Re: [time-nuts] Thunderbolt Rollover Testing
On Mon, 6 Mar 2017 00:38:35 +, you wrote: >Does it have a saved/surveyed position? With a saved position you can >reasonable time performance with 1 sat. Without a saved position all bets >are off, there is no way for the receiver to determine the receiver/satellite >clock difference. > >Trimble reports that the device is in "over-determined clock" mode if that is >how it is configured. Even if it is in "over-determined clock" mode the >receiver may not have enough data to do anything effective. Trimble's >overdetermined clock mode is basically a "position hold" mode. > It will stay in 2d/3d mode if there is no stored position. With a stored position the Resolution-T does seem to be pretty stable with only 1 SV. With the simulator it will switch to OD mode for about 2 seconds, then its status changes to "no SVs usable" and it stops using the simulated SV. I still have many navigation message changes to test out -- something may work. ___ 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] RFDO - Experience and questions
Hi, Indeed, the station is located in central France with a very powerful transmitter (up to 2MW). It covers all Europe and it was a real pain for me when they stopped broadcasting the France Inter Station. The longwave signal can be received anywhere, even in the basements (ground effect propagation). No need for an external full sky antenna etc… Hopefully they are still operating and sending the time code. And actually the signal is much clearer today in 2017 than when it was also amplitude modulated. Good news, but how long will it last ... ? Best, Gilles. > Le 5 mars 2017 à 23:42, Iain Young a écrit : > > On 05/03/17 20:23, paul swed wrote: > >> Gilles what signal is that at 162KHz. A European station? Nice thats its C >> controlled. > > That's TDF from France. Their equivalent of WWV/MSF/DCF. Used to carry > the AM Station France Inter as well, but that went when France turned > off all LW, MW, and LORAN stations at the end of 2016. > > The Time Signal is Phase Modulated (I have a gnuradio decoder which > works very well if anyone is interested) > > See https://en.wikipedia.org/wiki/TDF_time_signal and > https://en.wikipedia.org/wiki/Allouis_longwave_transmitter > > With no AM modulation, there are obvious benefits with regards to using > it as a frequency reference. Average phase and frequency deviation is > zero over 200msec (see link above for details) > > > Iain > > PS, The signal is used by the French railways SNCF, the electricity > distributor ENEDIS, airports, hospitals according to the Allouis link > above > > ___ > 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] RFDO - Experience and questions
Hi David, I have actually implemented the second option. Detecting the the sequences of "calms" where the modulation is off and gating the ADC sampling at those moments. There are plenty of calm zones between the sequence of modulated bits, in addition the modulation is off for the whole 59th second before each minute. I considered picking the signal only during that 59th second which could indeed lead to an improvement. Will try that. Thx, Gilles. > If the modulation is phased locked to the carrier which is common, > then that suggests two other ways to extract the timing from the > carrier without interference from the modulation. > 1. Integrate the phase comparison over a whole number of modulation > cycles; the modulation will then cancel out. This could be seen as > using a sin(x)/x frequency response with the nulls aligned to remove > just the modulation components of the signal. > > 2. Gate the phase comparison for periods where the modulation is not > occurring. > > On Sun, 5 Mar 2017 11:54:56 +0100, you wrote: > > >I have been working for a "while" > on a reference oscillator disciplined > >by an > >RF signal (162khz), Cs stabilized, but phase modulated with time coding > >information. The phase modulation is quite significant : +/-1rad 10Hz > >triangular shape, leading to a frequency shift of +/- 20PI (+/-6,3Hz). > >Extracting the base signal was quite an interesting challenge > I tried > >many > >options (and even a bit more > ) but it was - and is still - fun... > > > >... > > > >My questions to the respected audience: > >- Can I get any better? > >- Have I reached the limit of what the RF signal can provide? > >(with all the perturbations encountered on the path from the transmitter to > >my > >antenna...) > >- Am I limited by the local oscillator? > >- Or the measurement gear? > >- Or anything else > ? > > > >Thanks very much for your feedback, > > > >Gilles. ___ 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] Thunderbolt Rollover Testing
