[time-nuts] The effect of centrifugal force on a \n hourglass
https://www.youtube.com/watch?v=7cLjFAADM44 ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] uBlox F9T testing - best settings?
Hello Peter The aim of our study was to characterise the performance of single frequency receivers for time-transfer. The F9P was a late addition to our study and extending our software to dual frequency was too much work at the time. Having a measured ionosphere was not such a huge improvement anyway, because there are other ways to get an improved ionosphere correction when post-processing. Regards Michael On Mon, 23 Sep 2019 at 7:03 am, Peter Vince wrote: > Hello Michael, > > Thank you for your Powerpoint presentation slides - if the paper you > mentioned added some descriptive words, I would love to see that. > > Might I ask why you didn't use the F9P in dual-frequency mode, as I > understood that gives a much better result, being able to (almost?) > eliminate ionospheric effects? > > Regards, > > Peter > > > On Sun, 22 Sep 2019 at 01:00, Michael Wouters > wrote: > > > > We did some work on single-frequency time-transfer with the F9P earlier > > this year which we presented at IFCS-EFTF in April. > > http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf > > There's a paper too, which I should upload. > > In short, the F9P is very suitable for code-based time-transfer, and we > > will be using it , or the F9T, in the next iteration of our time-transfer > > system. > > ... > > Regards > > Michael > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] A simple sampling DMTD
Update: last Friday our students have populated a few prototype boards ( http://www.lartmaker.nl/time-nuts/dmtd-proto.jpg), and this weekend I managed to get some early code running on it. The good: Noise performance matches the datasheet (1.19LSB_RMS given, 1.21LSB_RMS measured). The 1/f corner is much lower than I feared ( http://www.lartmaker.nl/time-nuts/LTC2140-14%20noise%20corner.pdf ; measured at a sample rate of 10ksps with terminated inputs, PSD averaged over 500M samples in 1Msample chunks with a rectangular window), and direct measurements at a 10Hz beat frequency should be possible. (I don't completely trust this data yet; the absence of 50Hz lines in an unshielded setup makes me suspicious.) The bad: LF noise / drift is significant ( http://www.lartmaker.nl/time-nuts/LTC2140-14%20drift.pdf; vertical axis is in LSB). On a 0dBFS signal with a 10Hz beat note an uncertainty of 0.25LSB in the zero crossing point would translate to +/-1ps; what I'm seeing here would eat my entire error budget and then some. I need to find a computationally cheap way to filter this, or move to the FPGA after all. The ugly: I can't get the FT2232H channel A to work in asynchronous FIFO-mode. I have programmed the EEPROM wth the latest version of the FT_PROG tool, but the TXE# line stays high (under Linux; I'm reading data from /dev/ttyUSBx with ftdi_sio, a setup which FTDI hints should work). I haven't looked too hard yet as I have the serial port as a backup, but it would be nice to get this working. To be continued, JDB. [listadmin: do let me know if you feel these updates are more noise than signal] On Sat, Sep 14, 2019 at 2:25 PM Jan-Derk Bakker wrote: > Update: I have finished routing the board (placement diagram at > http://www.lartmaker.nl/time-nuts/DMTD%20rev1.00%20assembly.pdf ) and > ordered a few prototype PCBs. > > After the earlier discussions on the list I've grown sufficiently > concerned about the impact of 1/f converter noise that I have added headers > to the board to allow me to replace the D-flipflop sampler with an > FPGA-based I/Q downconverter. While the main PCBs are in production I'll > draw a simple daughterboard with dual ice40 UltraPlus FPGAs, If the FPGA > solution turns out to be necessary (or a noticeable improvement), I'll > redraw the main PCB. > > To be continued, > > JDB. > > On Sun, Sep 1, 2019 at 2:09 AM Jan-Derk Bakker wrote: > >> Dear all, >> >> I've been working on a design for a (relatively) simple, standalone >> sampling DMTD. Very rough preliminary schematics can be found at >> http://www.lartmaker.nl/time-nuts/DMTD_rev0.99.pdf . >> >> Design goals are: >> - ps-level accuracy >> - comparison of frequencies between at least 10 and 50MHz, preferably >> between 1 and 100MHz >> - comparison of (selected) different frequencies (in my case: 10MHz vs >> 50MHz) >> - standalone operation, field-portable >> - option for raw data sampling / (post)processing on a PC >> - option for generating a tuning voltage to lock the measured oscillator >> to the reference, so the DMTD can act as a PLL in phase noise test setups >> >> Context: you may remember that a year or two ago I posted to time-nuts >> about a GPSDO-design geared for mobile applications, which I was working on >> for an SDR-platform my students are working with. This SDR-platform has now >> grown to include a 100-channel phased array receiver. To validate the >> reference clock distribution in this array (amongst other things) I would >> like