital filter below? Now I was reminded by the KS-24361 holdover graphs from Hal. Is a proper digital filter something more than the LP-filter + PI-loop I use in the DIY Arduino GPSDO? What is used in commercial GPSDO´s? I am

Re: [time-nuts] More graphs: OCXO step, holdover recovery

Thanks for the graphs. Interesting to see the recovery from holdover on the KS-24361. What was the reason for holdover? What puzzles me is the large hump upwards in DACvalue. Anyone knows what is the reason? Could it be that the loop changes time constant? Even after the second holdover a

Re: [time-nuts] Cheap LEA-6T [was: Re: Precise Time transfer and relative position over ashort baseline]

The reason for the 2V out can be found in Gyros schematic in the eevblog thread. The problem is not the LEA module. The problem is that the LEA output is loaded with a diode (transistor BE) + 33ohm. Down in the eevblog thread a solution with a resistor between the LEA and the transistor base

Re: [time-nuts] BG7TBL GPS Disciplined Source

Hi If you are lucky the MV89 might be a very good OCXO and U-Blox makes very good GPS modules. The NEO-6M is not the best as it isn´t a timing module. But in your GPSDO the GPS module with an external antenna is not the limiting factor but more the controller and it´s limited resolution on the

Re: [time-nuts] HP 5065A repair

Hi Shouldn´t 5x10^-11 over 50C be 1x10^-12 / C? So with 2-4°C variation it is 2-4x10^-12. What about pressure variations for the HP5065 and other Rb´s? My LPRO have about 7x10^-14/mBar (hPa) so with 15-20mbar change, that can happen quite quick, it is also in the ^-12 range. The tempco for my

Re: [time-nuts] Conditioning Rubidium Oscillators

I read this but couldn´t understand why this is superior to the PI-loop with a pre-filter? http://ptfinc.com/wp-content/uploads/2016/03/App_37_RubContol-Rubidium-Control-%E2%80%93-A-Different-Approach.pdf Anybody can say why? Even if regression is very useful the limitation of the GPS and

Re: [time-nuts] Another Arduino GPSDO

Eric Williams wrote: I just saw Lars' postings on his design and thought I'd throw mine in since I've been working on a similar low-end goal but doing it a different way. Not really an Arduino, either, but it's based on an AVR processor and should be portable to an Arduino. Good to see

Re: [time-nuts] GPSDO simulation tool

Many thanks Tom for an excellent tool and also the data you have provided. You don´t happen to have data for a non sawtooth corrected M12? Another question: how do you insert the options for ticres and dacbits? With “gpsim1 avg1=10 gps-mtk3339.txt ocxo.dat gpsdo.txt” I managed to get

Re: [time-nuts] Another atomic clock question

Some clarifications on the ADC in the ATmega328 and how it is used in the Arduino GPSDO. The resolution is 10 bits but you can select Vref. In my Arduino GPSDO it is set to the internal Vref = 1.1V so 1LSB is 1.1mV. From the beginning I used 5V as Vref but if you plot the response from the

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

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

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

Re: [time-nuts] Arduino GPSDO with 1ns res TIC

/14 23:10, Lars Walenius wrote: I have just changed all my Swedish comments in my source code and attached it. I also copied the text to a Word-file so everybody can see it without the Arduino Environment. The Control loop (“PI-loop”) is more or less just two lines that you find approximately

Re: [time-nuts] TIC model

Hi Bruce You are absolute right that it is wise to put some time in the estimation of such effects as asynchronous Clocks. An iteration between thinking and building seems always to be necessary but we all have different capabilities for that. For the Arduino I came to an end with the

Re: [time-nuts] TIC model

Bob Stewart wrote: Tom tried to steer me to the PICTIC recently, and I sort of brushed him off, because, quite frankly I didn't understand. Now that I've really looked at it, it's a much better idea than using a dsPIC33 and brute-forcing it. But, I don't really need everything the

Re: [time-nuts] Arduino GPSDO with 1ns res TIC

Chris wrote: Från: Chris Albertson Skickat: ‎torsdag‎ den ‎13‎ ‎februari‎ ‎2014 ‎07‎:‎31 Till: time-nuts@febo.com 1) what connects to analog pins A1, A2, A3, A4, and A5. The schematic shows only A0 used for the TIC capacitor. A1 and A2 is connected to temperature sensors like the