Does it have a saved/surveyed position? With a saved position you can reasonable time performance with 1 sat. Without a saved position all bets are off, there is no way for the receiver to determine the receiver/satellite clock difference. Trimble reports that the device is in "over-determined clock" mode if that is how it is configured. Even if it is in "over-determined clock" mode the receiver may not have enough data to do anything effective. Trimble's overdetermined clock mode is basically a "position hold" mode. >I just re-checked this with a Resolution-T, and it does go into OD mode with >all but 1 SV masked from cold restart using a real SV. ___ 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] Thunderbolt Rollover Testing
On Sun, 5 Mar 2017 18:35:25 +0100, you wrote: >One thing a 6100 will let you do is to calibrate the PPS out of your gizmo >to +/- 5 ns (one sigma). While its >not an impressive number by TimeNuts standards, it is one of the few ways to >get that job done. I want to eventually characterize the delay of some amplified antennas. It's reported that delay varies significantly over temperature even for geodetic-grade antennas. >> multiple synchronized single channel units), as I haven't yet been >> able to get the Trimble Resolution boards to go into overdetermined >> mode with a single simulated SV. > >It would be a bit alarming if you *could* get it to show overdetermined with >only a single clock source :) It's quite odd at face value, but the Thunderbolt will go into "overdetermined" mode with only the 1simulated SV. I just re-checked this with a Resolution-T, and it does go into OD mode with all but 1 SV masked from cold restart using a real SV. ___ 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] RFDO - Experience and questions
On 05/03/17 20:23, paul swed wrote: Gilles what signal is that at 162KHz. A European station? Nice thats its C controlled. That's TDF from France. Their equivalent of WWV/MSF/DCF. Used to carry the AM Station France Inter as well, but that went when France turned off all LW, MW, and LORAN stations at the end of 2016. The Time Signal is Phase Modulated (I have a gnuradio decoder which works very well if anyone is interested) See https://en.wikipedia.org/wiki/TDF_time_signal and https://en.wikipedia.org/wiki/Allouis_longwave_transmitter With no AM modulation, there are obvious benefits with regards to using it as a frequency reference. Average phase and frequency deviation is zero over 200msec (see link above for details) Iain PS, The signal is used by the French railways SNCF, the electricity distributor ENEDIS, airports, hospitals according to the Allouis link above ___ 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] RFDO - Experience and questions
Gilles I should have mentioned. I use eLoran at 100 KHz in the US and am 400 miles from the transmitter. Measuring Cesium references I typically run down in the 5 e-12th. I see various noise at that level that says thats about the limit without some smarter filtering, tracking and plotting. The comparison units are austron 2100 series. The Cesium's are HP5061A's. Very interested in what you are doing. Regards Paul WB8TSL On Sun, Mar 5, 2017 at 11:35 AM, David wrote: > If the modulation is phased locked to the carrier which is common, > then that suggests two other ways to extract the timing from the > carrier without interference from the modulation. > > 1. Integrate the phase comparison over a whole number of modulation > cycles; the modulation will then cancel out. This could be seen as > using a sin(x)/x frequency response with the nulls aligned to remove > just the modulation components of the signal. > > 2. Gate the phase comparison for periods where the modulation is not > occurring. > > On Sun, 5 Mar 2017 11:54:56 +0100, you wrote: > > >I have been working for a "while"… on a reference oscillator disciplined > by an RF signal (162khz), Cs stabilized, but phase modulated with time > coding information. The phase modulation is quite significant : +/-1rad > 10Hz triangular shape, leading to a frequency shift of +/- 20PI (+/-6,3Hz). > Extracting the base signal was quite an interesting challenge… I tried many > options (and even a bit more…) but it was - and is still - fun... > > > >... > > > >My questions to the respected audience: > >- Can I get any better? > >- Have I reached the limit of what the RF signal can provide? > >(with all the perturbations encountered on the path from the transmitter > to my antenna...) > >- Am I limited by the local oscillator? > >- Or the measurement gear? > >- Or anything else…? > > > >Thanks very much for your feedback, > > > >Gilles. > ___ > 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] RFDO - Experience and questions