to have a DMTD. As the commercial offerings are outside the budget of >> our lab, I was planning to roll my own. >> >> The core of the system is a transformer-coupled LTC2140-14 dual 14-bit >> ADC, sampling at an offset frequency of nominally 10MHz+10Hz generated by a >> VCTCXO (with an option for an OCXO). The ADC was chosen for its large input >> bandwidth and small aperture jitter. Simulations of a simple software ZCD >> consisting of a digital filter and least-squares fitting showed that >> 100ksps would be more than enough to get the desired accuracy. As the ADC >> design is unable to achieve sample rates lower than 1MSPS, D-flipflops are >> used to decimate the samples. These DFFs are also used to multiplex the >> 2x14-bit samples to an 8-bit data bus going into one of the GPIO-ports of >> an XMega. The XMega runs the ZCD, and generates a tuning voltage for the >> offset oscillator. Communication to a logging PC is done with a >> galvanically isolated FT2232H, which has both an ASCII COM-port for the ZCD >> data and a control interface and an asynchronous FIFO to transfer raw >> samples. System power comes from the isolated USB bus or a barrel jack; BOM >> cost in qty10+ is around 100US$. >> >> (The DMTD has a few more power rails than I would have liked. Originally >> I had planned to use the LTC2295 and have a 3v3-only system, but after >> re-reading the NIST paper on SDR-as-a-DMTD I concluded that the single >> clocking path of the 2140 would likely have better aperture
Re: [time-nuts] uBlox F9T testing - best settings?
Hello Anders, Yes, we used TAPR TICCs do the testing. It’s a very economical solution for testing multiple receivers in parallel. The OpenTTP software mktimetx applies sawtooth corrections to the TIC measurements, as you guessed. The corrected TIC measurements are combined with the raw GNSS pseudo ranges, and then this is what goes into the output RINEX and what is used for CGGTTS generation. One complication is that the raw pseudo ranges have ms ambiguities in them. But mktimetx fixes that. I’ll put the paper on the openttp website. Unfortunately, it appears that it will otherwise be behind a paywall. Cheers Michael On Mon, 23 Sep 2019 at 12:00 am, Anders Wallin wrote: > Hi Michael, thanks for the reminder about your slides! > Your page 4 has the two setups. I think you are right in that the F9T > doesn't seem to take an external receiver clock (even if working with the > bare part, not the RCB-board). > (FWIW, AFAIK the not-so-low-cost septentrios use the left external receiver > clock scheme, while Dicom GTRs use the right - both in the 15k cost range) > > Did you use an external TIC (like the TICC?) - to get lower than the 8ns > granularity of the TIMEMARK? > > If I understand CGGTTS the TIC and sawtooth-correction are used to provide > one single time-offset value into the CGGTTS file, for each 780s=13 min > satellite track observed? > https://tycho.usno.navy.mil/cggtts.html > is that correct? > Can the same TIC-based sawtooth correction work for 30s RINEX data instead? > If gpsd can produce dual-frequency RINEX from the F9T, then the new > (software)part needed is the sawtooth-correction at 30s intervals applied > to the raw RINEX from the F9T. > https://gpsd.gitlab.io/gpsd/ppp-howto.html > > Anders > > > > On Sun, Sep 22, 2019 at 3:00 AM Michael Wouters > > wrote: > > > Hello Anders, > > > > We did some work on single-frequency time-transfer with the F9P earlier > > this year which we presented at IFCS-EFTF in April. > > http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf > > There's a paper too, which I should upload. > > In short, the F9P is very suitable for code-based time-transfer, and we > > will be using it , or the F9T, in the next iteration of our time-transfer > > system. > > > > But, I don't see how you can feed an external 10 MHz and 1 pps to the > F9T. > > There don't appear to be any inputs for this on the chip. The TIMEMARK > > inputs only seem to be useable for measurements. Have I missed something? > > > > Regards > > Michael > > > > > Further down the road, if the F9T really can do dual-frequency > > > observations, and either the receiver clock 1PPS measured (TICC?) > against > > > an external 1PPS, or the entire receiver clocked from external > 10M/1PPS - > > > and dual-frequency RINEX generated from this - then there seems to be > an > > > obvious opportunity for making a low-cost dual-frequency time-transfer > > > setup? Or am I missing something? > > > PPP with F9T seems to be possible: > > > https://gpsd.gitlab.io/gpsd/ppp-howto.html > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] U-Blox GPS Module At All-Electronics Corp
Hello Hal, The PPS signal is on pin #3 - on the lower right in the picture - you'll see the LED and the resistor - you should be able to pick off the PPS signal from there. 73's, John AJ6BC On Sat, Sep 21, 2019 at 5:00 PM Hal Murray wrote: > > j...@westmorelandengineering.com said: > > Just saw this at All-Electronics - thought some here could be interested: > > https://www.allelectronics.com/item/gps-8m/gps-module/1.html > > No obvious PPS connection. > > There may be a PPS LED where you could pick it up, but I don't see any > documentation. > > > -- > These are my opinions. I hate spam. > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] U-Blox GPS Module At All-Electronics Corp
