Re: [time-nuts] TruePosition GPSDO Holdover Issues

On Sun, May 13, 2018 at 10:57 PM, Artek Manuals wrote: > Nigel > As I recall there is more to it than just the number of satellites. > involved. Also factored in to all the math is the signal strength of the > sats plus there relative angles to your spot on the earth. If

Re: [time-nuts] nuts about position (cheap receiver)

On Sat, May 5, 2018 at 12:08 AM, Mark Sims wrote: > You could add doppler to the RINEX file. All the receivers with raw > messages seem to output that. I think the Doppler measurements can be omitted for static positioning. CSRS-PPP results for a submission with/without

Re: [time-nuts] nuts about position (cheap receiver)

I submitted 4 days (118-121) of RINEX files from an IGS station to CSRS-PPP, but with only the GPS C1, L1, and S1 observations. This is similar to what cheap receivers would be generating, but with probably lower noise. emr clocks/orbits were used. The east/north/up differences between the PPP

Re: [time-nuts] nuts about position (cheap receiver)

On Thu, May 3, 2018 at 9:40 AM, Mark Sims wrote: > G... Canada lives in the dark ages and does not accept RINEX version > 3... I'm now trying Australia... > > Version 3 is cleaner and easier to write than Version 2... > RTKLIB's RTKCONV can convert between RINEX

Re: [time-nuts] nuts about position

On Tue, May 1, 2018 at 2:14 PM, Hal Murray wrote: > > kb...@n1k.org said: >> One important qualifier to re-state. L1 post processing is very dependent on >> the distance to an “open” source of correction data. The spacing of those >> sites over the US is highly variable.

Re: [time-nuts] Cheap jitter measurements

On Mon, Apr 9, 2018 at 3:36 AM, Tom Van Baak wrote: > > My mental model of a black box computer running NTP is that I should be able > to give it a pulse (e.g., via parallel, serial, GPIO) and it tells me what > time it was. Use a GPSDO / Rb / picDIV to generate precise

Re: [time-nuts] Linux PPS clues?

On Fri, Oct 21, 2016 at 2:12 AM, Attila Kinali wrote: > > Going for an uC is easier in that regard as they have very little interrupt > latency (usually just 5-10 cycles), but then you have problems with > getting the output out of the uC as their I/O subsystems are usually >

Re: [time-nuts] Q/noise of Earth as an oscillator

On Sat, Jul 30, 2016 at 1:19 AM, Tom Van Baak wrote: > The remaining question in this thread is if earth Q measurement has actual > meaning, that is, if the concept of Q is valid for a slowly decaying rotating > object, as it is for a slowly decaying simple harmonic oscillator. And that's >

Re: [time-nuts] frequency generation algorithm.

I did something similar in the Beaglebone Black AM335x PRU. Division is done using a delay loop with variable number of cycles instead of an interrupt. Converting a delay with a fractional amount to integer is essentially a quantization problem. I'm using a triangular PDF dither and first order

Re: [time-nuts] Beaglebone NTP server

Hello all, School's about to end so I can finally work on this. I think there is a standard GPIO PPS driver, configured using the device tree but I haven't tried that. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to

Re: [time-nuts] Line Frequency

On Tue, Feb 11, 2014 at 1:57 AM, Tom Van Baak t...@leapsecond.com wrote: Alternatively, has anyone considered grabbing 50/60 Hz from the air? Just about any dangling unshielded wire will act as a pickup. Maybe not as robust a signal, but this is not so much a problem for solutions already

Re: [time-nuts] sub-minute time-precision in court-case

I noticed that my old Nokia phones kept time better than computers, then I learned that the oscillator in the phone is adjusted to match the BTS carrier [1]. To verify this I ran ntpd in an Android phone synced to a stratum 1 server via USB tethering. (USB has a lower latency and jitter than

Re: [time-nuts] Needed: The Real Serial USB Fix

For serial to Ethernet I use ser2net [1] on cheap wireless routers using the serial port pads on the board and a Beaglebone. The application I use (u-blox u-center) can use TCP connections, if you require a real COM port on Windows com0com and com2tcp [2] should work. ser2net sends one TCP packet

Re: [time-nuts] looking for low-power system for gps ntp timekeeping

I did a quick test using a modified Python script to measure the elapsed time of several NTP round trips http://code.activestate.com/recipes/117211-simple-very-sntp-client/ The script is run on the Atom machine, all of the servers are running ntpd 4.2.6p5 1.6 GHz Atom, loopback: 8100 req/s 400

Re: [time-nuts] Beaglebone NTP server

On Thu, Jun 20, 2013 at 3:39 AM, Chris Howard ch...@elfpen.com wrote: Are you using the original BeagleBone or the new BeagleBone Black? I'm using the original BeagleBone. it should work on the BeagleBone Black. Will you have any details available about what parts are needed to set it up? If

Re: [time-nuts] Beaglebone NTP server

ntpd (poll=1) loopstats and ppstest using an eCAP clocksource and PPS root@beaglebone:~# ppstest /dev/pps0 trying PPS source /dev/pps0 found PPS source /dev/pps0 ok, found 1 source(s), now start fetching data... source 0 - assert 1371666297.5, sequence: 15602 - clear 0.0,

Re: [time-nuts] Beaglebone NTP server

(yet), but I'm very interested in this. Are you going to post the driver somewhere when you're finished? Thanks, Jim I will post the sources and instructions when it's ready. On Sat, Jun 15, 2013 at 9:48 PM, Paul tic-...@bodosom.net wrote: On Fri Jun 14 20:13:51 EDT 2013, Gabs Ricalde wrote

[time-nuts] Beaglebone NTP server

As an alternative to the Net4501, the AM335x in the Beaglebone has timers that accept an external clock up to 25 MHz (TCLKIN) and can timestamp events on an input pin (TIMER4-TIMER7). Both sets of pins are available on the headers after an appropriate pinmux configuration. I'm finishing the

Re: [time-nuts] have 10MHz need 19.5Mhz

On Mon, Jun 3, 2013 at 4:30 AM, Gerd v. Egidy li...@egidy.de wrote: Hi Chris, The question is the best way to get from 10MHz to 19.5MHz. Must it be the RasPi or can it be another cheap Linux device? There are some out there which have a frequency which is simpler to reach than 19.5 MHz.