Gilles what signal is that at 162KHz. A European station? Nice thats its C controlled. Regards Paul WB8TSL On Sun, Mar 5, 2017 at 5:54 AM, Gilles Clement wrote: > Hi all, > > I have been working for a "while"… on a reference oscillator disciplined > by an RF signal (162khz), Cs stabilized, but phase modulated with time > coding information. The phase modulation is quite significant : +/-1rad > 10Hz triangular shape, leading to a frequency shift of +/- 20PI (+/-6,3Hz). > Extracting the base signal was quite an interesting challenge… I tried many > options (and even a bit more…) but it was - and is still - fun... > > Long story short, the "best" combination I came up with is the following: > 1- local oscillator built around: CD4060 Collpits + 5184Khz crystal + > pulled by varactor diode + divide by 32 > 2- Phase detection with 4046 (XOR) with pp ouput voltage limited to 1 volt > (input to 10bits ADC) > 3- Filtering and VCO controlling with a PIC16F876, programmed in assembly > language, implementing a 3rd order loop (much better than second order). > Poles at 1E-5 and 1E-3, Zero at 1E-4 => 1E-10 attenuation at 10Hz (if my > maths are correct). > 4- 13 bits 20Khz PWM control of the VCO (K0=10-3 Hz/volt) with strong > filtering (two RCs in cascade) > 5- Crystal is temp controlled (NTC resistor) as well as the whole circuits > placed in a foam isolated box. > 6- ADEV measurements perfomed with HP53132A counter (high stability option > 10 ocxo HP10811) frequency input to TIMELAB through HPIB connection (I > know it's not the best setup but simple and provides tool for comparison > between trials) > > Results to date : > . « Left side » of the ADEV 0.5s: pretty flat around 1E-9 up to > tau =10s > . « right side » of ADEV 0.5s plots: reaching 3*1E-11 at tau = > 3000s > > Comment: > 6,3Hz/162kHz = 4E-5 so attenuation of 1E10 should knock it down to 4E-15 > (well below 1E-11) ? > > My questions to the respected audience: > - Can I get any better? > - Have I reached the limit of what the RF signal can provide? > (with all the perturbations encountered on the path from the transmitter > to my antenna...) > - Am I limited by the local oscillator? > - Or the measurement gear? > - Or anything else…? > > Thanks very much for your feedback, > > Gilles. > > Note: 1E-3 = 0.001 > ___ > 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] RFDO - Experience and questions
If the modulation is phased locked to the carrier which is common, then that suggests two other ways to extract the timing from the carrier without interference from the modulation. 1. Integrate the phase comparison over a whole number of modulation cycles; the modulation will then cancel out. This could be seen as using a sin(x)/x frequency response with the nulls aligned to remove just the modulation components of the signal. 2. Gate the phase comparison for periods where the modulation is not occurring. On Sun, 5 Mar 2017 11:54:56 +0100, you wrote: >I have been working for a "while" on a reference oscillator disciplined by an >RF signal (162khz), Cs stabilized, but phase modulated with time coding >information. The phase modulation is quite significant : +/-1rad 10Hz >triangular shape, leading to a frequency shift of +/- 20PI (+/-6,3Hz). >Extracting the base signal was quite an interesting challenge I tried many >options (and even a bit more ) but it was - and is still - fun... > >... > >My questions to the respected audience: >- Can I get any better? >- Have I reached the limit of what the RF signal can provide? >(with all the perturbations encountered on the path from the transmitter to my >antenna...) >- Am I limited by the local oscillator? >- Or the measurement gear? >- Or anything else ? > >Thanks very much for your feedback, > >Gilles. ___ 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] Fwd: Dusty 53131A
