[time-nuts] A Breakthrough By Iridium® & Satelles — An Alternative To GPS Service
A Breakthrough By Iridium® & Satelles — An Alternative To GPS Service From SatNews Daily: "For the first time, end users now have access to accurate and resilient position, navigation and timing (PNT) technology that works anywhere on the planet, even indoors. " See: http://www.satnews.com/story.php?number=902636498 Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ 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] Looking for a Trimble Lassen SK-8 or SK II 5V GPS receiver
Dear Bob, In case you are looking for replacement, there is clone available for most of the old Trimble modules (Lassen, IQ, LP) : http://www.naelcom.com/ds/gps/ds_lassen_clone_series.pdf Regards, Luc -Message d'origine- De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Bob L. Envoyé : lundi 30 mai 2016 03:55 À : time-nuts@febo.com Objet : Re: [time-nuts] Looking for a Trimble Lassen SK-8 or SK II 5V GPS receiver Hi folks, I went with plan “B” and am no longer looking for relatively recent Lassen receivers. The clock using the older Lassen receiver speaks NMEA as well as Trimble protocols. I’m building a simple ExpressPCB board in the Trimble Lassen form factor to interface with a variety of more modern receivers. A few gates and a jumper enabled logic inversion now enable the clock to use most any 5V integrated antenna/receiver speaking NMEA or Trimble protocols at RS-232 or CMOS levels. Also found a pair of Garmin GPS18x LVC 5m on ebay which will be arriving next week about the time the bare boards get here. Problem solved, correct date restored! Many thanks! Bob L. bobhome at pacbell dot net ___ 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] How can I generate a very clean 1 W signal @ 116 MHz ?
On 30 May 2016 17:01, "Richard (Rick) Karlquist" wrote: > > On 5/30/2016 4:06 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: >> I'm wondering what's the best way to generate 116 MHz with very low phase >> noise. Phase noise at < 20 kHz offset is particularly important, but 200 > > The "best" way is clearly to use a 116 MHz 5th overtone crystal > oscillator, which can be locked to 10 MHz with no difficulty. > I designed hundreds of these sorts of things 40 years ago when > I worked for Zeta Labs. Please excuse my ignorance, but how would one lock a 116 MHz 5th overtone crystal oscillator to 10 MHz with no difficulty? Do you have a circuit you share that would give low phase noise, and if so how low? >From what I have read here before, amplifiers degrade the phase noise if driven to near the 1 dB compression point. So would the final amplifier need to have a 1dB compression point of 33, 36, 40 dBm? My next problem would be measuring the phase noise, but that's a different topic for another day. Dave. ___ 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] How can I generate a very clean 1 W signal @ 116 MHz ?
Hi > On May 31, 2016, at 6:30 AM, Dr. David Kirkby (Kirkby Microwave Ltd) > wrote: > > On 30 May 2016 17:01, "Richard (Rick) Karlquist" > wrote: >> >> On 5/30/2016 4:06 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: > >>> I'm wondering what's the best way to generate 116 MHz with very low phase >>> noise. Phase noise at < 20 kHz offset is particularly important, but 200 >> >> The "best" way is clearly to use a 116 MHz 5th overtone crystal >> oscillator, which can be locked to 10 MHz with no difficulty. >> I designed hundreds of these sorts of things 40 years ago when >> I worked for Zeta Labs. > > Please excuse my ignorance, but how would one lock a 116 MHz 5th overtone > crystal oscillator to 10 MHz with no difficulty? Do you have a circuit you > share that would give low phase noise, and if so how low? There are an enormous number of PLL chips that will do the trick for < $2 a pop. About the only external components are a couple of caps and resistors. > > From what I have read here before, amplifiers degrade the phase noise if > driven to near the 1 dB compression point. So would the final amplifier > need to have a 1dB compression point of 33, 36, 40 dBm? Indeed, no matter how you do it and no matter what your signal source, your amp will be an issue. A +40 dbm amp is a good starting point. You may get away with something a bit less. > > My next problem would be measuring the phase noise, but that's a different > topic for another day. Checking the phase noise will be part of the design no matter how you do it. Bob > > Dave. > ___ > 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] How can I generate a very clean 1 W signal @ 116 MHz ?