Re: [time-nuts] Legal Time dissemination

That looks like a server in an room with unstable temperature. Try graphing the server's frequency (ntpq rv or ntpdc loopinfo/kerninfo if enabled on the server), a rising frequency will correlate with a positive offset if that is the case. On Tue, May 28, 2013 at 7:52 PM, Miguel Barbosa Gonçalves

Re: [time-nuts] Legal Time dissemination

On Tue, May 28, 2013 at 9:26 PM, Miguel Barbosa Gonçalves m...@mbg.pt wrote: Hi! They've disabled the queries on both servers because I believe that don't want to see how badly they are configured... :-) Regards, Miguel That is better than the one I'm monitoring. They* were running an

Re: [time-nuts] Precise positions for GPSDOs

On Thu, May 2, 2013 at 5:29 PM, Stewart Cobb stewart.c...@gmail.com wrote: GPS surveying equipment can easily determine the position of your antenna to within a few centimeters (~20 ps). Unfortunately, such equipment is expensive and difficult to borrow. A high-end GPSDO designed today should

Re: [time-nuts] Logging the grid frequency....

Hello, I also don't have a Picotest or similar equipment but I've done similar things by using the line input of a soundcard. Multiply the recorded signal with a 60 Hz quadrature oscillator, apply a low pass filter then do some analysis on the resulting phasor. The stability of the sound card

[time-nuts] SSR-6Tr Motorola/u-blox mode not working

I have a couple of SSR-6Tr boards but can't talk to them properly. Here are the things I've tried: @@Am: @@As: Lat 0, Lon 0, Height -0.01 m @@Aw: 1 (UTC) @@Cj: Synergy copyright, version, etc. @@Ga: lat/lon/height I entered earlier @@Ge: TRAIM enabled @@Gf: TRAIM alarm: 500

Re: [time-nuts] Timing between two GPS PPS outputs.

David, Thanks for the update. The spikes I'm experiencing coincides with the time when there are 3 or less visible satellites, as predicted by the Trimble Planning software. On Mon, Jan 7, 2013 at 8:02 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: From: Gabs Ricalde [] Non-timing

Re: [time-nuts] Timing between two GPS PPS outputs.

Some tests of timing receivers' PPS: ftp://tycho.usno.navy.mil/pub/gps/Furuno/ http://www.cnssys.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf (Motorola M12M) http://www.cnssys.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf (u-blox LEA-6T) Non-timing receivers could be unsuitable

Re: [time-nuts] New to Time Synching hardware - needing some advice

It could be possible to use two Rb GPSDOs, one providing the PPS and another disciplined by GPS, then rotate them every month. On Fri, Dec 28, 2012 at 2:41 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 27 Dec 2012 10:19:46 -0800 Chris Albertson albertson.ch...@gmail.com wrote: Yes you

Re: [time-nuts] Just for Fun - Synergy Systems SSR-6T PPS Comparison

The Synergy site doesn't list the SSR-6Tr but I found a datasheet here: http://diydrones.com/forum/topics/finally-a-relatively-inexpensive-u-blox-lea-6t-board-in-the-us ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to

Re: [time-nuts] RaspberryPi and RADclock

On Thu, Dec 13, 2012 at 5:23 AM, Matt Davis m...@synclab.org wrote: Hey time-legumes, I figured a few of you all might be interested in some of the work that the team and I have been doing. We recently acquired a couple of RaspberryPis, and out of curiosity, we wanted to see how well our

Re: [time-nuts] PPS offset between GPS receivers

On Tue, Dec 11, 2012 at 5:55 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Gabs, I've seen similar jumps, and it happens when the GPS/PPS signal drops out for a while. In my case, the GPS receiver is sitting just in an upstairs room, not near a window or the root (as I normally

Re: [time-nuts] PPS offset between GPS receivers

On Tue, Dec 11, 2012 at 8:00 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: From: Gabs Ricalde [] David, I forgot to thank you for your helpful site and NTP plotter. I have the antenna outside with a 180 degree view of the sky, outages should be rare. Looking at the loopstats

Re: [time-nuts] PPS offset between GPS receivers

Date: Fri, 7 Dec 2012 22:28:20 -0500 From: Bob Camp lists at rtty.us Hi A lot depends on exactly what the interrupt structure is. It may also depend on the phase of the cpu clock relative to the pps signal. What's reasonably sure is that there is indeed some offset between the two where

Re: [time-nuts] PPS offset between GPS receivers

Hi everyone, As Tom suggested, I redid the test with less than 1 ft. of wire from the PPS output to the GPIO without any logic gates or line receivers. Same result, the SKG25A1 was 2 microseconds ahead of the 58534A. Without any other way of testing, I would probably trust the output of the

[time-nuts] PPS offset between GPS receivers

I'm using a Symmetricom 58534A GPS timing receiver and a GPS board with a SkyNav SKG25A1 module driving stratum 1 NTP servers. On one of the servers, the ppstest output while the 58534A is connected looks like: source 0 - assert 1354495734.00102 source 0 - assert 1354495735.00040 When I