Recently the fan in my 53131 has been making a pretty awful sound, so its time to replace it. When I disassembled the counter I found the trim cap had turned into a fur ball. Not that it really matters since it runs on an external reference, but its interesting to see if the dust has any effect. See https://www.flickr.com/photos/147407087@N06/32427230764/. So with the unit disassembled I logged the effect of removing the dust by logging a GPSDO during the cleaning process. Must of the dust was around the shroud of the trim cap. Near the mounting terminals there was fairly minimal amounts of dust. At least in this instance, if the dust had any impact on frequency, its orders of magnitude below the thermal instability of the AT crystal. The crystal appears to be in a to-39 3-lead package. It is also freestanding directly in front of the exhausting cooling fan... ___ 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] Thunderbolt Rollover Testing
Hi > On Mar 5, 2017, at 6:31 AM, Trevor N. wrote: > > On Sat, 4 Mar 2017 20:39:45 -0800, you wrote: > >> Matthias Jelen did a test on the Trimble Thunderbolt here: >> >> https://www.febo.com/pipermail/time-nuts/2014-September/086664.html >> https://www.febo.com/pipermail/time-nuts/2015-May/091805.html >> https://www.febo.com/pipermail/time-nuts/2015-May/091825.html >> > > > Thanks for the links, I didn't see the 2015 test. Currently the older > Spirent simulators are going for very resonable prices on the 'bay. > The GSS4100 can be had for under $200 and 6100s frequently pop up for > $150. One thing a 6100 will let you do is to calibrate the PPS out of your “gizmo” to +/- 5 ns (one sigma). While it’s not an impressive number by TimeNuts standards, it is one of the few ways to get that job done. > Anything newer is still very expensive, though. It may be > necessary to use a multichannel simulator for newer receivers (or > multiple synchronized single channel units), as I haven't yet been > able to get the Trimble Resolution boards to go into overdetermined > mode with a single simulated SV. It would be a bit alarming if you *could* get it to show overdetermined with only a single clock source :) Bob > ___ > 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.
[time-nuts] RFDO - Experience and questions
Hi all, I have been working for a "while"… on a reference oscillator disciplined by an RF signal (162khz), Cs stabilized, but phase modulated with time coding information. The phase modulation is quite significant : +/-1rad 10Hz triangular shape, leading to a frequency shift of +/- 20PI (+/-6,3Hz). Extracting the base signal was quite an interesting challenge… I tried many options (and even a bit more…) but it was - and is still - fun... Long story short, the "best" combination I came up with is the following: 1- local oscillator built around: CD4060 Collpits + 5184Khz crystal + pulled by varactor diode + divide by 32 2- Phase detection with 4046 (XOR) with pp ouput voltage limited to 1 volt (input to 10bits ADC) 3- Filtering and VCO controlling with a PIC16F876, programmed in assembly language, implementing a 3rd order loop (much better than second order). Poles at 1E-5 and 1E-3, Zero at 1E-4 => 1E-10 attenuation at 10Hz (if my maths are correct). 4- 13 bits 20Khz PWM control of the VCO (K0=10-3 Hz/volt) with strong filtering (two RCs in cascade) 5- Crystal is temp controlled (NTC resistor) as well as the whole circuits placed in a foam isolated box. 6- ADEV measurements perfomed with HP53132A counter (high stability option 10 ocxo HP10811) frequency input to TIMELAB through HPIB connection (I know it's not the best setup but simple and provides tool for comparison between trials) Results to date : . « Left side » of the ADEV 0.5s: pretty flat around 1E-9 up to tau =10s . « right side » of ADEV 0.5s plots: reaching 3*1E-11 at tau = 3000s Comment: 6,3Hz/162kHz = 4E-5 so attenuation of 1E10 should knock it down to 4E-15 (well below 1E-11) ? My questions to the respected audience: - Can I get any better? - Have I reached the limit of what the RF signal can provide? (with all the perturbations encountered on the path from the transmitter to my antenna...) - Am I limited by the local oscillator? - Or the measurement gear? - Or anything else…? Thanks very much for your feedback, Gilles. Note: 1E-3 = 0.001 ___ 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.