On 5/31/2016 3:30 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: Please excuse my ignorance, but how would one lock a 116 MHz 5th overtone crystal oscillator to 10 MHz with no difficulty? Do you have a circuit you share that would give low phase noise, and if so how low? If you extract the signal from the oscillator through the crystal (as done in the 10811), the oscillator will be inherently low phase noise, plenty good enough for your ham radio application. Hard to screw it up. If you phase lock the oscillator to 10 MHz using a very narrow bandwidth phase locked loop, say 10 Hz, you will not contaminate the crystal oscillator with reference noise. The purpose of the PLL here is not to "clean up" the XO, but to merely remove drift. Again, hard to screw it up. I can't quote exact phase noise numbers from 40 years ago, but the Zeta Labs sources were sold to very demanding aerospace customers, all big names you would have heard of. Rick N6RK ___ 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] Phase meter for synchronizing osc's to GPSDO
Back in the spring of 2012 an article was published in VHF Communications entitled "A Phase Meter: a help to synchronize oscillator's to GPSDO". In it the authors indicated that they hoped to add a "rotation counter" perhaps using Arduino.Does anyone know whether further work was done on this? Regards, Bud W0LCP ___ 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] Commercial software defined radio for clock metrology
Bob Camp: > In many DMTD (and single mixer) systems, a lowpass and high pass filter are > applied to the signal coming out of the mixer. > This is done to improve the zero crossing detection. It also effectively > reduces the “pre detection” bandwidth. My understanding > of the setup in your paper does not do this sort of filtering. It simply > operated directly on the downconverter signal. Is this correct? > I may have missed something really obvious in a quick read of the paper….. Yes. After the filtering and down-conversion in the FPGA, we applied no further filtering in software (except in very long data runs we averaged the phase in 1 second "chunks" of samples before recording). ADC zero offset (or slow fluctuations) is removed with a high-pass filter implemented in the FPGA. Following down-conversion, a series of decimating low-pass filters in hardware reduces the data rate (typically by a factor of ~100) and the bandwidth. Both of these have the same effect of reducing the "pre-detection" bandwidth with the trade-offs of a) reducing the noise bandwidth (but not the noise density floor), and b) reducing the data throughput. Best wishes, -js ___ 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] Commercial software defined radio for clock metrology
On Wed, 25 May 2016 16:01:51 + "Sherman, Jeffrey A. (Fed)" wrote: > We found that in the studied units the limiting non-stationary noise > source was likely the aperture jitter of the ADC (the instability of the > delay between an idealized sample trigger and actuation of the sample/hold > circuitry). However, the ADC's aperture jitter appears highly common-mode in > chips with a second "simultaneously-sampled" input channel, allowing for an > order-of-magnitue improvement after channel-to-channel subtraction. For > example, at 5 MHz, the SDR showed a time deviation floor of ~20 fs after > just 10 ms of averaging; the aperture jitter specification was 150 fs. We > also describe tests with maser signals lasting several days. I tried to understand where the aperture jitter comes from and why it has such a huge common-mode. I asked a professor from Stanford doing research on ADCs a couple of questions in this regard, especialy whether he had any good references to read. Apparently, most of the noise in ADCs is internally generated. The two biggest contributors to aperture jitter seem to be thermal noise in the clock path and power supply noise. Interestingly, power supply noise comes mostly from the ADC itself and not from the external power source. I've been told the voltage drop on the power grid due to current spiking on chip can reach several tens of mV. Beside that, most research on jitter induced ADC noise only considers the clock jitter as source. There are very few that consider supply induced jitter as well, but no numbers are given. A few also mention substrate coupled noise, but according to the professor that is negligible in reality. The professor was surprised at how much of the aperture jitter is common-mode. He asked whether there was any explanation given by Jeffrey or Roberts in the paper, which I had to deny. His best guess was that the common-mode came either from external supply or internal supply issues common to both channels. He also remarked that the phase noise spectrum could give hints. I personally do not think that the phase noise spectrum reviles anything. There is just too much going on to say anything. I think it would be interesting to try a board designed for low noise operation and see what that would show (partially working on that already for other reasons). I also found out that the sample-and-hold circuits have a input voltage dependent delay component. So there is potentially a phase shift dependent change in the noise floor. Attila Kinali -- Reading can seriously damage your ignorance. -- unknown ___ 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] Ublox Neo-6M time error.