From: Hal Murray Just saw this at All-Electronics - thought some here could be interested: https://www.allelectronics.com/item/gps-8m/gps-module/1.html No obvious PPS connection. There may be a PPS LED where you could pick it up, but I don't see any documentation. === Typically on the ublox chips the PPS is exposed on a pin and it's easy to solder to that pin. However, I've bought low-priced "8M" modules from China which turned out not to be 8M. One might also want to check that they are the 8M version which can be programmed to pick up Galileo satellites if that is of interest. I hope the OP is lucky! Cheers, David -- SatSignal Software - Quality software for you Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] U-Blox GPS Module At All-Electronics Corp
Looking closer at the picture provided at that link, it appears that pin 3 (TIMEPULSE) is broken out to a resistor and LED (toward the bottom right mounting hole). Probably still best to ask though. > On Sep 21, 2019, at 6:20 PM, Hal Murray wrote: > > > j...@westmorelandengineering.com said: >> Just saw this at All-Electronics - thought some here could be interested: >> https://www.allelectronics.com/item/gps-8m/gps-module/1.html > > No obvious PPS connection. > > There may be a PPS LED where you could pick it up, but I don't see any > documentation. > > > -- > These are my opinions. I hate spam. > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] HP 5061A modules available
Hi all, I have the following modules from a HP 5061A cesium standard available free for the cost of shipping from Melbourne, Australia A1 Synthesizer A3 Multiplier A8 Phase detector A9 Operational amplifier (the one with the brick module in it) A13 Buffer amplifier A15 Power regulator PCB Interested? Send me an email at vilgotch1(at)gmaildotcom Thanks, Morris ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] uBlox F9T testing - best settings?
Hi Michael, thanks for the reminder about your slides! Your page 4 has the two setups. I think you are right in that the F9T doesn't seem to take an external receiver clock (even if working with the bare part, not the RCB-board). (FWIW, AFAIK the not-so-low-cost septentrios use the left external receiver clock scheme, while Dicom GTRs use the right - both in the 15k cost range) Did you use an external TIC (like the TICC?) - to get lower than the 8ns granularity of the TIMEMARK? If I understand CGGTTS the TIC and sawtooth-correction are used to provide one single time-offset value into the CGGTTS file, for each 780s=13 min satellite track observed? https://tycho.usno.navy.mil/cggtts.html is that correct? Can the same TIC-based sawtooth correction work for 30s RINEX data instead? If gpsd can produce dual-frequency RINEX from the F9T, then the new (software)part needed is the sawtooth-correction at 30s intervals applied to the raw RINEX from the F9T. https://gpsd.gitlab.io/gpsd/ppp-howto.html Anders On Sun, Sep 22, 2019 at 3:00 AM Michael Wouters wrote: > Hello Anders, > > We did some work on single-frequency time-transfer with the F9P earlier > this year which we presented at IFCS-EFTF in April. > http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf > There's a paper too, which I should upload. > In short, the F9P is very suitable for code-based time-transfer, and we > will be using it , or the F9T, in the next iteration of our time-transfer > system. > > But, I don't see how you can feed an external 10 MHz and 1 pps to the F9T. > There don't appear to be any inputs for this on the chip. The TIMEMARK > inputs only seem to be useable for measurements. Have I missed something? > > Regards > Michael > > > Further down the road, if the F9T really can do dual-frequency > > observations, and either the receiver clock 1PPS measured (TICC?) against > > an external 1PPS, or the entire receiver clocked from external 10M/1PPS - > > and dual-frequency RINEX generated from this - then there seems to be an > > obvious opportunity for making a low-cost dual-frequency time-transfer > > setup? Or am I missing something? > > PPP with F9T seems to be possible: > > https://gpsd.gitlab.io/gpsd/ppp-howto.html > > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] overtone crystal question
Bernd, thanks for the excellent treatment on the subject glen On 21/09/2019 4:42 PM, Bernd Neubig wrote: Hi, There is nothing like a fixed ratio between R1 at 3rd or 5th overtone the R1 at fundamental mode. The best approach through C1 and Q. C1 reduces with the square of overtone N (for an infinite crystal plate). In reality C1(3rds about 85% of C1(fund/N^2. For the 5th and higher OT it is about 75 to 70% of C1(fund)/N^2.. Now Q comes into the game: The Q of a crystal designed for 3rd overtone is approximately s ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