I had two machines running Lady Heather with the singing chime clock mode enabled (that plays a chant from the Missa Assumpta on the quarter hours). One machine was connected to a Ublox Neo-6M receiver and another to a Z3801A. I noticed that the two machines sang their jaunty monk tunes offset by around one second. Since a man with two singing GPS clocks never knows what time it is, I replaced the Z3801A with a Jupiter-T and the two clocks were still out of sync. Finally I tried Motorola M12+ and UT receivers and the same thing happened. It looks like the Ublox time is ahead by a second compared to all the other receivers. I then specified a -1 second "rollover" correction to the Ublox machine and the two clocks sang in perfect harmony. Has anybody noticed such behavior with other receivers? BTW, note that the Ublox binary time message has a "fractional nanoseconds of the seconds field" (+/- 500,000 nanoseconds) correction that must be applied to the hrs:min:secs values (which I am doing). The fractional time offset forms a sawtooth with around a 120 second period. Attached is a GIF... white is the nanosecond fractional time offset. Magenta is the receiver estimate of its time error (both in nanoseconds). The Trimble Resolution-T receivers report a similar "local clock bias" value, but they don't seem to document what it actually is... ___ 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] Phase meter for synchronizing osc's to GPSDO
I looked through the complete index of the magazine for any further articles by the authors but no joy. It's fairly certain that they didn't do a followup in VHF Communications magazine (it ceased publication in 2013). The authors were A Daretti, and G Canale. You might search the web for those names and see if you can contact them for more info. Cheers, Dave M Bud Patten wrote: > Back in the spring of 2012 an article was published in VHF > Communications entitled "A Phase Meter: a help to synchronize > oscillator's to GPSDO". In it the authors indicated that they hoped > to add a "rotation counter" perhaps using Arduino.Does anyone > know whether further work was done on this? > > > > Regards, > > Bud > > W0LCP ___ 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] Ublox Neo-6M time error.
Yo Mark! On Wed, 1 Jun 2016 01:20:27 + Mark Sims wrote: > Has anybody noticed such behavior with other receivers? Yup. Quite common when the GPS is confused about the current leap seconds. Usually a GPS will download the correct offset withing 30 mins of cold start. RGDS GARY --- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588 pgpbcuWgOxO_C.pgp Description: OpenPGP digital signature ___ 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] Ublox Neo-6M time error.
Hi Mark, What does u-center report for the NEO-6M? Or how about TAC32? Check the precise alignment of the 1PPS and the NMEA/binary/SCPI message stream. Since the messages cannot coincide with the 1PPS, firmware has two choices: the message can describe the time of the previous 1PPS or the time of the next 1PPS. Vendors differ. Depending on your software or how you receive the 1PPS or how you interpret the packets, there are possibilities for off-by-one second errors due to this. The same issue occurs with sawtooth correction: is the correction for the 1PPS that just occurred a fraction of a second ago, or the correction for the 1PPS that will occur in a fraction of a second from now? Vendors differ. The good news is that vendors all agree on NMEA: it's the time of the current second, not the next second. But the bad news is that this makes it impossible to handle UTC leap seconds with standard NMEA. By the time you find out there was a leap second it's too late. At least one vendor has a custom leap second pending NMEA message to work-around this. /tvb - Original Message - From: "Mark Sims" To: Sent: Tuesday, May 31, 2016 6:20 PM Subject: [time-nuts] Ublox Neo-6M time error. I had two machines running Lady Heather with the singing chime clock mode enabled (that plays a chant from the Missa Assumpta on the quarter hours). One machine was connected to a Ublox Neo-6M receiver and another to a Z3801A. I noticed that the two machines sang their jaunty monk tunes offset by around one second. Since a man with two singing GPS clocks never knows what time it is, I replaced the Z3801A with a Jupiter-T and the two clocks were still out of sync. Finally I tried Motorola M12+ and UT receivers and the same thing happened. It looks like the Ublox time is ahead by a second compared to all the other receivers. I then specified a -1 second "rollover" correction to the Ublox machine and the two clocks sang in perfect harmony. Has anybody noticed such behavior with other receivers? BTW, note that the Ublox binary time message has a "fractional nanoseconds of the seconds field" (+/- 500,000 nanoseconds) correction that must be applied to the hrs:min:secs values (which I am doing). The fractional time offset forms a sawtooth with around a 120 second period. Attached is a GIF... white is the nanosecond fractional time offset. Magenta is the receiver estimate of its time error (both in nanoseconds). The Trimble Resolution-T receivers report a similar "local clock bias" value, but they don't seem to document what it actually is... > ___ > 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] Ublox Neo-6M time error.
The receiver is reporting the correct UTC offset and appears to be working properly... it's just that the time is one second off from what 7 other models of receivers are reporting... > Yup. Quite common when the GPS is confused about the current leap seconds. ___ 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.
